Association of ß-cell function and insulin sensitivity with fasting and 2-h plasma glucose in a large Chinese population

Aim: Our aim was to provide a quantitative analysis of the changes in the principal determinants of insulin sensitivity and secretion in relation to fasting plasma glucose (FPG) or 2-h plasma glucose (2h PG) in a Chinese population with a wide range of glucose tolerance. Methods: A total of 5728 adults spanning the entire range of glucose tolerance were included. Insulin sensitivity was measured by Matsuda insulin sensitivity index (ISIM) and homeostasis model assessment of 1/homeostasis model assessment of insulin resistance (HOMA-IR). beta-Cell function adjusted by insulin sensitivity was assessed from disposition index (DI) at early-phase DI30 and total DI120. The exponential curve was established as the best fit for the relationship between insulin sensitivity or beta-cell function and FPG or 2h PG. Results: Relative to the trend classified as increasing 2h PG, hepatic insulin sensitivity and insulin secretion showed a decreasing trend to a substantial degree as FPG increased. A 1 mmol/l increase in FPG and 2h PG concentration was associated with a -22 and -21% decline in ISIM, -16 and -4% in 1/HOMA-IR, -38 and -35% in DI30 and -36 and -26% in DI120. The decay constant of ISIM and DI30 in IFG or ISIM, 1/HOMA-IR, DI30 and DI120 in IGT was lower than that in normal glucose tolerance. Significant interactions between sex and glucose levels determining DI were found. Conclusions: We conclude that impairment of insulin sensitivity and insulin secretion contributes to both FPG or 2h PG hyperglycaemia in a Chinese population, but that the decline in insulin secretion is more pronounced with increasing fasting than 2h PG.