The dorsal vagal complex (DVC) is an important site in which ghrelin plays an orexigenic role. However, the relationship between ghrelin expression in DVC and the energy status of the organism is unclear, as well as the role of the vagus nerve in this process. In this study, ghrelin expression in DVC neurons of rats was detected, then levels of ghrelin expression were observed under the conditions of regular diet, fasting, high blood glucose, low blood glucose, and following subdiaphragmatic vagotomy and vagus nerve electrostimulation. The results showed the following: 1) there was positive staining of ghrelin neurons in DVC; 2) ghrelin protein and mRNA levels in DVC increased under fasting condition; 3) Hyperglycemia, induced by glucose production, decreased DVC ghrelin levels and levels did not increase under hypoglycemia induced by insulin injection; 4) the dorsal trunk of the subdiaphragmatic vagus transmits a stimulatory signal to increase DVC ghrelin levels, whereas the ventral trunk transmits inhibitory information; and 5) DVC ghrelin levels decreased with 20 Hz stimulation on the ventral or dorsal trunk of subdiaphragmatic vagus nerves but increased with 1 Hz stimulation on the dorsal trunk. These results indicate that endogenous ghrelin is synthesized in DVC neurons. Conditions such as fasting, hyperglycemia, and hypoglycemia result in changes in DVC ghrelin levels in which the dorsal and ventral trunks of subdiaphragmatic vagus play different modulation roles.
Lei Huang, Bin Qiu, Lin Yuan, Lili Zheng, Qiang Li and Shigong Zhu
Chun-Mei Li, Shinji Takahashi, Shinji Taneda, Chie Furuta, Gen Watanabe, Akira K Suzuki and Kazuyoshi Taya
The effects of 3-methyl-4-nitrophenol (PNMC), a component of diesel exhaust, on reproductive function were investigated in adult male Japanese quail. The quail were treated with a single i.m. dose of PNMC (78, 103 or 135 mg/kg body weight), and trunk blood and testes were collected 1, 2 or 4 weeks later. Various levels of testicular atrophy were observed in all groups treated with PNMC. Sperm formation, cloacal gland area, and plasma LH and testosterone concentrations were also reduced in birds with testicular atrophy. To determine the acute effect of PNMC on gonadotrophin from the pituitary, adult male quail were administrated a single i.m. injection of PNMC (25 mg/kg), and plasma concentrations of LH were measured at 1, 3 and 6 h. This dose significantly lowered plasma levels of LH at all three time points. These results suggest that PNMC acts on the hypothalamus–pituitary axis, by reducing circulating LH within a few hours of administration and subsequently reducing testosterone secretion. In addition, in order to investigate the direct effects of PNMC on the secretion of testosterone from testicular cells in quail testes, cultured interstitial cells containing Leydig cells were exposed to PNMC (10−6, 10−5 or 10−4 M) for 4, 8 or 24 h. These quantities of PNMC significantly reduced the secretion of testosterone in a time- and dose-dependent manner. The present findings also suggest a direct effect of PNMC on the testis to reduce testosterone secretion. This study clearly indicates that PNMC induces reproductive toxicity at both the central and testicular levels, and disrupts testicular function in adult male quail.
Xinrong Zhou, Bangguo Qian, Ning Ji, Conghui Lui, Zhiyuan Liu, Bing Li, Huarong Zhou and Caifeng Yan
Gastric bypass surgery produces clear antidiabetic effects in a substantial proportion of morbidly obese patients. In view of the recent trend away from ‘bariatric’ surgery and toward ‘metabolic’ surgery, it is important to elucidate the enhancing effect of bypass surgery on pancreatic β-cell mass, which is related to diabetes remission in non-obese patients. We investigated the effects of gastric bypass surgery on glycemic control and other pancreatic changes in a spontaneous non-obese type 2 diabetes Goto-Kakizaki rat model. Significant improvements in postprandial hyperglycemia and plasma c-peptide level were observed when glucose was administered orally post-surgery. Other important events observed after surgery were enhanced first phase insulin secretion in a in site pancreatic perfusion experiment, pancreatic hyperplasia, improved islet structure (revealed by immunohistochemical analysis), striking increase in β-cell mass, slight increase in ratio of β-cell area to total pancreas area, and increased number of small islets closely related to exocrine ducts. No notable changes were observed in ratio of β-cell to non-β endocrine cell area, β-cell apoptosis, or β-cell proliferation. These findings demonstrate that gastric bypass surgery in this rat model increases endocrine cells and pancreatic hyperplasia, and reflect the important role of the gastrointestinal system in regulation of metabolism.
Jia Sun, Haiping Zhu, Xiaorong Wang, Qiuqi Gao, Zhuoying Li and Huiya Huang
The molecular signaling mechanisms of Coenzyme Q10 (CoQ10) in diabetic nephropathy (DN) remain poorly understood. We verified that mitochondrial abnormalities, like defective mitophagy, the generation of mitochondrial reactive oxygen species (mtROS) and the reduction of mitochondrial membrane potential, occurred in the glomerulus of db/db mice, accompanied by reduced PINK and parkin expression and increased apoptosis. These changes were partially reversed following oral administration of CoQ10. In inner fenestrated murine glomerular endothelial cells (mGECs), high glucose (HG) also resulted in deficient mitophagy, mitochondrial dysfunction and apoptosis, which were reversed by CoQ10. Mitophagy suppression mediated by Mdivi-1 or siPINK abrogated the renoprotective effects exerted by CoQ10, suggesting a beneficial role for CoQ10-restored mitophagy in DN. Mechanistically, CoQ10 restored the expression, activity and nuclear translocation of Nrf2 in HG-cultured mGECs. In addition, the reduced PINK and parkin expression observed in HG-cultured mGECs were partially elevated by CoQ10. CoQ10-mediated renoprotective effects were abrogated by the Nrf2 inhibitor ML385. When ML385 abolished mitophagy and the renoprotective effects exerted by CoQ10, mGECs could be rescued by treatment with mitoTEMPO, which is a mtROS-targeted antioxidant. These results suggest that CoQ10, as an effective antioxidant in mitochondria, exerts beneficial effects in DN via mitophagy by restoring Nrf2/ARE signaling. In summary, CoQ10-mediated mitophagy activation positively regulates DN through a mechanism involving mtROS, which influences the activation of the Nrf2/ARE pathway.
Sung Wook Park, Shawna D Persaud, Stanislas Ogokeh, Tatyana A Meyers, DeWayne Townsend and Li-Na Wei
Excessive and/or persistent activation of calcium-calmodulin protein kinase II (CaMKII) is detrimental in acute and chronic cardiac injury. However, intrinsic regulators of CaMKII activity are poorly understood. We find that cellular retinoic acid-binding protein 1 (CRABP1) directly interacts with CaMKII and uncover a functional role for CRABP1 in regulating CaMKII activation. We generated Crabp1-null mice (CKO) in C57BL/6J background for pathophysiological studies. CKO mice develop hypertrophy as adults, exhibiting significant left ventricular dilation with reduced ejection fraction at the baseline cardiac function. Interestingly, CKO mice have elevated basal CaMKII phosphorylation at T287, and phosphorylation on its substrate phospholamban (PLN) at T17. Acute isoproterenol (ISO) challenge (80 mg/kg two doses in 1 day) causes more severe apoptosis and necrosis in CKO hearts, and treatment with a CaMKII inhibitor KN-93 protects CKO mice from this injury. Chronic (30 mg/kg/day) ISO challenge also significantly increases hypertrophy and fibrosis in CKO mice as compared to WT. In wild-type mice, CRABP1 expression is increased in early stages of ISO challenge and eventually reduces to the basal level. Mechanistically, CRABP1 directly inhibits CaMKII by competing with calmodulin (CaM) for CaMKII interaction. This study demonstrates increased susceptibility of CKO mice to ISO-induced acute and chronic cardiac injury due to, at least in part, elevated CaMKII activity. Deleting Crabp1 results in reduced baseline cardiac function and aggravated damage challenged with acute and persistent β-adrenergic stimulation. This is the first report of a physiological role of CRABP1 as an endogenous regulator of CaMKII, which protects the heart from ISO-induced damage.
Xuemei Tang, Jingwen Li, Wei Xiang, Ye Cui, Bin Xie, Xiaodong Wang, Zihui Xu and Lixia Gan
In addition to the ascertained efficacy as antidiabetic drug, metformin is increasingly being used as weight-loss agent in obesity, and as insulin sensitizer in nonalcoholic fatty liver disease (NAFLD). However, the mechanisms underlying these effects are still incompletely understood. Emerging evidence suggest metformin as leptin sensitizer to mediate the weight-loss effect in the brain. In this study, we investigated effects of metformin on expression of leptin receptors in liver and kidney in mice. C57BL/6 mice were fed with chow diet (CD) or high-fat diet (HF) for 5months. Afterward, mice were treated with metformin (50mg/kg or 200mg/kg) for 15days. Metabolic parameters and hepatic gene expression were analyzed at the end of the treatment. We also tested the effects of metformin on plasma-soluble leptin receptor (sOB-R) levels in newly diagnosed type 2 diabetes mellitus (T2DM) patients, and assessed its effect on hepatosteatosis in mice. Results showed that metformin upregulates the expression of leptin receptors (OB-Ra, -Rb, -Rc, and -Rd) in liver but not kidney. The stimulation effect is dose-dependent in both chow and HF mice. Upregulation of OB-Rb, long signaling isoform, needs a relatively higher dose of metformin. This effect was paralleled by increased sOBR levels in mice and T2DM patients, and decreased hepatic triglyceride (TG) content and lipogenic gene expression, including sterol regulatory element-binding protein 1c (SREBP-1c), fatty acid synthase (FAS) and acetyl-CoA carboxylase-1 (ACC-1). Taken together, these data identify hepatic leptin receptor as target gene being upregulated by metformin which may enhance leptin sensitivity in liver to alleviate steatosis.
Da-Long Ren, Ai-Ai Sun, Ya-Juan Li, Min Chen, Shu-Chao Ge and Bing Hu
Neutrophil migration to inflammatory sites is the fundamental process of innate immunity among organisms against pathogen invasion. As a major sleep adjusting hormone, melatonin has also been proved to be involved in various inflammatory events. This study aimed to evaluate the impact of exogenous melatonin on neutrophil migration to the injury site in live zebrafish and further investigate whether ERK signaling is involved in this process. Using the tail fin transection model, the fluorescently labeled neutrophil was in vivo visualized in transgenic Tg(lyz:EGFP), Tg(lyz:DsRed) zebrafish. We found that exogenous melatonin administration dramatically inhibited the injury-induced neutrophil migration in a dose-dependent and time-dependent manner. The inhibited effect of melatonin on neutrophil migration could be attenuated by melatonin receptor 1, 2, and 3 antagonists. The ERK phosphorylation level was significantly decreased post injury when treated with melatonin. The blocking of ERK activation with inhibitor PD0325901 suppressed the number of migrated neutrophils in response to injury. However, the activation of ERK with the epidermal growth factor could impair the inhibited effect of melatonin on neutrophil migration. We also detected that PD0325901 significantly suppressed the in vivo neutrophils transmigrating over the vessel endothelial cell using the transgenic Tg(flk:EGFP);(lyz:DsRed) line labeled as both vessel and neutrophil. Taking all of these data together, the results indicated that exogenous melatonin had an anti-migratory effect on neutrophils by blocking the ERK phosphorylation signal, and it led to the subsequent adhesion molecule expression. Thus, the crossing of the vessel endothelial cells of neutrophils became difficult.
Juan Kong, Yunzi Chen, Guojun Zhu, Qun Zhao and Yan Chun Li
Leptin is an adipose tissue-derived hormone that plays a critical role in energy homeostasis. Vitamin D has been shown to regulate energy metabolism, but the relationship between vitamin D and leptin is unclear. Leptin expression and secretion was reduced in vitamin D receptor (VDR)-null mice and increased in transgenic (Tg) mice overexpressing the VDR in adipocytes; however, as leptin is mainly determined by fat mass, it is unclear whether the vitamin D hormone directly regulates leptin expression. To address this question, we determined the effect of vitamin D on leptin expression in vivo and ex vivo. One-week treatment of WT mice with the vitamin D analog RO-27-5646 led to a significant increase in adipose leptin mRNA transcript and serum leptin levels. Moreover, in adipose tissue cultures, 1,25-dihydroxyvitamin D markedly stimulated mRNA expression and secretion of leptin, but not resistin, in adipose tissues obtained from WT mice, but not from VDR-null mice, and leptin upregulation induced by 1,25-dihydroxyvitamin D was more robust in adipose tissues obtained from VDR Tg mice compared with WT mice. These data demonstrate that 1,25-dihydroxyvitamin D stimulates adipose leptin production in a VDR-dependent manner, suggesting that vitamin D may affect energy homeostasis through direct regulation of leptin expression.
Yanwen Jiang, Lu Chen, Robert N Taylor, Chunjin Li and Xu Zhou
Retinol (vitamin A) and its derivatives, collectively known as retinoids, are required for maintaining vision, immunity, barrier function, reproduction, embryogenesis and cell proliferation and differentiation. Despite the fact that most events in the endometrium are predominantly regulated by steroid hormones (estrogens and progesterone), accumulating evidence shows that retinoid signaling is also involved in the development and maintenance of the endometrium, stromal decidualization and blastocyst implantation. Moreover, aberrant retinoid metabolism seems to be a critical factor in the development of endometriosis, a common gynecological disease, which affects up to 10% of reproductive age women and is characterized by the ectopic localization of endometrial-like tissue in the pelvic cavity. This review summarizes recent advances in research on the mechanisms and molecular actions of retinoids in normal endometrial development and physiological function. The potential roles of abnormal retinoid signaling in endometriosis are also discussed. The objectives are to identify limitations in current knowledge regarding the molecular actions of retinoids in endometrial biology and to stimulate new investigations toward the development potential therapeutics to ameliorate or prevent endometriosis symptoms.
Feng Ye, Bingyin Shi, Xiaoyan Wu, Peng Hou, Lei Gao, Xiaodan Ma, Li Xu and Liping Wu
CD40 plays an important role in the pathogenesis of Graves' disease (GD). Inhibition of CD40 expression may be a promising treatment for GD. In this study, we used an animal model to investigate whether lentivirus expressing siRNA for CD40 (LV-CD40-siRNA) could be useful for the therapy of GD. BALB/c mice were injected with PBS alone (PBS group), negative lentivirus (control siRNA group), or LV-CD40-siRNA (CD40 siRNA group), 3 days before being treated with adenovirus expressing human TSHR A subunit (Ad-TSHR289) three times at 3-week intervals to induce GD model. Sera thyroxine (T4) levels were assayed by RIA. The expression of CD40 was detected at the mRNA level by real-time PCR and protein level by flow cytometry. The expression of CD40, CD80, and CD86 was significantly decreased in the CD40 siRNA group (P<0.05), while FOXP3 expression was increased compared to the control siRNA group (P=0.05). Mean T4 levels were decreased 14% in the CD40 siRNA group compared to the control siRNA group. The rate of disease induction was similar among the three groups injected with Ad-TSHR289. LV-CD40-siRNA is a useful tool to inhibit the expression of CD40 in vivo, but it cannot decrease the incidence of hyperthyroidism in a limited period of time.