Altered renal sodium handling in men with abdominal adiposity: a link to hypertension

Objectives Central adiposity, insulin resistance and hypertension are clear ly interrelated but the mechanisms underlying this association have not bee n thoroughly elucidated. As renal sodium handling plays a central role in s alt-sensitive forms of hypertension, we investigated the relation of renal tubular sodium handling to abdominal adiposity, blood pressure and insulin sensitivity. Design Population-based study. Participants Five hundred and fifty-five untreated Olivetti male workers, a ged 25-75 years. Setting Olivetti factory medical centers in Pozzuoli and Marcianise (Naples , Italy) Main outcome measures Anthropometric indices, serum insulin, homeostatic mo del assessment index of insulin sensitivity, blood pressure, fractional exc retions of uric acid and exogenous lithium (as markers of renal tubular sod ium handling). Results In univariate analysis, measures of central adiposity (i.e. sagitta l abdominal diameter and umbilical circumference) were directly correlated with serum insulin (P < 0.001) and blood pressure levels (P < 0.001) and in versely associated with the fractional excretions of uric acid and lithium (P = 0.01-0.001). In multiple linear regression analysis, the same anthropo metric indices but not the measures of peripheral adiposity (arm circumfere nce and tricipital skinfold thickness), were significant predictors of the fractional excretion of uric acid and lithium, independently of age, blood pressure and serum insulin levels (P = 0.01-0.001). Conclusions Abdominal adiposity was associated with altered renal tubular s odium handling apart from insulin resistance and high blood pressure. The d ata indicate that men with prevalent abdominal adiposity have an enhanced r ate of tubular sodium reabsorption, mainly at proximal sites. These finding s provide a possible mechanistic link between central adiposity and salt-de pendent hypertension. J Hypertens 19:2157-2164 (C) 2001 Lippincott Williams & Wilkins.