Regulatory Role and Mechanism of the AMPK Signaling Pathway in Postmortem Lipid Metabolism and Its Impact on Meat Quality in Tan Sheep

To elucidate the regulatory role of the AMP-activated protein kinase (AMPK) signaling pathway in postmortem lipid metabolism and its impact on meat quality in Tan sheep, three groups were established, namely, an AICAR (5-aminoimidazole-4-carboxamide ribonucleotide) activation group, a compound C (dorsomorphin) inhibition group, and a blank control group. Dynamic changes during the postmortem aging process were characterized in AMPK and its downstream targets, energy metabolism, lipid-metabolizing enzyme activities, fatty acid composition, antioxidant capacity, lipid oxidation, and meat quality traits. The results indicated that, compared with the blank and compound C groups, the expressions of AMPK, phosphorylated AMPKα (p-AMPKα), and phosphorylated acetyl-CoA carboxylase (p-ACC) were significantly upregulated in the AICAR group (P < 0.05), while the activities of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) were reduced and adipose triglyceride lipase (ATGL) activity was enhanced, thereby facilitating fatty acid β-oxidation and resulting in a significant decrease in saturated fatty acids (SFAs) levels and accelerated oxidative degradation of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). In terms of energy metabolism, adenosine triphosphate (ATP) consumption was accelerated (P < 0.05), while adenosine monophosphate (AMP) remained relatively stable. Regarding antioxidant properties, total antioxidant capacity (T-AOC) was elevated and the accumulation rate of thiobarbituric acid reactive substances (TBARS) was slowed down. With respect to meat quality, higher lightness (L*), lower redness (a*), stable yellowness (b*), reduced cooking loss, increased myofibrillar fragmentation index (MFI), and decreased shear force were observed. Opposite trends were detected in the compound C group. In summary, the AMPK signaling pathway can improve the fatty acid composition, color, tenderness, and water-holding capacity of Tan sheep meat during postmortem aging by coordinately regulating lipid metabolism, fatty acid oxidation, energy metabolism remodeling, and antioxidant capacity. This finding provides theoretical and practical implications for optimizing meat quality.