Effects of electroacupuncture on food intake and expression of lipid receptors of taste buds in the tongue and hippocampus in obese rats

Abstract

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. 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. 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). 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.