Adiponectin receptor agonists inhibit leptin induced pSTAT3 and in vivo pancreatic tumor growth

Reevaluating Adiponectin's impact on obesity hypertension: a Chinese case-control study

BACKGROUND

Obesity and hypertension are major risk factors for cardiovascular diseases that affect millions of people worldwide. Both conditions are associated with chronic low-grade inflammation, which is mediated by adipokines such as adiponectin. Adiponectin is the most abundant adipokine that has a beneficial impact on metabolic and vascular biology, while high serum concentrations are associated with some syndromes. This "adiponectin paradox" still needs to be clarified in obesity-associated hypertension. The aim of this study was to investigate how adiponectin affects blood pressure, inflammation, and metabolic function in obesity hypertension using a Chinese adult case-control study.

METHODS

A case-control study that had finished recruiting 153 subjects divided as four characteristic groups. Adiponectin serum levels were tested by ELISA in these subjects among these four characteristic Chinese adult physical examination groups. Waist circumference (WC), body mass index (BMI), systolic blood pressure (SB), diastolic blood pressure (DB), and other clinical laboratory data were collected. Analyzation of correlations between the research index and differences between groups was done by SPSS.

RESULTS

Serum adiponectin levels in the| normal healthy group (NH group) were significantly higher than those in the newly diagnosed untreated just-obesity group (JO group), and negatively correlated with the visceral adiposity index. With multiple linear egression analysis, it was found that, for serum adiponectin, gender, serum albumin (ALB), alanine aminotransferase (ALT) and high-density lipoprotein cholesterol (HDLC) were the significant independent correlates, and for SB, age and HDLC were the significant independent correlates, and for DB, alkaline phosphatase (ALP) was the significant independent correlate. The other variables did not reach significance in the model.

CONCLUSIONS

Our study reveals that adiponectin's role in obesity-hypertension is multifaceted and is influenced by the systemic metabolic homeostasis signaling axis. In obesity-related hypertension, compensatory effects, adiponectin resistance, and reduced adiponectin clearance from impaired kidneys and liver all contribute to the "adiponectin paradox".

Exploring the logic and conducting a comprehensive evaluation of AdipoRon-based adiponectin replacement therapy against hormone-related cancers-a systematic review

The potential benefits of adiponectin replacement therapy extend to numerous human diseases, with current research showing particular interest in its effectiveness against specific cancer forms, especially hormone-related. However, limitations in the pharmacological use of the intact protein have led to a focus on alternative options. AdipoRon is an extensively studied non-peptidic drug candidate for adiponectin replacement therapy. While researchers have explored the efficacy and therapeutic applications of AdipoRon in various disease conditions, their effects against cancer models advanced more, with no review regarding AdipoRon's efficacy against hormone-related cancers being published. The present systematic review aims to fill this gap. Preclinical evidence was compiled from PubMed, EMBASE, COCHRANE, and Google Scholar following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the manuscript's quality assessment was conducted using the Joanna Briggs Institute (JBI) Checklist Critical Appraisal Tool for Systematic Reviews' Quality. The included nine studies incorporated various cell and animal models of the pancreas, gynaecological system, and osteosarcoma cancers. AdipoRon demonstrated effectiveness against pancreatic cancer by activating p44/42 MAPK, mitochondrial dysfunction, and AMPK-mediated inhibition of ACC1. In gynaecological cancers, it exhibited promising anticancer effects through the activation of AMPK, potential inhibition of mTOR, and modulation of the SET1B/BOD1/AdipoR1 signaling cascade. Against osteosarcoma, AdipoRon worked by perturbing ERK1/2 signaling and reducing p70S6K phosphorylation. AdipoRon shows promise in preclinical studies, but human trials are crucial for clinical safety and effectiveness. Caution is needed due to potential off-target effects, especially in cancer therapy with multi-target approaches. Structural biology and computational methods can help predict these effects.

Resistin in endocrine pancreas of sheep: Presence and expression related to different diets

Resistin (RETN), a recently discovered adipokine, is a cysteine-rich and secretory protein produced by adipocytes. RETN has been detected in several tissues, including human and laboratory animals' pancreas, wherein impairs glucose tolerance and insulin (INS) action and causes INS resistance. This study aims to evaluate the presence and expression of RETN in the pancreas of 15 adult female sheep reared on Apennine pastures, which show a decrease in their nutritional value due to the drought stress linked to the increasing summer aridity. The sheep were divided into 3 groups according to the diet they were subjected to: maximum pasture flowering (MxF) group, maximum pasture dryness (MxD) group, and experimental (Exp) group which received a feed supplementation in addition to the MxD group feeding. Immunohistochemistry and immunofluorescence were performed on formalin-fixed and paraffin-embedded sections of the pancreas to detect the RETN presence and to evaluate the co-localization of RETN with both glucagon (GCG)- and INS-producing cells. In addition, the expression of the three molecules was evaluated also in relation to different diets. RETN was observed only in the endocrine pancreas, showing a wide distribution throughout the pancreatic islets with few negative cells and the RETN producing cells colocalized with both α cells and ß cells. No differences in distribution and immunostaining intensity of RETN, GCG and INS were observed among the three groups. Quantitative PCR showed the expression of RETN, GCG and INS in all tested samples. No significant differences were observed for RETN and GCG among all three groups of sheep. Instead, a high statistically significant expression of INS was detected in the MxF group with respect to the Exp and MxD groups. These results highlight the localization of RETN in GCG- and INS-secreting cells involved in glucose homeostasis suggesting a modulatory role for RETN. Furthermore, the RETN expression is not influenced by food supplementation and thus is not affected by diet.

AdipoRon and ADP355, adiponectin receptor agonists, in Metabolic-associated Fatty Liver Disease (MAFLD) and Nonalcoholic Steatohepatitis (NASH): A systematic review

Adiponectin replacement therapy holds the potential to benefit numerous human diseases, and ongoing research applies particular interest in how adiponectin acts against Metabolic-associated Fatty Liver Disease (MAFLD) and Nonalcoholic Steatohepatitis (NASH). However, the pharmacological limitations of the intact protein have prompted a focus on alternative options, specifically peptidic and small molecule agonists targeting the adiponectin receptor. AdipoRon is an extensively researched non-peptidic drug candidate in adiponectin replacement therapy. In turn, ADP355 is an adiponectin-based active short peptide. They have garnered significant attention due to their potential as substitutes for adiponectin. Researchers have studied AdipoRon's and ADP355's efficacy and therapeutic applications in various disease conditions. However, the effects of AdipoRon and ADP355 against NAFLD and NASH models advanced more, and no systematic review explored this area before. This systematic review was conceived to address the deficiency mentioned above and consider the lack of clinical evidence. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were utilized. To assess the risk of bias in systematic review, The Joanna Briggs Institute (JBI) Critical Appraisal Checklist was employed. Results from pre-clinical evidence show that AdipoRon and ADP355 represent promising effects in NAFLD and NASH-related models, including reducing hepatic steatosis, modulating inflammation, improving insulin sensitivity, enhancing mitochondrial function, and protecting against liver fibrosis. While AdipoRon and ADP355 exhibit promise in pre-clinical studies and experimental models, additional clinical trials are necessary to assess their effectiveness, safety, and potential translational therapeutic potential uses in NAFLD and NASH human cases.

Decoding the obesity-cancer connection: lessons from preclinical models of pancreatic adenocarcinoma

Obesity is a metabolic state of energy excess and a risk factor for over a dozen cancer types. Because of the rising worldwide prevalence of obesity, decoding the mechanisms by which obesity promotes tumor initiation and early progression is a societal imperative and could broadly impact human health. Here, we review results from preclinical models that link obesity to cancer, using pancreatic adenocarcinoma as a paradigmatic example. We discuss how obesity drives cancer development by reprogramming the pretumor or tumor cell and its micro- and macro-environments. Specifically, we describe evidence for (1) altered cellular metabolism, (2) hormone dysregulation, (3) inflammation, and (4) microbial dysbiosis in obesity-driven pancreatic tumorigenesis, denoting variables that confound interpretation of these studies, and highlight remaining gaps in knowledge. Recent advances in preclinical modeling and emerging unbiased analytic approaches will aid in further unraveling the complex link between obesity and cancer, informing novel strategies for prevention, interception, and therapy in pancreatic adenocarcinoma and other obesity-associated cancers.

Sex-Specific Associations between Adiponectin and Leptin Signaling and Pancreatic Cancer Survival

BACKGROUND

Circulating adiponectin and leptin have been associated with risk of pancreatic cancer. However, the relationship between long-term exposure to these adipokines in the prediagnostic period with patient survival has not been investigated.

METHODS

Adipokine levels were measured in prospectively collected samples from 472 patients with pancreatic cancer. Because of sex-specific differences in adipokine levels, associations were evaluated separately for men and women. In a subset of 415 patients, we genotyped 23 SNPs in adiponectin receptor genes (ADIPOR1 and ADIPOR2) and 30 SNPs in the leptin receptor gene (LEPR).

RESULTS

Adiponectin levels were inversely associated with survival in women [HR, 1.71; 95% confidence interval (CI), 1.15-2.54]; comparing top with bottom quartile but not in men (HR, 0.89; 95% CI, 0.46-1.70). The SNPs rs10753929 and rs1418445 in ADIPOR1 were associated with survival in the combined population (per minor allele HR, 0.66; 95% CI, 0.51-0.84, and HR, 1.33; 95% CI, 1.12-1.58, respectively). Among SNPs in LEPR, rs12025906, rs3790431, and rs17127601 were associated with survival in the combined population [HRs, 1.54 (95% CI, 1.25-1.90), 0.72 (95% CI, 0.59-0.88), and 0.70 (95% CI, 0.56-0.89), respectively], whereas rs11585329 was associated with survival in men only (HR, 0.39; 95% CI, 0.23-0.66; Pinteraction = 0.0002).

CONCLUSIONS

High levels of adiponectin in the prediagnostic period were associated with shorter survival among women, but not among men with pancreatic cancer. Several polymorphisms in ADIPOR1 and LEPR are associated with patient survival.

IMPACT

Our findings reveal the association between adipokine signaling and pancreatic cancer survival and demonstrate the importance of examining obesity-associated pathways in relation to pancreatic cancer in a sex-specific manner.

SHP2 regulates adipose maintenance and adipocyte-pancreatic cancer cell crosstalk via PDHA1

Adipocytes are the most abundant cell type in the adipose tissue, and their dysfunction is a significant driver of obesity-related pathologies, such as cancer. The mechanisms that (1) drive the maintenance and secretory activity of adipocytes and (2) mediate the cancer cellular response to the adipocyte-derived factors are not fully understood. To address that gap of knowledge, we investigated how alterations in Src homology region 2-containing protein (SHP2) activity affect adipocyte function and tumor crosstalk. We found that phospho-SHP2 levels are elevated in adipose tissue of obese mice, obese patients, and differentiating adipocytes. Immunofluorescence and immunoprecipitation analyses as well as in-silico protein-protein interaction modeling demonstrated that SHP2 associates with PDHA1, and that a positive association promotes a reactive oxygen species (ROS)-driven adipogenic program. Accordingly, this SHP2-PDHA1-ROS regulatory axis was crucial for adipocyte maintenance and secretion of interleukin-6 (IL-6), a key cancer-promoting cytokine. Mature adipocytes treated with an inhibitor for SHP2, PDHA1, or ROS exhibited an increased level of pro-lipolytic and thermogenic proteins, corresponding to an increased glycerol release, but a suppression of secreted IL-6. A functional analysis of adipocyte-cancer cell crosstalk demonstrated a decreased migration, invasion, and a slight suppression of cell cycling, corresponding to a reduced growth of pancreatic cancer cells exposed to conditioned media (CM) from mature adipocytes previously treated with inhibitors for SHP2/PDHA1/ROS. Importantly, PDAC cell growth stimulation in response to adipocyte CM correlated with PDHA1 induction but was suppressed by a PDHA1 inhibitor. The data point to a novel role for (1) SHP2-PDHA1-ROS in adipocyte maintenance and secretory activity and (2) PDHA1 as a regulator of the pancreatic cancer cells response to adipocyte-derived factors.

Combined PI3K and MAPK inhibition synergizes to suppress PDAC

Oncogenic KRAS mutations are nearly ubiquitous in pancreatic ductal adenocarcinoma (PDAC), yet therapeutic attempts to target KRAS as well as its target MAPK pathway effectors have shown limited success due to the difficulty to pharmacologically target KRAS, inherent drug resistance in PDAC cells, and acquired resistance through activation of alternative mitogenic pathways such JAK-STAT and PI3K-AKT. While KRAS canonically drives the MAPK signaling pathway via RAF-MEK-ERK, it is also known to play a role in PI3K-AKT signaling. Our therapeutic study targeted the PI3K-AKT pathway with the drug Omipalisib (p110α/β/δ/γ and mTORC1/2 inhibitor) in combination with MAPK pathway targeting drug Trametinib (MEK1/2 inhibitor) or SHP099-HCL (SHP099), which is an inhibitor of the KRAS effector SHP2. Western blot analysis demonstrated that application of Trametinib or SHP099 alone selectively blocked ERK phosphorylation (pERK) but failed to suppress phosphorylated AKT (pAKT) and in some instances increased pAKT levels. Conversely, Omipalisib alone successfully inhibited pAKT but failed to suppress pERK. Therefore, we hypothesized that a combination therapeutic comprised of Omipalisib with either Trametinib or SHP099 would inhibit two prominent mitogenic pathways, MEK and PI3K-AKT, to more effectively suppress pancreatic cancer. In vitro studies demonstrated that both Omipalisib/Trametinib and Omipalisib/SHP099 combination therapeutic strategies were generally more effective than treatment with each drug individually at reducing proliferation, colony formation, and cell migration compared to vehicle controls. Additionally, we found that while combination Omipalisib/SHP099 treatment reduced implanted tumor growth in vivo , the Omipalisib/Trametinib treatment was significantly more effective. Therefore, we additionally tested the Omipalisib/Trametinib combination therapeutic in the highly aggressive PKT (Ptf1a cre , LSL-Kras G12D , TGFbR2 fl/fl ) spontaneous mouse model of PDAC. We subsequently found that PKT mice treated with the Omipalisib/Trametinib combination therapeutic survived significantly longer than mice treated with either drug alone, and more than doubled the mean survival time of vehicle control mice. Altogether, our data support the importance of a dual treatment strategy targeting both MAPK and PI3K-AKT pathways.

Assessment of the Role of Leptin and Adiponectinas Biomarkers in Pancreatic Neuroendocrine Neoplasms

Data on the possible connection between circulating adipokines and PanNENs are limited. This novel study aimed to assess the serum levels of leptin and adiponectin and their ratio in patients with PanNENs and to evaluate the possible relationship between them and PanNEN's grade or stage, including the presence of metastases. The study group consisted of PanNENs (n = 83), and healthy controls (n = 39). Leptin and adiponectin measurement by an ELISA assay was undertaken in the entire cohort. The serum concentration of adiponectin was significantly higher in the control group compared to the study group (p < 0.001). The concentration of leptin and adiponectin was significantly higher in females than in males (p < 0.01). Anincreased leptin-adiponectin ratio was observed in well-differentiated PanNENs (G1) vs. moderatelydifferentiated PanNENs (G2) (p < 0.05). An increased leptin-adiponectin ratio was found in PanNENs with Ki-67 < 3% vs. Ki-67 ≥ 3% (p < 0.05). PanNENs with distal disease presented lower leptin levels (p < 0.001) and a decreased leptin-adiponectin ratio (p < 0.01) compared with the localized disease group. Leptin, adiponectin, and the leptin-adiponectin ratio may serve as potential diagnostic, prognostic, and predictive biomarkers for PanNENs. Leptin levels and the leptin-adiponectin ratio may play an important role as predictors of malignancy and metastasis in PanNENs.

New insights into the role of adipocytes in pancreatic cancer progression: paving the way towards novel therapeutic targets

Pancreatic cancer (PC) remains one of the most lethal malignancies across the world, which is due to delayed diagnosis and resistance to current therapies. The interactions between pancreatic tumor cells and their tumor microenvironment (TME) allow cancer cells to escape from anti-cancer therapies, leading to difficulties in treating PC. With endocrine function and lipid storage capacity, adipose tissue can maintain energy homeostasis. Direct or indirect interaction between adipocytes and PC cells leads to adipocyte dysfunction characterized by morphological change, fat loss, abnormal adipokine secretion, and fibroblast-like transformation. Various adipokines released from dysfunctional adipocytes have been reported to promote proliferation, invasion, metastasis, stemness, and chemoresistance of PC cells via different mechanisms. Additional lipid outflow from adipocytes can be taken into the TME and thus alter the metabolism in PC cells and surrounding stromal cells. Besides, the trans-differentiation potential enables adipocytes to turn into various cell types, which may give rise to an inflammatory response as well as extracellular matrix reorganization to modulate tumor burden. Understanding the molecular basis behind the protumor functions of adipocytes in PC may offer new therapeutic targets.

Cell-Autonomous Cxcl1 Sustains Tolerogenic Circuitries and Stromal Inflammation via Neutrophil-Derived TNF in Pancreatic Cancer

We have shown that KRAS-TP53 genomic coalteration is associated with immune-excluded microenvironments, chemoresistance, and poor survival in pancreatic ductal adenocarcinoma (PDAC) patients. By treating KRAS-TP53 cooperativity as a model for high-risk biology, we now identify cell-autonomous Cxcl1 as a key mediator of spatial T-cell restriction via interactions with CXCR2+ neutrophilic myeloid-derived suppressor cells in human PDAC using imaging mass cytometry. Silencing of cell-intrinsic Cxcl1 in LSL-KrasG12D/+;Trp53R172H/+;Pdx-1Cre/+(KPC) cells reprograms the trafficking and functional dynamics of neutrophils to overcome T-cell exclusion and controls tumor growth in a T cell-dependent manner. Mechanistically, neutrophil-derived TNF is a central regulator of this immunologic rewiring, instigating feed-forward Cxcl1 overproduction from tumor cells and cancer-associated fibroblasts (CAF), T-cell dysfunction, and inflammatory CAF polarization via transmembrane TNF-TNFR2 interactions. TNFR2 inhibition disrupts this circuitry and improves sensitivity to chemotherapy in vivo. Our results uncover cancer cell-neutrophil cross-talk in which context-dependent TNF signaling amplifies stromal inflammation and immune tolerance to promote therapeutic resistance in PDAC.

SIGNIFICANCE

By decoding connections between high-risk tumor genotypes, cell-autonomous inflammatory programs, and myeloid-enriched/T cell-excluded contexts, we identify a novel role for neutrophil-derived TNF in sustaining immunosuppression and stromal inflammation in pancreatic tumor microenvironments. This work offers a conceptual framework by which targeting context-dependent TNF signaling may overcome hallmarks of chemoresistance in pancreatic cancer. This article is highlighted in the In This Issue feature, p. 1275.

Obesity and endocrine-related cancer: The important role of IGF-1

Obesity is increasingly becoming a global epidemic of concern and is considered a risk factor for several endocrine-related cancers. Moreover, obesity is associated with cancer development and poor prognosis. As a metabolic abnormality, obesity leads to a series of changes in insulin, IGF-1, sex hormones, IGFBPs, and adipokines. Among these factors, IGF-1 plays an important role in obesity-related endocrine cancers. This review describes the role of obesity in endocrine-related cancers, such as prostate cancer, breast cancer and pancreatic cancer, focusing on the mechanism of IGF-1 and the crosstalk with estrogen and adipokines. In addition, this review briefly introduces the current status of IGF-1R inhibitors in clinical practice and shows the prospect of IGF-1R inhibitors in combination with other anticancer drugs.

Targeting Adiponectin in Breast Cancer

Obesity and breast cancer are two major health issues that could be categorized as sincere threats to human health. In the last few decades, the relationship between obesity and cancer has been well established and extensively investigated. There is strong evidence that overweight and obesity increase the risk of postmenopausal breast cancer, and adipokines are the central players in this relationship. Produced and secreted predominantly by white adipose tissue, adiponectin is a bioactive molecule that exhibits numerous protective effects and is considered the guardian angel of adipokine. In the obesity-cancer relationship, more and more evidence shows that adiponectin may prevent and protect individuals from developing breast cancer. Recently, several updates have been published on the implication of adiponectin in regulating tumor development, progression, and metastases. In this review, we provide an updated overview of the metabolic signaling linking adiponectin and breast cancer in all its stages. On the other hand, we critically summarize all the available promising candidates that may reactivate these pathways mainly by targeting adiponectin receptors. These molecules could be synthetic small molecules or plant-based proteins. Interestingly, the advances in genomics have made it possible to create peptide sequences that could specifically replace human adiponectin, activate its receptor, and mimic its function. Thus, the obvious anti-cancer activity of adiponectin on breast cancer should be better exploited, and adiponectin must be regarded as a serious biomarker that should be targeted in order to confront this threatening disease.

Adiponectin Suppresses Metastasis of Nasopharyngeal Carcinoma through Blocking the Activation of NF-κB and STAT3 Signaling

Adiponectin is an adipocytokine with anti-inflammatory and anticancer properties. Our previous study has shown that blood adiponectin levels were inversely correlated to the risk of nasopharyngeal carcinoma (NPC), and that adiponectin could directly suppress the proliferation of NPC cells. However, the effect of adiponectin on NPC metastasis remains unknown. Here, we revealed in clinical studies that serum adiponectin level was inversely correlated with tumor stage, recurrence, and metastasis in NPC patients, and that low serum adiponectin level also correlates with poor metastasis-free survival. Coculture with recombinant adiponectin suppressed the migration and invasion of NPC cells as well as epithelial-mesenchymal transition (EMT). In addition, recombinant adiponectin dampened the activation of NF-κB and STAT3 signaling pathways induced by adipocyte-derived proinflammatory factors such as leptin, IL-6, and TNF-α. Pharmacological activation of adiponectin receptor through its specific agonist, AdipoRon, largely stalled the metastasis of NPC cells. Taken together, these findings demonstrated that adiponectin could not only regulate metabolism and inhibit cancer growth, but also suppress the metastasis of NPC. Pharmacological activation of adiponectin receptor may be a promising therapeutic strategy to stall NPC metastasis and extend patients' survival.

Obesity and Pancreatic Cancer: Recent Progress in Epidemiology, Mechanisms and Bariatric Surgery

More than 30% of people in the United States (US) are classified as obese, and over 50% are considered significantly overweight. Importantly, obesity is a risk factor not only for the development of metabolic syndrome but also for many cancers, including pancreatic ductal adenocarcinoma (PDAC). PDAC is the third leading cause of cancer-related death, and 5-year survival of PDAC remains around 9% in the U.S. Obesity is a known risk factor for PDAC. Metabolic control and bariatric surgery, which is an effective treatment for severe obesity and allows massive weight loss, have been shown to reduce the risk of PDAC. It is therefore clear that elucidating the connection between obesity and PDAC is important for the identification of a novel marker and/or intervention point for obesity-related PDAC risk. In this review, we discussed recent progress in obesity-related PDAC in epidemiology, mechanisms, and potential cancer prevention effects of interventions, including bariatric surgery with preclinical and clinical studies.

Integrating Gemcitabine-Based Therapy With AdipoRon Enhances Growth Inhibition in Human PDAC Cell Lines

Pancreatic ductal adenocarcinoma (PDAC) accounts for 90% of all pancreatic cancers. Albeit its incidence does not score among the highest in cancer, PDAC prognosis is tremendously fatal. As a result of either aggressiveness or metastatic stage at diagnosis, chemotherapy constitutes the only marginally effective therapeutic approach. As gemcitabine (Gem) is still the cornerstone for PDAC management, the low response rate and the onset of resistant mechanisms claim for additional therapeutic strategies. The first synthetic orally active adiponectin receptor agonist AdipoRon (AdipoR) has recently been proposed as an anticancer agent in several tumors, including PDAC. To further address the AdipoR therapeutic potential, herein we investigated its pharmacodynamic interaction with Gem in human PDAC cell lines. Surprisingly, their simultaneous administration revealed a more effective action in contrasting PDAC cell growth and limiting clonogenic potential than single ones. Moreover, the combination AdipoR plus Gem persisted in being effective even in Gem-resistant MIA PaCa-2 cells. While a different ability in braking cell cycle progression between AdipoR and Gem supported their cooperating features in PDAC, mechanistically, PD98059-mediated p44/42 MAPK ablation hindered combination effectiveness. Taken together, our findings propose AdipoR as a suitable partner in Gem-based therapy and recognize the p44/42 MAPK pathway as potentially involved in combination outcomes.

TNF-α Antagonizes the Effect of Leptin on Insulin Secretion through FOXO1-Dependent Transcriptional Suppression of LepRb in INS-1 Cells

Proinflammatory cytokines play a causal role in the development of hyperinsulinemia and T2MD. FOXO1, a transcription factor which is known to enhance proinflammation, was recently shown to be involved in obesity-induced β cell dysfunction. However, molecular mechanisms for the association remained elusive. In this study, we first found that both leptin (10 nM) and TNF-α (20 ng/ml) significantly inhibited glucose-stimulated insulin secretion (GSIS) of INS-1E cells. When in combination, the GSIS function of INS-1E cells was significantly increased compared with that of the leptin alone treatment, indicating that TNF-α attenuated the inhibiting effect of leptin on GSIS of INS-1E cells. Similarly, we found that TNF-α has the same inhibitory effect on leptin in regulating insulin synthesis and secretion, and the survival and apoptosis of insulin cells. Further studies showed that TNF-α blocks leptin pathway by reducing the expression of leptin receptor (LepRb, also called OBRb) and inhibiting the activation of STAT3, a key molecule involved in the leptin signaling pathway in INS-1E cells. Besides, the downregulated expression of phosphorylated FOXO1 was found to be involved in the possible mechanism of TNF-α. Overexpression of constitutively active FOXO1 markedly aggravated the LepRb reduction by TNF-α treatment of INS-1E cells, and the endogenous FOXO1 knockdown abolished the effect of TNF-α on INS-1E cells. Furthermore, we have proved that FOXO1 could directly bind to the promoter of LepRb as a negative transcription regulator. Taken together, the results of this study reveal that TNF-α-induced LepRb downregulated in pancreatic β cells and demonstrate that transcriptional reduction of FOXO1 might be the primary mechanism underlying TNF-α promoting INS-1E leptin resistance and β cell dysfunction. Conclusions. Our current studies based on INS-1E cells in vitro indicate that the inflammatory factor TNF-α plays an important role in the development of INS-1E leptin resistance and glucose metabolism disorders, probably through FOXO1-induced transcription reduction of LepRb promoter in pancreatic β cells, and FOXO1 may be a novel target for treating β cell dysfunction in obesity-induced hyperinsulinemia and T2DM.

Synthetic adiponectin-receptor agonist, AdipoRon, induces glycolytic dependence in pancreatic cancer cells

Obesity creates a localized inflammatory reaction in the adipose, altering secretion of adipocyte-derived factors that contribute to pathologies including cancer. We have previously shown that adiponectin inhibits pancreatic cancer by antagonizing leptin-induced STAT3 activation. Yet, the effects of adiponectin on pancreatic cancer cell metabolism have not been addressed. In these studies, we have uncovered a novel metabolic function for the synthetic adiponectin-receptor agonist, AdipoRon. Treatment of PDAC cells with AdipoRon led to mitochondrial uncoupling and loss of ATP production. Concomitantly, AdipoRon-treated cells increased glucose uptake and utilization. This metabolic switch further correlated with AMPK mediated inhibition of the prolipogenic factor acetyl coenzyme A carboxylase 1 (ACC1), which is known to initiate fatty acid catabolism. Yet, measurements of fatty acid oxidation failed to detect any alteration in response to AdipoRon treatment, suggesting a deficiency for compensation. Additional disruption of glycolytic dependence, using either a glycolysis inhibitor or low-glucose conditions, demonstrated an impairment of growth and survival of all pancreatic cancer cell lines tested. Collectively, these studies provide evidence that pancreatic cancer cells utilize metabolic plasticity to upregulate glycolysis in order to adapt to suppression of oxidative phosphorylation in the presence of AdipoRon.

Obesity and Pancreatic Cancer: Insight into Mechanisms

Simple Summary

Obesity is recognized as a chronic progressive disease and risk factor for many human diseases. The high and increasing number of obese people may underlie the expected increase in pancreatic cancer cases in the United States. There are several pathways discussed that link obesity with pancreatic cancer. Adipose tissue and adipose tissue-released factors may thereby play an important role. This review discusses selected mechanisms that may accelerate pancreatic cancer development in obesity.

Abstract

The prevalence of obesity in adults and children has dramatically increased over the past decades. Obesity has been declared a chronic progressive disease and is a risk factor for a number of metabolic, inflammatory, and neoplastic diseases. There is clear epidemiologic and preclinical evidence that obesity is a risk factor for pancreatic cancer. Among various potential mechanisms linking obesity with pancreatic cancer, the adipose tissue and obesity-associated adipose tissue inflammation play a central role. The current review discusses selected topics and mechanisms that attracted recent interest and that may underlie the promoting effects of obesity in pancreatic cancer. These topics include the impact of obesity on KRAS activity, the role of visceral adipose tissue, intrapancreatic fat, adipose tissue inflammation, and adipokines on pancreatic cancer development. Current research on lipocalin-2, fibroblast growth factor 21, and Wnt5a is discussed. Furthermore, the significance of obesity-associated insulin resistance with hyperinsulinemia and obesity-induced gut dysbiosis with metabolic endotoxemia is reviewed. Given the central role that is occupied by the adipose tissue in obesity-promoted pancreatic cancer development, preventive and interceptive strategies should be aimed at attenuating obesity-associated adipose tissue inflammation and/or at targeting specific molecules that mechanistically link adipose tissue with pancreatic cancer in obese patients.

Combined Blockade of MEK and CDK4/6 Pathways Induces Senescence to Improve Survival in Pancreatic Ductal Adenocarcinoma

Activating KRAS mutations, a defining feature of pancreatic ductal adenocarcinoma (PDAC), promote tumor growth in part through the activation of cyclin-dependent kinases (CDK) that induce cell-cycle progression. p16INK4a (p16), encoded by the gene CDKN2A, is a potent inhibitor of CDK4/6 and serves as a critical checkpoint of cell proliferation. Mutations in and subsequent loss of the p16 gene occur in PDAC at a rate higher than that reported in any other tumor type and results in Rb inactivation and unrestricted cellular growth. Therefore, strategies targeting downstream RAS pathway effectors combined with CDK4/6 inhibition (CDK4/6i) may have the potential to improve outcomes in this disease. Herein, we show that expression of p16 is markedly reduced in PDAC tumors compared with normal pancreatic or pre-neoplastic tissues. Combined MEK inhibition (MEKi) and CDK4/6i results in sustained downregulation of both ERK and Rb phosphorylation and a significant reduction in cell proliferation compared with monotherapy in human PDAC cells. MEKi with CDK4/6i reduces tumor cell proliferation by promoting senescence-mediated growth arrest, independent of apoptosis in vitro We show that combined MEKi and CDK4/6i treatment attenuates tumor growth in xenograft models of PDAC and improves overall survival over 200% compared with treatment with vehicle or individual agents alone in Ptf1acre/+ ;LSL-KRASG12D/+ ;Tgfbr2flox/flox (PKT) mice. Histologic analysis of PKT tumor lysates reveal a significant decrease in markers of cell proliferation and an increase in senescence-associated markers without any significant change in apoptosis. These results demonstrate that combined targeting of both MEK and CDK4/6 represents a novel therapeutic strategy to synergistically reduce tumor growth through induction of cellular senescence in PDAC.

PEGylated AdipoRon derivatives improve glucose and lipid metabolism under insulinopenic and high-fat diet conditions

The pleiotropic actions of adiponectin in improving cell survival and metabolism have motivated the development of small-molecule therapeutic agents for treating diabetes and lipotoxicity. AdipoRon is a synthetic agonist of the adiponectin receptors, yet is limited by its poor solubility and bioavailability. In this work, we expand on the protective effects of AdipoRon in pancreatic β-cells and examine how structural modifications could affect the activity, pharmacokinetics, and bioavailability of this small molecule. We describe a series of AdipoRon analogs containing amphiphilic ethylene glycol (PEG) chains. Among these, AdipoRonPEG5 induced pleiotropic effects in mice under insulinopenic and high-fat diet (HFD) conditions. While both AdipoRon and AdipoRonPEG5 substantially attenuate palmitate-induced lipotoxicity in INS-1 cells, only AdipoRonPEG5 treatment is accompanied by a significant reduction in cytotoxic ceramides. In vivo, AdipoRonPEG5 can substantially reduce pancreatic, hepatic, and serum ceramide species, with a concomitant increase in the corresponding sphingoid bases and improves insulin sensitivity of mice under HFD feeding conditions. Furthermore, hyperglycemia in streptozotocin (STZ)-induced insulinopenic adiponectin-null mice is also attenuated upon AdipoRonPEG5 treatment. Our results suggest that AdipoRonPEG5 is more effective in reducing ceramides and dihydroceramides in the liver of HFD-fed mice than AdipoRon, consistent with its potent activity in activating ceramidase in vitro in INS-1 cells. Additionally, these results indicate that the beneficial effects of AdipoRonPEG5 can be partially attributed to improved pharmacokinetics as compared with AdipoRon, thus suggesting that further derivatization may improve affinity and tissue-specific targeting.

Role of Perivascular Adipose Tissue-Derived Adiponectin in Vascular Homeostasis

Studies of adipose tissue biology have demonstrated that adipose tissue should be considered as both passive, energy-storing tissue and an endocrine organ because of the secretion of adipose-specific factors, called adipokines. Adiponectin is a well-described homeostatic adipokine with metabolic properties. It regulates whole-body energy status through the induction of fatty acid oxidation and glucose uptake. Adiponectin also has anti-inflammatory and antidiabetic properties, making it an interesting subject of biomedical studies. Perivascular adipose tissue (PVAT) is a fat depot that is conterminous to the vascular wall and acts on it in a paracrine manner through adipokine secretion. PVAT-derived adiponectin can act on the vascular wall through endothelial cells and vascular smooth muscle cells. The present review describes adiponectin's structure, receptors, and main signaling pathways. We further discuss recent studies of the extent and nature of crosstalk between PVAT-derived adiponectin and endothelial cells, vascular smooth muscle cells, and atherosclerotic plaques. Furthermore, we argue whether adiponectin and its receptors may be considered putative therapeutic targets.

AdipoRon: A Novel Insulin Sensitizer in Various Complications and the Underlying Mechanisms: A Review

BACKGROUND

AdipoRon is the first synthetic analog of endogenous adiponectin, an adipose tissue-derived hormone. AdipoRon possesses pharmacological properties similar to adiponectin and its ability to bind and activate the adipoR1 and adipoR2 receptors makes it a suitable candidate for the treatment of a multitude of disorders.

OBJECTIVE

In the present review, an attempt was made to compile and discuss the efficacy of adipoRon against various disorders.

RESULTS

AdipoRon is a drug that acts not only in metabolic diseases but in other conditions unrelated to energy metabolism. It is well- reported that adipoRon exhibits strong anti-obesity, anti-diabetic, anticancer, anti-depressant, anti-ischemic, anti-hypertrophic properties and also improves conditions like post-traumatic stress disorder, anxiety, and systemic sclerosis.

CONCLUSION

A lot is known about its effects in experimental systems, but the translation of this knowledge to the clinic requires studies which, for many of the potential target conditions, have yet to be carried out. The beneficial effects of AdipoRon in novel clinical conditions will suggest an underlying pathophysiological role of adiponectin and its receptors in previously unsuspected settings.

AdipoRon and Other Adiponectin Receptor Agonists as Potential Candidates in Cancer Treatments

The high mortality rate together with an ever-growing number of annual cases have defined neoplastic disorders as “the real 21st-century disease”. Its dubious distinction also results from conventional therapy failure, which has made cancer an orphan disease. Therefore, innovative and alternative therapeutic strategies are mandatory. The ability to leverage human naturally occurring anti-tumor defenses has always represented a fascinating perspective, and the immuno blockage approval in cancer treatment represents in timeline the latest success. As a multifunctional organ, adipose tissue releases a large amount of adipokines having both carcinogenic and antitumor properties. The negative correlation between serum levels and risk for developing malignancies, as well as the huge number of existing preclinical studies, have identified adiponectin as a potential anticancer adipokine. Nevertheless, its usage in clinical has constantly clashed with the inability to reproduce a mimic synthetic compound. Between 2011 and 2013, two distinct adiponectin receptor agonists were recognized, opening new scenarios even in cancer. Here, we review the first orally active adiponectin receptor agonists AdipoRon, from the discovery to the anticancer evidence. Including our latest findings in osteosarcoma models, we summarize AdipoRon and other existing agonists state-of-art, questioning about the feasibility assessment of this strategy in cancer treatment.

Adiponectin and Thyroid Cancer: Insight into the Association between Adiponectin and Obesity

In recent decades, the incidence and diagnosis of thyroid cancer have risen dramatically, and thyroid cancer has now become the most common endocrine cancer in the world. The onset of thyroid cancer is insidious, and its progression is slow and difficult to detect. Therefore, early prevention and treatment have important strategic significance. Moreover, an in-depth exploration of the pathogenesis of thyroid cancer is key to early prevention and treatment. Substantial evidence supports obesity as an independent risk factor for thyroid cancer. Adipose tissue dysfunction in the obese state is accompanied by dysregulation of a variety of adipocytokines. Adiponectin (APN) is one of the most pivotal adipocytokines, and its connection with obesity and obesity-related disease has gradually become a hot topic in research. Recently, the association between APN and thyroid cancer has received increasing attention. The purpose of this review is to systematically review previous studies, give prominence to APN, focus on the relationship between APN, obesity and thyroid cancer, and uncover the underlying pathogenic mechanisms.

Obesity reduces the anticancer effect of AdipoRon against orthotopic pancreatic cancer in diet-induced obese mice

The antidiabetic adiponectin receptor agonist AdipoRon has been shown to suppress the tumour growth of human pancreatic cancer cells. Because obesity and diabetes affect pancreatic cancer progression and chemoresistance, we investigated the effect of AdipoRon on orthotopic tumour growth of Panc02 pancreatic cancer cells in DIO (diet-induced obese) prediabetic mice. Administration of AdipoRon into DIO mice fed high-fat diets, in which prediabetic conditions were alleviated to some extent, did not reduce either body weight or tumour growth. However, when the DIO mice were fed low-fat diets, body weight and the blood leptin level gradually decreased, and importantly, AdipoRon became effective in suppressing tumour growth, which was accompanied by increases in necrotic areas and decreases in Ki67-positive cells and tumour microvessels. AdipoRon inhibited cell growth and induced necrotic cell death of Panc02 cells and suppressed angiogenesis of endothelial MSS31 cells. Insulin and IGF-1 only slightly reversed the AdipoRon-induced suppression of Panc02 cell survival but had no effect on the AdipoRon-induced suppression of MSS31 cell angiogenesis. Leptin significantly ameliorated AdipoRon-induced suppression of angiogenesis through inhibition of ERK1/2 activation. These results suggest that obesity-associated factors weaken the anticancer effect of AdipoRon, which indicates the importance of weight loss in combating pancreatic cancer.

Identification of an extracellular vesicle-related gene signature in the prediction of pancreatic cancer clinical prognosis

Although extracellular vesicles (EVs) in body fluid have been considered to be ideal biomarkers for cancer diagnosis and prognosis, it is still difficult to distinguish EVs derived from tumor tissue and normal tissue. Therefore, the prognostic value of tumor-specific EVs was evaluated through related molecules in pancreatic tumor tissue. NA sequencing data of pancreatic adenocarcinoma (PAAD) were acquired from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC). EV-related genes in pancreatic cancer were obtained from exoRBase. Protein–protein interaction (PPI) network analysis was used to identify modules related to clinical stage. CIBERSORT was used to assess the abundance of immune and non-immune cells in the tumor microenvironment. A total of 12 PPI modules were identified, and the 3-PPI-MOD was identified based on the randomForest package. The genes of this model are involved in DNA damage and repair and cell membrane-related pathways. The independent external verification cohorts showed that the 3-PPI-MOD can significantly classify patient prognosis. Moreover, compared with the model constructed by pure gene expression, the 3-PPI-MOD showed better prognostic value. The expression of genes in the 3-PPI-MOD had a significant positive correlation with immune cells. Genes related to the hypoxia pathway were significantly enriched in the high-risk tumors predicted by the 3-PPI-MOD. External databases were used to verify the gene expression in the 3-PPI-MOD. The 3-PPI-MOD had satisfactory predictive performance and could be used as a prognostic predictive biomarker for pancreatic cancer.

The Role of Dysfunctional Adipose Tissue in Pancreatic Cancer: A Molecular Perspective

Pancreatic cancer (PC) is a lethal malignancy with rising incidence and limited therapeutic options. Obesity is a well-established risk factor for PC development. Moreover, it negatively affects outcome in PC patients. Excessive fat accumulation in obese, over- and normal-weight individuals induces metabolic and inflammatory changes of adipose tissue microenvironment leading to a dysfunctional adipose “organ”. This may drive the association between abnormal fat accumulation and pancreatic cancer. In this review, we describe several molecular mechanisms that underpin this association at both local and systemic levels. We focus on the role of adipose tissue-derived circulating factors including adipokines, hormones and pro-inflammatory cytokines, as well as on the impact of the local adipose tissue in promoting PC. A discussion on potential therapeutic interventions, interfering with pro-tumorigenic effects of dysfunctional adipose tissue in PC, is included. Considering the raise of global obesity, research efforts to uncover the molecular basis of the relationship between pancreatic cancer and adipose tissue dysfunction may provide novel insights for the prevention of this deadly disease. In addition, these efforts may uncover novel targets for personalized interventional strategies aimed at improving the currently unsatisfactory PC therapeutic options.

Adiponectin and Its Mimics on Skeletal Muscle: Insulin Sensitizers, Fat Burners, Exercise Mimickers, Muscling Pills … or Everything Together?

Adiponectin (ApN) is a hormone abundantly secreted by adipocytes and it is known to be tightly linked to the metabolic syndrome. It promotes insulin-sensitizing, fat-burning, and anti-atherosclerotic actions, thereby effectively counteracting several metabolic disorders, including type 2 diabetes, obesity, and cardiovascular diseases. ApN is also known today to possess powerful anti-inflammatory/oxidative and pro-myogenic effects on skeletal muscles exposed to acute or chronic inflammation and injury, mainly through AdipoR1 (ApN specific muscle receptor) and AMP-activated protein kinase (AMPK) pathway, but also via T-cadherin. In this review, we will report all the beneficial and protective properties that ApN can exert, specifically on the skeletal muscle as a target tissue. We will highlight its effects and mechanisms of action, first in healthy skeletal muscle including exercised muscle, and second in diseased muscle from a variety of pathological conditions. In the end, we will go over some of AdipoRs agonists that can be easily produced and administered, and which can greatly mimic ApN. These interesting and newly identified molecules could pave the way towards future therapeutic approaches to potentially prevent or combat not only skeletal muscle disorders but also a plethora of other diseases with sterile inflammation or metabolic dysfunction.

AdipoRon Affects Cell Cycle Progression and Inhibits Proliferation in Human Osteosarcoma Cells

AdipoRon (AdipoR) is the first synthetic molecule acting as a selective and potent adiponectin receptor agonist. Recently, the possible pharmacological use of AdipoR in different pathological conditions has been addressed. Interestingly, initial evidence suggests that AdipoR may have anticancer properties in different preclinical models, such as pancreatic and ovarian cancer. To our knowledge, so far no research has been directed at determining the impact of AdipoR on osteosarcoma, the most aggressive and metastatic bone malignancy occurring in childhood and adolescence age. Here, we investigate the possible antitumor effects of AdipoR in osteosarcoma cell lines. MTT and cell growth curve assays clearly indicate that AdipoR inhibits, at different extents, proliferation in both U2OS and Saos-2 osteosarcoma cell lines, the latter being more sensitive. Moreover, flow cytometry-based assays point out a significant G0/G1 phase accumulation and a contemporary S phase decrease in response to AdipoR. Consistent with the different sensitivity, a strong subG1 appearance in Saos-2 after 48 and 72 hours of treatment is also observed. The investigation of the molecular mechanisms highlights a common and initial ERK1/2 activation in response to AdipoR in both Saos-2 and U2OS cells. Interestingly, a simultaneous and dramatic downregulation of p70S6K phosphorylation, one of the main targets of mTORC1 pathway, has also been observed in AdipoR-treated Saos-2, but not in U2OS cells. Importantly, a strengthening of AdipoR-induced effects was reported upon everolimus-mediated mTORC1 perturbation in U2OS cells. In conclusion, our findings provide initial evidence of AdipoR as an anticancer molecule differently affecting various signaling pathways involved in cell cycle and cell death in osteosarcoma cells and encourage the design of future studies to further understand its pattern of activities.

The Diverse Involvement of Cigarette Smoking in Pancreatic Cancer Development and Prognosis

Despite extensive research in the pathogenesis, early detection, and therapeutic approaches of pancreatic ductal adenocarcinoma (PDAC), it remains a devastating and incurable disease. As the global incidence and prevalence of PDAC continue to rise, there is a pressing need to place strong emphasis on its prevention. Although it is widely recognized that cigarette smoking, a potentially modifiable risk factor, has been linked to PDAC development, its contribution to prognosis is still uncertain. Moreover, the mechanistic pathways of PDAC progression secondary to smoking are various and lack a summative narration. Herein, we update and summarize the direct and indirect roles cigarette smoking plays on PDAC development, review literature to conclude the impact cigarette smoking has on prognosis, and postulate a comprehensive mechanism for cigarette smoking-induced PDAC.

Obesity and pancreatic cancer: An update of epidemiological evidence and molecular mechanisms

Despite advances in therapy and achievements in translational research, pancreatic cancer (PC) remains an invariably fatal malignancy. Risk factors that affect the incidence of PC include diabetes, smoking, obesity, chronic pancreatitis, and diet. The growing worldwide obesity epidemic is associated with an increased risk of the most common cancers, including PC. Chronic inflammation, hormonal effects, circulating adipokines, and adipocyte-mediated inflammatory and immunosuppressive microenvironment are involved in the association of obesity with PC. Herein, we systematically review the epidemiology of PC and the biological mechanisms that may account for this association. Included in this review is a discussion of adipokine-mediated inflammation, lipid metabolism, and the interactions of adipocytes with cancer cells. We consider the influence of bariatric surgery on the risk of PC risk as well as potential molecular targets of therapy. Our review leads us to conclude that targeting adipose tissue to achieve weight loss may represent a new therapeutic strategy for preventing and treating PC.

The Adiponectin-AdipoR1 Axis Mediates Tumor Progression and Tyrosine Kinase Inhibitor Resistance in Metastatic Renal Cell Carcinoma

The survival of patients diagnosed with metastatic renal cell carcinoma (RCC) is still limited and the current targeted therapies are only partially effective. Herein, we investigated the clinical value and functions of adiponectin receptors (AdipoR1 and AdipoR2) in metastatic renal cell carcinoma (RCC) patients treated with tyrosine kinase inhibitors (TKIs). A total of 127 mRCC patients treated with first-line TKIs between 2008 and 2017 at a single institution were collected. AdipoR1 and AdipoR2 expression was assessed by immunohistochemistry. AdipoR1 was positively expressed in 87.4% (111/127) of tumors, especially, highly expressed in pulmonary and bone lesions. Patients with low-AdipoR1 expression in primary tumor tissues were more likely to suffer from progressive disease during TKIs treatment (40.0% vs. 11.1%, P = 0 .02), and with decreased progression-free survival (PFS: 19.5 vs. 37.8 mo, P = .001) and overall survival (OS: 62.3 vs 101.1 mo, P = .004) compared to those with high-AdipoR1 expression. Moreover, low-AdipoR1 expression in metastatic tissues was also associated with poor PFS (P = .006) and OS (P = .037). In contrast, AdipoR2 expression was neither associated with sunitinib response nor patient survival. In vitro, we found that adiponectin inhibited migration, invasion and sensitized RCC cells to sunitinib though interacting with AdipoR1, but not AdipoR2. Furthermore, we demonstrated that adiponentin-AdipoR1 axis inhibits tumor cells migration and invasion by blocking the GSK3β/β-Catenin pathway and enhances sunitinib sensitivity via abrogating PI3K/AKT/NF-κB signaling. Our results suggest that adiponentin-AdipoR1 axis may serve as a predictor of TKIs response and could be a potential therapeutic target in the future treatment for metastatic RCC.

Role of Adiponectin in prostate cancer

Obesity is defined as a chronic and excessive growth of adipose tissue. It has been associated with a high risk for development and progression of obesity-associated malignancies, while adipokines may mediate this association. Adiponectin is an adipose tissue-derived adipokines, with significant anti-diabetic, anti-inflammatory, anti-atherosclerotic and anti-proliferative properties. Plasma adiponectin levels are decreased in obese individuals, and this feature is closely correlated with development of several metabolic, immunological and neoplastic diseases. Recent studies have shown that prostate cancer patients have lower serum adiponectin levels and decreased expression of adiponectin receptors in tumor tissues, which suggests plasma adiponectin level is a risk factor for prostate cancer. Furthermore, exogenous adiponectin has exhibited therapeutic potential in animal models. In this review, we focus on the potential role of adiponectin and the underlying mechanism of adiponectin in the development and progression of prostate cancer. Exploring the signaling pathways linking adiponectin with tumorigenesis might provide a potential target for therapy.

Adiponectin receptor agonist AdipoRon induces apoptotic cell death and suppresses proliferation in human ovarian cancer cells

We tested the hypothesis that stimulation of adiponectin receptors with the synthetic agonist AdipoRon suppresses proliferation and induces apoptotic death in human high grade serous ovarian tumor cell lines and in ex vivo primary tumors, mediated by activation of 5' AMP-activated protein kinase (AMPK) and inhibition of mechanistic target of rapamycin (mTOR). We determined the effect of AdipoRon on high grade serous ovarian tumor cells lines (OVCAR3, OVCAR4, A2780) and ex vivo primary tumor tissue. Western blotting analysis was performed to examine changes in activation of AMPK and mTOR signaling and flow cytometry was utilized to examine changes in cell cycle progression. Immunofluorescence of cleaved caspase-3 positive cells and flow cytometry of annexin V positive cells were used to determine changes in apoptotic response. The CyQUANT proliferation assay was used to assess cell proliferation. AdipoRon treatment increased AMPK phosphorylation (OVCAR3 P = 0.01; A2780 P = 0.02) but did not significantly alter mTOR activity. AdipoRon induced G1 cell cycle arrest in OVCAR3 (+ 12.1%, P = 0.03) and A2780 (+ 12.0%, P = 0.002) cells. OVCAR3 and OVCAR4 cells treated with AdipoRon underwent apoptosis based on cleaved caspase-3 and annexin V staining. AdipoRon treatment resulted in a dose dependent decrease in cell number versus vehicle treatment in OVCAR3 (-61.2%, P < 0.001), OVCAR4 (-79%, P < 0.001), and A2780 (-56.9%, P < 0.001). Ex vivo culture of primary tumors treated with AdipoRon resulted in an increase in apoptosis measured with cleaved caspase-3 immunohistochemistry. AdipoRon induces activation of AMPK and exhibits an anti-tumor effect in ovarian cancer cell lines and primary tumor via a mTOR-independent pathway.

Leptin-induced signaling pathways in cancer cell migration and invasion

BACKGROUND

Increasing evidence indicates that obesity is associated with tumor development and progression. Leptin is an adipocyte-related hormone with a key role in energy metabolism and whose circulating levels are elevated in obesity. The effect of leptin on cancer progression and metastasis and its underlying mechanisms are still unclear. Leptin can impact various steps in tumor metastasis, including epithelial-mesenchymal transition, cell adhesion to the extracellular matrix (ECM), and proteolysis of ECM components. To do so, leptin binds to its receptor (OB-Rb) to activate signaling pathways and downstream effectors that participate in tumor cell invasion as well as distant metastasis.

CONCLUSIONS

In this review, we describe metastasis steps in detail and characterize metastasis-related molecules activated by leptin, which may help to develop a roadmap that guides future work. In addition, we conclude that a profound understanding of the fundamental molecular processes that contribute to leptin-induced metastasis may pave the way for the development of new prognostic molecules and appropriate approaches to the treatment of obesity-related cancers.

Adiponectin Suppresses Human Pancreatic Cancer Growth through Attenuating the β-Catenin Signaling Pathway

Adipokines are emerging as a link between obesity and obesity-related cancers, including pancreatic cancer. Adiponectin is an abundant adipokine with pleiotropic beneficial roles in metabolic disorders. Low adiponectin levels are commonly observed in human obesity and have been associated with increased pancreatic cancer risk in prospective epidemiologic studies. Here, we investigated the direct effect of adiponectin on human pancreatic cancer in vitro and in vivo. Our results showed that adiponectin treatment significantly inhibited the proliferation of human pancreatic cancer cells. Knockdown of adiponectin receptors completely eliminated the antiproliferation effect of adiponectin and markedly promoted the growth of human pancreatic cancer xenografts in nude mice. Further analysis revealed that adiponectin blocked the phosphorylation/inactivation of GSK-3β, suppressed the intracellular accumulation of β-catenin, reduced the expression of cyclin D1, and consequently caused cell cycle accumulation at the G₀-G₁ phase in pancreatic cancer cells. Adiponectin-mediated attenuation of cell proliferation was abrogated by the GSK-3β inhibitor. In addition, a microarray analysis revealed that adiponectin also downregulated the expression of TCF7L2, a coactivator of β-catenin, at the transcriptional level in pancreatic cancer cells. These results indicated that the protective role of adiponectin against human pancreatic cancer might be attributed to its attenuating effect on the β-catenin signaling pathway. Taken together, our findings support a causal link between hypoadiponectinemia and increased pancreatic cancer risk, and suggest that activating adiponectin signaling could be a novel therapeutic strategy for obesity-related pancreatic cancer.

Potential Adiponectin Receptor Response Modifier Therapeutics

Many human diseases may benefit from adiponectin replacement therapy, but due to pharmacological disadvantages of the intact protein, druggable options focus on peptidic, and small molecule agonists of the adiponectin receptor. Peptide-based adiponectin replacement drug leads are derived from, or resemble, the active site of globular adiponectin. ADP355, the first-in-class such peptide, exhibits low nanomolar cellular activities, and clinically acceptable efficacies in a series of fibrotic and inflammation-derived diseases. The advantage of small molecule therapies, spearheaded by AdipoRon, is oral availability and extension of utility to a series of metabolic conditions. It is exactly the difficulties in the reliability and readout of the in vitro measures and the wealth of in vivo models that make comparison of the various drug classes complicated, if not impossible. While only a fewer number of maladies could take advantage of adiponectin receptor antagonists, the limited number of these available can be very useful tools in target validation studies. Alternative approaches to direct adiponectin signaling control use upstream adiponectin production inducing therapies but currently these offer relatively limited success compared to direct receptor agonists.

Examining the Potential of Developing and Implementing Use of Adiponectin-Targeted Therapeutics for Metabolic and Cardiovascular Diseases

Cardiometabolic diseases encompass those affecting the heart and vasculature as well as other metabolic problems, such as insulin resistance, diabetes, and non-alcoholic fatty liver disease. These diseases tend to have common risk factors, one of which is impaired adiponectin action. This may be due to reduced bioavailability of the hormone or resistance to its effects on target tissues. A strong negative correlation between adiponectin levels and cardiometabolic diseases has been well-documented and research shown that adiponectin has cardioprotective, insulin sensitizing and direct beneficial metabolic effects. Thus, therapeutic approaches to enhance adiponectin action are widely considered to be desirable. The complexity of adiponectin structure and function has so far made progress in this area less than ideal. In this article we will review the effects and mechanism of action of adiponectin on cardiometabolic tissues, identify scenarios where enhancing adiponectin action would be of clinical value and finally discuss approaches via which this can be achieved.

Pancreatic cancer associated with obesity and diabetes: an alternative approach for its targeting

BACKGROUND

Pancreatic cancer (PC) is among foremost causes of cancer related deaths worldwide due to generic symptoms, lack of effective screening strategies and resistance to chemo- and radiotherapies. The risk factors associated with PC include several metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus (T2DM). Studies have shown that obesity and T2DM are associated with PC pathogenesis; however, their role in PC initiation and development remains obscure.

MAIN BODY

Several biochemical and physiological factors associated with obesity and/or T2DM including adipokines, inflammatory mediators, and altered microbiome are involved in PC progression and metastasis albeit by different molecular mechanisms. Deep understanding of these factors and causal relationship between factors and altered signaling pathways will facilitate deconvolution of disease complexity as well as lead to development of novel therapies. In the present review, we focuses on the interplay between adipocytokines, gut microbiota, adrenomedullin, hyaluronan, vanin and matrix metalloproteinase affected by metabolic alteration and pancreatic tumor progression.

CONCLUSIONS

Metabolic diseases, such as obesity and T2DM, contribute PC development through altered metabolic pathways. Delineating key players in oncogenic development in pancreas due to metabolic disorder could be a beneficial strategy to combat cancers associated with metabolic diseases in particular, PC.

Activating Adiponectin Signaling with Exogenous AdipoRon Reduces Myelin Lipid Accumulation and Suppresses Macrophage Recruitment after Spinal Cord Injury

Myelin-laden macrophages (mye-MΦ), resulting primarily from internalization of myelin debris by infiltrating bone marrow-derived macrophages in spinal cord injury (SCI), trigger inflammatory responses that largely contribute to secondary injury. Adiponectin, which is secreted from adipose tissue, is an important hormone that modulates macrophage inflammation. In the present study, we examined the role of adiponectin on macrophage-mediated neuroinflammation after SCI. We found that in vitro activation of adiponectin receptors (AdipoRs) by their agonist AdipoRon suppressed myelin lipid accumulation in mye-MΦ through APPL1/PPARγ/LXRα/ABCA1-mediated lipid efflux, subsequently inhibiting inflammation and restoring normal function to mye-MΦ. In vivo data further confirmed that intravenous administration of AdipoRon after SCI dampened recruitment of macrophages and reduced myelin lipid accumulation. Accordingly, AdipoRon treatment ameliorated post-SCI tissue damage and astrogliosis, resulting in improved motor function. Although there was no significant pathological exacerbation in adiponectin-null mice subjected to SCI, our work reveals a functional link between adiponectin and hematogenous macrophages in the context of SCI, suggesting that activation of adiponectin signaling is a promising therapeutic approach to mitigate mye-MΦ-mediated neuroinflammation in neurological disorders involving demyelination.

The Role of Notch Signaling and Leptin-Notch Crosstalk in Pancreatic Cancer

There is accumulating evidence that deregulated Notch signaling affects cancer development, and specifically pancreatic cancer (PC) progression. Notch canonical and non-canonical signaling has diverse impact on PC. Moreover, the actions of RBP-Jk (nuclear partner of activated Notch) independent of Notch signaling pathway seem to affect differently cancer progression. Recent data show that in PC and other cancer types the adipokine leptin can modulate Notch/RBP-Jk signaling, thereby, linking the pandemic obesity with cancer and chemoresistance. The potential pivotal role of leptin on PC, and its connection with Notch signaling and chemoresistance are still not completely understood. In this review, we will describe the most important aspects of Notch-RBP-Jk signaling in PC. Further, we will discuss on studies related to RBP-Jk-independent Notch and Notch-independent RPB-Jk signaling. We will also discuss on the novel crosstalk between leptin and Notch in PC and its implications in chemoresistance. The effects of leptin-Notch/RBP-Jk signaling on cancer cell proliferation, apoptosis, and drug resistance require more investigation. Data from these investigations could help to open unexplored ways to improve PC treatment success that has shown little progress for many years.