Studies on the regulation, by proteins and amino acids of pathogenisis of hepatitis

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This study was undertaken to investigate the effects of dietary proteins and amino on LPS/Ga1N-induced hepatitis and to clarify the mechanism underlying the effects of proteins and amino acids in rats.(1)When rats were fed diets containing one of milk casein, whole egg protein, soybean protein, and wheat gluten as protein sources and then hepatitis was evoked by the injection of LPS/Ga1N, hepatitis was most potently suppressed by feeding of soybean protein. It was suggested that amino acid composition of soybean protein, in addition to impurities of the protein, might be participated in the effect of soybean protein.(2)Feeding of rats with low casein diet, as compared with standard or high casein diet, suppressed LPS/Ga1N-induced hepatitis and supplementation of the low casein diet with cysteine at a low level potentiated the supprerssive effect of low cvasein diet. These results indicate that low protein diet with a high nutritive value leads to marked suppression of LPS/Ga1N-induced hepatitis.(3)When 20 kinds of amino acids were added singly to the diet, LPS/Ga1N-induced hepatitis was markedly suppressed by cetrtain kinds of amino acids (Gly, val, lie, Lys, His).(4)The mechanism by which soybean protein and several amino acids suppressed LPS/Ga1N-induced hepatitis was investigated in terms of plasma cytokine and nitric oxide concentration. The results suggest that, in most cases, dietary protein and supplemented amino acids elicit their effect through inhibition of LPS-induced promotion of nitric oxide production rather than through inhibition of LPS-induced promotion of tumor necrosis factor alpha.(5)The results of this study show that liver function, especially the sensitivity of the liver to hepatitis, can be largely infuemced by dietary proteins and amino acids, suggesting that certain types of dietary proteins and amino acids might be useful to regulate the pathogenesis of hepatitis.