INSULIN SECRETION AND SENSITIVITY IN FIRST-DEGREE RELATIVES OF NIGERIAN PATIENTS WITH NON-INSULIN DEPENDENT DIABETES MELLITUS (NIDDM)

Abstract

The blood insulin and glucose concentrations were analysed before and during frequently sampled intravenous glucose tolerance tests (FSIGT) In 2 groups of Nigerian subjects: (1 ) Control group (n=18), without a positive family history of diabetes mellitus, and (2) Experimental group (n =16), comprising age, sex, and body mass-matched first degree relatives of patients with non-insulin dependent diabetes mellitus (NIDDM). In comparison with Group 1 subjects, those in group 2 had; higher fasting plasma glucose level (mean ± SEM, 4.1±0.1 Vs 3.8±0.11 mmol/L, p<0.05); Similar fasting serum insulin levels (6.7±1.19 vs 5.8±1.4 mU/L, p=NS); Lower mean incremental area under the first-phase (t= 0-10 min) post-glucose challenge insulin curve (378.0±2.1 vs 328.2 ± 1.2 mU/min/L, p<0.05); increased incremental area under the second-phase (t = 10-182 min) post-glucose challenge insulin curve (1554.2±5.6 vs 1959.0±4.5 mU.min/L, p<0.05); Reduced Kg rate constant of glucose elimination (0.97±0.12 Vs 1.41±0.12 %/min, p<0.05). These results suggest that the subjects with a positive family history of NIDDM have a reduced beta-Cell Insulin secretory reserve (from reduced first-phase insulin response), tendency to rebound hyperinsulinemia during the latter phase of the insulin secretory response, a degree of peripheral tissue insulin insensitivity (ss evident from high fasting plasma glucose despite similar insulin levels) and a diminished glucose disposal rate, in comparison with subjects without a family history of NIDDM. These features predict subsequent development of diabetes and suggest that as in Caucasians, first-degree relatives of Nigerian patients with NIDDM are at greater risk for future development of the disease.