COMBINED RENAL EFFECTS OF OVERWEIGHT AND HYPERTENSION

The existence of a direct relationship between body mass and arterial pressure is well recognized; however, the effect of obesity on known t arget organs of hypertension is not clearly understood. We undertook t he present studies to assess the influence of obesity on renal functio n and urinary albumin excretion in 40 normotensive subjects and 80 nev er-treated hypertensive patients matched for age, sex, arterial pressu re level, and known duration of hypertension in whom an oral glucose t olerance test was within normal limits. Glomerular filtration rate and effective renal plasma flow (expressed as absolute values or values n ormalized for height) were increased in overweight compared with lean subjects whether normotensive or hypertensive. Glomerular filtration r ate was positively correlated with protein intake (as assessed from ur inary excretion of urea) and fasting serum insulin level. Urinary excr etion of albumin but not IgG and beta(2) microglobulin was higher in h ypertensive patients compared with normotensive subjects. The overweig ht condition clearly enhanced the influence of arterial pressure on al buminuria; in fact, a steeper regression line between albumin excretio n rate and arterial pressure was found in overweight compared with lea n subjects. These results indicate that the overweight condition is as sociated with renal hyperfiltration and hyperperfusion, irrespective o f the presence of hypertension, and that obesity magnifies the effect of hypertension on albuminuria, thus raising the possibility of an inc reased susceptibility of obese hypertensive patients to the developmen t of renal damage.