Assessment of punctual ∆9-desaturase activity in porcine adipose tissue

Δ9-desaturase activity is often measured through the monounsaturated/saturated fatty acids ratio of adipose tissue. This value is the result of the whole of anabolic and catabolic lipid processes that happened throughout the entire life of the animal and does not reflect the activity at a given time. Moreover, this value is masked by fatty acids deposited directly from the diet. To evaluate the punctual activity of the stearoyl-CoA desaturase enzyme (SCD) an experiment was carried out by adding deuterium-labelled stearic acid (C18:0D35) to the diet. Thus, 24 growing pigs weighing 25-30kg were used: 8 entire F2 (Pietrain ♂ x (Duroc x Landrace) ♀) and 16 castrated purebred Duroc pigs, 8 CC/ 8 TT for the SCD genotype (g.2228T>C polymorphism in the promoter of the SCD responsible for enhanced biosynthesis of oleic acid by desaturating stearic acid). Each variety was subdivided in 2 groups that were fed for 7 days with 2 levels of crude protein [15% low protein (LP); 17% normal protein (NP)]. A 0.02% of C18:0D35 was incorporated in all diets. Blood samples were collected daily for 5 days before culling and subcutaneous adipose was sampled after culling. Desaturation ratio of stearic acid in adipose tissue (14.88±0.49; 12.49±0.49; 10.42±0.45 for F2, OO and NN respectively) was different among genotypes and higher than those reported at 90kg of live weight. No diet interaction was detected. Nevertheless, punctual Δ9-desaturase activity measured as desaturation ratio of C18:0D35, reach much lower values and differences between genotypes were only significant in the LP diet (0.083±0.014; 0.058±0.012; 0.016±0.012 for F2, OO and NN genotypes respectively).