Scientists Discover a Hidden Cause Explaining Muscle Weakness with Aging

🧬 A New Discovery Reveals the Cause of Muscle Weakness with Aging

Muscle weakness with aging is a natural phenomenon, but modern scientific research has revealed a hidden cause linked to a shift in muscle fiber type and changes in mitochondrial function. The new study explains that aging muscles sacrifice strength in favor of protection, opening the door to future treatments that target the root causes of muscle wasting.

🏃 Muscle Fiber Types and Their Role in Movement and Energy

Muscles are made up of muscle fibers with different functions, including fast-twitch fibers that generate quick and powerful movements but fatigue quickly, and slow-twitch fibers that support sustained activity and contain a larger number of mitochondria.

Mitochondria are cellular organelles responsible for producing the energy needed for muscle contraction, and this occurs within a complex system that plays a fundamental role in maintaining muscle activity.

With age, mitochondrial performance declines and muscle strength decreases, yet the proportion of slow-twitch fibers that rely heavily on those weakened mitochondria increases, creating a puzzle that has baffled scientists.

🧫 The Role of Cardiolipin in Mitochondrial Health

The study focused on cardiolipin, a special type of fat found mainly in the inner mitochondrial membrane. Cardiolipin maintains the folded and distinctive structure of the membrane, allowing mitochondria to perform their vital function properly.

A decrease in cardiolipin levels causes mitochondria to fail to produce enough energy and affects their ability to emit the chemical signals needed by cells, leading to problems in muscle function.

In both mice and humans, a decrease in cardiolipin was observed with aging or with diseases that lead to muscle loss. This decrease was also accompanied by changes in mitochondrial shape and a loss of their normal functions.

🧪 Experiments on Mice Reveal the Link Between Cardiolipin and Muscle Aging

By reducing cardiolipin levels in young mice, signs similar to what naturally happens with aging appeared, as muscle fibers shifted from the fast type to the slow type. Restoring cardiolipin to about two-thirds of its normal level stopped muscle wasting and prevented premature death in these animals.

🛡️ How Does This Shift Protect Muscles?

When cardiolipin is low, mitochondria produce large amounts of free radicals or Reactive Oxygen Species (ROS), which are active molecules that can damage cells, but they also trigger signals that stimulate the shift in muscle fiber types.

It became clear that this shift does not only reflect weakness, but is a protective response by cells, as muscles try to protect themselves from damage caused by free radicals.

When muscle cells resistant to cardiolipin reduction were treated with antioxidants, the shift from fast fibers to slow fibers decreased, indicating that free radicals play a vital role in this process.

A protein called ERRγ also had a central role in regulating the muscle response to these changes, as it controls mitochondrial remodeling and the alteration of fiber properties. Disabling this protein in laboratory cells completely stopped the shift between fiber types.

⚙️ The Function of the New Muscle Fibers in Protection

Mice with low cardiolipin levels consumed more glucose, but this energy was not mainly used to produce muscle energy. Instead, muscle cells redirected glucose to make antioxidants that help protect cells from free radical damage.

In this exchange, muscles sacrifice strength in return for greater protection, which explains why muscle performance declines with age despite the increase in the proportion of slow fibers.

💊 Promising Therapeutic Prospects for Combating Age-Related Muscle Wasting

These findings reveal the possibility of developing treatments that aim to restore cardiolipin levels or affect the ERRγ protein to stimulate healthy adaptations in muscles as they age.

The drug elamipretide, which stabilizes cardiolipin, recently received accelerated approval from regulatory authorities to treat a rare genetic disease, showing that targeting this molecule may be medically practical.

ERRγ is also being studied as a potential drug target, as this protein family belongs to nuclear receptors that many existing drugs already target.

In the researchers’ view, partially raising cardiolipin levels is enough to return muscles to a better healthy state, highlighting new possibilities for future treatment of age-related muscle wasting.

The research was conducted with the participation of more than 20 scientific institutions under the leadership of the NNF Center for Metabolic Research at the University of Copenhagen, with the participation of hospitals and global research organizations.

Source: Medicalxpress

📚 Related articles

Scientists Discover a protein switch That Burns Fat and Prevents the Formation of New Fat Cells

2026/09/07

A Natural Compound May Help Fight Rheumatoid Arthritis at Its Roots

2026/09/08

The Brain’s Actual Role in the Decision-Making Process May Not Be What Is Assumed

2026/09/24