Mouse study tests obesity-fertility link

Obese female mice have lower fertility than healthy weight mice, according to a study led by researchers from the University of Adelaide in Australia.

In the research the unlicensed experimental drugs salubrinal and BGP-15 - which is currently being tested in clinical trials as a treatment for type 2 diabetes - increased the number and quality of eggs produced by obese mice.

Despite a flurry of newspaper headlines proclaiming, for example, that 'health risks for obese mothers and their babies can be reversed', the 'immediate impact of this research to women is minimal' according to NHS Choices.

In the study, mice with a genetic predisposition to obesity - so-called 'Blobby mice' - were given IVF drugs to stimulate egg production. Obese Blobby mice produced fewer eggs than normal healthy weight mice, and the eggs they produced had signs of damage to the mitochondria, the miniature 'powerhouses' in cells.

Dr Rebecca Robker, a cell biologist and lead author of the study, said: 'Obesity can result in altered growth of babies during pregnancy and it permanently programs the metabolism of offspring, passing the damage caused by obesity from one generation to the next.'

In humans, obesity is associated with reduced fertility and higher risk of complications in pregnancy including miscarriage and stillbirth. Obese mothers are more likely to have overweight children and, although the biological mechanism is unclear, this is likely to result from both environmental and genetic factors.

The research also showed that when fertilised eggs from obese Blobby mice were implanted into normal weight mice, the resulting fetuses were heavier and had less mitochondrial DNA than fetuses from normal weight mice. Experimental drug treatment given to obese Blobby mice before egg collection, however, increased both the number of eggs and mitochondrial activity to normal levels.

Dr Robker says that the drugs 'were highly successful in preventing the stress response, thereby stopping the damage from obesity being passed on to the offspring'.

In fact, the idea that reduced mitochondrial activity can give rise to obesity in the offspring, is not yet established, but, says NHS Choices, remains a 'plausible explanation that will require further research'.

Furthermore, the drugs used in the study are unlicensed, although BGP-15 is currently in trials. Neither has been tested in humans as part of any fertility treatment.

Professor Adam Balen, chair of the British Fertility Society, who was not involved in the study, told the Independent that, while any drug treatment was a long way off, the findings were 'very interesting'. He added that the important message to take away from the study is that 'women need to be nutritionally healthy before they get pregnant'.