1: Am J Clin Nutr. 1984 May;39(5):722-9.

Diurnal variations in plasma concentrations of basic and neutral amino acids and
in red cell concentrations of aspartate and glutamate: effects of dietary protein
intake.

Maher TJ, Glaeser BS, Wurtman RJ.

The effects of dietary protein content on diurnal variations in plasma
concentrations of neutral and basic amino acids, and on red blood cell levels of
acidic amino acids, were studied in seven normal humans. The subjects consumed,
on three consecutive 3-day periods, diets containing 0, 75, or 150 g of egg
protein per day; blood was collected at 4-h intervals on the 2nd and 3rd days of
each diet. For each of the large neutral amino acids (LNAA; isoleucine, leucine,
tyrosine, phenylalanine, methionine, valine, and tryptophan) significant
correlations were observed between its plasma levels and the protein content of
the diet; highest levels were noted after consumption of the 150-g protein diet,
and lowest values after the O-g protein diet. For each LNAA, except tryptophan,
"fed" values (ie, those at 3 PM and 7 PM) were decreased relative to "fasting"
values (those at 3 AM and 7 AM) after consumption of the O-g protein-free diet,
but increased after consumption of the 150-g protein diet. Threonine, serine, and
proline behaved like the LNAA: in contrast, glycine and alanine rose after
protein-free meals and fell with the high-protein diet. The basic amino acids,
lysine, arginine, and histidine tended to respond like the LNAA to variations in
dietary protein content. Red blood cell concentrations of glutamate tended to
vary inversely with the protein content of the diet, while no relationship was
noted between red blood cell aspartate and dietary protein content. Food-induced
changes in plasma LNAA have been found to affect brain levels of amino acids that
are neurotransmitter precursors, as well as the syntheses of the transmitters
themselves.(ABSTRACT TRUNCATED AT 250 WORDS)


PMID: 6538743 [PubMed - indexed for MEDLINE]