Levine J A, Emery P W
Br J Cancer. 1987 Jul;56(1):73-8. doi: 10.1038/bjc.1987.157.
The results of 24 h food preference tests have suggested that learned food aversions may be involved in the development of anorexia in tumour bearing rats and in patients with cancer. We have performed similar tests over longer periods, up to 10 days, in male rats implanted with Leydig cell tumours, using semisynthetic diets containing differing proportions of fat, protein and carbohydrate. Tumour growth caused anorexia (16-30% decrease in food intake) and cachexia (78% decrease in body fat and 18% decrease in body protein, but 16% increase in body water). Both tumour bearing and control rats preferred a high carbohydrate diet to a high fat diet regardless of their previous diet: tumour bearing rats showed no evidence of a learned food aversion in these experiments. Tumour bearing rats did show an initial preference for a novel high protein diet when this was offered as an alternative to the normal protein diet they had previously been consuming, but this apparent learned food aversion disappeared on the second day of the test and was in fact reversed on all the subsequent days of the test. However, tumour bearing rats did show a sustained preference for a novel low protein diet when this was offered as an alternative to the normal protein diet they had previously been consuming. These results suggest that anorexia in the tumour bearing rats was not caused by a learned food aversion. However the results do indicate that the tumour bearing rats may have developed a specific aversion to protein in the diet. Leydig cell tumours are known to secrete large amounts of oestradiol. However injections of oestradiol in normal male rats caused an increase in body fat content and had no effect on the rats' preference for dietary protein. Clearly hypersecretion of oestradiol was not responsible for the loss of body fat, the fluid retention and the aversion to dietary protein which characterised the tumour bearing rats. The mechanisms by which tumour growth causes anorexia and cachexia in these rats remains obscure.
24小时食物偏好测试结果表明，习得性食物厌恶可能与荷瘤大鼠及癌症患者厌食症的发生有关。我们对植入睾丸间质细胞瘤的雄性大鼠进行了长达10天的类似测试，使用了含有不同比例脂肪、蛋白质和碳水化合物的半合成饮食。肿瘤生长导致厌食（食物摄入量减少16 - 30%）和恶病质（体脂减少78%，身体蛋白质减少18%，但身体水分增加16%）。无论先前饮食如何，荷瘤大鼠和对照大鼠都更喜欢高碳水化合物饮食而非高脂肪饮食：在这些实验中，荷瘤大鼠没有表现出习得性食物厌恶的迹象。当提供一种新型高蛋白饮食作为荷瘤大鼠先前食用的正常蛋白质饮食的替代品时，它们最初确实表现出偏好，但这种明显的习得性食物厌恶在测试的第二天就消失了，事实上在测试的后续所有日子里都发生了逆转。然而，当提供一种新型低蛋白饮食作为荷瘤大鼠先前食用的正常蛋白质饮食的替代品时，它们确实表现出持续的偏好。这些结果表明，荷瘤大鼠的厌食症不是由习得性食物厌恶引起的。然而，结果确实表明荷瘤大鼠可能对饮食中的蛋白质产生了特定的厌恶。已知睾丸间质细胞瘤会分泌大量雌二醇。然而，给正常雄性大鼠注射雌二醇会导致体脂含量增加，并且对大鼠对膳食蛋白质的偏好没有影响。显然，雌二醇分泌过多并不是荷瘤大鼠出现体脂减少、液体潴留和对膳食蛋白质厌恶的原因。肿瘤生长导致这些大鼠厌食和恶病质的机制仍不清楚。
