1Department of Animal Science, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Reproduction. 2022 Aug 1;164(3):97-108. doi: 10.1530/REP-22-0040. Print 2022 Sep 1.
Glucose is an important nutrient for the endometrium and embryo during pregnancy. This study shows that estradiol (E2)/IGF1 signaling stimulates glycogen synthesis in the uterine epithelium of cows, which could provide glucose when needed.
Glycogen storage in the uterine epithelium peaks near estrus and is a potential source of glucose for the endometrium and embryos. However, the hormonal regulation of glycogen synthesis in the uterine epithelium is poorly understood. Our objective was to evaluate the effect of E2 and insulin-like growth factor 1 (IGF1) on glycogenesis in immortalized bovine uterine epithelial (BUTE) cells. Treatment of BUTE cells with E2 (0.1-10 nM) did not increase glycogen levels. However, treatment of BUTE cells with IGF1 (50 or 100 ng/mL) resulted in a >2-fold increase in glycogen. To determine if the uterine stroma produced IGF1 in response to E2, bovine uterine fibroblasts were treated with E2, which increased IGF1 levels. Immunohistochemistry showed higher levels of IGF1 in the stroma on day 1 than on day 11, which coincides with higher glycogen levels in the uterine epithelium. Western blots revealed that IGF1 treatment increased the levels of phospho-AKT, phospho-GSKβ, hexokinase 1, and glycogen synthase in BUTE cells. Metabolomic (GC-MS) analysis showed that IGF1 increased 3-phosphoglycerate and lactate, potentially indicative of increased flux through glycolysis. We also found higher levels of N-acetyl-glucosamine and protein glycosylation after IGF1 treatment, indicating increased hexosamine biosynthetic pathway activity. In conclusion, IGF1 is produced by uterine fibroblasts due to E2, and IGF1 increases glucose metabolism and glycogenesis in uterine epithelial cells. Glycogen stored in the uterine epithelium due to E2/IGF1 signaling at estrus could provide glucose to the endometrium or be secreted into the uterine lumen as a component of histotroph.
葡萄糖是妊娠期间子宫内膜和胚胎的重要营养物质。本研究表明，雌二醇（E2）/胰岛素样生长因子 1（IGF1）信号刺激奶牛子宫上皮的糖原合成，这在需要时可为身体提供葡萄糖。
发情期附近，子宫上皮中的糖原储存达到峰值，这是子宫内膜和胚胎的潜在葡萄糖来源。然而，荷尔蒙对子宫上皮中糖原合成的调节知之甚少。我们的目的是评估雌二醇和胰岛素样生长因子 1（IGF1）对永生牛子宫上皮（BUTE）细胞中糖生成的影响。用 E2（0.1-10 nM）处理 BUTE 细胞不会增加糖原水平。然而，用 IGF1（50 或 100 ng/mL）处理 BUTE 细胞会导致糖原增加 2 倍以上。为了确定子宫基质是否会对 E2 产生 IGF1 做出反应，用 E2 处理牛子宫成纤维细胞，结果发现 IGF1 水平增加。免疫组织化学显示，基质中 IGF1 的水平在第 1 天高于第 11 天，这与子宫上皮中糖原水平较高的情况相符。Western blot 显示 IGF1 处理增加了 BUTE 细胞中磷酸化 AKT、磷酸化 GSKβ、己糖激酶 1 和糖原合酶的水平。代谢组学（GC-MS）分析显示 IGF1 增加了 3-磷酸甘油酸和乳酸，这可能表明糖酵解途径通量增加。我们还发现 IGF1 处理后 N-乙酰葡萄糖胺和蛋白质糖基化水平升高，表明己糖胺生物合成途径活性增加。总之，IGF1 是由子宫成纤维细胞因 E2 产生的，IGF1 增加了子宫上皮细胞中的葡萄糖代谢和糖原生成。发情期由于 E2/IGF1 信号而储存在子宫上皮中的糖原可以为子宫内膜提供葡萄糖，或者作为组织营养的一部分分泌到子宫腔中。
