Even Your Fat Cells Need Sleep, According to New Research: Page 2 of 3

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October 23, 2012

took an intravenous glucose tolerance test, which measures total-body insulin sensitivity. The researchers performed a biopsy, removing abdominal fat cells from the area near each volunteer's navel. Then they measured how these fat cells responded to insulin.

The researchers assessed insulin sensitivity at the molecular level by measuring the phosphorylation of a protein called Akt within fat cells. Akt phosphorylation is a crucial early chemical step in the cell's response to insulin. 

After four nights of short sleep, total-body insulin response decreased by an average of 16 percent. The insulin sensitivity of fat cells decreased by 30 percent. This reduction is comparable to the difference between cells from obese vs. lean participants or from people with diabetes versus non-diabetic controls.

They found that the sleep-deprived study participants had a decreased response to a range of doses of insulin. It took nearly three times as much insulin to provoke half of the maximum Akt response in volunteers who had been deprived of sleep.

"Sleeping four to five hours a night, at least on work days, is now a common behavior" said study author and sleep specialist Esra Tasali.

"Some people claim they can tolerate the cognitive effects of routine sleep deprivation," said co-author Eve Van Cauter, PhD, the Frederick H. Rawson Professor of Medicine and director of the sleep, metabolism and health center at the University of Chicago. "In this small but thorough study, however, we found that seven out of seven subjects had a significant change in insulin sensitivity. They are not tolerating the metabolic consequences."

The study was one of the first to bring together sleep research experts and biologists focused on energy regulation and metabolism in adipose tissue. The impetus came from a sleep-research graduate student, Josiane Broussard, PhD '10, lead author of the study and now a Society in Science-Branco Weiss fellow at Cedars-Sinai Medical Center in Los Angeles. She wanted to combine her interest in sleep and metabolism with research at the molecular level.

So she pulled together a team for this project that included the two sleep researchers, Tasali and Van Cauter, plus two specialists