Improvement of hyperlipidemia and proteinuria without noticeable growth retardation by feeding a methionine and threonine supplemented low-casein diet to nephritic rats.

We have previously demonstrated that low-casein diets supplemented with cystine and threonine reduced hyperlipidemia and proteinuria in nephritic rats without noticeable protein malnutrition. In the present study, we examined whether or not a low-casein diet supplemented with methionine, sulfur amino acid other than cystine, and threonine would ameliorate the symptoms without protein malnutrition in rats with nephrotoxic serum nephritis by feeding experimental diets for 10 days. A methionine-threonine-supplemented 8.5% casein diet (8.5 CMT), when compared with a basal 20% casein diet, improved hypoalbuminemia as well as hyperlipidemia and proteinuria without noticeable growth retardation and fatty liver induction in nephritic rats. Fecal bile acid excretion and microsomal cholesterol 7 alpha-hydroxylase activity were enhanced by 8.5CMT feeding. These results suggest that amino acid-balanced low protein diet would have a beneficial effect on the symptoms of nephritis. They also suggest that the hypocholesterolemic action of 8.5CMT may be, at least in part, due to increased fecal bile acid excretion accompanied by elevated microsomal cholesterol 7 alpha-hydroxylase activity.