The authors emphasize that skeletal muscle is not only the most abundant tissue in the human body but also a pivotal mediator of functions such as locomotion, respiration, metabolism, thermoregulation, and overall postural balance. With advancing age, muscle mass and function decline—a condition defined as sarcopenia—leading to a host of adverse outcomes such as reduced strength, impaired mobility, increased risk of falls, and even higher mortality.
The review underscores that sarcopenia is driven by complex, interlinked biological processes including decreased muscle protein synthesis, increased protein degradation, satellite cell dysfunction, impaired regenerative capacity, and importantly, chronic oxidative stress and low-grade inflammation.
Increased ROS Production:
With aging, there is an upregulation in the generation of reactive oxygen species (ROS) in skeletal muscle and its stem (satellite) cells. Aging muscle fibers show evidence of both elevated basal ROS levels and an augmented response to stress, leading to higher levels of oxidative damage.
Mechanisms of Damage:
ROS cause oxidative modifications in DNA, proteins, and lipids. Notably, oxidative damage contributes to:
Gatekeeper of Mitochondrial Dysfunction:
The authors discuss that ROS may act as a “gatekeeper” in skeletal muscle by triggering mitochondrial dysfunction. As mitochondria become damaged, they produce even more ROS, creating a vicious feedback cycle that accelerates muscle degeneration.
Chronic Low-Grade Inflammation:
Interplay Between ROS and Inflammation:
Excessive ROS can stimulate the production of inflammatory cytokines. In turn, chronic inflammation can further increase ROS production, thereby setting up a feedback loop that perpetuates muscle damage and hinders repair. This interplay is critical in the progression of sarcopenia.
Impact on Satellite Cells:
The regenerative capacity of skeletal muscle largely depends on satellite cells. However, both oxidative stress and chronic inflammation impair satellite cell function—reducing their capacity to activate, proliferate, and differentiate—thus leading to an impaired regenerative response in aging muscles.
Mitochondrial Dynamics:
Mitochondria maintain cellular energy balance and regulate apoptosis. The review outlines how imbalances in mitochondrial fusion and fission—and defective mitophagy—can exacerbate oxidative stress. Aging muscles often display alterations in mitochondrial dynamics (e.g., changes in the MFN2/DRP1 ratio) that correlate with reduced regenerative efficiency.
Satellite Cell Dysregulation:
The chronic oxidative and inflammatory environment in aged muscle negatively impacts the viability and self-renewal of satellite cells. These disruptions contribute to inadequate muscle repair and regeneration after injury or during regular turnover, further accelerating sarcopenia.
The paper reviews several interventions that have been explored, primarily in preclinical models, with an eye toward future clinical applications.
Dietary Antioxidants:
Substances such as vitamins (e.g., Vitamin C and E), polyphenols (e.g., resveratrol), and other natural antioxidants have been investigated for their potential to neutralize free radicals and reduce oxidative damage.
Specific Agents:
Acts as a free radical scavenger and metal chelator. Clinical and preclinical studies suggest that supplementation with carnosine (or its precursor, β-alanine) can improve muscle function and delay oxidative damage.
A medicinal mushroom rich in bioactive compounds (triterpenoids, polysaccharides, peptides) that exhibits antioxidant and anti-inflammatory properties. Preliminary data indicate that its extracts may protect muscle tissue from oxidative stress–induced damage and improve regenerative capacity.
EPA and DHA have anti-inflammatory properties and may improve mitochondrial function and reduce oxidative stress in muscle, thereby contributing to better muscle preservation.
Targeting Inflammatory Cytokines:
Approaches that aim to reduce levels of pro-inflammatory cytokines (such as IL-6 and TNF-α) are considered potential strategies to slow muscle degradation.
Agents with Dual Actions:
Many natural compounds and vitamins exhibit both antioxidant and anti-inflammatory effects, thereby tackling both key drivers of sarcopenia.
Exercise as a Gold Standard:
The review highlights that among the available strategies, physical exercise remains the only intervention that has unequivocally demonstrated benefits in delaying muscle loss in the elderly.
Synergistic Approaches:
It is suggested that combining exercise with antioxidant and anti-inflammatory therapies may yield the most efficient strategy for managing sarcopenia. The rationale is to not only reduce oxidative and inflammatory damage but also to support the muscle’s intrinsic capacity for repair and regeneration.
Mechanistic Complexity:
The authors stress the multifactorial nature of sarcopenia. Both oxidative stress and inflammation are interlinked with mitochondrial dysfunction and satellite cell impairment, leading to muscle loss. Future research is needed to untangle these pathways and understand their causal relationships better.
Translation to Human Studies:
While much of the evidence comes from in vitro and in vivo (animal model) studies, the review acknowledges the relative scarcity of robust human clinical trials. Future work should prioritize well-designed, randomized controlled trials to verify the efficacy and safety of antioxidant and anti-inflammatory interventions in the aging population.
Personalized and Combination Therapies:
There is an opportunity for developing personalized therapeutic regimens that combine nutritional strategies (e.g., antioxidant supplementation), pharmacological approaches (targeting key inflammatory pathways), and established interventions like exercise to comprehensively address sarcopenia.
Optimizing Mitochondrial Function:
Since mitochondrial health is central to muscle function, interventions aimed at preserving or restoring mitochondrial dynamics (e.g., via modulation of fusion–fission balance or enhancement of mitophagy) may also hold promise.
Addressing Satellite Cell Regeneration:
Strategies that protect or rejuvenate skeletal muscle satellite cells by reducing oxidative stress and inflammation may be critical for improving muscle regeneration in the elderly.
The paper provides a thorough review of the mechanisms by which oxidative stress and chronic inflammation contribute to sarcopenia in aging skeletal muscle. It outlines how elevated ROS levels and an inflammatory milieu disrupt mitochondrial function, impair muscle protein synthesis, and diminish satellite cell regenerative capacity—ultimately leading to a decline in muscle mass and strength.
It then describes several potential therapeutic strategies—including antioxidant supplementation (e.g., carnosine, Ganoderma lucidum extracts, omega-3 fatty acids), anti-inflammatory agents, and combined interventions with exercise—which have shown promise in preclinical studies. However, the authors acknowledge that more rigorous clinical research is needed in human populations to confirm efficacy, optimize dosing, and evaluate long-term outcomes.
The review concludes that a multifaceted approach combining lifestyle interventions (such as exercise), along with targeted antioxidant and anti-inflammatory therapies, is likely the most effective strategy to prevent or treat sarcopenia and improve the quality of life during aging.
Source Information
Article Title: Skeletal Muscle Oxidative Stress and Inflammation in Aging: Focus on Antioxidant and Anti-inflammatory Therapy
Authors: Mingming Chen, Yiyi Wang, Shoulong Deng, Zhengxing Lian, Kun Yu
Published In: Frontiers in Cell and Developmental Biology, 2022
Source Link: Frontiers in Cell and Developmental Biology: 10.3389/fcell.2022.964130/full
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