Markewicz B, Kuhmichel G, Schmidt I
W. G. Kerckhoff-Institut, Max-Planck-Institut für Physiologische und Klinische Forschung, Bad Nauheim, Germany.
Am J Physiol. 1993 Sep;265(3 Pt 1):E478-86. doi: 10.1152/ajpendo.1993.265.3.E478.
To study the first stages of excess fat deposition in Zucker rats, we artificially fed littermates with identical amounts of milk from 4 to 15-16 days of age while continuously recording oxygen consumption (VO2) and deep body temperature. Under intermittent cold loads simulating the periodic thermoregulatory stimulation experienced in the nest, differences between the amounts of body fat deposited by artificially reared fatty (fa/fa) and lean (Fa/-) pups were as large as those seen in mother-reared pups. The decreased VO2 of the cold-reared fatty pups could account for 90-100% of their extra fat deposition. At thermoneutrality, 16-day-old littermates reared with low feeding rates showed small but significant genotype differences in body fat that were not energetically accounted for by differences in VO2 or lean body mass. Slightly but significantly lower fecal energy losses indicated that differences in resorption might account for the positive energy balance of thermoneutrally reared fa/fa pups. Reduced energy expenditure thus efficiently fuels excess fat deposition but is not essential for the onset of excess fat deposition in fa/fa pups. Other factors than reduced sympathetic activation of brown adipose tissue must be considered as a primary cause for the development of fa/fa obesity.
为了研究Zucker大鼠脂肪过度沉积的早期阶段，我们在4至15 - 16日龄期间，给同窝幼崽人工喂养等量的牛奶，同时持续记录耗氧量（VO₂）和深部体温。在模拟巢穴中周期性体温调节刺激的间歇性冷负荷条件下，人工饲养的肥胖（fa/fa）幼崽和瘦型（Fa/-）幼崽的体脂沉积量差异，与由母鼠抚养的幼崽中观察到的差异一样大。冷饲养的肥胖幼崽VO₂的降低可解释其额外脂肪沉积的90 - 100%。在热中性条件下，以低喂养率饲养的16日龄同窝幼崽在体脂方面表现出微小但显著的基因型差异，而VO₂或去脂体重的差异并不能从能量角度对此进行解释。粪便能量损失略有但显著降低，这表明吸收差异可能是热中性饲养的fa/fa幼崽正能量平衡的原因。因此，能量消耗的减少有效地促进了脂肪的过度沉积，但对于fa/fa幼崽脂肪过度沉积的开始并非必不可少。除了棕色脂肪组织交感神经激活减少之外，其他因素必须被视为fa/fa肥胖发生的主要原因。
