SPECIFIC INSULIN AND PROINSULIN CONCENTRATIONS IN NONDIABETIC SOUTH INDIANS

The study was performed to determine plasma levels of proinsulin (PI) and specific insulin (SI) in normoglycemic (NGT) Asian Indians and to assess the effect of obesity and impaired glucose tolerance (IGT) on t hese concentrations, Blood samples from 151 adult nondiabetic South In dian subjects were collected during an epidemiological survey of diabe tes, Plasma SI and Pi levels were measured in fasting and 30-minute an d 120-minute samples of a glucose tolerance test (World Health Organiz ation criteria) using monospecific antibodies. The total insulin (TI) level was also measured by the nonspecific assay, The molar Patio of P I to SI (PI/SI) was calculated. Correlations of the peptides with anth ropometry, serum lipids, and blood pressure (BP) were studied by univa riate and multivariate analyses, Comparisons were also made in NGT ver sus IGT groups, As expected, TI values were higher than SI values, but the patterns of response were similar for bath, SI and PI responses i n NGT were similar to the values found in Mexican-Americans who had a higher body mass Ender (BMI). Asian Indians were thus found to have a high SI response despite a low BMI. Obesity and IGT produced an increa sed response of both PI and SI, with normal PI/SI Patios thus showing an absence of hyperproinsulinemia in either condition, Pasting PB show ed a strong association with serum triglycerides, and proinsulin at 12 0 minutes was associated with cholesterol. None of the peptides showed a correlation with BP. Using specific assays for insulin and Pd it is shown that Asian Indians with NGT have a hyperinsulinemic response de spite a low BMI, Obesity and mild hyperglycemia in IGT produce a simul taneous increase in PI and SI with no alteration in the PI/SI ratio. C opyright (C) 1998 by W.B. Saunders Company.