BACKGROUND:Osteoporosis is a significant contributor to the global burden of disease and disability.Plasma proteins are involved in complex biological processes and play a crucial role in uncovering disease mechanisms and identifying potential therapeutic targets.Although existing studies have suggested an association between plasma proteins and osteoporosis,the causal nature of these associations is not fully clarified.Therefore,it is imperative to identify the causal proteins associated with osteoporosis and potential therapeutic targets for the amelioration and management of this condition using large-scale plasma protein data.OBJECTIVE:To evaluate the causal relationship between plasma proteins and osteoporosis based on the UK Biobank database as source information using the two-sample Mendelian randomization.METHODS:A total of 1 001 plasma protein-related genome-wide significant quantitative trait loci(P<5×10-8)were obtained from the UK Biobank database and used as instrumental variables,with linkage disequilibrium excluded.Summary data on osteoporosis were collected from the FinnGen database,which included 438 872 individuals of European descent.The study was analyzed using inverse variance weighting,MR-Egger regression,weighted median,and several sensitivity analyses to ensure the robustness of the results.Further,a protein-protein interaction network was constructed,and Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis were conducted to explore the functional relevance and potential mechanisms of plasma proteins.RESULTS AND CONCLUSION:(1)The Mendelian randomization analysis using the inverse variance weighted method identified 50 plasma proteins that have causal associations with osteoporosis(P<0.05).Among them,20 plasma proteins,including chromosome 19 open reading frame 12(odds ratio[OR]=0.610;95%confidence interval[CI]:0.483-0.769,P=2.967×10-5)and epidermal growth factor(EGF;OR=0.877;95%CI:0.770-0.999,P=0.049),might be associated with a reduced risk of osteoporosis.In contrast,30 plasma proteins,such as C-C motif chemokine ligand(CCL)18(OR=1.091;95%CI:1.037-1.147,P=0.001)and CD209(OR=1.036;95%CI:1.003-1.070,P=0.034),might be associated with an increased risk of osteoporosis.After Bonferroni correction,only chromosome 19 open reading frame 12 showed a significant causal association with osteoporosis.(2)Multiple sensitivity analyses revealed no evidence of pleiotropy or heterogeneity,indicating the robustness of the results.(3)The construction of the PPI network identified core proteins such as EGF,CCL5,C-X-C motif chemokine ligand(CXCL)13,CXCL5,vascular endothelial growth factor C,CCL17,CCL18,TEK receptor tyrosine kinase,tyrosine kinase with immunoglobulin like and EGF like domains 1,and CCL23.(4)Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested that these plasma proteins play essential roles in the immune system,influencing osteoporosis through processes such as signal transduction,cell migration,and chemotaxis.(5)This study reveals the potential causal associations between 1 001 plasma proteins and osteoporosis,highlighting the utility of a large-scale,data-driven approach to identify new biomarkers and drug targets in diverse populations.Additionally,our findings suggest that processes such as immune signaling,cell migration,and chemotaxis play significant roles in the pathogenesis of osteoporosis,offering new directions for research under specific genetic backgrounds and environmental factors.Finally,the core proteins identified in this study(e.g.,EGF,CCL5,and CXCL13)may serve as novel biomarkers or therapeutic targets,providing a new basis for the precise prevention and treatment of osteoporosis.

BACKGROUND:Osteoporosis is a significant contributor to the global burden of disease and disability.Plasma proteins are involved in complex biological processes and play a crucial role in uncovering disease mechanisms and identifying potential therapeutic targets.Although existing studies have suggested an association between plasma proteins and osteoporosis,the causal nature of these associations is not fully clarified.Therefore,it is imperative to identify the causal proteins associated with osteoporosis and potential therapeutic targets for the amelioration and management of this condition using large-scale plasma protein data.OBJECTIVE:To evaluate the causal relationship between plasma proteins and osteoporosis based on the UK Biobank database as source information using the two-sample Mendelian randomization.METHODS:A total of 1 001 plasma protein-related genome-wide significant quantitative trait loci(P<5×10-8)were obtained from the UK Biobank database and used as instrumental variables,with linkage disequilibrium excluded.Summary data on osteoporosis were collected from the FinnGen database,which included 438 872 individuals of European descent.The study was analyzed using inverse variance weighting,MR-Egger regression,weighted median,and several sensitivity analyses to ensure the robustness of the results.Further,a protein-protein interaction network was constructed,and Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis were conducted to explore the functional relevance and potential mechanisms of plasma proteins.RESULTS AND CONCLUSION:(1)The Mendelian randomization analysis using the inverse variance weighted method identified 50 plasma proteins that have causal associations with osteoporosis(P<0.05).Among them,20 plasma proteins,including chromosome 19 open reading frame 12(odds ratio[OR]=0.610;95%confidence interval[CI]:0.483-0.769,P=2.967×10-5)and epidermal growth factor(EGF;OR=0.877;95%CI:0.770-0.999,P=0.049),might be associated with a reduced risk of osteoporosis.In contrast,30 plasma proteins,such as C-C motif chemokine ligand(CCL)18(OR=1.091;95%CI:1.037-1.147,P=0.001)and CD209(OR=1.036;95%CI:1.003-1.070,P=0.034),might be associated with an increased risk of osteoporosis.After Bonferroni correction,only chromosome 19 open reading frame 12 showed a significant causal association with osteoporosis.(2)Multiple sensitivity analyses revealed no evidence of pleiotropy or heterogeneity,indicating the robustness of the results.(3)The construction of the PPI network identified core proteins such as EGF,CCL5,C-X-C motif chemokine ligand(CXCL)13,CXCL5,vascular endothelial growth factor C,CCL17,CCL18,TEK receptor tyrosine kinase,tyrosine kinase with immunoglobulin like and EGF like domains 1,and CCL23.(4)Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested that these plasma proteins play essential roles in the immune system,influencing osteoporosis through processes such as signal transduction,cell migration,and chemotaxis.(5)This study reveals the potential causal associations between 1 001 plasma proteins and osteoporosis,highlighting the utility of a large-scale,data-driven approach to identify new biomarkers and drug targets in diverse populations.Additionally,our findings suggest that processes such as immune signaling,cell migration,and chemotaxis play significant roles in the pathogenesis of osteoporosis,offering new directions for research under specific genetic backgrounds and environmental factors.Finally,the core proteins identified in this study(e.g.,EGF,CCL5,and CXCL13)may serve as novel biomarkers or therapeutic targets,providing a new basis for the precise prevention and treatment of osteoporosis.