Pancreatic Islet Architecture Research Articles

Sex-specific regulatory architecture of pancreatic islets from subjects with and without type 2 diabetes.

Patients with type 2 and type 1 diabetes (T2D and T1D) exhibit sex-specific differences in insulin secretion, the mechanisms of which are unknown. We examined sex differences in human pancreatic islets from 52 donors with and without T2D combining single cell RNA-sequencing (scRNA-seq) and single nucleus ATAC-sequencing (snATAC-seq) with assays probing hormone secretion and bioenergetics. In non-diabetic (ND) donors, sex differences in islet cell chromatin accessibility and gene expression predominantly involved sex chromosomes. In contrast, islets from T2D donors exhibited similar sex differences in sex chromosome-encoded differentially expressed genes (DEGs) as ND donors, but also exhibited sex differences in autosomal genes. Comparing β cells from T2D and ND donors, gene enrichment of female β cells showed suppression in mitochondrial respiration, while male β cells exhibited suppressed insulin secretion, suggesting a role for mitochondrial failure in females in the transition to T2D. We finally performed cell type-specific, sex stratified, GWAS restricted to differentially accessible chromatin peaks across T2D, fasting glucose, and fasting insulin traits. We identified that differentially accessible regions overlap with T2D-associated variants in a sex- and cell type-specific manner.

A noncoding variant confers pancreatic differentiation defect and contributes to diabetes susceptibility by recruiting RXRA

Human genetics analysis has identified many noncoding SNPs associated with diabetic traits, but whether and how these variants contribute to diabetes is largely unknown. Here, we focus on a noncoding variant, rs6048205, and report that the risk-G variant impairs the generation of PDX1+/NKX6-1+ pancreatic progenitor cells and further results in the abnormal decrease of functional β cells during pancreatic differentiation. Mechanistically, this risk-G variant greatly enhances RXRA binding and over-activates FOXA2 transcription, specifically in the pancreatic progenitor stage, which in turn represses NKX6-1 expression. Consistently, inducible FOXA2 overexpression could phenocopy the differentiation defect. More importantly, mice carrying risk-G exhibit abnormal pancreatic islet architecture and are more sensitive to streptozotocin or a high-fat diet to develop into diabetes eventually. This study not only identifies a causal noncoding variant in diabetes susceptibility but also dissects the underlying gain-of-function mechanism by recruiting stage-specific factors.

Beneficial Effects of Probiotic Lactobacillus paraplantarum BGCG11 on Pancreatic and Duodenum Function in Diabetic Rats.

Diabetes mellitus, as a chronic metabolic disorder, significantly impacts the pancreas and among other organs, affects duodenal function. Emerging evidence suggests that probiotics can exert beneficial effects on gut health and metabolism. In our previous research, we evaluated the probiotic Lactobacillus paraplantarum BGCG11 primarily for its protective properties against diabetic rats' damaged liver and kidneys. In this work, we further examined the effects of probiotic strain BGCG11 on the function of the duodenum and pancreas in diabetic rats. We explored the potential mechanisms underlying the probiotic's effects, focusing on general indicators of diabetes, the architecture and morphology of pancreatic islets, duodenal integrity (measuring the transfer of fluid and serum zonulin level), and the modulation of gut microbiota composition. Our findings reveal the protective and regulatory roles of L. paraplantarum BGCG11 in mitigating diabetes-induced pancreatic and duodenal dysfunction regardless of its application time (pre- or post-treatment), highlighting its therapeutic potential in managing diabetes-related gastrointestinal complications.

Single cell regulatory architecture of human pancreatic islets suggests sex differences in β cell function and the pathogenesis of type 2 diabetes.

Type 2 and type 1 diabetes (T2D, T1D) exhibit sex differences in insulin secretion, the mechanisms of which are unknown. We examined sex differences in human pancreatic islets from 52 donors with and without T2D combining single cell RNA-seq (scRNA-seq), single nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq), hormone secretion, and bioenergetics. In nondiabetic (ND) donors, sex differences in islet cells gene accessibility and expression predominantly involved sex chromosomes. Islets from T2D donors exhibited similar sex differences in sex chromosomes differentially expressed genes (DEGs), but also exhibited sex differences in autosomal genes. Comparing β cells from T2D vs. ND donors, gene enrichment of female β cells showed suppression in mitochondrial respiration, while male β cells exhibited suppressed insulin secretion. Thus, although sex differences in gene accessibility and expression of ND β cells predominantly affect sex chromosomes, the transition to T2D reveals sex differences in autosomes highlighting mitochondrial failure in females.

Single cell regulatory architecture of human pancreatic islets suggests sex differences in β cell function and the pathogenesis of type 2 diabetes.

Biological sex affects the pathogenesis of type 2 and type 1 diabetes (T2D, T1D) including the development of β cell failure observed more often in males. The mechanisms that drive sex differences in β cell failure is unknown. Studying sex differences in islet regulation and function represent a unique avenue to understand the sex-specific heterogeneity in β cell failure in diabetes. Here, we examined sex and race differences in human pancreatic islets from up to 52 donors with and without T2D (including 37 donors from the Human Pancreas Analysis Program [HPAP] dataset) using an orthogonal series of experiments including single cell RNA-seq (scRNA-seq), single nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq), dynamic hormone secretion, and bioenergetics. In cultured islets from nondiabetic (ND) donors, in the absence of the in vivo hormonal environment, sex differences in islet cell type gene accessibility and expression predominantly involved sex chromosomes. Of particular interest were sex differences in the X-linked KDM6A and Y-linked KDM5D chromatin remodelers in female and male islet cells respectively. Islets from T2D donors exhibited similar sex differences in differentially expressed genes (DEGs) from sex chromosomes. However, in contrast to islets from ND donors, islets from T2D donors exhibited major sex differences in DEGs from autosomes. Comparing β cells from T2D and ND donors revealed that females had more DEGs from autosomes compared to male β cells. Gene set enrichment analysis of female β cell DEGs showed a suppression of oxidative phosphorylation and electron transport chain pathways, while male β cell had suppressed insulin secretion pathways. Thus, although sex-specific differences in gene accessibility and expression of cultured ND human islets predominantly affect sex chromosome genes, major differences in autosomal gene expression between sexes appear during the transition to T2D and which highlight mitochondrial failure in female β cells.

Evaluation of novel 2-(quinoline-2-ylthio)acetamide derivatives linked to diphenyl-imidazole as α-glucosidase inhibitors: Insights from in silico, in vitro, and in vivo studies on their anti-diabetic properties

The inhibition of the α-glucosidase enzyme is crucial for targeting type 2 diabetes mellitus (DM). This study introduces a series of synthetic analogs based on thiomethylacetamide-quinoline derivatives linked to diphenyl-imidazole as highly potential α-glucosidase inhibitors. Twenty derivatives were synthesized and screened in vitro against α-glucosidase, revealing IC50 values ranging from 0.18 ± 0.00 to 2.10 ± 0.07 μM, in comparison to the positive control, acarbose. Among these derivatives, compound 10c (IC50 = 0.180 μM) demonstrated the highest potency and revealed a competitive inhibitory mechanism in kinetic studies (Ki = 0.15 μM). Docking and molecular dynamic evaluations elucidated the binding mode of 10c with the active site residues of the α-glucosidase enzyme. Moreover, in vivo assessments on a rat model of DM affirmed the anti-diabetic efficacy of 10c, evidenced by reduced fasting and overall blood glucose levels. The histopathological evaluation enhanced pancreatic islet architecture and hepatocytes in liver sections. In conclusion, novel 2-(quinoline-2-ylthio)acetamide derivatives as potent α-glucosidase inhibitors were developed. Compound 10c emerged as a promising candidate for diabetes management, warranting further investigation for potential clinical applications and mechanistic insights.

Examining the pancreatic regenerative potential of Nigella sativa in diabetic rats: Evaluation of histological changes and transcription factors pdx-1 and neurog-3 levels

Pancreatic β cell neogenesis and proliferation represent promising avenues for diabetes management. Nigella sativa, known for its potent anti-inflammatory and antioxidant properties, has demonstrated efficacy in promoting regeneration across various organ systems. This study investigates the potential of Nigella sativa in pancreatic regeneration by examining pancreatic histology in addition, the expression levels of the key transcription factors, comprising NEUROG-3, PDX-1, INS-1, and INS-2. Twenty-four rats were categorized in 4sets that is negative control, positive control, normal, and treatment. Diabetes was prompted through intraperitoneal administration of alloxan hydrate. After 21 days of diabetes induction, the treatment set was applied with N. sativa extract, the positive control set was administered Glibenclamide, while the negative control group received no treatment. Parameters such as biochemical markers, oxidative stress markers, pancreatic islet architecture changes, and the expression levels of the NEUROG-3, PDX-1, INS-1, and INS-2 were assessed. Data analysis, conducted through DMR Test and ANOVA with a 5% threshold of significance, revealed significant insights into the consequence of N. sativa on the parameters under investigation. The results propose a possible part for N. sativa in promoting pancreatic regeneration and warrant further exploration for its application in diabetes management.

SAT052 Prolonged Nursing Augments Short Chain Fatty Acid Levels And Leads To Amelioration Of Type 1 Diabetes

Abstract Disclosure: S. rafiqi: None. Z. Zahid: None. R. Lamendella: None. O. aghogho: None. E. Gionfriddo: None. Y. Tao: None. J.C. Jaume: None. S. Imam: None. The infant gut microbiome essentially shifts to a diverse and complex microbial system during weaning on separation from the mother and any perturbations lead to pathological imprinting with lifelong implications. Apart from breast milk, the microbiota of the skin and the intimate niche between mother and offspring contribute to gut microbial composition. Gut microbiome dysbiosis has been ascribed in the initiation and/or perpetuation of type 1 diabetes (T1D) in human and animal models. The gut microbial diversification is manifested as change in microbial metabolites particularly short-chain fatty acids (SCFAs) that have direct and indirect roles in immune regulation and epithelial barrier integrity. In this study, we try to decipher the role of prolonged nursing of newborn mice (upto 45 days) in the amelioration of type 1 diabetes in the context of changes in the gut microbiome and microbial metabolites. The humanized T1D mice used in the study spontaneously develop T1D at 3-4 weeks of age and are normally weaned at 21 days. Our results revealed mice subjected to prolonged nursing had consistent increments in levels of butyric acid from 60 to 150 days of age as compared to normal weaned mice, owing to a stable population of SCFA-producing bacteria developed during prolonged nursing with the mother. The normal weaned mice had a transient increase of butyric acid at 60 days but it didn’t sustain till the 150th day. The steady levels of butyrate in prolonged nursed mice exerted immunoregulatory roles which manifested in the enrichment of regulatory T cells (Tregs) in the intestinal mesenteric epithelium, payer’s patches, peri pancreatic lymph nodes (PLN), pancreas (PN) and spleen. The enrichment of Tregs leads to the regulation of diabetogenic Th1, Th17, and interferon gamma-producing CD8 T cells (cytotoxic lymphocytes, CTLs) at PLN, PN, and spleen. This increased immune tolerance was mirrored by improved glucose homeostasis and fasting blood glucose levels in the prolonged nursing group. Prolonged nursing preserved the pancreatic islet architecture and significantly maintained the increased number of islets per pancreas as observed in H&E sections. Also, it could be inferred from the results that SCFA’s promoted intestinal integrity with increased submucosal thickening, longer villi, and shallower crypts in the intestine of prolonged nursed mice. In conclusion, prolonged nursing accounts for gradual and steady gut microbiota succession in infants that augments SCFA production leading to enrichment of T regulatory cells and less aggressive diabetes. Presentation: Saturday, June 17, 2023

Distinct physiological characteristics and altered glucagon signaling in GHRH knockout mice: Implications for longevity.

Our previous research has demonstrated that mice lacking functional growth hormone-releasing hormone (GHRH) exhibit distinct physiological characteristics, including an extended lifespan, a preference for lipid utilization during rest, mild hypoglycemia, and heightened insulin sensitivity. They also show a further increase in lifespan when subjected to caloric restriction. These findings suggest a unique response to fasting, which motivated our current study on the response to glucagon, a key hormone released from the pancreas during fasting that regulates glucose levels, energy expenditure, and metabolism. Our study investigated the effects of an acute glucagon challenge on female GHRH knockout mice and revealed that they exhibit reduced glucose production, likely due to suppressed gluconeogenesis. However, these mice showed an increase in energy expenditure. We also observed alterations in pancreatic islet architecture, with smaller islets and a reduction of insulin-producing beta cells but no changes in glucagon-producing alpha cells. Additionally, the analysis of hepatic glucagon signaling showed a decrease in glucagon receptor expression and phosphorylated CREB. In conclusion, our findings suggest that the unique metabolic phenotype observed in these long-lived mice may be partly explained by changes in glucagon signaling. Further exploration of this pathway may lead to new insights into the regulation of longevity in mammals.

Pancreatic regenerative potential of manuka honey evidenced through pancreatic histology and levels of transcription factors in diabetic rat model

BackgroundDiabetes mellitus is a commonly occurring metabolic disorder accompanied by high morbidity and alarming mortality. Besides various available therapies, induction of pancreatic regeneration has emerged as a promising strategy for alleviating the damaging effect of diabetes. Honey, a potent antioxidative and anti-inflammatory agent, has been reported in the literature archive to exhibit favourable results in the regeneration process of several organ systems. DesignThe current research work was intended to explore the potential role of manuka honey in pancreatic regeneration in alloxan-induced diabetic rats by accessing the pancreatic histology and levels of relevant transcription factors, including MAFA, PDX-1, INS-1, INS-2, NEUROG3, NKX6-1, and NEUROD. An equal number of rats were allocated to all four experimental groups: normal, negative control, positive control, and treatment group. Diabetes was induced in all groups except normal through a single intraperitoneal dose of alloxan monohydrate. No subsequent treatment was given to the negative control group, while the positive control and treatment groups were supplemented with metformin (150 mg/kg/day) and manuka honey (3 g/kg/day), respectively. ResultsStatistical comparison of glucose and insulin levels, oxidative stress indicators, changes in the architecture of pancreatic islets, and expression levels of regeneration-associated transcription factors advocated the potential role of manuka honey in ameliorating the alloxan-induced hyperglycaemia, hyperinsulinemia, oxidative stress, and necrotic changes in islets along with significant upregulation of relevant transcription factors. ConclusionThis suggests to us the auspicious role of antioxidants in honey in pancreatic regeneration and advocates the favourable role of manuka honey in combating diabetes mellitus.

The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity

ObjectiveTranscriptional complex activity drives the development and function of pancreatic islet cells to allow for proper glucose regulation. Prior studies from our lab and others highlighted that the LIM-homeodomain transcription factor (TF), Islet-1 (Isl1), and its interacting co-regulator, Ldb1, are vital effectors of developing and adult β-cells. We further found that a member of the Single Stranded DNA-Binding Protein (SSBP) co-regulator family, SSBP3, interacts with Isl1 and Ldb1 in β-cells and primary islets (mouse and human) to impact β-cell target genes MafA and Glp1R in vitro. Members of the SSBP family stabilize TF complexes by binding directly to Ldb1 and protecting the complex from ubiquitin-mediated turnover. In this study, we hypothesized that SSBP3 has critical roles in pancreatic islet cell function in vivo, similar to the Isl1::Ldb1 complex. MethodsWe first developed a novel SSBP3 LoxP allele mouse line, where Cre-mediated recombination imparts a predicted early protein termination. We bred this mouse with constitutive Cre lines (Pdx1- and Pax6-driven) to recombine SSBP3 in the developing pancreas and islet (SSBP3ΔPanc and SSBP3ΔIslet), respectively. We assessed glucose tolerance and used immunofluorescence to detect changes in islet cell abundance and markers of β-cell identity and function. Using an inducible Cre system, we also deleted SSBP3 in the adult β-cell, a model termed SSBP3Δβ-cell. We measured glucose tolerance as well as glucose-stimulated insulin secretion (GSIS), both in vivo and in isolated islets in vitro. Using islets from control and SSBP3Δβ-cell we conducted RNA-Seq and compared our results to published datasets for similar β-cell specific Ldb1 and Isl1 knockouts to identify commonly regulated target genes. ResultsSSBP3ΔPanc and SSBP3ΔIslet neonates present with hyperglycemia. SSBP3ΔIslet mice are glucose intolerant by P21 and exhibit a reduction of β-cell maturity markers MafA, Pdx1, and UCN3. We observe disruptions in islet cell architecture with an increase in glucagon+ α-cells and ghrelin+ ε-cells at P10. Inducible loss of β-cell SSBP3 in SSBP3Δβ-cell causes hyperglycemia, glucose intolerance, and reduced GSIS. Transcriptomic analysis of 14-week-old SSBP3Δβ-cell islets revealed a decrease in β-cell function gene expression (Ins, MafA, Ucn3), increased stress and dedifferentiation markers (Neurogenin-3, Aldh1a3, Gastrin), and shared differentially expressed genes between SSBP3, Ldb1, and Isl1 in adult β-cells. ConclusionsSSBP3 drives proper islet identity and function, where its loss causes altered islet-cell abundance and glucose homeostasis. β-Cell SSBP3 is required for GSIS and glucose homeostasis, at least partially through shared regulation of Ldb1 and Isl1 target genes.

Antidiabetic Effect of Actinodaphne angustifolia and Profiling of Bioactive Metabolites using UPLC-QToF/ESI-MS Method

Diabetes mellitus is a chronic disorder that causes elevated blood glucose levels due to a lack of insulin, either completely or partially. We investigated the antidiabetic property of Actinodaphne angustifolia in a rat model and identified the bioactive phytochemicals by using the UPLC-QTOF/ESI-MS method. The rats’ pancreatic structures, lipid profile and blood glucose were assessed after a one-week intervention. UPLC-QTOF/ESI-MS analysis was conducted to identify flavonoids and terpenoids in the leaf extract. Actinodaphne angustifolia extract markedly increased the high-density lipoprotein (HDL) (p<0.05) while reducing total cholesterol (TC), low-density lipoprotein (LDL) and blood glucose. Furthermore, the tissue architecture of pancreatic islets was also well recovered as compared to the control group. A total of 45 flavonoids and 109 terpenoid compounds were identified using UPLC-QTOF/ESI-MS-based analysis and additional studies should be undertaken to identify the potential antidiabetic agents.

Efficiency of Bone Marrow-Derived Mesenchymal Stem Cells and Hesperetin in the Treatment of Streptozotocin-Induced Type 1 Diabetes in Wistar Rats.

Type 1 diabetes mellitus (T1DM) was established to be ameliorated by islet transplantation, but the shortage of the transplanted human islet tissue and the use of immunosuppressive drugs to inhibit the rejection of allogeneic grafts make this type of therapy is limited. Nowadays, therapy with stem cells is one of the most promising future treatments. This kind of therapy could have a profound impact on both replacement, as well as regenerative therapies, to improve or even cure various disorders, including diabetes mellitus. Flavonoids have also been shown to possess anti-diabetic effects. Thus, this study aims to evaluate the effectiveness of the bone marrow-derived mesenchymal stem cells (BM-MSCs) and hesperetin in the treatment of a T1DM rat model. T1DM was induced in male Wistar rats that had been starved for 16 h via intraperitoneal injection of STZ at a dose of 40 mg/kg body weight (b.wt.). After 10 days of STZ injection, the diabetic rats were allocated into four groups. The first diabetic animal group was considered a diabetic control, while the other three diabetic animal groups were treated for six weeks, respectively, with hesperetin (given orally at a dose of 20 mg/kg b.wt.), BM-MSCs (injected intravenously at a dose of 1 × 106 cells/rat/week), and their combination (hesperetin and BM-MSCs). The use of hesperetin and BM-MSCs in the treatment of STZ-induced diabetic animals significantly improved the glycemic state, serum fructosamine, insulin and C-peptide levels, liver glycogen content, glycogen phosphorylase, glucose-6-phosphatase activities, hepatic oxidative stress, and mRNA expressions of NF-κB, IL-1β, IL-10, P53, and Bcl-2 in pancreatic tissue. The study suggested the therapy with both hesperetin and BM-MSCs produced marked antihyperglycemic effects, which may be mediated via their potencies to ameliorate pancreatic islet architecture and insulin secretory response, as well as to decrease hepatic glucose output in diabetic animals. The improvement effects of hesperetin and BM-MSCs on the pancreatic islets of diabetic rats may be mediated via their antioxidant, anti-inflammatory, and antiapoptotic actions.

Irisin administration restores beta-cell functional mass in a mouse model of type 2 diabetes

Aim: Irisin is a hormone secreted by skeletal muscle able to improve metabolic homeostasis. Serum irisin levels are reduced in type 2 diabetes (T2D), while exogenous irisin administration improves glycemic control in diabetic mice. We have previously demonstrated that irisin promotes beta-cell survival and function both in vitro and in vivo in healthy wild type mice. We have also demonstrated that irisin restores the defective glucose-stimulated insulin secretion (GSIS) and reduces apoptosis in human pancreatic islets from patients with T2D. Nevertheless, the beta-cellular effects of in vivo irisin administration to T2D mice are still unknown. Methods: C57Bl/6 mice (n = 8) were fed a high-fat diet (HFD, 60% of energy deriving from fat) for 10 weeks and then intraperitoneally injected with streptozotocin (STZ, 100 mg/kg) to induce diabetes. Four standard diet (SD)-fed mice were used as control. HFD/STZ mice were treated with 0.5 μg/g irisin (n = 4) or vehicle (n = 4), for 14 days. Fasting glycemia, insulinemia, body weight, glucose tolerance, and pancreatic islet function were assessed. Pancreatic islet architecture was also evaluated through immunofluorescence analyses. Results: Compared to SD mice, HFD/STZ mice showed higher fasting glycemia and body weight, glucose intolerance, and reduced GSIS; in addition, HFD/STZ mice showed reduced islet volume (-78%), beta-cell area (-35%), and insulin content (-60%), and increased alpha-cell area (+54%). Irisin administration significantly restored glycemia (-31%), body weight (-13%), glucose tolerance (-27%), GSIS (+23%), islet volume (+61%), beta-cell area (+34%) and alpha-cell area (-49%), and insulin content (+36%). Of note, irisin induced a 9-fold increase in beta-cell proliferation rate. Conclusions: These results show that irisin improves glycemic homeostasis and restores the functional beta-cell mass when administered in vivo to diabetic mice, probably by promoting beta-cell proliferation.

ISL1 controls pancreatic alpha cell fate and beta cell maturation

BackgroundGlucose homeostasis is dependent on functional pancreatic α and ß cells. The mechanisms underlying the generation and maturation of these endocrine cells remain unclear.ResultsWe unravel the molecular mode of action of ISL1 in controlling α cell fate and the formation of functional ß cells in the pancreas. By combining transgenic mouse models, transcriptomic and epigenomic profiling, we uncover that elimination of Isl1 results in a diabetic phenotype with a complete loss of α cells, disrupted pancreatic islet architecture, downregulation of key ß-cell regulators and maturation markers of ß cells, and an enrichment in an intermediate endocrine progenitor transcriptomic profile.ConclusionsMechanistically, apart from the altered transcriptome of pancreatic endocrine cells, Isl1 elimination results in altered silencing H3K27me3 histone modifications in the promoter regions of genes that are essential for endocrine cell differentiation. Our results thus show that ISL1 transcriptionally and epigenetically controls α cell fate competence, and ß cell maturation, suggesting that ISL1 is a critical component for generating functional α and ß cells.

Functional architecture of pancreatic islets identifies a population of first responder cells that drive the first-phase calcium response.

Insulin-secreting β-cells are functionally heterogeneous. Whether there exist cells driving the first-phase calcium response in individual islets, has not been examined. We examine “first responder” cells, defined by the earliest [Ca2+] response during first-phase [Ca2+] elevation, distinct from previously identified “hub” and “leader” cells. We used islets isolated from Mip-CreER; Rosa-Stop-Lox-Stop-GCamP6s mice (β-GCamP6s) that show β-cell-specific GCamP6s expression following tamoxifen-induced CreER-mediated recombination. First responder cells showed characteristics of high membrane excitability and lower electrical coupling to their neighbors. The first-phase response time of β-cells in the islet was spatially organized, dependent on the cell’s distance to the first responder cell, and consistent over time up to approximately 24 h. When first responder cells were laser ablated, the first-phase [Ca2+] was slowed down, diminished, and discoordinated compared to random cell ablation. Cells that were next earliest to respond often took over the role of the first responder upon ablation. In summary, we discover and characterize a distinct first responder β-cell state, critical for the islet first-phase response to glucose.

1375-P: Effects of Irisin Administration on Pancreatic Islets of Diabetic Mice

Irisin is a hormone secreted by skeletal muscle following exercise or excess of saturated fatty acids (SFAs) , able to improve metabolic homeostasis and promote energy expenditure. Serum irisin levels are reduced in type 2 diabetes (T2D) , while exogenous irisin administration improves glycemic control in diabetic mice. We have previously demonstrated that irisin protects human and rodent β-cells and pancreatic islets from SFAs-induced apoptosis, increases insulin biosynthesis and glucose-stimulated insulin secretion (GSIS) , and promotes β-cell proliferation, both in vitro and in vivo in healthy wild-type mice. Irisin may also restore the defective GSIS and reduce the high rate of apoptosis that are characteristic of islets from T2D patients. However, the β-cellular effects of irisin administration to diabetic mice are still unknown. 6 weeks-old C57Bl/6 mice (n = 8) were fed a high-fat diet (HFD, 60% of energy deriving from fat) for weeks and then intraperitoneally injected with streptozotocin (STZ, 100 mg/Kg) to induce diabetes. 4 standard diet (SD) -fed mice were used as control. HFD/STZ mice were then treated with 0.5 μg/g irisin (n = 4) or vehicle (n = 4) for 14 days. Glucose tolerance, glycemia, insulinemia, body weight, pancreatic islet architecture and function were assessed throughout the study. As expected, compared to SD mice, HFD/STZ mice showed higher glycemia and body weight, glucose intolerance, and reduced GSIS; in addition, HFD/STZ mice showed reduced islet volume (-78%) , β-cell area (-35%) , and insulin content (-60%) , while increased α-cell area (+54%) . Irisin administration significantly restored glycemia (-31%) , body weight (-13%) , glucose tolerance (-27%, AUC) , GSIS (+23%, AUC) , islet volume (+61%) , β-cell (+34%) and α-cell (-49%) areas, and insulin content (+36%) . Of note, irisin treatment induced a 9-fold increase in β-cell proliferation rate. These results show for the first time that irisin can restore β-cell functional mass when administered in vivo to diabetic mice. Disclosure N.Marrano: None. G.Biondi: None. A.Borrelli: None. L.Roberto: None. A.Cignarelli: None. S.Perrini: None. L.Laviola: Advisory Panel; Lilly Diabetes, Novo Nordisk, Roche Diabetes Care, Sanofi, Speaker's Bureau; A. Menarini Diagnostics, Abbott Diabetes, Medtronic, Terumo Corporation. F.Giorgino: Advisory Panel; AstraZeneca, Boehringer Ingelheim International GmbH, Novo Nordisk, Consultant; Lilly Diabetes, Sanofi, Research Support; Lilly Diabetes, Roche Diabetes Care, Takeda Pharmaceutical Company Limited. A.Natalicchio: Consultant; Novo Nordisk, Other Relationship; AstraZeneca, Lilly Diabetes, Sanofi. Funding EU – ESF PON R&I 2014-20, AIM

The Antidiabetic Effects and Modes of Action of the Balanites aegyptiaca Fruit and Seed Aqueous Extracts in NA/STZ-Induced Diabetic Rats.

Diabetes mellitus (DM) is a chronic metabolic disorder that threatens human health. Medicinal plants have been a source of wide varieties of pharmacologically active constituents and used extensively as crude extracts or as pure compounds for treating various disease conditions. Thus, the aim of this study is to assess the anti-hyperglycemic and anti-hyperlipidemic effects and the modes of action of the aqueous extracts of the fruits and seeds of Balanites aegyptiaca (B. aegyptiaca) in nicotinamide (NA)/streptozotocin (STZ)-induced diabetic rats. Gas chromatography–mass spectrometry analysis indicated that 3,4,6-tri-O-methyl-d-glucose and 9,12-octadecadienoic acid (Z,Z)- were the major components of the B. aegyptiaca fruit and seed extracts, respectively. A single intraperitoneal injection of STZ (60 mg/kg body weight (b.w.)) 15 min after intraperitoneal NA injection (60 mg/kg b.w.) was administered to induce type 2 DM. After induction was established, the diabetic rats were treated with the B. aegyptiaca fruit and seed aqueous extracts (200 mg/kg b.w./day) via oral gavage for 4 weeks. As a result of the treatments with the B. aegyptiaca fruit and seed extracts, the treated diabetic-treated rats exhibited a significant improvement in the deleterious effects on oral glucose tolerance; serum insulin, and C-peptide levels; liver glycogen content; liver glucose-6-phosphatase and glycogen phosphorylase activities; serum lipid profile; serum free fatty acid level; liver lipid peroxidation; glutathione content and anti-oxidant enzyme (glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase) activities; and the mRNA expression of the adipose tissue expression of the insulin receptor β-subunit. Moreover, the treatment with fruit and seed extracts also produced a remarkable improvement of the pancreatic islet architecture and integrity and increased the islet size and islet cell number. In conclusion, the B. aegyptiaca fruit and seed aqueous extracts exhibit potential anti-hyperglycemic and anti-hyperlipidemic effects, which may be mediated by increasing the serum insulin levels, decreasing insulin resistance, and enhancing the anti-oxidant defense system in diabetic rats.

Beneficial impact of Ac3IV, an AVP analogue acting specifically at V1a and V1b receptors, on diabetes islet morphology and transdifferentiation of alpha- and beta-cells.

Ac3IV (Ac-CYIQNCPRG-NH2) is an enzymatically stable vasopressin analogue that selectively activates Avpr1a (V1a) and Avpr1b (V1b) receptors. In the current study we have employed streptozotocin (STZ) diabetic transgenic Ins1Cre/+;Rosa26-eYFP and GluCreERT2;Rosa26-eYFP mice, to evaluate the impact of sustained Ac3IV treatment on pancreatic islet cell morphology and transdifferentiation. Twice-daily administration of Ac3IV (25 nmol/kg bw) to STZ-diabetic Ins1Cre/+;Rosa26-eYFP mice for 12 days increased pancreatic insulin (p<0.01) and significantly reversed the detrimental effects of STZ on pancreatic islet morphology. Such benefits were coupled with increased (p<0.01) beta-cell proliferation and decreased (p<0.05) beta-cell apoptosis. In terms of islet cell lineage tracing, induction of diabetes increased (p<0.001) beta- to alpha-cell differentiation in Ins1Cre/+;Rosa26-eYFP mice, with Ac3IV partially reversing (p<0.05) such transition events. Comparable benefits of Ac3IV on pancreatic islet architecture were observed in STZ-diabetic GluCreERT2;ROSA26-eYFP transgenic mice. In this model, Ac3IV provoked improvements in islet morphology which were linked to increased (p<0.05-p<0.01) transition of alpha- to beta-cells. Ac3IV also increased (p<0.05-p<0.01) CK-19 co-expression with insulin in pancreatic ductal and islet cells. Blood glucose levels were unchanged by Ac3IV in both models, reflecting the severity of diabetes induced. Taken together these data indicate that activation of islet receptors for V1a and V1b positively modulates alpha- and beta-cell turnover and endocrine cell lineage transition events to preserve beta-cell identity and islet architecture.

Single-Cell Transcriptomics Links Loss of Human Pancreatic β-Cell Identity to ER Stress.

The maintenance of pancreatic islet architecture is crucial for proper β-cell function. We previously reported that disruption of human islet integrity could result in altered β-cell identity. Here we combine β-cell lineage tracing and single-cell transcriptomics to investigate the mechanisms underlying this process in primary human islet cells. Using drug-induced ER stress and cytoskeleton modification models, we demonstrate that altering the islet structure triggers an unfolding protein response that causes the downregulation of β-cell maturity genes. Collectively, our findings illustrate the close relationship between endoplasmic reticulum homeostasis and β-cell phenotype, and strengthen the concept of altered β-cell identity as a mechanism underlying the loss of functional β-cell mass.