Relative contributions of insulin resistance and -cell dysfunction to the development of Type2 diabetes in Koreans

Aims Controversies still exist regarding the relative contributions of insulin resistance and -cell dysfunction to the pathogenesis of Type2 diabetes in different populations. We examined the associations of baseline insulin resistance and -cell function indices with the development of Type2 diabetes in Koreans. Methods We analysed the clinical and laboratory data of 17878 Korean adults (age 20-79years) who underwent routine medical examinations with a median interval of 3.5years (range 2.5-4.7years). Using the homeostasis model assessment, insulin resistance (HOMA-IR) and -cell function (HOMA-%B) indices at baseline were assessed. Results Those who developed diabetes (n=732, 4.1%) had significantly higher fasting serum insulin level (53.4 +/- 31.2 vs. 41.4 +/- 23.4pmol/l) and HOMA-IR (2.38 +/- 1.45 vs. 1.65 +/- 1.02) and lower HOMA-%B (74 +/- 47 vs. 85 +/- 48) at baseline (P<0.001 for all). Both high HOMA-IR and low HOMA-%B were independently associated with an increased odds ratio of incident Type2 diabetes. Among the participants who developed diabetes, 29% demonstrated predominant -cell dysfunction (HOMA-%B <25th percentile) and 51% had predominant insulin resistance (HOMA-IR >75th percentile). When we divided the participants according to the median BMI of the whole population (23.7kg/m(2)), 49% of participants in the low BMI group demonstrated predominant -cell dysfunction and 26% had predominant insulin resistance, whilst 21% in the high BMI group demonstrated mainly -cell dysfunction and 60% had mainly insulin resistance. Conclusions In individuals with low BMI, -cell dysfunction is the predominant defect, whereas insulin resistance is the predominant pathogenetic factor in individuals with high BMI in the development of Type2 diabetes in Koreans.