What leads to muscle weakness in long-time alcoholics

Muscle weakness is a common symptom of both long-time alcoholics and patients with mitochondrial disease, and now researchers have found a common link - mitochondria that are unable to self-repair.

The link to self-repair provides researchers both a new way to diagnose mitochondrial disease, and a new drug target.

Mitochondria-organelles that produce the energy needed for muscle, brain, and every other cell in the body-repair their broken components by fusing with other mitochondria and exchanging their contents. Damaged parts are segregated for recycling and replaced with properly functioning proteins donated from healthy mitochondria.

While fusion is one major method for mitochondrial quality control in many types of cells, researchers have puzzled over the repair mechanism in skeletal muscle-a type of tissue that relies constantly on mitochondria for power, making repair a frequent necessity. However, mitochondria are squeezed so tightly in between the packed fibers of muscle cells, that most researchers assumed that fusion among mitochondria in this tissue type was impossible.

An inkling that fusion might be important for the normal muscle function came from research on two mitochondrial diseases: Autosomal Dominant Optical Atropy (ADOA) disease, and a type of Charcot-Marie-Tooth disease (CMT). A symptom of both disease is muscle weakness and patients with both these diseases carry a mutation in one of the three genes involved in mitochondrial fusion.

The researcher team was led by Dr. Gyorgy Hajnoczky, M.D., Ph.D., Director of Jefferson's MitoCare Center and professor in the department of Pathology, Anatomy and Cell Biology.

"That alcohol can have a specific effect on this one gene involved in mitochondrial fusion suggests that other environmental factors may also specifically alter mitochondrial fusion and repair," Dr. Hajnoczky said.

"The work provides more evidence to support the concept that fission and fusion-or mitochondrial dynamics-may be responsible for more than just a subset of mitochondrial diseases we know of.

"In addition, knowing the proteins involved in the process gives us the possibility of developing a drug," Dr. Hajnoczky added.

The research is set to be published online in The Journal of Cell Biology.