We report the identification of a novel secreted peptide, INM02. The mRNA transcript of human INM02 gene is about 3.0 kb. Its open-reading frame contains 762 bps and encodes a protein of 254 amino acids. Northern blot analysis demonstrates that INM02 mRNA is widely expressed in rat tissues, especially with abundant quantities in pancreatic islets, testis, and bladder tissue. We have expressed recombinant INM02 protein and generated rabbit anti-INM02 polyclonal antibodies. We show here that INM02 could be detectable in human serum by ELISA. We also present evidence that INM02 mRNA expression could be regulated by glucose. Experiments on both MIN6 cells and intact isolated islets demonstrate that INM02 mRNA levels are increased more than threefold by high glucose (25 mM) when compared with low glucose (5.5 mM). ELISA analysis shows that secretion of INM02 is significantly augmented by high glucose in vitro. It is speculated that as a novel secreted protein, INM02 is associated with functions of pancreatic islets, especially of β-cells.
Xuanchun Wang, Wei Gong, Yu Liu, Zhihong Yang, Wenbai Zhou, Mei Wang, Zhen Yang, Jie Wen, and Renming Hu
Lin Xia, Zhongqiu Wang, Ying Zhang, Xiao Yang, Yibei Zhan, Rui Cheng, Shiming Wang, and Jianfa Zhang
A previous investigation has demonstrated that plasma 5′-AMP (pAMP) exacerbates and causes hyperglycemia in diabetic mice. However, the crosstalk between pAMP and insulin signaling to regulate glucose homeostasis has not been investigated in depth. In this study, we showed that the blood glucose level was more dependent on the ratio of insulin to pAMP than on the absolute level of these two factors. Administration of 5′-AMP significantly attenuated the insulin-stimulated insulin receptor (IR) autophosphorylation in the liver and muscle tissues, resulting in the inhibition of downstream AKT phosphorylation. A docking analysis indicated that adenosine was a potential inhibitor of IR tyrosine kinase. Moreover, the 5′-AMP treatment elevated the ATP level in the pancreas and in the isolated islets, stimulating insulin secretion and increasing the plasma level of insulin. The insulin administration decreased the 5′-AMP-induced hyper-adenosine level by the up-regulation of adenosine kinase activities. Our results indicate that blood glucose homeostasis is reciprocally regulated by pAMP and insulin.
Jing Li, Pan-Pan Zhao, Ting Hao, Dan Wang, Yu Wang, Yang-Zi Zhu, Yu-Qing Wu, and Cheng-Hua Zhou
Urotensin II (U-II), a cyclic peptide originally isolated from the caudal neurosecretory system of fishes, can produce proinflammatory effects through its specific G protein-coupled receptor, GPR14. Neuropathic pain, a devastating disease, is related to excessive inflammation in the spinal dorsal horn. However, the relationship between U-II and neuropathic pain has not been reported. This study was designed to investigate the effect of U-II antagonist on neuropathic pain and to understand the associated mechanisms. We reported that U-II and its receptor GPR14 were persistently upregulated and activated in the dorsal horn of L4–6 spinal cord segments after chronic constriction injury (CCI) in rats. Intrathecal injection of SB657510, a specific antagonist against U-II, reversed CCI-induced thermal hyperalgesia and mechanical allodynia. Furthermore, we found that SB657510 reduced the expression of phosphorylated c-Jun N-terminal kinase (p-JNK) and nuclear factor-κB (NF-κB) p65 as well as subsequent secretion of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α). It was also showed that both the JNK inhibitor SP600125 and the NF-κB inhibitor PDTC significantly attenuated thermal hyperalgesia and mechanical allodynia in CCI rats. Our present research showed that U-II receptor antagonist alleviated neuropathic pain possibly through the suppression of the JNK/NF-κB pathway in CCI rats, which will contribute to the better understanding of function of U-II and pathogenesis of neuropathic pain.
KH Lin, HY Lee, CH Shih, CC Yen, SL Chen, RC Yang, and CS Wang
Thyroid hormones (THs) regulate growth, development, differentiation and metabolic processes by interacting and activating thyroid hormone receptors (TRs). Although much progress has been made in our understanding of the transcriptional regulation of many TR target genes, little is known of the regulation of plasma protein gene expression by TRs. To investigate the role of TRs in plasma protein expression we used human hepatocellular carcinoma cell lines and carried out cDNA microarray analysis. Our results indicate that several plasma proteins including transferrin, prothrombin, angiotensinogen, haptoglobin, alpha-2-HS-glycoprotein alpha and beta chain, complement, lipoproteins and fibrinogen are up-regulated by THs. Furthermore, clusterin, alpha-2-macroglobulin precursor, prothymosin alpha and alpha-fetoprotein were found to be down-regulated by THs.Transferrin, an iron-binding protein expressed in all mammals, and mainly synthesized in the liver, was investigated further. Immunoblot and Northern blot analyses revealed that exposure of HepG2-TRalpha1 sub-lines and HepG2-Neo cells to tri-iodothyronine (T(3)) induced time- and dose-dependent increases in the abundance of transferrin mRNA and protein, with the extent of these effects correlating with the level of expression of TRalpha1. Nuclear run-on experiments indicate that this induction is functioning at the transcriptional level. Moreover, cyclohexamide treatment did not eliminate the induction of transferrin by TH. Thus, our results suggest that the induction of transferrin by TH is direct and may in fact be mediated by an as yet unidentified response element in the promoter region.
Shan-Jin Wang, Xin-Feng Li, Lei-Sheng Jiang, and Li-Yang Dai
Regulation of the physiological processes of endochondral bone formation during long bone growth is controlled by various factors including the hormones estrogen and leptin. The effects of estrogen are mediated not only through the direct activity of estrogen receptors (ERs) but also through cross talk with other signaling systems implicated in chondrogenesis. The receptors of both estrogen and leptin (OBR (LEPR)) are detectable in growth plate chondrocytes of all zones. In this study, the expression of mRNA and protein of OBR in chondrogenic ATDC5 cells and the effect of 17β-estradiol (E2) stimulation were assessed using quantitative PCR and western blotting. We have found that the mRNA of Obr was dynamically expressed during the differentiation of ATDC5 cells over 21 days. Application of E2 (10−7 M) at day 14 for 48 h significantly upregulated OBR mRNA and protein levels (P<0.05). The upregulation of Obr mRNA by E2 was shown to take place in a concentration-dependent manner, with a concentration of 10−7 M E2 having the greatest effect. Furthermore, we have confirmed that E2 affected the phosphorylation of ERK1/2 (MAPK1/MAPK3) in a time-dependent manner where a maximal fourfold change was observed at 10 min following application of E2. Finally, pretreatment of the cells with either U0126 (ERK1/2 inhibitor) or ICI 182 780 (ER antagonist) blocked the upregulation of OBR by E2 and prevented the E2-induced phosphorylation of ERK. These data demonstrate, for the first time, the existence of cross talk between estrogen and OBR in the regulation of bone growth whereby estrogen regulates the expression of Obr in growth plate chondrocytes via ERs and the activation of ERK1/2 signaling pathways.
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.
Xiwen Xiong, Xupeng Sun, Qingzhi Wang, Xinlai Qian, Yang Zhang, Xiaoyan Pan, and X Charlie Dong
Chronic exposure of pancreatic β-cells to abnormally elevated levels of free fatty acids can lead to β-cell dysfunction and even apoptosis, contributing to type 2 diabetes pathogenesis. In pancreatic β-cells, sirtuin 6 (SIRT6) has been shown to regulate insulin secretion in response to glucose stimulation. However, the roles played by SIRT6 in β-cells in response to lipotoxicity remain poorly understood. Our data indicated that SIRT6 protein and mRNA levels were reduced in islets from diabetic and aged mice. High concentrations of palmitate (PA) also led to a decrease in SIRT6 expression in MIN6 β-cells and resulted in cell dysfunction and apoptosis. Knockdown of Sirt6 caused an increase in cell apoptosis and impairment in insulin secretion in response to glucose in MIN6 cells even in the absence of PA exposure. Furthermore, overexpression of SIRT6 alleviated the palmitate-induced lipotoxicity with improved cell viability and increased glucose-stimulated insulin secretion. In summary, our data suggest that SIRT6 can protect against palmitate-induced β-cell dysfunction and apoptosis.
Lei Du, Yang Wang, Cong-Rong Li, Liang-Jian Chen, Jin-Yang Cai, Zheng-Rong Xia, Wen-Tao Zeng, Zi-Bin Wang, Xi-Chen Chen, Fan Hu, Dong Zhang, Xiao-Wei Xing, and Zhi-Xia Yang
Polycystic ovarian syndrome (PCOS) is a major severe ovary disorder affecting 5–10% of reproductive women around the world. PCOS can be considered a metabolic disease because it is often accompanied by obesity and diabetes. Brown adipose tissue (BAT) contains abundant mitochondria and adipokines and has been proven to be effective for treating various metabolic diseases. Recently, allotransplanted BAT successfully recovered the ovarian function of PCOS rat. However, BAT allotransplantation could not be applied to human PCOS; the most potent BAT is from infants, so voluntary donors are almost inaccessible. We recently reported that single BAT xenotransplantation significantly prolonged the fertility of aging mice and did not cause obvious immunorejection. However, PCOS individuals have distinct physiologies from aging mice; thus, it remains essential to study whether xenotransplanted rat BAT can be used for treating PCOS mice. In this study, rat-to-mouse BAT xenotransplantation fortunately did not cause severe rejection reaction, and significantly recovered ovarian functions, indicated by the recovery of fertility, oocyte quality, and the levels of multiple essential genes and kinases. Besides, the blood biochemical index, glucose resistance, and insulin resistance were improved. Moreover, transcriptome analysis showed that the recovered PCOS F0 mother following BAT xenotransplantation could also benefit the F1 generation. Finally, BAT xenotransplantation corrected characteristic gene expression abnormalities found in the ovaries of human PCOS patients. These findings suggest that BAT xenotransplantation could be a novel therapeutic strategy for treating PCOS patients.
C Y Shan, J H Yang, Y Kong, X Y Wang, M Y Zheng, Y G Xu, Y Wang, H Z Ren, B C Chang, and L M Chen
For centuries, Berberine has been used in the treatment of enteritis in China, and it is also known to have anti-hyperglycemic effects in type 2 diabetic patients. However, as Berberine is insoluble and rarely absorbed in gastrointestinal tract, the mechanism by which it works is unclear. We hypothesized that it may act locally by ameliorating intestinal barrier abnormalities and endotoxemia. A high-fat diet combined with low-dose streptozotocin was used to induce type 2 diabetes in male Sprague Dawley rats. Berberine (100 mg/kg) was administered by lavage to diabetic rats for 2 weeks and saline was given to controls. Hyperinsulinemia and insulin resistance improved in the Berberine group, although there was no significant decrease in blood glucose. Berberine treatment also led to a notable restoration of intestinal villi/mucosa structure and less infiltration of inflammatory cells, along with a decrease in plasma lipopolysaccharide (LPS) level. Tight junction protein zonula occludens 1 (ZO1) was also decreased in diabetic rats but was restored by Berberine treatment. Glutamine-induced glucagon-like peptide 2 (GLP2) secretion from ileal tissue decreased dramatically in the diabetic group but was restored by Berberine treatment. Fasting insulin, insulin resistance index, plasma LPS level, and ZO1 expression were significantly correlated with GLP2 level. In type 2 diabetic rats, Berberine treatment not only augments GLP2 secretion and improves diabetes but is also effective in repairing the damaged intestinal mucosa, restoring intestinal permeability, and improving endotoxemia. Whether these effects are mechanistically related will require further studies, but they certainly support the hypothesis that Berberine acts via modulation of intestinal function.
Qiaoli Cui, Yijing Liao, Yaojing Jiang, Xiaohang Huang, Weihong Tao, Quanquan Zhou, Anna Shao, Ying Zhao, Jia Li, Anran Ma, Zhihong Wang, Li Zhang, Zunyuan Yang, Yinan Liang, Minglin Wu, Zhenyan Yang, Wen Zeng, and Qinghua Wang
Glucagon-like peptide 1 (GLP-1) is an insulinotropic hormone and plays an important role in regulating glucose homeostasis. GLP-1 has a short half-life (t1/2<2 min) due to degrading enzyme dipeptidyl peptidase-IV and rapid kidney clearance, which limits its clinical application as a therapeutic reagent. We demonstrated recently that supaglutide, a novel GLP-1 mimetic generated by recombinant fusion protein techniques, exerted hypoglycemic and beta cell trophic effects in type 2 diabetes db/db mice. In the present study, we examined supaglutide’s therapeutic efficacy and pharmacokinetics in diabetic rhesus monkeys. We found that a single subcutaneous injection of supaglutide of tested doses transiently and significantly reduced blood glucose levels in a dose-dependent fashion in the diabetic monkeys. During a 4-weeks intervention period, treatment of supaglutide of weekly dosing dose-dependently decreased fasting and random blood glucose levels. This was associated with significantly declined plasma fructosamine levels. The repeated administration of supaglutide remarkably also decreased body weight in a dose-dependent fashion accompanied by decreased food intake. Intravenous glucose tolerance test results showed that supaglutide improved glucose tolerance. The intervention also showed enhanced glucose-stimulated insulin secretion and improved lipid profile in diabetic rhesus monkeys. These results reveal that supaglutide exerts beneficial effects in regulating blood glucose and lipid homeostasis in diabetic rhesus monkeys.