Effects of dietary n-3 fatty acids in fat metabolism and thyroid hormone levels when compared to dietary saturated fatty acids in chickens

The effects of n-3 fatty acids (FA) on serum thyroid hormones (T3, and T4), lipoprotein lipase (LPL), glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME), and L-3-hydroxyacyl-CoA-dehydrogenase (L3HOAD) activities were studied in chickens fed three diets: a basal diet low in fat and energy (BS) and two diets rich in n-3 polyunsaturated FA (10% linseed oil; LO) or in saturated FA (10% tallow; TA). Dietary FA profiles resulted in different profiles of FA in the tissues as expected. The BS diet caused lower LPL activity and fat deposition compared to the other diets. Chickens fed the LO diet showed lower abdominal fat deposition and higher L3HOAD activities (β-oxidation) and serum T3 levels than those fed the TA diet. There were no differences in lipid synthesis. Lipid β-oxidation may be more relevant than synthesis of FA in the lower fat deposition caused by n-3 FA compared to saturated FA in chicken diets. Higher serum T3 suggest a possible role of this hormone in the lower fat deposition caused by LO.