Effect Of Tannic Acid On The Expression Of Appetite Controlling Genes In The Arcuate Nucleus Of Hypothalamus And Serum Leptin Levels Of Brandt’s Voles (Lasiopodomys Brandtii)

Plant secondary metabolites (PSMs) are defence material produced in almost all of plants. Tannic acid is one of the important PSMs. It is bitter and astringent and can influence the feeding behavior of herbivorous animals. Neuropeptide Y (NPY), agouti-related protein (AgRP) and pro-opiomelanocortin (POMC) are secreted by neurons in arcuate nucleus of hypothalamus. NPY and AgRP can increase the appetite of animal. Meanwhile, pro-opiomelanocortin (POMC) reduce the appetite. All of them are regulated by the taste system. Serum leptin can interact with leptin receptor (OB-Rb) in the arcuate nucleus, regulate the expression NPY, AgRP and POMC, and participate in the regulation of energy balance. Brandt’s voles are the main herbivorous animals in Inner Mongolia, they feed on the plants that contain a lot of secondary compounds. In order to explore the effect of tannic acid on the feeding center of Brandt’s voles, verify the hypothesis that tannic acid could affect the feeding behavior of Brandt’s voles by suppressing their appetite, provide theoretical basis for maintaining the balance of prairie ecosystem and for the co-evolution between animals and plants, Brandt’s voles bred in lab were given 0%(control).3%(low dosage) and 6% (high dosage) tannic acid solution for different days(1d,5d, 10d and 20d), continuously. Then, the reverse transcription quantitative real-time PCR (RT-qPCR) was used to determine the changes of mRNA expression of the appetite controlling genes in the arcuate nucleus of hypothalamus, the method of Immunohistochemistry (IHC) was used to detect the content of the appetite controlling proteins in the arcuate nucleus of hypothalamus, and the changes of the serum leptin levels was detected by ELISA. The results were as follows:1. For male Brandt’s voles, when they were treated for 1 day, high dosage of tannic acid inhibited the expression of NPY and AgRP mRNA in the arcuate nucleus of hypothalamus, and promoted the expression of POMC mRNA in arcuate nucleus; After they were treated for 5 or 10 days, both of low and hige dosage of tannic acid could decrease the expression of NPY and AgRP mRNA in arcuate nucleus, and increase the expression of POMC mRNA; After they were treated for 20 days, only low dosage of tannic acid increased NPY mRNA expression in the arcuate nucleus of hypothalamus. For female Brandt’s voles, high dosage of tannic acid inhibited the expression of the mRNA of NPY and AgRP in arcuate nucleus, and promoted the expression of POMC mRNA in arcuate nucleus after they were treated for 1 day; Both of low dosage and hige dosage of tannic acid reduced the expression of NPY and AgRP mRNA in arcuate nucleus, and increased the expression of POMC mRNA after they were treated for 5,10 or 20 days. Tannic acid had no remarkable impact on the expression of OB-Rb mRNA in the arcuate nucleus of hypothalamus of male or female Brandt’s voles.2. The results of IHC showed that when male Brandt’s voles were given high dosage of tannic acid for 1 day, the content of POMC in the arcuate nucleus of hypothalamus increased; After they were treated for 5 days, both of low and high dosage of tannic acid could decrease the content of NPY and AgRP in arcuate nucleus, while high dosage of tannic acid could increase the expression of POMC in arcuate nucleus; After they were treated for 10 days, both of low and high dosage of tannic acid reduced the expression of NPY and AgRP in arcuate nucleus, and promoted the expression of POMC; After they were treated for 20 days, tannic acid had no significant effect on the expression of NPY, AgRP or POMC in arcuate nucleus. For female Brandt’s voles, high dosage of tannic acid increased the expression of POMC in the arcuate nucleus of hypothalamus when they were treated for 1 day; After they were treated for 5 days, both of low and high dosage of tannic acid inhibited the expression of NPY in arcuate nucleus, and promoted the expression of POMC in arcuate nucleus, while high dosage of tannic acid inhibited the expression of AgRP in arcuate nucleus; Both of low and high dosage of tannic acid reduced the expression of NPY and AgRP, and increased POMC expression in the arcuate nucleus of hypothalamus after they were treated for 10 or 20 days. Tannic acid had no prominent influence on the expression of OB-Rb in the arcuate nucleus of hypothalamus of male or female Brandt’s voles.3. After continuously dripping of different dosage of tannic acid onto the surface of the oral tongue of male or female Brandt’s voles, in four processing time, there were no significant differences in body weight among the control, low dosage and high dosage group. This showed that tannic acid had no significant effects on the body weight of Brandt’s voles.4. After continuously dripping of different dosage of tannic acid onto the surface of the oral tongue of male or female Brandt’s voles, in different days, there were no significant changes in the serum leptin levels of the control group, low dosage group and high dosage group. This meant that tannic acid had no significant influence on the serum leptin levels of Brandt’s voles.All of these results suggested that tannic acid can influence the feeding behaviors of Brandt’s voles by by regulating the expression of the mRNA and protein of NPY, AgRP and POMC in the arcuate nucleus of hypothalamus. And leptin was not involved in this mechanism.