Dark nights may restore metabolism disrupted by dim light at night

Mice exposed to dim light at night (dLAN) showed increased body mass gain compared to those in standard light-dark conditions.

• Mice initially placed in dLAN gained more weight than those in standard light-dark conditions after 4 weeks.
• Mice that were switched from dLAN to dark nights (dLAN/LD) exhibited similar weight gain to mice continuously in dark-night conditions (LD/LD).
• Mice continuously exposed to dLAN (dLAN/dLAN) had decreased glucose tolerance compared to all other groups, indicating impaired glucose metabolism.
• dLAN/LD mice had lower fat pad mass than dLAN/dLAN mice, suggesting recovery of metabolic function after returning to dark nights.
• Increased expression of MAC1 mRNA in dLAN/dLAN mice indicates that peripheral inflammation is associated with dLAN exposure but not sustained after returning to dark nights.

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