A bi-directional Mendelian randomization study of the sarcopenia-related traits and osteoporosis

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

Background

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

Methods

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

Results

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

Conclusion

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

The genetic causal effect of hand grip strength on osteoporosis and falling risk: a Mendelian randomization study

Background

Patients with osteoporosis (OP) are often associated with decreased hand grip strength and increased risk of falling. It remains unclear whether there is a genetic causal between hand grip strength and OP, falling risk.

Methods

The Mendelian randomization study was used to investigate the genetic causal effect of low hand grip strength on total body bone mineral density (BMD) at different ages, OP, and falling risk. Genes for low hand grip strength, total body BMD at different ages, OP, and falling risk were obtained from published genome-wide association studies. Inverse variance weighted, MR-Egger, and weighted median were applied to perform the MR analysis. The Cochran's Q test, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out analysis were used to detect the pleiotropy or heterogeneity.

Results

The results showed strong evidence that low hand grip strength was positively associated with OP (OR: 1.006, 95% CI: 1.003-1.010; P= 0.0001) and falling risk (OR: 1.069, 95% CI: 1.013-1.129; P= 0.0160), and could not directly affect the different ages of total body BMD (P> 0.05). There was no heterogeneity or horizontal pleiotropy in the sensitivity analysis (all P> 0.05).

Conclusion

The study found a positive causal relationship between low hand grip strength and higher risk of OP and falling, which should be taken into account in the development of future prevention and screening strategies for OP and falling.

Sarcopenic obesity and osteoporosis: Research progress and hot spots

Sarcopenic obesity (SO) and osteoporosis (OP) are associated with aging and obesity. The pathogenesis of SO is complex, including glucolipid and skeletal muscle metabolic disorders caused by inflammation, insulin resistance, and other factors. Growing evidence links muscle damage to bone loss. Muscle-lipid metabolism disorders of SO disrupt the balance between bone formation and bone resorption, increasing the risk of OP. Conversely, bones also play a role in fat and muscle metabolism. In the context of aging and obesity, the comprehensive review focuses on the effects of mechanical stimulation, mesenchymal stem cells (MSCs), chronic inflammation, myokines, and adipokines on musculoskeletal, at the same time, the impact of osteokines on muscle-lipid metabolism were also analyzed. So far, exercise combined with diet therapy is the most effective strategy for increasing musculoskeletal mass. A holistic treatment of musculoskeletal diseases is still in the preliminary exploration stage. Therefore, this article aims to improve the understanding of musculoskeletal -fat interactions in SO and OP, explores targets that can provide holistic treatment for SO combined with OP, and discusses current limitations and challenges. We hope to provide relevant ideas for developing specific therapies and improving disease prognosis in the future.

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.

Discovering Potential Mechanisms of Intervertebral Disc Disease Using Systematic Mendelian Randomization of Human Circulating Immunocytomics

BACKGROUND

Although intervertebral disc degeneration (IVDD) is a critical factor in many spine-related diseases and has an extremely high prevalence in the aging population, the potential pathogenesis remains to be clarified entirely. Immune cells have been found to perform an essential function during the onset and progression of IVDD in recent years. Therefore, we explored the association between immune cell characteristics and IVDD through Mendelian randomization (MR) analysis and further delved into the mediating role of potential metabolites.

METHODS

Based on the MR analysis, the association of 731 immune cell phenotypes and 1400 metabolites on IVDD were assessed. Single nucleotide polymorphisms were closely associated the expression levels of immune cell characteristics and the concentrations of metabolites and have been used as instrumental variables for deducing them as risk factors or protective factors for IVDD. In addition, mediation analyses have been performed to identify potential metabolite mediators between immune cell characteristics and IVDD.

RESULTS

MR analysis identified 27 immune cell phenotypes and 79 metabolites significantly associated with IVDD. In addition, mediation analysis was performed by selecting the immune cell phenotype that most significantly increased the risk of IVDD - CD86 on monocytes. A total of 4 metabolite-mediated mediation relationships were revealed (3 b-hydroxy-5-cholenoic acid, X-22509, N-acetyl-L-glutamine, and N2-acetyl, N6, N6-dimethyllysine).

CONCLUSIONS

The findings of this analysis identified underlying association between immune cell phenotypes, metabolite, and IVDD that may serve as predictive and prognostic clinical biomarkers and benefit IVDD pathogenesis research.

The impact of sarcopenia on the incidence of postoperative outcomes following spine surgery: Systematic review and meta-analysis

PURPOSE

Sarcopenia is considered to be an important predictor of adverse outcomes following spinal surgery, but the specific relationship between the two is not clear. The purpose of this meta-analysis is to systematically review all relevant studies to evaluate the impact of sarcopenia on spinal surgery outcomes.

METHODS

We systematically searched PubMed, Embase and the Cochrane Library for relevant articles published on or before January 9, 2023. The pooled odds ratio (OR) with 95% confidence intervals (CIs) was calculated in a random effects meta-analysis. The main outcome was the risk of adverse outcomes after spinal surgery, including adverse events and mortality. This systematic review and meta-analysis was conducted following the PRISMA guidelines to evaluate the impact of sarcopenia on spinal surgery outcomes. In addition, we also conducted a subgroup analysis and leave-one-out sensitivity analyses to explore the main sources of heterogeneity and the stability of the results.

RESULTS

Twenty-four cohort studies, with a total of 243,453 participants, met the inclusion criteria. The meta-analysis showed that sarcopenia was significantly associated with adverse events (OR 1.63, 95% CI 1.17-2.27, P < 0.001) but was no significantly associated with mortality (OR 1.17, 95% CI 0.93-1.46, P = 0.180), infection (OR 2.24, 95% CI 0.95-5.26, P < 0.001), 30-day reoperation (OR 1.47, 95% CI 0.92-2.36, P = 0.413), deep vein thrombosis (OR 1.78, 95% CI 0.69-4.61, P = 0.234), postoperative home discharge (OR 0.60, 95% CI 0.26-1.37, P = 0.002) and blood transfusion (OR 3.28, 95% CI 0.74-14.64, P = 0.015).

CONCLUSION

The current meta-analysis showed that patients with sarcopenia have an increased risk of adverse events and mortality after spinal surgery. However, these results must be carefully interpreted because the number of studies included is small and the studies are significantly different. These findings may help to increase the clinicians' awareness of the risks concerning patients with sarcopenia to improve their prognosis.

Nucleotide polymorphism-based study utilizes human plasma liposomes to discover potential therapeutic targets for intervertebral disc disease

Background

While intervertebral disc degeneration (IVDD) is crucial in numerous spinally related illnesses and is common among the elderly, the complete understanding of its pathogenic mechanisms is still an area of ongoing study. In recent years, it has revealed that liposomes are crucial in the initiation and progression of IVDD. However, their intrinsic mediators and related mechanisms remain unclear. With the development of genomics, an increasing amount of data points to the contribution of genetics in the etiology of disease. Accordingly, this study explored the causality between liposomes and IVDD by Mendelian randomization (MR) analysis and deeply investigated the intermediary roles of undetected metabolites.

Methods

According to MR analysis, 179 liposomes and 1400 metabolites were evaluated for their causal association with IVDD. Single nucleotide polymorphisms (SNPs) are strongly associated with the concentrations of liposomes and metabolites. Consequently, they were employed as instrumental variables (IVs) to deduce if they constituted risk elements or protective elements for IVDD. Furthermore, mediation analysis was conducted to pinpoint possible metabolic mediators that link liposomes to IVDD. The inverse variance weighting (IVW) was the main analytical technique. Various confidence tests in the causality estimates were performed, including consistency, heterogeneity, pleiotropy, and sensitivity analyses. Inverse MR analysis was also utilized to estimate potential reverse causality.

Results

MR analysis identified 13 liposomes and 79 metabolites markedly relevant to IVDD. Moreover, the mediation analysis was carried out by choosing the liposome, specifically the triacylglycerol (48:2) levels, which were found to be most notably associated with an increased risk of IVDD. In all, three metabolite-associated mediators were identified (3-methylcytidine levels, inosine 5'-monophosphate (IMP) to phosphate ratio, and adenosine 5'-diphosphate (ADP) to glycine ratio).

Conclusion

The analysis's findings suggested possible causal connections between liposomes, metabolites, and IVDD, which could act as both forecast and prognosis clinical indicators, thereby aiding in the exploration of the pathogenesis behind IVDD.

Causal associations between autoimmune diseases and sarcopenia-related traits: a bi-directional Mendelian randomization study

Background

Sarcopenia is common in patients with autoimmune diseases (ADs); however, the causal associations between ADs and sarcopenia remain unclear. Therefore, this study investigated the causal associations using bi-directional Mendelian randomization analysis.

Methods

Exposure-related single-nucleotide polymorphisms (SNPs) were extracted from genome-wide association studies (GWASs). GWAS statistics for common ADs [Crohn's disease (CD), ulcerative colitis (UC), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis (PSO), and multiple sclerosis (MS)] and sarcopenia-related traits [hand grip strength (HGS), appendicular fat-free mass (FFM), and walking pace] were obtained from public datasets. Inverse-variance weighting as the main method was used to evaluate the causal effect.

Results

Genetically predicted CD had causal effects on whole-body FFM (β = -0.005, p = 0.001), leg FFM (βleft = -0.006, p = 1.8E-4; βright = -0.007, p = 2.0E-4), and arm FFM (βleft = -0.005, p = 0.005; βright = -0.005, p = 0.001), while RA had causal effects on 8 sarcopenia-related traits, namely, HGS (βleft = -2.06, p = 2.8E-38; βright = -2.311, p = 2E-20), whole-body FFM (β = -0.842, p = 4.7E-10), leg FFM (βleft = -0.666, p = 2.6E-6; βright = -0.073, p = 2.1E-3), arm FFM (βleft = -0.63, p = 4.4E-6; βright = -0.736, p = 4.4E-8), and walking pace (β = -1.019, p = 6.2E-14). In the reverse direction, HGS (odds ratio [OR]left = 10.257, p = 3.6E-5; ORright = 16.445, p = 3.7E-7) had causal effects on CD, while HGS (ORleft = 0.994, p = 0.004; ORright = 0.993, p = 1.4E-4), leg FFM (ORleft = 1.003, p = 0.005; ORright = 1.005, p = 1.9E-4), and walking pace (OR = 0.985, p = 5.7E-5) were causally associated with RA. No evidence showed causal associations of UC, SLE, PSO, or MS with sarcopenia-related traits.

Conclusion

Our study demonstrated that the genetic susceptibility to CD and RA was associated with high risk of sarcopenia, and some sarcopenia-related traits had causal effects on CD or RA.

Gastroesophageal reflux disease increases the risk of essential hypertension: results from the Nationwide Readmission Database and Mendelian randomization analysis

BACKGROUND

The link between gastroesophageal reflux disease (GERD) and essential hypertension (EH) and its causal nature remains controversial. Our study examined the connection between GERD and the risk of hypertension and assessed further whether this correlation has a causal relationship.

METHODS

First, we utilized the National Readmission Database including 14 422 183 participants to conduct an observational study. Dividing the population into GERD and non-GERD groups, we investigated the correlation between GERD and EH using multivariate logistic regression. Next, bidirectional two-sample Mendelian randomization was adopted. The summary statistics for GERD were obtained from a published genome-wide association study including 78 707 cases and 288 734 controls. We collected summary statistics for hypertension containing 70 651 cases and 223 663 controls from the FinnGen consortium. We assessed causality primarily by the inverse-variance weighted method with validation by four other Mendelian randomization approaches as well as an array of sensitivity analyses.

RESULTS

In the unadjusted model, GERD patients had a higher risk of EH than the non-GERD group, regardless of gender (odds ratio, 1.43; 95% confidence interval: 1.42-1.43; P < .001). Further adjusting for critical confounders did not change this association. For Mendelian randomization, we found that genetically predicted GERD was causally linked to an enhanced risk of EH in inverse-variance weighted technique (odds ratio, 1.52; 95% confidence interval: 1.39-1.67; P = 3.51 × 10-18); conversely, EH did not raise the risk of GERD causally.

CONCLUSIONS

GERD is a causal risk factor for EH. Further research is required to probe the mechanism underlying this causal connection.

Association Between Advanced Glycation End Products and Sarcopenia: The Mediating Role of Osteoporosis

CONTEXT

Advanced glycation end products (AGEs) are a group of molecules formed through nonenzymatic reactions. These compounds are associated with several age-related diseases, including sarcopenia and osteoporosis.

OBJECTIVE

This work aimed to investigate the relationships between AGEs, osteoporosis, and sarcopenia in community-dwelling older adults.

METHODS

This cross-sectional study included 1991 older adults aged 72.37 ± 5.90 years from China. AGE levels were measured by the AGE Reader device. Bone mineral density was assessed using dual-energy X-ray absorptiometry, and osteoporosis was diagnosed based on a T score of less than -2.5. Sarcopenia was defined as loss of muscle mass plus loss of muscle strength and/or reduced physical performance. Presarcopenia was defined as low muscle mass with normal muscle strength and normal physical performance.

RESULTS

The prevalence of sarcopenia was 18.5%, and that of osteoporosis was 40.5%. Compared to the lowest AGE quartile, the highest AGE quartile showed a significant association with sarcopenia (odds ratio [OR] 2.42; 95% CI, 1.60-3.66) (P for trend <.001), but not with presarcopenia. Per-SD increase in AGE was associated with higher odds of sarcopenia (OR 1.44; 95% CI, 1.26-1.66). Additionally, in the mediation analysis, when AGEs were treated as a continuous variable (the mediation effect is denoted by Za*Zb = 18.81; 95% CI, 8.07-32.32]-the 95% CI does not contain zero, representing a significant mediating effect) or a categorical variable (the mediating effect is expressed as Zmediation = 3.01 > 1.96, which represents a significant mediating effect), osteoporosis played a partial mediating role in the association between AGEs and sarcopenia.

CONCLUSION

Elevated AGEs are associated with sarcopenia but not with presarcopenia. This association was partially mediated by osteoporosis.

Metabolic clues to aging: exploring the role of circulating metabolites in frailty, sarcopenia and vascular aging related traits and diseases

Background: Physical weakness and cardiovascular risk increase significantly with age, but the underlying biological mechanisms remain largely unknown. This study aims to reveal the causal effect of circulating metabolites on frailty, sarcopenia and vascular aging related traits and diseases through a two-sample Mendelian Randomization (MR) analysis. Methods: Exposures were 486 metabolites analyzed in a genome-wide association study (GWAS), while outcomes included frailty, sarcopenia, arterial stiffness, atherosclerosis, peripheral vascular disease (PAD) and aortic aneurysm. Primary causal estimates were calculated using the inverse-variance weighted (IVW) method. Methods including MR Egger, weighted median, Q-test, and leave-one-out analysis were used for the sensitive analysis. Results: A total of 125 suggestive causative associations between metabolites and outcomes were identified. Seven strong causal links were ultimately identified between six metabolites (kynurenine, pentadecanoate (15:0), 1-arachidonoylglycerophosphocholine, androsterone sulfate, glycine and mannose) and three diseases (sarcopenia, PAD and atherosclerosis). Besides, metabolic pathway analysis identified 13 significant metabolic pathways in 6 age-related diseases. Furthermore, the metabolite-gene interaction networks were constructed. Conclusion: Our research suggested new evidence of the relationship between identified metabolites and 6 age-related diseases, which may hold promise as valuable biomarkers.

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.

The association of lipid metabolism with bone metabolism and the role of human traits: a Mendelian randomization study

Background

The impact of lipid metabolism on bone metabolism remains controversial, and the extent to which human traits mediate the effects of lipid metabolism on bone metabolism remains unclear.

Objective

This study utilized mendelian randomization to investigate the effects of blood lipids on bone mineral density (BMD) at various skeletal sites and examined the mediating role of human traits in this process.

Methods

We leveraged genetic data from large-scale genome-wide association studies on blood lipids (n=1,320,016), forearm bone mineral density (FA-BMD) (n=10,805), lumbar spine bone mineral density (LS-BMD) (n=44,731), and femoral neck bone mineral density (FN-BMD) (n=49,988) to infer causal relationships between lipid and bone metabolism. The coefficient product method was employed to calculate the indirect effects of human traits and the proportion of mediating effects.

Results

The results showed that a 1 standard deviation(SD) increase in HDL-C, LDL-C and TC was associated with a decrease in LS-BMD of 0.039 g/cm2, 0.045 g/cm2 and 0.054 g/cm2, respectively. The proportion of mediating effects of systolic blood pressure (SBP) on HDL-C to LS-BMD was 3.17%, but suppression effects occurred in the causal relationship of LDL-C and TC to LS-BMD. Additionally, the proportion of mediating effects of hand grip strength (HGS) on the TC to LS-BMD pathway were 6.90% and 4.60% for the left and right hands, respectively.

Conclusion

In conclusion, a negative causal relationship was established between lipid metabolism and bone metabolism. Our results indicated that SBP and HGS served as mediators for the effects of lipid metabolism on bone metabolism.

Sarcopenia, osteoporosis and frailty

Muscles and bones are intricately connected tissues displaying marked co-variation during development, growth, aging, and in many diseases. While the diagnosis and treatment of osteoporosis are well established in clinical practice, sarcopenia has only been classified internationally as a disease in 2016. Both conditions are associated with an increased risk of adverse health outcomes such as fractures, dysmobility and mortality. Rather than focusing on one dimension of bone or muscle mass or weakness, the concept of musculoskeletal frailty captures the overall loss of physiological reserves in the locomotor system with age. The term osteosarcopenia in particular refers to the double jeopardy of osteoporosis and sarcopenia. Muscle-bone interactions at the biomechanical, cellular, paracrine, endocrine, neuronal or nutritional level may contribute to the pathophysiology of osteosarcopenia. The paradigm wherein muscle force controls bone strength is increasingly facing competition from a model centering on the exchange of myokines, osteokines and adipokines. The most promising results have been obtained in preclinical models where common drug targets have been identified to treat these conditions simultaneously. In this narrative review, we critically summarize the current understanding of the definitions, epidemiology, pathophysiology, and treatment of osteosarcopenia as part of an integrative approach to musculoskeletal frailty.

Determinants of bone mass in older adults with normal- and overweight derived from the crosstalk with muscle and adipose tissue

Lower bone mass in older adults may be mediated by the endocrine crosstalk between muscle, adipose tissue and bone. In 150 community-dwelling adults (59-86 years, BMI 17-37 kg/m²; 58.7% female), skeletal muscle mass index, adipose tissue and fat mass index (FMI) were determined. Levels of myokines, adipokines, osteokines, inflammation markers and insulin were measured as potential determinants of bone mineral content (BMC) and density (BMD). FMI was negatively associated with BMC and BMD after adjustment for mechanical loading effects of body weight (r-values between -0.37 and -0.71, all p < 0.05). Higher FMI was associated with higher leptin levels in both sexes, with higher hsCRP in women and with lower adiponectin levels in men. In addition to weight and FMI, sclerostin, osteocalcin, leptin × sex and adiponectin were independent predictors of BMC in a stepwise multiple regression analysis. Muscle mass, but not myokines, showed positive correlations with bone parameters that were weakened after adjusting for body weight (r-values between 0.27 and 0.58, all p < 0.01). Whereas the anabolic effect of muscle mass on bone in older adults may be partly explained by mechanical loading, the adverse effect of obesity on bone is possibly mediated by low-grade inflammation, higher leptin and lower adiponectin levels.