Adipocyte-derived Factors Research Articles

Hypoxia in Human Obesity: New Insights from Inflammation towards Insulin Resistance-A Narrative Review.

Insulin resistance (IR), marked by reduced cellular responsiveness to insulin, and obesity, defined by the excessive accumulation of adipose tissue, are two intertwined conditions that significantly contribute to the global burden of cardiometabolic diseases. Adipose tissue, beyond merely storing triglycerides, acts as an active producer of biomolecules. In obesity, as adipose tissue undergoes hypertrophy, it becomes dysfunctional, altering the release of adipocyte-derived factors, known as adipokines. This dysfunction promotes low-grade chronic inflammation, exacerbates IR, and creates a hyperglycemic, proatherogenic, and prothrombotic environment. However, the fundamental cause of these phenomena remains unclear. This narrative review points to hypoxia as a critical trigger for the molecular changes associated with fat accumulation, particularly within visceral adipose tissue (VAT). The activation of hypoxia-inducible factor-1 (HIF-1), a transcription factor that regulates homeostatic responses to low oxygen levels, initiates a series of molecular events in VAT, leading to the aberrant release of adipokines, many of which are still unexplored, and potentially affecting peripheral insulin sensitivity. Recent discoveries have highlighted the role of hypoxia and miRNA-128 in regulating the insulin receptor in visceral adipocytes, contributing to their dysfunctional behavior, including impaired glucose uptake. Understanding the complex interplay between adipose tissue hypoxia, dysfunction, inflammation, and IR in obesity is essential for developing innovative, targeted therapeutic strategies.

Enhancing insulin sensitivity in type 2 diabetes mellitus using apelin-loaded small extracellular vesicles from Wharton’s jelly-derived mesenchymal stem cells: a novel therapeutic approach

BackgroundType 2 diabetes mellitus (T2DM), characterized by β-cell dysfunction and insulin resistance (IR), presents considerable treatment challenges. Apelin is an adipocyte-derived factor that shows promise in improving IR; however, it is limited by poor targeting and a short half-life. In the present study, engineered small extracellular vesicles (sEVs) derived from Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) loaded with apelin were used to address the limitations of the therapeutic application of apelin.MethodsWJ-MSCs were transduced to obtain engineered sEVs loaded with overexpressed apelin (apelin-MSC-sEVs) and the control sEVs (MSC-sEVs). T2DM mice were injected with apelin-MSC-sEVs and MSC-sEVs, and blood glucose monitoring, glucose and insulin tolerance tests, confocal microscopy, and immunocytochemical analysis were performed. IR models of 3T3-L1 adipocytes were employed to detect GLUT4 expression in each group using western blotting; the affected pathways were determined by measuring the changes in Akt and AMPK signaling and phosphorylation.ResultsUpon successful engineering, WJ-MSCs demonstrated significant overexpression of apelin. The genetic modification did not adversely impact the characteristics of sEVs, ranging from surface protein markers, morphology, to particle size, but generated apelin-overexpressed sEVs. Apelin-MSC-sEVs treatment resulted in notable enhancement of Akt and AMPK pathway activities within 3T3-L1 adipocytes and adipose tissues of T2DM mice. Furthermore, the apelin-loaded sEVs significantly reduced plasma glucose levels, increased pancreatic β-cell proliferation, improved insulin and glucose tolerance, and modulated pro-inflammatory cytokine profiles, compared to mice treated with the control sEVs.ConclusionOur study developed novel genetically engineered apelin-loaded sEVs derived from WJ-MSCs, and demonstrated their potent role in augmenting insulin sensitivity and regulating inflammatory responses, highlighting their therapeutic promise in T2DM management. The findings open new avenues for the development of clinically viable treatments for T2DM in humans using the apelin-loaded sEVs.

Mitochondrial Ca2+ signaling is a hallmark of specific adipose tissue-cancer crosstalk

Obesity is associated with increased risk and worse prognosis of many tumours including those of the breast and of the esophagus. Adipokines released from the peritumoural adipose tissue promote the metastatic potential of cancer cells, suggesting the existence of a crosstalk between the adipose tissue and the surrounding tumour. Mitochondrial Ca2+ signaling contributes to the progression of carcinoma of different origins. However, whether adipocyte-derived factors modulate mitochondrial Ca2+ signaling in tumours is unknown. Here, we show that conditioned media derived from adipose tissue cultures (ADCM) enriched in precursor cells impinge on mitochondrial Ca2+ homeostasis of target cells. Moreover, in modulating mitochondrial Ca2+ responses, a univocal crosstalk exists between visceral adipose tissue-derived preadipocytes and esophageal cancer cells, and between subcutaneous adipose tissue-derived preadipocytes and triple-negative breast cancer cells. An unbiased metabolomic analysis of ADCM identified creatine and creatinine for their ability to modulate mitochondrial Ca2+ uptake, migration and proliferation of esophageal and breast tumour cells, respectively.

Impact of Perivascular Adipose Tissue on Neointimal Formation Following Endovascular Placement.

Following the placement of endovascular implants, perivascular adipose tissue (PVAT) becomes an early sensor of vascular injury to which it responds by undergoing phenotypic changes characterized by reduction in the secretion of adipocyte-derived relaxing factors and a shift to a proinflammatory and pro-contractile state. Thus, activated PVAT loses its anti-inflammatory function, secretes proinflammatory cytokines and chemokines, and generates reactive oxygen species, which are accompanied by differentiation of fibroblasts into myofibroblasts and proliferation of smooth muscle cells. These subsequently migrate into the intima, leading to intimal growth. In addition, periadventitial vasa vasorum undergoes neovascularization and functions as a portal for extravasation of inflammatory infiltrates and mobilization of PVAT resident stem/progenitor cells into the intima. This review focuses on the response of PVAT to endovascular intervention-induced injury and discusses potential therapeutic targets to suppress the PVAT-initiated pathways that mediate the formation of neointima.

Pharmacological HIF-1 activation upregulates extracellular vesicle production synergistically with adiponectin through transcriptional induction and protein stabilization of T-cadherin

Pharmacological activation of hypoxia-inducible factor 1 (HIF-1), a hypoxia-responsive transcription factor, has attracted increasing attention due to its efficacy not only in renal anemia but also in various disease models. Our study demonstrated that a HIF-1 activator enhanced extracellular vesicle (EV) production from cultured endothelial cells synergistically with adiponectin, an adipocyte-derived factor, through both transcriptional induction and posttranscriptional stabilization of an adiponectin binding partner, T-cadherin. Increased EV levels were observed in wild-type mice but not in T-cadherin null mice after consecutive administration of roxadustat. Adiponectin- and T-cadherin-dependent increased EV production may be involved in the pleiotropic effects of HIF-1 activators.

Unlocking the paracrine crosstalk: adipocyte-derived factors affect carbonic anhydrase IX expression in colon and breast cancer cells.

Obesity is a major public health concern because it increases the risk of several diseases, including cancer. Crosstalk between obesity and cancer seems to be very complex, and the interaction between adipocytes and cancer cells leads to changes in adipocytes' function and their paracrine signaling, promoting a microenvironment that supports tumor growth. Carbonic anhydrase IX (CA IX) is a tumor-associated enzyme that not only participates in pH regulation but also facilitates metabolic reprogramming and supports the migration, invasion, and metastasis of cancer cells. In addition, CA IX expression, predominantly regulated via hypoxia-inducible factor (HIF-1), serves as a surrogate marker of hypoxia. In this study, we investigated the impact of adipocytes and adipocyte-derived factors on the expression of CA IX in colon and breast cancer cells. We observed increased expression of CA9 mRNA as well as CA IX protein in the presence of adipocytes and adipocyte-derived conditioned medium. Moreover, we confirmed that adipocytes affect the hypoxia signaling pathway and that the increased CA IX expression results from adipocyte-mediated induction of HIF-1α. Furthermore, we demonstrated that adipocyte-mediated upregulation of CA IX leads to increased migration and decreased adhesion of colon cancer cells. Finally, we brought experimental evidence that adipocytes, and more specifically leptin, upregulate CA IX expression in cancer cells and consequently promote tumor progression.

The Effect of Adipocyte-Secreted Factors in Activating Focal Adhesion Kinase-Mediated Cell Signaling Pathway towards Metastasis in Breast Cancer Cells

Obesity-associated perturbations in the normal secretion of adipocytokines from white adipocytes can drive the metastatic progression of cancer. However, the association between obesity-induced changes in secretory factors of white adipocytes and subsequent transactivation of the downstream effector proteins impacting metastasis in breast cancer cells remains unclear. Focal adhesion kinase, a cytoplasmic signal transducer, regulates the biological phenomenon of metastasis by activating downstream targets such as beta-catenin and MMP9. Thus, the possible role of phosphorylated FAK in potentiating cancer cell migration was investigated. To elucidate this potential relationship, MCF7 (ER+), MDA-MB-231 (Triple Negative) breast cancer cells, and MCF-10A non-tumorigenic breast cells were exposed to in vitro murine adipocyte-conditioned medium derived from 3T3-L1 MBX cells differentiated to obesity with fatty acid supplementation. Our results show that the conditioned medium derived from these obese adipocytes enhanced motility and invasiveness of breast cancer cells. Importantly, no such changes were observed in the non-tumorigenic breast cells. Our results also show that increased FAK autophosphorylation was followed by increased expression of beta-catenin and MMP9 in the breast cancer cells when exposed to obese adipocyte-conditioned medium, but not in the MCF10A cells. These results indicate that adipocyte-derived secretory factors induced FAK activation through phosphorylation. This in turn increased breast cancer cell migration and invasion by activating its downstream effector proteins beta-catenin and MMP9.

Bariatric surgery decreases the capacity of plasma from obese asthmatic subjects to augment airway epithelial cell proinflammatory cytokine production.

Obesity is a risk factor for asthma. Individuals with asthma and obesity often have poor asthma control and do not respond as well to therapies such as inhaled corticosteroids and long-acting bronchodilators. Weight loss improves asthma control, with a 5%-10% loss in body mass necessary and sufficient to lead to clinically relevant improvements. Preclinical studies have demonstrated the pathogenic contribution of adipocytes from obese mice to the augmented production of proinflammatory cytokines from airway epithelial cells and the salutary effects of diet-induced weight loss to decrease these consequences. However, the effects of adipocyte-derived products on airway epithelial function in human obesity remain incompletely understood. We utilized samples collected from a 12-mo longitudinal study of subjects with obesity undergoing weight loss (bariatric) surgery including controls without asthma and subjects with allergic and nonallergic obese asthma. Visceral adipose tissue (VAT) samples were collected during bariatric surgery and from recruited normal weight controls without asthma undergoing elective abdominal surgery. Human bronchial epithelial (HBEC3-KT) cells were exposed to plasma or conditioned media from cultured VAT adipocytes with or without agonists. Human bronchial smooth muscle (HBSM) cells were similarly exposed to adipocyte-conditioned media. Proinflammatory cytokines were augmented in supernatants from HBEC3-KT cells exposed to plasma as compared with subsequent visits. Whereas exposure to obese adipocyte-conditioned media induced proinflammatory responses, there were no differences between groups in both HBEC3-KT and HBSM cells. These data show that bariatric surgery and subsequent weight loss beneficially change the circulating factors that augment human airway epithelial and bronchial smooth muscle cell proinflammatory responses.NEW & NOTEWORTHY This longitudinal study following subjects with asthma and obesity reveals that weight loss following bariatric surgery decreases the capacity for plasma to augment proinflammatory cytokine secretion by human bronchial epithelial cells, implicating that circulating but not adipocyte-derived factors are important modulators in obese asthma.

Glucocorticoid receptor-NECAB1 axis can negatively regulate insulin secretion in pancreatic β-cells

The mechanisms of impaired glucose-induced insulin secretion from the pancreatic β-cells in obesity have not yet been completely elucidated. Here, we aimed to assess the effects of adipocyte-derived factors on the functioning of pancreatic β-cells. We prepared a conditioned medium using 3T3-L1 cell culture supernatant collected at day eight (D8CM) and then exposed the rat pancreatic β-cell line, INS-1D. We found that D8CM suppressed insulin secretion in INS-1D cells due to reduced intracellular calcium levels. This was mediated by the induction of a negative regulator of insulin secretion—NECAB1. LC–MS/MS analysis results revealed that D8CM possessed steroid hormones (cortisol, corticosterone, and cortisone). INS-1D cell exposure to cortisol or corticosterone increased Necab1 mRNA expression and significantly reduced insulin secretion. The increased expression of Necab1 and reduced insulin secretion effects from exposure to these hormones were completely abolished by inhibition of the glucocorticoid receptor (GR). NECAB1 expression was also increased in the pancreatic islets of db/db mice. We demonstrated that the upregulation of NECAB1 was dependent on GR activation, and that binding of the GR to the upstream regions of Necab1 was essential for this effect. NECAB1 may play a novel role in the adipoinsular axis and could be potentially involved in the pathophysiology of obesity-related diabetes mellitus.

Adipose Tissue and Metabolic Health.

In this review, we provide a brief synopsis of the connections between adipose tissue and metabolic health and highlight some recent developments in understanding and exploiting adipocyte biology. Adipose tissue plays critical roles in the regulation of systemic glucose and lipid metabolism and secretes bioactive molecules possessing endocrine, paracrine, and autocrine functions. Dysfunctional adipose tissue has a detrimental impact on metabolic health and is intimately involved in key aspects of metabolic diseases such as insulin resistance, lipid overload, inflammation, and organelle stress. Differences in the distribution of fat depots and adipose characteristics relate to divergent degrees of metabolic dysfunction found in metabolically healthy and unhealthy obese individuals. Thermogenic adipocytes increase energy expenditure via mitochondrial uncoupling or adenosine triphosphate-consuming futile substrate cycles, while functioning as a metabolic sink and participating in crosstalk with other metabolic organs. Manipulation of adipose tissue provides a wealth of opportunities to intervene and combat the progression of associated metabolic diseases. We discuss current treatment modalities for obesity including incretin hormone analogs and touch upon emerging strategies with therapeutic potential including exosome-based therapy, pharmacological activation of brown and beige adipocyte thermogenesis, and administration or inhibition of adipocyte-derived factors.

METABOLİK SENDROM

Metabolic syndrome is a common health problem, is an important cause of mortality and morbidity. Metabolic syndrome is a type of disorder that occurs as a result of the coexistence of insulin resistance and obesity-like findings, hipertriglisemi, hypertension, Type 2 diabetes mellitus, dyslipidemia and non-alcoholic fatty liver disease, stress, low HDL, hyperglycemia, inflammation, adipocyte-derived aldosterone-releasing factors, sleep apnea, etc. The same criteria and symptoms are valid for the disease in animals, and similar definitions are made for animals. In recent years, interest in metabolic syndrome, its causes and consequences has increased in veterinary medicine as well as in human medicine. In the formation of the disease, with the development of industry and technology, besides genetic factors urbanization, sedentary life, fast and high-calorie food consumption and many environmental factors such as smoking and alcohol use play role. In addition to this, many situations are shown in animals such as breed, neutralism, relationship with the owner, ration content, loss of hunter, catcher, etc. characteristics by assimilating to today's conditions. Many internationally recognized institutions such as the National Cholesterol Education Program (NCEP) ATPIII, the International Diabetes Federation (IDF), the World Health Organization (WHO), the Turkish Society of Endocrinology and Metabolism have made definitions for metabolic syndrome. In this article, metabolic syndrome, which has a significant impact on human and animal life, is examined in general terms.

Abstract 041: Adipocyte (Pro)Renin Receptor Via SPRR Regulates Renal Sodium-glucose Cotransporter-2 Expression And Glomerular Filtration Rate In Mice

Evidence is available to suggest a potential role of adipocyte-derived factors to control renal function but the nature of these endocrine factors largely remains elusive. Sodium-glucose cotransporter 2 (SGLT2) controls Na + delivery to the macula densa thereby determining tubuloglomerular feedback and thus glomerular filtration rate (GFR), providing the molecular basis for attenuation of glomerular hyperfiltration and diabetic kidney disease by SGLT2 inhibitors. Furthermore, we previously reported that soluble (pro)renin receptor (sPRR) inhibits obesity-induced renal SGLT2 expression, thus reducing GFR and albuminuria in a mouse model of diet-induced obesity. In the present study, we examined adipocytes as a potential source of sPRR that acts in an endocrine manner to regulate renal function, particularly GFR, through regulation of renal SGLT2 expression. PRR floxed mice was crossed with Adipoq-CreERT2 mice and gene inactivation was induced by tamoxifen in adulthood (termed as Adipo PRR KO). Under basal condition, male 4-month old Adipo PRR KO mice exhibited a 33.65% increase in GFR as assessed by transdermal measurement of GFR as compared with floxed controls (1318.26± 38.35 in KO group vs . 986.33± 14.31 ul/min/100g b.w. in floxed group, n = 6, p < 0.01). Dapagliflozin-sensitive SGLT2 activity as assessed by 6-h urinary glucose excretion was increased by 1.93 folds in Adipo PRR KO mice (SGLT2 activity: 13.19± 1.64 in KO group vs. 6.83± 1.20 mg/6h in floxed group, n=7-10, p < 0.05). Immunoblotting analysis detected a more than 10-fold increase in renal protein abundance of SGLT2 in the null mice (12.38± 1.51 in KO group vs.1.00± 0.26 in floxed group, n=6, p < 0.01) whereas the increase in renal SGLT2 mRNA was quite modest (1.25± 0.08 in KO group vs . 1.00± 0.06 in floxed group; n = 6, p < 0.05). As compared with floxed mice, Adipo PRR KO mice showed a 44.62% fall in plasma sPRR concentration as assessed by ELISA (1.18± 0.09 in KO group vs . 2.12± 0.10 ng/ml in floxed group, n = 6, p < 0.01). Taken together, the present study, for the first time, provides evidence for an endocrine action of adipocyte PRR to regulate renal SGLT2 expression and GFR likely through sPRR.

Adipocyte-Derived Paracrine Factors Regulate the In Vitro Development of Bovine Mammary Epithelial Cells.

The mammary gland is composed of epithelial tissue forming ducts and lobules, and the stroma, composed of adipocytes, connective tissue, and other cell types. The stromal microenvironment regulates mammary gland development by paracrine and cell-cell interactions. In the present study, primary cultures of bovine mammary epithelial cells (bMEC) and bovine adipose-derived stem cells (bASC) subjected to adipogenic differentiation were used to investigate the influence of paracrine factors secreted by preadipocytes and adipocytes on bMEC development. Four types of conditioned media (CM) were collected from undifferentiated preadipocytes (preA) and adipocytes on days: 8, 12, 14 of differentiation. Next, bMEC were cultured for 24 h in CM and cell viability, apoptosis, migratory activity, ability to form spheroids on Matrigel, and secretory activity (alpha S1-casein concentration) were evaluated. CM derived from fully differentiated adipocytes (12 d and 14 d) significantly decreased the number of apoptotic cells in bMEC population and increased the size of spheroids formed by bMEC on Matrigel. CM collected from preadipocytes significantly enhanced bMEC's migration, and stimulated bMEC to produce alpha S1-casein, but only in the presence of prolactin. These results confirm that preadipocytes and adipocytes are important components of the stroma, providing paracrine factors that actively regulate the development of bovine mammary epithelium.

S-13-3: AN APPROACH TO IDENTIFY THE UNDETERMINED ADIPOCYTE-DERIVED FACTOR(S) THAT STIMULATE ALDOSTERONE SYNTHASE GENE (CYP11B2) EXPRESSION

Objectives: Hypertension is a frequently observed complication among obese patients. Recently, undetermined adipocyte-derived factor(s) have been recognized as one of the causes of the obesity-related hypertension independent of angiotensin (A) II. In this study, we aim to identify the undetermined adipocyte-derived factor(s) that stimulate aldosterone synthase gene (CYP11B2) expression aldosterone secretion that may induce hypertension. Methods: We first differentiated mouse fibroblast 3T3-L1 cells into adipocytes and collected their supernatants. The supernatants were incubated with human adrenocortical carcinoma H295R cells, and their CYP11B2 mRNA expression was measured by quantitative PCR with reverse transcription (qRT-PCR). Thereafter, the supernatants were fractionated by ammonium sulfate precipitation to purify adipocyte-derived factor(s) that stimulate CYP11B2 expression. The precipitates were collected in 30%, 60% and 90% saturated concentration of ammonium sulfate. Each of precipitates was concentrated using 100 kDa ultrafiltration membrane and incubated with H295R cells. CYP11B2 mRNA expression in H295R cells was measured by qRT-PCR. Then, we purified the precipitation of the supernatants that obtained in 60% ammonium sulfate by anion-exchange chromatography. Each of the fractions was incubated with human adrenocortical carcinoma H295R cells, and their CYP11B2 mRNA expression was measured by qRT-PCR. Results: The supernatants obtained from 3T3-L1 adipocytes were demonstrated to stimulate CYP11B2 expression. Fractionation of the supernatants by ammonium sulfate precipitation demonstrated that the ability to stimulate CYP11B2 expression was detected in fractions precipitated in 60% saturated concentration. Fractionation of the supernatants by anion-exchange chromatography demonstrated that the ability to stimulate CYP11B2 expression was detected in two specific fractions. Specific fractions were analyzed by mass spectrometry, resulting in the identification of 39 specific proteins. We are now investigating that the relationship between CYP11B2 gene expression and 39 proteins.

AGING-RELATED ADIPOSE REMODELING AND DYSFUNCTION

Abstract Aging is associated with insulin resistance, cardiovascular dysfunction, and many other chronic metabolic disorders, significantly shortening healthspan and lifespan. Fat (adipose) tissue, as the major site for energy storage, maintains whole-body energy homeostasis and insulin sensitivity. Adipose tissue has extraordinary plasticity, and it was not until recently that fat tissue remodeling during aging is considered to play an essential role in aging-associated metabolic disorders. Benefiting from recent technology advances, especially the single-cell technology and comprehensive genetic mouse models, we are beginning to unmask how adipose tissue remodels during aging cellularly and molecularly. This symposium features internationally-renowned aging research scientists whose work focuses on how aging remodels adipose tissues and how adipose tissue is vital for healthy aging and longevity. We will hear from Philipp Scherer from The University of Texas Southwestern Medical Center, who will present his research on the impact of adipocyte-derived factors on Healthspan and Lifespan; Hei Sook SUL from the University of California Berkeley will discuss “Aging dependent changes in adipose precursors”; Annabel Wang from the City of Hope will introduce her recent discovery of a new type of adipocyte progenitor cell that promotes aging-related visceral adiposity; and lastly, Gina Wade from the University of Wisconsin-Madison who will talk about “Regulation of aging energy expenditure by plasma lipid signaling”. Attendees will learn about the latest breakthroughs in adipose tissue aging, and the role of adipose tissue in maintaining and restoring metabolic health in aged individuals.

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.

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.

Neuregulin 4 suppresses NASH-HCC development by restraining tumor-prone liver microenvironment

The mammalian liver comprises heterogeneous cell types within its tissue microenvironment that undergo pathophysiological reprogramming in disease states, such as non-alcoholic steatohepatitis (NASH). Patients with NASH are at an increased risk for the development of hepatocellular carcinoma (HCC). However, the molecular and cellular nature of liver microenvironment remodeling that links NASH to liver carcinogenesis remains obscure. Here, we show that diet-induced NASH is characterized by the induction of tumor-associated macrophage (TAM)-like macrophages and exhaustion of cytotoxic CD8+ Tcells in the liver. The adipocyte-derived endocrine factor Neuregulin 4 (NRG4) serves as a hormonal checkpoint that restrains this pathological reprogramming during NASH. NRG4 deficiency exacerbated the induction of tumor-prone liver immune microenvironment and NASH-related HCC, whereas transgenic NRG4 overexpression elicited protective effects in mice. In a therapeutic setting, recombinant NRG4-Fc fusion protein exhibited remarkable potency in suppressing HCC and prolonged survival in the treated mice. These findings pave the way for therapeutic intervention of liver cancer by targeting the NRG4 hormonal checkpoint.

Abstract 3128: Paracrine adipocyte signaling promotes colorectal cancer growth in vitro

Abstract Purpose: To identify candidate mediators of paracrine signaling between adipocytes and colorectal cancer cells contributing to the obesity-cancer link. Background: The worldwide prevalence of obesity has nearly tripled over the last few decades and is a major public health concern. Obesity-associated inflammation in adipose tissue correlates with colorectal tumorigenesis and tumor proliferation. The altered secretome of obesity-associated adipose tissue also affects colon cancer growth and development. Hence, we sought to determine the role of adipocyte-derived secreted factors in mediating the tumor-promoting paracrine signaling observed in obesity. Methods: Adipocytes were isolated from the gonadal fat pad of C57BL/6J male mice fed either a low-fat (10 kcal% fat) or high-fat (60 kcal% fat) diet and cultured for 24 hours. Cytokine production from the cultured adipocytes was quantified using the Bio-Plex Pro mouse chemokine 33-plex panel. To determine if adipocyte-derived metabolites or growth factors promote cancer cell proliferation, human SW620 colon cancer cells were grown for 24 hours in conditioned media and cell viability was assessed using the MTT assay. To test whether a subset of these cytokines directly impacted cancer cell growth, SW620 cells were cultured with or without the addition of 20 ng/mL recombinant IL-6 or 50 ng/mL CCL5 to the culture media. Proliferation was measured using the MTT assay and gene expression was assessed via qPCR. Results: Adipocyte-conditioned media contained 19 detectable cytokines, with CCL2, CCL7, and CCL5 being the most abundant. IL-6, CCL12, CCL11, and CXCL16 were all significantly elevated (p<0.05, fold enrichment >2.0) in adipocyte-conditioned media from obese relative to lean mice. SW620 cells demonstrated a >20% increase in proliferation when grown in conditioned media from adipocytes isolated from either low-fat or high-fat fed mice. CCL5 stimulation for 24 hours resulted in a ~17% increase in SW620 cell viability when cultured under replete (10% FBS) growth factor conditions, but a ~8% decrease under reduced (0.5% FBS) growth factor conditions. IL-6 stimulation did not impact SW620 cell growth. To understand the downstream cell signaling effects of IL-6 and CCL5 stimulation, we performed qPCR analysis on EMT and Wnt signaling markers in SW620 cells after 4-hour cytokine stimulation in media without growth factors (0% FBS). IL-6-stimulated cells exhibited a significant increase in SOCS3 and PTHLH while CCL5-stimulated cells exhibited a significant decrease in TCF7L1. Conclusions: Overall, these data indicate tumor-promoting paracrine signaling from adipose tissue may potentiate colon cancer growth in part via adipocyte-derived cytokine production. Further work to delineate the mechanisms through which such paracrine signaling acts will be important to develop interventions to reduce the growing burden of obesity-driven colon cancer. Citation Format: Nivetha S. Ramasamy, Elaine M. Glenny, Qing Shi, Stephen D. Hursting. Paracrine adipocyte signaling promotes colorectal cancer growth in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3128.

Perivascular brown adipocytes-derived kynurenic acid relaxes blood vessel via endothelium PI3K-Akt-eNOS pathway.

Several metabolites from the kynurenine pathway of tryptophan metabolism play a critical role in vascular function and vascular wall remodeling. This study aimed to test whether metabolite kynurenic acid (KYNA) from the kynurenine pathway relaxes blood vessels. We employed histological staining, in vitro cell culture, Western blotting, real-time PCR, and nitric oxide detection to validate kynurenine aminotransferase (KAT) localization in the vasculature as well as KYNA action on endothelial cells. We also detected vascular reactivity by organ chamber and monitored blood pressure by telemetry to investigate the regulation effect of KYNA on vascular tone. The results presented that perivascular adipose tissue (PVAT) from mice thoracic aorta had robust staining of anti-KAT1 and KYNA than PVAT from the abdominal aorta and mesenteric artery, which is consistent with the expression profile of brown adipocyte marker uncoupling protein 1. KYNA, metabolized from kynurenine by KAT, relaxed pre-contracted both aortic ring and mesenteric artery. In addition, KYNA derived from KAT in PVAT participates in the cross-talk between PVAT and vessel by mediating PVAT inhibition on agonist-induced thoracic aorta contraction. Furthermore, intraperitoneal injection of KYNA in mice reduced blood pressure. The vessel relaxation effect of KYNA was through the endothelium-dependent PI3K-Akt-eNOS pathway. Finally, the high-fat diet decreased KAT1 expression in perithoracic aortic fat and led to KYNA reduction in blood. Our research identified KYNA generated by KAT as a novel perivascular brown adipocyte-derived vascular relaxation factor and suggests that KYNA reduction is a critical event in vascular dysfunction under obese condition.