Klotho expression in peripheral blood circulating cells is associated with vascular and systemic inflammation in atherosclerotic vascular disease

Association between the duration of smoking cessation and α-Klotho levels in the US middle-aged and elderly population

Background

α-Klotho is a molecule associated with aging and several diseases. Previous studies have reported decreased levels of serum α-Klotho (SαKl) in smokers compared to never smokers. Interestingly, we also found the SαKl level could partly recover in those who quit smoking. The objective of this study was to investigate SαKl levels in the US population who quit smoking for a certain period.

Methods

A total of 9268 participants, ranging in age from 40 to 79 years were enrolled in this cross-sectional study, 37.04 % were identified as former smoker. Data from the NHANES conducted between 2007 and 2016 were utilized for analysis. The association between the period of smoking cessation and SαKl levels was evaluated through multivariate linear regression models. Additionally, a detailed analysis stratified by key clinical factors was performed.

Results

The mean level of SαKl among the former smoker was 827.41 pg/mL. After full adjustment, the SαKl level increased over time after smoking cessation, with an increase of 1.20 pg/ml per year of abstinence (P = 0.005). The linear correlation persists regardless of the duration of the smoking habit before quitting. In the stratified analysis, a positive correlation was observed between duration of smoking cessation and SαKl levels in individuals aged 60-79 years, females, normal weight individuals, those involved in moderate or vigorous physical activity, and those with a history of cancer (all P<0.05).

Conclusion

This study showed a positive association between the duration of smoking cessation and SαKl levels in former smokers. Prolonged abstinence may contribute to increased SαKl levels which may protect people against aging-related diseases.

New insights into the role of Klotho in inflammation and fibrosis: molecular and cellular mechanisms

As the body's defense mechanism against damage and infection, the inflammatory response is a pathological process that involves a range of inflammatory cells and cytokines. A healthy inflammatory response helps the body repair by eliminating dangerous irritants. However, tissue fibrosis can result from an overly intense or protracted inflammatory response. The anti-aging gene Klotho suppresses oxidation, delays aging, and fosters development of various organs. Numerous investigations conducted in the last few years have discovered that Klotho expression is changed in a variety of clinical diseases and is strongly linked to the course and outcome of a disease. Klotho functions as a co-receptor for FGF and as a humoral factor that mediates intracellular signaling pathways such as transforming growth factor β (TGF-β), toll-like receptors (TLRs), nuclear factor-kappaB (NF-κB), renin -angiotensin system (RAS), and mitogen-activated protein kinase (MAPK). It also interferes with the phenotype and function of inflammatory cells, such as monocytes, macrophages, T cells, and B cells. Additionally, it regulates the production of inflammatory factors. This article aims to examine Klotho's scientific advances in terms of tissue fibrosis and the inflammatory response in order to provide novel therapy concepts for fibrotic and inflammatory disorders.

Local vascular Klotho mediates diabetes-induced atherosclerosis via ERK1/2 and PI3-kinase-dependent signaling pathways

BACKGROUND AND AIMS

Diabetes is one of the major causes of cardiovascular disease (CVD). As high as 29 % of patients with diabetes develop atherosclerosis. Vascular Smooth Muscle Cells (VSMCs) are a key mediator in the pathogenesis of atherosclerosis, generating pro-inflammatory and proliferative characteristics in atherosclerotic lesions.

METHODS

We used human atherosclerotic samples, developed diabetes-induced atherosclerotic mice, and generated loss of function and gain of function in Klotho human aortic smooth muscle cells to investigate the function of Klotho in atherosclerosis.

RESULTS

We found that Klotho expression is decreased in smooth muscle actin-positive cells in patients with diabetes and atherosclerosis. Consistent with human data, we found that Apoe knockout mice with streptozotocin-induced diabetes fed on a high-fat diet showed decreased expression of Klotho in SMCs. Additionally, these mice showed increased expression of TGF-β, MMP9, phosphorylation of ERK and Akt. Further, we utilized primary Human Aortic Smooth Muscle Cells (HASMCs) with d-glucose under dose-response and in time-dependent conditions to study the role of Klotho in these cells. Klotho gain of function and loss of function studies showed that Klotho inversely regulated the expression of atherosclerotic markers TGF-β, MMP2, MMP9, and Fractalkine. Further, High Glucose (HG) induced Akt, and ERK1/2 phosphorylation were enhanced or mitigated by endogenous Klotho deficiency or its overexpression respectively. PI3K/Akt and MAPK/ERK inhibition partially abolished the HG-induced upregulation of TGF-β, MMP2, MMP9, and Fractalkine. Additionally, Klotho knockdown increased the proliferation of HASMCs and enhanced α-SMA and TGF-β expression.

CONCLUSIONS

Taken together, these results indicate that local vascular Klotho is involved in diabetes-induced atherosclerosis, which is via PI3K/Akt and ERK1/2-dependent signaling pathways.

Pentoxifylline ameliorates subclinical atherosclerosis progression in patients with type 2 diabetes and chronic kidney disease: a randomized pilot trial

BACKGROUND

Diabetic kidney disease (DKD) is associated with a higher risk of cardiovascular disease (CVD). Pentoxifylline (PTF), a nonselective phosphodiesterase inhibitor with anti-inflammatory, antiproliferative, and antifibrotic actions, has demonstrated renal benefits in both clinical trials and meta-analyses. The present work aimed to study the effects of PTF on the progression of subclinical atherosclerosis (SA) in a population of patients with diabetes and moderate to severe chronic kidney disease (CKD).

METHODS

In this open-label, randomized controlled, prospective single-center pilot study the evolution of carotid intima-media thickness (CIMT) and ankle-brachial index (ABI) were determined in 102 patients with type 2 diabetes mellitus and CKD assigned to PTF, aspirin or control groups during 18 months. We also determined the variations in the levels of inflammatory markers and Klotho (KL), a protein involved in maintaining cardiovascular health, and their relationship with the progression of SA.

RESULTS

Patients treated with PTF presented a better evolution of CIMT, increased KL mRNA levels in peripheral blood cells (PBCs) and reduced the inflammatory state. The progression of CIMT values was inversely related to variations in KL both in serum and mRNA expression levels in PBCs. Multiple regression analysis demonstrated that PTF treatment and variations in mRNA KL expression in PBCs, together with changes in HDL, were significant determinants for the progression of CIMT (adjusted R2 = 0.24, P < 0.001) independently of traditional risk factors. Moreover, both variables constituted protective factors against a worst progression of CIMT [OR: 0.103 (P = 0.001) and 0.001 (P = 0.005), respectively].

CONCLUSIONS

PTF reduced SA progression assessed by CIMT variation, a beneficial effect related to KL gene expression in PBCs.

TRIAL REGISTRATION

The study protocol code is PTF-AA-TR-2009 and the trial was registered on the European Union Drug Regulating Authorities Clinical Trials (EudraCT #2009-016595-77). The validation date was 2010-03-09.

Klotho exerts protection in chronic kidney disease associated with regulating inflammatory response and lipid metabolism

BACKGROUND

The anti-aging protein Klotho plays a protective role in kidney disease, but its potential as a biomarker for chronic kidney disease (CKD) is controversial. Additionally, the main pathways through which Klotho exerts its effects on CKD remain unclear. Therefore, we used bioinformatics and clinical data analysis to determine its role in CKD.

RESULTS

We analyzed the transcriptomic and clinical data from the Nephroseq v5 database and found that the Klotho gene was mainly expressed in the tubulointerstitium, and its expression was significantly positively correlated with estimated glomerular filtration rate (eGFR) and negatively correlated with blood urea nitrogen (BUN) in CKD. We further found that Klotho gene expression was mainly negatively associated with inflammatory response and positively associated with lipid metabolism in CKD tubulointerstitium by analyzing two large sample-size CKD tubulointerstitial transcriptome datasets. By analyzing 10-year clinical data from the National Health and Nutrition Examination Survey (NHANES) 2007-2016, we also found that Klotho negatively correlated with inflammatory biomarkers and triglyceride and positively correlated with eGFR in the CKD population. Mediation analysis showed that Klotho could improve renal function in the general population by modulating the inflammatory response and lipid metabolism, while in the CKD population, it primarily manifested by mediating the inflammatory response. Restricted cubic spline (RCS) analysis showed that the optimal concentration range for Klotho to exert its biological function was around 1000 pg/ml. Kaplan-Meier curves showed that lower cumulative hazards of all-cause mortality in participants with higher levels of Klotho. We also demonstrated that Klotho could reduce cellular inflammatory response and improve cellular lipid metabolism by establishing an in vitro model similar to CKD.

CONCLUSIONS

Our results suggest that Klotho exerts protection in CKD, which may be mainly related to the regulation of inflammatory response and lipid metabolism, and it can serve as a potential biomarker for CKD.

Translational Relevance of Advanced Age and Atherosclerosis in Preclinical Trials of Biotherapies for Peripheral Artery Disease

Approximately 6% of adults worldwide suffer from peripheral artery disease (PAD), primarily caused by atherosclerosis of lower limb arteries. Despite optimal medical care and revascularization, many PAD patients remain symptomatic and progress to critical limb ischemia (CLI) and risk major amputation. Delivery of pro-angiogenic factors as proteins or DNA, stem, or progenitor cells confers vascular regeneration and functional recovery in animal models of CLI, but the effects are not well replicated in patients and no pro-angiogenic biopharmacological procedures are approved in the US, EU, or China. The reasons are unclear, but animal models that do not represent clinical PAD/CLI are implicated. Consequently, it is unclear whether the obstacles to clinical success lie in the toxic biochemical milieu of human CLI, or in procedures that were optimized on inappropriate models. The question is significant because the former case requires abandonment of current strategies, while the latter encourages continued optimization. These issues are discussed in the context of relevant preclinical and clinical data, and it is concluded that preclinical mouse models that include age and atherosclerosis as the only comorbidities that are consistently present and active in clinical trial patients are necessary to predict clinical success. Of the reviewed materials, no biopharmacological procedure that failed in clinical trials had been tested in animal models that included advanced age and atherosclerosis relevant to PAD/CLI.

Functional and Extracellular Production and Antitumor Activity of Mouse Alpha Klotho in Model Microalga Chlamydomonas reinhardtii

Klotho is a human protein with versatile functions associated with longevity and well-being. α-Klotho (α-KL) deficiency in the circulatory system is associated with reduced life expectancy with numerous disorders such as chronic kidney disease, atherosclerosis, infertility, skin atrophy, emphysema, and osteoporosis. The antagonistic effects of Klotho protein against intractable cancers have also been well documented over the past two decades. In addition, recent findings have also illuminated the importance of soluble Klotho during cognitive development, oxidative stress, cellular apoptosis, and neurodegenerative disorders. The low-cost and sustainable production of alpha Klotho protein is extremely important for its widespread use against different diseases. Here, we report heterologous, functional, and extracellular production of mouse α-KL (mα-KL) protein in model microalga Chlamydomonas reinhardtii. The secretion of mα-KL into the extracellular environment facilitated downstream processes and warranted low-cost purification in high-titer. Furthermore, the anticarcinogenic efficiency of recombinant mα-KL was examined and validated on Rattus norvegicus AR42J pancreas tumors. Microalgae-based photosynthetic, low-cost, and scalable production of mα-KL could be used to develop a variety of cosmetics, pharmaceuticals, and wellness products, all aimed at serving health and well-being.

Potential application of Klotho as a prognostic biomarker for patients with diabetic kidney disease: a meta-analysis of clinical studies

Background

Diabetic kidney disease (DKD) is a serious diabetic complication and the performance of serum Klotho in DKD's prognostic evaluation is controversial.

Objective

To assess the association of serum Klotho with adverse kidney and non-kidney clinical outcomes in patients with DKD.

Design

Clinical studies regarding the relationship of serum Klotho with DKD were included. Study quality was assessed using the Newcastle-Ottawa scale. Subgroup and sensitive analyses were performed to search for the source of heterogeneity.

Data sources and methods

We comprehensively searched PubMed, Embase, Web of Science, and Cochrane library databases up to 27 September 2022. The associations of Klotho with albuminuria, such as the urinary albumin creatinine ratio (UACR), kidney outcomes such as persistent albuminuria, estimated glomerular filtration rate decline, and non-kidney outcomes such as diabetic retinopathy, cardiovascular morbidity, and mortality, were evaluated. The indicators, such as the correlation coefficient (r), odds ratio (OR), relative risk, and hazard ratio, were retrieved or calculated from the eligible studies.

Results

In all, 17 studies involving 5682 participants fulfilled the inclusion criteria and were included in this meta-analysis. There was no significant association of serum Klotho with UACR in DKD patients [summary r, -0.28 (-0.55, 0.04)] with high heterogeneity. By contrast, a strong association was observed regarding serum Klotho with kidney outcomes [pooled OR, 1.60 (1.15, 2.23)], non-kidney outcomes [pooled OR, 2.78 (2.11, 3.66)], or combined kidney and non-kidney outcomes [pooled OR, 1.96 (1.45, 2.65)] with moderate heterogeneity. Subgroup analysis indicated that age, study design, and the estimated glomerular filtration rate may be the sources of heterogeneity.

Conclusion

A decreased serum Klotho level is possibly associated with an increased risk of developing kidney and non-kidney clinical outcomes in DKD patients; thus, Klotho may be a possible biomarker to predict DKD clinical outcomes. Additional studies are needed to clarify and validate Klotho's prognostic value.

Bio-Impedance Spectroscopy of Retained Cells Using a Micro-Perforated Sensing Membrane Filtrating Whole Blood Samples under High Flowrate

Blood filtration using micro-fabricated devices is an interdisciplinary topic of research and innovation driven by clinical applications in cytapheresis, cardiovascular disease monitoring, or liquid biopsy. In this paper, we demonstrate that a micro-perforated membrane can be equipped with sensing microelectrodes for detecting, in situ and in real-time, the capture of cellular material during ex vivo filtration of whole blood under high flow rates. This work describes the fabrication process of the sift and detection microdevice. We demonstrate that reliable electrical signals can be measured in whole blood samples flowing inside a fluidic system at typical flow rates, as large as 11.5 mL/min, hence allowing for large-volume sample processing. The in situ monitoring of the electrical impedance of the microelectrodes is shown to characterize the accumulation of living circulating cells retained by the filtrating membrane, opening interesting applications for monitoring blood filtration processes.

A Systematic Review of Interleukins as Diagnostic and Prognostic Biomarkers for Peripheral Artery Disease

Background: Peripheral artery disease (PAD) involves atherosclerosis of the lower extremity arteries and is a major contributor to limb loss and death worldwide. Several studies have demonstrated that interleukins (ILs) play an important role in the development and progression of PAD; however, a comprehensive literature review has not been performed. Methods: A systematic review was conducted and reported according to PRISMA guidelines. MEDLINE was searched from inception to 5 December 2022, and all studies assessing the association between ILs and PAD were included. Results: We included 17 studies from a pool of 771 unique articles. Five pro-inflammatory ILs (IL-1β, IL-2, IL-5, IL-6, and IL-8) and one pro-atherogenic IL (IL-12) were positively correlated with PAD diagnosis and progression. In contrast, two anti-inflammatory ILs (IL-4 and IL-10) were protective against PAD diagnosis and adverse limb events. Specifically, IL-6 and IL-8 were the most strongly associated with PAD and can act as potential disease biomarkers to support the identification and treatment of PAD. Conclusions: Ongoing work to identify and validate diagnostic/prognostic inflammatory biomarkers for PAD has the potential to assist clinicians in identifying high-risk patients for further evaluation and management which could reduce the risk of adverse cardiovascular and limb events.

Current Medical Therapy and Revascularization in Peripheral Artery Disease of the Lower Limbs: Impacts on Subclinical Chronic Inflammation

Peripheral artery disease (PAD), coronary artery disease (CAD), and cerebrovascular disease (CeVD) are characterized by atherosclerosis and inflammation as their underlying mechanisms. This paper aims to conduct a literature review on pharmacotherapy for PAD, specifically focusing on how different drug classes target pro-inflammatory pathways. The goal is to enhance the choice of therapeutic plans by considering their impact on the chronic subclinical inflammation that is associated with PAD development and progression. We conducted a comprehensive review of currently published original articles, narratives, systematic reviews, and meta-analyses. The aim was to explore the relationship between PAD and inflammation and evaluate the influence of current pharmacological and nonpharmacological interventions on the underlying chronic subclinical inflammation. Our findings indicate that the existing treatments have added anti-inflammatory properties that can potentially delay or prevent PAD progression and improve outcomes, independent of their effects on traditional risk factors. Although inflammation-targeted therapy in PAD shows promising potential, its benefits have not been definitively proven yet. However, it is crucial not to overlook the pleiotropic properties of the currently available treatments, as they may provide valuable insights for therapeutic strategies. Further studies focusing on the anti-inflammatory and immunomodulatory effects of these treatments could enhance our understanding of the mechanisms contributing to the residual risk in PAD and pave the way for the development of novel therapies.

Role of klotho on antidepressant and antisuicidal effects of low-dose ketamine infusion among patients with treatment-resistant depression and suicidal ideation

OBJECTIVE

Previous studies have found an association between klotho, an anti-aging hormone, and major depressive disorder. However, whether low-dose ketamine infusion alters klotho levels among patients with treatment-resistant depression (TRD) remains unknown.

METHODS

In total, 48 patients with TRD and strong suicidal ideation were randomly assigned to a single 0.5 mg/kg ketamine or 0.045 mg/kg midazolam regimen and were subjected to a 2-week follow-up. Depressive and suicidal symptoms were assessed before the infusion and during the follow-up. The serum levels of klotho were assessed at baseline and 3 days postinfusion.

RESULTS

A generalized linear model with adjustment of baseline klotho levels showed that, despite the fact that ketamine did not significantly increase levels of klotho, patients in the ketamine group had higher levels of klotho at Day 3 postinfusion than patients in the midazolam group (p = 0.043). However, we found no association between changes in klotho levels and changes in depressive and suicidal symptoms (all p > 0.05). Higher klotho levels at baseline were associated with poorer antidepressant effect of low-dose ketamine during postinfusion follow-up.

DISCUSSION

Klotho may play a role in the antidepressant effect of low-dose ketamine. Additional molecular studies are necessary to elucidate the neuromechanisms of TRD, ketamine, and klotho.

The Importance of α-Klotho in Depression and Cognitive Impairment and Its Connection to Glutamate Neurotransmission-An Up-to-Date Review

Depression is a serious neuropsychiatric disease affecting an increasing number of people worldwide. Cognitive deficits (including inattention, poor memory, and decision-making difficulties) are common in the clinical picture of depression. Cognitive impairment has been hypothesized to be one of the most important components of major depressive disorder (MDD; referred to as clinical depression), although typical cognitive symptoms are less frequent in people with depression than in people with schizophrenia or bipolar disorder (BD; sometimes referred to as manic-depressive disorder). The importance of α-Klotho in the aging process has been well-documented. Growing evidence points to the role of α-Klotho in regulating other biological functions, including responses to oxidative stress and the modulation of synaptic plasticity. It has been proven that a Klotho deficit may contribute to the development of various nervous system pathologies, such as behavioral disorders or neurodegeneration. Given the growing evidence of the role of α-Klotho in depression and cognitive impairment, it is assumed that this protein may be a molecular link between them. Here, we provide a research review of the role of α-Klotho in depression and cognitive impairment. Furthermore, we propose potential mechanisms (related to oxidative stress and glutamatergic transmission) that may be important in α-Klotho-mediated regulation of mental and cognitive function.

Emerging role of α-Klotho in energy metabolism and cardiometabolic diseases

BACKGROUND AND AIM

Klotho was first identified as a gene associated with aging and longevity in 1997. α-Klotho is an anti-aging protein and its role in energy metabolism, various cardiovascular diseases (CVDs), and metabolic disorders is increasingly being recognized. In this review, we aimed to outline the potential protective role and therapeutic prospects of α-Klotho in energy metabolism and cardiometabolic diseases (CMDs).

METHODS

We comprehensively reviewed the relevant literature in PubMed using the keywords 'Klotho', 'metabolism', 'cardiovascular', 'diabetes', 'obesity', 'metabolic syndrome', and 'nonalcoholic fatty liver disease'.

RESULTS

α-Klotho can be divided into membrane-bound Klotho, secreted Klotho, and the most studied circulating soluble Klotho that can act as a hormone. Klotho gene polymorphisms have been implicated in energy metabolism and CMDs. α-Klotho can inhibit insulin/insulin growth factor-1 signaling and its overexpression can lead to a 'healthy insulin resistance' and may exert beneficial effects on the regulation of glycolipid metabolism and central energy homeostasis. α-Klotho, mainly serum Klotho, has been revealed to be protective against CVDs, diabetes and its complications, obesity, and nonalcoholic fatty liver disease. Human recombinant Klotho protein/Klotho gene delivery, multiple drugs, or natural products, and exercise can increase α-Klotho expression.

CONCLUSION

Overall, α-Klotho has demonstrated its potential as a promising target for modulating energy metabolism and CMDs, and further research is needed to explore its utilization in clinical practice in the future.

Correlation between serum α-Klotho levels and different stages of periodontitis

BACKGROUND

Periodontitis is an inflammatory disease characterized by inflammation and progressive destruction of periodontal tissues including alveolar bone. α-klotho protein is a multifunctional protein related to age-related diseases, inflammatory diseases, and bone metabolism-related diseases. However, large-sample epidemiological research evidence on the correlation between α-Klotho and the aggravation of periodontitis stages is still lacking.

METHODS

Cross-sectional study data of participants aged between 40 and 79 years in the National Health and Nutrition Examination Survey 2013‒2014 were selected and analyzed. The stages of periodontitis of the participants were determined according to the 2018 World Workshop Classification of Periodontal and Peri-implant Diseases. The serum α-Klotho levels in people with periodontitis in different stages were evaluated. Then the correlation between serum α-Klotho levels and different stages of periodontitis was analyzed by multiple linear regression (stepwise regression method).

RESULTS

A total of 2378 participants were included in the study. The serum α-Klotho levels in people with stage I/II, III and IV periodontitis were 896.16 ± 304.84, 871.08 ± 266.42 and 840.52 ± 286.24 pg/mL, respectively. The levels of α-Klotho in people with stage IV periodontitis were significantly lower than those in people with stage I/II and III periodontitis. Linear regression analysis results showed that compared to stage I/II periodontitis, serum α-Klotho levels were significantly negatively correlated with stage III (B ± SE = -37.28 ± 16.00, 95% CI: -68.66 ~ -25.91, P = 0.020) and stage IV (B ± SE = -69.37 ± 16.11, 95% CI: -100.97 ~ -37.77, P < 0.001) periodontitis.

CONCLUSION

The serum α-Klotho levels were negatively correlated with the severity of periodontitis. With the aggravation of periodontitis stages, the serum α-Klotho levels gradually decreased.

Klotho inversely relates with carotid intima- media thickness in atherosclerotic patients with normal renal function (eGFR ≥60 mL/min/1.73m2): a proof-of-concept study

Introduction

Klotho protein is predominantly expressed in the kidneys and has also been detected in vascular tissue and peripheral blood circulating cells to a lesser extent. Carotid artery intima-media thickness (CIMT) burden, a marker of subclinical atherosclerosis, has been associated with reductions in circulating Klotho levels in chronic kidney disease patients, who show reduced levels of this protein at all stages of the disease. However, the contribution of serum Klotho and its expression levels in peripheral blood circulating cells and in the carotid artery wall on the CIMT in the absence of kidney impairment has not yet been evaluated.

Methods

We conducted a single-center study in 35 atherosclerotic patients with preserved kidney function (eGFR≥60 mL/min/1.73m2) subjected to elective carotid surgery. Serum levels of Klotho and cytokines TNFa, IL6 and IL10 were determined by ELISA and transcripts encoding for Klotho (KL), TNF, IL6 and IL10 from vascular segments were measured by qRT-PCR. Klotho protein expression in the intima-media and adventitia areas was analyzed using immunohistochemistry.

Results

APatients with higher values of CIMT showed reduced Klotho levels in serum (430.8 [357.7-592.9] vs. 667.8 [632.5-712.9] pg/mL; p<0.001), mRNA expression in blood circulating cells and carotid artery wall (2.92 [2.06-4.8] vs. 3.69 [2.42-7.13] log.a.u., p=0.015; 0.41 [0.16-0.59] vs. 0.79 [0.37-1.4] log.a.u., p=0.013, respectively) and immunoreactivity in the intimal-medial area of the carotids (4.23 [4.15-4.27] vs. 4.49 [4.28-4.63] log µm2 p=0.008). CIMT was inversely related with Klotho levels in serum (r= -0.717, p<0.001), blood mRNA expression (r=-0.426, p=0.011), and with carotid artery mRNA and immunoreactivity levels (r= -0.45, p=0.07; r= -0.455, p= 0.006, respectively). Multivariate analysis showed that serum Klotho, together with the gene expression levels of tumor necrosis factor TNFa in blood circulating cells, were independent determinants of CIMT values (adjusted R2 = 0.593, p<0.001).

Discussion

The results of this study in subjects with eGFR≥60mL/min/1.73m2 show that patients with carotid artery atherosclerosis and higher values of CIMT present reduced soluble Klotho levels, as well as decreased KL mRNA expression in peripheral blood circulating cells and Klotho protein levels in the intima-media of the carotid artery wall.

Anti-Inflammatory Klotho Protein Serum Concentration Correlates with Interferon Gamma Expression Related to the Cellular Activity of Both NKT-like and T Cells in the Process of Human Aging

Klotho is a beta-glucuronidase that reveals both anti-inflammatory and anti-oxidative properties that have been associated with mechanisms of aging. The study aimed to analyze the relationships between the serum concentration of soluble α-Klotho and cellular activity of two populations of lymphocytes; T and NKT-like cells corresponding to the level of cytokine secretion; i.e., IFN-γ, TNF-α, and IL-6. The studied population comprised three age groups: young individuals ('young'), seniors aged under 85 ('old'), and seniors aged over 85 ('oldest'). Both NKT-like and T cells were either non-cultured or cultured for 48 h and stimulated appropriately with IL-2, LPS or PMA with ionomycin to compare with unstimulated control cells. In all studied age groups non-cultured or cultured NKT-like cells revealed higher expressions of TNF-α, IL-6, and IFN-γ than T cells. α-Klotho concentration in serum decreased significantly in the process of aging. Intriguingly, only IFN-γ expression revealed a positive correlation with α-Klotho protein serum concentration in both non-cultured and cultured T and NKT-like cells. Since IFN-γ is engaged in the maintenance of immune homeostasis, the observed relationships may indicate the involvement of α-Klotho and cellular IFN-γ expression in the network of adaptive mechanisms developed during the process of human aging.

Low serum Klotho reflects senile inflammation in middle-aged and elderly patients with coronary atherosclerosis

BACKGROUND

Anti-aging protein Klotho has been reported to be associated with atherosclerosis, which was considered as a chronic inflammatory disease. However, the relationship between Klotho and senile inflammation remained unclear. The present study aims to ascertain the correlation of Klotho with inflammation in middle-aged and elderly coronary atherosclerotic disease (CAD).

METHODS

A total of 302 patients with CAD were included in this study. Coronary atherosclerosis was confirmed and quantified for all patients by coronary angiography. Serum Klotho was detected by enzyme linked immunosorbent assay. Serum concentrations of IL-6 and IL-8 were quantified by chemiluminescence assay. T-lymphocyte subsets were measured using flow cytometry.

RESULTS

Multivariate linear regression analysis showed that serum Klotho was an independent predictor for circulating monocytes (standard β = -0.321, P < 0.001) and CD4+/CD8+ ratio (standard β = -0.522, P < 0.001). After adjustment, serum Klotho was still independently associated with IL-6 (standard β = -0.395, P < 0.001) and IL-8 (standard β = -0.296, P < 0.001). Moreover, circulating monocytes, CD4+ and CD8+ lymphocytes were correlated with increased serum concentrations of IL-6 and IL-8, independent of CRP (P < 0.05). In receiver operating characteristic curve analysis, CD4+/CD8+ ratio (AUC = 0.863, P < 0.001), IL-6 (AUC = 0.893, P < 0.001) and IL-8 (AUC = 0.884, P < 0.001) presented the excellent predictive performance for significant CAD.

CONCLUSIONS

Decreased concentrations in serum Klotho reflect senile inflammation, which is related to the severity of CAD in middle-aged and elderly patients.

The Circulating Level of Klotho Is Not Dependent upon Physical Fitness and Age-Associated Methylation Increases at the Promoter Region of the Klotho Gene

(1) Background: Higher levels of physical fitness are believed to increase the physiological quality of life and impact the aging process with a wide range of adaptive mechanisms, including the regulation of the expression of the age-associated klotho (KL) gene and protein levels. (2) Methods: Here, we tested the relationship between the DNA methylation-based epigenetic biomarkers PhenoAge and GrimAge and methylation of the promoter region of the KL gene, the circulating level of KL, and the stage of physical fitness and grip force in two groups of volunteer subjects, trained (TRND) and sedentary (SED), aged between 37 and 85 years old. (3) Results: The circulating KL level is negatively associated with chronological age in the TRND group (r = -0.19; p = 0.0295) but not in the SED group (r = -0.065; p = 0.5925). The age-associated decrease in circulating KL is partly due to the increased methylation of the KL gene. In addition, higher plasma KL is significantly related to epigenetic age-deceleration in the TRND group, assessed by the biomarker of PhenoAge (r = -0.21; p = 0.0192). (4) Conclusions: The level of physical fitness, on the other hand, does not relate to circulating KL levels, nor to the rate of the methylation of the promoter region of the KL gene, only in males.

Pathobiology of the Klotho Antiaging Protein and Therapeutic Considerations

The α-Klotho protein (henceforth denoted Klotho) has antiaging properties, as first observed in mice homozygous for a hypomorphic Klotho gene (kl/kl). These mice have a shortened lifespan, stunted growth, renal disease, hyperphosphatemia, hypercalcemia, vascular calcification, cardiac hypertrophy, hypertension, pulmonary disease, cognitive impairment, multi-organ atrophy and fibrosis. Overexpression of Klotho has opposite effects, extending lifespan. In humans, Klotho levels decline with age, chronic kidney disease, diabetes, Alzheimer’s disease and other conditions. Low Klotho levels correlate with an increase in the death rate from all causes. Klotho acts either as an obligate coreceptor for fibroblast growth factor 23 (FGF23), or as a soluble pleiotropic endocrine hormone (s-Klotho). It is mainly produced in the kidneys, but also in the brain, pancreas and other tissues. On renal tubular-cell membranes, it associates with FGF receptors to bind FGF23. Produced in bones, FGF23 regulates renal excretion of phosphate (phosphaturic effect) and vitamin D metabolism. Lack of Klotho or FGF23 results in hyperphosphatemia and hypervitaminosis D. With age, human renal function often deteriorates, lowering Klotho levels. This appears to promote age-related pathology. Remarkably, Klotho inhibits four pathways that have been linked to aging in various ways: Transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), Wnt and NF-κB. These can induce cellular senescence, apoptosis, inflammation, immune dysfunction, fibrosis and neoplasia. Furthermore, Klotho increases cell-protective antioxidant enzymes through Nrf2 and FoxO. In accord, preclinical Klotho therapy ameliorated renal, cardiovascular, diabetes-related and neurodegenerative diseases, as well as cancer. s-Klotho protein injection was effective, but requires further investigation. Several drugs enhance circulating Klotho levels, and some cross the blood-brain barrier to potentially act in the brain. In clinical trials, increased Klotho was noted with renin-angiotensin system inhibitors (losartan, valsartan), a statin (fluvastatin), mTOR inhibitors (rapamycin, everolimus), vitamin D and pentoxifylline. In preclinical work, antidiabetic drugs (metformin, GLP-1-based, GABA, PPAR-γ agonists) also enhanced Klotho. Several traditional medicines and/or nutraceuticals increased Klotho in rodents, including astaxanthin, curcumin, ginseng, ligustilide and resveratrol. Notably, exercise and sport activity increased Klotho. This review addresses molecular, physiological and therapeutic aspects of Klotho.