The cause for premature ageing, which has long stymied scientists, has finally been discovered by researchers at the Swedish medical university Karolinska Institutet.
The normal ageing process has been linked to problems with cell respiration, the process through which the cells extract energy from nutrients.
The study showed that certain proteins that are synthesised in the cellular mitochondria - popularly known as the cells' power plants - become unstable and disintegrate, which in turn can impair cell respiration and cause premature ageing.
For cell respiration to function properly, it needs proteins synthesised outside and then imported into the mitochondria, and proteins synthesised within the mitochondria themselves from their own DNA (mtDNA).
It has long been known that an accumulation of harmful mutations of mtDNA can cause premature ageing.
The study involving mouse model revealed that changes in mtDNA can cause ageing by introducing errors into the proteins manufactured by the mitochondria.
The amount of protein is normal, but the proteins are rendered unstable and quickly disintegrate, leading eventually to the breakdown of cell respiration.
"Our results show that premature ageing is caused by point mutations in the mtDNA, which cause the mitochondrial proteins to become unstable and disintegrate," said Aleksandra Trifunovic, one of the scientists involved in the study.
The findings appear in journal Cell Metabolism.