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Weiwei Qin, Wenbao Lu, Hongwei Li, Xiaochen Yuan, Bingwei Li, Qiuju Zhang and Ruijuan Xiu

Matrix metalloproteinases (MMPs) have been involved in inflammatory and degradative processes in pathologic conditions. The purpose of this study was to investigate the protective effect of melatonin in human umbilical vein endothelial cell (HUVEC) monolayer permeability and the regulation of MMP9 induced by interleukin 1β (IL1β (IL1B)) in HUVECs. Protection studies were carried out with melatonin, a well-known antioxidant and antiinflammatory molecule. MMP9 expression was increased with IL1β induction in HUVECs. Melatonin showed a barrier-protective role by downregulation of MMP9 and upregulation of tissue inhibitor of metalloproteinase-1 expression in HUVECs. Meanwhile, melatonin also decreased sodium fluorescein permeability and counteracted the downregulation of vascular endothelial cadherin and occludin expression in HUVECs. During inflammatory stimulus, nuclear factor-κB (NF-κB) plays a significant role in regulating MMP genes expression, thus the function of NF-κB in HUVECs' barrier disruption was investigated. IL1β induced nuclear translocation of NF-κB in HUVECs and regulated MMP9 expression. However, NF-κB translocation into the nucleus was inhibited significantly by melatonin. Our results show that melatonin decreases the permeability of monolayer endothelial cell induced by IL1β. At the same time, melatonin decreased the expression and activity of MMP9 by a NF-κB-dependent pathway in HUVECs induced by IL1β.

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Chang-Jiang Li, Hui-Wen Sun, Fa-Liang Zhu, Liang Chen, Yuan-Yuan Rong, Yun Zhang and Mei Zhang

In this study, we investigated the in vivo role of adiponectin, an adipocytokine, on the development of atherosclerosis in rabbits mainly using adenovirus expressing adiponectin gene (Ad-APN) and intravascular ultrasonography. Serum adiponectin concentrations in rabbits after Ad-APN local transfer to abdominal aortas increased about nine times as much as those before transfer (P < 0.01), about ten times as much as the levels of endogenous adiponectin in adenovirus expressing β-galactosidase gene (Ad-β gal) treated rabbits (P < 0.01), and about four times as much as those in the aorta of non-injured rabbits on a normal cholesterol diet (P < 0.01). Ultrasonography revealed a significantly reduced atherosclerotic plaque area in abdominal aortas of rabbits infected through intima with Ad-APN, by 35.2% compared with the area before treatment (P < 0.01), and by 35.8% compared with that in Ad-β gal-treated rabbits (P < 0.01). In rabbits infected through adventitia, Ad-APN treatment reduced plaque area by 28.9% as compared with the area before treatment (P < 0.01) and 25.6% compared with that in Ad-β gal-treated rabbits (P < 0.01). Adiponectin significantly suppressed the mRNA expression of vascular cell adhesion molecule-1 (VCAM-1) by 18.5% through intima transfer (P < 0.05) and 26.9% through adventitia transfer (P < 0.01), and intercellular adhesion molecule-1 (ICAM-1) by 40.7% through intima transfer (P < 0.01), and 30.7% through adventitia transfer (P < 0.01). However, adiponectin had no effect on the expression of types I and III collagen. These results suggest that local adiponectin treatment suppresses the development of atherosclerosis in vivo in part by attenuating the expression of VCAM-1 and ICAM-1 in vascular walls.

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Peixin Li, Zhijian Rao, Brenton Thomas Laing, Wyatt Bunner, Taylor Landry, Amber Prete, Yuan Yuan, Zhong-Tao Zhang and Hu Huang

Vertical sleeve gastrectomy (VSG) is an effective surgery to treat obesity and diabetes. However, the direct effect of VSG on metabolic functions is not fully understood. We aimed to investigate if alterations in hypothalamic neurons were linked with perturbations in liver metabolism after VSG in an energy intake-controlled obese mouse model. C57BL/6 and hrNPY-GFP reporter mice received HFD for 12 weeks and were then divided into three groups: Sham (ad lib), Sham (pair-fed) with VSG and VSG. Food intake was measured daily, and blood glucose levels were measured before and after the study. Energy expenditure and body composition were determined. Serum parameters, liver lipid and glycogen contents were measured and gene/protein expression were analyzed. Hypothalamic POMC, AgRP/NPY and tyrosine hydroxylase-expressing neurons were counted. The following results were obtained. VSG reduced body weight gain and adiposity induced by HFD, increased energy expenditure independent of energy intake. Fed and fasted blood glucose levels were reduced in the VSG group. While serum active GLP-1 level was increased, the active ghrelin and triglycerides levels were decreased along with improved insulin resistance in VSG group. Liver lipid accumulation, glycogen content and gluconeogenic gene expression were reduced in the VSG group. In the hypothalamus, TH-expressing neuron population was decreased, and the POMC-expressing neuron population was increased in the VSG group. In conclusion, our data suggest that VSG improves metabolic symptoms by increasing energy expenditure and lowering lipid and glycogen contents in the liver. These physiological alterations are possibly related to changes in hypothalamic neuron populations.

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Ying Wang, Xiao-Hui Wang, Deng-Xuan Fan, Yuan Zhang, Ming-Qing Li, Hai-Xia Wu and Li-Ping Jin

Mammalian proprotein convertases (PCs) play an important role in folliculogenesis, as they proteolytically activate a variety of substrates such as the transforming growth factor beta (TGFβ) superfamily. PC subtilism/kexin 6 (PCSK6) is a member of the PC family and is ubiquitously expressed and implicated in many physiological and pathological processes. However, in human granulosa cells, the expression of the PC family members, their hormonal regulation, and the function of PCs are not clear. In this study, we found that PCSK6 is the most highly expressed PC family member in granulosa cells. LH increased PCSK6 mRNA level and PCSK6 played an anti-apoptosis function in KGN cells. Knockdown of PCSK6 not only increased the secretion of activin A and TGFβ2 but also decreased the secretion of follistatin, estrogen, and the mRNA levels of FSH receptor (FSHR) and P450AROM (CYP19A1). We also found that, in the KGN human granulosa cell line, TGFβ2 and activin A could promote the apoptosis of KGN cells and LH could regulate the follistatin level. These data indicate that PCSK6, which is regulated by LH, is highly expressed in human primary granulosa cells of pre-ovulatory follicles and plays important roles in regulating a series of downstream molecules and apoptosis of KGN cells.

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Lei Huang, Bin Qiu, Lin Yuan, Lili Zheng, Qiang Li and Shigong Zhu

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.

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Guoyue Yuan, Xia Chen, Qinyun Ma, Jie Qiao, Rongying Li, Xuesong Li, Shengxian Li, Jinfeng Tang, Libin Zhou, Huaidong Song and Mingdao Chen

C-reactive protein (CRP) is considered as one of the most sensitive markers of inflammation. The aim of the present study is to investigate the effects of CRP on the production of adiponectin in 3T3-L1 adipocytes. Northern and western blot analysis revealed that CRP treatment inhibited adiponectin mRNA expression and secretion in a dose- and time-dependent manner. Co-incubation of adipocytes with rosiglitazone and CRP decreased induction of adiponectin gene expression by rosiglitazone. However, luciferase reporter assays did not show that CRP affected the activity of ~2.1 kb adiponectin gene promoter, which was increased by rosiglitazone alone. Pharmacological inhibition of phosphatidylinositol (PI)-3 kinase by LY294002 partially reversed inhibition of adiponectin gene expression by CRP. These results collectively suggest that CRP suppresses adiponectin gene expression partially through the PI-3 kinase pathway, and that decreased production of adiponectin might represent a mechanism by which CRP regulates insulin sensitivity.

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Xiaoyi Ma, Fei Gao, Qi Chen, Xiuping Xuan, Ying Wang, Hongjun Deng, Fengying Yang and Li Yuan

The angiotensin-converting enzyme 2 (ACE2)/angiotensin 1–7 (A1–7)/MAS axis and glutamate decarboxylase 67 (GAD67)/gamma-aminobutyric acid (GABA) signal both exist in the islet and play important roles in regulating blood glucose metabolism. It has been reported that the activation of ACE2 in the brain increases GABA expression to improve biological effects; however, it is unclear whether there is functional correlation between the ACE2/A1–7/MAS axis and GAD67/GABA signal in the islet. In this study, we showed that the ACE2/A1–7/MAS and GABA signaling systems decreased in the islet of different metabolic stress models. In ACE2-knockout mice, we found that GAD67 and GABA expression decreased significantly, which was reversed by exogenous administration of A1–7. Furthermore, A1–7 mediated PDX1 and AKT activation was inhibited by allylglycine (a specific GAD67 inhibitor) in MIN6 cells. Moreover, giving A1–7 and GABA could significantly reduce beta-cell dedifferentiation and improved glucose metabolism during metabolic stress in vivo and in vitro. In conclusion, our study reveals that the ACE2/A1–7/MAS axis improves beta-cell function through regulating GAD67/GABA signal in beta cells and that up-regulating the ACE2/A1–7/MAS axis and GABA signals delays the development of obesity-induced diabetes.

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Baiyang You, Yaoshan Dun, Wenliang Zhang, Lingjun Jiang, Hui Li, Murong Xie, Yuan Liu and Suixin Liu

Mitochondrial quality control (MQC) and function are determinants for cellular energy metabolism, and their disorders are reported to play an important role in the development of insulin resistance (IR). Salidroside was reported to have beneficial effects on MQC through AMPK pathway; however, it is unknown whether salidroside exerts anti-IR effect with this action. This study sought to investigate the effects of salidroside on IR with an exploration of the mechanisms of its action. Experimental IR models were adopted in high-fat-diet (HFD)-fed mice and palmitate-treated C2C12 myotubes, respectively. Blood levels of glucose and insulin as well as cellular glucose uptake were determined, and mitochondrial function and MQC-associated parameters and reactive oxygen species (ROS) production were analyzed based on treatments with the activator (AICAR), inhibitors (compound C and EX-527) or specific siRNA of Ampk/Sirt1 and mitochondrial ROS scavenger (mito-TEMPO). Protein expression level was determined by Western blot, cellular observation by transmission electron microscope and ROS production by functional analysis kits. Salidroside reduced IR and activated insulin signaling along with the stimulation of AMPK/SIRT1 signaling and downstream regulation of MQC and ROS production. These salidroside effects were comparable to those of AICAR and could be prevented by AMPK/SIRT1 inhibitors or siRNAs, respectively. Salidroside reduces IR and regulates MQC and ROS production by activating AMPK/SIRT1 signaling pathway. Since IR is a critical issue for public health, to explore a potent agent against IR is of high interest. The anti-IR effects of salidroside warrant further experimental and clinical studies.

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Yan-Hong Bu, Yu-Ling He, Hou-De Zhou, Wei Liu, Dan Peng, Ai-Guo Tang, Ling-Li Tang, Hui Xie, Qiu-Xia Huang, Xiang-Hang Luo and Er-Yuan Liao

Insulin receptor substrate 1 (IRS1) is an essential molecule for the intracellular signaling of IGF1 and insulin, which are potent anabolic regulators of bone metabolism. Osteoblastic IRS1 is essential for maintaining bone turnover; however, the mechanism underlying this regulation remains unclear. To clarify the role of IRS1 in bone metabolism, we employed RNA interference to inhibit IRS1 gene expression and observed the effects of silencing this gene on the proliferation and differentiation of and the expression of matrix metallopeptidase (MMP) and tumor necrosis factor receptor superfamily, member 11b (TNFRSF11B) in MC3T3-E1 cells. Our results showed that IRS1 short hairpin RNAs can effectively suppress the expression of IRS1, and inhibit the phosphorylation of AKT in IRS1 pathway; reduce the expression of MMP2, MMP3, MMP13, and MMP14, decrease the expression of TNFRSF11B and RANKL (also known as tumor necrosis factor (ligand) superfamily, member 11), however increase the RANKL/TNFRSF11B ratio; decrease cell survival, proliferation, and mineralization, and impair the differentiation of MC3T3-E1 cells. The downregulation of IRS1 had no effect on the expression of MMP1. Our findings suggest that IRS1 not only promotes bone formation and mineralization but also might play roles in bone resorption partly via the regulation of MMPs and RANKL/TNFRSF11B ratio, thus regulates the bone turnover.

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Wang-Yang Xu, Yan Shen, Houbao Zhu, Junhui Gao, Chen Zhang, Lingyun Tang, Shun-Yuan Lu, Chun-Ling Shen, Hong-Xin Zhang, Ziwei Li, Peng Meng, Ying-Han Wan, Jian Fei and Zhu-Gang Wang

Obesity and type 2 diabetes (T2D) are both complicated endocrine disorders resulting from an interaction between multiple predisposing genes and environmental triggers, while diet and exercise have key influence on metabolic disorders. Previous reports demonstrated that 2-aminoadipic acid (2-AAA), an intermediate metabolite of lysine metabolism, could modulate insulin secretion and predict T2D, suggesting the role of 2-AAA in glycolipid metabolism. Here, we showed that treatment of diet-induced obesity (DIO) mice with 2-AAA significantly reduced body weight, decreased fat accumulation and lowered fasting glucose. Furthermore, Dhtkd1−/− mice, in which the substrate of DHTKD1 2-AAA increased to a significant high level, were resistant to DIO and obesity-related insulin resistance. Further study showed that 2-AAA induced higher energy expenditure due to increased adipocyte thermogenesis via upregulating PGC1α and UCP1 mediated by β3AR activation, and stimulated lipolysis depending on enhanced expression of hormone-sensitive lipase (HSL) through activating β3AR signaling. Moreover, 2-AAA could alleviate the diabetic symptoms of db/db mice. Our data showed that 2-AAA played an important role in regulating glycolipid metabolism independent of diet and exercise, implying that improving the level of 2-AAA in vivo could be developed as a strategy in the treatment of obesity or diabetes.