Abdominal Normothermic Regional Perfusion after Donation after Circulatory Death Improves Pancreatic Islet Isolation Yield.

Abdominal Normothermic Regional Perfusion (aNRP) is an in-situ normothermic oxygenated donor perfusion technique before procurement during controlled donation after circulatory death (cDCD) procedures and allows for organ quality evaluation. There are few data on the effect of aNRP on pancreatic islet isolation and subsequent transplantation outcomes. We aim to evaluate the impact of aNRP on cDCD pancreatic islet isolation and transplantation. A retrospective analysis was performed on pancreatic islet isolation outcomes from aNRP, cDCD, and Donation after Brain death (DBD) pancreases. Isolations were compared to previous donor age (60-75) matched isolations. Islet function was asses by a dynamic Glucose Stimulated Insulin Secretion (dGSIS). Donor baseline characteristics did not differ among groups. Isolations from aNRP pancreases (471,739 IEQ [655,435 - 244,851]) yielded more islets compared to cDCD (218,750 IEQ [375,951 - 112,364, p<0.01) and to DBD (206,522 IEQ [385,544 - 142,446, p=0.03) pancreases. dGSIS tests in seven aNRP islet preparations showed a mean stimulation index of 4.91, indicating good functionality. Bilirubin and alanine aminotransferase during aNRP correlated with islet yield (r2=0.685, p=0.002; r2=0.491, p=0.016 respectively). Islet isolation after aNRP in cDCD donors results in a high islet yield with viable functional islets. aNRP could increase the utilization of pancreases for islet transplantation.

Role of fatty acids in the pathogenesis of ß-cell failure and Type-2 diabetes.

Pancreatic ß-cells are glucose sensors in charge of regulated insulin delivery to the organism, achieving glucose homeostasis and overall energy storage. The latter function promotes obesity when nutrient intake chronically exceeds daily expenditure. In case of ß-cell failure, such weight gain may pave the way for the development of Type-2 diabetes. However, the causal link between excessive body fat mass and potential degradation of ß-cells remains largely unknown and debated. Over the last decades, intensive research has been conducted on the role of lipids in the pathogenesis of ß-cells, also referred to as lipotoxicity. Among various lipid species, the usual suspects are essentially the non-esterified fatty acids (NEFA), in particular the saturated ones such as palmitate. This review describes the fundamentals and the latest advances of research on the role of fatty acids in ß-cells. This includes intracellular pathways and receptor-mediated signaling, both participating in regulated glucose-stimulated insulin secretion as well as being implicated in ß-cell dysfunction. The discussion extends to the contribution of high glucose exposure, or glucotoxicity, to ß-cell defects. Combining glucotoxicity and lipotoxicity results in the synergistic and more deleterious glucolipotoxicity effect. In recent years, alternative roles for intracellular lipids have been uncovered, pointing to a protective function in case of nutrient overload. This requires dynamic storage of NEFA as neutral lipid droplets within the ß-cell, along with active glycerolipid/NEFA cycle allowing subsequent recruitment of lipid species supporting glucose-stimulated insulin secretion. Overall, the latest studies have revealed the two faces of the same coin.

Human pancreatic islet-derived stromal cells reveal combined features of mesenchymal stromal cells and pancreatic stellate cells.

BACKGROUND: Mesenchymal stromal cells (MSCs) are recognized for their potential in regenerative medicine, attributed to their multipotent differentiation capabilities and immunomodulatory properties. Despite this potential, the classification and detailed characterization of MSCs, especially those derived from specific tissues like the pancreas, remains challenging leading to a proliferation of terminology in the literature. This study aims to address these challenges by providing a thorough characterization of human pancreatic islets-derived mesenchymal stromal cells (hPD-MSCs). METHODS: hPD-MSCs were isolated from donor islets using enzymatic digestion, immortalized through lentiviral transduction of human telomerase reverse transcriptase (hTERT). Cells were characterized by immunostaining, flow cytometry and multilineage differentiation potential into adipogenic and osteogenic lineages. Further a transcriptomic analysis was done to compare the gene expression profiles of hPD-MSCs with other mesenchymal cells. RESULTS: We show that hPD-MSCs express the classical MSC features, including morphological characteristics, surface markers expression (CD90, CD73, CD105, CD44, and CD106) and the ability to differentiate into both adipogenic and osteogenic lineages. Furthermore, transcriptomic analysis revealed distinct gene expression profiles, showing notable similarities between hPD-MSCs and pancreatic stellate cells (PSCs). The study also identified specific genes that distinguish hPD-MSCs from MSCs of other origins, including genes associated with pancreatic function (e.g., ISL1) and neural development (e.g., NPTX1, ZNF804A). A novel gene with an unknown function (ENSG00000286190) was also discovered. CONCLUSIONS: This study enhances the understanding of hPD-MSCs, demonstrating their unique characteristics and potential applications in therapeutic strategies. The identification of specific gene expression profiles differentiates hPD-MSCs from other mesenchymal cells and opens new avenues for research into their role in pancreatic function and neural development.

Adropin Is Expressed in Pancreatic Islet Cells and Reduces Glucagon Release in Diabetes Mellitus.

Diabetes mellitus affects 537 million adults around the world. Adropin is expressed in different cell types. Our aim was to investigate the cellular localization in the endocrine pancreas and its effect on modulating pancreatic endocrine hormone release in streptozotocin (STZ)-induced diabetic rats. Adropin expression in the pancreas was investigated in normal and diabetic rats using immunohistochemistry and immunoelectron microscopy. Serum levels of insulin, glucagon pancreatic polypeptide (PP), and somatostatin were measured using a Luminex® χMAP (Magpix®) analyzer. Pancreatic endocrine hormone levels in INS-1 832/3 rat insulinoma cells, as well as pancreatic tissue fragments of normal and diabetic rats treated with different concentrations of adropin (10-6, 10-9, and 10-12 M), were measured using ELISA. Adropin was colocalized with cells producing either insulin, glucagon, or PP. Adropin treatment reduced the number of glucagon-secreting alpha cells and suppressed glucagon release from the pancreas. The serum levels of GLP-1 and amylin were significantly increased after treatment with adropin. Our study indicates a potential role of adropin in modulating glucagon secretion in animal models of diabetes mellitus.

Peptide-Coated Polycaprolactone-Benzalkonium Chloride Nanocapsules for Targeted Drug Delivery to the Pancreatic ß-Cell.

Targeting current therapies to treat or prevent the loss of pancreatic islet ß-cells in Type 1 Diabetes (T1D) may provide improved efficacy and reduce off-target effects. Current efforts to target the ß-cell are limited by a lack of ß-cell-specific targets and the inability to test multiple targeting moieties with the same delivery vehicle. Here, we fabricate a tailorable polycaprolactone nanocapsule (NC) in which multiple different targeting peptides can be interchangeably attached for ß-cell-specific delivery. Incorporation of a cationic surfactant in the NC shell allows for the attachment of Exendin-4 and an antibody for ectonucleoside triphosphate diphosphohydrolase 3 (ENTPD3) for ß-cell-specific targeting. The average NC size ranges from 250 to 300 nm with a polydispersity index under 0.2. The NCs are nontoxic, stable in media culture, and can be lyophilized and reconstituted. NCs coated with a targeting peptide were taken up by human cadaveric islet ß-cells and human stem cell-derived ß-like cells (sBC) in vitro with a high level of specificity. Furthermore, NCs successfully delivered both hydrophobic and hydrophilic cargo to human ß-cells. Additionally, Exendin-4-coated NCs were stable and targeted the mouse pancreatic islet ß-cell in vivo. Overall, our tailorable NCs have the potential to improve cell-targeted drug delivery and can be utilized as a screening platform to test the efficacy of cell-targeting peptides.

Microgravity Effect on Pancreatic Islets.

We previously demonstrated that boundary cap neural crest stem cells (BCs) induce the proliferation of beta-cells in vitro, increase survival of pancreatic islets (PIs) in vivo after transplantation, and themselves strongly increase their proliferation capacity after exposure to space conditions. Therefore, we asked if space conditions can induce the proliferation of beta-cells when PIs are alone or together with BCs in free-floating or 3D-printed form. During the MASER 15 sounding rocket experiment, half of the cells were exposed to 6 min of microgravity (µg), whereas another group of cells were kept in 1 g conditions in a centrifuge onboard. The proliferation marker EdU was added to the cells just before the rocket reached µg conditions. The morphological assessment revealed that PIs successfully survived and strongly proliferated, particularly in the free-floating condition, though the fusion of PIs hampered statistical analysis. Proliferation of beta-cells was displayed in 3D-printed islets two weeks after µg exposure, suggesting that the effects of µg may be delayed. Thus, PIs in 3D-printed scaffolds did not fuse, and this preparation is more suitable than free-floating specimens for morphological analysis in µg studies. PIs maintained their increased proliferation capacity for weeks after µg exposure, an effect that may not appear directly, but can emerge after a delay.

Immunodetection of selected pancreatic hormones under intragastric administration of apelin-13, a novel endogenous ligand for an angiotensin-like orphan G-protein coupled receptor, in unweaned rats.

Introduction: This study investigated the effects of intragastric administration of apelin-13 on the secretion of critical pancreatic hormones in a cohort of three-week-old Wistar rats. The research aimed to uncover apelin's modulatory roles in endocrine interactions dictating metabolic homeostasis during early life. Material and Methods: Rats were randomly assigned to control or experimental groups, receiving apelin-13 or saline for 14 days. The study population consisted of three-week-old Wistar rats of both sexes, weighing between 20 and 25 grams. Histological examination, analysis of variance and t-tests were employed to assess significant differences. Results: Distinctive alterations in large islet morphology were observed, indicating a notable reduction in size. Additionally, an increase in alpha- and beta-cell density within specific islet sizes was noted, suggesting significant changes in cell populations. The study found a substantial increase in mitotic activity and a decrease in apoptosis in small and medium-sized islets post apelin-13 administration, indicating its potential role in regulating cell survival and proliferation. Conclusion: The notable reduction in large islet size coupled with increased alpha and beta cell density implies a targeted impact of apelin-13 on pancreatic cell dynamics. Also, the observed increase in mitotic activity and decrease in apoptosis in small and medium-sized islets suggest its potential regulatory role in cell survival and proliferation within the pancreatic microenvironment.

Cadmium-induced pancreatic toxicity in rats: comparing vitamin C and Nigella sativa as protective agents: a histomorphometric and ultrastructural study.

The study aimed to assess the toxic effect of cadmium (Cd) on the exocrine and endocrine functions of pancreas, the changes in pancreatic tissue after Cd withdrawal, and the protective effects of vitamin C (VC) and Nigella sativa (NS) against Cd-induced damage. Rats were assigned to: control, Cd-treated (0.5 mg/kg/d intraperitoneal [IP] injection), VC and Cd-treated (receiving 100 mg/kg/d VC orally and Cd concomitantly), NS and Cd-treated (receiving 20 mg/kg/d NS and Cd, simultaneously), and Cd withdrawal (receiving Cd for 30 d then living free for recovery for other 30 d). Blood samples were collected and post-sacrifice pancreatic specimens were processed for light and electron microscope study. Quantitative analyses of pancreatic collagen area%, pancreatic islet parameters, ß cell density, and insulin immunoexpression were done. Fasting blood glucose was significantly increased in Cd-treated and Cd-withdrawal groups, while co-treatment with VC and NS caused significant reductions (p < 0.05). Cd-induced extensive degenerative changes in pancreatic acini and islets at light and ultrastructure levels. Obvious fibrosis and congestion of blood vessels were noticed. Significant reductions in pancreatic islet number, volume, and surface area and diminished beta cell count and insulin immunoexpression were observed. After withdrawal of Cd, the whole pancreatic tissue still showed a serious impact. Concomitant treatment with VC or NS obviously reduced these degenerative changes and significantly improved pancreatic islet parameters and insulin immunoexpression. VC showed a better amendment than NS, but this difference was statistically insignificant. Therefore, VC and NS could be used as prophylactic agents that lessen Cd consequences on the pancreas.

miR-146a-5p mediates inflammation-induced ß cell mitochondrial dysfunction and apoptosis.

We previously showed that miR-146a-5p is upregulated in pancreatic islets treated with pro-inflammatory cytokines. Others have reported that miR-146a-5p overexpression is associated with ß cell apoptosis and impaired insulin secretion. However, the molecular mechanisms mediating these effects remain elusive. To investigate the role of miR-146a-5p in ß cell function, we developed stable MIN6 cell lines to either overexpress or inhibit the expression of miR-146a-5p. Monoclonal cell populations were treated with pro-inflammatory cytokines (IL-1ß, IFNγ, and TNFα) to model type 1 diabetes (T1D) in vitro. We found that overexpression of miR-146a-5p increased cell death under conditions of inflammatory stress and led to mitochondrial membrane depolarization, whereas inhibition of miR-146a-5p reversed these effects. Additionally, inhibition of miR-146a-5p increased insulin secretion, mitochondrial DNA copy number, respiration rate, and ATP production Further, RNA sequencing data showed enrichment of pathways related to insulin secretion, apoptosis, and mitochondrial function when the expression levels of miR-146a-5p were altered. Finally, a temporal increase in miR-146a-5p expression levels and a decrease in mitochondria function markers was observed in islets derived from NOD mice. Collectively, these data suggest that miR-146a-5p may promote ß cell dysfunction and death during inflammatory stress by suppressing mitochondrial function.

The Proton Leak of the Inner Mitochondrial Membrane Is Enlarged in Freshly Isolated Pancreatic Islets.

In a number of investigations on the mechanism of the metabolic amplification of insulin secretion, differences between the response of freshly isolated islets and of islets cultured for one day have been observed. Since no trivial explanation like insufficient numbers of viable cells after cell culture could be found, a more thorough investigation into the mechanisms responsible for the difference was made, concentrating on the function of the mitochondria as the site where the metabolism of nutrient stimulators of secretion forms the signals impacting on the transport and fusion of insulin granules. Using combinations of inhibitors of oxidative phosphorylation, we come to the conclusion that the mitochondrial membrane potential is lower and the exchange of mitochondrial reducing equivalents is faster in freshly isolated islets than in cultured islets. The significantly higher rate of oxygen consumption in fresh islets than in cultured islets (13 vs. 8 pmol/min/islet) was not caused by a different activity of the F1F0-ATPase, but by a larger proton leak. These observations raise the questions as to whether the proton leak is a physiologically regulated pathway and whether its larger size in fresh islets reflects the working condition of the islets within the pancreas.

Adipose tissue-derived mesenchymal stem cells promote the vascularization of pancreatic islets transplanted into decellularized pancreatic skeletons.

We have recently developed a model of pancreatic islet transplantation into a decellularized pancreatic tail in rats. As the pancreatic skeletons completely lack endothelial cells, we investigated the effect of co-transplantation of mesenchymal stem cells and endothelial cells to promote revascularization. Decellularized matrix of the pancreatic tail was prepared by perfusion with Triton X-100, sodium dodecyl sulfate and DNase solution. Isolated pancreatic islets were infused into the skeletons via the splenic vein either alone, together with adipose tissue-derived mesenchymal stem cells (adMSCs), or with a combination of adMSCs and rat endothelial cells (rat ECs). Repopulated skeletons were transplanted into the subcutaneous tissue and explanted 9 days later for histological examination. Possible immunomodulatory effects of rat adMSCs on the survival of highly immunogenic green protein-expressing human ECs were also tested after their transplantation beneath the renal capsule. The immunomodulatory effects of adMSCs were also tested in vitro using the Invitrogen Click-iT EdU system. In the presence of adMSCs, the proliferation of splenocytes as a response to phytohaemagglutinin A was reduced by 47% (the stimulation index decreased from 1.7 to 0.9, P = 0.008) and the reaction to human ECs was reduced by 58% (the stimulation index decreased from 1.6 to 0.7, P = 0.03). Histological examination of the explanted skeletons seeded only with the islets showed their partial disintegration and only a rare presence of CD31-positive cells. However, skeletons seeded with a combination of islets and adMSCs showed preserved islet morphology and rich vascularity. In contrast, the addition of syngeneic rat ECs resulted in islet-cell necrosis with only few endothelial cells present. Live green fluorescence-positive endothelial cells transplanted either alone or with adMSCs were not detected beneath the renal capsule. Though the adMSCs significantly reduced in vitro proliferation stimulated by either phytohaemagglutinin A or by xenogeneic human ECs, in vivo co-transplanted adMSCs did not suppress the post-transplant immune response to xenogeneic ECs. Even in the syngeneic model, ECs co-transplantation did not lead to sufficient vascularization in the transplant area. In contrast, islet co-transplantation together with adMSCs successfully promoted the revascularization of extracellular matrix in the subcutaneous tissue.

The interplay of extracellular vesicles in the pathogenesis of metabolic impairment and type 2 diabetes.

The pathogenesis of type 2 diabetes (T2D) involves dysfunction in multiple organs, including the liver, muscle, adipose tissue, and pancreas, leading to insulin resistance and ß cell failure. Recent studies highlight the significant role of extracellular vesicles (EVs) in mediating inter-organ communication in T2D. This review investigates the role of EVs, focusing on their presence and biological significance in human plasma and tissues affected by T2D. We explore specific EV cargo, such as miRNAs and proteins, which affect insulin signaling and glucose metabolism, emphasizing their potential as biomarkers. By highlighting the diagnostic and therapeutic potential of EVs, we aim to provide new insights into their role in early detection, disease monitoring, and innovative treatment strategies for T2D.

Simultaneous Pancreatic and Kidney Transplant in Adult with Autosomal Dominant Polycystic Kidney Disease and Type I Diabetes Mellitus: Post Surgical Events and Genetic Review.

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited condition characterized by the growth of multiple bilateral cysts in the kidneys. We describe the case of a 35-year-old male with combined ADPKD and type 1 diabetes mellitus with a strong family history of both. At the age of 32, he developed end-stage kidney disease for which he underwent preemptive simultaneous pancreatic and kidney transplant, which in turn led to multiple perioperative complications. Evaluation of familial clustering of genetic disease is critical in genetic epidemiology and precision medicine as it enables estimation of lifetime disease risk and early assessment as well as detection of the disease among one's siblings.

Diabetes current and future translatable therapies.

Diabetes is one of the major diseases and concerns of public health systems that affects over 200 million patients worldwide. It is estimated that 90% of these patients suffer from diabetes type 2, while 10% present diabetes type 1. This type of diabetes and certain types of diabetes type 2, are characterized by dysregulation of blood glycemic levels due to the total or partial depletion of insulin-secreting pancreatic ß-cells. Different approaches have been proposed for long-term treatment of insulin-dependent patients; amongst them, cell-based approaches have been the subject of basic and clinical research since they allow blood glucose level sensing and in situ insulin secretion. The current gold standard for insulin-dependent patients is on-demand exogenous insulin application; cell-based therapies aim to remove this burden from the patient and caregivers. In recent years, protocols to isolate and implant pancreatic islets from diseased donors have been developed and tested in clinical trials. Nevertheless, the shortage of donors, along with the need of immunosuppressive companion therapies, have pushed researchers to focus their attention and efforts to overcome these disadvantages and develop alternative strategies. This review discusses current tested clinical approaches and future potential alternatives for diabetes type 1, and some diabetes type 2, insulin-dependent patients. Additionally, advantages and disadvantages of these discussed methods.

Immunoprotection Strategies in ß-Cell Replacement Therapy: A Closer Look at Porcine Islet Xenotransplantation.

Type 1 diabetes mellitus (T1DM) is characterized by absolute insulin deficiency primarily due to autoimmune destruction of pancreatic ß-cells. The prevailing treatment for T1DM involves daily subcutaneous insulin injections, but a substantial proportion of patients face challenges such as severe hypoglycemic episodes and poorly controlled hyperglycemia. For T1DM patients, a more effective therapeutic option involves the replacement of ß-cells through allogeneic transplantation of either the entire pancreas or isolated pancreatic islets. Unfortunately, the scarcity of transplantable human organs has led to a growing list of patients waiting for an islet transplant. One potential alternative is xenotransplantation of porcine pancreatic islets. However, due to inter-species molecular incompatibilities, porcine tissues trigger a robust immune response in humans, leading to xenograft rejection. Several promising strategies aim to overcome this challenge and enhance the long-term survival and functionality of xenogeneic islet grafts. These strategies include the use of islets derived from genetically modified pigs, immunoisolation of islets by encapsulation in biocompatible materials, and the creation of an immunomodulatory microenvironment by co-transplanting islets with accessory cells or utilizing immunomodulatory biomaterials. This review concentrates on delineating the primary obstacles in islet xenotransplantation and elucidates the fundamental principles and recent breakthroughs aimed at addressing these challenges.

The age-dependent regulation of pancreatic islet landscape is fueled by a HNF1a-immune signaling loop.

Animal longevity is a function of global vital organ functionality and, consequently, a complex polygenic trait. Yet, monogenic regulators controlling overall or organ-specific ageing exist, owing their conservation to their function in growth and development. Here, by using pathway analysis combined with wet-biology methods on several dynamic timelines, we identified Hnf1a as a novel master regulator of the maturation and ageing in the adult pancreatic islet during the first year of life. Conditional transgenic mice bearing suboptimal levels of this transcription factor in the pancreatic islets displayed age-dependent changes, with a profile echoing precocious maturation. Additionally, the comparative pathway analysis revealed a link between Hnf1a age-dependent regulation and immune signaling, which was confirmed in the ageing timeline of an overly immunodeficient mouse model. Last, the global proteome analysis of human islets spanning three decades of life largely backed the age-specific regulation observed in mice. Collectively, our results suggest a novel role of Hnf1a as a monogenic regulator of the maturation and ageing process in the pancreatic islet via a direct or indirect regulatory loop with immune signaling.

Regulatory Role of Fatty Acid Metabolism on Glucose-Induced Changes in Insulin and Glucagon Secretion by Pancreatic Islet Cells.

A detailed study of palmitate metabolism in pancreatic islets subject to different experimental conditions, like varying concentrations of glucose, as well as fed or starved conditions, has allowed us to explore the interaction between the two main plasma nutrients and its consequences on hormone secretion. Palmitate potentiates glucose-induced insulin secretion in a concentration-dependent manner, in a physiological range of both palmitate (0-2 mM) and glucose (6-20 mM) concentrations; at glucose concentrations lower than 6 mM, no metabolic interaction with palmitate was apparent. Starvation (48 h) increased islet palmitate oxidation two-fold, and the effect was resistant to its inhibition by glucose (6-20 mM). Consequently, labelled palmitate and glucose incorporation into complex lipids were strongly suppressed, as well as glucose-induced insulin secretion and its potentiation by palmitate. 2-bromostearate, a palmitate oxidation inhibitor, fully recovered the synthesis of complex lipids and insulin secretion. We concluded that palmitate potentiation of the insulin response to glucose is not attributable to its catabolic mitochondrial oxidation but to its anabolism to complex lipids: islet lipid biosynthesis is dependent on the uptake of plasma fatty acids and the supply of α-glycerol phosphate from glycolysis. Islet secretion of glucagon and somatostatin showed a similar dependence on palmitate anabolism as insulin. The possible mechanisms implicated in the metabolic coupling between glucose and palmitate were commented on. Moreover, possible mechanisms responsible for islet gluco- or lipotoxicity after a long-term stimulation of insulin secretion were also discussed. Our own data on the simultaneous stimulation of insulin, glucagon, and somatostatin by glucose, as well as their modification by 2-bromostearate in perifused rat islets, give support to the conclusion that increased FFA anabolism, rather than its mitochondrial oxidation, results in a potentiation of their stimulated release. Starvation, besides suppressing glucose stimulation of insulin secretion, also blocks the inhibitory effect of glucose on glucagon secretion: this suggests that glucagon inhibition might be an indirect or direct effect of insulin, but not of glucose. In summary, there seems to exist three mechanisms of glucagon secretion stimulation: 1. glucagon stimulation through the same secretion coupling mechanism as insulin, but in a different range of glucose concentrations (0 to 5 mM). 2. Direct or indirect inhibition by secreted insulin in response to glucose (5-20 mM). 3. Stimulation by increased FFA anabolism in glucose intolerance or diabetes in the context of hyperlipidemia, hyperglycemia, and hypo-insulinemia. These conclusions were discussed and compared with previous published data in the literature. Specially, we discussed the mechanism for inhibition of glucagon release by glucose, which was apparently contradictory with the secretion coupling mechanism of its stimulation.

Advancing Diabetes Research: A Novel Islet Isolation Method from Living Donors.

Pancreatic islet isolation is critical for type 2 diabetes research. Although -omics approaches have shed light on islet molecular profiles, inconsistencies persist; on the other hand, functional studies are essential, but they require reliable and standardized isolation methods. Here, we propose a simplified protocol applied to very small-sized samples collected from partially pancreatectomized living donors. Islet isolation was performed by digesting tissue specimens collected during surgery within a collagenase P solution, followed by a Lympholyte density gradient separation; finally, functional assays and staining with dithizone were carried out. Isolated pancreatic islets exhibited functional responses to glucose and arginine stimulation mirroring donors' metabolic profiles, with insulin secretion significantly decreasing in diabetic islets compared to non-diabetic islets; conversely, proinsulin secretion showed an increasing trend from non-diabetic to diabetic islets. This novel islet isolation method from living patients undergoing partial pancreatectomy offers a valuable opportunity for targeted study of islet physiology, with the primary advantage of being time-effective and successfully preserving islet viability and functionality. It enables the generation of islet preparations that closely reflect donors' clinical profiles, simplifying the isolation process and eliminating the need for a Ricordi chamber. Thus, this method holds promises for advancing our understanding of diabetes and for new personalized pharmacological approaches.

Marginal Zinc Deficiency Promotes Pancreatic Islet Enlargement While Zinc Supplementation Improves the Pancreatic Insulin Response in Zucker Diabetic Fatty Rats.

Zinc deficiency has been associated with the worsening of diabetes while zinc supplementation has been proposed to ameliorate diabetes. This study examined the effects of marginal zinc deficiency (MZD) and zinc supplementation (ZS) on obesity, glycemic control, pancreatic islets, hepatic steatosis and renal function of Zucker diabetic fatty (ZDF) rats. Male ZDF rats were fed an MZD, zinc control (ZC) or ZS diet (4, 30 and 300 mg Zn/kg diet, respectively), and lean Zucker rats were fed a ZC diet for 8 weeks. MZD and ZS did not alter body weight or whole-body composition in ZDF rats. MZD ZDF rats had reduced zinc concentrations in the femur and pancreas, a greater number of enlarged pancreatic islets and a diminished response to an oral glucose load based on a 1.8-fold greater incremental area-under-the-curve (AUC) for glucose compared to ZC ZDF. ZS ZDF rats had elevated serum, femur and pancreatic zinc concentrations, unchanged pancreatic parameters and a 50% reduction in the AUC for insulin compared to ZC ZDF rats, suggesting greater insulin sensitivity. Dietary zinc intake did not alter hepatic steatosis, creatinine clearance, or levels of proteins that contribute to insulin signaling, inflammation or zinc transport in epididymal fat. Potential adverse effects of ZS were suggested by reduced hepatic copper concentrations and elevated serum urea compared to ZC ZDF rats. In summary, ZS improved the pancreatic insulin response but not the glucose handling. In contrast, reduced zinc status in ZDF rats led to impaired glucose tolerance and a compensatory increase in the number and size of pancreatic islets which could lead to ß-cell exhaustion.

GHSR Deletion in ß-Cells of Male Mice: Ineffective in Obesity, but Effective in Protecting against Streptozotocin-Induced ß-Cell Injury in Aging.

Insulin secretion from pancreatic ß cells is a key pillar of glucose homeostasis, which is impaired under obesity and aging. Growth hormone secretagogue receptor (GHSR) is the receptor of nutrient-sensing hormone ghrelin. Previously, we showed that ß-cell GHSR regulated glucose-stimulated insulin secretion (GSIS) in young mice. In the current study, we further investigated the effects of GHSR on insulin secretion in male mice under diet-induced obesity (DIO) and streptozotocin (STZ)-induced ß-cell injury in aging. ß-cell-specific-Ghsr-deficient (Ghsr-ßKO) mice exhibited no glycemic phenotype under DIO but showed significantly improved ex vivo GSIS in aging. We also detected reduced insulin sensitivity and impaired insulin secretion during aging both in vivo and ex vivo. Accordingly, there were age-related alterations in expression of glucose transporter, insulin signaling pathway, and inflammatory genes. To further determine whether GHSR deficiency affected ß-cell susceptibility to acute injury, young, middle-aged, and old Ghsr-ßKO mice were subjected to STZ. We found that middle-aged and old Ghsr-ßKO mice were protected from STZ-induced hyperglycemia and impaired insulin secretion, correlated with increased expression of insulin signaling regulators but decreased pro-inflammatory cytokines in pancreatic islets. Collectively, our findings indicate that ß-cell GHSR has a major impact on insulin secretion in aging but not obesity, and GHSR deficiency protects against STZ-induced ß-cell injury in aging.