Unveiling the Emerging Role of Klotho: A Comprehensive Narrative Review of an Anti-aging Factor in Human Fertility.

Klotho, an anti-aging protein, plays a vital role in diverse biological functions, such as regulating calcium and vitamin D levels, preventing chronic fibrosis, acting as an antioxidant and anti-inflammatory agent, safeguarding against cardiovascular and neurodegenerative conditions, as well as exerting anti-apoptotic, anti-senescence effects. Additionally, it contributes to metabolic processes associated with diabetes and exhibits anti-cancer properties. This protein is commonly expressed in organs, such as kidneys, brain, pancreas, parathyroid glands, ovaries, and testes. Recent research has highlighted its significance in human fertility. This narrative review provides insight into the involvement of Klotho protein in male and female fertility, as well as its potential role in managing human infertility in the future. In this study, a search was conducted on literature spanning from November 1997 to June 2024 across multiple databases, including PUBMED, SCOPUS, and Google Scholar, focusing on Klotho proteins. The search utilized keywords, such as "discovery of Klotho proteins," "Biological functions of Klotho," "Klotho in female fertility," "Klotho and PCOS," "Klotho and cryopreservation," and "Klotho in male infertility." Inclusion criteria comprised full-length original or review articles, as well as abstracts, discussing the role of Klotho protein in human fertility, published in English in various peer-reviewed journals. Exclusion criteria involved articles published in languages other than English. Hence, due to its anti-aging characteristics, Klotho protein presents potential roles in male and female fertility and holds promising prospects for reproductive medicine. Further, it holds the potential to become a valuable asset in addressing infertility concerns for both males and females.

Association of Klotho with Neuropsychiatric Disorder: A Meta-Analysis.

Neuropsychiatric disorders are mainly concerned with the behavioural, emotional and cognition symptoms that may be due to disturbed cerebral functions or extracerebral disease. Klotho protein is an antiaging protein that is mostly associated with cognitive changes in these disorders and thus this meta-analysis is conducted in order to find Klotho proteins association with these disorders. We searched related topics in pubmed, by using the key word i.e. Klotho and related disorder from neuropsychiatry e.g. Klotho levels and schizophrenia, Klotho levels and parkinsonism etc. Total 82 studies were found till 9th February 2021 after extensive search and 10 studies were selected for further analysis. The meta-analysis of studies was performed using the Random effect model. The forest plot represented each study in the meta-analysis, so as to make the comparison of SMD value across studies. The meta-analysis outcome demonstrated that overall schizophrenia had higher klotho levels as compared with bipolar disorder, psychosocial stress, parkinsonism, multiple sclerosis, depression, Alzheimer's disease, and healthy controls, followed by MS. The meta-analysis also found that bipolar disorder and Alzheimer's disease were associated with low klotho levels as compared to schizophrenia. The results indicate a significant association of the klotho levels and schizophrenia. Further studies are needed to characterize the potential biological roles of klotho levels in psychiatric disorders.

The prognostic value of serum α-klotho in age-related diseases among the US population: A prospective population-based cohort study.

Objective: α-Klotho is a potential biological marker of aging with satisfactory clinical applicability. However, its prognostic significance in age-related diseases has largely been undermined. Therefore, we aimed to report the prognostic value of serum α-klotho levels in age-related diseases. Methods: Participants with available serum α-klotho data from the National Health and Nutrition Examination Survey (2007-2016) were included. Their survival status was collected at 7.62 ± 2.99 years after serum α-klotho data was collected, and the endpoint was all-cause and cardiovascular mortality. A Cox regression model was established to examine the association between serum α-klotho levels and all-cause and cardiovascular mortality. Results: The present study included 13,746 U.S. adults with a survey-weighted mean age of 56.19 ± 10.42 years old. Of these, 52.2 % were female and 72.9 % were non-Hispanic whites. The optimal cutoff value of serum α-klotho for predicting all-cause mortality risk in the general population was 603.5 pg/ml. Individuals with low serum α-klotho (<603.5 pg/ml) had a significantly higher risk of all-cause (adjusted HR: 1.34(1.18-1.52), P < 0.001) and cardiovascular mortality (adjusted HR: 1.63(1.27-2.10), P < 0.001). Subgroup analysis showed that low serum α-klotho level was an independent risk factor for all-cause and cardiovascular mortality in people with hypertension, congestive heart failure, diabetes mellitus, and emphysema, while it was an independent risk factor for all-cause mortality in patients with renal insufficiency. Conclusion: A low serum α-klotho concentration (<603.5 pg/ml) could serve as a marker of all-cause and cardiovascular mortality in the general population and in people with age-related diseases, including hypertension, congestive heart failure, diabetes mellitus, and emphysema.

Beneficial effects of physical exercise on the osteo-renal Klotho-FGF-23 axis in Chronic Kidney Disease: A systematic review with meta-analysis.

The aim of this study was to investigate the efficacy of physical exercise in chronic kidney disease, describing its impact on the Klotho-FGF23 axis. PubMed, Web of Science and Scopus databases, updated to January 2023, were searched. The present study employed mean difference and a 95% confidence interval (CI) to examine the efficacy of the intervention. Heterogeneity was assessed through inconsistency statistics (I2). Out of the 299 studies identified, a total of 4 randomized controlled trials (RCTs), comprising 272 participants, met the eligibility criteria. Compared with the control group, physical exercise significantly decreased the concentrations of FGF23 (MD: -102.07 Pg/mL, 95% CI: -176.23.47, -27.91 I2= 97%, p = 0.001), and a significantly increased the concentrations of Klotho protein: (MD: 158.82 Pg/mL, 95% CI: 123.33, -194.31, I2 = 0%, p = 0.001). The results of our study indicated that the exercise has a direct relationship with Klotho-FGF23 axis. We can conclude that physical exercise in patients with CKD produces beneficial effects on the pathophysiological components related to this disease, including cardiorespiratory fitness and vascular functions. As observed, both endurance and aerobic physical exercise increase Klotho production and decrease FGF23 levels. Evidence indicates that exercise attenuates the progression of CKD, improves uremic parameters and down-regulates inflammation-related markers.

The influence of Klotho protein and prooxidant-antioxidant balance combination on the mortality of HD patients.

PURPOSE: End-stage renal disease patients on chronic hemodialysis (HD) have a shortened life expectancy compared to the general population. The aim of this study was to evaluate a possible link between three new and emerging factors in renal pathophysiology: Klotho protein, telomere length in peripheral blood mononuclear cells (TL) and redox status parameters before HD (bHD) and after HD (aHD), and to test mortality prediction capability of these emerging parameters in a population of HD patients. METHODS: The study included 130 adult patients with average age 66 (54-72), on HD (3 times per week; 4-5 h per session). Klotho level, TL, routine laboratory parameters, dialysis adequacy and redox status parameters: advanced oxidation protein products (AOPP), prooxidant-antioxidant balance (PAB), superoxide anion (O2.-), malondialdehyde (MDA), ischemia-modified albumin (IMA), total sulfhydryl group content (SHG), and superoxide dismutase (SOD) were determined. RESULTS: Klotho concentration was significantly higher aHD; 68.2 (22.6-152.9) vs. bHD 64.2 (25.5-119.8) (p = 0.027). The observed increase in TL was not statistically significant. AOPP, PAB, SHG, and SOD activity were significantly increased aHD (p > 0.001). The patients with the highest mortality risk score (MRS) had significantly higher PAB bHD (p = 0.002). Significantly lower O2.- (p < 0.001), SHG content (p = 0.072), and IMA (p = 0.002) aHD were found in patients with the lowest MRS values. Principal component analysis revealed redox balance-Klotho factor as a significant predictor of high mortality risk (p = 0.014). CONCLUSION: Decreased Klotho and TL attrition as well as redox status disturbance could be connected with higher mortality rate in HD patients.

The correlation between serum Klotho levels and frailty in elderly people / 中华老年医学杂志

Objective:To examine the correlation between serum Klotho levels and frailty in elderly people.Methods:In this cross-sectional study, 150 community-dwelling elderly people aged 65 years and over were enrolled.Subjects were divided into a frail(n=50, 33.3%), a pre-frail(n=47, 31.3%)and a non-frail(n=53, 35.3%)group based on the Fried phenotype.General participant data, routine laboratory test results, short physical performance battery(SPPB)results and human body composition data were collected.Serum Klotho protein levels were measured by an enzyme-linked immunosorbent assay.The relationship between serum Klotho protein levels and frailty was analyzed by using Spearmen's correlation analysis and Logistic regression analysis.Results:Klotho protein levels were lower in the frail group than in the non-frail group( P=0.001), whereas differences between the frail group and the pre-frail group and between the pre-frail group and the non-frail group were not statistically significant(all P>0.05).When Klotho protein levels were classified into four quartiles, i.e., Q 1, Q 2, Q 3, and Q 4, using three cut-off vales(2.28, 3.52, and 5.09 mg/L), the prevalences of frailty were 51.4%(19/37), 39.5%(15/38), 24.3%(9/37)and 18.4%(7/38), respectively.The prevalence of frailty decreased with increasing Klotho protein levels( χ2=11.204, P=0.011).Spearman correlation analysis showed that the Klotho protein level was negatively correlated with frailty( r=-0.310, P<0.001).Multivariate Logistic regression analysis results showed that age( OR=1.109, 95% CI: 1.011-1.217, P=0.028)and sarcopenia( OR=6.511, 95% CI: 1.279-33.147, P=0.024)were risk factors for frailty, while walking( OR=0.104, 95% CI: 0.033-0.326, P<0.001), a high SPPB score( OR=0.780, 95% CI: 0.627-0.970, P=0.026), and a high Klotho protein level( OR=0.752, 95% CI: 0.581-0.974, P=0.031)were protective factors against frailty. Conclusions:The serum Klotho protein level may be used as a parameter for the assessment of frailty.It is negatively correlated with frailty, suggesting that elderly people with low serum Klotho protein levels are at high risk of developing frailty.

Correlation of serum soluble Klotho protein and tendino-C with severity of disease and oxidative stress in children with IgA nephropathy / 国际检验医学杂志

Objective To analyze the correlation between serum soluble Klotho protein(sKL)and tendino-C(TN-C)and the severity of disease and oxidative stress in children with immunoglobulin A(IgA)nephropa-thy.Methods A total of 85 children with IgA nephropathy admitted to the hospital from July 2019 to August 2022 were selected as IgA nephropathy group,and 85 healthy patients who underwent physical examination in the hospital during the same period were selected as healthy group.Serum sKL and TN-C levels were com-pared between the two groups.Receiver operating characteristic(ROC)curve was drawn to analyze the value of serum sKL,TN-C and their combination in predicting the occurrence of IgA nephropathy.IgA nephropathy group was divided into mild group(28 cases),moderate group(39 cases)and severe group(18 cases)accord-ing to 24 h urinary protein quantity.Serum sKL,TN-C levels and oxidative stress indexes[malondialdehyde(MDA),superoxide dismutase(SOD)and advanced oxidation protein product(AOPP)]of the three groups were compared.The correlation between serum sKL and TN-C levels and oxidative stress indexes was ana-lyzed by Spearman correlation,and the correlation between serum sKL and TN-C levels and the severity of IgA nephropathy in children was examined by Kendall's Tau-b.Results The serum sKL level in IgA ne-phropathy group was lower than that in healthy group,and the serum TN-C level was higher than that in healthy group,the difference was statistically significant(P＜0.05).ROC curve showed that the area under the curve and 95％CI of serum sKL,TNC and their combination predicted the occurrence of IgA nephropathy were 0.726(95％CI:0.648-0.803),0.853(95％CI:0.796-0.909)and 0.891(95％CI:0.845-0.937).The level of serum sKL in severe group was lower than that in moderate and mild groups,while the level of serum TN-C was higher than that in moderate and mild groups,and the difference was statistically significant(P＜0.05).The serum SOD level of severe group was lower than that of moderate group and mild group,and the serum AOPP and MDA levels were higher than those of moderate group and mild group,the difference was statistically significant(P＜0.05).Spearman correlation showed that sKL level was positively correlated with SOD(r＞0,P＜0.05),and negatively correlated with AOPP and MDA(r＜0,P＜0.05).TN-C level was negatively correlated with SOD(r＜0,P＜0.05),and positively correlated with AOPP and MDA(r＞0,P＜0.05).Conclusion The levels of serum sKL and TN-C in children with IgA nephropathy are related to the severity of disease and oxidative stress,and the combination of SKL and TN-C can effectively predict the occurrence of IgA nephropathy.

Analysis of the relationship between mild cognitive impairment and serum klotho protein and insulin-like growth factor-1 in the elderly.

BACKGROUND: Mild cognitive impairment (MCI) is a mild memory or cognitive impairment. OBJECTIVE: To explore the relationship between serum klotho (K1) protein and insulin-like growth factor-1 and mild cognitive impairment in the elderly in order to provide accurate and appropriate indicators for clinical diagnosis and treatment of MCI. METHODS: This randomized stratified study adopted a multistage cluster sampling method. 161 elderly patients with mild cognitive impairment were included as the MCI group, and 161 healthy people matched with the MCI group in gender, age and education were selected as the control group. RESULTS: The levels of serum K1 protein and insulin-like growth factor-1 in the MCI group were lower than those in the control group (P< 0.05). Both IGF-1 and K1 had predictive value for MCI (P< 0.05). The area under the curve (AUC) of IGF-1 for predicting MCI was 0.859 (95% CI: 0.790∼0.929), and the AUC of K1 for predicting MCI was 0.793 (95% CI: 0.694∼0.892). The value of joint prediction of the two indicators was the highest, with an AUC of 0.939 (95% CI: 0.896-0.993). CONCLUSION: High serum K1 and insulin-like growth factor-1 are the protective factors of cognitive impairment in MCI patients. Both IGF-1 and serum K1 proteins have predictive value for MCI, and the combination of the two indicators has the highest predictive value.

Branched Multimeric Peptides as Affinity Reagents for the Detection of α-Klotho Protein.

α-Klotho, an aging-related protein found in the kidney, parathyroid gland, and choroid plexus, acts as an essential co-receptor with the fibroblast growth factor 23 receptor complex to regulate serum phosphate and vitamin D levels. Decreased levels of α-Klotho are a hallmark of age-associated diseases. Detecting or labeling α-Klotho in biological milieu has long been a challenge, however, hampering the understanding of its role. Here, we developed branched peptides by single-shot parallel automated fast-flow synthesis that recognize α-Klotho with improved affinity relative to their monomeric versions. These peptides were further shown to selectively label Klotho for live imaging in kidney cells. Our results demonstrate that automated flow technology enables rapid synthesis of complex peptide architectures, showing promise for future detection of α-Klotho in physiological settings.

Bone disease in patients with cirrhosis of different etiology and severity; are Klotho protein and osteoprotegerin potential biomarkers?

BACKGROUND AND AIMS: Cirrhosis is associated with increased risk for osteoporosis and osteopenia. This study aims to further investigate this relationship by examining if etiology and severity of cirrhosis are independent predictors of bone mineral density (BMD) loss. Furthermore we examined the serum levels of osteoprotegerin (OPG) and Klotho proteins that have been involved in bone metabolism. METHODS: Seventy-four patients with cirrhosis of different etiology and 25 matched healthy controls were included in this study. Bone mineral densitometry at both lumbar spine and femoral neck was measured. Serum total OPG, Klotho protein and vitamin D levels were also determined. Comparisons were performed according to etiology and severity of cirrhosis. RESULTS: Decreased bone density was observed in cirrhotic patients compared to healthy controls with T = -1.46 and T = -1.37 in lumbar spine and femoral bone respectively compared to T = -0.396 and T = -0.672 in the control group. In the cirrhotic group, osteopenia was observed in 46% in lumbar spine and 51% in femoral bone whereas osteoporosis was observed in 20% in lumbar spine and 9% in femoral bone. Decreased bone density was confirmed, regardless of cirrhosis etiology or stage of liver function. Patients were found to have higher levels of OPG than the control group (136 pg/ml vs. 67 pg/ml, p < 0.001), but lower levels of Klotho protein (1051 pg/ml vs. 1842 pg/ml, p < 0.001) regardless etiology and severity of cirrhosis. High OPG levels were found to be associated with low femoral bone density. CONCLUSIONS: BMD is lower in cirrhotic patients regardless etiology and severity of liver disease with osteopenia and osteoporosis be present in 50% and 20%, respectively. Higher levels of OPG and lower levels of Klotho protein were observed in cirrhotic patients regardless etiology and severity in comparison to matched healthy group.

Klotho inhibits the formation of calcium oxalate stones by regulating the Keap1-Nrf2-ARE signaling pathway.

PURPOSE: Oxidative damage is important in calcium oxalate (CaOx) stone development but occurs via multiple pathways. Studies have shown that klotho plays an essential role in ameliorating oxidative damage. This study aims to explore the role of klotho in CaOx stones and whether the underlying mechanism is related to the regulation of Keap1-Nrf2-ARE signaling. METHODS: The levels of GSH, SOD, CAT, MDA, and ROS were examined by ELISA. The klotho, Bcl-2, caspase-3, Keap1, Nrf2, HO-1, and NQO1 mRNA levels were measured by qRT‒PCR, and their protein levels were detected by Western blotting. Renal tissue apoptosis was examined by TUNEL staining, and crystal cell adherence and apoptosis in HKC cells were assessed based on the Ca2+ concentrations and by flow cytometry. The renal pathological changes and the adhesion of CaOx crystals in the kidneys were examined by hematoxylin-eosin and von Kossa staining, respectively. RESULTS: We constructed a CaOx kidney stone model in vitro. By regulating the klotho gene, klotho overexpression inhibited the CaOx-induced promotion of crystal cell adherence and apoptosis in HKC cells, and these effects were reversed by klotho knockdown. Moreover, our in vivo assay demonstrated that klotho overexpression alleviated glyoxylate administration-induced renal oxidative damage, renal apoptosis, and crystal deposition in the kidneys of mice, and these effects were also associated with activation of the Keap1-Nrf2-ARE pathway. CONCLUSION: Klotho protein inhibits the oxidative stress response of HKC cells through the Keap1-Nrf2-ARE signaling pathway, reduces the apoptosis of and adhesion of CaOx crystals to HKC cells, and decreases the occurrence of CaOx kidney stones. CLINICAL TRIAL REGISTRATION: 20220304.

Relationship between serum MLT and Klotho protein and pro-inflammatory factors and efficacy in patients with primary angle-closure glaucoma / 国际检验医学杂志

Objective To investigate the relationship of serum melatonin(MLT)and Klotho protein with pro-inflammatory factors and the effect of surgical treatment in patients with primary angle-closure glaucoma(PACG).Methods A total of 149 PACG patients admitted to the Zigong Fourth People's Hospital from June 2018 to June 2021 were selected as the case group,and 149 healthy people who underwent physical examina-tion in the hospital during the same period were selected as the control group.The levels of MLT,Klotho pro-tein,interleukin-6(IL-6),interleukin-1β(IL-1β)and tumor necrosis factor-α(TNF-α)were compared be-tween the two groups.Pearson correlation analysis was used to analyze the correlation between MLT,Klotho protein and pro-inflammatory factors.Univariate and multivariate Logistic regression models were used to an-alyze the influencing factors of surgical treatment.Results Compared with the control group,the levels of MLT and Klotho protein in the case group were decreased(P<0.05),and the levels of IL-1β,IL-6 and TNF-α were increased(P<0.05).Pearson correlation analysis showed that serum MLT and Klotho protein were negatively correlated with the levels of pro-inflammatory factors IL-1β,IL-6,and TNF-α(P<0.05).After 12 months of surgical treatment,30 patients(20.13%)had no effect of surgical treatment(ineffective group).119 patients(79.87%)had effective surgical treatment(effective group).The univariate analysis showed that compared with the effective group,the preoperative intraocular pressure(IOP),proportion of chronic PACG,preoperative best corrected visual acuity,proportion of preoperative Angle adhesion>160° were significantly increased(P<0.05),and the preoperative anterior chamber depth,MLT,and Klotho protein levels were de-creased in the ineffective group(P<0.05).Multivariate Logistic regression analysis showed that elevated pre-operative IOP,chronic PACG,decreased MLT and Klotho levels were independent risk factors for ineffective surgical treatment(P<0.05).Conclusion serum MLT,Klotho protein levels in patients with PACG,closely associated with proinflammatory factor,is the related factors influencing the effect of surgical treatment.

Klotho Protein Decreases MMP-Mediated Degradation of Contractile Proteins during Ischaemia/Reperfusion Injury to the Cardiomyocytes.

Ischaemia, followed by reperfusion, causes the generation of reactive oxygen species, overproduction of peroxynitrite, activation of matrix metalloproteinases (MMPs), and subsequently the degradation of heart contractile proteins in the cardiomyocytes. Klotho is a membrane-bound or soluble protein that regulates mineral metabolism and has antioxidative activity. This study aimed to examine the influence of Klotho protein on the MMP-mediated degradation of contractile proteins during ischaemia/reperfusion injury (IRI) to the cardiomyocytes. Human cardiac myocytes (HCM) underwent in vitro chemical IRI (with sodium cyanide and deoxyglucose), with or without the administration of recombinant Klotho protein. The expression of MMP genes, the expression and activity of MMP proteins, as well as the level of contractile proteins such as myosin light chain 1 (MLC1) and troponin I (TnI) in HCM were measured. Administration of Klotho protein resulted in a decreased activity of MMP-2 and reduced the release of MLC1 and TnI that followed in cells subjected to IRI. Thus, Klotho protein contributes to the inhibition of MMP-dependent degradation of contractile proteins and prevents injury to the cardiomyocytes during IRI.

The effect of Klotho protein complexed with nanomaterials on bone mesenchymal stem cell performance in the treatment of diabetic ischaemic ulcer.

A lack of angiogenesis is the key problem in the healing of diabetic foot ulcers. Stem cells have already been proven to have a high potential for angiogenesis. The most important aspects of stem cell therapy are improving the microenvironment, cell homing and continuous factor stimulation. We investigated the effect of Klotho protein to heal wounds by promoting the proliferation and migration of bone mesenchymal stem cells and endothelial cells in vitro. Based on the above study, we produced a compound material by using poly(lactic-co-glycolic acid) (PLGA), chitosan microspheres and gelatin through electro spining technology. The structure of the compound material, just like a sandwich, is that two pieces of PLGA nanofiber films clamped gelatin film which contained chitosan microspheres. In the in vitro release experiment, we could detect the release of Klotho after seven days in the compound material, but the release time was approximately 40 hours for the chitosan microspheres. After seeded bone mesenchymal stem cells (BMSCs) on the surface of the compound material, we observed morphologies of the chitosan microsphere, the PLGA nanofiber and BMSCs by scanning electron microscopy. The nanofiber mesh biological tissue materials could supply an appropriate microenvironment and cell factors for the survival of BMSCs. Compared with the control group, the biological tissue material seeded with BMSCs significantly promoted angiogenesis in the lower limb of diabetic C57BL/6J mice and accelerated diabetic foot wound healing. The compound biomaterial which could continuously stimulate BMSCs through releasing Klotho protein could accelerate wound healing in the diabetic foot and other ischemic ulcers.

References Values of Soluble α-Klotho Serum Levels Using an Enzyme-Linked Immunosorbent Assay in Healthy Adults Aged 18-85 Years.

α-Klotho protein is a powerful predictor of the aging process and lifespan. Although lowered circulating soluble α-Klotho levels have been observed in aged non-healthy individuals, no specific reference values across a wide range of ages and sex using an enzyme-linked immunosorbent assay (ELISA) are available for larger cohorts of healthy individuals. The present analytical cross-sectional study was aimed to establish the reference values of soluble α-Klotho serum levels in healthy adults by age and sex groups. A total of 346 (59% women) healthy individuals aged from 18 to 85 years were recruited. Subjects were divided by sex and age as: (i) young (18−34.9 years), (ii) middle-aged (35−54.9 years), and (iii) senior (55−85 years) individuals. The soluble α-Klotho levels were measured in serum using ELISA. Senior adults were the age-group that presented the lowest soluble α-Klotho serum levels (p < 0.01), with age showing a negative association with soluble α-Klotho serum levels (p < 0.001). No differences between sexes were observed. Therefore, soluble α-Klotho levels were especially decreased­regardless of sex­in our cohort of healthy individuals because of the physiological decline derived from the aging process. We recommend routine assessments of soluble α-Klotho levels using ELISA as a simple and cheap detectable marker of aging that improves quality of life in the elderly.

Renal Function Mediates the Association Between Klotho and Congestive Heart Failure Among Middle-Aged and Older Individuals.

Objective: Using a newly released National Health and Nutrition Examination Survey (NHANES) data of serum Klotho, this study aimed to explore the relationship between Klotho and specific cardiovascular diseases (CVD), as well as the mediation effect of renal function, among middle-aged and older individuals within the general population. Methods: This nationally representative cross-sectional study analyzed data from the 2007-2016 NHANES. A total of 13,765 participants, who aged 40 years or older, from the general population were examined. Klotho were divided into four groups based on median and interquartile range. The associations among Klotho (exposure), congestive heart failure (CHF; outcome), and renal function markers [estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN), uric acid (UA), and urine albumin-to-creatinine ratio (UACR); mediators] were investigated using mediation analysis. Results: In comparison to the lowest quartile, Klotho in the highest quartile was independently associated with the prevalence of CHF (OR 0.59; 95% CI 0.46-0.77, p for trend = 0.001), but not with other individual CVDs. Klotho had a significant direct effect on the prevalence of CHF (all p < 0.001), while eGFR, BUN, UA, and UACR partly mediated the indirect effect of Klotho on the prevalence of CHF (all p < 0.05), explaining 19.51, 6.98, 13.93, and 0.71% of the association between Klotho and CHF, respectively. Additionally, restricted cubic spline regression demonstrated a linear association and negative correlation between Klotho level and CHF. Conclusion: These findings suggest that Klotho is closely linked to CHF and renal function may be a key mediator of this association.

Serum Klotho and pulse pressure; insight from NHANES.

BACKGROUND: Low levels of the Klotho protein are associated with accelerated tissue aging, including arterial stiffness, in patients with cardiovascular and renal diseases. However, this association has not been examined in a diverse cohort. We aimed to investigate the association between serum Klotho protein levels and pulse pressure, as an indicator of arterial stiffness, in a cohort representative of the US population. METHODS: We used the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Association between pulse pressure and Klotho levels as a continuous variable and in quartiles were examined using survey weight-adjusted linear regression models. Multivariable models were adjusted for age, gender, race, BMI, hypertension, diabetes, smoking, alcohol use, total cholesterol, and estimated GFR. RESULTS: Of the 13,362 participants, 3954(29.6%) were > 65 years, 5792(43%) were Caucasian, and 6773(50.7%) had hypertension. Mean(SD) Klotho was 0.85(0.31) ng/mL and pulse pressure was 55.8(18.5) mmHg. In unadjusted and adjusted models, each ng/mL increase in Klotho was associated with a 3.88mmHg (95%CI = -5.19,-2.57; P < 0.001) and 1.63mmHg (95%CI = -3.01,-0.24; P = 0.02) decrease in pulse pressure, respectively. Similarly, participants in the highest quartile of Klotho had lower pulse pressure than those in the lowest quartile (-3.05mmHg; 95%CI = -4.05,-2.05; P < 0.001), and this difference remained significant in adjusted models (-1.10mmHg; 95%CI = -2.20,-0.01; P = 0.05). CONCLUSION: In this large diverse cohort, we found an inverse and independent association between serum Klotho levels and pulse pressure suggesting that Klotho is associated with arterial stiffness. The mechanisms underlying this association need further study.

Astaxanthin extenuates the inhibition of aldehyde dehydrogenase and Klotho protein expression in cyclophosphamide-induced acute cardiomyopathic rat model.

This study evaluated the mechanistic sequel of aldehyde dehyrogenase (ALDH2) and Klotho protein in cyclophosphamide (CP)-induced cardiotoxicity in rats and the protective effect of astaxanthin (AST) against that sequel. A total of 40 male Wistar albino rats were divided into four groups of 10 animals each: Group 1 was injected intraperitoneally (i.p.) with normal saline for 10 successive days. Group 2 was injected with normal saline for 5 days before and after a single dose of CP (200 mg/kg, i.p.). Group 3 received AST (50 mg/kg/day, i.p.) for 10 days. Group 4 received CP as group 2 and AST as group 3. After the last dose of the treatment protocol, serum was separated to measure cardiotoxicity indices and the left ventricle was then dissected for mRNA and protein expression studies and histopathological examinations. Treatment with CP significantly increased serum lactate dehydrogenase (LDH), creatine kinase isoenzyme MB (CK-MB), and troponin, while significantly decreased soluble α Klotho protein and caused histopathological lesions in cardiac tissues. In cardiac tissues, CP significantly decreased gene expression of ALDH2, Klotho protein, mTOR, IGF, AKT, AMPK, BCL2, but significantly increased expression of BAX and caspase-8. Interestingly, administration of AST in combination with CP completely reversed all the biochemical, histopathological and gene expression changes induced by CP to the control values. The current study suggests that inhibition of ALDH2, Klotho protein, mTOR, and AMPK signals in cardiac tissues may contribute to CP-induced acute cardiomyopathy. AST supplementation attenuates CP-induced cardiotoxicity by modulating ALDH2 and Klotho protein expression in heart tissues, along with its downstream apoptosis effector markers.

The Klotho protein supports redox balance and metabolic functions of cardiomyocytes during ischemia/reperfusion injury.

BACKGROUND: Acute heart ischemia followed by reperfusion leads to overproduction of reactive oxygen/ /nitrogen species (ROS/RNS), disrupted expression of nitric oxide synthase (NOS) and unbalanced glucose metabolism. Klotho is a membrane-bound or soluble protein that exerts protective activity in many organs. While Klotho is produced mainly in the kidneys and brain, it has been recently proven that Klotho is expressed in the cardiomyocytes as well. This study aimed to show the influence of the Klotho protein on oxidative/nitrosative stress and metabolic function of the cardiomyocytes subjected to ischemia/reperfusion (I/R) injury. METHODS: Human cardiac myocytes underwent in vitro chemical I/R (with sodium cyanide and 2-deoxyglucose), in the presence or absence of the recombinant human Klotho protein. The present study included an investigation of cell injury markers, level of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), level of oxidative/nitrosative stress and metabolic processes of the cardiomyocytes. RESULTS: Administration of Klotho protein resulted in mitigation of injury, decreased level of NOX2 and NOX4, reduced generation of ROS/RNS and hydrogen peroxide (H2O2), decreased expression of inducible NOS and limited production of nitrates/nitrites in cells under I/R. Glucose uptake and lactate production in the cardiomyocytes subjected to I/R were normalized after Klotho supplementation. CONCLUSIONS: The Klotho protein participates in the regulation of redox balance and supports metabolic homeostasis of the cardiomyocytes and hence, contributes to protection against I/R injury.