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Association of the SLC30A8 missense polymorphism R325W with proinsulin levels at baseline and after lifestyle, metformin or troglitazone intervention in the Diabetes Prevention Program.

ABSTRACT: Individuals with impaired glucose tolerance have increased proinsulin levels, despite normal glucose or C-peptide levels. In the Diabetes Prevention Program (DPP), increased proinsulin levels predicted type 2 diabetes and proinsulin levels were significantly reduced following treatment with metformin, lifestyle modification or troglitazone compared with placebo. Genetic and physiological studies suggest a role for the zinc transporter gene SLC30A8 in diabetes risk, possibly through effects on insulin-processing in beta cells. We hypothesised that the risk allele at the type 2 diabetes-associated missense polymorphism rs13266634 (R325W) in SLC30A8 would predict proinsulin levels in individuals at risk of type 2 diabetes and may modulate response to preventive interventions.We genotyped rs13266634 in 3,007 DPP participants and examined its association with fasting proinsulin and fasting insulin at baseline and at 1 year post-intervention.We found that increasing dosage of the C risk allele at SLC30A8 rs13266634 was significantly associated with higher proinsulin levels at baseline (p?=?0.002) after adjustment for baseline insulin. This supports the hypothesis that risk alleles at SLC30A8 mark individuals with insulin-processing defects. At the 1 year analysis, proinsulin levels decreased significantly in all groups receiving active intervention and were no longer associated with SLC30A8 genotype (p?=?0.86) after adjustment for insulin at baseline and 1 year. We found no genotype × treatment interactions at 1 year.In prediabetic individuals, genotype at SLC30A8 predicts baseline proinsulin levels independently of insulin levels, but does not predict proinsulin levels after amelioration of insulin sensitivity at 1 year.

SUBMITTER: Majithia AR

PROVIDER: S-EPMC3444290 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Association of the SLC30A8 missense polymorphism R325W with proinsulin levels at baseline and after lifestyle, metformin or troglitazone intervention in the Diabetes Prevention Program.

Majithia A R AR Jablonski K A KA McAteer J B JB Mather K J KJ Goldberg R B RB Kahn S E SE Florez J C JC

Diabetologia 20110721 10

<h4>Aims/hypothesis</h4>Individuals with impaired glucose tolerance have increased proinsulin levels, despite normal glucose or C-peptide levels. In the Diabetes Prevention Program (DPP), increased proinsulin levels predicted type 2 diabetes and proinsulin levels were significantly reduced following treatment with metformin, lifestyle modification or troglitazone compared with placebo. Genetic and physiological studies suggest a role for the zinc transporter gene SLC30A8 in diabetes risk, possib ...[more]

PMID: 21779873

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Project description:Aims/hypothesisWe compared the associations of circulating biomarkers of inflammation, endothelial and adipocyte dysfunction and coagulation with incident diabetes in the placebo, lifestyle and metformin intervention arms of the Diabetes Prevention Program, a randomised clinical trial, to determine whether reported associations in general populations are reproduced in individuals with impaired glucose tolerance, and whether these associations are independent of traditional diabetes risk factors. We further investigated whether biomarker-incident diabetes associations are influenced by interventions that alter pathophysiology, biomarker concentrations and rates of incident diabetes.MethodsThe Diabetes Prevention Program randomised 3234 individuals with impaired glucose tolerance into placebo, metformin (850 mg twice daily) and intensive lifestyle groups and showed that metformin and lifestyle reduced incident diabetes by 31% and 58%, respectively compared with placebo over an average follow-up period of 3.2 years. For this study, we measured adiponectin, leptin, tissue plasminogen activator (as a surrogate for plasminogen activator inhibitor 1), high-sensitivity C-reactive protein, IL-6, monocyte chemotactic protein 1, fibrinogen, E-selectin and intercellular adhesion molecule 1 at baseline and at 1 year by specific immunoassays. Traditional diabetes risk factors were defined as family history, HDL-cholesterol, triacylglycerol, BMI, fasting and 2 h glucose, HbA1c, systolic blood pressure, inverse of fasting insulin and insulinogenic index. Cox proportional hazard models were used to assess the effects of each biomarker on the development of diabetes assessed semi-annually and the effects of covariates on these.ResultsE-selectin, (HR 1.19 [95% CI 1.06, 1.34]), adiponectin (0.84 [0.71, 0.99]) and tissue plasminogen activator (1.13 [1.03, 1.24]) were associated with incident diabetes in the placebo group, independent of diabetes risk factors. Only the association between adiponectin and diabetes was maintained in the lifestyle (0.69 [0.52, 0.92]) and metformin groups (0.79 [0.66, 0.94]). E-selectin was not related to diabetes development in either lifestyle or metformin groups. A novel association appeared for change in IL-6 in the metformin group (1.09 [1.021, 1.173]) and for baseline leptin in the lifestyle groups (1.31 [1.06, 1.63]).Conclusions/interpretationThese findings clarify associations between an extensive group of biomarkers and incident diabetes in a multi-ethnic cohort with impaired glucose tolerance, the effects of diabetes risk factors on these, and demonstrate differential modification of associations by interventions. They strengthen evidence linking adiponectin to diabetes development, and argue against a central role for endothelial dysfunction. The findings have implications for the pathophysiology of diabetes development and its prevention.

Project description:BackgroundAdults at high risk for diabetes may have reduced health-related quality of life (HRQoL).ObjectiveTo assess changes in HRQoL after interventions aimed at diabetes risk reduction.Design, setting, and participantsA randomized clinical trial, the Diabetes Prevention Program, was conducted in 27 centers in the United States, in 3,234 non-diabetic persons with elevated fasting and post-load plasma glucose, mean age 51 years, mean BMI 34 Kg/m(2); 68 % women, and 45 % members of minority groups.InterventionsIntensive lifestyle (ILS) program with the goals of at least 7 % weight loss and 150 min of physical activity per week, metformin (MET) 850 mg twice daily, or placebo (PLB).MeasurementsHRQoL using the 36-Item Short-Form (SF-36) health survey to evaluate health utility index (SF-6D), physical component summaries (PCS) and mental component summaries (MCS). A minimally important difference (MID) was met when the mean of HRQoL scores between groups differed by at least 3 %.ResultsAfter a mean follow-up of 3.2 years, there were significant improvements in the SF-6D (+0.008, p=0.04) and PCS (+1.57, p<0.0001) scores in ILS but not in MET participants (+0.002 and +0.15, respectively, p=0.6) compared to the PLB group. ILS participants showed improvements in general health (+3.2, p<0.001), physical function (+3.6, p<0.001), bodily pain (+1.9, p=0.01), and vitality (+2.1, p=0.01) domain scores. Treatment effects remained significant after adjusting sequentially for baseline demographic factors, and for medical and psychological comorbidities. Increased physical activity and weight reduction mediated these ILS treatment effects. Participants who experienced weight gain had significant worsening on the same HRQoL specific domains when compared to those that had treatment-related (ILS or MET) weight loss. No benefits with ILS or MET were observed in the MCS score.ConclusionOverweight/obese adults at high risk for diabetes show small improvement in most physical HRQoL and vitality scores through the weight loss and increased physical activity achieved with an ILS intervention.

Dataset Information

Association of the SLC30A8 missense polymorphism R325W with proinsulin levels at baseline and after lifestyle, metformin or troglitazone intervention in the Diabetes Prevention Program.

Publications

Association of the SLC30A8 missense polymorphism R325W with proinsulin levels at baseline and after lifestyle, metformin or troglitazone intervention in the Diabetes Prevention Program.

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