Serum Lipids of Rats Fed Excess L-Lysine and Different Carbohydrates

Liver and serum lipids were compared in male weanling rats fed 15% casein plus 5% lysine, threonine, valine or glutamic acid for 14 days. Lys increased liver total lipids, triglycerides and cholesterol 200, 600 and 200%, respectively, without affecting serum lipids. Thr and Val also increased liver triglycerides but only about 200%. Val feeding was associated with hypertriglyceridemia whereas arginine and Glu produced a slight hypercholesterolemia. Adding 1% methionine or Arg prevented the fatty liver of 5% Lys. Only liver triglycerides, the lipid class showing the greatest increases with Lys feeding were reduced significantly by Met, whereas Arg reduced all lipid classes nearly to control levels. One percent Met increased serum lipids, triglycerides, cholesterol and phospholipids 50, 30, 10 and 30%, respectively. Replacement of surcose by dextrin-sucrose reduced the liver lipid accumulation from 5% Lys slightly, while 7.5% cellulose in the sucrose diet made it greater. Neither glucose or fructose affected the liver lipid accumulation of 5% Lys but glucose with Lys reduced serum lipids. Rats fed 5% Lys for 6 weeks had no fatty livers. The data show that Lys but not Arg, Thr Val or Glu altered lipid metabolism and caused accumulation of lipids in the livers. Liver lipid accumulation was less pronounced with dextrin sucrose versus sucrose alone. The effect of sucrose was apparently not due to either glucose or fructose nor to a lack of cellulose. The Lys-induced fatty liver was almost completely prevented by Arg and appears due to Lys-Arg antagonism.