Novak Colleen M, Kotz Catherine M, Levine James A
Endocrine Research Unit, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905, USA.
Am J Physiol Endocrinol Metab. 2006 Feb;290(2):E396-403. doi: 10.1152/ajpendo.00293.2005. Epub 2005 Sep 27.
Nonexercise activity thermogenesis (NEAT), the most variable component of energy expenditure, can account for differential capacities for human weight gain. Also highly variable, spontaneous physical activity (SPA) may similarly affect weight balance in animals. In the following study, we utilized the rat model of obesity, the diet-induced obese (DIO) rat, as well as the diet-resistant (DR) rat strain, to investigate how access to a high-fat diet alters SPA and the associated energy expenditure (i.e., NEAT). DIO and DR rats showed no differences in the amount of SPA before access to the high-fat diet. After 29 days on a high-fat diet, the DIO rats showed significant decreases in SPA, whereas the DR rats did not. Next, we wanted to determine whether the DIO and DR rats showed differential sensitivity to microinjections of orexin into the paraventricular nucleus of the hypothalamus (PVN). Unilateral guide cannulae were implanted, aimed at the PVN. Orexin A (0, 0.125, 0.25, and 1.0 nmol in 500 nl) was microinjected through the guide cannula into the PVN, then SPA and energy expenditure were measured for 2 h. Using the response to vehicle as a baseline, the DR rats showed significantly greater increase in NEAT compared with the DIO rats. These data indicate that diet-induced obesity is associated with decreases in SPA and a lack of increase in NEAT. A putative mechanism for changes in NEAT that accompany obesity is a decreased sensitivity to the NEAT-activating effects of neuropeptides such as orexin.
非运动活动产热（NEAT）是能量消耗中变化最大的组成部分，可解释人类体重增加能力的差异。同样变化很大的自发身体活动（SPA）可能同样会影响动物的体重平衡。在以下研究中，我们利用肥胖大鼠模型——饮食诱导肥胖（DIO）大鼠以及抗饮食（DR）大鼠品系，来研究高脂饮食如何改变SPA以及相关的能量消耗（即NEAT）。在给予高脂饮食之前，DIO大鼠和DR大鼠在SPA量上没有差异。在高脂饮食29天后，DIO大鼠的SPA显著下降，而DR大鼠则没有。接下来，我们想确定DIO大鼠和DR大鼠对向丘脑室旁核（PVN）微量注射食欲肽是否表现出不同的敏感性。植入单侧引导套管，目标是PVN。将食欲肽A（500 nl中含0、0.125、0.25和1.0 nmol）通过引导套管微量注射到PVN中，然后测量2小时的SPA和能量消耗。以对溶媒的反应作为基线，与DIO大鼠相比，DR大鼠的NEAT显著增加。这些数据表明，饮食诱导的肥胖与SPA降低和NEAT缺乏增加有关。肥胖伴随的NEAT变化的一种可能机制是对诸如食欲肽等神经肽的NEAT激活作用的敏感性降低。
