[Neuromuscular abnormalities in disuse, ageing and cachexia]

Area of Science:

• Neuromuscular Science
• Muscle Physiology
• Aging Research

Context:

• The neuromuscular system is crucial for movement and is affected by aging, disuse, and cachexia.
• Understanding these effects is vital for managing age-related conditions and muscle wasting diseases.
• Previous research has explored individual factors, but a comprehensive review is needed.

Purpose:

• To review the effects of cachexia, ageing, and disuse on the human and animal neuromuscular system.
• To differentiate the specific impacts of each condition on muscle fibers and neuromuscular junctions.
• To highlight the mechanisms underlying muscle atrophy and functional decline.

Summary:

• Disuse leads to reduced muscle fiber diameter (type II), peripheral myofibril loss, and angular fiber shape, while preserving neuromuscular junction integrity.
• Ageing involves progressive denervation and reinnervation, motor unit loss, reduced acetylcholine release, and decreased mitochondrial capacity, favoring type I fibers.
• Cachexia causes muscle fiber diameter reduction (legs, then arms/trunk), type II atrophy, and decreased protein synthesis, with normal DNA levels.

Impact:

• Provides a consolidated understanding of neuromuscular system changes in ageing, disuse, and cachexia.
• Informs potential therapeutic strategies targeting muscle health in vulnerable populations.
• Establishes a foundation for further research into interventions for sarcopenia and cachexia.