Effects of saturated and unsaturated fatty acids on estimated desaturase activities during a controlled dietary intervention

Background and aimsDirect measurement of desaturase activities are difficult to obtain in humans. Consequently, surrogate measures of desaturase activity (estimated desaturase activities) have been frequently used in observational studies, and estimated Δ9- (or stearoyl-CoA-desaturase (SCD)), Δ6- and Δ5-desaturase activities have been associated with cardiometabolic disease. Data on how the markers of desaturase activities are modified by changes in dietary fat quality are lacking and therefore warrant examination.Methods and resultsIn a two-period (three weeks) strictly controlled cross-over study, 20 subjects (six women and 14 men) consumed a diet high in saturated fat (SAT-diet) and a rapeseed oil diet (RO-diet), rich in oleic acid (OA), linoleic acid (LA) and α-linolenic acid (ALA). Estimated desaturase activities were calculated as precursor to product FA ratios in serum cholesteryl esters and phospholipids. The estimated SCD [16:1 n-7/16:0] and Δ6-desaturase [20:3 n-6/18:2 n-6] was significantly higher while Δ5-desaturase [20:4 n-6/20:3 n-6] was significantly lower in the SAT-diet (P < 0.001 for all), compared to the RO-diet. The serum proportions of palmitic, stearic, palmitoleic and dihomo-γ-linolenic acids were significantly higher in the SAT-diet while the proportions of LA and ALA were significantly higher in the RO-diet.ConclusionThis is the first study to demonstrate that surrogate measures of desaturase activities change as a consequence of an alteration in dietary fat quality. Both the [16:1/16:0]-ratio and 16:1 seem to reflect changes in saturated fat intake and may be useful markers of saturated fat intake in Western countries.