Dataset Information

GIP contributes to islet trihormonal abnormalities in type 2 diabetes.

ABSTRACT:

Context

Research and clinical treatments on type 2 diabetes mainly focus on insulin deficiency with little attention paid to other islet hormones.

Objective

This study tested the hypothesis that glucose-dependent insulinotropic polypeptide (GIP) is involved in diabetes-associated multiislet hormone dysregulation.

Design

This paper included a case-control study involving 92 community-based volunteers from the Baltimore Longitudinal Study of Aging (BLSA): 23 with type 2 diabetes on glucose-lowering agents, 25 with newly diagnosed drug-naïve type 2 diabetes, 19 with prediabetes, and 25 with normal glucose tolerance; a separate intervention study with 13 non-BLSA volunteers with type 2 diabetes treated with diet alone, metformin, and/or metformin/sulfonylurea combination; a rodent study; and an in vitro cell line study.

Interventions

An oral glucose tolerance test was performed in the BLSA participants. For the intervention study, saline (0.9% NaCl) or synthetic human GIP (20 ng · kg(-1) · min(-1)) was administered to type 2 diabetes subjects for 180 minutes together with a meal, and plasma samples were obtained at predetermined intervals for 360 minutes. A bolus of GIP or placebo was given to C57BL/6 mice.

Main outcome measures

Plasma glucose, insulin, glucagon, pancreatic polypeptide (PP), glucagon-like peptide-1 (GLP-1), and GIP were measured.

Results

After an oral glucose tolerance test, glucose, glucagon, PP, GLP-1, and GIP levels were significantly elevated in type 2 diabetes groups, compared with normal and prediabetes groups. GIP infusion in type 2 diabetes subjects was associated with significantly elevated PP levels compared with placebo. The GIP bolus given to C57BL/6 mice was followed by increased PP levels. GIP receptors were found in both human and mouse PP cells.

Conclusions

Up-regulation of GIP production may play an important role in multihormonal dysregulation in type 2 diabetes, most likely through interaction with GIP receptors on islets.

SUBMITTER: Chia CW

PROVIDER: S-EPMC4079310 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Publications

GIP contributes to islet trihormonal abnormalities in type 2 diabetes.

Chia Chee W CW Odetunde Juliana O JO Kim Wook W Carlson Olga D OD Ferrucci Luigi L Egan Josephine M JM

The Journal of clinical endocrinology and metabolism 20140408 7

<h4>Context</h4>Research and clinical treatments on type 2 diabetes mainly focus on insulin deficiency with little attention paid to other islet hormones.<h4>Objective</h4>This study tested the hypothesis that glucose-dependent insulinotropic polypeptide (GIP) is involved in diabetes-associated multiislet hormone dysregulation.<h4>Design</h4>This paper included a case-control study involving 92 community-based volunteers from the Baltimore Longitudinal Study of Aging (BLSA): 23 with type 2 diabe ...[more]

PMID: 24712564

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Project description:OBJECTIVE:The incretin hormone GIP (glucose-dependent insulinotropic polypeptide) promotes pancreatic ?-cell function by potentiating insulin secretion and ?-cell proliferation. Recently, a combined analysis of several genome-wide association studies (Meta-analysis of Glucose and Insulin-Related Traits Consortium [MAGIC]) showed association to postprandial insulin at the GIP receptor (GIPR) locus. Here we explored mechanisms that could explain the protective effects of GIP on islet function. RESEARCH DESIGN AND METHODS:Associations of GIPR rs10423928 with metabolic and anthropometric phenotypes in both nondiabetic (N = 53,730) and type 2 diabetic individuals (N = 2,731) were explored by combining data from 11 studies. Insulin secretion was measured both in vivo in nondiabetic subjects and in vitro in islets from cadaver donors. Insulin secretion was also measured in response to exogenous GIP. The in vitro measurements included protein and gene expression as well as measurements of ?-cell viability and proliferation. RESULTS:The A allele of GIPR rs10423928 was associated with impaired glucose- and GIP-stimulated insulin secretion and a decrease in BMI, lean body mass, and waist circumference. The decrease in BMI almost completely neutralized the effect of impaired insulin secretion on risk of type 2 diabetes. Expression of GIPR mRNA was decreased in human islets from carriers of the A allele or patients with type 2 diabetes. GIP stimulated osteopontin (OPN) mRNA and protein expression. OPN expression was lower in carriers of the A allele. Both GIP and OPN prevented cytokine-induced reduction in cell viability (apoptosis). In addition, OPN stimulated cell proliferation in insulin-secreting cells. CONCLUSIONS:These findings support ?-cell proliferative and antiapoptotic roles for GIP in addition to its action as an incretin hormone. Identification of a link between GIP and OPN may shed new light on the role of GIP in preservation of functional ?-cell mass in humans.

Project description:Aims/hypothesisSphingolipids play important roles in beta cell physiology, by regulating proinsulin folding and insulin secretion and in controlling apoptosis, as studied in animal models and cell cultures. Here we investigate whether sphingolipid metabolism may contribute to the pathogenesis of human type 1 diabetes and whether increasing the levels of the sphingolipid sulfatide would prevent models of diabetes in NOD mice.MethodsWe examined the amount and distribution of sulfatide in human pancreatic islets by immunohistochemistry, immunofluorescence and electron microscopy. Transcriptional analysis was used to evaluate expression of sphingolipid-related genes in isolated human islets. Genome-wide association studies (GWAS) and a T cell proliferation assay were used to identify type 1 diabetes related polymorphisms and test how these affect cellular islet autoimmunity. Finally, we treated NOD mice with fenofibrate, a known activator of sulfatide biosynthesis, to evaluate the effect on experimental autoimmune diabetes development.ResultsWe found reduced amounts of sulfatide, 23% of the levels in control participants, in pancreatic islets of individuals with newly diagnosed type 1 diabetes, which were associated with reduced expression of enzymes involved in sphingolipid metabolism. Next, we discovered eight gene polymorphisms (ORMDL3, SPHK2, B4GALNT1, SLC1A5, GALC, PPARD, PPARG and B4GALT1) involved in sphingolipid metabolism that contribute to the genetic predisposition to type 1 diabetes. These gene polymorphisms correlated with the degree of cellular islet autoimmunity in a cohort of individuals with type 1 diabetes. Finally, using fenofibrate, which activates sulfatide biosynthesis, we completely prevented diabetes in NOD mice and even reversed the disease in half of otherwise diabetic animals.Conclusions/interpretationThese results indicate that islet sphingolipid metabolism is abnormal in type 1 diabetes and suggest that modulation may represent a novel therapeutic approach.Data availabilityThe RNA expression data is available online at https://www.dropbox.com/s/93mk5tzl5fdyo6b/Abnormal%20islet%20sphingolipid%20metabolism%20in%20type%201%20diabetes%2C%20RNA%20expression.xlsx?dl=0 . A list of SNPs identified is available at https://www.dropbox.com/s/yfojma9xanpp2ju/Abnormal%20islet%20sphingolipid%20metabolism%20in%20type%201%20diabetes%20SNP.xlsx?dl=0 .

Project description:ContextIn healthy individuals, glucose-dependent insulinotropic polypeptide (GIP) enhances insulin secretion and reduces bone resorption by up to 25% estimated by absolute placebo-corrected changes in carboxy-terminal type 1 collagen crosslinks (CTX) during GIP and glucose administration. In patients with type 2 diabetes (T2D), GIP's insulinotropic effect is impaired and effects on bone may be reduced.ObjectiveTo investigate GIP's effect on bone biomarkers in patients with T2D.DesignRandomized, double-blinded, crossover study investigating 6 interventions.PatientsTwelve male patients with T2D.InterventionsA primed continuous 90-minute GIP infusion (2 pmol/kg/min) or matching placebo (saline) administered at 3 plasma glucose (PG) levels (i.e., paired days with "insulin-induced hypoglycemia" (PG lowered to 3 mmol/L), "fasting hyperglycemia" (mean PG ~8 mmol/L), or "aggravated hyperglycemia" (mean PG ~12 mmol/L).Main outcome measuresBone biomarkers: CTX, procollagen type 1 N-terminal propeptide (P1NP) and PTH.ResultsOn days with insulin-induced hypoglycemia, CTX was suppressed by up to 40 ± 15% during GIP administration compared with 12 ± 11% during placebo infusion (P < 0.0001). On days with fasting hyperglycemia, CTX was suppressed by up to 36 ± 15% during GIP administration, compared with 0 ± 9% during placebo infusion (P < 0.0001). On days with aggravated hyperglycemia, CTX was suppressed by up to 47 ± 23% during GIP administration compared with 10 ± 9% during placebo infusion (P = 0.0005). At all glycemic levels, P1NP and PTH concentrations were similar between paired days after 90 minutes.ConclusionsShort-term GIP infusions reduce bone resorption by more than one-third (estimated by absolute placebo-corrected CTX reductions) in patients with T2DM, suggesting preserved bone effects of GIP in these patients.PrécisShort-term GIP infusions reduce the bone resorption marker CTX by one-third in patients with type 2 diabetes independent of glycemic levels.

Dataset Information

GIP contributes to islet trihormonal abnormalities in type 2 diabetes.

Context

Objective

Design

Interventions

Main outcome measures

Results

Conclusions

Publications

GIP contributes to islet trihormonal abnormalities in type 2 diabetes.

Similar Datasets

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