Steatosis in mice is associated with gender, folate intake, and expression of genes of one-carbon metabolism.
Disrupted choline metabolism may affect hepatic lipid metabolism and lead to steatosis. Because folate and the choline metabolite betaine independently serve as methyl donors for homocysteine (Hcy) remethylation to methionine, we assessed the impact of folate deficiency on steatosis, choline metabolism, and expression of 9 genes involved in folate-mediated one-carbon metabolism. Liver histology, choline metabolites, and mRNA and protein expression were examined in mice fed control (CD; 2 mg/kg folic acid) or folate-deficient diets (FD; 0.3 mg/kg folic acid) for 12 mo. Females fed CD were not steatotic (0/6), whereas males were mildly to moderately steatotic (5/6). Steatosis was observed in FD-fed males and females; it was more severe and more frequent in males (7/7) than in females (4/10) (P = 0.005). Hepatic betaine was lower in males (P = 0.014) and FD-fed mice (P < 0.001) and negatively correlated with steatosis severity in mice fed CD (r = -0.87; P = 0.001). Gender differences in the expression of 6 enzymes may contribute to increased steatosis susceptibility in males. Males relied more on betaine-dependent (folate-independent) Hcy remethylation [72% more betaine-Hcy methyltransferase (P < 0.001) and 28% less folate-dependent methionine synthase (MTR) (P < 0.001)]. FD-fed mice of both genders appeared to shift to betaine-dependent remethylation by reducing MTR expression 70% (P < 0.001) and increasing betaine demand; there was a correlation between MTR expression and betaine levels (r = 0.50; P = 0.031). Our work demonstrates that chronic folate insufficiency leads to steatosis in mice. Increased utilization of betaine for Hcy remethylation in males and in both genders during folate deficiency may lead to steatosis by disrupting choline metabolism.
Christensen
Karen E
KE
Department of Human Genetics, McGill University-Montreal Children's Hospital, Montreal, Quebec, Canada.
Wu
Qing
Q
Wang
Xiaoling
X
Deng
Liyuan
L
Caudill
Marie A
MA
Rozen
Rima
R
D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000235:genetics; D000818:Animals; D001622:Betaine / Q000032:analysis; D050940:Betaine-Homocysteine S-Methyltransferase / Q000235:genetics; D002244:Carbon / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D004032:Diet; D005234:Fatty Liver / Q000201:enzymology* / Q000209:etiology*; D005260:Female; D005287:Ferredoxin-NADP Reductase / Q000235:genetics; D005492:Folic Acid / Q000008:administration & dosage; D005494:Folic Acid Deficiency / Q000150:complications* / Q000201:enzymology; D015870:Gene Expression; D006710:Homocysteine / Q000097:blood / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000201:enzymology; D008297:Male; D008745:Methylation; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000032:analysis; D012737:Sex Factors
D012333:RNA, Messenger; D006710:Homocysteine; D001622:Betaine; D002244:Carbon; D005492:Folic Acid; C111241:methionine synthase reductase; D005287:Ferredoxin-NADP Reductase; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D050940:Betaine-Homocysteine S-Methyltransferase; D002794:Choline