The bidirectional differentiation potential of skeletal muscle satellite cells (SMSCs) enables them to differentiate into myofibers or intramuscular adipocytes, which affects meat quality in livestock. However, how insulin regulates ovine SMSC metabolism remains poorly understood. SMSCs were isolated from the longissimus dorsi muscle of 1-day-old Hu sheep, cultured, identified, and induced to differentiate with insulin. After induction, lipid droplet formation and the number of nuclei per cell were assessed, and samples were collected before adipogenic induction (No_AD) and after adipogenic induction (AD) for qPCR and whole-transcriptome sequencing. Immunofluorescence confirmed cells were positive for PAX7 and DESMIN. Bodipy, Oil Red O, and hematoxylin staining revealed lipid droplets and multinucleated cells. Sequencing and qPCR indicated that insulin promoted fatty acid uptake and utilization, inhibited adipogenic differentiation, and promoted myogenic differentiation. Integrated ceRNA analysis suggested that miR-2447-z and MSTRG.8123.1 may coordinate muscle development and lipid metabolism. In conclusion, under insulin induction, ovine SMSCs may undergo metabolic adaptation through the ceRNA network mediated by miR-2447-z and MSTRG.8123.1, exhibiting enhanced myogenesis, suppressed adipogenesis, and lipid droplet accumulation. These findings provide new insights into insulin-regulated SMSC metabolism, suggesting that leveraging the bidirectional differentiation potential of SMSCs to in-fluence muscle characteristics and fat deposition may be a feasible approach for im-proving meat production traits in sheep.

Grass carp are prone to excessive fat deposition in intensive aquaculture, which impairs their health and reduces economic returns. Here, we investigated the effects of replacing soybean meal with ultrafine pulverized mulberry leaves combined with multi-enzyme preparations on lipid metabolism in grass carp using phenotypic and multi-omics approaches. A total of 480 grass carp (8.45 ± 0.17 g) were fed a basal diet and two experimental diets (6% and 12%) containing mulberry leaf for 60 d. Replacing soybean meal with ultrafine pulverized mulberry leaf with multi-enzyme preparations reduced serum triglyceride, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and dorsal muscle ether extract levels, downregulated hepatic glycolysis (gk, pfk, pk) and lipogenesis (fas and acc) genes and increased intestinal lipase activity. Intestinal omics identified the lysine degradation pathway as a key pathway that regulates lipid metabolism. Reduced levels of multiple differential metabolites and enhanced microbial metabolic functions are closely associated with inhibition of lipid metabolism in grass carp. The reduction in fat deposition, particularly polyunsaturated fatty acids, the downregulation of antioxidant capacity, as indicated by decreased glutathione peroxidase and superoxide dismutase activities and reduced total antioxidant capacity, along with a decrease in malondialdehyde levels, suggests that the lipid-lowering effects could alleviate oxidative stress. Replacing soybean meal with ultrafine pulverized mulberry leaves combined with multi-enzyme preparations reduced lipid deposition and alleviated oxidative stress in grass carp by regulating the gut–liver axis. When replacing soybean meal, a 12% proportion of ultrafine pulverized mulberry leaves combined with multi-enzyme preparations in the diet is recommended.