Variation in longevity gene KLOTHO is associated with greater cortical volumes

Molecular mechanisms linking type 2 diabetes mellitus and late-onset Alzheimer's disease: A systematic review and qualitative meta-analysis

Research evidence indicating common metabolic mechanisms through which type 2 diabetes mellitus (T2DM) increases risk of late-onset Alzheimer's dementia (LOAD) has accumulated over recent decades. The aim of this systematic review is to provide a comprehensive review of common mechanisms, which have hitherto been discussed in separate perspectives, and to assemble and evaluate candidate loci and epigenetic modifications contributing to polygenic risk linkages between T2DM and LOAD. For the systematic review on pathophysiological mechanisms, both human and animal studies up to December 2023 are included. For the qualitative meta-analysis of genomic bases, human association studies were examined; for epigenetic mechanisms, data from human studies and animal models were accepted. Papers describing pathophysiological studies were identified in databases, and further literature gathered from cited work. For genomic and epigenomic studies, literature mining was conducted by formalised search codes using Boolean operators in search engines, and augmented by GeneRif citations in Entrez Gene, and other sources (WikiGenes, etc.). For the systematic review of pathophysiological mechanisms, 923 publications were evaluated, and 138 gene loci extracted for testing candidate risk linkages. 3 57 publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight insulin signalling, inflammation and inflammasome pathways, proteolysis, gluconeogenesis and glycolysis, glycosylation, lipoprotein metabolism and oxidation, cell cycle regulation or survival, autophagic-lysosomal pathways, and energy. Documented findings suggest interplay between brain insulin resistance, neuroinflammation, insult compensatory mechanisms, and peripheral metabolic dysregulation in T2DM and LOAD linkage. The results allow for more streamlined longitudinal studies of T2DM-LOAD risk linkages.

The possible anti-seizure properties of Klotho

Recurrent seizures in epilepsy may lead to progressive neuronal damage, which can diminish health-related quality of life. Evaluation and control of pathological processes in the brain is valuable. It seems imperative that new markers and approaches for seizure alleviation be discovered. Klotho (Kl), an antiaging protein, has protective effects in the brain against neurological disorders. It may also have antiseizure effects by improving creatine transfer to the brain, upregulating excitatory amino acid transporters, and inhibiting insulin/insulin-like growth factor-1 (IGF-1), Wingless (Wnt), transforming growth factor-beta (TGF-β), and retinoic-acid-inducible gene-I (RIG-I)/nuclear translocation of nuclear factor-κB (NF-κB) pathways. Stimulation and activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and apoptosis signal-regulating kinase 1 (ASK1)/p38 mitogen‑activated protein kinase (MAPK) signaling pathways could also be considered other possible antiseizure mechanisms of Kl. In the present review, the roles of Kl in the central nervous system as well as its possible anti-seizure properties are discussed for the first time.

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

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

Targeting neuroendocrine abnormalities in Parkinson's disease with exercise

Parkinson's Disease (PD) is a prevalent and complex age-related neurodegenerative condition for which there are no disease-modifying treatments currently available. The pathophysiological process underlying PD remains incompletely understood but increasing evidence points to multiple system dysfunction. Interestingly, the past decade has produced evidence that exercise not only reduces signs and symptoms of PD but is also potentially neuroprotective. Characterizing the mechanistic pathways that are triggered by exercise and lead to positive outcomes will improve understanding of how to counter disease progression and symptomatology. In this review, we highlight how exercise regulates the neuroendocrine system, whose primary role is to respond to stress, maintain homeostasis and improve resilience to aging. We focus on a group of hormones - cortisol, melatonin, insulin, klotho, and vitamin D - that have been shown to associate with various non-motor symptoms of PD, such as mood, cognition, and sleep/circadian rhythm disorder. These hormones may represent important biomarkers to track in clinical trials evaluating effects of exercise in PD with the aim of providing evidence that patients can exert some behavioral-induced control over their disease.

Platelet factors are induced by longevity factor klotho and enhance cognition in young and aging mice

Platelet factors regulate wound healing and can signal from the blood to the brain1,2. However, whether platelet factors modulate cognition, a highly valued and central manifestation of brain function, is unknown. Here we show that systemic platelet factor 4 (PF4) permeates the brain and enhances cognition. We found that, in mice, peripheral administration of klotho, a longevity and cognition-enhancing protein3-7, increased the levels of multiple platelet factors in plasma, including PF4. A pharmacologic intervention that inhibits platelet activation blocked klotho-mediated cognitive enhancement, indicating that klotho may require platelets to enhance cognition. To directly test the effects of platelet factors on the brain, we treated mice with vehicle or systemic PF4. In young mice, PF4 enhanced synaptic plasticity and cognition. In old mice, PF4 decreased cognitive deficits and restored aging-induced increases of select factors associated with cognitive performance in the hippocampus. The effects of klotho on cognition were still present in mice lacking PF4, suggesting this platelet factor is sufficient to enhance cognition but not necessary for the effects of klotho-and that other unidentified factors probably contribute. Augmenting platelet factors, possible messengers of klotho, may enhance cognition in the young brain and decrease cognitive deficits in the aging brain.

Longevity factor klotho enhances cognition in aged nonhuman primates

Cognitive dysfunction in aging is a major biomedical challenge. Whether treatment with klotho, a longevity factor, could enhance cognition in human-relevant models such as in nonhuman primates is unknown and represents a major knowledge gap in the path to therapeutics. We validated the rhesus form of the klotho protein in mice showing it increased synaptic plasticity and cognition. We then found that a single administration of low-dose, but not high-dose, klotho enhanced memory in aged nonhuman primates. Systemic low-dose klotho treatment may prove therapeutic in aging humans.

Relationships between serum Klotho concentrations and cognitive performance among older chronic kidney disease patients with albuminuria in NHANES 2011-2014

Background

The potential relationship between Klotho and cognitive function is limited and controversial. This study aimed to quantify the association of Klotho and cognitive impairment in chronic kidney disease (CKD) patients with albuminuria.

Methods

Serum Klotho was measured by enzyme-linked immunosorbent assay. Patients with urine albumin to creatinine ratio (UACR) > 30mg/g from the National Health and Nutrition Survey (NHANES) 2011-2014 were divided into 4 groups according to the quartile of Klotho. Cognitive function was examined using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), Digit Symbol Substitution Test (DSST), and Animal Fluency Test. The relationship between Klotho and cognitive function was analyzed by multivariable regression and subgroup analysis.

Results

Among 368 CKD patients with albuminuria, we found that Klotho was negatively associated with creatinine, and positively associated with hemoglobin, and estimated glomerular filtration rate. No significant linear relationship was showed between Klotho (as a continuous variable) and cognitive function. When regarded Klotho as a category variable, patients in the quartile 3 group were at a better cognitive performance for CEARD-word learning subset and DSST, especially in the CKD patients with 30 mg/g < UACR <300 mg/g, but not in participants with UACR > 300 mg/g.

Conclusions

The increased Klotho was associated with an increased cognitive function in CKD patients with microalbuminuria. Further studies are needed to demonstrate whether Klotho may be a beneficial biomarker of cognitive health and neurodegeneration.

Klotho Gene Expression Is Decreased in Peripheral Blood Mononuclear Cells in Patients with Alzheimer's Disease and Frontotemporal Dementia

BACKGROUND

The longevity gene Klotho (KL) was recently associated with neurodegenerative diseases including Alzheimer's disease (AD). Its role in the brain has not been completely elucidated, although evidence suggests that KL-VS heterozygosity is associated with a reduced risk of AD in Apolipoprotein E ɛ4 carriers. Conversely, no data about genetic association with frontotemporal dementia (FTD) are available so far.

OBJECTIVE

To investigate the involvement of KL in AD and FTD by the determination of the genetic frequency of KL-VS variant and the expression analysis of KL gene.

METHODS

A population consisting of 438 patients and 240 age-matched controls was enrolled for the study. KL-VS and APOE genotypes were assessed by allelic discrimination through a QuantStudio 12K system. KL gene expression analysis was performed in a restricted cohort of patients consisting of 43 AD patients, 41 FTD patients and 19 controls. KL gene expression was assessed in peripheral blood mononuclear cells with specific TaqMan assay. Statistical analysis was performed using GraphPad 9 Prims software.

RESULTS

KL-VS frequency was comparable to the ones found in literature and no differences were found in both allelic and genotypic frequencies between patients and controls were found. Conversely, KL expression levels were significantly lower in AD and FTD patients compared with controls (mean fold regulation - 4.286 and - 6.561 versus controls in AD and FTD, respectively, p = 0.0037).

CONCLUSION

This is the first study investigating KL in FTD. We showed a decreased expression of the gene in AD and FTD, independent of the genotype, suggesting a role of Klotho in common steps during neurodegeneration.

The Interrelated Multifactorial Actions of Cortisol and Klotho: Potential Implications in the Pathogenesis of Parkinson's Disease

The pathogenesis of Parkinson's disease (PD) is complex, multilayered, and not fully understood, resulting in a lack of effective disease-modifying treatments for this prevalent neurodegenerative condition. Symptoms of PD are heterogenous, including motor impairment as well as non-motor symptoms such as depression, cognitive impairment, and circadian disruption. Aging and stress are important risk factors for PD, leading us to explore pathways that may either accelerate or protect against cellular aging and the detrimental effects of stress. Cortisol is a much-studied hormone that can disrupt mitochondrial function and increase oxidative stress and neuroinflammation, which are recognized as key underlying disease mechanisms in PD. The more recently discovered klotho protein, considered a general aging-suppressor, has a similarly wide range of actions but in the opposite direction to cortisol: promoting mitochondrial function while reducing oxidative stress and inflammation. Both hormones also converge on pathways of vitamin D metabolism and insulin resistance, also implicated to play a role in PD. Interestingly, aging, stress and PD associate with an increase in cortisol and decrease in klotho, while physical exercise and certain genetic variations lead to a decrease in cortisol response and increased klotho. Here, we review the interrelated opposite actions of cortisol and klotho in the pathogenesis of PD. Together they impact powerful and divergent mechanisms that may go on to influence PD-related symptoms. Better understanding of these hormones in PD would facilitate the design of effective interventions that can simultaneously impact the multiple systems involved in the pathogenesis of PD.

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.

Association of Klotho Protein Levels and KL-VS Heterozygosity With Alzheimer Disease and Amyloid and Tau Burden

IMPORTANCE

Identification of proteins and genetic factors that reduce Alzheimer disease (AD) pathology is of importance when searching for novel AD treatments. Heterozygosity of the KL-VS haplotype has been associated with reduced amyloid and tau burden. Whether this association is mediated by the Klotho protein remains unclear.

OBJECTIVES

To assess concentrations of Klotho in cerebrospinal fluid (CSF) and plasma among cognitively healthy controls and patients with AD and to correlate these findings with KL-VS heterozygosity status and amyloid and tau burden.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study combined 2 independent case-control AD cohorts consisting of 243 referred patients with AD and volunteer controls recruited from January 1, 2009, to December 31, 2018. Klotho levels were measured in CSF and plasma and correlated with KL-VS heterozygosity status and levels of CSF amyloid-β 42 (Aβ42), total tau, and phosphorylated tau. Statistical analysis was performed from January 1, 2021, to March 1, 2022.

MAIN OUTCOMES AND MEASURES

Associations of Klotho levels in CSF and plasma with levels of CSF biomarkers were analyzed using linear regression. Association analyses were stratified separately by clinical groups, APOE4 status, and KL-VS heterozygosity. Pearson correlation was used to assess the correlation between CSF and plasma Klotho levels.

RESULTS

A total of 243 participants were included: 117 controls (45 men [38.5%]; median age, 65 years [range, 41-84 years]), 102 patients with mild cognitive impairment due to AD (AD-MCI; 59 men [57.8%]; median age, 66 years [range, 46-80 years]), and 24 patients with dementia due to AD (AD-dementia; 12 men [50.0%]; median age, 64.5 years [range, 54-75 years]). Median CSF Klotho levels were higher in controls (1236.4 pg/mL [range, 20.4-1726.3 pg/mL]; β = 0.103; 95% CI, 0.023-0.183; P = .01) and patients with AD-MCI (1188.1 pg/mL [range, 756.3-1810.3 pg/mL]; β = 0.095; 95% CI, 0.018-0.172; P = .02) compared with patients with AD-dementia (1073.3 pg/mL [range, 698.2-1661.4 pg/mL]). Higher levels of CSF Klotho were associated with lower CSF Aβ42 burden (β = 0.519; 95% CI, 0.201-0.836; P < .001) and tau burden (CSF total tau levels: β = -0.884; 95% CI, 0.223 to -0.395; P < .001; CSF phosphorylated tau levels: β = -0.672; 95% CI, -1.022 to -0.321; P < .001) independent of clinical, KL-VS heterozygosity, or APOE4 status. There was a weak correlation between Klotho CSF and plasma levels among the entire cohort (Pearson correlation r = 0.377; P < .001).

CONCLUSIONS AND RELEVANCE

The findings of this case-control study suggest that Klotho protein levels were associated with clinical stages of AD, cognitive decline, and amyloid and tau burden and that these outcomes were more clearly mediated by the protein directly rather than the KL-VS heterozygosity variant. When selecting individuals at risk for clinical trials, the Klotho protein level and not only the genetic profile should be considered.

An Integrated Analysis of Clinical, Genomic, and Imaging Features Reveals Predictors of Neurocognitive Outcomes in a Longitudinal Cohort of Pediatric Cancer Survivors, Enriched with CNS Tumors (Rad ART Pro)

Background

Neurocognitive deficits in pediatric cancer survivors occur frequently; however, individual outcomes are unpredictable. We investigate clinical, genetic, and imaging predictors of neurocognition in pediatric cancer survivors, with a focus on survivors of central nervous system (CNS) tumors exposed to radiation.

Methods

One hundred eighteen patients with benign or malignant cancers (median diagnosis age: 7; 32% embryonal CNS tumors) were selected from an existing multi-institutional cohort (RadART Pro) if they had: 1) neurocognitive evaluation; 2) available DNA; 3) standard imaging. Utilizing RadART Pro, we collected clinical history, genomic sequencing, CNS imaging, and neurocognitive outcomes. We performed single nucleotide polymorphism (SNP) genotyping for candidate genes associated with neurocognition: COMT, BDNF, KIBRA, APOE, KLOTHO. Longitudinal neurocognitive testing were performed using validated computer-based CogState batteries. The imaging cohort was made of patients with available iron-sensitive (n = 28) and/or T2 FLAIR (n = 41) sequences. Cerebral microbleeds (CMB) were identified using a semi-automated algorithm. Volume of T2 FLAIR white matter lesions (WML) was measured using an automated method based on a convolutional neural network. Summary statistics were performed for patient characteristics, neurocognitive assessments, and imaging. Linear mixed effects and hierarchical models assessed patient characteristics and SNP relationship with neurocognition over time. Nested case-control analysis was performed to compare candidate gene carriers to non-carriers.

Results

CMB presence at baseline correlated with worse performance in 3 of 7 domains, including executive function. Higher baseline WML volumes correlated with worse performance in executive function and verbal learning. No candidate gene reliably predicted neurocognitive outcomes; however, APOE ϵ4 carriers trended toward worse neurocognitive function over time compared to other candidate genes and carried the highest odds of low neurocognitive performance across all domains (odds ratio 2.85, P=0.002). Hydrocephalus and seizures at diagnosis were the clinical characteristics most frequently associated with worse performance in neurocognitive domains (5 of 7 domains). Overall, executive function and verbal learning were the most frequently negatively impacted neurocognitive domains.

Conclusion

Presence of CMB, APOE ϵ4 carrier status, hydrocephalus, and seizures correlate with worse neurocognitive outcomes in pediatric cancer survivors, enriched with CNS tumors exposed to radiation. Ongoing research is underway to verify trends in larger cohorts.

Leveraging large multi-center cohorts of Alzheimer disease endophenotypes to understand the role of Klotho heterozygosity on disease risk

Two genetic variants in strong linkage disequilibrium (rs9536314 and rs9527025) in the Klotho (KL) gene, encoding a transmembrane protein, implicated in longevity and associated with brain resilience during normal aging, were recently shown to be associated with Alzheimer disease (AD) risk in cognitively normal participants who are APOE ε4 carriers. Specifically, the participants heterozygous for this variant (KL-SVHET+) showed lower risk of developing AD. Furthermore, a neuroprotective effect of KL-VSHET+ has been suggested against amyloid burden for cognitively normal participants, potentially mediated via the regulation of redox pathways. However, inconsistent associations and a smaller sample size of existing studies pose significant hurdles in drawing definitive conclusions. Here, we performed a well-powered association analysis between KL-VSHET+ and five different AD endophenotypes; brain amyloidosis measured by positron emission tomography (PET) scans (n = 5,541) or cerebrospinal fluid Aβ42 levels (CSF; n = 5,093), as well as biomarkers associated with tau pathology: the CSF Tau (n = 5,127), phosphorylated Tau (pTau181; n = 4,778) and inflammation: CSF soluble triggering receptor expressed on myeloid cells 2 (sTREM2; n = 2,123) levels. Our results found nominally significant associations of KL-VSHET+ status with biomarkers for brain amyloidosis (e.g., CSF Aβ positivity; odds ratio [OR] = 0.67 [95% CI, 0.55-0.78], β = 0.72, p = 0.007) and tau pathology (e.g., biomarker positivity for CSF Tau; OR = 0.39 [95% CI, 0.19-0.77], β = -0.94, p = 0.007, and pTau; OR = 0.50 [95% CI, 0.27-0.96], β = -0.68, p = 0.04) in cognitively normal participants, 60-80 years old, who are APOE e4-carriers. Our work supports previous findings, suggesting that the KL-VSHET+ on an APOE ε4 genotype background may modulate Aβ and tau pathology, thereby lowering the intensity of neurodegeneration and incidence of cognitive decline in older controls susceptible to AD.

KL1 Domain of Longevity Factor Klotho Mimics the Metabolome of Cognitive Stimulation and Enhances Cognition in Young and Aging Mice

Cognitive deficits are a major biomedical challenge-and engagement of the brain in stimulating tasks improves cognition in aged individuals (Wilson et al., 2002; Gates et al., 2011) and rodents (Aidil-Carvalho et al., 2017), through unknown mechanisms. Whether cognitive stimulation alters specific metabolic pathways in the brain is unknown. Understanding which metabolic processes are involved in cognitive stimulation is important because it could lead to pharmacologic intervention that promotes biological effects of a beneficial behavior, toward the goal of effective medical treatments for cognitive deficits. Here we show using male mice that cognitive stimulation induced metabolic remodeling of the mouse hippocampus, and that pharmacologic treatment with the longevity hormone α-klotho (KL), mediated by its KL1 domain, partially mimicked this alteration. The shared, metabolic signature shared between cognitive stimulation and treatment with KL or KL1 closely correlated with individual mouse cognitive performance, indicating a link between metabolite levels and learning and memory. Importantly, the treatment of mice with KL1, an endogenous circulating factor that more closely mimicked cognitive stimulation than KL, acutely increased synaptic plasticity, a substrate of cognition. KL1 also improved cognition, itself, in young mice and countered deficits in old mice. Our data show that treatments or interventions mimicking the hippocampal metabolome of cognitive stimulation can enhance brain functions. Further, we identify the specific domain by which klotho promotes brain functions, through KL1, a metabolic mimic of cognitive stimulation.SIGNIFICANCE STATEMENT Cognitive deficits are a major biomedical challenge without truly effective pharmacologic treatments. Engaging the brain through cognitive tasks benefits cognition. Mimicking the effects of such beneficial behaviors through pharmacological treatment represents a highly valuable medical approach to treating cognitive deficits. We demonstrate that brain engagement through cognitive stimulation induces metabolic remodeling of the hippocampus that was acutely recapitulated by the longevity factor klotho, mediated by its KL1 domain. Treatment with KL1, a close mimic of cognitive stimulation, enhanced cognition and countered cognitive aging. Our findings shed light on how cognition metabolically alters the brain and provide a plausible therapeutic intervention for mimicking these alterations that, in turn, improves cognition in the young and aging brain.

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.

Circulating Klotho Is Higher in Cerebrospinal Fluid than Serum and Elevated Among KLOTHO Heterozygotes in a Cohort with Risk for Alzheimer's Disease

BACKGROUND

Klotho is a longevity and neuroprotective hormone encoded by the KLOTHO gene, and heterozygosity for the KL-VS variant confers a protective effect against neurodegenerative disease.

OBJECTIVE

Test whether klotho concentrations in serum or cerebrospinal fluid (CSF) vary as a function of KLOTHO KL-VS genotype, determine whether circulating klotho concentrations from serum and CSF differ from one another, and evaluate whether klotho levels are associated with Alzheimer's disease risk factors.

METHODS

Circulating klotho was measured in serum (n = 1,116) and CSF (n = 183) of cognitively intact participants (aged 62.4 ± 6.5 years; 69.5% female). KLOTHO KL-VS zygosity (non-carrier; heterozygote; homozygote) was also determined. Linear regression was used to test whether klotho hormone concentration varied as a function of KL-VS genotype, specimen source, and demographic and clinical characteristics.

RESULTS

Serum and CSF klotho were higher in KL-VS carriers than non-carriers. Klotho concentration was higher in CSF than in serum. Females had higher serum and CSF klotho, while younger age was associated with higher klotho in CSF.

CONCLUSION

In a cohort enriched for risk for Alzheimer's disease, heterozygotic and homozygotic carriers of the KL-VS allele, females, and younger individuals have higher circulating klotho. Fluid source, KL-VS genotype, age, and sex should be considered in analyses of circulating klotho on brain health.

The Socio-Political Roles of Neuroethics and the Case of Klotho

An increasing amount of very diverse scholarship self-identifies as belonging to the field of neuroethics, illuminating a need to provide some reference points for what that field actually entails. We argue that neuroethics is a single field with distinct perspectives, roles, and subspecialties. We propose that-in addition to the three traditional perspectives delineated by Eric Racine-a fourth, socio-political perspective, must be recognized in neuroethics. The socio-political perspective in neuroethics focuses on the interplay between the behavioral as well as the brain sciences and the socio-political system; this interplay includes social regulation in addition to all other realistic elements of social and political neurodiscourses. Thus, defining what-if any-roles the socio-political perspective in neuroethics might have is a pressing issue. Doing so could provide guidance for defining the criteria for prospective ethical evaluations in neuroethics. A promising approach to doing this could be by describing the roles of neuroethics in terms of the more concrete examples of the roles of political philosophy in general, as in the tradition of John Rawls. We take klotho, the supposed "longevity protein," as a modern neuroethics case to exemplify the obstacles faced in securing neuroethics' legitimacy and how the Rawlsian framework we propose may be applied to handle cases such as this. Ultimately, the socio-political perspective in neuroethics should not be swayed by the media hype and ought to offer useful ethical guidance and articulation of genuine ethical concerns to policy makers and the public alike.

Serum Levels of α-Klotho Are Correlated with Cerebrospinal Fluid Levels and Predict Measures of Cognitive Function

BACKGROUND

α-klotho might play a role in neurodegenerative diseases.

OBJECTIVE

To determine levels of α-klotho and apoE in serum and cerebrospinal fluid (CSF) samples and their relationship with the Mini-Mental State Examination (MMSE) and Clinical Dementia Rating (CDR).

METHODS

All subjects were between age 39 to 83+ (n = 94). CDR and MMSE were administered to all participants. CSF was collected in the early afternoon by lumbar puncture.

RESULTS

Serum and CSF levels of α-klotho are positively correlated and both predict scores on the MMSE and CDR, regardless of sex or apoE4 status.

CONCLUSION

Our results demonstrate that α-klotho may be an important biomarker of cognitive health and neurodegeneration, and that relatively non-invasive sampling of α-klotho from serum is likely highly reflective of CSF levels.

Apolipoprotein E levels in the amygdala and prefrontal cortex predict relative regional brain volumes in irradiated Rhesus macaques

In the brain, apolipoprotein E (apoE) plays an important role in lipid transport and response to environmental and age-related challenges, including neuronal repair following injury. While much has been learned from radiation studies in rodents, a gap in our knowledge is how radiation might affect the brain in primates. This is important for assessing risk to the brain following radiotherapy as part of cancer treatment or environmental radiation exposure as part of a nuclear accident, bioterrorism, or a nuclear attack. In this study, we investigated the effects of ionizing radiation on brain volumes and apoE levels in the prefrontal cortex, amygdala, and hippocampus of Rhesus macaques that were part of the Nonhuman Primate Radiation Survivor Cohort at the Wake Forest University. This unique cohort is composed of Rhesus macaques that had previously received single total body doses of 6.5-8.05 Gy of ionizing radiation. Regional apoE levels predicted regional volume in the amygdala and the prefrontal cortex. In addition, apoE levels in the amygdala, but not the hippocampus, strongly predicted relative hippocampal volume. Finally, radiation dose negatively affected relative hippocampal volume when apoE levels in the amygdala were controlled for, suggesting a protective compensatory role of regional apoE levels following radiation exposure. In a supplementary analysis, there also was a robust positive relationship between the neuroprotective protein α-klotho and apoE levels in the amygdala, further supporting the potentially protective role of apoE. Increased understanding of the effects of IR in the primate brain and the role of apoE in the irradiated brain could inform future therapies to mitigate the adverse effects of IR on the CNS.

Klotho inhibits neuronal senescence in human brain organoids

Aging is a major risk factor for many neurodegenerative diseases. Klotho (KL) is a glycosylated transmembrane protein that is expressed in the choroid plexus and neurons of the brain. KL exerts potent anti-aging effects on multiple cell types in the body but its role in human brain cells remains largely unclear. Here we show that human cortical neurons, derived from human pluripotent stem cells in 2D cultures or in cortical organoids, develop the typical hallmarks of senescent cells when maintained in vitro for prolonged periods of time, and that moderate upregulation or repression of endogenous KL expression in cortical organoids inhibits and accelerates senescence, respectively. We further demonstrate that KL expression alters the expression of senescence-associated genes including, extracellular matrix genes, and proteoglycans, and can act in a paracrine fashion to inhibit neuronal senescence. In summary, our results establish an important role for KL in the regulation of human neuronal senescence and offer new mechanistic insight into its role in human brain aging.

KL-VS heterozygosity is associated with lower amyloid-dependent tau accumulation and memory impairment in Alzheimer's disease

Klotho-VS heterozygosity (KL-VS^het) is associated with reduced risk of Alzheimer’s disease (AD). However, whether KL-VS^het is associated with lower levels of pathologic tau, i.e., the key AD pathology driving neurodegeneration and cognitive decline, is unknown. Here, we assessed the interaction between KL-VS^het and levels of beta-amyloid, a key driver of tau pathology, on the levels of PET-assessed neurofibrillary tau in 551 controls and patients across the AD continuum. KL-VS^het showed lower cross-sectional and longitudinal increase in tau-PET per unit increase in amyloid-PET when compared to that of non-carriers. This association of KL-VS^het on tau-PET was stronger in Klotho mRNA-expressing brain regions mapped onto a gene expression atlas. KL-VS^het was related to better memory functions in amyloid-positive participants and this association was mediated by lower tau-PET. Amyloid-PET levels did not differ between KL-VS^het carriers versus non-carriers. Together, our findings provide evidence to suggest a protective role of KL-VS^het against amyloid-related tau pathology and tau-related memory impairments in elderly humans at risk of AD dementia.

The KL-VS haplotype of the Klotho gene has been associated with reduced risk of Alzheimer’s disease and dementia. Here the authors show an association between the KL-VS haplotype and amyloid-dependent tau accumulation using PET data.

Exploiting the neuroprotective effects of α-klotho to tackle ageing- and neurodegeneration-related cognitive dysfunction

Cognitive dysfunction is a key symptom of ageing and neurodegenerative disorders, such as Alzheimer's disease (AD). Strategies to enhance cognition would impact the quality of life for a significant proportion of the ageing population. The α-klotho protein may protect against cognitive decline through multiple mechanisms: such as promoting optimal synaptic function via activation of N-methyl-d-aspartate (NMDA) receptor signalling; stimulating the antioxidant defence system; reducing inflammation; promoting autophagy and enhancing clearance of amyloid-β. However, the molecular and cellular pathways by which α-klotho mediates these neuroprotective functions have yet to be fully elucidated. Key questions remain unanswered: which form of α-klotho (transmembrane, soluble or secreted) mediates its cognitive enhancing properties; what is the neuronal receptor for α-klotho and which signalling pathways are activated by α-klotho in the brain to enhance cognition; how does peripherally administered α-klotho mediate neuroprotection; and what is the molecular basis for the beneficial effect of the VS variant of α-klotho? In this review, we summarise the recent research on neuronal α-klotho and discuss how the neuroprotective properties of α-klotho could be exploited to tackle age- and neurodegeneration-associated cognitive dysfunction.

Protective genes and pathways in Alzheimer's disease: moving towards precision interventions

Alzheimer's disease (AD) is a progressive, neurodegenerative disorder that is characterized by neurodegeneration, cognitive impairment, and an eventual inability to perform daily tasks. The etiology of Alzheimer's is complex, with numerous environmental and genetic factors contributing to the disease. Late-onset AD is highly heritable (60 to 80%), and over 40 risk loci for AD have been identified via large genome-wide association studies, most of which are common variants with small effect sizes. Although these discoveries have provided novel insight on biological contributors to AD, disease-modifying treatments remain elusive. Recently, the concepts of resistance to pathology and resilience against the downstream consequences of pathology have been of particular interest in the Alzheimer's field as studies continue to identify individuals who evade the pathology of the disease even into late life and individuals who have all of the neuropathological features of AD but evade downstream neurodegeneration and cognitive impairment. It has been hypothesized that a shift in focus from Alzheimer's risk to resilience presents an opportunity to uncover novel biological mechanisms of AD and to identify promising therapeutic targets for the disease. This review will highlight a selection of genes and variants that have been reported to confer protection from AD within the literature and will also discuss evidence for the biological underpinnings behind their protective effect with a focus on genes involved in lipid metabolism, cellular trafficking, endosomal and lysosomal function, synaptic function, and inflammation. Finally, we offer some recommendations in areas where the field can rapidly advance towards precision interventions that leverage the ideas of protection and resilience for the development of novel therapeutic strategies.

Impact of simulated military operational stress on executive function relative to trait resilience, aerobic fitness, and neuroendocrine biomarkers

PURPOSE

To study the impact of 48 h of simulated military operational stress (SMOS) on executive function, in addition to the role of trait resilience (RES) and aerobic fitness (FIT) on executive function performance. Associations between executive function and neuropeptide-Y (NPY), brain-derived neurotropic factor (BDNF), insulin-like growth factor-I (IGF-I), oxytocin, and α-klotho (klotho) were assessed to elucidate potential biomarkers that may contribute to cognitive performance during a multi-factorial stress scenario.

METHODS

Fifty-four service members (SM) (26.4 ± 5.4 years, 178.0 ± 6.5 cm, 85.2 ± 14.0 kg) completed the 5-day protocol, including daily physical exertion and 48 h of restricted sleep and caloric intake. Each morning subjects completed a fasted blood draw followed by Cognition, a 10-part cognitive test battery assessing executive function. SMs were grouped into tertiles [low (L-), moderate (M-), high (H-)] based on Connor Davidson Resilience Score (RES) and V˙O_2peak (FIT). Repeated measures ANOVA were run to analyze the effect of day on cognitive performance and biomarker concentration. Separate two-way mixed ANOVAs were run to determine the interaction of group by day on cognitive function. Friedman test with Bonferroni-corrected pairwise comparisons were used if assumptions for ANOVA were not met. Associations between changes in biomarkers and cognitive performance were analyzed using parametric and non-parametric correlation coefficients.

RESULTS

SMOS reduced SM vigilance -11.3% (p < 0.001) and working memory -5.6% (p = 0.015), and increased risk propensity +9.5% (p = 0.005). H-RES and H-FIT SMs demonstrated stable vigilance across SMOS (p > 0.05). Vigilance was compromised during SMOS in L- and M-RES (p = 0.007 and p = 0.001, respectively) as well as L- and M-FIT (p = 0.001 and p = 0.031, respectively). SMOS reduced circulating concentrations of α-klotho -7.2% (p = 0.004), NPY -6.4% (p = 0.001), and IGF-I -8.1% (p < 0.001) from baseline through the end of the protocol. BDNF declined -19.2% after the onset of sleep and caloric restriction (p = 0.005) with subsequent recovery within 48 h. Oxytocin remained stable (p > 0.05). Several modest associations between neuroendocrine biomarkers and cognitive performance were identified.

CONCLUSION

This study demonstrates H-FIT and H-RES may buffer the impact of SMOS on vigilance. SMOS negatively impacted circulating neuroendocrine biomarkers. While BDNF returned to baseline concentrations by the end of the 5 d protocol, NPY, IGF-I, and α-klotho may require a longer recovery period. These data suggest that the military may benefit by training and/or selection processes targeting at augmenting trait resilience and aerobic fitness for increased readiness.

Klotho, PTSD, and advanced epigenetic age in cortical tissue

This study examined the klotho (KL) longevity gene polymorphism rs9315202 and psychopathology, including posttraumatic stress disorder (PTSD), depression, and alcohol-use disorders, in association with advanced epigenetic age in three postmortem cortical tissue regions: dorsolateral and ventromedial prefrontal cortices and motor cortex. Using data from the VA National PTSD Brain Bank (n = 117), we found that rs9315202 interacted with PTSD to predict advanced epigenetic age in motor cortex among the subset of relatively older (>=45 years), white non-Hispanic decedents (corrected p = 0.014, n = 42). An evaluation of 211 additional common KL variants revealed that only variants in linkage disequilibrium with rs9315202 showed similarly high levels of significance. Alcohol abuse was nominally associated with advanced epigenetic age in motor cortex (p = 0.039, n = 114). The rs9315202 SNP interacted with PTSD to predict decreased KL expression via DNAm age residuals in motor cortex among older white non-Hispanics decedents (indirect β = -0.198, p = 0.027). Finally, in dual-luciferase enhancer reporter system experiments, we found that inserting the minor allele of rs9315202 in a human kidney cell line HK-2 genomic DNA resulted in a change in KL transcriptional activities, likely operating via long noncoding RNA in this region. This was the first study to examine multiple forms of psychopathology in association with advanced DNA methylation age across several brain regions, to extend work concerning the association between rs9315202 and advanced epigenetic to brain tissue, and to identify the effects of rs9315202 on KL gene expression. KL augmentation holds promise as a therapeutic intervention to slow the pace of cellular aging, disease onset, and neuropathology, particularly in older, stressed populations.

Association of Klotho-VS Heterozygosity With Risk of Alzheimer Disease in Individuals Who Carry APOE4

Importance

Identification of genetic factors that interact with the apolipoprotein e4 (APOE4) allele to reduce risk for Alzheimer disease (AD) would accelerate the search for new AD drug targets. Klotho-VS heterozygosity (KL-VSHET+ status) protects against aging-associated phenotypes and cognitive decline, but whether it protects individuals who carry APOE4 from AD remains unclear.

Objectives

To determine if KL-VSHET+ status is associated with reduced AD risk and β-amyloid (Aβ) pathology in individuals who carry APOE4.

Design, Setting, and Participants

This study combined 25 independent case-control, family-based, and longitudinal AD cohorts that recruited referred and volunteer participants and made data available through public repositories. Analyses were stratified by APOE4 status. Three cohorts were used to evaluate conversion risk, 1 provided longitudinal measures of Aβ CSF and PET, and 3 provided cross-sectional measures of Aβ CSF. Genetic data were available from high-density single-nucleotide variant microarrays. All data were collected between September 2015 and September 2019 and analyzed between April 2019 and December 2019.

Main Outcomes and Measures

The risk of AD was evaluated through logistic regression analyses under a case-control design. The risk of conversion to mild cognitive impairment (MCI) or AD was evaluated through competing risks regression. Associations with Aβ, measured from cerebrospinal fluid (CSF) or brain positron emission tomography (PET), were evaluated using linear regression and mixed-effects modeling.

Results

Of 36 530 eligible participants, 13 782 were excluded for analysis exclusion criteria or refusal to participate. Participants were men and women aged 60 years and older who were non-Hispanic and of Northwestern European ancestry and had been diagnosed as being cognitively normal or having MCI or AD. The sample included 20 928 participants in case-control studies, 3008 in conversion studies, 556 in Aβ CSF regression analyses, and 251 in PET regression analyses. The genotype KL-VSHET+ was associated with reduced risk for AD in individuals carrying APOE4 who were 60 years or older (odds ratio, 0.75 [95% CI, 0.67-0.84]; P = 7.4 × 10-7), and this was more prominent at ages 60 to 80 years (odds ratio, 0.69 [95% CI, 0.61-0.79]; P = 3.6 × 10-8). Additionally, control participants carrying APOE4 with KL-VS heterozygosity were at reduced risk of converting to MCI or AD (hazard ratio, 0.64 [95% CI, 0.44-0.94]; P = .02). Finally, in control participants who carried APOE4 and were aged 60 to 80 years, KL-VS heterozygosity was associated with higher Aβ in CSF (β, 0.06 [95% CI, 0.01-0.10]; P = .03) and lower Aβ on PET scans (β, -0.04 [95% CI, -0.07 to -0.00]; P = .04).

Conclusions and Relevance

The genotype KL-VSHET+ is associated with reduced AD risk and Aβ burden in individuals who are aged 60 to 80 years, cognitively normal, and carrying APOE4. Molecular pathways associated with KL merit exploration for novel AD drug targets. The KL-VS genotype should be considered in conjunction with the APOE genotype to refine AD prediction models used in clinical trial enrichment and personalized genetic counseling.

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.

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.

KL∗VS heterozygosity reduces brain amyloid in asymptomatic at-risk APOE∗4 carriers

KLOTHO∗VS heterozygosity (KL∗VS^HET+) was recently shown to be associated with reduced risk of Alzheimer's disease (AD) in APOE∗4 carriers. Additional studies suggest that KL∗VS^HET+ protects against amyloid burden in cognitively normal older subjects, but sample sizes were too small to draw definitive conclusions. We performed a well-powered meta-analysis across 5 independent studies, comprising 3581 pre-clinical participants ages 60-80, to investigate whether KL∗VS^HET+ reduces the risk of having an amyloid-positive positron emission tomography scan. Analyses were stratified by APOE∗4 status. KL∗VS^HET+ reduced the risk of amyloid positivity in APOE∗4 carriers (odds ratio = 0.67 [0.52-0.88]; p = 3.5 × 10^-3), but not in APOE∗4 non-carriers (odds ratio = 0.94 [0.73-1.21]; p = 0.63). The combination of APOE∗4 and KL∗VS genotypes should help enrich AD clinical trials for pre-symptomatic subjects at increased risk of developing amyloid aggregation and AD. KL-related pathways may help elucidate protective mechanisms against amyloid accumulation and merit exploration for novel AD drug targets. Future investigation of the biological mechanisms by which KL interacts with APOE∗4 and AD are warranted.

Intermittent fasting enhances long-term memory consolidation, adult hippocampal neurogenesis, and expression of longevity gene Klotho

Daily calorie restriction (CR) and intermittent fasting (IF) enhance longevity and cognition but the effects and mechanisms that differentiate these two paradigms are unknown. We examined whether IF in the form of every-other-day feeding enhances cognition and adult hippocampal neurogenesis (AHN) when compared to a matched 10% daily CR intake and ad libitum conditions. After 3 months under IF, female C57BL6 mice exhibited improved long-term memory retention. IF increased the number of BrdU-labeled cells and neuroblasts in the hippocampus, and microarray analysis revealed that the longevity gene Klotho (Kl) was upregulated in the hippocampus by IF only. Furthermore, we found that downregulating Kl in human hippocampal progenitor cells led to decreased neurogenesis, whereas Kl overexpression increased neurogenesis. Finally, histological analysis of Kl knockout mice brains revealed that Kl is required for AHN, particularly in the dorsal hippocampus. These data suggest that IF is superior to 10% CR in enhancing memory and identifies Kl as a novel candidate molecule that regulates the effects of IF on cognition likely via AHN enhancement.

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.

Klotho gene polymorphism, brain structure and cognition in early-life development

Variation in the klotho gene is linked to differences in health outcomes: klotho allele KL-VS heterozygosity is associated with longevity, better cognition and greater right frontal grey matter volume in late life. Contradicting reports, however, suggest that KL-VS’s effect on health might be age-dependent. Here we examine the relationship between KL-VS genotype, cognition and brain structure in childhood and adolescence. We hypothesized that KL-VS has early influences on cognitive and brain development. We investigated the associations of KL-VS carrier status with cognition and brain morphology in a cohort of 1387 children and adolescents aged 3–21 years, examining main effects and interactions between age, sex and socioeconomic circumstance. KL-VS had no main effect on either cognition or brain structure, though there was a significant KL-VS × age interaction for cognition (specifically executive function, attention, episodic memory, and general cognition), total grey matter and total brain volume. KL-VS heterozygotes had better cognition than non-carriers before age 11, but lower cognition after age 11. Heterozygotes had smaller brains than non-carriers did in early childhood. Sex moderated the association between KL-VS and white matter volume. Among girls, KL-VS heterozygotes had smaller white matter volumes than non-carriers. Among boys, heterozygotes had greater white matter volumes than non-carriers. However, a replication in a cohort of 2306 children aged 6–12 years showed no significant associations. In contrast to findings in late life, these results show that KL-VS does not have a main effect on cognition and brain structure. Furthermore, KL-VS’s influence may depend on age and sex.

Understanding brain resilience in superagers: a systematic review

PURPOSE

Superagers are older adults presenting excellent memory performance that may reflect resilience to the conventional pathways of aging. Our contribution aims to shape the evidence body of the known distinctive biomarkers of superagers and their connections with the Brain and Cognitive Reserve and Brain Maintenance concepts.

METHODS

We performed a systematic literature search in PubMed and ScienceDirect with no limit on publication date for studies that evaluated potential biomarkers in superagers classified by validated neuropsychological tests. Methodological quality was assessed using the QUADAS-2 tool.

RESULTS

Twenty-one studies were included, the majority in neuroimaging, followed by histological, genetic, cognition, and a single one on blood plasma analysis. Superagers exhibited specific regions of cortical preservation, rather than global cortical maintenance, standing out the anterior cingulate and hippocampus regions. Both superagers and controls showed similar levels of amyloid deposition. Moreover, the functional oscillation patterns in superagers resembled those described in young adults. Most of the quality assessment for the included studies showed medium risks of bias.

CONCLUSION

This systematic review supports selective cortical preservation in superagers, comprehending regions of the default mode, and salience networks, overlapped by stronger functional connectivity. In this context, the anterior cingulate cortex is highlighted as an imaging and histologic signature of these subjects. Besides, the biomarkers included pointed out that the Brain and Cognitive Reserve and Brain Maintenance concepts are independent and complementary in the superagers' setting.

PTSD and the klotho longevity gene: Evaluation of longitudinal effects on inflammation via DNA methylation

BACKGROUND

Longevity gene klotho (KL) is associated with age-related phenotypes including lifespan, cardiometabolic disorders, cognition, and brain morphology, in part, by conferring protection against inflammation. We hypothesized that the KL/inflammation association might be altered in the presence of psychiatric stress and operate via epigenetic pathways. We examined KL polymorphisms, and their interaction with posttraumatic stress disorder (PTSD) symptoms, in association with KL DNA methylation in blood. We further examined KL DNA methylation as a predictor of longitudinal changes in a peripheral biomarker of inflammation (C-reactive protein; CRP).

METHODS

The sample comprised 309 white non-Hispanic military veterans (93.5 % male; mean age: 32 years, range: 19-65; 30 % PTSD per structured diagnostic interview); 111 were reassessed approximately two years later.

RESULTS

Analyses revealed a methylation quantitative trait locus at rs9527025 (C370S, previously implicated in numerous studies of aging) in association with a Cytosine-phosphate-Guanine site (cg00129557; B = -.65, p =  1.29 X 10^-20), located within a DNase hypersensitivity site in the body of KL. There was also a rs9527025 x PTSD severity interaction (B = .004, p = .035) on methylation at this locus such that the minor allele was associated with reduced cg00129557 methylation in individuals with few or no PTSD symptoms while this effect was attenuated in those with elevated levels of PTSD. Path models revealed that methylation at cg00129557 was inversely associated with CRP over time (B = -.14, p = .005), controlling for baseline CRP. There was also an indirect effect of rs9527025 X PTSD on subsequent CRP via cg00129557 methylation (indirect B = -.002, p = .033).

CONCLUSIONS

Results contribute to our understanding of the epigenetic correlates of inflammation in PTSD and suggest that KL methylation may be a mechanism by which KL genotype confers risk vs. resilience to accelerated aging in those experiencing traumatic stress.

Identification of the cleavage sites leading to the shed forms of human and mouse anti-aging and cognition-enhancing protein Klotho

Klotho is an age-extending, cognition-enhancing protein found to be down-regulated in aged mammals when age-related diseases start to appear. Low levels of Klotho occur in neurodegenerative diseases, kidney disease and many cancers. Many normal and pathologic processes involve the proteolytic shedding of membrane proteins. Transmembrane (TM) Klotho contains two homologous domains, KL1 and KL2 with homology to glycosidases. After shedding by ADAM 10 and 17, a shed Klotho isoform is released into serum and urine by the kidney, and into the CSF by the choroid plexus. We previously reported that human Klotho contains two major cleavage sites. However, the exact cleavage site responsible for the cleavage between the KL1 and KL2 domains remains unknown for the human Klotho, and both sites are unknown for mouse Klotho. In this study, we aimed to identify the cleavage sites leading to the shed forms of human and mouse Klotho. Mutations in the region close to the TM domain of mouse Klotho result in the reduced shedding of the 130 kD (KL1+KL2) and 70 kD (KL1) fragments, suggesting that the cleavage site lies within the mutated region. We further identified the cleavage sites responsible for the cleavage between KL1 and KL2 of human and mouse Klotho. Moreover, mutated Klotho proteins have similar subcellular localization patterns as wild type Klotho. Finally, in an FGF23 functional assay, all Klotho mutants with a nine amino acid deletion can also function as an FGFR1 co-receptor for FGF23 signaling, however, the signaling activity was greatly reduced. The study provides new and important information on Klotho shedding, and paves the way for studies aimed to distinguish between the distinct roles of the various isoforms of Klotho.

Age-Related Differences in Brain Morphology and the Modifiers in Middle-Aged and Older Adults

Brain structural morphology differs with age. This study examined age-differences in surface-based morphometric measures of cortical thickness, volume, and surface area in a well-defined sample of 8137 generally healthy UK Biobank participants aged 45-79 years. We illustrate that the complexity of age-related brain morphological differences may be related to the laminar organization and regional evolutionary history of the cortex, and age of about 60 is a break point for increasing negative associations between age and brain morphology in Alzheimer's disease (AD)-prone areas. We also report novel relationships of age-related cortical differences with individual factors of sex, cognitive functions of fluid intelligence, reaction time and prospective memory, cigarette smoking, alcohol consumption, sleep disruption, genetic markers of apolipoprotein E, brain-derived neurotrophic factor, catechol-O-methyltransferase, and several genome-wide association study loci for AD and further reveal joint effects of cognitive functions, lifestyle behaviors, and education on age-related cortical differences. These findings provide one of the most extensive characterizations of age associations with major brain morphological measures and improve our understanding of normal structural brain aging and its potential modifiers.

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.

Activity-dependent neuronal Klotho enhances astrocytic aerobic glycolysis

Mutations of the β-glucuronidase protein α-Klotho have been associated with premature aging, and altered cognitive function. Although highly expressed in specific areas of the brain, Klotho functions in the central nervous system remain unknown. Here, we show that cultured hippocampal neurons respond to insulin and glutamate stimulation by elevating Klotho protein levels. Conversely, AMPA and NMDA antagonism suppress neuronal Klotho expression. We also provide evidence that soluble Klotho enhances astrocytic aerobic glycolysis by hindering pyruvate metabolism through the mitochondria, and stimulating its processing by lactate dehydrogenase. Pharmacological inhibition of FGFR1, Erk phosphorylation, and monocarboxylic acid transporters prevents Klotho-induced lactate release from astrocytes. Taken together, these data suggest Klotho is a potential new player in the metabolic coupling between neurons and astrocytes. Neuronal glutamatergic activity and insulin modulation elicit Klotho release, which in turn stimulates astrocytic lactate formation and release. Lactate can then be used by neurons and other cells types as a metabolic substrate.

The Transcriptional Landscape of Microglial Genes in Aging and Neurodegenerative Disease

Microglia, the brain-resident myeloid cells, are strongly implicated in Alzheimer's disease (AD) pathogenesis by human genetics. However, the mechanisms by which microglial gene expression is regulated in a region-specific manner over the course of normal aging and in neurodegenerative disease are only beginning to be deciphered. Herein, we used a specific marker of microglia (TMEM119) and a cell-type expression profiling tool (CellMapper) to identify a human microglial gene expression module. Surprisingly, we found that microglial module genes are robustly expressed in several healthy human brain regions known to be vulnerable in AD, in addition to other regions affected only later in disease or spared in AD. Surveying the microglial gene set for differential expression over the lifespan in mouse models of AD and a related tauopathy revealed that the majority of microglial module genes were significantly upregulated in cortex and hippocampus as a function of age and transgene status. Extending these results, we also observed significant upregulation of microglial module genes in several AD-affected brain regions in addition to other regions using postmortem brain tissue from human AD samples. In pathologically confirmed AD cases, we found preliminary evidence that microglial genes may be dysregulated in a sex-specific manner. Finally, we identified specific and significant overlap between the described microglial gene set—identified by unbiased co-expression analysis—and genes known to impart risk for AD. Our findings suggest that microglial genes show enriched expression in AD-vulnerable brain regions, are upregulated during aging and neurodegeneration in mice, and are upregulated in pathologically affected brain regions in AD. Taken together, our data-driven findings from multiple publicly accessible datasets reemphasize the importance of microglial gene expression alterations in AD and, more importantly, suggest that regional and sex-specific variation in microglial gene expression may be implicated in risk for and progression of neurodegenerative disease.

Peripheral levels of the anti-aging hormone Klotho in patients with depression

Klotho is a humoral factor with pleiotropic effects. Most notably, Klotho deficiency is associated with a phenotype comprising organ manifestations accompanying aging including atherosclerosis and cognitive impairment. Research on the role of Klotho in affective disorder is scarce, which is surprising in light of the fact that depression is associated with accelerated cellular aging as well as aging-related phenotypes and comorbidity observed in Klotho deficiency. Soluble α-Klotho (sKlotho) serum levels in patients with a major depressive episode and either undergoing electroconvulsive therapy (n = 16) or a monotherapy with an antidepressant (n = 37) were investigated. We measured the sKlotho serum levels in those patients before and after treatment and compared the baseline levels with those of age-matched healthy controls (n = 39). No group differences were found between the baseline sKlotho levels of patients and controls (573.5 pg/ml vs. 563.8 pg/ml; p = 0.80) and between pre- and post-treatment in the patients with depression (563.8 pg/ml vs. 561.8 pg/ml; p = 0.15), when treated either with electroconvulsive therapy or antidepressant. The major limitation of our study might be that peripheral material such as serum might not reliably reflect processes in the central nervous system. In sum, this first study on peripheral sKlotho levels in a clinical sample cannot confirm a global Klotho dysregulation in depression as it has been already suggested by others. Nonetheless, further preclinical and clinical studies on the involvement of Klotho in affective disorders should be carried out.

KLOTHO heterozygosity attenuates APOE4-related amyloid burden in preclinical AD

OBJECTIVE

To examine whether the KLOTHO gene variant KL-VS attenuates APOE4-associated β-amyloid (Aβ) accumulation in a late-middle-aged cohort enriched with Alzheimer disease (AD) risk factors.

METHODS

Three hundred nine late-middle-aged adults from the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center were genotyped to determine KL-VS and APOE4 status and underwent CSF sampling (n = 238) and/or 11C-Pittsburgh compound B (PiB)-PET imaging (n = 183). Covariate-adjusted regression analyses were used to investigate whether APOE4 exerted expected effects on Aβ burden. Follow-up regression analyses stratified by KL-VS genotype (i.e., noncarrier vs heterozygous; there were no homozygous individuals) evaluated whether the influence of APOE4 on Aβ was different among KL-VS heterozygotes compared to noncarriers.

RESULTS

APOE4 carriers exhibited greater Aβ burden than APOE4-negative participants. This effect was stronger in CSF (t = -5.12, p < 0.001) compared with PiB-PET (t = 3.93, p < 0.001). In the stratified analyses, this APOE4 effect on Aβ load was recapitulated among KL-VS noncarriers (CSF: t = -5.09, p < 0.001; PiB-PET: t = 3.77, p < 0 .001). In contrast, among KL-VS heterozygotes, APOE4-positive individuals did not exhibit higher Aβ burden than APOE4-negative individuals (CSF: t = -1.03, p = 0.308; PiB-PET: t = 0.92, p = 0.363). These differential APOE4 effects remained after KL-VS heterozygotes and noncarriers were matched on age and sex.

CONCLUSION

In a cohort of at-risk late-middle-aged adults, KL-VS heterozygosity was associated with an abatement of APOE4-associated Aβ aggregation, suggesting KL-VS heterozygosity confers protections against APOE4-linked pathways to disease onset in AD.

Klotho gene polymorphisms are associated with healthy aging and longevity: Evidence from a meta-analysis

Klotho gene polymorphisms have been implicated in healthy aging, but inconsistences in findings from previous case-control studies have raised concerns regarding the associations between KLOTHO gene polymorphisms and susceptibility to aging-related diseases and longevity. Hence, this meta-analysis was performed. We assessed the associations between two polymorphisms (G-395 A/rs1207568 and F352 V/rs9536314) and five parameters (urolithiasis, cognitive impairment, cardiovascular disease, cancer, and longevity) by calculating pooled odds ratios with 95% confidence intervals. According to the pooled results, the G allele of the G-395 A polymorphism conferred a significantly higher risk of urolithiasis; G-395 A was related to the susceptibility to cardiovascular disease under allele, dominant, and recessive models. There was no significant association between the G-395 A polymorphism and cognitive impairment among the elderly. The F allele of the F352 V polymorphism protected against breast and ovarian cancer susceptibility. Interestingly, based on the results of the subgroup analysis, the F352 V polymorphism was associated with the overall risk of neoplasms in BRCA1 mutation carriers but not in BRCA2 mutation carriers. Moreover, the F allele played a protective role in determining human longevity. In conclusion, Klotho G-395 A polymorphisms were associated with urolithiasis and cardiovascular disease but not with cognitive impairment. Additionally, Klotho F352 V polymorphisms were associated with cancers and longevity.

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.

Klotho, the Key to Healthy Brain Aging?

Brain expression of klotho was first described with the initial discovery of the klotho gene. The prominent age-regulating effects of klotho are attributed to regulation of ion homeostasis through klotho function in the kidney. However, recent advances identified brain functions and cell populations, including adult hippocampal neural progenitors, which require klotho. As well, both human correlational studies and mouse models of disease show that klotho is protective against multiple neurological and psychological disorders. This review focuses on current knowledge as to how the klotho protein effects the brain.

Klotho protein in neurodegenerative disorders

The Klotho protein is a recently discovered protein and its overexpression is associated with life extension. Klotho deficiency or silencing of the Klotho gene in mice leads to an accelerated aging and short life, whereas overexpression of Klotho in mice extends lifespan. Klotho participates in many metabolic pathways and is highly expressed in the kidneys, the choroid plexus and neurons. It plays a key role in the calcium-phosphate metabolism, remyelination, and cognitive processes. The present paper is a short review of the literature on the role of Klotho in neurodegenerative disorders, with special attention paid to multiple sclerosis. The neuroprotective function of Klotho is also reported. It is also important to consider potential clinical applications of Klotho that might be useful in the treatment of many diseases.

Electroconvulsive therapy enhances the anti-ageing hormone Klotho in the cerebrospinal fluid of geriatric patients with major depression

Klotho is a humoral factor with pleiotropic effects. Most notably, Klotho deficiency is associated with a phenotype comprising organ manifestations accompanying aging including atherosclerosis and cognitive impairment. Research on the role of Klotho in affective disorder is scarce, which is surprising in light of the fact that depression is associated with accelerated cellular aging as well as aging-related phenotypes and comorbidity observed in Klotho deficiency. On these grounds we investigated Klotho levels in the cerebrospinal fluid (CSF) and serum of eight geriatric patients undergoing electroconvulsive therapy (ECT) for severe depression. We hypothesize that ECT as a highly effective antidepressant treatment leads enhances Klotho levels. We found a significant difference between pre- and post-ECT CSF Klotho (792.5pg/ml vs. 991.3pg/ml, p=0.0020), but no difference in serum Klotho (602.5 vs. 594.3, p=0.32). Moreover, CSF Klotho increase positively correlated with the number of single ECT sessions that were performed in each patient (F1, 6)=7.84, p=0.031). Conjointly, the results of our exploratory study with a small sample size suggest a central nervous system-specific impact of ECT on Klotho, which may in turn partake in mediating the antidepressant effect of ECT. We suggest the modulation of neuroinflammatory processes, which have been ascribed pathophysiological relevance within the conceptual framework of the neuroinflammation hypothesis of depression, through ECT as a potential mechanism by which Klotho is enhanced in response to treatment. Further preclinical and clinical investigation should aim for a precise identification of the role of Klotho in depressive disorder.

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.

Systemic klotho is associated with KLOTHO variation and predicts intrinsic cortical connectivity in healthy human aging

Cognitive decline is a major biomedical challenge as the global population ages. Elevated levels of the longevity factor klotho suppress aging, enhance cognition, and promote synaptic plasticity and neural resilience against aging and Alzheimer’s disease (AD)-related pathogenic proteins. Here, we examined the relationship between human genetic variants of KLOTHO and systemic klotho levels – and assessed neuroanatomic correlates of serum klotho in a cohort of healthy older adults. Serum klotho levels were increased with KL-VS heterozygosity, as anticipated. We report, for the first time, that serum klotho levels were paradoxically decreased with KL-VS homozygosity. Further, we found that higher serum klotho levels were associated with measures of greater intrinsic connectivity in key functional networks of the brain vulnerable to aging and AD such as the fronto-parietal and default mode networks. Our findings suggest that elevated klotho promotes a resilient brain, possibly through increased network connectivity of critical brain regions.