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.

Fibroblast growth factor-23 and Alpha-Klotho concentrations in dogs with canine Leishmaniasis

This study aimed to assess the concentrations of Fibroblast Growth Factor-23 (FGF-23) and α-Klotho in healthy dogs and dogs at different stages of Canine Leishmaniasis (CanL), and investigate the changes of these parameters in relation to renal function and calcium‑phosphorus metabolism. A total of 74 dogs (22 healthy and 52 with CanL) of varying ages, sexes, and medium-sized breeds were included. Dogs with CanL were categorized into different stages (Stage I-IV) based on Leishvet recommendations. In addition to routine hematological parameters, plasma FGF-23, serum α-Klotho, urea, creatinine, phosphorus, calcium, parathormone, vitamin D concentrations, and urine protein/creatinine ratio were measured. Data from healthy dogs were compared to dogs with CanL overall and by stage. Dogs with CanL exhibited higher concentrations of FGF-23 (p < 0.05), α-Klotho, and parathormone (p < 0.001), as well as lower concentrations of vitamin D and calcium (p < 0.001). FGF-23 concentration was particularly elevated in Stage IV compared to other stages. However, no significant differences in α-Klotho levels were observed among the stages. FGF-23 levels showed a weak positive correlation with urea and creatinine concentrations and a moderate positive correlation with urine protein/creatinine ratio. This study demonstrated increased levels of FGF-23 and α-Klotho in dogs with CanL for the first time. The increase in FGF-23 levels was more prominent in advanced stages of the disease and correlated with higher urea and creatinine concentrations. These findings may serve as a basis for future diagnostic and therapeutic investigations, contributing to the understanding of the pathophysiology of kidney disease in CanL.

Effects of Klotho protein, vitamin D, and oxidative stress parameters on urinary stone formation and recurrence

PURPOSE

The present study aimed to investigate the effects of α-Klotho and oxidative stress markers on urinary stone disease (USD) and demonstrate their use as biochemical markers in USD.

METHODS

Among the 90 individuals included, 30 individuals were healthy controls (Group 1), 30 individuals presented with USD for the first time (Group 2), and 30 individuals demonstrated recurrent USD (Group 3). Serum levels of α-Klotho, vitamin D, malondialdehyde (MDA), total oxidant status, and total antioxidant status were determined using spectrophotometry analysis. Serum calcium and parathormone levels and 24-h urine calcium levels were measured via biochemical analysis.

RESULTS

No significant intergroup difference was noted in terms of age and sex. The groups had significant differences regarding α-Klotho, oxidative stress index (OSI), MDA, and 24-h urine calcium levels. α-Klotho was a determinant of 24-h urine calcium level and OSI. An increase of 1 pg/mL in α-Klotho level appeared to result in a decrease of 8.55 mg in 24-h urine calcium level and a decrease of 0.04 Arbitrary Unit in OSI. In patients experiencing USD for the first time, α-Klotho values were < 21.83 pg/mL and showed 66% sensitivity and 64% specificity. In individuals with recurrent stone formation, α-Klotho values below 19.41 pg/mL had 60% sensitivity and 77% specificity.

CONCLUSIONS

The biochemical markers investigated herein, i.e., α-Klotho, OSI, and MDA, were involved in the pathogenesis of stone formation and can be used in day-to-day clinical practices of urology clinics to identify patients at risk for both first time and recurrent USD.

Association between serum α-Klotho levels and osteoarthritis prevalence among middle-aged and older adults: an analysis of the NHANES 2007-2016

BACKGROUND

As individuals age, the prevalence of osteoarthritis tends to increase gradually. α-Klotho is a hormone renowned for its anti-aging properties. However, the precise role of serum α-Klotho in osteoarthritis is still not fully comprehended.

METHODS

We conducted a cross-sectional study utilizing data from the National Health and Nutrition Examination Survey (NHANES) spanning from 2007 to 2016. Serum α-Klotho levels were measured using an enzyme-linked immunosorbent assay (ELISA). Osteoarthritis was assessed through self-reported questionnaires. Through univariate and multivariate logistic regression analyses, smooth curve fitting, threshold effect analysis, and subgroup analyses, we delved into the potential association between them.

RESULTS

The study encompassed a cohort of 10,265 participants. In fully adjusted models of multivariate logistic regression analysis, we identified a negative correlation between serum ln α-Klotho and OA (OR = 0.77, 95% CI: 0.65-0.91, p = 0.003). When stratifying serum α-Klotho levels into tertiles, individuals in the highest tertile exhibited a 26% reduced risk of OA compared to those in the lowest tertile (OR = 0.84, 95% CI: 0.73-0.97, p = 0.014). Subsequent analyses indicated a linearly negative association. In subgroup analyses, we explored the relationship between serum ln α-Klotho and osteoarthritis across diverse populations, revealing the persistence of this association in the majority of subgroups.

CONCLUSION

Serum α-Klotho levels exhibit a significant negative linear correlation with the prevalence of osteoarthritis in middle-aged and elderly populations in the United States.

Placental and serum levels of human α-Klotho in preeclampsia & intra-uterine growth retardation: A potential sensitive biomarker?

INTRODUCTION

α-Klotho protein has three isoforms: a transmembrane (mKL), a shed- soluble isoform, and a circulating soluble isoform (sKL). mKL is expressed in the kidney and placenta, while sKL is detectable in blood and urine. It is known that α-Klotho levels fluctuate during pregnancy mainly in women with complications such as preeclampsia (PE) and intra-uterine growth restriction (IUGR).

METHODS

Forty-nine participants were divided into two groups: healthy and complicated pregnancy (PE, IUGR or both). Tissue samples (2 cm3) from the maternal side, Blood and urine samples were collected during pregnancy and postpartum. Samples were subjected to biochemical (WB), histological (H&E and IHC) staining as well as genetic analysis (qPCR).

RESULTS

Blood αKL levels were preserved in both healthy and complicated pregnancies. Significantly lower blood αKL concentrations were found in PE postpartum (PP) compared to levels during pregnancy, and were significantly lower compared with postpartum of a healthy pregnancy. αKL activity was reduced in complicated pregnancies vs. healthy pregnancies. Placen tal mKL levels (ELISA) and expression (WB) were lowered in complicated pregnancies compared with the healthy pregnancies group. Additionally, we found a significant decline in the expression of mKL mRNA in PE/IUGR placentas compared with the healthy group.

DISCUSSION

Several studies have focused on the involvement of αKL in normal placentation during pregnancy. Our results suggest lower function of sKL in complicated pregnancy compared with a control, and present differences in placental mKL levels as well as tissue and gene expression between healthy and complicated pregnancy. In light of our results, we conclude that complicated pregnancy is associated with in decline in mKL.

Overexpression of α-Klotho isoforms promotes distinct Effects on BDNF-Induced Alterations in Dendritic Morphology

α-Klotho (α-Kl) is a modulator of aging, neuroprotection, and cognition. Transcription of the Klotho gene produces two splice variants-a membrane protein (mKl), which can be cleaved and released into the extracellular milieu, and a truncated secreted form (sKl). Despite mounting evidence supporting a role for α-Kl in brain function, the specific roles of α-Kl isoforms in neuronal development remain elusive. Here, we examined α-Kl protein levels in rat brain and observed region-specific expression in the adult that differs between isoforms. In the developing hippocampus, levels of isoforms decrease after the third postnatal week, marking the end of the critical period for development. We overexpressed α-Kl isoforms in primary cultures of rat cortical neurons and evaluated effects on brain-derived neurotrophic factor (BDNF) signaling. Overexpression of either isoform attenuated BDNF-mediated signaling and reduced intracellular Ca2+ levels, with mKl promoting a greater effect. mKl or sKl overexpression in hippocampal neurons resulted in a partially overlapping reduction in secondary dendrite branching. Moreover, mKl overexpression increased primary dendrite number. BDNF treatment of neurons overexpressing sKl resulted in a dendrite branching phenotype similar to control neurons. In neurons overexpressing mKl, BDNF treatment restored branching of secondary and higher order dendrites close, but not distal, to the soma. Taken together, the data presented support the idea that sKl and mKl play distinct roles in neuronal development, and specifically, in dendrite morphogenesis.

α-Klotho levels in girls with central precocious puberty: potential as a diagnostic and monitoring marker

Background

Recent studies suggest a link between the Klotho protein, sex hormones, and insulin-like growth factor-1 (IGF-1), indicating that α-Klotho levels may rise during puberty, including in central precocious puberty (CPP) cases. This study aimed to explore α-Klotho levels in girls with CPP to assess its potential as a diagnostic and monitoring tool for this condition.

Methods

In total, 139 girls, comprising 82 patients diagnosed with CPP and 57 healthy prepubertal controls, were enrolled in this study. From March 2020 to May 2023, we assessed both α-Klotho levels and clinical parameters. α-Klotho concentrations were measured using an α-Klotho ELISA kit. For the girls with CPP, we additionally analyzed samples taken 6 months after GnRH agonist treatment.

Results

α-Klotho levels were higher in the CPP group compared with the control (CPP group: 2529 ± 999 ng/mL; control group: 1802 ± 675 pg/mL) (P < 0.001), and its level modest decreased after 6 months of GnRH agonist treatment (2147± 789 pg/mL) (P < 0.001). The association between α-Klotho and IGF-1 SDS, follicular stimulating hormone and baseline luteinizing hormone was assessed by partial correlation after adjusting for age, BMI SDS (r= 0.416, p= <0.001; r= 0.261, p= 0.005; r= 0.278, p= 0.002), respectively. Receiver operating characteristic curve analysis identified an α-Klotho cut-off differentiating CPP from controls, with a cut-off of 1914 pg/mL distinguishing girls with CPP from controls with a sensitivity of 69.5% and specificity of 70.2%; the area under the curve was 0.723.

Conclusion

The findings of our study are the first step towards deciphering the role of α-Klotho in puberty induction. With additional data and further research, α-Klotho could potentially be utilized as a significant diagnostic and monitoring tool for CPP.

Serum soluble α-Klotho levels in patients with diabetic nephropathy

BACKGROUND

The study aimed to determine the variability in the stages of diabetic nephropathy by examining specific biochemical functions associated with the target organ. As a result, various biochemical parameters were assessed in all of the groups under investigation.

MATERIAL AND METHODS

These parameters encompassed soluble α-Klotho and serum insulin, which were determined through ELISA. Additionally, spectrophotometric methods were employed to assess other parameters such as blood levels of urea in all groups. Instead of using HPLC method, HbA1c levels were determined. Blood and urine samples were obtained from a total of 90 participants, who were aged between 37 and 70 years. A total of 70 patients were categorized into three groups according to their ACR. The first group consisted of patients with an ACR value of less than 30 mg/g. The second group included patients with an ACR value ranging from 30 to 300 mg/g. The third group comprised patients with an ACR value greater than 300 mg. Additionally, the study also involved 20 healthy individuals.

RESULT

The serum soluble α-Klotho in the patient group was significantly lower than that of the healthy subjects. There were strong negative correlations between serum soluble α-Klotho and both ACR and HOMA-IR. The AUC value was excellent, measuring at 0.93 with a p < 0.0001.

CONCLUSIONS

Soluble α-Klotho levels in the sera of diabetic patients were shown to be lower and significantly linked to patients with diabetic nephropathy. This implies that klotho levels may be influenced by ACR in addition to playing a significant role in insulin resistance.

Serum α-Klotho and fibroblast growth factor 23 levels are not associated with non-proliferative diabetic retinopathy in type 1 diabetes mellitus

Diabetic retinopathy is a commonly observed cause of blindness and is a common problem in individuals with diabetes. Recent investigations have showed the capability of serum α-Klotho and FGF 23 in mitigating the effects of diabetic retinopathy. This study aimed to discover the correlation between FGF 23, α-Klotho, and diabetic retinopathy in type 1 diabetics. This case-control study included 63 diabetic patients and 66 healthy controls. Following an overnight duration of fasting, morning blood samples were taken from both the patient and the control groups. The serum concentrations of α-Klotho and FGF 23 were quantified. An experienced ophthalmologist inspected the retinopathy. All participants in this study have moderate non-proliferative retinopathy. A p value under 0.05 was considered statistically significant. The mean α-Klotho level for retinopathic diabetic patients was 501.7 ± 172.2 pg/mL and 579.6 ± 312.1 pg/mL for non-retinopathic diabetic patients. In comparison, α-Klotho level of the control group was 523.2 ± 265.4 pg/mL (p = 0.531). The mean of FGF 23 level did not demonstrate a significant difference (p = 0.259). The mean FGF 23 level were 75.7 ± 14.0 pg/mL, 74.0 ± 14.8 pg/mL and 79.3 ± 14.4 pg/mL in groups, respectively. In conclusion, there was no significant difference in FGF 23 and α-Klotho levels between type 1 diabetics with and without retinopathy when compared to the control group.

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

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

Klotho Overexpression Is Frequently Associated With Upstream Rearrangements in Fusion-Negative Phosphaturic Mesenchymal Tumors of Bone and Sinonasal Tract

Phosphaturic mesenchymal tumors (PMT) are uncommon neoplasms that cause hypophosphatemia/osteomalacia mainly by secreting fibroblast growth factor 23. We previously identified FN1::FGFR1/FGF1 fusions in nearly half of the PMTs and frequent KL (Klotho or α-Klotho) overexpression in only those with no known fusion. Here, we studied a larger cohort of PMTs for KL expression and alterations. By FN1 break-apart fluorescence in situ hybridization (FISH) and reappraisal of previous RNA sequencing data, 6 tumors previously considered "fusion-negative" (defined by negative results of FISH for FN1::FGFR1 fusion and FGF1 break-apart and/or of RNA sequencing) were reclassified as fusion-positive PMTs, including 1 containing a novel FN1::ZACN fusion. The final cohort of fusion-negative PMTs included 33 tumors from 32 patients, which occurred in the bone (n = 18), soft tissue (n = 10), sinonasal tract (n = 4), and brain (n = 1). In combination with previous work, RNA sequencing, RNA in situ hybridization, and immunohistochemistry showed largely concordant results and demonstrated KL/α-Klotho overexpression in 17 of the 28 fusion-negative and none of the 10 fusion-positive PMTs studied. Prompted by a patient in this cohort harboring germline KL upstream translocation with systemic α-Klotho overexpression and multifocal PMTs, FISH was performed and revealed KL rearrangement in 16 of the 33 fusion-negative PMTs (one also with amplification), including 14 of the 17 cases with KL/α-Klotho overexpression and none of the 11 KL/α-Klotho-low fusion-negative and 11 fusion-positive cases studied. Whole genomic sequencing confirmed translocation and inversion in 2 FISH-positive cases involving the KL upstream region, warranting further investigation into the mechanism whereby these rearrangements may lead to KL upregulation. Methylated DNA immunoprecipitation and sequencing suggested no major role of promoter methylation in KL regulation in PMT. Interestingly, KL-high/-rearranged cases seemed to form a clinicopathologically homogeneous group, showing a predilection for skeletal/sinonasal locations and typically matrix-poor, cellular solitary fibrous tumor-like morphology. Importantly, FGFR1 signaling pathways were upregulated in fusion-negative PMTs regardless of the KL status compared with non-PMT mesenchymal tumors by gene set enrichment analysis, perhaps justifying FGFR1 inhibition in treating this subset of PMTs.

Structural asymmetry in FGF23 signaling

Chen et al. have derived cryogenic electron microscopy (cryo-EM) structures of signaling complexes of the endocrine hormone fibroblast growth factor 23 (FGF23) with fibroblast growth factor receptor (FGFR), α-Klotho, and heparin sulfate. These structures are asymmetric, leading to questions concerning in vivo function, and will facilitate structure-based drug design to modulate FGF23 signaling.

L-shaped association of serum α-Klotho and frailty among the middle-aged and older adults: results from NHANES 2007-2016

BACKGROUND

Frailty is common and not limited to older age group. Serum α-Klotho works as a biomarker of anti-aging effect. However, there is limited research about the relationship between them in middle-aged and older people and controversy still exists.

METHODS

Based on data from National Health and Nutrition Examination Survey (NHANES) 2007-2016, we constructed weighted logistic regression models and conducted sensitivity tests to investigate the correlation between frailty and α-Klotho among people aged 40 to 79. And then their relationship was visualized by Restricted Cubic Spline (RCS). Finally, the stratified analyses and interaction tests of covariables was presented in the forest plot.

RESULTS

A total of 7052 individuals were involved in this study, with mean age of 62.76 ± 0.18 years and females accounting for 51.05%. 2554 of them were in "frailty". After adjustment for relevant covariables, weighted logistic regression models showed that the odds ratio and 95% confidence interval [ORs (95%CI)] of correlation between frailty and Natural Logarithm(ln)-transformed α- Klotho[ln(α-Klotho)] was 0.63 (0.50, 0.79); we then performed a sensitivity analysis and found that the results remained stable. In model 3, individuals in quartiles 2, 3, and 4 showed statistical differences compared with the lowest ln(α-Klotho) quartiles, ORs (95% CI) were 0.74 (0.59, 0.93), 0.72 (0.57, 0.91), 0.71 (0.57, 0.87), respectively. Subsequently, non-linear associations were exhibited by RCS (p<0.001). The turning point for α-Klotho and ln(α-Klotho) were 785.7(pg/ml) and 6.67, respectively. Finally, analysis of the relationship between different levels of ln(α-Klotho) and frailty in different populations revealed differences between groups. The results of the interaction test showed that no other covariables had significant interaction with serum α-Klotho in our study.

CONCLUSION

The L-shaped and negative correlation was found between α-Klotho and frailty among people aged 40 to 79 in the NHANES from 2007 to 2016.

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

BACKGROUND AND AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Association between serum soluble α-klotho and bone mineral density (BMD) in middle-aged and older adults in the United States: a population-based cross-sectional study

BACKGROUND

Osteoporosis is a degenerative disease defined by low bone mineral density, has a high prevalence, and causes fractures at multiple sites throughout the body, greatly affecting the quality of patients. α-Klotho is an endocrine factor involved in the regulation of various metabolic processes in humans, and its role in bone metabolism has attracted widespread attention. The relationship between α-klotho and bone mineral density has not been uniformly recognized, and no large-scale correlation analysis has been conducted in the middle-aged and elderly population.

OBJECTIVE

To determine the relationship between α-klotho and bone mineral density in middle-aged and elderly people.

METHODS

Population data of 3120 individuals aged 40-79 years were obtained from the NHANES database for the period 2011-2016. Regression analysis was performed using a general linear model with serum α-klotho as the independent variable and total bone mineral density, thoracic bone mineral density, lumbar bone mineral density, pelvic bone mineral density, and trunk bone mineral density as the dependent variables, respectively. The generalized additive model was also used for smoothing curve fitting and threshold effect analysis.

RESULTS

Serum α-klotho was positively correlated with total bone mineral density at lg (Klotho) < 2.97 and with thoracic bone mineral density at lg (Klotho) > 2.69 (β = 0.05, p = 0.0006), and negatively correlated (β = -0.27, p = 0.0341) with lumbar bone mineral density at lg (Klotho) < 2.69. It also positively correlated with trunk bone mineral density (β = 0.027, p = 0.03657) and had no segmental effect but did not correlate with pelvic bone mineral density. The positive association of serum α-klotho with those aged 40-49 years, female, non-Hispanic White, and without hypertension was clearer. In the population with diabetes, a significantly positive association between total (β = 0.15, p = 0.01), thoracic (β = 0.23, p = 0.0404), and lumbar (β = 0.22, p = 0.0424) bone mineral density and α-klotho was observed.

CONCLUSIONS

α-Klotho has different relationships with total, thoracic, lumbar, and trunk bone mineral density. Among them, the positive correlation between α-klotho and trunk bone mineral density is more valuable for predicting osteoporosis. The significant effect of α-klotho on bone mineral density in diabetes patients suggests its potential as a predictive marker of diabetes progression.

Serum Anti-Aging Protein α-Klotho Mediates the Association between Diet Quality and Kidney Function

Adherence to healthy dietary patterns is associated with a reduced risk of kidney dysfunction. Nevertheless, the age-related mechanisms that underpin the relationship between diet and kidney function remain undetermined. This study aimed to investigate the mediating role of serum α-Klotho, an anti-aging protein, in the link between a healthy diet and kidney function. A cross-sectional study was conducted on a cohort of 12,817 individuals aged between 40 and 79 years who participated in the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. For each participant, the Healthy Eating Index 2015 (HEI-2015) score was calculated as a measure of a healthy dietary pattern. Creatinine-based estimated glomerular filtration rate (eGFR) was used to assess kidney function. Multivariable regression models were used to analyze the association between the standardized HEI-2015 score and eGFR after adjusting for potential confounders. Causal mediation analysis was performed to assess whether serum α-Klotho influenced this association. The mean (±SD) eGFR of all individuals was 86.8 ± 19.8 mL/min per 1.73 m². A high standardized HEI-2015 score was associated with a high eGFR (β [95% CI], 0.94 [0.64-1.23]; p < 0.001). The mediation analysis revealed that serum α-Klotho accounted for 5.6-10.5% of the association of standardized overall HEI-2015 score, total fruits, whole fruits, greens and beans, and whole grain with eGFR in the NHANES. According to the results from the subgroup analysis, serum α-Klotho exerted a mediating effect in the participants aged 60-79 years and in males. A healthy diet may promote kidney function by up-regulating serum anti-aging α-Klotho. This novel pathway suggests important implications for dietary recommendations and kidney health.

The Role of Oxidative Stress and Antioxidants in Cardiovascular Comorbidities in COPD

Oxidative stress driven by several environmental and local airway factors associated with chronic obstructive bronchiolitis, a hallmark feature of COPD, plays a crucial role in disease pathomechanisms. Unbalance between oxidants and antioxidant defense mechanisms amplifies the local inflammatory processes, worsens cardiovascular health, and contributes to COPD-related cardiovascular dysfunctions and mortality. The current review summarizes recent developments in our understanding of different mechanisms contributing to oxidative stress and its countermeasures, with special attention to those that link local and systemic processes. Major regulatory mechanisms orchestrating these pathways are also introduced, with some suggestions for further research in the field.

Sex differences in the association between serum α-Klotho and depression in middle-aged and elderly individuals: A cross-sectional study from NHANES 2007-2016

BACKGROUND

Klotho is a well-known anti-aging protein that exerts pleiotropic effects; however, little is known regarding serum α-Klotho in the context of depression. Here, we evaluated the association between serum α-Klotho levels and depression in middle-aged and older individuals.

METHODS

In this cross-sectional study, data were collected from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016 with a total of 5272 participants who were ≥40 years of age. Depression was evaluated using the 9-item Patient Health Questionnaire (PHQ-9). The association between serum α-Klotho levels and depression was determined on the basis of multivariable logistic regression models.

RESULTS

The mean age of the enrolled adults was 58.94 ± 10.54 years, of which 49.5 % were female. When serum α-Klotho was log10-transformed, it was significantly inversely associated with depression in females in the final adjusted model (odds ratio [OR], 0.32; 95 % confidence interval [CI], 0.12-0.85). In the contrast, serum α-Klotho (log10) was significantly positively associated with depression in males in one of the adjusted models (OR, 3.71; 95 % CI, 1.17-11.8), and this disappeared after adjusting other covariates (all P > 0.05). Based on further stratified respective analyses of females and males, the results were stable.

LIMITATIONS

The cross-sectional study could not yield any conclusions regarding causality.

CONCLUSIONS

In the present study, serum α-Klotho levels were negatively related to the prevalence of depression in middle-aged and elderly women. This study provides new evidence of sex differences in the association between serum α-Klotho levels and depression.

Pathophysiological Implications and Therapeutic Approach of Klotho in Chronic Kidney Disease. A Systematic Review

The Klotho protein, known as an anti-aging protein, is expressed mainly in the kidney, and kidney disorders may contribute to disrupted expression of renal Klotho. The purpose of this systematic review was to determine if there are biological and nutraceutical therapies that increase the expression of Klotho and can help prevent complications associated with CKD. A systematic literature review was carried out through the consultation of PubMed, Scopus, and Web of Science. Records between the years 2012 and 2022 in Spanish and English were selected. Cross-sectional or prevalence and analytical studies were included that evaluated the effects of Klotho therapy. A total of 22 studies were identified after the critical reading of these selected studies. Three investigated the association between Klotho and growth factors; two evaluated the relationship between the concentration of Klotho and the type of fibrosis; three focused on the relationship between vascular calcifications and vitamin D; two assessed the relationship between Klotho and bicarbonate; two investigated the relationship between proteinuria and Klotho; one demonstrated the applicability of synthetic antibodies as a support for Klotho deficiency; one investigated Klotho hypermethylation as a renal biomarker; two investigated the relationship between proteinuria and Klotho; four linked Klotho as an early marker of CKD; one investigated Klotho levels in patients with autosomal dominant polycystic kidney disease. In conclusion, no study has addressed the comparison of these therapies in the context of their use with nutraceutical agents that raise the expression of Klotho.

Association between perfluoroalkyl and polyfluoroalkyl internal exposure and serum α-Klotho levels in middle-old aged participants

Purpose

Exposure to perfluoroalkyl and polyfluoroalkyl substances causes oxidative stress, which is strongly associated with adverse health effects. Klotho protein plays an anti-aging role via antioxidation activity.

Methods

We investigated the levels of serum α-Klotho and PFAS exposure in adults who participated in the National Health and Nutrition Examination Survey from 2013 to 2016. A nationally representative subsample of 1,499 adults aged 40-79 years was analyzed for the associations of serum α-Klotho levels with serum PFAS exposures by correlation analysis and multiple general linear models. Of note, the potential confounding factors including age and gender were adjusted. Quantile-based g-computation models were used to assess the effects of mixed PFAS exposure on serum α-Klotho levels.

Results

The weighted geometric mean of serum α-Klotho was 791.38 pg/mL for the subjects during 2013-2016. After adjusting for potential confounders, serum Klotho levels showed a statistically significant downward trend with increasing quartiles of PFOA and PFNA. Multivariate adjusted general linear regression analysis showed that increased exposure to PFNA was substantially associated with lower serum levels of α-Klotho, and each 1-unit increase in PFNA concentration was accompanied by a 20.23 pg/mL decrease in α-Klotho level; while no significant association was observed between other PFAS exposures and serum α-Klotho levels. It was negatively correlated between α-Klotho and Q4 for PFNA relative to the lowest quartile (Q1) of exposure (P = 0.025). It was found that the strongest negative correlation between PFNA exposure and serum α-Klotho levels was in the middle-aged (40-59 years) female participants. Furthermore, the mixture of the four PFAS substances showed an overall inverse association with serum α-Klotho concentrations, with PFNA being the major contributor.

Conclusions

Taken together, in a representative sample of the U.S. middle-aged and elderly populations, serum concentrations of PFAS, especially PFNA, have been negatively associated with serum levels of α-Klotho, which is strongly associated with cognition and aging. It was important to note that the majority of associations were limited to middle-aged women. It will be meaningful to clarify the causal relationship and the pathogenic mechanisms of PFAS exposure and α-Klotho levels, which is helpful to aging and aging-related diseases.

Fibrosis of Peritoneal Membrane, Molecular Indicators of Aging and Frailty Unveil Vulnerable Patients in Long-Term Peritoneal Dialysis

Peritoneal membrane status, clinical data and aging-related molecules were investigated as predictors of long-term peritoneal dialysis (PD) outcomes. A 5-year prospective study was conducted with the following endpoints: (a) PD failure and time until PD failure, (b) major cardiovascular event (MACE) and time until MACE. A total of 58 incident patients with peritoneal biopsy at study baseline were included. Peritoneal membrane histomorphology and aging-related indicators were assessed before the start of PD and investigated as predictors of study endpoints. Fibrosis of the peritoneal membrane was associated with MACE occurrence and earlier MACE, but not with the patient or membrane survival. Serum α-Klotho bellow 742 pg/mL was related to the submesothelial thickness of the peritoneal membrane. This cutoff stratified the patients according to the risk of MACE and time until MACE. Uremic levels of galectin-3 were associated with PD failure and time until PD failure. This work unveils peritoneal membrane fibrosis as a window to the vulnerability of the cardiovascular system, whose mechanisms and links to biological aging need to be better investigated. Galectin-3 and α-Klotho are putative tools to tailor patient management in this home-based renal replacement therapy.

Exposure to p-dichlorobenzene and serum α-Klotho levels among US participants in their middle and late adulthood

P-dichlorobenzene (p-DCB) is a volatile compound commonly used as pest repellent and air deodorant in the home and public buildings, leading to a widespread exposure in indoor environments. There has been an increasing concern about its metabolic and endocrine effects. In this study, we explored the relation between p-DCB exposure and serum levels of soluble α-Klotho, an anti-aging hormone, in US adults. A nationally representative subsample of 1485 adults 40-79 ages in the 2013-2016 National Health and Nutrition Examination Survey was analyzed for the association between p-DCB exposure, measured as urinary concentrations of 2,5-dichlorophenol (2,5-DCP), the major metabolite of p-DCB, and serum α-Klotho levels using multiple general linear models, adjusting for potential confounders. Age- and sex-specific analyses were further conducted. The weighted geometric mean of urinary 2,5-DCP was 2.43 μg/L and the weighted mean of serum α-Klotho was 831.97 pg/mL in the study participants during 2013-2016. After adjusting for potential confounders and urinary creatinine, urinary 2,5-DCP was significantly associated with decreased serum levels of α-Klotho (regression coefficient β = -9.88; p = 0.0133) in the total study population. When age- and sex-specific analyses being conducted, a significantly inverse association was found in older adults aged 60-79 years (β = -20.40; p = 0.0001) and in males (β = -13.81; p = 0.0097), but not in the middle ages (40-59 years) and in females. The strongest association was observed in older (60-79 years) male participants, with a 25.43 pg/mL reduction of α-Klotho levels per 1-unit increase of 2,5-DCP concentrations (p = 0.0008). This is the first study demonstrating a relation between p-DCB exposure, measured as 2,5-DCP, and decreased α-Klotho levels in older males. Additional studies would further explore these interactions and elucidate the pathogenesis of the potential effects of p-DCB exposure on aging.

Serum Levels of α-Klotho, Inflammation-Related Cytokines, and Mortality in Hemodialysis Patients

It has been hypothesized that α-Klotho deficiency might contribute to chronic inflammation in patients with end-stage renal disease (ESRD), especially those on hemodialysis (HD). Serum Klotho levels by some authors are considered a potential predictor of cerebrovascular events. Therefore, we analyzed serum levels of α-Klotho with ELISA and inflammation-related cytokines in HD patients. Sixty-seven HD patients and 19 healthy people were recruited between November 2017 and June 2021. A Cytometric Bead Array (CBA) was used to determine the level of different cytokines: IL-12p70, TNF, IL-10, IL-6, IL-1β, and IL-8. A human Klotho ELISA kit was used to determine the level of α-Klotho in the plasma samples of HD patients. There was no difference in serum levels of α-Klotho between HD patients and healthy people. Patients had increased serum IL-6 and IL-8. Significant positive correlations existed between the concentration of α-Klotho and the serum concentrations of IL-12p70, IL-10, and IL-1β. However, in a multivariable linear regression analysis, only patients' age was associated independently with α-Klotho level. Serum α-Klotho was not associated with higher mortality risk in HD patients. While these results draw attention to potential relationships between α-Klotho proteins and inflammatory markers in HD patients, our cross-sectional study could not confirm the pathogenic link between α-Klotho, inflammation, and cardiovascular mortality.

FGF23-Klotho Axis and Fractures in Patients Without and With Early CKD: A Case-Cohort Analysis of CARTaGENE

CONTEXT

Whether fibroblast growth factor-23 (FGF23) and α-Klotho are associated with fractures, especially in chronic kidney disease (CKD), remains controversial.

OBJECTIVE

We evaluated how FGF23, α-Klotho, and traditional mineral parameters predict fractures in individuals with and without early CKD.

METHODS

We conducted a stratified case-cohort analysis using CARTaGENE, a population-based survey from Quebec, Canada. Individuals aged 40 to 69 years were selected according to outcome and CKD status (non-CKD: eGFR > 60 mL/min/1.73 m2; CKD stage 3: eGFR 30-60 mL/min/1.73 m2]). Baseline levels of c-terminal FGF23 (cFGF23), α-Klotho, parathyroid hormone (PTH), phosphate, and calcium were analyzed for associations with osteoporotic fracture incidence from recruitment (2009-2010) through March 2016. Adjusted Cox models were used, and predictors were treated linearly or flexibly using splines.

RESULTS

A total of 312 patients (159 non-CKD; 153 CKD) were included; 98 had ≥ 1 fracture at any site during a median follow up of 70 months. Compared with non-CKD, CKD patients had increased levels of cFGF23 but similar levels of α-Klotho. cFGF23 was linearly associated with increased fracture incidence (adjusted HR = 1.81 [1.71, 1.93] per doubling for all participants). The association of α-Klotho with fracture followed a U-curve (overall P = 0.019) but was attenuated by adjustment for potential mediators (bone mineral density, phosphate, PTH). PTH and phosphate also had U-shaped associations with fracture. Associations were mostly similar between non-CKD and CKD. Adjustment for cFGF23 strongly attenuated the association between CKD status and fractures.

CONCLUSION

cFGF23 is associated linearly with fracture incidence while α-Klotho, PTH, and phosphate levels have a U-shaped association.

Orally-active, clinically-translatable senolytics restore α-Klotho in mice and humans

BACKGROUND

α-Klotho is a geroprotective protein that can attenuate or alleviate deleterious changes with ageing and disease. Declines in α-Klotho play a role in the pathophysiology of multiple diseases and age-related phenotypes. Pre-clinical evidence suggests that boosting α-Klotho holds therapeutic potential. However, readily clinically-translatable, practical strategies for increasing α-Klotho are not at hand. Here, we report that orally-active, clinically-translatable senolytics can increase α-Klotho in mice and humans.

METHODS

We examined α-Klotho expression in three different human primary cell types co-cultured with conditioned medium (CM) from senescent or non-senescent cells with or without neutralizing antibodies. We assessed α-Klotho expression in aged, obese, and senescent cell-transplanted mice treated with vehicle or senolytics. We assayed urinary α-Klotho in patients with idiopathic pulmonary fibrosis (IPF) who were treated with the senolytic drug combination, Dasatinib plus Quercetin (D+Q).

FINDINGS

We found exposure to the senescent cell secretome reduces α-Klotho in multiple nonsenescent human cell types. This was partially prevented by neutralizing antibodies against the senescence-associated secretory phenotype (SASP) factors, activin A and Interleukin 1α (IL-1α). Consistent with senescent cells' being a cause of decreased α-Klotho, transplanting senescent cells into younger mice reduced brain and urine α-Klotho. Selectively removing senescent cells genetically or pharmacologically increased α-Klotho in urine, kidney, and brain of mice with increased senescent cell burden, including naturally-aged, diet-induced obese (DIO), or senescent cell-transplanted mice. D+Q increased α-Klotho in urine of patients with IPF, a disease linked to cellular senescence.

INTERPRETATION

Senescent cells cause reduced α-Klotho, partially due to their production of activin A and IL-1α. Targeting senescent cells boosts α-Klotho in mice and humans. Thus, clearing senescent cells restores α-Klotho, potentially opening a novel, translationally-feasible avenue for developing orally-active small molecule, α-Klotho-enhancing clinical interventions. Furthermore, urinary α-Klotho may prove to be a useful test for following treatments in senolytic clinical trials.

FUNDING

This work was supported by National Institute of Health grants AG013925 (J.L.K.), AG062413 (J.L.K., S.K.), AG044271 (N.M.), AG013319 (N.M.), and the Translational Geroscience Network (AG061456: J.L.K., T.T., N.M., S.B.K., S.K.), Robert and Arlene Kogod (J.L.K.), the Connor Group (J.L.K.), Robert J. and Theresa W. Ryan (J.L.K.), and the Noaber Foundation (J.L.K.). The previous IPF clinical trial was supported by the Claude D. Pepper Older Americans Independence Centers at WFSM (AG021332: J.N.J., S.B.K.), UTHSCA (AG044271: A.M.N.), and the Translational Geroscience Network.

α-Klotho released from HK-2 cells inhibits osteogenic differentiation of renal interstitial fibroblasts by inactivating the Wnt-β-catenin pathway

Randall's plaques (RP) are well established as precursor lesions of idiopathic calcium oxalate (CaOx) stones, and the process of biomineralization driven by osteogenic-like cells has been highlighted in RP formation, but the mechanism is poorly understood. Given the inhibitory role of α-Klotho (KL), an aging suppressor protein with high expression in kidneys, in ectopic calcification and the close association between KL gene polymorphisms and urolithiasis susceptibility, we determined the potential role of KL in RP formation. This study found that both soluble KL (s-KL) and transmembrane KL (m-KL) were downregulated, and that s-KL but not m-KL was inversely correlated with upregulation of osteogenic markers in RP tissues. Additionally, s-KL expression was markedly suppressed in human renal interstitial fibroblasts (hRIFs) and slightly suppressed in HK-2 cells after osteogenic induction, intriguingly, which was echoed to the greater osteogenic capability of hRIFs than HK-2 cells. Further investigations showed the inhibitory effect of s-KL on hRIF osteogenic differentiation in vitro and in vivo. Moreover, coculture with recombinant human KL (r-KL) or HK-2 cells suppressed osteogenic differentiation of hRIFs, and this effect was abolished by coculture with KL-silenced HK-2 cells or the β-catenin agonist SKL2001. Mechanistically, s-KL inactivated the Wnt-β-catenin pathway by directly binding to Wnt2 and upregulating SFRP1. Further investigations identified activation of the Wnt-β-catenin pathway and downregulation of SFRP1 and DKK1 in RP tissues. In summary, this study identified s-KL deficiency as a pathological feature of RP and revealed that s-KL released from HK-2 cells inhibited osteogenic differentiation of hRIFs by inactivating the Wnt-β-catenin pathway, not only providing in-depth insight into the role of s-KL in renal interstitial biomineralization but also shedding new light on the interaction of renal tubular epithelial cells with interstitial cells to clarify RP formation.

Association of fibroblast growth factor 23 and α-klotho in hemodialysis patients during administration of ferric citrate hydrate: post hoc analysis of ASTRIO study

Background

Fibroblast growth factor-23 (FGF23) and α-klotho are associated with anemia in patients with chronic kidney disease. In this post hoc analysis of the ASTRIO study (UMIN000019176), we investigated the relationship between FGF23 and α-klotho during treatment with an iron-based phosphate binder, ferric citrate hydrate (FC), compared with non-iron-based phosphate binders in hemodialysis (HD) patients. We examined the effect of iron absorption by FC on the relationship between FGF23 and α-klotho. There have been few clinical studies evaluating these biomarkers simultaneously in HD patients.

Methods

The ASTRIO study was a 24-week, randomized, open-label, multicenter trial. HD patients taking non-iron-based phosphate binder(s) were randomized at a 1:1 ratio to continue other binder(s) (control group) or switch to FC (FC group). Serum phosphate (P) and hemoglobin (Hb) were maintained within 3.5–6.0 mg/dL and 10–12 g/dL, respectively. Plasma levels of intact FGF23 (i-FGF23), C-terminal FGF23 (c-FGF23), and α-klotho were measured, as were iron-related parameters. Association analyses of FGF23 and α-klotho were conducted.

Results

Patients were randomized to FC (n = 48) and control (n = 45) groups. Serum ferritin significantly increased from baseline to end-of-treatment (EOT) in the FC group, compared with the control group (adjusted mean difference [95% confidence interval]: 79.5 [44.7, 114.4] ng/mL; p <  0.001). The mean change from baseline to EOT in c-FGF23 was significantly different between the FC and control groups (mean ± standard deviation (SD): − 0.2 ± 0.8 log_e pg/mL vs. 0.2 ± 0.8 log_e pg/mL, respectively; p = 0.04). The mean change from baseline to EOT in i-FGF23 and α-klotho were not significantly different between the FC and control groups (mean ± SD: − 0.1 ± 0.8 log_e pg/mL vs. 0.1 ± 0.9 log_e pg/mL; p = 0.33, and 2.0 ± 91.5 pg/mL vs. − 8.9 ± 145.3; p = 0.58, respectively). However, both forms of FGF23 and α-klotho were not significantly associated with each other in both groups.

Conclusions

Iron absorbed via FC administration in HD patients did not influence the correlation relationship between plasma levels of FGF23 and α-klotho under the condition of serum P and Hb were maintained.

Trial registration

ASTRIO study (UMIN000019176, registered at UMIN Clinical Trials Registry on October 1, 2015).

METTL14 promotes glomerular endothelial cell injury and diabetic nephropathy via m6A modification of α-klotho

Background

N6-Methyladenosine (m6A) modification has been implicated in many bioprocesses. However, its functions in diabetic nephropathy (DN) have not been determined. Here, we investigated the role of METTL14, a key component of the m6A methyltransferase complex, in DN.

Methods

The expression of METTL14 was detected in DN patients and human renal glomerular endothelial cells (HRGECs). In vitro and in vivo experiments were performed to explore the functions of METTL14 on high glocse-induced HRGECs and renal injury of DN mice. We also investigated whether METTL14 works by regulating α-klotho expression through m6A modification.

Results

METTL14 were highly expressed in kidneys of DN patients and high glocse-induced HRGECs both at the mRNA and protein level. Overexpression of METTL14 increased ROS, TNF-α and IL-6 levels and apoptosis in HRGECs. Conversely, METTL14 silence decreased the levels of ROS, TNF-α and IL-6 and cell apoptosis. We confirmed that METTL14 down-regulated α-klotho expression in an m6A-dependent manner. In addition, we also found that METTL14 aggravated renal injury and inflammation of db/db mice, which could partially rescued by α-klotho.

Conclusion

Our data revealed that METTL14 plays a vital role in high glucose-induced glomerular endothelial cells and diabetic nephropathy through m6A modification of α-klotho.

Biofluids profile of α-Klotho in patients with Parkinson's disease

We measured α-Klotho in CSF and serum of PD patients at early stage of the disease, finding two distinct pools, the first increased, the second reduced. CSF α-Klotho was inversely associated with CSF α-synuclein levels. Our preliminary results suggest α-Klotho as potential biomarker or therapeutic target in PD.

Circulating α-klotho regulates metabolism via distinct central and peripheral mechanisms

Emerging evidence implicates the circulating α-klotho protein as a prominent regulator of energy balance and substrate metabolism, with diverse, tissue-specific functions. Despite its well-documented ubiquitous role inhibiting insulin signaling, α-klotho elicits potent antidiabetic and anti-obesogenic effects. α-Klotho facilitates insulin release and promotes β cell health in the pancreas, stimulates lipid oxidation in liver and adipose tissue, attenuates hepatic gluconeogenesis, and increases whole-body energy expenditure. The mechanisms underlying α-klotho's peripheral functions are multifaceted, including hydrolyzing transient receptor potential channels, stimulating integrin β1➔focal adhesion kinase signaling, and activating PPARα via inhibition of insulin-like growth factor receptor 1. Moreover, until recently, potential metabolic roles of α-klotho in the central nervous system remained unexplored; however, a novel α-klotho➔fibroblast growth factor receptor➔PI3kinase signaling axis in the arcuate nucleus of the hypothalamus has been identified as a critical regulator of energy balance and glucose metabolism. Overall, the role of circulating α-klotho in the regulation of metabolism is a new focus of research, but accumulating evidence identifies this protein as an encouraging therapeutic target for Type 1 and 2 Diabetes and obesity. This review analyzes the new literature investigating α-klotho-mediated regulation of metabolism and proposes impactful future directions to progress our understanding of this complex metabolic protein.

A feline-focused review of chronic kidney disease-mineral and bone disorders - Part 2: Pathophysiology of calcium disorder and extraosseous calcification

Derangements in mineral metabolism are one of the main entities in chronic kidney disease-mineral and bone disorder (CKD-MBD). This is the second of a two-part review of the physiology and pathophysiology of calcium homeostasis in feline CKD-MBD. While dysregulation in calcium homeostasis is known to contribute to the development of vascular calcification in CKD, evidence characterising the relationship between serum calcium concentration and nephrocalcinosis and nephrolithiasis is limited. Recently, fibroblast growth factor 23 (FGF23) and α-Klotho have gained increased research interest and been shown to be important biomarkers for the prediction of CKD progression in human patients. However, conflicting evidence exists on their role in calcium homeostasis and vascular and soft tissue calcification. This review details the pathophysiology of calcium disorders associated with CKD-MBD and its implications on vascular and soft tissue mineralisation in human and feline patients. Further prospective studies investigating the clinical consequences of calcium disturbances in cats with CKD are warranted and this may provide additional insight into the pathophysiology of feline CKD-MBD.

A feline-focused review of chronic kidney disease-mineral and bone disorders - Part 1: Physiology of calcium handling

Mineral derangements are a common consequence of chronic kidney disease (CKD). Despite the well-established role of phosphorus in the pathophysiology of CKD, the implications of calcium disturbances associated with CKD remain equivocal. Calcium plays an essential role in numerous physiological functions in the body and is a fundamental structural component of bone. An understanding of calcium metabolism is required to understand the potential adverse clinical implications and outcomes secondary to the (mal)adaptation of calcium-regulating hormones in CKD. The first part of this two-part review covers the physiology of calcium homeostasis (kidneys, intestines and bones) and details the intimate relationships between calcium-regulating hormones (parathyroid hormone, calcitriol, fibroblast growth factor 23, α-Klotho and calcitonin) and the role of the calcium-sensing receptor.

Roles for fibroblast growth factor-23 and α-Klotho in acute kidney injury

Acute kidney injury is a global disease with high morbidity and mortality. Recent studies have revealed that the fibroblast growth factor-23-α-Klotho axis is closely related to chronic kidney disease, and has multiple biological functions beyond bone-mineral metabolism. However, although dysregulation of fibroblast growth factor-23-α-Klotho has been observed in acute kidney injury, the role of fibroblast growth factor-23-α-Klotho in the pathophysiology of acute kidney injury remains largely unknown. In this review, we describe recent findings regarding fibroblast growth factor-23-α-Klotho, which is mainly involved in inflammation, oxidative stress, and hemodynamic disorders. Further, based on these recent results, we put forth novel insights regarding the relationship between the fibroblast growth factor-23-α-Klotho axis and acute kidney injury, which may provide new therapeutic targets for treating acute kidney injury.

Body composition, adipokines, FGF23-Klotho and bone in kidney transplantation: Is there a link?

BACKGROUND

Kidney transplantation-associated mineral and bone disorder (KT-MBD) still represents a black box on the long-term due to scarce available data. We aimed to investigate the impact of non-classical bone regulating factors (body composition, adipokines, inflammatory markers, fibroblast growth factor 23-FGF23 and α-Klotho) in long-standing kidney transplant (KT) recipients compared to the general population.

METHODS

Our cross-sectional study, enrolling 59 KT patients and age, sex and body mass index-matched healthy general population volunteers, assessed the predictive role of the body composition, serum adipokines (leptin, adiponectin, resistin), inflammatory markers (erythrocyte sedimentation rate, C-reactive protein) and parathyroid hormone (PTH)-FGF23/α-Klotho axis upon bone mineral density (BMD) and osteocalcin, using correlation and linear multiple regression.

RESULTS

The 59 KT recipients (mean transplantation span of 57.7 ± 7.2 months) had similar body composition but significantly lower BMD (p < 0.01) compared to the general population group. Total lean mass was independently associated with BMD in both groups. In KT patients, age, time spent on dialysis and PTH were the main negative independent predictors of BMD, after adjusting for possible confounders. Resistin and α-Klotho also negatively predicted lumbar bone density (p < 0.001), while adiponectin and α-Klotho positively predicted osteocalcin levels (p < 0.001) in KT recipients, independently of inflammatory markers. No significant associations were found between FGF23 and bone parameters in any of the groups.

CONCLUSIONS

Age, PTH, time on dialysis and lean mass are among the main bone density predictors in long-standing KT patients. The bone impact of adipokine dysregulation and of α-Klotho merits further investigations in KT-MBD. Preserving lean mass for improved bone outcomes should be part of KT-MBD management on the long-term.

Decreased ADAM17 expression in the lungs of α-Klotho reduced mouse

The deficiency of α-Klotho in mice causes phenotypes resembling human age-associated disorders at 3-4 weeks after birth and shows short lifespans of ∼2 months. One of the crucial symptoms is pulmonary emphysema, although α-Klotho is not expressed in the lungs. α-Klotho secreted from the kidneys is probably involved in the pathology of emphysema because kidney-specific knockout mice exhibit emphysematous structural changes. We examined whether any glycan changes in α-Klotho mouse lungs were observed, because α-Klotho is reported to have glycosidase activity. Here, we found the accumulation of heparan sulphate in the microsomal fraction of α-Klotho mouse lungs. Meanwhile, a disintegrin and metalloproteinase 17 (ADAM17) expression was decreased in α-Klotho mice. From these results, it is thought that the increase in heparan sulphate is due to insufficient cleavage of the core protein by ADAM17. Additionally, a reduction in α-Klotho and a decline of ADAM17 were also observed both in normal aged mice and in senescence marker protein-30 (SMP30) knockout mice, a mouse model of premature ageing. Thus, the decrease in ADAM17 is caused by the reduction in α-Klotho. These may be involved in the deterioration of lung function during ageing and may be associated with the pathology of pulmonary emphysema.

Could α-Klotho Unlock the Key Between Depression and Dementia in the Elderly: from Animal to Human Studies

α-Klotho is known for its aging-related functions and is associated with neurodegenerative diseases, accelerated aging, premature morbidity, and mortality. Recent literature suggests that α-Klotho is also involved in the regulation of mental functions, such as cognition and psychosis. While most of studies of α-Klotho are focusing on its anti-aging functions and protective role in dementia, increasing evidence showed many shared symptoms between depression and dementia, while depression has been proposed as the preclinical stage of dementia such as Alzheimer's disease (AD). To see whether and how α-Klotho can be a key biological link between depression and dementia, in this review, we first gathered the evidence on biological distribution and function of α-Klotho in psychiatric functions from animal studies to human clinical investigations with a focus on the regulation of cognition and mood. Then, we discussed and highlighted the potential common underlying mechanisms of α-Klotho between psychiatric diseases and cognitive impairment. Finally, we hypothesized that α-Klotho might serve as a neurobiological link between depression and dementia through the regulation of oxidative stress and inflammation.

Reduced Plasma Levels of α-Klotho and Their Correlation With Klotho Polymorphisms in Elderly Patients With Major Depressive Disorders

Background: Recent literature suggests that α-Klotho, a widely recognized anti-aging protein, is involved in longevity as well as in many diseases, including Alzheimer's disease, and depression. Although the Klotho gene encodes α-Klotho, a single transmembrane protein with intracellular and extracellular domains, the relationship between Klotho gene polymorphism and circulating α-Klotho levels in patients with major depressive disorder (MDD) is not clear. Methods: A total of 144 MDD patients and 112 age-matched healthy controls were included in this study. The Klotho genetic polymorphisms (rs9536314, rs9527025, and rs9315202) and plasma α-Klotho levels were measured by PCR and ELISA, respectively. The severity of depressive symptoms was estimated using the Hamilton Depression Scale (HAMD). Results: We found a significantly lower level of plasma α-Klotho in the MDD patients than in controls. Among them, only elderly MDD patients (first episode) showed significantly lower α-Klotho levels than the age-matched controls, while elderly recurrent and young MDD patients showed no difference in plasma α-Klotho levels from age-matched controls. The young MDD group showed a significantly earlier onset age, higher plasma α-Klotho levels, and lower HAMD scores than those in the elderly MDD group. While the plasma α-Klotho levels were higher in rs9315202 T alleles carrier regardless age or sex, the rs9315202 T allele was negatively correlated with disease severity only in the elderly MDD patients. Conclusion: The results of our study showed that only elderly MDD patients showed a decrease in plasma α-Klotho levels along with an increase in disease severity as well as an association with the number of rs9315202 T alleles, and not young MDD patients compared to age-matched controls. Our data suggest that circulating α-Klotho levels combined with Klotho genetic polymorphisms are important in elderly MDD patients, particularly carriers of the Klotho gene rs9315202 T allele.

Echinacoside protects adenine-induced uremic rats from sciatic nerve damage by up-regulating α-Klotho

OBJECTIVES

To investigate the therapeutic effect of Echinacoside on uremia-induced sciatic nerve injury and explore the specific molecular mechanism and role of α-Klotho.

METHODS

SD rats were given continuous gavage of adenine to prepare a uremia-induced sciatic nerve injury model. The model was given either Echinacoside or α-Klotho by gavage. Histopathological changes of kidney and sciatic nerve were detected by H&E staining. The changes of creatinine, urea nitrogen, and urine protein were detected by biochemical detection. The changes of IL-1β and IL-18 were detected by ELISA. Nerve activity-related indicators were detected by biochemical detection. Changes in related mRNA and protein expression were detected by qPCR and western blot.

RESULTS

Creatinine, urea nitrogen, urine protein, and malondialdehyde (MDA) in the model group were significantly increased and inhibited by Echinacoside and α-Klotho treatment with Echinacoside dose-dependence. Meanwhile, the activities of ATP concentration, potassium adenosine triphosphate (Na+, K+ ATPase), succinate dehydrogenase (SDH), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) showed opposite trends.

CONCLUSIONS

Echinacoside can significantly relieve uremia-induced sciatic nerve injury in rats. Its specific molecular mechanism is related to the inhibition of the classical cellular pyroptosis pathway, which is likely achieved by promoting α-Klotho expression.

Centrally circulating α-klotho inversely correlates with human obesity and modulates arcuate cell populations in mice

Objective

Our laboratory recently identified the centrally circulating α-klotho protein as a novel hypothalamic regulator of food intake and glucose metabolism in mice. The current study aimed to investigate novel molecular effectors of central α-klotho in the arcuate nucleus of the hypothalamus (ARC), while further deciphering its role regulating energy balance in both humans and mice.

Methods

Cerebrospinal fluid (CSF) was collected from 22 adults undergoing lower limb orthopedic surgeries, and correlations between body weight and α-klotho were determined using an α-klotho enzyme-linked immunosorbent assay (ELISA) kit. To investigate the effects of α-klotho on energy expenditure (EE), 2-day intracerebroventricular (ICV) treatment was performed in diet-induced obesity (DIO) mice housed in TSE Phenomaster indirect calorimetry metabolic cages. Immunohistochemical staining for cFOS and patch clamp electrophysiology were used to determine the effects of central α-klotho on proopiomelanocortin (POMC) and tyrosine hydroxylase (TH) neurons. Additional stainings were performed to determine novel roles for central α-klotho to regulate non-neuronal cell populations in the ARC. Lastly, ICV pretreatment with fibroblast growth factor receptor (FGFR) or PI3kinase inhibitors was performed to determine the intracellular signaling involved in α-klotho-mediated regulation of ARC nuclei.

Results

Obese/overweight human subjects had significantly lower CSF α-klotho concentrations compared to lean counterparts (1,044 ± 251 vs. 1616 ± 218 pmol/L, respectively). Additionally, 2 days of ICV α-klotho treatment increased EE in DIO mice. α-Klotho had no effects on TH neuron activity but elicited varied responses in POMC neurons, with 44% experiencing excitatory and 56% experiencing inhibitory effects. Inhibitor experiments identified an α-klotho→FGFR→PI3kinase signaling mechanism in the regulation of ARC POMC and NPY/AgRP neurons. Acute ICV α-klotho treatment also increased phosphorylated ERK in ARC astrocytes via FGFR signaling.

Conclusion

Our human CSF data provide the first evidence that impaired central α-klotho function may be involved in the pathophysiology of obesity. Furthermore, results in mouse models identify ARC POMC neurons and astrocytes as novel molecular effectors of central α-klotho. Overall, the current study highlights prominent roles of α-klotho→FGFR→PI3kinase signaling in the homeostatic regulation of ARC neurons and whole-body energy balance.

•

Human CSF α-klotho concentrations exhibit a strong, inverse correlation with body weight and BMI.

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ICV α-klotho treatment increases energy expenditure in DIO mice.

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α-Klotho.→FGFR→PI3kinase signaling modulates ARC NPY/AgRP and POMC neurons.

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α-Klotho.→FGFR→ERK signaling regulates ARC astrocytes.

Biomarkers of Bone Turnover Identify Subsets of Chronic Kidney Disease Patients at Higher Risk for Fracture

BACKGROUND

We sought to identify biomarkers that indicate low turnover on bone histomorphometry in chronic kidney disease (CKD) patients, and subsequently determined whether this panel identified differential risk for fractures in community-dwelling older adults.

METHODS

Among CKD patients who underwent iliac crest bone biopsies and histomorphometry, we evaluated candidate biomarkers to differentiate low turnover from other bone disease. We applied this biomarker panel to 641 participants in the Health Aging and Body Composition Study (Health ABC) study with estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m2 who were followed for fracture. Cox proportional hazards models evaluated the association of bone mineral density (BMD) with fracture risk and determined whether biomarker-defined low bone turnover modified fracture risk at any level of BMD.

RESULTS

In 39 CKD patients age 64 ± 13 years, 85% female, with mean eGFR 37 ± 14 mL/min/1.73 m2 who underwent bone biopsy, lower fibroblast growth factor (FGF)-23, higher ɑ-Klotho, and lower parathyroid hormone (PTH) indicated low bone turnover in accordance with bone histomorphometry parameters (individual area under the curve = 0.62, 0.73, and 0.55 respectively; sensitivity = 22%, specificity = 100%). In Health ABC, 641 participants with CKD were age 75 ± 3 years , 49% female, with mean eGFR 48 ± 10 mL/min/1.73 m2. For every SD lower hip BMD at baseline, there was an 8-fold higher fracture risk in individuals with biomarker-defined low turnover (hazard ratio 8.10 [95% CI, 3.40-19.30]) vs a 2-fold higher risk in the remaining individuals (hazard ratio 2.28 [95% CI, 1.69-3.08]) (Pinteraction = .082).

CONCLUSIONS

In CKD patients who underwent bone biopsy, lower FGF-23, higher ɑ-Klotho, and lower PTH together had high specificity for identifying low bone turnover. When applied to older individuals with CKD, BMD was more strongly associated with fracture risk in those with biomarker-defined low turnover.

Serum Klotho in Living Kidney Donors and Kidney Transplant Recipients: A Meta-Analysis

α-Klotho is a known anti-aging protein that exerts diverse physiological effects, including phosphate homeostasis. Klotho expression occurs predominantly in the kidney and is significantly decreased in patients with chronic kidney disease. However, changes in serum klotho levels and impacts of klotho on outcomes among kidney transplant (KTx) recipients and kidney donors remain unclear. A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through October 2019 to identify studies evaluating serum klotho levels and impacts of klotho on outcomes among KTx recipients and kidney donors. Study results were pooled and analyzed utilizing a random-effects model. Ten cohort studies with a total of 431 KTx recipients and 5 cohort studies with a total of 108 living kidney donors and were identified. After KTx, recipients had a significant increase in serum klotho levels (at 4 to 13 months post-KTx) with a mean difference (MD) of 243.11 pg/mL (three studies; 95% CI 67.41 to 418.81 pg/mL). Although KTx recipients had a lower serum klotho level with a MD of = -234.50 pg/mL (five studies; 95% CI -444.84 to -24.16 pg/mL) compared to healthy unmatched volunteers, one study demonstrated comparable klotho levels between KTx recipients and eGFR-matched controls. Among kidney donors, there was a significant decrease in serum klotho levels post-nephrectomy (day 3 to day 5) with a mean difference (MD) of -232.24 pg/mL (three studies; 95% CI -299.41 to -165.07 pg/mL). At one year following kidney donation, serum klotho levels remained lower than baseline before nephrectomy with a MD of = -110.80 pg/mL (two studies; 95% CI 166.35 to 55.24 pg/mL). Compared to healthy volunteers, living kidney donors had lower serum klotho levels with a MD of = -92.41 pg/mL (two studies; 95% CI -180.53 to -4.29 pg/mL). There is a significant reduction in serum klotho levels after living kidney donation and an increase in serum klotho levels after KTx. Future prospective studies are needed to assess the impact of changes in klotho on clinical outcomes in KTx recipients and living kidney donors.

A Land of Controversy: Fibroblast Growth Factor-23 and Uremic Cardiac Hypertrophy

Cardiac hypertrophy is a common feature in patients with CKD. Recent studies revealed that two phosphate regulators, fibroblast growth factor-23 and α-Klotho, are highly involved in the pathophysiologic process of CKD-induced cardiac hypertrophy. With decreasing renal function, elevated fibroblast growth factor-23 and decreased α-Klotho may contribute to cardiac hypertrophy by targeting the heart directly or by inducing systemic changes, such as vascular injury, hemodynamic disorders, and inflammation. However, several studies have demonstrated that disturbances in the fibroblast growth factor-23/α-Klotho axis do not lead to cardiac hypertrophy. In this review, we describe the cardiac effects of the fibroblast growth factor-23/α-Klotho axis and summarize recent progress in this field. In addition, we present not only the main controversies in this field but also provide possible directions to resolve these disputes.

Low magnesium diet aggravates phosphate-induced kidney injury

BACKGROUND

Magnesium is known to protect against phosphate-induced tubular cell injuries in vitro. We investigated in vivo effects of magnesium on kidney injuries and phosphate metabolism in mice exposed to a high phosphate diet.

METHODS

Heminephrectomized mice were maintained on a high phosphate/normal magnesium diet or a high phosphate/low magnesium diet for 6 weeks. We compared renal histology, phosphaturic hormones and renal α-Klotho expression between the two diet groups.

RESULTS

High phosphate diet-induced tubular injuries and interstitial fibrosis were remarkably aggravated by the low-magnesium diet. At 1 week after high phosphate feeding when serum creatinine levels were similar between the two groups, the low magnesium diet suppressed not only fecal phosphate excretion but also urinary phosphate excretion, resulting in increased serum phosphate levels. Parathyroid hormone (PTH) levels were not appropriately elevated in the low magnesium diet group despite lower 1,25-dihydroxyvitamin D and serum calcium levels compared with the normal magnesium diet group. Although fibroblast growth factor 23 (FGF23) levels were lower in the low magnesium diet group, calcitriol-induced upregulation of FGF23 could not restore the impaired urinary phosphate excretion. The low magnesium diet markedly downregulated α-Klotho expression in the kidney. This downregulation of α-Klotho occurred even when mice were fed the low phosphate diet.

CONCLUSIONS

A low magnesium diet aggravated high phosphate diet-induced kidney injuries. Impaired PTH secretion and downregulation of renal α-Klotho were likely to be involved in the blunted urinary phosphate excretion by the low magnesium diet. Increasing dietary magnesium may be useful to attenuate phosphate-induced kidney injury.

Positive correlation of serum fibroblast growth factor 23 with peripheral arterial stiffness in kidney transplantation patients

BACKGROUND

Fibroblast growth factor 23 (FGF-23) has a role in arterial stiffness (AS) apart from regulating mineral metabolism. We investigated the association between FGF-23 concentration and peripheral AS in renal transplantation (RT) recipients.

METHODS

The fasting blood samples of RT recipients (n = 66) were collected and analyzed.

RESULTS

A total of 29 (43.9%) RT recipients were classified under the peripheral AS group. The RT recipients in this group had a higher prevalence of diabetes (P < 0.001), hypertension (P = 0.001), and metabolic syndrome (P = 0.023); longer post-RT duration (P = 0.006); higher systolic blood pressure (P < 0.001) and diastolic blood pressure (P = 0.024); and higher fasting glucose (P = 0.002), total cholesterol (P = 0.049), blood urea nitrogen (P = 0.027), phosphorus (P = 0.047), and FGF-23 concentrations (P = 0.003) and FGF-23/α-klotho ratio (P < 0.001) but lower klotho concentrations (P = 0.025) than those in the control group. Moreover, FGF-23 concentration (adjusted odds ratio: 1.057, 95% confidence interval: 1.011-1.105, P = 0.015) was found to be an independent predictor of peripheral AS in RT recipients.

CONCLUSIONS

Serum FGF-23 concentration was a significant predictor of peripheral AS in RT recipients.

Protective potential of klotho protein on diabetic retinopathy: Evidence from clinical and in vitro studies

AIMS/INTRODUCTION

The purpose of the present study was to observe the relationship between serum α-klotho (KL) protein level and diabetic retinopathy (DR), and to further examine the effects of KL protein on apoptosis induced by palmitic acid (PA) in human retinal endothelial cells.

MATERIALS AND METHODS

A total of 17 healthy people and 60 type 2 diabetes patients were included. According to the results from fundus fluorescein angiography, the diabetes patients were divided into three subgroups: without DR, non-proliferative DR and proliferative DR. Serum KL level was measured by enzyme-linked immunosorbent assay. In vitro, human retinal endothelial cells were exposed to PA with or without KL protein. Apoptosis rates were analyzed by flow cytometry analysis. Apoptotic-related protein expressions were detected by western blotting analysis.

RESULTS

Serum KL level was lower in diabetes patients than that in healthy participants (P = 0.007), and was gradually decreased among the without DR, non-proliferative DR and proliferative DR subgroups (P = 0.045). A logistic regression analysis showed that after adjusting for the other confounding factors, serum KL level was independently and negatively related with DR (P = 0.049). Furthermore, the increased apoptosis rates induced by PA were inhibited with the addition of KL protein. Consistently, KL protein reversed the expression levels of the increased pro-apoptotic protein Bax and the decreased anti-apoptotic protein Bcl-2 induced by PA. However, the anti-apoptotic effect of KL protein was attenuated by LY294002 through the phosphatidylinositol 3 kinase-serine∕threonine kinase pathway.

CONCLUSIONS

The data suggested that KL protein was probably a potential protective factor against retinopathy in type 2 diabetes patients.

miR-15b induces premature ovarian failure in mice via inhibition of α-Klotho expression in ovarian granulosa cells

A thorough understanding of epigenetics regulatory mechanisms of premature ovarian failure (POF) is still lacking. Here, we found that cyclophosphamide induced significantly decrease in α-Klotho (Kl) expression in mouse ovarian granulosa cells (mOGCs), suggesting that cyclophosphamide inhibited Kl expression. Cyclophosphamide also significantly accelerated ageing and led to a decline in the pregnancy rate of C. elegans. We subsequently noted that the pathological condition exhibited by Kl^-/- mice was similar to that observed in cyclophosphamide-induced POF mice. Furthermore, the mOGCs in both types of mice showed significant signs of oxidative stress damage, including decreased SOD and ATP, increased ROS levels. Detailed analyses revealed that the decreased Kl expression led to the reduced expression of autophagy-related proteins in mOGCs, which resulted in decreased autophagy activity. Finally, we found that cyclophosphamide attenuated the autophagy function of mOGCs via upregulating microRNA-15b expression, which silenced the endogenous Kl mRNA expression and stimulated the activity of the downstream TGFβ1/Smad pathway. Therefore, we demonstrated that Kl was one of the key inhibitory factors in the development of POF. It elucidated the underlying epigenetic regulatory mechanism, whereby cyclophosphamide-dependent microRNA-15b inhibited Kl expression, leading to the reduced ability of mOGCs to induce autophagy and ROS scavenging, ultimately causing POF.

Implication of alpha-Klotho as the predictive factor of stress

Stress is known as a risk factor for both mental and physical health problems. While stress is known as one of the major health problems in modern society, a biomarker of stress has not yet been well established. In the present study, we focused on the serum levels of α-Klotho (αKl) as a possible objective biomarker of stress. Subjects included apparently healthy individuals who underwent a health examination in the Osaka University Health and Counseling Center. Physical and biochemical parameters were obtained from all subjects. Information regarding the lifestyle of each individual was obtained via questionnaires. Among male subjects, serum levels of soluble αKl (sαKl) were significantly elevated in subjects who had poor stress management and unsatisfactory sleep, suggesting that stress management and sleeping conditions influenced the serum levels of sαKl. The total Kessler Screening Scale for Psychological Distress (K6) score was significantly increased in subjects who reported experiencing considerable stress, had poor stress management and unsatisfactory sleep. Since serum levels of sαKl showed the same tendency as the K6 score in terms of the relationship between stress management and sleeping conditions in male subjects, increased sαKl levels could be associated with considerable psychological stress in healthy men.

Regulation of α-Klotho Expression by Dietary Phosphate During Growth Periods

Inorganic phosphate (Pi) is an essential nutrient for maintaining various biological functions, particularly during growth periods. Excess intake of dietary Pi increases the secretion of fibroblast growth factor 23 (FGF23) and parathyroid hormone to maintain plasma Pi levels. FGF23 is a potent phosphaturic factor that binds to the α-klotho/FGFR complex in the kidney to promote excretion of Pi into the urine. In addition, excess intake of dietary Pi decreases renal α-klotho expression. Down-regulation or lack of α-klotho induces a premature aging-like phenotype, resulting from hyperphosphatemia, and leading to conditions such as ectopic calcification and osteoporosis. However, it remains unclear what effects dietary Pi has on α-klotho expression at different life stages, especially during growth periods. To investigate this, we used C57BL/6J mice in two life stages during growing period. Weaned (3 weeks old) and periadolescent (7 weeks old) were randomly divided into seven experimental groups and fed with 0.02, 0.3, 0.6, 0.9, 1.2, 1.5, or 1.8% Pi diets for 7 days. As a result, elevated plasma Pi and FGF23 levels and decreased renal α-klotho expression were observed in weaned mice fed with a high Pi diet. In addition, a high Pi diet clearly induced renal calcification in the weaned mice. However, in the periadolescent group, renal calcification was not observed, even in the 1.8% Pi diet group. The present study indicates that a high Pi diet in weaned mice has much greater adverse effects on renal α-klotho expression and pathogenesis of renal calcification compared with periadolescent mice.

Expression of α-Klotho protein in human thyroid cancers - an immunohistochemical study

INTRODUCTION

The α-Klotho protein was discovered as a gene controlling the process of aging, but further studies indicated that it also plays the role of a tumour suppressor. Although numerous studies were performed on the role of the α-Klotho gene and protein in neoplasia, the data on α-Klotho protein expression in thyroid cancers are very scarce. Our study presents the immunohistochemical investigation of α-Klotho expression in benign and malignant thyroid tumours.

MATERIAL AND METHODS

The material included samples of benign (nodular hyperplasia, follicular adenoma), differentiated (follicular and papillary) cancers and aggressive thyroid cancers of low differentiation grade. The samples were immunostained using two different monoclonal anti-α-Klotho antibodies.

RESULTS

From the two antibodies used in this study, one (EPR6856) reacted probably with the soluble form of Klotho and immunostained mostly the colloid filling thyroid follicles and intravascular or extravascular serum deposits. The other (A-9 antibody) immunostained the follicular epithelium in benign thyroid lesions as well as the epithelial tumoural cells in differentiated thyroid (follicular and papillary cancers). In the thyroid cancers of high malignancy, the immunostaining with A-9 anti-α-Klotho antibody was (except in one case) negative or very weak.

CONCLUSION

Our results indicate that lowered expression of a- Klotho is involved in the process of thyroid neoplasia.

Fibroblast Growth Factor 23 to Alpha-Klotho Index Correlates with Systemic Sclerosis Activity: A Proposal for Novel Disease Activity Marker

Systemic sclerosis, a connective tissue disease, is characterized by thickening of the skin, massive fibrosis of internal organs, vasculopathy, and immune system functioning aberration. Recently, vitamin D (VD) deficit, seen almost universally in patients with systemic sclerosis (SSc), has gained much attention. VD metabolism is precisely orchestrated at the level of the kidney by regulators: parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) and their receptors with a FGF23 co-receptor—α-Klotho. The aim of this study was to assess the levels of VD, α-Klotho, FGF23 in SSc patients and to find the relationship between those parameters and disease activity. We enrolled 48 SSc patients with a diffuse variant of SSc and 23 sex- and age-matched healthy volunteers that served as the control group (CG). Patients were characterized by lower level of VD in comparison to CG (19.8 (12.6–28.9) vs. 24.5 (21.3–31.5) ng/mL; p < 0.01), significantly reduced levels of iFGF23 (19.3 (12.1–30.5) vs. 73.9 (59.7–110.2) pg/mL p < 0.001), and similar α-Klotho concentrations (1415 ± 557 vs. 1526 ± 397 pg/mL), respective. None of these parameters correlated with the extent of skin involvement (modified Rodnan Skin Score) and disease activity according to Eustar 2017 guidelines. The FGF23/α-Klotho index was significantly reduced in SSc patients (0.013 (0.0081–0.025) vs. 0.055 (0.038–0.095); p < 0.001), and its log₁₀ correlated (r = 0.35; p < 0.001) with disease activity score (Eular2017). Our data showed that the FGF23/α-Klotho index may be considered as a novel, potential marker of systemic sclerosis activity.