Energy balance and thermoregulation in many fat-storing seasonal hibernators show a circannual rhythm. To understand the physiological mechanisms of the seasonal pre-hibernation fattening related to the regulation of energy expenditure and thermogenesis, we cold-exposed fattening Daurian ground squirrels (Spermophilus dauricus) in late summer for 3 weeks. We predicted that cold-exposed squirrels would increase food intake rather than express torpor to accommodate both fattening and thermoregulatory fuel allocation. Food intake and body mass were quantified. After 3 weeks, body compositions, serum leptin concentration, expression of hypothalamic neuropeptides related to regulation of energy balance and uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) were measured. There was no change in body mass after 3-weeks of cold exposure. Hypothalamic orexigenic neuropeptides and UCP1 levels in BAT were up-regulated after cold exposure. Food intake, serum leptin concentration and the expression of leptin signal suppressors, suppressor of cytokine signaling 3 and protein tyrosine phosphatase 1B, in hypothalamus showed no differences compared with controls. The core body temperature was unaffected by cold exposure. Our data suggest that cold exposure affected fattening mainly because of the increased heat loss, whereas energy balance and thermoregulation are under control of a strong circannual rhythm in the Daurian ground squirrels.

中文翻译：

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寒冷暴露增加了育肥达乌尔地松鼠的下丘脑促食欲神经肽，但不增加食物摄入量

许多储存脂肪的季节性冬眠动物的能量平衡和体温调节显示出昼夜节律。为了了解与能量消耗和产热调节相关的季节性冬眠前育肥的生理机制，我们在夏末冷暴露育肥达乌尔地松鼠（Spermophilus dauricus）3周。我们预测，暴露在寒冷环境中的松鼠会增加食物摄入量，而不是表现出麻木，以适应增肥和体温调节燃料分配。食物摄入量和体重被量化。3 周后，测量身体成分、血清瘦素浓度、与能量平衡调节相关的下丘脑神经肽的表达以及棕色脂肪组织 (BAT) 中解偶联蛋白 1 (UCP1) 的表达。冷暴露 3 周后体重没有变化。低温暴露后下丘脑促食欲神经肽和 BAT 中的 UCP1 水平上调。与对照组相比，下丘脑的食物摄入、血清瘦素浓度和瘦素信号抑制因子、细胞因子信号抑制因子 3 和蛋白酪氨酸磷酸酶 1B 的表达没有显示出差异。核心体温不受寒冷暴露的影响。我们的数据表明，寒冷暴露影响育肥主要是因为热量损失增加，而能量平衡和体温调节受到道利地松鼠强烈的昼夜节律的控制。与对照组相比，下丘脑中没有显示差异。核心体温不受寒冷暴露的影响。我们的数据表明，寒冷暴露影响育肥主要是因为热量损失增加，而能量平衡和体温调节受到道利地松鼠强烈的昼夜节律的控制。与对照组相比，下丘脑中没有显示差异。核心体温不受寒冷暴露的影响。我们的数据表明，寒冷暴露影响育肥主要是因为热量损失增加，而能量平衡和体温调节受到道利地松鼠强烈的昼夜节律的控制。