Influence of Dietary Protein on 6- and 9-Desaturation of Fatty Acids in Rats of Different Ages and in Different Seasons

The effect of casein diets on the activity of linoleic acid desaturation to γ-linolenic acid by rat liver microsomes was studied. An increase in the enzymatic activity was shown to be produced when either linoleoyl-CoA or free acid were incubated with ATP, CoA, and NADH. The amount of protein needed to enhance the desaturation of linoleic acid must be of the order of 35% or higher. Protein-rich diets modified the Vmax of the reaction but not the Km. The 6-desaturation of linoleic acid and α-linolenic acid decreased, but the 9-desaturation of stearic acid increased with age of the animal. Besides, the response to dietary protein was higher in old rats than in young ones. A seasonal change was also found. In summer, the 6- and 9-desaturations were significantly reduced and the activating effect of protein was also reduced.