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Wailan Shan, Shiyin Lu, Biqian Ou, Jia Feng, Zixian Wang, Huixian Li, Xiaohua Lu, and Ma Yi

Obesity is strongly linked to male infertility. Apoptotic inflammatory response caused by oxidative stress in testicular spermatogenic cells is one of the important causes of obesity-related male infertility. Pituitary adenylate cyclase activating polypeptide (PACAP) as a bioactive peptide secreted by the pituitary gland, has a powerful triple role of anti-oxidation, anti-apoptosis and anti-inflammation, and is involved in male reproduction regulation, but the specific mechanism remains unknown. The purpose of the current study is to explore the role of PACAP in obesity-related male infertility. In cell-level experiments, Mouse spermatocytes (GC-2) were treated with palmitate (PA) to establish an high-fat injury cell model in vitro and then treated with PACAP. In animal-level experiments, C57BL/6 male mice were fed with a high-fat diet (HFD) to induce obesity and then treated with PACAP. The cell mechanism studies showed that PACAP selectively binds to the PAC1 receptor to attenuate palmitic acid-induced mouse spermatogenic cell (GC-2) oxidative damage and apoptotic inflammatory response via the PKA/ERK/Nrf2 signaling axis. However, this mechanism was inhibited in GC-2 cells inhibiting the activity of Nrf2. The animal experiment studies showed that PACAP treatment ameliorated obesity characteristics, including body weight, epididymal adipose weight, testes/body weight, serum lipids levels, and reproductive hormone levels in vivo. Additionally, PACAP was shown to improve the reproductive function of the obese mice, which was characterized by improved testis morphology and sperm parameters via Keap1/Nrf2/ARE pathway. These beneficial effects of PACAP were abolished in obese mice with testis-specific knockdown of Nrf2.

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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.