Yoon Hang Kim, MD, MPH

Board-Certified in Preventive Medicine | Integrative & Functional Medicine Physician

Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. The information presented reflects current preclinical and early clinical research and should not be used as a substitute for professional medical guidance. Always consult a qualified healthcare provider before making changes to your treatment plan.

Abstract

α-Klotho is an aging-suppressor protein existing in a membrane-bound form, where it acts as an obligate co-receptor for fibroblast growth factor 23 (FGF23), and as a circulating soluble form with endocrine effects on oxidative stress, inflammation, calcium handling, and fibrosis. Soluble α-Klotho declines with age and has been proposed as both a biomarker and a mechanistic contributor to cardiovascular disease (CVD). This article summarizes the current evidence and, equally, its limits. Human data are predominantly cross-sectional: lower serum α-Klotho is associated with prevalent congestive heart failure and myocardial infarction, with aortoiliac calcification burden and 10-year mortality in a single-center cohort, and inversely with vascular and systemic inflammatory markers. A meta-analysis restricted to chronic kidney disease found low Klotho associated with roughly doubled cardiovascular mortality, although composite cardiovascular events did not differ significantly. Mendelian randomization supports a protective causal effect for atrial fibrillation only — not for coronary artery disease, heart failure, or stroke. Preclinical evidence is substantially stronger. In rodent models and cell systems, Klotho attenuates ox-LDL–induced endothelial oxidative stress via PI3K/Akt/eNOS signaling and LOX-1 downregulation; reduces infarct size, hypertrophy, and fibrosis after myocardial infarction; and prevents CaMKII-dependent RyR2 hyperphosphorylation and arrhythmogenic calcium leak. Effects on vascular smooth muscle calcification are less consistent, with contradictory findings in human cells. Exercise is the only lifestyle intervention with randomized human evidence of raising soluble Klotho. No Klotho-based therapeutic has entered clinical use, no randomized supplementation trial has reported a cardiovascular endpoint, and available assays lack standardization.

Keywords: α-Klotho; soluble Klotho; cardiovascular disease; vascular calcification; endothelial dysfunction; myocardial infarction; FGF23; arterial aging; integrative medicine

Introduction: Why Klotho Deserves Your Attention

In the search for upstream drivers of cardiovascular aging, few molecules have generated as much scientific excitement as α-Klotho—a protein named for the gene first characterized in 1997 by Kuro-o and colleagues, when mice carrying a disrupting mutation in the Klotho gene developed a syndrome resembling accelerated aging, including vascular calcification, arterial stiffness, and shortened lifespan (Kuro-o et al., Nature, 1997). Nearly three decades later, the research picture has matured considerably: soluble α-Klotho is now recognized as a circulating factor with pleiotropic actions across the cardiovascular system, and declining Klotho levels are increasingly viewed not merely as a biomarker of aging but as a mechanistic contributor to cardiovascular disease (CVD) itself.

This article examines the current state of Klotho research as it pertains to CVD—from molecular mechanisms to clinical translation—and considers what these findings mean for integrative and functional medicine practitioners working with high-risk and aging populations.

Klotho Biology: A Brief Primer

The α-Klotho protein exists in two principal forms. The membrane-bound form functions as an obligate co-receptor for fibroblast growth factor 23 (FGF23), primarily in the kidney and parathyroid glands, where it regulates phosphate homeostasis, vitamin D metabolism, and mineral balance. The soluble (secreted) form—generated by cleavage of the membrane-bound protein or alternative splicing—circulates in the blood and cerebrospinal fluid and exerts wide-ranging endocrine effects on oxidative stress, inflammation, calcium handling, and fibrotic signaling across multiple organ systems.

Circulating soluble α-Klotho declines with age, paralleling the rising incidence of atherosclerosis, heart failure, chronic kidney disease (CKD), and vascular calcification. The magnitude of that decline varies considerably across published cohorts and assay platforms, and no single reference range is well established — a measurement caveat worth keeping in view when interpreting any individual result. Nonetheless, the temporal correlation, combined with the mechanistic data summarized below, has positioned Klotho as a target of interest for cardiovascular intervention.

The Human CVD–Klotho Connection

Observational data have consistently linked lower circulating soluble α-Klotho levels with higher prevalence of specific cardiovascular conditions. In a cross-sectional analysis of the National Health and Nutrition Examination Survey (NHANES), Xu and colleagues demonstrated significant associations between lower serum α-Klotho and the prevalence of congestive heart failure and myocardial infarction, though relationships with coronary heart disease and stroke were less robust (Xu et al., Front Cardiovasc Med, 2022). More recently, Hellou et al. studied 148 participants (mean age 72.4 years) at the Mayo Clinic and found that those with low arterial calcification had higher Klotho levels (669 versus 556 pg/mL; P < .01), with Klotho inversely correlated with calcification burden (r = −0.315). Over 10 years, low Klotho was independently associated with higher mortality (HR 3.06; 95% CI 1.29–7.88) (Hellou et al., J Am Heart Assoc, 2025). This is a modest single-center cohort, and the finding is associative.

On the inflammatory side, Martín-Núñez et al. conducted a small case-control study — 76 clients with cardiovascular disease versus 16 cadaveric organ donors as controls, an unusual comparison group worth noting — demonstrating that KLOTHO gene expression in peripheral blood circulating cells—monocytes, macrophages, and lymphocytes—was inversely associated with both vascular and systemic inflammatory markers in clients with atherosclerotic vascular disease (Martín-Núñez et al., Sci Rep, 2022). This inverse relationship between Klotho and inflammation appears bidirectional: inflammatory states suppress Klotho expression, and Klotho deficiency amplifies inflammatory signaling.

A systematic review and meta-analysis by Kanbay et al., restricted to CKD and end-stage kidney disease populations, pooled 14 studies and found that low Klotho was associated with roughly double the odds of cardiovascular mortality (OR 2.11; 95% CI 1.61–2.76) and increased all-cause mortality (OR 1.81; 95% CI 1.34–2.44). Notably, composite cardiovascular events did NOT differ significantly between low- and high-Klotho groups (OR 1.51; 95% CI 0.82–2.77; P = .18), with high heterogeneity (Kanbay et al., Clin Kidney J, 2024). The mortality signal is therefore considerably stronger than the event signal, and neither should be extrapolated to non-CKD populations.

Signals of Causality

The question of whether lower Klotho causes CVD—rather than merely accompanying it—remains largely open. A two-sample Mendelian randomization study by Sun et al. found a significant inverse causal association between genetically predicted circulating α-Klotho and atrial fibrillation (OR 0.96; 95% CI 0.93–0.99), but only a borderline signal for coronary artery disease (OR 0.97; 95% CI 0.94–1.00; P = .044). The authors’ own conclusion was explicit: evidence supported protection against atrial fibrillation, but no significant causal association was found with CAD, heart failure, stroke, or ischemic stroke subtypes (Sun et al., Front Endocrinol, 2022). This is an important corrective to summaries describing MR evidence as broadly supporting causality across cardiovascular disease — it does not. The mechanistic and animal data below are substantially stronger than the human causal evidence, and that asymmetry should be held in mind throughout.

Mechanisms Relevant to Cardiovascular "Reversal"

What makes Klotho particularly compelling from a functional medicine perspective is that it does not target a single downstream effector. Rather, it modulates multiple root processes in CVD pathophysiology simultaneously—the kind of multi-target upstream intervention that integrative practitioners often seek.

Vascular Calcification and Arterial Stiffness

Vascular calcification—the deposition of calcium-phosphate complexes within the arterial wall—is a hallmark of CKD-associated CVD and arterial aging. It is now understood as an active, cell-mediated process driven by osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs), which begin expressing bone-forming transcription factors such as RUNX2 under conditions of phosphate overload, uremic toxin exposure, or oxidative stress.

Klotho suppresses this osteogenic transformation through multiple pathways. In rat aortic VSMCs, recombinant Klotho ameliorated β-glycerophosphate-induced calcification and osteogenic transition by inhibiting the Wnt/β-catenin signaling pathway, blocking β-catenin binding to the RUNX2 promoter (Chen et al., Biomed Res Int, 2015). The landmark study by Hu et al. demonstrated that Klotho deficiency directly causes vascular calcification in a CKD mouse model, establishing Klotho deficiency as sufficient to produce the phenotype in that model (Hu et al., J Am Soc Nephrol, 2011). Klotho has also been reported to downregulate phosphate transport via PIT-1 and PIT-2 in VSMCs, reducing the intracellular phosphate burden that drives osteogenic reprogramming.

This picture is not uniform, and it would be misleading to present it as settled. Chen and colleagues note in their own paper that several groups have found no effect of Klotho on calcification in human and mouse VSMCs, and describe the question as controversial. Six et al. reported that soluble Klotho increased reactive oxygen species production in human vascular smooth muscle cells even while increasing nitric oxide production in endothelium — a cell-type-specific divergence that complicates any simple antioxidant narrative (Six et al., PLoS One, 2014). Much of the supportive calcification data comes from rodent cells and rodent models; the human VSMC data are more mixed.

Endothelial Dysfunction and Atherogenesis

Endothelial dysfunction—characterized by reduced nitric oxide (NO) bioavailability, increased oxidative stress, and a pro-inflammatory endothelial phenotype—is the earliest detectable abnormality in atherosclerosis and a central driver of plaque initiation and progression.

In human umbilical vein endothelial cells (HUVECs) exposed to oxidized low-density lipoprotein (ox-LDL), pre-treatment with recombinant Klotho significantly attenuated oxidative damage. Mechanistically, Klotho upregulated superoxide dismutase (SOD) activity and endothelial nitric oxide synthase (eNOS) expression via activation of the PI3K/Akt/eNOS signaling cascade, while simultaneously downregulating the lectin-like oxidized LDL receptor-1 (LOX-1), the primary receptor through which ox-LDL exerts its pro-atherogenic effects (Yao et al., Lipids Health Dis, 2017). The net result was improved NO production, reduced reactive oxygen species (ROS) generation, and restoration of endothelial viability—effects that parallel the goals of many integrative cardiovascular protocols.

Myocardial Remodeling Post–Myocardial Infarction

Perhaps the most striking recent finding comes from Vázquez-Sánchez et al., who demonstrated in a 2025 study published in The Journal of Pathology that recombinant soluble Klotho administration after myocardial infarction (MI) exerts broad cardioprotective effects in mice with preserved renal function. Klotho-treated mice showed reduced infarct area, attenuated cardiac hypertrophy and fibrosis, and preserved ejection fraction. Beyond structural improvements, Klotho treatment prevented MI-related electrocardiographic abnormalities—including prolonged QRS, QTc, and T-peak-to-T-end intervals—and reduced premature ventricular contractions.

The mechanistic core of these findings centered on intracellular calcium handling. In isolated cardiomyocytes from post-MI mice, Klotho restricted pathological systolic calcium (Ca²⁺) release, prevented excessive diastolic Ca²⁺ leak, and blocked pro-arrhythmogenic events by inhibiting activation of the Ca²⁺/calmodulin-dependent kinase type II (CaMKII) pathway and preventing ryanodine receptor type 2 (RyR2) hyperphosphorylation (Vázquez-Sánchez et al., J Pathol, 2025). Importantly, STEMI clients in the clinical arm of this study also showed lower circulating Klotho levels, with the lowest Klotho tertile corresponding to higher NT-proBNP levels—suggesting translational relevance. The authors are candid about a key limitation, however: no baseline pre-infarct Klotho levels were available for the STEMI clients, who presented unscheduled to the emergency department. The direction of causality in the human arm cannot be established from these data.

Additional preclinical work has demonstrated that Klotho cardioprotection against MI-induced heart failure operates through autophagy induction via PI3K/AKT/mTOR pathway inhibition, with concurrent reduction in inflammatory cytokines and myocardial apoptosis (Wang et al., Mech Ageing Dev, 2022). Separately, Klotho administration improved cardiac fibrosis, ferroptosis, and oxidative stress in MI mice through AMPK/mTOR signaling (Wang et al., J Physiol Biochem, 2023).

Oxidative Stress and NF-κB–Driven Inflammation

Across virtually all cardiovascular models studied, Klotho exerts potent anti-oxidative and anti-inflammatory effects. It mitigates NF-κB–driven inflammatory signaling—a pathway central to plaque progression, myocardial injury, and the transition from compensated to decompensated heart failure. These effects are mediated in part through PI3K/AKT/Nrf2/HO-1 activation, which enhances the cell's intrinsic antioxidant defense machinery. In H₂O₂-stressed endothelial cells, Klotho enhanced superoxide dismutase, catalase, and heme oxygenase-1 activity, scavenged ROS, suppressed TNF-α and IL-6 secretion, and reduced apoptosis—all effects abolished by PI3K inhibition (Cui et al., Can J Physiol Pharmacol, 2019).

Therapeutic Angles: Clinical Translation

No Klotho-based therapeutic has entered routine clinical use in the literature reviewed here, and no regulatory approval has been identified. Several therapeutic strategies are nonetheless under active investigation.

Recombinant Soluble α-Klotho

Direct supplementation with recombinant soluble α-Klotho has shown cardioprotection in ischemic and aging heart models. The post-MI data from Vázquez-Sánchez et al. (2025) represent one of the most comprehensive demonstrations to date. Biomarker work from STEMI clients supports the rationale for Klotho supplementation during the acute post-MI window. The development of novel purification procedures for recombinant soluble Klotho, as reported by Yanucil et al. in Kidney International (2022), demonstrated that soluble Klotho exhibits anti-hypertrophic effects in FGF23-treated cardiac myocytes. In fairness to that paper, its principal finding was not about Klotho: the authors report that heparin, routinely infused during hemodialysis, acts as an opposing co-factor that aggravates FGF23-induced cardiac hypertrophy. The Klotho result is a secondary finding within a study whose main clinical message concerns dialysis heparin exposure.

FGF23–Klotho Axis Modulation

In the CKD population—where cardiovascular mortality dramatically exceeds the general population—the FGF23-Klotho axis has emerged as a critical mediator. Elevated FGF23 promotes cardiac hypertrophy, while Klotho deficiency removes a protective brake. Correcting Klotho deficiency, rather than solely targeting FGF23, may be the more effective strategy for reducing vascular calcification and CVD burden in this population. The interplay between phosphate overload, Klotho loss, and VSMC osteogenic reprogramming creates a vicious cycle that standard phosphate binders alone cannot fully interrupt.

Lifestyle and Pharmacologic Upregulation

For integrative practitioners, the lifestyle connection is particularly relevant. A 12-week randomized controlled trial (the FIT-AGEING study) demonstrated that exercise training—across all three intervention arms: WHO-recommended physical activity, high-intensity interval training (HIIT), and HIIT combined with whole-body electromyostimulation—significantly increased circulating S-Klotho levels in 74 sedentary middle-aged adults, with no significant difference between modalities (Amaro-Gahete et al., J Sports Sci, 2019). A subsequent systematic review and meta-analysis confirmed that exercise consistently increases Klotho levels regardless of the specific intervention or population, positioning Klotho as an "emerging exerkine" (Corrêa et al., Sci Rep, 2022).

Certain nutraceuticals, agents that reduce systemic inflammation and oxidative stress, and dietary patterns that support renal function may also indirectly preserve or raise Klotho expression—though the human evidence base for specific supplements remains limited and warrants cautious interpretation.

Gene Therapy and Bioregulators

Preclinical work exploring Klotho gene delivery and related anti-aging pathways continues. Long-term effects of soluble Klotho treatment in wild-type mice have demonstrated enhanced longevity, physical well-being, and neurological resilience (Roig-Soriano et al., Mol Ther, 2025). Clinical readiness for gene-based approaches remains early, but the proof-of-concept data are accumulating.

Implications for Integrative and Functional Practice

The Klotho literature, while still dominated by preclinical data and associative human studies, already offers several actionable principles for integrative practitioners.

Measure what you can. This recommendation carries a real caveat that the cited literature makes explicit. Kanbay et al. identify variability in measured Klotho levels and the absence of standardized measurement protocols as a principal barrier to clinical integration, and available assays are largely research-grade rather than clinically validated. Published cutoffs vary several-fold across cohorts. Soluble α-Klotho is therefore best treated today as an investigational marker rather than a decision-making test, and clinicians should be clear with clients about that status — including cost and coverage — before ordering it. Where it is measured, interpretation alongside concurrent inflammatory markers is essential, given the inverse relationship between systemic inflammation and Klotho expression.

Target upstream drivers. The multi-target nature of Klotho's protective effects—anti-calcific, anti-inflammatory, antioxidant, anti-fibrotic, anti-arrhythmic—aligns naturally with the functional medicine principle of addressing root causes rather than isolated downstream events. Aggressively reducing oxidative stress and inflammation through diet, sleep optimization, structured exercise, and reduction of inflammatory burden is biologically rational. It should be stated plainly, though, that no specific supplement or nutraceutical has been shown in human trials to raise Klotho, and this article names none for that purpose. Exercise is the only lifestyle intervention with randomized human evidence of a Klotho effect. The exercise data are particularly compelling: the finding that multiple exercise modalities increase Klotho provides a strong rationale for prescribing physical activity as a cardiovascular longevity intervention.

Weight the evidence honestly. It is worth being explicit about where this literature is strong and where it is not. The mechanistic and animal data are robust and reproducible across independent groups. The human data are almost entirely cross-sectional and associative. The single Mendelian randomization study available supports causality only for atrial fibrillation. The one meta-analysis with hard outcomes is confined to CKD populations, and even there composite cardiovascular events were not significantly different. There are no randomized trials of Klotho supplementation in humans for any cardiovascular endpoint. Describing this literature as evidence that Klotho reverses cardiovascular disease would outrun the data considerably.

Watch the pipeline. Recombinant Klotho and Klotho-enhancing therapies are promising for CVD reversal endpoints—including cardiac remodeling, vascular calcification, and arrhythmia prevention—but await robust human trials. Integrative practitioners should remain informed about the progress of these interventions while continuing to optimize the modifiable factors that influence endogenous Klotho biology.

Conclusion

Klotho is no longer a niche finding from an aging mouse model. It is a pleiotropic cardioprotective protein with converging evidence across vascular calcification, endothelial function, post-MI remodeling, oxidative stress, and systemic inflammation—the very processes that drive the progression (and potential reversal) of cardiovascular disease. Clinical translation, however, remains early: the mechanistic clarity and consistency of preclinical results have not yet been matched by human interventional evidence, and the human causal data remain thin. Klotho is best described today as one of the most promising — not one of the most established — targets in cardiovascular longevity research. For practitioners working at the intersection of prevention, functional medicine, and cardiovascular care, Klotho offers a unifying framework for understanding—and intervening upon—the biology of cardiovascular aging.

References

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About Dr. Kim

Dr. Yoon Hang "John" Kim is a board-certified Preventive Medicine physician with over 20 years of clinical experience in integrative and functional medicine. A fellowship-trained Osher Fellow under Dr. Andrew Weil at the University of Arizona, he holds additional certifications in medical acupuncture (UCLA) and integrative/holistic medicine. Dr. Kim specializes in low-dose naltrexone (LDN), autoimmune conditions, chronic pain syndromes, integrative oncology, fibromyalgia, chronic fatigue syndrome, mast cell activation syndrome, and mold toxicity. He is the author of three books—including the LDN Primer and a clinical LDN textbook—and more than 20 peer-reviewed articles.

Professional: www.yoonhangkim.com  |  Clinical: www.directintegrativecare.com