18 May 2011

Unhappy childhood shortens life

Childhood stress accelerates cell aging
Kirill Stasevich, Compulenta

When comparing the DNA of orphaned children who grew up in an orphanage or foster families, it turned out that the telomeres, the chromosomal clock that determines the life span of a cell, are shortened faster in the former.

Human chromosome; green shows telomeric areas
(electronic micrography Science Photo Library.)

In our cells, there are biological clocks embedded in DNA that determine the lifetime of each cell and the entire organism. These are telomeres – the end sections of DNA in each chromosome. When a cell multiplies, its DNA doubles, but the protein machinery responsible for this process leaves a small end piece uncovered each time. With each cell division, telomeres decrease in size until the shortening reaches vital genes and the cell can no longer divide. But paired with telomeres, there is an enzyme called telomerase, which completes shortened telomeres. Telomerase, as it were, unscrews the DNA clock back and prolongs the life of the entire body.

Factors affecting the activity of telomerase and the rate of telomere shortening have long been the object of close attention of scientists. And now in the journal Molecular Psychiatry there was an article written by researchers from several American universities (Drury et al., Telomere length and early severe social deprivation: linking early adversity and cellular aging), which states that childhood stress contributes to the shortening of telomeres.

The authors analyzed the DNA of children from orphanages and compared it with the DNA of their peers who were brought up in families. The study involved 136 orphans aged 6 to 30 months, half of whom eventually left state shelters and began living in foster homes. When the children reached the age of 6-10 years, samples were taken from them again to measure telomeric sections of chromosomes. It turned out that the longer the children lived under the roof of an orphanage, the shorter their telomeres.

The period of early childhood, up to four or four and a half years, became critical; then staying in a shelter no longer had such a dramatic effect on the molecular well–being of cells.

The researchers attributed this to the inevitable stress experienced by a child in an orphanage: being in a large team, he cannot count on an individual approach and due attention, which is provided only by the family. The scientists' finding confirmed early episodic studies that indicated shortened telomeres of adults who experienced stressful effects in childhood. At the same time, it remains unclear why stress contributes to the shortening of telomeres. Researchers believe that this is due to the work of telomerase, since its activity during a person's life is considered the main factor inhibiting the reduction of telomeres. On the other hand, the shortening of chromosomal tails can be affected by chemical modification of telomeric DNA due to stress, which can make telomeres less stable and less accessible to telomerase.

Telomeric sites protect us from the development of various diseases, from diabetes to senile dementia, because during division they protect genes important for vital activity from damage. In this regard, the researchers intend to find out whether there is any difference in the mental and physical development of children who spent their childhood in different conditions. Stress is quite difficult to find a clear definition, but perhaps science will be able to make telomeres a kind of molecular marker that will allow us to judge the severity of stress.

Prepared based on Nature News: Stress can shorten telomeres in childhood.

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