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

Diabetologia. 2011 Oct;54(10):2570-4. doi: 10.1007/s00125-011-2234-1. Epub 2011 Jul 21.


Aims/hypothesis: 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.

Methods: 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.

Results: 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.

Conclusions/interpretation: 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • C-Peptide / blood
  • Cation Transport Proteins / genetics*
  • Chromans / therapeutic use*
  • Diabetes Mellitus / blood*
  • Diabetes Mellitus / drug therapy
  • Diabetes Mellitus / genetics*
  • Diabetes Mellitus / therapy
  • Diabetes Mellitus, Type 2 / genetics
  • Female
  • Humans
  • Insulin / blood
  • Male
  • Metformin / therapeutic use*
  • Middle Aged
  • Polymorphism, Genetic / genetics*
  • Proinsulin / blood*
  • Thiazolidinediones / therapeutic use*
  • Troglitazone
  • Zinc Transporter 8


  • C-Peptide
  • Cation Transport Proteins
  • Chromans
  • Insulin
  • SLC30A8 protein, human
  • Thiazolidinediones
  • Zinc Transporter 8
  • Proinsulin
  • Metformin
  • Troglitazone