source · text/markdown
source_9c41a4a1953e469a
sha256 94302417725edd00cec39ba00ccfb69a2b0a13e08f56a14b20744dcd5c89dd00
by researka:v2 · 2026-06-21 22:19:58.264326+04:00
# Adjacent Evidence Brief: Alpha-klotho — full paper ## Abstract Evidence-honesty note: The retained evidence has no direct interventional hard-endpoint evidence; indirect, review-level, adjacent, or mechanistic sources are used only to bound interpretation. The conclusion therefore does not support broad causal, clinical, or policy claims. This synthesis tests the thesis that evidence for Alpha-klotho is context-dependent, separating outcome-specific signals from broader claims and identifying the evidence gaps that should bound interpretation. Klotho, an anti-aging protein and key regulator of mineral-metabolism and vascular homeostasis, has attracted intense investigation as both a circulating biomarker and a candidate therapeutic target across chronic kidney disease, cardiometabolic syndromes, sarcopenia, and longevity, yet the clinical evidence base remains fragmented and directionally inconsistent across outcomes. We performed an AI-assisted structured evidence synthesis with a transparent audit trail, screening and extracting 52 curated references across observational cohorts, meta-analyses, and preclinical experiments, with every source traceable to a primary outcome class and effect direction. Across the corpus, the synthesis supports Klotho as a robust biomarker of renal function decline and a reproducible exerkine response, while its role as an independent prognostic marker for mortality and cardiovascular events is genuinely context-dependent and at times paradoxical. Whether Klotho-directed interventions can durably shift hard clinical endpoints remains uncertain, and randomized trials stratifying by baseline Klotho, CKD stage, and comorbidity burden are needed before any therapeutic claim can be made. **Evidence-abstraction note.** The 52 retained reference papers are not 52 independent primary clinical trials: 52 are review, indirect, mechanistic, or registered-protocol source-level summaries, and no source is classified as direct interventional hard-endpoint evidence, although human observational/prognostic evidence is present. Interpretation below therefore separates primary clinical-trial evidence from review-level, preclinical, and other indirect evidence. ## Methods ### Review type and protocol This manuscript is reported as a Thin-corpus evidence brief. A deterministic protocol governed source retrieval, screening, extraction, and synthesis; the protocol was frozen before manuscript rendering. The full audit trail is in the supplementary `methods_pack.json` and the timestamped submission directory `synthesis-klotho-v06-DAILY-2026-06-21T18-13-37Z`. ### Information sources Sources were retrieved across PubMed, Europe PMC, OpenAlex, Semantic Scholar, Crossref, DOAJ, OpenAIRE, PMC OAI, bioRxiv, medRxiv, arXiv, and ClinicalTrials.gov. Retrieval window: 2026-06-21. ### Search strategy The following topic-anchored queries were executed against the information sources listed above: - `klotho AND aging AND human` - `soluble klotho AND mortality AND cohort` - `klotho AND cognition AND older adults` - `klotho AND kidney disease AND aging` - `klotho protein AND vascular aging` ### Eligibility criteria - Sources whose primary content addresses klotho. - Sources with extractable quantitative or qualitative findings. - Peer-reviewed primary research, systematic reviews, or meta-analyses; preprints accepted only when source-traceable. - Sources with verifiable bibliographic identifiers (DOI / PMID / canonical handle). ### Selection of sources of evidence The synthesis did not begin from an unfiltered database export. It began from a pre-curated receipt-candidate set generated by the retrieval and claim-binding pipeline. Of 172 records in the receipt-candidate union, 52 were classified as source candidates and 52 were admitted as traceable synthesis sources. Mixed partial-or-none and partial-only rows are separate claim-binding audit buckets, not additive exclusion totals. No additional records were excluded after final source admission. ### source admission funnel | Admission bucket | n | |---|---:| | Receipt candidate union | 172 | | Classified source candidates | 52 | | No extractable claims | 28 | | None-only claim binding | 7 | | Mixed partial-or-none claim-binding candidates | 35 | | Partial-only claim-binding candidates | 18 | | Strict high-confidence sources | 32 | | Admitted final sources | 52 | ### Exclusion reasons - No records were excluded at the gates instrumented for this run: the eligibility criteria above were applied during retrieval and claim-binding but produced no post-screening exclusions with recorded counts for this corpus. ### Data items The following fields were extracted from each included source: study design, population / cohort, intervention or exposure, comparator, outcome class, effect direction, effect size, confidence interval or credible interval, p-value, sample size, follow-up duration, risk-of-bias rating. Under the calibration rule, source verification in the public bundle is limited to reference-level metadata; exact statistics and effect directions are drawn from these structured extraction artifacts (the synthesis manifest, risk-of-bias sidecar when populated, and claim registry) rather than from re-parsed full text. ### Risk-of-bias appraisal Risk-of-bias framework assignment follows study design (RoB-2 for RCTs, ROBINS-I for non-randomised studies, AMSTAR-2 for systematic reviews / meta-analyses). Public appraisal claims are limited to populated `risk_of_bias.json` rows; when no populated ratings are present, interpretation remains bounded by source tier and directness rather than formal RoB certification. ### Synthesis approach Evidence-tension synthesis: claims grouped by outcome class (cardiometabolic, contextual adjacent evidence, deficiency prevalence, dosing and pharmacokinetics, frailty, immune and inflammation, longevity, muscle function, safety and comorbidity, skeletal, fracture, and bone); within-class agreement, disagreement, and directness gaps surfaced explicitly. Quantitative pooling applied only where ≥3 sources reported a comparable endpoint with extractable effect estimates. ### AI-use disclosure Source retrieval, claim extraction, evidence routing, and prose drafting were assisted by large language models under a deterministic audit-trail protocol. Every manuscript claim is traceable to a source record in the supplementary `manifest.json`. Final eligibility and interpretation decisions are author-verified. ### Accountability Accountability is established through reproducible artifacts: a deterministic protocol (`methods_pack.json`), a complete claim and citation registry, extracted numeric trace, deterministic gates (`full_paper.journal_surface.json`, `pre_submit_gate.json`, `artifact_consistency.json`), and a versioned correction path documented in the run's submission record. Certification under the `researka_agent_certified` model verifies that the manuscript is machine-verifiable, internally consistent, provenance-traced, and format-checked against these artifacts; it does not adjudicate domain correctness, corpus fit, or novelty, which remain subject to expert and reader review. ## Results | Evidence domain | Corpus slice | Strongest signal | Directness | Main limitation | |---|---|---|---|---| | Safety and Comorbidity | n=15; claims=500 | no extracted directional signal in 5/15 sources | 9 indirect; 1 mechanistic; 5 review | limited corpus depth in this outcome class | | Contextual Adjacent Evidence | n=14; claims=637 | no extracted directional signal in 5/14 sources | 9 indirect; 5 review | limited corpus depth in this outcome class | | Deficiency Prevalence | n=9; claims=288 | mixed signal in 3/9 sources | 7 indirect; 2 review | limited corpus depth in this outcome class | | Longevity | n=4; claims=28 | negative signal in 2/4 sources | 2 indirect; 2 review | limited corpus depth in this outcome class | | Muscle Function | n=3; claims=210 | unclear signal in 1/3 sources | 3 review | limited corpus depth in this outcome class | | Cardiometabolic | n=2; claims=254 | negative signal in 1/2 sources | 1 indirect; 1 review | limited corpus depth in this outcome class | | Immune and Inflammation | n=2; claims=77 | no extracted directional signal in 2/2 sources | 2 indirect | limited corpus depth in this outcome class | | Dosing and Pharmacokinetics | n=1; claims=22 | positive signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating | | Frailty | n=1; claims=46 | positive signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating | | Skeletal, Fracture, and Bone | n=1; claims=21 | no extracted directional signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating | **Outcome-class note:** Contextual Adjacent Evidence denotes background, boundary-condition, or adjacent-outcome sources. It is not pooled with direct outcome evidence; these sources bound scope, safety, methods, and translation rather than serving as equal-weight support for the main efficacy claim. This evidence brief reports outcome packets as a map of retained evidence rather than as a full journal Results narrative or pooled effect estimate. ### Safety Comorbidity Outcomes 15 included sources were assigned to this outcome class. Directional coding: mixed=1, negative=4, null=5, positive=2, unclear=3. Directness coding: indirect=9, mechanistic=1, review=5. ### Contextual Adjacent Evidence Outcomes Evidence for this outcome class is represented in the structured results table, but the retained narrative paragraphs were more strongly assigned to adjacent outcome classes. The synthesis therefore treats this class as context for cross-domain interpretation rather than as a standalone prose claim. ### Deficiency Prevalence Outcomes See the structured evidence table for Deficiency Prevalence Outcomes signals. ### Longevity Outcomes See the structured evidence table for Longevity Outcomes signals. ### Muscle Function Outcomes 3 included sources were assigned to this outcome class. Directional coding: mixed=1, positive=1, unclear=1. Directness coding: review=3. ### Cardiometabolic Outcomes 2 included sources were assigned to this outcome class. Directional coding: mixed=1, negative=1. Directness coding: indirect=1, review=1. ### Immune Outcomes 2 included sources were assigned to this outcome class. Directional coding: null=2. Directness coding: indirect=2. ### Dosing Pharmacokinetics Outcomes 1 included source were assigned to this outcome class. Directional coding: positive=1. Directness coding: indirect=1. ### Frailty Outcomes 1 included source were assigned to this outcome class. Directional coding: positive=1. Directness coding: indirect=1. ### Skeletal Fracture Bone Outcomes 1 included source were assigned to this outcome class. Directional coding: null=1. Directness coding: indirect=1. ## Limitations **Verification note:** Reference-only or no-abstract records are treated as verification-limited context, not as equal-weight support for the main claim. Several outcome classes in the synthesis rest on a single primary source and cannot be triangulated within the corpus. Because these endpoints are touched by one source each, the magnitude and direction reported cannot be checked against an independent within-corpus replication, and any cross-study harmonization in the Results section is a re-presentation of one study's estimate rather than a meta-analytic summary. The frail / sarcopenic and nursing-home subgroup is restricted to Sanz 2021 and the meta-analytic inputs of Guldan 2026 and Ariadel-Cobo 2025, while the obesity / metabolic-syndrome slice is limited to Ariadel-Cobo 2026 (n=30), Zuo 2025, and the NHANES-based cross-sections. Consequently, externally valid inference ends where the corpus ends: the evidence does not support statements about healthy mid-life adults, non-CKD diabetic populations in low- and middle-income settings, or pediatric groups outside the CKD/ASD contexts already represented. Hard clinical endpoints are under-represented relative to surrogate biomarker endpoints. Endpoint scope is therefore biomarker-heavy and event-light, which limits any inference framed in terms of clinical benefit. Several clinically relevant claims in the synthesis are supported only by mechanistic or preclinical sources, leaving a mechanism-to-clinic gap. Rokhsati 2026 is a rat CKD / atrial-fibrillation model, Abstract the Klotho Protein 2025 reports vascular smooth-muscle ferroptosis suppression, and Lopez-Valdes 2025 summarizes anti-inflammatory actions in brain aging without primary clinical data. Where human correlates exist for the same pathway — e. For example, Mora-Fernandez 2022 reporting SGLT2i-mediated Klotho increases (P < 0.001) in diabetic kidney disease — the sample sizes are small, the comparators (DPP4i vs. SGLT2i) are indirect, and the downstream clinical event is not measured. Per Ioannidis 2005, surrogate associations of this kind do not guarantee hard-outcome validity, and the corpus does not contain the bridging trial that would close the gap. Any framing of klotho as a 'longevity protein' or as a mediator of drug-induced renoprotection must therefore be read as mechanistically suggestive rather than clinically established within this evidence base. ## Conclusion For Alpha-klotho, the final interpretation is deliberately tiered: the retained clinical and adjacent evidence profile defines a bounded geroscience rationale, but the corpus does not support treating mechanistic target engagement, intermediate biomarkers, and patient-relevant outcomes as interchangeable evidence. The closing claim should therefore be read as a map of what the retained studies can support, not as a clinical recommendation or a general anti-aging endorsement. Positive signals identify hypotheses and candidate contexts; null, mixed, or adverse signals identify the boundaries that future work must test directly. The evidence hierarchy remains load-bearing here: direct interventional hard-endpoint records carry more interpretive weight than adjacent clinical evidence, and both carry more translational weight than mechanistic or model systems. A stronger future conclusion would require larger direct human samples, prespecified endpoints, longer follow-up, comparable intervention characterization, transparent safety capture, and a consistent direction of effect across clinically proximate outcomes. Until that evidence exists, the paper's conclusion is that the topic is worth structured follow-up only within the boundaries defined by the included source set. That boundary is not a weakness in the paper; it is the main claim that keeps the synthesis reusable. Readers should carry forward the evidence classes separately: favorable mechanistic or surrogate findings can motivate experiments, indirect human findings can prioritize populations and endpoints, and direct clinical findings define the current ceiling for applied interpretation. The current corpus is non-supportive for clinical efficacy or general health-intervention claims; it supports only hypothesis generation and structured follow-up within the limits of indirect evidence. Any downstream use should preserve that tiered reading rather than compressing the corpus into a simple yes/no verdict for clinical practice or public messaging. ## What This Synthesis Adds This synthesis maps 52 included sources on Klotho across 10 outcome classes and 60 cross-study disagreements. It separates endpoint-specific evidence from broad geroprotection claims so that favorable biomarker signals are not treated as proof of durable healthspan benefit. Across 52 curated reference papers, the evidence base for klotho shows a context-dependent profile. Positive signals appear in: safety comorbidity, muscle function. Negative signals appear in: safety comorbidity, deficiency prevalence. Null findings dominate: contextual other, safety comorbidity. The synthesis surfaces cross-study disagreements across outcome classes — see Cross-Domain Synthesis. The klotho anti-aging case as currently constituted is incomplete: mechanistic plausibility coexists with mixed or sparse human-RCT evidence, and the boundary conditions remain to be established. The strongest unresolved contrast is the disagreement between Paradoxical Prognostic Role 2026 and Nong 2025 on longevity (severity 5/5), which defines the boundary condition future studies must test rather than smooth over. Prior reviews in the corpus (Oliveira 2026, Wungu 2024, Guldan 2026, Ariadel-Cobo 2025, Wang 2018) emphasize convergent signals on Klotho. This synthesis adds a design-level evidence-weighting layer and an explicit cross-study disagreement map, keeping boundary conditions visible instead of averaging them away in narrative summary. ### Boundary-Condition Matrix | Evidence domain | Direct sources | Indirect / mechanism sources | Direction profile | Interpretation boundary | |---|---:|---:|---|---| | longevity | 0 | 4 | negative, null, positive | conflict-resolution gap | | cardiometabolic | 0 | 2 | mixed, negative | direct interventional hard-endpoint gap | | frailty | 0 | 1 | positive | direct interventional hard-endpoint gap | | muscle function | 0 | 3 | mixed, positive, unclear | direct interventional hard-endpoint gap | | immune and inflammation | 0 | 2 | null | direct interventional hard-endpoint gap | | contextual adjacent evidence | 0 | 14 | mixed, null, positive, unclear | conflict-resolution gap | | deficiency prevalence | 0 | 9 | mixed, negative, null, positive, unclear | conflict-resolution gap | | safety and comorbidity | 0 | 15 | mixed, negative, null, positive, unclear | conflict-resolution gap | | dosing and pharmacokinetics | 0 | 1 | positive | direct interventional hard-endpoint gap | | skeletal, fracture, and bone | 0 | 1 | null | direct interventional hard-endpoint gap | ### Evidence-Gap Priority | Priority | Gap | Rationale | |---|---|---| | P1 | longevity: conflict-resolution gap | 0 direct and 4 indirect sources; direction profile: negative, null, positive | | P2 | cardiometabolic: direct interventional hard-endpoint gap | 0 direct and 2 indirect sources; direction profile: mixed, negative | | P3 | frailty: direct interventional hard-endpoint gap | 0 direct and 1 indirect source; direction profile: positive | | P4 | muscle function: direct interventional hard-endpoint gap | 0 direct and 3 indirect sources; direction profile: mixed, positive, unclear | | P5 | immune and inflammation: direct interventional hard-endpoint gap | 0 direct and 2 indirect sources; direction profile: null | ### Next-Study Design Recommendation The next high-yield study for Klotho should target the **longevity** evidence gap, pre-register the primary endpoint, separate clinical from mechanistic endpoints, preserve safety and adherence capture, and include an analysis plan that can falsify the current boundary-condition claim rather than only confirming a favorable direction. Minimum useful design: at least 200 participants per arm, a priority population of adults or older adults with baseline risk in the target outcome domain, and follow-up lasting at least 24 weeks; shorter or smaller studies should be treated as hypothesis-generating. ## Evidence Snapshot The manuscript foregrounds the load-bearing evidence; the full evidence tables remain in the supplement. ### Load-Bearing Included Studies - Oliveira 2026; tier=B1; directness=review; endpoint=muscle function; direction=positive; representative statistic=P < 0.00001. - Wungu 2024; tier=B1; directness=review; endpoint=contextual adjacent evidence; direction=mixed; representative statistic=P < 0.00001. - Guldan 2026; tier=B1; directness=review; endpoint=contextual adjacent evidence; direction=mixed; representative statistic=P < 0.0001. - Ariadel-Cobo 2025; tier=B1; directness=review; endpoint=muscle function; direction=mixed; representative statistic=P < 0.0001. - Wang 2018; tier=B1; directness=review; endpoint=safety comorbidity; direction=negative; representative statistic=P = 0.001. - Correa 2022; tier=B1; directness=review; endpoint=contextual adjacent evidence; direction=positive; representative statistic=P < 0.0001. - Castillo 2024; tier=B1; directness=review; endpoint=safety comorbidity; direction=null. - Edmonston 2024; tier=B1; directness=review; endpoint=deficiency prevalence; direction=null. - Mora-Fernandez 2022; tier=B1; directness=review; endpoint=cardiometabolic; direction=negative; representative statistic=P < 0.001. - Abstract the Klotho Protein 2025; tier=B1; directness=review; endpoint=muscle function; direction=unclear; representative statistic=P < 0.05. ### Source Classification Map Each retained source is mapped to its public evidence role so the evidence landscape can be checked without opening the supplement. - Effects of acute, subacute, and chronic exercise on plasma s-Klotho levels: a systematic review and meta-analysis: outcome=muscle function; directness=review; tier=B1; direction=positive; claims=151. - Role of klotho and fibroblast growth factor 23 in arterial calcification, thickness, and stiffness: a meta-analysis of observational studies: outcome=contextual adjacent evidence; directness=review; tier=B1; direction=mixed; claims=142. - Circulating α-Klotho and Multidimensional Aging and Frailty Outcomes: A Systematic Review and Meta-Analysis from the European Renal Association CKD-MBD Working Group: outcome=contextual adjacent evidence; directness=review; tier=B1; direction=mixed; claims=124. - Influence of Klotho Protein Levels in Obesity and Sarcopenia: A Systematic Review: outcome=muscle function; directness=review; tier=B1; direction=mixed; claims=57. - Correlation between Soluble α -Klotho and Renal Function in Patients with Chronic Kidney Disease: A Review and Meta-Analysis: outcome=safety comorbidity; directness=review; tier=B1; direction=negative; claims=44. - A systematic review and meta-analysis demonstrating Klotho as an emerging exerkine: outcome=contextual adjacent evidence; directness=review; tier=B1; direction=positive; claims=30. - Beneficial effects of physical exercise on the osteo-renal Klotho-FGF-23 axis in Chronic Kidney Disease: A systematic review with meta-analysis: outcome=safety comorbidity; directness=review; tier=B1; direction=null; claims=19. - Klotho and Clinical Outcomes in CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study.: outcome=deficiency prevalence; directness=review; tier=B1; direction=null; claims=4. - Sodium-glucose co-transporter-2 inhibitors increase Klotho in patients with diabetic kidney disease: A clinical and experimental study.: outcome=cardiometabolic; directness=review; tier=B1; direction=negative; claims=3. - Abstract 4365476: The Klotho Protein Reduces Vascular Calcification via Suppressing GPX4-mediated Ferroptosis in Vascular Smooth Muscle Cells: outcome=muscle function; directness=review; tier=B1; direction=unclear; claims=2. - Lower circulating soluble Klotho level is associated with increased risk of all-cause mortality in chronic kidney disease patients: a systematic review and meta-analysis.: outcome=longevity; directness=review; tier=B1; direction=negative; claims=2. - Age-related alterations in plasma biomarkers of relevance to Alzheimer's disease are attenuated in KLOTHO KL-VS heterozygotes: outcome=contextual adjacent evidence; directness=review; tier=B1; direction=unclear; claims=1. - Paradoxical prognostic role of alpha-klotho protein: a marker of increased mortality risk in the post-myocardial infarction setting: outcome=longevity; directness=review; tier=B1; direction=negative; claims=1. - Association between serum Klotho and thrombocytopenia in middle-aged and older adults: A cross-sectional study based on NHANES.: outcome=deficiency prevalence; directness=review; tier=B1; direction=unclear; claims=1. - Association of serum Klotho and fibroblast growth factor-23 levels with vascular calcification severity in patients with chronic kidney disease: an observational cohort study: outcome=cardiometabolic; directness=indirect; tier=B2; direction=mixed; claims=251. - Soluble Klotho, a biomarker and therapeutic strategy to reduce bronchopulmonary dysplasia and pulmonary hypertension in preterm infants: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=unclear; claims=136. - Serum klotho is inversely associated with metabolic syndrome in chronic kidney disease: results from the KNOW-CKD study: outcome=deficiency prevalence; directness=indirect; tier=B2; direction=mixed; claims=76. - Influence of exogenous growth hormone administration on circulating concentrations of α-klotho in healthy and chronic kidney disease subjects: a prospective, single-center open case-control pilot study: outcome=safety comorbidity; directness=indirect; tier=B2; direction=unclear; claims=70. - Associations Between Klotho/FGF-Related Protein Expression in Peripheral Blood Mononuclear Cells, Inflammation, and Muscle Function in Middle-Aged Adults with Obesity: A Pilot Study: outcome=immune; directness=indirect; tier=B2; direction=null; claims=67. - The FGF23–Klotho axis and cardiac tissue Doppler imaging in pediatric chronic kidney disease—a prospective cohort study: outcome=safety comorbidity; directness=indirect; tier=B2; direction=negative; claims=66. - Interaction Effect of Estimated Pulse Wave Velocity and Serum Klotho Level on Chronic Kidney Disease: outcome=deficiency prevalence; directness=indirect; tier=B2; direction=mixed; claims=51. - α -Klotho: An Early Risk-Predictive Biomarker for Acute Kidney Injury in Patients with Acute Myocardial Infarction: outcome=safety comorbidity; directness=indirect; tier=B2; direction=positive; claims=48. - α -klotho as a biomarker of amyloid β levels in the cerebrospinal fluid: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=mixed; claims=46. - Low serum klotho concentration is associated with worse cognition, psychological components of frailty, dependence, and falls in nursing home residents: outcome=frailty; directness=indirect; tier=B2; direction=positive; claims=46. - Association between serum α-Klotho levels and tinnitus stratified by sex and depression: A cross-sectional study from NHANES: outcome=deficiency prevalence; directness=indirect; tier=B2; direction=mixed; claims=42. - Association of magnesium depletion score with serum anti-aging protein Klotho in the middle-aged and older populations: outcome=deficiency prevalence; directness=indirect; tier=B2; direction=negative; claims=42. - Prognostic Value and Link to Atrial Fibrillation of Soluble Klotho and FGF23 in Hemodialysis Patients: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=41. - Interplay Between Fibroblast Growth Factor-19, Beta-Klotho, and Receptors Impacts Cardiovascular Risk in Chronic Kidney Disease: outcome=safety comorbidity; directness=indirect; tier=B2; direction=mixed; claims=35. - Role of soluble alpha-klotho as a novel biomarker for characterizing children with autism spectrum disorder in Kurdistan, Iraq: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=33. - The Prognostic Role of Klotho in Patients with Chronic Kidney Disease: A Systematic Review and Meta-analysis: outcome=safety comorbidity; directness=review; tier=B2; direction=unclear; claims=31. - Anti-aging protein α-Klotho is potential for reducing comorbidity risk of cardiometabolic diseases in vulnerable populations and enhancing long-term prognosis: outcome=safety comorbidity; directness=indirect; tier=B2; direction=unclear; claims=31. - Serum klotho is inversely associated with girth in older women but is not associated with falls or musculoskeletal measures in either sex: outcome=deficiency prevalence; directness=indirect; tier=B2; direction=negative; claims=30. - Sex differences in the association between Life’s Essential 8 and serum anti-aging Klotho protein levels: a cross-sectional analysis in middle-aged to older adults: outcome=deficiency prevalence; directness=indirect; tier=B2; direction=positive; claims=27. - The association between soluble klotho and cardiovascular parameters in chronic kidney disease: results from the KNOW-CKD study: outcome=safety comorbidity; directness=indirect; tier=B2; direction=negative; claims=26. - Associations of KLOTHO-VS heterozygosity and α-Klotho protein with cerebrospinal fluid Alzheimer's disease biomarkers: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=24. - Expression of Longevity Genes Induced by a Low-Dose Fluvastatin and Valsartan Combination with the Potential to Prevent/Treat “Aging-Related Disorders”: outcome=dosing pharmacokinetics; directness=indirect; tier=B2; direction=positive; claims=22. - Circulating Klotho and mortality patterns among US cancer survivors: A cohort study: outcome=longevity; directness=indirect; tier=B2; direction=positive; claims=22. - The effect of nephrectomy on Klotho, FGF-23 and bone metabolism: outcome=skeletal fracture bone; directness=indirect; tier=B2; direction=null; claims=21. - Modulation of PKCα/ETS1 by klotho restores CYB5R4-dependent mitochondrial function in proximal tubular epithelial cells to attenuate the progression of diabetic kidney disease: outcome=safety comorbidity; directness=indirect; tier=B2; direction=negative; claims=19. - Sex differences between atherogenic index of plasma and α-klotho levels in middle-aged and older adults: NHANES 2007–2016: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=mixed; claims=19. ### Classification Criteria - **Outcome class** is assigned from the source's bound endpoint, population, and claim text; adjacent/background sources are separated from clinical outcome slices. - **Directness** is coded as direct only when a source tests the topic against a clinically proximate outcome in the relevant population; a qualifying direct source would be a human interventional or hard-endpoint study of the topic itself. Indirect human, review-level, and mechanistic sources are weighted separately. - **Directional signal** is counted within the assigned outcome class only. A `no extracted directional signal` cell means the retained sources in that outcome slice did not yield a coded positive, negative, or mixed direction for that slice; it is not a claim that the source reports no associations anywhere else. - **Evidence tier** follows the deterministic tier/directness taxonomy used in the source builder; the prose writer cannot move a source between classes after sources are frozen. ### Load-Bearing Tensions - Severity 5 disagreement: Paradoxical Prognostic Role 2026 vs Nong 2025; Paradoxical Prognostic Role 2026 reports negative effect on longevity; Nong 2025 reports positive on the same outcome — direct conflict - Severity 5 disagreement: Pei 2023 vs Gan 2026; Pei 2023 reports positive effect on safety comorbidity; Gan 2026 reports negative on the same outcome — direct conflict - Severity 5 disagreement: Pei 2023 vs Lindblad 2017; Pei 2023 reports positive effect on safety comorbidity; Lindblad 2017 reports negative on the same outcome — direct conflict - Severity 5 disagreement: Pei 2023 vs Kim 2018; Pei 2023 reports positive effect on safety comorbidity; Kim 2018 reports negative on the same outcome — direct conflict - Severity 5 disagreement: Pei 2023 vs Wang 2018; Pei 2023 reports positive effect on safety comorbidity; Wang 2018 reports negative on the same outcome — direct conflict - Severity 5 disagreement: Zhuang 2025 vs Zeng 2025; Zhuang 2025 reports negative effect on deficiency prevalence; Zeng 2025 reports positive on the same outcome — direct conflict - Severity 5 disagreement: Zeng 2025 vs Dawson-Hughes 2025; Zeng 2025 reports positive effect on deficiency prevalence; Dawson-Hughes 2025 reports negative on the same outcome — direct conflict - Severity 5 disagreement: Nong 2025 vs Charoenngam 2020; Nong 2025 reports positive effect on longevity; Charoenngam 2020 reports negative on the same outcome — direct conflict Additional corpus sources included animal/preclinical evidence; additional corpus sources informed the synthesis without anchoring a foregrounded quantitative claim and are catalogued for completeness: Peng 2025, Batlahally 2020, Kim 2019, Adema 2018, Zou 2025, Raber 2025, Zhang 2026, Nowak 2014, Gonzalez-Rodriguez 2026, Allwsh 2026, Wang 2025, Liu 2019, Katonova 2025, Janic 2019, Kakareko 2017, Fan 2024, Ahmad 2025, Liu 2021, Kantar 2026, Yang 2025, Pei 2022, Corcillo 2020, Du 2025, Xin 2022, Cecati 2025, Driscoll 2026, Wang 2026. ## References - **Peng 2025.** _Association of serum Klotho and fibroblast growth factor-23 levels with vascular calcification severity in patients with chronic kidney disease: an observational cohort study._ International Urology and Nephrology, 2025. DOI: 10.1007/s11255-025-04475-5. PMID: 40167982. - **Oliveira 2026.** _Effects of acute, subacute, and chronic exercise on plasma s-Klotho levels: a systematic review and meta-analysis._ Journal of Physiology and Biochemistry, 2026. DOI: 10.1007/s13105-026-01182-2. PMID: 42067671. - **Wungu 2024.** _Role of klotho and fibroblast growth factor 23 in arterial calcification, thickness, and stiffness: a meta-analysis of observational studies._ Scientific Reports, 2024. DOI: 10.1038/s41598-024-56377-8. PMID: 38459119. - **Batlahally 2020.** _Soluble Klotho, a biomarker and therapeutic strategy to reduce bronchopulmonary dysplasia and pulmonary hypertension in preterm infants._ Scientific Reports, 2020. DOI: 10.1038/s41598-020-69296-1. PMID: 32704023. - **Guldan 2026.** _Circulating α-Klotho and Multidimensional Aging and Frailty Outcomes: A Systematic Review and Meta-Analysis from the European Renal Association CKD-MBD Working Group._ Calcified Tissue International, 2026. DOI: 10.1007/s00223-026-01537-3. PMID: 42060134. - **Kim 2019.** _Serum klotho is inversely associated with metabolic syndrome in chronic kidney disease: results from the KNOW-CKD study._ BMC Nephrology, 2019. DOI: 10.1186/s12882-019-1297-y. PMID: 30943913. - **Adema 2018.** _Influence of exogenous growth hormone administration on circulating concentrations of α-klotho in healthy and chronic kidney disease subjects: a prospective, single-center open case-control pilot study._ BMC Nephrology, 2018. DOI: 10.1186/s12882-018-1114-z. PMID: 30442108. - **Ariadel-Cobo 2026.** _Associations Between Klotho/FGF-Related Protein Expression in Peripheral Blood Mononuclear Cells, Inflammation, and Muscle Function in Middle-Aged Adults with Obesity: A Pilot Study._ International Journal of Molecular Sciences, 2026. DOI: 10.3390/ijms27041983. - **Lindblad 2017.** _The FGF23–Klotho axis and cardiac tissue Doppler imaging in pediatric chronic kidney disease—a prospective cohort study._ Pediatric Nephrology (Berlin, Germany), 2017. DOI: 10.1007/s00467-017-3766-5. PMID: 28795324. - **Ariadel-Cobo 2025.** _Influence of Klotho Protein Levels in Obesity and Sarcopenia: A Systematic Review._ International Journal of Molecular Sciences, 2025. DOI: 10.3390/ijms26051915. PMID: 40076542. - **Zou 2025.** _Interaction Effect of Estimated Pulse Wave Velocity and Serum Klotho Level on Chronic Kidney Disease._ Aging Medicine, 2025. DOI: 10.1002/agm2.70005. PMID: 39981292. - **Pei 2023.** _α -Klotho: An Early Risk-Predictive Biomarker for Acute Kidney Injury in Patients with Acute Myocardial Infarction._ International Journal of Clinical Practice, 2023. DOI: 10.1155/2023/8244545. PMID: 38187354. - **Raber 2025.** _α -klotho as a biomarker of amyloid β levels in the cerebrospinal fluid._ Frontiers in Aging Neuroscience, 2025. DOI: 10.3389/fnagi.2025.1599402. PMID: 40625374. - **Sanz 2021.** _Low serum klotho concentration is associated with worse cognition, psychological components of frailty, dependence, and falls in nursing home residents._ Scientific Reports, 2021. DOI: 10.1038/s41598-021-88455-6. PMID: 33907242. - **Wang 2018.** _Correlation between Soluble α -Klotho and Renal Function in Patients with Chronic Kidney Disease: A Review and Meta-Analysis._ BioMed Research International, 2018. DOI: 10.1155/2018/9481475. PMID: 30159331. - **Zhuang 2025.** _Association of magnesium depletion score with serum anti-aging protein Klotho in the middle-aged and older populations._ Frontiers in Nutrition, 2025. DOI: 10.3389/fnut.2025.1518268. PMID: 40212717. - **Zhang 2026.** _Association between serum α-Klotho levels and tinnitus stratified by sex and depression: A cross-sectional study from NHANES._ Medicine, 2026. DOI: 10.1097/MD.0000000000047973. PMID: 41842597. - **Rokhsati 2026.** _High-Intensity Interval and Aerobic Training Alleviate Cardiac Pathology, Apoptosis, and Atrial Fibrillation in Rats with Chronic Kidney Disease: The Roles of FGF23 and Klotho._ Biomolecules, 2026. DOI: 10.3390/biom16040513. PMID: 42072635. - **Nowak 2014.** _Prognostic Value and Link to Atrial Fibrillation of Soluble Klotho and FGF23 in Hemodialysis Patients._ PLoS ONE, 2014. DOI: 10.1371/journal.pone.0100688. PMID: 24991914. - **Gonzalez-Rodriguez 2026.** _Interplay Between Fibroblast Growth Factor-19, Beta-Klotho, and Receptors Impacts Cardiovascular Risk in Chronic Kidney Disease._ Journal of Clinical Medicine, 2026. DOI: 10.3390/jcm15031005. PMID: 41682686. - **Allwsh 2026.** _Role of soluble alpha-klotho as a novel biomarker for characterizing children with autism spectrum disorder in Kurdistan, Iraq._ World Journal of Clinical Pediatrics, 2026. DOI: 10.5409/wjcp.v15.i2.112164. PMID: 42220950. - **Wang 2025.** _Anti-aging protein α-Klotho is potential for reducing comorbidity risk of cardiometabolic diseases in vulnerable populations and enhancing long-term prognosis._ Scientific Reports, 2025. DOI: 10.1038/s41598-025-01580-4. PMID: 40369033. - **Liu 2019.** _The Prognostic Role of Klotho in Patients with Chronic Kidney Disease: A Systematic Review and Meta-analysis._ Disease Markers, 2019. DOI: 10.1155/2019/6468729. PMID: 31275449. - **Dawson-Hughes 2025.** _Serum klotho is inversely associated with girth in older women but is not associated with falls or musculoskeletal measures in either sex._ The Journal of Nutrition, Health & Aging, 2025. DOI: 10.1016/j.jnha.2025.100618. PMID: 40592050. - **Correa 2022.** _A systematic review and meta-analysis demonstrating Klotho as an emerging exerkine._ Scientific Reports, 2022. DOI: 10.1038/s41598-022-22123-1. PMID: 36266389. - **Zeng 2025.** _Sex differences in the association between Life’s Essential 8 and serum anti-aging Klotho protein levels: a cross-sectional analysis in middle-aged to older adults._ Frontiers in Aging, 2025. DOI: 10.3389/fragi.2025.1458571. PMID: 40519667. - **Kim 2018.** _The association between soluble klotho and cardiovascular parameters in chronic kidney disease: results from the KNOW-CKD study._ BMC Nephrology, 2018. DOI: 10.1186/s12882-018-0851-3. PMID: 29506503. - **Katonova 2025.** _Associations of KLOTHO-VS heterozygosity and α-Klotho protein with cerebrospinal fluid Alzheimer's disease biomarkers._ Journal of Alzheimer's Disease, 2025. DOI: 10.1177/13872877251326199. PMID: 40112321. - **Nong 2025.** _Circulating Klotho and mortality patterns among US cancer survivors: A cohort study._ Medicine, 2025. DOI: 10.1097/MD.0000000000043471. PMID: 40696614. - **Janic 2019.** _Expression of Longevity Genes Induced by a Low-Dose Fluvastatin and Valsartan Combination with the Potential to Prevent/Treat “Aging-Related Disorders”._ International Journal of Molecular Sciences, 2019. DOI: 10.3390/ijms20081844. PMID: 31013989. - **Kakareko 2017.** _The effect of nephrectomy on Klotho, FGF-23 and bone metabolism._ International Urology and Nephrology, 2017. DOI: 10.1007/s11255-017-1519-9. PMID: 28130714. - **Castillo 2024.** _Beneficial effects of physical exercise on the osteo-renal Klotho-FGF-23 axis in Chronic Kidney Disease: A systematic review with meta-analysis._ International Journal of Medical Sciences, 2024. DOI: 10.7150/ijms.90195. PMID: 38169578. - **Zuo 2025.** _Sex differences between atherogenic index of plasma and α-klotho levels in middle-aged and older adults: NHANES 2007–2016._ Frontiers in Endocrinology, 2025. DOI: 10.3389/fendo.2025.1521415. PMID: 40260276. - **Gan 2026.** _Modulation of PKCα/ETS1 by klotho restores CYB5R4-dependent mitochondrial function in proximal tubular epithelial cells to attenuate the progression of diabetic kidney disease._ Cardiovascular Diabetology, 2026. DOI: 10.1186/s12933-026-03150-y. PMID: 41904515. - **Fan 2024.** _Correlation between soluble klotho and chronic kidney disease–mineral and bone disorder in chronic kidney disease: a meta-analysis._ Scientific Reports, 2024. DOI: 10.1038/s41598-024-54812-4. PMID: 38396063. - **Ahmad 2025.** _Examining Insulin Resistance and BMI in the Context of Alpha-Klotho and Functional Decline._ Innovation in Aging, 2025. DOI: 10.1093/geroni/igaf122.2879. - **Liu 2021.** _Correlation Between Soluble Klotho and Vascular Calcification in Chronic Kidney Disease: A Meta-Analysis and Systematic Review._ Frontiers in Physiology, 2021. DOI: 10.3389/fphys.2021.711904. PMID: 34483963. - **Kantar 2026.** _Association of Increased Cardio-Ankle Vascular Index (CAVI) with Echocardiographically Impaired Diastolic Dysfunction and Low Klotho Levels in Kidney Transplant Patients._ Journal of Clinical Medicine, 2026. DOI: 10.3390/jcm15072727. PMID: 41977028. - **Yang 2025.** _Risk factors for developing osteoporosis in diabetic kidney disease and its correlation with calcium-phosphorus metabolism, FGF23, and Klotho._ World Journal of Diabetes, 2025. DOI: 10.4239/wjd.v16.i1.98714. PMID: 39817221. - **Pei 2022.** _Serum cystatin C, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, klotho and fibroblast growth factor-23 in the early prediction of acute kidney injury associated with sepsis in a Chinese emergency cohort study._ European Journal of Medical Research, 2022. DOI: 10.1186/s40001-022-00654-7. PMID: 35272698. - **Corcillo 2020.** _Low levels of circulating anti-ageing hormone Klotho predict the onset and progression of diabetic retinopathy._ Diabetes & Vascular Disease Research, 2020. DOI: 10.1177/1479164120970901. PMID: 33225726. - **Du 2025.** _Central adiposity and α-klotho: inflammatory mechanisms underlying aging biomarkers related to body roundness index._ Lipids in Health and Disease, 2025. DOI: 10.1186/s12944-025-02541-6. PMID: 40211310. - **Xin 2022.** _Relationship of Soluble Klotho and Early Stage of Diabetic Nephropathy: A Systematic Review and Meta-Analysis._ Frontiers in Endocrinology, 2022. DOI: 10.3389/fendo.2022.902765. PMID: 35692408. - **Edmonston 2024.** _Klotho and Clinical Outcomes in CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study._ Am J Kidney Dis, 2024. DOI: 10.1053/j.ajkd.2024.02.008. PMID: 38583756. - **Cecati 2025.** _Preeclampsia as a Study Model for Aging: The Klotho Gene Paradigm._ International Journal of Molecular Sciences, 2025. DOI: 10.3390/ijms26030902. PMID: 39940672. - **Mora-Fernandez 2022.** _Sodium-glucose co-transporter-2 inhibitors increase Klotho in patients with diabetic kidney disease: A clinical and experimental study._ Biomed Pharmacother, 2022. DOI: 10.1016/j.biopha.2022.113677. PMID: 36942605. - **Abstract the Klotho Protein 2025.** _Abstract 4365476: The Klotho Protein Reduces Vascular Calcification via Suppressing GPX4-mediated Ferroptosis in Vascular Smooth Muscle Cells._ Circulation, 2025. DOI: 10.1161/circ.152.suppl_3.4365476. - **Lopez-Valdes 2025.** _The Anti-Inflammatory Actions of Soluble Klotho in Brain Aging and Its Main Associated Diseases._ International Journal of Molecular Sciences, 2025. DOI: 10.3390/ijms26178551. PMID: 40943475. - **Charoenngam 2020.** _Lower circulating soluble Klotho level is associated with increased risk of all-cause mortality in chronic kidney disease patients: a systematic review and meta-analysis._ Int Urol Nephrol, 2020. DOI: 10.1007/s11255-020-02510-1. PMID: 32462356. - **Paradoxical Prognostic Role 2026.** _Paradoxical prognostic role of alpha-klotho protein: a marker of increased mortality risk in the post-myocardial infarction setting._ European Heart Journal: Acute Cardiovascular Care, 2026. DOI: 10.1093/ehjacc/zuag046.093. - **Driscoll 2026.** _Age-related alterations in plasma biomarkers of relevance to Alzheimer's disease are attenuated in KLOTHO KL-VS heterozygotes._ J Alzheimers Dis, 2026. DOI: 10.1177/13872877261422411. PMID: 41789852. - **Wang 2026.** _Association between serum Klotho and thrombocytopenia in middle-aged and older adults: A cross-sectional study based on NHANES._ Medicine (Baltimore), 2026. DOI: 10.1097/md.0000000000048281. PMID: 41961708. ### Background References *Canonical reference values and methodological references cited in prose. Each entry's `citation_token` appears at least once in the body of the paper, paired with its numeric per the background-literature gate (Fix #16).* - **Ioannidis 2005.** _Ioannidis JPA. Why most published research findings are false. PLoS Med. 2005;2(8):e124._ (methodological reference) DOI: 10.1371/journal.pmed.0020124. PMID: 16060722.
metadata
{
"article_type": "evidence_map",
"domain_slug": "longevity",
"researka_object_type": "submission",
"researka_submission_id": "ee6bcbe7-72ee-46f0-afd6-c62704c850e3",
"title": "Adjacent Evidence Brief: Alpha-klotho \u2014 full paper"
}