Muscle oxidative capacity during IL-6-dependent cancer cachexia

Area of Science:

• Mitochondrial biology
• Skeletal muscle physiology
• Cancer cachexia research

Background:

• Catabolic diseases often cause skeletal muscle wasting.
• Muscle metabolism, particularly glycolytic fiber susceptibility, is implicated in muscle wasting.
• Cancer cachexia involves complex mechanisms leading to muscle protein loss.

Purpose of the Study:

• To investigate the relationship between muscle oxidative capacity and muscle mass loss in hindlimb muscles during cancer cachexia development.
• To compare these changes in oxidative (red) and glycolytic (white) muscle fibers.

Main Methods:

• Excised gastrocnemius and soleus muscles from Apc(Min/+) mice at 20 weeks of age.
• Partitioned gastrocnemius into red and white portions for analysis.
• Measured body mass, muscle mass, fat pad mass, circulating IL-6, mitochondrial DNA/nuclear DNA ratio, and protein/mRNA expression of key mitochondrial and muscle-related factors.

Main Results:

• Severely cachectic mice showed significant reductions in body mass, muscle mass, and fat pad mass compared to mildly cachectic mice.
• Circulating IL-6 levels were markedly higher in severely cachectic mice.
• Cachexia reduced mitochondrial DNA/nuclear DNA ratio, cytochrome c, and Cox IV protein in both red and white muscles.
• PGC-1α expression was suppressed, while Mfn1/Mfn2 mRNA decreased and Fis1 mRNA increased, indicating altered mitochondrial dynamics and oxidative stress markers.

Conclusions:

• Cancer cachexia significantly impairs muscle oxidative capacity and mitochondrial dynamics in both oxidative and glycolytic muscle fibers.
• Reduced mitochondrial function and altered mitochondrial dynamics are associated with severe muscle wasting and elevated IL-6 levels.
• These findings highlight the systemic impact of cancer cachexia on muscle metabolism and integrity.