Interactive effects of emphysema and malnutrition on diaphragm structure and function

Area of Science:

• Respiratory Physiology
• Muscle Biology
• Nutritional Science

Background:

• Emphysema (EMP) is a chronic lung disease characterized by alveolar destruction.
• Nutritional deprivation (ND) can negatively impact muscle function and mass.
• The combined effects of EMP and ND on respiratory muscles like the diaphragm (DIA) are not well understood.

Purpose of the Study:

• To investigate the interactive effects of emphysema and prolonged nutritional deprivation on hamster diaphragm muscle properties.
• To examine contractile, morphometric, and metabolic adaptations in the diaphragm under combined disease and malnutrition conditions.

Main Methods:

• Emphysema was induced in hamsters via intratracheal elastase.
• Animals underwent 6 weeks of nutritional deprivation (ND) or served as controls (CTL).
• In vitro isometric contractile and fatigue properties of the diaphragm were assessed.
• Fiber type, cross-sectional area, succinate dehydrogenase activity, and capillary supply (C/F, C/A) were analyzed histochemically.

Main Results:

• ND caused significant body weight loss in both control and emphysema groups.
• Emphysema reduced diaphragm muscle specific force, an effect not altered by ND.
• ND attenuated the improved fatigue resistance observed in emphysema alone.
• ND induced atrophy in both type I and type II diaphragm fibers, abolishing adaptive hypertrophy in type II fibers of emphysema animals.
• Increased succinate dehydrogenase activity in emphysema was unaffected by ND.

Conclusions:

• Nutritional deprivation exacerbates diaphragm muscle atrophy in emphysema, particularly in type II fibers.
• Combined emphysema and nutritional deprivation negatively impact diaphragm fatigue resistance.
• Metabolic adaptations to emphysema in the diaphragm are preserved despite nutritional deprivation.