Human physiology can be rapidly altered by even a few days of staying awake all night and sleeping during the day, according to a study published this week in the journal PNAS. The proteomic study, done by University of Colorado Boulder researchers, found more than 100 proteins in the blood to be influenced by sleep and eating patterns, including those influencing blood sugar, energy, metabolism, and immune function, offering a mechanistic explanation for observational studies of night-shift workers.
Six healthy males in their 20s were recruited for the study. Each spent six days at CU’s clinical translational research center, where their meals, sleep, activity, and light exposure were tightly regulated. On the first two days, they were kept on a normal schedule, then gradually transitioned to a schedule that resembled that a night-shift worker would be following. This schedule involved staying up all night and an opportunity to sleep for eight hours during the day.
The researchers drew blood every four hours and assessed levels and time-of-day-patterns of 1,129 proteins. Of those proteins, they found 129 whose patterns were thrown off by the altered sleeping pattern.
One such protein was glucagon, known for its role in pushing more sugar into the blood. Subjects who stayed awake all night had glucagon levels that surged at night and peaked at higher levels. This could contribute to the higher levels of diabetes observed in night shift workers. On the other hand, fibroblast growth factor 19, which boosts calorie-burning or energy expenditure, was decreased. This could help explain the finding that subjects burned 10 percent fewer calories per minute with the night shift.
According to the scientist, this study is the first to examine how protein levels in human blood, known as the plasma proteome, vary over a 24-hour period and how altered sleep and meal timing affects them. By studying the actual proteins in the blood, they believe they can study a broader array and get a better picture of what’s happening compared to the standard method of looking at protein-coding genes in specific organs.
The findings could pave the way for new treatments for night shift workers and enable doctors to better time administration of drugs, vaccines, and diagnostic tests around the circadian clock.