Review highlights role of one-carbon metabolism in oocyte quality and ovarian ageing

A systematic review in Human Reproduction Update indicates that while one-carbon metabolism regulates key epigenetic and mitochondrial pathways in oocytes, current clinical data are insufficient to prove that nutritional interventions can delay human ovarian ageing.

Researchers conducted a systematic review of literature from January 2008 to September 2026 investigating one-carbon metabolism (OCM) in follicular, oocyte, and ovarian biology.

The review highlighted that reducing methionine from 50 to 10 µM in bovine embryo cultures altered DNA methylation across more than 1600 genes, and MAT2A inhibition halted development past the eight-cell stage.

In retrospective human cohorts, hyperhomocysteinaemia was associated with lower live birth rates (adjusted odds ratio of approximately 0.45), while combined 5-MTHF/B12/B6 supplementation was associated with a higher live birth rate (OR 1.83) than folic acid alone.

The authors noted that blood or somatic epigenetic clock measurements do not accurately represent oocyte biological age, and that a causal link between hydrogen sulfide (H2S) signalling and delayed ovarian ageing remains unestablished in humans.

The findings map the precise cellular mechanics through which dietary substrates and metabolic enzymes regulate DNA methylation and developmental competence in reproductive cells.

The analysis underscores a critical translational gap: while animal models show clear developmental responses to OCM modulation (such as 5-MTHF supplementation increasing bovine blastocyst yield to 34.9% from 17.1%), human evidence remains observational and lacks randomized controlled trial verification.

The review redefines how researchers should evaluate ovarian biological age, emphasizing that systemic epigenetic clocks cannot be used as surrogates for oocyte-specific ageing.

This analysis provides a rigorous scientific baseline for biotechnology companies targeting reproductive longevity, highlighting that therapeutic claims must be backed by oocyte-specific measurements rather than somatic biomarkers.

The lack of established clinical protocols for OCM-related interventions suggests that current consumer-facing longevity supplements marketed for fertility lack robust clinical validation for delaying ovarian senescence.

The development of tissue-specific epigenetic biomarkers and direct assays to measure OCM flux, SAM, and SAH ratios in ageing human oocytes.

The initiation of adequately powered, randomized clinical trials designed to assess reproductive outcomes and safety profiles of OCM nutritional interventions in humans.