APOC1 and vitamin B12 deficiency: 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.