<b>Role of leptin on body mass in high fat feeding striped field </b><b>m</b><b>ouse (</b><b><i>Apodemus agrarius</i></b><b>)</b>

Leptin is a hormone that regulates a variety of physiological processes. To investigate into the role of leptin in body mass in high-fat-fed animals. Male striped field mice (<i>Apodemus agrarius</i>) fed high-fat diets were given leptin (0.5μg/g.d) via intraperitoneal injection for 28 days. Their body mass, food intake, daily fecal output, apparent digestibility, hormone and enzyme activity, and hypothalamic neuropeptide expression were compared to those of the control and high-fat food groups, which received PBS injections. Firstly, it is worth noting that the high-fat diet did not cause weight gain in A. agrarius, and the animals on the diet ate less and had higher apparent digestibility. Furthermore, compared to animals fed a high-fat diet, peripheral leptin injection in A. agrarius reduced food intake, increased fecal content, and reduced apparent digestibility. Additionally, peripheral leptin injection inhibits the activity of AMPK in the hypothalamus, increased the activity of malonyl-CoA, inhibits the expression of phagotrophic neuropeptide mRNA, promoted the expression of phagotrophic neuropeptide mRNA, and thus reduces food intake and weight. Finally, exogenous leptin injection increased UCP1 protein content, T45'-DII activity, and COX activity in BAT, increased serum T3, and increased animal energy consumption. In conclusion, our data indicate that leptin affects body mass in animals on a high-fat diet in two ways: by inhibiting food intake and increasing energy expenditure.

瘦素（Leptin）是一种调控多种生理过程的激素。本研究旨在探究瘦素在高脂饲喂动物体质量调控中的作用。以饲喂高脂日粮的雄性黑线姬鼠（Apodemus agrarius）为研究对象，通过腹腔注射方式给予其瘦素（剂量为0.5μg/g·d），持续28天。将其体质量、摄食量、每日粪便排泄量、表观消化率、激素与酶活性以及下丘脑神经肽表达水平，与注射磷酸盐缓冲液（PBS）的对照组及高脂日粮组进行对比。首先需注意，高脂日粮并未使黑线姬鼠出现体质量增加的情况，该组小鼠摄食量更低且表观消化率更高。此外，与单纯饲喂高脂日粮的小鼠相比，经外周注射瘦素的黑线姬鼠摄食量降低、粪便排泄量增加且表观消化率下降。除此以外，外周注射瘦素可抑制下丘脑腺苷酸活化蛋白激酶（AMPK）的活性，提升丙二酰辅酶A（malonyl-CoA）的活性；同时，其可抑制促摄食神经肽的mRNA表达，促进抑摄食神经肽的mRNA表达，进而降低摄食量与体质量。最后，外源性瘦素注射可提升棕色脂肪组织（BAT）中解偶联蛋白1（UCP1）的蛋白含量、甲状腺素5'-脱碘酶II（T4 5'-DII）活性以及环氧化酶（COX）活性，升高血清三碘甲状腺原氨酸（T3）水平，进而提升动物的能量消耗。综上，本研究数据表明，瘦素可通过两种途径调控高脂日粮饲喂动物的体质量：一是抑制摄食量，二是提升能量消耗。