Adaptational modification of serine and threonine metabolism in the liver to essential amino acid deficiency in rats.
It is known that plasma serine and threonine concentrations are elevated in rats chronically fed an essential amino acid deficient diet, but the underlying mechanisms including related gene expressions or serine and threonine concentrations in liver remained to be elucidated. We fed rats lysine or valine deficient diet for 4 weeks and examined the mRNA expressions of serine synthesising (3-phosphoglycerate dehydrogenase, PHGDH) and serine/threonine degrading enzymes (serine dehydratase, SDS) in the liver. Dietary deficiency induced marked elevation of hepatic serine and threonine levels associated with enhancement of PHGDH mRNA expression and repression of SDS mRNA expression. Increases in plasma serine and threonine levels due to essential amino acid deficiency in diet were caused by marked increases in hepatic serine and threonine levels. Proteolytic responses to the amino acid deficiency may be lessened by storing amino radicals as serine and inducing anorexia through elevation of threonine.
Nagao
Kenji
K
Research Institute for Health Fundamentals, Ajinomoto Co., Inc., Kawasaki, Japan.
Bannai
Makoto
M
Seki
Shinobu
S
Mori
Masato
M
Takahashi
Michio
M
D000601:Amino Acids, Essential / Q000008:administration & dosage / Q000172:deficiency*; D000818:Animals; D004032:Diet; D005526:Food, Formulated; D015870:Gene Expression; D012695:L-Serine Dehydratase / Q000096:biosynthesis*; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D050543:Phosphoglycerate Dehydrogenase / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000097:blood / Q000378:metabolism*; D013912:Threonine / Q000097:blood / Q000378:metabolism*
D000601:Amino Acids, Essential; D012333:RNA, Messenger; D013912:Threonine; D012694:Serine; D050543:Phosphoglycerate Dehydrogenase; D012695:L-Serine Dehydratase