PFKM Modulates Porcine Skeletal Muscle Satellite Cell Differentiation Through Metabolic and Mitochondrial Pathways

To preliminarily elucidate the bidirectional metabolic effects caused by changes in PFKM expression, provide research clues for further investigation of the molecular mechanisms through which PFKM regulates porcine skeletal muscle metabolism and myogenic differentiation, and offer a reference for identifying candidate genes associated with meat production traits and studying gene regulation in pig breeding, this study compared skeletal muscle protein expression profiles between Large White and Bama pigs. Candidate regulatory factors related to muscle growth and energy metabolism were screened, and the effects of altered muscle-type phosphofructokinase (PFKM) expression on metabolic homeostasis and myogenic differentiation in porcine skeletal muscle satellite cells (SMSCs) were preliminarily evaluated. Longissimus dorsi muscle tissues from Large White and Bama pigs were analyzed using iTRAQ-based proteomics. A total of 2040 reliably quantified proteins were identified, of which 51 were relatively upregulated in Large White pigs and 73 were relatively upregulated in Bama pigs. Functional enrichment analysis showed that the differentially expressed proteins were mainly involved in glycolysis, mitochondrial energy metabolism, protein synthesis, and the regulation of muscle fiber structure and function. PFKM was therefore selected as a key candidate differentially expressed protein. Porcine SMSC models comprising a PFKM knockdown group (PFKM-KD), a PFKM overexpression group (PFKM-OE), and a normal control group (PFKM-CON) were subsequently established. Glucose consumption and lactate accumulation in the culture medium, ATP levels, reactive oxygen species (ROS), mitochondrial membrane potential, apoptosis, mitochondrial dynamics-related proteins, and myogenic differentiation markers were then examined. Compared with the PFKM-CON group, the PFKM-OE group showed significantly increased glucose consumption and lactate accumulation, together with significant increases in ROS levels, mitochondrial membrane potential, and apoptosis, whereas ATP levels were significantly reduced. In the PFKM-KD group, glucose consumption and lactate accumulation were significantly decreased, accompanied by reductions in mitochondrial membrane potential, ROS, ATP levels, and apoptosis. PFKM overexpression mainly induced oxidative stress, ATP depletion, and increased apoptosis, whereas PFKM knockdown primarily reduced mitochondrial membrane potential, ROS, and ATP levels, indicating a relatively low-metabolic state. Both treatments were accompanied by dysregulated expression of the mitochondrial dynamics-related proteins DRP1, MFN2, and OPA1, although their patterns of change were not identical. Western blotting and immunofluorescence consistently showed that the expression levels of the myogenic differentiation markers MyoD and MYH were significantly lower in both the PFKM-KD and PFKM-OE groups than in the control group, suggesting that either excessive or insufficient PFKM expression may impair the myogenic differentiation potential of SMSCs. In conclusion, changes in PFKM expression are closely associated with glycolysis-related metabolism, energy and redox homeostasis, mitochondrial function-related indicators, and myogenic differentiation capacity in porcine SMSCs. The normal biological function of PFKM may therefore depend on its expression being maintained within an appropriate range.