scholarly journals Tissue-dependent loss of phosphofructokinase-M in mice with interrupted activity of the distal promoter: impairment in insulin secretion

2007 ◽  
Vol 293 (3) ◽  
pp. E794-E801 ◽  
Author(s):  
Ann-Marie T. Richard ◽  
Dominic-Luc Webb ◽  
Jessie M. Goodman ◽  
Vera Schultz ◽  
John N. Flanagan ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Glucose Sensor ◽  
Tolerance Test ◽  
Proximal Promoter ◽  
M Gene ◽  
Glucose Levels ◽  
Insulin Tolerance ◽  
Key Enzyme ◽  
Glucose Stimulated Insulin Secretion ◽  
Distal Promoter

Phosphofructokinase is a key enzyme of glycolysis that exists as homo- and heterotetramers of three subunit isoforms: muscle, liver, and C type. Mice with a disrupting tag inserted near the distal promoter of the phosphofructokinase-M gene showed tissue-dependent differences in loss of that isoform: 99% in brain and 95–98% in islets, but only 50–75% in skeletal muscle and little if any loss in heart. This correlated with the continued presence of proximal transcripts specifically in muscle tissues. These data strongly support the proposed two-promoter system of the gene, with ubiquitous use of the distal promoter and additional use of the proximal promoter selectively in muscle. Interestingly, the mice were glucose intolerant and had somewhat elevated fasting and fed blood glucose levels; however, they did not have an abnormal insulin tolerance test, consistent with the less pronounced loss of phosphofructokinase-M in muscle. Isolated perifused islets showed about 50% decreased glucose-stimulated insulin secretion and reduced amplitude and regularity of secretory oscillations. Oscillations in cytoplasmic free Ca2+ and the rise in the ATP/ADP ratio appeared normal. Secretory oscillations still occurred in the presence of diazoxide and high KCl, indicating an oscillation mechanism not requiring dynamic Ca2+ changes. The results suggest the importance of phosphofructokinase-M for insulin secretion, although glucokinase is the overall rate-limiting glucose sensor. Whether the Ca2+ oscillations and residual insulin oscillations in this mouse model are due to the residual 2–5% phosphofructokinase-M or to other phosphofructokinase isoforms present in islets or involve another metabolic oscillator remains to be determined.

scholarly journals ARHGAP21 Acts as an Inhibitor of the Glucose-Stimulated Insulin Secretion Process

2020 ◽  
Vol 11 ◽  
Author(s):  
Sandra M. Ferreira ◽  
José M. Costa-Júnior ◽  
Mirian A. Kurauti ◽  
Nayara C. Leite ◽  
Fernanda Ortis ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Energy Metabolism ◽  
Cell Interaction ◽  
Tolerance Test ◽  
Functional Maturation ◽  
Secretion Process ◽  
Insulin Tolerance ◽  
Intracellular Calcium Dynamics ◽  
Glucose Stimulated Insulin Secretion ◽  
Adult Islet

ARHGAP21 is a RhoGAP protein implicated in the modulation of insulin secretion and energy metabolism. ARHGAP21 transient-inhibition increase glucose-stimulated insulin secretion (GSIS) in neonatal islets; however, ARHGAP21 heterozygote mice have a reduced insulin secretion. These discrepancies are not totally understood, and it might be related to functional maturation of beta cells and peripheral sensitivity. Here, we investigated the real ARHGAP21 role in the insulin secretion process using an adult mouse model of acute ARHGAP21 inhibition, induced by antisense. After ARHGAP21 knockdown induction by antisense injection in 60-day old male mice, we investigated glucose and insulin tolerance test, glucose-induced insulin secretion, glucose-induced intracellular calcium dynamics, and gene expression. Our results showed that ARHGAP21 acts negatively in the GSIS of adult islet. This effect seems to be due to the modulation of important points of insulin secretion process, such as the energy metabolism (PGC1α), Ca2+ signalization (SYTVII), granule-extrusion (SNAP25), and cell-cell interaction (CX36). Therefore, based on these finds, ARHGAP21 may be an important target in Diabetes Mellitus (DM) treatment.

scholarly journals Acid Hydrolyzed Silk Peptide Consumption Improves Anti-Diabetic Symptoms by Potentiating Insulin Secretion and Preventing Gut Microbiome Dysbiosis in Non-Obese Type 2 Diabetic Animals

Nutrients ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 311 ◽  
Author(s):  
Sunmin Park ◽  
Ting Zhang ◽  
Jing Yi Qiu ◽  
Xuangao Wu ◽  
Jeong-Yong Lee ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Normal Control ◽  
Positive Control ◽  
Control Group ◽  
Sensitivity Testing ◽  
Insulin Tolerance ◽  
Glucose Stimulated Insulin Secretion

Silk fibroin hydrolysates have been reported to reduce hyperglycemia, but the mechanism has not been determined in Asian type 2 diabetes (T2DM). We hypothesized that the consumption of acid hydrolyzed silk peptides (SPs) alleviates hyperglycemia by improving insulin sensitivity and subsequently normalizing glucose-stimulated insulin secretion in T2DM. We investigated this hypothesis in a partial pancreatectomized (Px) rat model. Px rats was assigned randomly to the following six groups and fed assigned diet for 8 weeks: the Px-control (0.5 g/kg/day dextrin), the SP-L (0.05 g/kg/day), the SP-M (0.1 g/kg/day), the SP-H (0.5 g/kg/day), the positive-control (40 mg/kg/day metformin), or the normal-control (sham-operated rats; 0.5 g/kg/day dextrin). SPs contained high levels of glycine, alanine, and serine. We found SPs dose-dependently increased food efficiency and body weight gain in Px rats. Animals in the Px-control group rats exhibited lower glucose metabolism, as evidenced by impaired glucose-stimulated insulin secretion coupled with impaired insulin sensitivity, and reduced bone mineral density (BMD) and lean body mass (LBM), compared to the normal-control. SPs and metformin similarly partially protected against Px-induced BMD loss in the lumbar spine and femur. Px-induced decreases in LBM were dose-dependently prevented by SPs, and muscle forces in the SP-M and SP-H groups were maintained at the normal-control level. Glucose tolerance was dose-dependently improved by SPs as determined by oral glucose tolerance and oral maltose tolerance tests, and glucose tolerances were similar in the SP-H and positive-control groups. Insulin tolerance, an index of insulin sensitivity, was dose-dependently enhanced by SPs, and the SP-H group exhibited better insulin tolerance than the positive-control group as determined by intraperitoneal insulin sensitivity testing. Insulin secretory capacity assessed using a hyperglycemic clamp improved in the following order: Px-control <SA-L <SA-M <positive-control <SA-H <normal-control. SP-M prevented gut microbiota dysbiosis. In conclusion, SPs administered at 0.1–0.5 g/kg/day improved glucose regulation by potentiating both insulin secretion and insulin sensitivity in non-obese T2DM rats.

scholarly journals Overexpression of the ped/pea-15 Gene Causes Diabetes by Impairing Glucose-Stimulated Insulin Secretion in Addition to Insulin Action

2004 ◽  
Vol 24 (11) ◽  
pp. 5005-5015 ◽  
Author(s):  
Giovanni Vigliotta ◽  
Claudia Miele ◽  
Stefania Santopietro ◽  
Giuseppe Portella ◽  
Anna Perfetti ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Transgenic Mice ◽  
Insulin Action ◽  
Glucose Levels ◽  
Beta Cell Line ◽  
Protein Kinase Cα ◽  
Glucose Stimulated Insulin Secretion

ABSTRACT Overexpression of the ped/pea-15 gene is a common feature of type 2 diabetes. In the present work, we show that transgenic mice ubiquitously overexpressing ped/pea-15 exhibited mildly elevated random-fed blood glucose levels and decreased glucose tolerance. Treatment with a 60% fat diet led ped/pea-15 transgenic mice to develop diabetes. Consistent with insulin resistance in these mice, insulin administration reduced glucose levels by only 35% after 45 min, compared to 70% in control mice. In vivo, insulin-stimulated glucose uptake was decreased by almost 50% in fat and muscle tissues of the ped/pea-15 transgenic mice, accompanied by protein kinase Cα activation and block of insulin induction of protein kinase Cζ. These changes persisted in isolated adipocytes from the transgenic mice and were rescued by the protein kinase C inhibitor bisindolylmaleimide. In addition to insulin resistance, ped/pea-15 transgenic mice showed a 70% reduction in insulin response to glucose loading. Stable overexpression of ped/pea-15 in the glucose-responsive MIN6 beta-cell line also caused protein kinase Cα activation and a marked decline in glucose-stimulated insulin secretion. Antisense block of endogenous ped/pea-15 increased glucose sensitivity by 2.5-fold in these cells. Thus, in vivo, overexpression of ped/pea-15 may lead to diabetes by impairing insulin secretion in addition to insulin action.

Cell-wide analysis of secretory granule dynamics in three dimensions in living pancreatic β-cells: evidence against a role for AMPK-dependent phosphorylation of KLC1 at Ser517/Ser520 in glucose-stimulated insulin granule movement

2010 ◽  
Vol 38 (1) ◽  
pp. 205-208 ◽  
Author(s):  
Angela McDonald ◽  
Sarah Fogarty ◽  
Isabelle Leclerc ◽  
Elaine V. Hill ◽  
D. Grahame Hardie ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Glutathione Transferase ◽  
Three Dimensions ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Glucose Levels ◽  
Insulin Granules ◽  
Elevated Glucose ◽  
Glucose Stimulated Insulin Secretion

Glucose-stimulated insulin secretion from pancreatic β-cells requires the kinesin-1/Kif5B-mediated transport of insulin granules along microtubules. 5′-AMPK (5′-AMP-activated protein kinase) is a heterotrimeric serine/threonine kinase which is activated in β-cells at low glucose concentrations, but inhibited as glucose levels increase. Active AMPK blocks glucose-stimulated insulin secretion and the recruitment of insulin granules to the cell surface, suggesting motor proteins may be targets for this kinase. While both kinesin-1/Kif5B and KLC1 (kinesin light chain-1) contain consensus AMPK phosphorylation sites (Thr693 and Ser520, respectively) only recombinant GST (glutathione transferase)–KLC1 was phosphorylated by purified AMPK in vitro. To test the hypothesis that phosphorylation at this site may modulate kinesin-1-mediated granule movement, we developed an approach to study the dynamics of all the resolvable granules within a cell in three dimensions. This cell-wide approach revealed that the number of longer excursions (>10 μm) increased significantly in response to elevated glucose concentration (30 versus 3 mM) in control MIN6 β-cells. However, similar changes were seen in cells overexpressing wild-type KLC1, phosphomimetic (S517D/S520D) or non-phosphorylatable (S517A/S520A) mutants of KLC1. Thus, changes in the phosphorylation state of KLC1 at Ser517/Ser520 seem unlikely to affect motor function.

Genetic and clinical characterisation of maturity-onset diabetes of the young in Spanish families

2000 ◽  
pp. 380-386 ◽  
Author(s):  
A Costa ◽  
M Bescos ◽  
G Velho ◽  
J Chevre ◽  
J Vidal ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Sensitivity ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Sequencing Analysis ◽  
Model Assessment ◽  
Maturity Onset Diabetes ◽  
Phenotypic Differences ◽  
Glucose Levels ◽  
Onset Diabetes

OBJECTIVE: To investigate the frequencies of the major maturity-onset diabetes of the young (MODY) subtypes in a panel of Spanish families and to assess phenotypic differences in patients with the different subtypes of MODY. METHODS: Forty-eight subjects from twenty families with clinical diagnosis of MODY were studied. They underwent a standardised clinical examination and a 75-g oral glucose tolerance test (OGTT) was performed. Estimations of insulin sensitivity (%S) and insulin secretion capacity (%B) were calculated by the computer-solved homeostasis model assessment (HOMA). Mutations in the coding regions of hepatocyte nuclear factor (HNF)-4alpha/MODY1, glucokinase (GCK/MODY2) and HNF-1alpha/MODY3 genes were investigated by single strand comformation polymorphism and sequencing analysis. RESULTS: Mutations in the GCK and HNF-1alpha genes were observed in 5 (25%) and 7 (35%) families respectively. Novel mutations included R385X, M238fsdelT, V226fsdelTinsAA and S418-7del11 in the GCK gene, and S121fsdelC, V133M, R159Q and V259D in the HNF-1alpha gene. No MODY1 families were found. Subjects which were neither MODY2 nor MODY3 (MODY-X) had a higher fasting glucose than subjects in the other groups. Insulin secretion capacity was similar in the three groups and the insulin sensitivity was decreased in MODY-X subjects. Glucose levels were significantly higher and insulin levels significantly lower, throughout the OGTT, in MODY3 compared with MODY2 subjects. CONCLUSIONS: Mutations in the GCK/MODY2 and HNF-1alpha/MODY3 genes account for the majority of cases in a panel of Spanish MODY families, with MODY3 being the most frequent subtype. The relative frequencies and the clinical characteristics of these MODY subtypes are in agreement with data previously reported in other European populations. MODY-X patients seem to present a heterogeneous clinical profile.

scholarly journals CYP2J2 attenuates metabolic dysfunction in diabetic mice by reducing hepatic inflammation via the PPARγ

2015 ◽  
Vol 308 (4) ◽  
pp. E270-E282 ◽  
Author(s):  
Rui Li ◽  
Xizhen Xu ◽  
Chen Chen ◽  
Yan Wang ◽  
Artiom Gruzdev ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Biological Effects ◽  
Tolerance Test ◽  
Mapk Signaling ◽  
Metabolic Dysfunction ◽  
Glucose Levels ◽  
Hepatic Cells ◽  
Insulin Tolerance

Epoxyeicosatrienoic acids (EETs) and arachidonic acid-derived cytochrome P450 (CYP) epoxygenase metabolites have diverse biological effects, including anti-inflammatory properties in the vasculature. Increasing evidence suggests that inflammation in type 2 diabetes is a key component in the development of insulin resistance. In this study, we investigated whether CYP epoxygenase expression and exogenous EETs can attenuate insulin resistance in diabetic db/db mice and in cultured hepatic cells (HepG2). In vivo, CYP2J2 expression and the accompanying increase in EETs attenuated insulin resistance, as determined by plasma glucose levels, glucose tolerance test, insulin tolerance test, and hyperinsulinemic euglycemic clamp studies. CYP2J2 expression reduced the production of proinflammatory cytokines in liver, including CRP, IL-6, IL-1β, and TNFα, and decreased the infiltration of macrophages in liver. CYP2J2 expression also decreased activation of proinflammatory signaling cascades by decreasing NF-κB and MAPK activation in hepatocytes. Interestingly, CYP2J2 expression and exogenous EET treatment increased glucose uptake and activated the insulin-signaling cascade both in vivo and in vitro, suggesting that CYP2J2 metabolites play a role in glucose homeostasis. Furthermore, CYP2J2 expression upregulated PPARγ, which has been shown to induce adipogenesis, which attenuates dyslipidemias observed in diabetes. All of the findings suggest that CYP2J2 expression attenuates the diabetic phenotype and insulin resistance via inhibition of NF-κB and MAPK signaling pathways and activation of PPARγ.

scholarly journals Effects of Liraglutide on β-Cell-Specific Glucokinase-Deficient Neonatal Mice

Endocrinology ◽  
2012 ◽  
Vol 153 (7) ◽  
pp. 3066-3075 ◽  
Author(s):  
Jun Shirakawa ◽  
Ritsuko Tanami ◽  
Yu Togashi ◽  
Kazuki Tajima ◽  
Kazuki Orime ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Glucose Sensor ◽  
Liver Steatosis ◽  
Survival Rates ◽  
Glycolytic Enzyme ◽  
Β Cells ◽  
Β Cell ◽  
Newborn Mice ◽  
Glucose Levels ◽  
Glucagon Like Peptide 1

The glucagon-like peptide-1 receptor agonist liraglutide is used to treat diabetes. A hallmark of liraglutide is the glucose-dependent facilitation of insulin secretion from pancreatic β-cells. In β-cells, the glycolytic enzyme glucokinase plays a pivotal role as a glucose sensor. However, the role of glucokinase in the glucose-dependent action of liraglutide remains unknown. We first examined the effects of liraglutide on glucokinase haploinsufficient (Gck+/−) mice. Single administration of liraglutide significantly improved glucose tolerance in Gck+/− mice without increase of insulin secretion. We also assessed the effects of liraglutide on the survival rates, metabolic parameters, and histology of liver or pancreas of β-cell-specific glucokinase-deficient (Gck−/−) newborn mice. Liraglutide reduced the blood glucose levels in Gck−/− neonates but failed to prolong survival, and all the mice died within 1 wk. Furthermore, liraglutide did not improve glucose-induced insulin secretion in isolated islets from Gck−/− neonates. Liraglutide initially prevented increases in alanine aminotransferase, free fatty acids, and triglycerides in Gck−/− neonates but not at 4 d after birth. Liraglutide transiently prevented liver steatosis, with reduced triglyceride contents and elevated glycogen contents in Gck−/− neonate livers at 2 d after birth. Liraglutide also protected against reductions in β-cells in Gck−/− neonates at 4 d after birth. Taken together, β-cell glucokinase appears to be essential for liraglutide-mediated insulin secretion, but liraglutide may improve glycemic control, steatosis, and β-cell death in a glucokinase-independent fashion.

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