Leptin Regulates Intervertebral Disc Calcification and Ossification by Promoting Glycolysis Through OCN/HIF-1α Axis

During intervertebral disc degeneration (IDD), cartilage endplate (CEP) cells undergo calcification and ossification, relying primarily on glycolysis for energy metabolism. Leptin (LEP) initiates the IDD, while its underlying mechanism related to glycolysis remains elusive in CEP cells. To investigate the underlying mechanism of LEP on IDD, an IDD rat model was established and LEP-added CEP cells were adopted, with a glycolysis inhibitor (2-DG) and sh-HIF-1α. A rat IDD model was successfully established, with the model group exhibiting endplate calcification, ossification, and increased LEP levels. In vitro experiments confirmed that LEP dose-dependently promotes calcification and ossification in CEP cells. LEP also upregulated calcification-related indicators (BMP-2, Sox9) and osteogenesis-related genes (OCN, Runx2), inducing the formation of calcified nodules and increased ALP activity. Mechanistic studies revealed that glycolysis-related proteins and lactic acid content in both IDD rat and LEP-added CEP cells were elevated. This process could be reversed using the glycolysis inhibitor 2-DG. Further experiments demonstrated that LEP promoted glycolysis by upregulating the OCN/HIF-1α axis; knockdown of either OCN or HIF-1α blocked LEP-induced calcification and ossification. LEP is elevated in IDD, and LEP accelerates the calcification and ossification through stimulating glycolysis by the OCN/HIF-1α axis.