Variable response of plasma C-peptide to hyperglycemia in Afro-Caribbean and Indian origin populations with high rates of diabetes mellitus - abstract

ABSTRACT

Recent monoclonal insulin assays have suggested decreased, not excess, circulating in non-insulin dependent diabetes mellitus (NIDDM). In a random sample of 344 men and women aged 45-74 years in North-West London, age-adjusted rates of NIDDM following oral glucose challenge (WHO criteria) were found to be 4 per cent in white, 26 per cent in Afro-Caribbean (AFC) and 30 per cent in Gujerati (Indian origin) people. The relationship of C-peptide (insulin's co-secreted fragment) to hyperglycemia has now been examined in a balanced sample of 160 of these subjects. The relative risk (95 per cent CLs) of undiagnosed (new) diabetes mellitus was 15.9 (2-138) for AFC and 16 (12-127) among Gujeratis compared with that for whites (=1). Mean (SD) fasting C-peptide levels were 0.72 (0.31) in whites (n=48), 0.70 (0.41) in AFC (n=50) but 0.88 (0.57) in Gujeratis (n=71) pmol/ml. By 2-hr. of the glucose tolerance test, these had risen to 2.79 (1.15), 2.45 (1.07) and 3.42 (1.17) pmol/ml, respectively (F = 8.8), p<0.01, anova). Thus one group with high rates of NIDDIM, the AFC had lower insulin secretory response relative to whites, while the other (Gujeratis) had a greater response. These data again indicate heterogenity of beta-cell function in NIDDM; the relative concentrations of C-peptide between ethnic groups also reflectes respective risks of coronary heart disease, for which C-peptide has recently been proposed as a marker (AU)