Yeast life-span extension by calorie restriction is independent of NAD fluctuation.
Level 5 - mechanism / opinion, no new human data
Mechanistic bench and in vitro laboratory research without human clinical data (Level 5).
PubMed 14605207 · doi:10.1126/science.1088697
What was done
The authors investigated the mechanism of Sir2 regulation during calorie restriction in Saccharomyces cerevisiae. They measured nuclear NAD+ levels in vivo under calorie-restricted conditions and evaluated the activity of yeast Sir2 and human SIRT1 across physiological alterations in the NAD+:NADH ratio.
What was found
The abstract provides directional findings without quantitative metrics. Calorie restriction reduced nuclear NAD+ levels in vivo. Furthermore, physiological alterations in the NAD+:NADH ratio did not affect the activity of Sir2 or SIRT1.
Why it matters
These results challenge the hypothesis that calorie restriction extends lifespan by increasing NAD+ availability for Sir2/SIRT1, pointing to alternative regulatory pathways.
Limits
The abstract contains no sample sizes, numerical values, or error ranges. Findings are limited to yeast and in vitro biochemical models, preventing direct extrapolation to human physiology.
Cited by
- contradicts Fasting raises NAD levels in both humans and yeast.