ArticlePDF Available

Splenda Alters Gut Microflora and Increases Intestinal P-Glycoprotein and Cytochrome P-450 in Male Rats

Authors:
  • Faculty of Pharmacy, Zagazig University, Egypt

Abstract

Splenda is comprised of the high-potency artificial sweetener sucralose (1.1%) and the fillers maltodextrin and glucose. Splenda was administered by oral gavage at 100, 300, 500, or 1000 mg/kg to male Sprague-Dawley rats for 12-wk, during which fecal samples were collected weekly for bacterial analysis and measurement of fecal pH. After 12-wk, half of the animals from each treatment group were sacrificed to determine the intestinal expression of the membrane efflux transporter P-glycoprotein (P-gp) and the cytochrome P-450 (CYP) metabolism system by Western blot. The remaining animals were allowed to recover for an additional 12-wk, and further assessments of fecal microflora, fecal pH, and expression of P-gp and CYP were determined. At the end of the 12-wk treatment period, the numbers of total anaerobes, bifidobacteria, lactobacilli, Bacteroides, clostridia, and total aerobic bacteria were significantly decreased; however, there was no significant treatment effect on enterobacteria. Splenda also increased fecal pH and enhanced the expression of P-gp by 2.43-fold, CYP3A4 by 2.51-fold, and CYP2D1 by 3.49-fold. Following the 12-wk recovery period, only the total anaerobes and bifidobacteria remained significantly depressed, whereas pH values, P-gp, and CYP3A4 and CYP2D1 remained elevated. These changes occurred at Splenda dosages that contained sucralose at 1.1-11 mg/kg (the US FDA Acceptable Daily Intake for sucralose is 5 mg/kg). Evidence indicates that a 12-wk administration of Splenda exerted numerous adverse effects, including (1) reduction in beneficial fecal microflora, (2) increased fecal pH, and (3) enhanced expression levels of P-gp, CYP3A4, and CYP2D1, which are known to limit the bioavailability of orally administered drugs.
1
Splenda Alters Gut Microflora and Increases Intestinal P-Glycoprotein and
Cytochrome P-450 in Male Rats
Journal of Toxicology and Environmental Health
2008, 71: 1415–1429
Mohamed B. Abou-Donia, Eman M. El-Masry, Ali A. Abdel-Rahman, Roger E.
McLendon, and Susan S. Schiffman
Authors are from the Departments of Pharmacology and Cancer Biology, Pathology,
and Psychiatry, Duke University Medical Center
FROM ABSTRACT:
Splenda is comprised of the high-potency artificial sweetener sucralose and the
fillers maltodextrin and glucose.
Splenda was administered by orally at 100, 300, 500, or 1000 mg/kg to male
Sprague-Dawley rats for 12-wk, during which fecal samples were collected weekly
for bacterial analysis and measurement of fecal pH.
After 12-wks, half of the animals from each treatment group were sacrificed to
determine the intestinal expression of the membrane efflux transporter P-
glycoprotein (P-gp) and the cytochrome P-450 (CYP) metabolism system by
Western blot.
The remaining animals were allowed to recover for an additional 12-wks, and
further assessments of fecal microflora, fecal pH, and expression of P-gp and CYP
were determined.
At the end of the 12-wks treatment period, the numbers of total anaerobes,
bifidobacteria, lactobacilli, Bacteroides, clostridia, and total aerobic bacteria were
significantly decreased.
Splenda also increased fecal pH and enhanced the expression of P-gp by 2.43-fold
[143%], CYP3A4 by 2.51-fold [151%], and CYP2D1 by 3.49-fold [249%].
Following the 12-wk recovery period, the total anaerobes and bifidobacteria
remained significantly depressed, and the pH values, P-gp, and CYP 450 isozymes
remained elevated.
These changes occurred at Splenda dosages that contained sucralose at 1.1–11
mg/kg (the US FDA Acceptable Daily Intake for sucralose is 5 mg/kg).
2
Evidence indicates that a 12-wk administration of Splenda exerted numerous
adverse effects, including:
1) Reduction in beneficial fecal microflora
2) Increased fecal pH
3) Enhanced expression levels of proteins which are known to limit the
bioavailability of orally administered drugs and nutrients.
THESE AUTHORS ALSO NOTE:
The artificial high-potency sweetening compound sucralose is a chlorinated
disaccharide.
“Sucralose is ubiquitous in the world food supply as an ingredient in over
4000 products, including tabletop sweeteners and sugar substitutes (e.g., Splenda),
baked goods, beverages such as soft drinks, coffee and tea, breakfast cereals,
chewing gum, desserts, and pharmaceutical products.”
“Because sucralose is approximately 600 times sweeter than sucrose by
weight sucralose formulations such as Splenda utilize fillers including maltodextrin
and glucose for volume.”
Sucralose is a chlorinated hydrocarbon, an organochlorine molecule with
appreciable lipid solubility. [Very Important]
Adverse consequences from the elevated presence of sucralose have been
reported in animal models, which included gastrointestinal tract DNA damage.
Unabsorbed sucralose in the gut may affect the intestinal microbial milieu.
Gut microflora carry out many important functions, including:
1) Fermentation of dietary carbohydrates,
2) Salvage of energy as short-chain fatty acids
3) Production of vitamins
4) Maintenance of normal immune system functioning
5) Gastrointestinal tract mobility
6) Inhibition of pathogens
7) Metabolism of drugs
The Splenda used in this study was purchased from the supermarket.
The dosage levels of sucralose given “were selected because they span the
range of values below and above the accepted daily intake for sucralose of 5
mg/kg/d established by the U.S. Food and Drug Administration (FDA).”
The following results were documented:
1) The lowest Splenda dose showed a significant increase in body weight gain
during and after Splenda supplementation.
3
2) “The number of total anaerobes and aerobic bacteria began to decrease
immediately after the beginning of oral administration of Splenda. By the end of the
12-wk dosing period, at the lowest dose (100 mg/kg/d) of Splenda, the number of
total anaerobes was reduced by 49.8% relative to control.”
3) “Higher doses of Splenda (300, 500, and 1000 mg/kg/d) produced significant
reduction in the number of total anaerobes and other anaerobic bacteria, ranging
from 47.4 to 79.7% of control.”
4) “Higher doses of Splenda (300, 500, or 1000 mg/kg/d) resulted in significant
reduction of the numbers of total aerobes, which ranged from 51.2 to 67.8%
compared to control groups.”
5) “Relative to control, at the end of 12-wks of Splenda treatment at dosages of
100, 300, 500, or 1000 mg/kg/d, there were significant increases in pH values.”
6) “At the end of the 12-wk treatment with Splenda, numerous alterations were
observed that did not occur in control animals, including lymphocytic infiltrates into
epithelium, epithelial scarring, mild depletion of goblet cells, glandular
disorganization, and focally dilated vessels stuffed with intravascular lymphocytes.”
DISCUSSION
This study showed that intake of Splenda for 12-wks exerted several adverse
effects on the intestines of rats, including a significant decrease in beneficial
intestinal bacteria, elevated fecal pH, histopathological changes in the colon,
increased body weight, and enhanced intestinal expression of proteins that inhibit
absorption of drugs and nutrients.
“The intake of Splenda by rats significantly reduced the number of indigenous
intestinal bacteria resident in the gut, with the greatest suppression for the
generally beneficial anaerobes (e.g., bifidobacteria, lactobacilli, and Bacteroides).”
“Disruption in the number and state of balance of intestinal microflora may
potentially interfere with many essential gut functions, including nutrient
metabolism, normal immune system functioning, gastrointestinal mobility, inhibition
of pathogens, vitamin synthesis (B group and K), and metabolism of drugs.”
“The reduction in intestinal bacteria in this study was accompanied by an
increase in fecal pH that typically occurs when there is a decrease in the production
of short-chain fatty acids (SCFA) by colonic bacteria. SCFA decrease luminal pH and
hence provide antagonistic properties against intestinal pathogens and invading
organisms. Suppression of bacteria, alterations in microbial composition, and
reduction in SCFA in the gut might have clinical significance for humans in the
management of many medical conditions such as irritable bowel syndrome,
inflammatory bowel disease, cardiovascular disease, obesity, and cancer, in which
gut flora play an important role.”
4
Splenda increased the expression of the intestinal proteins “at levels that
have been associated with reduced bioavailability of drugs and chemicals.” The
magnitudes of these increases “are greater than or comparable to those shown to
reduce the bioavailability of many drugs.”
“The present finding of increased expression of [intestinal] proteins by
Splenda at the low dosages used in this experiment is clinically important with
regard to potential drug interactions.”
Splenda suppresses beneficial bacteria and directly interferes with the
bioavailability of drugs and nutrients at doses that are approved by the FDA for use
in the food supply.
KEY POINTS FROM DAN MURPHY
1) “Splenda is comprised of the high-potency artificial sweetener sucralose and
the fillers maltodextrin and glucose.”
2) The US FDA Acceptable Daily Intake for sucralose is 5 mg/kg body weight.
3) In this study, a 12-wk administration of Splenda to mice in human dose
equivalents exerted numerous adverse effects, including:
A)) Reduction in beneficial fecal microflora
B)) Increased fecal pH
C)) Enhanced expression genes which reduce the absorption of orally
administered drugs.
4) The artificial high-potency sweetening compound sucralose is a chlorinated
disaccharide.
5) “Sucralose is ubiquitous in the world food supply as an ingredient in over
4000 products, including tabletop sweeteners and sugar substitutes (e.g., Splenda),
baked goods, beverages such as soft drinks, coffee and tea, breakfast cereals,
chewing gum, desserts, and pharmaceutical products.”
6) Sucralose is a chlorinated hydrocarbon, an organochlorine molecule.
7) Adverse consequences from the elevated presence of sucralose have been
reported in animal models, which included gastrointestinal tract DNA damage.
8) Unabsorbed sucralose in the gut affects the intestinal microbial milieu.
Gut microflora carry out many important functions, including:
A)) Fermentation of dietary carbohydrates,
B)) Salvage of energy as short-chain fatty acids
C)) Production of vitamins
D)) Maintenance of normal immune system functioning
E)) Gastrointestinal tract mobility
5
F)) Inhibition of pathogens
G)) Metabolism of drugs
9) The lowest Splenda dose showed a significant increase in body weight gain
during and after Splenda supplementation. [Very Ironic]
10) “At the end of the 12-wk treatment with Splenda, numerous alterations were
observed that did not occur in control animals, including lymphocytic infiltrates into
epithelium, epithelial scarring, mild depletion of goblet cells, glandular
disorganization, and focally dilated vessels stuffed with intravascular lymphocytes.”
11) The intake of Splenda for 12-wks exerted several adverse effects on the
intestines of these rats, including a significant decrease in beneficial intestinal
bacteria, elevated fecal pH, histopathological changes in the colon, and increased
body weight.
12) “Disruption in the number and state of balance of intestinal microflora may
potentially interfere with many essential gut functions, including nutrient
metabolism, normal immune system functioning, gastrointestinal mobility, inhibition
of pathogens, vitamin synthesis (B group and K), and metabolism of drugs.”
13) Sucralose ingestion “might have clinical significance for humans in the
management of many medical conditions such as irritable bowel syndrome,
inflammatory bowel disease, cardiovascular disease, obesity, and cancer, in which
gut flora play an important role.”
14) Splenda suppresses beneficial bacteria and directly interferes with the
bioavailability of drugs and nutrients at doses that are approved by the FDA for use
in the food supply.
... Gastrointestinal anatomy: ASs have been shown to cause hyperkeratosis, papillomas, ulcers in rats' glandular stomachs, (22) DNA damage in the stomach and colon, (22) and an osmotic impact (21) that raises the water content of stool. Colon histopathologic observations include scarring of the epithelial tissue, a modest decrease in the number of goblet cells, and lymphocyte infiltration into the epithelium. ...
... Gastrointestinal anatomy: ASs have been shown to cause hyperkeratosis, papillomas, ulcers in rats' glandular stomachs, (22) DNA damage in the stomach and colon, (22) and an osmotic impact (21) that raises the water content of stool. Colon histopathologic observations include scarring of the epithelial tissue, a modest decrease in the number of goblet cells, and lymphocyte infiltration into the epithelium. ...
Article
The health impacts of artificial sweeteners, which are commonly used as low-calorie sugar alternatives to treat diseases including diabetes and obesity, may be more complicated than previously thought, according to new research. Intriguingly, excessive intake has been linked to a higher risk of metabolic disorders, cardiovascular diseases, some types of cancer, weight gain, unfavourable pregnancy outcomes, and possible hazards for people with low seizure thresholds. Artificially sweetened beverages have been associated in studies, such as the Women's Health Initiative, with an increased risk of stroke, coronary heart disease, and death, regardless of known risk factors. ASs like saccharin have been connected to inflammatory bowel disorders, disruption of the gut microbiota, increased intestinal permeability, and dysbiosis, which can result in metabolic problems like impaired glucose tolerance, insulin resistance, and increased systemic inflammation. These concerns also extend to gut health. The development of metabolic diseases like type 2 diabetes mellitus is further facilitated by these disturbances, which lower the generation of short-chain fatty acids essential for insulin sensitivity. Given these possible health hazards, this review emphasizes the need for careful use, knowledgeable consumer choices, and strict regulatory monitoring. It also highlights the need for additional research to clarify long-term health impacts and create risk-reduction plans. Keywords: Artificial Sweeteners, Health Risks, Side Effects, Health
... The role of artificial sweeteners such as the ones found in mixture 5 on gut microbiota perturbations has also been suggested [32]. In particular, acesulfame-K [E950] and sucralose [E955] were observed to shape the microbial populations and lead to dysbiosis [33,34], which in turn may enhance glucose intolerance and changes in host physiology in mice. This was supported by the observation of similarities in microbial populations from noncaloric artificial sweeteners consumers and patients with type 2 diabetes [35]. ...
Article
Full-text available
Background Mixtures of food additives are daily consumed worldwide by billions of people. So far, safety assessments have been performed substance by substance due to lack of data on the effect of multiexposure to combinations of additives. Our objective was to identify most common food additive mixtures, and investigate their associations with type 2 diabetes incidence in a large prospective cohort. Methods and Findings Participants (n = 108,643, mean follow-up = 7.7 years (standard deviation (SD) = 4.6), age = 42.5 years (SD = 14.6), 79.2% women) were adults from the French NutriNet-Santé cohort (2009–2023). Dietary intakes were assessed using repeated 24h-dietary records, including industrial food brands. Exposure to food additives was evaluated through multiple food composition databases and laboratory assays. Mixtures were identified through nonnegative matrix factorization (NMF), and associations with type 2 diabetes incidence were assessed using Cox models adjusted for potential socio-demographic, anthropometric, lifestyle and dietary confounders. A total of 1,131 participants were diagnosed with type 2 diabetes. Two out of the five identified food additive mixtures were associated with higher type 2 diabetes incidence: the first mixture included modified starches, pectin, guar gum, carrageenan, polyphosphates, potassium sorbates, curcumin, and xanthan gum (hazard ratio (HR)per an increment of 1SD of the NMF mixture score = 1.08 [1.02, 1.15], p = 0.006), and the other mixture included citric acid, sodium citrates, phosphoric acid, sulphite ammonia caramel, acesulfame-K, aspartame, sucralose, arabic gum, malic acid, carnauba wax, paprika extract, anthocyanins, guar gum, and pectin (HR = 1.13 [1.08,1.18], p < 0.001). No association was detected for the three remaining mixtures: HR = 0.98 [0.91, 1.06], p = 0.67; HR = 1.02 [0.94, 1.10], p = 0.68; and HR = 0.99 [0.92, 1.07], p = 0.78. Several synergistic and antagonist interactions between food additives were detected in exploratory analyses. Residual confounding as well as exposure or outcome misclassifications cannot be entirely ruled out and causality cannot be established based on this single observational study. Conclusions This study revealed positive associations between exposure to two widely consumed food additive mixtures and higher type 2 diabetes incidence. Further experimental research is needed to depict underlying mechanisms, including potential synergistic/antagonist effects. These findings suggest that a combination of food additives may be of interest to consider in safety assessments, and they support public health recommendations to limit nonessential additives. Trial Registration The NutriNet-Santé cohort is registered at clinicaltrials.gov (NCT03335644). https://clinicaltrials.gov/study/NCT03335644.
... Sucralose, aspartame, and saccharin, which are sugar derivatives, have reportedly been implicated in upsetting the diversity and equilibrium of the gut's microbiota. The use of sucralose had significantly shown that the concentration of aerobic bacteria and clostridia in guts is higher; pH has also been reported to be higher in feces of those treated with sucralose than in those without sucralose [52]. In a similar way, mice dosed with sucralose for half a year increased expression in the gut of bacterial pro-inflammatory genes and disrupted fecal metabolites [53]. ...
Article
Full-text available
The symbiotic relationship between humans and microbes brings about a healthy lifestyle. The microbes reside all over the body. They have various key roles in maintaining metabolic activity by enhancing their catalytic role. Their beneficial perspective in human health is uplifting the immunological aspects. Microbes provide a fruitful diet in the form of fermented food, and it helps in enabling a good source for various metabolic disorders. Fermentative products have a distinct, able population of microorganisms. This microbe helps in interacting with the gut microbes, which makes them strong for digestion; ultimately, it boosts microbial distinctiveness and improves the immunological barrier. The fermentative food can also cause harmfulness and disturb the microbiome residing within the human body if the fermentation is carried out without proper implications, that is, pH and temperature. The current review considers the role of the microbial consortium of each part of the human body and its respective mechanism of action at various regions.
... for 12 weeks of Splenda® The quantities of overall anaerobes, bifidobacteria, lactobacilli, Bacteroides, clostridia, and total aerobic bacteria decreased. 44 Enterobacteria showed no discernible impact. ...
Article
Full-text available
Artificial sweeteners have emerged as popular alternatives to traditional sweeteners, driven by the growing concern over sugar consumption and its associated rise in obesity and metabolic disorders. Despite their widespread use, the safety and health implications of artificial sweeteners remain a topic of debate, with conflicting evidence contributing to uncertainty about their long-term effects. This review synthesizes current scientific evidence regarding the impact of artificial sweeteners on gut micro-biota and gastrointestinal health. Our analysis of in vitro experiments, animal models, and clinical trials reveals that artificial sweeteners can alter the composition and abundance of gut microbes. These changes raise concerns about their potential to affect overall gut health and contribute to gastrointestinal disorders. Additionally, artificial sweeteners have been shown to influence the production of metabolites by gut bacteria, further impacting systemic health. The findings suggest that artificial sweeteners may have complex and sometimes contradictory effects on gut microbiota. While some studies indicate potential benefits, such as reduced caloric intake and weight management, others highlight detrimental effects on microbial balance and metabolic functions. The inconsistent results underscore the need for further research to comprehensively understand the physiological impacts of various artificial sweeteners on human health. Future studies should aim for long-term, well-controlled investigations to clarify these relationships, ensuring evidence-based guidelines for the safe use of artificial sweeteners in diet management.
... Por lo que se recomienda que no se consuman más de 12 semanas y la dosis recomendada por la FDA es de 5 mg/kg de peso. 15 Los microorganismos se infiltran en estas células y las matan. De esta forma, bacterias como Enterococcus faecalis penetran en los ganglios linfáticos y se acumulan en el hígado y el bazo, lo que puede provocar infecciones e incluso septicemia. ...
Article
The consumption of artificial sweeteners has significantly increased globally, particularly as a substitute for sugar for the management of conditions such as diabetes and obesity, which are significant risk factors for cardiovascular disease. Despite their widespread use, the health impacts of artificial sweeteners remain contentious. Research has suggested that certain sweeteners may contribute to systemic inflammation, endothelial dysfunction, and disruptions in gut microbiota, potentially altering glucose metabolism and exacerbating metabolic conditions such as diabetes and obesity. However, other studies highlight potential benefits, such as weight control and improved glucose tolerance. Still, the long-term safety of artificial sweeteners, particularly with chronic consumption, remains uncertain. This literature review explores the cardiovascular risks associated with various artificial sweeteners, focusing on the 6 US Food and Drug Administration–approved nonnutritive sweeteners, aspartame, sucralose, saccharin, acesulfame K, cyclamate, and neotame, as well as nutritive sweeteners such as polyols (erythritol, xylitol, sorbitol, and maltitol). Ongoing research, including in vitro, animal, and clinical studies, aims to clarify the long-term cardiovascular and metabolic implications of artificial sweeteners and assess the safety of their widespread use across diverse populations.
Article
The search for cost-effective and innovative dietary fiber sources that promote probiotic growth and support healthy gut microbiota development has become increasingly important in food product innovation. The gut microbiota is crucial for various physiological functions, such as nutrient absorption, immune system enhancement, gut structural integrity, and detoxifying harmful substances. One effective way to foster a beneficial relationship with gut microbiota is through dietary choices, which significantly affect the microbiota's structure, composition, metabolism, and overall function. Notably, orange peels not only promote the growth of probiotic bacteria but also enable these beneficial microbes to convert the polyphenols in the peels into even more healthful forms. The combination of probiotics and orange peels can lead to the creation of synbiotics, which are functional foods aimed at improving human health. In contrast, the typical Western diet, high in refined sugars, trans fats, and sodium, negatively impacts gut health and the growth of beneficial gut microorganisms. To enhance gut microbiota health, there should be a focus on food products low in processed sugars, sodium, and unhealthy fats, while being high in dietary fiber and polyphenols. Orange peels are particularly notable for their high levels of dietary fiber and polyphenolic compounds, both of which can positively affect the growth of beneficial gut microorganisms.
Article
Full-text available
The cytochrome P450 enzymes are of great importance and interest because they catalyze reactions which have profound effects on the biological activities of drugs, environmental chemistry, and endogenous compounds. As a consequence, the literature on these enzymes is too voluminous to read, scan, or even cite. And while the pace accelerates and the scope broadens to include more biochemical aspects such as amino acid sequencing and three-dimensional structural models of isoenzymes, the bench scientists struggles to perceive where the new information fits and what applicability it has, if any, zo his/her work. Pharmacologists and toxicologists also feel swamped by the exponential increase in cytochrome P450 publications. The present paper is designed to assist by providing a framework for the prediction and interpretation of new data. It is an effort to summarize the functions of known human cytochrome P450s in terms of their specific catalytic activities, substrates, inducers, and inhibitors. Summaries are presented in tables for ready access of information. (Tables 5-21) The literature through 1996 is covered in the reference section. In some instances, references are to reviews that should be consulted for citations of the original literature. (Full text of the paper available through Informa Healthcare Publisher only, or download updated article: Summary of information on human CYP enzymes: human P450 metabolism data. Drug Metabolism Reviews 01/2002; 34(1-2):83-448.)
Chapter
Neotame is a high potency sweetener with a molecular formula of C 20H30N2O5. It is over 11,000 times sweeter by weight than sucrose at a sweetness equivalent to 5% sucrose (in water). Neotame reaches a maximum sweetness intensity equivalent to 15.1% sucrose. The temporal properties of neotame, like all other high potency sweeteners, differ somewhat from sucrose. The time of onset of sweetness of neotame is later than sucrose and it lingers longer. Cross-adaptation studies support ligand- receptor binding studies that indicate neotame along with aspartame and sucralose preferentially interact with the T1R2 subunit of the sweetener receptor. Neotame can substitute for 20-30% of the sweetness of soft drinks with no perceived difference in taste.
Article
The human large intestine contains a microbiota, the components of which are generically complex and metabolically diverse. Its primary function is to salvage energy from carbohydrate not digested in the upper gut. This is achieved through fermentation and absorption of the major products, short chain fatty acids (SCFA), which represent 40–50% of the available energy of the carbohydrate. The principal SCFA, acetate, propionate and butyrate, are metabolized by the colonic epithelium (butyrate), liver (propionate) and muscle (acetate). Intestinal bacteria also have a role in the synthesis of vitamins B and K and the metabolism of bile acids, other sterols and xenobiotics. The colonic microflora are also responsive to diet. In the presence of fermentable carbohydrate substrates such as non‐starch polysaccharides, resistant starch and oligosaccharides, bacteria grow and actively synthesize protein. The amount of protein synthesis and turnover within the large intestine is difficult to determine, but around 15 g biomass is excreted in faeces each day containing 1 g bacterial‐N. Whether bacterially synthesized amino acids are ever absorbed from the colon remains unclear. Finally, individual colonic micro‐organisms such as sulphate‐reducing bacteria, bifidobacteria and clostridia, respond selectively to specific dietary components in a way that may be important to health.
Article
P-glycoprotein (P-gp) is a 170-kDa membrane-bound glycoproteinshown to efflux a wide variety of chemicals, such as chemotherapeutic agents and carcinogens. Experiments were conducted using B16/F10 murine melanoma cells transfected with the human MDR1 gene (B16/hMDR1 cells), which codes for P-gp, to determine whether this transporter may contribute to the cellular efflux of some pesticides. Thirty-eight pesticides representing several classes of compounds were evaluated for their potential to bind to P-gp, as measured by the inhibition of efflux of the P-gp substrate doxorubicin. Carbamate and pyrethroid insecticides exhibited little interaction with P-gp, while many of the organophosphorus and organochlorine pesticides significantly inhibited the efflux of doxorubicin. Pesticides that significantly inhibited the efflux of doxorubicin were then assessed for P-gp-mediated efflux. One pesticide, endosulfan, exhibited slight though significant transport mediated by P-gp. Competition experiments performed with the P-glycoprotein ligand [3H]azidopine demonstrated that the P-gp inhibitory pesticides bound to P-gp. Both lipophilicity and molecular mass were major physical/chemical determinants in dictating pesticide binding to P-gp, with optimum binding occurring with compounds having a log Kow, value of 3.6–4.5 and a molecular weight of 391–490 Da. The transport substrate endosulfan possessed optimal binding characteristics. These results demonstrated that many pesticides are capable of binding to P-gp; however, binding does not infer transport.
Article
Severe losses are caused in some types of cheese by the growth of spore-forming anaerobes. The species most commonly involved is Clostridium butyricum and its variants, but other clostridia such as Cl. sporogenes (Bacillus putrificus of Dorner (1)) may also be concerned. Existing methods for the study of the properties of these organisms are inadequate, a fact on which Rosenberger(2) has commented. This work has been particularly concerned with devising a medium suitable for all clostridia, which is clear, simple to prepare, and which requires no special anaerobic precautions in its use.(Received July 15 1953)
Article
A modified Columbia agar medium, containing 5 or 10 ml/l propionic acid and adjusted to pH 5.0, is described. The medium is both elective and selective for bifidobacteria.
Article
Summary The health benefits of including sufficient dietary fibre in the diet have been well described and have formed the basis of dietary recommendations around the world. However, dietary fibre is a complex dietary entity, consisting of many non-digestible components of food. Debate surrounding the definition and measurement of dietary fibre has resulted in inconsistencies in labelling, description and recommendations set across the world. In the UK, dietary recommendations are made using the fraction of non-digestible material described as non-starch polysaccharide that is measured by the Englyst method. However, the Association of Official Analytical Chemists (AOAC) methods, used widely by the food industry, capture a much greater range of non-digestible material, that some suggest should be included in any definition of dietary fibre. An attempt to resolve such discrepancies, possibly by taking an approach that considers the health effects of fractions not captured in the Englyst method, is probably overdue. Additionally, it is clear that the effects of these various non-digestible components of dietary fibre are not interchangeable, and it is important that fibre comes from a range of sources to ensure maximum health benefits from the fibre in the diet. Traditional ‘insoluble’ fibres are required to add bulk as well as rapidly fermentable, viscous fibres to bring about cholesterol lowering. There is also a convincing argument for including slowly fermented components, such as resistant starches, that are well tolerated in the digestive system and can bring about improvements in gut function. Currently there is insufficient data from well designed human intervention trials to make specific recommendations on the amounts of these fibre components in the diet, but it may be useful for health professionals to talk in terms of the different food sources of these types of fibre, as well as total fibre amounts.
Article
Recent technologies have resulted in an explosion of information concerning the cytochrome P-450 isoenzymes and increased awareness of life-threatening interactions' with such commonly prescribed drugs as cisapride and some antihistamines. Knowledge of the substrates, inhibitors, and inducers of these enzymes assists in predicting clinically significant drug interactions. In addition to inhibition and induction, microsomal drug metabolism is affected by genetic polymorphisms, age, nutrition, hepatic disease, and endogenous chemicals. Of the more than 30 human isoenzymes identified to date, the major ones responsible for drug metabolism include CYP3A4, CYP2D6, CYP1A2, and the CYP2C subfamily.
Article
Protease production byBacteroides fragilis ATCC 25285 was determined in batch and continuous cultures. During exponential growth in batch culture, the majority of proteolysis was cell associated. However, as the bacteria reached stationary phase, most of the intracellular proteases were released into the culture medium. Measurements of alkaline phosphatase and -galactosidase, which are respectively periplasmic and cytoplasmic marker enzymes inB. fragilis, showed that secretion of proteases in the stationary phase was a discrete event and was not associated with a general release of cytoplasmic contents. When the bacterium was grown in continuous culture, cell-associated protease activity increased concomitantly with dilution rate (D=0.03–0.23/h). The ratio of intracellular to whole cell protease activity also increased with growth rate (11 at D=0.03/h; 11.7 at D=0.23/h). Extracellular protease activity was detected only in trace amounts in continuous cultures at the lowest dilution rate. Determinations of the distribution of extracellular protease activity in batch culture after 48 h incubation showed that the majority of proteolysis (ca. 90%) was soluble. Nevertheless, a proportion was associated with particulate fractions, which had high specific activities.