Klotho (biology)

Klotho is an is_associated_with::enzyme that in humans is encoded by the KL is_associated_with::gene.

This gene encodes a type-I membrane protein that is related to β-glucuronidases. Reduced production of this protein has been observed in patients with chronic renal failure (CRF), and this may be one of the factors underlying the degenerative processes (e.g., arteriosclerosis, osteoporosis, and skin atrophy) seen in CRF. Also, mutations within this protein have been associated with ageing and bone loss. Transgenic mice that overexpress Klotho live longer than wild-type mice.

Function
Klotho is a is_associated_with::transmembrane protein that, in addition to other effects, provides some control over the sensitivity of the organism to is_associated_with::insulin and appears to be involved in is_associated_with::aging. Its discovery was documented in 1997 by Kuro-o et al. The name of the gene comes from Klotho or is_associated_with::Clotho, one of the is_associated_with::Moirai, or Fates, in is_associated_with::Greek mythology.

The Klotho protein is a novel β-glucuronidase (EC number 3.2.1.31) capable of hydrolyzing is_associated_with::steroid β-glucuronides. Genetic variants in KLOTHO have been associated with human aging, and Klotho protein has been shown to be a circulating factor detectable in serum that declines with age.

Klotho-deficient mice manifest a is_associated_with::syndrome resembling accelerated human aging and display extensive and accelerated is_associated_with::arteriosclerosis. Additionally, they exhibit impaired is_associated_with::endothelium dependent is_associated_with::vasodilation and impaired is_associated_with::angiogenesis, suggesting that Klotho protein may protect the cardiovascular system through endothelium-derived NO production.

Although the vast majority of research has been based on lack of Klotho, it was demonstrated that an overexpression of Klotho in mice might extend their is_associated_with::average life span between 19% and 31% compared to normal mice. In addition, variations in the Klotho gene (SNP Rs9536314) are associated with both life extension and increased cognition in human populations.

The mechanism of action of klotho is not fully understood, but it changes cellular calcium homeostasis, by both increasing the expression and activity of is_associated_with::TRPV5 and decreasing that of is_associated_with::TRPC6. Additionally, klotho increases membrane expression of the inward rectifier channel is_associated_with::ROMK. Klotho-deficient mice show increased production of vitamin D, and altered mineral-ion homeostasis is suggested to be a cause of premature aging‑like phenotypes, because the lowering of vitamin D activity by dietary restriction reverses the premature aging‑like phenotypes and prolongs survival in these mutants. These results suggest that aging‑like phenotypes were due to klotho-associated vitamin D metabolic abnormalities (hypervitaminosis).