Association of Klotho polymorphisms with healthy aging: a systematic review and meta-analysis

Comparing Western and traditional Chinese medicine for male sexual dysfunction: can Klotho represent a silk road?

Traditional Chinese medicine (TCM) and Western Medicine both have shown efficacy in treating male sexual dysfunction (MSD). The aim of this perspective paper is to discuss a possible link between Western medicine and TCM in the MSD field as represented by the entity of Klotho. Klotho is a recently discovered protein, mainly expressed in the kidney, encoded by the anti-aging gene klotho. Not only is Klotho significantly correlated with the development and progression of kidney diseases and their complications, but increasing evidence indicates that it is also closely related to MSD. A comprehensive search within PubMed database was performed to retrieve available evidence on Klotho's roles, particularly in kidney and in MSD. Indeed, in the TCM theory, the concept of the "kidney" is entirely different from the Western medicine: it is closely related to metabolism and to the reproductive, nervous, endocrine systems, being more than just a urinary organ. According to the "Kidney storing essence (jīng) and governing reproduction" (KSEGR) theory, a cornerstone in TCM, the treatment of MSD mainly consists of restoring the kidney's function. Signs of decreasing kidney essence show a consistent similarity to deficiencies of Klotho, also for what regards the male sexual function. Based on the current evidence, Klotho may represent a potential biological indicator for sexual desire and sexual function and a kind of new scientific Silk Road between TCM and Western medicine for MSD; nevertheless, there is a need to conduct further high-quality research to prove this hypothesis.

KLOTHO KL-VS heterozygosity is associated with diminished age-related neuroinflammation, neurodegeneration, and synaptic dysfunction in older cognitively unimpaired adults

INTRODUCTION

We examined whether the aging suppressor KLOTHO gene's functionally advantageous KL-VS variant (KL-VS heterozygosity [KL-VSHET]) confers resilience against deleterious effects of aging indexed by cerebrospinal fluid (CSF) biomarkers of neuroinflammation (interleukin-6 [IL-6], S100 calcium-binding protein B [S100B], triggering receptor expressed on myeloid cells [sTREM2], chitinase-3-like protein 1 [YKL-40], glial fibrillary acidic protein [GFAP]), neurodegeneration (total α-synuclein [α-Syn], neurofilament light chain protein), and synaptic dysfunction (neurogranin [Ng]).

METHODS

This Alzheimer disease risk-enriched cohort consisted of 454 cognitively unimpaired adults (Mage = 61.5 ± 7.75). Covariate-adjusted multivariate regression examined relationships between age (mean-split[age ≥ 62]) and CSF biomarkers (Roche/NeuroToolKit), and whether they differed between KL-VSHET (N = 122) and non-carriers (KL-VSNC; N = 332).

RESULTS

Older age was associated with a poorer biomarker profile across all analytes (Ps ≤ 0.03). In age-stratified analyses, KL-VSNC exhibited this same pattern (Ps ≤ 0.05) which was not significant for IL-6, S100B, Ng, and α-Syn (Ps ≥ 0.13) in KL-VSHET. Although age-related differences in GFAP, sTREM2, and YKL-40 were evident for both groups (Ps ≤ 0.01), the effect magnitude was markedly stronger for KL-VSNC.

DISCUSSION

Higher levels of neuroinflammation, neurodegeneration, and synaptic dysfunction in older adults were attenuated in KL-VSHET.

HIGHLIGHTS

Older age was associated with poorer profiles across all cerebrospinal fluid biomarkers of neuroinflammation, neurodegeneration, and synaptic dysfunction. KLOTHO KL-VS non-carriers exhibit this same pattern, which is does not significantly differ between younger and older KL-VS heterozygotes for interleukin-6, S100 calcium-binding protein B, neurogranin, and total α-synuclein. Although age-related differences in glial fibrillary acidic protein, triggering receptor expressed on myeloid cells, and chitinase-3-like protein 1 are evident for both KL-VS groups, the magnitude of the effect is markedly stronger for KL-VS non-carriers. Higher levels of neuroinflammation, neurodegeneration, and synaptic dysfunction in older adults are attenuated in KL-VS heterozygotes.

Association of Klotho with Neuropsychiatric Disorder: A Meta-Analysis

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

Association of KLOTHO gene variants with metabolic and renal function parameters in Mexican patients living with type 2 diabetes

Objective

Type 2 diabetes (T2D) and high blood pressure are the main causes of chronic kidney disease (CKD) in adulthood. Both metabolic and oxidative stresses driven by hyperglycemia as well as genetic factors have been suggested as pathogenic causes of renal failure. Some single nucleotide variants (SNVs) on gene coding KLOTHO (KL) have been implicated in several clinical scenarios including hypertension, diabetes, and cardiovascular disease. The aim of this study was to analyze the association of rs1207568 (-395G > A), rs953614 (+ 1062T > G) and rs564481 (+ 1818 C > T) SNVs with metabolic and renal function parameters in Mexican patients living with type 2 diabetes.

Methods

A cross-sectional study was conducted in 637 Mexican patients with T2D, and/or hypertension without previous diagnosis of CKD. Anthropometric, metabolic, and renal function parameters were determined. Patients were genotyped for rs1207568, rs953614 and rs564481 SNVs and associations under a dominant genetic model were analyzed by logistic regression.

Results

For rs9536314, G-allele showed to be protective for hypo-HDL-C, albuminuria, and CKD. Carriers of minor allele of rs564481 had low odds for high glucose levels. No differences in genotype nor allele frequencies between the patients and the reference population were observed.

Conclusion

In Mexican patients living with type 2 diabetes, KL variant rs9536314 was found associated with low odds of hypo-HDL cholesterol, albuminuria and presence of CKD. Meanwhile the consensus of soluble KLOTHO measurement is reached, genetic variants in the KL gene could be considered as genetic markers for CKD susceptibility in patients at high-risk of vascular complications.

The relationship between klotho, testosterone, and sexual health parameters among US adult men

BACKGROUND

Klotho is a pleotropic hormone involved in a multitude of biological processes necessary for healthy aging, and affords protection from adverse events such as cardiovascular disease, inflammation, and various cancers. Emerging evidence suggests that klotho is also an important component of biochemical pathways that regulate hormone balance, which may include those pathways governing testosterone production and men's sexual health, though data are limited and results are mixed.

OBJECTIVE

Using a cohort of 767 men from the NHANES 2015-2016 survey cycle, we set out to quantify the association between serum klotho levels and serum testosterone levels, as well as clinical markers of men's sexual health (e.g., testosterone:estrogen ratio, bioavailable testosterone, and free testosterone).

METHODS

Multivariable linear and logistic regression models while controlling for potential confounders were constructed to quantify the relationship between serum klotho and testosterone, as well as between serum klotho and odds of low testosterone (serum testosterone < 300 ng/dL).

RESULTS

A positive association was observed between serum klotho and testosterone (β = 0.18, p = 0.04). Serum klotho levels were also stratified into quartiles, and we observed statistically significant increases in testosterone for increasing quartile level of klotho using the first quartile as the reference group (β = 90.51, p = 0.001, β = 106.93, p = 0.002, β = 95.33, p = 0.03 for quartiles 2, 3, and 4, respectively). The average testosterone values by quartiles of klotho were 306.9 ng/dL, 390 ng/dL, 409.3 ng/dL, and 436.6 ng/dL, respectively. We modeled important proxies for sexual health including bioavailable and free testosterone, the testosterone:estradiol ratio, and C-reactive protein. Men in the second quartile of klotho had a significantly lower odds of an abnormal testosterone:estradiol ratio compared to the first quartile [OR = 0.18, 95% CI = (0.03, 0.98)].We observed null associations between continuous serum klotho and odds of low testosterone [OR = 1.0, 95% CI = (1.0, 1.0)], and when stratified by quartile, we observed a significant decrease in the odds of low testosterone for individuals in the second quartile of klotho compared to the first quartile [OR = 0.21, 95% CI = (0.05, 0.91)]. In addition, C-reactive protein was inversely associated with testosterone in men (β = - 4.65, p = 0.001), and inversely associated with quartiles of klotho (β = - 2.28, p = 0.04, β = - 2.22, p = 0.04, β = - 2.28, p = 0.03, for quartiles 2, 3, and 4, respectively).

CONCLUSION

Our findings support previous studies suggesting a role for klotho in testosterone levels and sexual function among men. Future studies are warranted to corroborate these findings, determine clinical significance, and elucidate potential mechanisms underlying these associations.

Klotho: a potential therapeutic target in aging and neurodegeneration beyond chronic kidney disease-a comprehensive review from the ERA CKD-MBD working group

Klotho, a multifunctional protein, acts as a co-receptor in fibroblast growth factor 23 and exerts its impact through various molecular pathways, including Wnt, hypoxia-inducible factor and insulin-like growth factor 1 pathways. The physiological significance of Klotho is the regulation of vitamin D and phosphate metabolism as well as serving as a vital component in aging and neurodegeneration. The role of Klotho in aging and neurodegeneration in particular has gained considerable attention. In this narrative review we highlight several key insights into the molecular basis and physiological function of Klotho and synthesize current research on the role of Klotho in neurodegeneration and aging. Klotho deficiency was associated with cognitive impairment, reduced growth, diminished longevity and the development of age-related diseases in vivo. Serum Klotho levels showed a decline in individuals with advanced age and those affected by chronic kidney disease, establishing its potential diagnostic significance. Additionally, multiple medications have been demonstrated to influence Klotho levels. Therefore, this comprehensive review suggests that Klotho could open the door to novel interventions aimed at addressing the challenges of aging and neurodegenerative disorders.

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.

Rapamycin treatment increases survival, autophagy biomarkers and expression of the anti-aging klotho protein in elderly mice

Previous investigations have demonstrated that treatment of animals with rapamycin increases levels of autophagy, which is a process by which cells degrade intracellular detritus, thus suppressing the emergence of senescent cells, whose pro-inflammatory properties, are primary drivers of age-associated physical decline. A hypothesis is tested here that rapamycin treatment of mice approaching the end of their normal lifespan exhibits increased survival, enhanced expression of autophagic proteins; and klotho protein-a biomarker of aging that affects whole organism senescence, and systemic suppression of inflammatory mediator production. Test groups of 24-month-old C57BL mice were injected intraperitoneally with either 1.5 mg/kg/week rapamycin or vehicle. All mice administered rapamycin survived the 12-week course, whereas 43% of the controls died. Relative to controls, rapamycin-treated mice experienced minor but significant weight loss; moreover, nonsignificant trends toward decreased levels of leptin, IL-6, IL-1β, TNF-α, IL-1α, and IGF-1, along with slight elevations in VEGF, MCP-1 were observed in the blood serum of rapamycin-treated mice. Rapamycin-treated mice exhibited significantly enhanced autophagy and elevated expression of klotho protein, particularly in the kidney. Rapamycin treatment also increased cardiomyocyte Ca²⁺ -sensitivity and enhanced the rate constant of force re-development, which may also contribute to the enhanced survival rate in elderly mice.

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

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

Interaction between KLOTHO-VS Heterozygosity and APOE ε4 Allele Predicts Rate of Cognitive Decline in Late-Onset Alzheimer's Disease

KLOTHO-VS heterozygosity (KL-VShet+) promotes longevity and protects against cognitive decline in aging. To determine whether KL-VShet+ mitigates Alzheimer's disease (AD) progression, we used longitudinal linear-mixed models to compare the rate of change in multiple cognitive measures in AD patients stratified by APOE ε4 carrier status. We aggregated data on 665 participants (208 KL-VShet-/ε4-, 307 KL-VShet-/ε4+, 66 KL-VShet+/ε4-, and 84 KL-VShet+/ε4+) from two prospective cohorts, the National Alzheimer's Coordinating Center and the Alzheimer's Disease Neuroimaging Initiative. All participants were initially diagnosed with mild cognitive impairment, later developed AD dementia during the study, and had at least three subsequent visits. KL-VShet+ conferred slower cognitive decline in ε4 non-carriers (+0.287 MMSE points/year, p = 0.001; -0.104 CDR-SB points/year, p = 0.026; -0.042 ADCOMS points/year, p < 0.001) but not in ε4 carriers who generally had faster rates of decline than non-carriers. Stratified analyses showed that the protective effect of KL-VShet+ was particularly prominent in male participants, those who were older than the median baseline age of 76 years, or those who had an education level of at least 16 years. For the first time, our study provides evidence that KL-VShet+ status has a protective effect on AD progression and interacts with the ε4 allele.

High polygenic risk score for exceptional longevity is associated with a healthy metabolic profile

Healthy metabolic measures in humans are associated with longevity. Dysregulation leads to metabolic syndrome (MetS) and negative health outcomes. Recent exceptional longevity (EL) genome wide association studies have facilitated estimation of an individual's polygenic risk score (PRS) for EL. We tested the hypothesis that individuals with high ELPRS have a low prevalence of MetS. Participants were from five cohorts of middle-aged to older adults. The primary analyses were performed in the UK Biobank (UKBB) (n = 407,800, 40-69 years). Replication analyses were undertaken using three Australian studies: Hunter Community Study (n = 2122, 55-85 years), Older Australian Twins Study (n = 539, 65-90 years) and Sydney Memory and Ageing Study (n = 925, 70-90 years), as well as the Swedish Gothenburg H70 Birth Cohort Studies (n = 2273, 70-93 years). MetS was defined using established criteria. Regressions and meta-analyses were performed with the ELPRS and MetS and its components. Generally, MetS prevalence (22-30%) was higher in the older cohorts. In the UKBB, high EL polygenic risk was associated with lower MetS prevalence (OR = 0.94, p = 1.84 × 10^-42) and its components (p < 2.30 × 10^-8). Meta-analyses of the replication cohorts showed nominal associations with MetS (p = 0.028) and 3 MetS components (p < 0.05). This work suggests individuals with a high polygenic risk for EL have a healthy metabolic profile promoting longevity.

AD-associated CSF biomolecular changes are attenuated in KL-VS heterozygotes

Introduction

Dementia as an inevitable aging consequence has been challenged and underscores the need for investigations of the factors that confer resilience. We examine whether the functionally advantageous KL-VS variant of the putative aging suppressor KLOTHO gene attenuates age-related cognitive decline and deleterious biomolecular changes.

Methods

Trajectories of change in memory and executive function (N = 360; 2-12 visits) and cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarkers-amyloid beta (Aβ)42, total tau (t-tau), phosphorylated tau (p-tau) (N = 112; 2-4 samplings)-were compared between KL-VS non-carriers and heterozygotes in middle-aged and older adults from the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center studies.

Results

Memory and executive function declined (p's≤ 0.001) and CSF t-tau, p-tau, t-tau/Aβ42, and p-tau/Aβ42 levels increased (all p's≤ 0.004) with age. The rate of p-tau accumulation was attenuated for KL-VS heterozygotes (p = 0.03).

Discussion

KL-VS heterozygosity may confer resilience to AD-associated biomolecular changes.

Effects of physical distancing by COVID-19 pandemic on diet quality, neurological and immunological markers, and fecal microbiota of Brazilian older women

Physical distancing was used to prevent transmission of COVID-19, however there are concerns that this may promote harmful impacts on health, such as reduced levels of physical practice and changes in food intake and gut microbiota composition. This study evaluated the impacts of 6 months physical distancing on Brazilian older women upon body mass index (BMI), strength, physical activity level (IPAQ), eating habits, neurological markers (brain-derived neurotrophic factor-BDNF and cortisol), cytokines (IL-2, IL-5, IL-6, IL-10, interferon-IFN-γ, tumor necrosis factor-TNF-α), aging-associated markers (vascular endothelial growth factor-VEGF, insulin-like growth factor-IGF-1, klotho and thymic stromal lymphopoietin-TSLP), besides specific groups of fecal microbiota. Fifteen women, over 60 years old, residents of São Paulo state (Brazil), were evaluated in March and in September 2020. The older adult women, with a mean age 66 ± 6.2 years presented significantly increased BMI and high effect size for non-protective foods consumption, reduced light physical activity and strength 6 months following the physical distancing. Furthermore, the serum concentration of IFN-γ, IGF-1, and IFN-γ/IL-5 were significantly higher, while lower concentration of IL-2 and IL-5 were observed 6 months after the physical distancing. Significant increase was noted only to Blautia spp. abundance after 6 months of physical distancing. Several correlations were observed at both before and after physical distancing, however, interestingly, many of them were lost or inverted 6 months following, while new ones emerged. Taken together, these results showed that lifestyle changes and stress conditions addressed by physical distancing from the COVID-19 pandemic impacted the health of older women included in the present study. Therefore, future follow-up studies are essential to propose interventions in order to restore the health conditions observed before the pandemic period, and thus to maintain the quality of life of older adults in different socioeconomic contexts.

The role of oxidative stress in ovarian aging: a review

Ovarian aging refers to the process by which ovarian function declines until eventual failure. The pathogenesis of ovarian aging is complex and diverse; oxidative stress (OS) is considered to be a key factor. This review focuses on the fact that OS status accelerates the ovarian aging process by promoting apoptosis, inflammation, mitochondrial damage, telomere shortening and biomacromolecular damage. Current evidence suggests that aging, smoking, high-sugar diets, pressure, superovulation, chemotherapeutic agents and industrial pollutants can be factors that accelerate ovarian aging by exacerbating OS status. In addition, we review the role of nuclear factor E2-related factor 2 (Nrf2), Sirtuin (Sirt), mitogen-activated protein kinase (MAPK), protein kinase B (AKT), Forkhead box O (FoxO) and Klotho signaling pathways during the process of ovarian aging. We also explore the role of antioxidant therapies such as melatonin, vitamins, stem cell therapies, antioxidant monomers and Traditional Chinese Medicine (TCM), and investigate the roles of these supplements with respect to the reduction of OS and the improvement of ovarian function. This review provides a rationale for antioxidant therapy to improve ovarian aging.

Genes and Longevity of Lifespan

Aging is a complex process indicated by low energy levels, declined physiological activity, stress induced loss of homeostasis leading to the risk of diseases and mortality. Recent developments in medical sciences and an increased availability of nutritional requirements has significantly increased the average human lifespan worldwide. Several environmental and physiological factors contribute to the aging process. However, about 40% human life expectancy is inherited among generations, many lifespan associated genes, genetic mechanisms and pathways have been demonstrated during last decades. In the present review, we have evaluated many human genes and their non-human orthologs established for their role in the regulation of lifespan. The study has included more than fifty genes reported in the literature for their contributions to the longevity of life. Intact genomic DNA is essential for the life activities at the level of cell, tissue, and organ. Nucleic acids are vulnerable to oxidative stress, chemotherapies, and exposure to radiations. Efficient DNA repair mechanisms are essential for the maintenance of genomic integrity, damaged DNA is not replicated and transferred to next generations rather the presence of deleterious DNA initiates signaling cascades leading to the cell cycle arrest or apoptosis. DNA modifications, DNA methylation, histone methylation, histone acetylation and DNA damage can eventually lead towards apoptosis. The importance of calorie restriction therapy in the extension of lifespan has also been discussed. The role of pathways involved in the regulation of lifespan such as DAF-16/FOXO (forkhead box protein O1), TOR and JNK pathways has also been particularized. The study provides an updated account of genetic factors associated with the extended lifespan and their interactive contributory role with cellular pathways.

Taste receptor polymorphisms and longevity: a systematic review and meta-analysis

Bitter taste receptors (TAS2R) are involved in a variety of non-tasting physiological processes, including immune-inflammatory ones. Therefore, their genetic variations might influence various traits. In particular, in different populations of South Italy (Calabria, Cilento, and Sardinia), polymorphisms of TAS2R16 and TAS238 have been analysed in association with longevity with inconsistent results. A meta-analytic approach to quantitatively synthesize the possible effect of the previous variants and, possibly, to reconcile the inconsistencies has been used in the present paper. TAS2R38 variants in the Cilento population were also analysed for their possible association with longevity and the obtained data have been included in the relative meta-analysis. In population from Cilento no association was found between TAS2R38 and longevity, and no association was observed as well, performing the meta-analysis with data of the other studies. Concerning TAS2R16 gene, instead, the genotype associated with longevity in the Calabria population maintained its significance in the meta-analysis with data from Cilento population, that, alone, were not significant in the previously published study. In conclusion, our results suggest that TAS2R16 genotype variant is associated with longevity in South Italy.

Klotho overexpression suppresses apoptosis by regulating the Hsp70/Akt/Bad pathway in H9c2(2-1) cells

Early reperfusion is the most effective and important treatment for acute myocardial infarction. However, reperfusion therapy often leads to a certain degree of myocardial damage. The aim of the present study was to identify the role of klotho, and the molecular mechanism underlying its effects, in myocardial damage using a model of myocardial hypoxia injury. Hypoxia/reoxygenation (H/R) was used to mimic ischemia/reperfusion (I/R) injury in vitro. The expression and distribution of klotho in H9c2(2-1) cells was observed by fluorogenic scanning, and the apoptotic rate was determined by Annexin V-FITC/propidium iodide dual staining. Cell viability was determined by MTT assay, and caspase-3, cleaved caspase-3, Bcl-2, Bax, heat shock protein (Hsp) 70 and Akt levels were assessed by western blotting. A lactate dehydrogenase test was performed to determine the degree of H9c2(2-1) cell damage. The results revealed that klotho was primarily located in the cytoplasm of H9c2(2-1) cells. Klotho overexpression markedly suppressed H/R-induced H9c2(2-1) cell apoptosis. Furthermore, cell viability increased, and injury decreased in response to klotho. Klotho also suppressed the activation of caspase-3, upregulated Bcl2 and decreased Bax levels following H/R injury, as well as alleviating H/R injury by upregulating the expression of Hsp70 and increasing the levels of phosphorylated (p-)Akt and Bad. In conclusion, these results indicate that klotho suppressed H/R-induced H9c2(2-1) cell apoptosis by regulating the levels of Hsp70, p-Akt and p-Bad, which suggest that klotho could be a novel agent for the treatment of coronary disease.

Age-Related Tau Burden and Cognitive Deficits Are Attenuated in KLOTHO KL-VS Heterozygotes

BACKGROUND

Identification of new genetic variants that modify Alzheimer's disease (AD) risk will elucidate novel targets for curbing the disease progression or delaying symptom onset.

OBJECTIVE

To examine whether the functionally advantageous KLOTHO gene KL-VS variant attenuates age-related alteration in cerebrospinal fluid (CSF) biomarkers or cognitive function in middle-aged and older adults enriched for AD risk.

METHODS

Sample included non-demented adults (N = 225, mean age = 63±8, 68% women) from the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center who were genotyped for KL-VS, underwent CSF sampling and had neuropsychological testing data available proximal to CSF draw. Covariate-adjusted multivariate regression examined relationships between age group (Younger versus Older; mean split at 63 years), AD biomarkers, and neuropsychological performance tapping memory and executive function, and whether these relationships differed between KL-VS non-carriers (KL-VSNC) and heterozygote (KL-VSHET).

RESULTS

In the pooled analyses, older age was associated with higher levels of total tau (tTau), phosphorylated tau (pTau), and their respective ratios to amyloid-β (Aβ)42 (ps ≤ 0.002), and with poorer performance on neuropsychological tests (ps ≤ 0.001). In the stratified analyses, KL-VSNC exhibited this age-related pattern of associations with CSF biomarkers (all ps ≤ 0.001), and memory and executive function (ps ≤ 0.003), which were attenuated in KL-VSHET (ps ≥ 0.14).

CONCLUSION

Worse memory and executive function, and higher tau burden with age were attenuated in carriers of a functionally advantageous KLOTHO variant. KL-VS heterozygosity seems to be protective against age-related cognitive and biomolecular alterations that confer risk for AD.

A novel antibody for the detection of alternatively spliced secreted KLOTHO isoform in human plasma

αKlotho is primarily known to express as a transmembrane protein. Proteolytic cleavage results in shedding of the extracellular domain which enters systemic circulation. A truncated form of αKlotho resulting from alternative splicing of the αKLOTHO transcript exists and is believed to be secreted, thereby also entering systemic circulation. Existing ELISA methods fail to distinguish between the two circulating isoforms resulting in inconsistencies in assessing circulating αKlotho levels. We have exploited a unique 15aa peptide sequence present in the alternatively spliced secreted isoform to generate an antibody and show that it is able to specifically detect only the secreted Klotho isoform in human plasma. This finding will facilitate in distinguishing the levels of different circulating Klotho isoforms in health and disease and enhance their potential to serve as a biomarker for CKD and other conditions.

IGF-1 induces cellular senescence in rat articular chondrocytes via Akt pathway activation

Cellular senescence decreases cell proliferation over time and is characterized by typical markers, including larger cell volume, a flattened morphology, irreversible cell cycle arrest, augmentation of senescence-associated β-galactosidase (SA-β-gal) activity and senescence-associated secretory phenotype. A variety of factors are implicated in the process of cellular aging, which mediates an organisms' lifespan. Insulin-like growth factor-1 (IGF-1) serves an essential role in regulating cell growth, division, proliferation and senescence. In the present study, the role of IGF-1 and the downstream Akt signaling pathway in rat articular chondrocyte senescence was assessed. The results of the current study demonstrated that IGF-1 promoted cellular senescence in rat articular chondrocytes via activation of SA-β-gal and the upregulation of p53 and p21 mRNA and protein levels. IGF-1 enhanced Akt phosphorylation and treatment with Akt inhibitor, MK-2206, significantly suppressed the induction of these markers. Overall, the results indicated the involvement of IGF-1 and Akt in senescence exhibited by rat articular chondrocytes.

Donor Klotho KL-VS Polymorphism Predicts Allograft Glomerulosclerosis and Early Post-Transplant Kidney Function

BACKGROUND

The Klotho protein, encoded by the KL (Klotho) gene, exerts antiaging and antifibrotic effects. The KL-VS genotype diminishes Klotho expression and correlates with cardiovascular death, heart failure, and chronic kidney disease progression. The aim of this study was to analyze the contribution of donor Klotho rs9536314 and rs9527025 polymorphisms (KL-VS genotype) to renal allograft morphology and function in the early post-transplant period.

METHODS

Clinical data and biopsy reports of 170 deceased donor transplantations were retrieved from standard medical files. Donor DNA was genotyped for rs9527025 and rs9536314 SNPs using custom TaqMan assays.

RESULTS

As rs9527025 remained in full linkage with rs9536314, we report results for the latter. The analyses were performed for G dominant model (GG+GT vs TT). We found an association between reported SNP alleles, morphologic changes in the peritransplant biopsy, and kidney function 3 months after engraftment. A chronic glomerulopathy score of >0 was found in 12.2% of GG+GT cases and in 3.2% of TT cases (P = .023). For G allele carriers, the third month's median estimated glomerular filtration rate value was 35.0 (range, 20.4-76.6 mL/min), while for TT haplotype, the value was 46.3 (range, 15.5-96.8 mL/min), P = .001. At the third post-transplant month, proteinuria incidence was higher for organs with G allele than with TT haplotype (24.4% vs 9.5%; P = .030; odds ratio 3.09; 95% confidence interval 1.22-7.69).

CONCLUSION

Deceased donor KL-VS polymorphism, altering protein dimerization and coreceptor function, predicts early renal transplant glomerular lesions and function. Further analyses for mentioned effect durability are necessary.

ETHICS STATEMENT

This study complies with the Helsinki Congress and the Istanbul Declaration regarding donor source. Donors were not prisoners, and were not paid or coerced.

Increased Plasma Level of Longevity Protein Klotho as a Potential Indicator of Cognitive Function Preservation in Patients With Schizophrenia

Cognitive impairments are a core feature of schizophrenia. Klotho is an anti-aging protein with demonstrated cognitive-enhancing effects on the brain. The purpose of this study was to investigate the differences in levels of plasma klotho between patients with schizophrenia and healthy controls, as well as the relationship between klotho level and cognitive function in patients. Forty patients with schizophrenia and 40 gender- and age-matched healthy individuals were recruited. Positive and Negative Syndrome Scale (PANSS) was used to assess the psychopathology of patients. A neuropsychological battery was performed to evaluate the cognitive function of participants. Plasma klotho was measured using enzyme-linked immunosorbent assay. We show that patients with schizophrenia performed worse in the neurocognitive tests than the healthy controls. The levels of plasma klotho were significantly higher in schizophrenia patients than in healthy controls (p < 0.001). In patients, plasma klotho levels were positively correlated with cognitive function with regard to attention (p = 0.010), working memory (p < 0.001), verbal memory (p = 0.044), executive function (p < 0.001), and composite cognitive score (p < 0.001). Stepwise linear regression analysis shows that executive function had the highest correlation with plasma klotho levels (β = 0.896, t = 8.290, p < 0.001). Collectively, these results indicate that anti-aging protein klotho may be implicated in the pathogenesis of schizophrenia, and increased klotho may act as a compensatory factor for the preservation of cognitive function in schizophrenia. Further studies are needed to investigate the dynamic changes of klotho and the mechanisms by which klotho modulates cognition in schizophrenia.

P2X7 siRNA targeted to the kidneys increases klotho and delays the progression of experimental diabetic nephropathy

Previous studies in our laboratory have suggested that P2X7 could contribute to the progression of diabetic nephropathy and modulated klotho expression. The aim of this study was to investigate if P2X7 receptor is related to the expression of klotho in the onset of diabetic nephropathy in rats. Seven-week-old male Wistar rats weighing 210 g were all uninephrectomized; two-third of the animals were induced to diabetes with 60 mg/kg streptozotocin i.v., and one-third received its vehicle (control rats). At 4th day of the fifth week of the protocol, half of the diabetic rats received a small interfering RNA targeting for P2X7 mRNA, and the other half received its vehicle. Euthanasia was made at the eighth week. Diabetic animals reproduced all classic symptoms of the disease; besides, they showed reduced renal function and low NO bioavailability; also, SOD1, SOD2, and catalase were increased, probably due to the oxidative stress which was elevated in this situation. Metabolic data of diabetic rats did not change by silencing P2X7 receptor. For the other hand, silencing P2X7 was able to contribute to balance oxidative and nitrosative profile, ultimately improving the renal function and increasing plasma and membrane forms of klotho. These findings suggest that the management of P2X7 receptor can benefit the kidneys with diabetic nephropathy. Further studies are needed to show the therapeutic potential of this receptor inhibition to provide a better quality of life for the diabetic patient.

KLOTHO polymorphisms and age-related outcomes in community-dwelling older subjects: The São Paulo Ageing & Health (SPAH) Study

Defective KLOTHO gene expression in mice led to a syndrome resembling human ageing. This study evaluated three KLOTHO polymorphisms, namely G395A, C1818T, and C370S, in an elderly population (mean age of 73 years) and their associations with ageing-related outcomes (cardiovascular events, kidney function, osteoporosis, sarcopenia) and mortality. Estimated glomerular filtration rates (eGFR) was lower in subjects with 1818TT (P = 0.047) and 370SS (P = 0.046) genotypes. The 1818TT genotype (P = 0.006) and 1818T allele were associated with higher frequency of myocardial infarction (MI) (CC:1.7% vs. CT + TT:7.0%; P = 0.002). The 370SS genotype was associated with lower stroke frequency (P = 0.001). MI (OR 3.35 [95% CI: 1.29–8.74]) and stroke (OR 3.64 [95% CI: 1.48–8.97]) were associated with mortality. Regarding MI, logistic regression showed 1818T allele was a risk factor for death-related MI (OR 4.29 [95% CI: 1.60–11.52]; P = 0.003), while 370C was protective (OR 0.03 [95% CI: 0.01–0.08]; P < 0.001). Regarding stroke, the 395A and 370C alleles were protective factors (respectively: OR 0.28 [95% CI: 0.20–0.80]; P = 0.018; OR 0.10 [95% CI: 0.05–0.18]; P < 0.001). This is the first study to determine potential associations between common ageing-related outcomes/mortality and KLOTHO polymorphisms. The 1818T allele was a risk factor for MI-related death. The 395A and 370C alleles were protective factors for stroke-related death in elderly from community.

Klotho: An Elephant in Aging Research

The year 2017 marked the 20th anniversary of the first publication describing Klotho. This single protein was and is remarkable in that its absence in mice conferred an accelerated aging, or progeroid, phenotype with a dramatically shortened life span. On the other hand, genetic overexpression extended both health span and life span by an impressive 30%. Not only has Klotho deficiency been linked to a number of debilitating age-related illnesses but many subsequent reports have lent credence to the idea that Klotho can compress the period of morbidity and extend the life span of both model organisms and humans. This suggests that Klotho functions as an integrator of organ systems, making it both a promising tool for advancing our understanding of the biology of aging and an intriguing target for interventional studies. In this review, we highlight advances in our understanding of Klotho as well as key challenges that have somewhat limited our view, and thus translational potential, of this potent protein.

The goddess who spins the thread of life: Klotho, psychiatric stress, and accelerated aging

BACKGROUND

Longevity gene klotho (KL) is associated with age-related phenotypes but has not been evaluated against a direct human biomarker of cellular aging. We examined KL and psychiatric stress, including posttraumatic stress disorder (PTSD), which is thought to potentiate accelerated aging, in association with biomarkers of cellular aging.

METHODS

The sample comprised 309 white, non-Hispanic genotyped veterans with measures of epigenetic age (DNA methylation age), telomere length (n = 252), inflammation (C-reactive protein), psychiatric symptoms, metabolic function, and white matter neural integrity (diffusion tensor imaging; n = 185). Genotyping and DNA methylation were obtained on epi/genome-wide beadchips.

RESULTS

In gene by environment analyses, two KL variants (rs9315202 and rs9563121) interacted with PTSD severity (peak corrected p = 0.044) and sleep disturbance (peak corrected p = 0.034) to predict advanced epigenetic age. KL variant, rs398655, interacted with self-reported pain in association with slowed epigenetic age (corrected p = 0.048). A well-studied protective variant, rs9527025, was associated with slowed epigenetic age (p = 0.046). The peak PTSD interaction term (with rs9315202) also predicted C-reactive protein (p = 0.049), and white matter microstructural integrity in two tracts (corrected ps = 0.005 - 0.035). This SNP evidenced a main effect with an index of metabolic syndrome severity (p = 0.015). Effects were generally accentuated in older subjects.

CONCLUSIONS

Rs9315202 predicted multiple biomarkers of cellular aging such that psychiatric stress was more strongly associated with cellular aging in those with the minor allele. KL genotype may contribute to a synchronized pathological aging response to stress and could be a therapeutic target to alter the pace of cellular aging.

Aging and End Stage Renal Disease Cause A Decrease in Absolute Circulating Lymphocyte Counts with A Shift to A Memory Profile and Diverge in Treg Population

There is a growing number of elderly kidney transplant (Ktx) recipients. Elderly recipients present lower acute rejection rates but higher incidence of infection and malignancies. Aging per se seems to result in a shift to memory profile and chronic kidney disease (CKD) in premature immunological aging. Understanding aging and CKD effects on the immune system can improve elderly Ktx immunosuppression. We analyzed the effects of aging and CKD in the immune system, comparing healthy adults (HAd) (n=14, 26±2y), healthy elderly (HEld) (n=15, 79±7y), end stage renal disease (ESRD) adults (EnAd) (n=18, 36±7y) and ESRD elderly (EnEld) (n=31, 65±3y) prior to Ktx regarding their naïve, memory and regulatory T and B peripheral lymphocytes. Aging and ESRD presented additive effect decreasing absolute numbers of B and T-lymphocytes, affecting memory, naive and regulatory subsets without synergic effect. Both resulted in higher percentages of T memory subsets and opposing effects on regulatory T (TREG) subsets, higher percentage in aging and lower in ESRD. Combined effect of aging and ESRD also resulted in higher regulatory B cell percentages. In addition to global lymphopenia and TCD4⁺ memory shift in both aging and ESRD, aging shifts to an immunoregulatory profile, inducing a increase in TREG percentages, contrasting with ESRD that decreases TREGs. Differential immunosuppression regimens for elderly Ktx may be required. (ClinicalTrials.gov number: NTC01631058).

Klotho allele status is not associated with Aβ and APOE ε4-related cognitive decline in preclinical Alzheimer's disease

The longevity gene Klotho (KL), specifically the functional KL-VS variant, has previously been associated with cognition and rates of cognitive decline. This study aimed to determine whether KL-VS associations with cognition were observable in preclinical Alzheimer's disease (AD). The study also aimed to determine whether there was a combined influence of KL-VS, neocortical amyloid-β (Aβ) burden, and carriage of the apolipoprotein E (APOE) ε4 allele on cognitive decline. This study involved 581 Aβ-imaged, cognitively normal older adults, enrolled in the Australian Imaging, Biomarkers and Lifestyle Study of Aging. Linear mixed effects models revealed no significant associations between KL-VS and cognitive decline independently or in combination with Aβ burden and APOE ε4 genotype. Overall, previous associations reported between KL-VS and cognitive decline are not observed at the preclinical stages of AD. Furthermore, the results do not support the hypothesis that KL-VS has a modifying effect on Aβ burden and APOE ε4-driven cognitive decline in preclinical AD.

Secreted αKlotho isoform protects against age-dependent memory deficits

αKlotho is a gene regulator of aging, increasing life expectancy when overexpressed and accelerating the development of aging phenotypes when inhibited. In mice, expression levels of the secreted isoform Klotho (s-KL) are very high in the brain, suggesting that s-KL activity may have an important role in the nervous system. Here we study the functional relevance at behavioural level of modifying s-KL levels in the aging brain. We used AAVrh10 vectors to deliver and sustained expression of s-KL in 6- and 12-month-old wild-type C57BL/6J males. This study demonstrates for we believe the first time in vivo that 6 months after a single injection of s-KL into the central nervous system, long-lasting and quantifiable enhancement of learning and memory capabilities are found. More importantly, cognitive improvement is also observable in 18-month-old mice treated once, at 12 months of age. These findings demonstrate the therapeutic potential of s-KL as a treatment for cognitive decline associated with aging.

G-395A polymorphism in the promoter region of the KLOTHO gene associates with frailty among the oldest-old

Frailty is characterized by a decline in physiological reserve and increased vulnerability. Previous studies have shown that KLOTHO (KL) plays a protective role in several age-related diseases. We hypothesize a probable protective effect of KL on frailty in the elderly population and included a cohort of Chinese nonagenarians and centenarians for our study. This study is part of a cross-sectional study and secondary analysis of the Project of Longevity and Aging in Dujiangyan (PLAD) study, which was conducted in Southwest China. Community-dwelling Chinese residents aged 90 years or older were included in this study. Frailty was determined using the FRAIL scale as proposed by the International Association of Nutrition and Aging. On the FRAIL scale, frailty was defined by a score of ≥3. G-395A (rs1207568) genotyping of the promoter region of the KL gene was performed using TaqMan allelic discrimination assay. A total of 632 participants (68.4% females; mean age: 93.5 ± 3.2 years) were included. KL G-395A polymorphism genotype frequencies were 1.7% AA, 25.6% GA, and 72.7% GG in our sample. GG genotype frequencies for the frailty and control groups were 83.6% and 71.2%, respectively. Frailty prevalence was significantly lower in the GA+AA group when compared to the GG genotype group (6.9% vs. 13.3%, P = 0.026). In addition, subjects with a GA+AA genotype had a significantly lower risk of frailty (odds ratio (OR): 0.47, 95% confidence interval (CI) 0.23 to 0.97, P = 0.040) compared to the GG genotype after adjusting for age, gender, education level, smoking, alcohol consumption, exercise, body mass index (BMI), cognitive impairment, and other potential factors. KL-395A allele carrying genotypes (GA and AA) is associated with a lower risk of frailty relative to GG genotypes in a sample of Chinese nonagenarians and centenarians.

The longevity gene Klotho is differentially associated with cognition in subtypes of schizophrenia

Cognitive impairment is a core feature of schizophrenia and impacts negatively the functioning of affected individuals. Cognitive decline correlates with aging, and is the primary cause of loss of independence and reduced quality of life. The klotho gene is a key modulator of aging, with expression deficiency resulting in premature aging, while overexpression extends lifespan and enhances cognition. A haplotype and functional human variant of the gene, KL-VS, increases expression and promotes longevity. KL-VS heterozygosity is associated with enhanced cognition and a larger volume of the right dorsolateral prefrontal cortex, a region involved in planning and decision-making, which is especially susceptible to shrinkage with age. We examined the effect of KL-VS heterozygosity on cognition in 497 schizophrenia patients and 316 healthy controls from the Western Australian Family Study of Schizophrenia (WAFSS) who had been comprehensively characterised by neurocognitive tests and classified into cognitively deficient (CD) and cognitively "spared" (CS) clusters. An older, cognitively normal population sample from the Health in Men Study (HIMS) was included to allow assessment of heterozygosity and memory in aged individuals. We show that heterozygosity is associated with better learning and memory in the younger WAFSS healthy controls but not in the aging HIMS sample. However, in schizophrenia patients, KL-VS has a selective effect on memory, with heterozygotes in CD and CS clusters performing worse than non-carriers. This effect was significant and more severe in the CD cluster, reinforcing the utility of subtyping patients into CD and CS clusters that may differ in their genetic underpinnings.

FGF23-αKlotho as a paradigm for a kidney-bone network

The vertebrate endoskeleton is not a mere frame for muscle attachment to facilitate locomotion, but is a massive organ integrated with many physiologic functions including mineral and energy metabolism. Mineral balance is maintained by tightly controlled ion fluxes that are external (intestine and kidney) and internal (between bone and other organs), and are regulated and coordinated by many endocrine signals between these organs. The endocrine fibroblast growth factors (FGFs) and Klotho gene families are complex systems that co-evolved with the endoskeleton. In particular, FGF23 and αKlotho which are primarily derived from bone and kidney respectively, are critical in maintaining mineral metabolism where each of these proteins serving highly diverse roles; abound with many unanswered questions regarding their upstream regulation and downstream functions. Genetic lesions of components of this network produce discreet disturbances in many facets of mineral metabolism. One acquired condition with colossal elevations of FGF23 and suppression of αKlotho is chronic kidney disease where multiple organ dysfunction contributes to the morbidity and mortality. However, the single most important group of derangements that encompasses the largest breadth of complications is mineral metabolism disorders. Mineral metabolic disorders in CKD impact negatively and significantly on the progression of renal disease as well as extra-renal complications. Knowledge of the origin, nature, and impact of phosphate, FGF23, and αKlotho derangements is pivotal to understanding the pathophysiology and treatment of CKD.

The role of epigenetics in renal ageing

An ability to separate natural ageing processes from processes specific to morbidities is required to understand the heterogeneity of age-related organ dysfunction. Mechanistic insight into how epigenetic factors regulate ageing throughout the life course, linked to a decline in renal function with ageing, is already proving to be of value in the analyses of clinical and epidemiological cohorts. Noncoding RNAs provide epigenetic regulatory circuits within the kidney, which reciprocally interact with DNA methylation processes, histone modification and chromatin. These interactions have been demonstrated to reflect the biological age and function of renal allografts. Epigenetic factors control gene expression and activity in response to environmental perturbations. They also have roles in highly conserved signalling pathways that modulate ageing, including the mTOR and insulin/insulin-like growth factor signalling pathways, and regulation of sirtuin activity. Nutrition, the gut microbiota, inflammation and environmental factors, including psychosocial and lifestyle stresses, provide potential mechanistic links between the epigenetic landscape of ageing and renal dysfunction. Approaches to modify the renal epigenome via nutritional intervention, targeting the methylome or targeting chromatin seem eminently feasible, although caution is merited owing to the potential for intergenerational and transgenerational effects.

Lack of functional KL-VS polymorphism of the KLOTHO gene in the Korean population

The functional variant of the Klotho "KL-VS" stretch, which includes six polymorphisms in linkage disequilibrium, is reportedly associated with healthy aging and longevity in European and American populations. Among Asian populations, this variant has been observed in the Indian population but not in the Iranian population. An association between KL-VS polymorphism and aging has not been reported in Koreans. To investigate whether the KL-VS polymorphism could be associated with healthy aging and longevity in a Korean population, we analyzed genotype and allele frequencies of the KL-VS variant in a large Korean population sample. The KL-VS variant was not found in 874 Korean individuals. Thus, it is not possible to test its association to aging in the East Asian populations.

G-395A polymorphism in the promoter region of the KLOTHO gene associates with reduced cognitive impairment among the oldest old

This study aimed to examine the possible association between G-395A polymorphism in the promoter region of the KLOTHO gene and cognitive impairment among Chinese nonagenarians and centenarians. This study is a secondary analysis of the Project of Longevity and Aging in Dujiangyan (PLAD) study. Community-dwelling Chinese people aged 90 years or older were included. G-395A (rs1207568) genotyping in the promoter region of the KLOTHO gene was performed using the TaqMan allelic discrimination assay. Cognitive function was assessed with the mini-mental status examination (MMSE). A total of 706 participants (68.0 % female; mean age 93.5 ± 3.6 years) were included. The KLOTHO G-395A polymorphism genotype frequencies for the whole sample were 2.0 % AA, 30.3 % GA, and 67.7 % GG. The GG genotype frequencies for the cognitive impairment and control groups were 70.2 and 62.7 %, respectively. Cognitive impairment prevalence was significantly lower in the GA+AA group than in the GG genotype group (61.4 vs. 69.0 %, p = 0.044). GA+AA genotype subjects had a significantly lower risk of cognitive impairment (odds ratio 0.66; 95 % confidence interval 0.44 to 0.98) than GG genotype individuals after adjusting for age, gender, and other relevant risk factors. KLOTHO G-395A polymorphism associates with reduced cognitive impairment in a sample of Chinese nonagenarians and centenarians.

Secreted and Transmembrane αKlotho Isoforms Have Different Spatio-Temporal Profiles in the Brain during Aging and Alzheimer's Disease Progression

The Klotho protein is a β-glucuronidase, and its overexpression is associated with life extension. Its mechanism of action is not fully understood, although it has been recently reported that αKlotho improves synaptic and cognitive functions, and it may also influence a variety of structures and functions during CNS maturation and aging. The αKlotho gene has two transcripts, one encoding a transmembrane isoform (m-KL), and the other a putative secreted isoform (s-KL). Unfortunately, little is known about the secreted αKlotho isoform, since available antibodies cannot discriminate s-KL from the KL1 domain cleaved from the transmembrane isoform. This study shows, for the first time, that the klotho transcript produced by alternative splicing generates a stable protein (70 kDa), and that in contrast to the transmembrane Klotho isoform, it is ten times more abundant in the brain than in the kidney suggesting that the two isoforms may have different functions. We also studied whether klotho expression in the CNS was influenced by aging, Alzheimer's disease (AD), or a healthy lifestyle, such as voluntary moderate continuous exercise. We observed a strong correlation between high expression levels of the two klotho transcripts and the healthy status of the animals. Expression of Klotho in brain areas decayed more rapidly in the 3xTg-AD model of AD than in healthy animals, whilst moderate continuous exercise in adulthood prevents the decline in expression of both klotho transcripts.

α-Klotho Expression in Human Tissues

CONTEXT

α-Klotho has emerged as a powerful regulator of the aging process. To date, the expression profile of α-Klotho in human tissues is unknown, and its existence in some human tissue types is subject to much controversy.

OBJECTIVE

This is the first study to characterize systemwide tissue expression of transmembrane α-Klotho in humans. We have employed next-generation targeted proteomic analysis using parallel reaction monitoring in parallel with conventional antibody-based methods to determine the expression and spatial distribution of human α-Klotho expression in health.

RESULTS

The distribution of α-Klotho in human tissues from various organ systems, including arterial, epithelial, endocrine, reproductive, and neuronal tissues, was first identified by immunohistochemistry. Kidney tissues showed strong α-Klotho expression, whereas liver did not reveal a detectable signal. These results were next confirmed by Western blotting of both whole tissues and primary cells. To validate our antibody-based results, α-Klotho-expressing tissues were subjected to parallel reaction monitoring mass spectrometry (data deposited at ProteomeXchange, PXD002775) identifying peptides specific for the full-length, transmembrane α-Klotho isoform.

CONCLUSIONS

The data presented confirm α-Klotho expression in the kidney tubule and in the artery and provide evidence of α-Klotho expression across organ systems and cell types that has not previously been described in humans.

Insulin-like Growth Factors in a clinical setting: Review of IGF-I

BACKGROUND AND AIMS

Interest in growth hormone (GH) is inextricably linked to the need for in depth understanding of the somatomedins (insulin-like growth factors) which are polypeptides structurally similar to insulin and with broad physiological activity. To date, the most commonly known is Insulin-Like Growth Factor I (IGF-I). Despite considerable current knowledge of IGF-I, however, its bioactivity is incompletely understood. Measurement of IGF-I is of the utmost importance in the diagnosis and treatment of, for example acromegaly and growth hormone deficiency. The development of recombinant IGF-I, has allowed its use in such cases. Clinical practice, however, shows that few young/adult patients will benefit from treatment with the rIGF-I, mecasermin, given the number of adverse effects found. This review focuses on current knowledge mainly related to IGF-I and the use of its recombinant form (rIGF-I) in clinical practice. Several functions of IGI-II have been elucidated but their clinical significance is unclear.