Klotho
Return to Urinary System Menu
Klotho Supplement
Klotho: The Super-Antioxidant You’ve Never Heard of
Klotho is a renal protein antioxidant found in mammals that was first identified in 1997. When there was a defect in expression of the gene for Klotho, lab animals aged quickly and died prematurely. Overexpression of the Klotho gene resulted in lab animals living unexpectedly long lives. Destruction of the Klotho gene in mice resulted in accelerated aging and premature death.1 In addition to the shortened lifespan, it was also observed that Klotho-deficient mice fail to grow and had changes in multiple organs of the body, ectopic calcification, arteriosclerosis, osteoporosis, and atrophy of the skin. Although Klotho is most highly expressed in the kidneys and brain, it affects multiple organs in the body. Klotho deficiency is associated with multiple diseases of aging, and therapies to increase Klotho levels provide a new strategy for addressing the problems of an aging population.2
This protein of longevity was named for one of the three Fates in Greek mythology. The first Fate, Klotho, spun the web of life for each person, while the second Fate decided on the length of life and the third Fate cut the web of life. The Klotho protein is most noted for its effect on lifespan and kidney health but has far reaching consequences, including cardiovascular health, bone health, and blood sugar regulation, as well as cognition.
Klotho is an anti-aging single-pass membrane protein predominantly produced in the kidney, with shedding of the amino-terminal extracellular domain into the systemic circulation. Circulating levels of soluble Klotho decrease with age, and the klotho gene is associated with increased risk of age-related diseases
Klotho, Aging, and the Failing Kidney Klotho has been recognized as a gene involved in the aging process in mammals for over 30 years, where it regulates phosphate homeostasis and the activity of members of the fibroblast growth factor (FGF) family. The α-Klotho protein is the receptor for Fibroblast Growth Factor-23 (FGF23), regulating phosphate homeostasis and vitamin D metabolism. Phosphate toxicity is a hallmark of mammalian aging and correlates with diminution of Klotho levels with increasing age. As such, modulation of Klotho activity is an attractive target for therapeutic intervention in the diseasome of aging; in particular for chronic kidney disease (CKD), where Klotho has been implicated directly in the pathophysiology. A range of senotherapeutic strategies have been developed to directly or indirectly influence Klotho expression, with varying degrees of success. These include administration of exogenous Klotho, synthetic and natural Klotho agonists and indirect approaches, via modulation of the foodome and the gut microbiota. All these approaches have significant potential to mitigate loss of physiological function and resilience accompanying old age and to improve outcomes within the diseasome of aging.
The Klotho proteins in health and disease The Klotho proteins, αKlotho and βKlotho, are essential components of endocrine fibroblast growth factor (FGF) receptor complexes, as they are required for the high-affinity binding of FGF19, FGF21 and FGF23 to their cognate FGF receptors (FGFRs). Collectively, these proteins form a unique endocrine system that governs multiple metabolic processes in mammals. FGF19 is a satiety hormone that is secreted from the intestine on ingestion of food and binds the βKlotho–FGFR4 complex in hepatocytes to promote metabolic responses to feeding. By contrast, under fasting conditions, the liver secretes the starvation hormone FGF21, which induces metabolic responses to fasting and stress responses through the activation of the hypothalamus–pituitary–adrenal axis and the sympathetic nervous system following binding to the βKlotho–FGFR1c complex in adipocytes and the suprachiasmatic nucleus, respectively. Finally, FGF23 is secreted by osteocytes in response to phosphate intake and binds to αKlotho–FGFR complexes, which are expressed most abundantly in renal tubules, to regulate mineral metabolism. Growing evidence suggests that the FGF–Klotho endocrine system also has a crucial role in the pathophysiology of ageing-related disorders, including diabetes, cancer, arteriosclerosis and chronic kidney disease. Therefore, targeting the FGF–Klotho endocrine axes might have therapeutic benefit in multiple systems; investigation of the crystal structures of FGF–Klotho–FGFR complexes is paving the way for the development of drugs that can regulate these axes.
The role of klotho in chronic kidney disease Chronic kidney disease (CKD) is an inherently systemic disease that refers to a long-term loss of kidney function. The progression of CKD has repercussions for other organs, leading to many kinds of extrarenal complications. Intensive studies are now being undertaken to reveal the risk factors and pathophysiological mechanism of this disease. During the past 20 years, increasing evidence from clinical and basic studies has indicated that klotho, which was initially known as an anti-aging gene and is mainly expressed in the kidney, is significantly correlated with the development and progression of CKD and its complications. Here, we discuss in detail the role and pathophysiological implications of klotho in ion disorders, the inflammation response, vascular calcification, mineral bone disorders, and renal fibrosis in CKD. Based on the pathogenic mechanism of klotho deficiency and klotho decline in urine early in CKD stage 2 and even earlier in CKD stage 1, it is not difficult to understand that soluble klotho can serve as an early and sensitive marker of CKD. Moreover, the prevention of klotho decline by several mechanisms can attenuate renal injuries, retard CKD progression, ameliorate extrarenal complications, and improve renal function. In this review, we focus on the functions and pathophysiological implications of klotho in CKD and its extrarenal complications as well as its potential applications as a diagnostic and/or prognostic biomarker for CKD and as a novel treatment strategy to improve and decrease the burden of comorbidity in CKD.