One night's poor sleep disrupts gene expression

A study mimicking the effects of shift work has found that just one night without sleep alters the expression of bodyclock genes and disrupts metabolism.

While other research has shown altered gene expression after sleep loss, this is the first to show that the effect is increased in some bodily tissues and decreased in others.

'Previous research has shown that our metabolism is negatively affected by sleep loss, and sleep loss has been linked to an increased risk of obesity and type 2 diabetes. Our current results indicate that changes of our clock genes may be linked to such negative effects caused by sleep loss,' said Dr Jonathan Cedernaes, a researcher at Uppsala University, Sweden, and lead author of the study, which was published in the Journal of Clinical Endocrinology and Metabolism.

Dr Cedernaes and his team studied 15 healthy men of normal weight over two nights in their sleep lab. Half of the men had a good night's sleep followed by a night when they were kept up; the other half did the same but with the nights reversed.

Tissue biopsies were taken from the abdominal fat under their skin and from their thigh muscles — both areas known to be important metabolically. They found epigenetic changes in several clock genes. There was increased methylation in the CRY1 and PER1 genes in the fat tissue — the addition or deletion of methyl groups to the DNA tells an individual cell to either turn a gene 'on' or 'off'.

They also found changes in the level of gene expression. They were fewer copies of the clock genes BMAL1 and CRY1 in the men's muscle tissue after they had stayed awake all night. As expected, they also had impaired blood glucose levels on the day following their sleep disruption. Other studies have suggested that clock genes play a role in glucose metabolism.

'It was interesting that the methylation of these genes could be altered so quickly, and that it could occur for these metabolically important clock genes,' said Dr Cedernaes.

The different epigenetic changes between fat and muscle 'could suggest that these important molecular clocks are no longer synchronised between these two tissues', according to Dr Cedernaes. 'Clock desynchrony between tissues has been linked to metabolic pathologies, and this could suggest that these tissue-specific changes were linked to the impaired glucose tolerance that our participants demonstrated after the night that they had been kept awake.'

The researchers do not yet know how persistent these changes are. 'It could be that these changes are reset after one or several nights of good sleep,' said Dr Cedernaes. 'On the other hand, epigenetic marks are suggested to be able to function as a sort of metabolic memory, and have been found to be altered in... shift workers and people suffering from type 2 diabetes.'