Medical Devices Center, University of Minnesota, Minneapolis, MN, USA.
Minnesota Obesity Prevention Training Program, University of Minnesota, Minneapolis, MN, USA.
Int J Obes (Lond). 2018 Apr;42(4):737-745. doi: 10.1038/ijo.2017.276. Epub 2017 Nov 28.
BACKGROUND/OBJECTIVES: Low levels of orexin are associated with obesity and reduced physical activity in humans and animals.
SUBJECTS/METHODS: Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) selectively activated orexin neurons in mouse lateral hypothalamus (LH) to measure effects on spontaneous physical activity (SPA). DREADD targeting was achieved by stereotaxic injection of AAV vectors into caudal lateral LH of heterozygous orexin-Cre or C57/B6J mice. In one set of studies, excitation of orexin neurons was examined (virus: AAV2-EF1a-DIO-hM3Dq-mCherry), and test sessions began 3-4 h after light cycle onset. In a study examining the inhibition of orexin neurons (virus: AAV2-hSyn-DIO-hM4Di-mCherry), testing began 15 min prior to dark cycle onset. Clozapine n-oxide (CNO; 1 or 5 mg/kg) or saline was injected intraperitoneally and time spent moving in open field chambers was recorded for 2 h. Follow-up studies in separate mouse cohorts quantified SPA in parallel with changes in energy expenditure (EE) and chow intake using indirect calorimetry chambers (SableSystem™). Following acclimation, testing sessions (saline and/or CNO) took place over the course of ~1 week, with injections administered every day. Changes in SPA, EE, chow intake, fecal boli, and body composition (EchoMRI™) were measured. Additional mice cohorts were fed a high-fat diet (HFD) and injected with CNO daily up to 10 days to assess the potential for orexin activation to prevent diet-induced obesity.
Activation of orexin resulted in increases in SPA in male and female mice, and was accompanied by increases in energy expenditure without changes in overall chow intake. When orexin activation occurred in the context of high fat diet, weight gain and adiposity were significantly attenuated. SPA was decreased when DREADDs were used to inhibit orexin activity.
These results demonstrate that orexin neurons play a critical role in mediating physical activity and suggest a novel therapeutic target for treating obesity.
背景/目的：在人类和动物中，食欲素水平较低与肥胖和体力活动减少有关。
受试者/方法：通过立体定向注射 AAV 载体到杂交orexin-Cre 或 C57/B6J 小鼠的外侧下丘脑（LH）尾侧，选择性地激活小鼠外侧下丘脑（LH）中的食欲素神经元，以测量对自发体力活动（SPA）的影响。在一组研究中，检查了食欲素神经元的兴奋（病毒：AAV2-EF1a-DIO-hM3Dq-mCherry），并在光照周期开始后 3-4 小时开始测试。在研究抑制食欲素神经元的研究中（病毒：AAV2-hSyn-DIO-hM4Di-mCherry），在暗周期开始前 15 分钟开始测试。氯氮平 n-氧化物（CNO；1 或 5mg/kg）或生理盐水腹膜内注射，记录开放场室中移动的时间 2 小时。在单独的小鼠队列中进行的后续研究使用间接测热室（SableSystem™）平行量化 SPA 与能量消耗（EE）和饲料摄入的变化。适应后，在大约 1 周的时间内进行测试（盐水和/或 CNO），每天给药。测量 SPA、EE、饲料摄入、粪便球和身体成分（EchoMRI™）的变化。另外的小鼠队列喂食高脂肪饮食（HFD）并每天注射 CNO，最多 10 天，以评估食欲素激活预防饮食诱导肥胖的潜力。
激活食欲素会增加雄性和雌性小鼠的 SPA，同时增加能量消耗，而不改变总饲料摄入量。当食欲素在高脂肪饮食的背景下激活时，体重增加和肥胖明显减轻。当使用 DREADDs 抑制食欲素活性时，SPA 减少。
这些结果表明，食欲素神经元在介导体力活动中起关键作用，并为治疗肥胖提供了新的治疗靶点。
