PDK4 knockdown suppresses osteoclast differentiation in osteoporosis through glycolytic flux suppression and AMPK activation.

Abstract

Osteoporosis (OP) is a metabolic bone disorder primarily driven by excessive osteoclast-mediated bone resorption. Metabolic reprogramming, particularly a shift toward glycolysis, is crucial for osteoclast differentiation. However, the key regulators linking metabolism to bone resorption remain incompletely defined. Bioinformatic analysis identified pyruvate dehydrogenase kinase 4 (PDK4) as a key glycolysis-associated gene in OP. Its role was validated using PDK4-knockdown RAW264.7 cells stimulated with receptor activator of nuclear factor kappa-B ligand (RANKL) and ovariectomized (OVX) rat models treated with PDK4-knockdown lentivirus, with or without the AMP-activated protein kinase (AMPK) inhibitor Dorsomorphin in each setting. Western blot was conducted to assess the expression of osteoclast differentiation markers and glycolysis-associated proteins. Glycolytic flux was determined by measuring glucose uptake, intracellular ATP, and lactate levels. Bone microstructure was evaluated by micro-computed tomography, while osteoclast activity was examined by tartrate-resistant acid phosphatase (TRAP) staining. PDK4 was significantly upregulated in RANKL-induced osteoclasts. PDK4 knockdown suppressed the expression of osteoclast differentiation markers and glycolytic flux in vitro. Mechanistically, PDK4 silencing activated the AMPK pathway. The anti-osteoclastic effects of PDK4 knockdown were reversed by the AMPK inhibitor Dorsomorphin. In OVX rats, PDK4 knockdown ameliorated bone loss, reduced osteoclast activity and markers, and suppressed glycolysis-associated protein expression in femur tissues. These therapeutic benefits were again negated by co-administration of Dorsomorphin. PDK4 knockdown suppresses osteoclastogenesis and OP progression by suppressing glycolysis via activating the AMPK pathway. Targeting the PDK4-AMPK-glycolysis axis presents a novel metabolic strategy for OP treatment.