Male mice (4 months old) were fed green tea extract-(GTE; 0.25% w/w) and/or fish oil-(FO; 5% w/w) containing diets with 8 ppm methylmercury (MeHg) chloride for 4 months to investigate the effects of simultaneous intakes on brain functions, antioxidant defenses against MeHg, and MeHg accumulation in tissues. In mouse maze tests, intake of GTE or FO significantly improved the learning ability of MeHg-exposed mice. GTE and FO also significantly decreased liver and brain catalase activities in MeHg-exposed mice. Total Hg concentrations in muscle were significantly lowered by dietary GTE and FO in the MeHgexposed group, though no remarkable differences were observed in the brain. These data indicate that simultaneous intake of GTE and FO effectively prevents MeHg-mediated oxidative stress and reduces the effects of Hg exposure with fish consumption.Keywords: fish oil, green tea, methylmercury, ascorbic acid, thiobarbituric acid reactive substances *To whom correspondence should be addressed. E-mail: nshinya@affrc.go.jp
IntroductionFish contains several nutrients that are beneficial to human health. However, fish has been known to contain hazardous components such as methylmercury (MeHg), which has been linked to decreased neuropsychological function and increased risk of cardiovascular diseases (Choi et al., 2009;Virtanen et al., 2007). In contrast, n-3 polyunsaturated fatty acids (PUFA) contained in fish improve brain function (Guesnet et al., 2011;Mourek and Mourek, 2011) and reduce the risk of cardiovascular diseases (Cottin et al., 2011). Some reports indicate that dietary fat can influence oxidative DNA damage, nephrotoxicity, and steroidogenic enzyme activities after MeHg exposure (Grotto et al., 2011;Jin et al., 2008Jin et al., , 2009McVey et al., 2008). However, the human diet varies widely, and some reports have shown that foodstuffs other than seafood may also prevent MeHg toxicity and accumulation (Abdalla et al., 2010;Farina et al., 2005;Lee et al., 1999;Rowland et al., 1986;Sumathi et al., 2012). Therefore, daily fish consumption may alleviate relatively few health risks.In general, the Japanese drink a few cups of green tea every day, and often accompany sushi meals with green tea. Therefore, a close relationship exists between green tea and fish oil in the Japanese diet. Canuel et al. (2006) concluded that tea might accelerate the enterohepatic MeHg cycle and contribute to temporary MeHg bioamplification in the bloodstream. Green tea contains large quantities of polyphenols that have antioxidant effects and accelerate cadmium (Cd) excretion by forming chelates (Abib et al., 2011;Yu et al., 2007;Wang et al., 2012). Some studies indicate that green tea consumption reduces the risk of coronary heart disease (Bøhn et al., 2012;Chacko et al., 2010) and prevents agerelated neurodegeneration (Andrade and Assunção, 2012). Thus, these green tea polyphenol properties may be effective against MeHg toxicity.The aim of this study was to determine the interactive influence of fish oil and green tea on the effects o...