“Little old lady” is a phrase we use in everyday language, but what makes women lose their muscle size and function as they age? In a paper just out in Molecular & Cellular Proteomics, researchers tackled the molecular basis of this phenomenon in humans.
When aging-related muscle loss and function reaches a certain threshold, it gets labeled as a medical condition called sarcopenia. “The overall functional, structural and biochemical alterations in aging muscle have been extensively studied, but the molecular mechanisms involved remain unclear,” explains first author Laëtitia Théron at the French National Institute for Agricultural Research. “So far, studies have been mostly conducted in animal models. There are very few studies in humans.”
The investigators obtained muscle samples from 10 Dutch women undergoing hip surgery. They split the women into two groups. The “mature group” had an average age of 53; the “old group” had an average age of 78. “We studied postmenopausal women to avoid all hormonal side effects,” notes Théron.
The investigators analyzed the proteins in the muscle samples by liquid chromatography and mass spectrometry, a standard workhorse in proteomics. They identified 35 proteins that seemed to be linked to muscle condition. The proteins, which were expressed at lower quantities in the older women, appeared to fall into two classes: those involved in muscle cell contraction and structure and those involved in energy metabolism. Théron says these proteins could potentially work as biomarkers for sarcopenia.
The investigators are now doing similar experiments in men. They are also working on establishing where the 35 proteins they identified are located inside cells by mass spectrometry imaging. The goal is to see how these proteins form a network.