Relative contributions of insulin resistance and β‐cell dysfunction to the development of Type 2 diabetes in Koreans

AIMS: Controversies still exist regarding the relative contributions of insulin resistance and β-cell dysfunction to the pathogenesis of Type 2 diabetes in different populations. We examined the associations of baseline insulin resistance and β-cell function indices with the development of Type 2 diabetes in Koreans. METHODS: We analysed the clinical and laboratory data of 17 878 Korean adults (age 20-79 years) who underwent routine medical examinations with a median interval of 3.5 years (range 2.5-4.7 years). Using the homeostasis model assessment, insulin resistance (HOMA-IR) and β-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 ± 23.4 pmol/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 Type 2 diabetes. Among the participants who developed diabetes, 29% demonstrated predominant β-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 (23.7 kg/m²), 49% of participants in the low BMI group demonstrated predominant β-cell dysfunction and 26% had predominant insulin resistance, whilst 21% in the high BMI group demonstrated mainly β-cell dysfunction and 60% had mainly insulin resistance. CONCLUSIONS: In individuals with low BMI, β-cell dysfunction is the predominant defect, whereas insulin resistance is the predominant pathogenetic factor in individuals with high BMI in the development of Type 2 diabetes in Koreans.