[Model of development of diabetes mellitus in adult Chinese]

Abstract

Objective: To explore the model for development of non-insulin dependent diabetes and the roles of insulin resistance and insulin secretion impairment in the initiation of diabetes in adult Chinese.

Methods: 432 non-diabetics aged 24-74, 126 with normal glucose tolerance (NGT) and 307 with impaired glucose tolerance (IGT), were selected by standard oral glucose tolerance test (OGTT) and plasma insulin concentration measurement in Daqing, Heilongjiang Province, in 1986, and then followed up for six years. OGTT was conducted every two years. The subjects with fasting plasma glucose (FPG) > or = 7.8 mmol/L and/or two hour plasma glucose (PG2h) > or = 11.1 mmol/L were diagnosed as with diabetes. The effect of insulin resistance and insulin secretion at baselie on worsening of glucose tolerance in both NGT and IGT groups were analyzed using SAS software.

Results: 70% of DM cases developed from the insulin-resistant IGT subgroup at the end of the study. About 30% of DM cases were not insulin-resistant in their IGT stage. Proportional hazard analysis showed that the baseline PG2h and BMI significantly positively correlated to the development of diabetes during the six years follow-up period (RR = 1.35 and 1.32 respectively, P < 0.01). Dietary and exercise intervention significantly decreased such risk. With these confounders being controlled, baseline insulin sensitivity and insulin secretion index significantly negatively correlated to the development of diabetes in the IGT group (RR = 0.41 and 0.39 respectively, P < 0.01). Incidence of IGT (or DM) in the insulin resistant NGT subgroup was much higher than that in the non-insulin resistant NGT subgroup (34.5% vs 13.4%, P < 0.05), stepwise logistic regression analysis showed that only the baseline insulin sensitivity entered the model and negatively associated to the risk of worsening of glucose tolerance (P < 0.05).

Conclusion: A two-step model of development of diabetes mellitus is shown among most adult Chinese diabetics. In the first step NGT develops to IGT when insulin resistance play a major role. In the second step, IGT develops to diabetes when both insulin resistance and beta-cell secretion impairment play a major role.