Insulin sensitivity and cardiovascular risk factors in hypertensive and normotensive native Ghanaians.

AIMS/HYPOTHESIS: The objective of this study was to examine the relationships among insulin and insulin sensitivity and risk factors for cardiovascular diseases in native Ghanaians with and without hypertension.

METHODS: We measured the anthropometric parameters, systolic and diastolic blood pressure, fasting serum triglycerides, cholesterol and high-density lipoprotein cholesterol and fasting and stimulated glucose, insulin and C-peptide of 200 Ghanaian subjects, who were between 25 to 74 years of age, and residing in the Accra Metropolitan area. Serum glucose, C-peptide and insulin concentrations were measured at baseline (fasting) and also 2 h after 75 gm oral glucose drink. Homeostasis model assessment was used to measure insulin resistance. Hypertension was defined as a blood pressure higher than 140/90 mmHg.

RESULTS: There were 53 subjects with hypertension (HBP) and 147 subjects with normal blood pressure (NBP). The mean BMI, waist circumference and waist-to-hip circumference ratio for HBP and NBP subjects were 27.4+/-0.8, 24.8+/-0.4 kg/m(2); 89.8+/-11.7, 81.1+/-0.9 cm; and 0.87+/-0.08, 0.82+/-0.08 respectively, (p<0.05). The fasting and 2-h plasma glucose concentrations in HBP and NBP subjects were 5.5+/-0.2, 7.2+/-0.3 mmol/l and 5.2+/-01, 6.8+/-0.2 mmol/l respectively (p>0.05). The corresponding fasting and 2-h insulin concentrations were 10.0+/-0.7, 8.0+/-0.4 uU/ml and 47.3+/-3.7, 37.3+/-2.5 uU/ml respectively (p<0.05). The insulin resistance index (HOMA-IR) in the HBP and the NBP groups were 2.49+/-0.2 and 1.95+/-0.13 (p<0.05). The two groups had similar fasting and stimulated C-peptide, lipids and HDL concentrations. Correlations were found between blood pressure and the concentrations of lipids, HDL, fasting and stimulated insulin and C-peptide, and between fasting insulin and HOMA-IR with lipids and HDL concentrations. On multiple regression analysis, fasting insulin and HOMA-IR did not influence blood pressure variations significantly.

CONCLUSIONS/INTERPRETATION: We found clustering of hyperinsulinaemia, insulin resistance and truncal obesity in hypertensive Ghanaian subjects but dissociation between insulin resistance, hypertension and atherogenic lipid and lipoprotein profile.