Aims/hypothesis  

Central obesity, insulin resistance and beta cell dysfunction are independent risk factors for incident type 2 diabetes, although few studies have used detailed measures of these disorders. Our objective was to study the association of directly measured visceral and subcutaneous adipose tissue (VAT, SAT), insulin sensitivity (S _I) and the acute insulin response (AIR) with incident type 2 diabetes.

Methods  

Participants were 1,230 Hispanic-Americans and African-Americans in the Insulin Resistance Atherosclerosis Study (IRAS) Family Study who were free of type 2 diabetes at baseline (2000–2002). S _I and AIR were determined from frequently sampled IVGTTs with minimal model analysis. VAT and SAT were determined by computed tomography. Impaired fasting glucose and type 2 diabetes were defined according to American Diabetes Association criteria.

Results  

Incident type 2 diabetes was diagnosed in 90 participants after 5 years. After adjustment for age, sex, ethnicity, centre, impaired fasting glucose, triacylglycerol, HDL-cholesterol and systolic BP, both S_I and AIR were inversely associated with type 2 diabetes (S _I, OR 0.53, 95% CI 0.39–0.73; AIR, OR 0.22, 95% CI 0.14–0.34 per SD; both p < 0.001), while both VAT and SAT were positively associated with type 2 diabetes (VAT, OR 1.68, 95% CI 1.22–2.33; SAT, OR 1.49, 95% CI 1.13–1.99; both p < 0.01). In a model including all four factors, S _I and AIR (S _I, OR 0.55, 95% CI 0.37–0.80; AIR, OR 0.21, 95% CI 0.13–0.33; both p < 0.01) were significant predictors of type 2 diabetes, although associations with VAT and SAT were no longer significant. A significant sex × VAT interaction indicated a stronger association of VAT with type 2 diabetes in women than in men.

Conclusions/interpretation  

Insulin resistance, beta cell dysfunction and VAT predicted incident type 2 diabetes, with evidence of a stronger association of VAT with type 2 diabetes among women.