Gluconeogenesis and Energy Substrates: Shifting Paradigms in the Primate Ovary

描述(申请人提供)：卵母细胞需要葡萄糖来恢复减数分裂，并在排卵期促性腺激素刺激后受精。葡萄糖浓度从一个狭窄的浓度窗口变得过高或过低都会对卵母细胞和由此产生的胚胎产生深远的负面影响。这些因素可能包括受精率低、受精的卵母细胞、胚胎中的基因表达谱异常以及潜在的出生缺陷。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一种卵母细胞依赖于饮食中葡萄糖来源的系统。相反，我们在这里假设，卵巢卵泡的体细胞成分在排卵刺激下合成自己的葡萄糖，作为一种向卵母细胞提供可控数量的能量底物的手段。作为这一过程的一部分，体细胞(初级壁状颗粒细胞)将自身的能量利用从葡萄糖转移到储存的脂类上。据推测，这些脂类的分解既以脂肪酸氧化的形式提供能量，也提供甘油作为糖异生的前体。有几项初步数据支持这些假设。(1)壁层颗粒细胞的葡萄糖吸收和代谢方面受到排卵刺激的抑制，包括糖酵解途径中的基因表达。(2)能量底物利用的关键标志被排卵刺激从碳水化合物转移到脂肪氧化。(3)排卵刺激后，与糖异生有关的基因在壁层颗粒细胞中的表达增加。我们将通过三个关键的实验来检验这一假设，即壁层颗粒细胞在排卵刺激下发生糖异生。首先，我们将确认壁状颗粒细胞对葡萄糖的摄取减少。其次，我们将确定调节能量使用从碳水化合物转变为脂肪的机制，以响应排卵刺激。第三，我们将演示壁状颗粒细胞的糖异生作用。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、肥胖和糖尿病干扰的关键先驱。

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.