Gluconeogenesis and Energy Substrates: Shifting Paradigms in the Primate Ovary

描述（由申请人提供）：卵母细胞需要葡萄糖来恢复减数分裂，并在排卵促性腺激素刺激下受精。葡萄糖浓度范围超出一个狭窄的浓度窗口，变得过高或过低，对卵母细胞和由此产生的胚胎产生深远的负面影响。这些问题包括受精率低，受精卵受精率低，胚胎中基因表达谱异常，以及潜在的先天缺陷。由于卵母细胞健康对物种的重要性，灵长类动物似乎不太可能进化出卵母细胞依赖于饮食来源的葡萄糖的系统。相反，我们在这里假设卵泡的体细胞成分在排卵刺激下合成自己的葡萄糖，作为向卵母细胞提供受控量的能量基质的一种手段。作为这一过程的一部分，体细胞（初级壁粒细胞）将自身的能量消耗从葡萄糖转变为储存的脂质。这些脂质的分解被假定为提供脂肪酸氧化形式的能量，同时也提供用作糖异生前体的甘油。一些初步数据支持这些假设。(1)壁粒细胞的葡萄糖摄取和代谢方面受到排卵刺激的抑制，包括糖酵解途径中基因的表达。(2)在排卵刺激下，能量底物使用的关键标志物从碳水化合物转变为脂质氧化。(3)排卵刺激后，壁粒细胞糖异生相关基因表达增加。我们将通过三个关键实验来验证壁粒细胞在排卵刺激下进行糖异生的假设。首先，我们将证实壁粒细胞葡萄糖摄取的减少。其次，我们将确定在排卵刺激下调节能量使用从碳水化合物到脂质的转变的机制。第三，我们将展示壁粒细胞的糖异生。这些实验是了解卵母细胞发育的环境，以及这种环境如何受到饮食、压力、肥胖和糖尿病的干扰的重要前提。

DESCRIPTION (provided by applicant): The oocyte requires glucose to resume meiosis and to be fertilized following an ovulatory gonadotropin stimulus. Glucose concentrations ranging out of a narrow concentration window to become too high or too low have profoundly negative effects on the oocyte and the resulting embryo. These can include poor rates of fertilization and for those oocytes that are fertilized, abnormal gene expression profiles in the embryo and potential birth defects. Because of the importance of oocyte health to the species, it seems unlikely that primates evolved a system in which the oocyte is dependent upon dietary sources of glucose. Rather, we hypothesize here that the somatic component of the ovarian follicle synthesizes its own glucose in response to an ovulatory stimulus as a means to provide the oocyte with a controlled amount of energy substrate. As part of this process, the somatic cells (primary mural granulosa cells) shift their own energy use from glucose to stored lipids. The breakdown of these lipids is postulated to provide both energy in form of fatty acid -oxidation, and also provide glycerol for use as the precursor of gluconeogenesis. Several pieces of preliminary data support these hypotheses. (1) Aspects of glucose uptake and metabolism by mural granulosa cells are suppressed by an ovulatory stimulus, including expression of genes in the glycolytic pathway. (2) Key markers of energy substrate use are shifted by an ovulatory stimulus from carbohydrate to lipid oxidation. (3) The mural granulosa cell expression of genes involved in gluconeogenesis increase following an ovulatory stimulus. We will test the hypothesis that mural granulosa cells undergo gluconeogenesis in response to an ovulatory stimulus with three key experiments. First, we will confirm the reduction in glucose uptake by mural granulosa cells. Second, we will determine the mechanisms regulating the shift in energy use from carbohydrates to lipids in response to an ovulatory stimulus. Third, we will demonstrate gluconeogenesis by mural granulosa cells. These experiments are critical precursors to understanding the milieu in which the oocyte develops, and how this environment can be perturbed by diet, stress, obesity, and diabetes.