Does Chemical Composition of Dietary Fat Sources Alter mRNA Abundance of Genes Related to Lipid Digestion and Metabolism in Pigs?

Our objective was to determine the effect of dietary fat source on the mRNA abundance in porcine tissues of genes related to lipid digestion, lipogenesis, and lipolysis. A total of 48 Genetiporc 6.0 × Genetiporc F25 (PIC, Inc., Hendersonville, TN) barrows (initial BW of 9.9 ± 0.6 kg) were randomly allotted to 1 of 6 dietary treatments in a 56 d experiment. Each experimental diet included 95% of a corn-soybean meal basal diet and then 5% of either: corn starch (CNTR), animal-vegetable blend (AV; iodine value [IV = 70.9]), coconut oil (COCO: IV = 1.1), corn oil (CORO; IV = 131.9), fish oil (FO; IV = 140.0), or tallow (TAL; IV = 46.0). Pigs were fed these experimental diets from d 0-10 and d 46-56, and fed a common diet from d 10-46. Expression normalization across samples collected post-mortem (d 56) within tissue was performed by calculating a delta cycle threshold (Ct) value for each sample using RPL32, as transcript abundance was similar among treatments (P > 0.10). Delta delta Ct (ΔΔCt) values were calculated from delta Ct values using a reference sample pooled from all experimental samples within tissue. Data were analyzed using PROC MIXED with dietary treatment as a fixed effect, replicate (2 cohorts of 24 barrows each) as a random effect, and pig as the experimental unit. Including dietary fat decreased the mRNA abundance of fatty acid synthase in adipose tissue (AT; CNTR = -1.48, AV = 0.89, COCO = 0.26, CORO = -0.15, FO = 0.96, TAL = 1.10 ΔΔCt; P = 0.031). Including fat sources with greater concentrations of oleic or linoleic acid increased mRNA abundance in AT of sterol regulatory element-binding protein-1 (CNTR = 0.59, AV = -1.64, COCO = 0.30, CORO = -2.06, FO = 1.13, TAL = 0.08 ΔΔCt; P = 0.050). Including CORO or no added dietary fat versus including TAL tended to increase mRNA abundance of stearoyl CoA desaturase in AT (CNTR = -0.71, AV = 0.09, COCO = -0.32, CORO = -1.75, FO = 0.51, TAL = 2.14 ΔΔCt; P = 0.100). Dietary treatment had no impact on the mRNA abundance of acetyl CoA carboxylase (P = 0.377), ATP citrate lyase (P = 0.422), or peroxisome proliferator-activated receptor-α (P = 0.688) in AT. In conclusion, the chemical composition among dietary fat sources alters the mRNA abundance of genes related in the synthesis and desaturation of fatty acids in AT.