Effects of dietary lipids on renal function of aged rats

Normal aging is accompanied by renal functional and morphological deteriora tion and dietetic manipulation has been used to delay this age-related decl ine. We examined the effects of chronic administration of diets containing 5% lipid-enriched diet (LD, w/w) on renal function of rats at different age s. Three types of LD were tested: canola oil, fish oil and butter. Mean sys temic tail-cuff blood pressure and glycemia remained within the normal rang e whatever the age and the diet of the animals. Proteinuria began to rise f rom the 8th month in the groups ingesting LD, while in the control group it increased significantly (above 10 mg/24 h) only after the 10th month. With age, a significant and progressive decline in glomerular filtration rate ( GFR) and renal plasma flow was observed in the LD groups but after 6 months of lipid supplementation. the decline in these parameters was more marked in the butter and fish oil groups. By the 18th month, the lowest GFR level was observed in the group ingesting the butter diet (2.93 +/- 0.22 vs 5.01 +/- 0.21 mi min(-1) kg(-1) in control, P<0.05). Net acid excretion. evaluat ed in 9- and 18-month-old rats, was stimulated in the fish oil group when c ompared both to control and to the other two LD groups, These results sugge st that even low levels of LD in a chronic nutritional regimen can modify t he age-related changes in renal function and that the impact of different t ypes of lipid-supplemented diets on renal function depends on the kind of l ipid present in the diet.