Dim Light at Night Exaggerates Weight Gain and Inflammation Associated With a High-Fat Diet in Male Mice

Jul 18, 2013Endocrinology

Dim light at night increases weight gain and inflammation from a high-fat diet in male mice

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Abstract

Exposure to dim light at night (dLAN) and a high-fat diet (HFD) leads to significantly greater weight gain in mice compared to standard lighting and chow.

Mice exposed to dLAN and fed HFD exhibit increased body mass and reduced glucose tolerance.
The combination of dLAN and HFD produces additive effects on weight gain and insulin secretion.
Changes in gene expression associated with inflammation are observed in white adipose tissue after 4 weeks of exposure.
MAC1 gene expression increases more rapidly with HFD compared to dLAN alone.
HFD elevates microglia activation in the hypothalamus, while dLAN increases microglia activation only in chow-fed mice.

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Elevated nighttime light exposure is associated with symptoms of metabolic syndrome. In industrialized societies, high-fat diet (HFD) and exposure to light at night (LAN) often cooccur and may contribute to the increasing obesity epidemic. Thus, we hypothesized that dim LAN (dLAN) would provoke additional and sustained body mass gain in mice on a HFD. Male mice were housed in either a standard light/dark cycle or dLAN and fed either chow or HFD. Exposure to dLAN and HFD increase weight gain, reduce glucose tolerance, and alter insulin secretion as compared with light/dark cycle and chow, respectively. The effects of dLAN and HFD appear additive, because mice exposed to dLAN that were fed HFD display the greatest increases in body mass. Exposure to both dLAN and HFD also change the timing of food intake and increase TNFα and MAC1 gene expression in white adipose tissue after 4 experimental weeks. Changes in MAC1 gene expression occur more rapidly due to HFD as compared with dLAN; after 5 days of experimental conditions, mice fed HFD already increase MAC1 gene expression in white adipose tissue. HFD also elevates microglia activation in the arcuate nucleus of the hypothalamus and hypothalamic TNFα, IL-6, and Ikbkb gene expression. Microglia activation is increased by dLAN, but only among chow-fed mice and dLAN does not affect inflammatory gene expression. These results suggest that dLAN exaggerates weight gain and peripheral inflammation associated with HFD.

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Dim Light at Night Exaggerates Weight Gain and Inflammation Associated With a High-Fat Diet in Male Mice

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