Alcoholism saps muscle strength by robbing mitochondria - the powerhouse of cells - of its ability to self-repair, a new study has found.
In research conducted on rats, scientists found evidence that chronic heavy alcohol use affects a gene involved in mitochondrial repair and muscle regeneration.
"The finding gives insight into why chronic heavy drinking often saps muscle strength and it could also lead to new targets for medication development," said Dr George Koob, director of the National Institute on Alcohol Abuse and Alcoholism.
Mitochondria are cellular structures that generate most of the energy needed by cells. Skeletal muscle constantly relies on mitochondria for power, researchers said.
When mitochondria become damaged, they can repair themselves through a process called mitochondrial fusion — joining with other mitochondria and exchanging material such as DNA.
Although well known in many other tissues, the current study led by Dr Gyorgy Hajnoczky, from Thomas Jefferson University, is the first to show that mitochondria in skeletal muscle are capable of undergoing fusion as a repair mechanism.
It had been thought that this type of mitochondrial self-repair was unlikely in the packed fibres of the skeletal muscle cells, as mitochondria have little opportunity to interact in the narrow space between the thread-like structures called myofilaments that make up muscle.
By tagging mitochondria in the skeletal tissue of rats with different colours, the researchers were able to observe the process in action and confirm that mitochondrial fusion occurs in muscle cells.
They also identified a key protein in the process, mitofusin 1 (Mfn1) fusion proteins, and showed that chronic alcohol use interferes with the process.
In rats that were given an alcohol diet, Mfn1 levels decreased as much as 50 per cent while other fusion proteins were unchanged, researchers said.
This decrease in Mfn1 was coupled with a dramatic decrease in mitochondrial fusion. When Mfn1 returned to normal, mitochondrial fusion did as well.
"That alcohol can have a specific effect on this one gene involved in mitochondrial fusion suggests that other environmental factors may also alter specifically mitochondrial fusion and repair," said Hajnoczky.
The study was published in the Journal of Cell Biology.