L-serine supplementation lowers diabetes incidence and improves blood glucose homeostasis in NOD mice.
ABSTRACT: Sphingolipids are a diverse group of lipids with important roles in beta-cell biology regulating insulin folding and controlling apoptosis. Sphingolipid biosynthesis begins with the condensation of L-serine and palmitoyl-CoA. Here we tested the effect of L-serine supplementation on autoimmune diabetes development and blood glucose homeostasis in female NOD mice. We found that continuous supplementation of L-serine reduces diabetes incidence and insulitis score. In addition, L-serine treated mice had an improved glucose tolerance test, reduced HOMA-IR, and reduced blood glucose levels. L-serine led to a small reduction in body weight accompanied by reduced food and water intake. L-serine had no effect on pancreatic sphingolipids as measured by mass spectrometry. The data thus suggests that L-serine could be used as a therapeutic supplement in the treatment of Type 1 Diabetes and to improve blood glucose homeostasis.
Project description:BACKGROUND & AIMS:Metformin is currently the most widely used first-line hypoglycemic agent for diabetes mellitus. Besides glucose-lowering action, there is increasingly interest in the potential anti-inflammatory action of this drug. In the present study, we investigated the actions of metformin on experimental insulitis using STZ-induced diabetic mice. METHODS:Mice with acute diabetes induced by STZ were administered metformin by gavage. Changes of blood glucose and body weight, and the daily amount of food and water intake were measured. Pancreatic tissues were collected for histologic analyses. Pathological assessment and immunohistochemistry analysis were used to determine the effect of metformin on insulitis. Inflammatory cytokines in the pancreas and insulin levels were measured through ELISA analysis. RESULTS:Metformin significantly reduced blood glucose levels and improved aberrant water intake behavior in experimental diabetic mice. No significant differences were observed in terms of body weight and food intake behavior in metformin-treated animals. In the STZ-induced model of diabetes, we found the appearance of pronounced insulitis. However, metformin administration reduced the severity of insulitis assessed by blind pathological scoring. In addition, metformin treatment improved insulin levels in experimental diabetic mice. ELISA assay revealed decreased levels of inflammatory response marker IL-1? and TNF-? in the pancreatic tissues following metformin treatment. CONCLUSION:Metformin attenuated insulitis in the STZ-induced mice model of diabetes. This islet-protective effect might be partly correlated with the anti-inflammatory action of metformin.
Project description:AIMS/HYPOTHESIS:Sphingolipid metabolism regulates beta cell biology and inflammation and is abnormal at the onset of type 1 diabetes. Fenofibrate, a regulator of sphingolipid metabolism, is known to prevent diabetes in NOD mice. Here, we aimed to investigate the effects of fenofibrate on the pancreatic lipidome, pancreas morphology, pancreatic sympathetic nerves and blood glucose homeostasis in NOD mice. METHODS:We treated female NOD mice with fenofibrate from 3 weeks of age. The pancreatic lipidome was analysed using MS. Analysis of pancreas and islet volume was performed by stereology. Islet sympathetic nerve fibre volume was evaluated using tyrosine hydroxylase staining. The effect on blood glucose homeostasis was assessed by measuring non-fasting blood glucose from age 12 to 30 weeks. Furthermore, we measured glucose tolerance, fasting insulin and glucagon levels, and insulin tolerance. RESULTS:We found that fenofibrate selectively increases the amount of very-long-chain sphingolipids in the pancreas of NOD mice. In addition, we found that fenofibrate causes a remodelling of the pancreatic lipidome with an increased amount of lysoglycerophospholipids. Fenofibrate did not affect islet or pancreas volume, but led to a higher volume of islet sympathetic nerve fibres and tyrosine hydroxylase-positive cells. Fenofibrate-treated NOD mice had a more stable blood glucose, which was associated with reduced non-fasting and increased fasting blood glucose. Furthermore, fenofibrate improved glucose tolerance, reduced fasting glucagon levels and prevented fasting hyperinsulinaemia. CONCLUSIONS/INTERPRETATION:These data indicate that fenofibrate alters the pancreatic lipidome to a more anti-inflammatory and anti-apoptotic state. The beneficial effects on islet sympathetic nerve fibres and blood glucose homeostasis indicate that fenofibrate could be used as a therapeutic approach to improve blood glucose homeostasis and prevent diabetes-associated pathologies.
Project description:Glucose homeostasis is maintained by the orchestration of peripheral glucose utilization and hepatic glucose production, mainly by insulin. In this study, we found by utilizing a combined parallel chromatography mass profiling approach that lysophosphatidylcholine (LPC) regulates glucose levels. LPC was found to stimulate glucose uptake in 3T3-L1 adipocytes dose- and time-dependently, and this activity was found to be sensitive to variations in acyl chain lengths and to polar head group types in LPC. Treatment with LPC resulted in a significant increase in the level of GLUT4 at the plasma membranes of 3T3-L1 adipocytes. Moreover, LPC did not affect IRS-1 and AKT2 phosphorylations, and LPC-induced glucose uptake was not influenced by pretreatment with the PI 3-kinase inhibitor LY294002. However, glucose uptake stimulation by LPC was abrogated both by rottlerin (a protein kinase Cdelta inhibitor) and by the adenoviral expression of dominant negative protein kinase Cdelta. In line with its determined cellular functions, LPC was found to lower blood glucose levels in normal mice. Furthermore, LPC improved blood glucose levels in mouse models of type 1 and 2 diabetes. These results suggest that an understanding of the mode of action of LPC may provide a new perspective of glucose homeostasis.
Project description:Recent evidence suggests that enhanced protease-mediated inflammation may promote insulin resistance and result in diabetes. This study tested the hypothesis that serine protease plays a pivotal role in type 2 diabetes, and inhibition of serine protease activity prevents hyperglycemia in diabetic animals by modulating insulin signaling pathway. We conducted a single-center, cross-sectional study with 30 healthy controls and 57 patients with type 2 diabetes to compare plasma protease activities and inflammation marker between groups. Correlations of plasma total and serine protease activities with variables were calculated. In an in-vivo study, LDLR-/- mice were divided into normal chow diet, high-fat diet (HFD), and HFD with selective serine protease inhibition groups to examine the differences of obesity, blood glucose level, insulin resistance and serine protease activity among groups. Compared with controls, diabetic patients had significantly increased plasma total protease, serine protease activities, and also elevated inflammatory cytokines. Plasma serine protease activity was positively correlated with body mass index, hemoglobin A1c, homeostasis model assessment-insulin resistance index (HOMA-IR), tumor necrosis factor-?, and negatively with adiponectin concentration. In the animal study, administration of HFD progressively increased body weight, fasting glucose level, HOMA-IR, and upregulated serine protease activity. Furthermore, in-vivo serine protease inhibition significantly suppressed systemic inflammation, reduced fasting glucose level, and improved insulin resistance, and these effects probably mediated by modulating insulin receptor and cytokine expression in visceral adipose tissue. Our findings support the serine protease may play an important role in type 2 diabetes and suggest a rationale for a therapeutic strategy targeting serine protease for clinical prevention of type 2 diabetes.
Project description:Objective:Calcitonin Gene-Related Peptide ? (CGRP?) is a multifunctional neuropeptide found in the central and peripheral nervous system with cardiovascular, nociceptive, and gastrointestinal activities. CGRP? has been linked to obesity and insulin secretion but the role of this circulating peptide in energy metabolism remains unclear. Here, we thought to utilize a monoclonal antibody against circulating CGRP? to assess its ability to improve glucose homeostasis in mouse models of hyperglycemia and diabetes. Methods:We examined the outcome of anti-CGRP? treatment in mouse models of diabetes and diet-induced obesity, using db/db mice, Streptozotocin (STZ) treatment to eliminate pancreatic islets, and high fat diet-fed mice. We also correlated these data with application of recombinant CGRP? peptide on cultured mature adipocytes to measure its impact on mitochondrial bioenergetics and fatty acid oxidation. Furthermore, we applied recombinant CGRP? to primary islets to measure glucose-stimulated insulin secretion (GSIS) and gene expression. Results:BL6-db diabetic mice receiving anti-CGRP? treatment manifested weight loss, reduced adiposity, improved glucose tolerance, insulin sensitivity, GSIS and reduced pathology in adipose tissue and liver. Anti-CGRP? failed to modulate weight or glucose homeostasis in STZ-treated animals. High fat diet-fed mice showed reduced adiposity but no benefit on glucose homeostasis. Considering these findings, we postulated that CGRP? may have dual effects on adipocytes to promote lipid utilization while acting on pancreatic ?-cells to modulate insulin secretion. Analysis of CGRP? in the pancreas showed that the peptide localized to insulin-positive cells and perivascular nerves surrounding islets. Ex-vivo analysis of pancreatic islets determined that CGRP? blocked GSIS and reduced insulin-2 gene expression. Mechanistical analysis revealed that recombinant CGRP? was able to reduce glycolytic capacity as well as fatty acid oxidation in primary white adipocytes. Conclusions:These results establish a multifaceted role in energy metabolism for circulating CGRP?, with the ability to modulate thermogenic pathways in adipose tissue, as well as pancreatic ?-cell dependent insulin secretion. Reducing circulating CGRP? levels with monoclonal therapy presents therapeutic potential for type 2 diabetes as shown in BL6-db/db mice but has reduced potential for models of hyperglycemia resulting from loss of ?-cells (STZ treatment).
Project description:Sphingolipids are characterized by a broad range of bioactive properties. Particularly, the development of insulin resistance, a major pathophysiological hallmark of Type 2 Diabetes mellitus (T2D), has been linked to ceramide signaling. Since vitamin D supplementation may slow down T2D progression by improving glucose concentrations and insulin sensitivity, we investigated whether vitamin D supplementation impacts on plasma sphingolipid levels in T2D patients. Thus, plasma samples of 59 patients with non-insulin-requiring T2D from a placebo-controlled, randomized, and double-blind study were retrospectively analyzed. Once per week, patients received either 20 drops of Vigantol oil, corresponding to a daily dose of 1904 IU/d vitamin D (verum: n = 31), or a placebo oil consisting of medium chain triglycerides (placebo: n = 28). Blood samples were taken from all of the participants at three different time points: 1) at the beginning of the study (baseline), 2) after 6 months supplementation, and 3) after an additional 6 months of follow-up. Plasma sphingolipids were measured by high-performance liquid chromatography tandem mass spectrometry. At baseline and 6 months follow-up, no significant differences in plasma sphingolipid species were detected between the placebo and verum groups. After 6 months, vitamin D supplementation significantly enhanced plasma C18dihydroceramide (dhCer; N-stearoyl-sphinganine (d18:0/18:0)) and C18ceramide (Cer; N-stearoyl-sphingosine (d18:1/18:0)) levels were observed in the verum group compared to the placebo group. This was accompanied by significantly higher 25-hydroxyvitamin D₃ (25(OH)D₃) blood levels in patients receiving vitamin D compared to the placebo group. Taken together, vitamin D supplementation induced changes of the C18 chain-length-specific dhCer and Cer plasma levels in patients with T2D. The regulation of sphingolipid signaling by vitamin D may thus unravel a novel mechanism by which vitamin D can influence glucose utilization and insulin action. Whether this acts favorably or unfavorably for the progression of T2D needs to be clarified.
Project description:Aims:Emerging evidence has suggested a mechanistic link from vitamin D metabolism to glucose and insulin homeostasis. This study is aimed at specifically quantifying the direct effects of vitamin D supplementation on indexes of glucose and insulin homeostasis as well as incidence of type 2 diabetes (T2D) among nondiabetic adults. Methods:We systematically searched randomized controlled trials (RCTs) of vitamin D supplementation in nondiabetic adults in PubMed, EMBASE, and CENTRAL. Random-effects meta-analysis was conducted to pool the estimates. Results:Our meta-analysis included 47 RCTs involving 44,161 nondiabetic individuals with a median trial duration of 4 months and a median dose of 4000?IU/d. Vitamin D supplementation significantly reduced fasting glucose by 0.11?mmol/L, fasting insulin by 1.47?mIU/L, and HOMA-IR by 0.32 while increasing total 25 (OH) D levels by 40.14?nmol/L. We found no significant effects of vitamin D supplementation on insulin secretion or beta cell function indexes. Based on the data from six trials involving 39,633 participants and 2533 incident T2D cases, vitamin D supplementation was not associated with the risk of incident diabetes compared to placebo (pooled relative risk: 1.01, 95% confidence interval: 0.93 to 1.08). Conclusions:Our meta-analysis found that vitamin D supplementation might improve glucose and insulin metabolism without affecting the risk of T2D among nondiabetic adults.
Project description:Hepsin is a transmembrane serine protease primarily expressed in the liver. To date, the physiological function of hepsin remains poorly defined. Here we report that hepsin-deficient mice have low levels of blood glucose and lipids and liver glycogen, but increased adipose tissue browning and basal metabolic rates. The phenotype is caused by reduced hepatocyte growth factor activation and impaired Met signaling, resulting in decreased liver glucose and lipid metabolism and enhanced adipocyte browning. Hepsin-deficient mice exhibit marked resistance to high-fat diet-induced obesity, hyperglycemia, and hyperlipidemia. In db/db mice, hepsin deficiency ameliorates obesity and diabetes. These data indicate that hepsin is a key regulator in liver metabolism and energy homeostasis, suggesting that hepsin could be a therapeutic target for treating obesity and diabetes.
Project description:Although the regular consumption of resveratrol has been known to improve glucose homeostasis and reverse insulin resistance in type 2 diabetes mellitus (T2DM), the reported results are inconsistent. Thus, we aimed to assess the effects of resveratrol on glycemic control and insulin sensitivity among patients with T2DM. We searched for relevant articles published until June 2017 on PubMed-Medline, Embase, Cochrane Library, and Web of Science. Randomized controlled trials in T2DM patients administered with resveratrol as intervention were included. After study selection, quality assessment and data extraction were performed independently by two authors, and STATA and RevMan software were used for statistical analysis. Nine randomized controlled trials involving 283 participants were included. Meta-analysis showed that resveratrol significantly improved the fasting plasma glucose ( -0.29 mmol/l, 95% CI: -0.51, -0.06, p < 0.01) and insulin levels (-0.64 U/mL, 95% CI: -0.95, -0.32, p < 0.0001). The drug also reduced homeostasis model assessment of insulin resistance (HOMA-IR) index, systolic blood pressure, and diastolic blood pressure among participants with T2DM. The changes in hemoglobin A1c (HbA1c), low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were negligible. Subgroup analysis comparing the resveratrol supplementation doses of < 100 mg/d versus ? 100 mg/d revealed a significant difference in fasting plasma glucose. In particular, the latter dose presented more favorable results. This meta-analysis provides evidence that supplementation of resveratrol may benefit management of T2DM.
Project description:Purpose: The worldwide prevalence of metabolic disorders such as diabetes is increasing rapidly. Currently, the complications of diabetes are the major health concern. The aim of this study was to investigate the effect of high performance (HP) inulin supplementation on glucose homeostasis via KLF5 mRNA expression in adults with type 2 diabetes. Methods: In the present clinical trial conducted for a duration of 6 weeks, 46 volunteers diabetic patients referring to diabetes clinic in Tabriz, Iran, were randomly assigned into intervention (n= 23, consuming 10 gr/d HP inulin) and control groups (n= 23, consuming 10 gr/ d starch). We assessed glycemic and anthropometric indices, blood lipids and plasmatic level of miR-375 as well as KLF5 mRNA expression before and after the intervention. Results: Findings indicated that inulin supplementation significantly decreased fasting plasma glucose (FPG) in comparison to the placebo group (P<0.001). Also Intra-group and between group results showed that inulin supplementation resulted in significant decrease in KLF5 mRNA expression in peripheral blood mononuclear cells (PBMCs) (Fold change: 0.61± 0.11; P-value= 0.001) and significant increase in plasmatic level of miR-375 (Fold change: 3.75± 0.70; P-value=0.004). Conclusion: Considering the improvements of FPG level in diabetic patients, it seems that HP inulin supplementation may be beneficial in controlling diabetes via the expression of some genes. However, further studies are needed to achieve concise conclusions.