Genome-wide meta-analysis of muscle weakness identifies 15 susceptibility loci in older men and women

Association between grip strength and cognitive function in older adults: results from a cross-sectional study and Mendelian randomization analyses

BACKGROUND

Impaired cognitive function is a known marker of human aging, and the causal relationship between grip strength, as a part of physical activity, and cognitive function is still unclear.

METHOD

Data on grip strength and cognitive function were collected in a cross-sectional study conducted in Guangxi Gongcheng 2018-2019. Generalized linear regression models were utilized to assess the relationship between grip strength and cognitive impairment. A two-way two-sample MR study was used to further determine the causal relationship, mainly using Inverse variance weighted (IVW), weighted median, and MR-Egger. Sensitivity analysis was also used to confirm the robustness of the results. Finally, MVMR analysed BMI and CRP as potential confounders.

RESULT

A total of 1723 participants were included in the cross-sectional study. Generalized linear regression models showed that low grip strength was a risk factor for cognitive impairment after adjusting for covariates such as age, gender, and ethnicity (OR: 0.965; 95 % CI: 0.947 to 0.984), and the onset of cognitive impairment led to reduced grip strength (OR: 0.251; 95 % CI: 0.113 to 0.559). The results of the two-way two-sample MR also supported the mutual causal relationship between low grip strength (OR = 0.93; 95 % Cl: 0.89-0.97) and cognitive impairment (OR = 0.878; 95 % Cl: 0.794-0.971). The results of the MVMR analysis also proved this relationship.

CONCLUSION

Low grip strength increases the risk of cognitive impairment, and conversely, cognitive impairment contributes to an increased risk of reduced grip strength.

Association of frailty with respiratory tract infections: Evidence from cross-sectional analysis and mendelian randomization

BACKGROUND

Respiratory tract infections (RTI) remain a challenge to global health, particularly in the frail populations. However, an understanding of the causal relationship between frailty and RTI is limited.

METHODS

Two complementary approaches were used. First, we conducted a cross-sectional analysis to examine the association between frailty index (FI) and RTI, using data from the NHANES 2013-2014. We then introduced Mendelian randomization (MR) using genome-wide association study summary statistics to determine the causality between frailty index, low grip strength, walking pace, light physical activity, and upper (URTI) or lower RTI (LRTI). The primary method of inverse variance weighting and complementary MR methods were used to verify causality. Sensitivity analysis was conducted to confirm the robustness of the primary results.

RESULTS

A total of 2249 participants were enrolled in the cross-sectional study. Weighted multivariable-adjusted logistic regression analysis showed that the frailty index was positively associated with RTI after adjusting for covariates (Continuous FI, odds ratio [OR] = 4.95; 95 % confidence interval [CI], 1.69-14.50, P = 0.004; Categorical FI, OR = 1.51 [95 % CI, 1.11-2.06, P = 0.009]). Restricted cubic spline analysis showed a significant increase in the prevalence of RTI when FI was >0.24. The results of the MR analysis supported a causal relationship between the frailty index and LRTI (OR = 1.939 [95 % CI, 1.180-3.186, P = 0.009]). Sensitivity analysis further confirmed the robustness of these findings.

CONCLUSION

Our study identified a potential association between the FI and RTI at both phenotypic and genetic levels. The results revealed a causal relationship between the FI and LRTI.

Multivariate genome-wide analysis of sarcopenia reveals genetic comorbidity with urological diseases

INTRODUCTION

Sarcopenia is a prevalent age-related disorder characterized by progressive loss of muscle mass, strength, and physical performance. While genome-wide association studies (GWAS) have explored isolated traits, the multifactorial genetic architecture underlying sarcopenia remains poorly defined. In this study, we constructed a comprehensive genetic factor to explain the genetic architecture of sarcopenia, and explore causal associations, genetic comorbidities, and mediating pathways linking sarcopenia to 30 urological diseases.

METHODS

Based on the European Working Group on Sarcopenia in Older People (EWGSOP) criteria, six sarcopenia-related phenotypes were selected. A multivariate GWAS framework using genomic structural equation modeling (genomic SEM) was constructed, with an effective sample size of 651,820 individuals. Bidirectional Mendelian randomization (MR) was employed to assess causal relationships between sarcopenia and 30 urological diseases. Genetic correlation, tissue-specific heritability enrichment, shared risk genes, and gene set enrichment analyses were conducted to dissect genetic comorbidities between sarcopenia and urological diseases. Multi-omic mediation analysis was conducted to identify potential pathways mediated by blood proteins, metabolites, and immune traits.

RESULTS

Multivariate GWAS identified 215 loci and 30,869 single-nucleotide polymorphisms (SNPs) associated with polygenic architecture of sarcopenia. Bidirectional Mendelian randomization revealed causal links between sarcopenia and urological diseases, notably hyperplasia of prostate (BPH; OR = 1.17, P = 0.043) and acute tubulointerstitial nephritis (ATIN; OR = 1.14, P = 0.028). Genetic comorbidity analyses identified local genetic correlations between sarcopenia and BPH, and highlighted tissue-specific heritability enrichment in Cells Cultured fibroblasts tissue for both traits, while no genetic correlation was found with ATIN. We identified 75 shared risk genes for sarcopenia and BPH, which were enriched in cellular component biogenesis, RNA binding, and metabolic pathways. Multi-omic mediation analyses prioritized 17 metabolites and proteins linking sarcopenia to BPH and ATIN, though no significant immune mediators were identified.

CONCLUSION

These findings unveil a shared genetic architecture between sarcopenia and urological diseases, especially BPH, with heritability enrichment in fibroblast tissue and metabolic dysfunction emerging as the significant overlapping pathway.

Genome-wide association meta-analysis of age at onset of walking in over 70,000 infants of European ancestry

Age at onset of walking is an important early childhood milestone which is used clinically and in public health screening. In this genome-wide association study meta-analysis of age at onset of walking (N = 70,560 European-ancestry infants), we identified 11 independent genome-wide significant loci. SNP-based heritability was 24.13% (95% confidence intervals = 21.86-26.40) with ~11,900 variants accounting for about 90% of it, suggesting high polygenicity. One of these loci, in gene RBL2, co-localized with an expression quantitative trait locus (eQTL) in the brain. Age at onset of walking (in months) was negatively genetically correlated with ADHD and body-mass index, and positively genetically correlated with brain gyrification in both infant and adult brains. The polygenic score showed out-of-sample prediction of 3-5.6%, confirmed as largely due to direct effects in sib-pair analyses, and was separately associated with volume of neonatal brain structures involved in motor control. This study offers biological insights into a key behavioural marker of neurodevelopment.

Multi-modal microcarriers reprogram mitochondrial metabolism and activate efferocytosis in macrophages for osteoporotic bone repair

Osteoporotic bone repair remains challenging due to the ineffectiveness of traditional bone repair materials in adapting to the complex immune microenvironment of aging bone tissue. Exploiting the key role of macrophages in regulating this immune environment through the rational design of osteoimmunomodulatory biomaterials has emerged as a promising approach. However, current designs inadequately address the complexity of macrophage functions in aging environments, resulting in suboptimal regulatory effects. Hence, we explored multi-modal microcarriers for enhancing macrophage functionality. In this work, we developed a VGX-1027-loaded mesoporous silica nanosphere composite PLLA microcarrier. The dual-carrier system, featuring a micro-nano hybrid design by spatially separating the mesoporous silica nanoparticles and PLLA microspheres, enables sustained intracellular release of VGX-1027, addressing the chronic nature of osteoporotic fractures. Our studies demonstrate this VGX-1027 microcarrier (PMVGX) promotes M2 macrophage polarization by reprogramming mitochondrial metabolism. Simultaneously, it enhances efferocytosis, facilitating the clearance of dead or senescent cells and reducing inflammatory responses, thus reshaping the aging osteoimmunomodulatory. Furthermore, PMVGX induces macrophages to release osteogenic exosomes containing miR-5106 through paracrine signaling, significantly enhancing osteogenic function. In a postmenopausal osteoporosis animal model, PMVGX exhibited remarkable efficacy in repairing osteoporotic bone defects. This proof-of-concept study demonstrates that our multi-modal microcarrier effectively regulates macrophage functions via mitochondrial homeostasis, efferocytosis, and exosome content, offering great potential for osteoporotic bone repair.

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.

Variability in sensitivity to inflammation in muscle and lung of patients with COPD may underlie susceptibility to lung function decline

BACKGROUND

Muscle wasting and weakness (sarcopenia) are commonly associated with COPD causing frailty and reduced quality of life. The contribution of inflammation to muscle loss and the susceptibility to rapid lung function decline is debated. We hypothesised that comparing the muscle transcriptome to circulating inflammatory cytokine profiles in patients would identify any contribution of systemic inflammation to muscle atrophy.

METHODS

Quadriceps differential gene expression was determined between mild-COPD (n=28) and severe-COPD (n=51) using GSE100281. These microarray data were compared by biweight mid-correlation with lung function and plasma cytokine levels from the same patients.

RESULTS

Patients with severe COPD had reduced fat-free mass index (a measurement of muscle mass) compared with patients with mild COPD despite similar physical activity and inflammatory cytokine levels. Gene sets associated with inflammation and epithelial mesenchymal transition (EMT) were elevated in severe COPD, suggesting that inflammation may contribute to the loss of muscle mass. In patients with severe COPD, EMT and inflammation gene sets were strongly associated with circulating proinflammatory and anti-inflammatory cytokines. However, in patients with mild COPD, anti-inflammatory cytokines showed negative associations with these gene sets and associations with proinflammatory cytokines were weak. In data from lung and blood samples, patients with severe COPD had elevated inflammatory and EMT gene expression compared with patients with mild COPD suggesting that this phenomenon is not muscle-specific.

CONCLUSIONS

In patients at the severe end of the COPD spectrum, the proinflammatory response in muscle predominates, whereas in patients at the mild end of the spectrum, the anti-inflammatory response predominates. This suggestion needs confirming in a longitudinal cohort.

Smoking, alcohol and risk of sarcopenia: a Mendelian randomisation study

OBJECTIVE

Observational studies have found that cigarette smoking increased the prevalence and incidence of sarcopenia, whereas alcohol consumption appeared to decrease the risk. These findings, however, may be susceptible to either confounding bias or reverse causation. We conducted a Mendelian randomisation (MR) study to appraise the causal relation of cigarette smoking and alcohol consumption to the risk of sarcopenia.

METHODS

Genetic instruments associated with cigarette smoking (cigarettes per day) and alcohol consumption (drinks per week) were retrieved from the publicly available genome-wide association data. Individual-level, electronic medical record-linked data on sarcopenia, grip strength and appendicular lean mass were obtained from the UK Biobank. We performed two-sample univariable and multivariable MR analyses to examine the relation of genetically determined cigarette smoking and alcohol consumption to the risk of sarcopenia and its indices.

RESULTS

One SD increase of genetically determined cigarette smoking was associated with an increased risk of sarcopenia (OR=2.51, 95% CI: 1.26 to 5.01, p=0.001), decreased grip strength (β=-0.63 kg, 95% CI: -1.13 to -0.13, p=0.01) and less appendicular lean mass (β=-0.22 kg, 95% CI: -0.44 to -0.01, p=0.04). Although one SD increase of genetically determined alcohol consumption was associated with decreased grip strength (β=-1.15 kg, 95% CI: -2.09 to -0.10, p=0.02), no statistically significant causal association was observed between genetically determined alcohol consumption and either sarcopenia (OR=0.96, 95% CI: 0.35 to 2.62, p=0.94) or appendicular lean mass (β=-0.23 kg, 95% CI: -0.91 to 0.45, p=0.51).

CONCLUSIONS

Our findings showed that genetically determined cigarette smoking, but not alcohol consumption, was causally associated with the risk of sarcopenia.

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.

Exploring the causal relationship between delirium and sarcopenia using bidirectional two-sample Mendelian randomization study

BACKGROUND

Population-based studies have validated the significant associations between delirium and sarcopenia. Nonetheless, the causality remains ambiguous. This study aims to elucidate the causal associations between delirium and sarcopenia, as well as the causal effects of medication use on both conditions.

METHODS

A bidirectional two-sample Mendelian randomization (MR) analysis was performed based on public genome-wide association studies (GWAS) data. Causal effects were evaluated through the inverse-variance weighted (IVW) method as the principal analysis, supplemented by the weighted median, weighted mode. Cochran's Q test, MR-Egger regression, MR-PRESSO test and leave-one-out were applied for sensitivity analyses.

RESULTS

The IVW method indicated a causal relationship between genetically predicted low hand-grip strength and delirium (OR = 1.31, 95 % CI: 1.02-1.67, P = 0.032). Additionally, diuretics (OR = 1.05, 95 % CI: 1.03-1.07, P < 0.001) and glucocorticoids (OR = 1.06, 95 % CI: 1.01-1.12, P = 0.012) were causally associated with appendicular lean mass, and diabetes medications (OR = 1.04, 95 % CI: 1.02-1.06, P = 0.001) and immunosuppressants (OR = 1.05, 95 % CI: 1.02-1.09, P = 0.005) causally associated with low hand-grip strength. Alternative analytic methods yielded consistent results. Heterogeneity and horizontal pleiotropy were evident in associations between medication use and both delirium and sarcopenia, but the results remained consistent after excluding outliers.

CONCLUSION

This study provided evidence of a causal relationship between genetically predicted low hand-grip strength and delirium. However, the analysis revealed that medication use did not appear to act as a mediating factor between these two conditions. Larger population-based studies are needed to validate these findings.

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.

Genetic determinants of muscle health: A population-based study

BACKGROUND

Muscle mass is associated with physical and functional performance across adulthood. Its reduction plays a crucial role in the development of age-related conditions such as frailty and sarcopenia. Genetic variations potentially impact muscle health, particularly in an aged population.

OBJECTIVES

For this reason, we aimed to evaluate the association between genetic biomarkers and appendicular lean mass index (ALMI), a marker of muscle health, to identify possible risk factors for age-related sarcopenia in a population-based study.

MATERIALS AND METHODS

We cross-sectionally analyzed data collected in 2015 from the São Paulo Epidemiologic Sleep Study (EPISONO). Participants underwent bioelectrical impedance and genetic evaluations.

RESULTS

After adjusting the data for age and sex, 12 single nucleotide polymorphisms (SNP) were significantly associated with ALMI. Among them, rs9928094 (beta = -0.031 p = 0.029) and rs9930333 (beta = -0.030 p = 0.035) are located in the FTO gene, which is related to obesity and fat gain and, rs16839632 (beta = 0.038 p = 0.029) located in the FMN2 gene, responsible for actin cytoskeleton and cell polarity.

CONCLUSIONS

Poor muscle health is a multifactorial condition and genetic biomarkers can support the stratification of the risk for adverse body composition states affecting muscle and physical performance across adulthood.

A Causal Effect of Serum 25(OH)D Level on Appendicular Muscle Mass: Evidence From NHANES Data and Mendelian Randomization Analyses

BACKGROUND

Low serum vitamin D status was reported to be associated with reduced muscle mass; however, it is inconclusive whether this relationship is causal. This study used data from the National Health and Nutrition Examination Survey (NHANES) and two-sample Mendelian randomization (MR) analyses to ascertain the causal relationship between serum 25-hydroxyvitamin D [25(OH)D] and appendicular muscle mass (AMM).

METHODS

In the NHANES 2011-2018 dataset, 11 242 participants (5588 males and 5654 females) aged 18-59 years old were included, and multivariant linear regression was performed to assess the relationship between 25(OH)D and AMM measured by dual-energy X-ray absorptiometry. In two-sample MR analysis, 167 single nucleotide polymorphisms significantly associated with serum 25(OH)D at the genome-wide association level (p < 5 × 10-8) were applied as instrumental variables (IVs) to assess vitamin D effects on AMM in the UK Biobank (417 580 Europeans) using univariable and multivariable MR (MVMR) models.

RESULTS

In the NHANES dataset, serum 25(OH)D concentrations were positively associated with AMM (β = 0.013, SE = 0.001, p < 0.001) in all participants, after adjustment for age, race, season of blood collection, education, income, body mass index and physical activity. In stratification analysis by sex, males (β = 0.024, SE = 0.002, p < 0.001) showed more pronounced positive associations than females (β = 0.003, SE = 0.002, p = 0.024). In univariable MR, genetically higher serum 25(OH)D levels were positively associated with AMM in all participants (β = 0.049, SE = 0.024, p = 0.039) and males (β = 0.057, SE = 0.025, p = 0.021), but only marginally significant in females (β = 0.043, SE = 0.025, p = 0.090) based on IVW models was noticed. No significant pleiotropy effects were detected for the IVs in the two-sample MR investigations. In MVMR analysis, a positive causal effect of 25(OH)D on AMM was observed in the total population (β = 0.116, SE = 0.051, p = 0.022), males (β = 0.111, SE = 0.053, p = 0.036) and females (β = 0.124, SE = 0.054, p = 0.021).

CONCLUSIONS

Our results suggested a positive causal effect of serum 25(OH)D concentration on AMM; however, more researches are warranted to unveil the underlying biological mechanisms and evaluate the effects of vitamin D intervention on AMM.

Causal Associations with Arterial Stiffness and Sarcopenia: A Mendelian Randomization Analysis

Observational studies and clinical trials indicate a link between arterial stiffness (AS) and sarcopenia (SAR), yet the causal relationship between these remains unclear. The study aims to investigate the causal connection from AS to SAR by Mendelian randomization (MR). We analyzed Genome-Wide Association Studies data for AS indicators: pulse wave arterial stiffness index (PWASI) and pulse wave peak-to-peak time (PPT), and SAR indicators: low hand grip strength (LHGS), usual walking pace (UWP), moderate-to-vigorous physical activity levels (MVPA), and walk or cycle unassisted for 10 minutes. The inverse variance-weighted, MR-Egger, weighted mode, and weighted median were applied to MR. There is a bidirectional causal relationship between the AS and SAR. The PWASI has a causation with UWP (odds ratio [OR] = 0.97, 95% confidence interval [CI] = 0.94-0.99). The PPT has a causal association with MVPA (OR = 1.08, 95% CI = 1.002-1.144) and UWP (OR = 1.05, 95% CI = 1.017-1.096). The LHGS is causally associated with PPT (OR = 0.95, 95% CI = 0.91-0.98) and UWP has a causal association with PWASI (OR = 0.77, 95% CI = 0.65-0.90) and PPT (OR = 1.37, 95% CI = 1.17-1.60). The increased AS could reduce the motor ability slightly and the lower upper and lower limb strength could lead to the higher AS. This bidirectional causal relationship of the two may offer novel perspectives for advancing the understanding of the underlying mechanisms related to AS and muscle pathophysiology.

Polygenic Associations between Motor Behaviour, Neuromotor Traits, and Active Music Engagement in Four Cohorts

Phenotypic investigations have shown that actively engaging with music, i.e., playing a musical instrument or singing may be protective of motor decline in aging. For example, music training associated with enhanced sensorimotor skills accompanied by changes in brain structure and function. Although it is possible that the benefits of active music engagement "transfer" to benefits in the motor domain, it is also possible that the genetic architecture of motor behaviour and the motor system structure may influence active music engagement. This study investigated whether polygenic scores (PGS) for five behavioural motor traits, 12 neuromotor structural brain traits, and seven rates of change in brain structure traits trained from existing discovery genome-wide association studies (GWAS) predict active music engagement outcomes in four independent cohorts of unrelated individuals of European ancestry: the Canadian Longitudinal Study on Aging (CLSA; N=22,198), Wisconsin Longitudinal Study (WLS; N=4,605), Vanderbilt's BioVU Repository (BioVU; N=6,150), and Vanderbilt's Online Musicality study (OM; N=1,559). Results were meta-analyzed for each PGS main effect across outcomes and cohorts, revealing that PGS for a faster walking pace was associated with higher amounts of active music engagement. Within CLSA, a higher PGS for walking pace was associated with greater odds of engaging with music. Findings suggest a shared genetic architecture between motor function and active music engagement. Future intervention-based research should consider the genetic underpinnings of motor behavior when evaluating the effects of music engagement on motor function across the lifespan.

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.

Risk factors and predictive modeling in a US population with sarcopenia: a propensity score cohort study

Sarcopenia, characterized by loss of muscle mass and strength, particularly affects older adults and is linked to increased morbidity and mortality. The study aimed to investigate the relationship between biomarkers, including hemoglobin (Hb), lactate dehydrogenase (LDH), and Systemic Immune-Inflammation Index (SII), and sarcopenia in the US population. Utilizing NHANES data from 2003 to 2018, the study analyzed 5,615 participants, categorizing them based on quartiles of Hb, SII, and LDH levels. It employed logistic regression models to assess the relationship between these biomarkers and sarcopenia risk, adjusting for various confounders. High levels of LDH, Hb and SII were significantly associated with sarcopenia, with higher risk in the highest quartile. The AUC for all indicators in predicting sarcopenia was 0.925 (sensitivity 0.925; specificity 0.743). The study concludes that elevated Hb, LDH, and SII levels are significant biomarkers associated with sarcopenia, emphasizing the role of inflammation in its development and the potential for these markers in early detection and intervention.

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

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

Association Analysis of the Circulating Proteome With Sarcopenia-Related Traits Reveals Potential Drug Targets for Sarcopenia

BACKGROUND

Sarcopenia severely affects the physical health of the elderly. Currently, there is no specific drug available for sarcopenia. This study aims to identify pathogenic proteins and druggable targets for sarcopenia through Mendelian randomization (MR)-based analytical framework.

METHODS

A sequential stepwise screening method that includes two-sample MR, Steiger filtering test and colocalization (MRSC) was applied to identify causal proteins associated with sarcopenia-related traits. In the MR analyses, 4372 circulating proteins with valid instrumental variables (IVs) from eight proteomic genome-wide association studies were utilized as exposures, and nine sarcopenia-related traits were utilized as outcomes. IVs were classified into cis-protein quantitative trait loci (pQTLs) and trans-pQTLs based on their positions. We conducted cis-only MRSC analyses and cis + trans MRSC analyses using cis-pQTLs and cis + trans pQTLs as IVs, respectively. Post-MRSC analyses were conducted on the prioritized findings of MRSC, including annotation of protein-altering variants (PAVs), assessment of overlap between pQTLs and expression quantitative trait loci (eQTLs), protein-protein interaction (PPI) analysis, pathway enrichment analysis and annotation of drug targets. Utilizing data from the UK Biobank, we performed an observational study to explore the associations between baseline circulating protein levels and the longitudinal changes in nine sarcopenia-related traits.

RESULTS

A total of 181 causal associations for 65 proteins were prioritized by the cis-only MRSC analyses and 227 associations for 91 proteins were prioritized by the cis + trans MRSC analyses. Among the prioritized proteins, the majority of them employed non-PAVs as IVs and most of their cis-pQTLs overlapped with corresponding eQTLs and exhibited consistent directionality, with only one trans-pQTL overlapping with an eQTL. The PPI network of cis-only MRSC-prioritized proteins (p = 4.04 × 10-4) and cis + trans MRSC-prioritized proteins (p = 8.76 × 10-5) showed significantly more interactions than expected. Reactome, KEGG and GO pathway enrichment analyses for cis-only MRSC-prioritized proteins identified 52, 12 and 79 enriched pathways, respectively (adjusted p < 0.05). For proteins identified by cis + trans MRSC analyses, only 15 pathways were enriched through the GO pathway enrichment analyses. In the observational study, 197 circulating proteins were identified to be associated with one or more sarcopenia-related traits (p < 0.05/2923). Among them, the significant associations of CTSB (negative association) and ASGR1 (positive association) with sarcopenia-related traits were observed to have consistent directional associations in both MR-based studies and observational studies. Drug target annotations suggested that 52 MRSC-prioritized proteins and 145 biomarkers are drug targets or druggable.

CONCLUSIONS

This study identified 89 potential pathogenic proteins and 197 candidate biomarkers for sarcopenia, providing valuable clues for the development of therapeutic drugs for sarcopenia.

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.

Multi-trait Genome-Wide Analysis Identified 20 Novel Loci for Sarcopenia-Related Traits in UK Biobank

This study aims to identify novel loci associated with sarcopenia-related traits in UK Biobank (UKB) through multi-trait genome-wide analysis. To identify novel loci associated with sarcopenia, we integrated the genome-wide association studies (GWAS) of usual walking pace (UWP) and hand grip strength (HGS) to conduct a joint association study known as multi-trait analysis of GWAS (MTAG). We performed a transcriptome-wide association study (TWAS) to analyze the results of MTAG in relation to mRNA expression data for genes identified in skeletal muscle. Additionally, we utilized Weighted Gene Co-Expression Network Analysis (WGCNA) and Protein-Protein Interaction (PPI) networks to explore the relationships between the identified genes and hub genes related to sarcopenia. We identified 15 novel loci associated with UWP and 5 novel loci associated with HGS at the genome wide significance level (GWS, p < 5 × 10 - 8 ). After TWAS (p TWAS < 6.659 × 10 - 6 , 0.05 / 7509 ), we found two significant genes: PPP1R3A, located at 7q31.1 and associated with HGS, and ZBTB38, located at 3q23 and associated with UWP. 11 identified genes associated with hub genes for sarcopenia were obtained through WGCNA. Our findings offer new insights into biological mechanisms underlying sarcopenia and identify several novel genes related to sarcopenia that warrant in-depth study.

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 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.

Dynapenia-abdominal obesity and mortality risk, is independent effect obscured by age and frailty?:Birjand Longitudinal Aging Study (BLAS)

Background

Abdominal obesity and low muscle strength, known separately as risk factors for mortality, might have a synergistic effect when they co-occur. Dynapenic abdominal obesity (DAO) is a condition defined by the presence of both. However, DAO's independent and combined impact on mortality remains under investigation.

Objective

The objective of the present study was to evaluate the association of dynapenia, abdominal obesity, and dynapenic abdominal obesity with all-cause mortality among community-dwelling older adults.

Methods

This is a longitudinal study with a 5-year follow-up conducted involving 1,354 community-dwelling older adults (≥ 65 years) of the Birjand Longitudinal Aging Study (BLAS). Abdominal obesity and dynapenia were respectively defined based on waist circumference (> 102 cm for men and > 88 cm for women) and grip strength (< 26 kg for men and < 16 kg for women). The sample was divided into four groups: non-dynapenic/non-abdominal obesity (ND/NAO), dynapenic/non-abdominal obesity (D/NAO), non-dynapenic/abdominal obesity (ND/AO), and dynapenic/abdominal obesity (D/AO). The outcome was all-cause mortality registered through four methods: 1- telephone interview with the family of the participants during September 2018 and February 2024, 2- hospital information systems, 3- death registry of the deputy of the Health of Birjand University of Medical Sciences 4- in a subject who died at home or out of hospital death registry was verified by a verbal autopsy performed by a clinician. Univariate and multiple Logistic regression models were used to estimate the risk of all-cause mortality as a function of dynapenia and abdominal obesity in competing events controlled by age, sex, multi-morbidity, and frailty.

Results

The mean age of the study participants was 69.77 ± 7.55 years, and about 703 (51.71%) were female. There was a statistical difference between the alive and the deceased groups in terms of sex, age, multimorbidity, and frailty. Mortality was statistically higher among dynapenic participants (P < 0.001). Unadjusted logistic regression analysis explored the relationship between D/NAO and mortality (OR = 2.18; CI 95% 1.25-3.78). In the adjusted models, no significant relationships were observed. Age and frailty had significant associations with mortality.

Conclusion

While our study found an association between dynapenia without abdominal obesity and increased mortality risk, factors like age and frailty might play a stronger role. These require further investigation to understand the independent effect of dynapenia on mortality fully.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01501-8.

The Impact of SGLT1 Inhibition on Frailty and Sarcopenia: A Mediation Mendelian Randomization Study

BACKGROUND

Although pharmacological effects of SGLT2 inhibitors on the development of frailty and sarcopenia were known, the role of SGLT1 remained less clear. The present study investigated the possible effect of SGLT1 inhibition on these conditions and explored potential mediators.

METHODS

A two-sample Mendelian randomization (MR) analysis was performed to assess the effect of SGLT1 inhibition on frailty index (FI) and low grip strength in individuals aged 60 years and older using both the FNIH and EWGSOP criteria. Subsequently, a two-step MR analysis was conducted to investigate the mediating role of insulin resistance phenotype and identify potential mediators of the effect of SGLT1 inhibition on the FI and low grip strength from 1558 plasma proteins and 1352 metabolites.

RESULTS

Genetically predicted SGLT1 inhibition was associated with decreased FI (β: -0.290 [95% CI: -0.399, -0.181]) and reduced risk of low grip strength in individuals aged 60 years and older under both FNIH (β: -0.796 [95% CI: -1.216, -0.376]) and EWGSOP criteria (β: -0.287 [95% CI: -0.532, -0.041]). The two-step MR analysis demonstrated the role of insulin resistance phenotype in mediating SGTL1 inhibition on alleviating frailty (mediation proportion = 19.56% [95% CI: 8.42%, 30.70%]). After screening, 24 proteins and 16 metabolites were identified as mediators of the impact of SGLT1 inhibition on FI. Additionally, 13 proteins and 16 metabolites were found to mediate the effect of SGLT1 inhibition on low grip strength according to FNIH criteria while 22 proteins and 6 metabolites were shown to mediate the impact of SGLT1 inhibition on low grip strength under EWGSOP criteria.

CONCLUSIONS

SGLT1 inhibition potentially mitigated frailty and sarcopenia through several biological mediators, shedding new light for therapeutic intervention.

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.

Effect of muscle strength on deep vein thrombosis: A Mendelian randomization study

Deep vein thrombosis (DVT) is a serious condition characterized by blood clots in deep veins, posing a significant public health burden. Muscle strength has been implicated as a potential risk factor for DVT due to its influence on venous return. This study aims to investigate the causal association between muscle strength and DVT using a Mendelian randomization (MR) approach, leveraging genetic variants as instrumental variables (IVs). We conducted a 2-sample MR analysis using genome-wide association study (GWAS) data for hand-grip strength and DVT. IVs were selected based on their significant associations with muscle strength and DVT, as well as their linkage disequilibrium patterns. We employed statistical methods including inverse-variance weighting (IVW), MR-Egger, and weighted median to address pleiotropy bias. Sensitivity analyses were conducted to evaluate the robustness of the results. A total of 21 and 14 independent IVs were identified for hand grip strength (EWGSOP) and hand grip strength (FNIH), respectively. IVW analysis revealed a consistent causal and negative association between both definitions of hand grip strength and DVT (EWGSOP: OR = 0.702, 95% CI: 0.511-0.964, P = .029; FNIH: OR = 0.715, 95% CI: 0.570-0.898, P = .004). No directional pleiotropy was detected in MR-Egger and MR-PRESSO analyses for either definition (EWGSOP: MR-Egger Intercept P = .516; MR-PRESSO global test P = .162; FNIH: MR-Egger Intercept P = .569; MR-PRESSO global test P = .371).Sensitivity analyses demonstrated the stability of the causal effect estimates, with little influence from individual IVs. The MR analysis provided evidence of a causal association between muscle strength and DVT risk, suggesting that increasing muscle strength may have a protective effect. These findings have implications for preventive strategies and the promotion of resistance exercises and muscle-strengthening activities. Further research and validation of these results could inform clinical guidelines and interventions for DVT prevention.

GDF5 as a rejuvenating treatment for age-related neuromuscular failure

Sarcopenia involves a progressive loss of skeletal muscle force, quality and mass during ageing, which results in increased inability and death; however, no cure has been established thus far. Growth differentiation factor 5 (GDF5) has been described to modulate muscle mass maintenance in various contexts. For our proof of concept, we overexpressed GDF5 by AAV vector injection in tibialis anterior muscle of adult aged (20 months) mice and performed molecular and functional analysis of skeletal muscle. We analysed human vastus lateralis muscle biopsies from adult young (21-42 years) and aged (77-80 years) donors, quantifying the molecular markers modified by GDF5 overexpression in mouse muscle. We validated the major effects of GDF5 overexpression using human immortalized myotubes and Schwann cells. We established a preclinical study by treating chronically (for 4 months) aged mice using recombinant GDF5 protein (rGDF5) in systemic administration and evaluated the long-term effect of this treatment on muscle mass and function. Here, we demonstrated that GDF5 overexpression in the old tibialis anterior muscle promoted an increase of 16.5% of muscle weight (P = 0.0471) associated with a higher percentage of 5000-6000 µm2 large fibres (P = 0.0211), without the induction of muscle regeneration. Muscle mass gain was associated with an amelioration of 26.8% of rate of force generation (P = 0.0330) and better neuromuscular connectivity (P = 0.0098). Moreover, GDF5 overexpression preserved neuromuscular junction morphology (38.5% of nerve terminal area increase, P < 0.0001) and stimulated the expression of reinnervation-related genes, in particular markers of Schwann cells (fold-change 3.19 for S100b gene expression, P = 0.0101). To characterize the molecular events induced by GDF5 overexpression during ageing, we performed a genome-wide transcriptomic analysis of treated muscles and showed that this factor leads to a 'rejuvenating' transcriptomic signature in aged mice, as 42% of the transcripts dysregulated by ageing reverted to youthful expression levels upon GDF5 overexpression (P < 0.05). Towards a preclinical approach, we performed a long-term systemic treatment using rGDF5 and showed its effectiveness in counteracting age-related muscle wasting, improving muscle function (17.8% of absolute maximal force increase, P = 0.0079), ensuring neuromuscular connectivity and preventing neuromuscular junction degeneration (7.96% of AchR area increase, P = 0.0125). In addition, in human muscle biopsies, we found the same age-related alterations than those observed in mice and improved by GDF5 and reproduced its major effects on human cells, suggesting this treatment as efficient in humans. Overall, these data provide a foundation to examine the curative potential of GDF5 drug in clinical trials for sarcopenia and, eventually, other neuromuscular diseases.

Human umbilical cord mesenchymal stem cell-derived exosomes ameliorate muscle atrophy via the miR-132-3p/FoxO3 axis

Background

Muscle atrophy or sarcopenia is the loss of muscle mass and strength and leads to an increased risk of disability and death including osteoporotic fractures. Currently, there are no available clinical biologic agents for the treatment of sarcopenia. Since exosomes have become increasingly attractive as a novel therapeutic approach due to their ability to facilitate cell-cell transfer of proteins and RNAs, promoting cell repair and function recovery, we hypothesized that human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-Exos) might benefit muscle atrophy in age-related and dexamethasone-induced sarcopenia animal models.

Methods

HucMSC-Exos were harvested by ultrafast centrifugation and identified by transmission electron microscopy, particle size analysis, and Western blot analysis. The effects of hucMSC-Exos on muscle atrophy were evaluated using age-related and dexamethasone-induced muscle atrophy mice models. Body weight, grip strength, muscle weight, and muscle histology of these mice were assessed. The expression levels of muscle RING finger 1 (MuRF1) and muscle atrophy F-box (atrogin-1) were measured by Western blot. Dexamethasone-induced C2C12 myotube atrophy was used to establish the cell model of muscle atrophy. Myotube diameter was evaluated by immunofluorescence staining. Bioinformatic analysis, RNA sequencing analysis, and Western blot analysis were performed to explore the underlying mechanisms.

Results

In vivo experiments, hucMSC-Exos demonstrated a remarkable capacity to improve grip strength, increase muscle mass, and muscle fiber cross-sectional area, while concurrently reducing the expression of MuRF1 and atrogin-1 in age-related and dexamethasone-induced muscle atrophy mice. In vitro experiments, hucMSC-Exos can promote the proliferation of C2C12 cells, and rescue the dexamethasone-induced decline in the viability of C2C12 myotubes. In addition, hucMSC-Exos can increase the diameter of C2C12 myotubes, and reduce dexamethasone-induced upregulation of MuRF1 and atrogin-1. Combined with bioinformatics analysis and RNA sequencing analysis, we further showed that miR-132-3p was one of the essential miRNAs in hucMSC-Exos and played an important role by targeting FoxO3.

Conclusion

Our findings suggested that hucMSC-Exos can improve age-related and dexamethasone-induced muscle atrophy in mice models. This study first demonstrated that hucMSC-Exos may ameliorate muscle atrophy via the miR-132-3p/FoxO3 axis. These data may provide novel and valuable insights into the clinical transformation of hucMSC-Exos for the treatment of sarcopenia.

The translational potential of this article

HucMSC-Exos are easily available for clinical application, this study further consolidates the evidence for the clinical transformation potential of hucMSC-Exos for sarcopenia and provides its new target pathway.

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 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.

Causal Associations Between Sleep Traits and Low Grip Strength: A Bidirectional Mendelian Randomization Study

Background

Sleep disorders and low grip strength often co-occur clinically and are geriatric symptoms that cause significant socioeconomic burden. Previous observational studies have found an association between sleep behaviors and grip strength, but the causal relationship remains unclear.

Purpose

With the Mendelian randomization (MR) approach, the study aimed to determine the causal association between sleep traits (sleep duration, insomnia, daytime napping, sleep-wake disorders, chronotype) and low grip strength.

Methods

The study used genetic variants from the genome-wide association study (GWAS) archived in UK Biobank and FinnGen. We assessed the potential causal relationship between sleep behaviors and grip strength using inverse variance weighting (IVW), weighted median (WM), and MR-Egger. Additionally, we performed sensitivity analyses using Cochran's Q test, MR Egger Intercept test, funnel plots, and leave-one-out method.

Results

We found that sleep duration is causally negatively associated with low grip strength (OR = 0.618, 95% CI = 0.424-0.900, P = 0.012). Sleep-wake disorders have a positive association with low grip strength (OR = 1.018, 95% CI = 1.002-1.034, P = 0.029). Reversely, high low grip strength risk was causally associated with increased daytime napping (OR = 1.018, 95% CI = 1.004-1.032, P = 0.011).

Conclusion

The study revealed causal associations between sleep duration, sleep-wake disorders, and low grip strength. Understanding their relationship helps in early clinical intervention to improve the life quality of the elderly.

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.

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.

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.

Sarcopenia is a predictor for Alzheimer's continuum and related clinical outcomes

Low body mass index is closely related to a high risk of Alzheimer's disease (AD) and related biomarkers including amyloid-β (Aβ) deposition. However, the association between sarcopenia and Aβ-confirmed AD remains controversial. Therefore, we investigated the relationship between sarcopenia and the AD continuum. We explored sarcopenia's association with clinical implications of participants on the AD continuum. We prospectively enrolled 142 participants on the AD continuum (19 with preclinical AD, 96 with mild cognitive impairment due to AD, and 28 with AD dementia) and 58 Aβ-negative cognitively unimpaired participants. Sarcopenia, assessed using dual-energy X-ray absorptiometry and hand grip measurements, was considered a predictor. AD continuum, defined by Aβ deposition on positron emission tomography served as an outcome. Clinical severity in participants on the AD continuum assessed using hippocampal volume, Mini-Mental State Examination (MMSE), Seoul Verbal Learning Test (SVLT), and Clinical Dementia Rating Scale Sum of Boxes Scores (CDR-SOB) were also considered an outcome. Sarcopenia (odds ratio = 4.99, p = 0.004) was associated independently with the AD continuum after controlling for potential confounders. Moreover, sarcopenia was associated with poor downstream imaging markers (decreased hippocampal volume, β = - 0.206, p = 0.020) and clinical outcomes (low MMSE, β = - 1.364, p = 0.025; low SVLT, β = - 1.077, p = 0.025; and high CDR-SOB scores, β = 0.783, p = 0.022) in participants on the AD continuum. Sarcopenia was associated with the AD continuum and poor clinical outcome in individuals with AD continuum. Therefore, our results provide evidence for future studies to confirm whether proper management of sarcopenia can effective strategies are required for sarcopenia management to prevent the AD continuum and its clinical implications.

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.

Mendelian randomization study on association between grip strength and BMD in different age groups

INTRODUCTION

This study aimed to use the Mendelian randomization study method to verify the causal relationship between grip strength and bone mineral density (BMD) in different ages and different parts of the body.

MATERIALS AND METHODS

The analysis was based on pooled data from genome-wide association studies (GWAS). Hand grip strength (right) was used as the exposure variable and total body bone mineral density (BMD) of different age groups was used as the outcome variable. Single-nucleotide polymorphisms highly correlated with exposure variables were used as instrumental variables. The inverse variance weighted (IVW) method was used as the primary analysis method, and the Mendelian randomization Egger (MR-Egger) regression and weighted median methods were used as supplementary evidence for the IVW results. Horizontal pleiotropy and heterogeneity tests were conducted to ensure the stability of the results.

RESULTS

Analyzing the GWAS data on osteoporosis as the outcome variable, the IVW analysis showed that osteoporosis risk was associated with decreased grip strength in the 45-60 age group and the risk of declining lumbar spine BMD was associated with decreased grip strength. However, there was no significant correlation between the risk of osteoporosis in other age groups and changes in grip strength.

CONCLUSION

A causal relationship exists between decreased grip strength and osteoporosis risk in people aged 45-60 years. The risk of BMD declining in the lumbar spine was associated with reduced grip strength.

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.

Comprehensive landscapes of the causal network between immunity and sarcopenia

Background

Inflammaging, an immune status characterized by a sustained increase in pro-inflammatory markers and a decline in anti-inflammatory mechanisms, is a critical risk factor in the development of sarcopenia. Landscapes of the causal relationships between immunity and sarcopenia are needed to understand the mechanism of sarcopenia and provide novel treatments comprehensively.

Methods

We used Mendelian Randomization (MR) as the basic method in this study. By setting immune proteins, immune cells, and sarcopenia as exposures and outcomes alternatively, and then combining them in different directions, we potentially estimated their causal relationships and directions and subsequently mapped the comprehensive causal landscape based on this information efficiently. To further understand the network, we developed a method based on rank-sums to integrate multiple algorithms and identify the key immune cells and proteins.

Results

More than 1,000 causal relationships were identified between immune cell phenotypes, proteins, and sarcopenia traits (p < 0.05), and the causal maps of these linkages were established. In the threshold of FDR < 0.05, hundreds of causal linkages were still significant. The final comprehensive map included 13 immune cell phenotypes and 8 immune proteins. The star factors in the final map included EM CD8br %CD8br, EM DN (CD4- CD8-) %DN, SIRT2, and so on.

Conclusion

By reading the landscapes in this study, we may not only find the factors and the pathways that have been reported and proven but also identify multiple novel immunity cell phenotypes and proteins with enriched upstream and downstream pathways.

Circulating inflammatory cytokines and sarcopenia-related traits: a mendelian randomization analysis

Objective

To explore the causal relationships between 91 circulating inflammatory cytokines and sarcopenia-related traits (low hand grip strength, appendicular lean mass, and usual walking pace) by Mendelian randomized analysis.

Methods

Independent genetic variations of inflammatory cytokines and sarcopenia-related traits were selected as instrumental variables from publicly available genome-wide association studies (GWAS). The MR analysis was primarily conducted using the inverse variance-weighted (IVW) method. Sensitivity analyses included Steiger filtering and MR PRESSO, with additional assessments for heterogeneity and pleiotropy.

Results

The IVW method indicated a causal relationship between Vascular Endothelial Growth Factor A (VEGF-A) and low hand grip strength (OR = 1.05654, 95% CI: 1.02453 to 1.08956, P = 0.00046). Additionally, Tumor Necrosis Factor-beta (TNF-β) was found to have a causal relationship with appendicular lean mass (ALM) (β = 0.04255, 95% CI: 0.02838 to 0.05672, P = 3.96E-09). There was no evidence suggesting a significant causal relationship between inflammatory cytokines and usual walking pace.

Conclusion

Our research substantiated the causal association between inflammatory cytokines, such as VEGF-A and TNF-β, and sarcopenia. This finding may provide new avenues for future clinical treatments.

Causal association of circulating cytokines with sarcopenia-related traits: A Mendelian randomization study

BACKGROUND

Observational studies have reported that circulating cytokines are associated with sarcopenia. However, the causal relationship between circulating cytokines and sarcopenia has not been elucidated.

OBJECTIVES

This study aimed to investigate the causal relationship between circulating cytokines and sarcopenia with genetic data using Mendelian randomization (MR).

METHODS

Two-sample bidirectional MR analysis was performed to investigate the causal relationship in individuals of European ancestry. The publicly available genome-wide association study statistics were used to select the key eligible single nucleotide polymorphisms significantly associated with circulating cytokines. Multiple MR analysis approaches, including inverse variance weighted (IVW), MR-Egger, weighted median method (WMM), and MR-Pleiotropy residual Sum and Outlier (MR-PRESSO) methods, were used for the analysis. Sarcopenia-related traits were appendicular lean mass (ALM) and grip strength.

RESULTS

This study demonstrated the causal effect of genetically predicted circulating interleukin interleukin-16 (IL16) levels on both ALM [odds ratio (OR) = 0.990, 95% confidence interval (CI): 0.980-1.000, P = 0.049] and grip strength (OR = 0.971, 95% CI: 0.948-0.995, P = 0.020]. Additionally, C-X-C motif chemokine ligand 10 (CXCL10), interleukin-1beta (IL1B), and hepatocyte growth factor (HGF) were correlated with ALM, while vascular endothelial growth factor (VEGF), interleukin-12 (IL12), and interleukin-15 (IL15) were correlated with grip strength. The results of MR-Egger, weighted median, weighted mode, and simple mode methods were consistent with the IVW estimates. Sensitivity analysis revealed that horizontal pleiotropy did not bias the causal estimates.

CONCLUSION

These findings indicate that inflammatory cytokines exert a significant causal effect on sarcopenia and provide promising leads for the development of novel therapeutic targets for the disease. By evaluating the role of circulating cytokines in the pathologic condition via a genetic epidemiological approach, our study made contributions to a further investigation of underlying mechanisms of sarcopenia.