Effects of dietary methionine and glycine on serum lipoprotein profiles and fecal sterol excretion in normal and hepatoma-bearing rats.

The effects of concurrent addition of methionine (Met) and glycine (Gly) to a 20% casein diet on serum lipoprotein profiles and fecal sterol excretion were studied in male Donryu rats with or without subcutaneous implantation of an ascites hepatoma line of AH109A cells. The hepatoma-bearing rats fed on the 20% casein diet had a notable elevation in the very-low-density lipoprotein + low-density lipoprotein (VLDL + LDL)-cholesterol (Ch) level with a slight but significant decrease in high-density lipoprotein (HDL)-Ch level when compared to the hepatoma-free (normal) rats fed on the same diet. The dietary addition of 1.2% Met and 2.5% Gly in combination suppressed the hepatoma-induced elevation in the (VLDL + LDL)-Ch level with a prevention of the hepatoma-induced decrease in the HDL-Ch level. The addition of the two amino acids also lowered significantly the (VLDL + LDL)-Ch level without affecting the HDL-Ch level in tumor-free rats. Fecal excretion of both neutral and acidic sterols were reduced with growth of the hepatoma. The dietary addition of Met and Gly exerted no or little influence on neutral sterol excretion in both the tumor-free and -bearing states, but it enhanced acidic sterol excretion into feces in both states, especially in the hepatoma-bearing state at the last stage of feeding. These results suggest that the excretion and catabolism of Ch might be impaired in hepatoma-bearing rats with growth of the tumor, and that the supplemental Met and Gly in combination might enhance Ch catabolism by stimulating either synthesis or conjugation of bile acids, leading to a reduction of the (VLDL + LDL)-Ch level in the normal and hepatoma-bearing states.