A Rusted Key That No Longer Fits
FUKUOKA, Japan — As muscles age, they lose strength. The process is so gradual that many accept it as inevitable, but the underlying biology tells a different story. The repair system is not missing — it is broken. And now, scientists have found a way to fix it.
Researchers led by Professor Ryuichi Tatsumi at Kyushu University's Faculty of Agriculture have identified a molecule that protects and dramatically enhances the key signal involved in muscle repair. The results, published on July 24 in Scientific Reports, could open the door to new treatments for age-related muscle loss, extended bed rest, and muscle wasting conditions.
The Key and the Lock
The research focuses on hepatocyte growth factor, or HGF — a protein that serves as the master switch for skeletal muscle repair. Under normal conditions, HGF sits inactive within the structural network surrounding muscle fibers. When muscle tissue is injured, HGF is released and binds to c-met receptors on satellite cells — the stem cells responsible for rebuilding damaged muscle.
But aging disrupts this system. The team's earlier research found that HGF undergoes a chemical modification called nitration as we age — a nitro group gets added to two critical sites on the protein, Y198 and Y250, located precisely where HGF connects with its receptor. The result is a "rusted key" — a protein that can no longer fit its lock.
LASSS Creates a 'Super HGF'
The scientists tested two sulfur-based compounds: glutathione trisulfide (GSSSG) and lipoic acid trisulfide (LASSS). Both reduced nitration, but LASSS produced an unexpected result. At higher concentrations, mixing HGF with LASSS more than doubled its ability to bind to the c-met receptor — creating what the team calls "Super HGF."
"We knew trisulfides had diverse biological functions, but we never expected that simply mixing HGF with LASSS would produce such a striking effect," Tatsumi said.
LASSS not only neutralized damaging reactive molecules but appeared to induce a subtle structural change in HGF itself, making it bind more strongly to its receptor while resisting chemical damage. GSSSG did not produce the same effect.
Promising Results in Living Tissue
The team then tested LASSS in mice with muscle atrophy caused by tail suspension. Mice treated with LASSS before the procedure had significantly lower levels of HGF nitration than untreated mice. Once again, GSSSG provided no measurable protection.
A Future Treatment for Muscle Loss
The discovery could support entirely new approaches for preserving muscle repair during aging, extended bed rest, and other conditions involving long periods of inactivity. The researchers believe the effects may apply across multiple species — including humans and companion animals like cats and dogs.
"HGF is not necessarily missing as we age," Tatsumi explained. "Rather, it can be chemically altered after it is made. That led us to wonder whether a compound with strong antioxidant capacity might protect HGF."
The answer, it turns out, is LASSS — a molecule that does far more than protect. It transforms.
Further studies in aging animals will be required to determine safety and effectiveness before human trials can begin. But for the first time, scientists have a clear molecular strategy for restoring muscle repair machinery that age had seemingly rendered obsolete.
