Objective: To observe the effect of electroacupuncture (EA) on food intake, body weight, number of taste bud cells and the expression of lipid taste bud receptor (CD36), Gα-gustducin, post-synaptic density protein 95 (PSD95) and neurofilament light chain (NFL) proteins in the tongue or hippocampus in obese rats, so as to explore its mechanism underlying reducing body weight.
Methods: A total of 30 male SD rats were randomly divided into control, model and EA groups (n=10 in each group, 5 rats for H.E. staining and immunohistochemistry, and 5 for Western blot). The obesity model was established by feeding the rats with high fat diet for 11 weeks. Following successful modeling, EA (2 Hz/15 Hz, 1.0-1.2 mA) was applied to "Tianshu" (ST25) for 30 min, once a day, 5 times/week for 5 weeks. The body length, body weight and maximum daily food consumption were recorded every day, followed by calculating the lee's index. Histopathological changes of the circumvallate papillae (CVP) and number of taste bud cells and CD36 were detected by HE staining and immunohistochemistry (IHC), separately. The expression levels of CD36, PSD95 and NFL proteins in the hippocampus were detected by Western blot.
Results: The body weight, Lee's index and daily food consumption were significantly higher in the model group than in the control group (P<0.01), and were significantly lowered after EA intervention in comparison with the model group (P<0.01), suggesting an improvement of obesity. H.E. staining displayed that the CVP area and the number of taste bud cells were obviously decreased in the model group in contrast to the control group (P<0.01), and were notably increased in the EA group in contrast to the model group (P<0.05, P<0.01). IHC and Western blot showed that the expression levels of CD36 in the tongue and hippocampus were obviously up-regulated in the model group relevant to the control group (P<0.01, P<0.05), and considerably down-regulated in the EA group relevant to the model group (P<0.05, P<0.01). The expression levels of Gα-gustducin in the tongue, and PSD95 and NFL in the hippocampus were remarkably decreased in the model group relevant to the control group (P<0.01, P<0.05), and significantly increased in the EA group relevant to the model group (P<0.01, P<0.05).
Conclusion: EA can reduce daily food consumption and body weight in obese rats, which is associated with its effects in down-regulating the expression of CD36 in taste buds and hippocampus, and up-regulating the expression of Gα-gustducin in the tongue, and PSD95 and NFL proteins in the hippocampus. It suggests that EA may regulate the feeding behavior of obese rats by influencing the cognitive memory mechanism involved in CD36 in hippocampus.
目的：观察电针对肥胖大鼠味蕾和海马脂味觉受体表达的影响，探讨针刺减肥效应的可能机制。方法：将SD大鼠随机分成正常组、模型组和电针组，每组10只，其中正常组大鼠给予普通饲料喂养，模型组和电针组大鼠通过高脂饲料饲养以建立肥胖大鼠模型。选取电针组大鼠“天枢”进行电针干预，30 min/次，1次/d，5次/周，共5周。正常组和模型组仅在相同时间内给予同样方式固定30 min，不进行任何干预。记录各组大鼠身长、体质量和摄食量变化情况，计算Lee’s指数；用HE染色检测3组大鼠味蕾轮廓状乳头(CVP)的面积和味蕾细胞数；免疫组织化学法检测CVP中Gα-gustducin和味蕾脂味觉受体CD36的变化；Western blot法检测海马CD36、突触后致密物(PSD)95蛋白和神经丝轻链(NFL)蛋白的表达水平。结果：与正常组比较，造模后大鼠体质量明显升高，提示造模成功(P<0.01)。干预后与正常组比较，模型组大鼠体质量、Lee’s指数和摄食量明显增高(P<0.01)，CVP面积明显缩小(P<0.01)，CVP中味蕾细胞数量明显下降(P<0.01)，CVP中Gα-gustducin阳性表达、海马中PSD95及NFL蛋白表达均明显下降(P<0.01，P<0.05)，CVP中CD36阳性表达及海马中CD36蛋白表达均明显升高(P<0.01，P<0.05)；与模型组比较，电针组大鼠体质量、Lee’s指数和摄食量明显降低(P<0.01)，CVP面积增大(P<0.05)，CVP中味蕾细胞数明显增多(P<0.01),CVP中Gα-gustducin表达及海马中PSD95和NFL蛋白表达均明显升高(P<0.01，P<0.05)，CVP中CD36阳性表达及海马中CD36蛋白表达均明显降低(P<0.05，P<0.01)。结论：电针干预可降低肥胖大鼠体质量及摄食量，调节肥胖大鼠味蕾和海马内CD36的表达，并上调海马中PSD95和NFL表达，提示电针可能通过影响海马内CD36参与的认知记忆机制调控肥胖大鼠摄食行为。.
Keywords: Cognitive memory; Electroacupuncture; Hippocampus; Lipid taste receptor; Obesity; Taste buds.