After menopause, the development of cardiovascular disease (CVD) is due not only to estrogen decline but also to androgen decline. This study examined the effects of either estradiol (E2) or testosterone replacement alone or E2–testosterone combination on isolated myocytes in ovariectomized (Ovx) rats subjected to ischemia/reperfusion (I/R). Furthermore, we determined whether the effects are associated with β2-adrenoceptor (β2-AR). Five groups of adult female Sprague–Dawley rats were used: Sham operation (Sham) rats, bilateral Ovx rats, Ovx rats with E2 40 μg/kg per day (Ovx+E), Ovx rats with testosterone 150 μg/kg per day (Ovx+T), and Ovx rats with E2 40 μg/kg per day+testosterone 150 μg/kg per day (Ovx+E/T). We determined the lactate dehydrogenase (LDH) release, percentage of rod-shaped cells and apoptosis of ventricular myocytes from rats of all groups subjected to I/R. Then, we determined the above indices and contractile function with or without a selective β2-AR antagonist ICI 118 551. We also determined the expression of β2-AR. Our data show that either E2 or testosterone replacement alone or E2 and testosterone in combination decreased the LDH release, increased the percentage of rod-shaped cells, reduced apoptotic cells (%), and combination treatment appeared to be more effective than either E2 or testosterone replacement alone. ICI 118 551 abolished the effects of the three. Combination supplementation also enhanced the expression of β2-AR. We concluded that in Ovx rats, testosterone enhances E2's cardioprotection, while E2 and testosterone in combination was more effective and the protective effects may be associated with β2-AR. The study highlights the potential therapeutic application for CVD in postmenopausal women.
Aiying Liu, Liping Gao, Shoulei Kang, Ying Liu, Chuanying Xu, Hong Sun, Dongye Li, and Changdong Yan
Hong-Zhi Sun, Tong-Wei Yang, Wei-Jin Zang, and Shu-Fang Wu
Dehydroepiandrosterone (DHEA) is an endogenous steroid that is metabolized to androgens and/or estrogens in the human prostate. DHEA levels decline with age, and use of DHEA supplements to retard the aging process is of unproved effectiveness and safety. In this study, rat ventral prostatic epithelial cells were used to determine whether DHEA-modulated proliferation and prostate-specific antigen (PSA listed as KLKB1 in the MGI Database) production were mediated via the androgen receptor (AR) and its potential mechanism. We demonstrated that proliferation of prostatic epithelial cells and increase of PSA expression induced by DHEA were neutralized by Casodex or Ar siRNA, two specific AR blockers. DHEA stimulated Nfkb DNA binding activity, with this effect being blunted by Casodex or Ar siRNA. Moreover, the inhibition of the phosphatidylinositol 3-kinase (PI3K)/AKT nullified the effects of DHEA on NFKB activation. These findings suggested that DHEA stimulated normal prostatic epithelial cell proliferation, and AR is involved in DHEA-induced PSA expression in normal prostatic epithelial cells. This stimulation effect induced by DHEA is mediated by the activation of NFKB via PI3K/AKT pathway.
Soo Bong Choi, Jin Sun Jang, Sang Mee Hong, Dong Wha Jun, and Sunmin Park
Long-term dexamethasone (DEX) treatment is well known for its ability to increase insulin resistance in liver and adipose tissues leading to hyperinsulinemia. On the other hand, exercise enhances peripheral insulin sensitivity. However, it is not clear whether DEX and/or exercise affect β-cell mass and function in diabetic rats, and whether their effects can be associated with the modulation of the insulin/IGF-I signaling cascade in pancreatic β-cells. After an 8-week study, whole body glucose disposal rates in 90% pancreatectomized (Px) and sham-operated male rats decreased with a high dose treatment of DEX (0.1mg DEX/kg body weight/day)(HDEX) treatment, while disposal rates increased with exercise. First-phase insulin secretion was decreased and delayed by DEX via the impairment of the glucose-sensing mechanism in β-cells, while exercise reversed the impairment of first-phase insulin secretion caused by DEX, suggesting ameliorated β-cell functions. However, exercise and DEX did not alter second-phase insulin secretion except for the fact that HDEX decreased insulin secretion at 120 min during hyperglycemic clamp in Px rats. Unlike β-cell functions, DEX and exercise exhibited increased pancreatic β-cell mass in two different pathways. Only exercise, through increased proliferation and decreased apoptosis, increased β-cell mass via hyperplasia, which resulted from an enhanced insulin/IGF-I signaling cascade by insulin receptor substrate 2 induction. By contrast, DEX expanded β-cell mass via hypertrophy and neogenesis from precursor cells, rather than increasing proliferation and decreasing apoptosis. In conclusion, the improvement of β-cell function and survival via the activation of an insulin/IGF-I signaling cascade due to exercise has a crucial role in preventing the development and progression of type 2 diabetes.
Fengyue Wang, Jing Yang, Junfeng Sun, Yanli Dong, Hong Zhao, Hui Shi, and Lu Fu
Testosterone can affect cardiovascular disease, but its effects on mitochondrial dynamics in the post-infarct myocardium remain unclear. To observe the effects of testosterone replacement, a rat model of castration-myocardial infarction (MI) was established by ligating the left anterior descending coronary artery 2 weeks after castration with or without testosterone treatment. Expression of mitochondrial fission and fusion proteins was detected by western blot and immunofluorescence 14 days after MI. Cardiac function, myocardial inflammatory infiltration and fibrosis, cardiomyocyte apoptosis, mitochondrial microstructure, and ATP levels were also assessed. Compared with MI rats, castrated rats showed aggravated mitochondrial and myocardial insults, including mitochondrial swelling and disordered arrangement; loss of cristae, reduced mitochondrial length; decreased ATP levels; cardiomyocyte apoptosis; and impaired cardiac function. Results of western blotting analyses indicated that castration downregulated peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1A) and mitofusin 2, but upregulated dynamin-related protein 1. The results were also supported by results obtained using immunofluorescence. However, these detrimental effects were reversed by testosterone supplementation, which also elevated the upstream AMP-activated protein kinase (AMPK) activation of PGC1A. Thus, testosterone can protect mitochondria in the post-infarct myocardium, partly via the AMPK–PGC1A pathway, thereby decreasing mitochondrial dysfunction and cardiomyocyte apoptosis. The effects of testosterone were confirmed by the results of ELISA analyses.
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.
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.
Yeon-Ju Lee, Se-Hui Jung, JongYun Hwang, Sohee Jeon, Eun-Taek Han, Won Sun Park, Seok-Ho Hong, Young-Myeong Kim, and Kwon-Soo Ha
Cysteamine (an aminothiol), which is derived from coenzyme A degradation and metabolized into taurine, has beneficial effects against cystinosis and neurodegenerative diseases; however, its role in diabetic complications is unknown. Thus, we sought to determine the preventive effect of cysteamine against hyperglycemia-induced vascular leakage in the retinas of diabetic mice. Cysteamine and ethanolamine, the sulfhydryl group-free cysteamine analogue, inhibited vascular endothelial growth factor (VEGF)-induced stress fiber formation and vascular endothelial (VE)-cadherin disruption in endothelial cells, which play a critical role in modulating endothelial permeability. Intravitreal injection of the amine compounds prevented hyperglycemia-induced vascular leakage in the retinas of streptozotocin-induced diabetic mice. We then investigated the potential roles of reactive oxygen species (ROS) and transglutaminase (TGase) in the cysteamine prevention of VEGF-induced vascular leakage. Cysteamine, but not ethanolamine, inhibited VEGF-induced ROS generation in endothelial cells and diabetic retinas. In contrast, VEGF-induced TGase activation was prevented by both cysteamine and ethanolamine. Our findings suggest that cysteamine protects against vascular leakage through inhibiting VEGF-induced TGase activation rather than ROS generation in diabetic retinas.
Jung-Min Koh, Young-Sun Lee, Chang-Hyun Byun, Eun-Ju Chang, Hyunsoo Kim, Yong Hee Kim, Hong-Hee Kim, and Ghi Su Kim
Growing evidence has shown a biochemical link between increased oxidative stress and reduced bone density. Although α-lipoic acid (α-LA) has been shown to act as a thiol antioxidant, its effect on bone cells has not been determined. Using proteomic analysis, we identified six differentially expressed proteins in the conditioned media of α-LA-treated human bone marrow stromal cell line (HS-5). One of these proteins, receptor activator of nuclear factor κB ligand (RANKL), was significantly up-regulated, as confirmed by immunoblotting with anti-RANKL antibody. ELISA showed that α-LA stimulated RANKL production in cellular extracts (membranous RANKL) about 5-fold and in conditioned medium (soluble RANKL) about 23-fold, but had no effect on osteoprotegerin (OPG) secretion. Despite increasing the RANKL/OPG ratio, α-LA showed a dose-dependent suppression of osteoclastogenesis, both in a coculture system of mouse bone marrow cells and osteoblasts and in a mouse bone marrow cell culture system, and reduced bone resorption in a dose-dependent manner. In addition, α-LA-induced soluble RANKL was not inhibited by matrix metalloprotease inhibitors, indicating that soluble RANKL is produced by α-LA without any posttranslational processing. In contrast, α-LA had no significant effect on the proliferation and differentiation of HS-5 cells. These results suggest that α-LA suppresses osteoclastogenesis by directly inhibiting RANKL–RANK mediated signals, not by mediating cellular RANKL production. In addition, our findings indicate that α-LA-induced soluble RANKL is not produced by shedding of membranous RANKL.
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.
Lu Fu, Hongyuan Zhang, Jeremiah Ong’achwa Machuki, Tingting Zhang, Lin Han, Lili Sang, Lijuan Wu, Zhiwei Zhao, Matthew James Turley, Xide Hu, Hongjian Hou, Dongye Li, Sian E Harding, and Hong Sun
Currently, there are no conventional treatments for stress-induced cardiomyopathy (SCM, also known as Takotsubo syndrome), and the existing therapies are not effective. The recently discovered G protein- coupled estrogen receptor (GPER) executes the rapid effects of estrogen (E2). In this study, we investigated the effects and mechanism of GPER on epinephrine (Epi)-induced cardiac stress. SCM was developed with a high dose of Epi in adult rats and human-induced pluripotent stem cells–derived cardiomyocytes(hiPSC-CMs). (1) GPER activation with agonist G1/ E2 prevented an increase in left ventricular internal diameter at end-systole, the decrease both in ejection fraction and cardiomyocyte shortening amplitude elicited by Epi. (2) G1/ E2 mitigated heart injury induced by Epi, as revealed by reduced plasma brain natriuretic peptide and lactate dehydrogenase release into culture supernatant. (3) G1/E2 prevented the raised phosphorylation and internalization of β2-adrenergic receptors（β2AR）. (4) Blocking Gαi abolished the cardiomyocyte contractile inhibition by Epi. G1/E2 downregulated Gαi activity of cardiomyocytes and further upregulated cyclic adenosine monophosphate concentration in culture supernatant treated with Epi. (5) G1/E2 rescued decreased Ca2+ amplitude and Ca2+ channel current (ICa-L) in rat cardiomyocytes. Notably, the above effects of E2 were blocked by the GPER antagonist, G15. In hiPSC-CM (which expressed GPER, β1AR and β2ARs), knockdown of GPER by siRNA abolished E2 effects on increasing ICa-L and action potential duration in the stress state. In conclusion, GPER played a protective role against SCM. Mechanistically, this effect was mediated by balancing the coupling of β2AR to the Gαs and Gαi signalling pathways.