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Porcine skin gelatin hydrolysate as a dipeptidyl peptidase IV inhibitor improves glycemic control in streptozotocin-induced diabetic rats

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... Our research group has attempted a series of in vivo experiments which demonstrated that peptides from various protein sources were effective to lower blood glucose of diabetic rats by DPP-IV inhibition and/or GLP-1 stimulation. 14,15 The rationale of these research studies was to select protein sources with high Pro contents having the same potential as the precursors of DPP-IV inhibitors. The specificity of the proteases we used for hydrolysis was not considered, hence, the DPP-IV inhibitory activity of the obtained hydrolysates was various and could not be expected. ...
... The result was consistent with the previous study, which reported that porcine skin gelatin hydrolysates (300 mg per day) showed a hypoglycaemic effect on the STZ-induced rat model. 15 Our previous studies have reported that the oral administration of Atlantic salmon (300 mg per day) and tilapia (750 mg per kg per day) skin gelatin hydrolysates for 5 and 4 weeks, respectively, significantly lowered blood glucose levels of diabetic rats to a level similar to normal control rats. 14,27 The HFD-fed and low-dose STZ-induced diabetic rat model was first adopted in our study for type 2 diabetes simulating the human syndrome that is also suitable for testing antidiabetic agents for the treatment of type 2 diabetes. ...
... 28 The blood glucose levels of HFD-fed and low-dose STZ-treated rats during OGTT were much higher than those of STZ-nicotinamide (NA)-induced diabetic rats. 14,15 The plasma glucose AUC of STZ-NA-induced diabetic rats treated with porcine and Atlantic salmon skin gelatin was reduced by 10 and 33%, respectively, 14,15 meanwhile, that of HFD-fed and low-dose STZ-induced diabetic rats treated with 1CBR decreased 37% (Fig. 2). The result represents that the administration of 1CBR for 6 weeks is effective for the glycaemic control of diabetic rats, although the rats are still identified to be diabetic due to their blood glucose levels being over 200 mg dL −1 . ...
Article
The frequency (A), a novel in silico parameter, was developed by calculating the ratio of the number of truncated peptides with Xaa-proline and Xaa-alanine to all peptide fragments from a protein hydrolyzed with a specific protease. The highest in vitro DPP-IV inhibitory activity (72.7%) was observed in the hydrolysate of sodium caseinate by bromelain (Cas/BRO), and the constituent proteins of bovine casein also had relatively high A values (0.10-0.17) with BRO hydrolysis. 1CBR (the < 1 kDa fraction of Cas/BRO) showed the greatest in vitro DPP-IV inhibitory activity of 77.5% and was used for in vivo test by high-fat diet-fed and low-dose streptozotocin-induced diabetic rats. The daily administration of 1CBR for 6 weeks was effective to improve glycaemic control in diabetic rats. The results indicate that the novel in silico method has the potential as a screening tool to predict dietary proteins to generate DPP-IV inhibitory and antidiabetic peptides.
... [7] Some studies were done for investigating the inhibitory activity of gelatin and their hydrolysate against DP-4 covering porcine, bovine, and fish gelatin. [4,8,9] The application of porcine gelatin as source DP-4 inhibitor has been limited because this source is prohibited in Islam and Judaism. Fortunately, most of bovine and fish gelatin which was analyzed as DP-4 inhibitor were derived from the byproduct. ...
... [11] The aim of this research was to determine the percent inhibition of bovine, fish skin, and fish bone gelatin against DP-4 through their ratio inhibition compared to synthetic sitagliptin. In the previous studies, the quantified inhibitory activity of gelatin and another food-based protein against DP-4 enzymes do not use sitagliptin as standard, but diprotin A. [4,8,12] Actually, sitagliptin is a well-known synthetic DP-4 inhibitor in the market. [3,13] The seeking for DP-4 inhibitors from natural substances and gelatin is certainly intended to replacing this synthetics medicine. ...
... [2] Consequently, studies on seeking and characterization of DP-4 inhibitor have been growing rapidly; one among them is about gelatin. [4,8,25] Gelatin has been widely used for a long time as a safe and unique ingredient in food and pharmaceutical industries, and their imino acid (proline+hydroxyproline) composition also makes this colloid fit for DPP-IV inhibition. [4,8,25,26] The measurement of inhibitory activity against DP-4 enzyme uses sitagliptin as positive control, which was used as inhibitor of DP-4 and used as medicine for T2DM therapy as well as treatment manner. ...
Article
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The current study aims to determine the inhibition activity gelatin against dipeptidyl aminopeptidase 4 (DP-4). Two commercial gelatins, i.e., bovine and fish skin gelatin and one extracted (in our laboratory) gelatin, i.e., fish bone gelatin were selected for analysis. Each gelatin have same protein pattern (75–245 kDa) on sodium dodecyl sulfate polyacrylamide gel electrophoresis with mean of protein concentration of 1.72 mg/mL. The inhibition activity was measured on the capacity to inhibit DP-4 by using Gly-Pro-p-nitroanilide as their substrate. The sitagliptin was used as standard comparison. Based on the percent inhibition, gelatin has been shown to be the prospective DP-4 inhibitor.
... [7] Some studies were done for investigating the inhibitory activity of gelatin and their hydrolysate against DP-4 covering porcine, bovine, and fish gelatin. [4,8,9] The application of porcine gelatin as source DP-4 inhibitor has been limited because this source is prohibited in Islam and Judaism. Fortunately, most of bovine and fish gelatin which was analyzed as DP-4 inhibitor were derived from the byproduct. ...
... [11] The aim of this research was to determine the percent inhibition of bovine, fish skin, and fish bone gelatin against DP-4 through their ratio inhibition compared to synthetic sitagliptin. In the previous studies, the quantified inhibitory activity of gelatin and another food-based protein against DP-4 enzymes do not use sitagliptin as standard, but diprotin A. [4,8,12] Actually, sitagliptin is a well-known synthetic DP-4 inhibitor in the market. [3,13] The seeking for DP-4 inhibitors from natural substances and gelatin is certainly intended to replacing this synthetics medicine. ...
... [2] Consequently, studies on seeking and characterization of DP-4 inhibitor have been growing rapidly; one among them is about gelatin. [4,8,25] Gelatin has been widely used for a long time as a safe and unique ingredient in food and pharmaceutical industries, and their imino acid (proline+hydroxyproline) composition also makes this colloid fit for DPP-IV inhibition. [4,8,25,26] The measurement of inhibitory activity against DP-4 enzyme uses sitagliptin as positive control, which was used as inhibitor of DP-4 and used as medicine for T2DM therapy as well as treatment manner. ...
Article
The current study aims to determine the inhibition activity gelatin against dipeptidyl aminopeptidase 4 (DP-4). Two commercial gelatins, i.e., bovine and fish skin gelatin and one extracted (in our laboratory) gelatin, i.e., fish bone gelatin were selected for analysis. Each gelatin have same protein pattern (75-245 kDa) on sodium dodecyl sulfate polyacryla-mide gel electrophoresis with mean of protein concentration of 1.72 mg/mL. The inhibition activity was measured on the capacity to inhibit DP-4 by using Gly-Prop -nitroanilide as their substrate. The sitagliptin was used as standard comparison. Based on the percent inhibition, gelatin has been shown to be the prospective DP-4 inhibitor.
... While the DPP-IV inhibitory activities of food-derived peptides have been shown in numerous in vitro studies, the literatures on their effects in vivo remain sparse; however, some promising results have also been reported [37][38][39]. In our study, after STZ treatment, the blood concentrations of DPP-IV in mice increased and the concentrations of GLP-1 decreased ( Figure 3D,E). ...
... Subsequently, the mice respectively received gavage with ultrapure water, sitagliptin (4 mg/kg), and synthesized peptide II (400 mg/kg), according to the grouping every day from the fourth day after injection (Day 1). The doses of sitagliptin and peptide II were set according to research of Huang et al. [39], Hsieh et al. [37], and Uenishi et al. [38], as well as our preliminary experiment. ...
Article
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Dipeptidyl peptidase IV (DPP-IV) inhibitors occupy a growing place in the drugs used for the management of type 2 diabetes. Recently, food components, including food-derived bioactive peptides, have been suggested as sources of DPP-IV inhibitors without side effects. Chinese black tea is a traditional health beverage, and it was used for finding DPP-IV inhibitory peptides in this study. The ultra-filtrated fractions isolated from the aqueous extracts of black tea revealed DPP-IV inhibitory activity in vitro. Four peptides under 1 kDa were identified by SDS-PAGE and LC-MS/MS (Liquid Chromatography-Mass Spectrometry-Mass Spectrometry) from the ultra-filtrate. The peptide II (sequence: AGFAGDDAPR), with a molecular mass of 976 Da, showed the greatest DPP-IV inhibitory activity (in vitro) among the four peptides. After administration of peptide II (400 mg/day) for 57 days to streptozotocin (STZ)-induced hyperglycemic mice, the concentration of glucagon-like peptide-1 (GLP-1) in the blood increased from 9.85 ± 1.96 pmol/L to 19.22 ± 6.79 pmol/L, and the insulin level was increased 4.3-fold compared to that in STZ control mice. Immunohistochemistry revealed the improved function of pancreatic beta-cells and suppressed proliferation of pancreatic alpha-cells. This study provides new insight into the use of black tea as a potential resource of food-derived DPP-IV inhibitory peptides for the management of type 2 diabetes.
... To date, only several animal studies have evaluated the efficacy of DPP-IV inhibitory hydrolysates such as porcine skin [181], fish skin [55,182], rice bran [183], zein corn [184], and sodium caseinate [185] hydrolysate with significant positive results. In these research studies, the commercial proteases commonly used to release hydrolysate are flavourzyme [181,182,186], papain [183,184], and pepsin [183] due to their potent GLP-1 secretory activity in vitro and in vivo (flavourzyme and papain), and their partial simulation of gastric digestion (pepsin). ...
... To date, only several animal studies have evaluated the efficacy of DPP-IV inhibitory hydrolysates such as porcine skin [181], fish skin [55,182], rice bran [183], zein corn [184], and sodium caseinate [185] hydrolysate with significant positive results. In these research studies, the commercial proteases commonly used to release hydrolysate are flavourzyme [181,182,186], papain [183,184], and pepsin [183] due to their potent GLP-1 secretory activity in vitro and in vivo (flavourzyme and papain), and their partial simulation of gastric digestion (pepsin). Additionally, oral administration is preferred over subcutaneous administration in almost all animal models due to advantages including easier management, less complex handling, painless, and safety features. ...
Article
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Diabetes, a glucose metabolic disorder, is considered one of the biggest challenges associated with a complex complication of health crises in the modern lifestyle. Inhibition or reduction of the dipeptidyl peptidase IV (DPP-IV), alpha-glucosidase, and protein-tyrosine phosphatase 1B (PTP-1B) enzyme activities or expressions are notably considered as the promising therapeutic strategies for the management of type 2 diabetes (T2D). Various food protein-derived antidiabetic bioactive peptides have been isolated and verified. This review provides an overview of the DPP-IV, PTP-1B, and α-glucosidase inhibitors, and updates on the methods for the discovery of DPP-IV inhibitory peptides released from food-protein hydrolysate. The finding of novel bioactive peptides involves studies about the strategy of separation fractionation, the identification of peptide sequences, and the evaluation of peptide characteristics in vitro, in silico, in situ, and in vivo. The potential of bioactive peptides suggests useful applications in the prevention and management of diabetes. Furthermore, evidence of clinical studies is necessary for the validation of these peptides’ efficiencies before commercial applications.
... Thus, the statement related the correlation between the molecular weight (MW) with DPP-IV inhibition can not be fully accepted. In addition, study operated by Huang et al. (2014) which is using porcine gelatin hydrolysate was described that fraction <1.5 kDa and 1.5-2.5 kDa had similar inhibition rate of 35% roughly [39]. Study conducted by Hsu et al. (2013) found that inhibition rate of fraction 1.5-2.5 kDa from porcine gelatin hydrolysate was slightly higher than fraction <1.5 kDa [40]. ...
... Thus, the statement related the correlation between the molecular weight (MW) with DPP-IV inhibition can not be fully accepted. In addition, study operated by Huang et al. (2014) which is using porcine gelatin hydrolysate was described that fraction <1.5 kDa and 1.5-2.5 kDa had similar inhibition rate of 35% roughly [39]. Study conducted by Hsu et al. (2013) found that inhibition rate of fraction 1.5-2.5 kDa from porcine gelatin hydrolysate was slightly higher than fraction <1.5 kDa [40]. ...
Article
Full-text available
Bioactive peptides have been investigated largely for many biofunctional properties. The aim of this research was to determine the inhibitory activity of ultrafiltration (UF) and gel filtration (GF) fractions of gelatin derived from bone of Pangasius catfish against dipeptidyl peptidase IV (DPP-IV). Previous studies have shown that gelatin from skins of salmon, hake, halibut, milkfish, tilapia and bone of pangasius catfish have the activity in DPP-IV inhibition. While, as inhibitor, most of previous and recent studies shown that separation and fractination of gelatin hydrolysate increase their activity. This research was conducted in three stages including gelatin hydrolysates fractination by ultrafiltration (UF), UF fraction loaded into gel filtration (GF) and DPP-IV inhibition measurement. The fish bone gelatin was hydrolyzed using flavourzyme at three enzyme/substrate ratios (E/S of 3%, 6% and 9%) with incubation times 4, 6, and 8 h. Then, the hydrolysates fractioned by ultrafiltration with 3 kDa cutoff membrane continued with Superfine G-25 sephadex column (65 cm x 3 cm, flow rate 1 mL/min). The result shown that both group of fractions i.e UF and GF have inhibitory activity regarding their capacity to inhibit DPP-IV. The UF fraction >3 kDa derived from 9% (E/S) ratio for hdyrolysis were superb as DPP-IV inhibitor than other fractions, the highest one also has bioactivity higher than other previous fish gelatin fractions.
... In the past years, a range of collagen-derived DPP-IV inhibitory peptides has been discovered. Table 3 shows a summary of sequences and potencies of DPP-IV inhibitory peptides from different (Cai et al. 2015) collagenous sources, such as bovine collagen Lafarga, O'Connor, and Hayes 2014), Atlantic salmon gelatin , barbel fish gelatin (Sila et al. 2015), deer collagen (Jin et al. 2015), porcine skin gelatin (Huang et al. 2014) and silver carp collagen ). Interestingly, a common feature of the identified collagen-derived DPP-IV inhibitory peptides is that most of them share the similar repeating motif, Gly-X-Y sequence. ...
... Recently, Hsieh et al. (2015) reported that oral administration of Atlantic salmon skin gelatin hydrolysate at the dose of 300 mg/day for 5 weeks could inhibit GLP-1 degradation by DPP-IV, leading to the enhanced insulin secretion and improved glycemic control in streptozotocin-induced diabetic rats. Similarly, oral administration of porcine skin gelatin hydrolysate (300 mg per day for 42 days) can also improve the glucose tolerance in streptozotocin-induced diabetic rats through inhibition of plasma DPP-IV activity by 63.4% (Huang et al. 2014). However, the molecular mechanisms responsible for DPP-IV inhibition by collagen peptides remains to be unraveled. ...
Article
Full-text available
A large amount of food-grade animal by-products is annually produced during industrial processing and they are normally utilized as animal feed or other low-value purposes. These by-products are good sources of valuable proteins, including collagen or gelatin. The revalorization of collagen may lead to development of a high benefit-to-cost ratio. In this review, the major approaches for generation of collagen peptides with a wide variety of bioactivities were summarized, including antihypertensive, antioxidant and antidiabetic activities, and beneficial effects on bone, joint and skin health. The biological potentials of collagen peptides and their bioavailability were reviewed. Moreover, the unique advantages of collagen peptides over other therapeutic peptides were highlighted. In addition, the current challenges for development of collagen peptides as functional food ingredients were also discussed. This article discusses the opportunity to utilize collagen peptides as high value-added bio-functional ingredients in the food industry.
... In the past years, a range of collagen-derived DPP-IV inhibitory peptides has been discovered. Table 3 shows a summary of sequences and potencies of DPP-IV inhibitory peptides from different (Cai et al. 2015) collagenous sources, such as bovine collagen Lafarga, O'Connor, and Hayes 2014), Atlantic salmon gelatin , barbel fish gelatin (Sila et al. 2015), deer collagen (Jin et al. 2015), porcine skin gelatin (Huang et al. 2014) and silver carp collagen ). Interestingly, a common feature of the identified collagen-derived DPP-IV inhibitory peptides is that most of them share the similar repeating motif, Gly-X-Y sequence. ...
... Recently, Hsieh et al. (2015) reported that oral administration of Atlantic salmon skin gelatin hydrolysate at the dose of 300 mg/day for 5 weeks could inhibit GLP-1 degradation by DPP-IV, leading to the enhanced insulin secretion and improved glycemic control in streptozotocin-induced diabetic rats. Similarly, oral administration of porcine skin gelatin hydrolysate (300 mg per day for 42 days) can also improve the glucose tolerance in streptozotocin-induced diabetic rats through inhibition of plasma DPP-IV activity by 63.4% (Huang et al. 2014). However, the molecular mechanisms responsible for DPP-IV inhibition by collagen peptides remains to be unraveled. ...
Article
A large amount of food-grade animal by-products is annually produced during industrial processing and they are normally utilized as animal feed or other low-value purposes. These by-products are good sources of valuable proteins, including collagen or gelatin. The revalorization of collagen may lead to development of a high benefit-to-cost ratio. In this review, the major approaches for generation of collagen peptides with a wide variety of bioactivities were summarized, including antihypertensive, antioxidant and antidiabetic activities, and beneficial effects on bone, joint and skin health. The biological potentials of collagen peptides and their bioavailability were reviewed. Moreover, the unique advantages of collagen peptides over other therapeutic peptides were highlighted. In addition, the current challenges for development of collagen peptides as functional food ingredients were also discussed. This article discusses the opportunity to utilize collagen peptides as high value-added bio-functional ingredients in the food industry.
... Several collagen peptides with DPP-IV inhibitory activities have been identified and are shown in Table 4. Neves et al. (2017) separated four collagen peptides from salmon gelatin hydrolysates that have multifunctional bioactivities including inhibiting DPP-IV in vitro. Huang, Hung, Jao, Tung, and Hsu (2014) confirmed that collagen peptides have a hypoglycemic effect on diabetic rats by reducing the activity of DPP-IV in plasma. Jin et al. (2020) reported three collagen peptides separated from Atlantic salmon skin collagen hydrolysates with different DPP-IV inhibition patterns (LDKVFR: competitive inhibitor, VLATSGPG: non-competitive inhibitor, YYGYT-GAFR: mixed-type). ...
... The peptides with high DPP-IV inhibitory activity usually have 2-8 amino acid residues and have Pro or Ala at the second N-terminal residue (Huang et al., 2014). Collagen peptides sequenced in GPAE with the structural characteristics of preferred DPP-IV inhibitory peptides showed good DPP-IV inhibitory activity (IC 50 = 49.6 μM) (Li-Chan, Hunag, Jao, Ho, & Hsu, 2012). ...
Article
Full-text available
Collagen is the most abundant extracellular matrix protein in food-producing animals. Gelatin is partially degraded collagen. Collagen peptides refer to the peptides with specific properties identified from collagen hydrolysate who produced by hydrolysis of collagen/gelatin. Due to the specific structural and bio- and physical-chemical properties, collagen and its derivatives are used in the field of food industry. In this review, the structure of the collagen molecule and its biosynthetic process in vivo are introduced, and the production methods and structures of gelatin and collagen peptides described. Then the inherent self-assembly property of collagen, the mechanical properties of collagen and gelatin gels, functional properties of collagen and gelatin, and bioactive properties of collagen peptides are reviewed. Finally, the applications of collagen and its derivatives that are correlated with their properties in food industry are summarized. The mechanisms and advantages of the applications of collagen and its derivatives in food industry are raised, and the limitations and challenges of these applications are also discussed. And possible studies to address the challenges of the applications in different areas are indicated.
... abbreviate Ser. (Yuan, Gu, & Tang, 2008a), zebra blenny , porcine skin gelatin (Huang, Hung, Jao, Tung, & Hsu, 2014), and goby . ...
Chapter
In recent years, a great deal of interest has been expressed regarding the production, characterization, and applications of protein hydrolysates and food-derived biopeptides due to their numerous beneficial health effects. In this regard, research is mainly focused on investigating the therapeutic potential of these natural compounds. Based on their amino acids composition, sequences, hydrophobicity, and length, peptides released from food proteins, beyond their nutritional properties, can exhibit various biological activities including antihypertensive, antioxidative, antithrombotic, hypoglycemic, hypocholesterolemic, and antibacterial activities among others.
... Various reports have highlighted the possibility of using food-derived proteins and peptides as a natural source of DPP-IV inhibitors. These sources notably include milk [3], tuna [4], rice [5], cheese [6], salmon [7], pumpkin [8], porcine skin gelatin [9], and so on. ...
Article
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Chlorella vulgaris: is a nutritional food with high protein content. Thus, 43 protein sequences from C. vulgaris were in silico gastrointestinal digested with the aid of BIOPEP. A peptide library of 468 di- and tri-peptides was built from the produced peptides. Six peptides, AAR, VPA, VPW, IPL, IPR, and PPL, were selected for DPP-IV inhibitory assay based on their sequence feature with Pro or Ala at the second N-terminal site. VPA, VPW, IPL, and IPR had potency of DPP-IV inhibition. VPW and IPR with the same N-terminal and second N-terminal sites as those of diprotin A (IPI) and diprotin B (VPL) achieved relative inhibitory IC50 value of 6.4 and 6.9 versus IPI. These peptides were further demonstrated gastrointestinal stable in vitro and could also inhibit the DPP-IV in mouse serum. Molecular docking illustrated the inhibitory mechanism of VPW and IPR. Both VPW and IPR binding with DPP-IV through hydrogen bonds, van Edward Mars interactions, and hydrophobic interactions. However, VPW formed more stable interaction with DPP-IV. The results suggested that C. vulgaris proteins would be a good source for DPP-IV inhibitory peptides.
... In addition to synthetic compounds (Gooben & Gräber, 2012), bioactive peptides derived from various food proteins, such as milk proteins (Lacroix & Li-Chan, 2012a;, gelatin (Huang, Hung, Jao, Tung, & Hsu, 2014;Li-Chan, Huang, Jao, Ho, & Hsu, 2012), meat proteins (Lafarga, O'Connor, & Hayes, 2014), have been widely studied to show DPP-IV inhibitory activity (Power, Nongonierma, Jakeman, & FitzGerald, 2014). ...
Article
A total of 294 edible protein sequences and 5 commercial proteases listed in the BIOPEP database were analyzed in silico. The frequency (A), a parameter in silico described previously, was examined further to calculating the ratio of truncated peptides with Xaa-proline and/or Xaa-alanine to all peptide fragments in a protein hydrolyzed with a protease, using the BIOPEP database. Then the in vitro DPP-IV inhibitory activity was determined using the same 15 protein and protease combinations to evaluate their relationship. The result shows that A values considering the number of Xaa-proline+Xaa-alanine exhibited a strong correlation with in vitro DPP-IV inhibition rates by Pearson’s correlation analysis (r = 0.6993; P < 0.05). Therefore, the in silico approach is effective to predict DPP-IV inhibitory activities in vitro of protein hydrolysates.
... Recently, an in vitro approach involving live intestinal epithelial Caco-2 cells was developed by our team [42], and has since been used in several studies to assess DPP-IV-inhibitory activity [33,39,[42][43][44]. DPP-IV-inhibitory activity has also been measured ex vivo in rat and human plasma [13,[45][46][47][48]. ...
Article
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Dipeptidyl-peptidase IV (DPP-IV) plays an essential role in glucose metabolism by inactivating incretins. In this context, food-protein-derived DPP-IV inhibitors are promising glycemic regulators which may act by preventing the onset of type 2 diabetes in personalized nutrition. In this study, the DPP-IV-inhibitory potential of seven proteins from diverse origins was compared for the first time in vitro and in vivo in rat plasma after the intestinal barrier (IB) passage of the indigested proteins. The DPP-IV-inhibitory potentials of bovine hemoglobin, caseins, chicken ovalbumin, fish gelatin, and pea proteins were determined in rat plasma thirty minutes after oral administration. In parallel, these proteins, together with bovine whey and gluten proteins, were digested using the harmonized INFOGEST protocol adapted for proteins. The DPP-IV half-maximal inhibitory concentration (IC50) was determined in situ using Caco-2 cells. The DPP-IV-inhibitory activity was also measured after IB passage using a Caco2/HT29-MTX mixed-cell model. The peptide profiles were analyzed using reversed-phase high-performance liquid chromatography tandem mass spectrometry (RP-HPLC-MS/MS) with MS data bioinformatics management, and the IC50 of the identified peptides was predicted in silico. The in vitro and in vivo DPP-IV-inhibitory activity of the proteins differed according to their origin. Vegetable proteins and hemoglobin yielded the highest DPP-IV-inhibitory activity in vivo. However, no correlation was found between the in vivo and in vitro results. This may be partially explained by the differences between the peptidome analysis and the in silico predictions, as well as the study complexity.
... 18) Peptide substrates with Pro, Hyp, or Ala at the second amino-terminal position inhibit the activity of DPP-IV. 19) Enzymatic hydrolysates of food proteins, such as gelatin [20][21][22] and milk proteins, [23][24][25] have DPP-IV inhibitory activity, and structures of inhibitory peptides from food proteins were identified in various studies. 26) For example, Gly-Pro-Ala-Glu and Gly-Pro-Gly-Ala derived from gelatin exhibited high-inhibitory activity toward DPP-IV with IC 50 values of 49.6 and *Corresponding author. ...
Article
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Wheat gluten is a Pro-rich protein complex comprising glutenins and gliadins. Previous studies have reported that oral intake of enzymatic hydrolysates of gluten has beneficial effects, such as suppression of muscle injury and improvement of hepatitis. Here, we utilized ginger protease that preferentially cleaves peptide bonds with Pro at the P2 position to produce a novel type of wheat gluten hydrolysate. Ginger protease efficiently hydrolyzed gluten, particularly under weak acidic conditions, to peptides with an average molecular weight of <600 Da. In addition, the gluten hydrolysate contained substantial amounts of tripeptides, including Gln-Pro-Gln, Gln-Pro-Gly, Gln-Pro-Phe, Leu-Pro-Gln, and Ser-Pro-Gln (e.g. 40.7 mg/g at pH 5.2). These gluten-derived tripeptides showed high inhibitory activity on dipeptidyl peptidase-IV with IC50 values of 79.8, 70.9, 71.7, 56.7, and 78.9 μM, respectively, suggesting that the novel gluten hydrolysate prepared using ginger protease can be used as a functional food for patients with type 2 diabetes.
... Animal studies have suggested that hydrolysates with DPP-IV inhibitory activities generally yield antidiabetic effects after ingestion (Nongonierma & FitzGerald, 2016). For example, Huang, Hung, Jao, Tung, and Hsu (2014) demonstrated that daily administration of peptides generated from porcine skin gelatin using Flavorzyme were able to improve the glucose tolerance in streptozotocin-induced diabetic rats at days 21 and 42. These hydrolysates and peptides could be used as functional food ingredients for the management of Type 2 diabetes. ...
Article
The use of meat processing co-products to recover economically valuable food ingredients, with health-promoting properties represents an opportunity to enhance the economic performance of the meat industry and to reduce the environmental impact of meat production. This paper discusses the potential of meat processing co-products for use as substrates for bioactive peptide generation with varied bioactivities including antioxidant, antimicrobial, and antihypertensive properties. Moreover, the current state-of-art of meat-derived bioactive peptides is reviewed with a focus on peptides with proven in vivo bioactivities. Meat processing co-products represent a problem for meat processors due to the large volumes generated and its high pollutant load. These co-products are usually used for low-value purposes. However, co-products such as blood or lung can be used as resources for the generation of bioactive peptides with health-promoting properties which could be used as ingredients in the functional foods industry.
... Animal studies have suggested that hydrolysates with DPP-IV inhibitory activities generally yield antidiabetic effects after ingestion (Nongonierma & FitzGerald, 2016). For example, Huang, Hung, Jao, Tung, and Hsu (2014) demonstrated that daily administration of peptides generated from porcine skin gelatin using Flavorzyme were able to improve the glucose tolerance in streptozotocin-induced diabetic rats at days 21 and 42. These hydrolysates and peptides could be used as functional food ingredients for the management of Type 2 diabetes. ...
Article
Background: Response surface methodology (RSM) was used in a sequential manner to optimize solubilization and precipitation conditions in the recovery of protein from bovine lung using pH shift. Result: Separate D-optimal designs were employed for protein solubilization and precipitation. Independent variables investigated for protein solubilization were time (10-120 minutes), temperature (4-20 °C), pH (8-11) and solvent sample ratio (2.5-10). Variables for protein precipitation were time (0-60 minutes) and pH (4.25-6.00). Soluble protein yield ranged from 329 g kg(-1) to 647 g kg(-1) and the quadratic model for protein solubilisation revealed a coefficient of determination R(2) of 0.9958. Optimum conditions for maximum protein solubility were extraction time of 140 minutes, temperature 19°C, pH 10. 8 and solvent sample ratio 13.02. Protein precipitation yields varied from 407 g kg(-1) to 667 g kg(-1) giving a coefficient of determination R(2) of 0.9335. The optimum conditions for maximum protein precipitation were pH 5.03 and 60 minutes. Based on the RSM model, solubilization conditions were manipulated to maximize protein solubilization under reduced water and alkaline usage. These conditions were also validated. Conclusion: Models for solubilization and precipitation using bovine and porcine lung were validated; predicted and actual yields were in good agreement showing cross species applicability of the results.
... Recently, peptones from meat, milk and vegetable have proved to stimulate GLP-1 secretion on small intestine enteroendocrine L-cells (Pais, Gribble, & Reimann, 2016). A porcine skin gelatin hydrolysate showed an antidiabetic effect on STZ-induced diabetic rats characterised by elevated levels of GLP-1 (Huang, Hung, Jao, Tung, & Hsu, 2014). Protein GI digestion is also a way of generating peptides in the GI tract. ...
... Furthermore, in vivo animal studies demonstrated that hydrolysates from porcine skin gelatin with DPP-IV inhibitory activities exhibited antidiabetic effects (Nongonierma and FitzGerald, 2016). For instance, ingestion of gelatin hydrolysates (300 mg per day) from porcine skin can improve glucose tolerance in streptozotocin-induced diabetic rats after 21 and 42 days ( Huang et al., 2014). ...
... Gelatin hydrolysate prepared by partial hydrolysis of the extracted gelatin is widely used as supplemental food for its recently reported beneficial effects, such as reducing joint pain, 2,3 increasing bone density, 4,5 lowering blood pressure, 6,7 and lowering blood sugar levels. 8,9 Previous studies have also reported the bioactivities of collagen-derived oligopeptides constituting gelatin hydrolysate prepared by various combinations of enzymatic proteolysis. 10 For example, numerous Gly-X-Y-type tripeptides can be generated by collagenase digestion of gelatin. ...
Article
Recent studies have reported that oral intake of gelatin hydrolysate has various beneficial effects, such as reduction of joint pain and lowering of blood sugar levels. In this paper, we produced novel gelatin hydrolysate using cysteine-type ginger protease having unique substrate specificity with preferential peptide cleavage with Pro at the P2 position. Substantial amounts of X-hydroxyproline (Hyp)-Gly-type tripeptides were generated up to 2.5% (w/w) concomitantly with Gly-Pro-Y-type tripeptides (5%; w/w) using ginger powder. The in vivo absorption of the ginger-degraded gelatin hydrolysate was estimated using mice. The plasma levels of collagen-derived oligopeptides, especially X-Hyp-Gly, were significantly high (e.g., 2.3-fold for Glu-Hyp-Gly, p˂0.05) compared with that of the control gelatin hydrolysate, which was prepared using gastrointestinal proteases and did not contain detectable X-Hyp-Gly. This study demonstrated that orally administered X-Hyp-Gly was effectively absorbed into blood probably due to high protease resistance of this type of tripeptides.
... Regarding different E/S ratio for A, higher E/S concentration produced hydrolysates with lower IC 50 values while for P and AP higher E/S concentration seem to have no effect on DPP-IV IC 50 values. Similar results were also obtained for porcine skin gelatin hydrolysates obtained upon alcalase treatment where gradual increase in DPP-IV inhibition were obtained with increasing E/S ratio and hydrolysis times (Huang, Hung, Jao, Tung, & Hsu, 2014). The results obtained could be due to the substrate limitation and enzyme aggregation as explained for DH. ...
Article
In-vitro antidiabetic and antihypertensive properties of novel camel skin gelatin hydrolysates (CSGHs) were reported for the first time. Effect of different proteolytic enzymes, time of hydrolysis and enzyme: substrate (E/S) ratio on the bioactive (antidiabetic and antihypertensive) properties was explored. Results revealed that CSGHs exhibited highly potent inhibitory activity against dipeptidyl peptidase-IV (DPP-IV), pancreatic α-amylase (PA) and angiotensin-I converting enzyme (ACE) compared to non-hydrolyzed camel skin gelatin. All three enzyme combinations used produced highly potent PA inhibitory hydrolysates while for DPP-IV inhibitory property, protease and alcalase-protease (A/P) in combination produced more potent hydrolysates than alcalase generated hydrolysates. Moreover, alcalase and protease generated hydrolysates were highly active in inhibiting ACE activity in comparison to their combination (AP) (P < 0.05). Overall, no significant effect of E/S ratio and time of hydrolysis on production of DPP-IV, PA and ACE inhibitory peptides were observed. These findings suggest that both enzymes i.e. alcalase and protease alone or in combination were capable of producing camel skin gelatin hydrolysates with highly potent antidiabetic and antihypertensive properties. The present study presents the first report on the production of camel skin gelatin hydrolysates with strong in-vitro antidiabetic and antihypertensive potential. Future studies should be directed to identify the sequence of peptides responsibe for antidiabetic and antihypertensive activities.
... Çal›flmada, dipeptidil peptidaz-IV ve prolil endopeptidaz do¤al inhibitörleri için hidrolizatlar›n iyi bir kaynak oldu¤u ve bu hidrolizatlar›n nöropatolojik bozukluklar›n ve tip 2 diyabetin tedavisinde diyet katk› maddeleri olarak kullan›labilece¤i sonucuna ulafl›lm›flt›r. Baflka bir çal›flmada ise, domuz derisi jelatininden hidrolize edilen ve prolin içeren peptitin dipeptidil peptidaz-IV inhibitör aktivitesi belirlemifltir(44). Yap›lan di¤er in vivo çal›flmalarda da, jelatin ve kollajen peptitlerin biyolojik aktivitesi do¤rulam›flt›r.SONUÇG›da endüstrisinde özellikle helal ve kosher g›dalar için yeni jelatin kaynaklar›na talep artmaktad›r. ...
... Several peptides of various functionalities have been synthesized using tuna cooking juice as the protein source. Such peptides have been found to possess antioxidative (Hsu, Lu, and Jao 2009), anticancer (Huang et al. 2014) and DPP-IV inhibition (Huang et al. 2012) potentials. Huang et al. (2012) conducted a study to determine the potential of peptides enzymatically isolated from tuna cooking juice (5.44% protein content) in inhibiting DPP-IV. ...
Article
Diabetes, a metabolic syndrome of global importance has been on a progressive rise in recent years. Several pharmacological approaches have been made, which have proved effective, but with underlying side effects. Bioactive hydrolysates (BHs) and peptides (BPs) from food sources, however, have shown the relative advantage of imparting less adverse effects. Furthermore, BHs and BPs from food have been discovered to impart their antidiabetic potentials through one or more mechanisms such as inhibition of digestive enzymes, inhibition of the antigenic enzyme - Dipeptyl peptidase IV (DPP-IV), decrease in blood glucose levels and increase in insulin uptake. Several plants and animal sources have been used as protein sources for the isolation of antidiabetic hydrolysates and peptides through different mechanisms and analytical techniques. This review integrates recent research information about several popular and unconventional food sources of BHs and BPs, their isolation techniques, antidiabetic effects and protein profiles. In addition, the fractionation technique(s) employed in each study and inhibition potentials of BHs and BPs are reviewed. This article is intended to supplement accessible scholarly literature and intellectual awareness on the subject of food-oriented approach for the management of diabetes.
... ability against the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) (Lacroix & Li-Chan, 2016;Nongonierma & FitzGerald, 2015). DPP-IV inhibitory peptide has been developed as a potential approach in the therapy of type 2 diabetes, and a considerable amount of studies have revealed that plentiful food protein-derived peptides shown potent DPP-IV inhibitory activity, including plant-derived peptides such as casein, rice, and soy as well as animal-derived peptides such as milk and pork (Huang, Hung, Jao, Tung, & Hsu, 2014;. Several studies also suggested that CPs could significantly decrease the plasma DPP-IV activity as well as stimulate the secretion of active GLP-1 (Hira et al., 2009;Mochida, Hira, & Hara, 2010). ...
Article
Bioactive peptides are specific peptide fragments that positively exert various functional and biological activities and ultimately influence health. Corn protein are potential precursor proteins for bioactive peptides. This review encompasses the studies reported to date on the production, isolation, purification, and characterization technologies of bioactive corn peptides (CPs), with particular attention being devoted to these peptides’ different health effects, including antioxidant, antihypertensive, hepatoprotective, alcohol‐metabolism‐facilitating, anti‐inflammatory, anticancer, antimicrobial, and dipeptidyl peptidase IV (DPP‐IV) inhibitory activities. The review also describes studies examining the potential mechanisms believed to be involved in these bioactivities, and the possible absorption and transport pathways of CPs are summarized.
... Besides, several peptides obtained from other kinds of aquatic products such as sea cucumber protein (Gong et al. 2020) and Antarctic krill protein (Ji, Zhang, and Ji 2017) were showed strong DPP-IV inhibitory potency. Apart from dairy and aquatic products, gelatins are also potential sources of DPP-IV inhibitory peptides, such as pig skin (Huang et al. 2014), sheep skin (Wang, Yu, et al. 2021), camel skin ) and chicken feet (Casanova-Marti et al. 2019). In terms of eggs, three DPP-IV inhibitory peptides ADF (IC 50 = 16.83 mM), MIR (IC 50 = 4.86 mM) and FGR (IC 50 = 46.22 ...
Article
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Dipeptidyl Peptidase IV (DPP-IV) inhibitory peptides are attracting increasing attention, owing to their potential role in glycemic regulation by preventing the inactivation of incretins. However, few reviews have summarized the current understanding of DPP-IV inhibitory peptides and their knowledge gaps. This paper reviews the production, identification and structure-activity relationships (SAR) of DPP-IV inhibitory peptides. Importantly, their bioavailability and hypoglycemic effects are critically discussed. Unlike the traditional method to identifying peptides after separation step by step, the bioinformatics approach identifies peptides via virtual screening that is more convenient and efficient. In addition, the bioinformatics approach was also used to investigate the SAR of peptides. Peptides with proline (Pro) or alanine (Ala) residue at the second position of N-terminal are exhibit strong DPP-IV inhibitory activity. Besides, the bioavailability of DPP-IV inhibitory peptides is related to their gastrointestinal stability and cellular permeability, and in vivo studies showed that the glucose homeostasis has been improved by these peptides. Especially, the intestinal transport of DPP-IV inhibitory peptides and cell biological assays used to evaluate their potential role in glycemic regulation are innovatively summarized. For further successful development of DPP-IV inhibitory peptides in glycemic regulation, future study should elucidate their SAR and in vivo hypoglycemic effects .
... Ji et al. employed ultrafiltration to separate Antarctic krill hydrolysates into different fractions with three molecular weight (MW) ranges: >10 kDa, 3-10 kDa, and <3 kDa [42]. Huang et al. reported that a porcine skin gelatin hydrolysate was first divided into three fractions with MW ranges of >2.5 kDa, 1-2.5 kDa, and <1 kDa, and both the 1-2.5 kDa and <1 kDa fractions showed great DPP-IV inhibition [59]. Zhang et al. applied three MWCO membranes, of 3, 5, and 10 kDa, to separate silver carp protein hydrolysate into fractions of four different MW ranges [43]. ...
Article
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Diabetes is a chronic metabolic disorder which leads to high blood sugar levels over a prolonged period. Type 2 diabetes mellitus (T2DM) is the most common form of diabetes and results from the body’s ineffective use of insulin. Over ten dipeptidyl peptidase IV (DPP-IV) inhibitory drugs have been developed and marketed around the world in the past decade. However, owing to the reported adverse effects of the synthetic DPP-IV inhibitors, attempts have been made to find DPP-IV inhibitors from natural sources. Food-derived components, such as protein hydrolysates (peptides), have been suggested as potential DPP-IV inhibitors which can help manage blood glucose levels. This review focuses on the methods of discovery of food-derived DPP-IV inhibitory peptides, including fractionation and purification approaches, in silico analysis methods, in vivo studies, and the bioavailability of these food-derived peptides. Moreover, food-derived DPP-IV inhibitory peptides discovered during this decade are listed and distributed in a 3D scatter plot graph based on their IC50, molecular weight, and grand average of hydropathicity values, which can help us to understand the relationship between the features of the peptides and their activities.
... The diabetic rats were administered the peptide at a dose of 300 mg/kg body weight in an acute treatment. In another study, peptide (PGH) in a < 1 KDa ultrafiltration fraction of porcine skin gelatin hydrolyzed with flavourzyme exerted antidiabetic effects in vivo on streptozotocin (STZ) induced diabetic rat after 42 days of treatment (Huang et al. 2014). The peptide, administered by oral gavage at a daily dose (300 mg/day) lead to a significant increase in active plasma GLP-1 secretion, plasma insulin and glucagon levels, and caused a reduction in plasma DPP-IV activity and glycemia during an oral glucose tolerance test (OGTT). ...
Article
Diabetes mellitus, particularly type 2 diabetes, is a major global health issue, the prevalence of which seems to be on the rise worldwide. Interventions such as healthy diet, physical activity, maintaining a healthy weight, and medication (for those with a diagnosis of diabetes) are among the most effective strategies to prevent and control diabetes. Three-quarters of patients diagnosed with diabetes are in countries with poor financial infrastructure, nutritional awareness and health care systems. Concomitantly, the cost involved in managing diabetes through the intake of anti-diabetic drugs makes it prohibitive for majority of patients. Food protein-derived bioactive pepti-des have the potential of being formulated as nutraceuticals and drugs in combating the pathogenesis and pathophysiology of metabolic disorders with little or "no known" complications in humans. Coupled with lifestyle modifications, the potential of bioactive peptides to maintain normoglycemic range is actualized by influencing the activities of incretins, DPP-IV, a-amylase, and a-glucosidase enzymes. This article discusses the biofunctionality and clinical implications of anti-diabetic bioactive peptides in controlling the global burden of diabetes.
... The daily administration of this fraction to streptozotocin-induced diabetic rats at the dose of 300 mg/day improved glucose tolerance, reduced plasma DPP-IV activity, increased GLP-1 and insulin levels, and reduced glucagon content in these rats. GPFPLPD, GGKPSSMT, and GGHLFFC were the peptides identified from porcine skin gelatin hydrolysate (Huang, Hung, Jao, Tung, & Hsu, 2014). AGFAGDDAPR is a Chinese black tea-derived peptide with in vitro DPP-IV inhibitory properties. ...
Article
Full-text available
Diabetes mellitus, a group of metabolic disorders characterized by persistent hyperglycemia, affects millions of people worldwide and is on the rise. Dietary proteins, from a wide range of food sources, are rich in bioactive peptides with antidiabetic properties. Notable examples include AGFAGDDAPR, a black tea-derived peptide, VRIRLLQRFNKRS, a β-conglycinin-derived peptide, and milk-derived peptide VPP, which have shown antidiabetic effects in diabetic rodent models through variety of pathways including improving beta-cells function, suppression of alpha-cells proliferation, inhibiting food intake, increasing portal cholecystokinin concentration, enhancing insulin signaling and glucose uptake, and ameliorating adipose tissue inflammation. Despite the immense research on glucoregulatory properties of bioactive peptides, incorporation of these bioactive peptides in functional foods or nutraceuticals is widely limited due to the existence of several challenges in the field of peptide research and commercialization. Ongoing research in this field, however, is fundamental to pave the road for this purpose.
... Ultrafiltration is a very common and convenient method for separating bioactive substances. The substances with a molecular weight of 1-1.25 kDa separated by ultrafiltration exhibited the highest inhibition rate on DPP-4 after hydrolysis of porcine skin gelatin [37]. Ultrafiltration fractions of <1.5 kDa obtained from halibut skin gelatin hydrolysate (HSGH) and tilapia skin gelatin hydrolysate (TSGH) were also found to have the strongest DPP-4 inhibitory activity [38]. ...
Article
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This study investigated the inhibitory effect and mechanism of 12 LAB strains isolated from Chinese fermented foods on dipeptidyl peptidase-4 (DPP-4) using the Caco-2 cell model. The results showed that the inhibitory effect of cell-free extracts (CFEs) collected from each LAB strain on DPP-4 was higher than that of the cell-free excretory supernatants. The CFEs from Lactobacillus plantarum YE4 (YE4-CFE) exhibited the strongest DPP-4 inhibitory activity (24.33% inhibition). Furthermore, YE4-CFE altered the TNF and MAPK signaling pathways. Additionally, the YE4-CFE ultrafiltration fraction (<3 kDa) displayed a similar DPP-4 inhibitory activity to YE4-CFE. UHPLC-MS/MS identified 19 compounds with a relative proportion of more than 1% in the <3 kDa fraction, and adenine, acetylcholine, and L-phenylalanine were the top three substances in terms of proportion. Altogether, the inhibitory effect of YE4-CFE on DPP-4 was associated with the TNF and MAPK signaling pathways, and with the high proportion of adenine, acetylcholine, and L-phenylalanine.
... Peptide LPQNIPPL originated from water-soluble extract of a gouda-type cheese was reported to have DPP-4 inhibitory activities in vitro, and improve glucose tolerance as shown in oral glucose tolerance test in healthy rats when administrated together with glucose by intraperitoneal injection [138]. In addition, oral administration of peptides with DPP-4 inhibitory activity derived from the porcine skin gelatin hydrolysates were demonstrated to improve glucose tolerance in diabetic rats in 21 and 42 days after streptozotocin injection [139]. Three peptides, YINQMPQKSREA, VTGRFAGHPAAQ, and YINQMPQKSRE, with DPP-4 inhibitory activity have been identified in egg yolk protein, with YINQMPQKSRE being the most active one (IC50 = 222.8 ...
Article
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Type-2 diabetes (T2D) is one of the major global health challenges and a substantial economic burden. Egg and egg-derived components have been indicated to possess antioxidant, anti-inflammatory, anti-hypertensive, immunomodulatory, and anti-cancer activities. However, the scientific evidence about the benefits of egg on T2D is debatable. The relationship between egg consumption and the risk of T2D from observational epidemiological studies is not consistent. Interventional clinical studies, however, provide promising evidence that egg consumption ameliorates the risk of T2D. Current research progress also indicates that some egg components and egg-derived peptides might be beneficial in the context of T2D, in terms of insulin secretion and sensitivity, oxidative stress, and inflammation, suggesting possible application on T2D management. The current review summarizes recent clinical investigations related to the influence of egg consumption on T2D risk and in vivo and in vitro studies on the effect and mechanism of egg components and egg-derived peptides on T2D.
... This was generally consistent with earlier reports (Wang et al., 2013) that blood glucose, triglyceride, and cholesterol parameters increased several folds in the treatment group, confirming the validity of the evoked diabetic model in zebrafish used here. Interestingly, this result was similar with that observed in the experimental diabetic rat model (Huang et al., 2014). In order to evaluate the effects on glycemic hormones, the gene expression of insa, glucagon and pck1 was examined. ...
Article
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Ala-Pro (AP), Ile-Pro-Ala (IPA) and Ile-Pro-Ala-Val-Phe (IPAVF) as DPP-IV inhibitory peptides were purified from Antarctic krill protein hydrolysate (AKH). Diabetic zebrafish model was rapidly induced with combination of high glucose immersing and cholesterol diet for evaluation the three DPP-IV inhibitory peptides activity. Physiochemical indexes including DPP-IV activity, glucose, triglyceride and cholesterol; the relative gene (insa, glucagon and pck1) expressions levels were detected. The results showed that after 15 days of peptides treatment, the physiochemical index levels of peptide groups were significantly higher than that of negative control and showed dose-dependent effect. The insa gene expression level would be increased with the enhancement of peptide concentration, whereas gene expression levels of glucagon and pck1 would be decreased. These results indicated that three peptides all had hypoglycemic effects in different degree. It suggested the potential of AKH containing DPP-IV inhibitory peptides could be as functional food supplement to treat diabetes.
... Tak and others have demonstrated that dietary MCP can benefit blood glucose and lipid metabolism while reducing body fat or insulin sensitivity in diabetic patients and overweight people (Tak et al. 2019;Zhu et al. 2010). Oral administration of atlantic salmon skin-derived gelatin hydrolysate (300 mg/kg/day for five weeks) and porcine skin-derived gelatin hydrolysate (300 mg/day for 42 days) have similar effects of increasing insulin secretion in diabetic mice Huang et al. 2014). Wang's investigation showed that with the administration of tilapia skin gelatin hydrolysate for 30 days, glucose tolerance in rats with streptozotocin-induced diabetes improved, while the glucagon-like peptide 1 and insulin secretion were enhanced . ...
Article
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In 2020, the world’s food crisis and health industry ushered into a real outbreak. On one side, there were natural disasters such as the novel coronavirus (2019-nCoV), desert locusts, floods, and droughts exacerbating the world food crisis, while on the other side, the social development and changes in lifestyles prompted the health industry to gradually shift from a traditional medical model to a new pattern of prevention, treatment, and nourishment. Therefore, this article reviews animal by-products collagen and derived peptide, as important components of innovative sustainable food systems. The review also considered the preparation, identification, and characterization of animal by-product collagen and collagen peptides as well as their impacts on the food system (including food processing, packaging, preservation, and functional foods). Finally, the application and research progress of animal by-product collagen and peptide in the food system along with the future development trend were discussed. This knowledge would be of great significance for a comprehensive understanding of animal by-product collagen and collagen peptides and would encourage the use of collagen in food processing, preservation, and functional foods.
... Histological observations of liver tissue from the DC rats revealed degenerative changes such as hepatic necrosis, sinusoidal hemorrhages, and vacuolation in the hepatocytes, consistent with previous studies (Huang et al., 2014). These changes were reversed in the diabetic rats administered CMPH, wherein the hepatocytes appeared normal, with no accumulation of lipid droplets, along with less necrosis and improved liver architecture. ...
Article
This study investigated the effect of camel milk protein hydrolysates (CMPH) at 100, 500 and 1,000 mg/kg of body weight (BW) for 8 wk on hyperglycemia, hyperlipidemia, and associated oxidative stress in streptozotocin-induced diabetic rats. Body weights and fasting blood glucose levels were observed after every week until 8 wk, and oral glucose tolerance test (OGTT) levels and biochemical parameters were evaluated after 8 wk in blood and serum samples. Antioxidant enzyme activity and lipid peroxidation in the liver were estimated, and histological examination of the liver and pancreatic tissues was also conducted. Results showed that CMPH at 500 mg/kg of BW [camel milk protein hydrolysate, mid-level dosage (CMPH-M)] exhibited potent hypoglycemic activity, as shown in the reduction in fasting blood glucose and OGTT levels. The hypolipidemic effect of CMPH was indicated by normalization of serum lipid levels. Significant improvement in activity of superoxide dismutase and catalase, and reduced glutathione levels were observed, along with the attenuation of malondialdehyde content in groups fed CMPH, especially CMPH-M, was observed. Decreased levels of liver function enzymes (aspartate aminotransferase and alanine aminotransferase) in the CMPH-M group was also noted. Histology of liver and pancreatic tissue displayed absence of lipid accumulation in hepatocytes and preservation of β-cells in the CMPH-M group compared with the diabetic control group. This is the first study to report anti-hyperglycemic and anti-hyperlipidemic effect of CMPH in an animal model system. This study indicates that CMPH can be suggested for its therapeutic benefits for hyperglycemia and hyperlipidemia, thus validating its use for better management of diabetes and associated comorbidities.
... DPP4 inactivates incretin hormones (glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)). In this regard, DPP4 inhibitors (gliptins), which prevent N-terminal degradation of endogenous incretins in vivo and lead to an increased concentration of intact biologically active peptides, act in plasma as antidiabetic drugs, increasing glucose-mediated insulin secretion and suppressing glucagon secretion [119,120]. A potentially wide range of competitive DPP4 inhibitors are associated with a structural feature of the enzyme, namely, the presence of an extensive cavity in the region of the active center [121], into which molecules of various size and chemical nature can integrate. ...
Article
Background Proline specific peptidases (PSPs) are a unique group of enzymes that specifically cleave bonds formed by a proline residue. The study of PSPs is important due to their role in the maturation and degradation of peptide hormones and neuropeptides. In addition, changes in the activity of PSPs can result in pathological conditions, including various types of cancer. Scope of review PSPs annotated from the Homo sapiens genome were compared and classified by their physicochemical and biochemical features and roles in vital processes. In addition to catalytic activity, we discuss non-enzymatic functions that may regulate cellular activity. Major conclusions PSPs apparently have multiple functions in animals. Two functions rely on the catalytic activity of the enzyme: one involved in a regulatory pathway associated with the ability of many PSPs to hydrolyze peptide hormones and neuropeptides, and the other involved in the trophic pathway associated with the proteolysis of total cellular protein or Pro-containing dietary proteins in the digestive tract. PSPs also participate in signal transduction without proteolytic activity by forming protein-protein interactions that trigger or facilitate the performance of certain functions. General significance PSPs are underestimated as a unique component of the normal human peptidase degradome, providing the body with free proline. A comparative analysis of PSPs can guide research to develop inhibitors that counteract the abnormalities associated with changes in PSP activity, and identify natural substrates of PSPs that will enable better understanding of the mechanisms of the action of PSPs in biological processes and disease.
... Oral ingestion of collagen hydrolysate (also referred to as gelatin hydrolysate or collagen peptide) has been reported to have beneficial effects on bone, 1 joint, 2 skin, 3 blood sugar, 4 blood pressure, 5 lipid metabolism, 6 immune system, 7 and so on. Collagen contains a unique amino acid, 4-hydroxyproline (Hyp), which is post-translationally hydroxylated from Pro residues at the Yaa position of collagenous Gly-Xaa-Yaa repeats (∼100 residues/1000 amino acid residues). ...
Article
Collagen-derived hydroxyproline (Hyp)-containing oligopeptides, known to have various physiological functions, are detected in blood at markedly higher concentrations after oral ingestion of collagen hydrolysate. Monitoring the absorption and metabolism of the bioactive peptides is essential to investigate the beneficial effects of collagen hydrolysate. We previously developed an internal standard mixture by sequential protease digestion of stable isotope-labeled collagen, which enabled highly accurate quantitation of collagen-derived oligopeptides by liquid chromatography–mass spectrometry (LC–MS). However, the use of proteases caused a profound imbalance in the generated peptides. Here we employed partial acid hydrolysis to achieve more efficient and balanced peptide generation. Various stable isotope-labeled oligopeptides were detected after 0.5 h acid hydrolysis, and marked enhancement of peptide generation compared with the previous enzymatic method was observed, especially for Hyp-Gly (27.8 ± 0.6 ng/µg vs 0.231 ± 0.02 ng/µg). The acid hydrolysate was then heated to generate labeled cyclic dipeptides. Using the novel internal standard mixture in LC–MS, we were able to simultaneously quantitate 23 collagen-derived oligopeptides in human plasma and urine after oral administration of collagen hydrolysate.
... However, it has been shown that most of the GLP-1 degradation occurs immediately at the site of secretion, and only 10-15% active GLP-1 remains in the systemic circulation. 2,41 Although various hydrolysates have been reported to reduce the plasma DPP-IV activity after chronic treatments, [42][43][44] few studies have shown this reduction with acute treatments. Actually, whey protein has been reported to attenuate hyperglycaemia in part via inhibition of the DPP-IV activity in the small intestinal tissue, but not in the orbital vein. ...
Article
Herein, the potential of hydrolysates of chicken feet proteins as natural dipeptidyl-peptidase IV (DPP-IV) inhibitors was investigated; moreover, three hydrolysates were selected due to their high DPP-IV inhibitory capacity (>80% inhibition), showing the IC50 values of around 300 μg estimated protein per mL; one of them (named p4H) was selected for the posterior analysis. In addition, its effect on glucose tolerance was investigated in two rat models (diet and age-induced) of glucose-intolerance and healthy animals; the amount of 300 mg estimated peptide per kg body weight improved the plasma glucose profile in both glucose-intolerance models. Moreover, it stimulated active GLP-1 release in the enteroendocrine STC-1 cells and rat ileum tissue. In conclusion, our results indicate that chicken feet proteins are a good source of bioactive peptides as DPP-IV inhibitors. Moreover, our results highlight the potential of the selected hydrolysate p4H in the management of type 2 diabetes due to its dual function of inhibition of the DPP-IV activity and induction of the GLP-1 release.
... Recently, peptones from meat, milk and vegetable have proved to stimulate GLP-1 secretion on small intestine enteroendocrine L-cells (Pais, Gribble, & Reimann, 2016). A porcine skin gelatin hydrolysate showed an antidiabetic effect on STZ-induced diabetic rats characterised by elevated levels of GLP-1 (Huang, Hung, Jao, Tung, & Hsu, 2014). Protein GI digestion is also a way of generating peptides in the GI tract. ...
Article
The aim of the present study is to investigate how peptides released by gastrointestinal (GI) digestion of one dietary protein can interact with regulating processes of food intake. An in vitro GI digestion of bovine haemoglobin was carried out and the bioactivity of the digests on CCK and GLP-1 secretion and dipeptidyl peptidase IV (DPP-IV) activity was measured. Intestinal digests exhibited the most potent action on gut hormone release and DPP-IV activity inhibition. They also had the ability to promote hormone gene expression. As a conclusion, two fractions from final intestinal digest led to the greatest GLP-1 secretion increase and DPP-IV activity inhibition. These findings could be very useful in obesity and T2D management research.
Article
en Inhibition of dipeptidyl peptidase IV (DPP‐IV) and angiotensin converting enzyme (ACE) are considered useful in managing 2 often associated conditions: diabetes and hypertension. In this study, corolase PP was used to hydrolyze Antarctic krill protein. The hydrolysate (AKH) was isolated by ultrafiltration and purified by size‐exclusion chromatography, ion exchange chromatography and reversed‐phase high‐performance liquid chromatography (RP‐HPLC) sequentially. The in vitro inhibitory activities of all AKHs and several fractions obtained against ACE and DPP‐IV were assessed. Two peptides, purified with dual‐strength inhibitory activity against ACE and DPP‐IV, were identified by TOF‐MS/MS. Results indicated that not all fractions exhibited dual inhibitory activities of ACE and DPP‐IV. The purified peptide Lys‐Val‐Glu‐Pro‐Leu‐Pro had half‐maximal inhibitory concentrations (IC50) of 0.93±0.05 and 0.73±0.04 mg/mL against ACE and DPP‐IV, respectively. The other peptide Pro‐Ala‐Leu had IC50 values of 0.64±0.05 and 0.88±0.03 mg/mL against ACE and DPP‐IV, respectively. This study firstly reported the sequences of dual bioactive peptides from Antarctic krill proteins, further provided new insights into the bioactive peptides responsible for the ACE and DPP‐IV inhibitory activities from the Antarctic krill protein hydrolysate to manage hypertension and diabetes. Practical Application pt In this work, the aim was to isolate and purify peptides with dual angiotensin converting enzyme and dipeptidyl peptidase IV inhibitory activities from Antarctic krill. The results showed that Lys‐Val‐Glu‐Pro‐Leu‐Pro and Pro‐Ala‐Leu had dual ACE and DPP‐IV activity, which illustrated Antarctic krill protein hydrolysate had the potential to manage hypertension and diabetes.
Article
Hydroxyproline (Hyp) is a collagen-specific amino acid formed by post-translational hydroxylation of Pro residues. Various Hyp-containing oligopeptides are transported into the blood at high concentrations after oral ingestion of collagen hydrolysate. Here we investigated the angiotensin-converting enzyme (ACE) inhibitory activity of X-Hyp-Gly-type tripeptides. In an in vitro assay, ginger-degraded collagen hydrolysate enriched with X-Hyp-Gly-type tripeptides dose-dependently inhibited ACE, and various synthetic X-Hyp-Gly-type tripeptides showed ACE-inhibitory activity. In particular, strong inhibition was observed for Leu-Hyp-Gly, Ile-Hyp-Gly, and Val-Hyp-Gly with IC50 values of 5.5, 9.4, and 12.8 µM, respectively. Surprisingly, substitution of Hyp with Pro dramatically decreased inhibitory activity of X-Hyp-Gly, indicating that Hyp is important for ACE inhibition. This finding was supported by molecular docking experiments using Leu-Hyp-Gly/Leu-Pro-Gly. We further demonstrated that prolyl hydroxylation significantly enhanced resistance to enzymatic degradation by incubation with mouse plasma. The strong ACE-inhibitory activity and high stability of X-Hyp-Gly-type tripeptides highlight their potential for hypertension control.
Article
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The gut plays a central role in energy homeostasis. Food intake regulation strongly relies on the gut–brain axis, and numerous studies have pointed out the significant role played by gut hormones released from enteroendocrine cells. It is well known that digestive products of dietary protein possess a high satiating effect compared to carbohydrates and fat. Nevertheless, the processes occurring in the gut during protein digestion involved in the short-term regulation of food intake are still not totally unraveled. This review provides a concise overview of the current data concerning the implication of food-derived peptides in the peripheral regulation of food intake with a focus on the gut hormones cholecystokinin and glucagon-like peptide 1 regulation and the relationship with some aspects of glucose homeostasis. Keywords: protein digestion, bioactive peptides, food intake regulation, gut hormones, dipeptidyl peptidase IV , enteroendocrine cells
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Bioactive peptides (BPs) are fragments of 2–15 amino acid residues with biological properties. Dietary BPs derived from milk, egg, fish, soybean, corn, rice, quinoa, wheat, oat, potato, common bean, spirulina, and mussel are reported to possess beneficial effects on redox balance and metabolic disorders (obesity, diabetes, hypertension, and inflammatory bowel diseases (IBD)). Peptide length, sequence, and composition significantly affected the bioactive properties of dietary BPs. Numerous studies have demonstrated that various dietary protein-derived BPs exhibited biological activities through the modulation of various molecular mechanisms and signaling pathways, including Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2/antioxidant response element in oxidative stress; peroxisome proliferator-activated-γ, CCAAT/enhancer-binding protein-α, and sterol regulatory element binding protein 1 in obesity; insulin receptor substrate-1/phosphatidylinositol 3-kinase/protein kinase B and AMP-activated protein kinase in diabetes; angiotensin-converting enzyme inhibition in hypertension; and mitogen-activated protein kinase and nuclear factor-kappa B in IBD. This review focuses on the action of molecular mechanisms of dietary BPs and provides novel insights in the maintenance of redox balance and metabolic diseases of human.
Article
Glucagon-like peptide 1 (GLP-1) is an enterohormone with a key role in several processes controlling body homeostasis, including glucose homeostasis and food intake regulation. It is secreted by the intestinal cells in response to nutrients, such as glucose, fat and amino acids. In this review, we analyse the effect of protein on GLP-1 secretion and clearance. We review the literature on the GLP-1 secretory effects of protein and protein hydrolysates, and the mechanisms through which they exert these effects. We also review the studies on protein from different sources that has inhibitory effects on DPP4, the enzyme responsible for GLP-1 inactivation, with particular emphasis on specific sources and treatments, and the gaps there still are in knowledge. There is evidence that the protein source and the hydrolytic processing applied to them can influence the effects on GLP-1 signalling. The gastrointestinal digestion of proteins, for example, significantly changes their effectiveness at modulating this enterohormone secretion in both in vivo and in vitro studies. Nevertheless, little information is available regarding human studies and more research is required to understand their potential as regulators of glucose homeostasis.
Chapter
In recent years, there has been an unprecedented demand for inexpensive food-derived proteins, owing to their potential nutritional applications. This chapter will provide an insight into the preparation of protein hydrolysates via enzymatic and/or chemical hydrolysis. The bioactivity of these protein hydrolysates including antioxidant, antihypertensive, immuno-modulatory, anticancer and antidiabetic activities are discussed. Protein based edible films and coatings such as zein, wheat gluten, legumes, whey proteins and caseins are also discussed as they are good film formers and contribute to the reduction of environmental pollution. In addition, encapsulation of bioactive compounds like anthocyanins, flavanols, curcumin, flavan-3-ols, proanthocyanidins and phenolic acid derivates will be reviewed. Proteins have acquired considerable attention as encapsulating material due to degradation by digestive enzymes in GI tract. In this regard, this chapter also highlights proteins as nano–delivery systems for bioactive compounds.
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Background: Hydrolysis parameters affecting the release of dipeptidyl peptidase IV (DPP-IV) inhibitory and antioxidant peptides from milk proteins have not been extensively studied. Therefore, a multifactorial (i.e., pH, temperature and hydrolysis time) composite design was used to optimise the release of bioactive peptides (BAPs) with DPP-IV inhibitory and antioxidant (oxygen radical absorbance capacity - ORAC) properties from sodium caseinate (NaCN). Results: Fifteen NaCN hydrolysates (H1-H15) were generated with Protamex(TM) , a bacillus proteinase activity. Hydrolysis time (1 to 5 h) had the highest influence on both DPP-IV inhibitory properties and ORAC activity (p < 0.05). Alteration of incubation temperature (40 to 60 °C) and pH (6.5 to 8.0) had an effect on the DPP-IV inhibitory properties but not the ORAC activity of the Protamex NaCN hydrolysates. A multifunctional hydrolysate, H12, was identified having DPP-IV inhibitory (actual: 0.82 ± 0.24 vs. predicted: 0.68 mg mL(-1) ) and ORAC (actual: 639 ± 66 vs. predicted: 639 µmol TE g(-1) ) activity of the same order (p > 0.05) as the response surface methodology (RSM) predicted optimum bioactivities. Conclusion: Generation of milk protein hydrolysates through multifactorial design approaches may aid in the optimal enzymatic release of BAPs with serum glucose lowering and antioxidant properties.
Article
Background Diabetes, which currently affects 1 in 11 adults, is considered one of the biggest worldwide health crises of the 21st century. Over the last decade, synthetic inhibitors of the enzyme dipeptidyl-peptidase IV (DPP-IV) have emerged as an effective pharmaceutical approach for the management of type 2 diabetes. These molecules exert their beneficial effect by preventing the inactivation of gut-derived hormones that play a pivotal role in glycemic regulation. More recently, food components have been suggested as sources of DPP-IV inhibitors with the potential to help manage blood glucose levels. Scope and approach This review examines the sources, production, molecular characteristics and modes of action of food-derived DPP-IV inhibitors. Insights into the needs for future research to validate their efficacy and to establish their application in the management of type 2 diabetes are also discussed. Key findings and conclusions To date, hydrolysates of protein from a variety of food commodities, including both plant and animal sources, have been shown to be able to inhibit the activity of the DPP-IV enzyme. Moreover, a number of peptides, either isolated from these hydrolysates or synthetically produced, as well as non-protein-derived compounds such as polyphenols, have also been identified as DPP-IV inhibitors. These food-derived constituents present different degrees of potency and modes of action on the DPP-IV enzyme. While their effectiveness in humans is currently unknown, findings from in vitro and animal studies conducted to date warrant further research to evaluate their potential as functional food ingredients for glycemic regulation.
Article
Dipeptidyl peptidase IV (DPP-IV) played an important role in blood glucose regulation. Inhibition of DPP-IV may improve glycemic control in diabetics by preventing the rapid breakdown of incretin hormones and prolonging their physiological action. In this study, Antarctic krill (Euphausia superba) protein was hydrolyzed using animal proteolytic enzymes. The hydrolysate was purified sequentially by ultrafiltration, gel filtration chromatography and reversed phase high-performance liquid chromatography (RP-HPLC). DPP-IV inhibitory activity of the fractions achieved from Antarctic krill protein was determined by DPP-IV screening reagent kit. Two purified peptides were identified by Xevo G2-XS QTof mass spectrometer (QTOF-MS). One peptide purified was Ala-Pro (AP) with IC50 values of 0.0530mg/mL, the other Ile-Pro-Ala (IPA) with IC50 values of 0.0370mg/mL. They both exhibited strong DPP-IV inhibitory activity. The molecular docking analysis revealed that DPP-IV inhibition by AP and IPA was mainly due to formation of a strong interaction surface force with the 91-96 and 101-105 amino acids of the DPP-IV. Our results suggested that the protein hydrolysate from Antarctic krill can be considered as a promising natural source of DPP-IV inhibitory peptides in the management of diabetes.
Chapter
Z surowców ekologicznych, tj. szynki wieprzowej i słoniny, przygotowano sześć wariantów kiełbas: dwie próby kontrolne (Kd50 i Kd100) o zróżnicowanym dodatku NaNO2 (odpowiednio 50 i 100 mg/kg) oraz cztery próby badawcze: Kd50-O1 i Kd50-O2 (zawierające po 50 mg NaNO2/kg i 1 g lub 2 g liofilizatu z ostropestu plamistego/kg farszu) oraz Kd100-O1 i Kd100-O2 (zawierające po 100 mg NaNO2/kg i 1 g lub 2 g liofilizatu z ostropestu plamistego/kg farszu). Kiełbasy badano przez 12 tygodni, tj. po zakończeniu dojrzewania produkcyjnego (w 15°C przez 3 tygodnie) oraz po zakończeniu dojrzewania poprodukcyjnego w opakowaniach próżniowych (w 4°C, przez kolejne 9 tygodni). Określano wartość pH, aktywność wody, stabilność oksydacyjną (TBARS), trwałość barwy oraz jakość mikrobiologiczną wyrobów. Stwierdzono dodatnią korelację pomiędzy wyższym dodatkiem azotanu(III) sodu a trwałością oksydacyjną kiełbas, zarówno po dojrzewaniu produkcyjnym, jak i po kilkutygodniowym dojrzewaniu poprodukcyjnym. Dodatek liofilizowanego ostropestu, w obu stężeniach, dodatkowo obniżył stężenie wtórnych produktów oksydacji tłuszczu (wskaźnik TBARS) w kiełbasach. Zarówno aktywność wody, jak i wartość pH kiełbas dojrzewających były typowe dla tego typu produktów mięsnych, niezależnie od zastosowanego stężenia dodatku liofilizatu. Dodatek ostropestu nie wpłynął na trwałość barwy, której stabilność zależała wyłącznie od stężenia peklosoli. Stwierdzono, że dodatek roślinny nie ograniczał rozwoju bakterii kwaszących typu mlekowego w produkcie. Po zakończeniu dojrzewania wszystkie warianty charakteryzowały się wysoką liczbą LAB (> 8,2 log jtk/g), przy jednocześnie niskiej liczbie bakterii tlenowych (< 7,1 log jtk/g). Uzyskane wyniki wskazują, że możliwe jest wykorzystanie liofilizowanego ostropestu plamistego jako skutecznego przeciwutleniacza w technologii ekologicznych kiełbas dojrzewających o obniżonym dodatku NaNO2 (< 100 mg/kg)
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Since drug based inhibition of dipeptidyl peptidase IV (DPP-IV) is employed in type 2 (T2D) diabetes therapy, food protein hydrolysates which inhibit DPP-IV may also have potential in the management of T2D. Specific peptide motifs, consisting of an N-terminal Trp and/or a Pro at position 2, have been associated with relatively potent inhibition of DPP-IV. Different modes of inhibition which may, or may not, involve the active site of DPP-IV have been identified. Animal studies have shown that food protein hydrolysates having in vitro DPP-IV inhibitory activity generally yield antidiabetic effects in vivo. However, clear evidence of such effects in humans is still required in order to establish the potential role of food protein hydrolysates in the management of T2D.
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The current study reported oat protein as a precursor for α-amylase, α-glucosidase, and dipeptidyl peptidase (DPP)-IV inhibitory peptides and studied the antidiabetic activities related to their structures. Enzyme inhibition assays in vitro, using oat protein treated by alcalase and flavourzyme fractionated into different molecular weights and hydrophobicity, indicated that the relatively hydrophobic fraction of 1–5 kDa inhibited enzymes related to glucose digestion, absorption, and metabolism activities. The α-amylase and DPP-IV were inhibited 57 and 78%, respectively, even at low peptide concentrations. LC-MS/MS analysis of the most effective fractions disclosed two eight amino acid sequences, identified from 12S oat globulin (GDVVALPA and DVVALPAG), and other sequences rich in amino acids like proline, leucine, valine, phenylalanine, and glutamine. The results suggest that proline and hydrophobic amino acids may favor hydrophobic interactions and hydrogen bonding with the target enzymes, especially the Leu-Pro sequence found in potent DPP-IV inhibitors.
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Trypsin-treated β-lactoglobulin significantly decreased the glucose level after an oral glucose tolerance test using mice. We performed the present study to identify the active peptide inhibiting dipeptidyl peptidase-4 from trypsin-treated β-lactoglobulin. Trypsin-treated β-lactoglobulin showed a concentration-dependent inhibition for dipeptidyl peptidase-4, with an IC(50) value of 210 µM, although non-treated β-lactoglobulin showed no significant effect in the in vitro assay. The active peptide was isolated from trypsin-treated β-lactoglobulin and identified as the hexapeptide Val-Ala-Gly-Thr-Trp-Tyr (β-lactoglobulin f15-20). This hexapeptide also exhibited a concentration-dependent inhibitory effect and IC(50) value was 174 µM, suggesting that this hexapeptide is almost totally responsible for the DPP-4 inhibitory activity of trypsin-treated β-lactoglobulin.
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Barley (Hordeum vulgare L.) storage proteins, which have a high content of proline (Pro) and glutamine, are cleaved by cysteine endoproteases to yield peptides with a Pro next to the N-terminal and/or C-terminal amino acid residues. A peptidase cleaving after Xaa-Pro- at the N terminus of peptides was purified from green barley malt. It was identified as a serine-type dipeptidyl peptidase (DPP), based on inhibitor studies, and the nature of the cleavage product. It is a monomeric glycoprotein with an apparent molecular mass of 105 kD (85 kD after deglycosylation), with a pI of 3.55 and a pH optimum at 7.2. Substrate specificity was determined with a series of fluorogenic peptide substrates with the general formula Xaa-Pro-AMC, where Xaa is an unspecified amino acid and AMC is 7-amino-4-methylcoumarin. The best substrates were Xaa = lysine and arginine, while the poorest were Xaa = aspartic acid, phenylalanine, and glutamic acid. The K(m) values ranged from 0.071 to 8.9 microM, compared with values of 9 to 130 microM reported for mammalian DPP IVs. We discuss the possible role of DPP IV in the degradation of small Pro-containing peptides transported from the endosperm to the embryo of the germinating barley grain.
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Gastric inhibitory polypeptide (GIP) is susceptible to degradation, but only recently has dipeptidyl peptidase IV been identified as the enzyme responsible. Most RIAs recognize both intact GIP-(1-42) and the noninsulinotropic N-terminally truncated metabolite, GIP-(3-42), hampering measurement of plasma concentrations. The molecular nature of GIP was examined using high pressure liquid chromatography and a newly developed RIA specific for the intact N-terminus of human GIP. In healthy subjects after a mixed meal, intact GIP (N-terminal RIA) accounted for 37.0+/-2.5% of the total immunoreactivity determined by C-terminal assay. High pressure liquid chromatographic analysis of fasting samples by C-terminal assay revealed one major peak (73.8+/-2.9%) coeluting with GIP-(3-42). One hour postprandially, two major peaks were detected, corresponding to GIP-(3-42) and GIP-(1-42) (58.1+/-2.7% and 35.7+/-4.2%, respectively). GIP-(3-42) was not detected by N-terminal assay; the major peak coeluted with intact GIP (86.4+/-5.8% and 81.3+/-0.9%, 0 and 1 h, respectively). After iv infusion, intact GIP constituted 37.1+/-4.1% and 41.3+/-3.4% of the total immunoreactivity in healthy and type 2 diabetic subjects, respectively. The plasma t1/2 was shorter (P < 0.0001) when determined by N-terminal compared with C-terminal assay (7.3+/-1.0 vs. 16.8+/-1.6 and 5.2+/-0.6 vs. 12.9+/-0.9 min, healthy and diabetic subjects, respectively), and both t1/2 were shorter in the diabetic group (P < 0.05). We conclude that dipeptidyl peptidase IV is important in GIP metabolism in humans in vivo, and that an N-terminally directed assay is required for determination of plasma concentrations of biologically active GIP.
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This study was performed to determine the effects of a high-fat diet on glucose metabolism after an oral glucose challenge in high-fat diet-fed dipeptidyl peptidase IV (DPP-IV) positive (+) and deficient (-) Fischer 344 (F344) rats and the effects of novel DPP-IV inhibitor NVP-DPP728 (1-[2-[(5-cyanopyridin-2-yl)amino]ethylamino]acetyl-2-cyano-(S)-pyrrolidine monohydrochloride salt) on glucose tolerance in high-fat diet-fed F344 rats. In DPP-IV(+) rats, a high-fat diet load caused impaired glucose tolerance, such as increases of plasma insulin and blood glucose concentrations after oral glucose challenge, compared with a standard chow-fed group. In contrast, no marked change in glucose tolerance was induced by the high-fat diet in DPP-IV(-) rats. Blood glucose concentrations in DPP-IV(-) rats after glucose challenge were significantly lower than in DPP-IV(+) rats under high-fat diet load conditions. In standard chow and high-fat diet-fed DPP-IV(+) rats, NVP-DPP728 significantly suppressed glucose excursions after glucose challenge by inhibiting the plasma DPP-IV activity, associated with the stimulation of early insulin secretion. NVP-DPP728 did not affect glucose tolerance in DPP-IV(-) rats under both conditions. These results indicate that the amelioration of glucose tolerance by NVP-DPP728 in DPP-IV(+) rats was directly due to the inhibition of plasma DPP-IV activity, which might be via the subsequent increase in endogenous incretin action.
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Upon release into circulation, the potent insulin secretagogues glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are rapidly cleaved and inactivated by the enzyme dipeptidyl peptidase IV (DP IV). Long-term administration of specific DP IV inhibitors, so as to enhance circulating active GIP and GLP-1 levels, has been shown to improve glucose tolerance and beta-cell glucose responsiveness and to reduce hyperinsulinemia in the Vancouver diabetic fatty (VDF) rat model of type 2 diabetes. Using the VDF model, the current study was undertaken to examine the effects of long-term DP IV inhibitor treatment on insulin sensitivity. Euglycemic-hyperinsulinemic clamps were performed on two sets of conscious VDF rats treated with or without the DP IV inhibitor P32/98 (20 mg. kg(-1). day(-1) for 12 weeks). The protocol consisted of three sequential 90-min periods with insulin infusion rates of 0, 5, and 15 mU. kg(-1). min(-1) and included a constant infusion of [ (3)H]glucose for measure of hepatic and peripheral insulin sensitivity. Relative to untreated littermates, the treated animals showed a left shift in the sensitivity of hepatic glucose output to insulin (average reduction approximately 6 micro mol. kg(-1). min(-1)) and a marked gain in peripheral responsiveness to insulin, with glucose disposal rates increasing 105 and 216% in response to the two insulin steps (versus 2 and 46% in controls). These results provide the first demonstration of improved hepatic and peripheral insulin sensitivity after DP IV inhibitor therapy, and coupled with apparent improvements in beta-cell function, they offer strong support for the utility of these compounds in the treatment of diabetes.
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Recent studies into the physiology of the incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) have added stimulation of beta-cell growth, differentiation, and cell survival to well-documented, potent insulinotropic effects. Unfortunately, the therapeutic potential of these hormones is limited by their rapid enzymatic inactivation in vivo by dipeptidyl peptidase IV (DP IV). Inhibition of DP IV, so as to enhance circulating incretin levels, has proved effective in the treatment of type 2 diabetes both in humans and in animal models, stimulating improvements in glucose tolerance, insulin sensitivity, and beta-cell function. We hypothesized that enhancement of the cytoprotective and beta-cell regenerative effects of GIP and GLP-1 might extend the therapeutic potential of DP IV inhibitors to include type 1 diabetes. For testing this hypothesis, male Wistar rats, exposed to a single dose of streptozotocin (STZ; 50 mg/kg), were treated twice daily with the DP IV inhibitor P32/98 for 7 weeks. Relative to STZ-injected controls, P32/98-treated animals displayed increased weight gain (230%) and nutrient intake, decreased fed blood glucose ( approximately 26 vs. approximately 20 mmol/l, respectively), and a return of plasma insulin values toward normal (0.07 vs. 0.12 nmol/l, respectively). Marked improvements in oral glucose tolerance, suggesting enhanced insulin secretory capacity, were corroborated by pancreas perfusion and insulin content measurements that revealed two- to eightfold increases in both secretory function and insulin content after 7 weeks of treatment. Immunohistochemical analyses of pancreatic sections showed marked increases in the number of small islets (+35%) and total beta-cells (+120%) and in the islet beta-cell fraction (12% control vs. 24% treated) in the treated animals, suggesting that DP IV inhibitor treatment enhanced islet neogenesis, beta-cell survival, and insulin biosynthesis. In vitro studies using a beta-(INS-1) cell line showed a dose-dependent prevention of STZ-induced apoptotic cell-death by both GIP and GLP-1, supporting a role for the incretins in eliciting the in vivo results. These novel findings provide evidence to support the potential utility of DP IV inhibitors in the treatment of type 1 and possibly late-stage type 2 diabetes.
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The dipeptidyl peptidase IV inhibitor, vildagliptin, increases levels of intact glucagon-like peptide-1 (GLP-1) and improves glycemic control in patients with type 2 diabetes. Although GLP-1 is known to stimulate insulin secretion, vildagliptin does not affect plasma insulin levels in diabetic patients, suggesting that more sophisticated measures are necessary to ascertain the influence of vildagliptin on beta-cell function. This study examined the effects of 28-d treatment with vildagliptin (100 mg, twice daily; n = 9) vs. placebo (n = 11) on beta-cell function in diabetic patients using a mathematical model that describes the insulin secretory rate as a function of glucose levels (beta-cell dose response), the change in glucose with time (derivative component), and a potentiation factor, which is a function of time and may reflect the actions of nonglucose secretagogues and other factors. Vildagliptin significantly increased the insulin secretory rate at 7 mmol/liter glucose (secretory tone), calculated from the dose response; the difference in least squares mean (deltaLSM) was 101 +/- 51 pmol.min(-1).m(-2) (P = 0.002). The slope of the beta-cell dose response, the derivative component, and the potentiation factor were not affected. Vildagliptin also significantly decreased mean prandial glucose (deltaLSM, -1.2 +/- 0.4 mmol/liter; P = 0.01) and glucagon (deltaLSM, -10.7 +/- 4.8 ng/liter; P = 0.03) levels and increased plasma levels of intact GLP-1 (deltaLSM, +10.8 +/- 1.6 pmol/liter; P < 0.0001) and gastric inhibitory polypeptide (deltaLSM, +43.4 +/- 9.4 pmol/liter; P < 0.0001) relative to placebo. Vildagliptin is an incretin degradation inhibitor that improves beta-cell function in diabetic patients by increasing the insulin secretory tone.
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Vildagliptin is a selective dipeptidyl peptidase IV inhibitor that augments meal-stimulated levels of biologically active glucagon-like peptide-1. Chronic vildagliptin treatment decreases postprandial glucose levels and reduces hemoglobin A1c in type 2 diabetic patients. However, little is known about the mechanism(s) by which vildagliptin promotes reduction in plasma glucose concentration. Sixteen patients with type 2 diabetes (age, 48+/-3 yr; body mass index, 34.4+/-1.7 kg/m2; hemoglobin A1c, 9.0+/-0.3%) participated in a randomized, double-blind, placebo-controlled trial. On separate days patients received 100 mg vildagliptin or placebo at 1730 h followed 30 min later by a meal tolerance test (MTT) performed with double tracer technique (3-(3)H-glucose iv and 1-(14)C-glucose orally). After vildagliptin, suppression of endogenous glucose production (EGP) during 6-h MTT was greater than with placebo (1.02+/-0.06 vs. 0.74+/-0.06 mg.kg-1.min-1; P=0.004), and insulin secretion rate increased by 21% (P=0.003) despite significant reduction in mean plasma glucose (213+/-4 vs. 230+/-4 mg/dl; P=0.006). Consequently, insulin secretion rate (area under the curve) divided by plasma glucose (area under the curve) increased by 29% (P=0.01). Suppression of plasma glucagon during MTT was 5-fold greater with vildagliptin (P<0.02). The decline in EGP was positively correlated (r=0.55; P<0.03) with the decrease in fasting plasma glucose (change=-14 mg/dl). During MTT, vildagliptin augments insulin secretion and inhibits glucagon release, leading to enhanced suppression of EGP. During the postprandial period, a single dose of vildagliptin reduced plasma glucose levels by enhancing suppression of EGP.
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Hemorphins are endogenous peptides belonging to the family of "atypical" opioid peptides released from sequentially hydrolyzed hemoglobin. In this paper, we report an inhibitory effect of these peptides on dipeptidyl peptidase IV (DPPIV) activity, known to be involved in regulatory functions such as the activation or inactivation of peptides. The structure activity research revealed that hemorphins N-terminus sequence influences nature of the interaction between hemorphins and DPPIV. Kinetic studies conducted with purified DPPIV demonstrated that hemorphin-7 (H7) constitutes a good substrate (K(cat)/K(m) of 137 mM(-1) s(-1)) for this enzyme but could also act as a selective competitive inhibitor by substrate binding site competition. These blood-derived peptides could represent endogenous regulators of this enzyme activity.
Article
Barley (Hordeum vulgare L.) storage proteins, which have a high content of proline (Pro) and glutamine, are cleaved by cysteine endoproteases to yield peptides with a Pro next to the N-terminal and/or C-terminal amino acid residues. A peptidase cleaving after Xaa-Pro- at the N terminus of peptides was purified from green barley malt. It was identified as a serine-type dipeptidyl peptidase (DPP), based on inhibitor studies, and the nature of the cleavage product. It is a monomeric glycoprotein with an apparent molecular mass of 105 kD (85 kD after deglycosylation), with a pI of 3.55 and a pH optimum at 7.2. Substrate specificity was determined with a series of fluorogenic peptide substrates with the general formula Xaa-Pro-AMC, where Xaa is an unspecified amino acid and AMC is 7-amino-4-methylcoumarin. The best substrates were Xaa = lysine and arginine, while the poorest were Xaa = aspartic acid, phenylalanine, and glutamic acid. TheK m values ranged from 0.071 to 8.9 μm, compared with values of 9 to 130 μmreported for mammalian DPP IVs. We discuss the possible role of DPP IV in the degradation of small Pro-containing peptides transported from the endosperm to the embryo of the germinating barley grain.
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Synthetic inhibitors against the enzyme dipeptidyl peptidase (DPP)-IV, a serine protease implicated in the inactivation of incretin hormones, are currently used for the management of type 2 diabetes. The aim of the present study was to evaluate the potential of dietary proteins from various food commodities to serve as precursors of DPP-IV inhibitors by using an in silico approach. A total of 2256 fragments with peptide sequences matching those reported in the literature to present DPP-IV inhibitory activity were found in the 34 proteins that were investigated. Among those, Gly-Ala, Gly-Pro and Pro-Gly were the most frequently occurring sequences. Caseins from cow’s milk and collagens from bovine meat and salmon appeared to be the richest potential sources of DPP-IV inhibitors, whereas proteins from oat showed lower occurrence frequency values. This study suggests that dietary proteins could be used for generating DPP-IV inhibitory peptides.
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Introduction: Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) play an increasing role in the management of type 2 diabetes. Such incretin-based therapies offer some advantages over other glucose-lowering agents, but might be associated with an increased risk of acute pancreatitis. Areas covered: An extensive literature search was performed to analyze clinical cases of acute pancreatitis reported in the literature or to the Food and Drug Administration (FDA), in randomized clinical trials, and in observational studies with five DPP-4 inhibitors: sitagliptin, vildagliptin, saxagliptin, alogliptin, and linagliptin. Expert opinion: An increased risk of pancreatitis has been reported in diabetic versus nondiabetic patients. Several anecdotal clinical cases of pancreatitis have been reported with sitagliptin and vildagliptin and an increased relative risk reported to the FDA with sitagliptin versus other comparators, but reporting bias cannot be excluded. In rather short-term clinical trials with well-selected diabetic patients, no increased risk of acute pancreatitis has been observed with any of the five commercialized DPP-4 inhibitors: sitagliptin, vildagliptin, saxagliptin, alogliptin, and linagliptin. Similarly, real-life cohort studies showed no increased incidence of pancreatitis with gliptins compared with other glucose-lowering agents, a finding recently challenged by a case- control study. These results must be confirmed in postmarketing surveillance programs and in ongoing large prospective trials with cardiovascular outcomes.
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We examined the effects of the oral dipeptidyl peptidase-4 (DPP-4) inhibitor saxagliptin on glycaemic control and pancreatic β-cell mass and morphology in a mouse model of type 2 diabetes mellitus (T2DM). Male C57BL/6 mice (n = 12/group) aged 4 to 6 weeks and weighing >15 g received a high-fat diet throughout this 45-day study. After a 7-day handling period, baseline levels of plasma glucose, plasma insulin and glycated haemoglobin (HbA1c) were assessed. Animals were allocated to one of six groups: compound vehicle control, intraperitoneal streptozotocin (STZ, 50 mg/kg)-treated control and saxagliptin (10 mg/kg) or sitagliptin (10 mg/kg, positive control) initiated 7 days before or 1 day after STZ administration. Endpoints included changes in body weight, food and water consumption, glucose tolerance (approximately 3 weeks post-STZ), fasting glucose and HbA1c and immunohistochemical analyses of the pancreas. Body weight, weight gain and food intake were reduced in STZ versus control mice. DPP-4 inhibitor treatment did not affect these changes, but the increase in water intake observed post-STZ administration was significantly attenuated with DPP-4 inhibitors whether initiated before or after STZ injury. Small but significant improvements in glycaemic control were observed with DPP-4 inhibitors versus the STZ control. Improved β-cell mass and morphology were observed with saxagliptin given pre- or post-STZ and sitagliptin given post-STZ. Saxagliptin mitigated damage to β-cells and improved glycaemic control in this mouse model of T2DM.
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Dipeptidyl peptidase-4 (DPP-4) inhibitors are oral antidiabetic agents that hold the potential of slowing the progress of type 2 diabetes mellitus. Their long-term safety is still a subject of debate. A systematic review of randomized, controlled trials was undertaken to comprehensively profile the safety of chronic treatment of type 2 diabetes mellitus with DPP-4 inhibitors. We searched data sources including MEDLINE, CENTRAL, publishers' and manufacturers' databases. Eligible trials were double-blind, randomized, placebo or active-controlled trials with ≥18 weeks duration in patients with type 2 diabetes reporting safety outcomes. Meta-analysis was performed separately for trials in which the control group received placebo (44 studies), another gliptin (3 studies) and any other antidiabetic drug (20 studies). Risk ratios with 95% confidence intervals were computed using a Mantel-Haenszel fixed-effect model for general safety outcomes, hypoglycaemia and adverse events by system organ class. Of 307 publications retrieved, 67 randomized, controlled trials met the eligibility criteria and were included in this review (4 alogliptin, 8 linagliptin, 8 saxagliptin, 20 sitagliptin, and 27 vildagliptin trials). Adverse events with gliptin treatment were at placebo level (relative risk (RR) 1.02 [0.99, 1.04]). No increased risk of infections was detectable (RR 0.98 [0.93, 1.05] compared to placebo and 1.02 [0.97, 1.07] compared to other antidiabetic drugs). Asthenia (RR 1.57 [1.09, 2.27]) as well as cardiac (RR 1.37 [1.00, 1.89]) and vascular disorders (RR 1.74 [1.05, 2.86] for linagliptin) emerged as adverse events associated with DPP-4 inhibitor treatment. The risk of hypoglycaemia was low with DPP-4 inhibitor treatment (RR 0.92 [0.74, 1.15] compared to placebo, RR 0.20 [0.17, 0.24] compared to sulphonylureas) in the absence of sulphonylurea or insulin co-therapy, but significantly elevated for combination therapy of sulphonylurea or insulin with sitagliptin or linagliptin (RR 1.86 [1.46, 2.37] compared to placebo). A large body of data supports the long-term safety of gliptin treatment and refutes an increased risk of infections. Further research is needed to clarify a possible link to asthenia, cardiac and vascular events. For combination therapy with insulin or insulin secretagogues, a careful choice of the agent used may limit the risk of hypoglycaemia.
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Gelatin is a denatured, biodegradable protein obtained by acid and alkaline processing of collagen. This processing affects the electrical nature of collagen, yielding gelatin with different isoelectric points (IEPs). When mixed with positively or negatively charged gelatin, an oppositely charged protein will ionically interact to form a polyion complex. This review article describes protein release from charged gelatin matrices on the basis of this polyion complexation. The biodegradable hydrogel matrices are prepared by chemical crosslinking of acidic or basic gelatin and are enzymatically degraded in the body with time. The degradation is controllable by changing the extent of crosslinking, which, in turn, produces hydrogels with different water contents. The time course of protein release is in good accordance with the rate of hydrogel degradation. It is very likely that the protein drug complexed with gelatin hydrogel is released as a result of its biodegradation. This gelatin hydrogel system releases the protein drug under maintenance of biological activity. This article will focus on experimental data that sustained release of growth factor from the gelatin hydrogels is very effective in exerting the biological functions of the growth factor.
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The wide chemical and biological diversity observed in the marine environment makes the ocean an extraordinary source of high added value compounds (HAVC) which can be employed in many applications. Minerals, lipids, amino acids, polysaccharides and proteins from marine sources have unique features and, surprisingly, their highest concentration is often found in parts of marine organisms that are commonly discarded. Fish heads, viscera, skin, tails, offal and blood, as well as seafood shells possess several HAVC suitable for human health applications, yet most end up as residues throughout the raw material processing.This review updates information on this issue and conveys critical analysis of the chief methodologies to carry out extraction, purification and eventual transformation, with a focus on their actual and potential applications.
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The dipeptidyl-peptidase IV (DPP-IV)-inhibitory activity of peptides derived from Atlantic salmon skin gelatin hydrolyzed by alcalase (ALA), bromelain (BRO), and Flavourzyme (FLA) was determined. The FLA hydrolysate with the enzyme/substrate ratio of 6% showed the greatest DPP-IV-inhibitory activity. The hydrolysate was fractionated by ultrafiltration with 1 and 2.5 kDa cutoff membranes, and the <1 kDa fraction had the highest DPP-IV-inhibitory activity with an IC(50) value of 1.35 mg/mL. The F-1 fraction further isolated by HPLC showed the IC(50) value against DPP-IV of 57.3 μg/mL, and the peptide sequences were identified as Gly-Pro-Ala-Glu (372.4 Da) and Gly-Pro-Gly-Ala (300.4 Da). The synthetic peptides showed dose-dependent inhibition effects on DPP-IV with IC(50) values of 49.6 and 41.9 μM, respectively. The results suggest that the peptides derived from Atlantic salmon skin gelatin would be beneficial ingredients for functional foods or pharmaceuticals against type 2 diabetes.
Article
Preclinical and clinical studies suggest that whey proteins can reduce postprandial glucose levels and stimulate insulin release in healthy subjects and in subjects with type 2 diabetes by reducing dipeptidyl peptidase-4 (DPP-4) activity in the proximal bowel and hence increasing intact incretin levels. Our aim was to identify DPP-4 inhibitors among short peptides occurring in hydrolysates of β-lactoglobulin, the major whey protein found in the milk of ruminants. We proved that the bioactive peptide Ile-Pro-Ala can be regarded as a moderate DPP-4 inhibitor.
Article
In 2007 a question was raised about the causal relationship between the first of the glucagon-like peptide 1 receptor agonists, exenatide, and pancreatitis, as postmarketing reports of pancreatitis in patients treated with this agent had been received by the Food and Drug Administration (FDA). There had been six reports of hemorrhagic pancreatitis, with two of the cases resulting in death. An update of the package insert for Byetta was mandated. Sitagliptin entered the market about a year and a half later, and now there are similar reports of acute pancreatitis. As the number of patients treated with these agents increases, is it uncovering a risk not appreciated in the premarket phase or just what should be expected from the population treated with these agents? To date, 88 cases of acute pancreatitis have been reported to the FDA in patients taking sitagliptin (Januvia/Janumet). Of these, two cases have been hemorrhagic or necrotizing pancreatitis. A revision of the package insert for sitagliptin has been made recently. An examination of available data should help shed light on whether the relation is likely causal or merely incidental.
Article
Glucagon-like peptide-1 (GLP-1) is released from enteroendocrine cells (L cells) in response to food ingestion. The mechanism by which dietary peptides stimulate GLP-1 secretion in the gut is unknown. In the present study, we found that a hydrolysate prepared from zein, a major corn protein [zein hydrolysate (ZeinH)], strongly stimulates GLP-1 secretion in enteroendocrine GLUTag cells. Stimulatory mechanisms of GLP-1 secretion induced by ZeinH were investigated in the rat small intestine under anesthesia. Blood was collected through a portal catheter before and after ZeinH administration into different sites of the small intestine. The duodenal, jejunal, and ileal administration of ZeinH induced dose-dependent increases in portal GLP-1 concentration. GLP-1 secretion in response to the ileal administration of ZeinH was higher than that in the duodenal or jejunal administration. Capsaicin treatment on esophageal vagal trunks abolished the GLP-1 secretion induced by duodenal ZeinH but did not affect the secretion induced by jejunal or ileal ZeinH. These results suggest that ZeinH in the jejunum or ileum directly stimulates GLP-1 secretion but duodenal ZeinH indirectly stimulates GLP-1 secretion via the vagal afferent nerve. A direct blood sampling method from the duodenal vein and ileal mesenteric vein revealed that ZeinH administered into the ligated duodenal loop enhanced GLP-1 concentration in the ileal mesenteric vein but not in the duodenal vein. This confirmed that ZeinH in the duodenum induces GLP-1 secretion from L cells located in the ileum by an indirect mechanism. These results indicate that a potent GLP-1-releasing peptide, ZeinH, induces GLP-1 secretion by direct and indirect mechanisms in the rat intestine.
Article
The present study investigated the antidiabetic effects of the dipeptidyl peptidase (DPP)-IV inhibitors ASP8497 and vildagliptin, and the sulfonylureas glibenclamide and gliclazide in streptozotocin-nicotinamide-induced mildly diabetic mice. A single administration of ASP8497 and vildagliptin significantly improved glucose tolerance by increasing plasma insulin and glucagon-like peptide-1 levels. In addition, a single administration of glibenclamide and gliclazide also caused significant improvement in glucose tolerance with an accompanying increase in the plasma insulin level. Subsequently, the effects of a 1-week chronic daily dosing of DPP-IV inhibitors and sulfonylureas were investigated. All drugs significantly improved glucose tolerance on day 1 of chronic daily dosing. After 1 week of chronic daily dosing, the DPP-IV inhibitors caused a significant improvement in glucose tolerance similar to those observed on day 1 by increasing the plasma insulin and glucagon-like peptide-1 levels. In contrast, the sulfonylureas had no significant improving or insulinotropic effect. Furthermore, ASP8497 also had an antihyperglycemic effect and improved pancreatic histopathologic lesions in a 4-week chronic daily dosing study. These results suggest that chronic daily dosing of sulfonylureas had virtually no antidiabetic effects because of marked attenuation of the insulinotropic action in streptozotocin-nicotinamide-induced mildly diabetic mice. In contrast, the antidiabetic efficacy of DPP-IV inhibitors, including ASP8497, did not change even after chronic daily dosing; therefore, DPP-IV inhibitors are useful as a therapeutic agent for impaired glucose tolerance and type 2 diabetes mellitus.
Article
Pure dipeptidyl peptidase IV (X-prolyl dipeptidyl aminopeptidase), which did not contain aminopeptidase activity at all, was rapidly prepared from the human submaxillary gland by chromatography with concanavalin A-Sepharose and Gly-Pro-NH-(CH2)6-NH-Sepharose. The entire purification took only 3 days. Aminopeptidase, which was very difficult to separate from dipeptidyl peptidase IV by various chromatographic procedures, could be completely removed by chromatography with Gly-Pro-NH-(CH2)6-NH-Sepharose. On SDS gel electrophoresis the purified enzyme gave a single band with a molecular weight of 116,000. The apparent molecular weight of the enzyme was estimated to be 225,000 by gel filtration. Therefore, the enzyme consists of two identical subunits. It did not hydrolyze Ala p-nitroanilide at all, but the hydrolysis of the p-nitroanilides of Gyl-Pro, Lys-Pro and Arg-Pro at pH 8.0 was nearly specific.
Article
The combined actions of glucose-dependent insulinotropic polypeptide (GIP) and truncated glucagon-like peptide-1 (tGLP-1) may fully account for the incretin effect. These hormones are released from the small intestine in response to oral glucose and stimulate insulin release. Recently, evidence has been provided demonstrating the degradation of GIP-(1-42) and GLP-1-(7-36)NH2 by the serum enzyme dipeptidyl peptidase IV (DPP IV) into the biologically inactive products GIP-(3-42) and GLP-1-(9-36)NH2. The objective of the current investigation was to develop a method to monitor the degradation of these hormones in vivo. Synthetic peptides were radiolabeled and purified by HPLC. Subsequent degradation of the peptides under various conditions was then monitored by further HPLC analysis. Incubation of [125I]GIP-(1-42) or [125I]GLP-1-(7-36)NH2 with Wistar rat serum or purified DPP IV resulted in the major N-terminal-truncated products [125I]GIP-(3-42) and [125I]GLP-1-(9-36)NH2. These products were significantly reduced when the specific DPP IV inhibitor diprotin A was included in the incubation mixture and were absent when serum from DPP IV-deficient rats was used. When the labeled peptides were infused into rats at hormone levels within the physiological range, over 50% was metabolized to the truncated forms within 2 min. These products were absent when the tracers were infused into DPP IV-deficient animals. It is concluded that DPP IV may be a primary inactivating enzyme of both GIP and tGLP-1 in vivo. As the N-terminal-truncated products of the DPP IV cleavage may not be distinguished from the biologically active hormone by currently employed assays, reports of circulating hormone levels should be reconsidered. The method described in this manuscript may be useful for investigating the durations of action of GIP and tGLP-1 in normal and pathophysiological conditions.
Article
Proline is unique among the 20 amino acids due to its cyclic structure. This specific conformation imposes many restrictions on the structural aspects of peptides and proteins and confers particular biological properties upon a wide range of physiologically important biomolecules. In order to adequately deal with such peptides, nature has developed a group of enzymes that recognise this residue specifically. These peptidases cover practically all situations where a proline residue might occur in a potential substrate. In this paper we endeavour to discuss these enzymes, particularly those responsible for peptide or protein hydrolysis at proline sites. We have detailed their discovery, biochemical attributes and substrate specificities and have provided information as to the methodology used to detect and manipulate their activities. We have also described the roles, or potential roles that these enzymes may play physiologically and the consequences of their dysfunction in varied disease states.
Article
The search for intestinal factors regulating the endocrine secretion of the pancreas started soon after the discovery of secretin, i.e. nearly 100 years ago. Insulinotropic factors of the gut released by nutrients and stimulating insulin secretion in physiological concentrations in the presence of elevated blood glucose levels have been named incretins. Of the known gut hormones only gastric inhibitory polypeptide (GIP) and glucagon-like polypeptide-1 (GLP-1 [7-36] amide) fulfill this definition.--The incretin effect (i.e. the ratio between the integrated insulin response to an oral glucose load and an isoglycaemic intravenous glucose infusion) is markedly diminished in patients with type 2 diabetes mellitus, while the plasma levels of GIP and GLP-1 and their responses to nutrients are in the normal range. Therefore, a reduced responsiveness of the islet B-cells to incretins has been postulated. This insensitivity of the diabetic B-cells towards incretins can be overcome by supraphysiological (pharmacological) concentrations of GLP-1 [7-36], however not of GIP. Accordingly, fasting and postprandial glucose levels can be normalized in patients with type 2 diabetes by infusions of GLP-1 [7-36]. Further studies revealed that this is partially due to the fact that GLP-1 [7-36]--in addition to its insulinotropic effect--also inhibits glucagon secretion and delays gastric emptying. These three antidiabetic effects qualify GLP-1 [7-36] as an interesting therapeutic tool, mainly for type 2 diabetes. However, because of its short plasma half life time natural GLP-1 [7-36] is not suitable for subcutaneous application. At present methods are being developed to improve the pharmacokinetics of GLP-1 by inhibition of the cleaving enzyme dipeptidyl peptidase IV (DPP-IV) or by synthesis of DPP-IV resistant GLP-1 analogues. Also naturally occurring GLP-1 analogues (for instance exendin-4) with a much longer half life time than GLP-1 [7-36] are being tested.--Thus, after 100 years of speculations and experimentations, incretins and their analogues are emerging as new antidiabetic drugs.
Article
Glucagon-like peptide-1 is an insulinotropic hormone with antidiabetic potential due to its spectrum of effects, which include glucose-dependent stimulation of insulin and inhibition of glucagon secretion, tropic effects on the pancreatic beta-cells, inhibition of gastric emptying and the reduction of appetite. Glucagon-like peptide-1 is, however, extremely rapidly inactivated by the serine peptidase, dipeptidyl peptidase IV, so that the native peptide is not useful clinically. A new approach to utilise the beneficial effects of glucagon-like peptide-1 in the treatment of type 2 diabetes has been the development of orally active dipeptidyl peptidase IV inhibitors. Preclinical studies have demonstrated that this approach is effective in enhancing endogenous levels of glucagon-like peptide-1, resulting in improved glucose tolerance in glucose-intolerant and diabetic animal models. In recent studies of 3-12 months duration in patients with type 2 diabetes, dipeptidyl peptidase IV inhibitors have proved efficacious, both as monotherapy and when given in combination with metformin. Fasting and postprandial glucose concentrations were reduced, leading to reductions in glycosylated haemoglobin levels, while beta-cell function was preserved. Current information suggests dipeptidyl peptidase IV inhibitors are body weight neutral and are well tolerated. A number of dipeptidyl peptidase IV inhibitors are now in the late stages of clinical development. These have different properties, in terms of their duration of action and anticipated dosing frequency, but data from protracted dosing studies is presently not available to allow comparison of their clinical efficacy.
Article
Oxidative stress has been suggested to be a contributory factor in development and complication of diabetes. In the present study, we have investigated the effect of tetrahydrocurcumin (THC), one of the active metabolites of curcumin on antioxidants status in streptozotocin-nicotinamide induced diabetic rats. Oral administration of THC at 80 mg/kg body weight of diabetic rats for 45 days resulted in significant reduction in blood glucose and significant increase in plasma insulin levels. In addition, THC caused significant increase in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, reduced glutathione, vitamin C and vitamin E in liver and kidney of diabetic rats with significant decrease in thiobarbituric acid reactive substances (TBARS) and hydroperoxides formation in liver and kidney, suggesting its role in protection against lipid peroxidation induced membrane damage. These biochemical observations were supplemented by histopathological examination of liver and kidney section. The antidiabetic and antioxidant effects of THC are more potent than those of curcumin at the same dose. Results of the present study indicated that THC showed antioxidant effect in addition to its antidiabetic effect in type 2 diabetic rats.
Article
Hyperlipidaemia is an associated complication of diabetes mellitus. We recently reported that tetrahydrocurcumin lowered the blood glucose in diabetic rats. In the present study, we have investigated the effect of tetrahydrocurcumin, one of the active metabolites of curcumin on lipid profile and lipid peroxidation in streptozotocin-nicotinamide-induced diabetic rats. Tetrahydrocurcumin 80 mg/kg body weight was administered orally to diabetic rats for 45 days, resulted a significant reduction in blood glucose and significant increase in plasma insulin in diabetic rats, which proved its antidiabetic effect. Tetrahydrocurcumin also caused a significant reduction in lipid peroxidation (thiobarbituric acid reactive substances and hydroperoxides) and lipids (cholesterol, triglycerides, free fatty acids and phospholipids) in serum and tissues, suggesting its role in protection against lipid peroxidation and its antihyperlipidemic effect. Tetrahydrocurcumin showed a better effect when compared with curcumin. Results of the present study indicate that tetrahydrocurcumin showed antihyperlipidaemic effect in addition to its antidiabetic effect in type 2 diabetic rats.
Article
Glucagon-like peptide-1 (GLP-1) is a potent insulin secretagogue released from L-cells in the intestine. Meat hydrolysate (MH) is a powerful activator of GLP-1 secretion in the human enteroendocrine NCI-H716 cell line, but the mechanisms involved in nutrient-stimulated GLP-1 secretion are poorly understood. The objective of this study was to characterize the intracellular signalling pathways regulating MH- and amino acid-induced GLP-1 secretion. Individually, the pharmacological inhibitors, SB203580 (inhibitor of p38 mitogen-activated protein kinase (MAPK)), wortmannin (inhibitor of phosphatidyl inositol 3-kinase) and U0126 (inhibitor of mitogen activated or extracellular signal-regulated protein kinase (MEK1/2) upstream of extracellular signal-regulated kinase (ERK)1/2) all inhibited MH-induced GLP-1 secretion. Further examination of the MAPK pathway showed that MH increased the phosphorylation of ERK1/2, but not p38 or c-Jun N-terminal kinase over 2-15 min. Incubation with SB203580 resulted in a decrease in phosphorylated p38 MAPK and a concomitant increase in the phosphorylation of ERK1/2. Phosphorylation of ERK1/2 was augmented by co-incubation of MH with SB203580. Inhibitors of protein kinase A and protein kinase C did not inhibit MH-induced GLP-1 secretion. In contrast to non-essential amino acids, essential amino acids (EAAs) increased GLP-1 secretion and similar to MH, activated ERK1/2. However, they also activated p38-suggesting type of protein may affect GLP-1 secretion. In conclusion, there appears to be a crosstalk between p38 and ERK1/2 MAPK in the human enteroendocrine cell with the activation of ERK1/2 common to both MH and EAA. Understanding the cellular pathways involved in nutrient-stimulated GLP-1 secretion has important implications for the design of new treatments aimed at increasing endogenous GLP-1 release in type-2 diabetes and obesity.
Article
Inhibition of dipeptidyl peptidase 4 (DPP-4) is a novel treatment for type-2 diabetes. DPP-4 inhibition prevents the inactivation of glucagon-like peptide 1 (GLP-1), which increases levels of active GLP-1. This increases insulin secretion and reduces glucagon secretion, thereby lowering glucose levels. Several DPP-4 inhibitors are in clinical development. Most experience so far has been with sitagliptin (Merck; approved by the FDA) and vildagliptin (Novartis; filed). These are orally active compounds with a long duration, allowing once-daily administration. Both sitagliptin and vildagliptin improve metabolic control in type-2 diabetes, both in monotherapy and in combination with metformin and thiazolidinediones. A reduction in HbA(1c) of approximately 1% is seen in studies of DPP-4 inhibition of up to 52 weeks' duration. DPP-4 inhibition is safe and well tolerated, the risk of hypoglycaemia is minimal, and DPP-4 inhibition is body-weight neutral. DPP-4 inhibition is suggested to be a first-line treatment of type-2 diabetes, particularly in its early stages in combination with metformin. However, the durability and long-term safety of DPP-4 inhibition remain to be established.
Article
Dipeptidyl peptidase-IV (DPP-IV) inhibitors have been introduced as therapeutics for type 2 diabetes. They partially act by blocking degradation of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), thus increasing circulating levels of active hormones. In addition to their insulinotropic actions, GLP-1 and GIP also promote beta-cell proliferation and survival, and DPP-IV inhibitors exert similar effects in rodent type 2 diabetes models. The study objective was to establish whether DPP-IV inhibitor treatment prolonged survival of transplanted islets and to determine whether positron emission tomography (PET) was appropriate for quantifying the effect of inhibition on islet mass. Effects of the DPP-IV inhibitor MK0431 (sitagliptin) on glycemic control and functional islet mass in a st