Myokines secretion and their role in critically ill patients. A scoping review

This review aims to summarize the available evidence on myokine secretion and its potential local and systemic effects in critically ill patients. 

A scoping review was conducted based on Joana Briggs Institute recommendations. A systematic search of MEDLINE (Ovid), Embase (Ovid), CENTRAL, CINHAL (EBSCOhost), WoS, and Scopus was performed up to February 2023. The review included primary studies involving critically ill adults that evaluated myokine secretion or concentration induced by physical rehabilitation interventions. Two independent reviewers performed study selection and data extraction. 

Seventeen studies, published between 2007 and 2023, were included. Most of the studies were randomized clinical trials (47%). Some reports included patients within 48-72 hours from intubation and mechanical ventilation initiation while other authors focused on the chronic critically ill scenario (patients with 10 days on MV). The physical rehabilitation interventions included in the studies were NMES and passive and active mobilization. These interventions were delivered alone or in combination, in a single session or one to two sessions daily. The duration of the rehabilitation sessions ranged from 20 to 60 minutes. Twelve (70%) studies evaluated IL-6. Other myokines frequently studied were IL-10, TNF-α, IL-8, and Myostatin. Method and timing of myokine evaluation varied widely between studies. Thirteen (76%) studies reported changes in myokine secretion or gene expression. Most of them reported no consistent change regarding IL-6. Concentration of myokines related to muscle protein synthesis/breakdown, such as Myostatin, seem to potentially protect from muscle wasting and consequent weakness. 

Myokine dynamics in critically ill patients may play a role in the potential systemic impact of physical rehabilitation beyond its well-known local effects. In the past decade, this complex and emerging field has seen a growing interest, holding a great potential for research development. However, challenges such as study design, small sample sizes,and variations in physical therapy protocols and methods of myokine evaluation across clinical trials add difficulties in understanding myokine responses and their potential effects. 

The study of myokine dynamics in critically ill patients underscores the significance and potential systemic impact of physical rehabilitation, extending beyond the local and traditionally recognized effects.