Conjugated linoleic acid (t-10, c-12) reduces fatty acid synthesis de novo, but not expression of genes for lipid metabolism in bovine adipose tissue ex vivo

We hypothesized that exogenous fatty acids, and especially or 18:2 trans-10, cis-12 conjugated linoleic acid (CLA), would decrease adipogenic and lipogenic gene expression and de novo fatty acid biosynthesis in intramuscular (i.m.) and subcutaneous (s.c.) adipose tissues. Fresh i.m. and s.c. adipose tissues were collected from the longissimus thoracis muscle of Angus steers at 12, 14, and 16 months of age (n = 4 per time point). Adipose tissue explants were incubated in duplicate for 48 h with 40 μM α-linolenic (ALA), oleic, stearic, trans-vaccenic, or CLA. Adipocyte size, acetate and glucose incorporation into fatty acids in vitro and mRNA levels for C/EBPβ, CPT1β, GPR43, PPARγ, PRKAA1 (AMPKα) and SCD1 were measured following the incubations. PRKAA1 and SCD1gene expression were greater (P < 0.001) in s.c. adipose tissue than in i.m. adipose tissue and acetate incorporation into lipids and C/EBPβ, PPARγ, and SCD1gene expression were greater at 16 months of age than at 12 months of age in i.m. adipose (P < 0.01). C/EBPβ gene expression increased by 16 months of age and PRKAA1 gene expression decreased by 16 months of age in s.c. adipose tissue. All fatty acids increased s.c. adipocyte volumes whereas CLA decreased acetate incorporation into lipids in s.c. adipose tissue (P < 0.05), but none of the fatty acids affected gene expression in i.m. or s.c. adipose tissue (P > 0.10). Thus, CLA depressed de novo fatty acid biosynthesis from acetate but neither CLA nor other fatty acids significantly affected adipogenic or lipogenic gene expression.