UC Davis

High-grain diets are commonly fed to increase the deposition of marbling fat in finishing beef cattle. While feeding grain-based diets is essential for producing high-quality beef, it can shift ruminal biohydrogenation pathways towards t10-18:1 and t10, c12-CLA as intermediates instead of t11-18:1 and c9, t11-CLA. The t10, c12-CLA has been consistently shown to have anti-lipogenic properties in bovine adipocyte cultures. However, bioactivities of other biohydrogenation intermediates (BHI) including t10-18:1, t11-18:1, and c9, t11-CLA are still unclear. Therefore, we sought to provide a clearer view of adipogenic and lipogenic effects of key BHI (t10,c12-CLA, c9, t11-CLA, t10-18:1, and t11-18:1) on stromovascular fraction (SVF) and dedifferentiated fat (DFAT) cells obtained from beef intramuscular adipose tissue. Confluent SVF and DFAT cells were exposed to media containing adipogenic inducers (dexamethasone, 3-isobutyl-1-methylxanthine) and 0, 5, 10, or 20 µM of BHI treatments for 6 days followed by Oil Red O staining, fatty acid, qPCR, and GPDH activity assays. DFAT-derived mature adipocytes, regardless of the BHI treatment, showed a higher supplemented fatty acid incorporation and CCAAT/Enhancer-binding protein α (C/EBP α) expression compared to SVF adipocytes. Oil Red O staining showed that t10-18:1 treatment reduced lipid accumulation compared to other BHI treatments in both SVF and DFAT adipocytes, without impacting lipogenic genes. Conversely, t10, c12-CLA significantly reduced SCD1 expression compared to other BHI treatments in both cell models, which was accompanied by reduced 18:1/18:0 and 16:1/16:0 ratios. In conclusion, our findings suggest that both t10-18:1 and t10, c12 CLA may negatively impact marbling development in beef cattle, while t11-18:1 and c9, t11-CLA are neutral in this regard. More in vitro and in vivo studies are needed to elucidate the mechanisms by which t10-18:1 and t10, c12-18:2 may affect marbling development in beef cattle, including their potential synergistic effects on adipogenesis and lipogenesis in bovine adipocytes.