(PA-235) Imbalance of Glycine Metabolism Contributes to Osteolysis in Multiple Myeloma

Metabolic imbalance is a critical factor in the process of bone remodeling and regulation.Our previous work indicates that glycine is enriched in multiple myeloma (MM) and promotes the progression of MM. However, it remains unclear whether enriched glycine regulates bone remodeling in myeloma.

Methods:   

Bone marrow and serum samples of MM patients were collected in multiple clinical institutions. Differential metabolites were screened by targeted metabolomics and high performance liquid chromatography. Osteoclastogensis using Raw 264.7 cells in vitro, 5TGM1 MM mice fed with a high-level glycine diet in vivo were performed to explore the effect of glycine on osteolysis. Pull-down and chip screening methods were used to identify the interacting proteins with Biotin-Glycine in the process of osteoclastogensis.

Results:   

The concentration of glycine increased significantly in MM patients with osteolysis

To screen the differential metabolites between MM patients with and without osteolytic destruction , we analyzed the spectral intensities of metabolites using SIMCA-P 14.1 software and MetaboAnalyst 5.0. Targeted metabolomics Q300 sequencing analysis revealed the characteristic metabolites of osteolytic MM patients and identified multiple amino acid metabolic abnormalities. Especially, the concentration of glycine was significantly increased in MM patients with osteolysis. The clinical characteristic analysis showed that the glycine concentration in MM patients was positively correlated with bone dissolution.

High-level glycine promotes osteolysis in MM

To explore the underlying mechanisms of the effect of glycine on osteoclasts differentiation, we cultured PBMC/BMM/Raw 264.7 with different concentration of glycine media ，TRAP staining shows high-level glycine can promote osteoclast differentiation.Osteolysis in MM mice was more severe after being fed with high-level glycine feed，with higher concentrations of CTX-1 and PINP, together with lower BV/TV, Tb.N, and Tb.Th of micro-CT analysis. 

The interaction of PGK1/PKM and glycine promotes the formation of MM osteoclasts

To examine the molecular mechanism of glycine in osteolysis, Pull-down and chips assay were used to detect the proteins interacting with Biotin -Glycine in Raw 264.7 cells. Mass spectrometry detection revealed that most of the proteins interacting with glycine were involved in glucose metabolism and the tricarboxylic acid cycle,such as PGK1 and PKM. Knockdown PGK1/PKM leads to a decrease in osteoclast differentiation.The level of  PGK1 and PKM were significantly increased in MM patients with osteolytic destruction.The above results suggests that the interaction of PGK1/PKM and glycine promotes the osteoclasts differentiation.

Conclusions:   

In summary, our current research results indicate that the elevated glycine is associated with the occurrence of osteolysis in patients with MM, and glycine promotes the occurrence of osteolysis by interacting with glycolysis-related proteins PGK1 and PKM.