Changes of renal sinus fat and renal parenchymal fat during an 18-month randomized weight loss trial

Abstract

Data regarding the role of kidney adiposity, its clinical implications, and its dynamics during weight-loss are sparse. We investigated the effect of long-term weight-loss induced intervention diets on dynamics of renal-sinus-fat, an ectopic fat depot, and %renal-parenchymal-fat, lipid accumulation within the renal parenchyma. We randomized 278 participants with abdominal obesity/dyslipidemia to low-fat or Mediterranean/low-carbohydrate diets, with or without exercise. We quantified renal-sinus-fat and %renal-parenchymal-fat by whole body magnetic-resonance-imaging. Participants (age=48 years; 89% men; body-mass-index=31kg/m2) had 86% retention to the trial after 18 months. Both increased renal-sinus-fat and %renal-parenchymal-fat were directly associated with hypertension, and with higher abdominal deep-subcutaneous-adipose-tissue and visceral-adipose-tissue (p of trend<0.05 for all) after adjustment for body weight. Higher renal-sinus-fat was associated with lower estimated-glomerular-filtration-rate and with higher microalbuminuria and %HbA1C beyond body weight. After 18 months of intervention, overall renal-sinus-fat (-9%; p<0.05 vs. baseline) but not %renal-parenchymal-fat (-1.7%; p=0.13 vs. baseline) significantly decreased, and similarly across the intervention groups. Renal-sinus-fat and %renal-parenchymal-fat changes were correlated with weight-loss per-se (p<0.05). In a model adjusted for age, sex, and visceral-adipose-tissue changes, 18 months reduction in renal-sinus-fat associated with decreased pancreatic, hepatic and cardiac fats (p<0.05 for all) and with decreased cholesterol/high-density lipoprotein-cholesterol (HDL-c) (β=0.13; p=0.05), triglycerides/HDL-c (β=0.13; p=0.05), insulin (β=0.12; p=0.05) and gamma glutamyl transpeptidase (β=0.24; p=0.001), but not with improved renal function parameters or blood pressure. Decreased intake of sodium was associated with a reduction in %renal-parenchymal-fat, after adjustment for 18 months weight-loss (β=0.15; p=0.026) and hypertension (β=0.14; p=0.04). Renal-sinus-fat and renal-parenchymal-fat are fairly related to weight-loss. Decreased renal-sinus-fat is associated with improved hepatic parameters, independent of changes in weight or hepatic fat, rather than with improved renal function or blood pressure parameters. CLINICALTRIALS. NCT01530724.