The most widely accepted theory of ageing is that reactive atoms or molecules of oxygen, referred to collectively as reactive oxygen species (ROS), damage molecules like lipids, DNA and proteins. Accumulation of ROS has been implicated in many age-related diseases, including chronic obstructive pulmonary disease, chronic kidney disease, neurodegenerative diseases, and cancer.   

In a recent study published in Nature, a team of scientists from the University of Michigan and the Chinese Academy of Sciences have discovered that roundworms (Caenorhabditis elegans) exposed to high levels of ROS in the early stages of their development are more resistant to oxidative damage, and this allows them to live longer. Roundworms are powerful biological model organisms as most of their genes have functional counterparts in humans. So, this could illuminate how to mediate the effects of aging in humans, as well.

The group studied two different groups of roundworms who experienced different ROS levels during early development, allowing them to categorize the worms as being in one of two states: oxidative (stressed) and reduced (normal). Both groups of worms went on to have similar ROS levels to each other in early adult stages. However, by late adulthood (day 7 in worms), they saw that the oxidized group had significantly lower ROS levels than the reduced group, and they were living about 18% longer. 

The researchers also looked at gene expression patterns in the two groups of worms to determine the molecular mechanism of the stress resistance. They found a major difference in the way that proteins called histones function. Histones package and order DNA. An enzyme called H3K4me3, which alters the chemical structure on the surface of the DNA, was found to be reduced in the worms that had been part of the oxidated group early on. This modification acted as a form of memory for the cells and led to increased stress resistance in later life. 

This study establishes how early-life events alters DNA expression throughout an organism's life and ultimately leads to stress resistance and increased lifespan. One next step is to look for evidence that similar mechanisms play a role in human aging. This important study might eventually lead to improved treatments for age related degenerative diseases.