Ergothioneine (EGT), a sulfur-containing amino acid found in mushrooms and certain bacteria, dose-dependently restored circadian rhythm amplitude in PER2::LUC mouse embryonic fibroblasts without altering baseline period length. When NAD+ depletion was chemically induced via FK866 (a NAMPT inhibitor mimicking cellular aging), EGT co-treatment rescued rhythm amplitude, attenuated period lengthening, and reduced cycle-to-cycle variability. Crucially, EGT elevated both absolute NAD+ levels and the NAD+/NADH ratio under depletion conditions — an effect independent of simple cytoprotection.
The NAD+–SIRT1–circadian clock axis has gained significant traction in aging research, with SIRT1 deacetylating core clock proteins BMAL1 and PER2 to sustain rhythmicity. Most interventions targeting this axis — NMN, NR, or caloric restriction — work upstream by boosting NAD+ biosynthesis. EGT appears to modulate redox balance through a distinct mechanism, making it a potentially complementary rather than redundant strategy. Its documented ability to cross the blood-brain barrier is particularly consequential: suprachiasmatic nucleus deterioration drives systemic circadian fragmentation in aging, and few nutritional compounds reach central clock tissue at meaningful concentrations.
Limitations are substantial. This is a cell-culture model using a pharmacological aging proxy, not aged tissue or whole animals. Human circadian aging involves neurological and hormonal layers absent here. The finding is mechanistically intriguing and directionally plausible, but should be considered early-stage evidence warranting in vivo validation before any dietary guidance is inferred.
