Type 1 diabetes mellitus(T1DM) lacks insulin secretion due to autoimmune deficiency of pancreaticβ-cells.Protecting pancreatic islets and enhancing insulin secretion has been therapeutic approaches.Mannogalactoglucan...Type 1 diabetes mellitus(T1DM) lacks insulin secretion due to autoimmune deficiency of pancreaticβ-cells.Protecting pancreatic islets and enhancing insulin secretion has been therapeutic approaches.Mannogalactoglucan is the main type of polysaccharide from natural mushroom,which has potential medicinal prospects.Nevertheless,the antidiabetic property of mannogalactoglucan in T1DM has not been fully elucidated.In this study,we obtained the neutral fraction of alkali-soluble Armillaria mellea polysaccharide(AAMP-N) with the structure of mannogalactoglucan from the fruiting body of A.mellea and investigated the potential therapeutic value of AAMP-N in T1DM.We demonstrated that AAMP-N lowered blood glucose and improved diabetes symptoms in T1DM mice.AAMP-N activated unfolded protein response(UPR) signaling pathway to maintain ER protein folding homeostasis and promote insulin secretion in vivo.Besides that,AAMP-N promoted insulin synthesis via upregulating the expression of transcription factors,increased Ca^(2+) signals to stimulate intracellular insulin secretory vesicle transport via activating calcium/calmodulin-dependent kinase Ⅱ(CamkⅡ) and cAMP/PKA signals,and enhanced insulin secretory vesicle fusion with the plasma membrane via vesicle-associated membrane protein 2(VAMP2).Collectively,these studies demonstrated that the therapeutic potential of AAMP-N on pancreatic islets function,indicating that mannogalactoglucan could be natural nutraceutical used for the treatment of T1DM.展开更多
Background Both repaglinide and gliclazide are insulin secretagogues widely used in the treatment of type 2 diabetes.They stimulate insulin secretion through distinct mechanisms and may benefit patients from different...Background Both repaglinide and gliclazide are insulin secretagogues widely used in the treatment of type 2 diabetes.They stimulate insulin secretion through distinct mechanisms and may benefit patients from different aspects.The present study was to evaluate the effects of repaglinide or gliclazide on glycaemic control,insulin secretion,and lipid profiles in type 2 diabetes patients.Methods A total of 47 newly diagnosed type 2 diabetes patients were randomized 1：1 to receive a 4-week treatment with repaglinide or gliclazide.The standard mixed meal tolerance test was performed before and after the treatment.Plasma glucose （PG）,insulin concentration,and lipid profiles were measured.The area under insulin concentration curve （AUCins） and the early-phase insulin secretion index （△I30/△G3o） were calculated.Results After the trial,fasting and postprandial PG and postprandial insulin improved significantly in both groups （P〈0.05）.The maximum insulin concentration occurred earlier in the repaglinide group than that in the gliclazide group.AUCins increased in both groups （P 〈0.05）,but no significant difference was found between groups.△I30/△G30 increased in both groups （P 〈0.05）,especially in the repaglinide group （P 〈0.05）.Triglyceride and total cholesterol decreased significantly in the repaglinide group in some time points,while no significant change was observed in the gliclazide group.Conclusions Repaglinide and gliclazide had similar effects on glycaemic control and total insulin secretion,while repaglinide had more effects on improvements in β-cell function and lipid metabolism.展开更多
Background: We aimed to evaluate the short-term metabolic effects of a GLP-1a, (liraglutide) versus a DPP-4i, (vildagliptin) in a group of sub-Saharan type 2 diabetes patients. Methods: We conducted a randomized contr...Background: We aimed to evaluate the short-term metabolic effects of a GLP-1a, (liraglutide) versus a DPP-4i, (vildagliptin) in a group of sub-Saharan type 2 diabetes patients. Methods: We conducted a randomized controlled single blinded clinical trial in 14 uncontrolled type 2 diabetes patients (HbA1c ≥ 53 mmol/mol) with mean duration of diabetes of 8 [1 - 12] years and median age of 57 [49 - 61] years. Baseline treatment consisted of metformin in monotherapy or metformin plus sulfonylureas. Participants were randomly allocated to 2 groups of add-on 1.2 mg/day subcutaneous liraglutide in group 1 or 100 mg/day of oral vildagliptin in group 2 for 2 weeks. In all participants, insulin secretion in response to mixed meal tolerance test, insulin sensitivity by 80 mU/m<sup>2</sup>/min hyperinsulinemic-euglycemic clamp, body composition, and lipid profile were measured before and after intervention. Results: At the end of intervention, insulin sensitivity remained unchanged both with liraglutide from 6.6 [4.2 - 7.9] to 6.9 [4.3 - 10.8] mg/kg/min;p = 0.61 and vildagliptin from 7.1 [5.3 - 9.0] to 6.5 [5.6 - 9.4] mg/kg/min (p = 0.86). The area under the C-peptide curve varied from 5.5 [1.0 - 10.9] to 14.9 [10.8 - 17.2] nmol/L/120min, p = 0.09 in group 1 and from 1.1 [0.5 - 14.1] to 13.0 [9.6 - 16.9] nmol/L/120min (p = 0.17) in group 2. LDL Cholesterol levels decreased significantly with liraglutide from 0.85 g/L [0.51 - 1.02] to 0.54 g/L [0.50 - 0.73] (p = 0.04) but not with Vildagliptin. Body weight tended to decrease in group 1 (−0.6 kg) versus modest increase in group 2 (+1.1 kg). Conclusion: Short-term metabolic effects of Liraglutide and Vildagliptin add-on therapy are comparable in sub-Saharan type 2 diabetes patients with a more favorable trend for Liraglutide on body weight, lipid profile, and insulin secretion.展开更多
Chronic pancreatitis (CP) is a progressive inflammatory disorder of the pancreas. It is predominantly idiopathic (with an unknown cause) in India and mostly due to alcohol in the West. Diabetes that occur secondary to...Chronic pancreatitis (CP) is a progressive inflammatory disorder of the pancreas. It is predominantly idiopathic (with an unknown cause) in India and mostly due to alcohol in the West. Diabetes that occur secondary to chronic pancreatitis (T3c Diabetes) is often brittle, and is difficult to attain normoglycemia with conventional treatment requiring multiple doses of insulin. Mild and severe model of CP was induced in mice by repeated intraperitoneal injections of cerulein and L-arginine respectively with an intent to study islet dysfunction and develop therapeutic strategy in animal models of CP. Dietary intervention of epigallocatechin-3-gallate (EGCG) was tested in both the models of CP for its beneficial effects on insulin secretory functions. Pancreata collected upon euthanasia were used to study alterations in the morphology of pancreatic parenchyma and inflammation by staining with H&E and fibrotic changes by Masson’s trichrome and picrosirius staining. Insulin secretory functions of islets were evaluated to test the efficacy of the dietary intervention on β-cell functions. Intraperitoneal glucose tolerance test was performed to monitor the glucose homeostasis before and after the dietary intervention. Both the models resulted in CP with dispersed acini, inflammation and fibrosis. The loss of acini and extent of fibrosis was more in L-arginine model. 2-fold improvement in glucose-stimulated insulin secretory functions of islets was observed with 0.5% EGCG dietary intervention in cerulein model of CP and 1.6-fold in L-arginine model of CP. A further improvement in insulin secretion by 3.2-fold was observed with additional dietary supplements like N-acetyl cysteine, curcumin in combination with EGCG. Our results thus demonstrate and highlight the therapeutic potential of dietary green tea (EGCG) supplementation in reversing islet dysfunction and improving glucose homeostasis in experimental chronic pancreatitis in mice.展开更多
βcells are the main cells responsible for the hypoglycemic function of pancreatic islets,and the insulin secreted by these cells is the only hormone that lowers blood glucose levels in the human body.βcells are regu...βcells are the main cells responsible for the hypoglycemic function of pancreatic islets,and the insulin secreted by these cells is the only hormone that lowers blood glucose levels in the human body.βcells are regulated by various factors,among which neurotransmitters make an important contribution.This paper discusses the effects of neurotransmitters secreted by various sympathetic and parasympathetic nerves onβcells and summarizes the mechanisms by which various neurotransmitters regulate insulin secretion.Many neurotransmitters do not have a single source and are not only released from nerve terminals but also synthesized byβcells themselves,allowing them to synergistically regulate insulin secretion.Almost all of these neurotransmitters depend on the presence of glucose to function,and their actions are mostly related to the Ca^(2+)and cAMP concentrations.Although neurotransmitters have been extensively studied,many of their mechanisms remain unclear and require further exploration by researchers.展开更多
Objective:To evaluate anti-diabetic effect of Caulrpa kntillifera(C.lentillifera).Methods:The inhibitory effect of C.lentillifera extract on dipeptidyl peptidase-IV and a-glucosidase enzyme was measured in a cell free...Objective:To evaluate anti-diabetic effect of Caulrpa kntillifera(C.lentillifera).Methods:The inhibitory effect of C.lentillifera extract on dipeptidyl peptidase-IV and a-glucosidase enzyme was measured in a cell free system.Then,interleukin-1βand interferon-γinduced cell death and insulin secretion were measured in rat insulinoma(RIN)cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and ELISA kit,respectively.Glucose uptake and glucose transporter expression were measured by fluorometry and western blotting,using 3T3-Ll adipocytes.Results:C.lentillifera extract significantly decreased dipeptidyl peptidase-IV and a-glucosidase enzyme activities,and effectively inhibited cell death and iNOS expression in interleukin-1βand interfcron-γinduced RIK cells.Furthermore,C.lntillifera extract significantly enhanced insulin secretion in RTN cells and glucose transporter expression and glucose uptake in 3T3-L1adipocytes.Conclusions:Thus,our results suggest that C.lentillifera could be used as a potential antidiabetic agenl.展开更多
BACKGROUND:Sulfonylurea receptor 1(SUR1)and multidrug resistance protein 1(MRP1)are two prominent members of multidrug resistance proteins associated with insulin secretion. The aims of this study were to investigate ...BACKGROUND:Sulfonylurea receptor 1(SUR1)and multidrug resistance protein 1(MRP1)are two prominent members of multidrug resistance proteins associated with insulin secretion. The aims of this study were to investigate their expression in insulinomas and their sole and synergistic effects in modulating abnormal insulin secretion. METHODS:Fasting glucose,insulin and C-peptide were measured in 11 insulinoma patients and 11 healthy controls. Prolonged oral glucose tolerance tests were performed in 6 insulinoma patients.Insulin content,SUR1 and MRP1 were detected in 11 insulinoma patients by immunohistochemistry. SUR1 and MRP1 were also detected in 6 insulinoma patients by immunofluorescence. RESULTS:Insulinoma patients presented the typical demons-trations of Whipple’s triad.Fasting glucose of each insulinoma patient was lower than 2.8 mmol/L,and simultaneous insulin and C-peptide were increased in insulinoma patients. Prolonged oral glucose tolerance tests showed that insulin secretion in insulinoma patients were also stimulated by high glucose.Immunohistochemistry and immunofluorescence staining showed that SUR1 increased,but MRP1 decreased in insulinoma compared with the adjacent islets. CONCLUSIONS:The hypersecretion of insulin in insulinomas might be,at least partially,due to the enrichment of SUR1. In contrast,MRP1,which is down-regulated in insulinomas, might reflect a negative feedback in insulin secretion.展开更多
Background: Lack of first phase insulin secretion during oral glucose tolerance test [OGTT] in Type 2 Diabetes Mellitus (DM) is attributed to glucose toxicity. Alternatively, the role of insulin resistance in impaired...Background: Lack of first phase insulin secretion during oral glucose tolerance test [OGTT] in Type 2 Diabetes Mellitus (DM) is attributed to glucose toxicity. Alternatively, the role of insulin resistance in impaired insulin release secondary to lack of glucose entry into β cells may be responsible, but is not examined. Aim: The role of insulin sensitivity in 1st phase insulin secretion was assessed. Material and Methods: Plasma glucose (G) and insulin (I) concentrations were determined after an overnight fast (F) and upto 60 minutes during OGTT with glucose 75g in 12 normal (N), 14 with impaired glucose tolerance (IGT) and 41 subjects with Type 2 DM. First phase insulin secretion (Δ Insulin) was determined as a percentage rise from baseline 100x (Peak-Basal)/Basal. Insulin sensitivity was determined as FI x FG (mUxmM/L). Results: FG were normal (7.0 mM/L in Type 2 DM. FI x FG and ? insulin were 35 ± 4 and 389 ± 89% in N;77 ± 5 and 254 ± 65% in IGT;and 235 ± 19 and 95 ± 15% in Type 2 DM. Significant negative correlations were noted between ? insulin one hand and FI x FG on the other amongst all subjects [p < 0.0001 for all correlations]. Conclusion: Decline of 1st phase insulin secretion in IGT and Type 2 DM may be attributed to inhibited release of depleted insulin stores in the β Cells induced by impaired glucose entry due to insulin resistance, and is unlikely to be caused by glucose toxicity in IGT in presence of fasting euglycemia.展开更多
BACKGROUND Type 2 diabetes(T2 D) is characterized by insufficient insulin secretion caused by defective pancreatic β-cell function or insulin resistance,resulting in an increase in blood glucose.However,the mechanism...BACKGROUND Type 2 diabetes(T2 D) is characterized by insufficient insulin secretion caused by defective pancreatic β-cell function or insulin resistance,resulting in an increase in blood glucose.However,the mechanism involved in this lack of insulin secretion is unclear.The level of vascular endothelial growth factor B(VEGF-B) is significantly increased in T2 D patients.The inactivation of VEGF-B could restore insulin sensitivity in db/db mice by reducing fatty acid accumulation.It is speculated that VEGF-B is related to pancreatic β-cell dysfunction and is an important factor affecting β-cell secretion of insulin.As an in vitro model of normal pancreatic β-cells,the MIN6 cell line can be used to analyze the mechanism of insulin secretion and related biological effects.AIM To study the role of VEGF-B in the insulin secretion signaling pathway in MIN6 cells and explore the effect of VEGF-B on blood glucose regulation.METHODS The MIN6 mouse pancreatic islet β-cell line was used as the model system.By administering exogenous VEGF-B protein or knocking down VEGF-B expression in MIN6 cells,we examined the effects of VEGF-B on insulin secretion,Ca2+ and cyclic adenosine monophosphate(cAMP) levels,and the insulin secretion signaling pathway.RESULTS Exogenous VEGF-B inhibited the secretion of insulin and simultaneously reduced the levels of Ca2+ and cAMP in MIN6 cells.Exogenous VEGF-B also reduced the expression of phospholipase C gamma 1(PLCγ1),phosphatidylinositol 3-kinase(PI3 K),serine/threonine kinase(AKT),and other proteins in the insulin secretion pathway.Upon knockdown of VEGF-B,MIN6 cells exhibited increased insulin secretion and Ca2+ and cAMP levels and upregulated expression of PLCγ1,PI3 K,AKT,and other proteins.CONCLUSION VEGF-B can regulate insulin secretion by modulating the levels of Ca2+ and cAMP.VEGF-B involvement in insulin secretion is related to the expression of PLCγ1,PI3 K,AKT,and other signaling proteins.These results provide theoretical support and an experimental basis for the study of VEGF-B in the pathogenesis of T2 D.展开更多
To investigate the molecular mechanism of leptin regulating insulin secretion through determining the regulation of insulin secretion and the insulin receptor substrate (IRS)-2-associated phosphoinositide 3-kinase (PI...To investigate the molecular mechanism of leptin regulating insulin secretion through determining the regulation of insulin secretion and the insulin receptor substrate (IRS)-2-associated phosphoinositide 3-kinase (PI3K) activity by leptin in the isolated rat pancreatic islets, pancreatic islets were isolated from male SD rats by the collagenase method. The purified islets were incubated with leptin 2 nmol/L for 1 h in the presence of 5.6 mmol/L or 11.1 mmol/L glucose. Insulin release was measured using radioimmunoassay. IRS-2-associated activity of PI3K was determined by immunoprecipitate assay and Western blot. The results showed that in the presence of 5.6 mmol/L glucose, leptin had no significant effect on both insulin secretion and IRS-2-associated PI3K activity, but in the presence of 11.1 mmol/L glucose, insulin release was significantly inhibited after the islets were exposed to leptin for 1 h (P<0.01). PI3K inhibitor wortmannin blocked the inhibitory regulation of leptin on insulin release (P<0.05). Western Blot assay revealed that 2 nmol/L leptin could significantly increase the IRS-2-associated activity of PI3K by 51.5 % (P<0.05) in the presence of 11.1 mmol/L glucose. It was concluded that Leptin could significantly inhibit insulin secretion in the presence of 11.1 mmol/L glucose by stimulating IRS-2-associated activity of PI3K, which might be the molecular mechanism of leptin regulating insulin secretion.展开更多
To study the effects of free fatty acids on insulin secretion and expression of SUR1 gene in rat pancreatic B cells in vitro, and to explore the molecular mechanisms in lipotoxicity inducing insulin secretion dysfunc...To study the effects of free fatty acids on insulin secretion and expression of SUR1 gene in rat pancreatic B cells in vitro, and to explore the molecular mechanisms in lipotoxicity inducing insulin secretion dysfunction, pancreatic islet cells were isolated and digested from male SD rats. Purified islets were incubated with either 0.25 mmol/L palmitate or 0.125 mmol/L oleate for 48 h in vitro. Then islets were stimulated with either 5.6 mmol/L or 16.7 mmol/L glucose for 1 h. Insulin release was measured by using radioimmunoassay, and the expression of SUR1 gene mRNA was quantified by reserve transcription-polymerase chain reaction (RT-PCR). The islets exposed to both palmitate and oleate for 48 h showed an increased basal and a decreased glucose-indused insulin release as compared with control islets. Palmitate increased basal insulin secretion by 110 % (P<0.01), decreased glucose stimulated insulin secretion by 43 % (P<0.01); while oleate increased basal insulin secretion by 80 % (P<0.01) and decreased glucose stimulated insulin secretion by 32 % (P<0.05). RT-PCR showed that oleate significantly suppressed SUR1 gene expression by 64 % (P<0.01)as compared with the control group, while palmitate group manifested a light decrease of 15 % (P >0.05) of SUR1 gene expression. Our results suggested that chronic exposure to free fatty acids of pancreatic β cells inhibited glucose stimulated insulin secretion. Regulation of SUR1 gene expression may be involved in such effects, which may also be one of the molecular mechanisms in lipotoxocity inducing β cells secretion dysfunction.展开更多
Diabetes mellitus is a metabolic disease possible to treat via pancreas/islet transplantation but most immunosuppressive drugs are diabetogenic. In this letter, we review current up to date methods to assess insulin a...Diabetes mellitus is a metabolic disease possible to treat via pancreas/islet transplantation but most immunosuppressive drugs are diabetogenic. In this letter, we review current up to date methods to assess insulin action and secretion (using the surrogate indexes) suggesting their use in large studies in populations of pancreas/ islets transplanted patients.展开更多
Aim: To investigate the clinical characteristics of diabetic patients with a low-titer positive for the anti-glutamic acid decarboxylase 65 antibody (GAD antibody). Methods: The subjects were 420 diabetic inpatients. ...Aim: To investigate the clinical characteristics of diabetic patients with a low-titer positive for the anti-glutamic acid decarboxylase 65 antibody (GAD antibody). Methods: The subjects were 420 diabetic inpatients. The endogenous insulin secretion was estimated on the basis of the C-peptide immunoreactivity from a 24 h urine collection (uCPR). Clinical variables were compared between patients negative for the GAD antibody (GAD antibody titer < 1.5 U/mL), a low-titer positive GAD antibody (1.5 U/mL ≤ GAD antibody titer < 10 U/mL) and a high-titer positive GAD antibody (10 U/mL ≤ GAD antibody titer). Results: The low and high-titer positive GAD antibodies were found in 25 and 10 patients, respectively. The uCPR was significantly lower in both the patients with a low (37 ± 33 ug/24h) and high-titer (39 ± 27 ug/24h) positive GAD antibodies than in those negative for GAD antibodies (71 ± 52 ug/24h). The uCPR level was significantly lower in the low-titer positive GAD antibody group (29 ± 22 ug/24h) than in the negative group (67 ± 55 ug/24h) among the patients not taking insulin secretagogues. The difference disappeared in the subjects taking insulin secreagogues. In the stepwise multiple regression analysis, a low-titer positive GAD antibody was independently associated with the uCPR level. Conclusions: Endogenous insulin secretion is reduced in diabetic patients positive for GAD antibodies, even if the titer is low. Earlier initiation of insulin therapy might therefore protect the pancreatic β-cell function in diabetic patients with a low-titer positive GAD antibody.展开更多
The nature of the binding site(s) involved in the insulin secretory activity of imidazoline compo- unds remains unclear. An imidazoline I2 binding site (I2BS) has been neglected since the classic I2 ligand, idazoxan, ...The nature of the binding site(s) involved in the insulin secretory activity of imidazoline compo- unds remains unclear. An imidazoline I2 binding site (I2BS) has been neglected since the classic I2 ligand, idazoxan, does not release insulin. Using the rabbit as an appropriate model for the study of this type of binding sites, we have tried to re-evaluate the effects of idazoxan, the selective I2 compound BU 224, and efaroxan on insulin secretion. Mimicking efaroxan, idazoxan and BU 224 potentiated insulin release from perifused islets in the presence of 8 mM glucose. In static incubation, insulin secretion induced by idazoxan and BU 224 exhibited both dose and glucose dependencies. ATP-sensitive K+ (KATP) channel blockade, though at a different site from the SUR1 receptor, with subsequent Ca2+ entry, mediates the insulin releasing effect of the three ligands. However, additional MAO independent intracellular steps in stimulus- secretion coupling linked to PKA and PKC activation are only involved in the effect of BU 224. Therefore, both an I2 related binding site at the channel level shared by the three ligands and a putative I3-intracellularly located binding site stimulated by BU 224 would be mediating insulin release by these compounds. In vivo experiments reassess the abilities of idazoxan and BU 224 to enhance glucose-induced insulin secretion and to elicit a modest blood glucose lowering response.展开更多
A small nonpeptidyl compoud extracted from Pseudomassaria sp. was found to induce the activity of human insulin receptor tyrosine kinase in vitro. The compound was identified as demethylasterriquinone B-1 (DMAQ-B1). D...A small nonpeptidyl compoud extracted from Pseudomassaria sp. was found to induce the activity of human insulin receptor tyrosine kinase in vitro. The compound was identified as demethylasterriquinone B-1 (DMAQ-B1). DMAQ- B1 also induced an increase in [Ca2+]i and insulin secretion in mice pancreatic beta-cells at low glucose (3 mM) concentration via insulin receptor substrate-1/phosphatidylinositol-3-kinase (PI3 kinase) pathway. By using rat pancreatic perfusion technique, we found that 10 μM DMAQ-B1 directly stimulated insulin secretion up to 240% in normal rat pancreas. In the dosage from 1 to 20 μM, DMAQ-B1 stimulated insulin secretion in a dose dependent manner. Furthermore, DMAQ-B1 enhanced glucose-induced insulin secretion by 17.6% (first stage) and 19.0% (second stage), respectively. The PI3 kinase inhibitors, LY 294002 (3.9 μM) or wortmannin (100 nM), inhibited DMAQ-B1-induced insulin secretion by 46.3% and 57.4%, respectively. LY 294002 or wortmannin also inhibited DMAQ-B1 with10 mMglucose-induced insulin secretion by 70.3% and 79.0%, respectively. All the results suggested that DMAQ-B1 directly stimulated insulin secretion and enhanced glucose-induced insulin secretion. The effect of DMAQ-B1 may mediate through the activation of PI3 kinase pathway to stimulate insulin secretion in normal rat pancreas.展开更多
目的研究替米沙坦促进大鼠胰岛素分泌作用相关的信号通路。方法(1)分离成年Wistar大鼠胰腺获得胰岛和胰岛细胞,通过胰岛素分泌实验观察药物对胰岛素分泌的影响,通过钙成像实验和全细胞膜片钳技术观察药物对β细胞内Ca^(2+)浓度的变化和...目的研究替米沙坦促进大鼠胰岛素分泌作用相关的信号通路。方法(1)分离成年Wistar大鼠胰腺获得胰岛和胰岛细胞,通过胰岛素分泌实验观察药物对胰岛素分泌的影响,通过钙成像实验和全细胞膜片钳技术观察药物对β细胞内Ca^(2+)浓度的变化和对离子通道的作用。(2)使用过表达电压门控性钾(voltage-gated potassium channel,Kv)通道2.1亚型(Kv2.1)的慢病毒转染中国仓鼠卵巢(Chinese hamster ovary,CHO)细胞构建CHO-Kv2.1细胞系,使用膜片钳技术观察替米沙坦对Kv2.1通道的直接作用。结果缬沙坦和厄贝沙坦无类似替米沙坦的高糖浓度下促胰岛素分泌、升高β细胞内Ca^(2+)浓度和抑制β细胞的Kv通道等作用。过氧化物酶体增殖物激活受体γ(peroxisome proliferator-activated receptorγ,PPARγ)阻断剂GW9662亦未阻断替米沙坦的上述作用。而替米沙坦可以浓度依赖性地抑制CHO-Kv2.1细胞的Kv2.1通道电流。结论替米沙坦的促胰岛素分泌作用可能与血管紧张素Ⅱ-1型(angiotensin II type 1,AT-1)受体和PPARγ无关,但至少与对Kv2.1通道的直接抑制作用有关。展开更多
基金funded by the National Natural Science Foundation of China (32371341,31872674)the Scientific and Technologic Foundation of Jilin Province (20230202050NC)the Fundamental Research Funds for the Central Universities (CGZH202206)。
文摘Type 1 diabetes mellitus(T1DM) lacks insulin secretion due to autoimmune deficiency of pancreaticβ-cells.Protecting pancreatic islets and enhancing insulin secretion has been therapeutic approaches.Mannogalactoglucan is the main type of polysaccharide from natural mushroom,which has potential medicinal prospects.Nevertheless,the antidiabetic property of mannogalactoglucan in T1DM has not been fully elucidated.In this study,we obtained the neutral fraction of alkali-soluble Armillaria mellea polysaccharide(AAMP-N) with the structure of mannogalactoglucan from the fruiting body of A.mellea and investigated the potential therapeutic value of AAMP-N in T1DM.We demonstrated that AAMP-N lowered blood glucose and improved diabetes symptoms in T1DM mice.AAMP-N activated unfolded protein response(UPR) signaling pathway to maintain ER protein folding homeostasis and promote insulin secretion in vivo.Besides that,AAMP-N promoted insulin synthesis via upregulating the expression of transcription factors,increased Ca^(2+) signals to stimulate intracellular insulin secretory vesicle transport via activating calcium/calmodulin-dependent kinase Ⅱ(CamkⅡ) and cAMP/PKA signals,and enhanced insulin secretory vesicle fusion with the plasma membrane via vesicle-associated membrane protein 2(VAMP2).Collectively,these studies demonstrated that the therapeutic potential of AAMP-N on pancreatic islets function,indicating that mannogalactoglucan could be natural nutraceutical used for the treatment of T1DM.
文摘Background Both repaglinide and gliclazide are insulin secretagogues widely used in the treatment of type 2 diabetes.They stimulate insulin secretion through distinct mechanisms and may benefit patients from different aspects.The present study was to evaluate the effects of repaglinide or gliclazide on glycaemic control,insulin secretion,and lipid profiles in type 2 diabetes patients.Methods A total of 47 newly diagnosed type 2 diabetes patients were randomized 1：1 to receive a 4-week treatment with repaglinide or gliclazide.The standard mixed meal tolerance test was performed before and after the treatment.Plasma glucose （PG）,insulin concentration,and lipid profiles were measured.The area under insulin concentration curve （AUCins） and the early-phase insulin secretion index （△I30/△G3o） were calculated.Results After the trial,fasting and postprandial PG and postprandial insulin improved significantly in both groups （P〈0.05）.The maximum insulin concentration occurred earlier in the repaglinide group than that in the gliclazide group.AUCins increased in both groups （P 〈0.05）,but no significant difference was found between groups.△I30/△G30 increased in both groups （P 〈0.05）,especially in the repaglinide group （P 〈0.05）.Triglyceride and total cholesterol decreased significantly in the repaglinide group in some time points,while no significant change was observed in the gliclazide group.Conclusions Repaglinide and gliclazide had similar effects on glycaemic control and total insulin secretion,while repaglinide had more effects on improvements in β-cell function and lipid metabolism.
文摘Background: We aimed to evaluate the short-term metabolic effects of a GLP-1a, (liraglutide) versus a DPP-4i, (vildagliptin) in a group of sub-Saharan type 2 diabetes patients. Methods: We conducted a randomized controlled single blinded clinical trial in 14 uncontrolled type 2 diabetes patients (HbA1c ≥ 53 mmol/mol) with mean duration of diabetes of 8 [1 - 12] years and median age of 57 [49 - 61] years. Baseline treatment consisted of metformin in monotherapy or metformin plus sulfonylureas. Participants were randomly allocated to 2 groups of add-on 1.2 mg/day subcutaneous liraglutide in group 1 or 100 mg/day of oral vildagliptin in group 2 for 2 weeks. In all participants, insulin secretion in response to mixed meal tolerance test, insulin sensitivity by 80 mU/m<sup>2</sup>/min hyperinsulinemic-euglycemic clamp, body composition, and lipid profile were measured before and after intervention. Results: At the end of intervention, insulin sensitivity remained unchanged both with liraglutide from 6.6 [4.2 - 7.9] to 6.9 [4.3 - 10.8] mg/kg/min;p = 0.61 and vildagliptin from 7.1 [5.3 - 9.0] to 6.5 [5.6 - 9.4] mg/kg/min (p = 0.86). The area under the C-peptide curve varied from 5.5 [1.0 - 10.9] to 14.9 [10.8 - 17.2] nmol/L/120min, p = 0.09 in group 1 and from 1.1 [0.5 - 14.1] to 13.0 [9.6 - 16.9] nmol/L/120min (p = 0.17) in group 2. LDL Cholesterol levels decreased significantly with liraglutide from 0.85 g/L [0.51 - 1.02] to 0.54 g/L [0.50 - 0.73] (p = 0.04) but not with Vildagliptin. Body weight tended to decrease in group 1 (−0.6 kg) versus modest increase in group 2 (+1.1 kg). Conclusion: Short-term metabolic effects of Liraglutide and Vildagliptin add-on therapy are comparable in sub-Saharan type 2 diabetes patients with a more favorable trend for Liraglutide on body weight, lipid profile, and insulin secretion.
文摘Chronic pancreatitis (CP) is a progressive inflammatory disorder of the pancreas. It is predominantly idiopathic (with an unknown cause) in India and mostly due to alcohol in the West. Diabetes that occur secondary to chronic pancreatitis (T3c Diabetes) is often brittle, and is difficult to attain normoglycemia with conventional treatment requiring multiple doses of insulin. Mild and severe model of CP was induced in mice by repeated intraperitoneal injections of cerulein and L-arginine respectively with an intent to study islet dysfunction and develop therapeutic strategy in animal models of CP. Dietary intervention of epigallocatechin-3-gallate (EGCG) was tested in both the models of CP for its beneficial effects on insulin secretory functions. Pancreata collected upon euthanasia were used to study alterations in the morphology of pancreatic parenchyma and inflammation by staining with H&E and fibrotic changes by Masson’s trichrome and picrosirius staining. Insulin secretory functions of islets were evaluated to test the efficacy of the dietary intervention on β-cell functions. Intraperitoneal glucose tolerance test was performed to monitor the glucose homeostasis before and after the dietary intervention. Both the models resulted in CP with dispersed acini, inflammation and fibrosis. The loss of acini and extent of fibrosis was more in L-arginine model. 2-fold improvement in glucose-stimulated insulin secretory functions of islets was observed with 0.5% EGCG dietary intervention in cerulein model of CP and 1.6-fold in L-arginine model of CP. A further improvement in insulin secretion by 3.2-fold was observed with additional dietary supplements like N-acetyl cysteine, curcumin in combination with EGCG. Our results thus demonstrate and highlight the therapeutic potential of dietary green tea (EGCG) supplementation in reversing islet dysfunction and improving glucose homeostasis in experimental chronic pancreatitis in mice.
基金Supported by National Natural Science Foundation of China,No.81471081the Natural Science Foundation of Fujian Province,China,No.2019J01010+1 种基金Xiamen Research Foundation for Science and Technology Project No.3502Z20194037Scientific Research Foundation for Advanced Talents,Xiang’an Hospital of Xiamen University,No.PM201809170005.
文摘βcells are the main cells responsible for the hypoglycemic function of pancreatic islets,and the insulin secreted by these cells is the only hormone that lowers blood glucose levels in the human body.βcells are regulated by various factors,among which neurotransmitters make an important contribution.This paper discusses the effects of neurotransmitters secreted by various sympathetic and parasympathetic nerves onβcells and summarizes the mechanisms by which various neurotransmitters regulate insulin secretion.Many neurotransmitters do not have a single source and are not only released from nerve terminals but also synthesized byβcells themselves,allowing them to synergistically regulate insulin secretion.Almost all of these neurotransmitters depend on the presence of glucose to function,and their actions are mostly related to the Ca^(2+)and cAMP concentrations.Although neurotransmitters have been extensively studied,many of their mechanisms remain unclear and require further exploration by researchers.
基金Supported by the Ministry of Education.Science and Technology (Grant No.2012RTAL2009172)
文摘Objective:To evaluate anti-diabetic effect of Caulrpa kntillifera(C.lentillifera).Methods:The inhibitory effect of C.lentillifera extract on dipeptidyl peptidase-IV and a-glucosidase enzyme was measured in a cell free system.Then,interleukin-1βand interferon-γinduced cell death and insulin secretion were measured in rat insulinoma(RIN)cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and ELISA kit,respectively.Glucose uptake and glucose transporter expression were measured by fluorometry and western blotting,using 3T3-Ll adipocytes.Results:C.lentillifera extract significantly decreased dipeptidyl peptidase-IV and a-glucosidase enzyme activities,and effectively inhibited cell death and iNOS expression in interleukin-1βand interfcron-γinduced RIK cells.Furthermore,C.lntillifera extract significantly enhanced insulin secretion in RTN cells and glucose transporter expression and glucose uptake in 3T3-L1adipocytes.Conclusions:Thus,our results suggest that C.lentillifera could be used as a potential antidiabetic agenl.
文摘BACKGROUND:Sulfonylurea receptor 1(SUR1)and multidrug resistance protein 1(MRP1)are two prominent members of multidrug resistance proteins associated with insulin secretion. The aims of this study were to investigate their expression in insulinomas and their sole and synergistic effects in modulating abnormal insulin secretion. METHODS:Fasting glucose,insulin and C-peptide were measured in 11 insulinoma patients and 11 healthy controls. Prolonged oral glucose tolerance tests were performed in 6 insulinoma patients.Insulin content,SUR1 and MRP1 were detected in 11 insulinoma patients by immunohistochemistry. SUR1 and MRP1 were also detected in 6 insulinoma patients by immunofluorescence. RESULTS:Insulinoma patients presented the typical demons-trations of Whipple’s triad.Fasting glucose of each insulinoma patient was lower than 2.8 mmol/L,and simultaneous insulin and C-peptide were increased in insulinoma patients. Prolonged oral glucose tolerance tests showed that insulin secretion in insulinoma patients were also stimulated by high glucose.Immunohistochemistry and immunofluorescence staining showed that SUR1 increased,but MRP1 decreased in insulinoma compared with the adjacent islets. CONCLUSIONS:The hypersecretion of insulin in insulinomas might be,at least partially,due to the enrichment of SUR1. In contrast,MRP1,which is down-regulated in insulinomas, might reflect a negative feedback in insulin secretion.
文摘Background: Lack of first phase insulin secretion during oral glucose tolerance test [OGTT] in Type 2 Diabetes Mellitus (DM) is attributed to glucose toxicity. Alternatively, the role of insulin resistance in impaired insulin release secondary to lack of glucose entry into β cells may be responsible, but is not examined. Aim: The role of insulin sensitivity in 1st phase insulin secretion was assessed. Material and Methods: Plasma glucose (G) and insulin (I) concentrations were determined after an overnight fast (F) and upto 60 minutes during OGTT with glucose 75g in 12 normal (N), 14 with impaired glucose tolerance (IGT) and 41 subjects with Type 2 DM. First phase insulin secretion (Δ Insulin) was determined as a percentage rise from baseline 100x (Peak-Basal)/Basal. Insulin sensitivity was determined as FI x FG (mUxmM/L). Results: FG were normal (7.0 mM/L in Type 2 DM. FI x FG and ? insulin were 35 ± 4 and 389 ± 89% in N;77 ± 5 and 254 ± 65% in IGT;and 235 ± 19 and 95 ± 15% in Type 2 DM. Significant negative correlations were noted between ? insulin one hand and FI x FG on the other amongst all subjects [p < 0.0001 for all correlations]. Conclusion: Decline of 1st phase insulin secretion in IGT and Type 2 DM may be attributed to inhibited release of depleted insulin stores in the β Cells induced by impaired glucose entry due to insulin resistance, and is unlikely to be caused by glucose toxicity in IGT in presence of fasting euglycemia.
基金Supported by National Natural Science Foundation of China,No.31771284National Natural Science Foundation of China Youth Project,No.31702024+1 种基金Major Basic Research Project of Shandong Provincial Natural Science Foundation,No.ZR2019ZD27Shandong Province Higher Educational Science and Technology Plan Project,No.J17KA258。
文摘BACKGROUND Type 2 diabetes(T2 D) is characterized by insufficient insulin secretion caused by defective pancreatic β-cell function or insulin resistance,resulting in an increase in blood glucose.However,the mechanism involved in this lack of insulin secretion is unclear.The level of vascular endothelial growth factor B(VEGF-B) is significantly increased in T2 D patients.The inactivation of VEGF-B could restore insulin sensitivity in db/db mice by reducing fatty acid accumulation.It is speculated that VEGF-B is related to pancreatic β-cell dysfunction and is an important factor affecting β-cell secretion of insulin.As an in vitro model of normal pancreatic β-cells,the MIN6 cell line can be used to analyze the mechanism of insulin secretion and related biological effects.AIM To study the role of VEGF-B in the insulin secretion signaling pathway in MIN6 cells and explore the effect of VEGF-B on blood glucose regulation.METHODS The MIN6 mouse pancreatic islet β-cell line was used as the model system.By administering exogenous VEGF-B protein or knocking down VEGF-B expression in MIN6 cells,we examined the effects of VEGF-B on insulin secretion,Ca2+ and cyclic adenosine monophosphate(cAMP) levels,and the insulin secretion signaling pathway.RESULTS Exogenous VEGF-B inhibited the secretion of insulin and simultaneously reduced the levels of Ca2+ and cAMP in MIN6 cells.Exogenous VEGF-B also reduced the expression of phospholipase C gamma 1(PLCγ1),phosphatidylinositol 3-kinase(PI3 K),serine/threonine kinase(AKT),and other proteins in the insulin secretion pathway.Upon knockdown of VEGF-B,MIN6 cells exhibited increased insulin secretion and Ca2+ and cAMP levels and upregulated expression of PLCγ1,PI3 K,AKT,and other proteins.CONCLUSION VEGF-B can regulate insulin secretion by modulating the levels of Ca2+ and cAMP.VEGF-B involvement in insulin secretion is related to the expression of PLCγ1,PI3 K,AKT,and other signaling proteins.These results provide theoretical support and an experimental basis for the study of VEGF-B in the pathogenesis of T2 D.
基金This project was supported by Ministry of Education Re-turning Overseas Scholar science study Foundation( 2 0 0 2 2 47) ,province Hubei Natural Sciences Foundation( 2 0 0 2 AB13 6) ,Wuhan science and Technology ChenguangPlan Foundation( 9910 0 2 0 9)
文摘To investigate the molecular mechanism of leptin regulating insulin secretion through determining the regulation of insulin secretion and the insulin receptor substrate (IRS)-2-associated phosphoinositide 3-kinase (PI3K) activity by leptin in the isolated rat pancreatic islets, pancreatic islets were isolated from male SD rats by the collagenase method. The purified islets were incubated with leptin 2 nmol/L for 1 h in the presence of 5.6 mmol/L or 11.1 mmol/L glucose. Insulin release was measured using radioimmunoassay. IRS-2-associated activity of PI3K was determined by immunoprecipitate assay and Western blot. The results showed that in the presence of 5.6 mmol/L glucose, leptin had no significant effect on both insulin secretion and IRS-2-associated PI3K activity, but in the presence of 11.1 mmol/L glucose, insulin release was significantly inhibited after the islets were exposed to leptin for 1 h (P<0.01). PI3K inhibitor wortmannin blocked the inhibitory regulation of leptin on insulin release (P<0.05). Western Blot assay revealed that 2 nmol/L leptin could significantly increase the IRS-2-associated activity of PI3K by 51.5 % (P<0.05) in the presence of 11.1 mmol/L glucose. It was concluded that Leptin could significantly inhibit insulin secretion in the presence of 11.1 mmol/L glucose by stimulating IRS-2-associated activity of PI3K, which might be the molecular mechanism of leptin regulating insulin secretion.
基金ThisprojectwassupportedbyagrantfromtheScientificResearchFoundationfortheReturnedOverseasChineseScholarsbytheStateEducationMinistryofChina (No .2 0 0 2 2 4 7) ,theNaturalScienceFoundationofHubeiofChina (No .2 0 0 2AB136 )andWuhanFoundationofScienceandTech
文摘To study the effects of free fatty acids on insulin secretion and expression of SUR1 gene in rat pancreatic B cells in vitro, and to explore the molecular mechanisms in lipotoxicity inducing insulin secretion dysfunction, pancreatic islet cells were isolated and digested from male SD rats. Purified islets were incubated with either 0.25 mmol/L palmitate or 0.125 mmol/L oleate for 48 h in vitro. Then islets were stimulated with either 5.6 mmol/L or 16.7 mmol/L glucose for 1 h. Insulin release was measured by using radioimmunoassay, and the expression of SUR1 gene mRNA was quantified by reserve transcription-polymerase chain reaction (RT-PCR). The islets exposed to both palmitate and oleate for 48 h showed an increased basal and a decreased glucose-indused insulin release as compared with control islets. Palmitate increased basal insulin secretion by 110 % (P<0.01), decreased glucose stimulated insulin secretion by 43 % (P<0.01); while oleate increased basal insulin secretion by 80 % (P<0.01) and decreased glucose stimulated insulin secretion by 32 % (P<0.05). RT-PCR showed that oleate significantly suppressed SUR1 gene expression by 64 % (P<0.01)as compared with the control group, while palmitate group manifested a light decrease of 15 % (P >0.05) of SUR1 gene expression. Our results suggested that chronic exposure to free fatty acids of pancreatic β cells inhibited glucose stimulated insulin secretion. Regulation of SUR1 gene expression may be involved in such effects, which may also be one of the molecular mechanisms in lipotoxocity inducing β cells secretion dysfunction.
文摘Diabetes mellitus is a metabolic disease possible to treat via pancreas/islet transplantation but most immunosuppressive drugs are diabetogenic. In this letter, we review current up to date methods to assess insulin action and secretion (using the surrogate indexes) suggesting their use in large studies in populations of pancreas/ islets transplanted patients.
文摘Aim: To investigate the clinical characteristics of diabetic patients with a low-titer positive for the anti-glutamic acid decarboxylase 65 antibody (GAD antibody). Methods: The subjects were 420 diabetic inpatients. The endogenous insulin secretion was estimated on the basis of the C-peptide immunoreactivity from a 24 h urine collection (uCPR). Clinical variables were compared between patients negative for the GAD antibody (GAD antibody titer < 1.5 U/mL), a low-titer positive GAD antibody (1.5 U/mL ≤ GAD antibody titer < 10 U/mL) and a high-titer positive GAD antibody (10 U/mL ≤ GAD antibody titer). Results: The low and high-titer positive GAD antibodies were found in 25 and 10 patients, respectively. The uCPR was significantly lower in both the patients with a low (37 ± 33 ug/24h) and high-titer (39 ± 27 ug/24h) positive GAD antibodies than in those negative for GAD antibodies (71 ± 52 ug/24h). The uCPR level was significantly lower in the low-titer positive GAD antibody group (29 ± 22 ug/24h) than in the negative group (67 ± 55 ug/24h) among the patients not taking insulin secretagogues. The difference disappeared in the subjects taking insulin secreagogues. In the stepwise multiple regression analysis, a low-titer positive GAD antibody was independently associated with the uCPR level. Conclusions: Endogenous insulin secretion is reduced in diabetic patients positive for GAD antibodies, even if the titer is low. Earlier initiation of insulin therapy might therefore protect the pancreatic β-cell function in diabetic patients with a low-titer positive GAD antibody.
文摘The nature of the binding site(s) involved in the insulin secretory activity of imidazoline compo- unds remains unclear. An imidazoline I2 binding site (I2BS) has been neglected since the classic I2 ligand, idazoxan, does not release insulin. Using the rabbit as an appropriate model for the study of this type of binding sites, we have tried to re-evaluate the effects of idazoxan, the selective I2 compound BU 224, and efaroxan on insulin secretion. Mimicking efaroxan, idazoxan and BU 224 potentiated insulin release from perifused islets in the presence of 8 mM glucose. In static incubation, insulin secretion induced by idazoxan and BU 224 exhibited both dose and glucose dependencies. ATP-sensitive K+ (KATP) channel blockade, though at a different site from the SUR1 receptor, with subsequent Ca2+ entry, mediates the insulin releasing effect of the three ligands. However, additional MAO independent intracellular steps in stimulus- secretion coupling linked to PKA and PKC activation are only involved in the effect of BU 224. Therefore, both an I2 related binding site at the channel level shared by the three ligands and a putative I3-intracellularly located binding site stimulated by BU 224 would be mediating insulin release by these compounds. In vivo experiments reassess the abilities of idazoxan and BU 224 to enhance glucose-induced insulin secretion and to elicit a modest blood glucose lowering response.
文摘A small nonpeptidyl compoud extracted from Pseudomassaria sp. was found to induce the activity of human insulin receptor tyrosine kinase in vitro. The compound was identified as demethylasterriquinone B-1 (DMAQ-B1). DMAQ- B1 also induced an increase in [Ca2+]i and insulin secretion in mice pancreatic beta-cells at low glucose (3 mM) concentration via insulin receptor substrate-1/phosphatidylinositol-3-kinase (PI3 kinase) pathway. By using rat pancreatic perfusion technique, we found that 10 μM DMAQ-B1 directly stimulated insulin secretion up to 240% in normal rat pancreas. In the dosage from 1 to 20 μM, DMAQ-B1 stimulated insulin secretion in a dose dependent manner. Furthermore, DMAQ-B1 enhanced glucose-induced insulin secretion by 17.6% (first stage) and 19.0% (second stage), respectively. The PI3 kinase inhibitors, LY 294002 (3.9 μM) or wortmannin (100 nM), inhibited DMAQ-B1-induced insulin secretion by 46.3% and 57.4%, respectively. LY 294002 or wortmannin also inhibited DMAQ-B1 with10 mMglucose-induced insulin secretion by 70.3% and 79.0%, respectively. All the results suggested that DMAQ-B1 directly stimulated insulin secretion and enhanced glucose-induced insulin secretion. The effect of DMAQ-B1 may mediate through the activation of PI3 kinase pathway to stimulate insulin secretion in normal rat pancreas.
文摘目的研究替米沙坦促进大鼠胰岛素分泌作用相关的信号通路。方法(1)分离成年Wistar大鼠胰腺获得胰岛和胰岛细胞,通过胰岛素分泌实验观察药物对胰岛素分泌的影响,通过钙成像实验和全细胞膜片钳技术观察药物对β细胞内Ca^(2+)浓度的变化和对离子通道的作用。(2)使用过表达电压门控性钾(voltage-gated potassium channel,Kv)通道2.1亚型(Kv2.1)的慢病毒转染中国仓鼠卵巢(Chinese hamster ovary,CHO)细胞构建CHO-Kv2.1细胞系,使用膜片钳技术观察替米沙坦对Kv2.1通道的直接作用。结果缬沙坦和厄贝沙坦无类似替米沙坦的高糖浓度下促胰岛素分泌、升高β细胞内Ca^(2+)浓度和抑制β细胞的Kv通道等作用。过氧化物酶体增殖物激活受体γ(peroxisome proliferator-activated receptorγ,PPARγ)阻断剂GW9662亦未阻断替米沙坦的上述作用。而替米沙坦可以浓度依赖性地抑制CHO-Kv2.1细胞的Kv2.1通道电流。结论替米沙坦的促胰岛素分泌作用可能与血管紧张素Ⅱ-1型(angiotensin II type 1,AT-1)受体和PPARγ无关,但至少与对Kv2.1通道的直接抑制作用有关。
