Exogenous effects of alpha-linolenic and linoleic acid on the fatty acid distribution and the regulation of lipid metabolism in ruminant tissues
This work is concerned with the exogenous effects of alpha-linolenic (ALA) and linoleic acid (LA) on the fatty acid distribution and the regulation of lipid metabolism in ruminant tissues. Two animal experiments were conducted to investigate the effect of diets enriched in ALA or LA in German Simmental and Holstein bulls. The influence of LA and ALA enriched diets on the protein expression of lipogenic enzymes in cattle, the tissue specific differences and the relationship between protein expression of lipogenic enzymes, enzyme activities and the products of these enzymes as well as the absorption and deposition of n-3 and n-6 fatty acids in ruminants and beef products was analyzed. Feeding a diet enriched in LA or ALA results in an increased deposition of these fatty acids, induced chain elongation, desaturation and deposition of the long-chain products in tissues of ruminants. Essential fatty acids are preferentially deposited in longissimus muscle (MLD) compared to subcutaneous adipose tissue (SAT) and also preferred in erythrocytes; conclusively they are good long-time marker for the fatty acid intake. Despite the low proportion of de novo fatty acid synthesis in the liver of ruminants the concentration of n-3 fatty acids and de novo synthesised n-3 long chain polyunsaturated fatty acids is much higher compared to MLD. Summarizing, there is a tissue specific incorporation and deposition of n-6 and n-3 fatty acids depending on the function of the respective tissue. The production conditions of German Corned beef and tea sausage spread made from the meat of the German Holstein bulls did not lead to a loss of beneficial n-3 fatty acids. The SCD protein expression and the enzyme activity are more inhibited by n-3 fatty acids than by n-6 fatty acids in different tissues of bulls. It is of interest to figure out the mechanisms how the tissue-specific effect of Δ6D works on protein expression level and on the level of activity.