Folate metabolism enzyme variants
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About MTHFR – rs1801133, rs1801131
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About MTHFR – rs1801133, rs1801131
Overview and History
MTHFR rs1801133 (often called C677T) and rs1801131 (A1298C) are single nucleotide polymorphisms in the methylenetetrahydrofolate reductase gene. Biochemically, MTHFR is an enzyme in one‑carbon metabolism that produces 5‑methyl‑THF, the active folate form used to remethylate homocysteine to methionine and to support methylation reactions.
These variants were identified and studied over decades for their effects on enzyme activity; certain allele combinations are associated with reduced MTHFR activity in biochemical studies. The variants themselves are not diagnostic of disease but provide genetic context for differences in folate handling, homocysteine levels, and related metabolic patterns.
Interpreting Highs and Lows
When results show variants linked to reduced MTHFR activity, this is often associated with higher circulating homocysteine in some people, particularly if folate or B‑vitamin status is low. Conversely, genotypes without those variant alleles are typically associated with usual enzyme activity and fewer genotype-driven effects on homocysteine.
Genotype effects are only one part of the picture — actual homocysteine, folate, B12, kidney function, and other markers determine biochemical status. Clinicians interpret MTHFR variant results together with the full Cardio Zoomer panel to understand whether a genetic tendency is contributing to measured metabolic patterns.
Featured Test
Cardio Zoomer includes these MTHFR variants to help explain interindividual differences in folate metabolism and homocysteine handling. Knowing genotype provides context for inflammatory, metabolic, and redox markers and helps clinicians distinguish inherited tendencies from reversible biochemical causes—supporting more precise interpretation of cardiovascular‑related lab patterns.
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Mary Beth Augustine
DCN, RDN, FAND- Lead Clinical Educator
Suzanne Barker
MS, RDN, LD, CTTS, CGP- Clinical Educator
Suzette Garcia
MSc- MHNE- Clinical Educator
Brooke Mader Ganev
MS, CNS, LDN, FDN- Clinical Educator
Adair Anderson
MS, RDN, LDN- Clinical Educator
Lillie Luu Nguyen
DCN, CNS, LDN- Clinical Educator
Jason Barker
ND- Clinical Educator
Emaline Brown
ND- Clinical Educator
Dana Filatova
DCN, CNS, LDN- Clinical Educator
Jessy Dhanjal
ND- Clinical Educator
Nour Amri
MS, LDN, CNS, CKNS- Clinical Educator
