Affect Insulin Secretion Research Articles

Effect of TNF-α on the expression of ABCA1 in pancreatic β-cells.

ATP-binding cassette transporter A1 (ABCA1), a 254-kD membrane protein, is a key regulator of lipid efflux from cells to apolipoproteins. ABCA1 in pancreatic β-cells influences insulin secretion and cholesterol homeostasis. Tumor necrosis factor (TNF)-α is a pleiotropic cytokine that elicits a wide spectrum of physiological events, including cell proliferation, differentiation, and apoptosis, and is also known to decrease glucose-dependent insulin secretion in pancreatic islets. In the present study, we examined the role of TNF-α on ABCA1 expression in rat pancreatic islets and INS-1 cells. ABCA1 protein levels decreased in response to rising concentrations of TNF-α in pancreatic islets. Real-time polymerase chain reaction analysis showed a significant decrease in ABCA1 mRNA expression. In parallel with its effect on endogenous ABCA1 mRNA levels, TNF-α suppressed the activity of a reporter construct containing the ABCA1 promoter. This effect was abrogated by BIRB796, but not by SB203580 or PD98095. The constitutively active form of p38 mitogen-activated protein kinase (MAPK) γ suppressed ABCA1 promoter activity but not p38-MAPK (α, β), while a dominant-negative mutant of p38-MAPK γ blocked the effect of TNF-α on ABCA1 promoter activity. BIRB796 inhibited the increased cholesterol ester content induced by TNF-α. However, BIRB796 had no effect on the decreased insulin content nor ABCA1 suppression caused by TNF-α in INS-1 cells. In summary, TNF-α suppressed the expression of endogenous ABCA1 in pancreatic islets and INS-1 cells. These findings raise the possibility that TNF-α may affect insulin secretion by controlling ABCA1 expression.

Selective peroxisome proliferator-activated receptor-α modulator K-877 regulates the expression of ATP-binding cassette transporter A1 in pancreatic beta cells

ATP-binding cassette transporter A1 (ABCA1) protein is a pivotal regulator of cholesterol and phospholipid efflux from cells to high-density lipoprotein (HDL) particles. Pancreatic ABCA1 functions in beta cell cholesterol homeostasis and affects insulin secretion. We investigated the effect of pemafibrate (K-877), a novel selective PPARα modulator (SPPARMα), on pancreatic ABCA1 expression. In vivo experiment, mice were divided into four treatment groups, namely, normal food plus placebo, high fat diet (HFD) plus placebo, normal food plus K-877 (0.3 mg/kg/day), or HFD plus K-877 (0.3 mg/kg/day), and treated for eight weeks. The results in vitro experiment indicate that K-877 treatment increased levels of ABCA1 mRNA, as well as protein, subsequently reduced the cellular cholesterol content in INS-1 cells. PPARα specific antagonist GW6471 attenuate K-877 induced ABCA1 expression in INS-1 cells. ABCA1 promoter activity increased with K-877 treatment at concentration 1 μM and 10 μM. Glucose-stimulated insulin secretion was ameliorated by K-877 treatment in INS-1 cells and isolated mouse islets. Although the expression of ABCA1 was reduced in mice with HFD treatment, both ABCA1 protein and mRNA levels were increased in mice with K-877 treatment. K-877 treatment improved glucose intolerance induced by HFD in mice. These findings raise the possibility that K-877 may affect insulin secretion by controlling ABCA1 expression in pancreatic beta cells.

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

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

Effect of 12 wk of resistant starch supplementation on cardiometabolic risk factors in adults with prediabetes: a randomized controlled trial

Type 2 resistant starch (RS2) has been shown to improve glycemic control and some cardiovascular endpoints in rodent and human studies. The aim of this study was to perform one of the first randomized clinical trials in adults with prediabetes and one of the longest trials to test whether RS2 can improve cardiometabolic health. 68 overweight [body mass index (BMI) ≥27 kg/m2] adults aged 35-75 y with prediabetes were randomized to consume 45 g/d of high-amylose maize (RS2) or an isocaloric amount of the rapidly digestible starch amylopectin (control) for 12 wk. At baseline and postintervention, ectopic fat depots (visceral adipose tissue, intrahepatic lipids, and intramyocellular lipids) were measured by magnetic resonance imaging/spectroscopy, energy metabolism by respiratory chamber, and carbohydrate metabolism by glycated hemoglobin (HbA1c), an intravenous glucose tolerance test, and a meal tolerance test. Cardiovascular risk factors-serum lipids, blood pressure, heart rate, and inflammatory markers (high-sensitivity C-reactive protein [hs-CRP], interleukin-6, and tumor necrosis factor [TNF]-α)-were also measured. The primary endpoints were insulin sensitivity, insulin secretion, ectopic fat, and markers of inflammation. Data were primarily analyzed as treatment effects via a linear mixed model both with and without the addition of covariates. Relative to the control group, RS2 lowered HbA1c by a clinically insignificant 0.1±0.2% (Δ=-1±2 mmol/mol; P=0.05) but did not affect insulin secretion, insulin sensitivity, the disposition index, or glucose or insulin areas under the curve relative to baseline (P≥0.23). RS2 decreased heart rate by 5±9 beats/min (P=0.02) and TNF-α concentrations by 2.1±2.7 pg/mL (P=0.004), relative to the control group. Ectopic fat, energy expenditure, substrate oxidation, and all other cardiovascular risk factors were unaffected (P≥0.06). 12 wk of supplementation with resistant starch reduced the inflammatory marker TNF-α and heart rate, but it did not significantly improve glycemic control and other cardiovascular disease risk factors, in adults with prediabetes. This trial was registered at clinicaltrials.gov as NCT01708694.

KCNJ11 variants and their effect on the association between serum potassium and diabetes risk in the Atherosclerosis Risk in Communities (ARIC) Study and Jackson Heart Study (JHS) cohorts.

BackgroundIn the Atherosclerosis Risk in Communities (ARIC) Study and Jackson Heart Study (JHS) cohorts, serum potassium (K) is an independent predictor of diabetes risk, particularly among African-American participants. Experimental studies show that serum K levels affects insulin secretion. The KCNJ11 gene encodes for a K channel that regulates insulin secretion and whose function is affected by serum K levels. Variants in KCNJ11 are associated with increased diabetes risk. We hypothesized that there could be a gene-by-environment interaction between KCNJ11 variation and serum K on diabetes risk.MethodsEvaluating a combined cohort of ARIC and JHS participants, we sought to determine if KCNJ11 variants are risk factors for diabetes; and if KCNJ11 variants modify the association between serum K and diabetes risk. Among participants without diabetes at baseline, we performed multivariable logistic regression to determine the effect of serum K, KCNJ11 variants, and their interactions on the odds of incident diabetes mellitus over 8–9 years in the entire cohort and by race.ResultsOf 11,812 participants, 3220 (27%) participants developed diabetes. 48% and 47% had 1 or 2 diabetes risk alleles of rs5215 and rs5219, respectively. Caucasians had higher proportions of these risk alleles compared to African Americans (60% vs 17% for rs5215 and 60% vs 13% for rs5219, p<0.01). Serum K was a significant independent predictor of incident diabetes. Neither rs5215 nor rs5219 was associated with incident diabetes. In multivariable models, we found no statistically significant interactions between race and either rs5215 or rs5219 (P-values 0.493 and 0.496, respectively); nor between serum K and either rs5215 or rs5219 on odds of incident diabetes (P-values 0.534 and 0.687, respectively).ConclusionIn this cohort, rs5215 and rs5219 of KCNJ11 were not significant predictors of incident diabetes nor effect modifiers of the association between serum K and incident diabetes.

Caffeine and Glucose Metabolism at Rest Period, During, and Post Exercise in Diabetes Mellitus: A Systematic Review

Purpose: Diabetes Mellitus (DM) is correlated with a group of diseases related to the metabolism of glucose that is increasingly affecting the population, being considered a public health problem. Exercise increases absorption of glucose by the muscles during, pre- and post- periods of effort, therefore, it is an excellent treatment strategy to maintain the glycemic control of diabetic patients. Caffeine intake enhances Ca2+ concentration in β pancreatic cells, affecting insulin secretion. Materials and Methods: Systematic review with a sample of six scientific papers published in academic journals. Only studies involving soccer players (professionals and amateurs, except goalkeepers) were included in this review. Results and Conclusion: Studies included in this review concluded that caffeine might act in several ways in glucose metabolism; however, more researches are necessary to elucidate the real effects of this compound in the organism. Keywords: Diabetes mellitus, glucose control, glycemia, insulin, metabolism, pancreatic cells.

Remodeling of the Acetylproteome by SIRT3 Manipulation Fails to Affect Insulin Secretion or β Cell Metabolism in the Absence of Overnutrition

SUMMARYSIRT3 is a nicotinamide adenine dinucleotide (NAD+)- dependent mitochondrial protein deacetylase purported to influence metabolism through post-translational modification of metabolic enzymes. Fuel-stimulated insulin secretion, which involves mitochondrial metabolism, could be susceptible to SIRT3-mediated effects. We used CRISPR/Cas9 technology to manipulate SIRT3 expression in β cells, resulting in widespread SIRT3-dependent changes in acetylation of key metabolic enzymes but no appreciable changes in glucose- or pyruvate-stimulated insulin secretion or metabolomic profile during glucose stimulation. Moreover, these broad changes in the SIRT3-targeted acetylproteome did not affect responses to nutritional or ER stress. We also studied mice with global SIRT3 knockout fed either standard chow (STD) or high-fat and high-sucrose (HFHS) diets. Only when chronically fed HFHS diet do SIRT3 KO animals exhibit a modest reduction in insulin secretion. We conclude that broad changes in mitochondrial protein acetylation in response to manipulation of SIRT3 are not sufficient to cause changes in islet function or metabolism.

The Complement-1q-Like-3 Inhibits Insulin Secretion by an Adhesion G-Protein Coupled Receptor, BAI3 in Pancreatic ß Cells

Secreted proteins are important metabolic regulators and our objective was to identify proteins that are important regulators of β-cell function. Microarray data from multiple tissues including liver, adipose, gastrocnemius, islets from lean and obese mice were analyzed to identify candidate regulators. For this, we developed a data filtering approach to identify candidate secreted protein regulators. Next, cross-tissue correlation network and gene enrichment based analyses were performed to determine cellular pathways affected by each candidate secreted protein in the target tissue. By using this methodology, complement-1q-like-3 (C1ql3) was identified to affect ’secretory processes’ in islets. Preliminary data showed that the expression of C1ql3 was increased by 32-fold in islets of obese mice. Incubating islets with C1ql3 containing culture media inhibited high glucose, GLP-1 receptor agonist (exendin-4), cAMP, and potassium-induced insulin secretion in mouse islets. Interestingly, C1ql3 did not affect insulin secretion in response to low and submaximal concentrations of glucose, fatty acids, amino acids, and mitochondrial metabolites. We further observed that the expression of BAI3, a receptor for C1ql3, is elevated in islets of obese compared to lean mice. Knockdown of BAI3 in β-cells increased glucose-stimulated insulin secretion by 2-fold and soluble C1ql3-binding fragment of BAI3 completely blocked the inhibitory effects of C1ql3 on cAMP-stimulated insulin secretion. These findings report the identification of a novel pathway in C1ql3/BAI3 that antagonizes GLP-1/cAMP signaling to inhibit insulin secretion from β-cells. We propose that the activation of C1ql3/BAI3 signaling contributes to type 2 diabetes and may offer therapeutic alternatives to treat type 2 diabetes. Disclosure R. Gupta: None. M. Schaid: None. M.E. Kimple: None. J.E. Koltes: None. S. Bhatnagar: None.

Disruption of the Autophagy-Regulatory Becn1-Bcl2 Complex Impairs Insulin Storage and Secretion in Mice

Autophagy, a stress-induced lysosomal degradation pathway, has thought to exert similar metabolic effects in different organs. Yet the function and tissue-specific requirement of autophagy in metabolic regulation remain enigmatic. Here we establish a new model in which autophagy plays different roles in insulin-producing β cells vs. insulin-responsive cells, utilizing a point mutant (Becn1F121A) mouse model manifesting constitutively active autophagy under non-autophagy-inducing conditions. In response to high-fat diet challenge, we found unexpectedly that the autophagy-hyperactive mice show impaired glucose tolerance, but improved insulin sensitivity, compared to mice with normal levels of autophagy. We further demonstrated that autophagy hyperactivation increases insulin sensitivity in insulin-responsive cells, but decreases insulin load and secretion by sequestrating and degrading secretory vesicles containing insulin granules in β cells, a process we characterized as vesicophagy. The reduction in insulin secretion was not due to islet degeneration; instead, the β cell mass was expanded in the mutant mice, suggesting higher β cell regeneration. The reduction in insulin storage, insulin secretion, and glucose tolerance in autophagy-hyperactive mice can be reversed by transient treatment of an autophagy-blocking ULK1 kinase inhibitor. Thus, we conclude that β cells and insulin-responsive tissues require different levels of autophagy for their optimal functions. Importantly, our findings suggest that acute or intermittent, rather than chronic, activation of autophagy should be considered in therapeutic development against type 2 diabetes, to improve insulin sensitivity without negatively affecting insulin secretion. Disclosure S. Yamamoto: None. N. Wang: None. W. Zhang: None. C. He: None.

Role of ROCK1 in Pancreatic ß Cells

Insulin signaling in pancreatic β-cell is critical for normal insulin secretion. ROCK1 plays an important role in the regulation of insulin and leptin signaling in the context of glucose and energy metabolism. However, the role of ROCK1 in pancreatic β-cell remains unknown. The current study was to determine whether deleting ROCK1 from β-cell affects insulin secretion and glucose metabolism in mice and cultured cell lines. Here we show that β-cell-specific deletion of ROCK1 results in a significant decrease insulin secretion in mice fed a normal chow diet, leading to hyperglycemia. These effects were independent of changes in adiposity. Consistent with this, in vitro studies with INS-1 and MIN6 cells indicated that inhibition of ROCK1 decreased insulin secretion in response to glucose without changes in β-cell proliferation and apoptosis. In addition, β-cell-ROCK1 deficient mice displayed glucose intolerance, as evidenced by the fact that the area under the glucose curve was increased 53% in β-cell-ROCK1 deficient mice compared with control mice. However, neither body weight, food intake nor insulin sensitivity was changed in theses mice. Upon insulin stimulation, proximal insulin signaling components, including p-IRS2, p-PI3K and p-Akt were impaired when ROCK1 expression was inhibited in INS-1 cells, suggesting a role for ROCK1 in insulin signaling. These data indicate that activation of ROCK1 in pancreatic β-cell is required for the maintenance of normal insulin secretion. Thus, pancreatic ROCK1 might be a key regulator of glucose homeostasis. Disclosure B. Sung: None. K. Hur: None. J. Kim: None. Y. Kim: None.M. Lee: None.

Glucose Acutely Reduces Cytosolic and Mitochondrial H2O2 in Rat Pancreatic Beta Cells.

Aims: Whether H2O2 contributes to the glucose-dependent stimulation of insulin secretion (GSIS) by pancreatic β cells is highly controversial. We used two H2O2-sensitive probes, roGFP2-Orp1 (reduction/oxidation-sensitive enhanced green fluorescent protein fused to oxidant receptor peroxidase 1) and HyPer (hydrogen peroxide sensor) with its pH-control SypHer, to test the acute effects of glucose, monomethyl succinate, leucine with glutamine, and α-ketoisocaproate on β cell cytosolic and mitochondrial H2O2 concentrations. We then tested the effects of low H2O2 and menadione concentrations on insulin secretion. Results: RoGFP2-Orp1 was more sensitive than HyPer to H2O2 (response at 2-5 vs. 10 μM) and less pH-sensitive. Under control conditions, stimulation with glucose reduced mitochondrial roGFP2-Orp1 oxidation without affecting cytosolic roGFP2-Orp1 and HyPer fluorescence ratios, except for the pH-dependent effects on HyPer. However, stimulation with glucose decreased the oxidation of both cytosolic probes by 15 μM exogenous H2O2. The glucose effects were not affected by overexpression of catalase, mitochondrial catalase, or superoxide dismutase 1 and 2. They followed the increase in NAD(P)H autofluorescence, were maximal at 5 mM glucose in the cytosol and 10 mM glucose in the mitochondria, and were partly mimicked by the other nutrients. Exogenous H2O2 (1-15 μM) did not affect insulin secretion. By contrast, menadione (1-5 μM) did not increase basal insulin secretion but reduced the stimulation of insulin secretion by 20 mM glucose. Innovation: Subcellular changes in β cell H2O2 levels are better monitored with roGFP2-Orp1 than HyPer/SypHer. Nutrients acutely lower mitochondrial H2O2 levels in β cells and promote degradation of exogenously supplied H2O2 in both cytosolic and mitochondrial compartments. Conclusion: The GSIS occurs independently of a detectable increase in β cell cytosolic or mitochondrial H2O2 levels.

Prediction of Insulin Secretion Ability With Microcirculation Evaluated by Contrast-enhanced Ultrasonography in Pancreas Transplantation.

Contrast-enhanced ultrasonography can evaluate microcirculation. Thus, we used contrast-enhanced ultrasonography in evaluating pancreas graft perfusion and examined the relationship between graft circulation and function. Contrast-enhanced ultrasonography was performed in 17 cases within 24 hours and at 1, 3, 5, 7, 14, 21, and 28 days after transplantation (Tx). The time between the time to peak intensity in the parenchyma and that in the vein was defined as delta-Tp(P-V). Graft function was evaluated with oral glucose tolerance test (OGTT) at 1 and 3 months after Tx, and glucagon stimulation test at 1 month after Tx. Differences in delta-Tp(P-V) between individual cases were more significant early after Tx, and delta-Tp(P-V) within 24 hours (delta-Tp[P-V]24h) was used in the subsequent analysis. Delta-Tp(P-V)24 hours showed a negative correlation with C-peptide increment in the glucagon stimulation test and the area under the curve of insulin level in oral glucose tolerance test. The cases were divided into the following 2 groups: the standard group (delta-Tp[P-V]24h ≤6.10 seconds) and the delayed group (>6.10 seconds). The area under the curve of insulin level increased significantly from 1 to 3 months after Tx in the standard group only. These results suggest that delta-Tp(P-V)24 hours affects insulin secretion after Tx. Contrast-enhanced ultrasonography is useful in predicting endocrine function of the graft.

Synaptotagmin 4 Regulates Pancreatic β Cell Maturation by Modulating the Ca2+ Sensitivity of Insulin Secretion Vesicles

Islet β cells from newborn mammals exhibit high basal insulin secretion and poor glucose-stimulated insulin secretion (GSIS). Here we show that β cells of newborns secrete more insulin than adults in response to similar intracellular Ca2+ concentrations, suggesting differences in the Ca2+ sensitivity of insulin secretion. Synaptotagmin 4 (Syt4), a non-Ca2+ binding paralog of the β cell Ca2+ sensor Syt7, increased by ∼8-fold during β cell maturation. Syt4 ablation increased basal insulin secretion and compromised GSIS. Precocious Syt4 expression repressed basal insulin secretion but also impaired islet morphogenesis and GSIS. Syt4 was localized on insulin granules and Syt4 levels inversely related to the number of readily releasable vesicles. Thus, transcriptional regulation of Syt4 affects insulin secretion; Syt4 expression is regulated in part byMyt transcription factors, which repress Syt4 transcription. Finally, human SYT4 regulated GSIS in EndoC-βH1 cells, a human β cell line. These findings reveal the role that altered Ca2+ sensing plays in regulating β cell maturation.

Lipophilicity predicts the ability of nonsulphonylurea drugs to block pancreatic beta-cell KATP channels and stimulate insulin secretion; statins as a test case.

SummaryAims KATP ion channels play a key role in glucose‐stimulated insulin secretion. However, many drugs block KATP as “off targets” leading to hyperinsulinaemia and hypoglycaemia. As such drugs are often lipophilic, the aim was to examine the relationship between drug lipophilicity (P) and IC 50 for KATP block and explore if the IC 50's of statins could be predicted from their lipophilicity and whether this would allow one to forecast their acute action on insulin secretion.Materials and methodsA meta‐analysis of 26 lipophilic, nonsulphonylurea, blockers of KATP was performed. From this, the IC 50's for pravastatin and simvastatin were predicted and then tested experimentally by exploring their effects on KATP channel activity via patch‐clamp measurement, calcium imaging and insulin secretion in murine beta cells and islets.ResultsNonsulphonylurea drugs inhibited KATP channels with a Log IC 50 linearly related to their logP. Simvastatin blocked KATP with an IC 50 of 25 nmol/L, a value independent of cytosolic factors, and within the range predicted by its lipophilicity (21‐690 nmol/L). 10 μmol/L pravastatin, predicted IC 50 0.2‐12 mmol/L, was without effect on the KATP channel. At 10‐fold therapeutic levels, 100 nmol/L simvastatin depolarized the beta‐cell membrane potential and stimulated Ca2+ influx but did not affect insulin secretion; the latter could be explained by serum binding.ConclusionsThe logP of a drug can aid prediction for its ability to block beta‐cell KATP ion channels. However, although the IC 50 for the block of KATP by simvastatin was predicted, the difference between this and therapeutic levels, as well as serum sequestration, explains why hypoglycaemia is unlikely to be observed with acute use of this statin.

Polymorphisms Within RYR3 Gene Are Associated With Risk and Age at Onset of Hypertension, Diabetes, and Alzheimer's Disease.

Hypertension affects 33% of Americans while type 2 diabetes and Alzheimer's disease (AD) affect 10% of Americans, respectively. Ryanodine receptor 3 gene (RYR3) codes for the RYR which functions to release stored endoplasmic reticulum calcium ions (Ca2+) to increase intracellular Ca2+ concentration. Increasing studies demonstrate that altered levels of intracellular Ca2+ affect cardiac contraction, insulin secretion, and neurodegeneration. In this study, we investigated associations of the RYR3 genetic variants with hypertension, AD, and diabetes. Family data sets were used to explore association of RYR3 polymorphisms with risk and age at onset (AAO) of hypertension, diabetes, and AD. Family-based association tests using generalized estimating equations (FBAT-GEE) showed several unique or shared disease-1 associated variants in the RYR3 gene. Three single nuclear polymorphisms (SNPs; rs2033610, rs2596164, and rs2278317) are significantly associated with risk for hypertension, diabetes, and AD. Two SNPs (rs4780174 and rs7498093) are significantly associated with AAO of the 3 diseases. RYR3 variants are associated with hypertension, diabetes, and AD. Replication of these results of this gene in these 3 complex traits may help to better understand the genetic basis of calcium-signaling gene, RYR3 in association with risk and AAO of these diseases.

An SCFFBXO28 E3 Ligase Protects Pancreatic β-Cells from Apoptosis.

Loss of pancreatic β-cell function and/or mass is a central hallmark of all forms of diabetes but its molecular basis is incompletely understood. β-cell apoptosis contributes to the reduced β-cell mass in diabetes. Therefore, the identification of important signaling molecules that promote β-cell survival in diabetes could lead to a promising therapeutic intervention to block β-cell decline during development and progression of diabetes. In the present study, we identified F-box protein 28 (FBXO28), a substrate-recruiting component of the Skp1-Cul1-F-box (SCF) ligase complex, as a regulator of pancreatic β-cell survival. FBXO28 was down-regulated in β-cells and in isolated human islets under diabetic conditions. Consistently, genetic silencing of FBXO28 impaired β-cell survival, and restoration of FBXO28 protected β-cells from the harmful effects of the diabetic milieu. Although FBXO28 expression positively correlated with β-cell transcription factor NEUROD1 and FBXO28 depletion also reduced insulin mRNA expression, neither FBXO28 overexpression nor depletion had any significant impact on insulin content, glucose-stimulated insulin secretion (GSIS) or on other genes involved in glucose sensing and metabolism or on important β-cell transcription factors in isolated human islets. Consistently, FBXO28 overexpression did not further alter insulin content and GSIS in freshly isolated islets from patients with type 2 diabetes (T2D). Our data show that FBXO28 improves pancreatic β-cell survival under diabetogenic conditions without affecting insulin secretion, and its restoration may be a novel therapeutic tool to promote β-cell survival in diabetes.

Prior ingestion of exogenous ketone monoester attenuates the glycaemic response to an oral glucose tolerance test in healthy young individuals.

The recent development of exogenous ketone supplements allows direct testing of the metabolic effects of elevated blood ketones without the confounding influence of widespread changes experienced with ketogenic diets or prolonged fasting. In the present study, we determined the effect of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate ketone monoester on the glycaemic response and insulin sensitivity index during a 2h oral glucose tolerance test (OGTT) in humans. The results obtained show that consuming a ketone monoester supplement 30min prior to an OGTT reduced the glycaemic response and markers of insulin sensitivity without affecting insulin secretion. The findings of the present study provides evidence that ketone supplements could have therapeutic potential for future application as a glucose-lowering nutritional supplement. The main objectives of the present study were: (i) to determine whether acute ingestion of ketone monoester (Kme ); (R)-3-hydroxybutyl (R)-3-hydroxybutyrate impacts plasma glucose levels during a standardized oral glucose tolerance test (OGTT) and (ii) to compare changes in insulin concentrations and estimates of insulin sensitivity after acute Kme supplementation. Twenty healthy participants (n=10males/females) aged between 18 and 35years took part in a randomized cross-over study. After an overnight fast, participants consumed a Kme supplement (ΔG®; TΔS Ltd, UK, Oxford, UK; 0.45mlkg-1 body weight) or placebo (water) 30min before completing a 75g OGTT. Blood samples were collected every 15-30min over 2.5h. The participants and study personnel performing the laboratory analyses were blinded to the study condition. Kme acutely raised blood d-beta-hydroxybutyrate (β-OHB) to 3.2±0.6mm within 30min with levels remaining elevated throughout the entire OGTT. Compared to placebo, Kme significantly decreased the glucose area under the curve (AUC; -17%, P=0.001), non-esterified fatty acid AUC (-44%, P<0.001) and C-peptide incremental AUC (P=0.005), at the same time as improving oral glucose insulin sensitivity index by ∼11% (P=0.001). In conclusion, a Kme supplement that acutely increased β-OHB levels up to ∼3mm attenuated the glycaemic response to an OGTT in healthy humans. The reduction in glycaemic response did not appear to be driven by an increase in insulin secretion, although it was accompanied by improved markers of insulin sensitivity. These results suggest that ketone monoester supplements could have therapeutic potential in the management and prevention of metabolic diseases.

Plasma Circular RNA (0054633) Expression as a Biomarker for Prediabetes and Type 2 diabetes mellitus

Background: Circular RNAs are a type of closed non-coding RNAs, lack the terminating 5'-capand 3'-polyadenylated tail structures that present in linear RNAs. They have higher biologicalstability because of their resistance to RNA exonucleases and in some tissues; their expressionlevels are ten times higher than other types of RNA. CircRNAs act as biomarkers for variousdiseases including diabetes mellitus as they have been found to affect insulin secretion and β-cellrenewal. Objective: to investigate the role of circRNA (0054633) as a biomarker for pre-diabetesand T2DM. Subjects & Methods: A total number of 149 subjects, selected from endocrinologyunit of Internal Medicine Department, and Munshaat Sultan Family Medicine Clinic Menoufiauniversity hospital, classified into three groups : group I were 55 T2DM patients, group II were 44pre-diabetics and group III including 50 healthy subjects. Expression profile of circRNA(0054633) in plasma of the studied subjects was analyzed by quantitative real- time polymerasechain reaction (Q-PCR). Results: CircRNA (0054633) expression was significantly increasedgradually from controls to the pre-diabetes group to the T2DM group (p<0.05).The sensitivity ofCircRNA (0054633) expression for prediction of diabetes and prediabetes at cutoff point (2.95,1.95) was (92.7%, 77.3%) respectivily and the specificity was (98% and 98.6%) respectivily.The most significant pedictors for pre-diabetes were CircRNA (0054633) expression and BMI,OR (59.8, 24.9 respectivily). Conclusion: Plasma CircRNA (0054633) expression could beconsidered as a predictive and diagnostic biomarker for pre-diabetes and T2DM.

The EndoC-βH1 cell line is a valid model of human beta cells and applicable for screenings to identify novel drug target candidates

ObjectiveTo characterize the EndoC-βH1 cell line as a model for human beta cells and evaluate its beta cell functionality, focusing on insulin secretion, proliferation, apoptosis and ER stress, with the objective to assess its potential as a screening platform for identification of novel anti-diabetic drug candidates. MethodsEndoC-βH1 was transplanted into mice for validation of in vivo functionality. Insulin secretion was evaluated in cells cultured as monolayer and as pseudoislets, as well as in diabetic mice. Cytokine induced apoptosis, glucolipotoxicity, and ER stress responses were assessed. Beta cell relevant mRNA and protein expression were investigated by qPCR and antibody staining. Hundreds of proteins or peptides were tested for their effect on insulin secretion and proliferation. ResultsTransplantation of EndoC-βH1 cells restored normoglycemia in streptozotocin induced diabetic mice. Both in vitro and in vivo, we observed a clear insulin response to glucose, and, in vitro, we found a significant increase in insulin secretion from EndoC-βH1 pseudoislets compared to monolayer cultures for both glucose and incretins.Apoptosis and ER stress were inducible in the cells and caspase 3/7 activity was elevated in response to cytokines, but not affected by the saturated fatty acid palmitate.By screening of various proteins and peptides, we found Bombesin (BB) receptor agonists and Pituitary Adenylate Cyclase-Activating Polypeptides (PACAP) to significantly induce insulin secretion and the proteins SerpinA6, STC1, and APOH to significantly stimulate proliferation.ER stress was readily induced by Tunicamycin and resulted in a reduction of insulin mRNA. Somatostatin (SST) was found to be expressed by 1% of the cells and manipulation of the SST receptors was found to significantly affect insulin secretion. ConclusionsOverall, the EndoC-βH1 cells strongly resemble human islet beta cells in terms of glucose and incretin stimulated insulin secretion capabilities. The cell line has an active cytokine induced caspase 3/7 apoptotic pathway and is responsive to ER stress initiation factors. The cells' ability to proliferate can be further increased by already known compounds as well as by novel peptides and proteins. Based on its robust performance during the functionality assessment assays, the EndoC-βH1 cell line was successfully used as a screening platform for identification of novel anti-diabetic drug candidates.

Multipotent mesenchymal stromal cells enhance insulin secretion from human islets via N-cadherin interaction and prolong function of transplanted encapsulated islets in mice

BackgroundMultipotent mesenchymal stromal cells (MSC) enhance viability and function of islets of Langerhans. We aimed to examine the interactions between human MSC and human islets of Langerhans that influence the function of islets.MethodsHuman MSC and human islets (or pseudoislets, obtained after digestion and reaggregation of islet cells) were cocultured with or without cellular contact and glucose-stimulated insulin secretion assays were performed to assess cell function. The expression of several adhesion molecules, notably ICAM-1 and N-cadherin on islets and MSC, was investigated by qPCR. The role of N-cadherin was analyzed by adding an anti-N-cadherin antibody in islets cultured with or without MSC for 24 h followed by insulin measurements in static incubation assays. Islets and MSC were coencapsulated in new hydrogel microspheres composed of calcium alginate and covalently crosslinked polyethylene glycol. Encapsulated cells were transplanted intraperitoneally in streptozotocin-induced diabetic mice and glycemia was monitored. Islet function was evaluated by the intraperitoneal glucose tolerance test.ResultsIn vitro, free islets and pseudoislets cocultured in contact with MSC showed a significantly increased insulin secretion when compared to islets or pseudoislets cultured alone or cocultured without cell-to-cell contact with MSC (p < 0.05). The expression of ICAM-1 and N-cadherin was present on islets and MSC. Blocking N-cadherin prevented the enhanced insulin secretion by islets cultured in contact with MSC whereas it did not affect insulin secretion by islets cultured alone. Upon transplantation in diabetic mice, islets microencapsulated together with MSC showed significantly prolonged normoglycemia when compared with islets alone (median 69 and 39 days, respectively, p < 0.01). The intraperitoneal glucose tolerance test revealed an improved glycemic response in mice treated with islets microencapsulated together with MSC compared to mice transplanted with islets alone (p < 0.001).ConclusionsMSC improve survival and function of islets of Langerhans by cell-to-cell contact mediated by the adhesion molecule N-cadherin.