Methyl Donor Deficiency Blocks Colorectal Cancer Development by Affecting Key Metabolic Pathways

Abstract

Our understanding of the role of folate one-carbon metabolism in colon carcinogenesis remains incomplete. Previous studies indicate that a methyl donor deficient (MDD) diet lacking folic acid, choline, methionine, and vitamin B12 is associated with long-lasting changes to the intestinal epithelium and sustained tumor protection in Apc-mutant mice. However, the metabolic pathways by which the MDD diet effects these changes are unknown. Colon samples harvested from Apc Δ14/+ mice fed the MDD diet for 18 weeks were profiled using a GC-MS and LC-MS/MS metabolomics platform. Random forest and pathway analyses were used to identify altered metabolic pathways and associated gene expression changes were analyzed by RT-PCR. Approximately 100 metabolites impacted by the MDD diet were identified. As expected, metabolites within the methionine cycle, including methionine (−2.9-fold, P<0.001) and betaine (−3.3-fold, P<0.001), were reduced. Elevated homocysteine (110-fold, P<0.001) was associated with increased flux through the transsulfuration pathway. Unexpectedly, levels of deoxycholic acid (−4.5-fold, P<0.05) and several other secondary bile acids were reduced. There were also unexpected reductions in the levels of carnitine (−2.0-fold, P<0.01) and a panel of acylcarnitines involved in fatty acid β-oxidation. Finally, metabolites involved in redox balance, including ascorbate and hypotaurine, were found to be persistently elevated. These findings provide clues to the molecular changes underlying MDD-mediated tumor protection and identify regulatable metabolic pathways that may provide new targets for colon cancer prevention and treatment.

The Concept of Folic Acid in Health and Disease

“…In contrast, methyl donor-deficient diet (low in folic acid, choline, methionine, and vitamin B 12 ) is associated with sustained tumor protection of colonic mucosa in Apc -mutant mice (Apc Δ14/+ ) . Approximately 100 metabolites affected by the methyl-deficient diet were identified in colonic samples: reduced methionine (−2.9-fold, p < 0.001) and betaine (−3.3-fold, p < 0.001), elevated homocysteine (110-fold, p < 0.001) with activation with trans-sulfuration [ 165 ]. High-physiological folic acid concentrations differently influence malignant and non-malignant colonic cells that is clearly demonstrated in cell lines HT29 and HCEC, respectively.…”

Biochemical Mechanisms Associating Alcohol Use Disorders with Cancers

“…The influence of alcohol on folate metabolism plays a prominent and not yet well-understood role. The altered metabolism may induce malignant transformation, but cell proliferation in tumors requires complete folate metabolism to support the synthetic demands of the transformed cells [ 26 , 27 , 81 , 133 , 134 , 135 , 136 ]. Consequently, chemicals designed to target folate metabolism’s crucial steps are essential tools when treating or preventing cancer, whether ethanol or other known etiological factors play their part.…”

“…The figure depicts the main routes involved in transferring one-carbon modules (highlighted in red) from one metabolite to another. 1, Dihydrofolate reductase, EC 1.5.1.3; 2, Ser-hydroxymethyl transferase, EC 2.1.2.1; 3, methylene THF reductase, EC 1.5.1.20; 4, MS: Met synthase, EC 2.1.1.13; 5, methylenetetrahydrofolate reductase, EC 1.5.1.20; 6, 5-formyltetrahydrofolate cyclo-ligase, EC 6.3.3.2; 7, methyltetrahydrofolate ciclohydrolase, EC 3.5.4.9; 8, formate-tetrahydrofolate ligase, EC 6.3.4.3) 9, betaine: homocysteine methyltransferase, EC 2.1.1.5; 10, Met adenosyltransferase, EC 2.5.1.6; 11, methyltransferases, EC 2.1.1.; 12, S-adenosylhomocysteine hydrolase, EC 3.3.1.1; 13, SAM decarboxylase and other enzymes; 14, thymidylate synthase, EC 2.1.1.45; 15 indicates the transsulfuration pathway where several enzymes participate [ 76 , 117 , 124 , 128 , 130 , 136 , 137 , 138 , 139 ].…”

Biochemical Mechanisms Associating Alcohol Use Disorders with Cancers.

“…The influence of alcohol on folate metabolism plays a prominent and not yet well-understood role. The altered metabolism may induce malignant transformation, but, on the other hand, cell proliferation in tumors requires complete folate metabolism to support the synthetic demands of the transformed cells [26,27,81,[133][134][135][136]. Consequently, chemicals designed to target folate metabolism's crucial steps are essential tools when treating or preventing cancer, whether ethanol or other known aetiological factors play their part.…”

“…Homocysteine also serves as a substrate for the synthesis of GSH (reduced glutathione) through the transsulfuration pathway. THF (tetrahydrofolate); hCys (homocysteine); SAM (S-adenosylmethionine); SAH (S-adenosyl homocysteine); DMG (dimethylglycine); Me-substrate (methylated substrate).Numbers in blue color indicate enzyme activities: 1 (dihydrofolate reductase, EC 1.5.1.3); 2 (Serhydroxymethyl transferase, EC 2.1.2.1); 3 (methylene THF reductase, EC 1.5.1.20); 4 (MS: Met synthase, EC 2.1.1.13); 5 (methylenetetrahydrofolate reductase, EC 1.5.1.20); 6 (5-formyltetrahydrofolate cyclo-ligase, EC 6.3.3.2); 7 (methyltetrahydrofolate ciclohydrolase EC 3.5.4.9); 8 (formate-tetrahydrofolate ligase, EC 6.3.4.3) 9 (betaine: homocysteine methyltransferase, EC 2.1.1.5); 10 (Met adenosyltransferase, EC 2.5.1.6); 11 (methyltransferases, EC 2.1.1…); 12 (S-adenosylhomocysteine hydrolase, EC 3.3.1.1); 13 (SAM decarboxylase and other enzymes); 14 (thymidylate synthase, EC 2.1.1.45); 15 (indicates the transsulfuration pathway where several enzymes participate)[76,117,124,128,130,[136][137][138][139].…”