The genetic architecture of appendicular lean mass characterized by association analysis in the UK Biobank study

Unraveling the protein-metabolite network of sarcopenia in plasma: A large-scale Mendelian randomization study

BACKGROUND

Some plasma molecules may have an effect on sarcopenia, but it is not fully understood. We aimed to comprehensively explore the causal effects of plasma proteins and metabolites on sarcopenia traits, and to unravel their network.

METHODS

A two-sample Mendelian randomization design was adopted. The levels of 4,907 plasma proteins from 35,559 Icelanders, and 1,400 plasma metabolites from 8,299 Europeans, were set as exposures. Low handgrip strength, appendicular lean mass, and usual walking pace from Europeans were set as outcomes. Inverse-variance weighted (IVW) and four other methods, along with sensitivity analyzes, were performed to estimate the causal effects. Enrichment and pathway analyzes were conducted to present their characteristics. IVW was used to estimate the bidirectional relationships between sarcopenia-related proteins and metabolites, and to visualize them within a network.

RESULTS

We identified 76 relationships between proteins and sarcopenia traits. The absolute values of causal effects (βIVW) ranging from 0.01 to 0.35. IL2, AIF1, GDNF, CXCL13, LRRTM3, and SLPI were the top six proteins ranked by causal effects. Additionally, 22 relationships between metabolites and sarcopenia traits were identified, with absolute values of βIVW ranging from 0.02 to 0.22. Sulfate and serine/pyruvate ratio had the highest values. The network diagram showed some key nodes, such as ISOC1, GSTA1, tryptophan and 5α-androstan-3α,17β-diol monosulfate.

CONCLUSIONS

This work unraveled a molecular network of sarcopenia in plasma for the first time and identified some key proteins and metabolites. It may help to understand the mechanisms of sarcopenia, providing new insights for predicting, diagnosing and treating sarcopenia.

Osteosarcopenia, osteoarthritis and frailty: a two-sample Mendelian randomization study

BACKGROUND

Musculoskeletal disease, which has a complicated relationship with frailty, is a common clinical problem among elderly individuals.

AIMS

This study evaluated the potential causal relationships between osteosarcopenia, osteoarthritis and frailty by Mendelian Randomization (MR) analysis.

METHODS

This study employed a two-sample MR approach to investigate the causal relationships among osteosarcopenia, osteoarthritis and frailty. Published summary statistics were used to obtain instrumental variables at the genome-wide significance level.

RESULTS

Among the age groups with osteoporosis, high total bone mineral density (TBMD) (45-60, OR = 0.966, 95% CI 0.940-0.993, P = 0.013) and TBMD (over 60, OR = 0.974, 95% CI 0.954-0.994, P = 0.011) reduced the risk of frailty. Similarly, high forearm BMD (FA-BMD), high ultradistal forearm BMD (UFA-BMD), and high Heel-BMD at different sites also reduced the risk of frailty (OR = 0.966, 95% CI 0.936-0.996, P = 0.028; OR = 0.975, 95% CI 0.953-0.997, P = 0.029; OR = 0.981, 95% CI 0.967-0.995, P = 0.008). Among the characteristics related to sarcopenia, grip strength in the left hand, grip strength in the right hand, appendicular lean mass, and walking pace were all protective factors for frailty (OR = 0.788, 95% CI 0.721-0.862, P < 0.001; OR = 0.800, 95% CI 0.737-0.869, P < 0.001; OR = 0.955, 95% CI 0.937-0.974, P = 0.000; OR = 0.480, 95% CI 0.388-0.593, P < 0.001), with low grip strength in those over 60 years of age significantly positively correlated with frailty (OR = 1.168, 95% CI 1.059-1.289, P = 0.002). The MR results of osteoarthritis and frailty revealed a causal relationship between specific joint sites and frailty, including KOA (OR = 1.086, 95% CI 1.017-1.160, P = 0.014), HOA (OR = 1.028, 95% CI 1.007-1.049, P = 0.009), and KOA/HOA (OR = 1.082, 95% CI 1.053-1.113, P = 0.000), increasing the risk of frailty.

CONCLUSION

Osteosarcopenia, osteoarthritis and frailty exhibit significant causal effects, rendering them risk factors for frailty. Therefore, in clinical practice, patients with osteosarcopenia and osteoarthritis should be required to undergo relevant interventions to reduce the risk of frailty.

Dietary factors and oral cancer risk: a comprehensive Mendelian randomization analysis in a European population

BACKGROUND

Oral cancer is one of the most prevalent malignant tumors in the field of oral and maxillofacial surgery. The main etiological factors are tobacco and alcohol, and diet is now considered an important factor in its development. However, it remains to be elucidated whether the associations between specific diets and oral cancer risk are causal. Therefore, in this study, we performed two-sample Mendelian randomization (MR) analyses to estimate the associations of specific diets with the risk of oral cavity cancer (OCC).

METHODS

We conducted a two-sample MR analysis to assess the causal effect of diet on the risk of OCC. Six types of diets, including champagne or white wine (sample size: 175,549), red wine (sample size: 211,628), dried fruit (sample size: 409,125), fresh fruit (sample size: 433,186), average weekly beer plus cider (sample size: 327,634), and never eat eggs, dairy, wheat, sugar: wheat products (sample size: 461,046), were included as exposures. Summary statistics of OCC were obtained from a genome-wide association study (GWAS) including 1223 OCC cases and 2928 controls of European ancestry. We used the inverse-variance weighted (IVW) method as the primary method, with the weighted median and MR Egger used as supplementary methods for causal inference. Sensitivity analyses, including the Cochran Q test, Egger intercept test, MR-PRESSO test, and leave-one-out analysis, were performed to verify the robustness of the MR results.

RESULTS

The univariate MR showed that champagne or white wine consumption (β = 11.80, p = 0.006), average weekly beer plus cider intake (β = 4.73, p = 0.003), red wine consumption (β = 8.22, p = 0.024), and the never eat eggs, dairy, wheat, sugar: wheat products (β = 14.34, p = 0.002) increased the risk of OCC; Whereas fresh fruit consumption (β = - 3.20, p = 0.038), dried fruit consumption (β = - 2.98, p = 0.012) were protective. The multivariable MR estimates, after controlling for other diets, were as follows: when controlling for the never eat eggs, dairy, wheat, sugar: wheat products and fresh fruit consumption, the effect of average weekly beer plus cider intake on OCC risk was significant, and when controlling for dried fruit consumption, the effect had a P-value close to significant (p = 0.052). The two-step MR showed human characterization: When assessing the impact of dried fruit consumption and fresh fruit consumption, we observed a mediation effect of appendicular lean mass. Furthermore, when assessing the impact of dried fruit consumption and average weekly beer plus cider intake, we observed a mediation effect of standing height. Human system: When exploring the influence of never eat eggs, dairy, wheat, sugar: wheat products, we found a mediation effect of the occurrence of hypothyroidism. Likewise, when assessing the impact of fresh fruit consumption, we found the mediation effect of other diseases of the digestive system. Human metabolite: For the never eat eggs, dairy, wheat, sugar: wheat products, we observed a mediation effect of triglyceride levels in LDL and triglyceride levels in small LDL.

CONCLUSIONS

This study provides champagne or white wine consumption, average weekly beer plus cider intake, red wine consumption, and the never eat eggs, dairy, wheat, sugar: wheat products may increased the risk of OCC; Whereas fresh fruit and dried fruit consumption may were protective. This study analyzed the pathways by which dietary factors influence OCC in aspect of human characterization, human system, and human metabolite. These findings may help inform future research on preventing or treating OCC by modifying dietary factors.

Causal Associations of Inflammatory Cytokines With Osteosarcopenia: Insights From Mendelian Randomization and Single Cell Analysis

Background: Osteosarcopenia, the coexistence of osteoporosis and sarcopenia, poses significant challenges in aging populations due to its dual impact on bone and muscle health. Inflammation, mediated by specific cytokines, is thought to play a crucial role in the development of osteosarcopenia, though the underlying mechanisms are not fully understood. Objective: This study aimed to clarify the causal role of circulating cytokines in the pathogenesis of osteosarcopenia by employing mendelian randomization (MR) and single-cell RNA sequencing (scRNA-seq) to identify cell-specific cytokine expression patterns. The ultimate objective was to uncover potential pathological mechanisms and therapeutic targets for treating osteosarcopenia. Methods: A two-sample MR approach was employed, leveraging publicly available genome-wide association study (GWAS) data from multiple cohorts. A total of 91 circulating cytokines were examined using genetic instruments, and their causal effects on traits related to osteoporosis and sarcopenia were evaluated. Various complementary and sensitivity analyses were performed to ensure robust findings. Additionally, scRNA-seq datasets from human muscle and bone marrow were analyzed to validate the single-cell expression profiles of candidate cytokines. Results: MR analysis identified several cytokines with causal effects on osteosarcopenia traits, including LTA, CD40, CXCL6, CXCL10, DNER (delta and notch-like epidermal growth factor-related receptor), and VEGFA (vascular endothelial growth factor A). LTA and CD40 were protective for both bone and muscle, while VEGFA posed a risk. Other cytokines demonstrated opposite effects on bone and muscle. Single cell analysis revealed distinct expression patterns, with LTA highly expressed in lymphocytes, CD40 in immune cells, and VEGFA in various musculoskeletal cell types. Age-related differences in cytokine expression were also noted, with LTA more highly expressed in younger individuals, and VEGFA in older individuals. Conclusion: This study offers preliminary insights into the inflammatory mechanisms potentially driving osteosarcopenia, identifying key cytokines that may be involved in its pathogenesis. By integrating MR and scRNA-seq data, we highlight potential therapeutic targets, though further research is needed to confirm these findings and their implications for musculoskeletal health.

Identifying semaphorin 3C as a biomarker for sarcopenia and coronary artery disease via bioinformatics and machine learning

OBJECTIVE

Sarcopenia not only affects patients' quality of life but also may exacerbate the pathological processes of coronary artery disease (CAD). This study aimed to identify potential biomarkers to improve the combined diagnosis and treatment of sarcopenia and CAD.

METHODS

Datasets for sarcopenia and CAD were sourced from the Gene Expression Omnibus (GEO). Weighted gene co-expression network analysis (WGCNA) was used to identify key module genes. Functional enrichment analysis was conducted to explore biological significance. Three machine learning algorithms were applied to further determine candidate hub genes, including SVM-RFE, LASSO regression, and random forest (RF). Then, we generated receiver operating characteristic (ROC) curves to evaluate the diagnostic efficacy of the candidate genes. Moreover, mendelian randomization (MR) analysis was conducted based on GWAS summary data, along with sensitivity analysis to explore causal relationships.

RESULTS

WGCNA analysis identified 278 genes associated with sarcopenia and CAD. The results of the enrichment analysis indicated a complex interplay between RNA metabolism, signaling pathways, and cellular stress responses. Through machine learning methods and ROC curves, we identified the key gene semaphorin 3C (SEMA3C). MR analysis revealed that higher plasma levels of SEMA3C are associated with an increased risk of CAD (OR = 1.068, 95 % CI 1.012-1.128, P = 0.016) and low hand grip strength (HGS) (OR = 1.059, 95 % CI 1.010-1.110, P = 0.018) .

CONCLUSION

SEMA3C has been identified as a key gene for sarcopenia and CAD. This insight suggests that targeting SEMA3C may offer new therapeutic opportunities in related conditions.

Causal relationships of circulating amino acids with sarcopenia-related traits: A bidirectional Mendelian randomization study

BACKGROUND AND AIM

Recent studies have indicated a correlation between certain Amino acids (AAs) and sarcopenia. However, the exact causal relationship among these associations is still unclear. This study aims to elucidate the causal relationships between 20 types of AAs and the phenotypic characteristics associated with sarcopenia through Mendelian randomization (MR) analysis.

METHODS AND RESULTS

This MR study employed single nucleotide polymorphisms (SNPs) that were significantly associated with both AAs and the traits of sarcopenia as instrumental variables (IVs). The main method for estimating causal effects was the inverse-variance weighted (IVW) approach. To ensure the robustness of the findings, additional methods such as weighted median, weighted mode, and MR Egger regression were used. Sensitivity analyses included heterogeneity and pleiotropy tests. In this research, we discovered potential causal relationships between AAs and traits associated with sarcopenia. We not only found that AAs previously studied, such as Glutamine, Tyrosine, Glycine, and branched-chain amino acids, play positive roles in muscle metabolism. Additionally, our study identified the role of AAs previously neglected or not considered in earlier research, such as Alanine, Lysine, Cysteine, and Methionine, which exert potential effects on muscle metabolism and offer considerable research potential and value.

CONCLUSIONS

This MR study clarified the reciprocal effects between circulating levels of AAs and sarcopenia-related traits. These results indicate that AAs may be used as biomarkers for diagnosing sarcopenia or as intervention targets for its treatment in clinical practice.

Multiomics reveal key inflammatory drivers of severe obesity: IL4R, LILRA5, and OSM

Polygenic severe obesity (body mass index [BMI] ≥40 kg/m2) has increased, especially in Hispanic/Latino populations, yet we know little about the underlying mechanistic pathways. We analyzed whole-blood multiomics data to identify genes differentially regulated in severe obesity in Mexican Americans from the Cameron County Hispanic Cohort. Our RNA sequencing analysis identified 124 genes significantly differentially expressed between severe obesity cases (BMI ≥40 kg/m2) and controls (BMI <25 kg/m2); 33% replicated in an independent sample from the same population. Our integrative approach identified inflammatory genes, including IL4R, ZNF438, and LILRA5. Several genes displayed transcriptomic effects on severe obesity in subcutaneous adipose tissue. We further showed that the genetic regulation of these genes is associated with several traits in a large biobank, including bone fractures, obstructive sleep apnea, and hyperaldosteronism, illuminating potential risk mechanisms. Our findings furnish a molecular architecture of the severe obesity phenotype across multiple molecular domains.

Causal associations between Sarcopenia-related traits and obstructive sleep apnea: a mendelian randomization study

BACKGROUND

Evidence for a causal relationship between sarcopenia and obstructive sleep apnea (OSA) is scarce. This study aimed to investigate the causal association between sarcopenia-related traits and OSA utilizing Mendelian randomization (MR) analyses.

METHODS

MR analyses were conducted using genetic instruments for sarcopenia-related traits, including hand grip strength, muscle mass, fat mass, water mass, and physical performance. Data from large-scale genome-wide association studies (GWAS) were utilized to identify genetic variants associated with these traits. Causal associations with OSA were assessed using various MR methods, including the inverse variance-weighted (IVW) method, MR-Egger, and weighted median approaches. Pleiotropy and heterogeneity were evaluated through MR-PRESSO and other sensitivity analyses.

RESULTS

Low hand grip strength in individuals aged 60 years and older exhibited a positive correlation with the risk of OSA (IVW, OR = 1.190, 95% CI = 1.003-1.413, p = 0.047), while no significant causal effects were observed for grip strength in the left and right hands. Muscle mass, fat mass, and water mass were significantly associated with OSA, even after adjusting for multiple testing. Notably, higher levels of body fat percentage, trunk fat percentage, and limb fat percentage were strongly correlated with increased risk of OSA. Physical performance indicators such as walking pace demonstrated an inverse association with OSA, while a higher risk of OSA was observed with increased log odds of falling risk and greater frequency of falls in the last year. Additionally, a causal effect was found between long-standing illness, disability, or infirmity and OSA.

CONCLUSIONS

This comprehensive MR analysis provides evidence of a significant causal relationship between characteristics associated with sarcopenia, including low hand grip strength, muscle mass, fat mass, and physical performance, and the risk of OSA. These findings underscore the importance of addressing sarcopenia-related factors in the management and prevention of OSA.

Identification of Association Between Mitochondrial Dysfunction and Sarcopenia Using Summary-Data-Based Mendelian Randomization and Colocalization analyses

BACKGROUND

Mitochondrial dysfunction has been demonstrated to be an important hallmark of sarcopenia, yet its specific mechanism remains obscure. In this study, mitochondrial-related genes were used as instrumental variables to proxy for mitochondrial dysfunction, and summary data for sarcopenia-related traits were used as outcomes to examine their genetic association.

METHODS

A total of 1 136 mitochondrial-related genes from the human MitoCarta3.0 database were extracted. Genetic instruments for them were obtained from gene expression quantitative trait locus (eQTLs) study (n = 31 684). Aggregated data for sarcopenia-related traits including low hand grip strength (LHGS), appendiceal lean mass (ALM), and usual walking pace (UWP) were provided by large-scale genome-wide association studies (GWASs). We integrated eQTLs data with GWAS data to estimate genetic association between mitochondrial dysfunction and sarcopenia using summary-data-based Mendelian randomization (SMR) analysis. Additionally, we implemented colocalization analysis to strengthen their association. Finally, eQTLs data from skeletomuscular tissue (n = 706) was used to validate the primary findings.

RESULTS

By integrating the analysis results from the 3 sarcopenia-related traits, 2 mitochondrial genes genetically associated with sarcopenia were identified, namely UQCC1 (tier 2 evidence) and ETFDH (tier 3 evidence). Specifically, elevated expression levels of UQCC1 increased LHGS risk (OR = 1.114; 95% CI, 1.078-1.152; P-FDR = 1.70 × 10-7), which matched the negative association between it and UWP (Beta = -0.015; 95% CI, -0.021 to -0.010; P-FDR = 6.70 × 10-5). Furthermore, elevated expression levels of ETFDH were found to be associated with both lower ALM (Beta = 0.031; 95% CI, 0.020-0.042; P-FDR = 1.41 × 10-6) and UWP (Beta = 0.013; 95% CI, 0.006-0.021; P-FDR = 0.029). Of note, consistent results were replicated in specific skeletomuscular tissues, further suggesting our findings were robust.

CONCLUSIONS

Our analyses revealed the genetic association between 2 mitochondrial-related genes, ie, UQCC1 and ETFDH, and sarcopenia, highlighting the pivotal role of mitochondrial dysfunction driven by these genes in the pathogenesis of sarcopenia. Importantly, these candidate genes represent potential clinical drug targets for the treatment of sarcopenia.

Shared genetic architecture of type 2 diabetes with muscle mass and function and frailty reveals comorbidity etiology and pleiotropic druggable targets

BACKGROUND

Delineating the shared genetic architecture of type 2 diabetes with muscle mass and function and frailty is essential for unraveling the common etiology and developing holistic therapeutic strategies for these co-existing conditions.

METHODS

In this genome-wide pleiotropic association study, we performed multi-level pairwise trait pleiotropic analyses using genome-wide association study summary statistics from up to 461,026 European ancestry individuals to dissect the shared genetic factors and causal relationships of type 2 diabetes and seven glycemic traits with four muscle mass- and function-related phenotypes and the frailty index.

RESULTS

We first identified 27 pairs with significant genetic correlations through the linkage disequilibrium score regression and high-definition likelihood analysis. Then we determined 79 pleiotropic loci and 109 pleiotropic genes across linkage pairs via the pleiotropic analysis under the composite null hypothesis (PLACO), the colocalization, and the Multi-marker Analysis of GenoMic Annotation (MAGMA) analyses. We subsequently performed transcriptome-wide association study (TWAS) analyses using joint-tissue imputation, refined by gene-based integrative fine-mapping through a conditional TWAS approach, and identified 44 unique causal shared genes across 13 tissues in linkage pairs, including eight druggable genes (ABO, AOC1, FTO, GCKR, MTOR, POLK, PPARG, and APEH), with MTOR and PPARG categorized as clinically actionable. Two-sample Mendelian randomization analysis supported bidirectional causality between diabetes and frailty index and unidirectional causal effects of muscle phenotypes on glycemic profiles.

CONCLUSIONS

Our findings highlight the common genetic underpinnings between type 2 diabetes and muscle loss and frailty and inform drug targets with pleiotropic effects on both of these aging-related challenges.

Causal association of sarcopenia-related traits with brain cortical structure: a bidirectional Mendelian randomization study

BACKGROUND

Patients with sarcopenia often experience cognitive decline, affecting cortical structures, but the causal link remains unclear. We used bidirectional Mendelian randomization (MR) to explore the relationship between sarcopenia-related traits and cortical structure.

METHODS

We selected genetic variables from genome-wide association study data. Three different MR methods were used: inverse-variance weighted analysis, MR-Egger regression, and the weighted median test. For significant estimates, we further conducted Cochran's Q test, MR-Egger intercept test, leave-one-out analyses, and MR-PRESSO to assess heterogeneity.

RESULTS

In forward MR analysis, appendicular lean mass (ALM) decreased the thickness (TH) of lateral occipital gyrus and increased the TH of pars opercularis gyrus (β = -0.0079 mm, 95% CI: -0.0117 mm to -0.0041 mm, P < 0.0001; β = 0.0080 mm, 95% CI: 0.0042 mm to 0.0117 mm, P < 0.0001). In reverse MR analysis, a significant negative correlation was found between the TH of bankssts and ALM, while positive correlations were observed between the TH of frontal pole, rostral anterior cingulate, temporal pole, and ALM. The TH of temporal pole was positively correlated with right hand grip strength (HGS-R) (β = 0.1596 mm, 95% CI: 0.1349 mm to 0.1843 mm, P < 0.0001), and the TH of pars triangularis was positively correlated with left-hand grip strength (HGS-L) (β = 0.3251 mm, 95% CI: 0.2339 mm to 0.4163 mm, P < 0.0001).

CONCLUSIONS

Sarcopenia-related traits and cortical structure have bidirectional effects, supporting the muscle-brain axis theory. This links sarcopenia to neurocognitive diseases and provides new strategies for the prevention and intervention of both sarcopenia and cognitive decline.

Sarcopenia and Insulin Resistance Collective Effect on Atrial Fibrillation Risk: A Non-Diabetic Elderly Cohort Study

BACKGROUND

Appendicular skeletal muscle mass index (ASMI), a crucial indicator of sarcopenia and estimated glucose disposal rate (eGDR), a surrogate marker of insulin resistance (IR), are associated with the risk of cardiovascular diseases. However, it remains unclear whether the collective effects, including the impact of the temporal progression of ASMI and eGDR, affect atrial fibrillation (AF) risk. This study aims to elucidate the association between the collective effects of ASMI and eGDR and AF risk in the non-diabetic older population.

METHODS

A total of 8060 non-diabetic older individuals from a community-based cohort study were used to prospectively analyse the association between the collective effects of baseline ASMI and eGDR and AF risk. Among them, 7651 were eligible and used for dual-trajectory analysis of the association between dual trajectory of ASMI and eGDR and AF risk. The temporal development of ASMI and eGDR over time was determined using a dual-trajectory model. Statistical analyses involved restricted cubic splines and Fine-Gray competing risk models, adjusting for potential confounders.

RESULTS

In the prospective analysis, the hazard ratio (HR) of AF was 1.762 (95% confidence interval [CI]: 1.528-2.032) in the low ASMI group compared to the normal ASMI group in total participants. Restricted cubic splines analysis demonstrated L-shaped associations between AF risk and ASMI and eGDR, with inflection points at 7.23 kg/m2 and 7.85 mg/kg/min, respectively. Low ASMI and moderate and low eGDR exhibited a significant interplay for increasing AF risk (HR: 1.290 and 1.666, 95% CI: 1.136-1.464 and 1.492-1.861, respectively, padj. < 0.001). One-SD increment ASMI and eGDR synergistically reduced AF risk (HR: 0.896, 95% CI: 0.839-0.957, padj. < 0.001). In the dual-trajectory analysis for total participants, five distinct dual trajectories of ASMI and eGDR were identified. Group 4, characterized by moderate-stable ASMI and moderate-stable eGDR, exhibited the lowest incidence of AF (7.03 per 1000 person-years) and was used as a reference for further analyses. Group 1, characterized by high-decrease ASMI and high-decrease eGDR, had the highest AF risk (HR: 2.255, 95% CI: 1.769-2.876, padj. < 0.001), followed by Group 5, with high-decrease ASMI and low-stable eGDR (HR: 1.893, 95% CI: 1.491-2.403, padj. < 0.001) when compared to Group 4 after adjustment for potential confounders including baseline ASMI and eGDR.

CONCLUSIONS

The collective effects of ASMI and eGDR are significantly associated with AF risk in the non-diabetic older population. Collective management of skeletal muscle mass and IR might be a useful and effective management strategy for preventing and controlling AF.

Causal Associations Between Sarcopenia and Gestational Diabetes Mellitus

Introduction

Sarcopenia may affect the onset of gestational diabetes mellitus (GDM). However, the causal relationship between sarcopenia and GDM remains unclear. In this study, we used a bi-directional Mendelian randomization (MR) approach to explore this intricate relationship.

Methods

This study utilized data from FinnGen datasets and genome-wide association studies. A bi-directional MR study was conducted. First, a forward MR analysis evaluated the causality of sarcopenia on GDM risk, with sarcopenia-related traits as exposures and GDM as the outcome. Second, in the reverse MR analysis, we assessed whether GDM influenced sarcopenia-related traits. Finally, sensitivity analysis was conducted to assess the robustness of the MR analysis.

Results

Forward MR analysis revealed that appendicular lean mass (odds ratio [OR] = 1.2182, 95% confidence interval [CI]: 1.1397-1.3021, P < 0.0001), right-hand grip strength (OR= 1.4194, 95% CI: 1.0773-1.8701, P= 0.0128), left-hand grip strength (OR= 1.6064, 95% CI: 1.2829-2.0115, P < 0.0001), and usual walking pace (OR= 3.3676, 95% CI: 1.8769-6.0423, P < 0.0001) were associated with an increased risk of GDM. However, according to the reverse MR results, GDM had no causal effect on sarcopenia. No pleiotropy was observed.

Conclusion

In summary, sarcopenia had a significant causal influence on GDM, while GDM did not causally affect sarcopenia.

Exploring the Causal Relationship Between Frailty and Chronic Obstructive Pulmonary Disease: Insights From Bidirectional Mendelian Randomization and Mediation Analysis

Background

Observational studies have underscored a robust association between frailty and chronic obstructive pulmonary disease (COPD), yet the causality remains equivocal.

Methods

This study employed bidirectional two-sample Mendelian randomization (MR) analysis. Univariable MR investigated the causal relationship between frailty and COPD. Genetic correlation was assessed using linkage disequilibrium score (LDSC) regression. Multivariable MR and mediation analysis explored the influence of various confounders and their mediating effects. The primary analytic approach was inverse variance weighted (IVW).

Results

LDSC analysis revealed moderate genetic correlations between frailty and Global Biobank Meta-Analysis Initiative (GBMI) COPD (rg = 0.643, P = 6.66×10-62) as well as FinnGen COPD (rg = 0.457, P = 8.20×10-28). IVW analysis demonstrated that frailty was associated with increased risk of COPD in both the GBMI cohort (95% CI, 1.475 to 2.158; P = 2.40×10-9) and the FinnGen database (1.411 to 2.434; 9.02×10-6). Concurrently, COPD was identified as a susceptibility factor for frailty (P < 0.05). These consistent findings persisted after adjustment for potential confounders in MVMR. Additionally, mediation analysis revealed that walking pace mediated 19.11% and 15.40% of the impact of frailty on COPD risk, and 17.58% and 23.26% of the effect of COPD on frailty risk in the GBMI and FinnGen cohorts, respectively.

Conclusion

This study has strengthened the current evidence affirming a reciprocal causal relationship between frailty and COPD, highlighting walking pace as a pivotal mediator.

Association between non-insulin-based insulin resistance indicators and frailty progression: a national cohort study and mendelian randomization analysis

BACKGROUND

Insulin resistance (IR) is linked to an increased risk of frailty, yet it remains unclear whether the non-insulin-based IR indicators are associated with frailty trajectories and physical function decline. It aimed to examine the associations of triglyceride-glucose (TyG) index, metabolic score for insulin resistance (METS-IR), estimated glucose disposal rate (eGDR) and with long-term deficit-accumulation frailty trajectories and physical function decline.

METHODS

Data from 6722 participants in the China Health and Retirement Longitudinal Study (CHARLS) were analyzed. Baseline TyG index, METS-IR, eGDR, along with the frailty index (FI) over nine years, were calculated. FI trajectories were assessed using group-based trajectory model (GBTM). Logistic regression models were used to analyze the associations between IR indicators with FI trajectory and frailty risk. Restricted cubic splines (RCS) models were utilized to detect potential dose-response associations. Linear mixed-effects model was used to evaluate associations with FI development speed. Age, gender, educational level, marital status, smoking status, drinking status, life satisfaction, social activity and sleep duration were adjusted. Additionally, a two-sample Mendelian randomization (MR) was performed to assess the causality of observed associations.

RESULTS

Three FI trajectories including low-stable frailty, moderate-increasing frailty, and accelerated rising frailty were identified. Regarding the frail risk, each SD increment in TyG index was associated with a 16.1% increase in the risk of frailty (OR = 1.161; 95%CI: 1.092, 1.235). An inverse association was observed for eGDR with the OR (95%CI) being 0.741 (0.696, 0.788). A linear relationship was observed between baseline TyG index and frailty risk (P nonlinear = 0.696), but nonlinear association patterns for eGDR (P nonlinearity < 0.010) and METS-IR (P nonlinearity < 0.010). Each SD increment of TyG index was associated with greater FI increase (β = 0.005 SD/y; 95%CI = 0.002, 0.008 SD/y; P < 0.001). A similar association pattern was observed for METS-IR, and participants in the highest quartile of METS-IR showed significantly greater FI progression, with β value of 0.013 (95% CI = 0.004, 0.022). Each SD increment of eGDR was associated with a slower increase in FI (β=-0.006 SD/y, 95% CI=-0.009, -0.003 SD/y; P < 0.001). Participants in the highest quartile of eGDR presented a lower annual change in FI compared with participants in quartile 1 group during follow-up (β=-0.013 SD/y, 95% CI=-0.022, -0.005 SD/y; P for trend = 0.001). Similar findings were observed for physical function decline. Findings from MR analysis showed a causal relationship between higher TyG index and increased risk of frailty (β = 0.214, 95% CI = 0.079, 0.349; P = 0.002).

CONCLUSIONS

The non-insulin-based IR indicators, including TyG index, METS-IR and eGDR, were independently associated with the frailty progression and physical function decline. Monitoring and managing abnormal glucose metabolism should be recommended as a part of comprehensive strategies to prevent or delay the progression of frailty.

Genome-Wide Association Study of Exercise Addiction Among Elite Wrestlers

BACKGROUND

Exercise addiction, marked by an inability to control exercise and associated with distress that clinically impairs daily activities, is a significant but underrecognized issue in physical activity and health. While its physiological, psychological, and behavioral aspects have been studied, the genetic basis of exercise addiction remains poorly understood, requiring further investigation. The present study conducted a genome-wide association study of exercise addiction among elite Turkish wrestlers.

METHODS

The sample comprised 67 male wrestlers (34 freestyle wrestlers and 33 Greco-Roman wrestlers). Exercise addiction was assessed using the Exercise Addiction Scale. Whole-genome genotyping was performed using DNA microarray.

RESULTS

Using a genome-wide approach (p < 1.0 × 10-⁵), we identified six suggestively significant single-nucleotide polymorphisms (SNPs) associated with exercise addiction status. Of these, the high-addiction alleles of five SNPs (PRDM10 rs74345126, near PTPRU rs72652685, HADHB rs6745226, XIRP2 rs17614860, and near GAREM2 rs1025542) have previously been associated with an increased risk of mental health disorders such as anxiety and depression or higher levels of physical activity. We also examined potential associations between the genetic markers previously linked to addiction-related traits such as obsessive-compulsive disorder and cigarette smoking, and personality traits linked to negative emotions including neuroticism. Using this candidate gene approach (p < 0.05), we identified three additional SNPs associated with exercise addiction in the same direction of association (DEFB135 rs4841662, BCL11A rs7599488, and CSRNP3 rs1551336).

CONCLUSIONS

The present study provides preliminary evidence for the genetic basis of exercise addiction, highlighting specific SNPs that may play a role in the development of this condition among elite wrestlers.

Unravelling the Relationship Between Height, Lean Mass, Alzheimer's Disease and Cognition Through Mendelian Randomization

BACKGROUND

Genetic evidence from Mendelian randomization (MR) analyses suggests that higher lean mass causally protects against Alzheimer's disease (AD) and enhances cognitive function. However, the potential confounding role of height, which shares genetic etiology with lean mass, has not been fully examined.

METHODS

Genetic predictors of whole-body lean mass were obtained from a genome-wide association study (GWAS) performed in the UK Biobank cohort (UKB; n = 448,322). Genetic predictors of height were also obtained from UKB (height0.5M = 455,332) and from a GWAS meta-analysis (height1.5Mn = 1,578,425). The study outcomes included clinically diagnosed AD (21,982 cases and 41,944 controls) and cognitive performance (n = 269,867). All study participants were of European ancestry. We conducted univariable and multivariable MR analyses to examine the total and independent effects of lean mass and height on the specified outcomes under different statistical adjustment strategies.

RESULTS

In univariable MR analyses, genetically proxied lean mass (odds ratio [OR] per 1-standard deviation [SD] increase 0.81, 95% confidence interval [CI] 0.72-0.91, p = 3.8 × 10-4) and height (OR 0.90, 95% CI 0.84-0.96, p = 0.001) were associated with reduced risk of AD. Genetically proxied lean mass (β 0.10, 95% CI 0.08-0.12, p = 6.24 × 10-6) and height (β 0.07, 95% CI 0.05-0.08, p = 1.16 × 10-15) were further associated with improved cognitive performance. In multivariable MR analyses, adjustment for height1.5M partially attenuated the lean mass association with AD (OR 0.91, 95% CI 0.74-1.12, p = 0.40), whereas the height1.5M-AD association remained similar after adjusting for lean mass (OR 0.89, 95% CI 0.79-1.00, p = 0.04). Adjustment for height also attenuated the association of lean mass with cognitive performance (β 0.00, 95% CI -0.07-0.06, p = 0.94), whereas height maintained a similar association with improved cognitive performance after adjustment for lean mass (β 0.07, 95% CI 0.03-0.10, p = 0.001).

CONCLUSIONS

Height may confound the genetic associations between lean mass and both cognitive performance and AD risk. Residual direct effects of lean mass on AD risk cannot be excluded due to limitations in statistical power and genetic instrument strength in MVMR. These findings emphasize the necessity of adjusting for height when using MR to investigate the clinical effects of lean mass.

Cross-trait multivariate GWAS confirms health implications of pubertal timing

Pubertal timing is highly variable and is associated with long-term health outcomes. Phenotypes associated with pubertal timing include age at menarche, age at voice break, age at first facial hair and growth spurt, and pubertal timing seems to have a shared genetic architecture between the sexes. However, puberty phenotypes have primarily been assessed separately, failing to account for shared genetics, which limits the reliability of the purported health implications. Here, we model the common genetic architecture for puberty timing using a multivariate GWAS, with an effective population of 514,750 European participants. We find 266 independent variants in 197 loci, including 18 novel variants. Transcriptomic, proteome imputation and fine-mapping analyses reveal genes causal for pubertal timing, including KDM4C, LEPR, CCNC, ACP1, and PCSK1. Linkage disequilibrium score regression and Mendelian randomisation analysis establish causal associations between earlier puberty and both accelerated ageing and the risk of developing cardiovascular disease and osteoporosis. We find that alanine aminotransferase, glycated haemoglobin, high-density lipoprotein cholesterol and Parabacteroides levels are mediators of these relationships, and establish that controlling oily fish and retinol intake may be beneficial for promoting healthy pubertal development.

Sarcopenia and immune-mediated inflammatory diseases: Evaluating causality and exploring therapeutic targets for sarcopenia through Mendelian randomization

BACKGROUND

An increasing body of evidence has revealed the association between immune-mediated inflammatory diseases (IMIDs) and sarcopenia. However, a genetically direct causality between IMIDs and sarcopenia remains elusive.

METHODS

To investigate the relationship between IMIDs and sarcopenia-related traits and identify potential therapeutic targets, a Mendelian randomization (MR) was performed. We collected publicly available genome-wide association studies (GWAS) data for seven common IMIDs, including systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD), Crohn's disease (CD), ulcerative colitis (UC), psoriasis (PSO), ankylosing spondylitis (AS), and rheumatoid arthritis (RA). Additionally, summary-level GWAS data for sarcopenia-related traits, including appendicular lean mass (ALM), left-hand grip strength, and right-hand grip strength were collected. To search for therapeutic targets, we used two types of genetic instruments to proxy the exposure of druggable genes, including genetic variants within or nearby drug targets and expression quantitative trait loci (eQTLs) of drug targets. Two-sample MR and summary-data-based MR (SMR) were used to calculate effect estimates, and sensitivity analyses were implemented for robustness. Drug tractability, gene enrichment analysis, and protein-protein interaction (PPI) analysis were used to validate the biological and clinical significance of the selected drug targets.

RESULTS

The two-sample MR analysis indicated the existence of casual associations between IMIDs and sarcopenia-related traits in the overall and sex-stratified populations. In particular, PSO had causal effects on decreased ALM, which showed significance in all six MR analysis tests with directional consistency in the overall population. Grounded in this robust association, HLA-DRB5, HLA-DRB1, and AGER were identified as potential therapeutic targets for ALM decline by drug target MR and further confirmed by SMR analysis. These genes were associated with therapeutic agents currently undergoing evaluations in clinical trials. Gene enrichment and PPI analysis indicated a strong association of these genes with immune functions.

CONCLUSIONS

This MR study contributes novel genetic evidence supporting the causal link between IMIDs and sarcopenia, with a particular emphasis on the association between PSO and decreased ALM. Additionally, AGER, HLA-DRB1, and HLA-DRB5 emerge as potential therapeutic targets for ALM decline.

Association between immune cells, inflammatory cytokines, and sarcopenia: Insights from a Mendelian randomization analysis

BACKGROUND

Recent studies have suggested a possible link between sarcopenia, immune dysregulation, and chronic inflammation, although the specific immune components implicated remain unclear. This investigation employs Mendelian Randomization (MR) to explore the reciprocal relationship between immune cells, inflammatory markers, and sarcopenia.

METHOD

We performed two-sample and multivariate MR analyses using publicly accessible genome-wide association studies (GWAS) summary statistics. Our analyses included 731 immune cells, 41 inflammatory cytokines, and sarcopenia related traits (appendicular lean mass [ALM], low hand-grip strength [LHS], and walking pace [WP]), with additional sensitivity analyses conducted to confirm the findings.

RESULTS

After false discovery rate (FDR) correction, significant associations were found between ten immune traits and ALM, with the CD127 marker in the Treg panel showing consistent positive correlation across four sites. In contrast, NKT%lymphocyte negatively correlated with WP (OR = 0.99, P = 0.023). In terms of inflammatory cytokines, macrophage colony-stimulating factor (MCSF) (OR = 1.03, P = 0.024) and hepatocyte growth factor (HGF) (OR = 1.03, P = 0.002) demonstrated positive associations with ALM, while interleukin-16 (IL-16) (OR = 0.99, P = 0.006) was inversely related. The reverse Mendelian randomization analysis found no direct causal links between sarcopenia traits and immune or inflammatory markers. Sensitivity analyses underscored the findings' resilience to pleiotropy, and adjusting for inter-trait dynamics weakened these relationships in the multivariable MR analysis.

CONCLUSION

Our study reveals causal associations between specific immune phenotypes, inflammatory cytokines, and sarcopenia, providing insight into the development of sarcopenia and potential treatment strategies.

Causal Associations of Cognitive Reserve and Hierarchical Aging-Related Outcomes: A Two-Sample Mendelian Randomization Study

PURPOSE

Two-sample Mendelian randomization methods were used to explore the causal effects of cognitive reserve proxies, such as educational attainment, occupational attainment, and physical activity (PA), on biological (leukocyte telomere length), phenotypic (sarcopenia-related features), and functional (frailty index and cognitive performance) aging levels.

RESULTS

Educational attainment had a potential protective effect on the telomere length (β = 0.10, 95% CI: 0.08-0.11), sarcopenia-related features (β = 0.04-0.24, 95% CI: 0.02-0.27), frailty risk (β = -0.31, 95% CI: -0.33 to -0.28), cognitive performance (β = 0.77, 95% CI: 0.75-0.80). Occupational attainment was causally related with sarcopenia-related features (β = 0.07-0.10, 95% CI: 0.05-0.14), and cognitive performance (β = 0.30, 95% CI: 0.24-0.36). Device-measured PA was potentially associated with one sarcopenia-related feature (β = 0.14, 95% CI: 0.03-0.25).

CONCLUSIONS

Our findings support the potential causality of educational attainment on biological, phenotypic, and functional aging outcomes, of occupational attainment on phenotypic and functional aging-related outcomes, and of PA on phenotypic aging-related outcomes.

Causal Relationship Between Circulating Metabolites and Sarcopenia-Related Traits: A Mendelian Randomization and Experimental Study

Sarcopenia (SP), an age-associated condition marked by muscle weakness and loss has been strongly connected with metabolic factors according to substantial evidence. Nevertheless, the causal correlation between SP and serum metabolites, and the biological signaling pathways involved, is still not well understood. We performed a bidirectional two-sample Mendelian randomization (MR) analysis to examine the causal relationships between 1091 levels and 309 ratios of metabolites with SP traits, alongside investigating the relevant biological signaling pathways. Additionally, we explored the differential expression of plasma metabolites and potential biological signaling pathways in an animal model of SP. When SP was utilized as the outcome, we identified 11 robust causal associations between seven metabolite levels/ratios and SP-related traits using Bonferroni's correction (threshold: p < 0.05). We verified the stable causal association of glycine levels and SP in the validation. As for the reverse MR analysis, there were 11 strong causal relationships with 11 plasma metabolite levels/ratios remaining after multiple contrast correction. Additionally, biological signaling pathway analysis showed that glycine metabolism, insulin resistance, and cAMP signaling pathways may contribute to the connection between metabolites and SP. Mendelian validation of various datasets and observations in animal serum metabolomics suggests a strong association between glycine metabolism and SP. Our results indicate that the identified metabolites and biosignaling pathways could serve as important circulatory metabolic biomarkers for the screening and prevention of SP in clinical settings. Additionally, they represent potential molecules for future exploration of mechanisms and selection of drug targets.

Causal association between sarcopenia and cognitive impairment contributes to the muscle-brain axis: A bidirectional Mendelian randomization study

AIM

There is a growing body of evidence suggesting a correlation between sarcopenia (SP) and cognitive impairment (CI), but with conflict. This study employed a bidirectional Mendelian randomization (MR) approach to ascertain the causality between SP and CI.

METHOD

This study looked at whether there might be causality between SP and CI by using a bidirectional MR analysis on the GWAS summary datasets, which anyone can publicly access. The primary analysis employed inverse variance weighting (IVW), with MR-Egger, weighted median, and mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) serving as supplements. Multiple sensitivity analyses were performed to enhance the stability of the results, which encompassed heterogeneity tests and pleiotropy tests.

RESULTS

Appendicular lean mass (ALM), walking pace (WP), and grip strength (GS) were found to be causally connected to cognitive performance in forward MR analysis. In the reverse MR study, cognitive performance also had a causal impact on ALM and WP. Additionally, we discovered comparable outcomes in the replication samples, which strengthens the validity of our findings.

CONCLUSIONS

The results of our MR investigation revealed a definitive cause-and-effect association between SP and CI. Our findings provide additional supporting evidence for the muscle-brain axis, which may suggest that muscle strengthening has a significant impact on the management and avoidance of CI. Geriatr Gerontol Int 2025; 25: 116-122.

Causal relationship between lipid profile and muscle atrophy: A bi-directional Mendelian randomization study

BACKGROUND

The aim of this study was to analyze the bi-directional causal relationship between lipid profile and characteristics related to muscle atrophy by using a bi-directional Mendelian randomization (MR) analysis.

METHODS

The appendicular lean mass (ALM), whole body fat-free mass (WBFFM) and trunk fat-free mass (TFFM) were used as genome-wide association study (GWAS) data for evaluating muscle mass; the usual walking pace (UWP) and low grip strength (LGS) were used as GWAS data for evaluating muscle strength; and the triglycerides (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), apolipoprotein A-1 (Apo A-1), and apolipoprotein B (Apo B) were used as GWAS data for evaluating lipid profile. For specific investigations, we mainly employed inverse variance weighting for causal estimation and MR-Egger for pleiotropy analysis.

RESULTS

MR results showed that the lipid profile predicted by genetic variants was negatively correlated with muscle mass, positively correlated with UWP, and was not causally correlated with LGS. On the other hand, the muscle mass predicted by genetic variants was negatively correlated with lipid profile, the UWP predicted by genetic variants was mainly positively correlated with lipid profile, while the LGS predicted by genetic variants had no relevant causal relationship with lipid profile.

CONCLUSIONS

Findings of this MR analysis suggest that hyperlipidemia may affect muscle mass and lead to muscle atrophy, but has no significant effect on muscle strength. On the other hand, increased muscle mass may reduce the incidence of dyslipidemia.

Causality of genetically determined glucosamine supplementation on cognition and sarcopenia: a Mendelian randomization study

BACKGROUND

Evidence indicates a negative link between glucosamine and age-related cognitive decline and sarcopenia. However, the causal relationship remains uncertain. This study aims to verify whether glucosamine is causally associated with cognitive function and sarcopenia.

METHOD

Forty-eight genetic variants linked to glucosamine use were extracted from the MRC-IEU consortium. Besides, we gathered cognition proxy indicators [cognitive performance and fluid intelligence score (FIS)], and sarcopenia-related indicators, namely, appendicular lean mass (ALM), whole body fat-free mass (WBFM), low hand grip strength, facial aging (FA), moderate to vigorous physical activity levels, usual walking pace and DNA methylation GrimAge acceleration from the large publicly available genome-wide association studies. Initially, Mendelian randomization (MR) analyses were conducted to ascertain the causal impact of glucosamine on cognition and sarcopenia-related traits. Subsequently, the two-step MR and multivariable MR (MVMR) were employed to examine whether any mediators causally mediated the observed associations.

RESULT

MR analysis indicated that glucosamine was associated with increased cognitive performance (p = 8.46E-04), FIS (p = 7.50E-04), ALM (p = 6.45E-08), WBFM (p = 1.97E-03), usual walking pace (p = 2.55E-07), and moderate to vigorous physical activity levels (p = 3.29E-03), but associated with decreased FA risk (p = 3.77E-05) and DNA methylation GrimAge acceleration (p = 0.001). However, there were no significant causal associations between glucosamine and low hand grip strength. Multivariable MR showed that glucosamine continued to have a significant effect on cognitive performance, FIS, ALM, WBFM, usual walking pace, and moderate to vigorous physical activity levels after controlling for osteoarthritis (OA) and body mass index (BMI) (p < 0.05). We further found that C-reactive protein levels (CRP) may mediate the association of glucosamine and ALM, WBFM, usual walking pace, and physical activity (p < 0.05), and basal metabolic rate (BMR) may mediate the association of glucosamine and cognitive performance, FIS, ALM, WBFM, and usual walking pace (p < 0.05).

CONCLUSION

Regular glucosamine use enhances cognitive function and postpones sarcopenia for preserving the functional capacities necessary, and the impact of glucosamine on cognition and sarcopenia could be partially attributed to the mediation of BMR and CRP.

Sarcopenia Is Associated with Neoplasm of Bone and Articular Cartilage: Findings from Mendelian Randomized Study

Exploring the causal relationship between sarcopenia and neoplasm of bone and articular cartilage (NBAC) by bidirectional Mendelian randomization (MR). Genome-wide association study (GWAS) data on sarcopenia-associated traits including appendicular lean mass, low handgrip strength (including criteria from the European Working Group on Sarcopenia in Older People and the Foundation for the National Institutes of Health), and usual walking speeds were obtained from the UK Biobank. GWAS data for NBAC (benign and malignant) were provided by the Finnish Genetic Database. Three different methods of MR analysis, including inverse-variance weighted, Mendelian randomized Egger regression, and weighted median methods, were utilized. MR analysis showed that high appendicular lean mass was positively associated with the risk of developing benign NBAC (odds ratio and 95% confidence interval = 1.236 (1.026,1.489), p = 0.025). At the same time, there is no statistically significant association was found between traits related to sarcopenia and malignant neoplasm of bone and articular cartilage. There was also no reverse causal correlation between NBAC and traits related to sarcopenia. In European populations, better appendicular lean body mass is positively associated with the risk of benign neoplasm of bone and articular cartilage, representing the possibility that sarcopenia may be a protective factor against neoplasm of bone and articular cartilage.

The role of IGF1 in determining body composition in children and adolescents with growth hormone deficiency and those with idiopathic short stature

PURPOSE

Treatment with recombinant human growth hormone (rhGH) increases insulin growth factor-1 (IGF1) levels, therefore, monitoring both IGF1 and growth constitutes an acceptable parameter of therapeutic safety and efficacy. We aimed to investigate the relationship between IGF1 level and body composition in children and adolescents undergoing rhGH therapy for growth hormone deficiency (GHD) and idiopathic short stature (ISS).

METHODS

This observational retrospective study included the bioimpedance analysis (BIA) reports (n = 305) of 135 pediatric patients (age 5-18 years), 64 with GHD and 71 with ISS, conducted as part of routine clinic visits. Sociodemographic and clinical data were extracted from medical records. Generalized estimating equations linear models were used to explore the contributing factors for body composition components of fat percentage (FATP), appendicular skeletal muscle mass (ASMM) z-score, and muscle-to-fat ratio (MFR) z-score while adjusting for cumulative doses of rhGH.

RESULTS

Subjects with GHD exhibited higher body mass index z-scores (p < 0.001), higher FATP and truncal FATP scores, lower MFR z-score, and higher diastolic blood pressure percentiles than the ISS group (p = 0.010, p = 0.027, p = 0.050, and p = 0.050, respectively). Female sex (p < 0.001) and a GHD diagnosis (p < 0.001), were major contributors to higher FATP scores; female sex (p = 0.049) and ISS diagnosis (p = 0.005) were major contributors to higher MFR z-scores; and female sex (p < 0.001), older age (p < 0.001) and higher insulin-like growth factor 1 z-scores (p = 0.021) were major contributors to higher ASMM z-scores. Socioeconomic position and cumulative rhGH dose were not significant contributors to body composition parameters.

CONCLUSION

Children with GHD, including those undergoing rhGH treatment, may be at risk for increased adiposity and associated metabolic implications. Sex- and age-adjusted IGF1 levels were related to muscle mass but not to adiposity. Hence, rhGH treatment aimed at increasing IGF1 levels may alleviate these effects by promoting muscle growth.

Novel insights into the association between genetically proxied inhibition of proprotein convertase subtilisin/kexin type 9 and risk of sarcopenia

BACKGROUND

The effects of lipid-lowering drugs [including statins, ezetimibe, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors] on hyperlipidaemia have been established. Some may have treatment effects beyond their reported properties, offering potential opportunities for drug repurposing. Epidemiological studies have reported conflicting findings on the relationship between lipid-lowering medication use and sarcopenia risk.

METHODS

We performed a two-sample Mendelian randomization (MR) study to investigate the causal association between the use of genetically proxied lipid-lowering drugs (including statins, ezetimibe, and PCSK9 inhibitors, which use low-density lipoprotein as a biomarker), and sarcopenia risk. The inverse-variance weighting method was used with pleiotropy-robust methods (MR-Egger regression and weighted median) and colocalization as sensitivity analyses.

RESULTS

According to the positive control analysis, genetically proxied inhibition in lipid-lowering drug targets was associated with a lower risk of coronary heart disease [PCSK9 (OR, 0.67; 95% CI, 0.61 to 0.72; P = 7.7E-21); 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR; OR, 0.68; 95% CI, 0.57 to 0.82; P = 4.6E-05), and Niemann-Pick C1-like 1 (NPC1L1; OR, 0.53; 95% CI, 0.40 to 0.69; P = 3.3E-06)], consistent with drug mechanistic actions and previous trial evidence. Genetically proxied inhibition of PCSK9 (beta, -0.040; 95% CI, -0.068 to -0.012; P = 0.005) and circulating PCSK9 levels (beta, -0.019; 95% CI, -0.033 to -0.005; P = 0.006) were associated with reduced appendicular lean mass (ALM) with concordant estimates in terms of direction and magnitude. Validation analyses using a second instrument for PCSK9 yielded consistent results in terms of direction and magnitude [(PCSK9 to ALM; beta, -0.052; 95% CI, -0.074 to -0.032; P = 7.1E-7); (PCSK9 protein to ALM; beta, -0.060; 95% CI, -0.106 to -0.014; P = 0.010)]. Genetically proxied inhibition of PCSK9 gene expression in the liver may be associated with reduced ALM (beta, -0.013; 95% CI, -0.035 to 0.009; P = 0.25), consistent with the results of PCSK9 drug-target and PCSK9 protein MR analyses, but the magnitude was less precise. No robust association was found between HMGCR inhibition (beta, 0.048; 95% CI, -0.015 to 0.110; P = 0.14) or NPC1L1 (beta, 0.035; 95% CI, -0.074 to 0.144; P = 0.53) inhibition and ALM, and validation and sensitivity MR analyses showed consistent estimates.

CONCLUSIONS

This MR study suggested that PCSK9 is involved in sarcopenia pathogenesis and that its inhibition is associated with reduced ALM. These findings potentially pave the way for future studies that may allow personalized selection of lipid-lowering drugs for those at risk of sarcopenia.

Identifying the Shared Metabolite Biomarkers and Potential Intervention Targets for Multiple Sarcopenia-Related Phenotypes

The relationship between circulating metabolites and sarcopenia-related phenotypes remains unclear. We explored the causality between circulating metabolites and sarcopenia-related phenotypes. Instrumental variables for the human metabolome were derived from the recently published GWAS, which included 690 plasma metabolites. Summary statistics for four sarcopenia phenotypes (whole-body lean mass (WBLM), usual walking pace, appendicular lean mass (ALM), and handgrip strength (HGS)) (both sexes, males and females) were obtained from relevant GWASs. We used MR to evaluate the association between circulating metabolites and sarcopenia-related phenotypes. Colocalization analysis was utilized to determine whether two associated signals were consistent with a shared causal variant rather than the confounding effect of linkage disequilibrium. Subsequently, we explored associations between modifiable risk factors and sarcopenia-related metabolites to explore which metabolites may serve as potential intervention targets through lifestyle modification. Genetically predicted plasma levels of 95 known metabolites were associated with sarcopenia-related phenotypes, and 27 metabolites were supported by robust evidence of colocalization, among which 13 metabolites had a cross-sarcopenia effect. These metabolites primarily included acyl carnitines, amino acids and their derivatives, and phospholipids. Specifically, our analyses supported causal relationships between 23, 6, and 15 metabolites and ALM, HGS, and WBLM, respectively. Seven relevant metabolites might be associated with six modifiable factors. We identified 27 metabolite biomarkers with robust causal evidence for sarcopenia-related phenotypes, highlighting 13 metabolites with a cross-sarcopenia effect, and prioritized several metabolites as the potential interventional targets of lifestyle changes. Our study provided new insight into the etiology and prevention of sarcopenia.

Drug risks associated with sarcopenia: a real-world and GWAS study

INTRODUCTION

Drug-induced sarcopenia has not received adequate attention. Meanwhile, there is growing recognition of the importance of effective pharmacovigilance in evaluating the benefits and risks of medications.

AIMS

The primary aim of this study is to investigate the potential association between drug use and sarcopenia through an analysis of adverse event reports from the Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) and to evaluate the genetic factors contributing to drug-induced sarcopenia using summary-data-based Mendelian randomization (SMR).

METHODS

We obtained reports of adverse drug reactions from FAERS. Primary outcomes included sarcopenia and potential sarcopenia. We calculated the Proportional reporting ratio (PRR) to assess the risk of specific adverse events associated with various drugs, applying chi-square tests for statistical significance. Additionally, we used SMR based on Genome-wide association study (GWAS) to evaluate the potential associations between drug target genes of some significant medications and sarcopenia outcomes. The outcome data for sarcopenia included metrics as hand grip strength and appendicular lean mass (ALM).

RESULTS

A total of 55 drugs were identified as inducing potential sarcopenia, and 3 drugs were identified as inducing sarcopenia. The top 5 drugs causing a potential risk of sarcopenia were levofloxacin (PRR = 9.96, χ2 = 1057), pregabalin (PRR = 7.20, χ2 = 1023), atorvastatin (PRR = 4.68, χ2 = 903), duloxetine (PRR = 4.76, χ2 = 527) and venlafaxine (PRR = 5.56, χ2 = 504), and the 3 drugs that had been proved to induced sarcopenia included metformin (PRR = 7.41, χ2 = 58), aspirin (PRR = 5.93, χ2 = 35), and acetaminophen (PRR = 4.73, χ2 = 25). We identified electron-transfer flavoprotein dehydrogenase (ETFDH) and protein Kinase AMP-Activated Non-Catalytic Subunit Beta 1 (PRKAB1) as the primary drug target genes for metformin, while Prostaglandin-endoperoxide Synthase 1 (PTGS1) and Prostaglandin-endoperoxide Synthase 2 (PTGS2) were considered the primary action target genes for aspirin and acetaminophen according to DrugBank database. SMR showed that the expression abundance of ETFDH was negatively correlated with right hand grip strength (blood: OR = 1.01, p-value = 1.27e-02; muscle: OR = 1.01, p-value = 1.42e-02) and negatively correlated with appendicular lean mass (blood: OR = 1.03, p-value = 7.73e-08; muscle: OR = 1.03, p-value = 1.67e-07).

CONCLUSIONS

We find that metformin, aspirin, and acetaminophen are specifically noted for their potential to induce sarcopenia based on the analyses conducted. We perform signal mining for drug-associated sarcopenia events based on real-world data and provides certain guidance for the safe use of medications to prevent sarcopenia.

Causal linkage of Graves' disease with aging: Mendelian randomization analysis of telomere length and age-related phenotypes

BACKGROUND

Aging is an irreversible progressive decline in physical function. Graves' disease (GD) is a common cause of hyperthyroidism and is characterized by elevated levels of the thyroid hormone (TH). High TH levels are associated with aging and a shortened lifespan. The causal relationship between GD and aging has yet to be investigated.

METHODS

We used genome-wide association study (GWAS) datasets and Mendelian randomization (MR) analysis to explore the causal link between GD and aging. To assess the statistical power of instrumental variables (IVs), F-statistics and R2 were used. MR analysis was conducted using inverse-variance weighting (IVW), MR-Egger, weighted median, and weighted mode. The odds ratio (OR) and 95% CI were calculated to estimate the relative risk of GD to the outcomes. The Cochran Q test, I2, MR-PRESSO test, and MR-Egger regression intercept were calculated using statistical and leave-one-out analyses to test the heterogeneity, horizontal pleiotropy, and stability of the IVs on the outcomes.

RESULTS

F-statistics of the five IVs were greater than 10, and the R2 values ranged from 0.033 to 0.156 (R2 > 0.01). According to the results of the IVW analysis, GD had no causal effect on facial aging (p = 0.189), age-related macular degeneration (p = 0.346), and Alzheimer's disease (p = 0.479). There was a causal effect of GD on the remaining outcomes: telomere length (TL) (OR = 0.982; 95%CI:0.969-0.994; p = 0.004), senile cataract (OR = 1.031; 95%CI:1.002-1.060; p = 0.033), age-related hearing impairment (OR = 1.009; 95%CI:1.004-1.014; p = 0.001), chronic obstructive pulmonary disease (COPD) (OR = 1.055; 95%CI:1.008-1.103; p = 0.020), and sarcopenia (OR = 1.027; 95%CI:1.009-1.046; p = 0.004).

CONCLUSIONS

GD accelerates the occurrence of age-related phenotypes including TL, senile cataracts, age-related hearing impairment, COPD, and sarcopenia. In contrast, there are no causal linkages between GD and facial aging, age-related macular degeneration, or Alzheimer's disease. Further experimental studies could be conducted to elucidate the mechanisms by which GD facilitates aging, which could help slow down the progress of aging.

Causal relationship between sarcopenia and rotator cuff tears: a Mendelian randomization study

Background

Sarcopenia and rotator cuff tears are common among elderly patients. However, the role of sarcopenia in the management of rotator cuff tears has been often overlooked. This study aimed to elucidate the effects of sarcopenia-related traits on rotator cuff tears.

Methods

Two-sample Mendelian randomization (MR) analyses based on genome-wide association study data were used to evaluate the causal relationships among appendicular lean mass (ALM), usual walking pace, low hand grip strength, and rotator cuff tears. Multivariate Mendelian randomization (MVMR) analyses were used to evaluate the direct effects of each muscle trait on the causal relationship.

Results

Univariate MR analysis showed that ALM and usual walking pace were causally related to rotator cuff tears (odds ratio (OR) = 0.895; 95% confidence interval (CI), 0.758-0.966, P<0.001 and OR = 0.458, 95% CI, 0.276-0.762, P = 0.003, respectively), and there was no evidence of causality between low hand grip strength and rotator cuff tears (OR = 1.132, 95% CI, 0.913-1.404, P = 0.26). MVMR analysis confirmed the causal effects of ALM and walking pace on rotator cuff tears (OR = 0.918, 95% CI, 0.851-0.990, P = 0.03 and OR = 0.476, 95% CI, 0.304-0.746, P = 0.001, respectively).

Conclusion

A causal genetic relationship exists between sarcopenia and rotator cuff tears. Sarcopenia-related traits including low muscle mass and physical function, increase the risk of rotator cuff tears. These findings provide new clinical insights and evidence-based medicine to optimize management of rotator cuff tears.

Causal role of immune cells in muscle atrophy: mendelian randomization study

Immune system and inflammation had a great influence on the progression of muscle atrophy. However, the causal relationship with specific immune cell traits remained uncertain. The aim of this study was to elucidate the genetic influences on these associations, providing insights into the underlying mechanisms of muscle atrophy. A bidirectional two-sample Mendelian randomization (MR) analysis was conducted to investigate the causal relationship between immune cell phenotypes and muscle atrophy. Data on immune cell phenotypes were obtained from a research cohort containing data on 731 immune cell phenotypes and data on muscle atrophy were sourced from a Finnish database. MR analysis was performed using the MR-Egger method, weighted median, inverse variance weighting, heterogeneity testing, sensitivity analysis, and multiplicity analysis, with results subjected to false discovery rate(FDR) correction. Additionally, the UK Biobank cohort was utilized as an external validation. A total of 31 immune phenotypes with causal relationships with muscle atrophy were identified, including various phenotypes of conventional dendritic cells, myeloid cells, T cells/B cells/natural killer cells, regulatory cells, and T cell maturation stages. Among them, 12 immune phenotypes were identified as exhibiting a positive causal relationship with muscle atrophy, while 19 immune phenotypes were demonstrated to have a negative causal association, highlighting the complex interactions between immune cells and muscle health. The results of the reverse MR analysis indicated that a negative correlation between muscle atrophy and CD28 on secreting Treg (OR = 0.9038, 95%CI:0.8308 ~ 0.9832, P = 0.0186). A significant positive correlation was revealed by external datasets between the CD25 on IgD + CD38- immune phenotype and the risk of muscle atrophy, which was consistent with the trend observed in the training group (OR = 1.1041, 95% CI: 1.1005-1.1076, P = 0.0263). No evidence of pleiotropy was observed, and the reliability of these findings was demonstrated by the leave-one-out analysis. The findings highlight significant correlations between certain immune cell features and muscle atrophy, providing potential targets for further investigation of immunological mechanisms and therapeutic interventions for this condition.

Educational attainment, brain cortical structure, and sarcopenia: a Mendelian randomization study

Background

Previous observational studies have suggested associations between high-level educational attainment (EA) and a lower risk of sarcopenia. However, the causality inferred from those studies was subjected to residual confounding and reverse causation. The protective effect of EA on sarcopenia may be mediated via changes in brain cortical structure. The aim of this study was to use a two-step Mendelian randomization (MR) analysis to illustrate the causal relationship between EA, brain cortical structure, and sarcopenia.

Methods

Instrumental variables at the genome-wide significance level were obtained from publicly available datasets, and inverse variance weighted as the primary method was used for MR analysis. We perform several sensitivity analyses, including Cochran Q test, MR-Egger intercept test, leave-one-out analyses, and MR Pleiotropy Residual Sum and Outlier to evaluate the reliability of the results.

Results

EA was causally associated with increased appendicular lean mass (β = 0.25, 95% confidence interval (CI): 0.19 to 0.31, p = 2.25 × 10-15), hand grip strength (left: β = 0.042, 95% CI: 0.013 to 0.071, p = 4.77 × 10-3 and right: β = 0.050, 95% CI: 0.022 to 0.079, p = 5.17 × 10-4), and usual walking pace (β = 0.20, 95% CI: 0.18 to 0.22, p = 6.16 × 10-83). In addition, EA was associated with increased brain cortical surface area (β = 4082.36, 95% CI: 2513.35 to 5681.38, p = 3.40 × 10-7) and cortical thickness (TH) (β = 0.014, 95% CI: 0.0045 to 0.023, p = 3.45 × 10-3). Regarding the causal effect of EA on usual walking pace, the mediatory effect of TH was 0.0069 and the proportion of mediation by TH was 3.43%.

Conclusion

The study will have revealed the protective causal effect of EA on sarcopenia, which provides a reference for the prevention of sarcopenia at the public health level. We also will have found EA could affect the brain cortical structure, and the brain cortical structure could mediate the protective effect of EA against sarcopenia risk.

Causal associations between the insulin-like growth factor family and sarcopenia: a bidirectional Mendelian randomization study

Objective

Insulin-like growth factor (IGF) is closely associated with sarcopenia, yet the causal relationship of this association remains unclear. This study aims to explore the potential causal relationship between members of the IGF family and sarcopenia from a genetic perspective through bidirectional Mendelian randomization (MR) analysis using two-sample datasets.

Methods

Five genetically predicted factors of the IGF family (IGF-1, IGF-1R, IGF-2R, IGFBP-3, IGFBP-7) as one sample, while four relevant features of sarcopenia (low hand grip strength, appendicular lean mass, whole body fat-free mass, and walking pace) as another sample, in conducting a two-sample MR analysis.

Results

The forward MR results of the relationship between IGF and sarcopenia showed that elevated levels of IGF-1 reduced the risk of low hand grip strength (OR = 0.936, 95% CI=0.892-0.983, P = 0.008) and increased appendicular lean mass of the extremities and whole body fat-free mass (OR = 1.125, 95% CI=1.070-1.182,P = 0.000; OR =1.076, 95% CI=1.047-1.106, P=0.000), reduced the risk of sarcopenia. Elevated IGF-1R also favored an increase in whole body fat-free mass (OR=1.023, 95% CI=1.008-1.038, P =0.002), and the appendicular lean mass trait was more pronounced with elevated IGFBP-3 and IGFBP-7 (OR=1.034, 95% CI=1.024-1.044, P =0.000; OR=1.020, 95% CI=1.010-1.030, P=0.000). Inverse MR results of the effect of sarcopenia on IGF showed that decreased hand grip strength may elevate IGF-1 levels (OR=1.243, 95% CI=1.026-1.505,P =0.027), whereas improvements in appendicular lean mass, whole body fat-free mass traits, and increased walking pace decreased IGF-1 levels (OR=0.902, 95% CI: 0.877-0.927, P = 0.000; OR=0.903, 95% CI=0.859-0.949,P = 0.000; OR=0.209, 95% CI=0.051-0.862,P = 0.045). Also decreased hand grip strength may elevate IGF-1R levels (OR=1.454, 95% CI=1.108-1.909, P =0.007), and appendicular lean mass stimulated high expression of IGFBP-1 (OR=1.314, 95% CI=1.003-1.722, P =0.047). Heterogeneity and pleiotropy were not detected in all results, and the results were stable and reliable.

Conclusion

There is a bi-directional causal association between IGF family members and the risk of sarcopenia, which provides a more adequate basis for early biological monitoring of sarcopenia and may provide new targets for early intervention and treatment of sarcopenia.

Ischemic stroke and sarcopenia have an asymmetric bidirectional relationship based on a two-sample Mendelian randomization study

Background

We investigated the potential relationship between age-related conditions, particularly sarcopenia and ischemic stroke (IS), through a two-sample Mendelian randomization (MR) study.

Methods

We conducted a two-sample bidirectional MR study to investigate the relationship between sarcopenia and stroke. Genetic instruments for sarcopenia were derived from the UK Biobank, while data on IS and its subtypes were obtained from the MEGASTROKE consortium. Inverse variance weighting (IVW) served as the primary analytical method. Additionally, heterogeneity and pleiotropy were assessed to ensure the robustness of the findings.

Results

The analysis indicates a negative correlation between appendicular lean mass (ALM) and small vessel stroke (SVS; OR = 0.790, 95% CI: 0.703-0.888, p < 0.001), a positive correlation with cardioembolic stroke (CES; OR = 1.165, 95% CI: 1.058-1.284, p = 0.002), and no causal relationship with any ischemic stroke (AIS) or large artery stroke (LAS). Additionally, SVS is negatively associated with right-hand grip strength (OR = 0.639, 95% CI: 0.437-0.934, p = 0.021), while AIS, LAS, and CES do not exhibit a causal relationship with grip strength. Furthermore, no causal relationship was identified between left-hand grip strength, usual walking pace, and IS or its subtypes. MR analysis reveals only a negative association between CES and usual walking pace (OR = 0.989, 95% CI: 0.980-0.998, p = 0.013), with no associations found between other IS subtypes and sarcopenia-related traits.

Conclusion

This study demonstrates that a reduction in ALM and right-hand grip strength is associated with SVS, whereas decreased ALM may serve as a protective factor against CES. Conversely, our analysis suggests that CES can impact walking speed. Overall, these findings provide valuable insights into the prevention and treatment of these conditions.

Association between sarcopenia and osteoporosis: the cross-sectional study from NHANES 1999-2020 and a bi-directions Mendelian randomization study

Background

Osteoporosis (OP) and sarcopenia are prevalent musculoskeletal conditions among the elderly. Nevertheless, the causal relationship between sarcopenia and OP remains a subject of controversy and uncertainty. In this study, we employed cross-sectional analysis and Mendelian randomization (MR) to investigate the intricate relationship between sarcopenia and OP.

Methods

The cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) spanning 1999-2020, which involved in 116,876 participants. It assessed the correlation between sarcopenia, osteoporosis (OP), and bone mineral density (BMD) using Chi-square tests, T-tests, and a multiple logistic regression model. Additionally, we conducted Mendelian randomization (MR) analysis to investigate the causal effects of sarcopenia-related characteristics (ALM) on OP. We employed IVW, sensitivity analysis, heterogeneity testing, and other methods for MR. The ALM data was sourced from the UK Biobank (n=450,243), while the aggregated data on OP was obtained from GWAS statistics (n=53,236).

Results

In this cross-sectional analysis, we observed that in the multivariate logistic regression model, without adjusting for any variables, OP emerged as a risk factor for sarcopenia [OR 95% CI = 1.90 (1.13-3.18), P = 0.02]. Following adjustments for gender, age, BMI, and biochemical variables, OP retained its status as a risk factor for sarcopenia [OR 95% CI = 3.54 (1.91-6.54), P < 0.001]. Moreover, after accounting for all variables, OP emerged as an independent risk factor for sarcopenia [OR 95% CI = 4.57 (1.47-14.22), P = 0.01].In the MR analysis, we uncovered that femoral neck BMD (FN BMD), lumbar spine BMD (LS BMD), and forearm bone mineral density (FA BMD) exerted a direct causal influence on ALM [FA BMD: OR 95% CI = 1.028 (1.008, 1.049), p = 0.006; FN BMD: OR (95% CI) = 1.131 (1.092, 1.170), p = 3.18E-12; LS BMD: OR (95% CI) = 1.080 (1.062, 1.098), p = 2.86E-19].

Conclusion

Our study has revealed a positive correlation between OP and the prevalence of sarcopenia. It suggests a potentially robust causal relationship between OP and sarcopenia. Notably, OP appears to be associated with a higher likelihood of losing ALM, and a significant loss of ALM may contribute to a decline in LS BMD.

Investigating the Causal Effects of Exercise-Induced Genes on Sarcopenia

Exercise is increasingly recognized as an effective strategy to counteract skeletal muscle aging and conditions such as sarcopenia. However, the specific exercise-induced genes responsible for these protective effects remain unclear. To address this, we conducted an eight-week aerobic exercise regimen on late-middle-aged mice and developed an integrated approach that combines mouse exercise-induced genes with human GWAS datasets to identify causal genes for sarcopenia. This approach led to significant improvements in the skeletal muscle phenotype of the mice and the identification of exercise-induced genes and miRNAs. By constructing a miRNA regulatory network enriched with transcription factors and GWAS signals related to muscle function and traits, we focused on 896 exercise-induced genes. Using human skeletal muscle cis-eQTLs as instrumental variables, 250 of these exercise-induced genes underwent two-sample Mendelian randomization analysis, identifying 40, 68, and 62 causal genes associated with sarcopenia and its clinical indicators-appendicular lean mass (ALM) and hand grip strength (HGS), respectively. Sensitivity analyses and cross-phenotype validation confirmed the robustness of our findings. Consistently across the three outcomes, RXRA, MDM1, RBL2, KCNJ2, and ADHFE1 were identified as risk factors, while NMB, TECPR2, MGAT3, ECHDC2, and GINM1 were identified as protective factors, all with potential as biomarkers for sarcopenia progression. Biological activity and disease association analyses suggested that exercise exerts its anti-sarcopenia effects primarily through the regulation of fatty acid oxidation. Based on available drug-gene interaction data, 21 of the causal genes are druggable, offering potential therapeutic targets. Our findings highlight key genes and molecular pathways potentially responsible for the anti-sarcopenia benefits of exercise, offering insights into future therapeutic strategies that could mimic the safe and mild protective effects of exercise on age-related skeletal muscle degeneration.

Body shape from birth to adulthood is associated with skeletal development: A Mendelian randomization study

BACKGROUND

Observational studies have shown that childhood obesity is associated with adult bone health but yield inconsistent results. We aimed to explore the potential causal association between body shape and skeletal development.

METHODS

We used two-sample Mendelian randomization (MR) to estimate causal relationships between body shape from birth to adulthood and skeletal phenotypes, with exposures including placental weight, birth weight, childhood obesity, BMI, lean mass, fat mass, waist circumference, and hip circumference. Independent genetic instruments associated with the exposures at the genome-wide significance level (P < 5 × 10-8) were selected from corresponding large-scale genome-wide association studies. The inverse-variance weighted analysis was chosen as the primary method, and complementary MR analyses included the weighted median, MR-Egger, weighted mode, and simple mode.

RESULTS

The MR analysis shows strong evidence that childhood (β = -1.29 × 10-3, P = 8.61 × 10-5) and adulthood BMI (β = -1.28 × 10-3, P = 1.45 × 10-10) were associated with humerus length. Tibiofemoral angle was negatively associated with childhood BMI (β = -3.60 × 10-1, P = 3.00 × 10-5) and adolescent BMI (β = -3.62 × 10-1, P = 2.68 × 10-3). In addition, genetically predicted levels of appendicular lean mass (β = 1.16 × 10-3, P = 1.49 × 10-13), whole body fat mass (β = 1.66 × 10-3, P = 1.35 × 10-9), waist circumference (β = 1.72 × 10-3, P = 6.93 × 10-8) and hip circumference (β =1.28 × 10-3, P = 4.34 × 10-6) were all associated with tibia length. However, we found no causal association between placental weight, birth weight and bone length/width.

CONCLUSIONS

This large-scale MR analysis explores changes in growth patterns in the length/width of major bone sites, highlighting the important role of childhood body shape in bone development and providing insights into factors that may drive bone maturation.

Genetically proxied appendicular lean mass and stroke risk: A two-step mendelian randomization study

BACKGROUND AND PURPOSE

Prior observational studies have suggested a strong correlation between sarcopenia and stroke, but the causal link between them remains uncertain. This study aims to investigate the associations between genetically predicted sarcopenia-related traits and stroke using a two-step Mendelian randomization (MR) approach.

METHODS

Genome-wide association study (GWAS) summary data for sarcopenia-related traits were acquired from the UK Biobank. Genetic associations for ischemic stroke (IS) and its subtypes were selected from the MEGASTROKE consortium comprising European ancestry participants. GWAS summary data for cerebral hemorrhage were obtained from the FinnGen consortium, including intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH). MR estimates were calculated using the inverse-variance weighted (IVW) method. The robustness of results was assessed for heterogeneity and pleiotropy of individual single nucleotide polymorphisms (SNPs).

RESULTS

Higher appendicular lean mass (ALM) exhibited a potential causal association with a reduced incidence of large artery atherosclerosis (LAA) (odds ratio [OR] = 0.81, 95% confidence interval [CI]:0.71-0.93; P = 0.003) and small vessel disease (SVD) (OR = 0.83, 95% CI:0.74-0.94; P = 0.002). The associations of ALM with IS and ICH were compromised after adjusting for body fat and physical activity with multivariable MR. Two-step MR mediation analysis explored 33 candidate mediators, among which hypertension and SBP accounted for more than 10% of the mediation proportion in the relationship between ALM and stroke and its subtypes.

CONCLUSION

Our research findings indicate that lower ALM is associated with a increased risk of stroke . It is necessary to explore the specific protective mechanisms of higher ALM for preventing stroke occurrence.

Impact of multiple obesity metrics on hypertensive disorders of pregnancy: a meta-analysis and Mendelian randomisation study

BACKGROUND

The relationships between various obesity measures and hypertensive disorders of pregnancy (HDP) remain inadequately explored, and their causal links are not well understood. This study aims to clarify these associations and investigate the mediating role of triglycerides.

METHODS

We conducted a comprehensive meta-analysis of observational studies alongside Mendelian randomisation (MR) analysis to assess the impact of 10 obesity measures on HDP risk. Additionally, we evaluated the mediating effect of triglycerides.

RESULTS

Our meta-analysis revealed significant associations between maternal prepregnancy overweight/obesity and increased risks of gestational hypertension (GH) (overweight: OR=1.98, 95% CI 1.83 to 2.15; obesity: OR=3.77, 95% CI 3.45 to 4.13) and pre-eclampsia (overweight: OR=1.78, 95% CI 1.67 to 1.90; obesity: OR=3.46, 95% CI 3.16 to 3.79). Higher maternal waist circumference (WC) was also linked to increased pre-eclampsia risk (OR=1.45, 95% CI 1.14 to 1.83). MR analyses indicated that each 1-SD increase in genetically predicted obesity measures (whole body fat mass, body fat percentage, trunk fat mass, trunk fat percentage, body mass index, WC, hip circumference) was associated with higher risks of GH and pre-eclampsia. Triglycerides mediated 4.3%-14.1% of the total genetic effect of these obesity measures on GH and pre-eclampsia risks.

CONCLUSIONS

This study demonstrates that various obesity measures are causally linked to increased HDP risk and highlights the mediating role of triglycerides. These findings could inform clinical practices and public health strategies aimed at reducing HDP through targeted obesity and triglyceride management.

Causal relationship between non-alcoholic fatty liver disease and sarcopenia: a bidirectional Mendelian randomization study

Introduction

A correlation between non-alcoholic fatty liver disease and sarcopenia is demonstrated, but the causality remains unclear. Our study aims to clarify the point of genetics between non-alcoholic fatty liver disease (NAFLD) and sarcopenia at the level of gene prediction through two-sample Mendelian randomization (MR) analysis.

Methods

The study employed the two-sample MR approach to investigate the bi-directional causality between NAFLD and sarcopenia. Published summary statistics were used to obtain instrumental variables (IVs) at the genome-wide significance level.

Results

IVW analysis showed that the risk of NAFLD was reduced when walking pace was increased (OR = 0.435, 95%CI 0.240-0.789, p = 0.006); Increasing appendicular lean mass (ALM) decreased the risk of NAFLD (OR = 0.906, 95%CI 0.838-0.980, p = 0.014); Those older than 60 were more likely to suffer from NAFLD if they had low grip strength (OR = 1.411, 95%CI 1.087-1.830, p = 0.0012). In the reverse MR study, weight median analysis showed that NAFLD caused a decrease in ALM (OR = 0.953, 95%CI 0.957-0.994, p = 0.001); whereas NAFLD showed no correlation with usual walking pace or grip strength (all with p > 0.05). MR-Egger regression analysis showed that there was no horizontal pleiotropy in the SNPs (all with p > 0.05).

Conclusion

The characteristics related to sarcopenia (usual walking pace, appendicular lean mass and low hand grip strength) may play a causal role in the development of nonalcoholic fatty liver disease, although the underlying mechanisms need to be further investigated. The presence of specific single nucleotide polymorphisms (SNPs) such as rs3747207, rs429358, and rs73001065 has been identified in the PNPLA3, APOE, and MAU2 proteins. These genetic markers represent potential targets for future interventions aimed at addressing, managing, or mitigating the risk of NAFLD.

Lipid metabolites and sarcopenia-related traits: a Mendelian randomization study

OBJECTIVE

To explore the influence of lipid metabolism on the risk of sarcopenia.

METHODS

Two-sample Mendelian randomization (MR) analysis was used to determine causality. A total of 179 lipid metabolism data points were used for exposure, and the data were obtained from a plasma lipid metabolite study of 7174 participants. The total muscle mass and total muscle strength, as well as the muscle strength and muscle mass of different sex groups, were selected as the relevant traits of sarcopenia. Data for outcomes were obtained from the UK Biobank, and sample sizes ranged from 135 468 to 450 243. Inverse-variance weighted (IVW), as the main method for evaluating the causal relationship between lipid metabolites and sarcopenia, uses the false discovery rate (FDR) for multiple comparisons and conducts heterogeneity, pleiotropy, and reverse causality tests.

RESULTS

Twenty-seven lipid metabolites, mainly phosphatidylcholine, phosphatidylethanolamine, ceramide, triacylglycerol, sphingomyelin, and sterol ester, were found to be associated with the risk of sarcopenia. Ceramide (d40:1), ceramide (d40:2), and sterol ester are risk factors for decreased muscle mass and strength. There is a positive causal relationship between various phosphatidylcholine lipids and muscle mass and strength. Sphingomyelin (d42:2) is a protective factor for total muscle strength and female muscle strength. There are inconsistent effects between different lipid metabolites, triacylglycerol, and muscle strength and muscle mass.

CONCLUSIONS

There was a causal relationship between 27 lipid metabolites and sarcopenia traits, and targeting specific lipid metabolites may benefit sarcopenia diagnosis, disease assessment, and treatment.

Causality between sarcopenia and diabetic neuropathy

Background

Past studies have demonstrated that diabetic neuropathy is related to sarcopenia, but the further causal relation is still unclear. We sought to investigate the causal relationship by combining data from cross-sectional and Mendelian randomization (MR) studies.

Methods

The genome-wide association studies data were collected from the UK Biobank and the European Working Group on Sarcopenia to conduct a bi-directional two-sample MR study to explore the causality between diabetic neuropathy and relevant clinical traits of sarcopenia, including appendicular lean mass (ALM), walking speed and low hand grip strength. The inverse-variance weighted and various sensitivity analyses were used to obtain MR estimates. We also enrolled a total of 196 Type 2 diabetes patients from April 2021 to April 2024 and divided them into the Distal peripheral neuropathy (DPN) group (n=51) and non-DPN group (n=145) via vibration perception threshold (VPT) and neuropathy deficit score. Logistic regression and ROC curve analysis were used to investigate the relationship between DPN and relevant sarcopenia clinical features.

Results

According to a forward MR analysis, decreased walking speed (OR: 0.04, 95% confidence interval (CI): 0.01-0.16; P<0.001) and increased ALM (1.25 [1.05-1.50], P=0.012) had a causal effect on developing diabetic neuropathy. According to reverse MR results, developing diabetic neuropathy had a causal effect on decreased walking speed (0.99 [0.99-1.00], P=0.007) and low grip strength (1.05 [1.02-1.08], P<0.001). The cross-sectional study showed that 5-time stand time (P=0.002) and 6-meter walking speed (P=0.009) had an inverse association with DPN. Additionally, we discovered that ASMI (P=0.030) and 5-time stand time (P=0.013) were separate risk factors for DPN.ConclusionThe MR study suggested that diabetic neuropathy may have a causality with relevant clinical traits of sarcopenia, and our cross-sectional study further proved that sarcopenia indexes are predictors of diabetic neuropathy.

Comprehensive analysis of molecular, physiological, and functional biomarkers of aging with neurological diseases using Mendelian randomization

An increasing burden of neurological diseases (NDs) has been a public health challenge in an aging society. Age, especially biological age, is the most important risk factor for NDs. Identification of biomarkers of aging to capture NDs might lead to a better understanding of the underlying mechanisms of pathological brain aging and the implementation of effective intervention. We conducted a comprehensive two-sample Mendelian Randomization (MR) study to investigate the association between various biomarkers of aging and three leading causes of NDs: Alzheimer's disease (AD), vascular dementia (VaD), and ischemic stroke. Publicly available GWAS summary statistics on people from European ancestry were obtained for six molecular biomarkers, two physiological biomarkers, and eight functional biomarkers, and three NDs. Genetic variants serving as instrumental variables (IVs) were identified for each biomarker. The MR analysis included inverse variance weighted (IVW), weighted median, MR-Egger, and MR-PRESSO. We found that short telomere length and decrease in appendicular lean mass were associated with an increased risk for AD (OR IVW = 1.12 per 1SD decrease, 95% confidence interval 1.02-1.22, and OR IVW = 1.11, 1.06-1.16, respectively), whereas high frailty index showed a protective effect for AD. Accelerated BioAge appeared to be associated with increased risk for ischemic stroke (OR IVW = 1.3 per year in BioAge acceleration, 95% CI 1.19-1.41). Our findings implied a causal association of short telomere length and a decrease in appendicular lean mass with an increased risk for AD, while BioAge appeared to be a good biomarker for ischemic stroke. Further studies are needed to validate these associations and explore underlying mechanisms.

Sarcopenia as a predictor of nutritional status and comorbidities: a cross-sectional and mendelian randomization study

BACKGROUND

With the advancement of world population aging, age-related sarcopenia (SP) imposes enormous clinical burden on hospital. Clinical research of SP in non-geriatric wards has not been appreciated, necessitating further investigation. However, observational studies are susceptible to confounders. Mendelian randomization (MR) can effectively mitigate bias to assess causality.

OBJECTIVE

To investigate the correlation between SP and comorbidities in orthopedic wards, and subsequently infer the causality, providing a theoretical basis for developing strategies in SP prevention and treatment.

METHODS

Logistic regression models were employed to assess the correlation between SP and comorbidities. The MR analysis was mainly conducted with inverse variance weighted, utilizing data extracted from the UK and FinnGen biobank (Round 9).

RESULTS

In the cross-sectional analysis, SP exhibited significant associations with malnutrition (P = 0.013) and some comorbidities, including osteoporosis (P = 0.014), body mass index (BMI) (P = 0.021), Charlson Comorbidity Index (CCI) (P = 0.006). The MR result also provided supporting evidence for the causality between SP and hypertension, osteoporosis and BMI. These results also withstood multiple sensitivity analyses assessing the validity of MR assumptions.

CONCLUSION

The result indicated a significant association between SP and BMI, CCI, malnutrition, and osteoporosis. We highlighted that SP and comorbidities deserved more attention in non-geriatric wards, urging further comprehensive investigation.

A causal relationship between sarcopenia and cognitive impairment: A Mendelian randomization study

OBJECTIVE

Sarcopenia and cognitive impairment often coexist in the elderly. In this study, we investigated the causal relationship between sarcopenia-related muscle characteristics and cognitive performance.

METHODS

We used linkage disequilibrium score regression (LDSC) and Mendelian Randomization (MR) analyses to estimate genetic correlations and causal relationships between genetically predicted sarcopenia-related muscle traits and cognitive function, as well as cognitive function-based discovery samples and replicated samples. Estimated effect sizes were derived from a fixed-effects meta-analysis.

RESULTS

Our univariate genome-wide association study (GWAS) meta-analysis indicated a causal relationship between appendicular lean mass (ALM) (β = 0.049; 95% confidence interval (CI): 0.032-0.066, P < 0.001) and walking pace (β = 0.349; 95% CI: 0.210-0.487, P < 0.001) with cognitive function, where a causal relationship existed between ALM in both male and female (βALM-Male(M) = 0.060; 95% CI: 0.031-0.089, PALM-M < 0.001; βALM-Female(F) = 0.045; 95% CI: 0.020-0.069, PALM-F < 0.001) with cognitive function. Low grip strength was not causally associated with cognitive function (β = -0.045; 95% CI: -0.092 - -0.002, P = 0.062). A reverse causality GWAS meta-analysis showed a causal relationship between cognitive function and ALM (β = 0.033; 95% CI: 0.018-0.048, P < 0.001) and walking pace (β = 0.039; 95% CI: 0.033-0.051, P < 0.001), where ALM in both male and female showed a causality (βALM-M = 0.041; 95% CI: 0.019-0.063, PALM-M < 0.001; βALM-F = 0.034; 95% CI: 0.010-0.058, PALM-F = 0.005). Cognitive function was not causally related to low grip strength (β = -0.024; 95% CI: -0.073-0.025, P = 0.344). Multivariable MR1 (MVMR1) analyses showed a significant causal relationship for ALM (β = 0.077; 95% CI: 0.044-0.109, P = 0.000) and walking pace (β = 0.579; 95% CI: 0.383-0.775, P = 0.000) and cognitive function. Multivariable MR2 (MVMR2) multivariate analysis showed that ALM causality remained (β = 0.069; 95% CI: 0.033-0.106, P = 0.000), and walking pace (β = 0.589; 95% CI: 0.372-0.806, P = 0.000).

CONCLUSIONS

Bidirectional two-sample MR demonstrated that sarcopenia-related muscle characteristics and cognitive performance were positive causal genetic risk factors for each other, while a multivariable MR study demonstrated that low ALM and a slow walking pace were causally involved in reduced cognitive performance. This study suggests a causal relationship between sarcopenia and cognitive impairment in older adults and provide new ideas for prevention and treatment.

Thyroid dysfunction and sarcopenia: a two-sample Mendelian randomization study

Objective

Observational studies have shown positive associations between thyroid dysfunction and risk of sarcopenia. However, the causality of this association remains unknown. This study aimed to evaluate the potential causal relationship between thyroid dysfunction and sarcopenia using Mendelian randomization (MR).

Methods

This study collected pooled data from genome-wide association studies focusing on thyroid dysfunction and three sarcopenia-related features: low hand grip strength, appendicular lean mass (ALM), and walking pace, all in individuals of European ancestry. The primary analytical method used was inverse-variance weighted, with weighted median and MR-Egger serving as complementary methods to assess causal effects. Heterogeneity and pleiotropy tests were also performed, and the stability of the results was evaluated using the Leave-one-out.

Results

The MR analysis indicated that hyperthyroidism could lead to a significant decrease in ALM in the extremities (OR = 1.03; 95% CI = 1.02 to 1.05; P < 0.001). The analysis also found that hypothyroidism could cause a notable reduction in grip strength (OR = 2.03; 95% CI = 1.37 to 3.01; P < 0.001) and walking pace (OR = 0.83; 95% CI = 0.77 to 0.90; P < 0.001). There was a significant association between subclinical hyperthyroidism and a reduced walking pace (OR = 1.00; 95% CI = 0.99 to 1.00; P = 0.041).

Conclusion

This study provides evidence that hyperthyroidism, hypothyroidism, and subclinical hyperthyroidism can all increase the risk of sarcopenia.

Causal Relationship Between Gut Microbiota, Metabolites, and Sarcopenia: A Mendelian Randomization Study

BACKGROUND

Gut microbiota imbalance and sarcopenia are frequently observed in older adults. Gut microbiota and their metabolites are considered risk factors contributing to the heightened risk of sarcopenia, but whether these associations are causal remains unclear.

METHODS

We conducted linkage disequilibrium score regression and 2-sample Mendelian randomization (MR) methods with single-nucleotide polymorphisms sourced from large-scale genome-wide association studies as instrumental variables to examine the causal associations linking gut microbiota with their metabolites to the sarcopenia. Following the MR analysis, subsequent sensitivity analyses were conducted to reinforce the robustness and credibility of the obtained results.

RESULTS

MR analysis yielded compelling evidence demonstrating the correlation between genetically predicted gut microbiota and metabolites and the risk of sarcopenia. The abundance of Porphyromonadaceae, Rikenellaceae, Terrisporobacter, and Victivallis was found to be associated with walking pace. Our study also found suggestive associations of 12 intestinal bacteria with appendicular lean mass, and of Streptococcaceae, Intestinibacter, Paraprevotella, Ruminococcaceae UCG009, and Sutterella with grip strength. Specifically, we identified 21 gut microbiota-derived metabolites that may be associated with the risk of sarcopenia.

CONCLUSIONS

Utilizing a 2-sample MR approach, our study elucidates the causal interplay among gut microbiota, gut microbiota-derived metabolites, and the occurrence of sarcopenia. These findings suggest that gut microbiota and metabolites may represent a potential underlying risk factor for sarcopenia, and offer the promise of novel therapeutic focal points.

Exploring causal effects of sarcopenia on risk and progression of Parkinson disease by Mendelian randomization

Previous observational studies suggested that sarcopenia is associated with Parkinson disease (PD), but it is unclear whether this association is causal. The objective of this study was to examine causal associations between sarcopenia-related traits and the risk or progression of PD using a Mendelian randomization (MR) approach. Two-sample bidirectional MR analyses were conducted to evaluate causal relationships. Genome-wide association study (GWAS) summary statistics for sarcopenia-related traits, including right handgrip strength (n = 461,089), left handgrip strength (n = 461,026), and appendicular lean mass (n = 450,243), were retrieved from the IEU OpenGWAS database. GWAS data for the risk of PD were derived from the FinnGen database (4235 cases; 373,042 controls). Summary-level data for progression of PD, including progression to Hoehn and Yahr stage 3, progression to dementia, and development of levodopa-induced dyskinesia, were obtained from a recent GWAS publication on progression of PD in 4093 patients from 12 longitudinal cohorts. Significant causal associations identified in MR analysis were verified through a polygenic score (PGS)-based approach and pathway enrichment analysis using genotype data from the Parkinson's Progression Markers Initiative. MR results supported a significant causal influence of right handgrip strength (odds ratio [OR] = 0.152, 95% confidence interval [CI] = 0.055-0.423, adjusted P = 0.0036) and appendicular lean mass (OR = 0.597, 95% CI = 0.440-0.810, adjusted P = 0.0111) on development of levodopa-induced dyskinesia. In Cox proportional hazard analysis, higher PGSs for right handgrip strength (hazard ratio [HR] = 0.225, 95% CI = 0.095-0.530, adjusted P = 0.0019) and left handgrip strength (HR = 0.303, 95% CI = 0.121-0.59, adjusted P = 0.0323) were significantly associated with a lower risk of developing levodopa-induced dyskinesia, after adjusting for covariates. Pathway enrichment analysis revealed that genome-wide significant single-nucleotide polymorphisms for right handgrip strength were substantially enriched in biological pathways involved in the control of synaptic plasticity. This study provides genetic evidence of the protective role of handgrip strength or appendicular lean mass on the development of levodopa-induced dyskinesia in PD. Sarcopenia-related traits can be promising prognostic markers for levodopa-induced dyskinesia and potential therapeutic targets for preventing levodopa-induced dyskinesia in patients with PD.