In 1997, a Japanese lab accidentally created a mouse that aged so fast it looked like a cartoon of human decline — hunched spine, thin skin, vascular calcification, short lifespan. The mutation disrupted a single gene. They named it Klotho, after the Greek Fate who spins the thread of life. Nearly three decades later, Klotho longevity research has expanded from that original discovery into one of the most intriguing stories in the aging field: a circulating hormone that affects kidney function, vascular health, and — most remarkably — cognition, in mice and humans alike. This article walks through what is solid, what is promising, and where the therapeutic efforts stand in 2026.
What Is Klotho?
Klotho is a transmembrane protein that also exists as a cleaved, circulating soluble hormone. It was discovered by Makoto Kuro-o's group and reported in Nature in 1997. The paper described mice with a transposon insertion that disrupted the Klotho gene; these mice developed premature aging phenotypes — infertility, atherosclerosis, osteoporosis, thymic atrophy, pulmonary emphysema — and had a median lifespan of about 8 to 9 weeks. Overexpression of Klotho, in a 2005 Science follow-up, extended mouse lifespan by roughly 20 to 30 percent.
There are actually several Klotho-family proteins. The original is now called α-Klotho, expressed primarily in kidney, choroid plexus, and parathyroid. Its best-characterized role is as an obligate co-receptor for FGF23, the phosphate-regulating hormone — α-Klotho and FGF receptors together form the signaling complex that controls phosphate excretion and vitamin D metabolism.
β-Klotho, expressed mainly in liver and adipose tissue, is the co-receptor for FGF21, a hormone linked to metabolism, fasting response, and longevity.
The transmembrane α-Klotho is shed by proteases, releasing a soluble ectodomain that circulates in blood and cerebrospinal fluid. This soluble Klotho appears to have its own signaling activities distinct from the FGF23 co-receptor function — and it is the soluble form that has attracted most of the brain-related interest.
The Science: Multiple Roles in Multiple Tissues
Klotho does not fit neatly into one pathway. Its biology is spread across several organ systems.
Kidney and mineral metabolism. Kidney α-Klotho controls phosphate handling via FGF23 signaling. Chronic kidney disease is characterized by dramatic loss of renal Klotho expression, rising FGF23, phosphate dysregulation, and vascular calcification. Orlando Gutierrez, Orson Moe, and others have shown that low Klotho is both a marker and a mechanism of CKD progression, and Klotho replacement protects the kidney in preclinical models.
Vascular and endothelial function. Klotho deficiency produces arterial stiffness, calcification, and endothelial dysfunction. This overlaps with CKD mineral bone disorder but also appears to be partly independent.
Brain and cognition. This is where the story gets most interesting. Dena Dubal at UCSF has led much of the work on Klotho and cognition. In a landmark 2014 Cell Reports paper, Dubal and colleagues showed that elevated Klotho enhanced synaptic plasticity and improved learning and memory in mice. Crucially, they extended the finding to humans: people carrying the KL-VS variant — a common haplotype that increases circulating Klotho levels — performed better on cognitive tests across the lifespan, and had greater brain volume in prefrontal regions.
Later work from the Dubal lab showed that peripheral administration of Klotho to mice rapidly boosted cognition, even though the protein is too large to cross the blood-brain barrier intact — suggesting the effect is mediated indirectly, perhaps through circulating factors or immune signaling. A 2020 Dubal lab paper in Nature Aging showed cognitive enhancement in aged nonhuman primates after single peripheral Klotho injections, strengthening the translational case.
The Evidence
Kuro-o 1997, Nature. The founding discovery: Klotho-deficient mice show accelerated aging phenotypes.
Kurosu 2005, Science. Klotho overexpression extends lifespan in mice and suppresses insulin/IGF-1 signaling.
Dubal 2014, Cell Reports. KL-VS carriers have higher serum Klotho, better cognitive function, and greater prefrontal volume; mice with elevated Klotho show improved spatial and working memory.
Dubal 2020, Nature Aging. Single peripheral Klotho injections enhanced cognition in aged rhesus macaques, suggesting a translational path for recombinant Klotho therapy.
CKD observational data. Numerous studies tie low serum Klotho to adverse kidney, cardiovascular, and mortality outcomes in CKD populations.
Exercise elevates Klotho. Several human studies — including work from the Dubal lab and others — have shown that regular aerobic exercise raises circulating Klotho in humans. This is one of the mechanisms proposed to link cardiovascular fitness to brain aging. See our exercise longevity and VO2 max evidence review.
Current Interventions: What People Are Actually Doing
Unlike autophagy inducers or senolytics, Klotho is not something you can easily take as a supplement. There is no oral Klotho. The protein itself, soluble Klotho, is a challenging therapeutic modality — it is large, unstable, and has to reach peripheral tissues (and somehow signal the brain) at meaningful concentrations.
Current practical interventions that are known to raise endogenous Klotho include:
- Aerobic exercise. Moderate to vigorous aerobic training consistently raises serum Klotho in human studies. This is probably the single most evidence-supported intervention.
- Vitamin D sufficiency. Vitamin D regulates Klotho expression in the kidney. Avoiding deficiency appears to be necessary but not sufficient.
- Managing CKD risk factors. Blood pressure control, avoiding nephrotoxins, glycemic control — all help preserve kidney Klotho production in at-risk populations.
- Genetic testing. Knowing your KL-VS status is possible via consumer genetics, though the cognitive effect size per copy is modest.
Some longevity clinics offer "Klotho testing" — measuring serum soluble α-Klotho — but the assays are not fully standardized, reference ranges vary by kit, and the clinical actionability is limited. It is interesting data, not treatment guidance.
Connection to Gene Editing and Peptides
Klotho signals a class of circulating factors that shape tissue communication with age — the altered intercellular communication hallmark of aging. The therapeutic question is how to restore these signals.
Recombinant soluble Klotho. The most direct approach. Several biotech efforts have tried to produce a stable, pharmacologically useful recombinant Klotho. Unity Biotechnology, founded by Nathaniel David and Judy Campisi, publicly explored Klotho alongside its senolytic work. Jag Therapeutics has pursued Klotho-related programs. Sage Therapeutics has had pipeline interest in Klotho-adjacent approaches to CNS disease. As of early 2026, no Klotho protein therapeutic has reached late-stage clinical trials — the molecule's stability, delivery, and tissue penetration remain real engineering problems.
Klotho gene therapy. AAV delivery of α-Klotho has been tested in preclinical CKD and neurodegeneration models with promising results. Translating this to humans is the natural next step but has not yet entered clinical trials.
Peptides and mimetics. Small-molecule and peptide Klotho pathway activators are in preclinical development. These would sidestep the recombinant protein challenges but so far lack convincing efficacy.
Base editing the KL-VS variant. In theory, introducing the favorable KL-VS allele at the endogenous locus is possible with base editing. There is no active program, but it is a conceptually clean target because the variant is a single well-characterized change with a well-characterized phenotype.
Limitations and Open Questions
How does Klotho affect the brain without crossing the blood-brain barrier? The indirect signaling hypothesis is the leading candidate but is not fully worked out.
What is the optimal circulating level? We know low is bad (CKD), and we know higher is better in observational and KL-VS data. Whether there is a therapeutic ceiling or a dose-response plateau is unknown.
Assay standardization. Commercial Klotho tests can give quite different absolute numbers. This makes longitudinal tracking in an individual more useful than absolute reference ranges.
Human outcome trials are missing. We have mechanistic, observational, and primate data. We do not have randomized trials showing that raising Klotho in humans improves cognitive or functional outcomes.
Will a Klotho drug ever happen? The biology is compelling but the modality is hard. Decades in, no approved therapeutic exists. It remains one of the most "promising but stuck" longevity targets.
FAQ
Can I take Klotho as a supplement?
No. Klotho is a large protein that would be digested if taken orally. No effective oral or injectable Klotho supplement is available. Claims otherwise should be treated skeptically.
What is the KL-VS variant?
KL-VS is a common haplotype of the KLOTHO gene that increases circulating soluble Klotho. Heterozygous carriers (roughly 20 to 25 percent of people of European descent) tend to have better cognitive function and greater longevity. Homozygotes for the variant paradoxically show no benefit, for reasons that are still debated.
How do I raise my Klotho naturally?
Aerobic exercise is the most evidence-backed intervention. Correcting vitamin D deficiency, managing kidney health, and avoiding nephrotoxic exposures are also reasonable.
Does Klotho really help the brain?
Preclinical and primate data say yes, and human KL-VS carrier data is consistent with this. We do not yet have randomized human trials of Klotho administration for cognitive endpoints.
Is Klotho testing worth it?
Maybe as a research-oriented biomarker alongside other aging blood markers. It is not clinically actionable on its own as of 2026.
What companies are developing Klotho therapies?
Unity Biotechnology, Jag Therapeutics, and others have pursued Klotho-related programs at various points. No Klotho protein or gene therapy has reached late-stage trials.
