The discovery that some of these variants (e.g., rs34182948 [NRTN] and rs112528434 [APOC1]) also display pleiotropic associations with other metabolic traits—including vitamin B complex deficiencies and triglyceride and total cholesterol levels—further supports the idea that liver enzyme pathways are integral to broader metabolic homeostasis 13. Here, NRTN is linked to vitamin B12 deficiency.