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

脂联素/GBP 28是一种与脂肪组织特异性内分泌的血浆蛋白，近年来发现其具有降低血浆脂肪酸浓度和改善胰岛素抵抗的活性。本研究通过建立脂联素/GBP 28转基因小鼠（Tg）和抗转基因小鼠（anti-Tg），探讨脂联素是否在能量稳态调节中发挥作用。虽然野生小鼠仅在脂肪组织中表达脂联素/GBP 28，但Tg小鼠在所有组织中表达该蛋白。Tg小鼠脂联素/GBP 28的血浆浓度在幼年期高于野生小鼠，随着生长逐渐下降，与野生小鼠的水平相同;抗Tg小鼠的血浆脂联素/GBP 28浓度始终低于野生小鼠。值得注意的是，成熟雌性小鼠的脂联素/GBP 28的血浆浓度随月经周期的变化而变化，在禁食条件下，抗Tg小鼠的体重下降速度快于野生型和Tg小鼠。有趣的是，抗Tg小鼠在禁食48小时后倾向于死亡。我们还发现，抗-Tg小鼠在禁食48小时后显著降低了运动活动和体温。抗Tg小鼠的死亡原因可能是细菌攻击引起的肠出血。研究结果表明，脂联素/GBP 28在生物防御系统中发挥作用，以及调节脂质代谢。因此，脂联素/GBP 28基因的缺失可能降低了抗Tg小鼠对环境条件变化的调节反应。当抗Tg小鼠暴露于5℃的寒冷环境中时，抗Tg小鼠的体温下降速度比野生型小鼠快。这一结果支持脂联素/GBP 28基因缺失导致脂代谢紊乱从而维持体温。

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.