Muscular myostatin gene expression and plasma concentrations are decreased in critically ill patients

Myokine Secretion Dynamics and Their Role in Critically Ill Patients: A Scoping Review

Background/Objectives: Myokines can modulate organ function and metabolism, offering a protective profile against ICU complications beyond preventing local muscle wasting. This scoping review aims to explore and summarize the evidence regarding the secretion of myokines and their potential local or systemic effects in critically ill patients. Methods: A scoping review following Joana Briggs Institute recommendations was conducted. A systematic search of MEDLINE (Ovid), Embase (Ovid), CENTRAL, CINAHL (EBSCOhost), WoS, and Scopus was conducted from inception to February 2023. We included primary studies evaluating myokine secretion/concentration in critically ill adults undergoing physical rehabilitation interventions. Two independent reviewers performed study selection and data extraction. Results: Seventeen studies published between 2012 and 2023 were included. Most were randomized clinical trials (47%). Physical rehabilitation interventions included electrical muscle stimulation, as well as passive and active mobilization, delivered alone or combined, in single or daily sessions lasting 20-60 min. Twelve studies (70%) evaluated interleukin-6, while interleukin-10, tumour necrosis factor-α, Interleukin-8, and myostatin were also commonly studied. Thirteen studies (76%) reported changes in myokine secretion or gene expression, although no clear concentration change pattern emerged. Myokines involved in muscle protein synthesis and breakdown may protect against muscle waste and weakness. Conclusions: The study of myokine dynamics in critically ill patients highlights the systemic impact of physical rehabilitation. This emerging field has grown in interest over the past decade, offering significant research potential. However, challenges such as study design, small sample sizes, and variability in physical therapy protocols hinder a comprehensive understanding of myokine responses.

Myostatin gene invalidation does not prevent skeletal muscle mass loss during experimental sepsis in mice

Loss of muscle mass and function induced by sepsis contributes to physical inactivity and disability in intensive care unit patients. Limiting skeletal muscle deconditioning may thus be helpful in reducing the long-term effect of muscle wasting in patients. We tested the hypothesis that invalidation of the myostatin gene, which encodes a powerful negative regulator of skeletal muscle mass, could prevent or attenuate skeletal muscle wasting and improve survival of septic mice. Sepsis was induced by caecal ligature and puncture (CLP) in 13-week-old C57BL/6J wild-type and myostatin knock-out male mice. Survival rates were similar in wild-type and myostatin knock-out mice seven days after CLP. Loss in muscle mass was also similar in wild-type and myostatin knock-out mice 4 and 7 days after CLP. The loss in muscle mass was molecularly supported by an increase in the transcript level of E3-ubiquitin ligases and autophagy-lysosome markers. This transcriptional response was blunted in myostatin knock-out mice. No change was observed in the protein level of markers of the anabolic insulin/IGF1-Akt-mTOR pathway. Muscle strength was similarly decreased in wild-type and myostatin knock-out mice 4 and 7 days after CLP. This was associated with a modified expression of genes involved in ion homeostasis and excitation-contraction coupling, suggesting that a long-term functional recovery following experimental sepsis may be impaired by a dysregulated expression of molecular determinants of ion homeostasis and excitation-contraction coupling. In conclusion, myostatin gene invalidation does not provide any benefit in preventing skeletal muscle mass loss and strength in response to experimental sepsis. KEY POINTS: Survival rates are similar in wild-type and myostatin knock-out mice seven days after the induction of sepsis. Loss in muscle mass and muscle strength are similar in wild-type and myostatin knock-out mice 4 and 7 days after the induction of an experimental sepsis. Despite evidence of a transcriptional regulation, the protein level of markers of the anabolic insulin/IGF1-Akt-mTOR pathway remained unchanged. RT-qPCR analysis of autophagy-lysosome pathway markers indicates that activity of the pathway may be altered by experimental sepsis in wild-type and myostatin knock-out mice. Experimental sepsis induces greater variations in the mRNA levels of wild-type mice than those of myostatin knock-out mice, without providing any significant catabolic resistance or functional benefits.

The Significance of Selected Myokines in Predicting the Length of Rehabilitation of Patients after COVID-19 Infection

In the context of the global COVID-19 pandemic, understanding the intricate mechanisms of the body's response to infection and inflammation has become a priority for the medical and research communities. It has been proven that during COVID-19 infection, molecules are secreted-namely organokines, which may directly or indirectly play a role in the pathophysiology of COVID-19. The objective of this study was to scrutinize the potential correlation between the levels of selected myokines (myostatin, agrin, irisin, and myonectin) and the duration of rehabilitation in post-COVID-19 patients. Additionally, the study aimed to investigate whether there is a correlation between the levels of these myokines and the length of hospitalization during COVID-19 treatment. The study was conducted at the Rehabilitation Hospital in Szczecin (Poland). Patients in the study participated in a comprehensive rehabilitation program following COVID-19 treatment. In order to assess the effectiveness of rehabilitation, the following tests were performed: a 6 min walk test with an assessment of exercise tolerance (Borg scale), an assessment of dyspnea severity (mMRC scale), a spirometric assessment of respiratory function, a measurement of arm strength, and an assessment of fatigue using the Fatigue Assessment Scale (FAS). Myokine levels were measured using commercially available enzyme-linked immunosorbent assays (ELISA) according to the manufacturer's instructions. Statistical analysis was performed using Statistica 13.1 software. Lower concentrations of irisin and myonectin and higher concentrations of myostatin correlated with longer rehabilitation time. Baseline levels of specific myokines in post-COVID-19 patients could play a crucial role in anticipating the duration of rehabilitation. The duration of hospitalization for the infection may influence myokine levels in patients recovering from COVID-19.