FOXO Transcription Factors

What they are

FOXO (Forkhead box O) transcription factors are the mammalian relatives of C. elegans DAF-16. They translocate to the nucleus when insulin/IGF-1 signalling is low and turn on genes for stress resistance, DNA repair, antioxidant defence, autophagy, and cell-cycle arrest.

Why they matter

• FOXO3 variants are among the most replicated human longevity loci, associated with extreme longevity across diverse populations (Ashkenazi, Okinawan, German, Italian).
• FOXO3 over-expression extends mouse lifespan in tissue-specific contexts.
• Loss of FOXO accelerates phenotypes of aging.

What activates FOXO

• Reduced insulin/IGF-1 signalling.
• Oxidative stress.
• Sirtuin-mediated deacetylation.
• AMPK activation.
• Exercise (acutely and chronically).
• Caloric restriction.

What FOXO turns on

• Manganese superoxide dismutase (MnSOD/SOD2).
• Catalase, GADD45.
• p27, p21 (cell cycle).
• Autophagy genes.
• DNA-damage response genes.

Longevity relevance

The FOXO (Forkhead box class O) transcription factors are the mammalian homologues of daf-16 in C. elegans — the pathway whose mutation quadruples worm lifespan and whose discovery launched the molecular genetics of aging.

Family and function

• FOXO1, FOXO3, FOXO4, FOXO6: partly overlapping roles.
• Activated by:
  • Reduced insulin/IGF-1 signalling (Akt phosphorylation inhibits FOXO).
  • Oxidative stress.
  • Nutrient deprivation.
• Drive expression of:
  • Antioxidant genes (SOD2, catalase).
  • Autophagy genes.
  • DNA-repair genes.
  • Cell-cycle regulators (p27).

FOXO3 human genetics

FOXO3 variants are among the most-replicated longevity-associated loci in human centenarian studies (particularly Ashkenazi and Japanese long-lived cohorts).

Interventions that activate FOXO

• Caloric restriction and prolonged fasting.
• Exercise (both aerobic and resistance).
• Metformin via AMPK-mediated Akt inhibition.
• Direct FOXO activators are being investigated preclinically.

Related entries

Insulin/IGF-1 signalling, FOXO3, Caloric restriction, Cynthia Kenyon.

Related entries

Insulin/IGF-1 signalling, Sirtuins, AMPK.