AdipoR2 inhibits human glioblastoma cell growth through the AMPK/mTOR pathway.

BACKGROUND: AdipoR2, which belongs to the seven-transmembrane-domain receptor family, has been shown to play an important role in the development of human tumours, but the underlying mechanisms are poorly understood. In this study, we found that AdipoR2 expression correlates with glioma grade. In addition, we also investigated the mechanisms behind the antiproliferative effects of AdipoR2 in U251 cells (a human glioma cell line) using colony formation and WST-8 growth assays. METHODS: The U251 cell line was cultured in vitro. Western blotting was used to detect the expression of relevant proteins. Quantitative RT-PCR was used to detect AdipoR1 and AdipoR2 expression. Flow cytometry was used to detect cell cycle assay results. The gene expression profiles of glioma samples from the CGGA database were analysed by MATLAB and GSEA software. RESULTS: The AMPK/mTOR pathway plays a central role in the regulation of cell proliferation, differentiation and migration and may promote tumorigenesis. Therefore, we can control cancer progression by modulating the AMPK/mTOR pathway. However, there is no information on the relationship between AdipoR and AMPK/mTOR in central nervous system tumours such as GBM. In this study. We found 648 upregulated genes and 436 downregulated genes correlated with AdipoR2 expression in 158 glioma samples. GSEA suggested that AdipoR2 is a cell cycle-associated gene. The results of the flow cytometry analysis indicated that AdipoR2 induced G0/G1 cell cycle arrest in U251 cells. Furthermore, we identified the AMPK/mTOR signalling axis to be involved in AdipoR2-induced cell cycle arrest. CONCLUSIONS: Our results suggest that AdipoR2 may represent a novel endogenous negative regulator of GBM cell proliferation. These findings also suggest that AdipoR2 may be a promising therapeutic target in GBM patients.

Adiponectin suppresses amyloid-ß oligomer (AßO)-induced inflammatory response of microglia via AdipoR1-AMPK-NF-κB signaling pathway.

BACKGROUND: Microglia-mediated neuroinflammation is important in Alzheimer's disease (AD) pathogenesis. Extracellular deposition of ß-amyloid (Aß), a major pathological hallmark of AD, can induce microglia activation. Adiponectin (APN), an adipocyte-derived adipokine, exerts anti-inflammatory effects in the periphery and brain. Chronic APN deficiency leads to cognitive impairment and AD-like pathologies in aged mice. Here, we aim to study the role of APN in regulating microglia-mediated neuroinflammation in AD. METHODS: Inflammatory response of cultured microglia (BV2 cells) to AßO and effects of APN were studied by measuring levels of proinflammatory cytokines (tumor necrosis factor α [TNFα] and interleukin-1ß [IL-1ß]) in cultured medium before and after exposure to AßO, with and without APN pretreatment. Adiponectin receptor 1 (AdipoR1) and receptor 2 (AdipoR2) were targeted by small interference RNA. To study the neuroprotective effect of APN, cultured HT-22 hippocampal cells were treated with conditioned medium of AßO-exposed BV2 cells or were co-cultured with BV2 cells in transwells. The cytotoxicity of HT-22 hippocampal cells was assessed by MTT reduction. We generated APN-deficient AD mice (APN-/-5xFAD) by crossing APN-knockout mice with 5xFAD mice to determine the effects of APN deficiency on microglia-mediated neuroinflammation in AD. RESULTS: AdipoR1 and AdipoR2 were expressed in BV2 cells and microglia of mice. Pretreatment with APN for 2 h suppressed TNFα and IL-1ß release induced by AßO in BV2 cells. Additionally, APN rescued the decrease of AMPK phosphorylation and suppressed nuclear translocation of nuclear factor kappa B (NF-κB) induced by AßO. Compound C, an inhibitor of AMPK, abolished these effects of APN. Knockdown of AdipoR1, but not AdipoR2 in BV2 cells, inhibited the ability of APN to suppress proinflammatory cytokine release induced by AßO. Moreover, pretreatment with APN inhibited the cytotoxicity of HT-22 cells co-cultured with AßO-exposed BV2 cells. Lastly, APN deficiency exacerbated microglia activation in 9-month-old APN-/-5xFAD mice associated with upregulation of TNFα and IL-1ß in the cortex and hippocampus. CONCLUSIONS: Our findings demonstrate that APN inhibits inflammatory response of microglia to AßO via AdipoR1-AMPK-NF-κB signaling, and APN deficiency aggravates microglia activation and neuroinflammation in AD mice. APN may be a novel therapeutic agent for inhibiting neuroinflammation in AD.

Expression of Adiponectin Receptor-1 and Prognosis of Epithelial Ovarian Cancer Patients.

BACKGROUND Adiponectin receptor-1 (AdipoR1) has been reported to be associated with the risk of obesity-associated malignancies, including epithelial ovarian cancer (EOC). The aim of this study was to determine if AdipoR1 could serve as a prognosis indicator for patients with EOC. MATERIAL AND METHODS In this study, expression of AdipoR1 in 73 EOC patients consecutively admitted to our hospital was detected by immunohistochemical staining. Univariate and multivariate analyses were performed to assess the relationship between AdipoR1 expression level and progression-free survival (PFS) and overall survival (OS) rates in patients. RESULTS A relatively lower expression of AdipoR1 in the cancerous tissues was detected compared to normal ovarian tissues, but the difference was not significant (p>0.05). AdipoR1 expression level in EOC patients was negatively correlated with advanced FIGO stages in patients and tumor differentiation, but had no correlation with pathological types, presenting of ascites, shorter platinum-free interval (PFI), diabetes, preoperative and postoperative body mass index (BMI), or platelet counts (p>0.05). Moreover, patients with AdipoR1 expression had a significantly longer PFS and OS compared to the negative expression group (p<0.001). CONCLUSIONS Our findings suggest that AdipoR1 expression level in cancerous tissues might serve as an independent prognostic indicator in EOC patients and is associated with longer PFS and OS.

Expression of adiponectin receptors in human and rat intervertebral disc cells and changes in receptor expression during disc degeneration using a rat tail temporary static compression model.

BACKGROUND: Adipose tissue is a large endocrine organ known to secret adiponectin, which has anti-diabetic, anti-atherogenic, and anti-inflammatory properties. Adiponectin is widely involved in systemic disease, diabetes mellitus, and cardiac infraction. This study aimed to investigate the involvement of adiponectin in intervertebral disc (IVD) degeneration. METHODS: Adipose and IVD tissues were obtained from human patients undergoing surgery (n = 4) and from skeletally mature Sprague-Dawley rats (n = 21). Tissues were stained immunohistochemically for adiponectin and adiponectin receptors AdipoR1 and AdipoR2. Changes in adiponectin receptor expression with IVD degeneration severity were then investigated using a rat tail temporary compression model. Rat IVD tissues were stained immunohistochemically with AdipoR1 or AdipoR2, and immunopositive cell percentages were calculated. Rat nucleus pulposus (NP) and annulus fibrosus (AF) tissues were isolated separately and treated with recombinant adiponectin (Ad 0.1 or 1.0 µg/ml) and/or interleukin-1 beta (IL-1ß) (0.2 µg/ml) for 24 h. The four groups were as follows: control group (no treatment), IL-1ß group (IL-1ß-only treatment), IL-1ß+Ad (0.1) group (IL-1ß and adiponectin [0.1 µg/ml] treatment), and IL-1ß+Ad (1.0) group (IL-1ß and adiponectin [1.0 µg/ml]). Real-time reverse transcription-polymerase chain reaction was performed to evaluate messenger-RNA (mRNA) expression of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). RESULTS: Adiponectin was widely expressed in human subcutaneous and epidural adipose tissue. In rat IVD tissue, adiponectin was not observed in NP and AF. However, both AdipoR1 and AdipoR2 were widely expressed in both human and rat IVD tissues, with no significant differences in expression levels between receptors. Furthermore, expression levels of AdipoR1 and AdipoR2 were gradually decreased with increased IVD degeneration severity. Interestingly, mRNA expression levels of TNF-α and IL-6 were significantly upregulated by IL-1ß stimulation. TNF-α expression in the IL-1ß+Ad 1.0 group was significantly lower than that in the IL-1ß group in both NP and AF cells (P < 0.05). Finally, IL-6 expression was not affected by adiponectin treatment in IVD cells. CONCLUSIONS: This study investigated for the first time the expression of adiponectin receptors in human and rat IVD cells. The findings indicate that adiponectin produced by the systemic or epidural adipose tissue may be involved in the pathomechanism of IVD degeneration.

Dietary α-linolenic acid-rich flaxseed oil prevents against alcoholic hepatic steatosis via ameliorating lipid homeostasis at adipose tissue-liver axis in mice.

Low levels of n-3 polyunsaturated fatty acids (PUFAs) in serum and liver tissue biopsies are the common characteristics in patients with alcoholic liver disease. The α-linolenic acid (ALA) is a plant-derived n-3 PUFA and is rich in flaxseed oil. However, the impact of ALA on alcoholic fatty liver is largely unknown. In this study, we assessed the potential protective effects of ALA-rich flaxseed oil (FO) on ethanol-induced hepatic steatosis and observed that dietary FO supplementation effectively attenuated the ethanol-induced hepatic lipid accumulation in mice. Ethanol exposure stimulated adipose lipolysis but reduced fatty acid/lipid uptake, which were normalized by FO. Our investigations into the corresponding mechanisms demonstrated that the ameliorating effect of FO might be associated with the lower endoplasmic reticulum stress and normalized lipid metabolism in adipose tissue. In the liver, alcohol exposure stimulated hepatic fatty acid uptake and triglyceride synthesis, which were attenuated by FO. Additionally, dietary FO upregulated plasma adiponectin concentration, hepatic adiponectin receptor 2 expression, and the activation of hepatic adenosine monophosphate-activated protein kinase. Collectively, dietary FO protects against alcoholic hepatic steatosis by improving lipid homeostasis at the adipose tissue-liver axis, suggesting that dietary ALA-rich flaxseed oil might be a promising approach for prevention of alcoholic fatty liver.

in vitro Anti-Proliferative Effect of Adiponectin on Human Endometriotic Stromal Cells through AdipoR1 and AdipoR2 Gene Receptor Expression.

BACKGROUND: Endometriosis is a complex disorder in reproductive age women which consist of stromal and epithelial cells implantation outside the uterine cavity. Adiponectin is a member of cytokine family with various metabolic roles and proliferation inhibition of many cancer cells. The aim of the present research was to determine adiponectin effect on human endometriotic stromal cells (ESCs) proliferation and their expression of adiponectin receptors. METHODS: In this experimental study, endometrial biopsies (n=7) were taken. ESCs isolation was done by enzymatic digestion and cell filtrations. ESCs of each biopsy were divided into four groups: 0 (control), 10, 100, and 200 ng/ml adiponectin concentrations in three different times (24, 48 or 72 h). The effect of adiponectin on ESC viability and expression of mRNA Adipo receptor1 (R1) and Adipo receptor2 (R2) was determined by Trypan blue staining and semi-quantitative RT-PCR, respectively. Data were analyzed by one-way ANOVA and unpaired student's t-test, and P<0.05 was considered statistically significant. RESULTS: Adiponectin inhibited human endometriotic stromal cell proliferation in time- and dose-dependent manners significantly (P=0.001). Expression of AdipoR1 and AdipoR2 gene receptors was increased in human ESCs significantly (P<0.05). CONCLUSIONS: Adiponectin can suppress endometriosis by inhibiting ESC proliferation and increased AdipoR1 and AdipoR2 expression.

Role of adiponectin in adipose tissue wound healing.

The purpose of this study was to investigate the mechanism behind adipose tissue wound healing (ATWH). The preadipocyte cell line 3T3-L1 was cultured and expression of adiponectin receptors (AdipoR1/2) was detected by immunohistochemistry and reverse transcription polymerase chain reaction. The concentration of adiponectin secreted at different cell densities was measured by enzyme-linked immunosorbent assay, while preadipocyte proliferation and migration were determined in vitro by MTT and wound closure assays. AdipoR1/2 were found to be expressed in 3T3-L1 preadipocytes. There were no statistically significant differences in the concentrations of adiponectin secreted by cell solutions of different densities (P > 0.05). In addition, adiponectin was seen to promote the growth and migration of preadipocytes. In conclusion, adiponectin may regulate ATWH by promoting preadipocyte proliferation and migration, and its systemic and/or local application is proposed as a promising therapeutic approach for the treatment of wounds incurred as a result of surgery.

Tumor expression of adiponectin receptor 2 and lethal prostate cancer.

To investigate the role of adiponectin receptor 2 (AdipoR2) in aggressive prostate cancer we used immunohistochemistry to characterize AdipoR2 protein expression in tumor tissue for 866 men with prostate cancer from the Physicians' Health Study and the Health Professionals Follow-up Study. AdipoR2 tumor expression was not associated with measures of obesity, pathological tumor stage or prostate-specific antigen (PSA) at diagnosis. However, AdipoR2 expression was positively associated with proliferation as measured by Ki-67 expression quartiles (P-trend < 0.0001), with expression of fatty acid synthase (P-trend = 0.001), and with two measures of angiogenesis (P-trend < 0.1). An inverse association was observed with apoptosis as assessed by the TUNEL assay (P-trend = 0.006). Using Cox proportional hazards regression and controlling for age at diagnosis, Gleason score, year of diagnosis category, cohort and baseline BMI, we identified a statistically significant trend for the association between quartile of AdipoR2 expression and lethal prostate cancer (P-trend = 0.02). The hazard ratio for lethal prostate cancer for the two highest quartiles, as compared to the two lowest quartiles, of AdipoR2 expression was 1.9 (95% confidence interval [CI]: 1.2-3.0). Results were similar when additionally controlling for categories of PSA at diagnosis and Ki-67 expression quartiles. These results strengthen the evidence for the role of AdipoR2 in prostate cancer progression.

Adipo-R1 and adipo-R2 expression in colorectal adenomas and carcinomas.

BACKGROUND: Human adiponectin (ApN), a 30 kDa glycoprotein of 244-amino acids which is predominantly produced by adipocytes, exerts its effects via two receptors, namely adiponectin receptor-1 (adipo-R1) and adiponectin receptor-2 (adipo-R2) with differential binding affinity to globular adiponectin. Adiponectin receptor expression has been studied in several cancer tissues. However, there are no studies of colorectal adenomas which are considered to be precursors for colorectal carcinoma (CRC). OBJECTIVES: In the present study, the expression of adipo-R1 and adipo-R2 was investigated immunohistochemically in colorectal adenomas and colorectal carcinoma tissues in an attempt to determine associations with these tumors. MATERIALS AND METHODS: The study enrolled 50 CRC patients with tumor resection and 82 patients who were diagnosed with adenomatous polyps, classified as negative for neoplasia, low-grade dysplasia (L-GD) or high- grade dysplasia (H-GD). RESULTS: Expression of both adipo-R1 and adipo-R2 was found to be significantly lower in the CRCs than in colorectal adenomas (tubular and tubulovillous, p=0.009 and p<0.001, respectively). Adipo-R1 and adipo-R2 expression was also significantly lower in the CRC group when compared with the groups of patients with low grade dysplasia, high-grade dysplasia or no neoplasia (p=0.012 and p<0.001, respectively). In addition, it was observed that adipo-R2 expression was generally positive in the non-neoplastic group irrespective of the adipo-R2 expression. In the L-GD, H-GD and CRC groups, the adipo-R2 result was positive whenever adipo-R1 result was positive but some patients with negative adipo-R1 had positive adipo-R2 (p<0.001, p=0.004, p<0.001, respectively). CONCLUSIONS: This study indicated that ApN may play a role in the progression of colorectal adenomatous polyps to carcinoma through actions on adipo-R1 and adipo-R2 receptors.

Adiponectin inhibits VEGF-A in prostate cancer cells.

A role of adiponectin in tumorigenesis has recently been appreciated. Although plasma adiponectin levels in subjects with prostate cancer have been found to be significantly lower than in subjects with benign prostatic hyperplasia or in normal healthy controls, the underlying molecular mechanisms remain unknown. Here, we not only detected significant decreases in plasma adiponectin levels in prostate cancer patients, but also showed significant decreases in adiponectin receptor I (AdipoR1) levels in the resected prostate cancer specimen. Prostate cancer cell lines examined in the current study had all lower levels of adiponectin and AdipoR1, compared to normal healthy prostate tissue. Moreover, overexpression of adiponectin in prostate cancer cells decreased production of vascular endothelial growth factor A (VEGF-A), while adiponectin depletion increased VEGF-A. Furthermore, adiponectin seemed to activate AMPK/TSC2 to inhibit mTor-mediated activation of VEGF-A. Taken together, our data suggest that adiponectin may play an essential role in suppressing growth of prostate cancer cells through inhibition of VEGF-A-mediated cancer neovascularization.

Adiponectin receptor and adiponectin signaling in human tissue among patients with end-stage renal disease.

BACKGROUND: Adiponectin plasma levels in chronic kidney disease (CKD) are two to three times higher than in individuals with normal kidney function. Despite adiponectin's anti-diabetic, anti-inflammatory and anti-atherogenic properties, patients with CKD have insulin resistance, systemic inflammation and accelerated atherogenesis. Hence, although adiponectin production is increased by adipose tissue in end-stage renal disease (ESRD), it is unclear if its effects on metabolism remain intact. METHODS: To determine if there is adiponectin resistance in ESRD, we measured tissue levels of adiponectin receptor-1 (AdipoR1) and adiponectin downstream effectors in ESRD patients compared with normal kidney function controls. Blood and tissue samples were obtained from participants at the time of kidney transplantation or kidney donation. A follow-up blood sample was obtained 3-6 months after transplantation. RESULTS: AdipoR1 was higher in muscle and peripheral blood mononuclear cells collected from ESRD patients. There was also a nonsignificant increase in AdipoR1 in visceral fat of ESRD compared with controls. Compared with controls, phosphorylation of the adiponectin downstream effector adenosine monophosphate-activated protein kinase (AMPK) was higher in ESRD while acetyl-CoA carboxylase phosphorylation (ACC-P) and carnitine palmitoyl transferase-1 (CPT-1) levels were lower. In vitro, exposure of C2C12 cells to uremic serum resulted in upregulation of AdipoR1 and increased phosphorylation of AMPK but decreased ACC-P and CPT-1 expression. CONCLUSION: Both our in vivo and in vitro observations indicate that uremia results in upregulation of AdipoR1 but adiponectin resistance at the post-receptor level.

Multifaceted roles of adiponectin in cancer.

Obesity is linked to increased cancer risk. Pathological expansion of adipose tissue impacts adipocyte function and secretion of hormonal factors regulating tissue homeostasis and metabolism. Adiponectin is an adipocyte-secreted, circulating hormone with pleiotropic functions in lipid and glucose metabolism, and beneficial roles in cardiovascular functions and inflammation. In obesity, decreased Adiponectin plasma levels correlate with tumor development and progression. The association of Adiponectin with potential tumor-limiting functions has raised significant interest in exploring this adipokine as a target for cancer-diagnostic and therapeutic applications. Recent studies, however, also implicate Adiponectin in supporting malignancy. This review highlights the evidence that links Adiponectin signaling to either cancer-protective or cancer-supporting functions. In this context, we discuss Adiponectin interactions with its receptors and associated signaling pathways. Despite significant advances in understanding Adiponectin functions and signaling mechanisms, its role in cancer remains multifaceted and subject to controversy.

Activation of the LH receptor up regulates the type 2 adiponectin receptor in human granulosa cells.

PURPOSE: Adiponectin is a predominantly adipocyte-derived hormone which influences insulin sensitivity and energy homeostasis through at least two receptors, AdipoR1 and AdipoR2. In animal models, adiponectin may regulate ovarian steroidogenesis, folliculogenesis, and ovulation. The receptors AdipoR1 and AdipoR2 are present in the human ovary, but their regulation is unknown. In these studies, we determined the effects of LH receptor activation on the expression and function of the two adiponectin receptors in human granulosa cells. METHODS: Granulosa cells were obtained at the time of oocyte retrieval in women undergoing in vitro fertilization (IVF). Cells were isolated and cultured for 48 h in DMEM/F12 medium with 5 % FBS and 50 ug/ml gentamicin. Medium was changed to low serum for 12 h and cells were treated with hCG (100 ng/ml), forskolin (30 µMol/L), or FSH (1 IU/ml) for 24 h for mRNA experiments. mRNA was isolated and RT PCR was performed using Taqman assays and quantification with the delta delta CT method. For immunocytochemistry, cells were grown on chamber slides and treated with hCG for 1 to 24 h and fixed with acetone. ICC was performed with polyclonal rabbit primary antibodies followed by alexa fluor goat anti-rabbit antibody and imaging with a fluorescence microscope and Zeiss software analysis. 3ß-hydroxysteroid dehydrogenase (3ßHSD) enzyme activity was determined by measuring the progesterone produced when cells were provided with an excess of 22-hydroxy-cholesterol as substrate following an incubation with hCG (1 IU/ml) and/or adiponectin (10 ng/ml). Progesterone content in the media was determined by ELISA. RESULTS: Messenger RNA for the two Adiponectin receptors is differentially regulated by activation of LHR with hCG treatment. AdipoR2 was increased nearly 4-fold (p < 0.05), whereas AdipoR1 expression was not changed by hCG treatment. Treatment with either FSH or forskolin (an activator of cAMP) had similar effects. Basal AdipoR2 protein was fairly low in granulosa cells in culture however treatment of cells with hCG resulted in a discernible increase in immunodetectable cytoplasmic protein as early as 6 h after treatment and was maintained for at least 24 h. The number of cells positive for AdipoR2 at 6 h increased from a basal of 20 % to almost 60 % (p < 0.05). Adiponectin treatment of hCG-primed cells resulted in increased 3ßHSD activity by approximately 60 % over hCG alone and more than 3-fold over basal levels. CONCLUSIONS: AdipoR2 is regulated by the LH receptor function via a cAMP dependant mechanism. Increased expression of adipoR2 prior to and following ovulation may contribute to enhanced 3ßHSD activity and increased progesterone secretion by the corpus luteum of the ovary. Dysregulation of adiponectin that may occur with PCOS may impair normal progesterone production.

Expression of adiponectin, leptin, and their receptors in ovarian endometrioma.

OBJECTIVE: To evaluate the expression of leptin, leptin receptor (ObR), adiponectin, and adiponectin receptor (AdipoR) in ovarian endometriomas compared with normal endometrium, and to analyze relationships among adipokines and their receptors. DESIGN: Experimental study. SETTING: A clinic for the treatment of endometriosis and basic research laboratories. PATIENT(S): Forty-four women with endometriosis and 42 age-matched women with no laparoscopic evidence of endometriosis as control subjects. INTERVENTION(S): Endometrial tissue samples were obtained during laparoscopic surgery. MAIN OUTCOME MEASURE(S): Immunohistochemical staining for leptin, ObR, adiponectin, and AdipoR was performed with the use of tissue microarray. Clinical characteristics were reviewed from the patient's medical records. The effect of leptin on the expression of adiponectin was evaluated in endometriotic cell line using real-time reverse-transcription polymerase chain reaction. RESULT(S): Positive expression rates of leptin and ObR were significantly higher in ovarian endometrioma compared with normal endometrium, but those of adiponectin and AdipoR were similar (ovarian endometrioma vs. normal endometrium, respectively: leptin 100% vs. 59.5%; ObR 72.7% vs. 33.3%; adiponectin 31.8% vs. 42.9%; AdipoR 88.6% vs. 73.8%). Expression of adipokines and their receptors did not show any correlation with disease stage. A positive correlation was found between expression of ObR and adiponectin (correlation coefficient 0.488; P=.001). Leptin treatment in endometriotic cells induced mRNA expression of adiponectin. CONCLUSION(S): These data suggest that leptin and its receptor are induced in ovarian endometriomas, and that the leptin/ObR system regulates adiponectin gene expression in endometriotic cells.

Decreased adiponectin level is associated with aggressive phenotype of tongue squamous cell carcinoma.

Circulating adiponectin levels are inversely associated with risk of various obesity-related cancers. However, the effect of adiponectin on carcinogenesis and progression of tongue squamous cell carcinoma (TSCC) remains unknown. We measured serum adiponectin levels in 59 patients with TSCC and 50 healthy controls. Expression of adiponectin and its receptors in paired tumor and paracancerous specimens were determined by immunohistochemical staining (n = 37) and western blot (n = 30), respectively. Serum adiponectin level was lower in patients than in controls (5.0 ± 2.4 vs 8.4 ± 3.5 µg/mL, P < 0.01), and was inversely associated with histological grade and lymph node metastasis but not tumor size. Local adiponectin levels in tumor tissue gradually decreased as tumor-node-metastasis stage increased, while the expression of adiponectin receptors was unchanged. In addition, serum adiponectin levels in the TSCC patients without metabolic and cardiovascular diseases, or without smoking and drinking habits, were still lower than in controls. Furthermore, adiponectin inhibited the migration, but not proliferation, of SCC15 cells in vitro. These results indicate that a decreased adiponectin level is associated with risk of TSCC. Hypoadiponectinemia might be used as a biomarker to predict an aggressive phenotype of TSCC.

Expression levels of adiponectin receptors are decreased in human endometrial adenocarcinoma tissues.

Adiponectin is a cytokine secreted by adipocytes, whose plasma levels are decreased in obesity. Adiponectin has insulin-sensitizing, antiatherogenic, and antidiabetogenic effects. It has been shown that adiponectin may also exert antineoplastic activity through suppression of tumor proliferation and neoangiogenesis and through induction of apoptosis. Recently, low adiponectin serum concentration has been found in obesity-related malignancies, including endometrial cancer. In addition, the expression of adiponectin receptors (AdipoR1 and AdipoR2) has been documented in several human cancer tissues, but the expression has previously not been assessed in human endometrial cancer tissues. In this study, we analyzed the immunohistochemical expression of AdipoR1 and AdipoR2 in a series of surgically resected human endometrioid adenocarcinoma tissues from a total of 141 cases. Decreased AdipoR1 or AdipoR2 expression was significantly associated with histological higher grade (P=0.0026 and 0.0004, respectively). Decreased expression of AdipoR1 was associated with myometrial invasion and lymph node metastasis of endometrioid adenocarcinoma (P=0.0039 and P=0.0069, respectively). AdipoR1 and AdipoR2 immunoexpression was significantly associated with the expression of the progesterone receptor, although it was not significantly correlated with the expression of the estrogen receptor, Ki-67 or p53. Our present study raises the possibility that decreased expression of adiponectin receptors is implicated in the development, invasion, and metastasis of human endometrioid adenocarcinoma. Our findings, moreover, indicate that adiponectin receptors could be considered as therapeutic targets for endometrioid adenocarcinoma. In adiponectin receptor-positive endometrioid adenocarcinoma, we think adiponectin-based anticancer therapy is useful; however, in histological high-grade endometrioid adenocarcinoma, in which the expression levels of adiponectin receptors are relatively low, adiponectin therapy supported by adiponectin receptor induction is needed.

Gene expression pattern of adiponectin and adiponectin receptors in dominant and atretic follicles and oocytes screened based on brilliant cresyl blue staining.

Adiponectin and its receptors (AdipoR1 and AdipoR2) are novel endocrine systems that act at various levels to control male and female fertility. The aim of this study was to determine whether adiponectin and its receptors gene expression levels differ between dominant follicle (DF) and atretic follicle (AF) and also between oocytes which were stained positively and negatively with brilliant cresyl blue (BCB(+) and BCB(-)). Based on estradiol/progesterone ratio, follicles from ovaries were classified as AFs and DFs. The stages of estrous cycle (follicular or luteal phases) were defined by macroscopic observation of the ovaries and the uterus. Oocytes were stained with BCB for 90 min. The relative expression of adiponectin, AdipoR1 and AdipoR2 mRNA in theca and cumulus cells and oocytes of different follicles were determined by quantitative real time PCR. Adiponectin and its receptors genes were clearly expressed higher (P<0.05) in theca and cumulus cells and oocytes of DFs than those of AFs during the follicular and luteal phases. BCB(+) oocytes showed a higher (P<0.05) expression of adiponectin and its receptors compared with their BCB(-) counterparts. Positive correlation (r>0.725, P<0.001) was observed between adiponectin mRNA level in ovarian cells of DFs and follicular fluid E2 concentration in follicular phase. Adiponectin mRNA abundance in ovarian cells of AFs showed a significant negative correlation with follicular fluid progesterone concentration in follicular and luteal phases (r<-0.731, P<0.001). This work has revealed the novel association of adiponectin and its receptors genes with follicular dominance and oocyte competence, thereby opening several new avenues of research into the mechanisms of dominance and competence in animal and human.

Effect of adiponectin on cardiac allograft vasculopathy.

BACKGROUND: The role of adiponectin (APN), an adipose tissue-specific secretory protein, on chronic rejection after cardiac transplantation in APN-sense transgenic mice (APN-SE) was evaluated. METHODS AND RESULTS: Heterotopic cardiac transplantation in major histocompatibility complex class II-mismatched mice was performed. B6.C-H-2(bm12)KhEg (Bm12) hearts were transplanted into APN-SE, and allografts were harvested at 8 weeks after transplantation. Quantitative polymerase chain reaction (PCR) and immunohistochemical staining showed that the expression of both AdipoR1 and AdipoR2 was induced in APN-SE recipients. Neointimal hyperplasia was significantly decreased in allografts transplanted into APN-SE (luminal occlusion, 8.9 ± 2.2%) compared to those transplanted into controls (49.4 ± 10.5%; P=0.011). APN-SE showed significantly reduced mRNA levels of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, IL-6, and monocyte chemoattractant protein-1 (MCP-1) by quantitative PCR. Western blot analysis revealed that the protein levels of IFN-γ and MCP-1 were reduced in APN-SE recipients. Proliferation of smooth muscle cells stimulated with activated T cells was suppressed by APN addition, and this effect was canceled by treatment with an adenosine monophosphate-activated protein kinase (AMPK) inhibitor. CONCLUSIONS: APN plays a critical role in the attenuation of chronic rejection by suppressing inflammatory cytokine and chemokine expression and enhancing APN receptor expression. APN plays a beneficial role in reducing the progression of cardiac allograft vasculopathy through the AMPK pathway.

Role of the energy sensor adenosine monophosphate-activated protein kinase in the regulation of immature gonadotropin-releasing hormone neuron migration.

BACKGROUND: The 5'-AMP-activated protein kinase (AMPK) plays a fundamental role in regulating energy homeostasis as well as feeding and metabolism, through central and peripheral actions. AMPK is activated by conditions causing ATP depletion and by different metabolic molecules, such as adiponectin and AMPK agonist, such as 5-aminoimidazole- 4-carboxamide-1-ß-D-ribofuranoside (AICAR). AMPK activation has also been shown to affect the migration of different cell types and to participate in the central control of reproductive function, although information concerning AMPK and the development of the hypothalamic reproductive compartment is lacking. AIM: To explore whether AMPK activation by globular adiponectin (gAdipo) and AICAR may affect the migratory ability of GnRH neurons. MATERIALS AND METHODS: We used GN11 immature GnRH neurons (in vitro model system), RT-PCR and Western blot analysis, and Boyden's chamber assay. RESULTS: gAdipo did not affect FBS-stimulated migration of GN11 cells and activated AMPK through the mandatory phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and Akt, which also interact one to each other. AICAR treatment inhibited FBS-stimulated GN11 cell migration, through a long-lasting activation of AMPK. A downstream activation of ERK1/2 by AICAR was also observed and inhibition of ERK1/2 amplified AICAR-induced inhibition of migration. CONCLUSIONS: The direct, but not the indirect, activation of AMPK appears to negatively affect FBSinduced GN11 cell migration, suggesting that the final balance between pro-migratory and anti-migratory actions may also depend upon the specific sequence of intracellular signals activated by one agent.

Adiponectin modulates C-jun N-terminal kinase and mammalian target of rapamycin and inhibits hepatocellular carcinoma.

BACKGROUND & AIMS: Epidemiological studies have shown that obesity is a risk factor for hepatocellular carcinoma (HCC). Lower adiponectin levels are associated with poor prognosis in obese HCC patients, hence it is plausible that adiponectin acts as a negative regulator of HCC. We investigated the effects of adiponectin on HCC development and its molecular mechanisms. METHODS: Assays with Huh7 and HepG2 HCC cells were used to examine the signal transduction pathways involved in the protective functions of adiponectin in HCC. These studies were followed by in vivo approaches using HCC xenografts and tumor analysis. Results from in vitro and in vivo findings were corroborated using human HCC tissue microarray and analysis of clinicopathological characteristics. RESULTS: Adiponectin increased apoptosis of HCC cells through activation of caspase-3. Adiponectin increased phosphorylation of c-Jun-N-terminal kinase (JNK) and inhibition of c-Jun-N-terminal kinase-phosphorylation inhibited adiponectin-induced apoptosis and caspase-3 activation. Adiponectin increased phosphorylation of 5'-adenosine monophosphate-activated protein kinase and tumor suppressor tuberous sclerosis complex 2 and inhibited mammalian target of rapamycin phosphorylation. Inhibition of 5'-adenosine monophosphate-activated protein kinase phosphorylation not only inhibited adiponectin-induced c-Jun-N-terminal kinase phosphorylation, but also blocked biological effects of adiponectin. Adiponectin substantially reduced liver tumorigenesis in nude mice. Importantly, analysis of adiponectin expression levels in tissue microarray of human HCC patients revealed an inverse correlation of adiponectin expression with tumor size. CONCLUSIONS: Adiponectin protects against liver tumorigenesis; its reduced expression is associated with poor prognosis in obese patients with HCC.