Influence of Age on Skeletal Muscle Hypertrophy and Atrophy Signaling: Established Paradigms and Unexpected Links

Sarcopenia and Cardiovascular Diseases

Sarcopenia is the loss of muscle strength, mass, and function, which is often exacerbated by chronic comorbidities including cardiovascular diseases, chronic kidney disease, and cancer. Sarcopenia is associated with faster progression of cardiovascular diseases and higher risk of mortality, falls, and reduced quality of life, particularly among older adults. Although the pathophysiologic mechanisms are complex, the broad underlying cause of sarcopenia includes an imbalance between anabolic and catabolic muscle homeostasis with or without neuronal degeneration. The intrinsic molecular mechanisms of aging, chronic illness, malnutrition, and immobility are associated with the development of sarcopenia. Screening and testing for sarcopenia may be particularly important among those with chronic disease states. Early recognition of sarcopenia is important because it can provide an opportunity for interventions to reverse or delay the progression of muscle disorder, which may ultimately impact cardiovascular outcomes. Relying on body mass index is not useful for screening because many patients will have sarcopenic obesity, a particularly important phenotype among older cardiac patients. In this review, we aimed to: (1) provide a definition of sarcopenia within the context of muscle wasting disorders; (2) summarize the associations between sarcopenia and different cardiovascular diseases; (3) highlight an approach for a diagnostic evaluation; (4) discuss management strategies for sarcopenia; and (5) outline key gaps in knowledge with implications for the future of the field.

Sarcopenia Is a Cause and Consequence of Metabolic Dysregulation in Aging Humans: Effects of Gut Dysbiosis, Glucose Dysregulation, Diet and Lifestyle

Skeletal muscle mass plays a critical role in a healthy lifespan by helping to regulate glucose homeostasis. As seen in sarcopenia, decreased skeletal muscle mass impairs glucose homeostasis, but it may also be caused by glucose dysregulation. Gut microbiota modulates lipopolysaccharide (LPS) production, short-chain fatty acids (SCFA), and various metabolites that affect the host metabolism, including skeletal muscle tissues, and may have a role in the sarcopenia etiology. Here, we aimed to review the relationship between skeletal muscle mass, glucose homeostasis, and gut microbiota, and the effect of consuming probiotics and prebiotics on the development and pathological consequences of sarcopenia in the aging human population. This review includes discussions about the effects of glucose metabolism and gut microbiota on skeletal muscle mass and sarcopenia and the interaction of dietary intake, physical activity, and gut microbiome to influence sarcopenia through modulating the gut–muscle axis. Emerging evidence suggests that the microbiome can regulate both skeletal muscle mass and function, in part through modulating the metabolisms of short-chain fatty acids and branch-chain amino acids that might act directly on muscle in humans or indirectly through the brain and liver. Dietary factors such as fats, proteins, and indigestible carbohydrates and lifestyle interventions such as exercise, smoking, and alcohol intake can both help and hinder the putative gut–muscle axis. The evidence presented in this review suggests that loss of muscle mass and function are not an inevitable consequence of the aging process, and that dietary and lifestyle interventions may prevent or delay sarcopenia.

Total hip arthroplasty or hemiarthroplasty for femoral neck fractures in elderly patients with neuromuscular imbalance

AIM

This study aimed at comparing clinical outcomes between total hip arthroplasty (THA) and hemiarthroplasty (HA) in elderly patients with neuromuscular imbalance (stroke, Parkinsonism, etc.).

METHODS

A total of 226 elderly patients with neuromuscular imbalance and femoral neck fractures treated with THA or HA were recruited at a single center, and their clinical data retrospectively reviewed. Mean follow-up time was 40.5 months (range 24-78), the primary outcome was secondary hip procedure while secondary outcomes included function, pain, health-related quality of life, complications, and death. Kaplan-Meier survival curves were used to determine the estimated survivorship, with re-operation as the end point. Logistic regression analyses were performed to assess the effects of different surgical procedures on mortality while linear regression analysis was used to evaluate the function, pain and quality of life.

RESULTS

Kaplan-Meier survivorship, with an end point of re-operation for any reason in the THA group, was 90.3% (95% CI 82.3-98.3), which was not significantly different from 95.9% (95% CI 93.0-98.8) for the HA group (p = 0.137). The most common cause of re-operation in both groups was dislocation. There were no significant differences with regards to postoperative complications (including dislocation). Compared to HA, THA exhibited better functional outcomes, quality of life and low pain intensity. Notably, there was no difference in 2 year mortality rates between the groups, however, HA was associated with a higher mortality rate beyond 2 years (OR 0.137; 95% CI 0.030-0.630; p = 0.011).

CONCLUSION

THA is an effective therapeutic procedure for femoral neck fractures in elderly patients with neuromuscular imbalance.