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Tong Sun, Wen-Bo Deng, Hong-Lu Diao, Hua Ni, Yu-Yan Bai, Xing-Hong Ma, Li-Bin Xu and Zeng-Ming Yang

Prostaglandin (PGE) 2 is the most common prostanoid and plays an important role in female reproduction. The aim of this study was to examine the expression and regulation of microsomal (m) PGE synthase (PGES)-1 and cytosolic (c) PGES in the mouse ovary during sexual maturation, gonadotropin treatment and luteal development by in situ hybridization and immunohistochemistry. Both mPGES-1 mRNA signals and immunostaining were localized in the granulosa cells, but not in the thecal cells and oocytes. cPGES mRNA signals were localized in both granulosa cells and oocytes, whereas cPGES immunostaining was exclusively localized in the oocytes. In our superovulated model of immature mice, there was a basal level of mPGES-1 mRNA signals in the granulosa cells at 48 h after equine chorionic gonadotropin (eCG) treatment. mPGES-1 mRNA level was induced by human chorionic gonadotropin (hCG) treatment for 0.5 h, whereas mPGES-1 immunostaining was slightly induced at 0.5 h after hCG treatment and reached a maximal level at 3 h after hCG treatment. eCG treatment had no obvious effects on either cPGES mRNA signals or immunostaining. A strong level of cPGES immunostaining was present in both unstimulated and eCG-treated groups. Both mPGES-1 mRNA signals and immunostaining were highly detected in the corpus luteum 2 days post-hCG injection and declined from days 3 to 7 post-hCG injection. cPGES immunostaining was at a basal level or not detectable from days 1 to 7 after hCG injection and was highly expressed in the corpus luteum from days 9 to 15 post-hCG injection. PGE2 biosynthesized through the mPGES-1 pathway may be important for follicular development, ovulation and luteal formation.

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Hong-Hui Wang, Qian Cui, Teng Zhang, Lei Guo, Ming-Zhe Dong, Yi Hou, Zhen-Bo Wang, Wei Shen, Jun-Yu Ma and Qing-Yuan Sun

As a fat storage organ, adipose tissue is distributed widely all over the body and is important for energy supply, body temperature maintenance, organ protection, immune regulation and so on. In humans, both underweight and overweight women find it hard to become pregnant, which suggests that appropriate fat storage can guarantee the female reproductive capacity. In fact, a large mass of adipose tissue distributes around the reproductive system both in the male and female. However, the functions of ovary fat pad (the nearest adipose tissue to ovary) are not known. In our study, we found that the ovary fat pad-removed female mice showed decreased fertility and less ovulated mature eggs. We further identified that only a small proportion of follicles developed to antral follicle, and many follicles were blocked at the secondary follicle stage. The overall secretion levels of estrogen and FSH were lower in the whole estrus cycle (especially at proestrus); however, the LH level was higher in ovary fat pad-removed mice than that in control groups. Moreover, the estrus cycle of ovary fat pad-removed mice showed significant disorder. Besides, the expression of FSH receptor decreased, but the LH receptor increased in ovary fat pad-removed mice. These results suggest that ovary fat pad is important for mouse reproduction.

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Hong Ma, Jin Yuan, Jinyu Ma, Jie Ding, Weiwei Lin, Xinlei Wang, Mingliang Zhang, Yi Sun, Runze Wu, Chun Liu, Cheng Sun and Yunjuan Gu

Bone morphogenetic protein 7 (BMP7), a member of the transforming growth factor-β (TGF-β) family, plays pivotal roles in energy expenditure. However, whether and how BMP7 regulates hepatic insulin sensitivity is still poorly understood. Here, we show that hepatic BMP7 expression is reduced in high-fat diet (HFD)-induced diabetic mice and palmitate (PA)-induced insulin-resistant HepG2 and AML12 cells. BMP7 improves insulin signaling pathway in insulin resistant hepatocytes. On the contrary, knockdown of BMP7 further impairs insulin signal transduction in PA-treated cells. Increased expression of BMP7 by adenovirus expressing BMP7 improves hyperglycemia, insulin sensitivity and insulin signal transduction. Furthermore, BMP7 inhibits mitogen-activated protein kinases (MAPKs) in both the liver of obese mice and PA-treated cells. In addition, inhibition of MAPKs recapitulates the effects of BMP7 on insulin signal transduction in cultured hepatocytes treated with PA. Activation of p38 MAPK abolishes the BMP7-mediated upregulation of insulin signal transduction both in vitro and in vivo. Together, our results show that hepatic BMP7 has a novel function in regulating insulin sensitivity through inhibition of MAPKs, thus providing new insights into treating insulin resistance-related disorders such as type 2 diabetes.

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Jiean Xu, Qiuhua Yang, Xiaoyu Zhang, Zhiping Liu, Yapeng Cao, Lina Wang, Yaqi Zhou, Xianqiu Zeng, Qian Ma, Yiming Xu, Yong Wang, Lei Huang, Zhen Han, Tao Wang, David Stepp, Zsolt Bagi, Chaodong Wu, Mei Hong and Yuqing Huo

Insulin resistance-related disorders are associated with endothelial dysfunction. Accumulating evidence has suggested a role for adenosine signaling in the regulation of endothelial function. Here, we identified a crucial role of endothelial adenosine kinase (ADK) in the regulation of insulin resistance. Feeding mice with a high-fat diet (HFD) markedly enhanced the expression of endothelial Adk. Ablation of endothelial Adk in HFD-fed mice improved glucose tolerance and insulin sensitivity and decreased hepatic steatosis, adipose inflammation and adiposity, which were associated with improved arteriole vasodilation, decreased inflammation and increased adipose angiogenesis. Mechanistically, ADK inhibition or knockdown in human umbilical vein endothelial cells (HUVECs) elevated intracellular adenosine level and increased endothelial nitric oxide synthase (NOS3) activity, resulting in an increase in nitric oxide (NO) production. Antagonism of adenosine receptor A2b abolished ADK-knockdown-enhanced NOS3 expression in HUVECs. Additionally, increased phosphorylation of NOS3 in ADK-knockdown HUVECs was regulated by an adenosine receptor-independent mechanism. These data suggest that Adk-deficiency-elevated intracellular adenosine in endothelial cells ameliorates diet-induced insulin resistance and metabolic disorders, and this is associated with an enhancement of NO production caused by increased NOS3 expression and activation. Therefore, ADK is a potential target for the prevention and treatment of metabolic disorders associated with insulin resistance.