School of Psychological Science, La Trobe University, Melbourne, VIC 3086, Australia.
Physiol Behav. 2012 Dec 5;107(5):762-72. doi: 10.1016/j.physbeh.2012.06.009. Epub 2012 Jun 18.
Due to previous work where we have demonstrated attenuated febrile responses post-lipopolysaccharide (LPS) in calorie restricted (CR) rodents we aimed to explore metabolic rate and behavioral thermoregulation in these CR animals post-LPS. Male Sprague-Dawley rats fed ad libitum (AL) or restricted to 50% (CR50%) of the AL animals' food intake for 28 days were injected on the 29th day with 50 μg/kg of LPS. Core body temperature (T(b)), self-selected self-selected ambient temperature (T(a)), indirect calorimetry [to determine energy expenditure (EE) and respiratory quotient (RQ)] were measured in AL and CR animals for 8 hours post-LPS. The CR rats chose to sit at a higher T(a) (28.1±0.4°C) compared to the AL rats (23.7±1.4°C) at baseline and the AL rats chose to sit at a warmer T(a) from 30 min until 420 min post-LPS; however, the CR rats selected a warmer T(a) only at 270 min post-LPS. AL rats demonstrated a higher T(b) compared to baseline at 120, 150, and from 240 until 480 min post-LPS. In contrast to our previous findings the CR rats also demonstrated a higher T(b) compared to baseline for most of the time between 270 and 420 min post-LPS. When allowed to select a warmer T(a) the CR rats do so and thereby mount a febrile response, although significantly delayed and shorter-lived. In the indirect calorimetry experiment the AL rats demonstrated an elevated T(b) from 150 until 480 min post-LPS; however, the CR rats fever profile was attenuated, with the only increase occurring at 270 min post-LPS. Indirect calorimetry indicated that the CR rats demonstrated significantly reduced EE (-17.9%±1.3) compared to the AL rats at baseline. After LPS, the AL rats demonstrated an increase in EE at multiple time points between 90 and 420 min, whereas no change was observed in the CR rats. The AL and CR rats demonstrated similar profiles of RQ at baseline and after LPS the AL rats demonstrated a decrease in their RQ at 360, 450, and 480 min, whereas the CR rats demonstrated no difference. The metabolic cost for rats to mount a fever during a period of low food availability may outweigh the benefits of producing a febrile response to a relatively small dose of LPS.
由于我们之前的工作表明，在接受脂多糖 (LPS) 治疗后，热量限制 (CR) 啮齿动物的发热反应减弱，因此我们旨在探索这些 CR 动物在接受 LPS 治疗后的代谢率和行为性体温调节。雄性 Sprague-Dawley 大鼠接受自由进食 (AL) 或限制为 AL 动物食物摄入量的 50% (CR50%) 喂养 28 天，然后在第 29 天接受 50μg/kg LPS 注射。在 LPS 注射后 8 小时，AL 和 CR 动物测量核心体温 (T(b))、自我选择的环境温度 (T(a))、间接测热法[以确定能量消耗 (EE) 和呼吸商 (RQ)]。在基线时，CR 大鼠选择的 T(a) 较高（28.1±0.4°C），而 AL 大鼠选择的 T(a) 较低（23.7±1.4°C），AL 大鼠从 30 分钟开始至 LPS 注射后 420 分钟一直选择更温暖的 T(a)；然而，CR 大鼠仅在 LPS 注射后 270 分钟选择较温暖的 T(a)。AL 大鼠在 LPS 注射后 120、150 和 240 分钟至 480 分钟时，T(b) 比基线高。与我们之前的发现相反，CR 大鼠在 LPS 注射后 270 至 420 分钟的大部分时间内也表现出比基线更高的 T(b)。当允许选择较温暖的 T(a)时，CR 大鼠会这样做，并由此引发发热反应，尽管发热反应明显延迟且持续时间较短。在间接测热实验中，AL 大鼠在 LPS 注射后 150 至 480 分钟时 T(b) 升高；然而，CR 大鼠的发热情况减弱，仅在 LPS 注射后 270 分钟时出现增加。间接测热法表明，CR 大鼠在基线时的 EE 显著降低（-17.9%±1.3），与 AL 大鼠相比。在 LPS 之后，AL 大鼠在 90 至 420 分钟的多个时间点显示 EE 增加，而 CR 大鼠则没有观察到变化。AL 和 CR 大鼠在基线和 LPS 后表现出相似的 RQ 谱，AL 大鼠在 360、450 和 480 分钟时 RQ 降低，而 CR 大鼠则没有差异。在食物供应不足的情况下，大鼠产生发热的代谢成本可能超过对相对较小剂量 LPS 产生发热反应的益处。
