Obese children have far less of the “natural killer” (NK) cells that play a crucial part in helping the body fight off diseases such as type 2 diabetes and certain cancers, a new study has found.
This compromised immunity starts early in obese children, but can be reversed if the child’s weight is brought back within healthy levels, according to Andrew Hogan, one of the study’s authors.
Dr Hogan, a lecturer at Maynooth University, said he and fellow researcher, Dónal O’Shea, set out to look at what stage the immune system starts to become compromised in obese children, and were surprised to find it was as early as age six.
“We looked at 6- to 16-year-olds and we thought we’d see defects in the 15-year-olds or the children aged 16. In fact, we saw defects in children as young as six. That is quite stark,” said Dr Hogan.
“We are aware that obesity in adults causes chronic inflammatory disease such as cancer and diabetes due to changes in their immune system. We wanted to see if the same changes were present in obese children.”
Prof O’Shea, HSE national lead for obesity, said policymakers need to take note of the results, which show that “the“seeds of adult chronic obesity-driven diseases” are being nurtured in childhood.
“We know obesity is responsible for our trolley crisis through driving multiple common diseases,” said Prof O’Shea. “This work shows that we simply have to increase the efforts at preventing overweight and physical inactivity in children.”
The study involved 100 children attending the endocrine clinic at Our Lady’s Children’s Hospital in Crumlin, 50 of whom were obese and 50 of whom were within a healthy weight range.
Samples of the NK cells were taken from the children and were challenged with killing tumour cells. After leaving the culture for four hours, the scientists discovered the NK cells of obese children were roughly half as effective at eliminating the tumour cells as those taken from their leaner counterparts.
“We found that the levels of NK cells present in the bodies of obese children were about 50% less than those present in those of normal weight,” said Dr Hogan.
NK cells are an integral part of the mechanism that targets infected and cancerous cells. A lack of fully functional NK cells has been linked in patients with incidence of certain cancers and recurring viral infections.
“We know that obese children get more viral infections and that they are, in general, harder to treat and can end up in ICU,” said Dr Hogan,
There are also reports of worse outcomes in hematological cancers in obese children, such as acute myeloblastic leukemia.
“While this is bad news for those suffering from childhood obesity, the situation is far from hopeless,” said Dr Hogan.
“Research suggests that the damage to immune systems can be reversed and the frequency and functionality of the NK cells restored once a child’s weight is brought back within healthy levels.”
The study — entitled ‘NK cells in childhood obesity are activated, metabolically stressed, and functionally deficient’ — was funded by the National Children’s Research Centre and Children’s Medical Research Foundation.
The report is published in the Journal of Clinical Investigation.
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