Association Between Autoimmune Diseases and Sarcopenia: A Two-Sample Mendelian Randomization Study

Late-onset Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multisystem autoimmune rheumatic disease (ARD) that results from the dysregulation of multiple innate and adaptive immune pathways. Late-onset SLE (Lo-SLE) is the term used when the disease is first diagnosed after 50-65 years, though the standard age cut-off remains undefined. Defining "late-onset" as lupus with onset after 50 years is more biologically plausible as this roughly corresponds to the age of menopause. Lo-SLE comprises nearly 20% of all cases of lupus. With advancing age, the female predominance of lupus declines to nearly 4:1 to even 1.1:1. The natural history of the disease varies, with lesser major organ involvement like nephritis but higher damage accrual. The latter is possibly owed to the atypical presentation and hesitation among physicians to diagnose SLE at this age, a diagnostic delay with late treatment initiation may accelerate the damage accrual. Multimorbidity is a central issue in these patients, which includes osteoporosis, sarcopenia, accelerated atherosclerosis in the background of existing dyslipidemia, diabetes mellitus, major depression, hypertension, coronary artery disease and other thrombotic events.With the rising ages of populations worldwide, awareness about late-onset lupus is paramount, especially due to the associated diagnostic delays and higher overlap with Sjogren's disease. Also, pharmacotherapeutics must be optimized considering factors associated with ageing like declining glomerular filtration rate (GFR), sarcopenia, osteoporosis, and the associated comorbidities. Measures to minimize the exposure to long-term exposure to high-dose steroids are crucial. Beyond this, it is of essence to adopt non-pharmacological interventions as an adjunct to traditional immunosuppression to improve pain, fatigue, depression, and anxiety, improve cardiovascular health and overall better quality of life with favourable long-term outcomes.

Do Patients with Rheumatoid Arthritis Have an (In)Adequate Level of Physical Activity? A Latent Class Analysis Approach

INTRODUCTION

Regular physical activity (PA) has a beneficial effect on joint pain, stiffness, strength, flexibility, and aerobic capacity in patients with rheumatoid arthritis (RA).

OBJECTIVE

The aim of this study was to assess the level of PA in patients with rheumatoid arthritis and to identify potential barriers to this activity.

MATERIAL AND METHODS

The study involved 132 patients with RA. Participants completed the International Physical Activity Questionnaire (IPAQ), the Functional Assessment of Chronic Illness Therapy-Fatigue Scale (FACIT-F), the Tampa Scale for kinesiophobia (TSK), Strength, Ambulation, Rising from a chair, Stair climbing and history of Falling questionnaire (SARC-F) for sarcopenia assessment, and the Patient Health Questionnaire-9 (PHQ-9) for depression. Basic socio-epidemiological data, disease activity score in 28 joints (DAS28), duration of disease, and therapy information were retrieved from electronic patient records. Latent class analysis (LCA) was used to identify subpopulations of patients.

RESULTS

The study included 109 women (82.6%) and 23 men (17.4%). Low levels of PA were observed in 16 patients (12%), moderate levels in 70 patients (53%), and high levels in 42 patients (35%). Symptoms of pronounced fatigue were significantly associated with low PA (28.5 ± 11.3 vs. 37 ± 7 vs. 37 ± 10; p = 0.002). The risk of sarcopenia was significantly higher in RA patients with low PA (p = 0.05). Kinesiophobia was present in all three groups (65.2%). LCA identified two classes. In the first class, patients were more likely to be non-exercisers compared to the second class. Patients in the first class were characterized by a higher probability of being female, obese, with lower education levels. Patients in the first class had pronounced fatigue, kinesiophobia and more frequent symptoms of depression. The second class (65% of the total population) included patients who exercised moderately to frequently (93%) and were middle-aged. They were less obese, highly educated, employed, and majority of them achieved low disease activity or remission. In addition, they had lower risks for sarcopenia, depression, fatigue, and kinesiophobia.

CONCLUSIONS

This study showed that RA patients with moderate and high levels of PA have better disease control, fewer symptoms of fatigue and depression, and a lower risk of sarcopenia. However, kinesiophobia was significantly present in all three groups, indicating a need for further promotion of this non-pharmacological treatment.

The harmful effect of ankylosing spondylitis on diabetes mellitus: new evidence from the Mendelian randomization analysis

Background

While observational research has highlighted a possible link between ankylosing spondylitis (AS) and type 2 diabetes (T2DM), the quality of evidence remains limited, and the causal relationship is yet to be established. This study aims to explore the causal link between AS and T2DM, as well as its impact on traits related to glucose metabolism.

Method

To infer a causal relationship between AS and various diabetes-related traits, including type 1 diabetes (T1DM), T2DM, blood glucose levels, fasting glucose, glycated hemoglobin, and fasting insulin, we employed Mendelian randomization (MR) analysis. We sourced GWAS summary data for both exposure and outcome variables from the IEU OpenGWAS database, GWAS Catalog, and FinnGen database. To synthesize the results of the MR analyses, we applied meta-analysis techniques using either a fixed or random effects model. For identifying and excluding instrumental variants (IVs) that exhibit horizontal pleiotropy with the outcomes, we utilized the MR-PRESSO method. Sensitivity analyses were conducted using the MR-Egger method, along with Q and I^2 tests, to ensure the robustness of our findings.

Results

Our analysis revealed a significant association between AS and an increased risk of T1DM with an odds ratio (OR) of 1.5754 (95% CI: 1.2935 to 1.9187) and T2DM with an OR of 1.0519 (95% CI: 1.0059 to 1.1001). Additionally, AS was associated with elevated levels of fasting glucose (beta coefficient = 0.0165, 95% CI: 0.0029 to 0.0301) and blood glucose (beta coefficient = 0.0280, 95% CI: 0.0086 to 0.0474), alongside a decrease in fasting insulin levels (beta coefficient = -0.0190, 95% CI: -0.0330 to -0.0050).

Conclusion

Our findings collectively underscore the detrimental impact of AS on the development of diabetes, highlighting the critical influence of autoimmune disorders in diabetes onset. This provides profound insights into the pathogenesis of diabetes from an immunological standpoint.

Evaluation of Sarcopenia by Psoas Muscle Measurements in Bullous Pemphigoid: A Single-Institution Survey in Japan

Bullous pemphigoid (BP) is a rare autoimmune blistering disease that primarily affects elderly individuals. Based on the Bullous Pemphigoid Disease Area Index (BPDAI) severity assessment, immunosuppressive drugs are recommended for severe cases that fall within the more than moderate classes. Sarcopenia, which is characterized by decreased skeletal muscle mass and function in elderly patients, is a progressive and widespread skeletal muscle disease. We retrospectively surveyed patients who received treatment for BP at our hospital between 2012 and 2024 to evaluate the relevance of sarcopenia, as assessed using the psoas muscle mass index (PMI), and to investigate the benefit of relapse-free survival (RFS). A total of 59 patients with BP were included in this study. A total of 57.6% (34 of 59 patients) of the BP patients had sarcopenia, as measured by PMI. Kaplan-Meier analysis showed that the sarcopenia group (n = 34) had a median RFS of 394 days, which was not longer than that of the non-sarcopenia group (n = 25, 275 days) (p = 0.894). No significant difference in RFS was observed in the subgroup analysis based on the severity of BPDAI. Our real-world data confirmed the high prevalence of sarcopenia in the BP population and the efficacy of standard treatment centered on immunosuppressive therapy based on the severity of BPDAI. There is little basis for reducing oral corticosteroids below 0.5 mg/kg based solely on the patient's perceived frailty, regardless of the severity of the BPDAI. Limited evidence is available to assess the association between sarcopenia and autoimmune diseases in terms of their etiology. As populations continue to age globally, it is important for clinicians to prioritize addressing diseases while considering whether patients experience frailty in daily practice.

Causal association of rheumatoid arthritis with frailty and the mediation role of inflammatory cytokines: A Mendelian randomization study

BACKGROUND

Previous observational studies have suggested the association between rheumatoid arthritis (RA) and frailty. However, it remains obscure whether this association is causal. This study aims to investigate the causal association of RA with frailty and the mediation effect of inflammatory cytokines using Mendelian randomization (MR) design.

METHODS

Summary-level data for RA (N = 58,284), frailty index (FI) (N = 175,226), Fried frailty score (FFS) (N = 386,565), and 41 inflammatory cytokines (N = 8,293) were obtained from recent genome-wide association studies. Univariable and multivariable MR analyses were conducted to investigate and verify the causal association of RA with frailty. The potential mediation effects of inflammatory cytokines were estimated using two-step MR.

RESULTS

Univariable inverse variance weighted MR analysis suggested that genetically determined RA was associated with increased FI (beta=0.021; 95 % CI: 0.012, 0.03; p = 2.2 × 10-6) and FFS (beta=0.011; 95 %CI: 0.007, 0.015; p = 8.811 × 10-8). The consistent results were observed in multivariable MR analysis after adjustment for asthma, smoking, BMI, physical activity, telomere length, and depression. Mediation analysis showed evidence of an indirect effect of RA on FI through monokine induced by interferon-gamma (MIG) with a mediated proportion of 9.8 % (95 %CI: 4.76 %, 19.05 %), on FFS via MIG and stromal cell-derived factor-1 alpha with a mediated proportion of 9.6 % (95 %CI: 0 %, 18.18 %) and 8.44 % (95 %CI: 0 %, 18.18 %), respectively.

CONCLUSION

This study provided credible evidence that genetically predicted RA was associated with a higher risk of frailty. Additionally, inflammatory cytokines were involved in the mechanism of RA-induced frailty.

Prevalence of Sarcopenia and Dynapenia and Related Clinical Outcomes in Patients with Type 1 Diabetes Mellitus

BACKGROUND

Sarcopenia has recently been recognized as a complication of diabetes. However, there are few results about the prevalence of sarcopenia and dynapenia and the related clinical outcomes in type 1 diabetes mellitus (T1DM). Our objectives were to evaluate the prevalence of sarcopenia and dynapenia and to determine whether there are any associations with disease-related factors in people with T1DM.

METHODS

A cross-sectional study was conducted in people with T1DM. We assessed appendicular skeletal mass index (ASMI) using bioimpedance 50 Hz (Nutrilab Akern). Muscle function was assessed through handgrip strength (HGS) using a Jamar dynamometer. Sarcopenia was defined as a low HGS with low ASMI, whereas dynapenia was defined as low HGS with a normal ASMI. We used HGS data from the Spanish population percentile table and a cut-off point at p5 as dynapenia. The association of clinical, metabolic, and lifestyle variables with sarcopenia and dynapenia was studied.

RESULTS

This study included 62 T1DM patients (66% females, mean age of 38 ± 14 years, body mass index (BMI) of 24.9 ± 4.7 kg/m2). The prevalence of sarcopenia and dynapenia was 8% and 23%, respectively. In our sample, there were more men in the sarcopenic and dynapenic groups. The sarcopenic group showed a significantly higher mean HbA1c value. Lower diabetes duration, PREDIMED score, BMI, and muscle mass measures (fat-free mass index (FFMI), ASMI, and body cell mass index (BCMI)) were significantly associated with sarcopenia. Decreased diabetes duration, PREDIMED score, phase angle (PhA), and HGS values showed a significant association with dynapenia.

CONCLUSIONS

The prevalence of sarcopenia and dynapenia was high in people with T1DM in our study. Specifically, the proportion of dynapenia was quite high. HGS and ASMI are practical tools for the assessment of muscle health status in T1DM, and low values are associated with poor glycemic control, underweight, and low adherence to the Mediterranean diet. Thus, dynapenia may predict accelerated muscle aging in T1DM.

Causality between urate levels with sarcopenia-related traits: a bi-directional Mendelian randomization study

Background

Observational studies have suggested associations between serum urate levels and sarcopenia, but the causality underlying this correlation remains uncertain. The principal objective of this study is to investigate a causal relationship of serum urate levels with sarcopenia-related traits (hand grip strength, lean mass, walking pace) using bidirectional two-sample Mendelian randomization (MR) approach. The utilization of MR methodology serves to minimize bias caused by reverse causality and confounding factors from observational studies.

Methods

The summary statistics of serum urate levels were derived from a cohort consisting of 288,659 individuals participating in CKDGen study. The parameters of right-hand grip strength (N=461,089), left-hand grip strength (N=461,026), appendicular lean mass (ALM) (N=450,243), whole-body lean mass(N=454,850),right-leg fat-free mass(FFM;N=454,835),left-leg FFM(N=454,805), right-arm FFM(N=454,753),left-arm FFM(N=454,672) and walking pace (N=459,915)were sourced from the UK Biobank. MR analysis was conducted utilizing inverse variance weighted (IVW), weighted median, and MR-Egger to evaluate causality. Sensitivity analysis was performed using Cochran's Q test, MR-Egger intercept test, leave-one-out analysis and the funnel plot.

Results

IVW estimates demonstrated that serum urate levels exhibited no causal association with sarcopenia-related traits. In the inverse MR investigation, we had exclusively discerned an inverse correlation between walking pace and serum urate levels. No compelling evidence had surfaced to substantiate any association of other sarcopenia-related traits with serum urate. Supplemental MR methods consistently validated the findings obtained from the primary analysis. Sensitivity analysis demonstrated the robustness of findings.

Conclusion

Our MR study revealed the absence of the bidirectional causal relationship between serum urate levels and sarcopenia. It is imperative to acknowledge that advanced age and an individual's health status are pivotal determinants influencing urate level and the initiation and advancement of sarcopenia. However, it is worth underscoring that these aspects remain unexamined within the purview of this study. Thus, future investigations should delve deeper into these intricate facets.