New research indicates that people who had more infections as babies harbor a key marker of cellular aging as young adults: the protective stretches of DNA which “cap” the ends of their chromosomes are shorter than in adults who were healthier as infants.
The 46 chromosomes of the human genome, with telomeres highlighted in white
“These are important and surprising findings because — generally speaking — shorter chromosome ‘caps’ are associated with a higher burden of disease later in life,” said lead author Dan Eisenberg, an assistant professor of anthropology at the University of Washington.
The ‘caps’ Eisenberg and his co-authors measured are called telomeres. These are long stretches of DNA at the ends of our chromosomes, which protect our genes from damage or improper regulation. One Nobel Prize-winning scientist who studies telomeres has compared them to aglets — the plastic or metal sheath covering ends of shoelaces. When aglets wear down, the shoelace is exposed to fraying and degradation from environmental forces.
Like aglets, telomeres don’t last forever. In most of our cells, telomeres get shorter each time that cell divides. And when they get too short, the cell either quits dividing or dies.
That makes telomere length particularly important for the cells of our immune system, especially the white blood cells circulating in our bloodstream. When activated against a pathogen, white blood cells undergo rapid rounds of cell division to raise a defensive force against the infectious invader. But if telomeres in white blood cells are already too short, the body may struggle to mount an effective immune response.
“Many studies — in laboratory animals and humans — have associated shorter telomeres with poor health outcomes, especially in adults,” said Eisenberg. But few studies have addressed whether or not events early in a person’s life might affect telomere length. To get at this question, Eisenberg turned to the Cebu Longitudinal Health and Nutrition Survey, which has tracked the health of over 3,000 infants born in 1983-1984 in Cebu City in the Philippines. Researchers collected detailed data every two months from mothers on the health and feeding habits of their babies up through age two. Mothers reported how often their babies had diarrhea — a sign of infection — as well as how often they breastfed their babies. As these babies grew up, scientists collected additional health data during follow-up surveys over the next 20 years. In 2005, 1,776 of these offspring donated a blood sample. By then, they were 21- or 22-year-old young adults.
Eisenberg measured telomere length in cells from those blood samples. He then combined the data on adult telomere length with information about their health and feeding habits as babies. He found that babies with higher reported cases of diarrhea at 6 to 12 months also had the shortest telomeres as adults.
The findings have been published in the American Journal of Human Biology.