Background: A high-fat diet (HFD) is a well-known risk factor for cardio-cerebrovascular disease but the relationship between a HFD and depressive symptoms remains unknown.
Objective: Compare changes in behavioral and measures of brain glucose metabolism in rats fed a HFD to those of rats fed a standard diet.
Methods: Twenty male Sprague-Dawley rats were randomly assigned to a study group (n=10) that received a high fat diet for 9 weeks or a control group (n=10) that received a standard diet for 9 weeks. At baseline and at the end of the 9-week trial assessments included body weight, serum lipids (total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol), the sucrose preference test, and the open field test. The rate of brain glucose metabolism in different brain regions (assessed using micro-positron emission tomography) at the end of the trial was also compared between the two groups of rats.
Results: Nine weeks of a HFD in rats resulted in the expected increase in weight and changes in serum lipid levels, but it was also associated with a decreased preference for sucrose (which may be due to a loss of interest in pleasurable activities), increased weight-adjusted water intake, and a significant deactivation of the right thalamus and right striatum (based on decreased rates of glucose metabolism). In the HFD group the magnitude of the drop in the sucrose preference was strongly correlated to the magnitude of the deactivation of the right thalamus (r=0.78) and the right striatum (r=0.81).
Conclusions: These findings support hypotheses about the role of a HFD in the causal pathway for depressive symptoms. Further work is needed to clarify the underling mechanism, but it appears that the interaction between the content of the diet and the limbic system-striatum-thalamus circuit plays a role in both eating behavior and depressive symptoms.
背景: 高脂肪饮食（HFD）是心脑血管疾病的一个众所周知的危险因素，但HFD和抑郁症状之间的关系仍然不明。
目的: 大鼠喂食高脂饮食后，与喂食普通食物的大鼠对照比较对行为和脑葡萄糖代谢的改变的差异。
方法: 20只雄性SD大鼠被随机分为研究组（n=10）、对照组（n=10），分别予高脂肪或标准喂食9周。基线和试验9周后的评估包括体重，血脂（总胆固醇，甘油三酯，高密度脂蛋白胆固醇，和低密度脂蛋白胆固醇），蔗糖偏好测试，以及旷场试验。在试验结束时再比较两组大鼠的不同脑区的大脑葡萄糖代谢率（采用小动物正电子发射断层扫描评估）。
结果: 正如预期，HFD组大鼠9周后体重增加、血清脂质水平出现变化，这些变化还与蔗糖偏好程度降低（这可能是由于对愉快性行为失去兴趣）、体重调整的水份摄入量增加、以及右丘脑和右侧纹状体的显著失活（基于糖代谢率的降低）有关。在HFD组中，蔗糖偏好的下降程度与右丘脑（r=0.78）和右纹状体（r=0.81）的失活程度显著相关。
结论: 这些发现支持了HFD与抑郁症状的产生过程有关的假说。目前看来，食物和边缘系统—纹状体—丘脑环路之间的相互作用在进食行为和抑郁症状的发生中起到一定作用，但还需要进一步研究来探索其内在机制。
Keywords: animal model; depression; glucose metabolism; high-fat diet; micro-PET.