Factors contributing to the resistivity of a higher casein diet against choline deficiency-induced hyperhomocysteinemia in rats.
The mechanism by which feeding a higher casein diet results in resistance to choline deprivation-induced hyperhomocysteinemia was investigated in rats. Plasma homocysteine concentration was significantly lower in rats fed a 30% casein diet (30C) than in rats fed a 10% casein diet (10C). Choline deprivation did not enhance plasma homocysteine concentration in rats fed 30C, while it significantly enhanced plasma homocysteine concentration in rats fed 10C. The choline deprivation-induced enhancement of plasma homocysteine concentration in rats fed 10C was significantly suppressed by methionine supplementation in a dose-dependent manner in the range of 0.1 to 0.3%, but the suppressive effect of methionine became smaller with an increase in supplementation level in the range of 0.3 to 0.5%. At a 0.5% supplementation level, methionine did not exhibit any suppressive effect on choline deprivation-induced hyperhomocysteinemia. The higher plasma homocysteine concentration in rats fed choline-deprived 10C+0.5% methionine was significantly decreased by concurrent supplementation with 0.32% glycine+0.94% serine to the level of rats fed 10C. Raising dietary total amino acid level by adding 3.61% branched-chain amino acids (BCAA)+4.5% acidic amino acids (AAA) to choline-deprived 10C+0.5% methionine+0.32% glycine+0.94% serine resulted in a further decrease in plasma homocysteine concentration to a level lower than the level in rats fed 10C. Choline deprivation-induced increases in hepatic S-adenosylhomocysteine and homocysteine concentrations were significantly suppressed by supplementation with glycine+serine and further suppressed by BCAA+AAA. Hepatic cystathionine β-synthase activity and its gene expression were significantly increased by BCAA+AAA. Hepatic triglyceride concentration changed in a manner similar to that of plasma homocysteine concentration. The results indicate that there are at least three factors contributing to the resistivity of rats fed a higher casein diet (30C) to choline deprivation-induced hyperhomocysteinemia, i.e., higher intake of methionine, higher intake of glycine and serine, and higher intake of other amino acids such as BCAA and AAA.
The United Graduate School of Agricultural Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan.
Yi-qun
YQ
Liu
Ying
Y
Liu
Tatsuya
T
Morita
Makoto
M
Mori
Kimio
K
Sugiyama
D000818:Animals; D002364:Caseins / Q000008:administration & dosage*; D002794:Choline / Q000008:administration & dosage; D002796:Choline Deficiency / Q000150:complications*; D004032:Diet; D005998:Glycine / Q000008:administration & dosage; D006710:Homocysteine / Q000097:blood; D020138:Hyperhomocysteinemia / Q000209:etiology*; D008297:Male; D008715:Methionine / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000008:administration & dosage
D002364:Caseins; D006710:Homocysteine; D012694:Serine; D008715:Methionine; D002794:Choline; D005998:Glycine