Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA.
Lab of Ornithology, Cornell University, Ithaca, New York, USA.
Chronobiol Int. 2024 Jan;41(1):93-104. doi: 10.1080/07420528.2023.2288223. Epub 2024 Jan 15.
Seasonal affective disorder (SAD) is a recurrent depression triggered by exposure to short photoperiods, with a subset of patients reporting hypersomnia, increased appetite, and carbohydrate craving. Dysfunction of the microbiota - gut - brain axis is frequently associated with depressive disorders, but its role in SAD is unknown. Nile grass rats () are potentially useful for exploring the pathophysiology of SAD, as they are diurnal and have been found to exhibit anhedonia and affective-like behavior in response to short photoperiods. Further, given grass rats have been found to spontaneously develop metabolic syndrome, they may be particularly susceptible to environmental triggers of metabolic dysbiosis. We conducted a 2 × 2 factorial design experiment to test the effects of short photoperiod (4 h:20 h Light:Dark (LD) . neutral 12:12 LD), access to a high concentration (8%) sucrose solution, and the interaction between the two, on activity, sleep, liver steatosis, and the gut microbiome of grass rats. We found that animals on short photoperiods maintained robust diel rhythms and similar subjective day lengths as controls in neutral photoperiods but showed disrupted activity and sleep patterns (i.e. a return to sleep after an initial bout of activity that occurs ~ 13 h before lights off). We found no evidence that photoperiod influenced sucrose consumption. By the end of the experiment, some grass rats were overweight and exhibited signs of non-alcoholic fatty liver disease (NAFLD) with micro- and macro-steatosis. However, neither photoperiod nor access to sucrose solution significantly affected the degree of liver steatosis. The gut microbiome of grass rats varied substantially among individuals, but most variation was attributable to parental effects and the microbiome was unaffected by photoperiod or access to sucrose. Our study indicates short photoperiod leads to disrupted activity and sleep in grass rats but does not impact sucrose consumption or exacerbate metabolic dysbiosis and NAFLD.
季节性情感障碍（SAD）是一种由暴露于短光照周期引起的复发性抑郁，其中一部分患者报告出现嗜睡、食欲增加和对碳水化合物的渴望。微生物群-肠道-大脑轴的功能障碍常与抑郁障碍有关，但它在 SAD 中的作用尚不清楚。尼罗河草鼠（）可能有助于探索 SAD 的病理生理学，因为它们是昼行性动物，并且已被发现对短光照周期表现出快感缺失和类似情感的行为。此外，鉴于草鼠已被发现自发出现代谢综合征，它们可能特别容易受到代谢失调的环境触发因素的影响。我们进行了一项 2×2 析因设计实验，以测试短光照周期（4 小时：20 小时光照：黑暗（LD），中性 12：12 LD）、高浓度（8%）蔗糖溶液的摄入以及两者之间的相互作用对草鼠的活动、睡眠、肝脂肪变性和肠道微生物组的影响。我们发现，处于短光照周期的动物保持了强大的昼夜节律，并且在中性光照周期下与对照组具有相似的主观日照时间，但表现出活动和睡眠模式的破坏（即在活动初始发作后返回睡眠，该发作发生在熄灯前约 13 小时）。我们没有发现光照周期会影响蔗糖消耗的证据。实验结束时，一些草鼠超重，并出现非酒精性脂肪性肝病（NAFLD）的迹象，包括微脂肪变性和大脂肪变性。然而，光照周期或蔗糖溶液的摄入都没有显著影响肝脂肪变性的程度。草鼠的肠道微生物组在个体之间差异很大，但大多数变异归因于亲本效应，并且光照周期或蔗糖溶液的摄入对微生物组没有影响。我们的研究表明，短光照周期导致草鼠活动和睡眠紊乱，但不会影响蔗糖消耗或加剧代谢失调和 NAFLD。
