Studies on the impact of dietary fat composition on proteinuria in diabetic rats

Rats with streptozotocin diabetes were pair-fed diets containing 20% beef tallow (BT), fish oil (FO), or safflower oil (SO) for up to six months. After one month, differences in glucose control were not observed but rats fed FO had more renal hypertrophy. FO reduced glomerular prostaglandin E2 and 6-keto F1 alpha, and BT increased thromboxane B2 production, but there were no differences in glomerular filtration rate (GFR) or renal plasma flow (RPF). Animals fed BT needed more insulin after two months than rats fed FO followed by SO. After six months, diabetic rats fed FO had larger relative kidney weights than SO or BT, but a similar pattern was present in non-diabetic controls fed the same diets. Diabetic rats fed BT had more proteinuria than diabetic rats fed SO but not FO. However, FO-fed controls had more proteinuria than controls fed SO and similar levels of proteinuria as diabetic rats fed FO. The composition of dietary fat alters glucose tolerance in diabetic rats after two months. BT increases glomerular thromboxane production and hastens proteinuria compared to SO. FO enhances renal growth and proteinuria, but this effect is independent of the diabetic condition.