Relationship between diet and sex of offspring

描述(由申请人提供)：在哺乳动物中，改变母亲吃的食物的质量或数量是否会影响所生后代的性别比例，这一点存在相当大的争议。在最初的实验中，我们比较了来自NIH瑞士和CF1杂交小鼠的幼鼠的性别比例，这些小鼠喂食了两种不同脂肪含量的营养完整的日粮。前者总甘油三酯含量低，但碳水化合物含量高(LF，低脂饮食)，而后者提供60%的热量作为猪油(VHF，非常高的脂肪)。饮食对胎仔大小和孕期长短都没有影响，但高脂肪饮食的母亲生下的男孩比女孩多得多，生下的男孩偏向男性的比例很高，而低脂肪饮食的情况正好相反。性别比偏斜与饮食有关，与母亲体重无关。然而，年龄是一个重要的变量。只有成熟的小鼠提供的性别比在第一次怀孕时受到饮食的高度倾斜。第一个目标将是产生关于饮食的性质和时间与性别比例之间的关系的信息。其目的将是：1)当小鼠在受孕前和怀孕早期只被提供有限的一段时间的饲料时，跟踪幼鼠的性别比；2)通过测试几个具有不同遗传背景的近交系小鼠以分析性别偏见现象的遗传基础来确认观察的一般性；3)测试增加饮食中n-3不饱和脂肪酸的量是否会像人类所建议的那样影响后代的性别比；4)确定减少VHF饮食中小鼠的卡路里摄入量是否会导致幼崽的性别比向下调整。第二个目标将是确定雌性交配后性别比例的偏差何时发生，并了解可能的机制。实验将显示在VHF小鼠的生殖道中，Y-精子是否比X-精子有一定的优势，同样，在LF小鼠中，X-精子是否有一些优势。我们将测试是否根据受精后而不是受精前的性别来选择胚胎，如果是的话，选择过程是发生在植入之前还是之后。最后，我们将检查实验饮食是否会导致血清激素、血液电解质和代谢物的变化，以及生殖道环境的变化，从而使一种性别的受孕在宫内具有相对于另一种性别的竞争优势。我们的观察可能对控制人类生育能力具有重大意义，为一系列实验室和农场动物提供了一种根据它们的喂养方式调整后代性别的实用方法，并进一步证明了哺乳动物性别分配过程的争议存在，这取决于食物资源的可用性和质量。

DESCRIPTION (provided by applicant): There is considerable controversy whether in mammals altering the quality or quantity of food eaten by the mother can bias the sex ratio of offspring born. In initial experiments we compared the sex ratio of pups from NIH Swiss and CF 1 outbred mice fed two nutritionally complete diets that differed in their content of fat. The first was low in total triglyceride but high in carbohydrate (LF, low fat diet), while the second provided 60% of the calories as lard (VHF, very high fat). The diets had no effect on either litter size or gestation length, but mothers on high fat produced many more sons than daughters and a striking proportion of male-biased litters, while the reverse was true on the low fat diet. The sex ratio skewing correlated with diet and was independent of maternal weight. Age was an important variable, however. Only mature mice provided sex ratios that were highly skewed by diet at first pregnancy. The first goal will be to generate information on the relationship between the nature and timing of the diet and sex ratio. The aims will be to; 1) follow sex ratios of pups when mice are provided the diets only for a limited period during the period preceding conception and during early pregnancy; 2) confirm the generality of the observations by testing several inbred strains of mouse with different genetic backgrounds with the long term goal of analyzing the genetic basis of the sex biasing phenomenon; 3) test whether increasing the amount of n-3 unsaturated fatty acids in the diet influences sex ratio of offspring, as has been suggested for humans; 4) determine whether reducing the caloric intake of mice on the VHF diet causes a downwards readjustment of the sex ratio of pups. A second goal will be to determine when the skewing in sex ratios in bred females occurs and to understand what mechanisms might be responsible. The experiments will show whether Y-sperm have some advantage over X-sperm in either reaching or fertilizing oocytes in the reproductive tract of VHF mice, and, likewise, whether X-sperm have some advantage in LF mice. We shall test whether conceptuses are selected according to sex after fertilization rather than before, and, if so, whether the selection process occurs prior to or subsequent to implantation. Finally, we shall examine whether the experimental diets cause changes in serum hormones, blood electrolytes and metabolites, and alterations in the reproductive tract environment in such a manner that conceptuses of one sex might have an in utero competitive advantage over the other. Our observations could have major implications for control of human fertility, provide a practical way of adjusting the sex of progeny for a range of laboratory and farm animals according to how they are fed, and lend further credence for the controversial existence of a process of sex allocation in mammals that depends on the availability and quality of food resources.