Just a few days of night shift work is enough to throw off the protein rhythms associated with blood sugar regulation, energy metabolism and inflammatory responses. These processes can influence the development of chronic metabolic diseases. The results of a study led by scientists from Washington State University and the Pacific Northwest National Laboratory provide new insights into why night shift workers are more prone to diabetes, obesity and other metabolic disorders.

Early Intervention to Prevent Diabetes and Obesity

“There are processes associated with the master biological clock in our brain that say day is day and night is night, and other processes that follow rhythms set elsewhere in the body that say night is day and day is night,” explained senior study author Hans Van Dongen, a professor in the WSU Elson S. Floyd College of Medicine. When the internal rhythms are disrupted, our system experiences prolonged stress, which experts believe has long-term health consequences.

Although more research is needed, Van Dongen said the study shows that these disrupted rhythms are apparent after just three days, suggesting that early intervention may be possible to prevent diabetes and obesity. Such intervention could also help reduce the risk of heart disease and stroke, which are also increased in night shift workers.

The study, published in the Journal of Proteome Research, involved a controlled laboratory experiment in which volunteers worked simulated night or day shifts over three days. After their last shift, the participants were kept awake for 24 hours under constant conditions of light, temperature, posture and food intake to measure their internal biological rhythms without interference from external influences.

Glucose Levels in Night Shift Workers are no Longer Synchronized

Blood samples were taken and analyzed at regular intervals during the 24-hour period to identify proteins present in blood-based cells of the immune system. Some proteins had rhythms that were closely linked to the master biological clock that keeps the body on a 24-hour rhythm. The master clock is insensitive to changes in shift schedules, so these protein rhythms did not change significantly in response to the night shift schedule. However, most other proteins had rhythms that changed significantly in night shift participants compared to day shift participants.

Upon taking a closer look at proteins involved in glucose regulation, the researchers observed an almost complete reversal of glucose rhythms in the night shift participants. They also found that those processes involved in insulin production and sensitivity, which normally work together to keep glucose levels in a healthy range, were no longer synchronized in the night shift participants. The researchers stated that this effect could be caused by insulin regulation attempting to reverse the glucose changes triggered by the night shift schedule. They said that this might be a healthy response in the moment, as altered glucose levels can damage cells and organs, but could be problematic in the long run.

“We were able to show that there is indeed a difference in molecular patterns between volunteers with normal work schedules and those with schedules that don’t align with their biological clock,” said Jason McDermott, a computer scientist in PNNL’s Division of Biological Sciences. ”The effects of this misalignment had not been characterized before at this molecular level and in this controlled fashion.” The researchers’ next step will be to study real-world workers to see if night shifts cause similar protein changes in long-term shift workers.