Symposium and workshop: Skeletal muscle research – from cell to human, which is held regularly at Faculty of Medicine, University of Ljubljana, aims to present and discuss skeletal muscle from a range of perspectives, with energy metabolism in the centre. The main focus of the 2024 Symposium and workshop: Skeletal muscle research – from cell to human is experimental models used to reveal and illuminate the structure and function of skeletal muscle. We are taking this opportunity to launch a Research Topic that focuses extensively on energy metabolism in skeletal muscle. This topic will cover a wide range of areas from physiology to pharmacology and will include a special emphasis on experimental models.

The ensemble of skeletal muscles can be considered the largest metabolic and endocrine organ of the human body. The more than 600 skeletal muscles, which under physiological conditions account for ~40% of body weight and ~20% of resting metabolic rate, have the largest endogenous glycogen, protein and potassium stores and are an important site for the metabolic conversion of lipids and glucose. At rest, 70% of muscle energy consumption comes from fatty acids. A switch to glucose metabolism occurs after a meal, when skeletal muscle is the main site for insulin-stimulated glucose utilisation. Between the resting and actively contracting states, metabolic rate, glucose and lipid utilisation as well as transmembrane potassium and sodium transport increase enormously. It is clear that skeletal muscle is not only the largest but also one of the most dynamic metabolic and ion transporting organs.

Such dynamism requires tight coupling between energy metabolism and the functional requirements, including those of contractile apparatus and ion homeostasis, of the muscles both at rest and during contraction. Although metabolic pathways in skeletal muscle are regulated by a variety of factors, including metabolic hormones, contractions, reactive oxygen species, hypoxia and NO, skeletal muscle does not merely respond passively to regulatory signals. In fact, skeletal muscle is an important source of signaling molecules (myokines) that are involved in inter-organ communication and actively modulate energy metabolism in other organs.

Given the size of skeletal muscle and the variety of metabolic functions it fulfils, it is not surprising that metabolic dysfunction of skeletal muscle, such as insulin resistance, disrupts systemic metabolic homeostasis. Furthermore, via regular physical activity and exercise, skeletal muscle plays a key role in safeguarding overall human health. Maintaining an adequate muscle quality through the lifespan is linked to the prevention of most, if not all, degenerative diseases, including sarcopenia and neurodegenerative disorders that are known to be associated with metabolic dysfunction and unhealthy ageing. Pharmacological modulation of energy metabolism in skeletal muscle is therefore a promising strategy to combat chronic non-communicable diseases.

The endeavor to untangle energy metabolism in skeletal muscle will not only push the frontiers of our understanding of physiology, but will also have important practical implications, including the development of new pharmacotherapies.

Types of papers: Different types of manuscripts, including original research, methodological studies as well as reviews, will be considered.

Topics: The suggested topics include, but are not limited to:
• Experimental models, including cell cultures and isolated organs, for investigation of skeletal muscle energy metabolism
• Systematic comparison of experimental models for investigation of skeletal muscle energy metabolism, including in vitro models vs. in vivo models and comparison of various in vivo models
• Extrapolation of findings from in vitro and animal studies to human physiology, pathophysiology, and pharmacology: opportunities and limitations
• Effect of physical (in)activity on skeletal muscle energy metabolism: from in vitro exercise, such as electrical pulse stimulation, to in vivo interventions.
• Imaging studies in the assessment of human skeletal muscle structure and function in vivo
• Regulation of metabolic pathways in skeletal muscle, including intracellular signaling.
• Skeletal muscle as a target and source of signal molecules, including metabolic hormones and myokines, which regulate energy metabolism and participate in cross-talk between skeletal muscles and other organs.
• Metabolites involved in inter-organ communication and regulation of energy metabolism.
• Mitochondrial function in skeletal muscle in health and disease.
• Ageing-related alterations in the metabolic function of skeletal muscle.
• Links between regulation of ion transport and energy metabolism in skeletal muscle.
• Mechanisms underlying insulin resistance in skeletal muscle.
• Pharmacological modulation of energy metabolism in skeletal muscle.
• Mechanisms leading to dysregulation of energy metabolism in skeletal muscle in chronic inflammatory disorders, obesity, and diabetes mellitus.
• The role of skeletal muscle innervation in regulation of energy metabolism.
• Regulation of muscle mass, hypertrophy, sarcopenia and aging.
• Cancer cachexia and muscle wasting.

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Frontiers in Physiology

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