Decreased Β-cell Mass Research Articles

Gender Specific Effects of Nr4a1 in Obese Mice

A central aspect of type 2 diabetes disease progression is impaired functional β-cell mass. The hyperglycemic and hyperlipidemic environment present in type 2 diabetes corresponds with impaired beta cell function. The orphan nuclear receptor Nr4a1 is critical for fuel utilization in various tissues, however little is known regarding its function in the β-cell. Nr4a1 expression is decreased in the β-cell of rodent models of type 2 diabetes, as well as in primary human islets from type 2 diabetics. Here we demonstrate sex specific effects of β-cell specific Nr4a1 deletion under high fat chow feeding. While female and male βNr4a1−/− mice were no different than wild type controls when fed a standard chow diet, a clear sex dependent difference is observed when fed a high fat diet. While high fat fed male βNr4a1−/− have improved fasting and non-fasting blood glucose levels and no change in glucose tolerance, high fat fed female βNr4a1−/− mice have impaired glucose tolerance as early as one month after beginning high fat feeding. We also found that βNr4a1−/− female mice have decreased β-cell mass and decreased expression in known targets of Nr4a1 regulation including Eno1 and SDHβ. Our data suggest that Nr4a1 is critical for maintenance of beta cell function, and that loss of Nr4a1 under conditions of obesity and overnutrition in females results in impaired beta cell compensation and function. NIH R15DK124835-01A1. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Overexpression of UBE2E2 in Mouse Pancreatic β-Cells Leads to Glucose Intolerance via Reduction of β-Cell Mass.

Genome-wide association studies have identified several gene polymorphisms, including UBE2E2, associated with type 2 diabetes. Although UBE2E2 is one of the ubiquitin-conjugating enzymes involved in the process of ubiquitin modifications, the pathophysiological roles of UBE2E2 in metabolic dysfunction are not yet understood. Here, we showed upregulated UBE2E2 expression in the islets of a mouse model of diet-induced obesity. The diabetes risk allele of UBE2E2 (rs13094957) in noncoding regions was associated with upregulation of UBE2E2 mRNA in the human pancreas. Although glucose-stimulated insulin secretion was intact in the isolated islets, pancreatic β-cell-specific UBE2E2-transgenic (TG) mice exhibited reduced insulin secretion and decreased β-cell mass. In TG mice, suppressed proliferation of β-cells before the weaning period and while receiving a high-fat diet was accompanied by elevated gene expression levels of p21, resulting in decreased postnatal β-cell mass expansion and compensatory β-cell hyperplasia, respectively. In TG islets, proteomic analysis identified enhanced formation of various types of polyubiquitin chains, accompanied by increased expression of Nedd4 E3 ubiquitin protein ligase. Ubiquitination assays showed that UBE2E2 mediated the elongation of ubiquitin chains by Nedd4. The data suggest that UBE2E2-mediated ubiquitin modifications in β-cells play an important role in regulating glucose homeostasis and β-cell mass.

DYRK1A inhibitors leucettines and TGF-β inhibitor additively stimulate insulin production in beta cells, organoids, and isolated mouse islets.

The decreased β-cell mass and impaired β-cell functionality are the primary causes of diabetes mellitus (DM). Nevertheless, the underlying molecular mechanisms by which β-cell growth and function are controlled are not fully understood. In this work, we show that leucettines, known to be DYRK1A kinase inhibitors, can improve glucose-stimulated insulin secretion (GSIS) in rodent β-cells and isolated islets, as well as in hiPSC-derived β-cells islets. We confirm that DYRK1A is expressed in murine insulinoma cells MIN6. In addition, we found that treatment with selected leucettines stimulates proliferation of β-cells and promotes MIN6 cell cycle progression to the G2/M phase. This effect is also confirmed by increased levels of cyclin D1, which is highly responsive to proliferative signals. Among other leucettines, leucettine L43 had a negligible impact on β-cell proliferation, but markedly impair GSIS. However, leucettine L41, in combination with LY364947, a, a potent and selective TGF-β type-I receptor, significantly promotes GSIS in various cellular diabetic models, including MIN6 and INS1E cells in 2D and 3D culture, iPSC-derived β-cell islets derived from iPSC, and isolated mouse islets, by increased insulin secretion and decreased glucagon level. Our findings confirm an important role of DYRK1A inhibitors as modulators of β-cells function and suggested a new potential target for antidiabetic therapy. Moreover, we show in detail that leucettine derivatives represent promising antidiabetic agents and are worth further evaluation, especially in vivo.

Gabaergic System in the Regulation of the Functioning of Pancreas Beta-Cells in Normal Physiological Conditions and in Diabetes

Abstract—The incidence of diabetes mellitus (DM) is steadily increasing all over the world, and at the same time there is an increase in its complications, which are the main causes of early disability and premature death. The pathogenesis of DM is based on a steady decrease in pancreatic β-cells. A decrease in β-cell mass leads to a decrease in insulin production and the development of hyperglycemia and associated severe complications. Therefore, the need to prevent the death of β-cells and stimulate their regeneration is obvious. In recent literature, much attention has been paid to the role of GABA in the regulation of the function of α- and β-cells of the pancreas and carbohydrate metabolism, which is the subject of this review. Gamma-aminobutyric acid (GABA) in β-cells and pancreatic islets is determined in quantities comparable to those in the brain. It also contains a high amount of glutamadecarboxylase, an enzyme that synthesizes GABA. In DM, the level of GABA in pancreatic β-cells decreases and this correlates with the severity of DM. GABA plays an important role in the paracrine regulation of α- and β-cell functions and carbohydrate homeostasis. The potential possibility of using GABA to achieve a decrease in apoptosis and, at the same time, an increase in the regeneration of β-cells, an increase in the β-cell mass of the pancreas has been proven. It has been proven that the positive effect of GABA on the structure and functions of pancreatic β-cells in DM can be significantly higher when combined with antidiabetic agents: GLP-1 receptor agonists, DPP-4 inhibitors, SGLT-2 inhibitors, and others. The antidiabetic properties of GABA are explained by its interaction with various signaling proteins (Kloto protein, SIRT, PI3K/Akt, CREB-IRS2, NF-kB, Nrf2 and many others), through which these effects are realized. Data on the pancreatic protective effect of GABA and its derivatives can form the basis for the development of a new pharmacotherapeutic strategy for the treatment of DM and associated complications.

Clearance of p16Ink4a-positive cells in a mouse transgenic model does not change β-cell mass and has limited effects on their proliferative capacity

Type 2 diabetes is partly characterized by decreased β-cell mass and function which have been linked to cellular senescence. Despite a low basal proliferative rate of adult β-cells, they can respond to growth stimuli, but this proliferative capacity decreases with age and correlates with increased expression of senescence effector, p16Ink4a. We hypothesized that selective deletion of p16Ink4a-positive cells would enhance the proliferative capacity of the remaining β-cells due to the elimination of the local senescence-associated secretory phenotype (SASP). We aimed to investigate the effects of p16Ink4a-positive cell removal on the mass and proliferative capacity of remaining β-cells using INK-ATTAC mice as a transgenic model of senolysis. Clearance of p16Ink4a positive subpopulation was tested in mice of different ages, males and females, and with two different insulin resistance models: high-fat diet (HFD) and insulin receptor antagonist (S961). Clearance of p16Ink4a-positive cells did not affect the overall β-cell mass. β-cell proliferative capacity negatively correlated with cellular senescence load and clearance of p16Ink4a positive cells in 1-year-old HFD mice improved β-cell function and increased proliferative capacity in a subset of animals. Single-cell sequencing revealed that the targeted p16Ink4a subpopulation of β-cells is non-proliferative and non-SASP producing whereas additional senescent subpopulations remained contributing to continued local SASP secretion. In conclusion, deletion of p16Ink4a cells did not negatively impact beta-cell mass and blood glucose under basal and HFD conditions and proliferation was restored in a subset of HFD mice opening further therapeutic targets in the treatment of diabetes.

Role of natural mTOR inhibitors in treatment of diabetes mellitus.

Diabetes mellitus is one of the most common and complex problems in today's society and is responsible for many socio-economic problems. Type 1 diabetes is due to a defect in insulin secretion caused by a destruction of pancreatic β cells. In contrast, the pathogenesis of type 2 diabetes is associated with the development of insulin resistance in the liver and peripheral tissues, a decrease in β-cell mass, and a defect in insulin secretion. Various factors such as inflammation, stress, obesity, and lifestyle are involved in diabetes. Long-term or chronic increase in glucose in these patients is the leading causes of secondary disorders such as micro- and macro-angiopathy, weakness of the antioxidant defense system, and metabolic disorders and altered lipid profile. The above conditions lead to short-term and long-term complications. These complications cause damage to the physical and physiological function of diverse organs of the body and threaten human health. Late complications of diabetes, including nephropathy, retinopathy, cardiovascular complications, neuropathy, hypertension, and weight gain, are common, and more research has been done on them. Numerous drugs such as meglitinides, biguanides, and thiazolidinedione have been proposed to reduce high blood sugar, but due to the lack of complete cure of this disease with the use of existing drugs, the tendency to use alternative and traditional therapies has increased. In the meantime, the role of herbs with hypoglycemic properties in the treatment of diabetic patients cannot be ignored. The consumption of herbs by people with diabetes has become widespread even in Western countries. The use of herbs could be considered when conventional therapies cannot control the disease, and the patient needs to be prescribed insulin. The mammalian target of rapamycin, mTOR, plays a significant role in regulating cell growth, cellular metabolic status in response to nutrients, many extracellular cues, and growth factors. Impaired insulin secretion can lead to altered mTOR signaling. The mTOR pathway has shown different behaviors depending on the situation. It has been shown that mTOR can regulate the adaptation of β cells to blood sugar, and chronic inhibition of the mTOR pathway can also induce diabetes. Here, we have reviewed recent findings on the role of mTOR in major metabolic organs, such as the liver, pancreas, brain, and adipose tissue and muscle, and discussed its potential as a diabetes-related drug target.

12-OR: Preventing ß-Cell Death under Glucotoxic Conditions: The Role of ChREBPb

Glucotoxicity is a major mediator of β-cell dysfunction derived from prolonged hyperglycemia. A better understanding of glucotoxicity and preservation of β-cell mass are urgently needed. Carbohydrate response element binding protein (ChREBP) is a glucose-responsive, lipogenic transcription factor with two splice isoforms, ChREBPα and ChREBPβ. We previously showed ChREBPβ is induced by glucose and is required for glucose-stimulated β-cell proliferation in both rodent and human β-cells. In addition, we identified ChREBPβ as a marker for hyperglycemia in β-cells, with its nuclear expression reflecting the progression and severity of the diabetic state. Here, we demonstrate that β-cell death due to glucolipotoxicity (20 mM glucose + 1 mM palmitate) can be prevented by silencing ChREBPβ (6.5±3.1% TUNEL+/Insulin+ in ChREBPβ knock-out islets compared with 47.2±13.6% in control islets, N=7) , most likely via inhibition of lipogenesis and prevention of ceramide-mediated β-cell death. Furthermore, we generated mice with β-cell specific overexpression of ChREBPβ. These mice exhibited increased non-fasting blood glucose levels, impaired glucose tolerance and a marked decrease in β-cell mass, all in a gene dose-dependent manner (OE of one or two alleles of ChREBPβ, N=5) . ChREBPβ overexpression in human beta cells also mimicked glucotoxicity (93.6±3.1% TUNEL+/Insulin+, N=3) . Importantly, we show that ChREBPβ-mediated rodent and human β-cell death was rescued by co-expression with ChREBPα, or by pharmacological activation of Nrf2, a downstream effector of ChREBPα (6.6±1.9 and 2.8±0.9%, respectively, TUNEL+/Insulin+, N=3) . Altogether, our data demonstrate that ChREBPβ is a marker and a causative effector of glucotoxicity, and that downregulating ChREBPβ levels or upregulating ChREBPα levels or its downstream effector (NRF2) rescues β-cells from glucotoxicity. These results position ChREBPβ as a therapeutic target for the prevention of β-cell loss in T2D, an important unmet need in diabetes research. Disclosure L.S.Katz: None. G.Brill: None. M.A.Herman: Research Support; Eli Lilly and Company. A.Garcia-ocana: Consultant; Sun Pharmaceutical Industries Ltd. D.Scott: None. Funding NIH, R01DK130300NIH, R01DK114338NIH, R01DK108905

1446-P: Sex-Specific Effects of Nr4a1 in the Pancreatic Beta Cell

A central aspect of type 2 diabetes disease progression is impaired functional β-cell mass. The hyperglycemic and hyperlipidemic environment present in type 2 diabetes corresponds with impaired beta cell function. The orphan nuclear receptor Nr4a1 is critical for fuel utilization in various tissues, however little is known regarding its function in the β-cell. Nr4a1 expression is decreased in the β-cell of rodent models of type 2 diabetes, as well as in primary human islets from type 2 diabetics. Here we demonstrate sex specific effects of β-cell specific Nr4a1 deletion under high fat chow feeding. While female and male βNr4a1-/- mice were no different than wild type controls when fed a standard chow diet, a clear sex dependent difference is observed when fed a high fat diet. High fat fed male βNr4a1-/- have improved fasting and non-fasting blood glucose levels, high fat fed female βNr4a1-/- mice have impaired glucose tolerance as early as two months after beginning high fat feeding. Furthermore, female βNr4a1-/- mice have decreased β-cell mass and improved insulin tolerance. Given the sex specific differences in glucose tolerance, we demonstrated that female mice fed a high fat diet have increased circulating estrogen, and that treatment of INS-1 832/13 cells and primary mouse islets with estradiol resulted in increased expression of Nr4a1 and not the other two Nr4a family members. Our data suggest that Nr4a1 is critical for estrogen mediated maintenance of beta cell function and mass under obesogenic conditions, and that loss of Nr4a1 under conditions of obesity and overnutrition in females results in impaired beta cell compensation and function. Disclosure J.S.Tessem: None. J.Herring: None. Funding National Institutes of Health (1R15DK124835-01A1)

Beneficial effects of physical exercise for β-cell maintenance in a type 1 diabetes mellitus animal model.

What is the central question of this study? Type 1 diabetes mellitus (T1D) leads to hyperglycaemia owing to pancreatic β-cell destruction by the immune system. Physical exercise has been shown to have potentially beneficial protective roles against cytokine-induced pancreatic β-cell death, but its benefits are yet to be proved and should be understood better, especially in the islet environment. What is the main finding and its importance? Physical exercise protects against β-cell loss in a well-described animal model for T1D, induced by multiple low doses of streptozotocin. This seems to be related to reduced cytokine-induced β-cell death and increased islet cell proliferation. Contributions of islet neogenesis and/or transdifferentiation of pancreatic non-β-cells into β-cells cannot be excluded. Physical exercise has beneficial effects on pancreatic β-cell function and survival in a pro-inflammatory environment. Although these effects have been linked to decreased islet inflammation and modulation of pro-apoptotic pathways, little is known about the islet microenvironment. Our aim was to evaluate the effects of physical exercise in islet histomorphology in a mouse model of type1 diabetes mellitus induced by multiple low doses of streptozotocin. As expected, induction of type1 diabetes mellitus led to β-cell loss and, consequently, decreased islet area. Interestingly, although the decrease in islet area was not prevented by physical exercise, this was not the case for the decrease in β-cell mass. This was probably related to induction of β-cell regeneration, because we observed increased proliferation and regeneration markers, such as Ki67 and Pcna, in islets of trained mice. These were found in the central and peripheral regions of the islets. An increase in the percentage of α- and δ-cells in these conditions, combined with an increase in proliferation and Pax4 labelling in peripheral regions, suggest that β-cell regeneration might also occur by transdifferentiation. This agrees with the presence of cells double stained for insulin and glucagon only in islets of diabetic trained mice. In addition, this group had more extra-islet insulin-positive cells and islets associated with ducts than diabetic mice. Physical exercise also decreased nuclear factor-κB activation in islet cells of diabetic trained compared with diabetic untrained mice, indicating a decrease in pro-inflammatory cytokine-induced β-cell death. Taken together, these findings indicate that preservation of β-cell mass induced by physical exercise involves an increase in β-cell replication and decrease in β-cell death, together with islet neogenesis and islet cell transdifferentiation.

Nuclear Factor-Y in Mouse Pancreatic β-Cells Plays a Crucial Role in Glucose Homeostasis by Regulating β-Cell Mass and Insulin Secretion.

Pancreatic β-cell mass and insulin secretion are determined by the dynamic change of transcription factor expression levels in response to altered metabolic demand. Nuclear factor-Y (NF-Y) is an evolutionarily conserved transcription factor playing critical roles in multiple cellular processes. However, the physiological role of NF-Y in pancreatic β-cells is poorly understood. The current study was undertaken in a conditional knockout of Nf-ya specifically in pancreatic β-cells (Nf-ya βKO) to define the essential physiological role of NF-Y in β-cells. Nf-ya βKO mice exhibited glucose intolerance without changes in insulin sensitivity. Reduced β-cell proliferation resulting in decreased β-cell mass was observed in these mice, which was associated with disturbed actin cytoskeleton. NF-Y-deficient β-cells also exhibited impaired insulin secretion with a reduced Ca2+ influx in response to glucose, which was associated with an inefficient glucose uptake into β-cells due to a decreased expression of GLUT2 and a reduction in ATP production resulting from the disruption of mitochondrial integrity. This study is the first to show that NF-Y is critical for pancreatic islet homeostasis and function through regulation in β-cell proliferation, glucose uptake into β-cells, and mitochondrial energy metabolism. Modulating NF-Y expression in β-cells may therefore offer an attractive approach for therapeutic intervention.

A Brief Review of the Mechanisms of β-Cell Dedifferentiation in Type 2 Diabetes.

Diabetes is a metabolic disease characterized by hyperglycemia. Over 90% of patients with diabetes have type 2 diabetes. Pancreatic β-cells are endocrine cells that produce and secrete insulin, an essential endocrine hormone that regulates blood glucose levels. Deficits in β-cell function and mass play key roles in the onset and progression of type 2 diabetes. Apoptosis has been considered as the main contributor of β-cell dysfunction and decrease in β-cell mass for a long time. However, recent studies suggest that β-cell failure occurs mainly due to increased β-cell dedifferentiation rather than limited β-cell proliferation or increased β-cell death. In this review, we summarize the current advances in the understanding of the pancreatic β-cell dedifferentiation process including potential mechanisms. A better understanding of β-cell dedifferentiation process will help to identify novel therapeutic targets to prevent and/or reverse β-cell loss in type 2 diabetes.

Ternary complex factor regulates pancreatic islet size and blood glucose homeostasis in transgenic mice

A hallmark of diabetes mellitus is the inability of pancreatic β-cells to secrete sufficient amounts of insulin for maintaining normoglycemia. The formation of smaller islets may underlie the development of a diabetic phenotype, as a decreased β-cell mass will produce an insufficient amount of insulin. For a pharmacological intervention it is crucial to identify the proteins determining β-cell mass. Here, we identified the ternary complex factor (TCF) Elk-1 as a regulator of the size of pancreatic islets. Elk-1 mediates, together with a dimer of the serum-response factor (SRF), serum response element-regulated gene transcription. Elk-1 is activated in glucose-treated pancreatic β-cells but the biological functions of this protein in β-cells are so far unknown. Elk-1 and homologous TCF proteins are expressed in islets and insulinoma cells. Gene targeting experiments revealed that the TCF proteins show redundant activities. To solve the problem of functional redundancy of these homologous proteins, we generated conditional transgenic mice expressing a dominant-negative mutant of Elk-1 in pancreatic β-cells. The mutant competes with the wild-type TCFs for DNA and SRF-binding. Expression of the Elk-1 mutant in pancreatic β-cells resulted in the generation of significantly smaller islets and increased caspase-3 activity, indicating that apoptosis was responsible for the reduction of the pancreatic islet size. Glucose tolerance tests revealed that transgenic mice expressing the dominant-negative mutant of Elk-1 in pancreatic β-cells displayed impaired glucose tolerance. Thus, we show here for the first time that TCF controls important functions of pancreatic β-cells in vivo. Elk-1 may be considered as a new therapeutic target for the treatment of diabetes.

Administration of mulberry leaves maintains pancreatic \u03b2-cell mass in obese/type 2 diabetes mellitus mouse model

BackgroundType 2 diabetes mellitus is characterized by insulin resistance and pancreatic β-cell dysfunction. A decrease in β-cell mass, which occurs during the progression of Type 2 diabetes mellitus, contributes to impaired insulin secretion. Mulberry leaves contain various nutritional components that exert anti-diabetic and anti-atherogenic effects. The present study analyzed the effects of mulberry leaf intake on pancreatic β-cells to clarify the mechanisms underlying its anti-diabetic function.MethodsMulberry leaves (Morus alba L.) were dried at 180 °C for 8 s in a hot-air mill and fed to obesity/Type 2 diabetes mellitus db/db mouse models at 5% (w/w) as part of a normal diet from 7 to 10, 15, or 20 weeks of age. An intraperitoneal glucose tolerance test was then performed on the mice. To evaluate the β-cell mass, the pancreas was subjected to immunohistological analysis with an anti-insulin antibody. A TUNEL assay and immunohistological analysis with a proliferation marker was also performed. Expression levels of endoplasmic reticulum stress-responsible genes and proliferation markers were assessed by quantitative RT-PCR.ResultsIntake of mulberry leaves maintained the β-cell function of db/db mice. Moreover, oral administration of mulberry leaves significantly decreased cell death by reducing endoplasmic reticulum stress in the pancreas. Mulberry leaves significantly increased proliferation of β-cells and the expression of pancreatic duodenal homeobox1 mRNA in the pancreas.ConclusionConsidered together, these results indicate that dietary mulberry leaf administration can maintain insulin levels and pancreatic β-cell mass, at least in part, by suppressing endoplasmic reticulum stress in Type 2 diabetes mellitus mouse models.

Decreased striatal vesicular monoamine transporter 2 (VMAT2) expression in a type 1 diabetic rat model: A longitudinal study using micro-PET/CT

AimsDiabetes mellitus is a risk factor for Parkinson's disease. These diseases share similar pathogenic pathways, such as mitochondrial dysfunction, inflammation, and altered metabolism. Despite these similarities, the pathogenic relationship between these two diseases is unclear. [18F]FP-(+)-DTBZ is a promising radiotracer targeting VMAT2, which has been used to measure β-cell mass and to diagnose Parkinson's disease. The aim of this study was to examine the effect of type 1 diabetes on VMAT2 expression in the striatum using [18F]FP-(+)-DTBZ. Materials and methodsA longitudinal study of type 1 diabetic rats was established by intraperitoneally injecting male Wistar rats with streptozotocin. Rats injected with saline were used as the control group. Glucose level, body weight, and [18F]FP-(+)-DTBZ uptake in the striatum and pancreas were evaluated at 0.5, 1, 4, 6 and 12 months after STZ or saline injection. ResultsAt one-half month post-STZ injection, the glucose levels in these rats increased and then returned to a normal level at 6 months. Along with increased glucose levels, body weight was also decreased significantly and returned slowly to a normal level. β-Cell mass and striatal [18F]FP-(+)-DTBZ uptake were impaired significantly at 2 weeks post-STZ injection in type 1 diabetic rats and returned to a normal level at 6 and 4 months post-STZ injection. ConclusionsDue to increased glucose levels and decreased β-cell mass, decreased [18F]FP-(+)-DTBZ uptake in the striatum was observed in type 1 diabetic rats. Decreased BCM and increased glucose levels were correlated with VMAT2 expression in the striatum which indicated DM is a risk factor for PD.

Serotonin Regulates Adult β-Cell Mass by Stimulating Perinatal β-Cell Proliferation.

A sufficient β-cell mass is crucial for preventing diabetes, and perinatal β-cell proliferation is important in determining the adult β-cell mass. However, it is not yet known how perinatal β-cell proliferation is regulated. Here, we report that serotonin regulates β-cell proliferation through serotonin receptor 2B (HTR2B) in an autocrine/paracrine manner during the perinatal period. In β-cell-specific Tph1 knockout (Tph1 βKO) mice, perinatal β-cell proliferation was reduced along with the loss of serotonin production in β-cells. Adult Tph1 βKO mice exhibited glucose intolerance with decreased β-cell mass. Disruption of Htr2b in β-cells also resulted in decreased perinatal β-cell proliferation and glucose intolerance in adulthood. Growth hormone (GH) was found to induce serotonin production in β-cells through activation of STAT5 during the perinatal period. Thus, our results indicate that GH-GH receptor-STAT5-serotonin-HTR2B signaling plays a critical role in determining the β-cell mass by regulating perinatal β-cell proliferation, and defects in this pathway affect metabolic phenotypes in adults.

Fetal androgen signaling defects affect pancreatic β-cell mass and function, leading to glucose intolerance in high-fat diet-fed male rats.

We previously demonstrated that androgen signaling expands pancreatic β-cell mass in the sexual maturation period (Am J Physiol Endocrinol Metab 314: E274-E286, 2018). The aim of this study was to elucidate whether fetal androgen signaling plays important roles in β-cell mass development and β-cell function in adulthood, defects of which are associated with type 2 diabetes mellitus. In the pancreas of male fetuses, androgen receptor (AR) was strongly expressed in the cytoplasm and at the cell membrane of Nkx6.1-positive β-cell precursor cells but was markedly reduced in insulin-positive β-cells. Administration of the anti-androgen flutamide to pregnant dams during late gestation reduced β-cell mass and Ki67-positive proliferating β-cells at birth in a male-specific manner without affecting body weight. The decrease of β-cell mass in flutamide-exposed male rats was not recovered when rats were fed a standard diet, whereas it was fully recovered when rats were fed a high-fat diet (HFD), at 6 and 12 wk of age. Flutamide exposure in utero led to the development of glucose intolerance in male rats due to a decrease in insulin secretion when fed HFD but not standard diet. Insulin sensitivity did not differ between the two groups irrespective of diet. These results indicated that the action of fetal androgen contributed to β-cell mass expansion in a sex-specific manner at birth and to the development of glucose intolerance by decreasing the secretion of insulin in HFD-fed male rats. Our data demonstrated the involvement of fetal androgen signaling in hypothesized sex differences in the developmental origins of health and disease by affecting pancreatic β-cell function.

2162-P: Autophagy Deficiency Cumulatively Causes ß-Cell Failure in Mice

Autophagy is known to play a pivotal role in intracellular quality control through the degradation of damaged organelles and components. We previously reported that β-cell specific autophagy deficient mice (βAtg7KO), which lack Atg7 in β cells throughout their lives after birth, exhibited impaired glucose tolerance accompanied by decreased β-cell mass. Since the phenotypes in βAtg7KO mice result from life-long autophagic failure, it remains unclear as to when and how autophagy deficiency affects β-cell homeostasis. To address these questions, we have generated the inducible β-cell-specific Atg7-knockout mice (iβAtg7KO), by crossing mice carrying floxed Atg7 allele with MIP-Cre/ERT mice that induce Cre-mediated recombination in a tamoxifen-inducible manner under the control of mouse Ins1 promoter. When the autophagy deficiency was induced for 2 weeks (between 10 and 12 weeks of age), the iβAtg7KO2W mice exhibited normal glucose tolerance during IPGTT. On the other hand, the prolonged autophagy deficiency for 6 weeks (between 6 and 12 weeks of age) in iβAtg7KO6W mice caused glucose intolerance with significantly impaired insulin secretion. Thus, the short-term Atg7 deficiency in iβAtg7KO2W mice did not apparently deteriorate β-cell function, whereas the long-term Atg7 deficiency for 6 weeks in iβAtg7KO6W mice caused β-cell failure. In order to investigate the underlying molecular mechanisms by which the autophagy deficiency links to β-cell failure, RNA-sequencing was performed with the isolated islets from iβAtg7KO2w, iβAtg7KO6w mice and control littermates. Among more than 13,000 genes expressed in the islets, we identified a gene that was expressed >50-fold higher in iβAtg7KO2W and iβAtg7KO6w mice than in the control littermates, and that are highly expressed in diabetic db/db mice. Taken together, these findings suggest that the autophagy failure cumulatively leads to β-cell failure after a certain interval, accompanied by stepwise alteration of gene expression patterns. Disclosure L. Suzuki: None. T. Miyatsuka: None. M. Himuro: None. M. Miura: None. T. Katahira: None. K. Komiya: None. Y. Fujitani: Research Support; Self; Takeda Pharmaceutical Company Limited. Y. Nishida: None. H. Watada: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Kissei Pharmaceutical Co., Ltd., Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Pfizer Inc., Sanofi, Sumitomo Dainippon Pharma Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited. Speaker's Bureau; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Takeda Pharmaceutical Company Limited, Terumo Medical Corporation. Other Relationship; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Kowa Pharmaceutical Europe Co. Ltd., Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Sanwa Chemical Industry Co. Ltd., Takeda Pharmaceutical Company Limited. Funding Japan Society for the Promotion of Science

2134-P: Protection of Beta-Cell Mass from Diabetogenic Condition-Induced Apoptosis by the Inhibition of Mammalian STE20-Like Protein Kinase 1 (MST1)

Impaired insulin secretion, a characteristic of type 2 diabetes (T2D) is partly attributed to decreased β-cell mass due to apoptotic cell death under diabetogenic conditions. Current therapies for diabetes do not address apoptotic cell death mediated β-cell deterioration. Mammalian STE20-like protein kinase 1 (MST1) is reported as one of the critical regulators of β-cell apoptosis under diabetogenic conditions, and therefore, inhibition of MST1 in β-cells may offer β-cell protection and preserve β-cell mass under diabetogenic conditions. We carried out an investigation of MST1 modulation, apoptotic signaling in islet samples from healthy controls, T2D patients and in pancreatic cell lines using MST1 specific siRNAs, and a small molecule inhibitor of MST1 (XMU-MP-1, IC50 ∼100 nM) under diabetogenic conditions. Elevated levels of phospho-MST1, cleaved MST1, and pro-apoptotic markers such as cleaved caspase-3 and BIM were observed in islet samples from T2D patients as compared to healthy control, suggesting the activation of MST1 mediated apoptotic pathway under diabetogenic conditions. Similar findings were observed when pancreatic samples from ob/ob mice and control mice were used. siRNA against MST1 and XMU-MP-1 rescued high glucose (25 mM)/high palmitate (500 µM) induced apoptosis in Min6 and INS-1E cells. The rescue of MIN6 and INS-1E cells were associated with the lowering of phospho-MST1, cleaved MST1 and pro-apoptotic markers such as cleaved caspase-3, phospho-H2B, and BIM. Further, once daily (1 mg/kg) dosing of XMU-MP-1 protected the β-cells in an acute streptozotocin-induced diabetic animal model. Increased numbers of insulin-stained pancreatic islets were observed in XMU-MP-1 treated group compared to disease control. Our data suggest that inhibition of MST1 can protect β-cell mass under diabetogenic conditions. Identification and development of specific small molecule inhibitors of MST1 are underway. Disclosure Z. Sameermahmood: None. D. Sivanandhan: None. B. Kalita: None. S. Ramaiah: None. A. Siddiqui: None. B.R. Zope: None. S.V. Kadnur: None. M. Kanavalli: None. K. V.: None. S. Swaminathan: None. R. G.: None. S. Mohire: None. R.R. Burri: None. R. Kristam: None. J. D.a: None. S. Rajagopal: None. S. Dhakshinamoorthy: None. Funding Jubilant Innovation Inc.

Effects of islet neogenesis associated protein depend on vascular endothelial growth factor gene expression modulated by hypoxia-inducible factor 1-alpha

BackgroundPharmacology has provided efficient tools to improve insulin effect/secretion but the decrease in β-cell mass remains elusive. INGAP-PP could provide a therapeutic alternative to meet that challenge. AimTo further understand the mechanism that links INGAP-PP effects upon β-cell mass and function with islet angiogenesis. MethodologyNormal male Wistar rats were divided into 2 groups and injected with a single dose of 100 mg/Kg suramin or saline. Both groups were divided into 2 subgroups that received daily doses of 2 mg/kg INGAP-PP or saline for ten days. Plasma glucose, triacylglycerol, TBARS, and insulin levels were measured. Pancreas immunomorphometric analyses were also performed. Pancreatic islets were isolated to measure glucose-stimulated insulin secretion (GSIS). Specific islet mRNA levels were studied by qRT-PCR. Statistical analysis was done using ANOVA. ResultsNo differences were recorded in body weight, food intake, or any other plasma parameter measured in all groups. Islets from INGAP-PP-treated rats significantly increased GSIS, β-cell mass, and mRNA levels of Bcl-2, Ngn-3, VEGF-A, VEGF-R2, CD31, Ang1 and Ang2, Laminin β-1, and Integrin β-1, and decreased mRNA levels of Caspase-8, Bad, and Bax. Islets from suramin-treated rats showed significant opposite effects, but INGAPP-PP administration rescued most of the suramin effects in animals treated with both compounds. ConclusionOur results reinforce the concept that INGAP-PP enhances insulin secretion and β-cell mass, acting through PI3K/Akt/mTOR pathways and simultaneously activating angiogenesis through HIF-1α-mediated VEGF-A secretion. Therefore, INGAP-PP might be a suitable antidiabetic agent able to overcome two major alterations present in T2D.

METTL14 is essential for β-cell survival and insulin secretion

Defects in the development, maintenance or expansion of β-cell mass can result in impaired glucose metabolism and diabetes. N6-methyladenosine affects mRNA stability and translation efficiency, and impacts cell differentiation and stress response. To determine if there is a role for m6A in β-cells, we investigated the effect of Mettl14, a key component of the m6A methyltransferase complex, on β-cell survival and function using rat insulin-2 promoter-Cre-mediated deletion of Mettl14 mouse line (βKO). We found that βKO mice with normal chow exhibited glucose intolerance, lower levels of glucose-stimulated insulin secretion, increased β-cell death and decreased β-cell mass. In addition, HFD-fed βKO mice developed glucose intolerance, decreased β-cell mass and proliferation, exhibited lower body weight, increased adipose tissue mass, and enhanced insulin sensitivity due to enhanced AKT signaling and decreased gluconeogenesis in the liver. HFD-fed βKO mice also showed a decrease in de novo lipogenesis, and an increase in lipolysis in the liver. RNA sequencing in islets revealed that Mettl14 deficiency in β-cells altered mRNA expression levels of some genes related to cell death and inflammation. Together, we showed that Mettl14 in β-cells plays a key role in β-cell survival, insulin secretion and glucose homeostasis.