It is known that ethanol and its metabolites influence several key enzymes of the methionine-homocysteine cycle (Figure 1, e.g., they inhibit methionine synthase (MS), activate betaine homocysteine methyltransferase (BHMT), and possibly inhibit methionine adenosyltransferase (MAT)) and thus ethanol has a homocysteine-increasing effect, depletes liver S-adenosylmethionine (SAM), and causes fatty liver disease [9]. The gene discussed is BHMT; the disease is fatty liver disease.