BACKGROUND: Pancreatic β-cells elevate insulin production and secretion through a compensatory mechanism to override insulin resistance under metabolic stress conditions. Deficits in β-cell compensatory capacity result in hyperglycemia and type 2 diabetes (T2D). However, the mechanism in the regulation of β-cell compensative capacity remains elusive. Nuclear factor-Y (NF-Y) is critical for pancreatic islets' homeostasis under physiological conditions, but its role in β-cell compensatory response to insulin resistance in obesity is unclear. METHODS: In this study, using obese ( ob/ob ) mice with an absence of NF-Y subunit A (NF-YA) in β-cells ( ob , Nf-ya βKO) as well as rat insulinoma cell line (INS1)-based models, we determined whether NF-Y-mediated apoptosis makes an essential contribution to β-cell compensation upon metabolic stress. RESULTS: Obese animals had markedly augmented NF-Y expression in pancreatic islets. Deletion of β-cell Nf-ya in obese mice worsened glucose intolerance and resulted in β-cell dysfunction, which was attributable to augmented β-cell apoptosis and reactive oxygen species (ROS). Furthermore, primary pancreatic islets from Nf-ya βKO mice were sensitive to palmitate-induced β-cell apoptosis due to mitochondrial impairment and the attenuated antioxidant response, which resulted in the aggravation of phosphorylated c-Jun N-terminal kinase (JNK) and cleaved caspase-3. These detrimental effects were completely relieved by ROS scavenger. Ultimately, forced overexpression of NF-Y in INS1 β-cell line could rescue palmitate-induced β-cell apoptosis, dysfunction, and mitochondrial impairment. CONCLUSION Pancreatic NF-Y might be an essential regulator of β-cell compensation under metabolic stress.
Rats ; Mice ; Animals ; Reactive Oxygen Species/metabolism* ; Diabetes Mellitus, Type 2/metabolism* ; Insulin Resistance ; Insulin ; Insulin-Secreting Cells/metabolism* ; Apoptosis ; Stress, Physiological ; Transcription Factors/metabolism* ; Palmitates/pharmacology* ; Obesity/metabolism*

OBJECTIVE: To investigate the effect of ferulic acid, a natural compound, on pancreatic beta cell viability, Ca²⁺ channels, and insulin secretion. METHODS: We studied the effects of ferulic acid on rat insulinoma cell line viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay. The whole-cell patch-clamp technique and enzyme-linked immunosorbent assay were also used to examine the action of ferulic acid on Ca²⁺ channels and insulin secretion, respectively. RESULTS: Ferulic acid did not affect cell viability during exposures up to 72 h. The electrophysiological study demonstrated that ferulic acid rapidly and concentration-dependently increased L-type Ca²⁺ channel current, shifting its activation curve in the hyperpolarizing direction with a decreased slope factor, while the voltage dependence of inactivation was not affected. On the other hand, ferulic acid have no effect on T-type Ca²⁺ channels. Furthermore, ferulic acid significantly increased insulin secretion, an effect inhibited by nifedipine and Ca²⁺-free extracellular fluid, confirming that ferulic acid-induced insulin secretion in these cells was mediated by augmenting Ca²⁺ influx through L-type Ca²⁺ channel. Our data also suggest that this may be a direct, nongenomic action. CONCLUSION This is the first electrophysiological demonstration that acute ferulic acid treatment could increase L-type Ca²⁺ channel current in pancreatic β cells by enhancing its voltage dependence of activation, leading to insulin secretion.
Rats ; Animals ; Insulin Secretion ; Insulin/pharmacology* ; Insulin-Secreting Cells/metabolism* ; Coumaric Acids/metabolism* ; Calcium/metabolism*

Insulin is produced and secreted by pancreatic β cells in the pancreas, which plays a key role in maintaining euglycemia. Insufficient secretion or deficient usage of insulin is the main cause of diabetes mellitus (DM). Drug therapy and islets transplantation are classical treatments for DM. Pancreatic β cell replacement therapy could help patients to get rid of drugs and alleviate the problem of lacking in transplantable donors. Pancreatic β-like cells can be acquired by cell reprogramming techniques or directed induction of stem cell differentiation. These cells are proved to be functional both in vitro and in vivo. Some hospitals have already performed clinical trials for pancreatic β cell replacement therapy. Functional pancreatic β-like cells, which obtained from in vitro pathway, could be a reliable source of cell therapy for treating DM. In this review, the approaches of obtaining pancreatic β cells are summarized and the remaining problems are discussed. Some thoughts are provided for further acquisition and application of pancreatic β cells.
Cell Differentiation ; Diabetes Mellitus/therapy* ; Humans ; Insulin/metabolism* ; Insulin-Secreting Cells/metabolism* ; Islets of Langerhans Transplantation ; Pancreas/metabolism*

The present study investigated the anti-oxidative and anti-apoptotic effects and molecular mechanisms of catalpol on the H_2O_2-induced pancreatic β-cells(INS-1 cells).The oxidative damage model of INS-1 cells was induced and optimized by the stimulation of H_2O_2 of different concentrations for different time.CCK-8 assay was used to detect cell viability after catalpol intervention(1, 5, 10, 20, 40, 80, and 160 μmol·L~(-1)) for 24 h.Intracellular reactive oxygen species(ROS), superoxide dismutase(SOD), and lipid peroxide malondialdehyde(MDA) were measured by DCFH-DA fluorescent probe, WST-1, and TBA respectively.Moreover, the apo-ptotic effect was detected by AO-EB and Annexin V-FITC/PI staining.In addition, the protein expression levels were detected by Wes-tern blot, and intracellular insulin concentration was measured by ELISA.The results showed that the oxidative damage model of INS-1 cells was stably induced by 50 μmol·L~(-1) H_2O_2 treatment for 2 h, and catalpol at 1-80 μmol·L~(-1) did not affect cell viability of INS-1 cells.Compared with the conditions in the model group, 1, 5, and 10 μmol·L~(-1) catalpol intervention for 2 h could protect INS-1 cells from oxidative damage(P<0.001), reduce ROS and MDA, increase SOD, and inhibit excessive cell apoptosis.Moreover, 1, 5, and 10 μmol·L~(-1) catalpol could also up-regulate the phosphorylation of nuclear transcription factor NF-E2 related factors, negatively regulate Kelch-like ECH-associated protein 1(Keap1), phosphorylation of extracellular signal-regulated kinase(ERK), and heme oxyge-nase 1(HO-1), and promote the protein expression of pancreatic-duodenal homeobox factor-1(PDX-1) and glucose transporter 2(GLUT2).In addition, 1, 5, and 10 μmol·L~(-1) catalpol increased insulin secretion of INS-1 cells under oxidative damage in the high-glucose culture medium, indicating function recovery of pancreatic β cells.PDX-1 is a key nuclear transcription factor of pancreatic β cell function that directly regulates GLUT2 and insulin synthesis, and affects glucose homeostasis.In conclusion, catalpol can reduce the oxidative damage and apoptosis of INS-1 cells, activate antioxidant pathway, protect the function of pancreatic β cells, and improve insulin synthesis and secretion.
Apoptosis ; Glucose/metabolism* ; Insulin/metabolism* ; Insulin-Secreting Cells/metabolism* ; Iridoid Glucosides ; Kelch-Like ECH-Associated Protein 1/metabolism* ; NF-E2-Related Factor 2/metabolism* ; Oxidative Stress ; Reactive Oxygen Species/metabolism* ; Superoxide Dismutase/metabolism*

Type 2 diabetes mellitus( T2 DM) is a common chronic metabolic disease characterized by persistent hyperglycemia and insulin resistance. In pancreatic β-cells,glucose-stimulated insulin secretion( GSIS) plays a pivotal role in maintaining the balance of blood glucose level. Previous studies have shown that geniposide,one of the active components of Gardenia jasminoides,could quickly regulate the absorption and metabolism of glucose,and affect glucose-stimulated insulin secretion in pancreatic β cells,but the specific mechanism needs to be further explored. Emerging evidence indicated that glycosylation of glucose transporter( GLUT) has played a key role in sensing cell microenvironmental changes and regulating glucose homeostasis in eucaryotic cells. In this study,we studied the effects of geniposide on the key molecules of GLUT2 glycosylation in pancreatic β cells. The results showed that geniposide could significantly up-regulate the mRNA and protein levels of Glc NAc T-Ⅳa glycosyltransferase( Gn T-Ⅳa) and galectin-9 but had no signi-ficant effect on the expression of clathrin,and geniposide could distinctively regulate the protein level of Gn T-Ⅳa in a short time( 1 h) under the conditions of low and medium glucose concentrations,but had no significant effect on the protein level of galectin-9. In addition,geniposide could also remarkably affect the protein level of glycosylated GLUT2 in a short-time treatment. The above results suggested that geniposide could quickly regulate the protein level of Gn T-Ⅳa,a key molecule of protein glycosylation in INS-1 rat pancreatic βcells and affect the glycosylation of GLUT2. These findings suggested that the regulation of geniposide on glucose absorption,metabolism and glucose-stimulated insulin secretion might be associated with its efficacy in regulating GLUT2 glycosylation and affecting its distribution on the cell membrane and cytoplasm in pancreatic β cells.
Animals ; Diabetes Mellitus, Type 2/metabolism* ; Glucose/metabolism* ; Glycosylation ; Insulin/metabolism* ; Insulin-Secreting Cells/metabolism* ; Iridoids ; Rats

Lycopene is an antioxidant which has potential anti-diabetic activity, but the cellular mechanisms have not been clarified. In this study, different concentrations of lycopene were used to treat pancreatic alpha and beta cell lines, and the changes of cell growth, cell apoptosis, cell cycle, reactive oxygen species (ROS), ATP levels and expression of related cytokines were determined. The results exhibited that lycopene did not affect cell growth, cell apoptosis, cell cycle, ROS and ATP levels of alpha cells, while it promoted the growth of beta cells, increased the ratio of S phase, reduced the ROS levels and increased the ATP levels of beta cells. At the same time, lycopene treatment elevated the mRNA expression levels of tnfα, tgfβ and hif1α in beta cells. These findings suggest that lycopene plays cell-specific role and activates pancreatic beta cells, supporting its application in diabetes therapy.
Adenosine Triphosphate ; metabolism ; Apoptosis ; Carotenoids ; pharmacology ; Cell Cycle ; Cells, Cultured ; Cytokines ; metabolism ; Glucagon-Secreting Cells ; drug effects ; Humans ; Insulin-Secreting Cells ; drug effects ; Lycopene ; pharmacology ; Reactive Oxygen Species ; metabolism

The influence of β-cell function on cardiovascular autonomic neuropathy (CAN), an important diabetes-related complication, is still unclear. In this study, we aimed to investigate the association between residual β-cell function and CAN in patients newly diagnosed with type 2 diabetes. We enrolled 90 newly-diagnosed type 2 diabetic patients and 37 participants with normal glucose tolerance as controls. The patients were divided into a CAN+ group (diabetic patients with CAN, n = 20) and a CAN- group (diabetic patients without CAN, n = 70) according to the standard Ewing battery of tests. Fasting and postprandial plasma glucose, insulin, and C-peptide were measured. Homeostasis model assessment-beta cells (HOMA-B) and HOMA-insulin resistance (IR) were calculated. The prevalence of CAN in this population was 22.2%. Compared with the CAN- group, the CAN+ group had significantly lower fasting plasma insulin (6.60 ± 4.39 vs 10.45 ± 7.82 μ/L, P = 0.029), fasting C-peptide (0.51 ± 0.20 vs 0.82 ± 0.51 nmol/L, P = 0.004), and HOMA-B (21.44 ± 17.06 vs 44.17 ± 38.49, P = 0.002). Fasting C-peptide was correlated with the Valsalva ratio (r = 0.24, P = 0.043) and the 30:15 test (r = 0.26, P = 0.023). Further analysis showed that fasting C-peptide (OR: 0.041, 95% CI 0.003-0.501, P = 0.012) and HOMA-B (OR: 0.965, 95% CI 0.934-0.996, P = 0.028) were independently associated with cardiovascular autonomic nerve function in this population. The patients with fasting C-peptide values < 0.67 nmol/L were more likely to have CAN than those with C-peptide levels ≥0.67 nmol/L (OR: 6.00, 95% CI 1.815-19.830, P = 0.003). A high prevalence of CAN was found in patients with newly-diagnosed type 2 diabetes. Decreased β-cell function was closely associated with CAN in this population.
Adult ; Asian Continental Ancestry Group ; Blood Glucose ; analysis ; Diabetes Mellitus, Type 2 ; complications ; metabolism ; Diabetic Neuropathies ; etiology ; Fasting ; physiology ; Female ; Glucose ; metabolism ; Humans ; Insulin ; metabolism ; Insulin Resistance ; physiology ; Insulin-Secreting Cells ; metabolism ; Male ; Middle Aged

BACKGROUND: Emerging evidence suggests that sphingolipids may be involved in type 2 diabetes. However, the exact signaling defect through which disordered sphingolipid metabolism induces β-cell dysfunction remains unknown. The current study demonstrated that sphingosine-1-phosphate (S1P), the product of sphingosine kinase (SphK), is an essential factor for maintaining β-cell function and survival via regulation of mitochondrial action, as mediated by prohibitin (PHB). METHODS: We examined β-cell function and viability, as measured by mitochondrial function, in mouse insulinoma 6 (MIN6) cells in response to manipulation of cellular S1P and PHB levels. RESULTS: Lack of S1P induced by sphingosine kinase inhibitor (SphKi) treatment caused β-cell dysfunction and apoptosis, with repression of mitochondrial function shown by decreases in cellular adenosine triphosphate content, the oxygen consumption rate, the expression of oxidative phosphorylation complexes, the mitochondrial membrane potential, and the expression of key regulators of mitochondrial dynamics (mitochondrial dynamin-like GTPase [OPA1] and mitofusin 1 [MFN1]). Supplementation of S1P led to the recovery of mitochondrial function and greatly improved β-cell function and viability. Knockdown of SphK2 using small interfering RNA induced mitochondrial dysfunction, decreased glucose-stimulated insulin secretion (GSIS), and reduced the expression of PHB, an essential regulator of mitochondrial metabolism. PHB deficiency significantly reduced GSIS and induced mitochondrial dysfunction, and co-treatment with S1P did not reverse these trends. CONCLUSION: Altogether, these data suggest that S1P is an essential factor in the maintenance of β-cell function and survival through its regulation of mitochondrial action and PHB expression.
Adenosine Triphosphate ; Animals ; Apoptosis ; GTP Phosphohydrolases ; Insulin ; Insulin-Secreting Cells ; Insulinoma ; Membrane Potential, Mitochondrial ; Metabolism ; Mice ; Mitochondria ; Mitochondrial Dynamics ; Oxidative Phosphorylation ; Oxygen Consumption ; Phosphotransferases ; Repression, Psychology ; RNA, Small Interfering ; Sphingolipids ; Sphingosine

OBJECTIVETo explore the association of insulin resistance and β cell function with lipid metabolism in middle-aged and elderly Hui and Han populations.

METHODSA total of 1000 subjects age over 40 years were recruited from five urban communities in Yinchuan and Wuzhong cities of Ningxia. The composition ratio between Hui and Han nationality was 1:2. A questionnaire-based survey was performed. Physical examinations were carried out to measure the height, body mass, waistline, and hipline. The levels of triglyceride (TG), total cholesterol (TC), blood uric acid (BUA), fasting blood glucose and insulin were measured. The boby mass index (BMI), waist-hip ratio (WHR), and secretion related index including insulin resistance index (IR), insulin sensitivity index (IAI), and beta cell function index (HBCI) were calculated.

RESULTSThe BMI, WHR, IAI, HBCI, and the prevalence rate of diabetes in Hui nationality were significantly higher than those in Han nationality (P<0.01). The levels of BUA, fasting blood glucose, TC, and IR in Han nationality were significantly lower than those in Hui nationality (P<0.01). In Hui populations, TG, BMI, WHR, and BUA were positively correlated with IR (r=0.234, r=0.193, r=0.143, and r=0.129, respectively; P<0.01) and were negatively correlated with IAI (r=-0.234, r=-0.193, r=-0.143, r=-0.129, respectively; P<0.01), whereas TC was negatively correlated with HBCI (r=-0.169, P<0.01). In Han populations, TC, TG, BMI, WHR, and BUA were positively correlated with IR (r=0.140, r=0.257, r=0.288, r=0.163, r=0.104, P<0.01) and negatively correlated with IAI (r=-0.140, r=-0.257, r=-0.288, r=-0.163, and r=-0.104, P<0.01), whereas BMI was negatively correlated with HBCI (r=-0.111, P<0.01). After the influential factors such as gender, nationality, and age were adjusted, the TC, TG, BMI, WHR, BUA levels were positively correlated with IR (r=0.109, r=0.256, r=0.253, r=0.139, and r=0.142, P<0.01) and negatively correlated with IAI (r=-0.109, r=-0.256, r=-0.253, r=-0.139, and r=-0.142, P<0.01). TC and BMI were negatively correlated with HBCI (r=-0.113, r=-0.086, P<0.01). TG and BMI were independently associated with IR and IAI (r=0.218, r=0.182, r=-0.218, r=-0.182), while TC and BMI were independently associated with HBCI (r=-0.113, r=-0.086).

CONCLUSIONSThe distributions of TC, TG, BMI, WHR, BUA, IR, IAI, and HBCI differ between Han and Hui populations. The development of insulin resistance is closely related with the increased levels of TC, TG, BMI, WHR, and BUA. However, the HBCI increases with the increased level of TC and BMI. TG and BMI may be related with insulin resistance. Also, TC and BMI may affect the secretion function of β cells.

Aged ; Asian Continental Ancestry Group ; Blood Glucose ; analysis ; Body Mass Index ; Cholesterol ; blood ; Ethnic Groups ; Humans ; Insulin ; blood ; Insulin Resistance ; Insulin-Secreting Cells ; cytology ; Lipid Metabolism ; Middle Aged ; Triglycerides ; blood ; Uric Acid ; blood

OBJECTIVETo investigate the effects of berberine (BBR) and cinnamic acid (CA), the main active components in Jiaotai Pill (, JTP), on palmitic acid (PA)-induced intracellular triglyceride (TG) accumulation in NIT-1 pancreatic β cells.

METHODSCells were incubated in culture medium containing PA (0.25 mmol/L) for 24 h. Then treatments with BBR (10 μmol/L), CA (100 μmol/L) and the combination of BBR and CA (BBR+CA) were performed respectively. Intracellular lipid accumulation was assessed by Oil Red O staining and TG content was measured by colorimetric assay. The expression of adenosine monophosphate-activated protein kinase (AMPK) protein and its downstream lipogenic and fatty acid oxidation genes, including fatty acid synthase (FAS), acetyl-coA carboxylase (ACC), phosphorylation acetyl-coA carboxylase (pACC), carnitine acyl transferase 1 (CPT-1) and sterol regulating element binding protein 1c (SREBP-1c) were determined by Western blot or real time polymerase chain reaction.

RESULTSPA induced an obvious lipid accumulation and a significant increase in intracellular TG content in NIT-1 cells. PA also induced a remarkable decrease in AMPK protein expression and its downstream targets such as pACC and CPT-1. Meanwhile, AMPK downstream lipogenic genes including SREBP-1c mRNA, FAS and ACC protein expressions were increased. Treatments with BBR and BBR+CA, superior to CA, significantly reversed the above genes changes in NIT-1 pancreatic β cells. However, the synergistic effect of BBR and CA on intracellular TG content was not observed in the present study.

CONCLUSIONIt can be concluded that in vitro, BBR and BBR+CA could inhibit PA-induced lipid accumulation by decreasing lipogenesis and increasing lipid oxidation in NIT-1 pancreatic β cells.

AMP-Activated Protein Kinases ; metabolism ; Animals ; Berberine ; chemistry ; pharmacology ; Cell Line ; Cinnamates ; chemistry ; pharmacology ; Fatty Acids ; metabolism ; Gene Expression Regulation ; drug effects ; Insulin-Secreting Cells ; drug effects ; metabolism ; Intracellular Space ; metabolism ; Lipogenesis ; drug effects ; genetics ; Mice ; Oxidation-Reduction ; drug effects ; Palmitic Acid ; toxicity ; Triglycerides ; metabolism