Glucose and insulin responses in offspring of Nigerian Type 2 diabetics

Type 2 diabetes mellitus has a strong genetic basis by a concordance rate ranging between 60 and 90% in monozygotic twins. Glucose and insulin responses to an oral glucose load were measured in 52 offspring of Nigerian Type 2 diabetics and 50 control subjects selected to achieve a similar distribution of age and gender. All subject studied were glucose tolerant. In comparison with control subjects, offspring of Type 2 diabetics had a significantly higher mean (SD) (i) fasting plasma glucose level [69.2 (13.0) mg/dl vs. 62.2 (7.6) mg/dl; P = 0.0012] (ii) fasting plasma insulin level [26.6 (15.4) microIU/ml vs 14.8 (6.8) microIU/ml; P < 0.0001] (iii) 2 hours post glucose load plasma insulin level [59.8 (33.9) microIU/ml vs. 40.9 (24.2) microIU/ml; P = 0.0028]. The mean (SD) 2-hour post glucose load plasma glucose level did not differ significantly between both groups of subjects [92.8 (23.8) mg/dl vs. 85.5 (21.3) mg/dl; P = 0.11]. Further multiple regressional analysis showed that the differences in fasting plasma insulin and 2-hour post glucose load insulin observed were only accounted for by the presence of a parental history of diabetes and were not influenced significantly by BMI, waist and hip circumferences. This study shows that offspring of Nigerian Type 2 diabetics have hyperinsulinaemia, despite being glucose tolerant and this supports the insulin-resistance hypothesis for Type 2 DM. This implies that they are at a greater risk for developing diabetes mellitus and are therefore an important group for the primary prevention of Type 2 DM.