Purpose: The beneficial effects of a seafood-rich diet are highly documented and can be attributed to both n-3 polyunsaturated fatty acids and other less studied nutritional components including protein and antioxidants. The aim of the work was to investigate whether an under-utilized seafood source, eggs (roe) and sperm (milt) from herring (Clupea harengus), can affect lipid metabolism and inflammation in a mouse model transgenic for human tumor necrosis factor alpha (hTNFα).
Methods: A high-fat control diet (25% total fats, 20% protein, w/w) or high-fat diets supplemented with herring roe (3.7% fat, 15% protein, w/w), or milt (1.3% fat, 15% protein) were administered to female C57BL/6 hTNFα mice. After 2 weeks, hepatic enzyme activity, gene expression, lipid and fatty acid composition, fatty acid composition of epididymal adipose tissue, and plasma lipid and cytokine levels were determined.
Results: Animals fed herring roe and milt displayed an increased hepatic fatty acid β-oxidation and reduced fatty acid synthase activity. However, while plasma TAG was reduced, hepatic TAG and plasma and hepatic cholesterol levels were increased by the herring diets. Both herring diets led to a substantial shift in the n-6:n-3 ratio in both liver and ovarian white adipose tissue. The herring diets also increased plasma carnitine and reduced the carnitine precursor trimethyllysine. Plasma short-chained acylcarnitine esters were significantly increased, which may reflect an increased β-oxidation of long-chained fatty acids. In addition, the diets tended to reduce the plasma levels of pro-inflammatory cytokines.
Conclusion: Herring roe or milt diets enhanced lipid catabolism and influenced the chronic inflammatory state in hTNFα-transgenic mice.