What Is Klotho?
Klotho is a transmembrane anti-aging protein encoded by the KL gene. The human KL gene encodes three distinct protein subfamilies — α-Klotho, β-Klotho, and γ-Klotho — of which α-Klotho is the longevity-associated form of primary research interest. α-Klotho is expressed mainly in the renal distal convoluted tubule, with additional expression in the choroid plexus, parathyroid gland, and sex organs (ovary, placenta, testis). Within α-Klotho, three structural forms are recognized: full-length membrane-bound Klotho, which acts as a co-receptor for FGF23 regulating phosphate excretion and vitamin D metabolism; soluble Klotho (s-Klotho, ~130 kDa), shed from the membrane and circulating as a pleiotropic protective hormone with an estimated plasma half-life of ~7.5 hours; and a secreted splice variant with similar systemic effects.
In peptide research, Klotho appears in two distinct contexts:
- Endogenous Klotho protein and its domains (KL1/KL2) as a therapeutic target and biomarker studied across CKD, cardiovascular disease, neurodegeneration, and aging.
- Klotho-derived peptides — especially KP1, a 30-amino-acid fragment (residues 56–87) designed to block TGF-β/TβR2 signaling — engineered to recapitulate Klotho's anti-fibrotic activity in a smaller, drug-like format.
Mice lacking Klotho develop an accelerated-aging syndrome (arteriosclerosis, osteoporosis, early death); overexpression extends lifespan 20–30%. Low Klotho levels in humans correlate with CKD progression, vascular calcification, cognitive decline, and frailty. No human trials have yet administered exogenous Klotho protein or KP1 — all RUO vendor materials are sold strictly for research use.
Serum α-Klotho Reference Ranges (Healthy Adults)
Circulating soluble α-Klotho declines progressively with age regardless of sex — a trend attributed to physiological aging rather than disease:
| Age Range | Mean Serum Klotho |
|---|---|
| 18–35 years | ~932 pg/mL |
| 35–55 years | ~797 pg/mL |
| 55–85 years | ~612 pg/mL |
pg = picogram; 1,000 pg = 1 ng. Total circulating s-Klotho body pool is estimated at ~2.5–15 μg, with older individuals at the lower end and younger individuals at the upper end.
Quick Reference
Member reference tables summarize the compound's research parameters.
Key Benefits (Preclinical & Observational)
- Anti-aging & lifespan extension — Klotho overexpression extends lifespan ~20–30% in mouse models; suppresses insulin/IGF-1 and Wnt pathways to attenuate cellular senescence and preserve stem-cell pools.
- Kidney and anti-fibrotic protection — s-Klotho blocks TGF-β and Wnt/β-catenin to prevent fibroblast activation and chronic fibrosis; KP1 accumulates in injured kidneys and reduces creatinine, BUN, and fibrosis markers in preclinical CKD models.
- Cardiovascular health — reduces vascular calcification, cardiac fibrosis, and endothelial dysfunction; enhances nitric oxide (NO) production to promote vasodilation and improved blood flow; associated with lower cardiovascular event rates in observational human cohorts.
- Neuroprotection & cognition — even a single s-Klotho injection improved cognition in aged mice; the KL-VS variant (higher Klotho expression) confers measurable cognitive advantages across the human lifespan.
- Metabolic regulation — safeguards pancreatic islets, enhances insulin production, and reduces blood glucose; relevant to diabetes and metabolic syndrome models.
- Anti-inflammatory & antioxidant — suppresses NF-κB signaling and upregulates antioxidant defenses, lowering oxidative damage and pro-inflammatory cytokines.
- Mitochondrial biogenesis — upregulates mitochondrial mass and density in high-energy organs (heart, brain, kidney, lung, and skeletal muscle); this systemic energy upgrade underlies many of Klotho's multi-organ protective effects, distinguishing it from mitochondria-targeted peptides like SS-31 or MOTS-c.
- Pulmonary health — circulating α-Klotho protects lung tissue via a pulmonary-renal crosstalk axis; Klotho deficiency (from aging or CKD) markedly increases susceptibility to acute lung injury and chronic pulmonary dysfunction.
- Physical endurance & muscle preservation — Klotho-deficient mice show significantly reduced exercise capacity; higher serum Klotho correlates inversely with low muscle mass (sarcopenia) in middle-aged adults; preclinical data suggest augmented basal metabolic rate and energy expenditure.
Mechanism of Action
FGF23-dependent mineral metabolism: Membrane Klotho forms a complex with FGFR1c, acting as the obligate co-receptor for FGF23 in renal tubular cells. This axis governs phosphate excretion, vitamin D (1,25-OH₂D) activation, and calcium balance — all critical for bone density and vascular health. Circulating s-Klotho additionally acts as a portable FGF23 co-receptor, extending FGF23-dependent mineral regulation to tissues that do not express membrane Klotho.
Soluble Klotho as endocrine hormone: s-Klotho (shed from the membrane) circulates in blood, CSF, and urine and exerts effects independent of FGF23:
- Anti-fibrotic — blocks TGF-β and Wnt/β-catenin, preventing fibroblast activation and ECM deposition in kidney, lung, and heart.
- Anti-inflammatory — suppresses NF-κB; reduces TNF-α, IL-6, and other pro-inflammatory cytokines.
- Antioxidant — upregulates endogenous antioxidant defenses; reduces reactive oxygen species and oxidative damage.
- Ion channel regulation — modulates Ca²⁺, K⁺, and other channels and transporters in renal and vascular tissue.
- Tumor suppressor — attenuates oncogenic signaling in select cancer contexts.
Aging & stem-cell preservation: Klotho suppresses insulin/IGF-1 and Wnt signaling, attenuates telomere shortening, preserves stem-cell pools, and upregulates mitochondrial biogenesis — increasing mitochondrial mass and density in high-energy organs (heart, brain, kidney, lung, and skeletal muscle) to drive its systemic anti-aging and organ-resilience effects.
KP1 mechanism (Klotho-derived peptide 1): KP1 is a 30-residue peptide derived from Klotho's sequence that specifically binds TGF-β receptor 2 (TβR2) with Kd ≈ 1.4 μM, blocking TGF-β/TβR2 engagement. This inhibits downstream Smad2/3 and MAPK activation, repressing fibroblast activation and preventing upregulation of fibronectin and α-SMA. In UUO and ischemia-reperfusion mouse models, IV KP1 preferentially accumulates in injured kidneys, reduces creatinine and BUN, ameliorates fibrosis, and restores endogenous Klotho expression.
Research Indications
Research Protocols
As reported in cited literature and research-community logs (see Research Citations below), not a personal dosing recommendation.
This member section describes parameters reported in the research literature.
Peptide Interactions
This member section summarizes reported compound interactions and evidence limitations.
Reported Research Time Points
This member section summarizes reported research time points.
Safety Notes
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
This member section discusses research safety considerations and uncertainties.
Quality Indicators
Research Citations
- A Klotho-derived peptide protects against kidney fibrosis by targeting TGF-β signaling
Yuan Q, Ren Q, Li L et al., 2022, Nat Commun - Klotho-derived peptide 6 ameliorates diabetic kidney disease by targeting Wnt/β-catenin signaling
Chen X, Tan H, Xu J et al., 2022, Kidney Int - Klotho-derived peptide 1 inhibits cellular senescence in the fibrotic kidney by restoring Klotho expression via posttranscriptional regulation
Zhang X, Li L, Tan H et al., 2024, Theranostics - Regulation of FGF23 production and phosphate metabolism by bone-kidney interactions
Agoro R, White KE, 2023, Nat Rev Nephrol - Suppression of aging in mice by the hormone Klotho
Kurosu H, Yamamoto M, Clark JD et al., 2005, Science