Metabolic Biomarkers Differentiate a Surgical Intervertebral Disc from a Nonsurgical Intervertebral Disc

Bioenergetic dysfunction in the pathogenesis of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a frequent cause of low back pain and is the most common cause of disability. Treatments for symptomatic IVD degeneration, including conservative treatments such as analgesics, physical therapy, anti-inflammatories and surgeries, are aimed at alleviating neurological symptoms. However, there are no effective treatments to prevent or delay IVD degeneration. Previous studies have identified risk factors for IVD degeneration such as aging, inflammation, genetic factors, mechanical overload, nutrient deprivation and smoking, but metabolic dysfunction has not been highlighted. IVDs are the largest avascular structures in the human body and determine the hypoxic and glycolytic features of nucleus pulposus (NP) cells. Accumulating evidence has demonstrated that intracellular metabolic dysfunction is associated with IVD degeneration, but a comprehensive review is lacking. Here, by reviewing the physiological features of IVDs, pathological processes and metabolic changes associated with IVD degeneration and the functions of metabolic genes in IVDs, we highlight that glycolytic pathway and intact mitochondrial function are essential for IVD homeostasis. In degenerated NPs, glycolysis and mitochondrial function are downregulated. Boosting glycolysis such as HIF1α overexpression protects against IVD degeneration. Moreover, the correlations between metabolic diseases such as diabetes, obesity and IVD degeneration and their underlying molecular mechanisms are discussed. Hyperglycemia in diabetic diseases leads to cell senescence, the senescence-associated phenotype (SASP), apoptosis and catabolism of extracellualr matrix in IVDs. Correcting the global metabolic disorders such as insulin or GLP-1 receptor agonist administration is beneficial for diabetes associated IVD degeneration. Overall, we summarized the recent progress of investigations on metabolic contributions to IVD degeneration and provide a new perspective that correcting metabolic dysfunction may be beneficial for treating IVD degeneration.

Causal associations between gut microbiota with intervertebral disk degeneration, low back pain, and sciatica: a Mendelian randomization study

PURPOSE

Although studies have suggested that gut microbiota may be associated with intervertebral disk disease, their causal relationship is unclear. This study aimed to investigate the causal relationship between the gut microbiota and its metabolic pathways with the risk of intervertebral disk degeneration (IVDD), low back pain (LBP), and sciatica.

METHODS

Genetic variation data for 211 gut microbiota taxa at the phylum to genus level were obtained from the MiBioGen consortium. Genetic variation data for 105 taxa at the species level and 205 metabolic pathways were obtained from the Dutch Microbiome Project. Genetic variation data for disease outcomes were obtained from the FinnGen consortium. The causal relationships between the gut microbiota and its metabolic pathways and the risk of IVDD, LBP, and sciatica were evaluated via Mendelian randomization (MR). The robustness of the results was assessed through sensitivity analysis.

RESULTS

Inverse variance weighting identified 46 taxa and 33 metabolic pathways that were causally related to IVDD, LBP, and sciatica. After correction by weighted median and MR-PRESSO, 15 taxa and nine pathways remained stable. After FDR correction, only the effect of the genus_Eubacterium coprostanoligenes group on IVDD remained stable. Sensitivity analyses showed no evidence of horizontal pleiotropy, heterogeneity, or reverse causation.

CONCLUSION

Some microbial taxa and their metabolic pathways are causally related to IVDD, LBP, and sciatica and may serve as potential intervention targets. This study provides new insights into the mechanisms of gut microbiota-mediated development of intervertebral disk disease.