Lack of Protective Effect of Menhaden Oil Supplementation on Rat Liver Steatosis induced by a Carbohydrate-rich Diet

Liver steatosis is often attributed to dietary habits. Our previous results have shown that fatty acid synthesis is considerably increased by high carbohydrates–fat free diet (HCFF) given to rats after fasting, and leads to lipid accumulation and morphological alterations in the liver, defined as steatosis. As n-3 polyunsaturated fatty acids are able to counteract lipogenesis induction in vivo and in vitro, we hypothesized that the addition of menhaden oil in a carbohydrate-rich diet might be able to protect the liver against steatosis induced by a fasting–re-feeding transition. Male Wistar rats were first fasted for 48 hr, then re-fed ad lib. for 24 hr with either (1) standard diet; (2) high carbohydrates–fat free diet (HCFF), containing 40% (w/w) starch, 40% saccharose, 16% casein and 4% vitamin–mineral mix; or (3) the latter diet containing additionally 5% menhaden oil (HCMO) for 24 hr. Triglyceride (TG) accumulation occurred in liver tissue of rats re-fed with HCFF and HCMO diets after fasting. The addition of menhaden oil led to a strong decrease in serum TG; however, both TG and phopholipid (PL) levels, as well as fatty acid synthase activity, were increased in the liver of HCMO rats as compared with the values obtained in HCFF re-fed rats. Histologically diagnosed steatosis was even more severe when rats received HCMO than HCFF. These results indicate that menhaden oil supplementation does not avoid, but even increases, the degree of steatosis generated in vivo by re-feeding a high carbohydrate diet after fasting.