Mothers-to-be who eat oily fish could protect their children from developing schizophrenia in later life

Eating oily fish while pregnant may protect children from developing schizophrenia when they grow older, new research suggests.

In trials on mice, scientists found mice deprived of omega-3 fatty acids in the womb displayed signs of the mental health disorder as adults.

The nutrient, abundant in salmon, mackerel and sardines, is already known to be good the brain - but the new study is the first to show a link to schizophrenia.

Japanese researchers also discovered similar effects for pregnant mice who had a lack of omega-6, found in mayonnaise, sunflower seeds and flaxseed oil.

Both nutrients change the way genes are expressed, a process called 'epigenetics', the scientists behind the landmark study believe.

They said the study provides 'evidence' of a potential new treatment that could revert the gene expression through giving patients the essential fatty acids. 

But the study is in contrast to NHS guidelines that recommend mothers-to-be to not eat any more than two portions of oily fish each week. 

Researchers at the RIKEN Brain Science Institute, Tokyo, assessed both fatty acids because of their strong links to mental development.

Schizophrenic characteristics, such as impaired memory and depression, were seen in the adult mice whose mothers went without the nutrients. 

Why do omega-3 and 6 affect the brain? 

To determine why, the scientists then looked at gene expression in the part of the brain that is linked to the condition - the prefrontal cortex.

Humans in the early stages of the mental illness are known to have abnormal brain function in this region, located at the front of the brain.

It is involved in attention, complex planning, decision making, impulse control, thinking, personality development, risk management and short term memory.

Among the hundreds of affected genes, they found a group where activity was dramatically reduced in in both humans and the symptomatic mice.

These genes are related to oligodendrocytes, cells in the brain that surround neurons and help the transmission of signals.

What else did they find? 

They also found the expression of some genes were altered in ways that mimicked findings from the postmortem brains of people with schizophrenia - a condition which affects around 1 per cent of the world, figures suggest.

Gene expression can be controlled by a certain class of proteins called nuclear receptors, the researchers said in the journal Translational Psychiatry.

When the team conducted further analysis of the fatty acid deprived mice they found several of these nuclear receptor genes had been turned off. 

The abnormal expression of the oligodendrocyte-related genes could be traced directly back to the low expression of these nuclear receptors. 

Once they knew which nuclear receptor genes were down-regulated, the team were able to think about how to reverse the process.

Testing a new drug 

When they gave mice a drug that acts on nuclear receptors, they found the affected genes were up-regulated - and some of the abnormal motor behaviour was reduced. 

Lead author Dr Motoko Maekawa said: 'Our work is the first in the field of psychiatry to identify a molecular cascade that links nutritional environment to disease risk.

'This was evidence that drugs acting on nuclear receptors can be a new therapy for schizophrenia.'

The researchers said 'the next step' is to test the effectiveness of drugs that target these nuclear receptors in patients. 

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