<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）是一类调控多种生理过程的激素。本研究旨在探究瘦素在高脂喂养动物体重调控中的作用。研究人员对饲喂高脂日粮的雄性黑线姬鼠（Apodemus agrarius）进行为期28天的腹腔注射，注射剂量为0.5μg/g·d的瘦素，并将该实验组与注射磷酸盐缓冲液（Phosphate Buffered Saline, PBS）的对照组及高脂膳食组进行对比，检测指标包括体重、摄食量、每日粪便排泄量、表观消化率、激素与酶活性，以及下丘脑神经肽的表达水平。 首先值得注意的是，高脂膳食并未使黑线姬鼠出现体重增加的现象，该膳食组小鼠摄食量更低且表观消化率更高。进一步对比高脂膳食组小鼠，外周注射瘦素可降低黑线姬鼠的摄食量、增加粪便排泄量并降低表观消化率。此外，外周注射瘦素可抑制下丘脑中腺苷酸活化蛋白激酶（AMP-activated protein kinase, AMPK）的活性，提升丙二酰辅酶A（malonyl-CoA）的活性，抑制摄食抑制型神经肽的mRNA表达，同时促进摄食促进型神经肽的mRNA表达，进而降低摄食量与体重。 最后，外源性瘦素注射可提升棕色脂肪组织（Brown Adipose Tissue, BAT）中解偶联蛋白1（Uncoupling Protein 1, UCP1）的蛋白含量、甲状腺素5'-脱碘酶Ⅱ（T4 5'-Deiodinase Ⅱ, DII）活性以及细胞色素C氧化酶（Cytochrome C Oxidase, COX）的活性，升高血清三碘甲状腺原氨酸（T3）水平，从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影响高脂膳食动物的体重：一是抑制摄食量，二是增加能量消耗。