Effect of supplementing low protein diets with the limiting amino acids on the excretion of N1-methylnicotinamide and its pyridones in rats.
We have hypothesized that the ratio of the excreted by-products of niacin metabolism, N1-methyl-2-pyridone-5-carboxamide (2-pyr) + N1-methyl-4-pyridone-3-carboxamide (4-pyr)/N1-methylnicotinamide (MNA), might be useful as an index to assess the adequacy of amino acid intake in rats. The experiment reported herein was performed to test this hypothesis. When a 10, 20 or 40% casein diet supplemented with 0.1, 0.2 or 0.4% L-methionine, respectively, was fed to rats, the urinary excretion of MNA decreased, and that of 4-pyr increased, as the level of dietary casein and methionine increased. Therefore, the ratio of (2-pyr + 4-pyr)/MNA increased with increasing dietary casein and methionine levels. When the limiting amino acids of casein or soy protein isolate were added to a low casein or low soy protein isolate diet, the urinary ratio of (2-pyr + 4-pyr)/MNA also increased. These results indicate that the increased urinary ratio of (2-pyr + 4-pyr)/MNA can serve as a biological marker for adequate amino acid intake.
Shibata
K
K
Department of Food Science and Nutrition, Teikoku Women's University, Osaka, Japan.
Matsuo
H
H
D000596:Amino Acids / Q000008:administration & dosage*; D000818:Animals; D001835:Body Weight; D002364:Caseins / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage*; D004435:Eating; D008715:Methionine / Q000008:administration & dosage; D008780:Methyltransferases / Q000032:analysis; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine; D050903:Nicotinamide N-Methyltransferase; D011728:Pyridones / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013025:Glycine max
D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D011728:Pyridones; D009536:Niacinamide; D008715:Methionine; D008780:Methyltransferases; D050903:Nicotinamide N-Methyltransferase; C008472:N-methylnicotinamide