Islet Size Research Articles

Chronic Fetal Leucine Infusion Does Not Potentiate Glucose-Stimulated Insulin Secretion or Affect Pancreatic Islet Development in Late-Gestation Growth-Restricted Fetal Sheep

Growth-restricted fetuses have attenuated glucose-stimulated insulin secretion (GSIS), smaller pancreatic islets, less pancreatic β-cells, and less pancreatic vascularization compared with normally growing fetuses. Infusion of leucine into normal late-gestation fetal sheep potentiates GSIS, as well as increases pancreatic islet size, the proportion of the pancreas and islet comprising β-cells, and pancreatic and islet vascularity. In addition, leucine stimulates hepatocyte growth factor (HGF ) mRNA expression in islet endothelial cells isolated from normal fetal sheep. We hypothesized that a 9-d leucine infusion would potentiate GSIS and increase pancreatic islet size, β-cells, and vascularity in intrauterine fetal growth restriction (IUGR) fetal sheep. We also hypothesized that leucine would stimulate HGF mRNA in islet endothelial cells isolated from IUGR fetal sheep. Late-gestation Columbia-Rambouillet IUGR fetal sheep (singleton or twin) underwent surgeries to place vascular sampling and infusion catheters. Fetuses were randomly allocated to receive a 9-d leucine infusion to achieve a 50-100% increase in leucine concentrations or a control saline infusion. GSIS was measured and pancreas tissue was processed for histologic analysis. Pancreatic islet endothelial cells were isolated from IUGR fetal sheep and incubated with supplemental leucine. Data were analyzed by mixed-models ANOVA; Student, Mann-Whitney, or a paired t test; or a test of equality of proportions. Chronic leucine infusion in IUGR fetuses did not affect GSIS, islet size, the proportion of the pancreas comprising β-cells, or pancreatic or pancreatic islet vascularity. In isolated islet endothelial cells from IUGR fetuses, HGF mRNA expression was not affected by supplemental leucine. IUGR fetal sheep islets are not responsive to a 9-d leucine infusion with respect to insulin secretion or any histologic features measured. This is in contrast to the response in normally growing fetuses. These results are important when considering nutritional strategies to prevent the adverse islet and β-cell consequences in IUGR fetuses.

Effects of sustained GABA releasing implants on pancreatic islets in mice.

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that is strongly and selectively synthesized in and secreted from pancreatic beta cells. Exogenously delivered GABA has been proposed to induce beta cell regeneration in type 1 diabetes, but these results have been difficult to replicate and may depend on the specifics of the animal model and drug delivery method used. Here, we developed a GABA-releasing ethylene-vinyl acetate polymer implant for sustained GABA delivery to the intraperitoneal space as an alternative to injected or oral GABA. We explored the effect of the GABA-releasing polymer implantscompared to implanted osmotic pumps loaded with GABA on islet size in non-diabetic, outbred mice. We also attempted to monitor in vivo GABA release using HPLC on blood samples, but these measurements were confounded by high variability within treatment groups and unexpectedly high serum GABA levels in mice receiving GABA-negative implants. The ethylene-vinyl acetate polymer implants became heavily fibrosed with abdominal adhesion tissue, while the osmotic pumps had no macroscopic fibrosis. Histological analysis showed no significant effect of the sustained GABA delivery polymer or osmotic pumps on islet size, alpha cell to beta cell ratio, or the number of Ki67-positive islet cells. The GABA treatment time course was limited to two weeks due to the drug-release window of the polymer, while others reported islet-trophic effects of GABA after 10 to 12 weeks of treatment. In summary, our study is consistent with the concept that exogenous GABA administration does not significantly alter islet cell mass in non-diabetic CD-1 mice in the short-term. However, more data are needed including higher GABA doses and more prolonged treatment regimens for a better comparison with contrasting reports.

Anti-hyperglycaemic and insulin-releasing effects of Camellia sinensis leaves and isolation and characterisation of active compounds.

Anti-diabetic actions of Camellia sinensis leaves, used traditionally for type 2 diabetes (T2DM) treatment, have been determined. Insulin release, membrane potential and intra-cellular Ca were studied using the pancreatic β-cell line, BRIN-BD11 and primary mouse pancreatic islets. Cellular glucose-uptake/insulin action by 3T3-L1 adipocytes, starch digestion, glucose diffusion, dipeptidyl peptidase-4 (DPP-IV) activity and glycation were determined together with in vivo studies assessing glucose homoeostasis in high-fat-fed (HFF) rats. Active phytoconstituents with insulinotropic activity were isolated using reversed-phase HPLC, LCMS and NMR. A hot water extract of C. sinensis increased insulin secretion in a concentration-dependent manner. Insulinotropic effects were significantly reduced by diazoxide, verapamil and under Ca-free conditions, being associated with membrane depolarisation and increased intra-cellular Ca2+. Insulin-releasing effects were observed in the presence of KCl, tolbutamide and isobutylmethylxanthine, indicating actions beyond K+ and Ca2+ channels. The extract also increased glucose uptake/insulin action in 3T3L1 adipocyte cells and inhibited protein glycation, DPP-IV enzyme activity, starch digestion and glucose diffusion. Oral administration of the extract enhanced glucose tolerance and insulin release in HFF rats. Extended treatment (250 mg/5 ml per kg orally) for 9 d led to improvements of body weight, energy intake, plasma and pancreatic insulin, and corrections of both islet size and β-cell mass. These effects were accompanied by lower glycaemia and significant reduction of plasma DPP-IV activity. Compounds isolated by HPLC/LCMS, isoquercitrin and rutin (464·2 Da and 610·3 Da), stimulated insulin release and improved glucose tolerance. These data indicate that C. sinensis leaves warrant further evaluation as an effective adjunctive therapy for T2DM and source of bioactive compounds.

Chronological study in microanatomy of human foetal pancreatic tissue

Introduction: The name of pancreas derives from the Greek’ word. The pancreas involves in diseases like diabetes mellitus and pancreatic cancer. It is contains Endocrine cells or Islets of Langerhans that secrete insulin, glucagon and somatostatin, which regulate blood glucose levels.1 The exocrine pancreatic acini secretes pancreatic enzymes and alpha fetoprotein which change the expression level during development and influences development and differentiation of pancreas.2 Endocrine disease causes diabetes which affects at least 200 million people worldwide, and this number is to be doubled by 2025.1 The exocrine part leads to pancreatic cancer causing about 65,000 deaths in European countries which is virtually incurable. Aims: The purpose of the current study was to investigate microanatomy (Histogenesis) of Pancreas in aborted fresh human foetuses without any congenital abnormality. So the present study was conducted to know the development of acini and islets and their clinical correlation. Materials and Methods: Foetuses aged between 12 to 40 weeks of gestational age and they were collected from Obstetrics and Gynaecology department of Kamineni Institute of Medical Sciences, Narkatpally, Nalgonda (Dt), Telangana, (India) and Kamineni Academy of Medical Sciences and Research centre, L.B. Nagar, Hyderabad. The histogenic procedures were employed at all gestational ages and were discussed with the available literature because various studies have proved that the islets of pancreas are necessary for the transplantation of pancreas, but very few studies showed the importance of pancreatic acini. Results and Conclusion: In the early weeks (12-18 weeks) the parenchyma forms primitive tubules with small lobes and lobules of acini and small spherical islets. As the age advances (18-24 weeks) the size and number of Islets are increased with encapsulation and proliferation of acinar cells. To conclude, at the age of 18-24 weeks the fetal pancreas is suitable for organ transplantation in patients with diabetes mellitus and pancreatic cancer. Keywords: Histogenesis, Gestational period, Pancreas, Serous acini, Islets of Langerhans, Microanatomy, Ducts, Alpha fetoprotein (AFP).

Role Of Vitamin D Deficiency On Induction Of Diabetes in Albino Rats

Background: Vitamin D3 has the potential to modulate both endocrine and immune system. Evidence increased on non-classical role of vitamin D in many autoimmune diseases. Vitamin D deficiency is considered as a global health problem and has been suggested based on animal studies to be associated with prevalence of glucose intolerance.Aim: Investigate the effect of vit. D deficiency on the blood glucose level and the structure of pancreas of albino rat.Material and methods:Thirty adult male, Sprague Dawley, albino rats were used in the current study, and were divided into two groups; Group I (Control) was fed vit. D balanced diet and exposed to sun light, and Group II was fed vit. D deficient diet and deprived from sun light exposure. Group II was further subdivided into IIa which was sacrificed after 1 month and IIb which was sacrificed after 2 months. Pancreata were collected from all group and prepared for histopathological examination. Morphometric measurements were done using image analyzer and blood glucose level was measured and all data were statistically analyzed. Results: Group IIa showed fewer and smaller islets of Langerhans compared with those of the control group while Group IIb showed marked decrease in the number and size of islets of Langerhans with disfigurement. Blood glucose level of group IIb showed highly significant increase compared to the control.Conclusion: there is an inverse correlation between serum vitamin D and insulin resistance. Persistent vitamin D deficiency status may lead to metabolic disorders including insulin resistance and raised blood glucose.

Hypoglycemic, antidyslipidemic and antioxydant effects of Vitellaria paradoxa barks extract on high-fat diet and streptozotocin-induced type 2 diabetes rats

BackgroudVitellaria paradoxa is a plant belonging to the Sapotaceae family and used in traditional medicine in the treatment of diabetes mellitus. The aim of this work was to evaluate the hypoglycemic, antidyslipidemic and antioxidant effects of V. paradoxa on type 2 diabetic rats. MethodsTo induce type 2 diabetes mellitus (T2DM), animals were fed a high-fat diet for 4 weeks followed by an intraperitoneal injection of 35 mg/kg of streptozotocin. Diabetic rats were divided into groups and treated for 28 days with V. paradoxa extract (AEVP) at doses of 125, 250 and 500 mg/kg. Body weight, urine volume, food and water consumption were assessed at the start and end of treatment. The glucose tolerance test was performed on the last day of treatment. Blood samples were taken for the assay of biochemical parameters, organs (kidneys and liver) for markers of oxidative stress and pancreas for histological sections. ResultsAEVP (250 and 500 mg/kg) improved the drop in body weight, polyphagia, polydipsia and polyuria in diabetic rats. AEVP significantly reduced the concentrations of glucose, total cholesterol, triacylglycerol, urea, creatinine, activities of transaminases, and increased the levels of high density lipoprotein cholesterol and serum insulin. AEVP resulted in a decrease in malondialdehyde levels and an increase in catalase and superoxide dismutase activities. An increase in the size and number of islets in the pancreas has also been observed after administration of the extract. ConclusionAEVP has antidiabetic, antidyslipidemic and antioxidant properties, thus confirming its traditional use for the treatment of diabetes. These effects could be due to the presence of phytoconstituents, phenols and flavonoids presents in the plant extract.

Influence of Ocimum sanctum (L.) Extract on the Activity of Gliclazide in Alloxan-induced Diabetes in Rats

Ocimum sanctum L. is widely used as traditional remedy to manage hyperglycemia. This study was aimed to evaluate the effect of aqueous-methanolic extract of O. sanctum leaves (OSE) on the anti-diabetic activity of gliclazide in alloxan-induced diabetes in Wistar rats. Diabetes was induced by intraperitoneally injecting alloxan (120 mg/kg b.w.) in rats. Treatments including OSE (100 mg/kg b.w.), gliclazide (100 mg/kg b.w.), and in combination were given daily to diabetic rats till the 21st day of study. Body weight and fasting blood glucose levels were determined at regular intervals, while blood and organ samples were taken at the end of the study for biochemical and histopathological studies. Results showed that treatments exhibited anti-hyperglycemic activity through significantly (p [ 0.05) restoring body weight, fasting blood glucose level, and serum levels of glucose, insulin and HbA1c. The anti-lipidemic activity was noticed as total cholesterol (TC), triglyceride (TG), high-/low density-lipoproteins (HDL-C, LDL-C) levels were restored in treated diabetic rats. Ameliorative effects of treatments were observed as significant (p [ 0.05) reduction in serum levels of liver function biomarkers (alanine aminotransferase; ALT, aspartate aminotransferase; AST, alkaline phosphatase; ALP and bilirubin; BIL) and restoration of oxidative stress biomarkers (catalase; CAT, superoxide dismutase; SOD and malondialdehyde; MDA) in liver tissue. Histopathological findings supported these results as an increase in pancreatic islets size and protective effects on liver tissue was observed in diabetic rats treated with gliclazide and OSE alone and their combination. Conclusively, the combination of OSE and gliclazide produced a synergistic anti-diabetic effect as compared to that of alone treatment.

Hypoglycemic activity of the ethyl acetate extract from Smilax glabra Roxb in mice: Biochemical and histopathological studies.

Objective(s):This research was carried out to investigate the hypoglycemic activity of the ethyl acetate (EtOAc) extract from the roots of Smilax glabra Roxb, which strongly exhibit inhibitory activity against α-glucosidase and α-amylase on in vivo type 2 diabetic model. Materials and Methods:Column chromatography combined with crystallization was used to isolate the active fraction and compounds. Chemical structures of the compounds were determined based on the analysis of the spectroscopic data and comparison with the literature data. The α-glucosidase inhibitory activity (AGI) and the α-amylase inhibitory activity (AAI) were determined quantitatively spectrophotometrically using p-nitrophenyl α-D-glucopyranoside and soluble starch as substrates, respectively. The hypoglycemic activity was examined by evaluating its effects on glucose and insulin levels, insulin resistance, and histopathology of the pancreatic islets and livers in diabetic induced mice administrated with nicotinamide-streptozotocin. Results:The EtOAc extract and the bioactive compounds astilbin and 5-O-caffeoylshikimic acid in the extract were isolated and confirmed in structures, AGI, and AAI. The treatment at the doses of 500 and 1000 µg/kg of body weight reduced blood glucose levels down to the physiological level of the physical controls in the diabetic mice after two weeks (P<0.05). Moreover, the treatment improved insulin sensitivity. Histopathology analysis showed recovering effects in the size of the pancreatic islets and no damaging effects on the liver after treatment compared with the control group. Conclusion:Our data suggest that the EtOAc extract possesses hypoglycemic activity and has an antidiabetic potential for therapeutic applications.

Abstract 15122: Il18 Uses Both Il18 Receptor and Na-cl Co-transporter to Support Islet β Cell Proliferation and Insulin Secretion

Introduction: The regeneration of pancreatic β cells to restore insulin production is a promising therapeutic strategy for insulin-dependent type-1 (T1D) and type-2 diabetes (T2D). Plasma IL18 levels are increased in these patients. Prior studies suggest a role for IL18 in inducing islet insulin production. IL18 administration suppressed autoimmune diabetes in non-obese diabetic mice. We recently discovered that IL18 uses two receptors IL18r and NCC (Na-Cl co-transporter) with equal binding kinetics. Hypothesis: IL18r and NCC use different mechanisms to mediate IL18 activity in islet β cell insulin production. Methods and Results: Immunoblot and immunofluorescent staining localized IL18 on islet α cells, NCC on islet β cells, and IL18r on pancreas acinar cells. Development of T1D or T2D increased the α cell IL18 expression. From high fat diet (HFD)-induced T2D, deficiency of IL18r ( Il18r -/- ) or NCC ( Ncc -/- ), or combined deficiency of both receptors ( Il18r -/- Ncc -/- ) reduced insulin secretion, exacerbated β cell failure, decreased α cell content, reduced islet size, reduced β cell proliferation, and decreased the expression of islet proliferation markers. Deficiency of IL18r in Il18r -/- and Il18r -/- Ncc -/- mice aggravated β cell content and size reductions and glucose metabolism and increased β cell apoptosis after streptozotocin (STZ)-induced T1D. Il18r -/- Ncc -/- mice also showed increased macrophage accumulation in the islets from both T1D and T2D mice. Using α cell-selective IL18-deficient Gcg CreERT2 IL18 fl/fl mice, acinar cell-selective IL18r-deficient Mist1 CreERT2 Il18r fl/fl mice, and β cell NCC-deficient Ins1 Cre Ncc fl/fl mice, we demonstrated that these mice showed impaired insulin secretion and glucose metabolism, exacerbated β cell failure, and aggravated HFD-induced T2D. Mechanistic studies suggested that IL18 uses NCC on β cells to promote insulin secretion and uses IL18r on acinar cells to assist β cell development. Conclusions: Islet α cell IL18 uses NCC on β cells to promote β cell proliferation and uses IL18r on acinar cells to produce inflammatory molecules to assist β cell generation and insulin secretion. Both the IL18r and NCC signaling pathways are essential to β cell function in diabetic patients.

NANOCHROMIUM CITRATE: ANTIHYPERGLYCEMIC AND PANCREATOPROTECTIVE ACTION AGAINST UNDERLYING DEXAMETHASONE-INDUCED DIABETES MELLITUS

INTRODUCTION: The Ukrainian State Scientific-Research Institute of Nanobiotechnology and Resources Saving has received nanochromium citrate (NCC), a new chrome compound, by means of the electric pulse aquananotechnology method.&#x0D; &#x0D; OBJECTIVES: to determine nanochromium citrate efficacy with experimental dexamethasone-induced diabetes through the results of antihyperglycemic activity and its effect on the pancreatic histological structure.&#x0D; &#x0D; METHODS: diabetes mellitus was simulated by dexamethasone administration on 18-month male rats. The morphological structure of the pancreas was examined in comparison with metformin. Examination of the pancreas morphological structure considered the amount, distribution and size of the pancreatic islets and their cellular shape.&#x0D; &#x0D; RESULTS: on the 14th day of simulated diabetes mellitus the preventitive -therapeutic indication of nanochromium citrate promoted a decrease of glycemia level twice. The administration of nanochromium citrate with underlying diabetes mellitus is not inferior to metformin and its protective effect on the pancreas morphological structure exceeds the effect of metformin.&#x0D; &#x0D; CONCLUSION: nanochromium citrate of experimental dexamethasone-induced diabetes mellitus in rats decreases the glycemia level twice which does not differ reliably from the effect of metformin antihyperglycemic. The cytoprotective effect of nanochromium citrate produced on the histological structure of the pancreas is found to exceed metformin action.

Morphometric Study of Changes in GAD 65 Expressing Beta Cell Mass In The Islets Of Langerhans In Pregnant Mice

INTRODUCTION: This study explored the adaptive changes in pancreatic islets by assessing the maternal pancreatic β-cell mass (PβCM), islets size, number, shape, distribution and vascularity using the anti-GAD65 Ab as a marker in pregnant mice. MATERIALS AND METHODS: Fourty female Swiss-Webster mice were randomly divided into two age matched groups of 20 animals each, pregnant and control (non-pregnant) groups. The pregnant mice were sacrificed at Day 19 of gestation and the control group was sacrificed 19 days after observation in the same environmental conditions. Specimens of pancreata were fixed in 10% formal-saline, and processed for light microscopy. Paraffin sections were stained with chromogen DAB. Image scope (APERIO) with Image J software was used for morphometric study. RESULTS: Islets cells showed specific reaction with GAD65 Ab. There was an increase in the cellularity and vascularity of the PβCM. A significant increase in the islets area of the pregnant group ranging between 32-723 µm2 in comparison with the control group that ranged between 5–210 µm2 , the islet size and numbers also increased; there were numerous newly formed islets and coalescence of adjacent islets, positive reactivity of β-cells toward antiGAD65 during pregnancy, the mean of positive granulation in PβCM in pregnant group was 8273.5±SE 831.35 while in control group was 34±SE 0.2. CONCLUSION: The changes for alteration in PβCM such as increase in cells number, size, positive anti-GAD65 reactivity and their vascularity during pregnancy is related to the adaptation for hormonal and nutritional demands of both foetus and mother.

Gestational diabetes adversely affects pancreatic islet architecture and function in the male rat offspring

Fetal exposure to gestational diabetes mellitus (GDM) and poor postnatal diet are strong risk factors for type 2 diabetes development later in life, but the mechanisms connecting GDM exposure to offspring metabolic health remains unclear. In this study, we aimed to determine how GDM interacts with the postnatal diet to affect islet function in the offspring as well as characterize the gene expression changes in the islets. GDM was induced in female rats using a high-fat, high-sucrose (HFS) diet, and litters from lean or GDM dams were weaned onto a low-fat (LF) or HFS diet. Compared with the lean control offspring, GDM exposure reduced glucose-stimulated insulin secretion in islets isolated from 15-week-old offspring, which was additively worsened when GDM exposure was combined with postnatal HFS diet consumption. In the HFS diet-fed offspring of lean dams, islet size and number increased, an adaptation that was not observed in the HFS diet-fed offspring of GDM dams. Islet gene expression in the offspring of GDM dams was altered in such categories as inflammation (e.g., Il1b, Ccl2), mitochondrial function/oxidative stress resistance (e.g., Atp5f1, Sod2), and ribosomal proteins (e.g., Rps6, Rps14). These results demonstrate that GDM exposure induced marked changes in gene expression in the male young adult rat offspring that cumulatively interact to worsen islet function, whole-body glucose homeostasis, and adaptations to HFS diets.

Female mice exposed to low doses of dioxin during pregnancy and lactation have increased susceptibility to diet-induced obesity and diabetes

ObjectiveExposure to persistent organic pollutants is consistently associated with increased diabetes risk in humans. We investigated the short- and long-term impact of transient low-dose dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) exposure during pregnancy and lactation on glucose homeostasis and beta cell function in female mice, including their response to a metabolic stressor later in life. MethodsFemale mice were injected with either corn oil (CO; vehicle control) or 20 ng/kg/d TCDD 2x/week throughout mating, pregnancy and lactation, and then tracked for 6–10 weeks after chemical exposure stopped. A subset of CO- and TCDD-exposed dams was then transferred to a 45% high-fat diet (HFD) or remained on a standard chow diet for an additional 11 weeks to assess the long-term effects of TCDD on adaptability to a metabolic stressor. To summarize, female mice were transiently exposed to TCDD and then subsequently tracked beyond when TCDD had been excreted to identify lasting metabolic effects of TCDD exposure. ResultsTCDD-exposed dams were hypoglycemic at birth but otherwise had normal glucose homeostasis during and post-TCDD exposure. However, TCDD-exposed dams on a chow diet were modestly heavier than controls starting 5 weeks after the last TCDD injection, and their weight gain accelerated after transitioning to a HFD. TCDD-exposed dams also had an accelerated onset of hyperglycemia, impaired glucose-induced plasma insulin levels, reduced islet size, increased MAFA-ve beta cells, and increased proinsulin accumulation following HFD feeding compared to controls. Overall, our study demonstrates that low-dose TCDD exposure during pregnancy has minimal effects on metabolism during the period of active exposure, but has detrimental long-term effects on metabolic adaptability to HFD feeding. ConclusionsOur study suggests that transient low-dose TCDD exposure in female mice impairs metabolic adaptability to HFD feeding, demonstrating that dioxin exposure may be a contributing factor to obesity and diabetes pathogenesis in females.

Evaluation of the Antidiabetic and Insulin Releasing Effects of A. squamosa, Including Isolation and Characterization of Active Phytochemicals.

Annona squamosa is generally referred to as a ‘custard apple’. Antidiabetic actions of hot water extract of Annona squamosa (HWAS) leaves together with isolation of active insulinotropic compounds were studied. Insulin release, membrane potential and intracellular Ca2+ were determined using BRIN-BD11 cells and isolated mouse islets. 3T3L1 adipocytes and in vitro models were used to determine cellular glucose uptake, insulin action, starch digestion, glucose diffusion, DPP-IV activity and glycation. Glucose intolerant high-fat fed rats were used for in vivo studies. Active compounds were isolated and characterized by HPLC, LCMS and NMR. HWAS stimulated insulin release from clonal β-cells and mouse islets. Using fluorescent indicator dyes and modulators of insulin secretion, effects could be attributed to depolarization of β-cells and influx of Ca2+. Secretion was stimulated by isobutylmethylxanthine (IBMX), tolbutamide or 30 mM KCl, indicating additional non-KATP dependent pathways. Extract stimulated cellular glucose uptake and insulin action and inhibited starch digestion, protein glycation, DPP-IV enzyme activity and glucose diffusion. Oral HWAS improved glucose tolerance and plasma insulin in high-fat fed obese rats. Treatment for 9 days with HWAS (250 mg/5 mL/kg), partially normalised energy intake, body weight, pancreatic insulin content, and both islet size and beta cell mass. This was associated with improved oral glucose tolerance, increased plasma insulin and inhibition of plasma DPP-IV activity. Isolated insulinotropic compounds, including rutin (C27H30O16), recapitulated the positive actions of HWAS on beta cells and in vivo glucose tolerance and plasma insulin responses. Annona squamosa is attractive as a dietary adjunct in treatment of T2DM and as a source of potential antidiabetic agents including rutin.

Mitochondria-Targeted Small Peptide, SS31 Ameliorates Diabetes Induced Mitochondrial Dynamics in Male TallyHO/JngJ Mice.

The escalating burden of type 2 diabetes (T2D) and its related complications has become a major public health challenge worldwide. Substantial evidence indicates that T2D is one of the culprits for the high prevalence of Alzheimer's disease (AD) in diabetic subjects. This study aimed to investigate the possible mitochondrial alterations in the pancreas induced by hyperglycemia in diabetes. We used a diabetic TallyHO/JngJ (TH) and non-diabetic, SWR/J mice strains. The diabetic and non-diabetic status in animals was assessed by performing intraperitoneal glucose tolerance test at four time points, i.e., 4, 8, 16, and 24weeks of age. We divided 24-week-old TH and SWR/J mice into 3 groups: controls, diabetic TH mice, and diabetic TH mice treated with SS31 peptide. After the treatment of male TH mice with SS31, intraperitoneally, for 4weeks, we studied mitochondrial dynamics, biogenesis, and function. The mRNA and protein expression levels of mitochondrial proteins were evaluated using qPCR and immunoblot analysis. The diabetic mice after 24weeks of age showed overt pancreatic injury as demonstrated by disintegration and atrophy of β cells with vacuolization and reduced islet size. Mitochondrial dysfunction was observed in TH mice, as evidenced by significantly elevated H2O2 production, lipid peroxidation, and reduced ATP production. Furthermore, mRNA expression and immunoblot analysis of mitochondrial dynamics genes were significantly affected in diabetic mice, compared with controls. However, treatment of animals with SS31 reduced mitochondrial dysfunction and restored most of the mitochondrial functions and mitochondrial dynamics processes to near normal in TH mice. In conclusion, mitochondrial dysfunction is established as one of the molecular events that occur in the pathophysiology of T2D. Further, SS31 treatment may confer protection against the mitochondrial alterations induced by hyperglycemia in diabetic TallyHO/JngJ mice.

Therapeutic Effects of Canagliflozin and Zinc Sulphate Alone and in Combination on Pancreatic Histology in Type-2 Diabetic Rat Model

Introduction: Diabetes Mellitus is a common metabolic syndrome characterized by persistently elevated blood glucose levels. Canagliflozin is an SGLT-2 inhibitor that controls hyperglycemia by reducing the reabsorption of filtered glucose and excreting it in the urine. Zinc sulphate exhibits some beneficial role in diabetes mellitus but has not been compared to canagliflozin individually and in combination. Aims &amp; Objectives: To observe the effects of treatment with canagliflozin and zinc sulphate on pancreatic histology in streptozotocin induced type-2 diabetic rat model. Place and duration of study: The study was conducted in the Department of Pharmacology, KEMU and PGMI, Lahore for the period of two months. Material &amp; Methods: It was an animal experimental study of eight weeks duration in which 48 adult healthy albino rats of male gender were divided into six groups and were provided the high fat diet throughout the study period. Groups A and B were maintained as healthy and diseased controls respectively. Groups B, C, D, E and F were administered single I/P dose streptozotocin (35mg/kg) at day 22 for inducing diabetes. Upon confirmation of diabetes after a week the rats were further treated as per group designation orally for 4 weeks , individually or in combination with full or half doses of canagliflozin (10 mg /kg/day, 5mg/kg/day ) and zinc sulphate (30mg/kg/day, 15mg/kg/day) . All animals were euthanized at the completion of study duration. The pancreatic tissue was taken out and examined for the histopathological changes (size and number of pancreatic islets, karyolysis and ballooning degeneration). Results: There was a marked improvement in the size and number of islets as well as the inflammatory changes in the combined treatment group (with canagliflozin in full as well as half dose of zinc sulphate) as compared to the groups given zinc sulphate and canagliflozin separately. Conclusion: Combined treatment with canagliflozin and zinc sulphate has a better protective effect on the pancreatic tissue in diabetes than either of them used alone.

Tectorigenin enhances PDX1 expression and protects pancreatic β-cells by activating ERK and reducing ER stress

Pancreas/duodenum homeobox protein 1 (PDX1) is an important transcription factor that regulates islet β-cell proliferation, differentiation, and function. Reduced expression of PDX1 is thought to contribute to β-cell loss and dysfunction in diabetes. Thus, promoting PDX1 expression can be an effective strategy to preserve β-cell mass and function. Previously, we established a PDX1 promoter-dependent luciferase system to screen agents that can promote PDX1 expression. Natural compound tectorigenin (TG) was identified as a promising candidate that could enhance the activity of the promoter for the PDX1 gene. In this study, we first demonstrated that TG could promote the expression of PDX1 in β-cells via activating extracellular signal-related kinase (ERK), as indicated by increased phosphorylation of ERK; this effect was observed under either normal or glucotoxic/lipotoxic conditions. We then found that TG could suppress induced apoptosis and improved the viability of β-cells under glucotoxicity and lipotoxicity by activation of ERK and reduction of reactive oxygen species and endoplasmic reticulum (ER) stress. These effects held true in vivo as well: prophylactic or therapeutic use of TG could obviously inhibit ER stress and decrease islet β-cell apoptosis in the pancreas of mice given a high-fat/high-sucrose diet (HFHSD), thus dramatically maintaining or restoring β-cell mass and islet size, respectively. Accordingly, both prophylactic and therapeutic use of TG improved HFHSD-impaired glucose metabolism in mice, as evidenced by ameliorating hyperglycemia and glucose intolerance. Taken together, TG, as an agent promoting PDX1 expression exhibits strong protective effects on islet β-cells both in vitro and in vivo.

A Chronic Fetal Leucine Infusion Potentiates Fetal Insulin Secretion and Increases Pancreatic Islet Size, Vascularity, and β Cells in Late-Gestation Sheep

Background:Infusion of a complete amino acid mixture into normal late-gestation fetal sheep potentiates glucose-stimulated insulin secretion (GSIS). Leucine acutely stimulates insulin secretion in late-gestation fetal sheep and isolated fetal sheep islets in vitro. Objectives:We hypothesized that a 9-d leucine infusion would potentiate GSIS in fetal sheep. Methods:Columbia-Rambouillet fetal sheep at 126 days of gestation received a 9-d leucine infusion to achieve a 50%–100% increase in leucine concentrations or a control infusion. At the end of the infusion we measured GSIS, pancreatic morphology, and expression of pancreatic mRNAs. Pancreatic islet endothelial cells (ECs) were isolated from fetal sheep and incubated with supplemental leucine or vascular endothelial growth factor A (VEGFA) followed by collection of mRNA. Data measured at multiple time points were compared with a repeated-measures 2-factor ANOVA. Data measured at 1 time point were compared using Student's t test or the Mann–Whitney test. Results:Glucose-stimulated insulin concentrations were 80% higher in leucine-infused (LEU) fetuses than in controls (P < 0.05). In the pancreas, LEU fetuses had a higher proportion of islets >5000 μm2 than controls (75% more islets >5000 μm2; P < 0.05) and a larger proportion of the pancreas that stained for β cells (12% greater; P < 0.05). Pancreatic and pancreatic islet vascularity were both 25% greater in LEU fetuses (P < 0.05). PancreaticVEGFAand hepatocyte growth factor (HGF) mRNA expressions were 38% and 200% greater in LEU fetuses than in controls (P < 0.05), respectively. In isolated islet ECs,HGFmRNA was 20% and 50% higher after incubation in ce:supplemental leucine (P < 0.05) or VEGFA (P < 0.01), respectively. Conclusions:A 9-d leucine infusion potentiates fetal GSIS, demonstrating that glucose and leucine act synergistically to stimulate insulin secretion in fetal sheep. A greater proportion of the pancreas being comprised of β cells and higher pancreatic vascularity contributed to the higher GSIS.

γ-aminobutyric acid stimulates β-cell proliferation through the mTORC1/p70S6K pathway, an effect amplified by Ly49, a novel γ-aminobutyric acid type A receptor positive allosteric modulator.

To examine the mechanism of action of γ-aminobutyric acid (GABA) on β-cell proliferation and investigate if co-treatment with Ly49, a novel GABA type A receptor positive allosteric modulator (GABAA -R PAM), amplifies this effect. Human or mouse islets were co-treated for 4-5 days with GABA and selected receptor or cell signalling pathway modulators. Immunofluorescence was used to determine protein co-localization, cell number or proliferation, and islet size. Osmotic minipumps were surgically implanted in mice to assess Ly49 effects on pancreatic β-cells. Amplification of GABAA -R signalling enhanced GABA-stimulated β-cell proliferation in cultured mouse islets. Co-treatment of GABA with an inhibitor specific for PI3K, mTORC1/2, or p70S6K, abolished GABA-stimulated β-cell proliferation in mouse and human islets. Nuclear p-AktSer473 and p-p70S6KThr421/Ser424 expression in pancreatic β-cells was increased in GABA-treated mice compared with vehicle-treated mice, an effect augmented with GABA and Ly49 co-treatment. Mice co-treated with GABA and Ly49 exhibited enhanced β-cell area and proliferation compared with GABA-treated mice. Furthermore, S961 injection (an insulin receptor antagonist) resulted in enhanced plasma insulin in GABA and Ly49 co-treated mice compared with GABA-treated mice. Importantly, GABA co-treated with Ly49 increased β-cell proliferation in human islets providing a potential application for human subjects. We show that GABA stimulates β-cell proliferation via the PI3K/mTORC1/p70S6K pathway in both mouse and human islets. Furthermore, we show that Ly49 enhances the β-cell regenerative effects of GABA, showing potential in the intervention of diabetes.

Insulin2Q104del (Kuma) mutant mice develop diabetes with dominant inheritance

Insulin gene mutations have been identified to cause monogenic diabetes, and most of which developed permanent neonatal diabetes at young ages before 6 months of age in humans. To establish an animal model of permanent diabetes, we performed genome editing using the CRISPR/Cas9 system. We generated a novel Kuma mutant mice with p.Q104del in the Insulin2 (Ins2) gene in a BRJ background that exhibits a severe immune deficiency. Kuma mutant mice are non-obese and developed hyperglycemia from 3 weeks after birth in both males and females, which are inherited in a dominant mode. Kuma mutant mice displayed reduced insulin protein levels from 3-weeks-old, which seem to be caused by the low stability of the mutant insulin protein. Kuma mutant showed a reduction in islet size and islet mass. Electron microscopic analysis revealed a marked decrease in the number and size of insulin granules in the beta-cells of the mutant mice. Hyperglycemia of the mutant can be rescued by insulin administration. Our results present a novel insulin mutation that causes permanent early-onset diabetes, which provides a model useful for islet transplantation studies.