Effects of weight loss on renal function in overweight Japanese men

Obesity is known as an independent risk factor for renal injury. Sympathetic nerve activation may have an important role of the pathogenesis of obesity, and hypertension may underpin the development of cardiovascular events. In the present study, we evaluated the effects of weight loss (WL) on renal function, especially focusing on sympathetic nervous activity. In 154 overweight or obese Japanese men (89 normotensive and 65 untreated mild hypertensive subjects), body weight, body mass index (BMI), total body fat mass, blood pressure (BP), serum creatinine, blood urea nitrogen, creatinine clearance (CCr) (calculated with the Cockcroft-Gault equation) and plasma norepinephrine (NE) were measured before and after a 12-month period of WL with a mild caloric-restricted diet and exercise. A significant WL was defined as 10% or more WL compared with the entry period. In total, 97 (63.0%) subjects succeeded in significant (by 14.3%) WL at 12 months, and 57 subjects (37.0%) did not succeed in significant WL but they lost 7.7% weight. At entry, levels of plasma NE, serum creatinine and fat mass were significantly lower and CCr was greater in the group with a significant WL compared with those without WL. BMI, total body fat mass and plasma NE significantly decreased, and CCr increased with WL. At both baseline and at the 12-month period, fat mass and plasma NE negatively correlated with CCr and positively correlated with creatinine at each time point. Changes in fat mass and plasma NE over 12 months correlated with changes in creatinine, and only changes in fat mass negatively correlated with changes in CCr. Basal fat mass and plasma NE correlated positively with serum creatinine at 12 months and negatively with CCr at the same time point. In multiple regression analyses, basal plasma NE and fat mass were significant determinants of serum creatinine levels and CCr at 12 months. In conclusion, WL improved renal function (as evident from measures of creatinine and CCr) in overweight individuals. Basal plasma NE levels and total body fat mass could be predictors for improvement in renal function associated with WL. Suppression of sympathetic nervous activation associated with WL may have a role in the ameliorative effects on renal function.