Table 6.

Two-sample Mendelian randomization results for FN-BMD and LS-BMD

Exposure (Metabolite)	Outcome (BMD)	IVW beta	IVW p-value	Weighted median beta	Weighted median p-value	Q statistic p-value	Egger regression intercept p-value
leucine	FN BMD	−0.028	0.63	−0.057	0.34	0.22	0.75
	LS BMD	0.071	0.19	0.074	0.24	0.35	0.72
glycine	FN BMD	−0.033	2.51×10−5	−0.040	6.82×10−4	0.98	0.87
	LS BMD	−0.013	0.14	−0.017	0.16	0.89	0.71
creatinine	FN BMD	0.074	0.39	0.169	0.03	0.01	1.08×10−4
	LS BMD	0.146	0.02	0.164	0.04	0.16	3.90×10−3
PC	FN BMD	−0.066	6.89×10−3	−0.043	0.19	0.84	0.05
	LS BMD	−0.136	1.84×10−7	−0.106	2.96×10−3	0.57	0.30
SM	FN BMD	−0.017	0.75	−0.011	0.84	0.06	0.21
	LS BMD	−0.145	0.01	−0.164	7.41×10−3	0.05	0.03
TAG	FN BMD	−0.065	7.46×10−3	−0.033	0.35	0.78	0.59
	LS BMD	−0.070	0.02	−0.039	0.35	0.18	0.54

Genetic information of above six metabolites (exposure) and two outcomes, FN-BMD and LS-BMD, are available from the summary statistics of GWAS.^23,24 IVW (inverse variance weighted) beta estimates the causal effect of each selected metabolite on BMD, either FN-BMD or LS-BMD. Q statistic p-value less than 0.05 indicates the instrumental heterogeneity for each selected metabolite. Egger regression intercept p-value less than 0.05 implicates the horizontal pleiotropy for the instrumental variants of each selected metabolite. IVW p-value less than 0.05 while both Q-statistics p-value and Egger regression intercept p-value greater than 0.05 was set as the significance level. Bold ones are the metabolites with significant causal effect on either FN-BMD or LS-BMD. BMD=bone mineral density. FN=femoral neck. LS=lumbar spine. IVW=inverse-variance weighted. PC=phosphatidylcholine. SM=Sphingomyelin. TAG=Triacylglycerol.