Impaired Beta-cell Function Research Articles

Prenatal androgen excess impairs beta-cell function by decreased sirtuin 3 expression.

Prenatal androgen exposure induces metabolic disorders in female offspring. However, the long-term effect of maternal testosterone excess on glucose metabolism, especially on pancreatic beta-cell function, is rarely investigated. Our current study mainly focused on the effects of prenatal testosterone exposure on glucose metabolism and pancreatic beta- cell function in aged female offspring. By using maternal mice and their female offspring as animal models, we found that prenatal androgen treatment induced obesity and glucose intolerance in aged offspring. These influences were accompanied by decreased fasting serum insulin concentration, elevated serum triglyceride, and testosterone concentrations. Glucose stimulated insulin secretion in pancreatic beta cells of aged female offspring was also affected by prenatal testosterone exposure. We further confirmed that increased serum testosterone contributed to downregulation of sirtuin 3 expression, activated oxidative stress, and impaired pancreatic beta-cell function in aged female offspring. Moreover, over-expression of sirtuin 3 in islets isolated from female offspring treated with prenatal testosterone normalized the oxidative stress level, restored cyclic AMP, and ATP generation, which finally improved glucose-stimulated insulin secretion in beta cells. Taken together, these results demonstrated that prenatal testosterone exposure caused a metabolic disturbance in aged female offspring via suppression of sirtuin 3 expression and activation of oxidative stress in pancreatic beta cells.

Combination of human tau and islet amyloid polypeptide exacerbates metabolic dysfunction in transgenic mice.

Amyloid plaques and neurofibrillary tangles composed of hyperphosphorylated tau are important contributors to Alzheimer's disease (AD). Tau also impacts pancreatic beta cell function and glucose homeostasis. Amyloid deposits composed of islet amyloid polypeptide (IAPP) are a pathological feature of type 2 diabetes (T2D). The current study investigates the role of human tau (hTau) in combination with human IAPP (hIAPP) as a potential mechanism connecting AD and T2D. Transgenic mice expressing hTau and hIAPP in the absence of murine tau were generated to determine the impact of these pathological factors on glucose metabolism. Co-expression of hIAPP and hTau resulted in mice with increased hyperglycaemia, insulin resistance, and glucose intolerance. The hTau-hIAPP mice also exhibited reduced beta cell area, increased amyloid deposition, impaired insulin processing, and reduced insulin content in islets. Tau phosphorylation also increased after stimulation with high glucose. In addition, brain insulin content and signalling were reduced, and tau phosphorylation was increased in these animals. These data support a link between tau and IAPP amyloid, which seems to act co-ordinately to impair beta cell function and glucose homeostasis, and suggest that the combined pathological actions of these proteins may be a potential mechanism connecting AD and T2D. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Human Pluripotent Stem Cells to Model Islet Defects in Diabetes.

Diabetes mellitus is characterized by elevated levels of blood glucose and is ultimately caused by insufficient insulin production from pancreatic beta cells. Different research models have been utilized to unravel the molecular mechanisms leading to the onset of diabetes. The generation of pancreatic endocrine cells from human pluripotent stem cells constitutes an approach to study genetic defects leading to impaired beta cell development and function. Here, we review the recent progress in generating and characterizing functional stem cell-derived beta cells. We summarize the diabetes disease modeling possibilities that stem cells offer and the challenges that lie ahead to further improve these models.

Investigation of the progress in the women with gestational diabetes mellitus postpartum

Aims: Our aim was to evaluate the uptake of postpartum screening, the prevalence and the risk factors for glucose intolerance in women with a recent history of gestational diabetes mellitus (GDM). Methods: All women with a history of GDM are advised to undergo a 75g oral glucose tolerance test (OGTT) around 6 - 12 weeks postpartum. Indices of insulin sensitivity (the Matsuda index and the reciprocal of the homeostasis model assessment of insulin resistance, HOMA-IR) and an index of beta-cell function, the Insulin Secretion-Sensitivity Index-2 (ISSI-2) were calculated based on the OGTT postpartum. Multivariable logistic regression was used to some factors. Results: Of all women (135) who received an OGTT postpartum, 42.2% (57) had glucose intolerance (11.8% impaired fasting glucose, 24.4% impaired glucose tolerance and 6.0% both impaired fasting and impaired glucose tolerance) and 1.5% (2) had overt diabetes. Compared to women with a normal OGTT postpartum, women with glucose intolerance and diabetes were older (32.5 ± 4.3 vs. 30.8 ± 4.8 years, p = 0.049), were more often obese (34.5% vs. 17.3%, p = 0.023). In the multivariable logistic regression, an EM background [OR = 2.76 (1.15 - 6.62), p = 0.023] and the HbA1c level at the time of the OGTT in pregnancy [OR = 4.78 (1.19 - 19.20), p = 0.028] remained significant predictors for glucose intolerance postpartum. Women with glucose intolerance and diabetes postpartum had a similar insulin sensitivity [Matsuda index 0.656 (0.386 - 1.224) vs. 0.778 (0.532 - 1.067), p = 0.709; HOMA-IR 0.004 (0.002 - 0.009) vs. 0.064 (0.003 - 0.007), p = 0.384] but a lower beta-cell function compared to women with a normal OGTT postpartum, remaining significant after adjustment for confounders [ISSI-2 1.6 (1.2 - 2.1) vs. 1.9 (1.7 - 2.4), p = 0.002]. Conclusions: Glucose intolerance is very frequent in early postpartum in women with GDM these women have an impaired beta-cell function. Nearly one third of women did not attend the scheduled OGTT postpartum and these women have an adverse risk profile. More efforts are needed to engage and stimulate women with GDM to attend the postpartum OGTT.

Purification of pancreatic endocrine subsets reveals increased iron metabolism in beta-cells

Abstract Objectives The main endocrine cell types in pancreatic islets are alpha, beta, and delta cells. Although these cell types have distinct roles in the regulation of glucose homeostasis, inadequate purification methods preclude the study of cell type-specific effects. We developed a reliable approach that enables simultaneous sorting of live alpha, beta, and delta cells from mouse islets for downstream analyses. Methods We developed an antibody panel against cell surface antigens to enable isolation of highly purified endocrine subsets from mouse islets based on the specific differential expression of CD71 on beta cells and CD24 on delta cells. We rigorously demonstrated the reliability and validity of our approach using bulk and single cell qPCR, immunocytochemistry, reporter mice, and transcriptomics. Results Pancreatic alpha, beta, and delta cells can be separated based on beta cell-specific CD71 surface expression and high expression of CD24 on delta cells. We applied our new sorting strategy to demonstrate that CD71, which is the transferrin receptor mediating the uptake of transferrin-bound iron, is upregulated in beta cells during early postnatal weeks. We found that beta cells express higher levels of several other genes implicated in iron metabolism and iron deprivation significantly impaired beta cell function. In human beta cells, CD71 is similarly required for iron uptake and CD71 surface expression is regulated in a glucose-dependent manner. Conclusions This study provides a novel and efficient purification method for murine alpha, beta, and delta cells, identifies for the first time CD71 as a postnatal beta cell-specific marker, and demonstrates a central role of iron metabolism in beta cell function.

Oral Glucose Tolerance Test with Insulin Assay and the evaluation of Insulin Resistance and Impaired Beta-cell function in primary prevention for Type 2 Diabetes

Background: Insulin resistance and impaired beta-cell function are associated with type 2 diabetes mellitus (T2DM). Many insulin resistance and beta-cell function indices have been developed using the data from an oral glucose tolerance test (OGTT) with insulin assay. However, insulin assays are not widely used along with the OGTT in primary prevention outpatient clinics. We aimed to evaluate the association of having impaired fasting glucose (IFG), impaired glucose tolerance (IGT), isolated or combined, with insulin resistance and impaired beta-cell function in subjects at risk for T2DM. Methods: This is a cross-sectional study that included 376 subjects who underwent an OGTT who had at least two risk factors for T2DM without any chronic disease. Results: Participants were 51.6±8.2 years old, 71.8% were women, had a mean body mass index (BMI) of 30.1±6.5 kg/m2, 42.4% had obesity and 26.7% hypertension. A HOMA-IR ≥2.5 was independently associated with male sex, BMI>25kg/m2, and with isolatedIFG, isolated-IGT, or combined (p<0.05 for all). On the other hand, only overweight, but not obesity, was independently associated with impaired beta-cell function (disposition index <1.24). Additionally, combined IFG and IGT had 29.7 higher odds to have impaired beta-cell function compared with those that had a normal OGTT. Conclusions: IFG alone, IGT alone, or the presence of both, are associated with higher odds to have insulin resistance and impaired beta-cell function in asymptomatic subjects at risk for T2DM without any chronic disease. Further studies are needed to evaluate this associations with the risk to develop T2DM, cardiovascular events and mortality.

HbA1c during early pregnancy reflects beta-cell dysfunction in women developing GDM

IntroductionIt is of current interest to assess eligibility of hemoglobin A1c (HbA1c) as a screening tool for earlier identification of women with risk for more severe hyperglycemia in pregnancy but...

Noradrenergic fibers are associated with beta-cell dedifferentiation and impaired beta-cell function in humans

Aims/hypothesisType 2 diabetes (T2D) is characterized by a progressive loss of beta-cell function, and the “disappearance” of beta-cells in T2D may also be caused by the process of beta -cell dedifferentiation. Since noradrenergic innervation inhibits insulin secretion and density of noradrenergic fibers is increased in type 2 diabetes mouse models, we aimed to study the relation between islet innervation, dedifferentiation and beta-cell function in humans. MethodsUsing immunohistochemistry and electron microscopy, we analyzed pancreata from organ donors and from patients undergoing pancreatic surgery. In the latter, a pre-surgical detailed metabolic characterization by oral glucose tolerance test (OGTT) and hyperglycemic clamp was performed before surgery, thus obtaining in vivo functional parameters of beta-cell function and insulin secretion. ResultsThe islets of diabetic subjects were 3 times more innervated than controls (0.91 ± 0.21 vs 0.32 ± 0.10, n.fibers/islet; p = 0.01), and directly correlated with the dedifferentiation score (r = 0.39; p = 0.03). In vivo functional parameters of insulin secretion, assessed by hyperglycemic clamp, negatively correlated with the increase in fibers [beta-cell Glucose Sensitivity (r = −0.84; p = 0.01), incremental second-phase insulin secretion (r = −0.84, p = 0.03) and arginine-stimulated insulin secretion (r = −0.76, p = 0.04)]. Moreover, we observed a progressive increase in fibers, paralleling worsening glucose tolerance (from NGT through IGT to T2D). Conclusions/interpretationNoradrenergic fibers are significantly increased in the islets of diabetic subjects and this positively correlates with beta-cell dedifferentiation score. The correlation between in vivo insulin secretion parameters and the density of pancreatic noradrenergic fibers suggests a significant involvement of these fibers in the pathogenesis of the disease, and indirectly, in the islet dedifferentiation process.

The role of the CCL25-CCR9 axis in beta-cell function: potential for therapeutic intervention in type 2 diabetes

Background and purposeChemokines are known to play essential roles mediating immunity and inflammation in many physiological and pathophysiological processes, with reports linking their action to the development of obesity, insulin resistance and type 2 diabetes (T2D). Given our findings of highly upregulated mRNA expression of the chemokine receptor CCR9 in islets from obese human donors, we have determined the effects of CCR9 activation by CCL25 on islet function and viability. Basic proceduresRT-qPCR was used to measure expression of 384 GPCR mRNAs in human islets from organ donors with normal and elevated BMI. mRNA encoding CCR9, a receptor that was highly upregulated in islets from obese donors, was also quantified in islets from lean and high-fat diet (HFD) mice. The effects of CCR9 activation by exogenous CCL25 in human and mouse islets and its inhibition by the CCR9 antagonist vercirnon on insulin secretion, apoptosis and cAMP accumulation were examined using standard techniques. Main findingsThe qPCR analysis showed altered expression of several GPCRs in islets isolated from lean and obese donors. CCR9 displayed over 90-fold upregulation in islets from obese individuals, and it was also significantly upregulated in islets from obese mice. In isolated human and mouse islets exogenous CCL25 inhibited glucose-induced insulin secretion in a concentration-dependent manner, enhanced cytokine-induced apoptosis and significantly reduced forskolin-induced elevation in cAMP levels. These detrimental effects of CCL25 in islets were blocked by vercirnon, which had no effect on its own. Principal conclusionsWe have shown that CCL25 acts via the Gαi-coupled receptor CCR9 to impair beta-cell function by inhibiting insulin secretion and promoting cytokine-induced apoptosis. Upregulation of CCR9 in islets in obesity, possibly secondary to accumulation of passenger immune cells, may predispose to metabolic dysfunction and our data suggest that CCL25 downregulation or CCR9 inhibition could be explored to treat T2D.

Adipocyte Reprogramming by the Transcriptional Coregulator GPS2 Impacts Beta Cell Insulin Secretion

SummaryGlucose homeostasis is maintained through organ crosstalk that regulates secretion of insulin to keep blood glucose levels within a physiological range. In type 2 diabetes, this coordinated response is altered, leading to a deregulation of beta cell function and inadequate insulin secretion. Reprogramming of white adipose tissue has a central role in this deregulation, but the critical regulatory components remain unclear. Here, we demonstrate that expression of the transcriptional coregulator GPS2 in white adipose tissue is correlated with insulin secretion rate in humans. The causality of this relationship is confirmed using adipocyte-specific GPS2 knockout mice, in which inappropriate secretion of insulin promotes glucose intolerance. This phenotype is driven by adipose-tissue-secreted factors, which cause increased pancreatic islet inflammation and impaired beta cell function. Thus, our study suggests that, in mice and in humans, GPS2 controls the reprogramming of white adipocytes to influence pancreatic islet function and insulin secretion.

Purification of pancreatic endocrine subsets reveals increased iron metabolism in beta cells

ObjectivesThe main endocrine cell types in pancreatic islets are alpha, beta, and delta cells. Although these cell types have distinct roles in the regulation of glucose homeostasis, inadequate purification methods preclude the study of cell type-specific effects. We developed a reliable approach that enables simultaneous sorting of live alpha, beta, and delta cells from mouse islets for downstream analyses. MethodsWe developed an antibody panel against cell surface antigens to enable isolation of highly purified endocrine subsets from mouse islets based on the specific differential expression of CD71 on beta cells and CD24 on delta cells. We rigorously demonstrated the reliability and validity of our approach using bulk and single cell qPCR, immunocytochemistry, reporter mice, and transcriptomics. ResultsPancreatic alpha, beta, and delta cells can be separated based on beta cell-specific CD71 surface expression and high expression of CD24 on delta cells. We applied our new sorting strategy to demonstrate that CD71, which is the transferrin receptor mediating the uptake of transferrin-bound iron, is upregulated in beta cells during early postnatal weeks. We found that beta cells express higher levels of several other genes implicated in iron metabolism and iron deprivation significantly impaired beta cell function. In human beta cells, CD71 is similarly required for iron uptake and CD71 surface expression is regulated in a glucose-dependent manner. ConclusionsThis study provides a novel and efficient purification method for murine alpha, beta, and delta cells, identifies for the first time CD71 as a postnatal beta cell-specific marker, and demonstrates a central role of iron metabolism in beta cell function.

The Effect of Gaseous Ozone Therapy in Conjunction with Periodontal Treatment on Glycated Hemoglobin Level in Subjects with Type 2 Diabetes Mellitus: An Unmasked Randomized Controlled Trial

Background: It is established that inflammation is involved in the pathogenesis of Type 2 Diabetes Mellitus (T2DM) by promoting insulin resistance and impaired beta cell function in the pancreas. Among the hypothesized independent risk factors implicated in the pathogenetic basis of disease, periodontal infection has been proposed to promote an amplification of the magnitude of the advanced glycation end product (AGE)-mediated upregulation of cytokine synthesis and secretion. These findings suggest an interrelationship between periodontal disease and type 2 diabetes, describing poor metabolic control in subjects with periodontitis as compared to nondiabetic subjects and more severe periodontitis in subjects with T2DM as compared to a healthy population, with a significant positive correlation between periodontal inflammatory parameters and glycated hemoglobin level. Results from clinical trials show that periodontal treatment is able to improve glycemic control in subjects with diabetes. Many therapeutic strategies have been developed to improve periodontal conditions in conjunction with conventional treatment, among which ozone (O3) is of specific concern. The principal aim of this trial was to compare the clinical effectiveness of an intensive periodontal intervention consisting of conventional periodontal treatment in conjunction with ozone gas therapy in reducing glycated hemoglobin level in type 2 diabetic patients and standard periodontal treatment. Methods: This study was a 12-month unmasked randomized trial and included 100 patients aged 40–74 years older, with type 2 diabetes mellitus diagnosed. All the patients received conventional periodontal treatment, or periodontal treatment in conjunction with ozone gas therapy in a randomly assigned order (1:1). The primary outcome was a clinical measure of glycated hemoglobin level at 3, 6, 9 and 12 months from randomization. Secondary outcomes were changes in periodontal inflammatory parameters. Results: At 12 months, the periodontal treatment in conjunction with ozone gas therapy did not show significant differences than standard therapy in decreasing glycated hemoglobin (HbA1C) level and the lack of significant differences in balance is evident. Conclusions: Although the change was not significant, periodontal treatment in conjunction with the gaseous ozone therapy tended to reduce the levels of glycated hemoglobin. The study shows a benefit with ozone therapy as compared to traditional periodontal treatment.

Pancreatic Steatosis Associates With Impaired Insulin Secretion in Genetically Predisposed Individuals.

ContextPancreatic steatosis leading to beta-cell failure might be involved in type 2 diabetes (T2D) pathogenesis.ObjectiveWe hypothesized that the genetic background modulates the effect of pancreatic fat on beta-cell function and investigated genotype × pancreatic fat interactions on insulin secretion.DesignTwo observational studies.SettingUniversity hospital.Patients or participantsA total of 360 nondiabetic individuals with elevated risk for T2D (Tuebingen Family Study [TUEF]), and 64 patients undergoing pancreatectomy (Pancreas Biobank [PB], HbA1c <9%, no insulin therapy).Main Outcome MeasuresInsulin secretion calculated from 5-point oral glucose tolerance test (TUEF) and fasting blood collection before surgery (PB). A genome-wide polygenic score for T2D was computed from 484,788 genotyped variants. The interaction of magnetic resonance imaging-measured and histologically quantified pancreatic fat with the polygenic score was investigated. Partitioned risk scores using genome-wide significant variants were also computed to gain insight into potential mechanisms.ResultsPancreatic steatosis interacted with genome-wide polygenic score on insulin secretion (P = 0.003), which was similar in the replication cohort with histological measurements (P = 0.03). There was a negative association between pancreatic fat and insulin secretion in participants with high genetic risk, whereas individuals with low genetic risk showed a positive correlation between pancreatic fat and insulin secretion. Consistent interactions were found with insulin resistance-specific and a liver/lipid-specific polygenic scores.ConclusionsThe associations suggest that pancreatic steatosis only impairs beta-cell function in subjects at high genetic risk for diabetes. Genetically determined insulin resistance specifically renders pancreatic fat deleterious for insulin secretion.

Loss of Caveolin-1 Is Associated with a Decrease in Beta Cell Death in Mice on a High Fat Diet.

Elevated free fatty acids (FFAs) impair beta cell function and reduce beta cell mass as a consequence of the lipotoxicity that occurs in type 2 diabetes (T2D). We previously reported that the membrane protein caveolin-1 (CAV1) sensitizes to palmitate-induced apoptosis in the beta pancreatic cell line MIN6. Thus, our hypothesis was that CAV1 knock-out (CAV1 KO) mice subjected to a high fat diet (HFD) should suffer less damage to beta cells than wild type (WT) mice. Here, we evaluated the in vivo response of beta cells in the pancreatic islets of 8-week-old C57Bl/6J CAV1 KO mice subjected to a control diet (CD, 14% kcal fat) or a HFD (60% kcal fat) for 12 weeks. We observed that CAV1 KO mice were resistant to weight gain when on HFD, although they had high serum cholesterol and FFA levels, impaired glucose tolerance and were insulin resistant. Some of these alterations were also observed in mice on CD. Interestingly, KO mice fed with HFD showed an adaptive response of the pancreatic beta cells and exhibited a significant decrease in beta cell apoptosis in their islets compared to WT mice. These in vivo results suggest that although the CAV1 KO mice are metabolically unhealthy, they adapt better to a HFD than WT mice. To shed light on the possible signaling pathway(s) involved, MIN6 murine beta cells expressing (MIN6 CAV) or not expressing (MIN6 Mock) CAV1 were incubated with the saturated fatty acid palmitate in the presence of mitogen-activated protein kinase inhibitors. Western blot analysis revealed that CAV1 enhanced palmitate-induced JNK, p38 and ERK phosphorylation in MIN6 CAV1 cells. Moreover, all the MAPK inhibitors partially restored MIN6 viability, but the effect was most notable with the ERK inhibitor. In conclusion, our results suggest that CAV1 KO mice adapted better to a HFD despite their altered metabolic state and that this may at least in part be due to reduced beta cell damage. Moreover, they indicate that the ability of CAV1 to increase sensitivity to FFAs may be mediated by MAPK and particularly ERK activation.

Sarcopenia in women with hip fracture: A comparison of hormonal biomarkers and their relationship to skeletal muscle mass and function

ObjectivesSarcopenia is a decline in skeletal muscle mass and function. It is associated with adverse outcomes and increased mortality. Sarcopenia is also reported to be prevalent in the hip fracture population. Our aims in this study are to compare the hormonal profile in women with hip fracture to controls, and to assess the relationship between hormonal biomarkers to skeletal muscle mass and function in these women. MethodsA cross sectional study was performed enrolling women above age 60 years old with hip fracture as a study group. For comparison healthy women from the community were recruited. Peripheral blood samples were obtained for analysis of hormonal profiles. Measures of skeletal muscle mass and function by muscle area on computed tomography, dual energy X-ray absorptiometry, bioelectrical impedance analysis, and grip strength was performed. ResultsA high proportion of sarcopenic individuals were detected in the hip fracture group (60%). Women with hip fracture compared to controls were older (P = 0.073), had lower serum albumin levels (P < 0.001), serum insulin-like growth factor-1 (IGF-1) (P < 0.001), insulin-like growth factor binding protein −3 (IGFBP-3) (P < 0.001), free testosterone levels (P = 0.001), and impaired beta cell function by homeostasis model assessment (HOMA beta) (P = 0.038). ConclusionsThere is a high proportion of sarcopenic individuals in the hip fracture group. Lowered serum levels of IGF-1 and IGFBP-3, HOMA beta cell function, and free testosterone levels were detected in this group and may serve as potential biomarkers of sarcopenia.

1574-P: Insulin Resistance, but Not Impaired Beta-Cell Function, at Type 2 Diabetes Diagnosis Is Associated with Mortality

We hypothesized that individuals with type 2 diabetes and low insulin resistance in combination with impaired beta cell function at diabetes diagnosis have lower mortality compared to those with high insulin resistance in combination with preserved beta cell function. In this prospective cohort study, 864 individuals with type 2 diabetes (median age 60 years) had fasting glucose and fasting C-peptide measured at the time of diabetes diagnosis or up to five years before diagnosis. Insulin resistance was estimated with HOMA-%S and beta cell function with HOMA-%B. Four groups based on the median of HOMA-%S and HOMA-%B were formed: 1) low HOMA-%S and high HOMA-%B, 2) low HOMA-%S and low HOMA-%B, 3) high HOMA-%S and high HOMA-%B, and 4) high HOMA-%S and low HOMA-%B (reference group). Mortality was registered during a median follow up of 15 years after diabetes diagnosis, and the associations between the four groups and mortality was estimated with Cox regression adjusted for gender and age at diabetes diagnosis (model 1) and adjusted for gender, age at diabetes diagnosis, smoking, hypertension, BMI and total cholesterol (model 2). Group 1 had higher total mortality (model 2: HR 1.58, 95% CI 1.06−2.36) compared to the reference group 4. Group 1 was also associated with higher cardiovascular mortality (model 1: HR 2.24, 95% CI 1.08−4.66), but this difference was no longer significant in model 2. Insulin resistance in combination with preserved beta cell function at the time of diabetes diagnosis is an independent risk factor for total mortality. Insulin resistance in combination with preserved beta cell function increases the risk for cardiovascular mortality but not independent of conventional risk factors. Thus, treatment of type 2 diabetes should focus not only on normalizing blood glucose levels but also improve insulin resistance. Disclosure J. Otten: None. B. Tavelin: None. S. Söderberg: None. O. Rolandsson: None.

259-OR: Epigenetic Coregulation of Beta-Cell Function and Survival in Postnatal Life

Both type 1 and type 2 diabetes are caused by inadequate functional beta-cells. Loss of beta-cells in diabetes is preceded by progressive beta-cell failure due to impaired beta-cell function and adaptive capacity, driven by cellular stress. While plenty of evidence suggests that beta-cell function and mass are co-regulated to dictate adaptive capacity, the molecular mechanisms that direct such co-regulation and are disrupted by cellular stress remain unclear. In the present study, we show that the CCCTC binding factor, CTCF is a novel epigenetic regulator of beta-cell functional maturity and mass. CTCF is a zinc finger protein that regulates 3D chromatin architecture and epigenetic stability towards transcriptional regulation, and plays an important role in cell differentiation, self-renewal, and survival. In addition, the levels of CTCF are sensitive to cellular-stress. Our data show that the beta-cell specific CTCF knockout mice (CTCF-BKO) become diabetic by 4-5 months of age, due to a progressive loss of beta-cell maturity and viability that mirrors evolving T2D. The CTCF-BKO mice have impaired glucose stimulated insulin secretion (GSIS), with metabolic, epigenetic, and gene expression profiles that resemble functionally immature neonatal beta-cells, around 1-2 months of age. This is followed by progressive loss of beta-cell mass due to p53 dependent apoptosis. In addition, mice with haplo-insufficiency of CTCF in their beta-cells display impaired GSIS and a deficit in the adaptive beta-cell expansion in response to high-fat diet challenge. Finally, we show that the CTCF program is disrupted in islets of diabetic mice. Taken together, these studies provide a novel insight into the epigenetic regulation of functional beta-cell mass and adaptive capacity in postnatal life. Disclosure S. Dhawan: None. T. Gurlo: None. J.K. Wang: None.

SUN-128 Impaired Fasting Glucose Is Associated with Insulin Resistance in Patients with Germline Mutations in the Multiple Endocrine Neoplasia Type 1 (MEN1) Gene

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant syndrome characterized by hyperparathyroidism, pituitary adenomas, and gastro-entero-pancreatic neuroendocrine tumors. Patients with MEN1 mutations have impaired glucose homeostasis, but the role of insulin resistance and beta-cell function is unclear.METHODS: Using a case-control study design, a retrospective analysis of germline mutation-positive MEN 1 patients (n=289) seen at our institution between 1991-2019 was performed. Patients with diabetes and/or insulinoma were excluded. Subjects were age, BMI, sex and race matched 1:1 to unrelated, healthy controls. Fasting glucose, insulin, c-peptide, calcium, PTH, 25-OH vitamin D, cholesterol, LDL, HDL and triglycerides (TG) were compared between two groups. Homeostasis model assessment (HOMA-IR) and HOMA-beta cell function (HOMA-b) were used as surrogate measures of insulin resistance and beta-cell function, respectively. Data is presented as mean ± SD.RESULTS: MEN1 subjects (n=40; age 41±11 years; BMI 29.2±7.2 kg/m2) were matched to healthy controls (age 41±11 years; BMI 29.1±7.5 kg/m2). Only 3 MEN1 patients had no evidence of pancreatic neuroendocrine tumors. Impaired fasting glucose was more prevalent in MEN1 compared with controls (53% vs 10%, p<0.0001). HOMA-IR was positively associated with BMI, but not age, sex, calcium or vitamin D levels in either cohort. HOMA-IR adjusted for age, BMI, and sex was higher in patients with MEN1 compared with controls (4.01 vs. 2.44, adjusted ratio of means 1.54, 95% CI [1.14, 2.07], p=0.005). HOMA-b was not significantly different between the groups (177 vs. 129, adjusted ratio of means 1.17, 95% CI [0.86, 1.58], p=0.23). There were no significant differences in total cholesterol, LDL, HDL, and TG between the groups.CONCLUSION: Lower insulin sensitivity, but not impaired beta cell function may contribute to the higher prevalence of impaired fasting glucose in MEN1 patients compared with controls. Mechanistic studies into the role of menin loss in glucose homeostasis are warranted.

Arf6 Heterozygosity Results in Impaired Glucose Tolerance Due to Abberant Hepatic Gluconeogenesis

Adenosine diphosphate (ADP) ribosylation factor 6 (Arf6) is a small GTPase that plays a critical role in numerous cellular processes including proliferation and membrane trafficking. Arf6 has been found to be dysregulated in diseases such as diabetic retinopathy and tumor metastasis. Furthermore, genetic insufficiency or pharmacological inhibition of Arf6 is protective in the aforementioned diseases, suggesting that Arf6 may be a potential therapeutic target. Here, we assessed the metabolic consequences of a reduction in Arf6 expression by performing glucose (GTT: 2 g/kg, ip), insulin (ITT: 1 U/kg, ip) and pyruvate (PTT: 2 g/kg, ip) tolerance tests in 3–4 mo old whole body Arf6 heterozygote (Arf6+/−) and wildtype (Arf6+/+) littermate control mice. Both protein and gene expression of Arf6 in the liver were 40–50% lower (p&lt;0.05) in Arf6+/− mice compared to Arf6+/+. Body mass was higher in normal chow fed Arf6+/− compared to Arf6+/+ mice (30.3±0.9 vs 36.4±2.0 g, p&lt;0.05). Blood glucose at 15, 30, and 60 min after injection during the GTT were 20–30% higher in Arf6+/− mice compared to Arf6+/+ (each p&lt;0.05). Likewise, the area under the GTT time response curve was ~15% higher in Arf6+/− compared to Arf6+/+ (p&lt;0.05), indicating impaired glucose metabolism. To examine the underlying cause of this glucose intolerance, we performed an ITT and assessed insulin‐stimulated suppression of plasma free fatty acids 15, and 30 min after insulin injection. We found no groups differences between the ITT time response curves (p&gt;0.05) and no difference in the percent decrease in plasma FFAs from fasted between Arf6+/− and Arf6+/+ mice (~50% vs ~50% p&gt;0.05). Likewise, fasted and glucose‐stimulated (2g/kg, ip) serum insulin were not different between the groups (2.44±0.58 vs 1.73±0.28, fasted; 4.54±1.74 vs 4.03±1.68 insulin stimulated; both p&gt;0.05), suggesting that reductions in Arf6 expression do not impact pancreatic beta cell insulin secretion. Collectively, these measures suggest that neither peripheral insulin resistance nor impaired pancreatic beta cell function underlie glucose intolerance in Arf6+/− mice. To determine the contribution of hepatic gluconeogenesis to the observed glucose intolerance in the Arf6+/− mice, we performed a PTT and found that Arf6+/− mice exhibited a 15–25% increase in blood glucose over time compared to Arf6+/+ mice (p&lt;0.05), suggesting a role for elevated hepatic gluconeogenesis. Taken together, this study demonstrates that Arf6 heterozygosity impairs glucose metabolism that is associated with aberrant hepatic gluconeogenesis but is independent of peripheral insulin resistance or pancreatic beta cell dysfunction.Support or Funding InformationNIA R01 AG048366, R01 AG050238 and K02 AG045339, R01 AG060395 and US Department of Veterans Affairs I01 BX002151, I01 BX004492.

Beta-Cell Function, Self-rated Health, and Lifestyle Habits in 64-Year-Old Swedish Women with Metabolically Healthy Obesity Phenotype.

BackgroundA subset of obese individuals do not present metabolic abnormalities that commonly define the metabolic syndrome (MetS). This is referred to as a metabolically healthy obese (MHO) phenotype. The aim of the present study was to evaluate the prevalence of the MHO phenotype and its relationship with beta cell dysfunction by measuring C-peptide and proinsulin, anthropometric-, metabolic- and lipid appearance, as well as lifestyle behaviors and self-rated health in a cohort of 64-year-old Swedish women.MethodsThe National Cholesterol Education Program definition was used to assess MetS. We defined normal weight as body mass index (BMI) 18.5–24.9 kg/m2 and obesity as BMI ≥30 kg/m2 to categorize participants as metabolically healthy normal weight, MHO, and metabolically unhealthy obese.ResultsThe MHO phenotype represented 36.3% of obese participants and 16.3% of total participants. The MHO group were at greater risk of having proinsulin levels >11 pmol/L, indicating impaired beta cell function. Further, homeostatic model assessment for insulin resistance, fasting plasma levels of insulin, and C-peptide showed significant trends, with the MHO phenotype group having intermediate levels among three groups. Health behaviors such as leisure time physical activity and alcohol intake were also intermediate in individuals with the MHO phenotype.ConclusionIn this study, we demonstrate that over a third of the obese women in our sample were MHO. Further, women with the MHO phenotype showed intermediate profiles considering beta cell function and insulin resistance, as well as metabolic variables, and tended to rate their general health as worse than otherwise similar individuals of normal weight.