Just one night of sleep loss has a tissue-specific effect on gene expression and metabolism regulation in humans, according to a new study by researchers at Uppsala University in Sweden.

The findings, published in the journal Science Advances, may help explain how over time, shift work and chronic sleep loss can impair metabolism and adversely affect body composition.

Previous research has shown that the risk for obesity and type 2 diabetes is elevated in those who suffer from chronic sleep loss or who carry out shift work. Other studies have shown a link between disrupted sleep and adverse weight gain, in which fat accumulation is increased while muscle mass is decreased, a combination associated with a number of poor health consequences.

But until now, it has remained unknown whether sleep loss by itself can cause molecular changes at the tissue level and lead to increased risk of adverse weight gain.

In the new study, the researchers observed 15 healthy normal-weight individuals who participated in two in-lab sessions in which activity and meal patterns were highly standardized. In randomized order, the subjects got one night of normal sleep (over eight hours) and on the other night, they were kept awake the entire time.

The morning after each night-time intervention, small tissue samples (biopsies) were taken from the participants’ subcutaneous fat and skeletal muscle. These two tissues often reveal disrupted metabolism in conditions such as obesity and diabetes. Blood samples were also taken in the morning to analyze metabolites such as sugar molecules and fatty and amino acids.

The findings reveal that sleep loss results in a tissue-specific change in DNA methylation, a process involved in regulating how the genes of each cell in the body are turned on or off. DNA methylation is impacted by both hereditary as well as environmental factors, such as physical exercise.

“Our new findings indicate that sleep loss causes tissue-specific changes to the degree of DNA methylation in genes spread throughout the human genome,” said study leader Jonathan Cedernaes, M.D., Ph.D.

“We therefore think that the changes we have observed in our new study can constitute another piece of the puzzle of how chronic disruption of sleep and circadian rhythms may impact the risk of developing for example obesity.”

“We also noted changes in skeletal muscle levels of proteins involved [in] handling blood glucose, and this could help explain why the participants’ glucose sensitivity was impaired following sleep loss. Taken together, these observations may provide at least partial mechanistic insight as to why chronic sleep loss and shift work can increase the risk of adverse weight gain as well as the risk of type 2 diabetes,” said Cedernaes.

Since the researchers only studied the effects of one night of sleep loss, they do not know how other forms of sleep or disruption of circadian misalignment would affect tissue metabolism.

“It will be interesting to investigate to what extent one or more nights of recovery sleep can normalize the metabolic changes that we observe at the tissue level as a result of sleep loss,” Cedernaes said.

“Diet and exercise are factors that can also alter DNA methylation, and these factors can thus possibly be used to counteract adverse metabolic effects of sleep loss.”

Source: Uppsala University