Figure 1: Cellular metabolism of betaine. Betaine is found in beets, wheat bran, seafood, and spinach. Once it enters the cell through betaine/GABA transporter 1 (BGT-1- SLC6A12) and proton/amino acid transporters (PAT1 and PAT2, SLC36A1 and A2 respectively), it is metabolized according to the methionine cycle to synthesize methionine from homocysteine. Also, in the mitochondria, betaine can be directly synthesized from choline in small quantities. All the pathway enzymes refer human metabolism: Choline dehydrogenase (CDH); Betaine-aldehyde dehydrogenase (BADH); Betaine-homocysteine methyltransferase (BHMT); Methionine synthase (MS); Methionine adenosyltransferase (MAT).