Cardiolipin decline flips muscle fiber types

Aging-associated loss of the mitochondrial lipid cardiolipin triggers increased reactive oxygen species that activate the nuclear receptor ERRγ, causing muscle cells to reprogram from fast‑twitch to slow‑twitch fibers; in mice, antioxidants blunt the ROS signal but worsen function, while partial restoration of cardiolipin restores muscle properties. This reframes the fast→slow twitch shift as an adaptive protection (trading power for protection) rather than simple failure. — This matters for aging research, clinical trials and public health because it suggests both a new therapeutic target (cardiolipin or ERRγ) and a cautionary tale about simplistic antioxidant fixes that could harm rather than help.