Several common mechanisms between two or more of these conditions have been advocated, including

oxidative stress, CYP2E1 induction, increased fat synthesis and mobilization, selected gut bacteria, free fatty acids, ER stress, immune response, among others.[22-25] Because IDO inhibitor of page limitations, only the first two mechanisms (oxidative stress and CYP2E1 induction) will be discussed. Oxidative stress due to alcohol has been discussed earlier. Obesity involves the accumulation of body fat and is a major risk factor for metabolic syndrome, which is characterized by hyperglycemia, dyslipidemia, and hypertension.[26] Increased oxidative stress in accumulated fat has been reported as a pathogenic mechanism of obesity-associated metabolic syndrome. In nondiabetic humans, MG 132 systemic oxidative stress correlated positively with fat accumulation and negatively with plasma adiponectin levels. In obese mice, ROS production was selectively increased in adipose tissue, and was accompanied by enhanced expression of NADPH oxidase and decreased expression of anti-oxidative enzymes such as superoxide dismutase in white adipose tissue and GPx in liver.[27] In cultured adipocytes, mitochondrial and peroxisomal oxidation of fatty acids activates

NADPH oxidase resulting in increased oxidative stress, which caused increase in messenger RNA (mRNA) expression of inflammatory (PAI-1, TNF-α, IL-6, and monocyte chemotactic protein-1), check details and suppression of mRNA and secretion of anti-inflammatory (adiponectin, leptin) adipocytokines. Conversely, in obese KKAy mice, treatment with apocynin, an NADPH oxidase inhibitor, reduced ROS production in adipose tissue, increased plasma adiponectin levels, and improved hyperlipidemia and hepatic steatosis. Because oxidative stress underlies the pathophysiology of hepatic steatosis,[28] these results suggest that increased oxidative stress in obese individuals could be further exacerbated by oxidative stress due to chronic heavy alcohol consumption. Infection with HCV, in most cases, develops

into chronic disease which is manifested by steatosis and fibrosis, as well as HCC. HCV replication induces oxidative stress (Figure 2), which contributes to insulin and interferon resistance, as well as disorders of iron metabolism. Specifically, virus core and nonstructural NS5A proteins increase ROS levels through alteration of calcium homeostasis[29] via a primary effect on the uniporter,[30] and the induction of NADPH oxidase 4.[31] In addition, E1 and E2 and the transmembrane protein NS4B increase ROS generation via ER stress and unfolded protein response,[32, 33] and activates the antioxidant defense regulated by NF-E2-related factor 2.[34] Furthermore, HCV causes mitochondrial damage and induction of double-stranded DNA breaks mediated by NO and ROS, which is abolished by NO and ROS inhibitors.