Signaling In Adipocytes Research Articles

L-Fucose Suppresses Lipid Accumulation via the AMPK Pathway in 3T3-L1 Adipocytes.

L-fucose (Fuc), a monosaccharide with different biological functions in various organisms, exhibits potent anti-obesity effects in obese mice. However, the mechanisms underlying its anti-obesity effects remain largely unknown. In this study, we aimed to investigate the effects of Fuc on lipid metabolism and insulin signaling in 3T3-L1 adipocytes. We found that Fuc treatment suppressed lipid accumulation during adipocyte differentiation. Additionally, Fuc treatment enhanced the phosphorylation of AMP-activated kinase (AMPK) and its downstream pathways, responsible for the regulation of fatty acid oxidation and lipolysis. Furthermore, Fuc-induced activation of the AMPK pathway was diminished by the AMPK inhibitor Compound C, and Fuc treatment considerably promoted glucose uptake via Akt activation in an insulin-resistant state. These findings provide a basis for elucidating the mechanism underlying the anti-obesity effect of Fuc, which may, in the future, be considered as a therapeutic compound for treating obesity and related diseases.

FABP4 Controls Fat Mass Expandability (Adipocyte Size and Number) through Inhibition of CD36/SR-B2 Signalling

Adipose tissue hypertrophy during obesity plays pleiotropic effects on health. Adipose tissue expandability depends on adipocyte size and number. In mature adipocytes, lipid accumulation as triglycerides into droplets is imbalanced by lipid uptake and lipolysis. In previous studies, we showed that adipogenesis induced by oleic acid is signed by size increase and reduction of FAT/CD36 (SR-B2) activity. The present study aims to decipher the mechanisms involved in fat mass regulation by fatty acid/FAT-CD36 signalling. Human adipose stem cells, 3T3-L1, and its 3T3-MBX subclone cell lines were used in 2D cell cultures or co-cultures to monitor in real-time experiments proliferation, differentiation, lipolysis, and/or lipid uptake and activation of FAT/CD36 signalling pathways regulated by oleic acid, during adipogenesis and/or regulation of adipocyte size. Both FABP4 uptake and its induction by fatty acid-mediated FAT/CD36-PPARG gene transcription induce accumulation of intracellular FABP4, which in turn reduces FAT/CD36, and consequently exerts a negative feedback loop on FAT/CD36 signalling in both adipocytes and their progenitors. Both adipocyte size and recruitment of new adipocytes are under the control of FABP4 stores. This study suggests that FABP4 controls fat mass homeostasis.

Adipocyte signaling affects thyroid-specific gene expression via down-regulation of TTF-2/FOXE1.

Obesity affects thyroid gland function. Hypothyroidism, thyroid nodules, goiter, and thyroid cancer are more frequent in patients with higher body mass index values. Although these data are supported by many clinical and epidemiological studies, very scarce is our knowledge at the molecular level. In this study, we present the first experimental evidence that adipocyte signaling down-regulates the expression of thyroid-specific transcription factor 2 (TTF-2/FOXE1). It plays a crucial role in thyroid development and thyroid homeostasis and it is strictly connected to thyroid cancer as well. We provide in vivo and in vitro evidence that inhibition of TTF-2/FOXE1 gene expression is mediated by adipocyte signaling.

Update on the Role of Glucocorticoid Signaling in Osteoblasts and Bone Marrow Adipocytes During Aging.

Bone marrow adipose tissue (BMAT) in the skeleton likely plays a variety of physiological and pathophysiological roles that are not yet fully understood. In elucidating the complex relationship between bone and BMAT, glucocorticoids (GCs) are positioned to play a key role, as they have been implicated in the differentiation of bone marrow mesenchymal stem cells (BMSCs) between osteogenic and adipogenic lineages. The purpose of this review is to illuminate aspects of both endogenous and exogenous GC signaling, including the influence of GC receptors, in mechanisms of bone aging including relationships to BMAT. Harmful effects of GCs on bone mass involve several cellular pathways and events that can include BMSC differentiation bias toward adipogenesis and the influence of mature BMAT on bone remodeling through crosstalk. Interestingly, BMAT involvement remains poorly explored in GC-induced osteoporosis and warrants further investigation. This review provides an update on the current understanding of the role of glucocorticoids in the biology of osteoblasts and bone marrow adipocytes (BMAds).

Orphan receptor GPR50 attenuates inflammation and insulin signaling in 3T3-L1 preadipocytes.

Type 2 diabetes (T2DM) is characterized by insulin secretion deficiencies and systemic insulin resistance (IR) in adipose tissue, skeletal muscle, and the liver. Although the mechanism of T2DM is not yet fully known, inflammation and insulin resistance play a central role in the pathogenesis of T2DM. G protein-coupled receptors (GPCRs) are involved in endocrine and metabolic processes as well as many other physiological processes. GPR50 (G protein-coupled receptor 50) is an orphan GPCR that shares the highest sequence homology with melatonin receptors. The aim of this study was to investigate the effect of GPR50 on inflammation and insulin resistance in 3T3-L1 preadipocytes. GPR50 expression was observed to be significantly increased in the adipose tissue of obese T2DM mice, while GPR50 deficiency increased inflammation in 3T3-L1 cells and induced the phosphorylation of AKT and insulin receptor substrate (IRS) 1. Furthermore, GPR50 knockout in the 3T3-L1 cell line suppressed PPAR-γ expression. These data suggest that GPR50 can attenuate inflammatory levels and regulate insulin signaling in adipocytes. Furthermore, the effects are mediated through the regulation of the IRS1/AKT signaling pathway and PPAR-γ expression.

Anti-diabetic effects of GLP1 analogs are mediated by thermogenic interleukin-6 signaling in adipocytes

Mechanisms underlying anti-diabetic effects of GLP1 analogs remain incompletely understood. We observed that in prediabetic humans exenatide treatment acutely induces interleukin-6 (IL-6) secretion by monocytes and IL-6 in systemic circulation. We hypothesized that GLP1 analogs signal through IL-6 in adipose tissue (AT) and used the mouse model to test if IL-6 receptor (IL-6R) signaling underlies the effects of the GLP1-IL-6 axis. We show that liraglutide transiently increases IL-6 in mouse circulation and IL-6R signaling in AT. Metronomic liraglutide treatment resulted in AT browning and thermogenesis linked with STAT3 activation. IL-6-blocking antibody treatment inhibited STAT3 activation in AT and suppressed liraglutide-induced increase in thermogenesis and glucose utilization. We show that adipose IL-6R knockout mice still display liraglutide-induced weight loss but lack thermogenic adipocyte browning and metabolism activation. We conclude that the anti-diabetic effects of GLP1 analogs are mediated by transient upregulation of IL-6, which activates canonical IL-6R signaling and thermogenesis.

Apolipoprotein A-IV reduced metabolic inflammation in white adipose tissue by inhibiting IKK and JNK signaling in adipocytes

Apolipoprotein A-IV (ApoA-IV) plays a role in satiation and serum lipid transport. In diet-induced obesity (DIO) C57BL/6J mice, ApoA-IV deficiency induced in ApoA-IV−/−knock-out (KO mice) resulted in increased bodyweight, insulin resistance (IR) and plasma free fatty acid (FFA), which was partially reversed by stable ApoA-IV-green fluorescent protein (KO-A4-GFP) transfection in KO mice. DIO KO mice exhibited increased M1 macrophages in epididymal white adipose tissue (eWAT) as well as in the blood. Based on RNA-sequencing analyses, cytokine-cytokine receptor interactions, T cell and B cell receptors, and especially IL-17 and TNF-α, were up-regulated in eWAT of DIO ApoA-IV KO compared with WT mice. Supplemented ApoA-IV suppressed lipopolysaccharide (LPS)-induced IKK and JNK phosphorylation in Raw264.7 macrophage cell culture assays. When the culture medium was supplemented to 3T3-L1 adipocytes they exhibited an increased sensitivity to insulin. ApoA-IV protects against obesity-associated metabolic inflammation mainly through suppression in M1 macrophages of eWAT, IL17-IKK and IL17-JNK activity.

TonEBP in Myeloid Cells Promotes Obesity-Induced Insulin Resistance and Inflammation Through Adipose Tissue Remodeling.

The phenotypic and functional plasticity of adipose tissue macrophages (ATMs) during obesity plays a crucial role in orchestration of adipose and systemic inflammation. Tonicity-responsive enhancer binding protein (TonEBP) (also called NFAT5) is a stress protein that mediates cellular responses to a range of metabolic insults. Here, we show that myeloid cell-specific TonEBP depletion reduced inflammation and insulin resistance in mice with high-fat diet-induced obesity but did not affect adiposity. This phenotype was associated with a reduced accumulation and a reduced proinflammatory phenotype of metabolically activated macrophages, decreased expression of inflammatory factors related to insulin resistance, and enhanced insulin sensitivity. TonEBP expression was elevated in the ATMs of obese mice, and Sp1 was identified as a central regulator of TonEBP induction. TonEBP depletion in macrophages decreased induction of insulin resistance-related genes and promoted induction of insulin sensitivity-related genes under obesity-mimicking conditions and thereby improved insulin signaling and glucose uptake in adipocytes. mRNA expression of TonEBP in peripheral blood mononuclear cells was positively correlated with blood glucose levels in mice and humans. These findings suggest that TonEBP in macrophages promotes obesity-associated systemic insulin resistance and inflammation, and downregulation of TonEBP may induce a healthy metabolic state during obesity.

FAM96A is essential for maintaining organismal energy balance and adipose tissue homeostasis in mice

The iron (Fe) metabolism plays important role in regulating systemic metabolism and obesity development. The Fe inside cells can form iron-sulfur (Fe–S) clusters, which are usually assembled into target proteins with the help of a conserved cluster assembly machinery. Family with sequence similarity 96A (FAM96A; also designated CIAO2A) is a cytosolic Fe–S assembly protein involved in the regulation of cellular Fe homeostasis. However, the biological function of FAM96A in vivo is still incompletely defined. Here, we tested the role of FAM96A in regulating organismal Fe metabolism, which is relevant to obesity and adipose tissue homeostasis. We found that in mice genetically lacking FAM96A globally, intracellular Fe homeostasis was interrupted in both white and brown adipocytes, but the systemic Fe level was normal. FAM96A deficiency led to adipocyte hypertrophy and organismal energy expenditure reduction even under nonobesogenic normal chow diet-fed conditions. Mechanistically, FAM96A deficiency promoted mechanistic target of rapamycin (mTOR) signaling in adipocytes, leading to an elevation of de novo lipogenesis and, therefore, fat mass accumulation. Furthermore, it also caused mitochondrial defects, including defects in mitochondrial number, ultrastructure, redox activity, and metabolic function in brown adipocytes, which are known to be critical for the control of energy balance. Moreover, adipocyte-selective FAM96A knockout partially phenocopied global FAM96A deficiency with adipocyte hypertrophy and organismal energy expenditure defects but the mice were resistant to high-fat diet-induced weight gain. Thus, FAM96A in adipocytes may autonomously act as a critical gatekeeper of organismal energy balance by coupling Fe metabolism to adipose tissue homeostasis.

Astragaloside IV Regulates Insulin Resistance and Inflammatory Response of Adipocytes via Modulating CTRP3 and PI3K/AKT Signaling.

Emerging evidence showed that adipocytes are important regulators in controlling insulin resistance in type 2 diabetes mellitus (T2DM). So far, compounds isolated from natural plants have been widely studied for their roles in alleviating T2DM-associated complications. This work evaluated the actions of astragaloside IV (AS-IV) on insulin resistance and inflammatory biomarker expression in adipocytes and explored the potential mechanisms. Glucose consumption of the adipocytes was determined by a glucose assay kit; the mRNA expression levels of glucose transporter type 4 (GLUT-4), interleukin-6 (IL-6), TNF-α and C1q tumor necrosis factor-related protein 3 (CTRP3) were measured by quantitative real-time PCR (qRT-PCR); the protein levels were determined by western blot assay and enzyme-linked immunosorbent assay. AS-IV concentration-dependently increased glucose consumption in the insulin resistance adipocytes. Further qRT-PCR results showed that AS-IV concentration-dependently reduced adipocyte IL-6 and TNF-α expression. Moreover, GLUT-4 expression in adipocytes was also significantly upregulated by AS-IV. Furthermore, we found that AS-IV concentration-dependently increased CTRP3 expression in adipocytes. CTRP3 silence decreased glucose consumption, upregulated IL-6 and TNF-α expression and downregulated GLUT-4 mRNA expression in 200µM AS-IV-treated adipocytes. Moreover, AS-IV treatment enhanced the activity of phosphoinositide 3-kinase (PI3K)/AKT signaling in adipocytes, which was markedly attenuated by CTRP3 silencing. Importantly, inhibition of PI3K/AKT signaling also attenuated AS-IV induced an increase in glucose consumption and GLUT-4 expression and a decrease in IL-6 and TNF-α expression of adipocytes. Collectively, our data indicated that AS-IV attenuated insulin resistance and inflammation in adipocytes via targeting CTRP3/PI3K/Akt signaling.

Vitamin D3 affects browning of white adipocytes by regulating autophagy via PI3K/Akt/mTOR/p53 signaling in vitro and in vivo.

Promoting brown fat-like phenotype in white adipose tissue has been a promising strategy for the treatment of obesity. Vitamin D3 (VD3) has been indicated to affect differentiation of white and brown adipocytes. Nevertheless, its potential mechanism involved in obesity development is unclear. Oil red O staining was utilized to detect lipid formation in 3T3-L1 adipocytes. CKK-8 assay was used for measurement of cell viability. RT-qPCR and western blotting were implemented for expression detection of markers for white adipocyte browning, autophagy- and PI3K/Akt/mTOR/p53 signaling-associated proteins. Immunofluorescence staining was conducted for assessment of autophagy. An obese mouse model was established by high-fat VD deficient diet. VD3 suppressed lipid formation in 3T3-L1 adipocytes. VD3 downregulated markers for white adipocyte browning (PPAR-γ, PGC-1α, UCP1), enhanced autophagy, activated p53 signaling and inactivated PI3K/Akt/mTOR signaling in 3T3-L1 adipocytes and HF-VDD-induced mice. VD3 suppressed HF-VDD-induced weight gain in mice. VD3 inhibits the expression of markers for white adipocyte browning in vitro and in vivo by enhancing autophagy and regulating PI3K/Akt/mTOR/p53 signaling pathway.

Disruption of mitochondria-associated ER membranes impairs insulin sensitivity and thermogenic function of adipocytes.

The prevalence and healthcare burden of obesity and its related metabolic disorders such as type 2 diabetes (T2D) are increasing rapidly. A better understanding of the pathogenesis of these diseases helps to find the therapeutic strategies. Mitochondria and endoplasmic reticulum (ER) are two important organelles involved in the maintenance of intracellular Ca2+ and ROS homeostasis. Their functional defects are thought to participate in the pathogenesis of insulin resistance or T2D. The proper structure and function of the mitochondria-associated ER membranes (MAMs) is required for efficient communication between the ER and mitochondria and defects in MAMs have been shown to play a role in metabolic syndrome and other diseases. However, the detailed mechanism to link MAMs dysfunction and pathogenesis of insulin resistance or T2D remains unclear. In the present study, we demonstrated that the proteins involved in .MAMs structure are upregulated and the formation of MAMs is increased during adipogenic differentiation of 3T3-L1 preadipocytes. Disruption of MAMs by knocking down GRP75, which is responsible for connecting ER and mitochondria, led to the impairment of differentiation and ROS accumulation in 3T3-L1 preadipocytes. Most importantly, the differentiated 3T3-L1 adipocytes with GRP75 knockdown displayed inactivation of insulin signaling pathway upon insulin stimulation. Moreover, GRP75 knockdown impaired thermogenesis and glucose utilization in brown adipocytes, the adipocytes with abundant mitochondria that regulate whole-body energy homeostasis. Taken together, our findings suggest that MAMs formation is essential for promoting mitochondrial function and maintaining a proper redox status to enable the differentiation of preadipocytes and normal functioning such as insulin signaling and thermogenesis in mature adipocytes.

Betulinic acid improves TNF-α-induced insulin resistance by inhibiting negative regulator of insulin signalling and inflammation-activated protein kinase in 3T3-L1 adipocytes

Context Obesity is related to insulin resistance, and adipose tissue-secreted TNF-α may play a role in inducing obesity. TNF-α activates inflammatory protein kinase and impairs insulin signalling. Objectives We investigated the effect of betulinic acid on insulin resistance caused by TNF-α treatment in 3T3-L1 adipocytes. Material and methods 3T3-L1 was exposed to TNF-α in the presence and absence of betulinic acid. Various parameters such as glucose uptake assay, cell viability, expression of proteins involved in insulin resistance were studied. Results Betulinic acid increased glucose uptake in TNF-α pre-treated cells and inhibited the activation of PTP1B and JNK and reduced IκBα degradation. Tyrosine phosphorylation was increased, and serine phosphorylation was decreased in IRS-1. Discussion Betulinic acid restored TNF-α impaired insulin signalling and increased PI3K activation and phosphorylation of Akt and increased plasma membrane expression of GLUT 4, which stimulated glucose uptake concentration-dependently. Conclusion These results suggest that betulinic acid is effective at improving TNF-α-induced insulin resistance in adipocytes via inhibiting the activation of negative regulator of insulin signalling and inflammation-activated protein kinase and may potentially improve insulin resistance.

The Stress-Responsive microRNA-34a Alters Insulin Signaling and Actions in Adipocytes through Induction of the Tyrosine Phosphatase PTP1B.

Metabolic stresses alter the signaling and actions of insulin in adipocytes during obesity, but the molecular links remain incompletely understood. Members of the microRNA-34 (miR-34 family play a pivotal role in stress response, and previous studies showed an upregulation of miR-34a in adipose tissue during obesity. Here, we identified miR-34a as a new mediator of adipocyte insulin resistance. We confirmed the upregulation of miR-34a in adipose tissues of obese mice, which was observed in the adipocyte fraction exclusively. Overexpression of miR-34a in 3T3-L1 adipocytes or in fat pads of lean mice markedly reduced Akt activation by insulin and the insulin-induced glucose transport. This was accompanied by a decreased expression of VAMP2, a target of miR-34a, and an increased expression of the tyrosine phosphatase PTP1B. Importantly, PTP1B silencing prevented the inhibitory effect of miR-34a on insulin signaling. Mechanistically, miR-34a decreased the NAD+ level through inhibition of Naprt and Nampt, resulting in an inhibition of Sirtuin-1, which promoted an upregulation of PTP1B. Furthermore, the mRNA expression of Nampt and Naprt was decreased in adipose tissue of obese mice. Collectively, our results identify miR-34a as a new inhibitor of insulin signaling in adipocytes, providing a potential pathway to target to fight insulin resistance.

Anti-inflammatory and Insulin Signaling Phenotype Induced by Repeated Lipopolysaccharide Stimulation in 3T3-L1 Adipocytes.

Lipopolysaccharide (LPS) is thought to be a causative agent of type 2 diabetes, because it has been shown that a single LPS stimulation in vitro induces chronic inflammation and reduces insulin signaling in adipocytes. However, oral LPS administration prevents type 2 diabetes, and this effect does not correspond to a single LPS adipocyte stimulation. In this study, the response of adipocytes to single and repeated stimulation with LPS was examined. 3T3-L1 cells were differentiated into adipocytes and stimulated with LPS once or thrice every 24 h. The expression levels of inflammatory and anti-inflammatory factors and insulin sensitivity-related factors were measured. Single stimulation with LPS increased the mRNA and protein expression of inflammatory factors (interleukin-6 and monocyte chemotactic protein 1), but this increase was inhibited by repeated stimulation. In contrast, the mRNA expression levels of anti-inflammatory factors (proliferator-activated receptor γ and peroxisome proliferator-activated receptor gamma coactivator1 α) were increased by repeated LPS stimulation. Additionally, the mRNA expression levels of insulin sensitivity-related factors (glucose transporter type 4, insulin receptor, insulin receptor substrate 1 and thymoma viral proto-oncogene 2) in adipocytes were increased upon repeated LPS stimulation. Repetitive LPS stimulation, unlike single stimulation of adipocytes, upregulates anti-inflammatory and insulin signaling-related factors.

Novel soybean peptide iglycin ameliorates insulin resistance of high-fat diet fed C57BL/6J mice and differentiated 3T3L1 adipocytes with improvement of insulin signaling and mitochondrial function

Soy consumption has been associated with potential health benefits in reducing chronic diseases. These physiological functions have been attributed to soy proteins or more commonly to bioactive peptides. Thus, more studies are required to identify these bioactive peptides, and elucidate their biological mechanisms of action. In the present study, a novel peptide iglycin was purified from soybean seeds with a molecular mass of 3.88 kDa. Thereafter, iglycin reduced fasting blood glucose and restored insulin sensitivity of C57BL/6J mice on a high-fat diet with increased phosphorylation of insulin receptor substrate 1 (IRS1) and AKT in adipose tissue. Furthermore, it improved glucose uptake, induced translocation of intracellular GLUT4 to plasma membrane and activation of insulin signaling in adipocytes under insulin-resistant condition. In addition, it decreased reactive oxygen species production, lipid peroxidation and inhibited adipocyte apoptosis with improved mitochondrial function as evidenced by up-regulation of succinate dehydrogenase activity, mitochondrial membrane potential and intracellular ATP store. These data suggested that iglycin ameliorated insulin resistance via activation of insulin signaling, which was associated with inhibition of oxidative stress, adipocyte apoptosis, and improvement of mitochondrial function.

Development of a physiological insulin resistance model in human stem cell-derived adipocytes.

Adipocytes are key regulators of human metabolism, and their dysfunction in insulin signaling is central to metabolic diseases including type II diabetes mellitus (T2D). However, the progression of insulin resistance into T2D is still poorly understood. This limited understanding is due, in part, to the dearth of suitable models of insulin signaling in human adipocytes. Traditionally, adipocyte models fail to recapitulate in vivo insulin signaling, possibly due to exposure to supraphysiological nutrient and hormone conditions. We developed a protocol for human pluripotent stem cell–derived adipocytes that uses physiological nutrient conditions to produce a potent insulin response comparable to in vivo adipocytes. After systematic optimization, this protocol allows robust insulin-stimulated glucose uptake and transcriptional insulin response. Furthermore, exposure of sensitized adipocytes to physiological hyperinsulinemia dampens insulin-stimulated glucose uptake and dysregulates insulin-responsive transcription. Overall, our methodology provides a novel platform for the mechanistic study of insulin signaling and resistance using human pluripotent stem cell–derived adipocytes.

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.

4-OR: IL6R Signaling in Adipogenesis Mediates GLP-1 Analog Effects on Adipose Tissue Beiging

Mechanisms underlying antidiabetes effects of GLP-1 analogs such as liraglutide, collectively termed incretins, remain incompletely understood. While incretins boost insulin secretion, they also modulate the immune system and have anti-obesity effects. We discovered that prediabetic patients treated with incretins have increased thermogenic gene expression in supraclavicular adipose tissue (AT) . Interestingly, incretin-treated patients were found to have elevated levels of IL6 plasma, consistent with the observation that incretin treatment induces IL6 secretion by human monocytes. We hypothesized that incretins induce adipocyte browning via IL6 and used the mouse model to test if IL6 receptor (IL6Ra) signaling underlies the effects of the incretin-IL6 axis. We show that liraglutide transiently increases IL6 in circulation and ILRa signaling in AT while metronomic liraglutide treatment results in AT browning and improved glucose clearance in mice. IL6-blocking antibody treatment inhibited the thermogenic and antidiabetes effects of liraglutide. Based on the observation that IL6 induces thermogenic gene expression in cultured adipocytes, we hypothesized that the incretin-IL6 axis directly induces adipocyte browning. To test this, we generated mice with IL6Ra knockout in Pdgfrb-positive adipocyte progenitors (APC-KO) and in adipocytes (AD-KO) . We show that liraglutide-induced weight loss does not depend on IL6 signaling in the adipocyte lineage. However, both IL6Ra APC-KO and AD-KO mice failed to undergo thermogenic adipocyte browning and glucose utilization increase in response to liraglutide treatment. We conclude that the antidiabetes effects of metronomically administered incretins are mediated by transient upregulation of IL6, which activates canonical ILRa signaling and thermogenesis in adipocytes. Disclosure A.D.Gutierrez: None. Z.Gao: None. Y.Yu: None. M.Kolonin: n/a. Funding National Institutes of Health (NIDDK 5R21DK122234)

2-OR: Exosomes from Adipose Tissue Macrophages Can Mediate Insulin-Sensitizing Effects of Rosiglitazone

Background: The beneficial metabolic effects of the PPARγ agonist rosiglitazone (Rosi) are associated with anti-inflammatory changes in adipose tissue macrophages (ATMs) . One study aim was to characterize the in vivo Rosi-induced phenotypic switch of ATMs using a variety of macrophage markers, including the lipid-associated macrophage markers CD9 and Trem2. As a second aim, since ATM-derived exosomes can exert insulin-sensitizing or desensitizing effects dependent on ATM cell context, we assessed the effects of ATM exosomes from Rosi-treated obese mice on in vitro insulin actions. Research Design and Method: ATMs were isolated from 4 months HFD/obese mice treated for the last month with Rosi (60 mg/kg HFD) compared to HFD or chow-fed controls. Among CD11b+F4/80+ or CD64+ macrophages, we identified pro-inflammatory (“M1-like” CD11c+ and/or CD9+) , anti-inflammatory (“M2-like” CD11c-CD206+) and lipid-associated (CD9+ and/or Trem2+) ATMs by flow cytometry. Bone marrow-derived macrophages (BMDMs) were treated in vitro with µM Rosi for 24h. 3T3-L1 adipocytes, L6 myotubes, and primary hepatocytes were cultured 24h with exosomes isolated from ATMs of Rosi treated obese mice or in vitro Rosi treated BMDMs and then assessed for insulin sensitivity. Results: Rosi treatment reduced adipose tissue inflammation, as seen by reduced numbers of pro-inflammatory (“M1-like”) ATMs and increased the Trem2 signature in “M2-like” ATMs. Importantly, Rosi directly induced Trem2 expression in vitro in BMDMs. Additionally, exosomes isolated from Rosi-treated obese mice or M1 BMDMs increased glucose uptake and insulin signalling (pAKT) in adipocytes and myotubes and reduced glucose production in hepatocytes compared to control exosomes. Conclusion: Our data indicate that Trem2 is a PPARγ target gene. Since exosomes from Rosi treated ATMs or BMDMs enhance cellular insulin action, this could provide a new explanation for the well-known insulin-sensitizing effects of PPARγ agonists. Disclosure T.V.Rohm: None. F.C.G.Reis: None. R.Isaac: None. M.Paszek: None. G.Bandyopadhyay: None. J.M.Olefsky: None. Funding Swiss National Science Foundation (SNF) Early Postdoc.Mobility grant (to T.R.) .