大鼠降钙素水平的终身饮食调节。

Kalu D N, Cockerham R, Yu B P, Roos B A

Endocrinology. 1983 Dec;113(6):2010-6. doi: 10.1210/endo-113-6-2010.

Studies were carried out on specific pathogen-free rats to evaluate the effects of aging and dietary manipulation on serum and thyroid calcitonin (CT) levels. Male Fischer 344 rats were randomized at 6 weeks of age to six dietary groups and subsequently maintained on the following dietary regimens. Group 1 rats were fed ad libitum throughout life; group 2 rats were fed 60% of the ad libitum food uptake, but received the same amounts of calcium, phosphorus, and vitamin D; group 3 rats were fed as the group 2 animals until 6 months of age and from then on were fed ad libitum; group 4 rats were fed ad libitum until 6 months of age and then switched to 60% food restriction; group 5 rats were fed ad libitum on food isocaloric with that of group 1 rats, but containing only 60% of the protein. Group 6 rats were killed at 6 weeks of age to serve as baseline controls. Ten rats were killed in each of the remaining five groups 15 h postprandial at 6-month intervals. The following observations were made. Serum CT increased with age similarly in the ad libitum fed group 1 and 5 rats. Food restriction markedly inhibited the increase in serum CT, and the effect was more profound in animals whose food intake was restricted after 6 months of age (group 4) than in animals on lifelong food restriction (group 2). In rats switched from food restriction to ad libitum feeding (group 3) at 6 months of age, serum CT increased with age to levels identical with those of lifelong ad libitum fed group 1 animals. Thyroid CT showed a similar pattern of age-dependent and dietary modulated changes. In contrast, aging and dietary modulation had no appreciable effect on serum calcium levels, except at 27 months of age when the serum calcium level of group 1 animals increased dramatically from the level for 24-month-old animals. There was a weak positive correlation between serum calcium and serum CT (r = 0.627; P = 0.02) and a highly significant positive correlation between serum CT and thyroid CT (r = 0.917; P = 0.001). These findings indicate that elective and therapeutic restriction of food intake might also attenulate CT levels in humans, with potentially adverse implications for skeletal homeostasis.

在无特定病原体的大鼠身上进行了研究，以评估衰老和饮食控制对血清及甲状腺降钙素（CT）水平的影响。雄性Fischer 344大鼠在6周龄时被随机分为6个饮食组，随后按照以下饮食方案饲养。第1组大鼠终生随意进食；第2组大鼠的进食量为随意进食量的60%，但钙、磷和维生素D的摄入量相同；第3组大鼠在6月龄前与第2组动物的喂养方式相同，此后改为随意进食；第4组大鼠在6月龄前随意进食，然后改为60%的食物限制；第5组大鼠随意进食与第1组大鼠热量相同但蛋白质含量仅为60%的食物。第6组大鼠在6周龄时处死作为基线对照。其余5组每组10只大鼠在6个月的间隔时间内，餐后15小时处死。得到了以下观察结果。在随意进食的第1组和第5组大鼠中，血清CT随年龄增长的变化相似。食物限制显著抑制了血清CT的升高，且在6月龄后限制食物摄入的动物（第4组）中这种作用比终生食物限制的动物（第2组）更为显著。在6月龄时从食物限制改为随意进食的大鼠（第3组）中，血清CT随年龄增长至与终生随意进食的第1组动物相同的水平。甲状腺CT呈现出类似的年龄依赖性和饮食调节变化模式。相比之下，衰老和饮食调节对血清钙水平没有明显影响，除了在27月龄时第1组动物的血清钙水平从24月龄动物的水平急剧升高。血清钙与血清CT之间存在弱正相关（r = 0.627；P = 0.02），血清CT与甲状腺CT之间存在高度显著的正相关（r = 0.917；P = 0.001）。这些发现表明，选择性和治疗性的食物摄入限制也可能降低人类的CT水平，对骨骼内环境稳定可能产生潜在的不利影响。