Metabolic signatures of genetically elevated vitamin D among Chinese: observational and Mendelian randomization study

BACKGROUND Observational studies have suggested that higher circulating 25-hydroxyvitamin D [25(OH)D] levels were associated with favorable serum lipids and related metabolites. However, if such observations reflect causality remains unclear. OBJECTIVE We aimed to investigate the causal effect of elevated 25(OH)D with the detailed systemic metabolite profile in Chinese adults. METHODS A total of 225 lipid and other metabolites were quantified in 4,662 individuals in China Kadoorie Biobank. Instrumental variable analyses were performed to test the causal associations of plasma 25(OH)D with the lipids and metabolites. RESULTS Higher plasma 25(OH)D was related to favorable lipid profiles in observational analyses. The genetic risk score was robustly correlated with observed 25(OH)D (beta[SE]= 3.54 [0.32]; P<1×10 -5, F-statistic =122.3) and explained 8.4% of the variation in 25(OH)D in the Chinese population. For all individual metabolites, the causal estimates were not significant for at the threshold P<5×10 -4 (multiple testing corrected). However, the MR estimate showed that per 1-SD increase in genetically determined 25(OH)D was suggestive associated with decreased levels of cholesterol, lipoprotein particle, phospholipids within very small very low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL) (P≤0.05, nominal significance). For amino acids, fatty acids, ketone bodies, glycoprotein acetyls, fatty acids and other traits, we did not observe any significant causal association. CONCLUSIONS The MR analysis of metabolic data based a population-based cohort suggested a potential causal association of plasma 25(OH)D with cholesterol, lipoprotein particle, phospholipids concentrations and total lipids within very small VLDL and IDL. Our findings highlight long-term effect of 25(OH)D levels in maintaining healthy lipid metabolism.