The influence of insulin resistance on plasma aldosterone concentration in obese persons with essential hypertension

Abstract

Introduction: Obesity-related metabolic abnormalities are discussed intensively in a context of risk factors for cardiovascular diseases.

Aim : To assess plasma aldosterone concentration in abdominally obese adults with essential hypertension, according to insulin resistance observed.

Material and methods : Centrally obese (IDF 2005 criteria) adult Caucasians with essential hypertension, presenting no acute and chronic disease, using no medication, underwent clinical examination (i.e. body mass index [BMI], % of body fat, blood pressure). After oral glucose tolerance test (OGTT), assessing fasting (G0') and 2-h (G120') glycemia, newly diagnosed type 2 diabetics were excluded. Plasma lipids: T-C, HDL-C, TAG (bioMérieux), insulin (ELISA-BioSource) and aldosterone (RIA, Immunotech) concentrations were determined fasting. LDL-C was calculated due to Friedewald formula. Insulin-resistance indices, including IR = Ins 0'/G 0' and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were estimated. Finally, non-IR group (n = 21; aged 48 ±10; 9 males, 12 females) with IR < 0.3 and IR group (n = 22; aged 46 ±11; 7 males, 15 females) with IR >= 0,3, with comparable prevalence of normoglycemia and pre-diabetes (50%), were studied. Statistical analysis was performed using Statistica 6.0 program.

Results : 1. In the IR group increased BMI, FAT and HOMA-IR were observed comparing with non-IR group. 2. The IR subjects presented higher aldosterone than non-IR individuals (92.9 ±62.8 pg/ml vs. 51.9 ±30.8 pg/ml; p = 0.032). 3. No correlations between aldosterone and other metabolic parameters were identified in neither studied groups.

Conclusions: The mechanisms of insulin resistance might contribute elevated plasma aldosterone concentration, which seems to be independent cardiovascular risk factors, in obese essential hypertensive subjects.