An Adipocyte-specific Plasma Protein, Adiponectin/GBP28, functions as a mediator of biological defense mechanism.

近年来，脂联素/GBP28被发现具有降低血浆脂肪酸浓度和改善胰岛素抵抗的活性。脂联素/GBP28是一种与脂肪组织特异性内分泌的血浆蛋白。这些活性表明脂联素/GBP28与代谢综合征有关。本研究通过脂联素/ gbp28转基因小鼠（Tg）和抗脂联素转基因小鼠（anti-Tg）来研究脂联素是否在调节能量稳态中发挥作用。野生小鼠仅在脂肪组织中表达脂联素/GBP28，而Tg小鼠在所有组织中表达该蛋白。Tg小鼠幼年期血浆脂联素/GBP28浓度高于野生小鼠，随着生长逐渐降低，与野生小鼠水平相当；抗tg小鼠总比野生小鼠少。值得注意的是，成熟雌性小鼠在月经周期下血浆脂联素/GBP28浓度的变化。在空腹条件下，抗Tg小鼠的体重下降速度比野生小鼠和Tg小鼠快。有趣的是，抗tg小鼠在禁食48小时后趋于死亡。我们还发现抗tg小鼠在禁食48小时后运动活动和体温显著降低。肠道出血可能是由细菌攻击引起的，似乎是抗tg小鼠死亡的原因。提示脂联素/GBP28在生物防御系统和脂质代谢调节中发挥作用。因此，有一种可能性被认为是脂联素/GBP28的缺失降低了对环境条件变化的调节反应。当抗tg小鼠暴露在5℃低温环境下时，抗tg小鼠的体温下降速度比野生小鼠快。该结果支持脂联素/GBP28缺失导致脂质代谢紊乱以维持体温。

Recently, adiponectin/GBP28, a plasma protein which is specifically endocrined with adipose tissue, has been found to have the activities that decreased plasma fatty acids concentration and improve insulin resistance. These activities indicate that adiponectin/GBP28 relates to metabolic syndrome.In this study, we produced adiponectin/GBP28-transgenic mice (Tg) and anti-transgenic mice (anti-Tg) to investigate whether adiponectin plays a role in regulation of energy homeostasis. While the wild mice expressed adiponectin/GBP28 in adipose tissue only, Tg mice expressed the protein in all tissues. The plasma concentration of adiponectin/GBP28 of Tg mice was higher than that of wild mice during juvenile stage and decreased in the same level as that of wild mice as they grow ; that of anti-Tg mice was always less than that of wild mice. It is notable that mature female mice changed the plasma concentration of adiponectin/GBP28 under the cycle of menstrual period.Under fasting conditions, anti-Tg mice decreased their body weight faster than wild and Tg mice. Interestingly, the anti-Tg mice tended to die after 48-hr fasting. We also found that the anti-Tg mice significantly reduced locomotion activities and body temperature after 48-hr fasting. Intestinal bleeding which might be caused by bacterial attacking seemed to be the cause of the anti-Tg mice's death. The findings suggested that adiponectin/GBP28 plays a role in biological defense systems as well as regulation of lipid metabolism. Thus, a possibility was considered that the deletion of adiponectin/GBP28 decreased a regulatory response against the changes of environmental conditions.When anti-Tg mice were exposed under cold circumstance at 5℃, the anti-Tg mice decreased their body temperature faster than wild mice. This results support that the deletion of adiponectin/GBP28 caused the disorder of lipid metabolism to maitain body temperature.