Intramuscular fat (IMF) is closely related to the tenderness, juiciness, and flavor of beef, and is an important indicator for beef quality assessment internationally. The main components of skeletal intramuscular fat (IMF) are phospholipids and triacylglycerols (TAG), and the final step of TAG biosynthesis is catalyzed by diacylglycerol acyltransferase 2 (DGAT2). To explore the effect of DGAT2 on the differentiation of bovine muscle satellite cells (BSCs) and its role in the signaling pathway related to lipid metabolism, the adenovirus overexpression and interference vector of the DGAT2 gene was constructed in this study, and the overexpression adenovirus Ad-DGAT2 and interfering adenovirus sh-DGAT2 were used to infect BSCs. Overexpression of DGAT2 resulted in a significant increase in the contents of TAG and ADP, and the mRNA and protein expression levels of PPARγ, C/EBPα, and SREBF1 (p < 0.05). Interfering with the expression of DGAT2 reduced the intracellular TAG content and lipid droplet accumulation. Furthermore, the mRNA and protein expression levels of PPARγ, C/EBPα, and SREBF1 (p < 0.05) were significantly downregulated. Transcriptome sequencing showed that a total of 598 differentially expressed genes (DEGs) were screened in BSCs infected with Ad-DGAT2, and these DEGs included 292 upregulated genes and 306 downregulated genes. A total of 49 DEGs were screened in BSCs infected with sh-DGAT2, and these DEGs included 25 upregulated and 24 downregulated genes. KEGG enrichment analysis showed that the DEGs, after overexpression of DGAT2, were mainly enriched in the PPAR signaling pathway, and the fat digestion and absorption, glycerophospholipid metabolism, fatty acid biosynthesis, and AMPK signaling pathways. The DEGs obtained after interfering with DGAT2 were mainly enriched in the metabolic pathways, such as the PPAR signaling pathway and PI3K/AKT signaling pathway. In summary, our study demonstrated that the lipid droplet formation, TAG accumulation, and adipogenic gene expression in BSCs overexpressing DGAT2 were higher than those in the control cells. These results highlight the important role of DGAT2 in regulating BSCs during adipogenic transdifferentiation and underscore the complexity of intramuscular adipogenesis.

Skeletal muscle satellite cells have the ability to differentiate into various cells under different conditions. This study aimed to investigate the effects of different concentrations of oleic acid (50, 100, and 200 µmol/L) on the process of lipogenic transdifferentiation in Yanbian bovine satellite cells, as well as its molecular regulatory mechanism. After inducing differentiation with oleic acid for 96 h, it was observed that the addition of oleic acid resulted in the formation of lipid droplets in the bovine satellite cells, and the triglyceride content showed a dose-dependent relationship with the concentration of OA. qPCR results demonstrated a significant downregulation of myogenesis-related factors (Pax3 and MyoD) and upregulation of lipogenesis-related factors (C/EBP-β and PPARγ) (p < 0.05). Fatty acid metabolism-related factors, SCD and PLIN2, were also significantly upregulated (p < 0.05). These finding were consistent with the results obtained from Western blotting. Transcriptome sequencing analysis identified 278 differentially expressed genes between the control group and the groups treated with OA. KEGG enrichment analysis showed that differentially expressed genes were mainly concentrated in the adenosine monophosphate-activated protein kinase signaling pathway and fatty acid metabolic pathway. Our study presents that the OA induction of Yanbian bovine skeletal muscle satellite cells can promote cellular lipid transdifferentiation and reveals the potential genes and pathways related to OA induction of these satellite cells.

This study developed a compound enzyme-assisted microbially fermented concentrate for Yanbian steers. The enzyme formulation was optimized using response surface methodology, with acid-soluble protein/crude protein ratio (ASP/CP), ammonia-N/total N ratio (AN/TN), and pH as response variables. The optimized enzyme preparation contained 619.15 U/g protease, 742.08 U/g amylase, and 257.75 U/g β-mannanase. The measured ASP/CP, AN/TN, and pH values were 31.74%, 3.56%, and 4.32, respectively, closely agreeing with the predicted values of 32.00%, 3.55%, and 4.28. Membership function analysis, which normalized positive and negative indicators to a common 0–1 scale and integrated them into a comprehensive score, supported the selection of day 5 as the most balanced fermentation duration under the primary equal-indicator weighting scheme. Thirty Yanbian steers were randomly assigned to receive microbially fermented concentrate without compound enzyme addition (MF) or compound enzyme-assisted microbially fermented concentrate (MEF) at 500 g/head/day on an as-fed basis for 100 days. After adjustment for initial body weight using ANCOVA, MEF increased final body weight by 3.9% and average daily gain by 35.7% compared with MF (both p < 0.001). MEF also increased dry matter intake by 12.1% (p = 0.018) and reduced feed conversion ratio by 18.4% (p = 0.008). MEF increased dry matter, crude protein, neutral detergent fiber, and acid detergent fiber digestibility by 4.3%, 5.4%, 22.6%, and 15.6%, respectively, and reduced blood urea nitrogen by 18.9%. MEF also increased ruminal total volatile fatty acids and decreased ruminal NH₃-N and the acetate-to-propionate ratio (p < 0.05). Observed ASVs, Chao1, and Shannon indices did not differ between treatments, whereas PERMANOVA detected a significant difference in overall rumen bacterial community structure (R² = 0.180, p = 0.023). VIF-based redundancy analysis indicated that variation in rumen bacterial community structure were correlated with crude protein digestibility, total volatile fatty acids, and blood urea nitrogen. Overall, within the microbial-fermentation system evaluated in this study, compound enzyme addition increased growth performance and apparent nutrient digestibility, reduced ruminal NH₃-N and blood urea nitrogen concentrations, and improved feed efficiency in Yanbian steers.