Associations of β-Cell Function and Insulin Resistance with Youth-Onset Type 2 Diabetes and Prediabetes Among Asian Indians

Aim: This study examined beta-cell function and insulin resistance (homeostasis model assessment-insulin resistance [HOMA-IR]) in Asian Indian youth with type 2 diabetes mellitus (T2DM-Y) and prediabetes. Subjects and Methods: Eighty-two subjects with non-insulin-requiring type 2 diabetes and age of onset below 25 years were recruited within 18 months of diagnosis and compared with age- and sex-matched subjects with prediabetes (n = 31) and normal glucose tolerance (NGT) (n = 83). Body mass index (BMI) and waist circumference were measured, and blood samples were taken in the fasting state and after 30, 60, 90, and 120 min of an oral glucose load for assessment of plasma glucose and insulin levels. Insulin sensitivity/resistance measures was calculated by using the reciprocal of the fasting insulin, the HOMA-IR equation, and the composite whole body insulin sensitivity index (Matsuda Index), and beta-cell function was calculated by the oral disposition index (DIo). Results: T2DM-Y and prediabetes subjects had higher BMI, waist circumference, and fasting insulin than NGT subjects (P < 0.05 for each). The 30-min insulin levels were lower in T2DM-Y and higher in prediabetes subjects compared with NGT (57 and 140 vs. 129 mu IU/mL, P < 0.001). The T2DM-Y group had greater insulin resistance (HOMA-IR, 1.87 vs. 0.97; P < 0.05) and lower beta-cell function (DIo, 0.36 vs. 3.28; P < 0.001) than NGT. In separate models, the Matsuda Index and DIo were independently associated with prediabetes and T2DM-Y (P < 0.05). However, when both were included together, only DIo remained associated with T2DM-Y, whereas both DIo and Matsuda Index were associated with prediabetes (P < 0.05). When controlled for adiposity (BMI and waist circumference), an association was observed but in opposite directions, with waist being positively associated with prediabetes (P = 0.016) and BMI negatively associated with T2DM-Y (P = 0.009). Conclusions: Among Asian Indians, beta-cell dysfunction appears to be more strongly associated with T2DM-Y than insulin resistance.