Current understanding of klotho

The effects of Klotho delivering mesenchymal stem cell-derived small extracellular vesicles on acute kidney injury

Acute kidney injury (AKI) is a life-threating syndrome characterized by sudden loss of kidney function, and its management is challenging and often suboptimal. Mesenchymal stem cells (MSCs) have shown promise in AKI therapy in pre-clinical and clinical trials; however, their clinical application still faces many challenges. MSC-derived small extracellular vesicles (sEV) may help overcome these challenges. In the current study, we overexpressed Klotho in MSCs and then isolated Klotho-loaded sEV (Klotho-sEV) using anion-exchange chromatography. Klotho-sEV displayed characteristics comparable to those of sEV in terms of size, morphology, conventional markers, and biosafety, as well as a higher abundance of Klotho protein. In rhabdomyolysis-induced AKI, sEV showed preferential tropism in injured kidneys. We found significantly and stably accelerated renal recovery, mitigated functional and histological abnormalities, stimulated tubular cell proliferation, reduced injury and inflammatory marker expression, and restored endogenous Klotho loss in mice after the administration of Klotho-sEV. In addition, Klotho-sEV treatment activated the mTOR and MEK1/2 signaling pathways. Proteomics and small RNA sequencing analyses of sEV and Klotho-sEV revealed abundant proteins and miRNAs involved in anti-inflammation and reno-protection, and Klotho-sEV showed characteristics that were different from those of sEV. In conclusion, Klotho-sEV may be a promising cell-free strategy for the treatment of AKI.

Relationship of α-Klotho with Frailty Index and Sarcopenia: A Bidirectional Mendelian Randomization Study

Previous studies have established associations between α-Klotho and frailty or sarcopenia; however, the causal nature of these relationships remains unclear. This study investigates the causal effects of α-Klotho on frailty and sarcopenia-related traits using Mendelian randomization (MR). Genetic instruments for circulating α-Klotho concentrations, frailty index (FI), low grip strength (LGS), appendicular lean mass (ALM), and walking pace were developed based on data from large genome-wide association studies. Two-sample MR analyses were performed, supplemented by sensitivity analyses to ensure the robustness of the findings. Reverse MR analyses were also conducted to explore potential reverse causation. The findings demonstrated an inverse causal relationship of circulating α-Klotho levels with FI (β = -0.020, 95% confidence interval [95% CI] = -0.036 to -0.004; p = 0.017) and LGS (β = -0.033, 95% CI = -0.061 to -0.004; p = 0.023). However, no causal relationship was observed between circulating α-Klotho levels and ALM or walking pace. Additionally, no evidence of reverse causation was identified between FI or sarcopenia-related traits and circulating α-Klotho levels. In conclusion, this MR analysis establishes an inverse causal relationship of circulating α-Klotho levels with both FI and LGS.

Sex-specific association between serum α-klotho levels and sleep disturbances in the elderly: a cross-sectional study

BACKGROUND

Sleep disturbances (SD) exhibit a high prevalence among older adults and exert considerable influence on cardiovascular health, quality of life, and other facets of well-being. α-Klotho, an anti-aging factor that diminishes with advancing age, has been implicated in a multitude of age-related conditions. However, the relationship between SD and α-klotho levels in the elderly remains inadequately investigated, and potential sex-specific differences in this association warrant further exploration.

METHODS

This study utilized data from the National Health and Nutrition Examination Survey (NHANES) to initially investigate the association between α-klotho levels and SD, with analyses conducted separately for both sexes. In addition, the relationship was further delineated using restricted cubic spline (RCS) curves.

RESULTS

A total of 5,957 elderly adults participated in this study, revealing a prevalence of SD at 29.5%. Notably, females exhibited a higher prevalence of SD compared to men (33.6% for females vs. 25.3% for males). After adjusting for covariates, higher α-klotho levels were hypothesized to be associated with a decreased incidence of SD. Differences also existed between sexes, as demonstrated by a significant correlation between serum α-klotho and SD in females, but not in males. Results from the RCS analysis indicated a negative and nonlinear relationship between α-klotho levels and SD, consistent across both sexes and the general population.

CONCLUSIONS

The findings of the current study revealed a negative association between α-klotho levels and the development of SD in the elderly population, with notable sex-specific differences.

Anti-aging protein α-Klotho is potential for reducing comorbidity risk of cardiometabolic diseases in vulnerable populations and enhancing long-term prognosis

This study investigated the impact of anti-aging protein α-Klotho on cardiometabolic diseases (CMDs) among middle-aged and elderly population. A total of 11,198 participants aged 40-79 years were included in the National Health and Nutrition Examination Survey (NHANES) spanning 2007-2016. Serum α-Klotho levels were quantified via enzyme-linked immunosorbent assays. CMDs comprised cardiovascular disease (CVD), and four metabolic disorders: type 2 diabetes (T2DM), obesity, chronic kidney disease (CKD), and non-alcoholic fatty liver disease (NAFLD). Weighted logistic regression analysis, subgroup analysis, mediation analysis, restricted cubic splines (RCS), and Cox proportional hazards regression analysis were used. α-Klotho exhibited negative associations with each single CMD except T2DM, and RCS showed U-shape and L-shape dose-response relationships of α-Klotho with risk of T2DM and CKD, respectively. Ordered logistic regression analysis revealed that higher levels of Klotho markedly reduced the cumulative number of metabolic comorbidities complicating CVD (OR 0.56 (0.35, 0.91)). Simple mediation analysis showed CKD may explain up to 20.42% of the association between Klotho and CVD. Notably, α-Klotho's association with cardiometabolic comorbidities was particularly evident among individuals who were widowed/divorced/separated, non-Hispanic Black, lower-income, or less educated, with hypertension, current smokers, lower leisure and commuting physical activity, but higher work-related physical activity. Regarding long-term effects, higher α-Klotho levels were associated with lower all-cause mortality among participants with CMDs, but not among those without CMDs. Higher α-Klotho levels were associated with lower CMD prevalence, particularly in high-risk cardiovascular populations with lower socioeconomic status and unfavorable lifestyles and reduced all-cause mortality risk among CMD patients.

Molecular mechanisms of neuroprotection: The interplay of Klotho, SIRT-1, Nrf2, and HO-1 in neurological health

Neurological disorders significantly impair neuronal function and lead to cognitive and motor deficits. This review manuscript explores the therapeutic potential of key proteins-Klotho, SIRT-1, Nrf2, and HO-1-in combating these disorders. Neurological conditions encompass neurotraumatic, neurodegenerative, and neuropsychiatric diseases, all characterized by neuronal loss and dysfunction. The complex functions of Klotho, an anti-aging protein, and SIRT-1, a histone deacetylase, highlight their roles in neuronal survival and neuroprotection through the enhancement of antioxidant defences and the modulation of stress responses. Nrf2 functions as the principal regulator of the antioxidant response, whereas HO-1 facilitates the control of oxidative stress and the resolution of inflammation. Evidence suggests that the interplay between these proteins facilitates neuroprotection by decreasing oxidative damage and promoting cognitive function. The study emphasises the significance of signalling pathways, particularly the Nrf2/HO-1 axis, which are essential in mitigating oxidative stress and inflammation linked to neurodegenerative disorders. Future therapeutic strategies must consider personalized approaches, innovative drug delivery systems, and early intervention to optimize outcomes. This review provides a comprehensive framework for understanding how targeting these pathways can mitigate the burden of neurological disorders, advancing the development of effective interventions for enhancing brain health.

Klotho alleviates oxidative stress and mitochondrial dysfunction through the Nrf2/HO-1 pathway, thereby reducing renal senescence induced by calcium oxalate crystals

Klotho is an antiaging protein that is primarily secreted by the kidneys. This study aimed to explore the protective effects of Klotho against calcium oxalate (CaOx) crystal-induced renal aging and the underlying mechanisms involved. We established a mouse model of CaOx crystal deposition via the intraperitoneal injection of glyoxylate (Gly) and constructed an in vitro model by stimulating HK2 cells with calcium oxalate monohydrate (COM). Renal aging levels were assessed through β-galactosidase (SA-β-gal) staining and the detection of senescence-associated markers. By overexpressing Klotho both in vitro and in vivo, we examined oxidative stress, mitochondrial function, and renal aging levels. We then evaluated the role of Nrf2/HO-1 signalling pathway-mediated oxidative stress in CaOx crystal-induced renal aging by applying the oxidative stress scavenger N-acetylcysteine (NAC) and overexpressing or inhibiting Nrf2 in HK2 cells. We subsequently overexpressed Klotho while inhibiting Nrf2 to confirm that Klotho exerts its protective effects through the Nrf2/HO-1 pathway. Finally, we measured the methylation levels of the Klotho promoter and assessed the degree of renal aging induced by CaOx crystals after the inhibition of Klotho DNA methylation. We found that the overexpression of Klotho alleviated CaOx crystal-induced oxidative stress and mitochondrial dysfunction, thereby reducing renal aging. NAC mitigated CaOx crystal-induced renal aging. The overexpression of Nrf2 alleviated CaOx crystal-induced oxidative stress and mitochondrial dysfunction, thus reducing renal aging, whereas the knockdown of Nrf2 exacerbated CaOx crystal-induced oxidative stress and mitochondrial dysfunction, leading to more severe renal aging. The combination of Klotho overexpression and Nrf2 knockdown reversed the protective effects of Klotho. CaOx crystals induced an increase in the DNA methylation levels of Klotho in the kidneys, and the inhibition of DNA methylation alleviated CaOx-induced renal aging. This study revealed that Klotho plays a crucial role in calcium oxalate crystal-induced kidney senescence by influencing kidney oxidative stress and mitochondrial function through the Nrf2/HO-1 pathway.

Influence of Klotho Protein Levels in Obesity and Sarcopenia: A Systematic Review

The Klotho gene is recognized for its anti-aging properties. Its downregulation leads to aging-like phenotypes, whereas overexpression can extend lifespan. Klotho protein exists in three forms: α-klotho, β-klotho and γ-klotho. The α-klotho has two isoforms: a membrane-bound form, primarily in the kidney and brain, and a secreted klotho protein present in blood, urine, and cerebrospinal fluid. Klotho functions as a co-receptor for fibroblast growth factor-23 (FGF23), regulating phosphate metabolism. The membrane-bound form controls various ion channels and receptors, while the secreted form regulates endocrine FGFs, including FGF19 and FGF21. The interaction between β-klotho and FGF21 in muscle is critical in the development of sarcopenic obesity. This systematic review, registered in PROSPERO and conducted following PRISMA guidelines, evaluates klotho levels in individuals with obesity or sarcopenic obesity. The study includes overweight, obese, and sarcopenic obese adults compared to those with a normal body mass index. After reviewing 713 articles, 20 studies were selected, including observational, cross-sectional, cohort studies, and clinical trials. Significant associations between klotho levels and obesity, metabolic syndrome (MS), and cardiovascular risk were observed. Exercise and dietary interventions positively influenced klotho levels, which were linked to improved muscle strength and slower decline. Klotho is a potential biomarker for obesity, MS, and sarcopenic obesity. Further research is needed to explore its mechanisms and therapeutic potential.

Association between weight-adjusted-waist index and serum anti-aging protein α-Klotho in U.S. adults: Evidence from NHANES 2007-2016

BACKGROUND

As unhealthy diets have proliferated, there has been an increasing trend in the prevalence of obesity along with socioeconomic progress. WWI, mainly representing weight-independent central obesity, is a more accurate indicator of obesity than BMI and WC. Klotho is known to be one of the root causes of several age-related illnesses. There has never been any prior evidence associating WWI and serum α-Klotho levels.

METHODS

The current cross-sectional investigation used data from the National Health and Nutrition Examination Survey (NHANES) 2013-2016. The calculation of each participant's WWI involved dividing their waist circumference in centimeters by the square root of their weight in kilograms. Using multivariable linear regression models, the association between serum Klotho concentrations and WWI was analyzed. Smoothed curve fitting was utilized to investigate the nonlinear connection. In addition, interaction tests and other subgroup analyses were carried out.

RESULTS

With an average age of 57.57 ± 10.81 years, 13,172 participants were enrolled in this study, of whom 51.45 % were female. After full adjustment, each unit increase in WWI was significantly associated with a decrease in Klotho by 23.18 ng/ml [β(95%CI) = -23.18 (-31.34, -15.02)]. Moreover, we uncovered that WWI had a stronger negative correlation with Klotho than other obesity markers, such as WC, body mass index (BMI), and a body shape index (ABSI).

CONCLUSIONS

To sum up, weight-adjusted-waist index levels were negatively associated with serum Klotho protein concentration and showed a stronger correlation than other obesity markers. Our findings indicated that WWI may be a predictor of reduced Klotho levels, and that controlling obesity in accordance with WWI may help lower the Klotho levels.

The Impact of Klotho in Cancer: From Development and Progression to Therapeutic Potential

Klotho, initially identified as an anti-aging gene, has been shown to play significant roles in cancer biology. Alongside α-Klotho, the β-Klotho and γ-Klotho isoforms have also been studied; these studies showed that Klotho functions as a potential tumor suppressor in many different cancers by inhibiting cancer cell proliferation, inducing apoptosis and modulating critical signaling pathways such as the Wnt/β-catenin and PI3K/Akt pathways. In cancers such as breast cancer, colorectal cancer, hepatocellular carcinoma, ovarian cancer, and renal cell carcinoma, reduced Klotho expression often correlates with a poor prognosis. In addition, Klotho's role in enhancing chemotherapy sensitivity and its epigenetic regulation further underscores its potential as a target for cancer treatments. This review details Klotho's multifaceted contributions to cancer suppression and its potential as a therapeutic target, enhancing the understanding of its significance in cancer treatment and prognoses.

Association of Klotho Gene Polymorphism and Serum Level of α Klotho Protein with Different Tumor Grades, Overall Survival and Cytokine Profile in Glioma Patients

Gliomas are the most common and lethal forms of malignant brain tumors. We attempted to identify the role of the aging-suppressor Klotho gene and Klotho protein in the immunopathogenesis of gliomas. We examined Klotho genetic variants by PCR-RFLP and measured serum Klotho levels using the ELISA method. We found a statistically significantly increased frequency of rs1207568A allele and rs1207568 GA genotypes in co-dominant, dominant and over-dominant models in grade IV as compared to grade II and III glioma patients. The levels of soluble α Klotho (sαKL) were significantly lower in grade III and IV glioma patients than in healthy controls (p = 0.034; 0.0083). Patients with sαKL levels above 2500 pg/mL survived significantly longer than patients with sαKL below 2500 pg/mL (p = 0.038). We also found a positive correlation of the serum levels of sαKL with seven biomarkers, like angiogenic vascular endothelial growth factor (p = 0.0008), chemokine fractalkine (p = 0.0009), interferon γ (p = 0.003), glial derived neurotrophic factor (p = 0.0268), pro-inflammatory and pro-Th1 cytokine IL-6 (p = 0.0347), anti-inflammatory, pro-Th2 cytokines IL-4 (p = 0.0037) and IL-13 (p = 0.0004). Our results suggest the impact of Klotho genetic variants and Klotho levels on advanced-grade glioma.

GLP-1 Receptor Agonists Alleviate Diabetic Kidney Injury via β-Klotho-Mediated Ferroptosis Inhibition

Semaglutide (Smg), a GLP-1 receptor agonist (GLP-1RA), shows renal protective effects in patients with diabetic kidney disease (DKD). However, the exact underlying mechanism remains elusive. This study employs transcriptome sequencing and identifies β-Klotho (KLB) as the critical target responsible for the role of Smg in kidney protection. Smg treatment alleviates diabetic kidney injury by inhibiting ferroptosis in patients, animal models, and HK-2 cells. Notably, Smg treatment significantly increases the mRNA expression of KLB through the activation of the cyclic adenosine monophosphate (cAMP) signaling pathway, specifically through the phosphorylation of protein kinase A (PKA) and cAMP-response element-binding protein (CREB). Subsequently, the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway is activated, reprograming the key metabolic processes of ferroptosis such as iron metabolism, fatty acid synthesis, and the antioxidant response against lipid peroxidation. Suppression of ferroptosis by Smg further attenuates renal inflammation and fibrosis. This work highlights the potential of GLP-1RAs and KLB targeting as promising therapeutic approaches for DKD management.

Endurance Effort Affected Expression of Actinin 3 and Klotho Different Isoforms Basing on the Arabian Horses Model

BACKGROUND

Among numerous genes that have been a focus of equine genetic research, the KL (Klotho) and ACTN3 (Alpha-actinin-3) genes stand out due to their significant roles in muscle function and overall health, as well as performance ability. Previous studies on Arabian horses and other mammalians have shown that both KL and ACTN3 occur in different isoforms that seem to have different roles in metabolism. The main purpose of this present study was to describe different isoforms (ACTN3, ACTN3-201, ACTN3-202, KL, KL-202, KL-203) expression levels affected by the endurance effort in Arabian horses.

METHODS

Blood samples were taken from a group of n = 10 Arabian horses taking part in a long-distance 120 km endurance ride. After RNA isolation and reverse transcription, real-time PCR was performed. The expression levels (Relative Quantity, RQ) were calculated using the delta-delta CT method. The results showed surprisingly large differences between different isoforms expression levels which brought us to the conclusion that both KL and ACTN3 genes are suitable genetic markers to measure endurance performance. Moreover, the correlation network analyses showed that the MIOX (myo-inositol oxygenase), SH3RH2 (SH3 domain-containing ring finger 2) and TNNI2 (Troponin I2, fast skeletal type) genes are significantly involved in the endurance effort metabolism.

Sex differences in mortality risk and U-shaped relationship with klotho levels: A long-term cohort study

BACKGROUNDS

It remains unclear whether there are sex differences in the correlation between klotho and mortality risk. The purpose of our study is to investigate the relationship between klotho levels and all-cause mortality, specifically examining potential sex disparities.

METHODS

The study utilized data from the National Health and Nutrition Examination Survey. The study employed the Cox proportional hazards model and Kaplan-Meier survival curves to conduct multivariate analyses investigating the associations between klotho and mortality. The impact of klotho level on mortality was assessed by a restricted cubic spline curve.

RESULTS

Our study included 13,748 participants. The hazard ratios (HR) for all-cause mortality were found to be higher in males compared to females. The risk of all-cause mortality decreased until the klotho level reached 959 pg/mL in all-cause mortality, then increased thereafter in females (P value for nonlinearity = 0.01, P overall = 0.02); no curved relationship was observed in males.

CONCLUSION

Klotho levels and mortality follow a U-shaped curve, with sex differences in the relationship. Males with higher klotho levels have a higher risk of all-cause death than females.

Respiratory dysfunction in old mice could be related to inflammation and lung fibrosis induced by hyperphosphatemia

BACKGROUND

With age, lungs undergo typical changes that lead to a deterioration of respiratory function. Our aim was to assess the role of age-associated hyperphosphatemia in these changes.

METHODS

We used C57BL6 mice to study an ageing model in vivo and human lung fibroblasts were treated with a phosphate donor, beta-glycerophosphate (BGP), to explore mechanisms involved. Respiratory function was registered with a double chamber plethysmograph. Lung structure was analysed by different staining, phosphate and cytokines levels by colorimeric kits, expression of fibrosis, inflammation and ET-1 system by western blot or RT-PCR.

RESULTS

Old mice showed hyperphosphatemia, along with lung fibrosis, loss of elastin, increased expression of pro-inflammatory cytokines and impaired respiratory function. BGP induced inflammation and fibrosis in fibroblasts through the activation and binding of NFkB to the MCP-1 or FN promoters. BGP increased ECE-1 expression by inducing NFkB binding to the ECE-1 promoter. QNZ, an NFkB inhibitor, blocked these effects. When ECE-1 was inhibited with phosphoramidon, BGP-induced inflammation and fibrosis were significantly reduced, suggesting a role for ET-1 in BGP-mediated effects.ET-1 produced effects similar to those of BGP, which were also dependent on NFkB. To study the pathophysiological relevance of hyperphosphatemia in vivo, a low-P diet was administered to a group of old animals, showing an improvement in fibrosis, inflammation and respiratory function compared to old mice on a standard diet.

CONCLUSION

These results suggest that age-related hyperphosphatemia induces inflammation, fibrosis, and impaired respiratory function in old mice; these effects appear to be mediated by ET-1 and NFkB activation.

Association of serum klotho with cognitive function among individuals with nonalcoholic fatty liver disease

Introduction

This study investigated the potential link between serum klotho levels and cognitive function in patients with non-alcoholic fatty liver disease (NAFLD).

Materials and Methods

Utilizing NHANES data from 2011 to 2014, the research included 356 eligible participants. NAFLD was identified with the United States Fatty Liver Index (US-FLI), and cognition was measured by various tests including the Animal Fluency Test (AFT), Digit Symbol Substitution Test (DSST), Immediate Recall Test (IRT), and Delayed Recall Test (DRT). Weighted logistic regression and restricted cubic splines were employed to analyze the relationship between klotho levels and cognitive scores.

Results

A significant nonlinear association was observed between klotho levels and the performance in DSST and Delayed Recall Test (DRT). After controlling for confounding factors, the study found a positive association between higher serum klotho levels and improved cognitive performance in both AFT and DSST. However, there was no significant relationship between klotho levels and the IRT or DRT, regardless of whether the natural logarithm or quartile was considered.

Discussion

The findings suggest that a higher serum klotho level may be positively correlated with better cognitive performance in NAFLD patients.

Positive association of the anti-aging protein α-Klotho with insulin resistance and its inverse L-shaped relationship with glycaemic control in the middle-aged and elderly population

PURPOSE

α-Klotho has been linked to insulin resistance (IR) in basic research. However, experimental evidence is inconsistent, and there is a lack of data from human research. This study seeks to elucidate the association of α-Klotho with IR in a nationwide, multiracial population.

METHODS

A total of 5289 participants aged 40-79 years were included in the National Health and Nutrition Examination Survey (NHANES) spanning 2007-2016. Serum α-Klotho was measured using enzyme-linked immunosorbent assays (ELISA), and IR was evaluated by the homeostatic model assessment of insulin resistance (HOMA-IR). Weighted multivariate logistic and linear regression analysis, subgroup analysis stratified by demographic characteristics, medical condition or obesity status, and sensitivity analysis using propensity score matching (PSM) were performed. Restricted cubic splines (RCS) were performed to explore the nonlinear relationship.

RESULTS

In the fully adjusted logistic regression model, a significant positive association was observed between log-transformed α-Klotho and IR (OR = 3.63, 95% CI: 1.56, 8.45), particularly in males or nonobese individuals (Pinteraction < 0.05). In the linear regression model, log10(α-Klotho) was associated with fasting blood glucose (FBG, β = 1.25, 95% CI: 0.74, 1.76) and glycosylated hemoglobin (HbA1c, β = 0.49, 95% CI: 0.20, 0.77). RCS revealed an inverse L-shaped dose-response relationship of α-Klotho with FBG and HbA1c (Pnonlinear <0.05). Beyond the inflection point of log10(α-Klotho) at 2.79, β coefficients sharply rose for these glycaemic control indicators.

CONCLUSION

The study provides clinical evidence supporting a positive association between α-Klotho and IR. Moreover, the inverse L-shaped relationship suggests that α-Klotho should reach a certain level to predict glycaemic changes effectively.

Soluble klotho induces the heat shock factor 1 through EGR1 expression

Klotho is an antiaging protein that has multiple functions. The purpose of this study is to investigate whether soluble klotho plays a role in cellular stress response pathways. We found that klotho deficiency (kl-/-) largely decreased HSF1 levels and impaired heat shock protein expression. Interestingly, recombinant soluble klotho-induced HSF1 and HSPs such as HSP90, HSP70, and HSP27 in kl-/- mouse embryonic fibroblasts (MEFs). Soluble Klotho treatment also induced cell proliferation and HSF1 promoter activity in MEF kl-/- cells in a concentration-dependent manner. Furthermore, using point mutagenesis, we identified regulatory/binding sites of transcription factors EGR1 regulated by soluble klotho in the HSF1 promoter. Taken together, our findings unravel the molecular basis of klotho and provide molecular evidence supporting a direct interaction between soluble klotho and HSF1-mediated stress response pathway.

Klotho: molecular mechanisms and emerging therapeutics in central nervous system diseases

Klotho is recognized as an aging-suppressor protein that is implicated in a variety of processes and signaling pathways. The anti-inflammatory, anti-apoptotic, anti-oxidant, and anti-tumor bioactivities of klotho have extended its application in neurosciences and made the protein popular for its lifespan-extending capacity. Furthermore, it has been demonstrated that klotho levels would reduce with aging and numerous pathologies, particularly those related to the central nervous system (CNS). Evidence supports the idea that klotho can be a key therapeutic target in CNS diseases such as amyotrophic lateral sclerosis, Parkinson's disease, stroke, and Alzheimer's disease. Reviewing the literature suggests that the upregulation of klotho expression regulates various signaling pathways related to autophagy, oxidative stress, inflammation, cognition, and ferroptosis in neurological disorders. Therefore, it has been of great interest to develop drugs or agents that boost or restore klotho levels. In this regard, the present review was designed and aimed to gather the delegated documents regarding the therapeutic potential of Klotho in CNS diseases focusing on the molecular and cellular mechanisms.

Relationship between uric acid to high-density cholesterol ratio (UHR) and circulating α-klotho: evidence from NHANES 2007-2016

OBJECTIVE

To investigate the relationship between uric acid to high-density lipoprotein cholesterol ratio (UHR) and circulating α-klotho levels in U.S. adults.

METHODS

A cross-sectional study used data from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Circulating α-klotho was defined as the dependent variable and UHR was defined as the independent variable. Multivariable linear regression was performed to assess the relationship between the independent and dependent variables. The nonlinear relationship and effect size between UHR and α-klotho were evaluated using smooth curve fitting and threshold effect analysis. Subgroup analysis and sensitivity analysis were conducted to determine the stability of the results. The diagnostic performance of UHR and α-klotho in common elderly diseases was compared using ROC (Receiver Operating Characteristic) analysis.

RESULTS

Among 12,849 participants, there was a negative relationship between the UHR and circulating α-klotho. In the fully adjusted overall model, each unit increase in UHR was associated with a decrease of 4.1 pg/mL in α-klotho. The threshold effect analysis showed that before the inflection point of 8.2, each unit increase in UHR was associated with a decrease of 15.0 pg/mL in α-klotho; beyond the inflection point of 8.2, each unit increase in UHR was associated with a decrease of 2.8 pg/mL in α-klotho. Subgroup analyses and sensitivity analysis indicated that the relationship between UHR and α-klotho remained stable across most populations. The ROC diagnostic test indicated that the evaluative efficacy of UHR in diagnosing age-related diseases was comparable to that of α-klotho.

CONCLUSION

This study revealed that the UHR was associated with the circulating α-klotho concentration, with a negative association observed in most cases. This finding suggested that the UHR might be a promising indicator for evaluating circulating α-klotho levels.

Association between the triglyceride-glucose index and serum soluble Klotho in middle-aged and older adults from NHANES 2007-2016

Klotho, an anti-aging protein, is believed to participate in metabolic diseases and play a potential protective role by regulating insulin sensitivity. This study aimed to explore the relationship between the triglyceride-glucose (TyG) index (a simple marker of insulin resistance) and serum soluble Klotho (S-Klotho) levels. The cross-sectional study comprised 5237 adults aged 40-79 years who participated in the National Health and Nutrition Examination Surveys (NHANES) 2007-2016. The TyG index was calculated as ln [fasting triglycerides (mg/dL) × fasting glucose (mg/dL)/2]. The serum levels of S-Klotho were measured by enzyme-linked immunosorbent assay. The association between the TyG index and S-Klotho levels was investigated by multiple linear regression models, smoothed curve fitting, segmented linear regression models, subgroup analyses, and interaction tests. The TyG index was inversely associated with serum S-Klotho level after full adjustment (β = - 45.11, 95% CI (- 79.53, - 10.69), P = 0.011). Furthermore, we also found a non-linear correlation and saturation phenomenon between the TyG index and serum S-Klotho levels, with a turning point of 9.56. In addition, a significant interaction effect of sex was found between the two (P for interaction < 0.001), with a more pronounced association observed in females. Further studies are required to explore the mechanisms and verify the correlation.

Triiodothyronine enhances various forms of kidney-specific Klotho protein and suppresses the Wnt/β-catenin pathway: Insights from in-vitro, in-vivo and in-silico investigations

Age-related diseases are intricately linked to the molecular processes underlying aging, with the decline of the antiaging protein Klotho being a key factor. Investigating these processes is crucial for developing therapeutic strategies. The age-associated reduction in Klotho expression, coupled with a decline in the endocrine hormone triiodothyronine (T3), prompted a detailed exploration of their potential interplay. Our research, conducted through both in-vitro and in-vivo studies on BALB/c mice, unveiled a significant capacity of T3 to upregulate various forms of Klotho via ATF-3/p-c-Jun transcription factor. This effect was particularly noteworthy in aged individuals, where Klotho expression had waned compared to their younger counterparts. Importantly, T3 demonstrated a promising therapeutic impact in rejuvenating Klotho expression in this context. Further investigations elucidated the molecular mechanisms underlying T3's impact on aging-related pathways. In-vitro and in-vivo experiments established T3's ability to downregulate the Wnt/β-Catenin pathway by enhancing Klotho expression. In-silico analyses provided insights into Klotho's intricate role, showing its capacity to inhibit Wnt ligands such as Wnt3 and Wnt8a, consequently disrupting their interaction with the Wnt receptor. Additionally, T3 was found to downregulate kidney-specific GSK-3β expression through the augmentation of Klotho expression. The study also highlighted T3's role in maintaining calcium and phosphate homeostasis via Klotho. This comprehensive investigation not only sheds light on the intricate mechanisms governing aging processes but also presents promising avenues for therapeutic interventions targeting the Wnt/β-Catenin pathway implicated in various age-associated diseases.

Association between smoking, smoking cessation and serum α-klotho levels among American adults: National Health and Nutrition Examination Survey

α-klotho is an anti-aging protein. The correlation between smoking, smoking cessation and serum α-klotho levels remains controversial. The aim of this study was to investigate the association between smoking, smoking cessation and serum α-klotho levels. This cross-sectional study finally included 4877 participants, aged 40-79 years, who participated in the National Health and Nutrition Examination Survey studies from 2013 to 2016. Of these, 2312 (47.4%) were men and 894 (18.3%) were current smokers, and the mean age of the participants was 57.8±10.7 years. Multivariate linear regression modeling was used to assess the association between smoking, smoking cessation and serum α-klotho levels. After adjustment for multiple confounders, this study observed that smoking was negatively associated with serum α-klotho levels (β: -58.3; 95% confidence interval CI: -82.0 to -34.6; p<0.001), whereas smoking cessation was positively associated with serum α-klotho levels (β: 52.3; 95% CI: 24.1 to 80.6; p<0.001). In subgroup and interaction analyses, p-value for the interaction between smoking and race on serum klotho levels was found to be less than 0.001. The correlation between smoking, smoking cessation and serum α-klotho levels remained stable after propensity score matching (β: -54.1; 95% CI: -81.5 to -26.7; p<0.001, β: 54.8; 95% CI: 24.2 to 85.4; p<0.001). In a large sample population, the present study found that smoking, smoking cessation and serum α-klotho levels were associated in opposite directions.

KDM6A Demethylase Regulates Renal Sodium Excretion and Blood Pressure

BACKGROUND

KDM6A (Lysine-Specific Demethylase 6A) is a specific demethylase for histone 3 lysine (K) 27 trimethylation (H3K27me3). The purpose of this study is to investigate whether KDM6A in renal tubule cells plays a role in the regulation of kidney function and blood pressure.

METHODS

We first crossed Ksp-Cre+/- and KDM6Aflox/flox mice for generating inducible kidney-specific deletion of KDM6A gene.

RESULTS

Notably, conditional knockout of KDM6A gene in renal tubule cells (KDM6A-cKO) increased H3K27me3 levels which leads to a decrease in Na excretion and elevation of blood pressure. Further analysis showed that the expression of NKCC2 (Na-K-2Cl cotransporter 2) and NCC (Na-Cl cotransporters) was upregulated which contributes to impaired Na excretion in KDM6A-cKO mice. The expression of AQP2 (aquaporin 2) was also increased in KDM6A-cKO mice, which may facilitate water reabsorption in KDM6A-cKO mice. The expression of Klotho was downregulated while expression of aging markers including p53, p21, and p16 was upregulated in kidneys of KDM6A-cKO mice, indicating that deletion of KDM6A in the renal tubule cells promotes kidney aging. Interestingly, KDM6A-cKO mice developed salt-sensitive hypertension which can be rescued by treatment with Klotho. KDM6A deficiency induced salt-sensitive hypertension likely through downregulation of the Klotho/ERK (extracellular signal-regulated kinase) signaling and upregulation of the WNK (with-no-lysine kinase) signaling.

CONCLUSIONS

This study provides the first evidence that KDM6A plays an essential role in maintaining normal tubular function and blood pressure. Renal tubule cell specific KDM6A deficiency causes hypertension due to increased H3K27me3 levels and the resultant downregulation of Klotho gene expression which disrupts the Klotho/ERK/NCC/NKCC2 signaling.

Protein interaction networks characterizing the A549 cells Klotho transfected are associated with activated pro-apoptotic Bim and suppressed Wnt/β-catenin signaling pathway

Invasive assays and lung tumor-bearing mice models using a human lung adenocarcinoma cell line A549 cells transfected with the Klotho (KL) gene, A549/KL cells, have confirmed that KL suppresses invasive/metastatic potential. This study aimed to identify the co-expression protein networks and proteomic profiles associated with A549/KL cells to understand how Klotho protein expression affects molecular networks associated with lung carcinoma malignancy. A two-step application of a weighted network correlation analysis to the cells' quantitative proteome datasets of a total of 6,994 proteins, identified by mass spectrometry-based proteomic analysis with data-independent acquisition (DIA), identified one network module as most significantly associated with the A549/KL trait. Upstream analyses, confirmed by western blot, implicated the pro-apoptotic Bim (Bcl-2-like protein 11) as a master regulator of molecular networks affected by Klotho. GeneMANIA interaction networks and quantitative proteome data implicated that Klotho interacts with two signaling axes: negatively with the Wnt/β-catenin axis, and positively by activating Bim. Our findings might contribute to the development of future therapeutic strategies.

Imbalanced lipid homeostasis caused by membrane αKlotho deficiency contributes to the acute kidney injury to chronic kidney disease transition

After acute kidney injury (AKI), renal tubular epithelial cells (RTECs) are pathologically characterized by intracellular lipid droplet (LD) accumulation, which are involved in RTEC injury and kidney fibrosis. However, its pathogenesis remains incompletely understood. The protein, αKlotho, primarily expressed in RTECs, is well known as an anti-aging hormone wielding versatile functions, and its membrane form predominantly acts as a co-receptor for fibroblast growth factor 23. Here, we discovered a connection between membrane αKlotho and intracellular LDs in RTECs. Fluorescent fatty acid (FA) pulse-chase assays showed that membrane αKlotho deficiency in RTECs, as seen in αKlotho homozygous mutated (kl/kl) mice or in mice with ischemia-reperfusion injury (IRI)-induced AKI, inhibited FA mobilization from LDs by impairing adipose triglyceride lipase (ATGL)-mediated lipolysis and lipophagy. This resulted in LD accumulation and FA underutilization. IRI-induced alterations were more striking in αKlotho deficiency. Mechanistically, membrane αKlotho deficiency promoted E3 ligase peroxin2 binding to ubiquitin-conjugating enzyme E2 D2, resulting in ubiquitin-mediated degradation of ATGL which is a common molecular basis for lipolysis and lipophagy. Overexpression of αKlotho rescued FA mobilization by preventing ATGL ubiquitination, thereby lessening LD accumulation and fibrosis after AKI. This suggests that membrane αKlotho is indispensable for the maintenance of lipid homeostasis in RTECs. Thus, our study identified αKlotho as a critical regulator of lipid turnover and homeostasis in AKI, providing a viable strategy for preventing tubular injury and the AKI-to-chronic kidney disease transition.

The significance of serum Klotho to hearing loss: a potential protector under noise pollution

The issue of hearing protection in the presence of noise pollution is of great importance in the fields of environmental science and clinical medicine. Currently, the clinical significance of Klotho in relation to hearing has not been revealed. The aim of this study was to examine the correlation between serum Klotho levels and Pure Tone Average (PTA) hearing thresholds among individuals in the U.S.. The analysis involved a sample of 1,781 individuals aged 20 to 69, obtained from the 2007-2012 National Health and Nutrition Examination Survey. Various methods were utilized for the analysis, including univariate and multivariate linear regression, stratified analysis, smooth curve fitting, a two-segment linear regression model, and log-likelihood ratio analysis. The results of the univariate analysis indicated that serum Klotho concentration, age, education level, hypertension, diabetes, and smoking all exhibited a significant influence on PTAs. After adjusting for potential confounding factors, it was observed that a decrease in serum Klotho was significantly associated with PTA thresholds at low frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.004), speech frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.007), and high frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.045). Specifically, for every 1 pg/ml decrease in serum Klotho concentration, the PTAs increased by 0.002 dB. Moreover, age and gender-specific analyses revealed significant associations. For individuals aged 59-69, a significant association was found between serum Klotho concentration and high-frequency PTA (β = -4.153; 95% CI: -7.948, -0.358; P = 0.032). Additionally, among females, significant associations were observed between serum Klotho concentration and speech-frequency PTA (β = -1.648, 95% CI: -3.197, -0.099; P = 0.037) as well as high-frequency PTA (β = -3.046; 95% CI: -5.319, -0.772; P = 0.009). Finally, the results of smooth curve fitting and threshold effect analyses indicated a potential negative linear correlation between serum Klotho concentration and PTA thresholds. In conclusion, a lower level of serum Klotho was found to be associated with increased hearing thresholds, particularly among the elderly population. This finding has significant implications for the prevention and treatment of hearing damage.

Cell Survival, Death, and Proliferation in Senescent and Cancer Cells: the Role of (Poly)phenols

Cellular senescence has long been considered a permanent state of cell cycle arrest occurring in proliferating cells subject to different stressors, used as a cellular defense mechanism from acquiring potentially harmful genetic faults. However, recent studies highlight that senescent cells might also alter the local tissue environment and concur to chronic inflammation and cancer risk by secreting inflammatory and matrix remodeling factors, acquiring a senescence-associated secretory phenotype (SASP). Indeed, during aging and age-related diseases, senescent cells amass in mammalian tissues, likely contributing to the inevitable loss of tissue function as we age. Cellular senescence has thus become one potential target to tackle age-associated diseases as well as cancer development. One important aspect characterizing senescent cells is their telomere length. Telomeres shorten as a consequence of multiple cellular replications, gradually leading to permanent cell cycle arrest, known as replicative senescence. Interestingly, in the large majority of cancer cells, a senescence escape strategy is used and telomere length is maintained by telomerase, thus favoring cancer initiation and tumor survival. There is growing evidence showing how (poly)phenols can impact telomere maintenance through different molecular mechanisms depending on dose and cell phenotypes. Although normally, (poly)phenols maintain telomere length and support telomerase activity, in cancer cells this activity is negatively modulated, thus accelerating telomere attrition and promoting cancer cell death. Some (poly)phenols have also been shown to exert senolytic activity, thus suggesting both antiaging (directly eliminating senescent cells) and anticancer (indirectly, via SASP inhibition) potentials. In this review, we analyze selective (poly)phenol mechanisms in senescent and cancer cells to discriminate between in vitro and in vivo evidence and human applications considering (poly)phenol bioavailability, the influence of the gut microbiota, and their dose-response effects.

Association between klotho and non-alcoholic fatty liver disease and liver fibrosis based on the NHANES 2007-2016

INTRODUCTION AND OBJECTIVES

This study aims to explore the association between Klotho and Non-Alcoholic Fatty Liver Disease (NAFLD), a condition affecting millions worldwide. Klotho may have a protective effect against NAFLD mechanisms like inflammation, oxidative stress, and fibrosis. The study will use FLI and FIB-4 score to diagnose NAFLD in a large population for investigating the link between Klotho and NAFLD.

MATERIALS AND METHODS

The study aimed to explore the association between Klotho and NAFLD by measuring the α-Klotho protein levels in the participants' blood using ELISA. Patients with underlying chronic liver diseases were excluded. The severity of NAFLD was evaluated using FLI and FIB-4, and logistic regression models were used to analyze the data obtained from NHANES. Subgroup analyses were conducted to study Klotho's effect on hepatic steatosis and fibrosis in diverse subpopulations.

RESULTS

The study found that low levels of α-Klotho were associated with NAFLD, with ORs ranging from 0.72 to 0.83. However, high levels of α-Klotho were associated with NAFLD-related fibrosis. The Q4 group showed significant results in individuals aged 51 years or younger and in females. Non-Hispanic White ethnicity, education level of high school or above, non-smoking, non-hypertension, and non-diabetic groups showed negative correlations.

CONCLUSIONS

Our study suggests a potential correlation between α-Klotho levels in the blood and NAFLD in adult patients, especially among younger individuals, females and Non-Hispanic Whites. Elevated α-Klotho levels may have therapeutic benefits in treating NAFLD. Further research is required to validate these findings, but they provide new insights for managing this condition.

Metformin: A New Inhibitor of the Wnt Signaling Pathway in Cancer

The biguanide drug metformin is widely used in type 2 diabetes mellitus therapy, due to its ability to decrease serum glucose levels, mainly by reducing hepatic gluconeogenesis and glycogenolysis. A considerable number of studies have shown that metformin, besides its antidiabetic action, can improve other disease states, such as polycystic ovary disease, acute kidney injury, neurological disorders, cognitive impairment and renal damage. In addition, metformin is well known to suppress the growth and progression of different types of cancer cells both in vitro and in vivo. Accordingly, several epidemiological studies suggest that metformin is capable of lowering cancer risk and reducing the rate of cancer deaths among diabetic patients. The antitumoral effects of metformin have been proposed to be mainly mediated by the activation of the AMP-activated protein kinase (AMPK). However, a number of signaling pathways, both dependent and independent of AMPK activation, have been reported to be involved in metformin antitumoral action. Among these, the Wingless and Int signaling pathway have recently been included. Here, we will focus our attention on the main molecular mechanisms involved.

Associations between klotho and telomere biology in high stress caregivers

Aging biomarkers may be related to each other through direct co-regulation and/or through being regulated by common processes associated with chronological aging or stress. Klotho is an aging regulator that acts as a circulating hormone with critical involvement in regulating insulin signaling, phosphate homeostasis, oxidative stress, and age-related inflammatory functioning. Both klotho and telomere length are biomarkers of biological aging and decrease with age; however, the relationship between them is not well understood. Here we test the association between klotho levels and the telomere length of specific sorted immune cells among a healthy sample of mothers caregiving for a child with autism spectrum disorder (ASD; i.e., experiencing higher caregiving stress) or a child without ASD, covarying age and body mass index, in order to understand if high stress associated with caregiving for a child with an ASD may be involved in any association between these aging biomarkers. In 178 caregiving women (n = 90 high-stress mothers of children with ASD, n = 88 low-stress mothers of neurotypical children), we found that klotho levels were positively associated with telomere length in PBMCs (an effect driven by CD4+ and CD8+CD28- T cells) among high-stress mothers of children with an ASD but not among low-stress mothers of neurotypical children. There were no significant associations between klotho and telomerase activity in either group, across cell types assessed here. Our results suggest that klotho levels and telomere length may be associated through a coordinated downregulation of longevity factors occurring under higher stress caregiving conditions.

Research Progress on the Anti-Aging Potential of the Active Components of Ginseng

Aging is a cellular state characterized by a permanent cessation of cell division and evasion of apoptosis. DNA damage, metabolic dysfunction, telomere damage, and mitochondrial dysfunction are the main factors associated with senescence. Aging increases β-galactosidase activity, enhances cell spreading, and induces Lamin B1 loss, which further accelerate the aging process. It is associated with a variety of diseases, such as Alzheimer's disease, Parkinson's, type 2 diabetes, and chronic inflammation. Ginseng is a traditional Chinese medicine with anti-aging effects. The active components of ginseng, including saponins, polysaccharides, and active peptides, have antioxidant, anti-apoptotic, neuroprotective, and age-delaying effects. DNA damage is the main factor associated with aging, and the mechanism through which the active ingredients of ginseng reduce DNA damage and delay aging has not been comprehensively described. This review focuses on the anti-aging mechanisms of the active ingredients of ginseng. Furthermore, it broadens the scope of ideas for further research on natural products and aging.

Klotho reduces the risk of osteoporosis in postmenopausal women: a cross-sectional study of the National Health and Nutrition Examination Survey (NHANES)

BACKGROUND

Osteoporosis (OP) is one of the diseases that endanger the health of the elderly population. Klotho protein is a hormone with anti-aging effects. A few studies have discussed the relationship between Klotho and OP. However, there is still a lack of research on larger populations. This study aims to evaluate the association between OP and Klotho in American postmenopausal women.

METHODS

This is a retrospective study. We searched the National Health and Nutrition Examination Survey (NHANES) database and collected data of 3 survey cycles, finally involving 871 postmenopausal women over 50 years old in the present study. All participants took dual-energy X-ray absorptiometry examination and serum Klotho testing at the time of investigation. After adjusting the possible confounding variables, a multivariate regression model was employed to estimate the relationship between OP and Klotho proteins. Besides, the P for trend and restricted cubic spline (RCS) were applied to examine the threshold effect and calculate the inflection point.

RESULTS

Factors influencing the occurrence of OP included age, ethnicity, body mass index and Klotho levels. Multivariate regression analysis indicated that the serum Klotho concentration was lower in OP patients than that in participants without OP (OR[log2Klotho] = 0.568, P = 0.027). The C-index of the prediction model built was 0.765, indicating good prediction performance. After adjusting the above-mentioned four variables, P values for trend showed significant differences between groups. RCSs revealed that when the Klotho concentration reached 824.09 pg/ml, the risk of OP decreased drastically.

CONCLUSION

Based on the analysis of the data collected from the NHANES database, we propose a correlation between Klotho and postmenopausal OP. A higher serum Klotho level is related to a lower incidence of OP. The findings of the present study can provide guidance for research on diagnosis and risk assessment of OP.

Klotho Null Mutation Involvement in Adenosine A2B Receptor-Related Skeletal Muscle Degeneration

Klotho is known for its age-suppressing function and has been implicated in sarcopenia pathology. It has recently been proposed that the adenosine A2B receptor plays a crucial role in skeletal muscle energy expenditure. However, the association between Klotho and A2B remains elusive. In this study, Klotho knockout mice, aged 10 weeks, and wild-type mice, aged 10 and 64 weeks, were used for comparison in indicators of sarcopenia (n = 6 for each group). PCR was performed to confirm the mice genotypes. Skeletal muscle sections were analyzed using hematoxylin and eosin staining as well as immunohistochemistry staining. The skeletal muscle cross-sectional area was significantly reduced in Klotho knockout mice and wild-type mice, aged 64 weeks, when compared with wild-type mice, aged 10 weeks, with a decreased percentage of type IIa and IIb myofibers. Likely impaired regenerative capacity, as reflected by the reduction of paired box 7 (Pax7)- and myogenic differentiation protein 1 (MyoD)-positive cells, was also observed in Klotho knockout mice and aged wild-type mice. 8-Hydroxy-2-deoxyguanosine expression was enhanced with Klotho knockout and aging, indicating higher oxidative stress. Adenosine A2B signaling was impaired, with a lower expression of the A2B receptor and the cAMP-response element binding protein in Klotho knockout and aged mice. The present study provides the novel finding that sarcopenia involves adenosine signaling under the influence of Klotho knockout.

Change in circulating klotho in response to weight loss, with and without exercise, in adults with overweight or obesity

Introduction: Klotho is a protein associated with protection from aging-related diseases and health conditions. Obesity is associated with lower Klotho concentrations. Thus, this secondary analysis of adults with obesity examined 1) the change in serum Klotho concentration in response to a behavioral weight loss intervention by the magnitude of weight loss achieved; and 2) the association among serum Klotho concentration and weight, body composition, and cardiorespiratory fitness. Methods: Participants were randomized to either diet alone (DIET), diet plus 150 min of physical activity per week (DIET + PA150), or diet plus 250 min of physical activity per week (DIET + PA250). Participants [n = 152; age: 45.0 ± 7.9 years; body mass index (BMI): 32.4 ± 3.8 kg/m2] included in this secondary analysis provided blood samples at baseline, 6-, and 12 months, and were classified by weight loss response (Responder: achieved ≥10% weight loss at 6 or 12 months; Non-responder: achieved <5% weight loss at both 6 and 12 months). Serum Klotho was measured using a solid-phase sandwich enzyme-linked immunosorbent assay (ELISA). Analyses of covariance (ANCOVA's) were used to examine changes in weight, body composition, cardiorespiratory fitness, and Klotho concentration by weight loss response across the 12-month weight loss intervention. Results: Responders had a greater reduction in measures of weight and body composition, and a greater increase in cardiorespiratory fitness, compared to Non-Responders (p < 0.05). Change in Klotho concentration differed between Responders and Non-Responders (p < 0.05), with the increase in Klotho concentration from baseline to 6 months for Responders being statistically significant. The 6-month change in Klotho concentration was inversely associated with the 6-month change in weight (r s = -0.195), BMI (r s = -0.196), fat mass (r s = -0.184), and waist circumference (r s = -0.218) (p-values <0.05). Discussion: Findings provide evidence within the context of a behavioral intervention, with and without exercise, that change in Klotho concentration is significantly different between adults with weight loss ≥10% compared to <5% across 12 months. These findings suggest that weight loss and reduction in fat mass may be favorably associated with the change in Klotho concentration. This may reduce the risk of negative health consequences associated with accelerated aging in middle-aged adults.

Genomically anchored vitamin D receptor mediates an abundance of bioprotective actions elicited by its 1,25-dihydroxyvitamin D hormonal ligand

The nuclear vitamin D receptor (VDR) mediates the actions of its physiologic 1,25-dihydroxyvitamin D3 (1,25D) ligand produced in kidney and at extrarenal sites during times of physiologic and cellular stress. The ligand-receptor complex transcriptionally controls genes encoding factors that regulate calcium and phosphate sensing/transport, bone remodeling, immune function, and nervous system maintenance. With the aid of parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23), 1,25D/VDR primarily participates in an intricate network of feedback controls that govern extracellular calcium and phosphate concentrations, mainly influencing bone formation and mineralization, ectopic calcification, and indirectly supporting many fundamental roles of calcium. Beyond endocrine and intracrine effects, 1,25D/VDR signaling impacts multiple biochemical phenomena that potentially affect human health and disease, including autophagy, carcinogenesis, cell growth/differentiation, detoxification, metabolic homeostasis, and oxidative stress mitigation. Several health advantages conferred by 1,25D/VDR appear to be promulgated by induction of klotho, an anti-aging renal peptide hormone which functions as a co-receptor for FGF23 and, like 1,25D, regulates nrf2, foxo, mTOR and other cellular protective pathways. Among hundreds of genes for which expression is modulated by 1,25D/VDR either primarily or secondarily in a cell-specific manner, the resulting gene products (in addition to those expressed in the classic skeletal mineral regulatory tissues kidney, intestine, and bone), fall into multiple biochemical categories including apoptosis, cholesterol homeostasis, glycolysis, hypoxia, inflammation, p53 signaling, unfolded protein response and xenobiotic metabolism. Thus, 1,25D/VDR is a bone mineral control instrument that also signals the maintenance of multiple cellular processes in the face of environmental and genetic challenges.

Hypertension and cellular senescence

Essential or primary hypertension is a wordwide health problem. Elevated blood pressure (BP) is closely associated not only with increased chronological aging but also with biological aging. There are various common pathways that play a role in cellular aging and BP regulation. These include but not limited to inflammation, oxidative stress, mitochondrial dysfunction, air pollution, decreased klotho activity increased renin angiotensin system activation, gut dysbiosis etc. It has already been shown that some anti-hypertensive drugs have anti-senescent actions and some senolytic drugs have BP lowering effects. In this review, we have summarized the common mechanisms underlying cellular senescence and HT and their relationships. We further reviewed the effect of various antihypertensive medications on cellular senescence and suggest further issues to be studied.

mTORC1-induced bone marrow-derived mesenchymal stem cell exhaustion contributes to the bone abnormalities in klotho-deficient mice of premature aging

Stem cell exhaustion is a hallmark of aging. Klotho-deficient mice (kl/kl mice) is a murine model that mimics human aging with significant bone abnormalities. The aim of this study is using kl/kl mice to investigate the functional change of bone marrow-derived mesenchymal stem cells (BMSCs) and explore the underlying mechanism. We found klotho-deficiency leads to bone abnormalities. In addition, kl/kl BMSCs manifested hyper-active proliferation but functional declined both in vivo and in vitro. mTORC1 activity was higher in freshly isolated kl/kl BMSCs and autophagy in kl/kl BMSCs were significantly decreased, possibly through mTORC1 activation. Conditional medium containing soluble Klotho protein (sKL) rescued hyper-proliferation of kl/kl BMSCs by inhibiting mTORC1 activity and restoring autophagy. Finally, intraperitoneally injection of mTORC1 inhibitor rapamycin restored BMSC quiescence, ameliorated bone phenotype and increased lifespan of kl/kl mice in vivo. This research highlights a therapeutic strategy to maintain the homeostasis of adult stem cell pool for healthy bone aging.

Reduced Klotho expression and its prognostic significance in canine hepatocellular carcinoma

Klotho is an anti-ageing gene and is known to act as a tumour suppressor in human hepatocellular carcinoma (HCC). According to a previous study, Klotho is present in normal canine mammary glands, and down-expression in tumours is positively associated with negative prognosis. However, the presence and significance of Klotho in canine HCC has not yet been reported. This study aimed to confirm Klotho expression in normal canine liver tissues using western blotting and immunohistochemistry, and whether the expression differed in non-neoplastic liver disease and HCC. Furthermore, correlation between clinicopathologic features and expression of Klotho was evaluated. All of the normal liver tissues showed the presence of Klotho, and Klotho expression was significantly decreased in the HCC tissue as compared to the non-neoplastic hepatic tissue. Additionally, Klotho expression was significantly associated with tumour size (P = .045), liver enzyme (alanine aminotransferase (ALT)) (P = .018), and metastasis (P = .024). Analysis of the survival curve revealed that reduced Klotho expression was significantly associated with poor disease-free survival (P = .041) in HCC. These results show that Klotho expression is present in normal canine liver tissue and that reduced Klotho expression is associated with poor prognosis in canine HCC. Thus, Klotho was presumed to be a potential clinical prognostic marker for canine HCC.

The expression of anti-aging protein Klotho is increased during neural differentiation of bone marrow-derived mesenchymal stem cells

Klotho, as an antiaging protein, is involved in the maintenance and differentiation of neuronal or glial cells and, therefore, has been noticed as a potential therapeutic target for neurodegenerative disorders. Expression of Klotho has been examined in different cells and organs, however, our information about the developmental pattern of this protein during differentiation of mesenchymal stem cells (MSCs) into neuron-like cells is limited. In this study, we conducted neural differentiation of mouse bone marrow-derived-MSCs and monitored the expression of Klotho together with selected neuron-specific genes at messenger RNA (mRNA) on days 7 and 14 of differentiation using quantitative real-time PCR. In addition, Klotho status at protein level was evaluated by immunocytochemistry. The results showed a significant change in the morphology of MSCs towards neuron-like cells. These changes were observed with progressive growth and formation of cell connections towards the formation of a chain of neuron-like cells which occurred in the second week of differentiation. Morphological changes were associated with a significant increase in the expression of neuron-specific genes like pax-6, neuN and, neurofilaments (NfL). Likewise, there was an increased expression of Klotho mRNA, and accumulation of Klotho protein in neuronal cell bodies, during the cellular differentiation of MSCs. These findings provided new evidence that neuronal differentiation from the MSCs is associated with increased expression of Klotho. These data may provide insight into the importance of Klotho protein in stem cell differentiation and regeneration in response to cell death in the central nervous system.

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.

Effect of a hyaluronic acid-based mesotherapeutic injectable on the gene expression of CLOCK and Klotho proteins, and environmentally induced oxidative stress in human skin cells

OBJECTIVE

Normal circadian rhythms are essential to the repair mechanisms of oxidative stress implicated in skin aging. Given reports that hyaluronic acid (HA) homeostasis exhibits a different profile in chronological skin aging, as compared to environmental or extrinsic aging, an improved understanding of the way HA interacts with its surroundings, and the impact of HA injectables in replacing lost HA and encouraging rejuvenation, is of key benefit to skin aging treatments. The objectives of these current studies were twofold. Firstly, to demonstrate the in vitro effects of two lightweight hyaluronic-based injectables on the expression of CLOCK protein in human skin fibroblasts, and their effects on Klotho protein expression as a marker for circadian rhythms in a combined human keratinocyte and Merkel cell model. Secondly, to ascertain whether these findings could be correlated with in vitro effects on various environmental oxidative stress aging markers (blue light, UVA/UVB, Urban Dust, and IR exposures).

METHODS

Oxidative stress studies were aimed to highlight possible protective effects through different challenge conditions in two models, ex vivo human skin explants and in vitro monolayer cultures of normal human dermal fibroblasts (NHDF). The protective effects of the test products were evaluated against an increase of cyclobutene pyrimidine dimers (CPDs) abundance within epidermal section of ex vivo skin explants after UVA/UVB radiation; effects of blue light on gene expression from NHDFs fibroblasts; effects of pollutants (Urban dust, UbD) on gene expression in NHDFs fibroblasts; and an increase of reactive oxygen species (ROS) production by NHDFs fibroblasts after infrared-A radiation. Gene expression was assayed and analyzed utilizing microfluidic TaqMan qPCR arrays. CLOCK expression was measured in young and senescing NHDFs by immunostaining, and Klotho and melatonin expression by immunostaining in Merkel cell-enriched normal adult human epidermal cell cultures.

RESULTS

In an aging culture of mixed keratinocyte and Merkel skin cells, activation of Klotho expression was induced by the application of both HA test products. Moreover, the HA products increase Klotho protein expression in both Merkel cells and keratinocytes. The observed positive effect of the tested products on melatonin receptors 1A and 1B expression in aging Merkel cell culture and keratinocytes is also interesting. HA-Y (developed for patients 25+ years old) stimulated melatonin receptors type 1B expression in aging cell cultures more strongly than HA-S (developed for patients 35-65 years old). In age (stressed) cells, a lower expression of Klotho protein and melatonin receptors 1A and 1B is apparent. The addition of HA-Y and HA-S stimulates their expression thus providing a "protective" effect. The blue light irradiation at 40 J/cm² performed in NHDF fibroblast cultures led to a modification of the expression of several genes, all involved in mechanisms known to be modulated in case of solar radiation stress.

CONCLUSIONS

Although these are preliminary findings, they are the first we know of that demonstrate HA facial injectables having a benefit and possibilities beyond the "physical filling" of the skin. As regards the beneficial effects against blue light-induced oxidative stress, and a return to cellular homeostasis, there is a need to conduct further and more precise investigations into HA-S. Furthermore, the benefit of these HA injectables (Novacutan®) in the modulation of oxidative stressed circadian rhythms widens their potential benefit.

Clinical Relevance of Serum Klotho Concentration and Sagittal Abdominal Diameter

Klotho is an anti-aging gene. Studies have revealed its association with insulin resistance. Visceral fat is related to insulin resistance, and the sagittal abdominal diameter (SAD) can serve as a biomarker for visceral fat (VF). This study investigated the association between SAD and serum Klotho concentration (SKC). We enrolled 2301 participants from the 2011−2012 National Health and Nutrition Examination Survey (NHANES) dataset, and 49.2% of the enrolled individuals were male. Qualified participants were separated into four quartiles according to the SAD value. SKC values were obtained by ELISA. Demographic characteristics, body mass index (BMI), systolic blood pressure, and biochemistry parameters with significance were analyzed using multivariate linear regression models. The mean age of the study participants was 57.22 ± 10.53 years. The fully adjusted regression model showed a negative association between SAD and SKC (p < 0.05), with a β-coefficient of −12.02. We also analyzed subgroups of participants according to age and BMI. Participants with an age ≥65 and <65 years old were each negatively associated with SKC, and this association was significant for participants with a BMI ≥ 30 kg/m2 (p = 0.001, β-coefficient: −18.83). We also found a concentration-dependent relationship between SAD and SKC. In conclusion, VF and SKC are associated, and SAD can serve as a surrogate of VF and an indicator of SKC.

Neuroprotective action of α-Klotho against LPS-activated glia conditioned medium in primary neuronal culture

The α-Klotho is an anti-aging protein that, when overexpressed, extends the life span in humans and mice. It has an anti-inflammatory and protective action on renal cells by inhibiting NF-κB activation and production of inflammatory cytokines in response to TNF-α. Furthermore, studies have shown the neuroprotective effect of α-Klotho against neuroinflammation on different conditions, such as aging, animal models of neurodegenerative diseases, and ischemic brain injury. This work aimed to evaluate the effects of α-Klotho protein on primary glial cell culture against the proinflammatory challenge with LPS and how this could interfere with neuronal health. Cortical mixed glial cells and purified astrocytes were pretreated with α- α-Klotho and stimulated with LPS followed by TNFα, IL-1β, IL-6, IFN-γ levels, and NF-κB activity analysis. Conditioned medium from cortical mixed glia culture treated with LPS (glia conditioned medium (GCM) was used to induce neuronal death of primary cortical neuronal culture and evaluate if GCM-KL (medium from glia culture pretreated α-Klotho followed by LPS stimulation) or GCM + LPS in the presence of KL can reverse the effect. LPS treatment in glial cells induced an increase in proinflammatory mediators such as TNF-α, IL-1β, IL-6, and IFN-γ, and activation of astrocyte NF-κB. GCM treated-cortical neuronal culture induced a concentration-dependent neuronal death. Pretreatment with α-Klotho decreased TNF-α and IL-6 production, reverted NF-κB activation, and decreased neuronal death induced by GCM. In addition, KL incubation together with GCM + LPS completely reverts the neuronal toxicity induced by low concentration of GCM-LPS. These data suggest an anti-inflammatory and neuroprotective effect of α-Klotho protein in the CNS. This work demonstrated the therapeutic potential of α-Klotho in pathological processes which involves a neuroinflammatory component.

Upregulation of Klotho Aggravates Insulin Resistance in Gestational Diabetes Mellitus Trophoblast Cells

OBJECTIVE

Insulin resistance (IR) plays a key role in gestational diabetes mellitus (GDM) pathogenesis. The antiaging protein klotho has been proven to be closely related to IR. The purpose of this study was to investigate the effect of klotho on IR in GDM trophoblast cells.

METHODS

The GDM cell model of HTR-8/SVneo cells was induced by high glucose (HG). Plasmid transfection was used to mediate the overexpression or silencing of klotho. The effects of klotho on cell viability, IR, and the IGF-1/PI3K pathways were observed by RT-qPCR, western blot, Cell Counting Kit-8 detection, glucose uptake assay, and immunofluorescence detection.

RESULTS

Klotho expression was up-regulated in HG-induced cells. Overexpression of klotho could reduce the cell viability, insulin signaling molecules (INSR-α, INSR-β, IRS1, IRS2, and GLUT4), and glucose uptake in HTR-8/SVneo cells of the HG group. In addition, the overexpression of klotho inhibited the levels of IGF-1, IGF-1R/p-IGF-1R, and the phosphorylation and activation of the signal transduction molecules PI3K/Akt/mTOR. On the contrary, klotho deletions could reverse these changes of HTR-8/SVneo cells induced by HG. Conclusion. In a word, the results of this study showed that the regulation of klotho played an important role in the IR of trophoblast cells induced by HG, which was mediated at least in part by the IGF-1/PI3K/Akt/mTOR pathway.

Controversial Interactions of Tacrolimus with Dietary Supplements, Herbs and Food

Tacrolimus is an immunosuppressive calcineurin inhibitor used to prevent rejection in allogeneic organ transplant recipients, such as kidney, liver, heart or lung. It is metabolized in the liver, involving the cytochrome P450 (CYP3A4) isoform CYP3A4, and is characterized by a narrow therapeutic window, dose-dependent toxicity and high inter-individual and intra-individual variability. In view of the abovementioned facts, the aim of the study is to present selected interactions between tacrolimus and the commonly used dietary supplements, herbs and food. The review was based on the available scientific literature found in the PubMed, Scopus and Cochrane databases. An increase in the serum concentration of tacrolimus can be caused by CYP3A4 inhibitors, such as grapefruit, pomelo, clementine, pomegranate, ginger and turmeric, revealing the side effects of this drug, particularly nephrotoxicity. In contrast, CYP3A4 inducers, such as St. John’s Wort, may result in a lack of therapeutic effect by reducing the drug concentration. Additionally, the use of Panax ginseng, green tea, Schisandra sphenanthera and melatonin in patients receiving tacrolimus is highly controversial. Therefore, since alternative medicine constitutes an attractive treatment option for patients, modern healthcare should emphasize the potential interactions between herbal medicines and synthetic drugs. In fact, each drug or herbal supplement should be reported by the patient to the physician (concordance) if it is taken in the course of immunosuppressive therapy, since it may affect the pharmacokinetic and pharmacodynamic parameters of other preparations.

Pathophysiology and genetics of salt-sensitive hypertension

Most hypertensive cases are primary and heavily associated with modifiable risk factors like salt intake. Evidence suggests that even small reductions in salt consumption reduce blood pressure in all age groups. In that regard, the ACC/AHA described a distinct set of individuals who exhibit salt-sensitivity, regardless of their hypertensive status. Data has shown that salt-sensitivity is an independent risk factor for cardiovascular events and mortality. However, despite extensive research, the pathogenesis of salt-sensitive hypertension is still unclear and tremendously challenged by its multifactorial etiology, complicated genetic influences, and the unavailability of a diagnostic tool. So far, the important roles of the renin-angiotensin-aldosterone system, sympathetic nervous system, and immune system in the pathogenesis of salt-sensitive hypertension have been studied. In the first part of this review, we focus on how the systems mentioned above are aberrantly regulated in salt-sensitive hypertension. We follow this with an emphasis on genetic variants in those systems that are associated with and/or increase predisposition to salt-sensitivity in humans.

Association between environmental exposure to perchlorate, nitrate, and thiocyanate and serum α-Klotho levels among adults from the National Health and nutrition examination survey (2007–2014)

Background & aims

Aging is a pathophysiological process driven by a diverse set of complex biological processes, and environmental pollution plays an important role in this process. This study aimed to explore the association between serum α-Klotho levels and urinary perchlorate, nitrate, and thiocyanate levels.

Methods

This secondary dataset analysis included 4875 participants (mean age, 57.69 year; male, 49.58%; non-Hispanic White, 47.67%) from the US National Health and Nutrition Examination Survey (2007–2014). Enzyme-linked immunosorbent assay was used to quantify α-Klotho levels, and ion chromatography coupled with electrospray tandem mass spectrometry was used to quantify thiocyanate, nitrate, and perchlorate levels. Multivariate linear regression models were applied to estimate the association between perchlorate, nitrate, and thiocyanate levels and serum α-Klotho levels.

Results

Urinary thiocyanate levels were negatively associated with α-Klotho levels (β = − 0.006; 95% confidence interval, − 0.010 to − 0.003; P = 0.0004) after adjusting for age, sex, body mass index, race, alcohol consumption, estimated glomerular filtration rate, underlying disease, physical activity, smoking status, usual energy intake, and urinary creatinine and serum cotinine levels and mutual adjustment of urinary perchlorate, urinary nitrate, and urinary thiocyanate levels. The α-Klotho level in participants in the highest quartile was higher by 50.567 ng/mL (β = 50.567; 95% confidence interval, 14.407 to 86.726; P = 0.009) than that in participants in the lowest quartile of urinary perchlorate. A linear relationship was observed between urinary thiocyanate and α-Klotho levels.

Conclusions

Urinary thiocyanate levels were negatively associated with serum α-Klotho levels. Urinary thiocyanate should be further investigated as a potential mediator of aging and age-related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03444-2.

Aging impairs arterial compliance via Klotho-mediated downregulation of B-cell population and IgG levels

OBJECTIVE

Aging is associated with compromised immune function and arterial remodeling and stiffness. The purpose of this study is to investigate whether in vivo AAV-based delivery of secreted Klotho (SKL) gene (AAV-SKL) improves aging- and senescence-associated immune dysfunction and arterial stiffness.

METHODS AND RESULTS

Senescence-accelerated mice prone strain 1 (SAMP1, 10 months) and old mice (20 months) were used. Serum SKL levels, B-cell population and serum IgG levels were markedly decreased in SAMP1 and old mice. Rescue of downregulation of serum SKL levels by in vivo AAV2-based delivery of SKL gene (AAV-SKL) increased B-cell population and serum IgG levels and attenuated arterial stiffness in SAMP1 and old mice. Thus, Klotho deficiency may play a role in senescence- and aging-associated humoral immune dysfunction and arterial stiffness. Vascular infiltration of inflammatory cells and expression of TGFβ1, collagen 1, scleraxis, MMP-2 and MMP-9 were increased while the elastin level was decreased in aortas of SAMP1 and old mice which can be rescued by AAV-SKL. Interestingly, treatment with IgG effectively rescued arterial inflammation and remodeling and attenuated arterial stiffness and hypertension in aging mice. In cultured B-lymphoblast cells, we further showed that SKL regulates B-cell proliferation and maturation partly via the NFkB pathway.

CONCLUSION

Aging-associated arterial stiffening may be largely attributed to downregulation of B-cell population and serum IgG levels. AAV-SKL attenuates arterial stiffness in aging mice partly via restoring B-cell population and serum IgG levels which attenuates aging-associated vascular inflammation and arterial remodeling.

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.