Mitochondrial involvement and impact in aging skeletal muscle

Area of Science:

• Gerontology
• Skeletal Muscle Physiology
• Mitochondrial Biology

Background:

• Skeletal muscle atrophy is a hallmark of aging, leading to weakness and frailty.
• Mitochondrial dysfunction is frequently implicated as a primary mechanism in age-related muscle atrophy.
• Previous research shows inconsistent changes in mitochondrial respiration and reactive oxygen species emission in aging muscle.

Purpose of the Study:

• To investigate intrinsic mitochondrial function in aging skeletal muscle.
• To explore the role of extrinsic factors, such as oxidative stress, in modulating mitochondrial function during aging.
• To determine the contribution of denervation to mitochondrial alterations in very advanced age muscle atrophy.

Main Methods:

• Analysis of mitochondrial respiration and reactive oxygen species emission in aging rat and human skeletal muscle.
• Assessment of mitochondrial permeability transition sensitivity.
• Investigation of the impact of the aging milieu and oxidative stress on mitochondrial function in vivo and ex vivo.

Main Results:

• Mitochondrial respiration and reactive oxygen species emission changes were inconsistent in atrophying rat muscles and normal in active septuagenarian humans.
• A generalized sensitization to mitochondrial permeability transition was observed in aging atrophying muscle, including in active older adults.
• Oxidative stress in the aging environment depresses mitochondrial respiratory function in vivo, an effect not seen ex vivo.

Conclusions:

• Intrinsic mitochondrial respiration may not be consistently impaired in aging muscle atrophy, challenging its role as a universal driver.
• Increased mitochondrial permeability transition is a consistent feature of aging muscle atrophy, suggesting it as a potential therapeutic target.
• Future research must differentiate between primary mitochondrial defects and secondary alterations due to denervation in very advanced age muscle atrophy to clarify therapeutic relevance.