Investigating the impact of dim light at night on metabolic disease

A new study from Ohio State researchers provides evidence that exposure to dim light at night (dLAN) can lead to increased body mass, without changes in total food intake or activity. The team of Ohio State researchers includes Randy Nelson, PhD and Jeremy Borniger, PhD candidate, both from the Department of Neuroscience; and Santosh Maurya, PhD and Muthu Periasamy, PhD from the Department of Physiology and Cell Biology.

Circadian rhythms, which are set by light-dark cycles, affect energy homeostasis and are controlled by an endogenous biological clock in the suprachiasmatic nuclei (SCN) of the hypothalamus. Intrinsically photosensitive retinal ganglion cells innervate the SCN and aberrant light exposure can lead to circadian disruption. 

In the study, the team exposed adult mice either to dLAN (14:10 light/dim light cycle at ~150 lux during the day and ~5 lux during the night) or a traditional light:dark cycle (LD 14:10 light/dark cycle; ~150 lux during the day and ~0 lux at night) for 2 weeks. Mice in the dLAN group increased body mass and rates of body mass change compared to mice in the LD group, despite equivalent food intake. This difference was not attributed to activity levels, as the average total activity counts were similar between the two groups. Therefore, these data suggest that the presence of dim light at night deregulates metabolic processes. Additional studies conducted by this group have shown both a link between dLAN and impaired cell-mediated immunity and an effect of exposure to artificial light at night during early life on weight gain and anxiety-like behavior in adulthood.

The increasing prevalence of light exposure at night in the developed world makes the need for more studies in this area of research essential to a better understanding of the physiological effects of light at night on humans and other animals.