Inflammatory, mitochondrial, and senescence-related markers: Underlying biological pathways of muscle aging and new therapeutic targets

Diet and Muscle Metabolism

Advancing age is associated with a progressive loss of muscle mass and strength/function, termed sarcopenia, which leads to a wide spectrum of adverse outcomes including falls, institutionalization, loss of independence, and mortality [...].

Serum Proteomic and Metabolomic Signatures of High Versus Low Physical Function in Octogenarians

Physical function declines with aging, yet there is considerable heterogeneity, with some individuals declining very slowly while others experience accelerated functional decline. To gain insight into mechanisms promoting high physical function with aging, we performed proteomics, targeted metabolomics, and targeted kynurenine-focused metabolomic analyses on serum specimens from three groups of octogenarians: High-functioning master athletes (HF, n = 16), healthy normal-functioning non-athletes (NF, n = 12), and lower functioning non-athletes (LF, n = 11). Higher performance status was associated with evidence consistent with: Lower levels of circulating proinflammatory markers, as well as unperturbed tryptophan metabolism, with the normal function of the kynurenic pathway; higher circulating levels of lysophosphatidylcholines that have been previously associated with better mitochondrial oxidative capacity; lower activity of the integrated stress response; lower levels of circulating SASP protein members; and lower levels of proteins that reflect neurodegeneration/denervation. Extending the observations of previous studies focused on the biomarkers of aging that predict poor function, our findings show that many of the same biomarkers associated with poor function exhibit attenuated changes in those who maintain a high function. Because of the cross-sectional nature of this study, results should be interpreted with caution, and bidirectional causality, where physical activity behavior is both a cause and outcome of differences in the biomarker changes, remains a possible interpretation.

Association between the systemic immune-inflammation index and sarcopenia in older adults: a cross-sectional study

BACKGROUND

Chronic inflammation is increasingly recognized as a crucial contributor to sarcopenia pathogenesis, but accurate diagnosis remains a challenge.

AIM

Our study aims to investigate the relationship between sarcopenia and the Systemic Immune-Inflammation Index (SII), a comprehensive indicator of inflammation.

METHODS

This cross-sectional study enrolled 632 patients. All participants underwent a comprehensive geriatric assessment. Sarcopenia was assessed through the evaluation of handgrip strength and calf circumference. To determine the SII, we used the formula: Platelet count (109/mm3)×Neutrophil count (109/mm3) / Lymphocyte count (109/mm3).

RESULTS

The average age of the participants was 74.8 ± 6.4, and 62.3% (n = 394) were female. Patients were grouped as non-sarcopenic and sarcopenic. The non-sarcopenic group had 536 patients (84.8%), while the sarcopenic group comprised 96 patients (15.2%). Sarcopenic patients showed a higher median SII score than the non-sarcopenic group (p < 0.001). Multivariate logistic regression analysis revealed that the SII score was significantly and independently associated with sarcopenia even after adjusting for potential confounding factors (β = 1.002, 95% CI = 1.001-1.003, p < 0.001). The ROC analysis identified the optimal cut-off for SII in predicting sarcopenia as > 765. At this threshold, the negative predictive values were determined to be 88.1%, with a specificity of 88%.

CONCLUSION

SII is significantly associated with sarcopenia in a geriatric outpatient population, and a population-specific SII cut-off may serve as a novel, simple, and practical biomarker for diagnosing sarcopenia.

Genetics of Female Pelvic Organ Prolapse: Up to Date

Pelvic organ prolapse (POP) is a benign disease characterized by the descent of pelvic organs due to weakened pelvic floor muscles and fascial tissues. Primarily affecting elderly women, POP can lead to various urinary and gastrointestinal tract symptoms, significantly impacting their quality of life. The pathogenesis of POP predominantly involves nerve-muscle damage and disorders in the extracellular matrix metabolism within the pelvic floor. Recent studies have indicated that genetic factors may play a crucial role in this condition. Focusing on linkage analyses, single-nucleotide polymorphisms, genome-wide association studies, and whole exome sequencing studies, this review consolidates current research on the genetic predisposition to POP. Advances in epigenetics are also summarized and highlighted, aiming to provide theoretical recommendations for risk assessments, diagnoses, and the personalized treatment for patients with POP.

Mitochondrial mechanisms in the pathogenesis of chronic inflammatory musculoskeletal disorders

Chronic inflammatory musculoskeletal disorders characterized by prolonged muscle inflammation, resulting in enduring pain and diminished functionality, pose significant challenges for the patients. Emerging scientific evidence points to mitochondrial malfunction as a pivotal factor contributing to these ailments. Mitochondria play a critical role in powering skeletal muscle activity, but in the context of persistent inflammation, disruptions in their quantity, configuration, and performance have been well-documented. Various disturbances, encompassing alterations in mitochondrial dynamics (such as fission and fusion), calcium regulation, oxidative stress, biogenesis, and the process of mitophagy, are believed to play a central role in the progression of these disorders. Additionally, unfolded protein responses and the accumulation of fatty acids within muscle cells may adversely affect the internal milieu, impairing the equilibrium of mitochondrial functioning. The structural discrepancies between different mitochondrial subsets namely, intramyofibrillar and subsarcolemmal mitochondria likely impact their metabolic capabilities and susceptibility to inflammatory influences. The release of signals from damaged mitochondria is known to incite inflammatory responses. Intriguingly, migrasomes and extracellular vesicles serve as vehicles for intercellular transfer of mitochondria, aiding in the removal of impaired mitochondria and regulation of inflammation. Viral infections have been implicated in inducing stress on mitochondria. Prolonged dysfunction of these vital organelles sustains oxidative harm, metabolic irregularities, and heightened cytokine release, impeding the body's ability to repair tissues. This review provides a comprehensive analysis of advancements in understanding changes in the intracellular environment, mitochondrial architecture and distribution, biogenesis, dynamics, autophagy, oxidative stress, cytokines associated with mitochondria, vesicular structures, and associated membranes in the context of chronic inflammatory musculoskeletal disorders. Strategies targeting key elements regulating mitochondrial quality exhibit promise in the restoration of mitochondrial function, alleviation of inflammation, and enhancement of overall outcomes.

Systemic immune-inflammation index and all-cause and cause-specific mortality in sarcopenia: a study from National Health and Nutrition Examination Survey 1999-2018

Background

Sarcopenia, common in the elderly, often linked to chronic diseases, correlates with inflammation.The association between SII and mortality in sarcopenia patients is underexplored, this study investigates this relationship in a U.S. adult cohort.

Methods

We analyzed 1999-2018 NHANES data, focusing on 2,974 adults with sarcopenia. Mortality outcomes were determined by linking to National Death Index (NDI) records up to December 31, 2019. Using a weighted sampling design, participants were grouped into three groups by the Systemic Immune-Inflammation Index (SII). We used Cox regression models, adjusting for demographic and clinical variables, to explore SII's association with all-cause and cause-specific mortality in sarcopenia, performing sensitivity analyses for robustness.

Results

Over a median follow-up of 9.2 years, 829 deaths occurred. Kaplan-Meier analysis showed significant survival differences across SII groups. The highest SII group showed higher hazard ratios (HRs) for all-cause and cause-specific mortality in both crude and adjusted models. The highest SII group had a higher HR for all-cause(1.57, 1.25-1.98), cardiovascular(1.61, 1.00-2.58), cancer(2.13, 1.32-3.44), and respiratory disease mortality(3.21, 1.66-6.19) in fully adjusted models. Subgroup analyses revealed SII's association with all-cause mortality across various demographics, including age, gender, and presence of diabetes or cardiovascular disease. Sensitivity analyses, excluding participants with cardiovascular diseases, those who died within two years of follow-up, or those under 45 years of age, largely reflected these results, with the highest SII group consistently demonstrating higher HRs for all types of mortality in both unadjusted and adjusted models.

Conclusion

Our study is the first to demonstrate a significant relationship between SII and increased mortality risks in a sarcopenia population.

Restoring Mitochondrial Function and Muscle Satellite Cell Signaling: Remedies against Age-Related Sarcopenia

Sarcopenia has a complex pathophysiology that encompasses metabolic dysregulation and muscle ultrastructural changes. Among the drivers of intracellular and ultrastructural changes of muscle fibers in sarcopenia, mitochondria and their quality control pathways play relevant roles. Mononucleated muscle stem cells/satellite cells (MSCs) have been attributed a critical role in muscle repair after an injury. The involvement of mitochondria in supporting MSC-directed muscle repair is unclear. There is evidence that a reduction in mitochondrial biogenesis blunts muscle repair, thus indicating that the delivery of functional mitochondria to injured muscles can be harnessed to limit muscle fibrosis and enhance restoration of muscle function. Injection of autologous respiration-competent mitochondria from uninjured sites to damaged tissue has been shown to reduce infarct size and enhance cell survival in preclinical models of ischemia-reperfusion. Furthermore, the incorporation of donor mitochondria into MSCs enhances lung and cardiac tissue repair. This strategy has also been tested for regeneration purposes in traumatic muscle injuries. Indeed, the systemic delivery of mitochondria promotes muscle regeneration and restores muscle mass and function while reducing fibrosis during recovery after an injury. In this review, we discuss the contribution of altered MSC function to sarcopenia and illustrate the prospect of harnessing mitochondrial delivery and restoration of MSCs as a therapeutic strategy against age-related sarcopenia.

Association of composite dietary antioxidant index and muscle mass in individuals with metabolic associated fatty liver disease

BACKGROUND

There is mounting evidence indicating the association between oxidative stress and the detrimental effect it poses on muscle mass. However, the crucial interplay between the Composite Dietary Antioxidant Index (CDAI), a key metric of antioxidant-rich diets, and the occurrence of muscle loss has remained largely unexplored. Hence, in this study, we aim to investigate the potential relationship between CDAI and muscle loss METHODS: This cross-sectional investigation harnessed data sourced from the National Health and Nutrition Examination Survey (2017 and 2018) to meticulously scrutinize the correlation between the CDAI and the occurrence of muscle loss. To unravel this intricate relationship, we engaged in multivariate weighted logistic regression analysis and employed smooth curve fitting techniques. Additionally, subgroup analyses were meticulously performed.

RESULTS

A total of 956 participants, with an average age of 42.15 years, were included in the final analysis, of which 52.19 % were males. Notably, the prevalence of low muscle mass among the study population was observed to be 15.48 %. The utilization of smooth curve fitting analysis underscored a nearly linear association between the CDAI and the presence of low muscle mass. Employing multivariate weighted logistic regression analysis, it was determined that the odds ratio (OR) between CDAI and low muscle mass was 0.88 (95 % [CI], 0.73-0.95). Through subgroup analyses, we further validated that CDAI independently mitigated the risk of muscle loss.

CONCLUSION

Higher CDAI levels were found to be associated with an reduced risk of low muscle mass in adults with metabolic associated fatty liver disease (MAFLD).

Association between systemic immune-inflammation index and low muscle mass in US adults: a cross-sectional study

BACKGROUND

Chronic inflammatory responses have been reported to be associated with low muscle mass and systemic immune-inflammation index(SII) is a novel indicator of inflammation. The purpose of our study was to clarify the relationship between SII and low muscle mass.

METHODS

This study was a cross-sectional study based on National Health and Nutrition Examination Survey (2011-2018). SII was calculated as the platelet count × neutrophil count/lymphocyte count. Appendicular skeletal muscle index was used to define low muscle mass. The individuals were divided into four groups by the quartile of SII (Q1-Q4). Multivariate weighted logistic regression analysis, smooth curve fitting and subgroup analysis were used to investigate the relationship between SII and sarcopenia. Subgroup analysis were based on demographic and clinical variables.

RESULTS

There were 10,367 individuals enrolled in our final analysis. The overall mean age was 39.39 years and 49.17% were males. The overall prevalence of low muscle mass in the study population was 8.77%. The smooth curve fitting analysis indicated a near-linear relationship between SII and low muscle mass. In multivariate weighted logistic regression analysis, the odds ratio (OR) of Q4 is 1.28 (95% CI, 1.16-1.40) for low muscle mass when compared to lowest quartile of the SII. In subgroup analysis, SII still increased the risk of low muscle mass independently.

CONCLUSION

The increased SII levels were associated with an increased risk of low muscle mass in a large population. Our study increased the understanding between inflammation and low muscle mass. Anti-inflammation therapy may be important for low muscle mass.