Differential effects of dietary casein and soybean protein isolate on lipopolysaccharide-induced hepatitis in D-galactosamine-sensitized rats

Effects of dietary protein type on lipopolysaccharide (LPS)-induced hepatitis, as assessed by plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, were investigated in D-galactosamine (GalN)-sensitized rats. The plasma ALT and AST activities in rats fed on 25% soybean protein isolate (SPI) diet were significantly suppressed to about 1/4 and 1/5 of the values in rats fed on 25% casein diet, respectively, 8 h after the injection of LPS + GalN. Although hepatic ALT and AST activities of normal rats were also lower in the SPI group than in the casein group, this could not explain the differences in plasma enzyme activities between the two groups. The hepatic glutathione concentration of normal rats was lower in the SPI group than in the casein group, but it was reversed in rats injected with drugs. The results suggest that SPI can protect animals from LPS + GalN-induced hepatitis, and that the hepatic glutathione level may participate in the effects of SPI.