Maintain Islet Function Research Articles

Endothelial Cells Promote Pseudo-islet Function Through BTC-EGFR-JAK/STAT Signaling Pathways.

Interactions between cells are of fundamental importance in affecting cell function. In vivo, endothelial cells and islet cells are close to each other, which makes endothelial cells essential for islet cell development and maintenance of islet cell function. We used endothelial cells to construct 3D pseudo-islets, which demonstrated better glucose regulation and greater insulin secretion compared to conventional pseudo-islets in both in vivo and in vitro trials. However, the underlying mechanism of how endothelial cells promote beta cell function localized within islets is still unknown. We performed transcriptomic sequencing, differential gene analysis, and enrichment analysis on two types of pseudo-islets to show that endothelial cells can promote the function of internal beta cells in pseudo-islets through the BTC-EGFR-JAK/STAT signaling pathway. Min6 cells secreted additional BTC after co-culture of endothelial cells with MIN6 cells outside the body. After BTC knockout in vitro, we found that beta cells functioned differently: insulin secretion levels decreased significantly, while the expression of key proteins in the EGFR-mediated JAK/STAT signaling pathway simultaneously decreased, further confirming our results. Through our experiments, we elucidate the molecular mechanisms by which endothelial cells maintain islet function in vitro, which provides a theoretical basis for the construction of pseudo-islets and islet cell transplants for the treatment of diabetes mellitus.

Efficacy of Regimens in the Treatment of Latent Autoimmune Diabetes in Adults: A Network Meta-analysis.

Latent autoimmune diabetes in adults (LADA) is a highly heterogeneous autoimmune condition with clinical and genetic characteristics that fall between those of type 1 diabetes mellitus and type 2 diabetes mellitus; therefore, there are no uniform criteria for the selection of therapeutic agents. We conducted a network meta-analysis to evaluate the efficacy of various therapeutic agents for LADA by comparing their effects on various indicators used to reflect LADA. We searched the PubMed, Cochrane Library, Embase and Web of Science databases from their inception to March 2023 and collected data from 14 randomized controlled trials on glucose-lowering drugs for LADA, including 23 studies and 15 treatment regimens. The effectiveness of drugs was ranked and evaluated by combining surface under the cumulative ranking (SUCRA) plots and forest plots. Factors that may influence study heterogeneity were also searched and analyzed by combining subgroup analysis, publication bias, funnel plots and sensitivity analysis. The results of the network meta-analysis showed that insulin had the most significant effect on the control of change from baseline in glycosylated hemoglobin, type A1 (ΔHbA1c). Insulin combined with dipeptidyl peptidase-4 (DPP-4) inhibitors performed the best in reducing fasting blood glucose and body mass index. Treatment regimens involving thiazolidinediones were the most advantageous in HbA1c, fasting C-peptide and postprandial C-peptide control. Longer dosing may be more beneficial in maintaining islet β-cell function in the LADA population. LADA is an immune condition with high heterogeneity, and treatment should be administered according to the C-peptide level of the LADA population. For this population with LADA with a certain level of β-cell function, combinations of insulin with DPP-4 inhibitors or thiazolidinediones probably can be more effective treatment options to maintain islet function and normal blood glucose. PROSPERO CRD42023410795.

Inhibition of Lincpint expression affects insulin secretion and apoptosis in mouse pancreatic β cells.

LncRNAs have been reported to maintain islet function and are associated with the development of diabetes. Here, we investigated Lincpint biological functions in mouse pancreatic β cells both in vivo and in vitro. We observed that Lincpint was highly expressed in BALB/c mouse islets and downregulated in db/db mouse islets by using qRT-PCR. Lincpint could be regulated by different concentrations of glucose in MIN6 cells. MTT and flow cytometry showed that silencing Lincpint expression in vitro increased cell apoptosis. In a GSIS assay, we detected that inhibition of the expression of Lincpint suppressed insulin synthesis and secretion. In male BALB/c mouse, blood glucose and serum insulin were decreased after knockdown of Lincpint expression as detected by IPGTT and ELISA. Immunohistochemistry indicated that positive islet area and expression of Pdx1 and Glut2 was reduced after Lincpint silencing in male BALB/c mouse. These findings suggest that Lincpint may play an important role in maintaining islet β cell function and is worthy of further investigation due to its potential in diabetes treatment.

Impact of Oxygen on Pancreatic Islet Survival.

Pancreatic islet transplantation is a promising treatment option for individuals with type 1 diabetes; however, maintaining islet function after transplantation remains a large challenge. Multiple factors, including hypoxia associated events, trigger pretransplant and posttransplant loss of islet function. In fact, islets are easily damaged in hypoxic conditions before transplantation including the preparation steps of pancreas procurement, islet isolation, and culture. Furthermore, after transplantation, islets are also exposed to the hypoxic environment of the transplant site until they are vascularized and engrafted. Because islets are exposed to such drastic environmental changes, protective measures are important to maintain islet viability and function. Many studies have demonstrated that the prevention of hypoxia contributes to maintaining islet quality. In this review, we summarize the latest oxygen-related islet physiology, including computational simulation. Furthermore, we review recent advances in oxygen-associated treatment options used as part of the transplant process, including up-to-date oxygen generating biomaterials as well as a classical oxygen inhalation therapy.

Deficient Glucagon Response to Hypoglycemia During a Mixed Meal in Total Pancreatectomy/Islet Autotransplantation Recipients.

Total pancreatectomy and intrahepatic islet autotransplantation (TP/IAT) is performed to alleviate severe abdominal pain, avoid narcotic use, maintain islet function, and avoid diabetes in patients with chronic pancreatitis. However, many TP/IAT recipients complain of postprandial hypoglycemia. This study was designed to discover the mechanisms of this problem. Participants consumed a triple-isotope mixed meal. This study was performed in a hospital research unit. We studied 10 TP/IAT recipients and 10 age- and body mass index-matched control subjects. Seven of 10 recipients had a history of postprandial hypoglycemia. Participants were given a [1-13C]-labeled mixed meal and two tracer infusions ([6,6-2H2]- and [6-3H]-glucose). Glucose kinetics and concentrations of regulatory hormones were determined. Immediately after the meal, peak glucose was elevated in recipients compared with control subjects [266 ± 20 mg/dL (14.8 ± 1.1 mmol/L) vs 185 ± 13 mg/dL (10.3 ± 0.7 mmol/L); P = 0.01]. However, mean Δ glucose for TP/IAT recipients between minutes 240 and 360 postprandially was significantly lower than for control subjects (P < 0.05); six of the seven recipients with a history of hypoglycemia experienced abnormally low postprandial Δ glucose. Δ Glucagon remained unchanged (minutes 240 to 360; P = 0.58) in TP/IAT recipients despite abnormal decreases in postprandial glucose. Radioisotopic studies revealed that meal appearance, glucose disappearance, and endogenous glucose production in TP/IAT recipients were not different from control subjects. Initially high glucose levels followed by hypoglycemia with an absent glucagon response is a mechanistic sequence that contributes to postprandial hypoglycemia after TP/IAT.

Islet encapsulation with polyphenol coatings decreases pro-inflammatory chemokine synthesis and T cell trafficking.

Type 1 Diabetes (T1D) is a chronic pro-inflammatory autoimmune disease consisting of islet-infiltrating leukocytes involved in pancreatic β-cell lysis. One promising treatment for T1D is islet transplantation; however, clinical application is constrained due to limited islet availability, adverse effects of immunosuppressants, and declining graft survival. Islet encapsulation may provide an immunoprotective barrier to preserve islet function and prevent immune-mediated rejection after transplantation. We previously demonstrated that a novel cytoprotective nanothin multilayer coating for islet encapsulation consisting of tannic acid (TA), an immunomodulatory antioxidant, and poly(N-vinylpyrrolidone) (PVPON), was efficacious in dampening invitro immune responses involved in transplant rejection and preserving invitro islet function. However, the ability of (PVPON/TA) to maintain islet function invivo and reverse diabetes has not been tested. Recent evidence has demonstrated that modulation of redox status can affect pro-inflammatory immune responses. Therefore, we hypothesized that transplanted (PVPON/TA)-encapsulated islets can restore euglycemia to diabetic mice and provide an immunoprotective barrier. Our results demonstrate that (PVPON/TA) nanothin coatings can significantly decrease invitro chemokine synthesis and diabetogenic T cell migration. Importantly, (PVPON/TA)-encapsulated islets restored euglycemia after transplantation into diabetic mice. Our results demonstrate that (PVPON/TA)-encapsulated islets may suppress immune responses and enhance isletallograft acceptance in patients with T1D.

Collagen matrix support of pancreatic islet survival and function

Diabetes mellitus is a chronic condition resulting from insufficient β-cell mass, which leads to improper glycemia regulation. Research efforts have focused on expanding islets and β-cells in vitro for use in cell-based therapies to cure diabetes. Collagens are triple-helix extracellular matrix proteins with widespread expression in mammals. With multiple functions, collagen can provide structural integrity in addition to mediating cellular signaling. In the pancreas, collagens I and IV are abundant and support cell structures while also stimulating cell surface receptors to influence pancreatic cell processes. Collagen-based materials and scaffolds have also been used to assist in the maintenance and expansion of islet cells in vitro, primarily through integrin and discoindin domain receptors. Islet transplantation using collagen-based scaffolds may improve long-term glycemic control, but progressive research efforts are required to realize this potential in humans. This review will outline the critical role played by native collagens I and IV and their receptors in maintaining islet function. The advantages of using collagens I and IV as culture gels/scaffolds and islet encapsulation vehicles for transplantation will be described.

Developmental and environmental epigenetic programming of the endocrine pancreas: consequences for type 2 diabetes.

The development of the endocrine pancreas is controlled by a hierarchical network of transcriptional regulators. It is increasingly evident that this requires a tightly interconnected epigenetic "programme" to drive endocrine cell differentiation and maintain islet function. Epigenetic regulators such as DNA and histone-modifying enzymes are now known to contribute to determination of pancreatic cell lineage, maintenance of cellular differentiation states, and normal functioning of adult pancreatic endocrine cells. Persistent effects of an early suboptimal environment, known to increase risk of type 2 diabetes in later life, can alter the epigenetic control of transcriptional master regulators, such as Hnf4a and Pdx1. Recent genome-wide analyses also suggest that an altered epigenetic landscape is associated with the β cell failure observed in type 2 diabetes and aging. At the cellular level, epigenetic mechanisms may provide a mechanistic link between energy metabolism and stable patterns of gene expression. Key energy metabolites influence the activity of epigenetic regulators, which in turn alter transcription to maintain cellular homeostasis. The challenge is now to understand the detailed molecular mechanisms that underlie these diverse roles of epigenetics, and the extent to which they contribute to the pathogenesis of type 2 diabetes. In-depth understanding of the developmental and environmental epigenetic programming of the endocrine pancreas has the potential to lead to novel therapeutic approaches in diabetes.

Sustained Neurog3 expression in hormone-expressing islet cells is required for endocrine maturation and function

Neurog3 (Neurogenin 3 or Ngn3) is both necessary and sufficient to induce endocrine islet cell differentiation from embryonic pancreatic progenitors. Since robust Neurog3 expression has not been detected in hormone-expressing cells, Neurog3 is used as an endocrine progenitor marker and regarded as dispensable for the function of differentiated islet cells. Here we used 3 independent lines of Neurog3 knock-in reporter mice and mRNA/protein-based assays to examine Neurog3 expression in hormone-expressing islet cells. Neurog3 mRNA and protein are detected in hormone-producing cells at both embryonic and adult stages. Significantly, inactivating Neurog3 in insulin-expressing beta cells at embryonic stages or in Pdx1-expressing islet cells in adults impairs endocrine function, a phenotype that is accompanied by reduced expression of several Neurog3 target genes that are essential for islet cell differentiation, maturation, and function. These findings demonstrate that Neurog3 is required not only for initiating endocrine cell differentiation, but also for promoting islet cell maturation and maintaining islet function.