[Effect of insulin in hypertension with high and low levels of renin].

BACKGROUND

Setback in insulin resistance has been described in patients with essential hypertension. The aim of our study was to verify at the receptor and postreceptor levels the presence of insulin resistance in patients with high or low renin activity.

METHODS AND RESULTS

Six patients with the renal artery stenosis (20 to 65 years, average age was 51 +/- 12 years, BMI: 27 +/- 2.0 kg.m2) and six patients with primary hyperaldosteronism (28 to 61 years, average age was 50 +/- 13 years, BMI: 26.9 +/- 3.2 kg.m2) were investigated. Their diagnose was confirmed by laboratory examination, computer tomography, and duplex sonography. Blood pressure was monitored for 24 hours with Spacelab tonometer (SBP: 161 +/- 29 mmHg, DBP: 98 +/- 12 mmHg versus SBP: 168 +/- 21 mmHg, DBP: 103 +/- 9 mmHg; plasma renin activity was 8.1 +/- 5.6 versus 0.3 +/- 0.4 ng.ml-1.h-1, p < 0.001; recumbent plasma aldosterone level was 98 +/- 31 versus 358 +/- 103 pg.ml-1, p < 0.001, normal value till 150 pg/ml, serum potassium was 3.9 +/- 0.4 and 3.5 +/- 0.6 mmol/l). All patients had normal course of the oral glucose tolerance test. Six volunteers of corresponding age and BMI formed the control group. Patients had normal values of the basal morning glycemia (4.9 +/- 0.5 and 5.0 +/- 0.6 versus 4.9 +/- 0.6 mmol/l), basal insulinemia level was 28.8 +/- 12.4 and 21.0 +/- 10.2 versus 15.9 +/- 8.8 mU.l-1 in healthy controls. Insulin effect was tested using isoglycemic hyperinsulinemic clamp method on Biostator with insulin infusion of 1 mU.kg.min-1. Plasma potassium concentration was kept at constant physiological levels using linear infusion pump (in patients with primary hyperaldosteronism after the prior supplementation). In patients with high-renin or low-renin hypertension, the glucose consumption during clamping was lower than that of healthy controls (M, glucose disposal rate: 23.7 +/- 4.8 and 19.5 +/- 3.4 versus 33.0 +/- 5.7 mumol.kg.-1.min-1, p < 0.001), increase of the metabolic glucose clearance (MCRG: 5.1 +/- 1.5 and 3.9 +/- 0.7 versus 7.9 +/- 1.4 ml.kg-1.min-1, p < 0.001) and tissue insulin sensitivity index (M/I: 24.3 +/- 10.1 and 26.4 +/- 8.3 versus 38.4 +/- 10.1 mumol.kg-1.min-1 to mU.l-1 x 100, p < 0.001).

CONCLUSIONS

Patients with high-renin and low-renin hypertension have the insulin effectiveness significantly impaired. Such insulin resistance probably does not depend on the renin activity, plasma aldosterone concentration or on serum potassium level. The ethiopathogenesis of the described changes will be the aim of our next study.