Effect of dietary linoleic acid on the tryptophan-niacin metabolism in streptozotocin diabetic rats.
To make clear the mechanism of change of tryptophan-niacin metabolism in diabetic rats, we investigated the effect of dietary linoleic acid on the tryptophan-niacin metabolites and the activity of liver, alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSD), a key enzyme of tryptophan-niacin metabolism, in streptozotocin diabetic rats. Moreover, we investigated the involvement of linoleic acid in the induction of hepatic ACMSD activity by streptozotocin diabetes. In diabetic rats, the sum of urinary excretion of nicotinamide, N1-methylnicotinamide (MNA), N1-methyl-2-pyridone-5-carboxamide (2-Py) and N1-methyl-4-pyridone-3-carboxamide (4-Py) was higher in the fat free diet group than in the linoleic acid group, that was accompanied by the increase of tryptophan intake and reduction of body weight in the fat free diet group. In diabetic rats, hepatic ACMSD activity was higher in the fat free diet group than in the linoleic acid group. The results indicated that the induction of hepatic ACMSD activity by diabetes was not due to removal of the suppressive effect of the linoleic acid on the enzyme. In the diabetic+insulin group, hepatic ACMSD activity was significantly lower than in the diabetic group.
Egashira
Y
Y
Department of Bioproduction Science, Faculty of Horticulture, Chiba University, Matsudo, Japan.
Nakazawa
A
A
Ohta
T
T
Shibata
K
K
Sanada
H
H
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004032:Diet; D004435:Eating; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000494:pharmacology*; D008297:Male; D009525:Niacin / Q000378:metabolism*; D009536:Niacinamide / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014364:Tryptophan / Q000378:metabolism*
D008041:Linoleic Acids; D009536:Niacinamide; D009525:Niacin; D014364:Tryptophan; D019787:Linoleic Acid