Blue light at night acutely impairs glucose tolerance and increases sugar intake in the diurnal rodent Arvicanthis ansorgei in a sex‐dependent manner

Abstract

In our modern society, the exposure to light at night (LAN) has increased considerably, which may impact human health negatively. Especially exposure to light at night containing short wavelength emissions (~450–500 nm) can disrupt the normal function of the biological clock, altering sleep‐wake cycles and inducing metabolic changes. Recently, we reported that light at night acutely impairs glucose tolerance in nocturnal rats. However, light at night in nocturnal rodents coincides with their activity period, in contrast to artificial light at night exposure in humans. The aim of this study was to evaluate the acute effects of blue (λ = 490 ± 20 nm) artificial light at night (bALAN) on glucose metabolism and food intake in both male and female diurnal Sudanian grass rats (Arvicanthis ansorgei) fed either regular chow or a free choice high‐fat high sucrose diet (HFHS). In both chow and HFHS fed male Arvicanthis, 1‐hour of bALAN exposure induced a higher glucose response in the oral glucose tolerance test (OGTT) accompanied by a significant decrease in plasma insulin. Furthermore, in HFHS fed animals, bALAN induced an increase in sucrose intake during the dark phase in males but not in females. Additionally, 1‐h of bALAN increased the nonfasted glucose levels together with plasma corticosterone in female grass rats. These results provide new and further evidence for the deleterious effects of exposure to short wavelength emission‐containing artificial light at night on glucose metabolism in a diurnal rodent in a sex‐dependent manner.

Metabolic Effects of Light at Night are Time‐ and Wavelength‐Dependent in Rats

“…Moreover, animals were fasted for a few hours before the glucose tolerance tests, and the fasting state not only changes the glucose response but also changes SCN activity (26,27). Moreover, when the Arvicanthis were not fasted (25) we did not observe any significant effects of ALAN on basal plasma glucose concentrations, whereas in the current experiment, we found that blue light reduced blood glucose. The difference between the effects of blue light on nonfasted blood glucose in these two experiments could be because Arvicanthis are diurnal rodents, whereas here we used nocturnal rats.…”

“…Surprisingly, white and green light-exposed animals showed no significant changes in plasma glucose values. Previously, our laboratory showed that ALAN, especially white and green light, acutely impaired glucose tolerance in rats (12) and we observed a similar effect with blue light in the diurnal rodent Arvicanthis ansorgei (25). However, in both these experiments, a glucose tolerance test was used to investigate glucose metabolism, which prevents a direct comparison with the current results.…”

“…In the existing literature, conflicting results have been reported regarding changes in corticosterone levels in response to acute LAN. Direct changes in absolute levels have not always been reported, and even opposite changes can be found (3,(11)(12)25,30,31). These inconsistent findings may be related to differences among studies including the intensity, duration, wavelength, and circadian phase of the light exposure as well as sex and species involved.…”

Nighttime Light Hurts Mammalian Physiology: What Diurnal Rodent Models Are Telling Us

“…In the diurnal rodent Arvicanthis ansorgei, a single exposure to blue light at the beginning of the night (rest period) dysregulates glucose metabolism and induces feeding. In fact, animals exposed to 1 h of blue light and to a glucose tolerance test showed glucose intolerance and a reduced insulin secretion, possibly by a decreased beta cell activity [ 115 ]. No effects were observed on leptin concentrations by NLE.…”

Blue Light Exposure Effect on Circadian Rhythm and Nutrition

“…Geceleri mavi yapay ışığa maruziyetin uyku-uyanıklık ve enerji metabolizmasının kontrolü üzerindeki etkisini değerlendirmeyi amaçlayan bir insan çalışması yapılmıştır. Bu çalışma sonucunda; enerji harcaması, oksijen tüketimi, karbondioksit üretimi ve kahvaltının termik etkisinin ışığa maruz kalmayan bireylere göre geceleri mavi yapay ışığa maruz kalanlar bireylerde önemli ölçüde düşük olduğu bildirilmiştir [21]. Düşük yağlı beslenen ve yüksek yağlı, yüksek sükrozlu beslenen dişi ve erkek fareler üzerinde geceleri mavi yapay ışığa (bALAN) maruz kalmanın etkileri ile ilgili yapılan çalışmanın sonuçları özellikle geceleri yapay ışığa maruz kalmanın erkek farelerde, uzun vadede diyabet gelişimine yol açabilen glikoz metabolizmasını bozduğunu göstermektedir.…”