GLUCOSE-TOLERANCE IN RURAL DIABETIC THAIS, FIRST-DEGREE RELATIVES ANDNONDIABETIC CONTROLS

To determine whether non-insulin-dependent diabetes mellitus (NIDDM) i n a rural Thai population is characterised by insulin resistance and h yperinsulinaemia, 17 unselected diabetic outpatients from a regional h ospital, five first-degree relatives and 10 healthy controls were stud ied. Subjects in these groups were matched as closely as possible for age and sex, and mean body mass indices were similar (mean +/- S.D.; 2 1.8 +/- 5.5, 20.6 +/- 1.4 and 21.8 +/- 2.3 kg/m(2) respectively, P > 0 .5), Beta-cell function (%B) and insulin sensitivity (%S), expressed r elative to values for non-diabetic Caucasians, were assessed mathemati cally using the 'CIGMA' model and plasma glucose and insulin achieved after a standard 1-h glucose infusion. The diabetic patients had highe r fasting plasma glucose concentrations than the controls (8.6 +/- 4.0 vs, 4.6 +/- 0.4 mmol/l, P < 0.01) but plasma insulin levels were comp arable (geometric mean [-S.D.-+S.D.]; 4.0 [1.7-9.4] vs. 4.0 [1.7-9.2] mU/l, P > 0.1). %B in the diabetic group (21% [10-41]) was lower than in the controls (128% [88-187], P < 0.001) while %S tended to be highe r (185% [86-400] vs. 111% [49-251], 0.1 > P > 0.05). Relatives had int ermediate values of both variables. %S and %B correlated poorly in the diabetic group (P > 0.1) but together accounted for 90% of the variat ion in basal plasma glucose (multiple r = 0.95, n = 17, P < 0.0001). B eta-cell dysfunction appears the primary defect in diabetic patients f rom a Thai subsistence farming population. Insulin resistance may not always characterise NIDDM in geographical areas where a 'thrifty genot ype' would be expected; other factors associated with diabetes in deve loping countries (such increased susceptibility to serious infections) may also influence diabetes prevalence.