GWAS META-analysis followed by MENDELIAN randomisation revealed potential control mechanisms for circulating α-klotho levels

Genetically determined α-Klotho levels and causal association with aging-related lung diseases

BACKGROUND

Abnormal α-Klotho (KL) levels play an essential role in the pathogenesis of aging-related lung diseases. However, the correlation between circulating KL levels and aging-related lung diseases has not been determined. This study aimed to determine whether circulating KL levels causally affect aging-related lung diseases using Mendelian randomization (MR).

METHODS

Five KL-associated Single-nucleotide polymorphisms (SNPs) were analyzed using two-sample MR to assess their effects on three aging-related lung diseases: idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), and lung cancer.

RESULTS

Based on a main casual effects model with MR analyses by the inverse variance weighted (IVW) method including multiplicative random-effects model (IVW-mre) and fixed-effects inverse variance-weighted model (IVW-fe), genetically predicted circulating KL levels were negatively related with risk of IPF (Odds ratio (ORIVW-mre), 0.999, 95 % CI, 0.999-1.000, PIVW-mre = 0.008; OR IVW-fe, 0.999, 95 % CI, 0.999-1.000, PIVW-fe = 0.042). Inversely, the circulating levels of KL displayed no clear association with COPD and lung cancer. No pleiotropy was detected.

CONCLUSIONS

Genetically predicted circulating KL was causally associated with a lower risk of IPF, suggesting a protective effect in preventing IPF risk. Therefore, KL may be a promising target for the prevention and therapeutic intervention in patients with IPF.

Short sleep duration and daytime outdoor activities effects on adolescents mental health: A stress susceptibility-recovery model analysis

BACKGROUND

Mental health disorders are a growing public health challenge globally. This study aimed to utilize the Stress Susceptibility-Recovery Model to identify the relationship between sleep duration, daytime outdoor activities, and major mental health outcomes among adolescents.

METHODS

Data from the Yunnan Students' Common Disease Survey was analyzed. Multi-factorial logistic regression assessed the impact of each variable on mental health, while subgroup analyses and interaction tests examined the stability of the association between sleep duration, daytime outdoor activity, and mental health. Mendelian Randomization analysis assessed causal effects.

RESULTS

The analysis included 204,158 participants aged 12-18 from 953 surveillance schools. After adjusting for covariates, the prevalence of depressive mood increased from 18.81 % (12-13 years) to 24.89 % (16-18 years); Females had a higher prevalence than males (1:1.36). Senior high school students (26.04 %) had a significantly higher rate than junior high school (21.41 %), and vocational high school students (18.42 %). Students with <2 h of daytime outdoor activity had a higher prevalence of depressive mood (24.40 %) compared to those with 2 or more hours of daytime outdoor activity (19.96 % for 2 h and 19.70 % for 3 or more hours). Short sleep duration mediated the association between reduced daytime outdoor activity and increased depressive mood or affective disorders risk, supporting the Stress Susceptibility-recovery Model.

CONCLUSIONS

Sleep duration and daytime outdoor activity were key determinants of emotional well-being, considering aging and gender disparities.

LIMITATIONS

Potential sampling bias due to differences in baseline characteristics between participants with and without missing data.

The association between low-concentration heavy metal exposure and chronic kidney disease risk through α-klotho

Although the association between pollution exposure and chronic kidney disease (CKD) has been explored, previous studies have focused on specific effects observed via in vitro or animal experiments. We first conducted a priority screening of pollutants for population CKD risk by using machine learning approaches. We then used the National Health and Nutrition Examination Survey (NHANES) 2007-2016 data from 2415 adults aged 40 years and over to study the joint effects of low-concentration metal exposure and the mediating effects of α-klotho by using Bayesian kernel machine regression (BKMR) and mediation analyses. Priority screening revealed that cadmium (Cd), mercury (Hg), lead (Pb), and thallium (Tl) were associated with the highest risk of developing CKD. The BKMR model revealed a negative joint effect of mixed-metal exposure on CKD risk. Tl presented the highest posterior inclusion probability (PIP) of 1.0000, followed by Pb, with a PIP of 0.6080. Significant mediating effects of α-klotho on Hg-CKD associations were observed. Mendelian randomization demonstrated that a high level of α-klotho is associated with a decreased risk of developing CKD. This is the first study to reveal the risk prioritization of various pollutants in CKD patients, as well as the coexposure effects of metals. Our study also provides insight into the potential mechanisms underlying the association between metal exposure and CKD risk.

Klotho antiaging protein: molecular mechanisms and therapeutic potential in diseases

Klotho, initially introduced as an anti-aging protein, is expressed in the brain, pancreas, and most prominently in the kidney. The two forms of Klotho (membrane-bound and soluble form) have diverse pharmacological functions such as anti-inflammatory, anti-oxidative, anti-fibrotic, tumour-suppressive etc. The membrane-bound form plays a pivotal role in maintaining kidney homeostasis by regulating fibroblast growth factor 23 (FGF 23) signalling, vitamin D metabolism and phosphate balance. Klotho deficiency has been linked with significantly reduced protection against various kidney pathological phenotypes, including diabetic kidney disease (DKD), which is a major cause of chronic kidney disease leading to end-stage kidney disease. Owing to the pleiotropic actions of klotho, it has shown beneficial effects in DKD by tackling the complex pathophysiology and reducing kidney inflammation, oxidative stress, as well as fibrosis. Moreover, the protective effect of klotho extends beyond DKD in other pathological conditions, including cardiovascular diseases, alzheimer's disease, cancer, inflammatory bowel disease, and liver disease. Therefore, this review summarizes the relationship between Klotho expression and various diseases with a special emphasis on DKD, the distinct mechanisms and the potential of exogenous Klotho supplementation as a therapeutic strategy. Future research into exogenous Klotho could unravel novel treatment avenues for DKD and other diseases.

Effects of Klotho in epilepsy: An umbrella review of observational and mendelian randomization studies

BACKGROUND

Klotho is a geroprotective protein which has been recognized for its anti-aging properties. Pre-clinical evidence suggested that boosting Klotho might hold therapeutic potential in ageing and disease. Epilepsy is a neurological disorder characterized by its recurrent seizures. The complex interplay between Klotho and epilepsy has not been elucidated. The main objective was to investigate the role of Klotho in epilepsy with combination of observational and mendelian randomization (MR) studies.

METHODS

The observational data set comprised 13,766 adults who were aged 20-80 years from the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2016. We used weighted multivariable-adjusted logistic regression models to examine the association between Klotho and epilepsy. We also applied MR to discern if a causal link is present between Klotho and epilepsy.

RESULTS

In NHANES study, the incidence of epilepsy tended to decline with an increase of Klotho levels after covariate adjustments. Klotho was identified to have causal effects on epilepsy. MR analyses revealed that higher transformed Klotho (by rank-based inverse normal transformation) levels were correlated with a higher likelihood of developing generalized epilepsy, lesion-negative focal epilepsy, and focal epilepsy, indicating that higher Klotho concentrations were associated with reduced risks of epilepsy. The sensitivity analyses upheld these consistent relationships.

CONCLUSIONS

Our research, encompassing comprehensive NHANSE analysis and MR methods, revealed that an increase in Klotho levels was associated with a reduced risk of epilepsy, suggesting that increasing or restoring Klotho might play a protective role and offer new anti-aging therapeutic potential in epilepsy.

Association between sex steroid hormones and α-klotho: Results from the NHANES 2013-2016 and Mendelian randomization study

PURPOSE

This study aimed to explore the association and causal links between sex steroid hormones and the anti-aging protein α-Klotho, extending to investigate the mediation effects of potential mediators.

METHODS

Based on data from the National Health and Nutrition Examination Survey (NHANES) 2013-2016, this study performed weighted multivariable-adjusted logistic regression to evaluate the association between sex steroid hormones and α-Klotho. Then, utilizing summary data from genome-wide association studies (GWAS), a bidirectional two-sample Mendelian randomization (MR) was conducted to assess the causal relationship between sex steroid hormones and α-Klotho. Finally, mediation analysis was conducted to delineate the influence of five identified potential mediators on the sex steroid hormones-α-Klotho association.

RESULTS

In men, significant positive correlations with α-Klotho were consistent across both unadjusted and fully adjusted models for total testosterone (TT), bio-available testosterone (Bio-T), estradiol (E2) and sex hormone-binding globulin (SHBG) (Model 3: TT: β = 3.54, 95 % CI: 1.63-5.44, P = 0.0003; Bio-T: β = 1.74, 95 % CI: 0.73-2.74, P = 0.0007; E2: β = 0.25, 95 % CI: 0.11-0.38, P = 0.0003; SHBG: β = 0.95, 95 % CI: 0.63-1.27, P < 0.0001); In premenopausal women, we detected a potential nonlinear relationship between TT levels and α-Klotho, with α-Klotho levels rising to a peak at a TT level of 72.2 ng/mL, after which they declined. Furthermore, results from MR analyses reaffirmed positive associations of TT and Bio-T with α-Klotho in men (TT: β = 3.54, 95 % CI: 1.63-5.44, P = 0.0003; Bio-T: β = 1.74, 95 % CI: 0.73-2.74, P = 0.0007). Finally, significant mediation effects were observed for uric acid (β = 0.27, 95 % CI: 0.15-0.67, P < 0.0001) and creatinine (β = 0.05, 95 % CI: 0.01-0.16, P = 0.0060), accounting for 26.7 % and 5.23 % of the total mediation effect, respectively.

CONCLUSION

In conclusion, our results demonstrate that both TT and Bio-T enhance the expression of α-Klotho in men. The positive association observed may be partly mediated by uric acid and creatinine.

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

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

Causal association between circulating α-Klotho levels and venous thromboembolism: a two-sample Mendelian randomization study

BACKGROUND

α-Klotho may involve in the occurrence and development of venous thromboembolism (VTE). However, the underlying relationship between circulating α-Klotho levels and VTE is still unclear.

METHODS

This two-sample Mendelian Randomization (MR) study aims to explore the causal associations of circulating α-Klotho levels with different types of venous thromboembolism. Data of exposure and outcomes were extracted from the genome-wide association study (GWAS) of the MRC Integrative Epidemiology Unit (MRC-IEU). The fixed inverse variance weighted (IVW), MR-Egger, MR-Robust Adjusted Profile Score (RAPS) and the weighted-median methods were utilized to investigate the causal associations of circulating α-Klotho levels with different types of VTE. The effect size was expressed as odds ratios (ORs) and 95% confidence intervals (CIs), and the False Discovery Rate (FDR) test was used for correction. The MR scatter plot and leave-one-out test were used for sensitivity analysis. In addition, reverse causal associations were assessed.

RESULTS

IVW estimates suggested that an elevated circulating α-Klotho level was associated with lower odds of deep vein thrombosis (DVT) of lower extremities (OR = 0.992, 95%CI: 0.986-0.998, P = 0.0074), pulmonary embolism (PE) (OR = 0.474, 95%CI: 0.255-0.881, P = 0.0183), and DVT of lower extremities combined with PE (OR = 0.984, 95%CI: 0.971-0.997, P = 0.0175). However, after the FDR correction, only negatively causal association between circulating α-Klotho level and increased odds of lower-extremity DVT was statistically significant (FDR P = 0.0296). Also, there were no reverse causal associations between the circulating α-Klotho levels and different types of VTE (all P > 0.05). Additionally, both the MR scatter plots and leave-one-out test results showed that these causal associations were relatively robust.

CONCLUSION

An elevated circulating α-Klotho levels was associated with lower risk of DVT of lower extremities, PE, and DVT of lower extremities combined with PE, indicating α-Klotho has the potential to act as a target for early screening or treatment for VTE. However, the specific mechanism that α-Klotho influencing the occurrence of VTE still needed further exploration.

α-klotho reduces susceptibility to osteoarthritis: evidence from cross-sectional studies and Mendelian randomization

Background

Despite extensive research, the association between serum α-klotho levels and osteoarthritis (OA) remains unclear, predominantly relying on findings from OA mouse models. This study used data from the National Health and Nutrition Examination Survey (NHANES) to conduct a cross-sectional study examining the relationship between α-klotho and human OA. In addition, we used Mendelian randomization (MR) to genetically infer a causal relationship between serum α-klotho and the three OA subtypes.

Method

A cohort of 12,037 subjects from NHANES (2007-2016) was analyzed. Multivariate logistic regression was utilized to examine the association between α-klotho concentration and OA, alongside subgroup analysis and interaction tests. Additionally, a two-sample bi-directional MR analysis was conducted to evaluate the relationship between serum α-klotho and three OA subtypes, including all OA, hip OA, and knee OA, employing the inverse variance weighting (IVW) method as the primary approach.

Results

Following adjustment for covariates, a nonlinear negative correlation between serum α-klotho and OA was observed (OR=0.77; 95% CI, 0.68-0.88, p < 0.0001). The IVW method revealed that higher serum α-klotho levels were associated with decreased susceptibility to hip OA (OR = 0.92, 95% CI: 0.87-0.98, P = 9.64×10-3). However, MR analysis did not establish a causal relationship between serum α-klotho and OA or knee OA. Inverse MR also indicated that the three subtypes of OA do not causally affect serum α-klotho concentrations.

Conclusions

In cross-sectional studies, α-klotho showed a nonlinear negative correlation with OA. MR analysis of outcomes was not identical to cross-sectional studies.

Causal association of epigenetic aging and osteoporosis: a bidirectional Mendelian randomization study

BACKGROUND

The relationship between aging and osteoporosis is well established. However, the relationship between the body's physiological age, i.e. epigenetic age, and osteoporosis is not known. Our goal is to analyze the bidirectional causal relationship between epigenetic clocks and osteoporosis using a bidirectional Mendelian randomization study.

METHODS

We used SNPs closely associated with GrimAge, Hannum, PhenoAge, and HorvathAge in epigenetic age and SNPs closely associated with femoral neck bone mineral density, lumbar spine bone mineral density, and forearm bone mineral density as instrumental variables, respectively, using the inverse variance weighting method and several other MR methods to assess the bidirectional causal relationship between epigenetic age and osteoporosis.

RESULT

There was no evidence of a clear causal relationship of epigenetic age (GrimAge, Hannum, PhenoAge, and HorvathAge) on femoral neck bone mineral density, lumbar spine bone mineral density, and forearm bone mineral density. In reverse Mendelian randomization analysis showed a significant causal effect of lumbar spine bone mineral density on GrimAge: odds ratio (OR) = 0.692, 95% confidence interval (CI) = (0.538-0.890), p = 0.004. The results suggest that a decrease in lumbar spine bone mineral density promotes an acceleration of GrimAge.

CONCLUSION

There was no significant bidirectional causal relationship between epigenetic age and osteoporosis A decrease in lumbar spine bone density may lead to an acceleration of the epigenetic clock "GrimAge". Our study provides partial evidence for a bidirectional causal effect between epigenetic age and Osteoporosis.

Upstream and downstream regulators of Klotho expression in chronic kidney disease

Klotho is a critical protein that protects the kidney. Klotho is severely downregulated in chronic kidney disease (CKD), and its deficiency is implicated in the pathogenesis and progression of CKD. Conversely, an increase in Klotho levels results in improved kidney function and delays CKD progression, supporting the notion that modulating Klotho levels could represent a possible therapeutic strategy for CKD treatment. Nevertheless, the regulatory mechanisms responsible for the loss of Klotho remain elusive. Previous studies have demonstrated that oxidative stress, inflammation, and epigenetic modifications can modulate Klotho levels. These mechanisms result in a decrease in Klotho mRNA transcript levels and reduced translation, thus can be grouped together as upstream regulatory mechanisms. However, therapeutic strategies that aim to rescue Klotho levels by targeting these upstream mechanisms do not always result in increased Klotho, indicating the involvement of other regulatory mechanisms. Emerging evidence has shown that endoplasmic reticulum (ER) stress, the unfolded protein response, and ER-associated degradation also affect the modification, translocation, and degradation of Klotho, and thus are proposed to be downstream regulatory mechanisms. Here, we discuss the current understanding of upstream and downstream regulatory mechanisms of Klotho and examine potential therapeutic strategies to upregulate Klotho expression for CKD treatment.

B4GALNT3 regulates glycosylation of sclerostin and bone mass

BACKGROUND

Global sclerostin inhibition reduces fracture risk efficiently but has been associated with cardiovascular side effects. The strongest genetic signal for circulating sclerostin is in the B4GALNT3 gene region, but the causal gene is unknown. B4GALNT3 expresses the enzyme beta-1,4-N-acetylgalactosaminyltransferase 3 that transfers N-acetylgalactosamine onto N-acetylglucosaminebeta-benzyl on protein epitopes (LDN-glycosylation).

METHODS

To determine if B4GALNT3 is the causal gene, B4galnt3^-/- mice were developed and serum levels of total sclerostin and LDN-glycosylated sclerostin were analysed and mechanistic studies were performed in osteoblast-like cells. Mendelian randomization was used to determine causal associations.

FINDINGS

B4galnt3^-/- mice had higher circulating sclerostin levels, establishing B4GALNT3 as a causal gene for circulating sclerostin levels, and lower bone mass. However, serum levels of LDN-glycosylated sclerostin were lower in B4galnt3^-/- mice. B4galnt3 and Sost were co-expressed in osteoblast-lineage cells. Overexpression of B4GALNT3 increased while silencing of B4GALNT3 decreased the levels of LDN-glycosylated sclerostin in osteoblast-like cells. Mendelian randomization demonstrated that higher circulating sclerostin levels, genetically predicted by variants in the B4GALNT3 gene, were causally associated with lower BMD and higher risk of fractures but not with higher risk of myocardial infarction or stroke. Glucocorticoid treatment reduced B4galnt3 expression in bone and increased circulating sclerostin levels and this may contribute to the observed glucocorticoid-induced bone loss.

INTERPRETATION

B4GALNT3 is a key factor for bone physiology via regulation of LDN-glycosylation of sclerostin. We propose that B4GALNT3-mediated LDN-glycosylation of sclerostin may be a bone-specific osteoporosis target, separating the anti-fracture effect of global sclerostin inhibition, from indicated cardiovascular side effects.

FUNDING

Found in acknowledgements.

Circulating α-Klotho Levels in Relation to Cardiovascular Diseases: A Mendelian Randomization Study

BACKGROUND

Several studies have reported a protective role of circulating α-Klotho on cardiovascular diseases (CVD); however, the causality remains unclear. We aim to elucidate whether genetically predicted circulating α-Klotho levels were causally associated with the risk of coronary artery disease (CAD), atrial fibrillation (AF), heart failure (HF), stroke, ischemic stroke (IS), and IS subtypes.

METHODS

A two-sample Mendelian randomization (MR) study was designed, with 5 single-nucleotide polymorphisms associated with circulating α-Klotho levels utilized as instrumental variables. MR estimates on each CVD outcome derived from the fixed-effects inverse-variance weighted (IVW) approach in different data sources were combined by the fixed-effects meta-analysis approach, complemented by several sensitivity analyses including the simple median, the weighed median, MR-Egger regression, and MR-pleiotropy residual sum and outlier.

RESULTS

In the meta-analysis combining different data sources, suggestive inverse causal association of circulating α-Klotho concentrations with CAD [Odds ratio (OR), 0.97; 95% confidence interval (CI), 0.94, 1.00; P = 0.044] and significant inverse association of circulating α-Klotho concentrations with AF (OR, 0.96; 95% CI, 0.93, 0.99; P = 0.005) was observed. However, there was no causal association of α-Klotho with HF, any stroke, IS, or IS subtypes neither in different data sources nor in the meta-analysis. Complementary sensitivity analyses showed consistent and robust results in general.

CONCLUSION

Evidence was found for a protective effect of circulating α-Klotho on the prevention of AF risk. However, no significant causal association between genetically predicted circulating α-Klotho levels and risk of CAD, HF, stroke, IS, or IS subtypes was found.