Researchers at the University of São Paulo (USP) in Brazil have shown for the first time that stimulating expression of a protein naturally produced by the human body can be a strategy to combat loss of skeletal muscle mass, which happens normally with aging
"We were able to demonstrate that overexpression of protein kinase A [PKA] significantly improved muscle resistance to fatigue in mice.
The beneficial role of PKA in muscles, which consists of stimulating anabolism and strength, is unique to all known proteins
the hormone adrenalin not only breaks down energy sources such as lipids and carbohydrate but also inhibits degradation of the proteins in muscle fibers.
drugs similar to the hormone (sympathomimetics) … can have effects that damage the organism and may even be deadly because of cardiac hypertrophy."
The main problem with using synthetic adrenalin and sympathomimetics, he added, is that they have systemic effects and cannot be targeted to specific muscles.
Muscles grew owing basically to two mechanisms: direct action of the drug inhibiting protein degradation, and increased secretion of insulin, a well-known anabolic hormone
The group decided to study PKA as a potential solution to the problem by means of selective gene transfer, targeting a specific muscle. "PKA was known to be activated by adrenalin and hence associated with lipid and carbohydrate breakdown for energy. However, PKA is located inside muscle cells and adrenalin is a circulating hormone. This difference enabled us to target the effect of PKA on a specific muscle in mice.