The study evaluated the effects of astaxanthin (ASX) in mice rendered obese by feeding an unbalanced diet. Adult male mice of body weight 25-35 g were fed either normal chow or a high fat-high fructose diet (HFFD). Fifteen days later, mice in each group were divided in to two and treated with either ASX (6 mg/kg b.w.) in olive oil or olive oil alone. The mice were killed at the end of 60 days. Insulin sensitivity, markers of liver injury, inflammation and nitro-oxidative stress, antioxidants and cytochrome P 4502E1 (CYP2E1) activity were assayed. Liver structural integrity was also assessed by histology with hemotoxylin and eosin and Masson's trichrome stains. HFFD-fed mice registered significant increase in body weight and liver weight and displayed hyperglycemia, hyperinsulinemia and insulin resistance and elevated plasma aminotransferases. Lipid deposition, oxidative damage, defective antioxidant system and upregulated transforming growth factor-beta (TGF-beta 1) expression were observed in HFFD-fed mice. ASX supplementation promoted insulin sensitivity and prevented liver injury by decreasing CYP2E1, myeloperoxidase, and nitro-oxidative stress and by improving the antioxidant status in them. Lipid deposition and increased TGF-beta 1 expression induced by HFFD were also abolished by ASX. This study provides new data showing the beneficial effects of ASX in obese mice. (C) 2010 Elsevier Ltd. All rights reserved,