Mechanisms of Adipose Tissue Metabolism in Naturally Grazing Sheep at Different Growth Stages: Insights from mRNA and miRNA Profiles

Adipose tissue metabolism plays a crucial role in sheep meat quality and the optimization of adipose tissue utilization. To reveal the molecular mechanisms of adipose tissue metabolism during growth in naturally grazing sheep, we investigated the mRNA and miRNA profiles in subcutaneous adipose tissue (SAT) from naturally grazing Sunit sheep at 6, 18, and 30 months of age (Mth-6, Mth-18, and Mth-30). We identified 927 differentially expressed (DE) genes and 134 DE miRNAs in the SAT of sheep at different growth stages. Specifically, the expressions of <i>ACACA</i>, <i>FASN</i>, <i>DGAT2</i>, <i>GPAM</i>, <i>SCD</i>, <i>ELOVL6</i>, <i>HSD17B12</i>, <i>TECR</i>, <i>PKM</i>, <i>TKT</i>, <i>PCK1</i>, <i>CD44</i>, and <i>THBS2S</i> genes were significantly upregulated in Mth-18 and Mth-30 compared to that in Mth-6. These genes promoted fatty acid synthesis, triglyceride synthesis, gluconeogenesis, and extracellular matrix-receptor interaction and decreased glycolysis, leading to increased adipocyte proliferation and fat deposition. Notably, our findings suggested that the reduced activity of the AMPK signaling pathway may be regulated by <i>CAMKK2</i> and <i>PP2A</i> during sheep growth. Furthermore, our results revealed several DE miRNAs, <i>mml-miR-320b</i>, <i>chi-miR-1388-3p</i>, <i>bta-miR-6715</i>, <i>oar-miR-143</i>, and <i>miR-424</i>, that potentially influence fat metabolism. Overall, this study provides a theoretical basis and new insights into the molecular mechanisms of adipose tissue metabolism during growth in naturally grazing sheep.