Pancreatic Β-cell Function Research Articles

Alpha-lipoic acid treatment improves adverse cardiac remodelling in the diabetic heart – The role of cardiac hydrogen sulfide-synthesizing enzymes

IntroductionAlpha-lipoic acid (ALA) is a licensed drug for the treatment of diabetic neuropathy. We recently reported that it also improves diabetic cardiomyopathy (DCM) in type 2 diabetes mellitus (T2DM). In this study, we present evidence supporting our hypothesis that the cardioprotective effect of ALA is via upregulation of cardiac hydrogen sulfide (H2S)-synthesizing enzymes. MethodsFollowing 12 h of overnight fasting, T2DM was induced in 23 out of 30 male Sprague-Dawley rats by intraperitoneal administration of nicotinamide (110 mg/kg) followed by streptozotocin (55 mg/kg) while the rest served as healthy control (HC). T2DM rats then received either oral administration of ALA (60 mg/kg/day; n = 7) or 40 mg/kg/day DL-propargylglycine (PAG, an endogenous H2S inhibitor; n = 7) intraperitoneally for 6 weeks after which all rats were sacrificed and samples collected for analysis. Untreated T2DM rats served as diabetic control (DCM; n = 9). ResultsT2DM resulted in weight loss, islet destruction, reduced pancreatic β-cell function and hyperglycemia. Histologically, DCM rats showed significant myocardial damage evidenced by myocardial degeneration, cardiomyocyte vacuolation and apoptosis, cardiac fibrosis and inflammation, which positively correlated with elevated levels of cardiac damage markers compared to HC rats (p < 0.001). These pathological alterations worsened significantly in PAG-treated rats (p < 0.05). However, ALA treatment restored normoinsulemia, normoglycemia, prevented DCM, and improved lipid and antioxidant status. Mechanistically, ALA significantly upregulated the expression of cardiac H2S-synthesizing enzymes and increased plasma H2S concentration compared to DCM rats (p < 0.001). ConclusionALA preserves myocardial integrity in T2DM likely by maintaining the expression of cardiac H2S-synthezing enzymes and increasing plasma H2S level.

Investigating the protective effects of estrogen on β-cell health and the progression of hyperglycemia-induced atherosclerosis.

Sex differences in the prevalence and development of diabetes and associated cardiometabolic complications are well established. The objective of this study was to analyze the effects of estrogen on the maintenance of β-cell health/function and atherosclerosis progression, using a mouse model of hyperglycemia-induced atherosclerosis, the ApoE-/-:Ins2+/Akita mouse. ApoE-/-:Ins2+/Akita mice exhibit sexual dimorphism in the control of blood glucose levels. Male ApoE-/-:Ins2+/Akita mice are chronically hyperglycemic due to a significant reduction in pancreatic β-cell mass. Female mice are only transiently hyperglycemic, maintain β-cell mass, and blood glucose levels normalize at 35 ± 1 days of age. To determine the effects of estrogen on pancreatic β-cell health and function, ovariectomies and estrogen supplementation experiments were performed, and pancreatic health and atherosclerosis were assessed at various time points. Ovariectomized ApoE-/-:Ins2+/Akita mice developed chronic hyperglycemia with significantly reduced β-cell mass. To determine whether the observed effects on ovariectomized ApoE-/-:Ins2+/Akita mice were due to a lack of estrogens, slow-releasing estradiol pellets were inserted subcutaneously. Ovariectomized ApoE-/-:Ins2+/Akita mice treated with exogenous estradiol showed normalized blood glucose levels and maintained β-cell mass. Exogenous estradiol significantly reduced atherosclerosis in both ovariectomized female and male ApoE-/-:Ins2+/Akita mice relative to controls. Together, these findings suggest that estradiol confers significant protection to pancreatic β-cell health and can directly and indirectly slow the progression of atherosclerosis.NEW & NOTEWORTHY This study examines the effect(s) of estrogen on β cell and cardiometabolic health/function in a novel mouse model of hyperglycemia-induced atherosclerosis (ApoE-/-:Ins2+/Akita). Using a combination of estrogen deprivation (ovariectomy) and supplementation strategies, we quantify effects on glucose homeostasis and atherogenesis. Our results clearly show a protective role for estrogen on pancreatic β-cell health and function and glucose homeostasis. Furthermore, estrogen supplementation dramatically reduces atherosclerosis progression in both male and female mice.

Activation of renal CSE/H2S pathway by alpha-lipoic acid protects against histological and functional changes in the diabetic kidney

IntroductionWe previously reported that alpha-lipoic acid (ALA) supplementation protects against progression of diabetic kidney disease (DKD). In this study, we aim to investigate whether the mechanism of renal protection by ALA involves renal cystathionine γ-lyase/hydrogen sulfide (CSE/H2S) system in type 2 diabetes mellitus (T2DM). MethodsThirty-seven male Sprague-Dawley rats underwent 12 h of overnight fasting. To induce T2DM, 30 of these rats received intraperitoneal administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). T2DM rats then received either oral administration of ALA (60 mg/kg/day) or intraperitoneal administration of 40 mg/kg/day DL-propargylglycine (PAG, a CSE inhibitor) or both for 6 weeks after which rats were sacrificed and samples collected for analysis. Untreated diabetic and non-diabetic rats served as diabetic and healthy controls respectively. ResultsT2DM was characterized by reduced pancreatic β-cell function and hyperglycemia. Histologically, untreated diabetic rats showed significantly damaged pancreatic islets, glomerular and tubular injury, with elevated levels of renal function markers compared to healthy control rats (p < 0.001). These pathological changes worsened significantly following PAG administration (p < 0.05). While some renal protection was observed in ALA+PAG rats, ALA administration in untreated diabetic rats provided superior protection comparable to healthy control rats, with improved antioxidant status, lipid profile and reduced inflammation. Mechanistically, ALA significantly activated renal CSE/H2S system in diabetic rats, which was markedly suppressed in PAG-treated rats (p < 0.001). ConclusionOur data suggest that ALA protects against DKD development and progression by activating renal CSE/H2S pathway. Hence, CSE/H2S pathway may represent a therapeutic target in the treatment or prevention of DKD in diabetic patients.

(Invited) Real-Time Detection of Insulin Secreted By Pancreatic β-Cells Using Single-Walled Carbon Nanotube Sensors

Quantification of insulin is essential for diabetes research in general, and for the study of pancreatic β-cell function in particular. Fluorescent single-walled carbon nanotubes (SWCNTs) find many applications as optical nanosensors for biomolecules, proteins, and enzyme, with real-time feedback on target analyte binding1–4. Herein, fluorescent SWCNT are used for the recognition and real-time quantification of insulin5. Two approaches for rendering the SWCNT sensors for insulin are compared, using surface functionalization with either a natural insulin aptamer with known affinity to insulin, or a synthetic lipid-PEG, both of which show a modulation of the emitted fluorescence in response to insulin. Although the PEGylated-lipid has no prior affinity to insulin, its response to insulin is more stable and reproducible compared to the insulin aptamer-SWCNTs. The SWCNT sensors successfully detect and quantify insulin secreted by β-cells within the complex environment of the conditioned media, and the results are found to be in agreement with an enzyme-linked immunosorbent assay5. This novel analytical tool for real time quantification of insulin secreted by β-cells provides new opportunities for rapid assessment of β-cell function.(1) Bisker, G.; Dong, J.; Park, H. D.; Iverson, N. M.; Ahn, J.; Nelson, J. T.; Landry, M. P.; Kruss, S.; Strano, M. S. Protein-Targeted Corona Phase Molecular Recognition. Nat. Commun. 2016, 7, 1–14.(2) Bisker, G.; Bakh, N. A.; Lee, M. A.; Ahn, J.; Park, M.; O’Connell, E. B.; Iverson, N. M.; Strano, M. S. Insulin Detection Using a Corona Phase Molecular Recognition Site on Single-Walled Carbon Nanotubes. ACS Sensors 2018, 8 (2), 367–377.(3) Amir, D.; Hendler-Neumark, A.; Wulf, V.; Ehrlich, R.; Bisker, G. Oncometabolite Fingerprinting Using Fluorescent Single-Walled Carbon Nanotubes. Adv. Mater. Interfaces 2021.(4) Wulf, V.; Slor, G.; Rathee, P.; Amir, R. J.; Bisker, G. Dendron-Polymer Hybrids as Tailorable Coronae of Single-Walled Carbon Nanotube. ChemRxiv 2021. https://doi.org/10.26434/ChemRxiv.14452785.V1.(5) Ehrlich, R.; Hendler‐Neumark, A.; Wulf, V.; Amir, D.; Bisker, G. Optical Nanosensors for Real‐Time Feedback on Insulin Secretion by Β‐Cells. Small 2021, 17 (30), 2101660.

Mechanisms Linking Vitamin D Deficiency to Impaired Metabolism: An Overview.

Vitamin D deficiency is a common health problem worldwide. Despite its known skeletal effects, studies have begun to explore its extra-skeletal effects, that is, in preventing metabolic diseases such as obesity, hyperlipidemia, and diabetes mellitus. The mechanisms by which vitamin D deficiency led to these unfavorable metabolic consequences have been explored. Current evidence indicates that the deficiency of vitamin D could impair the pancreatic β-cell functions, thus compromising its insulin secretion. Besides, vitamin D deficiency could also exacerbate inflammation, oxidative stress, and apoptosis in the pancreas and many organs, which leads to insulin resistance. Together, these will contribute to impairment in glucose homeostasis. This review summarizes the reported metabolic effects of vitamin D, in order to identify its potential use to prevent and overcome metabolic diseases.

Acacetin antagonized lipotoxicity in pancreatic β-cells via ameliorating oxidative stress and endoplasmic reticulum stress.

During the pathogenesis and progression of diabetes, lipotoxicity is a major threat to the function and survival of pancreatic β-cells. To battle against the lipotoxicity induced cellular damages, the present study investigated the beneficial effects of acacetin, a natural antioxidant, on free fatty acid (FFA) stressed RINm5F cells and the potential mechanism involved. RINm5F cells with or without 1h pretreatment of acacetin were treated with 0.35mM sodium palmitate for 24h. Cell viability, intracellular reactive oxygen species (ROS) level, antioxidant capacity, cellular apoptosis, and endoplasmic reticulum (ER) stress biomarker expression were investigated. Our experiments demonstrated that acacetin treatment significantly scavenged the intracellular ROS, upregulated the endogenous antioxidant enzymes, and diminished the sub-G1 DNA fraction in the cells exposed to FFA, suggesting its efficacy against oxidative stress. Meanwhile, acacetin treatment significantly mitigated the overload of intracellular Ca2+ and reduced the pro-apoptotic protein expression in the FFA stimulated cells, and thereby attenuated the ER stress-mediated cell apoptosis. Furthermore, siRNA interference results confirmed that the suppressing of C/EBP-homologous protein (CHOP) was critical to improve FFA-induced reduction in cell viability and ameliorated the ER stress caused by FFA stimulation. Acacetin may antagonize lipotoxicity in pancreatic cells by attenuating the oxidative stress and ER stress.

Curcuma longa modulates Islet β-cell function and insulin resistance in diabetic rat.

Objective: To analyze modulating effect of Curcuma longa on Pancreatic Islet β-cell function and insulin resistance in alloxan induced diabetic rat model. Study Design: Experimental study. Setting: Department of Anatomy, Pharmacology and Pathology, SRMCH, T. Adam. Period: February 2019 to January 2020. Material &amp; Methods: One hundred adult male rats were selected according to criteria and grouped A to E. Group A and B was negative and positive control rats, and C –E were diabetic experimental rats. Alloxan (120 mg/Kg body weight) was injected intraperitoneally (i.p) to induce diabetes mellitus. Curcuma longa was used in doses of 200, 300 and 500 mg/d for 28 days. Body weight, blood glucose, HbA1c, insulin and C-peptide were estimated. Insulin resistance (HOMA-IR) and β- cell function (HOMA-β) were calculated by formulae. Data was analyzed on SPSS package ver. 21.0 (IBM, incorporation, USA) (p≤ 0.05). Results: Twenty eight days therapy of Curcuma longa extract ameliorates blood glucose, A1C, serum Insulin levels and C-peptide levels. Insulin resistance (HOMA-IR) was found improved and β- cell function (HOMA-β) was augmented in in Curcuma longa treated experimental rats (P=0.0001). Conclusion: Administration of Curcuma longa positively modulates the Islet β-cell function and insulin resistance in alloxan induced diabetic rats.

Therapeutic Efficacy of Polyphenol-Rich Fraction of Boesenbergia rotunda in Diabetic Rats: A Focus on Hypoglycemic, Antihyperlipidemic, Carbohydrate Metabolism, Antioxidant, Anti-Inflammatory and Pancreato-Protective Activities.

Boesenbergia rotunda is a famous culinary/medicinal herb native to Southeast Asia region and it is traditionally used in the treatment of several diseases. This study investigated the anti-diabetic properties of Boesenbergia rotunda polyphenol extract (BRE) in high fructose/streptozotocin-induced diabetic rats. The in vitro antioxidant activity was evaluated using DPPH and ABST colorimetric assays, while the Folin-Ciocalteu method was used for the total phenolic content of BRE. For diabetes induction, a combination of high fructose solution and streptozotocin was administered to the rats and diabetic rats were orally administrated with BRE (100 and 400 mg/kg) for 5 weeks. The fasting blood glucose, body weight gain, food and water consumption were determined during the treatment period. BRE showed excellent in vitro DPPH and ABTS scavenging activity with high phenolic content. BRE significantly lowered fasting blood glucose level, HbA1c, lipid profile, hepatorenal biochemical parameters and ameliorated the IPGTT in diabetic rats. Additionally, BRE reversed body weight loss, attenuated food and water intake, serum insulin level, pancreatic β-cell function and pancreatic cell morphology. Furthermore, fructose 1,6 biphosphatase, glucose-6-phosphatase, malondialdehyde (MDA) and proinflammatory cytokines levels were also ameliorated in the BRE-treated diabetic rats, while pancreatic antioxidant enzymes activities (GSH, SOD and CAT) were significantly increased in the treated rats. In conclusion, the results showed that BRE effectively displayed antidiabetic effects and has possible value for antidiabetic oral medication.

Perioperative C-peptide index is associated with the status of diabetes management after pancreatectomy.

Aims/IntroductionThis study aimed to identify the clinical factors affecting postoperative residual pancreatic β‐cell function, as assessed by the C‐peptide index (CPI), and to investigate the association between perioperative CPI and the status of diabetes management after pancreatectomy.Materials and MethodsThe associations between perioperative CPI and clinical background, including surgical procedures of pancreatectomy, were analyzed in 47 patients who underwent pancreatectomy, and were assessed for pre‐and postoperative CPI. The association between perioperative CPI and glycemic control after pancreatectomy was investigated.ResultsThe low postoperative CPI group (CPI <0.7) had longer duration of diabetes (17.5 ± 14.5 vs 5.5 ± 11.0 years, P = 0.004), a higher percentage of sulfonylurea users (41.7 vs 8.7%, P = 0.003) and a greater number of drug categories used for diabetes treatment (1.9 ± 1.1 vs 0.8 ± 0.8, P <0.001) than did the high postoperative CPI group. Postoperative CPI was higher (1.4 ± 1.2 vs 0.7 ± 0.6, P = 0.039) in patients with low glycosylated hemoglobin (<7.0%) at 6 months after pancreatectomy; preoperative (2.0 ± 1.5 vs 0.7 ± 0.5, P = 0.012) and postoperative CPI (2.5 ± 1.4 vs 1.4 ± 1.1, P = 0.020) were higher in non‐insulin users than in insulin users at 6 months after surgery.ConclusionsThe duration of diabetes and preoperative diabetes treatment were associated with residual pancreatic β‐cell function after pancreatectomy. Furthermore, perioperative β‐cell function as assessed by CPI was associated with diabetes management status after pancreatectomy.

Oral fat tolerance testing identifies abnormal pancreatic β-cell function and insulin resistance in individuals with normal glucose tolerance.

Insulin sensitivity and β-cell function are affected by lipid metabolism disorders, even before the onset of type 2 diabetes. People are in the postprandial state most of the time. Therefore, identifying postprandial hyperlipemia is important. This study aimed to assess patients with abnormalities in lipid metabolism, but with normal glucose tolerance, using oral fat tolerance testing (OFTT) to identify defects in insulin sensitivity and β-cell function. We included 248 volunteers with normal glucose tolerance who underwent OFTT. They were divided into three groups in accordance with their fasting and 4-h postprandial triglyceride (TG) concentrations. Their lipid concentrations during OFTT were compared. The disposition index (DI) was applied to estimate β-cell function, and the Matsuda insulin sensitivity index (ISIM ) was used to assess insulin sensitivity. We used multiple linear regression analysis to estimate the relationships of fasting and postprandial TG concentrations with β-cell function and insulin sensitivity . The changes in TG concentrations during OFTT were more marked than those in low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol or total cholesterol concentrations. As lipid metabolism deteriorated, the ISIM and the DI gradually decreased. Multiple linear regression analysis showed that fasting and 4-h postprandial TG concentrations affected LnISIM and LnDI. In individuals with normal glucose tolerance, β-cell function and insulin sensitivity gradually decrease with a deterioration in the lipid profile. Not only fasting TG, but also postprandial TG concentrations are independent risk factors for impaired β-cell function and insulin resistance.

Non-HLA Gene Polymorphisms in the Pathogenesis of Type 1 Diabetes: Phase and Endotype Specific Effects.

The non-HLA loci conferring susceptibility to type 1 diabetes determine approximately half of the genetic disease risk, and several of them have been shown to affect immune-cell or pancreatic β-cell functions. A number of these loci have shown associations with the appearance of autoantibodies or with progression from seroconversion to clinical type 1 diabetes. In the current study, we have re-analyzed 21 of our loci with prior association evidence using an expanded DIPP follow-up cohort of 976 autoantibody positive cases and 1,910 matched controls. Survival analysis using Cox regression was applied for time periods from birth to seroconversion and from seroconversion to type 1 diabetes. The appearance of autoantibodies was also analyzed in endotypes, which are defined by the first appearing autoantibody, either IAA or GADA. Analyzing the time period from birth to seroconversion, we were able to replicate our previous association findings at PTPN22, INS, and NRP1. Novel findings included associations with ERBB3, UBASH3A, PTPN2, and FUT2. In the time period from seroconversion to clinical type 1 diabetes, prior associations with PTPN2, CD226, and PTPN22 were replicated, and a novel association with STAT4 was observed. Analyzing the appearance of autoantibodies in endotypes, the PTPN22 association was specific for IAA-first. In the progression phase, STAT4 was specific for IAA-first and ERBB3 to GADA-first. In conclusion, our results further the knowledge of the function of non-HLA risk polymorphisms in detailing endotype specificity and timing of disease development.

Therapeutic Effects of Insulin-Producing Human Umbilical Cord-Derived Mesenchymal Stem Cells in a Type 1 Diabetes Mouse Model.

In patients with type 1 diabetes (T1D), compromised pancreatic β-cell functions are compensated through daily insulin injections or the transplantation of pancreatic tissue or islet cells. However, both approaches are associated with specific challenges. The transplantation of mesenchymal stem cells (MSCs) represents a potential alternative, as MSCs have tissue-forming capacity and can be isolated from various tissues. The human umbilical cord (hUC) is a good source of freely available MSCs, which can be collected through pain-free, non-invasive methods subject to minimal ethical concerns. We sought to develop a method for the in vitro generation of insulin-producing cells (IPCs) using MSCs. We examined the potential therapeutic uses and efficacy of IPCs generated from hUC-derived MSCs (hUC-IPCs) and human adipose tissue (hAD)-derived MSCs (hAD-IPCs) through in vitro experiments and streptozotocin (STZ)-induced C57BL/6 T1D mouse models. We discovered that compared to hAD-IPCs, hUC-IPCs exhibited a superior insulin secretion capacity. Therefore, hUC-IPCs were selected as candidates for T1D cell therapy in mice. Fasting glucose and intraperitoneal glucose tolerance test levels were lower in hUC-IPC-transplanted mice than in T1D control mice and hAD-IPC-transplanted mice. Our findings support the potential use of MSCs for the treatment of T1D.

اكتشاف جين جديد يساهم في الإصابة بمرض السكري ويؤثر في استقلاب الغلوكوز

الملخص المقدمة وهدف الدراسة: يعدّ مرض السكري من النوع الثاني مرضًا متعدد العوامل والجينات. وقد تم اكتشاف أكثر من 140 متغيرًا جينيًا وراثيًا مرتبطًا بسببية المرض، ولكنها تفسر فقط 10% من الأسباب الوراثية للسكري. لهذا، تسعى هذه الدراسة إلى استخدام نهج جديد تُحدَّد من خلاله جينات جديدة مشارِكة في فسيولوجية مرض السكري وإفراز الإنسولين. طريقة البحث: تم تحليل بيانات تسلسل الحمض النووي الريبوزي من جزر البنكرياس البشرية جُمعت من 89 متبرعًا. كما أُجريت سلسلة من التجارب الوظيفية في خلايا بيتا الحيوانية (INS-1) من الفئران للتحقق من الدور المحتمل للجين المرشح بما في ذلك تثبيط نشاطه، وإفراز الإنسولين، وحيوية الخلية، وموت الخلية المبرمج، والتعبير الجيني. النتائج: قد أظهر تحليل التعبير الجيني التفاضلي لبيانات تسلسل الحمض النووي الريبوزي أن 231 جينًا كان لها تعبير منخفض على نحو ملحوظ في جزر البنكرياس من المتبرعين المرضى بالسكري مقارنة بالأصحاء. وتم خفض عدد الجينات إلى 37 من جراء تطبيق قطع إحصائي أكثر صرامة. ومن بين تلك الجينات، تم اختيار (PPP1R1A) كجين مرشح بسبب ارتباطه القوي مع معدل السكري التراكمي، وتعبيره الجيني المرتفع في جزر البنكرياس البشرية مقارنة بباقي الجينات. وأيضًا، وُجد أن تعبير الجينات الوظيفية المهمة في خلايا بيتا مثل (INS) و(PDX1) و(GLUT2) و(INSR) انخفض على نحو كبير في الخلايا التي ثُبّط فيها نشاط (PPP1R1A). وخلصت الدراسة إلى أن (PPP1R1A) جين منظّم لوظيفة خلايا بيتا وإفراز الإنسولين، كما سلطت الضوء على قائمة من الجينات التي قد يكون لها دور وتأثير في مرض السكري. Background: Type 2 diabetes (T2D) is a multifactorial polygenic disease with an unclear causative mechanism. Close to 140 genetic variants are associated with T2D, but they only explain 10% of the heritability. Aim: In this study, we employed a novel approach to identify novel genes involved in the pathophysiology of T2D and insulin secretion. Methods: We analyzed RNA-sequencing data from human pancreatic islets at a global level. Furthermore, we performed a serial of functional experiments in rat pancreatic β-cells to validate the potential role of the candidate gene including siRNA silencing, insulin secretion, cell viability, apoptosis, QPCR, and western blot expression of the key molecule in β-cells. Results: Differential expression analysis reveals those 231 genes are significantly (P&lt;0.05) downregulated in diabetic islets compared to nondiabetics. However, the number of genes was restricted to 37 genes by applying a cutoff of (P&lt;0.01). Of these genes, PPP1R1A was selected as a candidate gene due to its strong correlation with HbA1c and high expression in human pancreatic islets. Silencing of PPP1R1A in INS-1 cells was markedly reduced, insulin secretion while cell viability and apoptosis were not affected. In addition, the expression of Insulin, PDX1, GLUT2, and INSR was significantly down-regulated in PPP1R1A-silenced cells. Expression of NEUROD1 and GCK was not affected. Conclusion: The study identifies PPP1R1A as a novel regulator of pancreatic β-cell function and insulin secretion. Moreover, it introduces a list of potential genes to be explored for their role in the pathogenesis of T2D.

1468-P: Effect of Kcnq1ot1 on Influencing the Function of Pancreatic ß-Cells Targeting miR-92a-1-5p

Objective: To study the role and mechanism of Kcnq1ot1 by targeting to regulate miR-92a-1-5p to effect insulin secretion in pancreatic β cells. Methods: The qRT-PCR was used to detect the expression of Kcnq1ot1 in different tissues of C57BL/6J mice, Min6 with PA intervention, islets of T2D model mice and the serum of T2D patients. The biological information website was used to predict that Kcnq1ot1 had complementary binding sites with miR-92a-1-5p, which was verified by the luciferase reporting gene system. The si-Kcnq1ot1, miR-92a-1-5p mimics, miR-92a-1-5p inhibitors and their respective controls were respectively transfected into Min6, and the effect of Ins1, Ins2, Insr, Nkx6.1, Irs1 and Ngn3 were detected by qRT-PCR, the Western blot method was used to detect the expression of insulin and Insr, and the GSIS experiment was used to detect its effect on insulin secretion. Results: The expression of Kcnq1ot1 in pancreas was significantly higher than that in other tissues. Compared with the control group, the expression of Kcnq1ot1 in T2D patients' serum, Min6 after PA treatment and the islets of T2D model mice were lower. And the expression of Kcnq1ot1 in serum is negatively correlated with FBG or HbA1c. Low expression of Kcnq1ot1 led to remarkable reduction of insulin secretion in Min6 cells. Down-regulation of Kcnq1ot1 or overexpression of miR-92a-1-5p reduced the mRNA expression levels of Ins1, Ins2, Insr, Nkx6.1, Irs1 and Ngn3, and the protein levels of insulin and Insr. We screened miR-92a-1-5p as targets of Kcnq1ot1, and their interaction was validated with dual luciferase reporter gene experiment. After knocking down Kcnq1ot1, the expression of miR-92a-1-5p was found to increase. Further rescue experiments showed that down-regulation of miR-92a-1-5p could reverse the effect of low Kcnq1ot1 expression on the function of pancreatic β-cells. Conclusion: Kcnq1ot1 may regulate the function of pancreatic β cells by targeting to negatively regulate miR-92a-1-5p. Disclosure Y.Chen: None. Y.Li: None. W.Xu: None. B.Lin: None. X.Mai: None. Y.Peng: None. D.Chen: None. Y.Su: None. W.Li: n/a. Funding Science &amp; Technology Project of Guangzhou（202102010175）

1455-P: The Loss of Pancreatic ß-Cell Complement 1q-Like-3 Secreted Protein Increases Insulin Secretion in Lean and Obese Mice

Previously, we identified complement-1q like-3 (C1ql3) secreted protein as a hub gene affecting pancreatic islet function in obese mice using network biology. We demonstrated that the recombinant C1ql3 protein inhibits insulin secretion stimulated by exendin-4 (an agonist for GLP-1 receptor) from human and mouse islets. Our goal is to investigate the role of β-cell C1ql3 in pancreatic β-cell function in physiological and pathophysiological states. We generated mice with β-cell-specific deletion of C1ql3 (βKO) by crossing C1ql3fl/fl and RIP-Cre+ mice. C1ql3 βKO mice showed significantly improved glucose clearance after oral glucose challenge than control mice, whereas no difference in insulin action was observed. Moreover, the plasma insulin levels were significantly increased at 15 min after the glucose challenge in the C1ql3 βKO vs. control mice. C1ql3 βKO islets significantly increased insulin secretion stimulated by cAMP and Exendin-4 than control islets. These results suggest that the loss of C1ql3 in β-cells increases insulin secretion to improve glucose tolerance. Obesity increases the expression-coupled secretion of C1ql3 from mouse islets. Adenovirus mediated overexpression of C1ql3 in islets showed increased ER stress - a key trigger for β-cell dysfunction in obesity- as well as decreased expression of genes involving β-cell function and maintenance. Interestingly, reduction in C1ql3 secretion is inversely correlated with increased glucose stimulated insulin secretion from islets of C1ql3 βKO Leptinob/ob compared to Leptinob/ob control mice. These findings identify that the loss of β-cell C1ql3 maintains ER stress to compensate β-cell workload during obesity and increases insulin secretion to maintain glucose homeostasis. Our work shows that an autocrine regulation of the C1ql3-signaling pathway contributes to β-cell dysfunction in obesity and type 2 diabetes. Disclosure M.Rahman: None. H.Alsharif: n/a. S.Bhatnagar: None. Funding American Diabetes Association (1-18-PDF-103) ; 1R01DK120684-01

Caffeic acid regulates glucose homeostasis and inhibits purinergic and cholinergic activities while abating oxidative stress and dyslipidaemia in fructose-streptozotocin-induced diabetic rats.

The antidiabetic potential of caffeic acid in fructose/streptozotocin-induced type 2 diabetic rats was examined in this study. Male Sprague-Dawley rats were supplied with 10% fructose solution for 14 days followed by an intraperitoneal injection of 40 mg/kg bw streptozotocin to induce type 2 diabetes (T2D). Rats were treated with both low (150 mg/kg bw) and high (300 mg/kg bw) doses of caffeic acid for 5 weeks, while the positive control group was treated with metformin (200 mg/kg bw). Treatment with caffeic acid significantly decreased blood glucose levels and elevated serum insulin levels while improving glucose tolerance, pancreatic β-cell function and morphology. It also led to a significant reduction of serum cholesterol, triglyceride, LDL-cholesterol, ALT, AST, creatinine, urea and uric acid levels, while increasing HDL cholesterol levels. Caffeic acid significantly (P < 0.05) elevated hepatic glycogen level, serum and pancreatic glutathione level, superoxide dismutase and catalase activities with a concomitant decrease in malondialdehyde level, α-amylase, lipase, adenosine triphosphatase (ATPase), ectonucleoside triphosphate diphosphohydrolase (ENTPDase), 5'-nucleotidase (5'-NTD) and acetylcholinesterase activities. The results suggest caffeic acid as a potent natural product with therapeutic effects against T2D. Further molecular and clinical studies are, however, required to ascertain these findings.

Effects of Sodium-Glucose Co-Transporter-2 Inhibitors on Pancreatic β-Cell Mass and Function.

Sodium-glucose co-transporter-2 inhibitors (SGLT2is) not only have antihyperglycemic effects and are associated with a low risk of hypoglycemia but also have protective effects in organs, including the heart and kidneys. The pathophysiology of diabetes involves chronic hyperglycemia, which causes excessive demands on pancreatic β-cells, ultimately leading to decreases in β-cell mass and function. Because SGLT2is ameliorate hyperglycemia without acting directly on β-cells, they are thought to prevent β-cell failure by reducing glucose overload in this cell type. Several studies have shown that treatment with an SGLT2i increases β-cell proliferation and/or reduces β-cell apoptosis, resulting in the preservation of β-cell mass in animal models of diabetes. In addition, many clinical trials have shown that that SGLT2is improve β-cell function in individuals with type 2 diabetes. In this review, the preclinical and clinical data regarding the effects of SGLT2is on pancreatic β-cell mass and function are summarized and the protective effect of SGLT2is in β-cells is discussed.

Potency of Antidiabetic Effects of the Combination of Syzygium cumini and Andrographis paniculata in Rats with High-Fat Dietand Streptozotocin-Induced Diabetes

Andrographis paniculata (AP) and Syzygium cumini (SC) are known for their antihyperglycemic effects. However, the combined effects of these plants have not yet been assessed. This study evaluated the oral acute toxicity and in vivo antihyperglycemic effects of the extract combining AP and SC (SCAP) in rats with high-fat diet- and streptozotocin (STZ)-induced diabetes. Thirteen female DDY mice for toxicity test were divided into three groups and orally administered one dose SCAP (0, 300, or 2000 mg/kg). On day 15, animals were euthanized, their internal organs were observed, and blood samples were collected for clinical biochemistry analyses. In vivo antihyperglycemic activity was examined in male Sprague- Dawley rats-induced diabetes. Diabetic rats were assigned to once-daily oral treatment with metformin, AP, SC or SCAP for 1 week. Concerning toxicity, SCAP had no effects on liver and kidney and histology of these organs displayed no abnormalities. Blood glucose levels had a tendency to reduce in treatment groups compared with the findings in the diabetic control group. SCAP treatment protected rats against pancreatic damage. These results illustrated that the combined SCAP treatment had beneficial effects on blood glucose levels and pancreatic β-cell function, in rats-induced diabetes.

NF-κB-inducing kinase (NIK) is activated in pancreatic β-cells but does not contribute to the development of diabetes

The transcription factor nuclear factor-κB (NF-κB) has a key role in the pathogenesis of diabetes and its complications. Although activation of the canonical NF-κB pathway in β-cells is generally deleterious, little is known about the role of the non-canonical NF-κB signalling and its main regulator, the NF-κB-inducing kinase (NIK), on pancreatic β-cell survival and function. Previous studies based on models of NIK overexpression in pancreatic islet cells showed that NIK induced either spontaneous β-cell death due to islet inflammation or glucose intolerance during diet-induced obesity (DIO) in mice. Therefore, NIK has been proposed as a potential target for diabetes therapy. However, no clear studies showed whether inhibition of NIK improves diabetes development. Here we show that genetic silencing of NIK in pancreatic β-cells neither modifies diabetes incidence nor inflammatory responses in a mouse model of immune-mediated diabetes. Moreover, NIK silencing in DIO mice did not influence body weight gain, nor glucose metabolism. In vitro studies corroborated the in vivo findings in terms of β-cell survival, function, and downstream gene regulation. Taken together, our data suggest that NIK activation is dispensable for the development of diabetes.

Glucose-Dependent miR-125b Is a Negative Regulator of β-Cell Function.

Impaired pancreatic β-cell function and insulin secretion are hallmarks of type 2 diabetes. miRNAs are short, noncoding RNAs that silence gene expression vital for the development and function of β cells. We have previously shown that β cell-specific deletion of the important energy sensor AMP-activated protein kinase (AMPK) results in increased miR-125b-5p levels. Nevertheless, the function of this miRNA in β cells is unclear. We hypothesized that miR-125b-5p expression is regulated by glucose and that this miRNA mediates some of the deleterious effects of hyperglycemia in β cells. Here, we show that islet miR-125b-5p expression is upregulated by glucose in an AMPK-dependent manner and that short-term miR-125b-5p overexpression impairs glucose-stimulated insulin secretion (GSIS) in the mouse insulinoma MIN6 cells and in human islets. An unbiased, high-throughput screen in MIN6 cells identified multiple miR-125b-5p targets, including the transporter of lysosomal hydrolases M6pr and the mitochondrial fission regulator Mtfp1. Inactivation of miR-125b-5p in the human β-cell line EndoCβ-H1 shortened mitochondria and enhanced GSIS, whereas mice overexpressing miR-125b-5p selectively in β cells (MIR125B-Tg) were hyperglycemic and glucose intolerant. MIR125B-Tg β cells contained enlarged lysosomal structures and had reduced insulin content and secretion. Collectively, we identify miR-125b as a glucose-controlled regulator of organelle dynamics that modulates insulin secretion.