Klotho

What it is

Klotho exists as a transmembrane co-receptor for FGF23 (kidney, parathyroid) and as a circulating cleaved form that acts as a hormone. Mice lacking Klotho show accelerated aging, vascular calcification, hypogonadism, osteoporosis, and short lifespan. Mice over-expressing Klotho live longer.

Why it matters

Higher serum Klotho associates with better cognitive function, reduced frailty, and lower all-cause mortality in human cohorts. The KL-VS variant carrier state (~25% of Europeans) is associated with higher serum Klotho and modestly improved cognition.

Mechanisms

• Regulates phosphate/calcium homeostasis via FGF23.
• Suppresses insulin/IGF-1 signalling.
• Inhibits Wnt and TGF-β signalling.
• Suppresses oxidative stress and apoptosis.
• Cross-talk with sphingolipid metabolism.

Therapeutic interest

Klotho gene therapy and recombinant Klotho protein are in pre-clinical development for chronic kidney disease, cardiovascular disease, and neurodegeneration. None are approved.

Longevity relevance

Klotho is one of the strongest single-gene modifiers of mammalian aging biology: mice lacking klotho develop accelerated aging phenotypes at 3-4 weeks and die at ~2 months; klotho-overexpressing mice live 20-30% longer.

Molecular biology

• α-Klotho: primarily renal-expressed transmembrane protein; shed extracellular domain circulates as soluble klotho.
• β-Klotho: liver and adipose-expressed; FGF21 co-receptor.
• Functions as:
  • FGF23 co-receptor (phosphate homeostasis).
  • Modulator of insulin/IGF-1 signalling.
  • Regulator of Wnt signalling.
  • Vitamin D metabolism regulator.

Human relevance

• Serum α-Klotho declines with age and predicts mortality, cardiovascular events, and cognitive impairment.
• KL-VS heterozygosity in humans is associated with increased longevity and cognitive resilience.

Therapeutic potential

• Direct klotho-protein administration extends healthspan in mouse models.
• KL-VS phenotype-mimicking small molecules are being pursued preclinically.
• The KL genotype-directed CETP-inhibitor trial is one example of how klotho biology may inform pharmacogenomics.

Related entries

Klotho serum, Chronic kidney disease, FGF21.

Related entries

Insulin/IGF-1, Chronic kidney disease, Altered intercellular communication.