Hartmann K, Weber A, Hartmann N
Acta Biol Med Ger. 1979;38(7):1013-28.
Rats were rendered obese by feeding them a fatty diet (HFD, fat: 50% of weight). At the end of the experimental period the animals were divided, also the control rats, which were fed a low-fat diet (LFD, fat: 3% of weight), in light and heavy weight groups. The heavy and obese HFD groups showed, unlike the light LFD-animals, equal absolute but significantly lower relative thyroidal weights. The absolute thyroidal weights of light and heavy animal groups, which received in each case the same diet, were identical, the relative thyroidal weights of the heavy rats on the other hand decreased significantly. The iodoamino acid distribution in the thyroid of rats showed no variation in animals fed various diets and differed in body mass and fat content. The T4 serum levels of the HFD-, in comparison to the LFD-animals increased significantly. Between light and heavy animals in equal diet groups no differences were obtained for the T4 serum values. The serum T3 levels of LFD- and HFD-rats were also equal. The heavy HFD- showed in comparison to the light LFD-animals a significantly lower T4 clearance and in the higher age groups a significantly extended T4 half-life time. The HFD- and LFD-rats with approximately equal body mass and body fat content showed no differences in T4 half-life time and T4 clearance rate depending on diet. A relation between higher body fat content and increased serum T4 levels as a possible adaption to obesity in heavy HFD-rats is discussed. By the comparison of younger and older rats in the most investigated diet and weight groups the older animals showed a decreasing tendency for K and TD/100 g KM and a significant decrease in the clearance rate and in the TD for T4, related to body mass. An influence of diet, body mass or fat content on the decrease of the T4 metabolism of rats with increased age is not evident. The T4 serum levels were not different in dependence on age, but the free T4 serum level was significantly lower in the older rats.
通过给大鼠喂食高脂饮食（HFD，脂肪：占体重的50%）使其肥胖。在实验期结束时，将动物（包括喂食低脂饮食（LFD，脂肪：占体重的3%）的对照大鼠）分为轻、重体重组。与轻体重的LFD组动物不同，重体重的肥胖HFD组甲状腺绝对重量相同，但相对重量显著更低。在每种情况下接受相同饮食的轻、重动物组的甲状腺绝对重量相同，而重体重大鼠的相对甲状腺重量则显著下降。给大鼠喂食不同饮食，其甲状腺中的碘氨基酸分布在体重和脂肪含量不同的动物中没有差异。与LFD组动物相比，HFD组动物的血清T4水平显著升高。在相同饮食组的轻、重动物之间，血清T4值没有差异。LFD组和HFD组大鼠的血清T3水平也相同。与轻体重的LFD组动物相比，重体重的HFD组动物的T4清除率显著更低，且在较高年龄组中T4半衰期显著延长。体重和体脂含量大致相同的HFD组和LFD组大鼠，其T4半衰期和T4清除率在饮食方面没有差异。讨论了较高的体脂含量与血清T4水平升高之间的关系，这可能是重体重HFD组大鼠对肥胖的一种适应性反应。通过比较大多数研究饮食和体重组中的年轻和老年大鼠，老年动物的K和TD/100 g KM呈下降趋势，且与体重相关的T4清除率和TD显著降低。饮食、体重或脂肪含量对年龄增长的大鼠T4代谢下降没有明显影响。血清T4水平不随年龄变化，但老年大鼠的游离T4血清水平显著更低。
