Article

Glucose-responsive insulin activity by covalent modification with aliphatic phenylboronic acid conjugates

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Abstract

Since its discovery and isolation, exogenous insulin has dramatically changed the outlook for patients with diabetes. However, even when patients strictly follow an insulin regimen, serious complications can result as patients experience both hyperglycemic and hypoglycemic states. Several chemically or genetically modified insulins have been developed that tune the pharmacokinetics of insulin activity for personalized therapy. Here, we demonstrate a strategy for the chemical modification of insulin intended to promote both long-lasting and glucose-responsive activity through the incorporation of an aliphatic domain to facilitate hydrophobic interactions, as well as a phenylboronic acid for glucose sensing. These synthetic insulin derivatives enable rapid reversal of blood glucose in a diabetic mouse model following glucose challenge, with some derivatives responding to repeated glucose challenges over a 13-h period. The best-performing insulin derivative provides glucose control that is superior to native insulin, with responsiveness to glucose challenge improved over a clinically used long-acting insulin derivative. Moreover, continuous glucose monitoring reveals responsiveness matching that of a healthy pancreas. This synthetic approach to insulin modification could afford both long-term and glucose-mediated insulin activity, thereby reducing the number of administrations and improving the fidelity of glycemic control for insulin therapy. The described work is to our knowledge the first demonstration of a glucose-binding modified insulin molecule with glucose-responsive activity verified in vivo.

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... (e) The same group also derivatised residue B29 with a molecule containing a PBA and a polyol group (black lines with red circles), leading to multi-hexameric complexes in vitro that could dissociate in a glucose-dependent fashion [110]. (f) Chou and colleagues [112] created a GRI that contained a PBA derivative coupled via a fatty-acyl linker (black jagged line) to Lys B29 . They hypothesised that this analogue would bind to albumin (blue oval) below a threshold level of blood glucose, being liberated during hyperglycaemia as glucose-modified PBA-insulin, which was envisioned to have decreased affinity for albumin; however, the GRI-responsive mechanism of lower affinity of the glucose-modified PBA-insulin for albumin was not confirmed [112]. ...
... (f) Chou and colleagues [112] created a GRI that contained a PBA derivative coupled via a fatty-acyl linker (black jagged line) to Lys B29 . They hypothesised that this analogue would bind to albumin (blue oval) below a threshold level of blood glucose, being liberated during hyperglycaemia as glucose-modified PBA-insulin, which was envisioned to have decreased affinity for albumin; however, the GRI-responsive mechanism of lower affinity of the glucose-modified PBA-insulin for albumin was not confirmed [112]. Figure adapted from [145] Fig. 4 Biomimetic and chemical strategies to bind glucose vs fructose. ...
... Novel use of a PBA-based GRI was described by Chou and colleagues [112] who employed an acylated insulin analogue (insulin detemir) in which myristic acid was coupled onto lysine (Lys B29 ) to mediate binding to serum albumin and, so, provide a long-lived circulating depot of insulin. The hydrocarbon acyl tag was further derivatised with PBA so that its affinity for albumin might be glucose responsive. ...
Article
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Insulin replacement therapy for diabetes mellitus seeks to minimise excursions in blood glucose concentration above or below the therapeutic range (hyper- or hypoglycaemia). To mitigate acute and chronic risks of such excursions, glucose-responsive insulin-delivery technologies have long been sought for clinical application in type 1 and long-standing type 2 diabetes mellitus. Such ‘smart’ systems or insulin analogues seek to provide hormonal activity proportional to blood glucose levels without external monitoring. This review highlights three broad strategies to co-optimise mean glycaemic control and time in range: (1) coupling of continuous glucose monitoring (CGM) to delivery devices (algorithm-based ‘closed-loop’ systems); (2) glucose-responsive polymer encapsulation of insulin; and (3) mechanism-based hormone modifications. Innovations span control algorithms for CGM-based insulin-delivery systems, glucose-responsive polymer matrices, bio-inspired design based on insulin’s conformational switch mechanism upon insulin receptor engagement, and glucose-responsive modifications of new insulin analogues. In each case, innovations in insulin chemistry and formulation may enhance clinical outcomes. Prospects are discussed for intrinsic glucose-responsive insulin analogues containing a reversible switch (regulating bioavailability or conformation) that can be activated by glucose at high concentrations. Graphical abstract
... Matrix-Based Insulin Delivery Matrix-based insulin delivery devices consist of the following three aspects: a glucose-sensing motif, a stimuli-responsive material, and a system for insulin release [67,68]. Current glucoseresponsive drug delivery systems predominantly rely on the specific recognition or affinity between glucose molecules and the glucose-sensitive motifs and can broadly be classified into the following three systems: glucose oxidase (GOx)-based [69], glucose-binding proteins [70] or aptamer-mediated [71], and phenylboronic acid (PBA)-based systems [51,72,73]. ...
... Molecular Glucose-Responsive Insulin Molecular glucose-responsive insulin represents another important strategy that focuses on the modification of insulin to generate engineered insulin analogs with glucose-dependent properties [73,[95][96][97] ( Figure 1C). The intent of these designer analogs is to increase the safety margin of insulin treatment associated with overdosage or delivery-induced hypoglycemia and to mitigate the need for other glucose-responsive insulin delivery devices or formulations. ...
... They further conjugated boronate-polyols with insulin to reversibly form soluble high molecular weight hexamerhexamer self-assemblies, which were shown to release insulin in response to carbohydrate intake [97]. Chou et al. synthesized a class of insulin derivatives covalently conjugated with an aliphatic moiety and a PBA moiety [73]. Here, the aliphatic domain serves as an anchoring site for serum albumin or other hydrophobic components to achieve a prolonged half-life in the systemic circulation, while the PBA domain confers glucose-responsive activity at physiologic pH. ...
Article
Individuals with type 1 and advanced type 2 diabetes require daily insulin therapy to maintain blood glucose levels in normoglycemic ranges to prevent associated morbidity and mortality. Optimal insulin delivery should offer both precise dosing in response to real-time blood glucose levels as well as a feasible and low-burden administration route to promote long-term adherence. A series of glucose-responsive insulin delivery mechanisms and devices have been reported to increase patient compliance while mitigating the risk of hypoglycemia. This review discusses currently available insulin delivery devices, overviews recent developments towards the generation of glucose-responsive delivery systems, and provides commentary on the opportunities and barriers ahead regarding the integration and translation of current glucose-responsive insulin delivery designs.
... Indeed, promising recent studies included various PBA moieties covalently bonded to an acylated insulin analog (insulin detemir, which contains myristic acid coupled to Lys B29 ). The detemir allows for binding to serum albumin to prolong insulin's half-life in the circulation, and PBA provided reversible glucose binding (Chou et al., 2015). The most promising of the PBA-modified conjugates showed higher potency and responsiveness in lowering blood glucose levels compared with native insulin in diabetic mouse models and decreased hypoglycemia in healthy mice, although the molecular mechanisms have not yet been determined (Chou et al., 2015). ...
... The detemir allows for binding to serum albumin to prolong insulin's half-life in the circulation, and PBA provided reversible glucose binding (Chou et al., 2015). The most promising of the PBA-modified conjugates showed higher potency and responsiveness in lowering blood glucose levels compared with native insulin in diabetic mouse models and decreased hypoglycemia in healthy mice, although the molecular mechanisms have not yet been determined (Chou et al., 2015). ...
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Both type 1 and type 2 diabetes mellitus are advancing at exponential rates, placing significant burdens on health care networks worldwide. Although traditional pharmacologic therapies such as insulin and oral antidiabetic stalwarts like metformin and the sulfonylureas continue to be used, newer drugs are now on the market targeting novel blood glucose-lowering pathways. Furthermore, exciting new developments in the understanding of beta cell and islet biology are driving the potential for treatments targeting incretin action, islet transplantation with new methods for immunologic protection, and the generation of functional beta cells from stem cells. Here we discuss the mechanistic details underlying past, present, and future diabetes therapies and evaluate their potential to treat and possibly reverse type 1 and 2 diabetes in humans. SIGNIFICANCE STATEMENT: Diabetes mellitus has reached epidemic proportions in the developed and developing world alike. As the last several years have seen many new developments in the field, a new and up to date review of these advances and their careful evaluation will help both clinical and research diabetologists to better understand where the field is currently heading.
... Upon binding of the PBA to glucose, formation of a hydrophilic phenylborate is formed, shifting the equilibrium balance from amphiphilic to hydrophilic and resulting in micelle collapse and the release of insulin [213]. Other similar PBA-based carriers have been examined, with in vivo results showing faster insulin release following a glucose challenge compared to injectable insulin, and reduced hypoglycemic index when administered during normoglycemia in mice [214]. Even though these examples are promising novel approaches to utilizing PBA, there are still some issues that need to be addressed. ...
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In this review, the history of boron’s early use in drugs, and the history of the use of boron functional groups in medicinal chemistry applications are discussed. This includes diazaborines, boronic acids, benzoxaboroles, boron clusters, and carboranes. Furthermore, critical developments from these functional groups are highlighted along with recent developments, which exemplify potential prospects. Lastly, the application of boron in the form of a prodrug, softdrug, and as a nanocarrier are discussed to showcase boron’s emergence into new and exciting fields. Overall, we emphasize the evolution of organoboron therapeutic agents as privileged structures in medicinal chemistry and outline the impact that boron has had on drug discovery and development.
... Glucose-responsive insulin (GRI) derivatives have been developed to address this challenge by making the insulin conjugate itself with a higher glucose-lowering effect in response to elevated blood glucose levels (Veiseh et al., 2015;Bakh et al., 2017;Rege et al., 2017;Disotuar et al., 2020;Jarosinski et al., 2021). To date, carbohydrates (Brownlee and Cerami, 1979;Wang et al., 2017;Kaarsholm et al., 2018), hydrazones (Mannerstedt et al., 2021), and phenylboronic acids (PBA) (Hoeg-Jensen et al., 2005a;Hoeg-Jensen et al., 2005b;Chou et al., 2015;Qiu et al., 2019;Chen et al., 2021) have been conjugated to insulin to achieve glucose responsiveness through different mechanisms. ...
Article
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Glucose-responsive insulin represents a promising approach to regulate blood glucose levels. We previously showed that attaching two fluorophenylboronic acid (FPBA) residues to the C-terminal B chain of insulin glargine led to glucose-dependent solubility. Herein, we demonstrated that relocating FPBA from B chain to A chain increased the baseline solubility without affecting its potency. Furthermore, increasing the number of FPBA groups led to increased glucose-dependent solubility.
... polymer systems inherently suffer from time-lagged and irreversible insulin release, and no such glucose-sensitive insulin systems have reached clinical trials. Insulin with glucose-responsive activity controlled in the circulation may be an approach to secure a fast and reversible response, but such systems are more difficult to engineer [86][87][88]. Oligomannosyl/fucosyl-insulin conjugates have been discovered and developed, which can be glucose-sensitively cleared by binding preferentially to the mannose receptor (MR) at low blood glucose while binding to the IR at high blood glucose. One such analog, MK-2640 ( Figure 2G), was investigated in a Phase I clinical trial [89] but showed very low in vivo potency, probably because high background clearance via the MR led to~25-fold lower glucodynamic potency than for human insulin. ...
Article
The life-saving discovery of insulin in Toronto in 1921 is one of the most impactful achievements in medical history, at the time being hailed as a miracle treatment for diabetes. The insulin molecule itself, however, is poorly amenable as a pharmacological intervention, and the formidable challenge of optimizing insulin therapy has been ongoing for a century. We review early academic insights into insulin structure and its relation to self-association and receptor binding, as well as recombinant biotechnology, which have all been seminal for drug design. Recent developments have focused on combining genetic and chemical engineering with pharmaceutical optimization to generate ultra-rapid and ultra-long-acting, tissue-selective, or orally delivered insulin analogs. We further discuss these developments and propose that future scientific efforts in molecular engineering include realizing the dream of glucose-responsive insulin delivery.
... Such may be credited for the rise in the degree of breakage of ties in side the chains of polymer at great heat as well as therefore the fast drug release. Too, the great temperature leads to the unsteadiness of The tie physical powers amongst the polymer as well as the drug material which laden as well as there fore rises release rate of drug in the solution [58], and then examine of the increasing ratio Release%, by outcomes exposed in the shapes (26, 27, 28 and 29) a manifest rise in the ratioson39C ° C than at physiological heat (37 ° C) That rises by rising concentration of glucose. CONCLUSION Being compared to GOx-as well as sensors that are Con A-based glucose, boronic acid-having hydrogel displays promising features being an implantable substance that is glucose-sensitive containing stability, durability, elongated lifespan as well as little cost. ...
Article
Quick as well as vigorous hydrogels are necessary in comprehending incessant glucose observing in diabetes observing. Nevertheless, persisting hydrogels are restricted in satisfying wholly of the sensory demands like finding range, response time, recoverability as well as biocompatibility. In the present work, diverse kinds of glucose-responsive polymers are prepared thru polymerization of diverse monomers(Methylacrylamide (MAAm), Methyl acrylic acid (MAA), Methylacrylate(MA), Chitosan(Cs), Polyvinyl alcohol (PVA),and Dimethylaminoethyl acrylate(DMAEMA)) by the attendance of ethylene glycol dimethacrylate (EGDMA) as well as 1,6-Hexanediol diacrylate (HDODA) , 4-vinyl phenyl boronic acid (4-VPBA)via polymerization that is radical that is free being a crosslinking agents as well as Potassium Peroxodisulfate, Sodium metabisulfite being an initiators. That is manipulated to glucose sensing because of its capability of shape complexes by diols at diverse pH estimates as well as at dissimilar sugar concentrations. PBA-moiety gains a capability of contrary crosslinks thru glucose-diols as well as makes the greatest steady boronate ester complexes. To attain real-time observing of glucose. The empirical outcome s display which this hydrogel owns improved binding features for glucose underneath physiological circumstances (pH 7.0-7.5) as well as concentration of blood glucose (BGC). Furthermore, our hydrogel demonstrated a quick reply time to glucose, great biocompatibility within vivo thru an animal exemplary. The insulin release in vitro on physiological pH, dissimilar glucose concentrations as well as diverse times were likewise examined. The outcomes display the steady free of insulin came first thru the unexpected insulin release because of the existence of big sums of the diols of the particles of sugar, like great release ratio of great glucose concentrations that reduces once concentration of glucose falls. The hydrogel owns an abundant potential being a sensitive glucose probe aimed at implantable incessant glucose sensors. The made polymers were confirmed through manipulating the FTIR as well as 1 HNMR procedures. The Thermal constancy of all polymers is too considered manipulated the TGA as well as DSC methods.
... Compared to traditional whole body administration, the local administration of hydrogels has advantages including: (i) stabilization of drug molecules and maintenance of activity, (ii) control and extended release of drug molecules and (iii) direct delivery to the disease site, reducing waste and toxic side effects [14]. Glucose-responsive hydrogels using glucose binding protein (GBP) [16][17][18], phenylboronic acid [19,20] or glucose oxidase (GOx) [21] have been proposed for the regulation of blood glucose. Hydrogels based on GOx are of particular interest owing to their convenient use and excellent safety. ...
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Silk fibroin (SF) has attracted much attention due to its high, tunable mechanical strength and excellent biocompatibility. Imparting the ability to respond to external stimuli can further enhance its scope of application. In order to imbue stimuli-responsive behavior in silk fibroin, we propose a new conjugated material, namely cationic SF (CSF) obtained by chemical modification of silk fibroin with ε-Poly-(L-lysine) (ε-PLL). This pH-responsive CSF hydrogel was prepared by enzymatic crosslinking using horseradish peroxidase and H2O2. Zeta potential measurements and SDS-PAGE gel electrophoresis show successful synthesis, with an increase in isoelectric point from 4.1 to 8.6. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) results show that the modification does not affect the crystalline structure of SF. Most importantly, the synthesized CSF hydrogel has an excellent pH response. At 10 wt.% ε-PLL, a significant change in swelling with pH is observed. We further demonstrate that the hydrogel can be glucose-responsive by the addition of glucose oxidase (GOx). At high glucose concentration (400 mg/dL), the swelling of CSF/GOx hydrogel is as high as 345 ± 16%, while swelling in 200 mg/dL, 100 mg/dL and 0 mg/dL glucose solutions is 237 ± 12%, 163 ± 12% and 98 ± 15%, respectively. This shows the responsive swelling of CSF/GOx hydrogels to glucose, thus providing sufficient conditions for rapid drug release. Together with the versatility and biological properties of fibroin, such stimuli-responsive silk hydrogels have great potential in intelligent drug delivery, as soft matter substrates for enzymatic reactions and in other biomedical applications.
... Alternatively, chemically controlled glucoseresponsive closed-loop systems have been widely investigated over the last few decades [20][21][22][23][24][25]. These systems typically employ glucose-responsive elements, including glucose oxidase (GOx) [26][27][28], phenylboronic acid (PBA) [29][30][31][32][33], glucose binding proteins [34][35][36], and glucose transporter [37,38], which could program the insulin release rate in response to different glucose concentrations. GOx is a glucose-specific enzyme that can convert the glucose into gluconic acid in the presence of oxygen [39]: Given the high specificity of GOx to the glucose molecule, a series of GOx-based insulin delivery systems have been reported [40,41]. ...
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Glucose-responsive insulin delivery systems show great promise to improve therapeutic outcomes and quality of life for people with diabetes. Herein, a new microneedle-array patch containing pH-sensitive insulin-loaded nanoparticles (NPs) (SNP(I)) together with glucose oxidase (GOx)- and catalase (CAT)-loaded pH-insensitive NPs (iSNP(G+C)) is constructed for transcutaneous glucose-responsive insulin delivery. SNP(I) are prepared via double emulsion from a pH-sensitive amphiphilic block copolymer, and undergo rapid dissociation to promote insulin release at a mild acidic environment induced by GOx in iSNP(G+C) under hyperglycemic conditions. CAT in iSNP(G+C) can further consume excess H2O2 generated during GOx oxidation, and thus reduce the risk of inflammation toward the normal skin. The in vivo study on type 1 diabetic mice demonstrates that the platform can effectively regulate blood glucose levels within normal ranges for a prolonged period.
... These technologies include closed-loop insulin pump systems, 162 glucose-responsive insulin devices, 163−167 and glucose-responsive modified insulin analogues. 168,169 Some of these technologies involve the use of swellable hydrogels coupled with glucose-sensing groups to allow glucose-responsive delivery of therapeutic hormones (e.g., insulin). 170,171 Importantly, the size of the hydrogel is pivotal for accurately mimicking physiological response times with nano-or microsized hydrogels having more rapid and physiologically 162,173 "smart" glucagon devices, 24,174 and somatostatin receptor type 2 antagonists (SSTR2A). ...
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Globally, a rising burden of complex diseases takes a heavy toll on human lives and poses substantial clinical and economic challenges. This review covers nanomedicine and nanotechnology-enabled advanced drug delivery systems (DDS) designed to address various unmet medical needs. Key nanomedicine and DDSs, currently employed in the clinic to tackle some of these diseases, are discussed focusing on their versatility in diagnostics, anticancer therapy, and diabetes management. First-hand experiences from our own laboratory and the work of others are presented to provide insights into strategies to design and optimize nanomedicine- and nanotechnology-enabled DDS for enhancing therapeutic outcomes. Computational analysis is also briefly reviewed as a technology for rational design of controlled release DDS. Further explorations of DDS have illuminated the interplay of physiological barriers and their impact on DDS. It is demonstrated how such delivery systems can overcome these barriers for enhanced therapeutic efficacy and how new perspectives of next-generation DDS can be applied clinically.
... The development of a selfregulating system to modulate blood glucose levels provides a novel approach for the treatment of diabetes. Recently, organoboron polymers have attracted great consideration because of possible applications in drug delivery systems [1][2][3], recognition and separation of glycolproteins [4][5][6], self-healing materials [7][8][9], flame retardants [10][11][12], HIV barriers [13,14], glucose sensing, and diabetes treatment [15][16][17][18]. ...
Article
Herein, a glucose-responsive polymer featuring boronic acid has been synthesized that operates under physiological conditions. Phenylboronic acid-containing polymer has been successfully synthesized in two reaction steps using atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) and post-polymerization modification of the obtained polyHEMA with 4-carboxyphenylboronic acid. The structure of the synthesized polyHEMA and polyHEMA-PBA has been investigated by size exclusion chromatography (SEC), proton nuclear magnetic resonance (¹H NMR), and Fourier-transform infrared spectrometer (FT-IR). Interaction of polyHEMA-PBA with D(+)-glucose has been studied by Ultraviolet visible (UV-vis.) spectroscopy. Determined pKa values were approximately 7.8 and 7.9 by pH titration and Spectral Difference Methods, respectively. Also, the binding constant of polyHEMA-PBA with glucose has been determined 121 M⁻¹ by Spectral Difference Methods. Dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM) have been utilized to investigate dual pH- and diol (glucose)-responsive behavior of polyHEMA-PBA. Aggregates and unimers (smaller objects) have been observed below and above the pKa of the polyHEMA-PBA, respectively. Upon addition of glucose to polyHEMA-PBA solution at pH = 7.4 aggregates dissociated into molecularly dissolved unimers of polyHEMA-PBA.
... Where the treatment of diabetic rats ( induced by Alloxan ) with the prepared solutions of polymers loaded with insulin through intra-peritoneal injection with a dose of 3 ml / kg body weight, which was studied in the experimental test to determine the approximate duration of one-dose effect in infected rats with diabetes by alloxan , Where was given a single dose of rats from each group (T2-T5), after 3 days of induction of diabetes, where the amount of blood glucose level (320±6.2) mg/dl after as the (92.1±0.15)mg/dl , and then follow-up the glucose level in rats for every 24 hours, where it reached the level of glucose mg / dl (3.15 ± 128.6) after 24 hours of treatment , as noted the resumption of the rise to the level of glucose extent mg / dl (2.1 ± 268) after 48 hours of treatment, suggesting a decline in the influence of dosage and adopted as a dose used to evaluate the effect of liberation of insulin loaded on polymers in reducing the level of glucose in the rat experiment [66] treatment by polymers loaded with insulin (T2-T5) for 30 days . The results indicated in Table (3) showed a significant decrease in the level of glucose in the treatment rats (T2-T5) on the seventh day compared with the alloxan-stimulating group (T1) while still significantly higher than the healthy control group (C), which reduced in the tenth day of treatment , and consistently treatment there is a significant decrease compared with the animals stimulating alloxan-group (T1) and a healthy control group (C) , where was noted in the day 30 of treatment the presence of a large significant decrease in the level of sugar in the rats treated (T2-T5) compared to With the alloxan-stimulating group (T1) , while there is no significant difference compared to healthy control groups (C) , which indicates improved control of the state of hyperglycemia in rats, and the effectiveness of treatment in reducing the level of diabetes significantly for all treatment groups (T2-T5) compared with Alloxan group (T1) as shown in the Table (4), these results are consistent with previous studies [65] and [48] which confirmed the effective effect of PBA-polymers loaded with insulin in the gradual release of insulin and reduced blood sugar level in treated rats. ...
... Pharmaceutics 2022,14,21 ...
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Recent advances in polymer chemistry, materials sciences, and biotechnology have allowed the preclinical development of sophisticated programmable nanomedicines and materials that are able to precisely respond to specific disease-associated triggers and microenvironments. These stimuli, endogenous to the targeted diseases, include pH, redox-state, small molecules, and protein upregulation. Herein, recent advances and innovative approaches in programmable soft materials capable of sensing the aforementioned disease-associated stimuli and responding via a range of dynamic processes including morphological and size transitions, changes in mobility and retention, as well as disassembly are described. In this field generally, the majority of ongoing and past research effort has focused on oncology. Given this interest, examples of the latest innovative approaches to chemo- and immunotherapy treatment strategies for cancer are presented. Moreover, as the field broadens its attention, applications of programmable materials in other diseases are highlighted, with a special focus on cardiovascular disease and diabetes mellitus, where limited attention is paid by the field, but where many promising avenues exist with high potential impact.
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The administration of exogenous insulin is an important treatment for improving diabetic patients’ health but involves multiple daily subcutaneous injections. The development of insulin formulations for long-acting effects has been hampered by short pharmacokinetics and reduced bioactivity due to long-term storage. To solve this, we developed a formulation with a high insulin loading efficiency achieved via the self-assembly of an amphiphilic polymer (P1M10) and insulin. In a type 1 diabetic rat model, P1M10@insulin micelles quickly and continuously controlled the blood glucose level without risk of hypoglycemia, showing a better therapeutic index than the commercial long-acting insulin glargine. In addition, the P1M10 polymer could protect insulin in solution at room temperature in the long term. Owing to this protection, P1M10@insulin micelles could be lyophilized and reconstituted without any loss of insulin bioactivity, allowing for convenient transportation and storage of therapeutic proteins under normal conditions, which would greatly expand their application scenarios.
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Advances in artificial/synthetic cells have drawn a new era of nanobiotechnology, which have shown broad prospects in biomedical applications. The rational nanoengineering of synthetic cells that can closely substitute the systematic biological functions of cells is a next grand challenge. Here, a genetically encoded synthetic beta cell, which can sense hyperglycemic conditions to initiate programmed biosynthesis and secretion of insulin is reported. By encapsulating different metal–organic framework‐based artificial organelles with distinctive bifunctionalities, the synthetic cell can undergo programmed, sequential subcellular events, including glucose sensing, initiation of insulin gene transcription and translation, and finally excretion of functional insulin, under hyperglycemic conditions. Glucose uptake assay suggests that the insulin produced by the synthetic cells can successfully promote glucose uptake into mammalian cells. The construction of a higher‐order cell cluster by ligand‐mediated super‐assembly of the synthetic cells is further demonstrated. Such a robust and smart synthetic system that closely mimics the cellular activities of beta cells in response to glucose levels is promising for improving clinical outcomes in diabetes treatment.
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Diabetes can cause various complications and affect the normal functioning of the human body. A theranostic and diagnostic platform for real-time glycemia sensing and simultaneous self-regulated release of insulin is desired to improve diabetic patients' life quality. Here, we describe a theranostic microneedle array patch, which enables the achievement of visualization quantification of glycemia and simultaneously self-regulated release of insulin. The microneedle patch (MNDF) was fabricated by crosslinking of 3-aminophenylboronic acid (ABA)-modified sodium alginate and chondroitin sulfate. The hierarchical structure consisted of a tip part containing mineralized insulin particles and glucose oxidase (GOD) for insulin release, and a base surface embodying 3,3',5,5'-tetramethylbenzidine (TMB) and (horseradish peroxidase) HRP for real-time glycemia sensing. In the presence of glucose, GOD converts glucose into H+ and H2O2, driving gradual dissolution of the calcium layer of insulin particles, resulting in long-acting release of insulin. By the bio-catalytic action of HRP, the generated H2O2 brings about a visible color change allowing the glucose level at the base surface to be read out. We believe that the theranostic microneedle array patch can act as a promising alternative for future clinical applications.
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Design of “first-generation” insulin analogs over the past three decades has provided pharmaceutical formulations with tailored pharmacokinetic (PK) and pharmacodynamic (PD) properties. Application of a molecular tool-kit—integrating protein sequence, chemical modification and formulation—has thus led to improved prandial and basal formulations for the treatment of diabetes mellitus. Although PK/PD changes were modest in relation to prior formulations of human and animal insulins, significant clinical advantages in efficacy (mean glycemia) and safety (rates of hypoglycemia) were obtained. Continuing innovation is providing further improvements to achieve ultra-rapid and ultra-basal analog formulations in an effort to reduce glycemic variability and optimize time in range. Beyond such PK/PD metrics, next-generation insulin analogs seek to exploit therapeutic mechanisms: glucose-responsive (“smart”) analogs, pathway-specific (“biased”) analogs, and organ-targeted analogs. Smart insulin analogs and delivery systems promise to mitigate hypoglycemic risk, a critical barrier to glycemic control, whereas biased and organ-targeted insulin analogs may better recapitulate physiologic hormonal regulation. In each therapeutic class considerations of cost and stability will impact utilization and global distribution. This review highlights structural principles underlying next-generation design efforts, their respective biological rationale and potential clinical applications.
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Cucurbit[7]uril (CB[7]) is a supramolecular binding host for peptides and proteins with N-terminal Phe. However, the low occurrence of such peptides and proteins limits broader applications of this unique host-guest interaction. Here, we report a strategy to expand the scope of CB[7]-peptide interaction by site-specifically introducing N-terminal substitutions (e.g. benzyl groups) using reductive alkylation. N-terminal benzylated peptides have similar affinity to CB[7] as native peptides with N-terminal Phe and even stronger interactions can be achieved using better ligands. We further expanded this host-guest interaction to be stimuli responsive. By introducing benzyl carboxylate substituents, the CB[7]-peptide interaction shows pH-dependent binding. Furthermore, benzyl boronate substituents led to saccharide-dependent CB[7]-peptide interactions. We demonstrated that using this strategy to introduce stronger CB[7] binders to the N-terminus of human calcitonin (hCT) results in increased aggregation stability in the presence of CB[7]. This strategy to expand CB[7]-peptide interaction scope opens opportunities for future applications in peptides and proteins.
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Topical eye drops still face challenges of low-drug treatment effects and frequent dosing in ophthalmic applications due to the low preocular retention rate and low transcorneal permeability. Thus, we designed and synthesized a phenylboronic acid conjugated chitosan oligosaccharide-vitamin E copolymer (PBA-CS-VE) for use in mucoadhesive voriconazole (VRC)-loaded nanomicelles for fungal keratitis. In vitro mucin binding and ex vivo eyeball adhesion tests show that the copolymer has strong mucoadhesion. The transportation of coumarin-6 (C6) across a monolayer of HCE-T cells and 3D cell spheroids confirm the strong corneal penetration ability of PBA-CS-VE. The mechanism of promoting corneal penetration was studied in terms of intracellular calcium-ion concentration, cell membrane potential, cell membrane fluidity, and the tight junctions of cells. The pharmacokinetics in the aqueous humor were examined to evaluate the ability of nanomicelles in promoting corneal penetration and prolonging ocular retention. VRC-loaded PBA-CS-VE nanomicelles (PBA-CS-VE-VRC) yielded a very favorable therapeutic effect on a rabbit model of fungal keratitis in vivo as compared to the free drug. Overall, the results indicate that PBA-CS-VE nanomicelles are a mucoadhesive candidate with enhanced transcorneal permeability and prolonged preocular retention for efficient delivery of topical ocular drugs. Statement of significance Although eye drops are widely used in ocular drug delivery, the disadvantages such as short retention time and weak corneal penetrating ability still seriously affect the therapeutic effect of the drug. Therefore, the mucoadhesive carrier seems to be an interesting strategy for ocular drug delivery. Herein, a novel phenylboronic acid conjugated chitosan oligosaccharide-vitamin E copolymer was designed and constructed as mucoadhesive nanomicelles loaded with voriconazole for fungal keratitis. These nanomicelles were able to improve the in vitro mucin binding and to prolong the residence time of the drug on the surface of the eyeball. Moreover, the nanomicelles exhibited an enhanced drug permeability in cell monolayer models and 3D cell culture models. This work provides a promising ocular drug delivery system.
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Diabetes, and its complications, is a major threat to human health. In this research, we successfully synthesized a new type of glucose‐responsive poly(3‐acrylamidophenylboronic acid‐co‐pterostilbene) (p(AAPBA‐co‐PTE) nanoparticle. The nanoparticles are round in shape with a size between 150 and 200 nm. Insulin‐loaded p(AAPBA‐co‐PTE) nanoparticles can self‐adjust according to the changes in glucose concentration in vitro to achieve effective and sustained levels of insulin. P(AAPBA‐co‐PTE) nanoparticles have good stability, and the drug loading of insulin‐loaded p(AAPBA‐co‐PTE) nanoparticles is up to 16.7%, the encapsulation efficiency is up to 82.4% and the release rate of pterostilbene in vitro is up to 81%. The p(AAPBA‐co‐PTE) nanoparticles have low toxicity toward cells, and can effectively reduce blood sugar within 24 h. After 14 days of treatment, an animal model of myocardial ischemia‐reperfusion injury (MI/RI) was established. After treatment with the insulin‐loaded p(AAPBA‐co‐PTE) nanoparticles, the rat heart function was significantly improved, and the levels of inflammatory factors were significantly reduced. P(AAPBA‐co‐PTE) nanoparticles were therefore successfully synthesized, and had good performance. P(AAPBA‐co‐PTE) nanoparticles appear to have the effect of reducing blood sugar and preventing MI/RI, and may be valuable for the development of treatments for MI/RI.
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Inflammation is mediated by various pathogenic factors including elevated reactive oxygen species (ROS). Glucocorticoids are widely used to reduce inflammation in many diseases, but their bioavailability is limited by rapid metabolism, poor water‐solubility, and harmful side‐effects. We here synthesize a PEGylated, phenylboronic acid‐modified L‐DOPA pro‐antioxidant (pPAD) that can self‐assemble into nanoparticles (pPADN) for loading of a model glucocorticoid dexamethasone (Dex) through 1,3‐diol/phenylboronic acid chemistry and hydrophobic interaction for more effective treatment of inflammation. Upon exposure to ROS, pPADN convert into the active form of L‐DOPA, followed by a cascade of oxidative reactions to transform into antioxidative melanin‐like materials. Concomitantly, the structural transformation of pPADN triggers specific release of Dex, along with the acidic pH of inflammatory tissue. In a rat model of osteoarthritis, Dex‐loaded pPADN markedly mitigate synovial inflammation, suppress joint destruction and cartilage matrix degradation, with negligible in vivo toxicity. Moreover, in‐situ structural transformation makes pPADN suitable for noninvasive monitoring of therapeutic effects as a photoacoustic imaging contrast agent. Overall, this antioxidative pPADN‐based dual‐responsive anti‐inflammatory delivery system offers a precise and potent theranostic strategy for inflammatory diseases.
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Background The discovery of insulin in 1921 and its near-immediate clinical use initiated a century of innovation. Advances extended across a broad front from stabilizing formulations of animal insulins to the frontiers of synthetic peptide chemistry and in turn from the advent of recombinant DNA manufacture to structure-based protein analog design. In each case a creative interplay was observed between pharmaceutical applications and then-emerging principles of protein science; indeed, translational objectives contributed to a growing molecular understanding of protein structure, aggregation and misfolding. Scope of Review Pioneering crystallographic analyses—beginning with Hodgkin’s solving of the 2-Zn insulin hexamer—elucidated general features of protein self-assembly, including zinc coordination and the allosteric transmission of conformational change. Crystallization of insulin was exploited both as a step in manufacturing and as a means to obtain protracted action. Forty years ago, the confluence of recombinant human insulin with techniques for site-directed mutagenesis initiated the present era of insulin analogs. Variant or modified insulins were developed that exhibit improved prandial or basal pharmacokinetic (PK) properties. Encouraged by clinical trials demonstrating the long-term importance of glycemic control, regimens based on such analogs sought to more closely resemble daily patterns of endogenous β-cell secretion, ideally with reduced risk of hypoglycemia. Future Implications Next-generation insulin analog design seeks to explore new frontiers, including glucose-responsive insulins, organ-selective analogs and biased agonists tailored to address yet-unmet clinical needs. In the coming decade we envision ever-more powerful scientific synergies at the interface of structural biology, molecular physiology and therapeutics.
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The number of people affected by diabetes mellitus increases globally year on year. Elevated blood glucose levels may result from a lack of insulin to manage these levels and can, over a prolonged period, lead to serious repercussions. Diabetes mellitus patients must monitor and control their blood-glucose levels with invasive testing and often alongside administration of intravenous doses of insulin, which can often lead to suboptimal compliance. To mitigate these issues, “closed-loop” insulin delivery systems are deemed to be among superior options for rapid relief from the demanding and troublesome necessity of self-directed care. The reversible dynamic covalent chemistry of boronic acid derivatives and their competitive affinity to 1,2- and 1,3-diols (such as those present in saccharides) allows for the design and preparation of responsive self-regulated insulin delivery materials which respond to elevated and changing glucose levels. A range of meritorious and noteworthy contributions in the domain of boron-mediated insulin delivery materials is surveyed, and providing a multidisciplinary context in the realisation of the ambitious goal of ultimately addressing the desire to furnish glucose-responsive insulin delivery materials through innovative synthesis and rigorous testing is targetted.
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Insulin-signaling requires conformational change: whereas the free hormone and its receptor each adopt autoinhibited conformations, their binding leads to structural reorganization. To test the functional coupling between insulin's "hinge opening" and receptor activation, we inserted an artificial ligand-dependent switch into the insulin molecule. Ligand-binding disrupts an internal tether designed to stabilize the hormone's native closed and inactive conformation, thereby enabling productive receptor engagement. This scheme exploited a diol sensor (meta-fluoro-phenylboronic acid at GlyA1) and internal diol (3,4-dihydroxybenzoate at LysB28). The sensor recognizes monosaccharides (fructose > glucose). Studies of insulin-signaling in human hepatoma-derived cells (HepG2) demonstrated fructose-dependent receptor autophosphorylation leading to appropriate downstream signaling events, including a specific kinase cascade and metabolic gene regulation (gluconeogenesis and lipogenesis). Addition of glucose (an isomeric ligand with negligible sensor affinity) did not activate the hormone. Similarly, metabolite-regulated signaling was not observed in control studies of 1) an unmodified insulin analog or 2) an analog containing a diol sensor without internal tethering. Although secondary structure (as probed by circular dichroism) was unaffected by ligand-binding, heteronuclear NMR studies revealed subtle local and nonlocal monosaccharide-dependent changes in structure. Insertion of a synthetic switch into insulin has thus demonstrated coupling between hinge-opening and allosteric holoreceptor signaling. In addition to this foundational finding, our results provide proof of principle for design of a mechanism-based metabolite-responsive insulin. In particular, replacement of the present fructose sensor by an analogous glucose sensor may enable translational development of a "smart" insulin analog to mitigate hypoglycemic risk in diabetes therapy.
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Feedback-controlled detection of subtle changes of extracellular biomolecules as known from cells is also needed in protocells. Artificial organelles, located in protocells, detect the small variation in pH which is triggered by different amounts of invading glucose, converted by glucose-oxidase into gluconic acid. The approach paves the way for using pH fluctuations-detecting artificial organelles in the lumen of protocells.
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Résumé Cette revue est consacrée à l'histoire des insulines synthétiques et biosynthétiques. Plutôt que de rester dans le cadre purement descriptif de la chronologie historique de leur développement au cours des 40 dernières années, nous avons élargi notre démarche en faisant une analyse plus approfondie des découvertes fondamentales qui ont mené à nos avancées technologiques, les plus marquantes dans ce domaine. L'insuline est une hormone peptidique formée par 2 chaînes d'acides aminés (A et B) reliées par 2 ponts disulfures avec un pont disulfure supplémentaire à l'intérieur de la chaîne A. Tous les acides aminés (des résidus cystéine) impliqués dans les ponts disulfures et quelques autres comme ceux qui sont situés entre B25 et B26 sont cruciaux pour le maintien de l'activité insulinique. Pour cette raison, toute modification dans la structure de l'insuline doit être soigneusement analysée pour éviter des effets néfastes quand certains acides aminés sont remplacés par d'autres. En revanche, des effets bénéfiques peuvent être obtenus après des modifications ciblées : a) en position B28-B29 pour réduire l'autoassociation des unités insuliniques et pour produire des analogues rapides ; b) avec addition de 2 résidus arginine à l'extrémité de la chaîne B pour modifier le point isoélectrique des préparations (par exemple la glargine) ; et c) avec insertion d'un acide gras en B29 pour obtenir des insulines acylées, qui se « protractent » dans le tissu cellulaire sous-cutané avec une fixation ultérieure sur l'albumine plasmatique. Les deux dernières modifications sont utilisées pour la production des analogues à action prolongée. Toutes sont obtenues grâce à la technologie de l'acide désoxyribonucléique (ADN) recombinant qui fut appliquée pour la première fois dans le domaine de l'insuline dans les années 1980-1990. Elle a permis la production d'une grande variété de préparations insuliniques destinées à individualiser le traitement des personnes ayant un diabète traité par insuline. Une fois de plus, nous insisterons sur le fait que la compréhension du point de départ (la chimie de l'insuline) pour décrire le point d'arrivée (la pharmacocinétique et la pharmacodynamie de l'insuline) est la démarche principale que nous avons utilisée tout au long de cette revue.
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Diabetes Mellitus refers to a group of metabolic disorders which affect how the body uses glucose impacting approximately 9% of the population worldwide. This review covers the most recent technological advances envisioned to control and/or reverse Type 1 diabetes mellitus (T1DM), many of which will also prove effective in treating the other forms of diabetes mellitus. Current standard therapy for T1DM involves multiple daily glucose measurements and insulin injections. Advances in glucose monitors, hormone delivery systems, and control algorithms generate more autonomous and personalised treatments through hybrid and fully automated closed-loop systems, which significantly reduce hypo- and hyperglycaemic episodes and their subsequent complications. Bi-hormonal systems that co-deliver glucagon or amylin with insulin aim to reduce hypoglycaemic events or increase time spent in target glycaemic range, respectively. Stimuli responsive materials for the controlled delivery of insulin or glucagon are a promising alternative to glucose monitors and insulin pumps. By their self-regulated mechanism, these “smart” drugs modulate their potency, pharmacokinetics and dosing depending on patients’ glucose levels. Islet transplantation is a potential cure for T1DM as it restores endogenous insulin and glucagon production, but its use is not yet widespread due to limited islet sources and risks of chronic immunosuppression. New encapsulation strategies that promote angiogenesis and oxygen delivery while protecting islets from recipients’ immune response may overcome current limiting factors.
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A "closed-loop" insulin delivery system that can mimic the dynamic and glucose-responsive insulin secretion as islet β-cells is desirable for the therapy of type 1 and advanced type 2 diabetes mellitus (T1DM and T2DM). Herein, we introduced a kind of "core-shell"-structured glucose-responsive nanoplatform to achieve intravenous "smart" insulin delivery. A finely controlled one-pot biomimetic mineralization method was utilized to coencapsulate insulin, glucose oxidase (GOx), and catalase (CAT) into the ZIF-8 nanoparticles (NPs) to construct the "inner core", where an efficient enzyme cascade system (GOx/CAT group) served as an optimized glucose-responsive module that could rapidly catalyze glucose to yield gluconic acid to lower the local pH and effectively consume the harmful byproduct hydrogen peroxide (H2O2), inducing the collapse of pH-sensitive ZIF-8 NPs to release insulin. The erythrocyte membrane, a sort of natural biological derived lipid bilayer membrane which has intrinsic biocompatibility, was enveloped onto the surface of the "inner core" as the "outer shell" to protect them from elimination by the immune system, thus making the NPs intravenously injectable and could stably maintain a long-term existence in blood circulation. The in vitro and in vivo results indicate that our well-designed nanoplatform possesses an excellent glucose-responsive property and can maintain the blood glucose levels of the streptozocin (STZ)-induced type 1 diabetic mice at the normoglycemic state for up to 24 h after being intravenously administrated, confirming an intravenous insulin delivery strategy to overcome the deficits of conventional daily multiple subcutaneous insulin administration and offering a potential candidate for long-term T1DM treatment.
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Patients who have diabetes must receive insulin administration two to three times every day via subcutaneous (SC) injection after measurement of blood glucose levels (BGLs) using lancet/blood-glucose meter with the side effects of pain and lipodystrophy. Achieving instrument-free glucose-biosensing and persistent glycaemic control in a painless and safe way is the ultimate goal of diabetes management. Here, we report the design of a microneedles (MNs) set comprising a glucose-biosensing microneedle patch (GBMP) and an insulin-delivery MP (IDMP). Once in the skin, the skin interstitial fluid (ISF) would diffuse into GBMP from epidermis to develop colour in abnormal glucose concentration which then quantified by smartphone. Subsequently, the IDMP composing of free insulin and biodegradable insulin-loaded glucose-responsive nanovesicles (IG-NVs) as an artificial on-skin pancreas, could be applied for hyperglycaemia-triggered insulin release to self-regulate BGLs and improve the health and quality of life for patients with type 1 and advanced type 2 diabetes. In chemically induced type 1 diabetic rats, the BGLs can be rapidly measured by GBMP and the BGLs can also be immediately reduced to and kept at normoglycaemic levels for up to 13 h by IDMP. The whole system permits the syringe-free diabetes management, avoiding both hyperglycaemia and hypoglycaemia.
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Fructose consumption and its implications on public health are currently under study. This work reviewed the metabolic fate of dietary fructose based on isotope tracer studies in humans. The mean oxidation rate of dietary fructose was 45.0% +/- 10.7 (mean +/- SD) in non-exercising subjects within 3--6 hours and 45.8% +/- 7.3 in exercising subjects within 2--3 hours. When fructose was ingested together with glucose, the mean oxidation rate of the mixed sugars increased to 66.0% +/- 8.2 in exercising subjects. The mean conversion rate from fructose to glucose was 41% +/- 10.5 (mean +/- SD) in 3--6 hours after ingestion. The conversion amount from fructose to glycogen remains to be further clarified. A small percentage of ingested fructose (<1%) appears to be directly converted to plasma TG. However, hyperlipidemic effects of larger amounts of fructose consumption are observed in studies using infused labeled acetate to quantify longer term de novo lipogenesis. While the mechanisms for the hyperlipidemic effect remain controversial, energy source shifting and lipid sparing may play a role in the effect, in addition to de novo lipogenesis. Finally, approximately a quarter of ingested fructose can be converted into lactate within a few of hours. The reviewed data provides a profile of how dietary fructose is utilized in humans.
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To determine the safety and efficacy of the long-acting analog insulin glargine compared with NPH insulin in patients with type 2 diabetes who were previously treated with insulin alone. A total of 518 subjects with type 2 diabetes who were receiving NPH insulin with or without regular insulin for postprandial control were randomized to receive insulin glargine (HOE 901) once daily (n = 259) or NPH insulin once or twice daily in = 259) for 28 weeks in an open-label, multicenter trial. Doses were adjusted to obtain target fasting glucose <6.7 mmol/l. At study end point, the median total daily insulin dose in both treatment groups was 0.75 IU/kg. The treatment groups showed similar improvements in HbA1c from baseline to end point on intent-to-treat analysis. The mean change (means +/- SD) in HbA1c from baseline to end point was similar in the insulin glargine group (-0.41 +/- 0.1%) and the NPH group (-0.59 +/- 0.1%) after patients began with an average baseline HbA1c of approximately 8.5%. The treatments were associated with similar reductions in fasting glucose levels. Overall, mild symptomatic hypoglycemia was similar in insulin glargine subjects (61.4%) and NPH insulin subjects (66.%) However, nocturnal hypoglycemia in the insulin glargine group was reduced by 25% during the treatment period after the dose-titration phase(26.5 vs. 35.5%, P = 0.0136). Subjects in the insulin glargine group experienced less weight gain than those in the NPH group (0.4 vs. 1.4 kg, P < 0.0007). In patients with type 2 diabetes, once-daily bedtime insulin glargine is as effective as once- or twice-daily NPH in improving and maintaining glycemic control. In addition, insulin glargine deonstrates a lower risk of nocturnal hypoglycemia and less weight gain compared with NPH insulin.
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Hypoglycemia is a cause of significant morbidity among patients with diabetes and may be associated with greater risk of death. We conducted a retrospective study to determine whether patient self-report of severe hypoglycemia is associated with increased mortality. Adult patients (N = 1,020) seen in a specialty diabetes clinic between August 2005 and July 2006 were questioned about frequency of hypoglycemia during a preencounter interview; 7 were lost to follow-up and excluded from analysis. Mild hypoglycemia was defined as symptoms managed without assistance, and severe hypoglycemia was defined as symptoms requiring external assistance. Mortality data, demographics, clinical characteristics, and Charlson comorbidity index (CCI) were obtained from the electronic medical record after 5 years. Patients were stratified by self-report of hypoglycemia at baseline, demographics were compared using the two-sample t test, and risk of death was expressed as odds ratio (95% CI). Associations were controlled for age, sex, diabetes type and duration, CCI, HbA(1c), and report of severe hypoglycemia. In total, 1,013 patients with type 1 (21.3%) and type 2 (78.7%) diabetes were questioned about hypoglycemia. Among these, 625 (61.7%) reported any hypoglycemia, and 76 (7.5%) reported severe hypoglycemia. After 5 years, patients who reported severe hypoglycemia had 3.4-fold higher mortality (95% CI 1.5-7.4; P = 0.005) compared with those who reported mild/no hypoglycemia. Self-report of severe hypoglycemia is associated with 3.4-fold increased risk of death. Patient-reported outcomes, including patient-reported hypoglycemia, may therefore augment risk stratification and disease management of patients with diabetes.
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To examine patient and physician beliefs regarding insulin therapy and the degree to which patients adhere to their insulin regimens. Internet survey of 1250 physicians (600 specialists, 650 primary care physicians) who treat patients with diabetes and telephone survey of 1530 insulin-treated patients (180 with Type 1 diabetes, 1350 with Type 2 diabetes) in China, France, Japan, Germany, Spain, Turkey, the UK or the USA. Results: One third (33.2%) of patients reported insulin omission/non-adherence at least 1 day in the last month, with an average of 3.3 days. Three quarters (72.5%) of physicians report that their typical patient does not take their insulin as prescribed, with a mean of 4.3 days per month of basal insulin omission/non-adherence and 5.7 days per month of prandial insulin omission/non-adherence. Patients and providers indicated the same five most common reasons for insulin omission/non-adherence: too busy; travelling; skipped meals; stress/emotional problems; public embarrassment. Physicians reported low patient success at initiating insulin in a timely fashion and adjusting insulin doses. Most physicians report that many insulin-treated patients do not have adequate glucose control (87.6%) and that they would treat more aggressively if not for concern about hypoglycaemia (75.5%). Although a majority of patients (and physicians) regard insulin treatment as restrictive, more patients see insulin treatment as having positive than negative impacts on their lives. Glucose control is inadequate among insulin-treated patients, in part attributable to insulin omission/non-adherence and lack of dose adjustment. There is a need for insulin regimens that are less restrictive and burdensome with lower risk of hypoglycaemia.
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In our continuing efforts into designing boronic acid-based sensors that recognize cell-surface carbohydrates, it has been necessary to examine various factors that affect the binding affinity between a boronic acid moiety and a diol. The current prevailing view is that the strongest boronic acid/diol complexes are generated by a combination of high solution pH and a low boronic acid pKa. However, there has never been a systematic examination of the relationship among the binding constants, boronic acid pKa, and the pH of the solution. Herein we report our findings with a series of 25 arylboronic acids with various substituents and their binding affinities with diols. We have found that (1) the relationship between the pKa of monosubstituted phenylboronic acid and its substituents can be described using a Hammet plot; (2) the optimal pH for binding is not always above the pKa of the boronic acid, and is affected by the pKa values of the boronic acid and the diol, and other unknown factors; and (3) the general belief that boronic acids with lower pKa values show greater binding affinities for diols is not always true.
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Boronic acids bind with compounds containing diol moieties with high affinity through reversible boronate formation. However, the conditions that foster tight binding between the diol and the boronic acid are not well understood. Also, due to the multiple ionic states of both the boronic acid and boronate ester, the equilibrium constants reported in the literature have not always been strictly defined, and therefore there is a lack of “comparability” between the reported values. To address these issues, we have developed a method for examining boronate ester stability using the fluorescent reporter Alizarin Red S. We have used this system to determine the binding constants of a series of diols, and as a basis from which to derive a number of relationships that correlate the various equilibrium constants in the literature.
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Phenyl boronic acids (PBA) are important binding ligands to pendant diols useful for saccharide recognition. The aromatic ring can also function to anchor an otherwise hydrophilic polymer backbone to the surface of hydrophobic graphene or carbon nanotube. In this work, we demonstrate both functions using a homologous series of seven phenyl boronic acids conjugated to a polyethylene glycol, eight-membered, branched polymer (PPEG8) that allows aqueous dispersion of single-walled carbon nanotubes (SWNT) and quenching of the near-infrared fluorescence in response to saccharide binding. We compare the 2-carboxyphenylboronic acid (2CPBA); 3-carboxy- (3CPBA) and 4-carboxy- (4CPBA) phenylboronic acids; N-(4-phenylboronic)succinamic acid (4SCPBA); 5-bromo-3-carboxy- (5B3CPBA), 3-carboxy-5-fluoro- (5F3CPBA), and 3-carboxy-5-nitro- (5N3CPBA) phenylboronic acids, demonstrating a clear link between SWNT photoluminescence quantum yield and boronic acid structure. Surprisingly, quantum yield decreases systematically with both the location of the BA functionality and the inclusion of electron-withdrawing or -donating substituents on the phenyl ring. For three structural isomers (2CPBA, 3CPBA, and 4CPBA), the highest quantum yields were measured for para-substituted PBA (4CPBA), much higher than ortho- (2CPBA) and meta- (3CPBA) substituted PBA, indicating the first such dependence on molecular structure. Electron-withdrawing substituents such as nitro groups on the phenyl ring cause higher quantum yield, while electron-donating groups such as amides and alkyl groups cause a decrease. The solvatochromic shift of up to 10.3 meV was used for each case to estimate polymer surface coverage on an areal basis using a linear dielectric model. Saccharide recognition using the nIR photoluminescence of SWNT is demonstrated, including selectivity toward pentoses such as arabinose, ribose, and xylose to the exclusion of the expected fructose, which has a high selectivity on PBA due to the formation of a tridentate complex between fructose and PBA. This study is the first to conclusively link molecular structure of an adsorbed phase to SWNT optical properties and modulation in a systematic manner.
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These studies were designed to evaluate some of the in vivo characteristics of the insulin derivative, succinyl amido phenyl glucopyranoside insulin (SAPG-insulin). The in vitro bioeffectiveness studies in isolated rat fat cells demonstrated that the monosubstituted SAPG-insulin derivatives retained their full biological activity, while disubstituted SAPG-insulin had a reduced bioactivity. This is in good agreement with previous in vivo biological assay results. The antigenicity of both SAPG-insulin and native bovine insulin was examined in a rabbit model; no antibody formation was observed, indicating that the derivatization of insulin does not result in an immune response. In addition, plasma disappearance and liver uptake studies in dogs demonstrated that SAPG-insulin is handled in the same manner as native insulin in vivo.
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Intensive basal-bolus insulin therapy has been shown to improve glycaemic control and reduce the risk of long-term complications that are associated with type 1 diabetes mellitus. Insulin degludec is a new, ultra-longacting basal insulin. We therefore compared the efficacy and safety of insulin degludec and insulin glargine, both administered once daily with mealtime insulin aspart, in basal-bolus therapy for type 1 diabetes. In an open-label, treat-to-target, non-inferiority trial, undertaken at 79 sites (hospitals and centres) in six countries, adults (aged ≥18 years) with type 1 diabetes (glycated haemoglobin [HbA(1c)] ≤10% [86 mmol/mol]), who had been treated with basal-bolus insulin for at least 1 year, were randomly assigned in a 3:1 ratio, with a computer-generated blocked allocation sequence, to insulin degludec or insulin glargine without stratification by use of a central interactive response system. The primary outcome was non-inferiority of degludec to glargine, assessed as a reduction in HbA(1c) after 52 weeks, with the intention-to-treat analysis. This trial is registered with ClinicalTrials.gov, number NCT00982228. Of 629 participants, 472 were randomly assigned to insulin degludec and 157 to insulin glargine; all were analysed in their respective treatment groups. At 1 year, HbA(1c) had fallen by 0·40% points (SE 0·03) and 0·39% points (0·07), respectively, with insulin degludec and insulin glargine (estimated treatment difference -0·01% points [95% CI -0·14 to 0·11]; p<0·0001 for non-inferiority testing) and 188 (40%) and 67 (43%) participants achieved a target HbA(1c) of less than 7% (<53 mmol/mol). Rates of overall confirmed hypoglycaemia (plasma glucose <3·1 mmol/L or severe) were similar in the insulin degludec and insulin glargine groups (42·54 vs 40·18 episodes per patient-year of exposure; estimated rate ratio [degludec to glargine] 1·07 [0·89 to 1·28]; p=0·48). The rate of nocturnal confirmed hypoglycaemia was 25% lower with degludec than with glargine (4·41 vs 5·86 episodes per patient-year of exposure; 0·75 [0·59 to 0·96]; p=0·021). Overall serious adverse event rates (14 vs 16 events per 100 patient-years of exposure) were similar for the insulin degludec and insulin glargine groups. Insulin degludec might be a useful basal insulin for patients with type 1 diabetes because it provides effective glycaemic control while lowering the risk of nocturnal hypoglycaemia, which is a major limitation of insulin therapy. Novo Nordisk.
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A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin delivery system. A phenylboronic acid (PBA) moiety was incorporated in poly(N-vinyl-2-pyrrolidone) [poly(NVP-co-PBA) ] as a glucose sensor molecule by the radical copolymerization of N-vinyl-2-pyrrolidone with m-acrylamidophenylboronic acid. Complex formation as well as dissociation was estimated by viscosity changes in the complex solution. A positive viscosity change was observed for the poly (vinyl alcohol) (PVA)/poly(NVP-co-PBA) complex system due to complex formation between PVA diol units and poly(NVP-co-PBA) boronate units; minimal or no change in viscosity was observed for either PVA/boric acid or PVA/poly(NVP). The viscosity of the PVA/poly(NVP-co-PBA) system is able to be controlled through changes in polymer molecular weight and/or polymer concentration. The maximum point in viscosity was observed at a molar ratio of PVA to poly (NVP-co-PBA) of 4:1 in this system. The diol-boronate complex interaction was further investigated by following decreased complex viscosity with the addition of a competitive polyol: glucose, tris(hydroxymethyl)aminomethane (TRIS) or (±)-3-amino-1,2-propanediol (APD). The viscosity decreased steeply when glucose was added while minimal change in viscosity was observed when either TRIS or APD was added. This suggested that the chemical structure of the diol compound had an important role in exchange with the diol-boronate complex. These results point to the promising use of PVA/poly(NVP-co-PBA) complex systems in the development of a novel glucose responsive insulin release system.
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Different glycosylated human insulins were synthesized through the covalent attachment of p-succinyl amidophenyl glyco-pyranoside (SAPG) moiety (ies) to insulin amino groups GlyA1, LysB29 and PheB1. All 7 possible glucosyl derivatives were purified to homogeneity. All but GlyA1, LysB29 disubstituted and trisubstituted products maintained bioactivity similar to native insulin. The mono and diSAPG insulins (especially PheB1 substituted) showed decreased association as determined by GPC and dynamic light scattering. PheB1 substituted and/or di-and trisubstituted insulins demonstrated higher long term stability than native insulin as assessed by the fraction of remaining nonaggregated protein. Because of possible clinical applications, the immunogenicity of different glycosylated insulins was also investigated using two different strains of mice: A/J (H-2a) and C57BL/10ScSn (H-2b). Generally, monosubstituted derivatives provoked immunological responses in vivo and in vitro comparable to regular insulin whereas disubstituted derivatives displayed elevated responses both in vivo and in vitro. Ongoing insulin receptor binding studies revealed that GlyA1 glycosylation negatively affects the binding constant, whereas LysB29 modification in the GlyA1, LysB29 disubstituted derivative has no additional effect. Clinical studies with GlyA1 SAPG insulin demonstrated that important pharmacological parameters were unchanged (blood glucose level, C-peptide concentration) compared to insulin, with the exception of an elevated concentration of GlyA1 SAPG insulin in the blood. This may explain the preserved bioactivity of GlyA1 SAPG insulin despite its attenuated affinity for the insulin receptor.
Article
A derivatized insulin, succinyl amido phenyl-α-d-glycopyranoside insulin (SAPG-insulin) has been synthesized for use in a self-regulating insulin delivery system. The product was a heterogenous mixture of glycosylated insulins differing in their degree and site of substitution. These products were purified and separated using Con A affinity chromatography followed by fast protein liquid chromatography (FPLC) on an anion exchange column. The resultant 4 products were isolated and characterized by end group analysis, sugar group quantitation and isoelectric focusing. In addition, radioimmunoassay cross-reactivity and in vivo biological activity were assessed. The major peak was B-1 phenylalanine monosubstituted SAPG-insulin, which had a potency equivalent to native bovine insulin. This makes the purified fraction, B-1 phenylalanine monosubstituted SAPG-insulin, an ideal candidate for use in the self-regulating insulin delivery system. The method utilized in this work is also potentially useful in the modification of proteins or peptides for enhanced gastrointestinal absorption.
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The lock-and-key principle of natural systems is based on complex interactions like hydrogen bonding. Many synthetic systems that attempt to mimic natural systems have also used hydrogen bonding as the main binding force and have met with great success in non-hydrogen-bonding solvents that do not compete with the guest for the binding pocket. In contrast, natural systems function in water, a very competitive solvent. Synthetic hydrogen-bonding systems may yet evolve to be successful in water. If this transition can not be made, synthetic answers can nevertheless take inspiration from nature without slavishly following the blue print. This is not an attempt to reinvent the “lock”: a new locking mechanism merely replaces the existing one. The inspiration might be the view of the hydrogen bond as an easily reversible “covalent” bond. Screening the literature we rediscovered boronic acids, which have been known for over 100 years. Conveniently, boronic acids rapidly and reversibly form cyclic esters with diols in basic aqueous media. Saccharides and other related “keys” contain a contiguous array of cyclic alcohols. In this work we hope to demonstrate that saccharide “keys” and boronic acid “locks” can open the door to a new and exciting field of research.
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Chronically elevated blood glucose levels are associated with significant morbidity and mortality. Many diabetes patients will eventually require insulin treatment to maintain good glycaemic control. There are still uncertainties about the optimal insulin treatment regimens for type 2 diabetes, but the long-acting insulin analogues seem beneficial. Several reviews have compared either insulin detemir or insulin glargine to NPH insulin, but research directly comparing both insulin analogues is limited. To assess the effects of insulin detemir and insulin glargine compared with each other in the treatment of type 2 diabetes mellitus. We searched MEDLINE, EMBASE, The Cochrane Library, online registries of ongoing trials and abstract books. Date of last search was January 2011. All randomised controlled trials comparing insulin detemir with insulin glargine with a duration of 12 weeks or longer were included. Two authors independently selected the studies and extracted the data. Pooling of studies by means of random-effects meta-analysis was performed. This review examined four trials lasting 24 to 52 weeks involving 2250 people randomised to either insulin detemir or glargine. Overall, risk of bias of the evaluated studies was high. Insulin glargine was dosed once-daily in the evening. Insulin detemir was initiated once-daily in the evening with the option of an additional dose in the morning in three studies and initiated twice-daily in one study. Of randomised patients 13.6% to 57.2% were injecting insulin detemir twice-daily at the end of trial.Glycaemic control, measured by glycosylated haemoglobin A1c (HbA1c) and HbA1c equal to or less than 7% with or without hypoglycaemia, did not differ statistically significantly between treatment groups.The results showed no significant differences in overall, nocturnal and severe hypoglycaemia between treatment groups.Insulin detemir was associated with less weight gain. Treatment with insulin glargine resulted in a lower daily basal insulin dose and a lower number of injection site reactions.There was no significant difference in the variability of FPG or glucose values in 24-hour profiles between treatment groups. It was not possible to draw conclusions on quality of life, costs or mortality. Only one trial reported results on health-related quality of life and showed no significant differences between treatment groups. Our analyses suggest that there is no clinically relevant difference in efficacy or safety between insulin detemir and insulin glargine for targeting hyperglycaemia. However, to achieve the same glycaemic control insulin detemir was often injected twice-daily in a higher dose but with less weight gain, while insulin glargine was injected once-daily, with somewhat fewer injection site reactions.
Article
The incidence of type 1 diabetes in children younger than 15 years is increasing. Prediction of future incidence of this disease will enable adequate fund allocation for delivery of care to be planned. We aimed to establish 15-year incidence trends for childhood type 1 diabetes in European centres, and thereby predict the future burden of childhood diabetes in Europe. 20 population-based EURODIAB registers in 17 countries registered 29 311 new cases of type 1 diabetes, diagnosed in children before their 15th birthday during a 15-year period, 1989-2003. Age-specific log linear rates of increase were estimated in five geographical regions, and used in conjunction with published incidence rates and population projections to predict numbers of new cases throughout Europe in 2005, 2010, 2015, and 2020. Ascertainment was better than 90% in most registers. All but two registers showed significant yearly increases in incidence, ranging from 0.6% to 9.3%. The overall annual increase was 3.9% (95% CI 3.6-4.2), and the increases in the age groups 0-4 years, 5-9 years, and 10-14 years were 5.4% (4.8-6.1), 4.3% (3.8-4.8), and 2.9% (2.5-3.3), respectively. The number of new cases in Europe in 2005 is estimated as 15 000, divided between the 0-4 year, 5-9 year, and 10-14 year age-groups in the ratio 24%, 35%, and 41%, respectively. In 2020, the predicted number of new cases is 24 400, with a doubling in numbers in children younger than 5 years and a more even distribution across age-groups than at present (29%, 37%, and 34%, respectively). Prevalence under age 15 years is predicted to rise from 94 000 in 2005, to 160 000 in 2020. If present trends continue, doubling of new cases of type 1 diabetes in European children younger than 5 years is predicted between 2005 and 2020, and prevalent cases younger than 15 years will rise by 70%. Adequate health-care resources to meet these children's needs should be made available. European Community Concerted Action Program.
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A stable, biologically active glycosylated insulin derivative that is complementary to the major combining site of concanavalin A has been synthesized. Hormone release is proportional to the quantity of glucose present. Glucose regulation of exogenous insulin delivery could have important applications in the therapy of diabetes mellitus.
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Detailed studies of the optical rotatory dispersion and circular dichroism spectra of insulin were carried out to define the difficulties encountered at present in the analysis of protein optical activity in terms of specific conformations. Spectra were recorded at 27°, at elevated temperatures, and subsequent to reaction with N-acetylimidazole. Tyrosine acetylation resulted in a marked diminution and blue shifting of the near-ultraviolet circular dichroism spectrum ; the 274-nm extremum was broadened into two distinct extrema, indicating a major contribution from tyrosine moieties to the near-ultraviolet circular dichroism spectrum. The contribution of unordered polypeptide segments to the far-ultraviolet circular dichroism spectrum of insulin was assessed from circular dichroism spectra of thermally denatured insulin. At 70° the far-ultraviolet circular dichroism spectrum of insulin is quite different from that usually obtained with unordered polypeptides in solution, suggesting the maintenance of appreciable amounts of residual order. Lack of a blue shift of the 209-nm extremum at 70° suggested that the negative band of the unordered conformation is located above 200 nm, as is found in polypeptide films. Heating to 70° resulted in a marked reduction of intensity in the near-ultraviolet region with no blue shift. The far-ultraviolet circular dichroism spectrum of native insulin contains two anomalous qualitative features: the position of the positive extremum at 196 nm and the high magnitude of the 209-nm extremum relative to that at 222 nm. These were analyzed in terms of shifts in position and intensity of α-helical and β-structure transitions. The principal limitations to interpreting these spectra exactly are the inadequacy of polypeptide models for protein polypeptide optical activity and the inability to assess quantitatively the contributions made by side chains to far-ultraviolet circular dichroism.
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Our observation that hypoglycemia, often self-diagnosed by our patients, was seldom confirmed led the authors to establish norms for the glucose tolerance test. We first obtained values for 650 patients who were entirely free from symptoms before and during testing. The median nadir in this group was 64 mg/dl. Ten percent of the patients had plasma glucose nadirs of 47 mg/dl or below and 2.5% had values of 39 mg/dl or less. Utilizing these values in combination with clinical criteria, we confirmed hypoglycemia after glucose load in 16 (median nadir 39.5 mg/dl) of 118 patients presenting with this diagnosis, and only 5 of the 16 were hypoglycemic after their usual meals. The other 102 patients, whose many complaints were unrelated to measured plasma glucose levels, had nadirs similar to those of the control group. Placebo tests performed on 14 nonhypoglycemic patients provoked symptoms (recorded by the patients themselves) and they considered indicative of hypoglycemia. Some accepted other diagnoses after we demonstrated that their symptoms occurred when they were normoglycemic. Since nadirs of hypoglycemics and control subjects overlap, we conclude that accurate diagnosis of hypoglycemia requires that symptoms develop concurrently with low blood sugar and that they are absent at other times. Low plasma glucose must be considered only one of the criteria in diagnosing functional hypoglycemia along with a relationship between food intake, timing of symptoms, correlation of symptoms and low glucose levels, and reproducibility of test results.
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Products of advanced protein glycosylation (advanced glycation end products, or AGEs) accumulate in tissues as a function of time and sugar concentration. AGEs induce permanent abnormalities in extracellular matrix component function, stimulate cytokine and reactive oxygen species production through AGE-specific receptors, and modify intracellular proteins. Pharmacologic inhibition of AGE formation in long-term diabetic animals prevents diabetic retinopathy, nephropathy, neuropathy, and arterial abnormalities in animal models. Clinical trials in humans are currently in progress.
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Albumin is a multifunctional transport protein that binds a wide variety of endogenous substances and drugs. Insulins with affinity for albumin were engineered by acylation of the epsilon-amino group of LysB29 with saturated fatty acids containing 10-16 carbon atoms. The association constants for binding of the fatty acid acylated insulins to human albumin are in the order of 10(4)-10(5) M-1. The binding apparently involves both non-polar and ionic interactions with the protein. The acylated insulins bind at the long-chain fatty acid binding sites, but the binding affinity is lower than that of the free fatty acids and depends to a relatively small degree on the number of carbon atoms in the fatty acid chain. Differences in affinity of the acylated insulins for albumin are reflected in the relative timing of the blood-glucose-lowering effect after subcutaneous injection into rabbits. The acylated insulins provide a breakthrough in the search for soluble, prolonged-action insulin preparations for basal delivery of the hormone to the diabetic patient. We conclude that the biochemical concept of albumin binding can be applied to protract the effect of insulin, and suggest that derivatization with albumin-binding ligands could be generally applicable to prolong the action profile of peptide drugs.
Article
Insulins acylated with fatty acids at the epsilon-amino group of LysB29 constitute a new class of insulin analogs, which are prolonged-acting due to albumin binding. In the present study it is shown that the affinity of fatty acid acylated insulins for albumin varies considerably (> 50-fold) among species. The relative affinities of acylated insulin for albumin in human, pig, and rabbit serum are about 1:1:5:35. The several fold higher binding affinity in rabbit serum than in pig serum is reflected in a relatively more protracted effect after sc injection in rabbits than in pigs. Due to the similar binding affinities in pig serum and human serum, the pig model should provide a useful estimate of the degree of protraction of acylated insulin in humans. The results emphasize that species differences in ligand binding can be of major importance in the preclinical evaluation of highly albumin bound drugs.
Article
Treatment of diabetes mellitus by insulin injections provides long-term control of the disease but lacks any feedback response to glucose concentration changes, which finally leads to a number of life-threatening conditions. The purpose of this study was to improve and optimize an implantable, concanavalin A (Con A) based, glucose-responsive insulin delivery system studied earlier [Jeong, S. Y., Kim, S. W., Holmberg, D. L., and McRea, J. C. (1985) J. Controlled Release 2, 143-152], which can be used for long-term diabetes treatment. To optimize the "insulin component" of the delivery system, we prepared PheB1 insulin amino group monosubstituted monoglucosylpoly(ethylene glycol) (G-PEG) insulin conjugates (PEG M(r) 600 or 2000), which showed preserved bioactivity, significantly improved solubility and solution stability at neutral pH, and substantially suppressed hexamerization/dimerization. To improve the delivery system further, we synthesized and characterized a conjugate of Con A and monomethoxypoly(ethylene glycol) (mPEG, M(r) 5000) grafted hydrophilic poly(vinylpyrrolidone-co-acrylic acid) (PVPAA) with M(r) of 250,000. The optimal conjugate contained around eight PEG chains and two to three Con A tetramers attached through the amide bonds to the PVPAA chain. The Con A sugar binding characteristics were preserved, and, more importantly, Con A solubility at pH 7.4 substantially increased. This also holds true for a complex formed by the Con A conjugate and G-PEG insulin, which is soluble and does not precipitate under the physiologically relevant conditions under which the complex formed by the Con A conjugate and glycosyl insulin immediately precipitates. Finally, no leakage of the Con A conjugate from a membrane device was detected. Preliminary in vitro release experiments with Con A conjugate and G-PEG insulin complex enclosed in the membrane device showed a pulsative, reversible release pattern for G-PEG insulin in response to glucose challenges of 50-500 mg/dL, demonstrating the feasibility of the release system for use in planned, chronic in vivo studies with diabetic (pancreatectomized) dogs.
Article
Since the introduction of insulin therapy 80 years ago, the lives of millions of patients with diabetes have been saved, prolonged and immeasurably improved. However, restoring normal glucose levels in diabetic patients through administering insulin by subcutaneous injection has proved virtually impossible. The consequences for patients are serious complications, including diabetic retinopathy and nephropathy, which tend to result from persistent hyperglycaemia. Maximizing glucose control in diabetic patients requires several daily injections. In an effort to reduce this burden, alternative and less-intrusive routes for the administration of insulin are being explored.
Article
Insulin detemir has been found in clinical trials to be absorbed with very low variability. A series of experiments were performed to elucidate the underlying mechanisms. The disappearance from an injected subcutaneous depot and elimination studies in plasma were carried out in pigs. Size-exclusion chromatography was used to assess the self-association and albumin binding states of insulin detemir and analogs. Disappearance T50% from the injection depot was 10.2+/-1.2 h for insulin detemir and 2.0+/-0.1 h for a monomeric acylated insulin analog. Self-association of acylated insulin analogs with same albumin affinity in saline correlated with disappearance rate and addition of albumin to saline showed a combination of insulin detemir self association and albumin binding. Intravenous kinetic studies showed that the clearance and volume of distribution decreased with increasing albumin binding affinity of different acylated insulin analogs. The protracted action of detemir is primarily achieved through slow absorption into blood. Dihexamerization and albumin binding of hexameric and dimeric detemir prolongs residence time at the injection depot. Some further retention of detemir occurs in the circulation where albumin binding causes buffering of insulin concentration. Insulin detemir provides a novel principle of protraction, enabling increased predictability of basal insulin.
Article
Derivatization of insulin with phenylboronic acids is described, thereby equipping insulin with novel glucose sensing ability. It is furthermore demonstrated that such insulins are useful in glucose-responsive polymer-based release systems. The preferred phenylboronic acids are sulfonamide derivatives, which, contrary to naïve boronic acids, ensure glucose binding at physiological pH, and simultaneously operate as handles for insulin derivatization at LysB29. The glucose affinities of the novel insulins were evaluated by glucose titration in a competitive assay with alizarin. The affinities were in the range 15-31 mM (K(d)), which match physiological glucose fluctuations. The dose-responsive glucose-mediated release of the novel insulins was demonstrated using glucamine-derived polyethylene glycol polyacrylamide (PEGA) as a model, and it was shown that Zn(II) hexamer formulation of the boronated insulins resulted in steeper glucose sensitivity relative to monomeric insulin formulation. Notably, two of the boronated insulins displayed enhanced insulin receptor affinity relative to native insulin (113%-122%) which is unusual for insulin LysB29 derivatives.