Acute dim light at night increases body mass, alters metabolism, and shifts core body temperature circadian rhythms

Jun 17, 2014Chronobiology international

Low light at night quickly increases body weight, changes metabolism, and shifts daily body temperature patterns

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Abstract

Mice exposed to dim light at night gained significantly more mass after just 2 weeks.

Short-term exposure to dim light at night is associated with increased body mass in mice.
Mice exposed to dim light showed reduced overall energy expenditure compared to those in darkness.
A shift towards carbohydrate oxidation over fat oxidation was observed in dim light-exposed mice.
Body temperature and activity rhythms were altered in mice exposed to dim light, despite similar locomotor levels.
Deregulation of body temperature may contribute to metabolic issues due to misalignment of circadian rhythms.

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The circadian system is primarily entrained by the ambient light environment and is fundamentally linked to metabolism. Mounting evidence suggests a causal relationship among aberrant light exposure, shift work, and metabolic disease. Previous research has demonstrated deleterious metabolic phenotypes elicited by chronic (>4 weeks) exposure to dim light at night (DLAN) (∼ 5 lux). However, the metabolic effects of short-term (<2 weeks) exposure to DLAN are unspecified. We hypothesized that metabolic alterations would arise in response to just 2 weeks of DLAN. Specifically, we predicted that mice exposed to dim light would gain more body mass, alter whole body metabolism, and display altered body temperature (Tb) and activity rhythms compared to mice maintained in dark nights. Our data largely support these predictions; DLAN mice gained significantly more mass, reduced whole body energy expenditure, increased carbohydrate over fat oxidation, and altered temperature circadian rhythms. Importantly, these alterations occurred despite similar activity locomotor levels (and rhythms) and total food intake between groups. Peripheral clocks are potently entrained by body temperature rhythms, and the deregulation of body temperature we observed may contribute to metabolic problems due to "internal desynchrony" between the central circadian oscillator and temperature sensitive peripheral clocks. We conclude that even relatively short-term exposure to low levels of nighttime light can influence metabolism to increase mass gain.

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Acute dim light at night increases body mass, alters metabolism, and shifts core body temperature circadian rhythms

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