In a new study, researchers found that exposure to a light-dark cycle that mimics the schedule of human shift workers could change insulin sensitivity and glucose tolerance.
This could start the development of type 2 diabetes.
The research was conducted by a team at Southern Medical University in China.
Biological clocks, synchronized with environmental light and dark cycles, are responsible for not only mediating the timing of sleep and hunger cues but regulating glucose homeostasis and metabolism.
Studies have previously shown that mutations in key clock genes can lead mice to rapidly develop metabolic disorder and obesity.
In the new work, the researchers exposed female mice to a constantly shifting light-dark cycle.
After four weeks of this alternating schedule, the researchers measured the glucose tolerance, insulin tolerance, and insulin secretion of the mice at multiple time points throughout the day, as well as food intake and physical activity.
They found that the shift work schedule increased levels of fasting blood glucose and hepatic glycogen in the early stages of the light period compared to the control group.
Moreover, insulin sensitivity was increased in the middle of the light period.
However, restricting feeding to a fixed 12-hour period eliminated this change to insulin sensitivity.
While average daily glucose tolerance was unchanged by the shift work schedule, the normal daily rhythms of glucose tolerance were shifted and had an attenuation in amplitude.
The team says night shift work could lead to a mismatch between glucose uptake rhythms and meal timing, with glucose intolerance occurring during meals.
Changes to both insulin sensitivity and glucose tolerance could put shift workers at greater risk of developing Type II diabetes.
The lead author of the study is Bo Zhang of Southern Medical University.
The study is published in the open-access journal PLOS ONE.
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