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Objectives: This study aimed to present an innovative method for synthesizing pH-thermo-glucose responsive poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles via single-step aqueous free radical polymerization. Methods: The synthesis process involved free radical polymerization in an aqueous solution, and the resulting nanoparticles were characterized for their physical and chemical properties by 1H NMR, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). Insulin-loaded poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles were prepared and evaluated for their insulin capture and release properties at different pH and temperature, in addition to different glucose concentrations, with the release profile of insulin quantitatively evaluated using the Bradford method. Results: 1H NMR results confirmed successful PBA incorporation, and DLS outcomes consistently indicated a transition to a more hydrophobic state above the Lower Critical Solution Temperature (LCST) of NIPA and DMAEMA. While pH responsiveness exhibited variation, insulin release generally increased with rising pH from acidic to neutral conditions, aligning with the anticipated augmentation of anionic PBA moieties and increased hydrogel hydrophilicity. Increased insulin release in the presence of glucose, particularly for formulations with the lowest mol % PBA, along with a slight increase for the highest mol % PBA formulation when increasing glucose from 1 to 4 mg/mL, supported the potential of this approach for nanoparticle synthesis tailored for glucose-responsive insulin release. Conclusions: This work successfully demonstrates a novel method for synthesizing responsive hydrogel nanoparticles and underscores their potential for controlled insulin release in response to glucose concentrations. The observed pH-dependent insulin release patterns and the influence of PBA content on responsiveness highlight the versatility and promise of this nanoparticle synthesis approach for applications in glucose-responsive drug delivery systems. Poly(NIPA) nanoparticles containing PBA moieties are normally synthesized in two or more steps in the presence of organic solvents. Here we propose a new method for the synthesis of multiresponsive hydrogel poly(NIPA-co-DMAEMA)-PBA nanoparticles in aqueous medium in a single reaction to provide a fast and effective strategy for the production of glucose-responsive multi-systems in aqueous media from free radical polymerization [ABSTRACT FROM AUTHOR]

Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is an important regulatory protein responsible for maintaining calcium homeostasis within cells. Impairment of SERCA associated with activity/expression decrease has been implicated in multiple chronic conditions, including cardiovascular diseases, diabetes, cancer, neurodegenerative diseases, and skeletal muscle pathologies. Natural polyphenols have been recognized to interact with several target proteins involving SERCA. To date, only a limited number of polyphenolic compounds or their derivatives have been described either to increase SERCA activity/expression directly or to affect Ca2+ signaling pathways. In this study, we tested polyphenols for their ability to activate SERCA1a in the absence or presence of methylglyoxal or palmitate and to impact insulin release in pancreatic beta cells. The protective effects of these compounds against methylglyoxal- or palmitate-induced injury were evaluated. Results indicate that 6-gingerol, resveratrol, and ellagic acid activate SERCA1a and protect against activity decrease induced by methylglyoxal and palmitate. Molecular docking analysis revealed the binding of these polyphenols to Glu439 in the SERCA1a P-domain, suggesting a critical role in the stimulation of enzyme activity. Ellagic acid was found to directly stimulate the activity of SERCA1a, marking the first instance of such an observation.

β3-Adrenoceptors mediate several functions in rodents that could be beneficial for the treatment of obesity and type 2 diabetes. This includes promotion of insulin release from the pancreas, cellular glucose uptake, lipolysis, and thermogenesis in brown adipose tissue. In combination, they lead to a reduction of body weight in several rodent models including ob/ob mice and Zucker diabetic fatty rats. These findings stimulated drug development programs in various pharmaceutical companies, and at least nine β3-adrenoceptor agonists have been tested in clinical trials. However, all of these projects were discontinued due to the lack of clinically relevant changes in body weight. Following a concise historical account of discoveries leading to such drug development programs we discuss species differences that explain why β3-adrenoceptors are not a meaningful drug target for the treatment of obesity and type 2 diabetes in humans. [ABSTRACT FROM AUTHOR]

The present study was carried out to investigate the effects of garlic (Allium sativum Linn) and leek (Allium porrum L.) on biochemical parameters, lipid profile and gene expression in high fructose diet (HDF)- induced diabetes in rat. In this study, we used 80 males Wistar rats for 18 weeks, HDF was administered daily in diet to induce diabetes. A high and low dose of garlic oil and leek powder were given orally daily to HDF-diabetic rats. Compared to rats in the diabetic groups, the garlic oil and leek powder reduced serum cholesterol, triacylglycerol, low-density lipoprotein-cholesterol (LDL-c) and very low density lipoprotein-cholesterol (VLDL-c) levels. The garlic oil and leek powder also helped reduce hepatic destruction. A reduction was found in the gene expression in the hepatic homogenate of activating transcription factor 6 (ATF6) and X-Box Binding Protein1 (XBP1), Binding immunoglobulin protein (BIP), C/EBP homologous protein (CHOP), Jun N-terminal kinase (JNK), and peroxisome proliferator- activated receptor gamma (PPAR-γ). On the other hand, there was a significant upregulation in the mRNA expression of has been found in the promoter of glucose transporter 2 (Glut2), and miRNA 27a which is also a dose- and time-dependent manner. These results suggest that H2S donor as garlic oil and leek powder exhibits therapeutic potential for diabetes, which is most likely related to its protective effects against ER stress and regulating miRNA 27a and its target gene. [ABSTRACT FROM AUTHOR]

Holarrhena pubescens is widely used in Indian and Chinese medicine in the treatment of diabetes. The current work determined the oral hypoglycemic and antidiabetic effects of seed extract in rats. The probable mechanism of action was evaluated in-vitro by α - glucosidase inhibition, glucose metabolism in insulinoma (INS-1) cells to reflect secretion of insulin, and protein glycation inhibition. Its potential for herb-drug interaction was evaluated in the cytochrome P450 3A4 (CYP3A4) inhibition assay. The seed extract increased serum insulin levels and reduced serum blood glucose levels in the oral glucose tolerance test. It also reduced the serum glucose levels in streptozocin-induced diabetes. The extract also inhibited α –glucosidase enzyme activity and demonstrated that it can increase the secretion of insulin from INS to 1-rat insulinoma cell line cells in-vitro in a concentration-dependent manner. However, it had a very weak inhibitory effect on protein glycation and it did not affect the activity of CYP3A4. The results of the study showed that H. pubescens seed extract increases insulin secretion and inhibits glucose absorption both in-vivo and in-vitro with a weak protein glycation inhibitory effect. The herb is devoid of CYP3A4 inhibitory effect indicating that it may not have pharmacokinetic interaction with the drug metabolized by this enzyme.

The secretion of insulin from the pancreas relies on both gap junctions and subpopulations of beta cells with specific intrinsic properties.

In order to investigate the chronic effects of basic amino acids (BAA) on β-cell metabolism and insulin secretion, INS-1 β-cells were randomly assigned to cultures in standard medium (Con), standard medium plus 10 mM L-Arginine (Arg), standard medium plus 10 mM L-Histidine (His) or standard medium plus 10 mM L-Lysine (Lys) for 24 h. Results showed that insulin secretion was decreased by the Arg treatment but was increased by the His treatment relative to the Con group (p < 0.05). Higher BAA concentrations reduced the high glucose-stimulated insulin secretions (p < 0.001), but only Lys treatment increased the intracellular insulin content than that in the Con group (p < 0.05). Compared with Arg and Lys, the His treatment increased the mitochondrial key enzyme gene expressions including Cs, mt-Atp6, mt-Nd4l and Ogdh, and caused a greater change in the metabolites profiling (p < 0.05). The most significant pathways affected by Arg, His and Lys were arginine and proline metabolism, aminoacyl-tRNA biosynthesis and pyrimidine metabolism, respectively. Regression analysis screened 7 genes and 9 metabolites associated with insulin releases during BAA stimulations (p < 0.05). Together, different BAAs exerted dissimilar effects on β-cell metabolism and insulin outputs. [ABSTRACT FROM AUTHOR]

Purpose: Insulin is highly sensitive to an acidic pH medium and degrades faster. The encapsulation of insulin with chitosan (CS) particulates could partially solve this issue. Since the formation of particles involves different parameters, the unoptimized parameters and formulation result in unstable particles that exhibit a burst release in an acidic medium (pH = 1.20). On the other hand, the CS is poorly or partially soluble in PBS medium (pH = 7.40) and results in a limited insulin release. Therefore, the current study was conducted to prevent the insulin from degrading in an acidic medium and provide a sustained release in a PBS medium. Methods: In this research, the chitosan-tripolyphosphate (CS-TPP) microparticles (MPs) were prepared and characterized in terms of size, PDI, and zeta potential. Furthermore, the effects of different parameters on the size, PDI, and zeta potential were determined. The experimental data for all these properties were validated using the artificial neural network (ANN) technique. The best conditions and formulation were used for insulin encapsulation and prepared MPs were characterized by FTIR, DSC, FESEM, and EDX. Afterwards, insulin release experiments were conducted in acidic (pH = 1.2) and PBS medium (pH = 7.4) for 8 h and release kinetics was conducted to estimate the release rate and mechanism of insulin release from different formulations. Results: The MPs prepared with optimized conditions such as CS concentration = 0.20% w/v, CS pH = 5.30, CS:TPP volume ratio = 3:1, mixing time = 1 h, and stirring speed = 1100 rpm possessed a particle size of 2.90 ± 0.33 μm and a high zeta potential of 55.65 ± 0.68 mV. These optimum conditions were further used for the formation of CS-insulin-TPP MPs that possessed a zeta potential of 25.41 ± 1.64 mV, 1.92 ± 0.07 μm size. Among different CS:TPP volume ratios, the MPs formed with 3:1 exhibited a cumulative insulin release of 55.78 ± 1.42% in 0.10 N HCl medium (pH = 1.20) and 60.79 ± 0.71% in the PBS medium (pH = 7.40). The insulin release occurred due to both diffusion and erosion mechanisms. The predominance of the mechanism for insulin release varied with time from diffusion to polymer chain relaxation. Conclusions: Current findings revealed that MPs prepared with optimized formulation and operating conditions protected the insulin from burst release in the acidic medium and provided a controlled release in the PBS medium. These MPs sufficiently controlled the insulin release rate and can be its good carrier. [ABSTRACT FROM AUTHOR]

Successful management of type 2 diabetes mellitus (T2DM), a complex and chronic disease, requires a combination of anti-hyperglycemic and anti-inflammatory agents. Here, we have conceptualized and tested an integrated “closed-loop mimic” in the form of a glucose-responsive microgel (GRM) based on chitosan, comprising conventional insulin (INS) and curcumin-laden nanoparticles (nCUR) as a potential strategy for effective management of the disease. In addition to mimicking the normal, on-demand INS secretion, such delivery systems display an uninterrupted release of nCUR to combat the inflammation, oxidative stress, lipid metabolic abnormality, and endothelial dysfunction components of T2DM. Additives such as gum arabic (GA) led to a fivefold increased INS loading capacity compared to GRM without GA. The GRMs showed excellent invitro on-demand INS release, while a constant nCUR release is observed irrespective of glucose concentrations. Thus, this study demonstrates a promising drug delivery technology that can simultaneously, and at physiological/pathophysiological relevance, deliver two drugs of distinct physicochemical attributes in the same formulation. [ABSTRACT FROM AUTHOR]

The aim of the study is to characterize synthesized spherical morphological polymeric hydrogel membranes (SMPHMs), especially their swelling properties, and to show the usability of these SMPHMs in the biomedical applications such as drug delivery systems. Insulin used in the treatment of diabetes mellitus disease was chosen as a model drug to demonstrate the usability of these SMPHMs as a drug delivery system. For this purpose, poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) [P(HEMA-GMA)] SMPHMs were prepared by photopolymerization technique using different monomers mole ratios. Characterization of SMPHMs was carried out with SEM and FTIR analyses. Swelling experiments were conducted in water. Equilibrium percentage swelling values of SMPHMs were calculated and found as in the range of 40–122%, depending on hydrophilic structure of SMPHMs. Swelling kinetic parameters were determined, and the diffusion behaviour of water was also investigated. Water diffusion into the SMPHMs was found to shift from non-Fickian diffusion to Fickian diffusion when HEMA/GMA mole ratio was decreased in the structure of SMPHMs. In the final part of study, insulin release conditions from SMPHMs were optimized. For this purpose, insulin release studies were carried out to investigate the effect of monomer ratios, pH, temperature, and initial insulin concentration. The amount of maximum cumulative insulin release was found as 3747.73 µg/g in pH 7.4, at 25 °C, in the 0.5 mg/mL insulin concentration from SMPHMs-3 in seven hours. According to these obtained results, these SMPHMs can be used as alternative systems for biotechnological applications such as swelling-controlled drug delivery systems. [ABSTRACT FROM AUTHOR]

Holarrhena pubescens is widely used in Indian and Chinese medicine in the treatment of diabetes. The current work determined the oral hypoglycemic and antidiabetic effects of seed extract in rats. The probable mechanism of action was evaluated in-vitro by α - glucosidase inhibition, glucose metabolism in insulinoma (INS-1) cells to reflect secretion of insulin, and protein glycation inhibition. Its potential for herb-drug interaction was evaluated in the cytochrome P450 3A4 (CYP3A4) inhibition assay. The seed extract increased serum insulin levels and reduced serum blood glucose levels in the oral glucose tolerance test. It also reduced the serum glucose levels in streptozocin-induced diabetes. The extract also inhibited α –glucosidase enzyme activity and demonstrated that it can increase the secretion of insulin from INS to 1-rat insulinoma cell line cells in-vitro in a concentration-dependent manner. However, it had a very weak inhibitory effect on protein glycation and it did not affect the activity of CYP3A4. The results of the study showed that H. pubescens seed extract increases insulin secretion and inhibits glucose absorption both in-vivo and in-vitro with a weak protein glycation inhibitory effect. The herb is devoid of CYP3A4 inhibitory effect indicating that it may not have pharmacokinetic interaction with the drug metabolized by this enzyme. [ABSTRACT FROM AUTHOR]

The host‐defense peptide ocellatin‐3N (GIFDVLKNLAKGVITSLAS.NH2), first isolated from the Caribbean frog Leptodactylus nesiotus, inhibited growth of clinically relevant Gram‐positive and Gram‐negative bacteria as well as a strain of the major emerging yeast pathogen Candida parapsilosis. Increasing cationicity while maintaining amphipathicity by the substitution Asp4→Lys increased potency against the microorganisms by between 4‐ and 16‐fold (MIC ≤3 μM) compared with the naturally occurring peptide. The substitution Ala18→Lys and the double substitution Asp4→Lys and Ala18→Lys had less effects on potency. The [D4K] analog also showed 2.5‐ to 4‐fold greater cytotoxic potency against non‐small‐cell lung adenocarcinoma A549 cells, breast adenocarcinoma MDA‐MB‐231 cells, and colorectal adenocarcinoma HT‐29 cells (LC50 values in the range of 12–20 μM) compared with ocellatin‐3N but was less hemolytic to mouse erythrocytes. However, the peptide showed no selectivity for tumor‐derived cells [LC50 = 20 μM for human umbilical vein endothelial cells (HUVECs)]. Ocellatin‐3N and [D4K]ocellatin‐3N stimulated the release of insulin from BRIN‐BD11 clonal β‐cells at concentrations ≥1 nM, and [A18K]ocellatin‐3N, at concentrations ≥0.1 nM. No peptide stimulated the release of lactate dehydrogenase at concentrations up to 3 μM, indicating that plasma membrane integrity had been preserved. The three peptides produced an increase in intracellular [Ca2+] in BRIN‐BD11 cells when incubated at a concentration of 1 μM. In view of its high insulinotropic potency and relatively low hemolytic activity, the [A18K] ocellatin analog may represent a template for the design of agents with therapeutic potential for the treatment of patients with type 2 diabetes. [ABSTRACT FROM AUTHOR]

We developed insulin loaded biomimetic microsphere by laccase-mediated crosslinking using a microfluidic device in the water-in-oil emulsion system as an injectable vehicle for the repair of sciatic tissue. Aqueous polymeric solution of phenol-substituted hyaluronic acid (HAPh) and collagen (ColPh) containing insulin and laccase flowed from the inner channel into oil flow within an outer channel which leads formation of hydrogel microsphere. The physical properties of prepared specimens including swelling rate, mechanical resistance and the prolonged release rate of microspheres proved applicability of fabricated vehicles for tissue engineering and drug delivery systems. The growth profile and behavior of cells in microspheres indicated cytocompatibility of the method and prepared vehicles for microtissue development. Histopathological examination revealed a significant increase in axonal regeneration, and remyelination process in injured sciatic nerve following treatment with HAPh/ColPh microspheres containing insulin compared to control groups. Also, the functional characteristic of sciatic tissue showed that the presence of biomimetic microsphere and insulin simultaneously had improved sciatic tissue functions including functional sciatic index (SFI) values, reaction to hot plate and muscle weight of rats. In summary, the results proved that composite biomimetic microspheres containing insulin effectively improved nerve regeneration in the rat model. [ABSTRACT FROM AUTHOR]

Glucose selective oxidizing enzyme of glucose oxidase (GOD) was immobilized on the carboxyl group (–COOH) functionalized porous polyimide (PI) film (PI-GOD film). The –COOH functionalized film was fabricated by the modified breath figure method (BF) by casting the PI solution under humid conditions containing KOH. The amine group of GOD was covalently bonded to the PI-COOH film under catalytic conditions for the PI-GOD film. The PI-GOD film induced the color change of the bromothymol blue (BTB) indicator solution from green to yellow by adding glucose due to the oxidation of glucose by GOD to gluconic acid acting as an acidic source. Amine-terminated pH-sensitive polymethacrylic acid polymer (PMAA) was additionally immobilized to the PI-GOD film for the PI-GOD-PMAA film. The morphology of the pore surface of the PI-GOD-PMAA film was changed by the addition of glucose due to the coil-to-globule transition of the pH-sensitive polymer by the production of gluconic acid as a result of the reaction between glucose and GOD. The insulin adsorbed on the film was released by adding glucose due to the morphology change of the pH-sensitive polymer. The detection sensitivity of glucose was increased by the pore-selectively immobilized GOD acting as a micro-reactor. [Display omitted] • Pore-selective –COOH functionalized film was prepared by polyimide(PI) under KOH. • The film was immobilized by glucose oxidaze (GOD) and pH-sensitive polymer of polymethyl methacrylic acid. • Pore-selective immobilized GOD selectively oxidized glucose for the production of gluconic acid. • The gluconic acid induced the color change of bromothymol blue indicator' • The gluconic acid acts as a H+ source to change the morphology of pore surface. [ABSTRACT FROM AUTHOR]

Diabetes causes macrovascular and microvascular complications such as peripheral neuropathy. Glutamate regulates insulin secretion in pancreatic β-cells, and its increased activity in the central nervous system is associated with peripheral neuropathy in animal models of diabetes. One strategy to modulate glutamatergic activity consists in the pharmacological manipulation of metabotropic glutamate receptors (mGluRs), which, compared to the ionotropic receptors, allow for a fine-tuning of neurotransmission that is compatible with therapeutic interventions. mGluRs are a family of eight G-protein coupled receptors classified into three groups (I-III) based on sequence homology, transduction mechanisms, and pharmacology. Activation of group II and III or inhibition of group I represents a strategy to counteract the glutamatergic hyperactivity associated with diabetic neuropathy. In this review article, we will discuss the role of glutamate receptors in the release of insulin and the development/treatment of diabetic neuropathy, with particular emphasis on their manipulation to prevent the glutamatergic hyperactivity associated with diabetic neuropathy. [ABSTRACT FROM AUTHOR]

β3-Adrenoceptors mediate several functions in rodents that could be beneficial for the treatment of obesity and type 2 diabetes. This includes promotion of insulin release from the pancreas, cellular glucose uptake, lipolysis, and thermogenesis in brown adipose tissue. In combination, they lead to a reduction of body weight in several rodent models including ob/ob mice and Zucker diabetic fatty rats. These findings stimulated drug development programs in various pharmaceutical companies, and at least nine β3-adrenoceptor agonists have been tested in clinical trials. However, all of these projects were discontinued due to the lack of clinically relevant changes in body weight. Following a concise historical account of discoveries leading to such drug development programs we discuss species differences that explain why β3-adrenoceptors are not a meaningful drug target for the treatment of obesity and type 2 diabetes in humans.

Introduction: Type 2 Diabetes Mellitus (T2DM), a common metabolic disorder characterised by hyperglycaemia is caused due to an absolute or relative insulin deficiency and/or insulin resistance. Vitamin D, a steroid hormone beyond its primary role on calcium and bone metabolism, also has been shown to have multiple other effects. Vitamin D levels have been studied in relation to glucose metabolism as role in insulin secretion and insulin resistance by many studies in the past. Aim: To estimate the levels of serum 25-OH vitamin D and to correlate with glycaemic status among uncontrolled T2DM patients. Materials and Methods: A case-control study was conducted during August-September 2021 at Melmaruvathur Adhiparasakthi Institute of Medical Sciences and Research in Melmaruvthur, Tamil Nadu, India. In this study, 50 cases (uncontrolled T2DM) and 50 controls (healthy individuals), of both sexes aged between 40- 60 years were included. Blood samples were analysed for serum 25-OH cholecalciferol (Vitamin D), fasting and postprandial plasma glucose levels and statistical analysis was done by Independent sample t-test for significance testing, odds ratio for exposureoutcome association by logistic regression and Pearson coefficient for correlation using Statistical Package for the Social Sciences (SPSS) software version 18.0. Results: Serum 25-OH vitamin D levels were significantly {p

Abstract Islets organoids would have value in the cell replacement therapy for diabetes apart from usual personalized drug screening routes. Generation of a large number of Islets like clusters, with ability to respond to glucose stimulation appears to be an ideal choice. In this study we have generated islet organoids with the ability to respond to glucose stimulation by insulin release. The source of the cells was an iPSC cell line differentiated into the pancreatic progenitors. These cells were assembled in matrigel or cross-linked collagen scaffold and compared for their efficacy to release insulin upon stimulation with glucose. The assembled organoids were examined by immunohistochemistry and expression of the relevant marker genes. The organoids showed expression of islet like markers in both - matrigel and crosslinked collagen scaffold. The islet organoids in both the cases showed release of insulin upon stimulation with glucose. The crosslinked collagen scaffold is quite stable and supports islet cells growth and function.

Objective: Type 2 diabetes with obesity is regarded as an incurable, progressive disease with many complications. The hypothesis was tested that glycated haemoglobin (HbA1c) and the insulin release curve can be restored by traceable systematic methods. Methods: 122 people with diabesity were investigated before and after three and 6 months of traceable systematic management methods. Basal body mass index (BMI), fatty liver, HbA1c, and insulin release curve were measured. Results: After 3 months of traceable systematic management, BMI decreased from 30.76 ± 0.48 to 21.86 ± 0.09 kg/m2 (p < 0.001) and remained stable during the last 3 months (21.82 ± 0.09 kg/m2 at 6 months). Colour Doppler ultrasound showed non-alcoholic fatty liver disease (NAFLD) in all diabesity participants at baseline. At 3 months, only one participant had low-grade fatty liver, and fatty liver was reversed in other participants (p < 0.001). The number and grade of fatty liver at 6 months were the same as at 3 months. Fasting plasma glucose decreased and continued to decrease thereafter (p < 0.001). Two-hour postprandial plasma glucose decreased and continued to decline until 6 months (p < 0.001). HbA1c also decreased and maintained this level at 6 months. At baseline, the peak value of insulin release was 1,141.09 ± 43.02 pmol/L at 2 h after meals, and the early phase of insulin secretion was lost. After 3 months of management, the insulin concentration was 621.62 ± 19.32 pmol/L at 2 h after meals. After 6 months, the value decreased, and the early phase of insulin secretion recovered. Conclusions: Normalization of the insulin release curve in type 2 diabetes was achieved by traceable systematic methods. This was associated with recovery from NAFLD. Diabesity is reversible by traceable systematic management. [ABSTRACT FROM AUTHOR]

Despite the potential benefits of close-looped insulin delivery systems in regulating glycemic homeostasis and effectively alleviating diabetes, they still encounter challenges such as limited effectiveness in preventing low glycemic episodes due to sluggish glucose response, and issues with the instability of enzymes and carriers. In this study, dually-crosslinked and glucose oxidase (GOx)-immobilized insulin nanogels (DC-NGs@Ins) are developed for rapid-responsive and sustained hypoglycemic therapy. The DC-NGs@Ins with the phenylborate ester linker enabled the insulin release in a close-looped fashion, and moreover, immobilized GOx-generated hydrogen peroxide (H 2 O 2 ) by consuming the glucose, which can further bind to phenylborate ester for enhancing glucose response and accelerating the insulin release. The dually-crosslinked structure (phenylboronic ester and UV-crosslinking) effectively minimized the initial burst release of insulin, thus preventing the potential risk of hypoglycemia. More interestingly, GOx immobilized in the nanogels mitigated GOx leakage and enhanced its multiple utilization compared to free GOx. In vivo study demonstrated that DC-NGs@Ins effectively maintained glycemic levels (BGLs) below 200 mg dL -1 for at least 8 h compared to singly-crosslinked nanogels (SC-NGs@Ins). Therefore, this intelligent insulin delivery system shows potential applications in diabetes treatment., (© 2024 Wiley‐VCH GmbH.)

Glucose-responsive closed-loop insulin delivery systems represent a promising treatment strategy for diabetes, but current systems generally cannot achieve long-term effects. In this study, we designed an erythrocyte-biomimetic glucose-responsive system (EGRS) by coupling glucose-responsive nanoparticles (GRNs) to red blood cells; these nanoparticles exhibited the dual functions of glucose-responsiveness and persistent presence in circulation. GRNs are generated by encapsulating with insulin through ion crosslinking, followed by coloading with glucose oxidase (GOx) and catalase (CAT), a process that endows the nanoparticles with glucose-responsiveness. Simultaneously, the GRNs are coupled with red blood cells to camouflage them from the immune system, therefore, these erythrocyte-coupled GRNs can circulate in the blood for a long time. Under conditions of hyperglycemia, GOx acts on blood glucose to produce gluconic acid, which causes the rupture of GRNs and efficient release of insulin. Conversely, insulin is only released at the basic rate during hypoglycemia. Thus, EGRS can efficiently and continuously respond to hyperglycemia to maintain blood glucose levels within the normal range. [ABSTRACT FROM AUTHOR]

• Ca2+ spiking in INS-1 cells can trigger simultaneous vesicle fusions. • Genetically encoded biosensors allow co-imaging of Ca2+ spiking and vesicle fusions. • Dual color total internal reflection fluorescence microscopy resolves processes. • Synchronization of Ca2+ spikes acutely triggering vesicle fusions is detectable. • Majority of fusion events is, however, not synchronized with Ca2+ spiking. The basal and glucose-induced insulin secretion from pancreatic beta cells is a tightly regulated process that is triggered in a Ca2+-dependent fashion and further positively modulated by substances that raise intracellular levels of adenosine 3′,5′-cyclic monophosphate (cAMP) or by certain antidiabetic drugs. In a previous study, we have temporally resolved the subplasmalemmal [Ca2+] i dynamics in beta cells that are characterized by trains of sharply delimited spikes, reaching peak values up to 5 µM. Applying total internal reflection fluorescence (TIRF) microscopy and synaptopHluorin to visualize fusion events of individual granules, we found that several fusion events can coincide within 50 to 150 ms. To test whether subplasmalemmal [Ca2+] i microdomains around single or clustered Ca2+ channels may cause a synchronized release of insulin-containing vesicles, we applied simultaneous dual-color TIRF microscopy and monitored Ca2+ fluctuations and exocytotic events in INS-1 cells at high frame rates. The results indicate that fusions can be triggered by subplasmalemmal Ca2+ spiking. This, however, does account for a minority of fusion events. About 90 %-95 % of fusion events either happen between Ca2+ spikes or incidentally overlap with subplasmalemmal Ca2+ spikes. We conclude that only a fraction of exocytotic events in glucose-induced and tolbutamide- or forskolin-enhanced insulin release from INS-1 cells is tightly coupled to Ca2+ microdomains around voltage-gated Ca2+ channels. [Display omitted] [ABSTRACT FROM AUTHOR]

Previous work demonstrated that arginine is one of the strongest insulin secretagogues. However, knowledge of the mechanisms linking chronic arginine metabolism with β‐cell function and insulin secretion is relatively limited. After preliminary selection of concentration according to the cell proliferation, the MIN6 pancreatic β‐cells were randomly assigned to culture in 0.04 mM (low‐arginine, LA), 0.4 mM (standard‐arginine, SA), or 8 mM arginine (high‐arginine, HA) for 24 h. Following the treatment, a combination of transcriptomics and metabolomics, together with a series of molecular biological tests were performed to investigate the responses of β‐cells to varied arginine availability. Our results showed that HA treatment reduced the chronic insulin releases, and LA and HA treatments decreased the glucose‐stimulated insulin secretions (GSIS) of β‐cells relative to the SA group (p < .05). Transcriptomics analysis indicated that LA administration significantly inhibited oxidative phosphorylation and ATP metabolic process but promoted DNA repair and mRNA processing in β‐cells, while HA administration affected ammonium ion metabolic process and mRNA export (p < .05). Both LA and HA regulated the expressions of genes involved in DNA replication, cell‐cycle phase transition, and response to oxidative stress (p < .05). Protein‐protein interaction and transcription factor analyses suggested that Trp53 and Nr4a2 genes may play key roles during arginine stimulation. On the contrary, metabolomics analysis demonstrated that the differentially expressed metabolites (DEM) of MIN6 β‐cells induced by LA were mainly enriched in glycerophospholipid metabolism, linoleic acid metabolism, and purine metabolism, while most DEMs between LA vs. SA comparison belonged to amino acid metabolism. When combined the three groups, co‐expression analysis suggested that insulin secretions had strong associations with L‐pyroglutamic acid, L‐glutamate, and creatine concentrations, while intracellular insulin contents were mainly correlated to L‐arginine, argininosuccinic acid, and phosphorylcholine. At last, integrated analysis of transcriptomics and metabolomics showed that glycerophospholipid metabolism, biosynthesis of unsaturated fatty acids, and amino acid metabolism were the most relevant pathways in β‐cells exposed to abnormal arginine supply. This descriptive bioinformatics analysis suggested that the disturbed carbohydrate, lipid, and amino acid metabolisms, as well as the increased apoptosis and elevated oxidative stress, contributed to the reduced insulin secretion and lower GSIS in β‐cells induced by LA or HA treatments, while some underlying mechanisms need to be further explored. [ABSTRACT FROM AUTHOR]

Glucagon‐like peptide‐1 (GLP‐1) receptor agonists are effective treatments for type 2 diabetes as they stimulate insulin release and promote weight loss through appetite suppression. Their main side effect is nausea. All approved GLP‐1 agonists are full agonists across multiple signalling pathways. However, selective engagement with specific intracellular effectors, or biased agonism, has been touted as a means to improve GLP‐1 agonists therapeutic efficacy. In this review, I critically examine how GLP‐1 receptor‐mediated intracellular signalling is linked to physiological responses and discuss the implications of recent studies investigating the metabolic effects of biased GLP‐1 agonists. Overall, there is little conclusive evidence that beneficial and adverse effects of GLP‐1 agonists are attributable to distinct, nonoverlapping signalling pathways. Instead, G protein‐biased GLP‐1 agonists appear to achieve enhanced anti‐hyperglycaemic efficacy by avoiding GLP‐1 receptor desensitisation and downregulation, partly via reduced β‐arrestin recruitment. This effect seemingly applies more to insulin release than to appetite regulation and nausea, possible reasons for which are discussed. At present, most evidence derives from cellular and animal studies, and more human data are required to determine whether this approach represents a genuine therapeutic advance. LINKED ARTICLES: This article is part of a themed issue on GLP1 receptor ligands (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.4/issuetoc [ABSTRACT FROM AUTHOR]

3D bioprinting additively assembles bio‐inks to manufacture tissue‐mimicking biological constructs, but with the typical building blocks limited to 1D filaments. Here, it is developed a voxelated bioprinting technique for the digital assembly of spherical particles (DASP), which are effectively 0D voxels—the basic unit of 3D structures. It is shown that DASP enables on‐demand generation, deposition, and assembly of viscoelastic bio‐ink droplets. A two‐parameter diagram is developed to outline the viscoelasticity of bio‐inks required for printing spherical particles of good fidelity. Moreover, a strategy is developed for engineering bio‐inks with independently controllable viscoelasticity and mesh size, two of the most important yet intrinsically coupled physical properties of biomaterials. Using DASP, mechanically robust, multiscale porous scaffolds composed of interconnected yet distinguishable hydrogel particles are created. Finally, it is demonstrated the application of the scaffolds in encapsulating human pancreatic islets for sustained responsive insulin release. Together with the knowledge of bio‐ink design, DASP might be used to engineer highly heterogeneous, yet tightly organized tissue constructs for therapeutic applications. [ABSTRACT FROM AUTHOR]

Pancreatic β-cells can secrete insulin via 2 pathways characterized as KATP channel -dependent and -independent. The KATP channel–independent pathway is characterized by a rise in several potential metabolic signaling molecules, including the NADPH/NADP+ ratio and α-ketoglutarate (αKG). Prolyl hydroxylases (PHDs), which belong to the αKG-dependent dioxygenase superfamily, are known to regulate the stability of hypoxia-inducible factor α. In the current study, we assess the role of PHDs in vivo using the pharmacological inhibitor dimethyloxalylglycine (DMOG) and generated β-cell-specific knockout (KO) mice for all 3 isoforms of PHD (β-PHD1 KO, β-PHD2 KO, and β-PHD3 KO mice). DMOG inhibited in vivo insulin secretion in response to glucose challenge and inhibited the first phase of insulin secretion but enhanced the second phase of insulin secretion in isolated islets. None of the β-PHD KO mice showed any significant in vivo defects associated with glucose tolerance and insulin resistance except for β-PHD2 KO mice which had significantly increased plasma insulin during a glucose challenge. Islets from both β-PHD1 KO and β-PHD3 KO had elevated β-cell apoptosis and reduced β-cell mass. Isolated islets from β-PHD1 KO and β-PHD3 KO had impaired glucose-stimulated insulin secretion and glucose-stimulated increases in the ATP/ADP and NADPH/NADP+ ratio. All 3 PHD isoforms are expressed in β-cells, with PHD3 showing the most distinct expression pattern. The lack of each PHD protein did not significantly impair in vivo glucose homeostasis. However, β-PHD1 KO and β-PHD3 KO mice had defective β-cell mass and islet insulin secretion, suggesting that these mice may be predisposed to developing diabetes. [ABSTRACT FROM AUTHOR]

Expanding the functions and applications of DNA by integrating noncanonical bases and structures into biopolymers is a continuous scientific effort. An adenine-rich strand (A-strand) is introduced as functional scaffold revealing, in the presence of the low-molecular-weight cofactor cyanuric acid (CA, p K a 6.9), supramolecular hydrogel-forming efficacies demonstrating multiple pH-responsiveness. At pH 1.2, the A-strand transforms into a parallel A-motif duplex hydrogel cross-linked by AH + -H + A units due to the protonation of adenine (p K a 3.5). At pH 5.2, and in the presence of coadded CA, a helicene-like configuration is formed between adenine and protonated CA, generating a parallel A-CA triplex cross-linked hydrogel. At pH 8.0, the hydrogel undergoes transition into a liquid state by deprotonation of CA cofactor units and disassembly of A-CA triplex into its constituent components. Density functional theory calculations and molecular dynamics simulations, supporting the structural reconfigurations of A-strand in the presence of CA, are performed. The sequential pH-stimulated hydrogel states are rheometrically characterized. The hydrogel framework is loaded with fluorescein-labeled insulin, and the pH-stimulated release of insulin from the hydrogel across the pH barriers present in the gastrointestinal tract is demonstrated. The results provide principles for future application of the hydrogel for oral insulin administration for diabetes.

The basal and glucose-induced insulin secretion from pancreatic beta cells is a tightly regulated process that is triggered in a Ca 2+ -dependent fashion and further positively modulated by substances that raise intracellular levels of adenosine 3',5'-cyclic monophosphate (cAMP) or by certain antidiabetic drugs. In a previous study, we have temporally resolved the subplasmalemmal [Ca 2+ ] i dynamics in beta cells that are characterized by trains of sharply delimited spikes, reaching peak values up to 5 µM. Applying total internal reflection fluorescence (TIRF) microscopy and synaptopHluorin to visualize fusion events of individual granules, we found that several fusion events can coincide within 50 to 150 ms. To test whether subplasmalemmal [Ca 2+ ] i microdomains around single or clustered Ca 2+ channels may cause a synchronized release of insulin-containing vesicles, we applied simultaneous dual-color TIRF microscopy and monitored Ca 2+ fluctuations and exocytotic events in INS-1 cells at high frame rates. The results indicate that fusions can be triggered by subplasmalemmal Ca 2+ spiking. This, however, does account for a minority of fusion events. About 90 %-95 % of fusion events either happen between Ca 2+ spikes or incidentally overlap with subplasmalemmal Ca 2+ spikes. We conclude that only a fraction of exocytotic events in glucose-induced and tolbutamide- or forskolin-enhanced insulin release from INS-1 cells is tightly coupled to Ca 2+ microdomains around voltage-gated Ca 2+ channels., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Aims/hypothesis: ZBED6 (zinc finger, BED-type containing 6) is known to regulate muscle mass by suppression of Igf2 gene transcription. In insulin-producing cell lines, ZBED6 maintains proliferative capacity at the expense of differentiation and beta cell function. The aim was to study the impact of Zbed6 knockout on beta cell function and glucose tolerance in C57BL/6 mice. Methods: Beta cell area and proliferation were determined in Zbed6 knockout mice using immunohistochemical analysis. Muscle and fat distribution were assessed using micro-computed tomography. Islet gene expression was assessed by RNA sequencing. Effects of a high-fat diet were analysed by glucose tolerance and insulin tolerance tests. ZBED6 was overexpressed in EndoC-βH1 cells and human islet cells using an adenoviral vector. Beta cell cell-cycle analysis, insulin release and mitochondrial function were studied in vitro using propidium iodide staining and flow cytometry, ELISA, the Seahorse technique, and the fluorescent probes JC-1 and MitoSox. Results: Islets from Zbed6 knockout mice showed lowered expression of the cell cycle gene Pttg1, decreased beta cell proliferation and decreased beta cell area, which occurred independently from ZBED6 effects on Igf2 gene expression. Zbed6 knockout mice, but not wild-type mice, developed glucose intolerance when given a high-fat diet. The high-fat diet Zbed6 knockout islets displayed upregulated expression of oxidative phosphorylation genes and genes associated with beta cell differentiation. In vitro, ZBED6 overexpression resulted in increased EndoC-βH1 cell proliferation and a reduced glucose-stimulated insulin release in human islets. ZBED6 also reduced mitochondrial JC-1 J-aggregate formation, mitochondrial oxygen consumption rates (OCR) and mitochondrial reactive oxygen species (ROS) production, both at basal and palmitate + high glucose-stimulated conditions. ZBED6-induced inhibition of OCR was not rescued by IGF2 addition. ZBED6 reduced levels of the mitochondrial regulator PPAR-γ related coactivator 1 protein (PRC) and bound its promoter/enhancer region. Knockdown of PRC resulted in a lowered OCR. Conclusions/interpretation: It is concluded that ZBED6 is required for normal beta cell replication and also limits excessive beta cell mitochondrial activation in response to an increased functional demand. ZBED6 may act, at least in part, by restricting PRC-mediated mitochondrial activation/ROS production, which may lead to protection against beta cell dysfunction and glucose intolerance in vivo. [ABSTRACT FROM AUTHOR]

Initiated by the specific binding between D‐glucose and biological receptors, the human body has a delicate metabolic system to regulate blood D‐glucose levels, but failing to release insulin would induce hyperglycemia or type I diabetes. While insulin delivery is an effective form of hyperglycemia therapy, the self‐regulated triggering of insulin release for on‐demand supplementation remains inadequate. Here, a biomimetic glucose trigger‐insulin release system, that is, a bidentate β‐cyclodextrin‐based hydrogel with preloaded insulin is presented; the dual self‐regulated system shows a specific D‐glucose response to realize accurate monitoring and simultaneous on‐demand trigger insulin release. The specific binding between D‐glucose and the bidentate β‐cyclodextrin induces the release of protons, causing macroscopic swelling of the hydrogel, subsequently triggering the on‐demand and long‐term supplementation of insulin. On the contrary, isomers of D‐glucose, such as D‐fructose and D‐galactose, cause shrinking of the hydrogel, and retard insulin release. In‐vivo studies in type I diabetic mice model ascertain that although the bidentate β‐CD hydrogel is preloaded with short‐activity insulin, it exerts long‐activity control of blood glucose level over 12 h. [ABSTRACT FROM AUTHOR]

Elevated intracellular cAMP concentrations potentiate insulin secretion from pancreatic β cells. Phosphodiesterase 3B (PDE3B) is highly expressed in these cells and plays a role in the regulation of insulin secretion. In this study, effects of amrinone, an inhibitor of PDE3B on insulin release from isolated pancreatic islets, were determined. Exposure of islets to amrinone for 15, 30 and 90 min markedly increased secretion induced by 6.7 mM glucose. Amrinone enhanced also secretion stimulated by 6.7 mM glucose and DB-cAMP, an activator of PKA. It was also demonstrated that amrinone potentiated insulin secretion induced by 6.7 mM glucose in the combination with PMA (activator of PKC) or acetylcholine. However, the insulin-secretory response to glucose and glibenclamide was unchanged by amrinone. These results indicate that amrinone is capable of increasing insulin secretion; however, its action is restricted. [ABSTRACT FROM AUTHOR]

Background/Aims: MicroRNAs (miRNAs) are a novel class of small RNAs that participate in a variety of biological processes. Although miRNAs have been linked to insulin synthesis and glucose homeostasis, their role in the targeting of mitochondrial uncoupling protein 2 (UCP2), a negative modulator of insulin secretion, remains unclear. Methods: miRNA levels were determined by real-time quantitative PCR analysis using TaqMan probes, and insulin secretion from isolated islets was quantified by ELISA. Effects of miRNAs on UCP2 expression were checked with a luciferase assay and western blotting analysis. Results: An overall change in a set of miRNAs was discovered, with miR-15a, miR-424, miR-497, and miR-185 coinciding with insulin levels in islets maintained under high-glucose conditions. Moreover, experiments in MIN6 cells illustrated that miR-15a, miR-424, miR-497, and miR-185 positively regulated insulin biosynthesis by co-inhibiting UCP2 expression. Furthermore, the four miRNAs were found to post-transcriptionally repress UCP2 expression by directly targeting the 3’UTR of UCP2 mRNA. Conclusions: Thus, our results shed further light on the regulatory network in β-cells consisting of miRNAs, UCP2, and insulin and provide novel therapeutic targets for diabetes.

The tolerability and efficacy of low-frequency, low-intensity therapeutic ultrasound-induced insulin release was investigated in a pre-clinical in vivo murine model. The treatment groups received a single 5-min continuous sonication at 1 MHz and 1.0 W/cm2. Insulin and glucagon levels in the serum were determined using enzyme-linked immunosorbent assay. The pancreas was excised and sectioned for histologic analysis. In terminal studies, we observed a moderate (∼50 pM) but significant increase in blood insulin concentration in vivo immediately after sonication compared with a decrease of approximately 60 pM in sham animals (n < 6, p < 0.005). No difference was observed in the change in glucose or glucagon concentrations between groups. Comparisons of hematoxylin and eosin-stained terminal and survival pancreatic tissue revealed no visible differences or evidence of damage. This study is the first step in assessing the translational potential of therapeutic ultrasound as a treatment for early stages of type 2 diabetes. [ABSTRACT FROM AUTHOR]

The study investigates conformational analysis and the in vitro cytokine-mediated immunomodulatory and insulin-releasing activities of rhinophrynin-27 (ELRLPEIARPVPEVLPARLPLPALPRN; RP-27), a proline-arginine-rich peptide first isolated from skin secretions of the Mexican burrowing toad Rhinophrynus dorsalis (Rhinophrynidae). In both water and 50% trifluoroethanol-water, the peptide adopts a polyproline type II helical conformation with a high degree of deviation from the canonical collagen-like folding and a pronounced bend in the molecule at the Glu13 residue. Incubation of mouse peritoneal cells with RP-27 significantly (P < 0.05) inhibited production of the pro-inflammatory cytokines TNF-α and IL-1β and stimulated production of the anti-inflammatory cytokine IL-10. The peptide significantly (P < 0.01) stimulated release of insulin from BRIN-BD11 rat clonal β-cells at concentrations ≥ 1 nM while maintaining the integrity of the plasma membrane and also stimulated insulin release from isolated mouse islets at a concentration of 10−6 M. Increasing the cationicity of RP-27 by substituting glutamic acid residues in the peptide by arginine and increasing hydrophobicity by substituting alanine residues by tryptophan did not result in analogues with increased activity with respect to cytokine production and insulin release. The combination of immunosuppressive and insulinotropic activities together with very low cytotoxicity suggests that RP-27 may represent a template for the development of an agent for use in anti-inflammatory and Type 2 diabetes therapies. Image 1 • In water and 50% TFE-water, RP-27 adopts a polyproline type II helical conformation. • The conformation contains a marked bend at the site of E13. • RP-27 inhibited production of TNF-α and IL-1β and stimulated production of IL-10. • RP-27stimulated release of insulin from BRIN-BD11 clonal β-cells at concentrations ≥1 nM. [ABSTRACT FROM AUTHOR]

Clonal insulin-secreting BRIN-BD11 cells were used to examine effects of chronic 72-144 h exposure to the sulphonylureas tolbutamide and glibenclamide on insulin release, cellular insulin content, and mRNA levels of the Kir6.2 and SUR1 subunits of the beta-cell KATP channel. Chronic exposure for 72-144 h to 5-100 µM tolbutamide and glibenclamide resulted in a time- and concentration-dependent irreversible decline in sulphonylurea-induced insulin secretion. In contrast, the decline in cellular insulin content induced by chronic exposure to high concentrations of sulphonylureas was readily reversible. Chronic exposure to tolbutamide or glibenclamide had no effect upon transcription of the Kir6.2 or SUR1 subunits of the pancreatic beta-cell KATP channel. Whilst further studies are required to understand the precise nature of the chronic interactions of sulphonylurea with the insulin exocytotic mechanism, these observations may partially explain the well-known progressive failure of sulphonylurea therapy in type 2 diabetes.

Abstract Background One of the most common side effects of the immunosuppressive drug tacrolimus (FK506) is the increased risk of new-onset diabetes mellitus. However, the molecular mechanisms underlying this association have not been fully clarified. Methods We studied the effects of the therapeutic dose of tacrolimus on mitochondrial fitness in beta-cells. Results We demonstrate that tacrolimus impairs glucose-stimulated insulin secretion (GSIS) in beta-cells through a previously unidentified mechanism. Indeed, tacrolimus causes a decrease in mitochondrial Ca2+ uptake, accompanied by altered mitochondrial respiration and reduced ATP production, eventually leading to impaired GSIS. Conclusion Our observations individuate a new fundamental mechanism responsible for the augmented incidence of diabetes following tacrolimus treatment. Indeed, this drug alters Ca2+ fluxes in mitochondria, thereby compromising metabolism-secretion coupling in beta-cells.

Background: The rapidly increasing use of mobile phones has led to public concerns about possible health effects of these popular communication devices. This study is an attempt to investigate the effects of radiofrequency (RF) radiation produced by GSM mobile phones on the insulin release in rats. Methods: Forty two female adult Sprague Dawley rats were randomly divided into 4 groups. Group1 were exposed to RF radiation 6 hours per day for 7 days. Group 2 received sham exposure (6 hours per day for 7 days). Groups 3 and 4 received RF radiation 3 hours per day for 7 days and sham exposure (3 hours per day), respectively. The specific absorption rate (SAR) of RF was 2.0W/kg. Results: Our results showed that RF radiations emitted from mobile phone could not alter insulin release in rats. However, mild to severe inflammatory changes in the portal spaces of the liver of rats as well as damage in the cells of islet of Langerhans were observed. These changes were linked with the duration of the exposures. Conclusion: RF exposure can induce inflammatory changes in the liver as well causing damage in the cells of islet of Langerhans.

Given the global epidemic in type 2 diabetes, novel antidiabetic drugs with increased efficacy and reduced side effects are urgently needed. Previous work has shown that M3 muscarinic acetylcholine (ACh) receptors (M3Rs) expressed by pancreatic β cells play key roles in stimulating insulin secretion and maintaining physiological blood glucose levels. In the present study, we tested the hypothesis that a positive allosteric modulator (PAM) of M3R function can improve glucose homeostasis in mice by promoting insulin release. One major advantage of this approach is that allosteric agents respect the ACh-dependent spatiotemporal control of M3R activity. In this study, we first demonstrated that VU0119498, a drug known to act as a PAM at M3Rs, significantly augmented ACh-induced insulin release from cultured β cells and mouse and human pancreatic islets. This stimulatory effect was absent in islets prepared from mice lacking M3Rs, indicative of the involvement of M3Rs. VU0119498 treatment of wild-type mice caused a significant increase in plasma insulin levels, accompanied by a striking improvement in glucose tolerance. These effects were mediated by β-cell M3Rs, since they were absent in mutant mice selectively lacking M3Rs in β cells. Moreover, acute VU0119498 treatment of obese, glucose-intolerant mice triggered enhanced insulin release and restored normal glucose tolerance. Interestingly, doses of VU0119498 that led to pronounced improvements in glucose homeostasis did not cause any significant side effects due to activation of M3Rs expressed by other peripheral cell types. Taken together, the data from this proof-of-concept study strongly suggest that M3R PAMs may become clinically useful as novel antidiabetic agents. [ABSTRACT FROM AUTHOR]

The naturally occurring quassinoid compound brusatol improves the survival of insulin-producing cells when exposed to the proinflammatory cytokines IL-1β and IFN-γ in vitro. The aim of the present study was to investigate whether brusatol also promotes beneficial effects in mice fed a high-fat diet (HFD), and if so, to study the mechanisms by which brusatol acts. In vivo, we observed that the impaired glucose tolerance of HFD-fed male C57BL/6 mice was counteracted by a 2 wk treatment with brusatol. Brusatol treatment improved both β-cell function and peripheral insulin sensitivity of HFD-fed mice. In vitro, brusatol inhibited β-cell total protein and proinsulin biosynthesis, with an ED50 of ~40 nM. In line with this, brusatol blocked cytokine-induced iNOS protein expression via inhibition of iNOS mRNA translation. Brusatol may have affected protein synthesis, at least in part, via inhibition of eukaryotic initiation factor 5A (eIF5A) hypusination, as eIF5A spermidine association and hypusination in RIN-5AH cells was reduced in a dose- and time-dependent manner. The eIF5A hypusination inhibitor GC7 promoted a similar effect. Both brusatol and GC7 protected rat RIN-5AH cells against cytokine-induced cell death. Brusatol reduced eIF5A hypusination and cytokine-induced cell death in EndoC-βH1 cells as well. Finally, hypusinated eIF5A was reduced in vivo by brusatol in islet endocrine and endothelial islet cells of mice fed an HFD. The results of the present study suggest that brusatol improves glucose intolerance in mice fed an HFD, possibly by inhibiting protein biosynthesis and eIF5A hypusination. [ABSTRACT FROM AUTHOR]

Abstract Designing strategies for the use of biopolymer-based nanoparticles as drug delivery carriers is a considerable challenge in pharmaceutical science. Present study reports synthesis of a novel glucose responsive and in-vitro pH triggered insulin delivery system comprised of glucose oxidase immobilized on acryloyl crosslinked dextran dialdehyde (ACDD) nanoparticles. Scanning electron microscopy, transmission electron microscopy and particle size analysis data revealed that these carriers possess nanosize which is an important parameter for drug delivery applications. In-vitro insulin release studies were performed under artificial gastric fluid (AGF, pH 1.2) and artificial intestinal fluid conditions (AIF, pH 7.4) at physiological temperature (37 °C). Insulin release profile showed controlled release of about 70% under AIF conditions for 24 h. Insulin release mechanism studied using different kinetic models revealed that Korsmeyer-Peppas model appropriately explained the mechanism as ʻnon-Fickian' diffusion release of insulin. These glucose responsive stimuli sensitive nanocarriers exhibited controlled release of about 90% under AIF conditions in the presence of glucose. These findings revealed that these nanoparticles are promising and reliable delivery systems to overcome problems related with subcutaneous insulin therapy. Graphical abstract Unlabelled Image Highlights • Glucose oxidase immobilized-acryloyl crosslinked dextran dialdehyde (ACDD) nanoparticles were synthesized. • Synthesized nanoparticles studied for in-vitro insulin release • Nanoparticles exhibited controlled release (70%) under pH 7.4 for 24 h. • Nanocarriers behaved as cost-effective and biocompatible glucose sensitive insulin carriers. [ABSTRACT FROM AUTHOR]

Key points: A paternal high‐fat diet/obesity before mating can negatively influence the metabolism of offspring.Exercise only early in life has a remarkable effect with respect to reprogramming adult rat offspring exposed to detrimental insults before conception.Exercise only early in life normalized adult whole body and muscle insulin resistance as a result of having a high‐fat fed/obese father.Unlike the effects on the muscle, early exercise did not normalize the reduced adult pancreatic beta cell mass as a result of having a high‐fat fed/obese father.Early‐life exercise training may be able to reprogram an individual whose father was obese, inducing long‐lasting beneficial effects on health. A paternal high‐fat diet (HFD) impairs female rat offspring glucose tolerance, pancreatic morphology and insulin secretion. We examined whether only 4 weeks of exercise early in life could reprogram these negative effects. Male Sprague–Dawley rats consumed a HFD for 10 weeks before mating with chow‐fed dams. Female offspring remained sedentary or performed moderate intensity treadmill exercise (5 days week−1, 60 min day−1, 20 m min−1) from 5 to 9 weeks of age. Paternal HFD impaired (P < 0.05) adult offspring whole body insulin sensitivity (i.p. insulin sensitivity test), as well as skeletal muscle ex vivo insulin sensitivity and TBC1D4 phosphorylation. It also lowered β‐cell mass and reduced in vivo insulin secretion in response to an i.p. glucose tolerance test. Early‐life exercise in offspring reprogrammed the negative effects of a paternal HFD on whole body insulin sensitivity, skeletal muscle ex vivo insulin‐stimulated glucose uptake and TBC1D4 phosphorylation and also increased glucose transporter 4 protein. However, early exercise did not normalize the reduced pancreatic β‐cell mass or insulin secretion. In conclusion, only 4 weeks of exercise early in life in female rat offspring reprograms reductions in insulin sensitivity in adulthood caused by a paternal HFD without affecting pancreatic β‐cell mass or insulin secretion. Key points: A paternal high‐fat diet/obesity before mating can negatively influence the metabolism of offspring.Exercise only early in life has a remarkable effect with respect to reprogramming adult rat offspring exposed to detrimental insults before conception.Exercise only early in life normalized adult whole body and muscle insulin resistance as a result of having a high‐fat fed/obese father.Unlike the effects on the muscle, early exercise did not normalize the reduced adult pancreatic beta cell mass as a result of having a high‐fat fed/obese father.Early‐life exercise training may be able to reprogram an individual whose father was obese, inducing long‐lasting beneficial effects on health. [ABSTRACT FROM AUTHOR]

Background/Aims: In pancreatic β-cells, the intracellular Ca2+ homeostasis is an essential regulator of the cells’ major functions. The endoplasmic reticulum (ER) as interactive intracellular Ca2+ store balances cellular Ca2+. In this study basal ER Ca2+ homeostasis was evaluated in order to reveal potential β-cell-specificity of ER Ca2+ handling and its consequences for mitochondrial Ca2+, ATP and respiration. Methods: The two pancreatic cell lines INS-1 and MIN-6, freshly isolated pancreatic islets, and the two non-pancreatic cell lines HeLA and EA.hy926 were used. Cytosolic, ER and mitochondrial Ca2+ and ATP measurements were performed using single cell fluorescence microscopy and respective (genetically-encoded) sensors/dyes. Mitochondrial respiration was monitored by respirometry. GSK3β activity was measured with ELISA. Results: An atypical ER Ca2+ leak was observed exclusively in pancreatic islets and β-cells. This continuous ER Ca2+ efflux is directed to mitochondria and increases basal respiration and organellar ATP levels, is established by GSK3β-mediated phosphorylation of presenilin-1, and is prevented by either knockdown of presenilin-1 or an inhibition/knockdown of GSK3β. Expression of a presenlin-1 mutant that mimics GSK3β-mediated phosphorylation established a β-cell-like ER Ca2+ leak in HeLa and EA.hy926 cells. The ER Ca2+ loss in β-cells was compensated at steady state by Ca2+ entry that is linked to the activity of TRPC3. Conclusion: Pancreatic β-cells establish a cell-specific ER Ca2+ leak that is under the control of GSK3β and directed to mitochondria, thus, reflecting a cell-specific intracellular Ca2+ handling for basal mitochondrial activity. [ABSTRACT FROM AUTHOR]

Ghrelin, a 28-amino acid peptide, is a strong growth hormone secretagogue and a regulator of food intake. In addition, ghrelin is thought to play a role in insulin secretion and in glucose homeostasis. A lot of contradictory data have been reported in the literature regarding the co-localization of ghrelin with other hormones in the islet of Langerhans, its role in insulin secretion and attenuation of type 2 diabetes mellitus. In this study, we investigate the effect of chronic ghrelin treatment on glucose, body weight and insulin level in normal and streptozotocin-induced diabetic male Wistar rats. We have also examined the distribution pattern and co-localization of ghrelin with insulin in pancreatic islet cells using immunohistochemistry and immune-electron microscopy and the ability of ghrelin to stimulate insulin release from the CRL11065 beta cell line. Control, non-diabetic groups received intraperitoneal injection of normal saline, while treated groups received intraperitoneal injection of 5 µg/kg body weight of ghrelin (amino acid chain 24–51) on a daily basis for a duration of four weeks. Our results show that the administration of ghrelin increases the number of insulin-secreting beta cells and serum insulin level in both normal and diabetic rats. We also demonstrated that ghrelin co-localizes with insulin in pancreatic islet cells and that the pattern of ghrelin distribution is altered after the onset of diabetes. Moreover, ghrelin at a dose of 10−6 M and 10−12 M increased insulin release from the CRL11065 beta cell line. In summary, ghrelin co-localizes with insulin in the secretory granules of pancreatic beta cells and enhances insulin production.