Prof Jun-Ichi Hayashi from the University of Tsukuba led the study about the role glycine in ageing Tsukuba University

The process of ageing could possibly be reversed by regulating two genes, claims a Japanese study that suggests glycine, the simplest amino acid, could hold the key.

Led by Professor Jun-Ichi Hayashi from the University of Tsukuba, scientists have shown reversal of age-related respiratory function by tweaking two genes involved with the production of glycine.

The Tsukuba team's earlier research has led them to propose that age-associated mitochondrial defects are not controlled by the accumulation of mutations in the mitochondrial DNA (as believed popularly) but by another form of genetic regulation.

The team had found that there was no difference in DNA damage in human fibroblast cells derived from young and old people.

This suggested another form of genetic regulation, epigenetic regulation, may be responsible for the age-associated effects seen in the mitochondria and not mutations.

Epigenetic regulation refers to changes in the expression of genes by turning them on or off.

Unlike mutations, these do not affect the DNA sequence itself but only how it is read.

To test the theory, the team reprogrammed the fibroblast lines from the young and elderly groups to take them back to the embryonic stem cell state and then allowed them to grow back.

On examining the cell lines, they found respiration rates comparable in both groups, implying the function was controlled by gene expression.

The search for the genes responsible landed them with CGAT and SHMT2, two genes that regulate glycine production in mitochondria.

This was further confirmed when glycine was added to the culture media of a 97-year-old fibroblast cell line and its respiratory function was restored.

The next step would be to see if glycine and the two genes can be regulated to reverse the ageing process per se.