Adiponectin receptors are downregulated in human gastric cancer

Beyond Body Size: Adiponectin as a Key Player in Obesity-Driven Cancers

Obesity, a complex and multifactorial disease influenced by genetic, environmental, and psychological factors, has reached epidemic proportions globally, posing a significant health challenge. In addition to its established association with cardiovascular disease and type II diabetes, obesity has been implicated as a risk factor for various cancers. However, the precise biological mechanisms linking obesity and cancer remain largely understood. Adipose tissue, an active endocrine organ, produces numerous hormones and bioactive molecules known as adipokines, which play a crucial role in metabolism, immune responses, and systemic inflammation. Notably, adiponectin (APN), the principal adipocyte secretory protein, exhibits reduced expression levels in obesity. In this scoping review, we explore and discuss the role of APN in influencing cancer in common malignancies, including lung, breast, colorectal, prostate, gastric, and endometrial cancers. Our review aims to emphasize the critical significance of investigating this field, as it holds great potential for the development of innovative treatment strategies that specifically target obesity-related malignancies. Furthermore, the implementation of more rigorous and comprehensive prevention and treatment policies for obesity is imperative in order to effectively mitigate the risk of associated diseases, such as cancer.

Visceral-to-subcutaneous fat ratio independently predicts the prognosis of locally advanced gastric cancer----- highlighting the role of adiponectin receptors and PPARα, β/ δ, ɤ

BACKGROUND

Results of computed tomography body composition (CTBC) predicting long-term outcomes of gastric cancer have been mixed and the plausible mechanism remains elusive.

METHODS

We retrospectively enrolled a cohort of stage III gastric cancer who had undergone curative-intent gastrectomy. Clinicopathological variables, preoperative CTBC including abdominal muscle, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT), and nutritional and inflammatory index were taken together to construct prognostic analysis. In vitro tests using co-culture system of gastric cancer cell lines and visceral adipocytes were conducted.

RESULTS

A total of 191 eligible patients were enrolled. By multivariate analysis, SAT and VAT/ SAT ratio were prognostic factors of disease-free survival, while sarcopenia was not. SAT remained as a prognostic factor of overall survival. SAT index was positively correlated with prognostic nutritional index, while VAT HU was positively correlated with platelet-to-lymphocyte ratio. Expression of adiponectin receptor 1 and 2 (AdipoR1, R2), and peroxisome proliferator-activated receptor (PPAR) α, β/δ, ɤ of patients with higher VAT/SAT ratio were decreased as compared to those with lower VAT/SAT ratio. Proliferation of gastric cancer cells co-cultured with adipocytes was increased by 50-100% and accompanied by down-regulation of mRNAs of AdipoR1, 2, PPARα, β/δ, ɤ, and pro-apoptotic genes, as compared to their controls.

CONCLUSION

SAT and VAT played exactly opposite prognostic roles of locally advanced gastric cancers, which might work through modulation of AdipoR1, 2 and PPARα, β/δ, ɤ. Preoperative CTBC, supplementary to classic TNM system, helps clinicians tailor individualized adjuvant therapy and/or nutritional support.

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.

The Role of Adipokines in the Establishment and Progression of Head and Neck Neoplasms

Adipokines constitute a family of protein factors secreted by white adipose tissue (WAT), that regulate the functions of WAT and other sites. Leptin, adiponectin and resistin, are the main adipokines present in serum and saliva, targeting several tissues and organs, including vessels, muscles, liver and pancreas. Besides body mass regulation, adipokines affect glucose homeostasis, inflammation, angiogenesis, cell proliferation and apoptosis, and other crucial cell procedures. Their involvement in tumor formation and growth is well established and deregulation of adipokine and adipokine receptors' expression is observed in several malignancies including those located in the head and neck region. Intracellular effects of adipokines are mediated by a plethora of receptors that activate several signaling cascades including Janus kinase/ Signal transducer and activator of transcription (JAK/ STAT pathway), Phospatidylinositol kinase (PI3/ Akt/ mTOR) and Peroxisome proliferator-activated receptor (PPAR). The present review summarizes the current knowledge on the role of adipokines family members in carcinogenesis of the head and neck region. The diagnostic and prognostic significance of adipokines and their potential role as serum and saliva biomarkers are also discussed.

Lack of any prognostic relationship between adiponectin receptor (Adipo R1/R2) expression for early/advanced stage gastric cancer

INTRODUCTION

Adiponectin (ApN) is a complement C1q-related protein, mainly secreted from adipose tissue, that signals through ApN receptor 1 (Adipo-R1) and ApN receptor 2 (Adipo-R2). Low serum ApN concentrations are associated with obesity-related malignancies. However, there are very few studies on any prognostic role of ApN receptors in gastric cancer.

OBJECTIVES

The aim of this study is to investigate the relationship between AdipoR1/R2 expression and early/advanced stage gastric cancer in terms of clinicopathologic characteristics and survival.

MATERIALS AND METHODS

Eighteen patients with early and 39 with advanced stage gastric cancer who underwent surgical gastric resection were included in this study.

RESULTS

Adipo-R1 expression was low in 2 of the 18 patients with early stage gastric cancer (11.1%), while 4 had low Adipo-R2 expression (22.2%). In those with advanced stage gastric cancer, 7 of 39 had low Adipo-R1 expression (17.9%) and 16 had low Adipo-R2 expression (41%). Adipo-R2 expression was significantly higher (p=0.011) in moderately differentiated tumors when compared to well-differentiated tumors. While there was nearly a statistically significant relationship between TNM stage (T, tumor size; N, regional lymph node; M, whether distant metastases exist) and Adipo-R2 expression (p=0.054), there was no relationship between Adipo-R1/-R2 expression with tumor stage and survival.

CONCLUSION

Adipo-R1/-R2 expression has no prognostic significance of in early/advanced stage gastric cancer.

Genetic evidence for PLASMINOGEN as a shared genetic risk factor of coronary artery disease and periodontitis

BACKGROUND

Genetic studies demonstrated the presence of risk alleles in the genes ANRIL and CAMTA1/VAMP3 that are shared between coronary artery disease (CAD) and periodontitis. We aimed to identify further shared genetic risk factors to better understand conjoint disease mechanisms.

METHODS AND RESULTS

In-depth genotyping of 46 published CAD risk loci of genome-wide significance in the worldwide largest case-control sample of the severe early-onset phenotype aggressive periodontitis (AgP) with the Illumina Immunochip (600 German AgP cases, 1448 controls) and the Affymetrix 500K array set (283 German AgP cases and 972 controls) highlighted ANRIL as the major risk gene and revealed further associations with AgP for the gene PLASMINOGEN (PLG; rs4252120: P=5.9×10(-5); odds ratio, 1.27; 95% confidence interval, 1.3-1.4 [adjusted for smoking and sex]; 818 cases; 5309 controls). Subsequent combined analyses of several genome-wide data sets of CAD and AgP suggested TGFBRAP1 to be associated with AgP (rs2679895: P=0.0016; odds ratio, 1.27 [95% confidence interval, 1.1-1.5]; 703 cases; 2.143 controls) and CAD (P=0.0003; odds ratio, 0.84 [95% confidence interval, 0.8-0.9]; n=4117 cases; 5824 controls). The study further provides evidence that in addition to PLG, the currently known shared susceptibility loci of CAD and periodontitis, ANRIL and CAMTA1/VAMP3, are subjected to transforming growth factor-β regulation.

CONCLUSIONS

PLG is the third replicated shared genetic risk factor of atherosclerosis and periodontitis. All known shared risk genes of CAD and periodontitis are members of transforming growth factor-β signaling.

Association of variants on ADIPOQ and AdipoR1 and the prognosis of gastric cancer patients after gastrectomy treatment

Adiponectin is a protein hormone secreted exclusively by adipocytes and it is responsible for insulin sensitization in the human body. Deregulation of adiponectin and its downstream signaling pathway genes have been found to be involved in the gastric cancer carcinogenesis; however, whether the variants on adiponectin (ADIPOQ) and adiponectin receptor 1 (ADIPOR1) affect the prognosis of gastric cancer patients are still unknown. Here we have recruited 455 gastric cancer patients, who have received the gastrectomy treatment to evaluate the prognostic effects of variants on ADIPOQ (rs266729 and rs822395) and AdipoR1 (rs12733285 and rs1342387) for the gastric cancer patients. No significant association between the four variants and the overall survival of the gastric cancer patients was found. However, for those patients without a previous history of alcohol drinking, the rs266729 GG/CG genotype carriers showed a significantly decreased gastric cancer mortality compared to homogeneity CC patients (HR 0.74, 95 % CI 0.56-0.97; p = 0.032) after adjustment for variants age, sex, smoking status, tumor stage, tumor location and post-surgery chemotherapy. No significant association between the variant rs266729 genotypes and overall survival for the gastric cancer patients with an alcohol drinking habit. These data suggested that the variant rs266729 was an independent prognostic factor for the never drinking gastric cancer patients who received surgical treatment.

Leptin and adiponectin receptor expression in oesophageal cancer

BACKGROUND

Oesophageal adenocarcinoma is an exemplar model of an obesity-associated adenocarcinoma. Altered secretion of adipokines by visceral fat is believed to play a key role in tumorigenesis. This study examined leptin receptor (ObR) and adiponectin receptor (AdipoR1 and AdipoR2) expression in oesophageal cancer, and its relationship with patient obesity status, clinicopathological data and patient survival.

METHODS

Tissue microarrays were constructed from paraffin-embedded oesophagectomy specimens. ObR, AdipoR1 and AdipoR2 expression was quantified by immunohistochemistry. Anthropometric data were measured at the time of diagnosis, and obesity status was assessed using visceral fat area determined by computed tomography and body mass index. Receptor expression was correlated with various clinicopathological and anthropometric variables. Patient survival was estimated using the Kaplan-Meier method, and results compared between those with low versus high receptor expression. A Cox multivariable regression model was used to assess the relationship between survival and a number of co-variables.

RESULTS

All 125 tumours analysed expressed AdipoR1 and AdipoR2, whereas 96·8 per cent expressed ObR. There was no significant difference in tumour pathological features or patient obesity status between tumours with low versus high ObR expression. A high level of AdipoR1 expression was significantly associated with increased patient age, obesity and less advanced tumour (T) category. Expression of AdipoR2 was inversely associated with T category (P = 0.043). Low AdipoR1 expression was an independent predictor of improved overall survival (hazard ratio 0.56, 95 per cent confidence interval 0.35 to 0.90; P = 0.017).

CONCLUSION

The association between adiponectin receptor expression, obesity status and tumour category and survival suggests a potential mechanism linking obesity and oesophageal cancer.

Adiponectin receptor expression predicts favorable prognosis in cases of hepatocellular carcinoma

Obesity influences risk, progression and prognosis of various cancers including hepatocellular carcinoma (HCC). Adipose-tissue-derived adipokines has been considered to be involved in tumorigenesis and adiponecin, one such adipokine, has antiproliferative effect on obesity-related malignancies, though variable signal pathway mediated by adiponectin receptors-AdipoR1 and AdipoR2. In this study, we investigated expression of adiponectin and adiponectin receptors in tumor and non-tumorous hepatic tissues of HCC patients and its clinicopathological significance. We collected 75 HCC tissues and 70 non-tumorous hepatic tissues from HCC patients who underwent surgical resection. The tissue microarrays were constructed and immunohistochemical study for adiponectin, AdipoR1 and AipoR2 was performed. Adiponectin and AdipoR1 expression rates were significantly lower in HCC than non-neoplastic hepatic tissues (82.7 % vs. 97.1 % and 24.0 % vs. 90 %, P = 0.005 and <0.001, respectively). Immunopositivity for adiponectin was associated with small tumor size, low Edmonson-Steiner grade and absence of other organ invasion (P = 0.015, 0.021 and 0.028, respectively). AdipoR1 expression had association with absence of vascular invasion (P = 0.028) and AdipoR2 expression was correlated with lower histologic grade and low pathologic T-stage (P = 0.003 and 0.008, respectively). Cox regression analysis revealed that low expression of AdipoR1 and AdipoR2 were associated with increased risk of recurrence and death, respectively (hazard ration = 3.222 and 14.797, respectively). These findings suggest that loss of adiponectin, and adiponectin receptors expression is associated with aggressive clinicopathological features of HCC and AdipoR1 and AdipoR2 might serve as the independent prognostic factors for HCC patients.

Adiponectin receptors: a review of their structure, function and how they work

The discovery of adiponectin and subsequently the receptors it acts upon have lead to a great surge forward in the understanding of the development of insulin resistance and obesity-linked diseases. Adiponectin is a hormone that is derived from adipose tissue and is reduced in obesity-linked diseases including insulin resistance/type 2 diabetes and atherosclerosis. Adiponectin exerts its effects by binding to adiponectin receptors, two of which, AdipoR1 and AdipoR2, have been cloned. This has enabled researchers to carry out detailed studies elucidating the role played by these receptors and the metabolic pathways that are involved following their activation. Such studies have clearly shown that the stimulation of these receptors is associated with glucose homeostasis and ongoing research into their role will clarify the underlying molecular mechanisms of adiponectin. Such knowledge can then be used to provide therapeutic targets aimed at managing obesity-linked diseases including type 2 diabetes and metabolic syndrome.

Role of adiponectin and its receptors in cancer

Adiponectin (APN), a novel hormone/cytokine derived from adipocyte tissue, is involved in various physiological functions. Genetics, nutrition, and adiposity are factors contributing to circulating plasma concentrations of APN. Clinical correlation studies have shown that lower levels of serum APN are associated with increased malignancy of various cancers, such as breast and colon cancers, suggesting that APN has a role in tumorigenesis. APN affects insulin resistance, thus further influencing cancer development. Tumor cells may express receptors for APN. Cellular signaling is the mechanism by which APN exerts its host-protective responses. These factors suggest that serum APN levels and downstream signaling targets of APN may serve as potential diagnostic markers for malignancies. Further research is necessary to clarify the exact role of APN in cancer diagnosis and therapy.

Adiponectin receptor as a key player in healthy longevity and obesity-related diseases

Adiponectin is a fat-derived hormone whose reduction plays central roles in obesity-linked diseases including insulin resistance/type 2 diabetes and atherosclerosis. The cloning of Adiponectin receptors AdipoR1 and AdipoR2 has stimulated adiponectin research, revealing pivotal roles for AdipoRs in pleiotropic adiponectin actions, as well as some postreceptor signaling mechanisms. Adiponectin signaling has thus become one of the major research fields in metabolism and clinical medicine. Studies on AdipoRs will further our understanding of the role of adiponectin in obesity-linked diseases and shortened life span and may guide the design of antidiabetic and antiaging drugs with AdipoR as a target.

Adiponectin receptor 2 is negatively associated with lymph node metastasis of colorectal cancer

Adiponectin is a hormone secreted by adipose tissue and has a variety of functions including the inhibition of tumor growth. The expression and function of the two major adiponectin receptors, AdipoR1 and AdipoR2, in malignant tissue have not been well characterized. In the present study, we evaluated the mRNA levels of AdipoR1 and AdipoR2 expression in 48 surgically resected colorectal cancer specimens, as well as normal colonic mucosa, by quantitative RT-PCR. The values obtained were standardized by β-actin mRNA, and the correlation between their relative expression levels and the clinicopathological characteristics of the patients was examined. The relative expression levels of AdipoR1 and AdipoR2 were significantly reduced in cancer tissue compared with normal tissue (AdipoR1: 0.97±0.39 vs. 1.37±0.41, P<0.0001; AdipoR2: 0.92±0.31 vs. 1.60±0.46, P<0.0001). AdipoR1 and AdipoR2 levels were further reduced in tumors with nodal metastases and the difference was statistically significant in the case of AdipoR2 (0.79±0.27 vs. 1.02±0.30, P=0.012). The results of this study demonstrated that the expression levels of adiponectin receptors are reduced in cancer specimens compared to normal tissue, indicating a downregulation in the course of the development and progression of colorectal cancer. Since adiponectin is abundantly present in the whole body and has inhibitory effects on cancer cells, this downregulation of the receptors may be an escape mechanism of malignant cells from the suppressive effects of adiponectin.

[Obesity and gastrointestinal cancer-related factor]

Despite a higher incidence and less favorable outcome of malignant tumors in obese patients, much less recognized is the link between obesity and cancer. The mechanism of the association of obesity with carcinogenesis remains incompletely understood. Postulated mechanisms include insulin resistance, insulin-like growth factor signaling, chronic inflammation, immunomodulation, hyperglycemia-induced oxidative stress, and changes of intestinal microbiome. Insulin resistance leads to direct mitogenic and antiapoptotic signaling by insulin and the insulin-like growth factor axis. Obesity can be considered to be a state of chronic low-grade inflammation. In obesity, numerous proinflammatory cytokines are released from adipose tissue which may involve in carcinogenesis. Hyperglycemia in susceptible cells results in the overproduction of superoxide and this process is the key to initiating all damaging pathways related to diabetes. This hyperglycemia-induced oxidative stress could be one possible link among obesity, diabetes, and cancer development. The role of obesity-related changes in the intestinal microbiome in gastrointestinal carcinogenesis deserves further attention.

Adiponectin receptor-1 expression is associated with good prognosis in gastric cancer

Background

Adiponectin is inversely related to BMI, positively correlates with insulin sensitivity, and has anti-atherogenic effects. In recent years, adiponectin has been well studied in the field of oncology. Adiponectin has been shown to have antiproliferative effects on gastric cancer, and adiponectin expression is inversely correlated with clinical staging of the disease. However, no studies have reported the correlation between serum adiponectin and receptor expression with disease progression.

Methods

In this study, we evaluated expression levels of 2 adiponectin receptors--AdipoR1 and AdipoR2--and attempted to correlate their expression with prognosis in gastric cancer patients. AdipoR1 and AdipoR2 expression in gastric cancer cell lines (MKN45, TMK-1, NUGC3, and NUGC4) was evaluated by western blotting analysis, and the antiproliferative potential of adiponectin was examined in vitro. Serum adiponectin levels were evaluated in 100 gastric cancer patients, and the expression of AdipoR1 and AdipoR2 was assessed by immunohistochemical staining.

Results

MKN45 and NUGC3 expressed higher levels of AdipoR1 compared to NUGC4, even though there was no significance in AdipoR2 expression. The antiproliferative effect of adiponectin was confirmed in MKN45 and NUGC3 at 10 μg/ml. No significant associations were observed between serum adiponectin levels and clinicopathological characteristics, but lymphatic metastasis and peritoneal dissemination were significantly higher in the negative AdipoR1 immunostaining group (24/32, p = 0.013 and 9/32, p = 0.042, respectively) compared to the positive AdipoR1 group (lymphatic metastasis, 33/68; peritoneal dissemination, 8/68). On the other hand, AdipoR2 expression was only associated with histopathological type (p = 0.001). In survival analysis, the AdipoR1 positive staining group had significantly longer survival rates than the negative staining group (p = 0.01). However, multivariate analysis indicated that AdipoR1 was not an independent prognostic factor on patient's survival on gastric cancer.

Conclusions

In gastric cancer, adiponectin has the possibility to be involved in cell growth suppression via AdipoR1. The presence of AdipoR1 could be a novel anticancer therapeutic target in gastric cancer.

Serum adiponectin levels and tissue expression of adiponectin receptors are associated with risk, stage, and grade of colorectal cancer

Adiponectin has been associated with colorectal cancer (CRC) risk. This study aims to investigate the association of both adiponectin and tissue expression of its receptors with CRC risk as well as clinicopathological characteristics, notably stage and grade. Determination of serum adiponectin and immunohistochemical expression of adiponectin receptors in adenocarcinoma/normal colorectal tissue was performed in samples from 104 newly diagnosed CRC patients and 208 age- and sex-matched controls. Multiple logistic regression odds ratios and 95% confidence intervals for CRC risk were derived, controlling for a series of covariates. Serum adiponectin was negatively associated with CRC risk (odds ratio, 0.72; confidence interval, 0.53-0.99) and also with tumor grade (P = .05). Expression of both adiponectin receptors was stronger in adenocarcinoma vs normal tissue (P = .001). AdipoR1 expression was negatively associated with nodal stage (P = .03); AdipoR2 expression was positively associated with tumor, node, metastasis stage (P = .01). Established positive associations with red meat consumption and diabetes, and negative associations with physical exercise and plant food consumption were confirmed along with a more than 60% higher risk associated with central obesity. Adiponectin levels and tissue expression of hormonal receptors seem to be associated not only with CRC risk but also with components of clinicopathological characteristics; given power limitations, these results should be interpreted with caution. The exact nature of the association and the underlying pathophysiological mechanisms need to be further examined in large prospective studies assessing adiponectin and its receptors as novel targets for exploring CRC growth.

The implication of adiponectin and resistin in gastrointestinal diseases

Adiponectin and resistin, members of the adipokine family, are multi-task hormones involved in several disorders, including those of the alimentary tract. In the present review, eligible studies focusing on the role of adiponectin and resistin in gastrointestinal diseases are manifested together and classified according to anatomic criteria. In addition, similarities and common patterns have been recognized, ultimately revealing an inverse association: the down-regulation of adiponectin and up-regulation of resistin - both in vitro and in vivo - in gastrointestinal disorders, irrespective of their diverse nature - inflammatory, autoimmune or malignant - or anatomic position - esophageal, gastric, of the small intestine, colonic. Finally, a potential role for both adipokines in alimentary tract-related carcinogenesis has been identified, possibly representing a missing link between obesity and cancer.

Excess body weight and obesity--the link with gastrointestinal and hepatobiliary cancer

Excess body weight (EBW) is an independent risk factor for many human malignancies, including cancers throughout the gastrointestinal and hepatobiliary tract from the esophagus to the colorectum. The relative risk of gastrointestinal cancer in obese individuals is approximately 1.5-2.0 times that for normal weight individuals, with organ-specific and gender-specific differences for specific cancers. The association between EBW and risk of premalignant stages of gastrointestinal carcinogenesis, such as colorectal adenoma and Barrett esophagus, is similar, implying a role for EBW during the early stages of carcinogenesis that could be relevant to preventative strategies. EBW also impacts negatively on gastrointestinal cancer outcomes. The mechanistic basis of the association between EBW and carcinogenesis remains incompletely understood. Postulated mechanisms include increased insulin and insulin-like growth factor signaling and chronic inflammation (both linked to the metabolic syndrome), as well as signaling via adipokines, such as leptin. The role of obesity-related changes in the intestinal microbiome in gastrointestinal carcinogenesis deserves further attention. Whether weight loss leads to reduced future gastrointestinal and liver cancer risk has yet to be fully explored. There is some support for the idea that weight loss negatively regulates colorectal carcinogenesis. In addition, data suggest a reduction in risk of several cancers in the first 10 years after bariatric surgery.