TITLE:
Uniqueness of Tryptophan in the Transport System in the Brain and Peripheral Tissues
AUTHORS:
Mutsumi Ogawa, Fumiko Shimizu, Yukie Ishii, Tetsuya Takao, Akikazu Takada
KEYWORDS:
Glucose, Sucrose, Insulin, Amino Acids, Transporter, mTORC1
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.14 No.5,
May
19,
2023
ABSTRACT: Amino acids are important substances that must be transported to tissues such as the brain and muscles. The
process is considered insulin dependent. It is not known whether all the amino
acids are almost equally dependent in their transportation to tissues. We want
to know whether some important amino acids are transported differently from
other amino acids. Especially tryptophan is important because it is converted
to serotonin, melatonin or kynurenine.
Results showed that Amino acids levels in the
plasma were measured after
the intakes of 50 grams of glucose or sucrose to young (18 - 22 years
old) and old (≥50 years old) men. Total amino acids in the plasma decreased after the intakes of
glucose. Total amino acids levels decreased more significantly in
old men after the administration of sucrose. Total and non-essential amino acids in the plasma
decreased significantly at 120 min after the intakes of glucose in young and
old men, but only sucrose caused their decreases in both aged and young men.
Both glucose and sucrose intakes decreased
significantly the plasma levels of the total essential and branched
amino acids in young and old men. Surprisingly, plasma levels of tryptophan did
not decrease upon the administration of glucose but only slightly decreased
upon the administration of sucrose in young men. In conclusion, not all the amino acids were transported well into tissues upon the
administration of glucose or sucrose. Tryptophan seems to be relatively
resistant for insulin to facilitate the transportation into tissues.