Insulin, renin-aldosterone system and blood pressure in obese people

OBJECTIVE: To evaluate the relationship between insulin, the renin-aldosterone system and blood pressure in obese subjects. DESIGN AND METHODS: A cross sectional study of a group of severely obese normotensive subjects who were surgical candidates (n = 39; mean BMI: 47.8 +/- 1.4) and a group of hypertensive patients (n = 57; mean BMI: 28.0 +/- 0.7) twenty-nine of whom had BMI > 27. All subjects were studied after 15 days on a balanced diet. Insulin, plasma renin activity and aldosterone were measured. RESULTS: Fasting insulin, plasma renin activity and aldosterone were higher in severely obese normotensive subjects than in hypertensive subjects (respectively 32.3 +/- 3.0 vs 13.1 +/- 1.0 mU/I, P = 0.0001; 1.34 +/- 0.22 vs 0.88 +/- 0.12 ng/ml/h, P = 0.04; 137.2 +/- 16.2 vs 87.9 +/- 12.1 pg/ml, P = 0.015). Insulin was related to BMI and to aldosterone both in normotensive and in hypertensive patients. CONCLUSION: Hyperinsulinemia itself does not determine hypertension; in some people it could play a vasodilator role in opposition to the renin-aldosterone system.