Sarcopenia: Molecular mechanism & treatment strategies

Declining skeletal muscle mass and strength is a common accompaniment of old age referred to as sarcopenia. International Classification of Diseases (ICD) in its 10^th revision (ICD-10 code) has identified sarcopenia as a disease entity. Marked by progressive and generalized loss of skeletal muscle mass and decline in strength, sarcopenia is correlated with physical disability, malnutrition, poor quality of life and death. Its risk factors include increasing age, malnutrition, level of physical activity and presence of chronic catabolic states such as malignancy, rheumatoid arthritis, chronic kidney and liver diseases. While clinical diagnosis may be often obvious from appearance, several diagnostic criteria have been proposed by expert groups from different geographic locations with the consideration, there are considerable differences in body composition determined by genetics, race, gender and food habits. Relevance of sarcopenia in clinical practice lies in the fact that sarcopenia is the most obvious phenotypic expression of frailty, which is emerging as an important health issue in the older population. The exact mechanism by which muscle cells die is not clear, and as a result, there is no definitive treatment strategy for sarcopenia available with the current state of knowledge and understanding. It is a common practice to advise a high protein diet and physical exercise for low muscle mass by commonsense though the exact mechanism by which it helps building and rebuilding of muscle mass remains presumptive.

This book provides a holistic approach to the issue; by examining the structural and functional issues associated with sarcopenia. The book is divided into 18 Chapters that provide insight into the genesis of sarcopenia and some answers to many of the unresolved questions in muscle cell biology. All possible mechanisms of sarcopenia have been dealt with the most recent evidence and hypotheses derived from them.

Mitochondria, neuromuscular junction and muscle stem cells are the areas that have been deeply researched and summarized. The usual theories of ageing related to intra- and extracellular mechanisms hold true for sarcopenia as well. Recent thinking about muscle stem cells and their possible utilization in clinical settings are an interesting proposition. Changing focus to mechanisms, the editor has compiled some very seminal questions of biogerontology in the genesis of sarcopenia, namely enhanced inflammatory cytokines expression, defects of autophagy signaling and mitophagy and finally, sarcopenic obesity to draw attention to obesity as a risk factor for sarcopenia and other age related pathological states.

Diet and exercise are two interventions well known for their impact on shaping an athletic and muscular body frame. The mechanism of both these interventions in reversing sarcopenia has received justifiable attention from the editor. A new thinking that skeletal muscles behave as endocrine organs and secrete various proteins/peptides, known as myokines, into the extracellular space and some of these regulate myogenesis and protein metabolism. Myokines are secreted as a response to exercise in young adults and their secretion may get dysregulated and can be associated with sarcopenia. The research on myokines is expanding very fast. Myokines may have a role as a biomarker or therapeutic agent in management, although evidence at this point is scarce. Chapters on the quality of sarcopenic muscles, its bidirectional association with vascular ageing can provide some research ideas to young researchers, while sarcopenia as a cause of dysphagia in cachexia of old age gives a new clinical insight.

As the name suggests, ‘Sarcopenia Molecular Mechanism and Treatment Strategies’ is a publication focusing on basic issues related to sarcopenia. With thousands of references, this book is an asset for researchers of muscle biology and biogerontology and a must buy for academic libraries. Some important derivatives of the deliberations in the book are potential of stem muscle cells in management, realistic evaluation of myokines as diagnostic and therapeutic agents and detailed assessment of diet and nutrition in the management of sarcopenia.