Branched chain amino acids supplementation modulates TGF-1/Smad signaling pathway and interleukins in CCl4-induced liver fibrosis

The alterations and low levels of circulating branched chain amino acids (BCAAs), leucine, isoleucine, and valine, are associated with liver diseases. The study was designed to evaluate hepatoprotective effect of BCAAs on CCl4-induced liver fibrosis and to investigate the molecular mechanisms underlying these effects in rats. In all, 30 male rats were divided into three groups. Control group (n = 10) and CCl4 group (n = 10), where rats were injected with CCl4 (1 mL/kg of 0.5 : 1 v/v injected i.p. twice weekly for 12 weeks). In CCl4 + BCAAs group (n = 10), rats were injected with similar doses of CCl4 and supplemented with a mixture of 600 mg/kg BCAAs (2 : 1 : 1.2 leucine : isoleucine : valine) by oral gavage, three times/week for 12 weeks. Liver fibrosis was assessed by measuring total bilirubin, total protein, alanine aminotransferase, and aspartate aminotransferase, hydroxyproline content, and serum IL-6 and IL-10. Histopathologic studies and -smooth muscle actin (-SMA) were detected immunohistochemically in liver. Serum insulin level, blood glucose, liver malodialdehyde concentration (MDA), glutathione peroxidase, and superoxide dismutase (SOD) activities were quantified. TGF-1, Smad3, and Smad7 gene expressions were estimated by qRT-PCR. BCAAs suppressed liver fibrosis induced by CCl4 treatment. BCAAs modulated liver indices and downregulated TGF-1, Smad3, and Smad7 expressions in hepatocytes. BCAAs enhanced liver antioxidant enzyme activities (P < 0.001), reduced serum levels of TGF-1, IL-6, and IL-10 compared to CCL4 group and ameliorated histopathologic changes in rat liver. BCAAs may have a protective role against liver fibrosis via antioxidant and anti-inflammatory mechanisms.