ABSTRACT
OBJECTIVES: To investigate the relationship between salt sensitivity and hyperinsulinaemia in rural black African subjects. DESIGN: An intervention study where 27 subjects were divided into two groups; group 1 was initially salt loaded (300 mmol Na+/day), while group 2 was salt restricted (25 mmol Na+/day), each for 4 days, after which a cross-over study was done. SETTING: Chidamoyo, a rural area 383 km north of Harare, Zimbabwe. SUBJECTS: Twenty-seven rural volunteers (16 women, 11 men). OUTCOME MEASURES: Systolic and diastolic blood pressures, salt sensitivity, insulin and glucose levels, body mass index and mean arterial pressure. RESULTS: Mean arterial pressure, which was 91 +/- 2 mmHg on a low-salt diet, increased significantly (P < 0.01) to 105 +/- 3 mmHg on high-salt diet in the salt-sensitive subjects. In the same salt-sensitive subjects, the fasting insulin level was 8.4 +/- 0.8 microU/ml on a low-salt and 6.1 +/- 1.0 microU/ml on a high-salt diet. The difference was not statistically significant. CONCLUSIONS: Although salt pressor sensitivity was demonstrated in the subjects, there was no accompanying increase but rather a decrease in fasting insulin levels, suggesting that in the short term, salt sensitivity and hyperinsulinaemia are not linked in raising blood pressure in this sample of rural Zimbabwean subjects.
Subject(s)
Black or African American , Hyperinsulinism/ethnology , Hyperinsulinism/etiology , Rural Population , Sodium Chloride, Dietary/adverse effects , Adult , Black People , Blood Glucose/analysis , Blood Pressure/drug effects , Body Mass Index , Cross-Over Studies , Female , Humans , Hyperinsulinism/blood , Hypoglycemic Agents/blood , Insulin/blood , Male , Middle Aged , ZimbabweABSTRACT
Insulin resistance has been associated with essential hypertension, obesity and old age. Likewise high blood pressure has been observed to develop in some rural people who migrate to urban areas in developing countries like Zimbabwe. The pathogenesis of this urbanisation-related hypertension is still unknown. We therefore investigated aspects of insulin resistance in urbanisation-related hypertension in Zimbabwean blacks using oral glucose tolerance tests. Thirty normotensive subjects and 30 newly diagnosed hypertensive patients participated in this study. All subjects had blood pressures measured by random zero sphygmomanometry. Fasting blood samples were taken before a 75 g oral glucose load was given. Four other blood samples were subsequently collected at 30 minute intervals and determination of blood glucose and insulin levels was made. Fasting glucose (mmol/l) and fasting insulin (in microU/ml) levels were, respectively, 4.8 +/- 0.2 and 19 +/- 2 in hypertensive patients which were significantly higher than 4.0 +/- 0.2 and 13 +/- 1.6 in normotensive patients (P < 0.05). In addition the area under the insulin curve was significantly higher in hypertensive than in normotensive patients (P < 0.05). These findings suggest that insulin resistance may play a role in urbanisation-related hypertension.
