Association of an APOC3 promoter variant with type 2 diabetes risk and need for insulin treatment in lean persons

AIMS/HYPOTHESIS: An APOC3 promoter haplotype has been previously associated with type 1 diabetes. In this population-based study, we investigated whether APOC3 polymorphisms increase type 2 diabetes risk and need for insulin treatment in lean participants. METHODS: In the Rotterdam Study, a population-based prospective cohort (n = 7,983), Cox and logistic regression models were used to analyse the associations and interactive effects of APOC3 promoter variants (−482C > T, −455T > C) and BMI on type 2 diabetes risk and insulin treatment. Analyses were followed by replication in an independent case–control sample (1,817 cases, 2,292 controls) and meta-analysis. RESULTS: In lean participants, the −482T allele was associated with increased risk of prevalent and incident type 2 diabetes: OR −482CT 1.47 (95% CI 1.13–1.92), −482TT 1.40 (95% CI 0.83–2.35), p = 0.009 for trend; HR −482CT 1.35 (95% CI 0.96–1.89), −482TT 1.68 (95% CI 0.91–3.1), p = 0.03 for trend, respectively. These results were confirmed by replication. Meta-analysis was highly significant (−482T meta-analysis p = 1.1 × 10(-4)). A borderline significant interaction was observed for insulin use among participants with type 2 diabetes (−482CT*BMI p = 0.06, −455TC*BMI p = 0.02). CONCLUSIONS/INTERPRETATION: At a population-based level, the influence of APOC3 promoter variants on type 2 diabetes risk varies with the level of adiposity. Lean carriers of the −482T allele had increased type 2 diabetes risk, while such an effect was not observed in overweight participants. Conversely, in overweight participants the −455C allele seemed protective against type 2 diabetes. The interaction of the variants with need for insulin treatment may indicate beta cell involvement in lean participants. Our findings suggest overlap in the genetic backgrounds of type 1 diabetes and type 2 diabetes in lean patients.