Adipose Tissue Of Obese Mice Research Articles

Abstract 2518: Elucidating the impact of obesity and weight loss on breast cancer tumor progression

Abstract Obesity is an established risk factor for breast cancer and worsened prognosis, however the mechanisms for this link have not been fully elucidated. Additionally, the consequence of weight loss (WL) prior to the diagnosis of cancer has not been fully explored. One possible link is via the immune system. Obesity is associated with metabolic dysfunction as well as inflammation of the adipose tissue. While WL is a great tool to combat metabolic dysfunction, we have shown that following WL the adipose tissue does not properly reprogram its immunophenotype and remains in a heightened inflammatory state. Accompanying the heightened inflammatory state and increased immune infiltration found in obesity, a novel subset of macrophages termed “lipid associated macrophages” (LAMs) with high expression of triggering receptor expressed on myeloid cells 2 (Trem2) have been discovered in adipose tissue of obese mice and humans. Data from our lab shows LAMs are found at low levels in the adipose tissue of lean mice and enhanced in weight gain (WG) and WL mice. While other investigators have shown Trem2-expressing tumor associated macrophages contribute to immunosuppression in the tumor microenvironment, the implications of enhanced Trem2+ LAMs found in obesity and WL have not been explored in the context of cancer. The purpose of this study is to elucidate the impact of obesity and WL on breast cancer tumor progression. Female mice were ovariectomized to model post-menopause and to enable greater weight gain. High fat diet (HFD) and low fat diet (LFD) feeding paradigms were used to produce three diet groups: lean, WG, and WL. Lean mice were maintained on LFD for the entirety of the study. WG mice were fed LFD for 12 weeks followed by HFD for 12 weeks. Mice in the WL group were fed HFD for 12 weeks to establish obesity and then fed LFD for 12 weeks to achieve WL. Four weeks prior to the end of the dietary paradigm, mice were injected with E0771 mammary cancer cells into the mammary fat pad. We confirmed that obesity drives accelerated tumor growth progression resulting in significantly increased tumor mass. We found that WL results in an intermediate phenotype between the lean and obese models, suggesting WL may provide some protection to tumor growth, but does not restore the tumor-bearing host to the same level of protection as a consistently lean model. We also demonstrated significantly increased gene expression of both Adgre1 (gene for F4/80) and Trem2 in obese ovarian and mammary adipose tissue compared to lean adipose tissue. Future studies will focus on understanding the mechanistic links between heightened inflammation in obese and WL adipose tissue and tumor progression. Additionally, we aim to elucidate the contribution of Trem2-expressing immune cells to tumor progression in the obese and WL contexts. Citation Format: Elysa M. Wolf, Barbara Fingleton, Alyssa H. Hasty. Elucidating the impact of obesity and weight loss on breast cancer tumor progression [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 2518.

The crude guava polysaccharides ameliorate high-fat diet-induced obesity in mice via reshaping gut microbiota

Guava is a popular fruit consumed worldwide with beneficial effects in regulation of glucose and lipid metabolism. Although polysaccharides are a major phytochemical component of guava, to date, the alleviative effects of polysaccharides from the guava fruit against diet-induced obesity remain unclear. The relationship between the anti-obesity effects of guava polysaccharide (GP) and gut microbiota is unknown. In current study, seven-week-old C57BL/6 mice were fed high-fat diet (HFD) supplemented with GP (100 mg/kg) by oral gavage for 11 weeks. GP supplementation alleviated HFD-induced body weight gain and visceral obesity, and reduced serum cholesterol, triglyceride, and LDL-C levels. In addition, GP ameliorated insulin resistance and prevented hepatic lipid accumulation and meta-inflammation in both liver and adipose tissues in obese mice. Remarkably, GP treatment restored the Firmicutes/Bacteroidetes ratio, induced growth of beneficial bacteria including Clostridium XlVa, Parvibacter, and Enterorhabdus, and decreased in inflammation-related bacteria Mucispirillum in mice fecal samples, accompanied with enhanced production of colonic short chain fatty acids especially butyric acid. However, the metabolic benefits of GP diminished in antibiotics-treated HFD-fed mice. Overall, GP improved metabolic profiles in HFD-induced obese mice via the mediation of gut microbiota-dependent pathways. GP might be developed and utilized as prebiotics in nutraceutical and food industry.

Diet-induced obesity promotes CD11c+ T-bet+ B cell expansion in liver and adipose tissue

Abstract Immune cells are increasingly appreciated to play a role in inflammation in adipose and hepatic tissue during obesity and may contribute to the development of non-alcoholic fatty liver disease (NAFLD). Both invariant Natural Killer T (iNKT) cells and B cells are enriched in the liver and adipose tissues of humans and mice, but the degree and nature of their influence in the development of NAFLD remains unclear. iNKT cells interact with B cells in many contexts, including during the chronic inflammation associated with autoimmune disease and infection, so it is likely they interact during obesity. Emerging evidence implicates intrahepatic B cells in the progression of human NAFLD, and proinflammatory B cells increase in the steatotic livers of HFD-fed mice. Our preliminary studies demonstrate an iNKT cell-dependent expansion of inflammatory CD11c+ T-bet+ B cells in the subcutaneous adipose tissue of obese humans and perigonadal adipose tissue of obese mice. We now extend those findings to other iNKT cell-rich fatty depots. Flow cytometry identified increased frequencies of T-bet+ B cells in the livers, but not the omenta or mesenteric adipose tissue, of obese mice. In parallel to the in vivo studies, in vitro co-cultures revealed that iNKT cells are sufficient to mediate expansion of T-bet+ B cells. Ongoing experiments will examine the potential role and mechanism of iNKT cells in mediating hepatic Tbet+ B cell expansion. Characterization of the specific contribution of immune inflammation in the progression NAFLD to NASH will allow for the design of successful therapeutic interventions for this increasingly frequent public health problem. Funding support from NIH K12GM111726 (BTE), NIH TL1 TR002647 (TS), Swedish Research Council (TH), and NIH R01 AI32798-01A1 (EAL).

Coffee intake mitigated high fat diet‐induced whitening of brown adipose tissue in obese mice

The aim of this study was to evaluate the preventive and therapeutic effect of coffee consumption on metabolic and molecular aspects of adipose tissue (AT) remodeling in a high‐fat diet‐induced obesity mice. Our hypothesis is that coffee consumption mitigates brown adipose tissue (BAT) whitening and prevent obesity related comorbidities. 50 male mice of 90 days of the C57BL6 lineage divided into 3 groups: Control (C); High‐fat (HF) and prevention 1% w/w coffee (HF‐CP). After 10 weeks, the HF group gave rise to the treatment 1% w/w coffee group (HF‐CT), totaling 4 different groups for another 4 weeks, totaling 14 weeks of experiment. The HF‐CP group has lower body mass than the high fat (HF) group (‐8%, p < 0.05), better AT distribution, with smaller adipocytes and smaller mean sectional area (p<0.05). Both groups that received coffee associated with a high‐fat diet (HF‐CP and HF‐CT) improved glucose metabolism when compared to the HF group, the glucose tolerance test in the HF‐CP group was similar to the C. Coffee consumption prevented hyperinsulinemia and hyperleptinemia in the HF‐CP group, this group did not develop insulin resistance and in the group that consumed coffee after induction of obesity (HF‐CT) the hyperinsulinemia was attenuated. The plasma concentration of IL‐6 was reduced (p<0.05) in HF‐CP and HF‐CT when compared to the HF group. The immunofluorescence expression of UCP‐1was more intense in BAT of HF‐CP compared to others groups. Thermogenesis and mitochondrial biogenesis in BAT were higher with increased gene expression of UCP‐1, PPARγ, PRDM16, PCG1α, Rβ3A, OPA‐1in HF‐CP. Coffee has better effects when consumed preventively with better AT remodeling, with maintenance of the brown phenotype, thermogenic activity in BAT. Furthermore, coffee consumption was able to attenuate body mass gain, improve glucose and leptin homeostasis. When consumed after obesity induction, as a treatment, it was not as effective as prevention, however, there was also better BAT remodeling with attenuation of lightening, greater expression of thermogenic genes and reversal of hyperinsulinemia.

Adipose tissue stiffness in the development of metabolic diseases

Obesity, defined as an expansion of white adipose tissue, is also accompanied by interstitial fibrosis and overexpression of extracellular matrix (ECM) in adipose tissue in recent studies. We hypothesize that obesity induces adipose tissue ECM crosslinking and stiffening, leading to adipocyte dysfunction. First, we applied a collagen gel system to investigate the effect of ECM stiffness on adipogenesis and mature adipocyte functions. Our results showed that increased ECM stiffness impaired adipogenesis; and blunted the sensitivity to insulin and lipolytic cues, as well as secretion of adipokines, in differentiated adipocytes. In contrast, increased ECM stiffness exacerbated the sensitivity to inflammatory stimulation. Next, we found that ob/ob adipose tissue exhibited an increased signal in the polarized view of picrosirius red stained section, as well as increased crosslinks and aggregated collagen in second harmonics generation (SHG) imaging. These results suggest that ECM crosslinking was upregulated in the adipose tissue of obese mice. Ex vivo crosslinking inhibition in ob/ob adipose tissue explants increased insulin sensitivity, adiponectin expression and lipolytic activity. Finally, in vivo crosslinking inhibition reversed metabolic impairments and adipocyte functional signature genes in ob/ob mice. Taken together, our study underscores that adipose tissue crosslinking and stiffening may orchestrate metabolic disorders resulting from adipocyte dysfunction in obesity.

Strength training alters the tissue fatty acids profile and slightly improves the thermogenic pathway in the adipose tissue of obese mice

Obesity is a disease characterized by the exacerbated increase of adipose tissue. A possible way to decrease the harmful effects of excessive adipose tissue is to increase the thermogenesis process, to the greater energy expenditure generated by the increase in heat in the body. In adipose tissue, the thermogenesis process is the result of an increase in mitochondrial work, having as substrate H+ ions, and which is related to the increased activity of UCP1. Evidence shows that stress is responsible for increasing the greater induction of UCP1 expression via β-adrenergic receptors. It is known that physical exercise is an important implement for sympathetic stimulation promoting communication between norepinephrine/epinephrine with membrane receptors. Thus, the present study investigates the influence of short-term strength training (STST) on fatty acid composition, lipolysis, lipogenesis, and browning processes in the subcutaneous adipose tissue (sWAT) of obese mice. For this, Swiss mice were divided into three groups: lean control, obesity sedentary, and obese strength training (OBexT). Obese animals were fed a high-fat diet for 14 weeks. Trained obese animals were submitted to 7 days of strength exercise. It was demonstrated that STST sessions were able to reduce fasting glycemia. In the sWAT, the STST was able to decrease the levels of the long-chain fatty acids profile, saturated fatty acid, and palmitic fatty acid (C16:0). Moreover, it was showed that STST did not increase protein levels responsible for lipolysis, the ATGL, ABHD5, pPLIN1, and pHSL. On the other hand, the exercise protocol decreased the expression of the lipogenic enzyme SCD1. Finally, our study demonstrated that the STST increased browning process-related genes such as PGC-1α, PRDM16, and UCP1 in the sWAT. Interestingly, all these biomolecular mechanisms have been observed independently of changes in body weight. Therefore, it is concluded that short-term strength exercise can be an effective strategy to initiate morphological changes in sWAT.

Anti-obesity effect of fermented lemon peel on high-fat diet-induced obese mice by modulating the inflammatory response.

Inflammation is a characteristic of obesity. The rich compounds in lemon peel have anti-inflammatory effects. This study examined whether fermented lemon peel can have an anti-obesity effect on obese mice induced by a high-fat diet (HFD) by regulating inflammation. The lemon peel fermentation supernatant (LPFS) could inhibit the weight gain of mice and improve the lesions of the liver and epididymal adipose tissue. In addition, LPFS regulates blood lipids, liver function, and inflammation-related indicators in the serum of obese mice. LPFS plays a positive role in regulating the inflammation and obesity-related genes in liver tissue and adipose tissue of obese mice. High-performance liquid chromatography showed an increase in the contents of compounds with antioxidant or/and anti-inflammatory effects and compounds with anti-obesity effects. These results suggest that the LPFS could help reduce obesity in obese mice induced by an HFD by adjusting the balance of the inflammatory response. PRACTICAL APPLICATIONS: Obesity often increases the risk of chronic diseases, and mild inflammation is a feature of obesity. Therefore, timely suppression of inflammation in the body can help control the occurrence of obesity. This study clarified the anti-obesity effect of fermented lemon peel on a high-fat diet (HFD)-induced obese mice by regulating the body's inflammatory response and confirmed that fermentation improves the anti-inflammatory activity of lemon peel. This study provides important references for future investigation, prophylaxis, and treatment of inflammation and obesity-related diseases, as well as the advances in functional foods and fermented foods with anti-inflammatory and anti-obesity activities.

Obesity aggravates contact hypersensitivity reaction in mice.

Obesity is associated with chronic, low-grade inflammation in tissues and predisposes to various complications, including inflammatory skin diseases. However, the link between obesity and contact hypersensitivity (CHS) is not fully understood. We sought to determine the influence of obesity on T helper 1 (Th1)-mediated CHS. The activity/phenotype/cytokine profile of the immune cells was tested in vivo and in vitro. Using quantitative polymerase chain reaction (qPCR) and fecal microbiota transplantation (FMT), we tested the role of a high-fat diet (HFD)-induced gut microbiota (GM) dysbiosis in increasing the effects of CHS. Exacerbated CHS correlates with an increased inflammation-inducing GM in obese mice. We showed a proinflammatory milieu in the subcutaneous adipose tissue of obese mice, accompanied by proinflammatory CD4+ T cells and dendritic cells in skin draining lymph nodes and spleen. Obese interleukin (IL)-17A-/-B6 mice are protected from CHS aggravation, suggesting the importance of IL-17A in CHS aggravation in obesity. Obesity creates a milieu that induces more potent CHS-effector cells but does not have effects on already activated CHS-effector cells. IL-17A is essential for the pathogenesis of enhanced CHS during obesity. Our study provides novel knowledge about antigen-specific responses in obesity, which may help with the improvement of existing treatment and/or in designing novel treatment for obesity-associated skin disorders.

IL-4 polarized human macrophage exosomes control cardiometabolic inflammation and diabetes in obesity

Cardiometabolic disease is an increasing cause of morbidity and death in society. While M1-like macrophages contribute to metabolic inflammation and insulin resistance, those polarized to an M2-like phenotype exert protective properties. Building on our observations reporting M2-like macrophage exosomes in atherosclerosis control, we tested whether they could serve to control inflammation in the liver and adipose tissue of obese mice. In thinking of clinical translation, we studied human THP-1 macrophages exposed to interleukin (IL)-4 as a source of exosomes (THP1-IL4-exo). Our findings show that THP1-IL4-exo polarized primary macrophages to an anti-inflammatory phenotype and reprogramed their energy metabolism by increasing levels of microRNA-21/99a/146b/378a (miR-21/99a/146b/378a) while reducing miR-33. This increased lipophagy, mitochondrial activity, and oxidative phosphorylation (OXPHOS). THP1-IL4-exo exerted a similar regulation of these miRs in cultured 3T3-L1 adipocytes. This enhanced insulin-dependent glucose uptake through increased peroxisome proliferator activated receptor gamma (PPARγ)-driven expression of GLUT4. It also increased levels of UCP1 and OXPHOS activity, which promoted lipophagy, mitochondrial activity, and beiging of 3T3-L1 adipocytes. Intraperitoneal infusions of THP1-IL4-exo into obese wild-type and Ldlr-/- mice fed a Western high-fat diet reduced hematopoiesis and myelopoiesis, and favorably reprogramed inflammatory signaling and metabolism in circulating Ly6Chi monocytes. This also reduced leukocyte numbers and inflammatory activity in the circulation, aorta, adipose tissue, and the liver. Such treatments reduced hepatic steatosis and increased the beiging of white adipose tissue as revealed by increased UCP1 expression and OXPHOS activity that normalized blood insulin levels and improved glucose tolerance. Our findings support THP1-IL4-exo as a therapeutic approach to control cardiometabolic disease and diabetes in obesity.

Discovery of (E)-4-styrylphenoxy-propanamide: A dual PPARα/γ partial agonist that regulates high-density lipoprotein-cholesterol levels, modulates adipogenesis, and improves glucose tolerance in diet-induced obese mice

Peroxisome proliferator-activated receptors are promising therapeutic targets for metabolic diseases, including obesity, diabetes, and dyslipidemia. This study describes the design, synthesis and pharmacological evaluation of stilbene-based compounds as dual PPARα/γ partial agonists with potency in the nanomolar range. In vitro and in vivo assays revealed that the lead compound (E)-4-styrylphenoxy-propanamide (5b) removed 14C-cholesterol from the foam cells through apolipoprotein A-I and High-Density Lipoprotein-2. In the high-fat diet-induced obesity mouse model, the oral administration of compound 5b increased HDL levels, paraoxonase-1 activity, and insulin sensitivity, and decreased glucose levels. Moreover, the adipogenesis pathway and triglyceride accumulation slightly changed in the adipocyte cells upon treatment with compound 5b, without affecting the body weight and adipose tissue in obese mice. Compound 5b did not affect the plasma levels of hepatic and renal injury biomarkers. Thus, stilbene-based compound 5b is a promising prototype for developing novel candidates to treat dyslipidemia and diabetes.

Non-heat-stressed Method to Isolate Hepatic Stellate Cells From Highly Steatotic Tumor-bearing Liver Using CD49a.

Non-heat-stressed Method to Isolate Hepatic Stellate Cells From Highly Steatotic Tumor-bearing Liver Using CD49a.

Inhibitory Effect of Lactobacillus plantarum KFY02 Fermented Lemon Juice on Obesity and Intestinal Regulation in Mice Fed with High-fat Diet

The purpose of this study was to observe the fat reducing effect of lemon juice fermented by Lactobacillus plantarum KFY02 and its regulation on intestinal flora. This study induced obesity in mice through the establishment of high-fat diet, the experimental mice were divided into normal group, model group, Lactobacillus plantarum KFY02 group, unfermented lemon juice group and fermented lemon juice group, and biochemical kits, section observation and quantitative PCR were used to detect the related indexes of mouse serum and tissue, and the composition of intestinal microorganisms was observed by detecting the expression of microorganisms in feces. The results showed that Lactobacillus plantarum KFY02, unfermented lemon juice and fermented lemon juice could effectively reduce the body weight of obese mice, reduce the organ index of liver and epididymal adipose tissue in obese mice, and reduce the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C) and raise high density lipoprotein cholesterol (HDL-C) in serum and liver tissue of obese mice, and also could increase the contents of total cholesterol (TC), triglyceride (TG) and total protein (TP) in mouse feces. H&E pathological observation showed that Lactobacillus plantarum KFY02, unfermented lemon juice and fermented lemon juice could also reduce liver tissue lesions and adipocyte enlargement and accumulation caused by obesity. qPCR results showed that Lactobacillus plantarum KFY02, unfermented lemon juice and fermented lemon juice could up-regulate PPAR-α, CPT-1, LPL, CYP7A1 and down-regulate C/EBPα, PPAR-γ mRNA expression in liver tissue of obese mice induced by high fat diet, meanwhile, they could also up-regulate the expression of Bacteroidetes, Lactobacillus sp., Bifidobacterium sp. and down-regulate the expression of Firmicutes. These results showed that Lactobacillus plantarum KFY02, unfermented lemon juice and fermented lemon juice could reduce fat in mice, and the effect of fermented lemon juice was the best. The fat reduction effect of fermented lemon juice on mice was directly related to its regulation of intestinal function and microbial composition. It could be seen that lemon juice fermented by Lactobacillus plantarum KFY02 had good lipid-lowering and intestinal regulation in obese mice.

Abstract 13903: Adipocyte PGC1-α and NOV/CCN3: Novel Targets in the Management of Obesity-Linked Cardiomyopathy

Introduction: Chronic Obesity is frequently associated cardiac remodeling and the development of myocardial dysfunction. Oxidative stress and mitochondrial dysfunction are major factors in the development of obesity-related cardiomyopathy. Peroxisome proliferator-activated receptor-gamma coactivator 1 alpha &ltPGC-1α &gt is key in maintaining energy homeostasis and promotes reprogram white adipose into beige adipose tissue. We have reported a downregulation in epicardial PGC-1α levels in human and mice are associated with a reduction in cardiac function while increases in nephroblastoma overexpressed NOV/CCN3 is associated with severe inflammation and oxidative stress in multiple tissues. Hypothesis: Concomitant activation of PGC-1α and inhibition of NOV in the epicardial fat promotes adipocyte browning and alleviates obesity-related cardiomyopathy. Methods: Effect of PGC-1α over expression and NOV inhibition &ltshNOV&gt in transgenic mic selectively in adipose tissue on the heart in mice fed a high-fat diet &ltHFD&gt Mice were randomly divided into 4 groups &ltn= 5 -6> 1; lean &ltnormal diet&gt, 2; HFD , 3; transgenic mice on HFD + shNOV or 4; PGC-1α . Blood pressure, cardiac and adipose fibrosis and oxygen consumption , metabolic and mitochondrial markers were studied. Results: Mice fed a HFD developed decreased mitochondrial respiration. Inhibiting NOV expression in adipose tissue of obese mice in transgenic mice resulted in an increased heart mitochondria biogenesis &ltPGC-1α&gt, HO-1 and activation of mitophagy and autophagy &ltLC3B and PINK1&gt. Transgenic PGC-1α mice exhibited increased mitochondria biogenesis, integrity and beige adipocyte markers &ltPRDM16, FGF21&gt, insulin receptor phosphorylation and reduced inflammation. Conclusion: Inhibiting NOV or overexpression of PGC-1α in the epicardial fat improve the quality of adipose tissue with a positive impact on the heart by inducing mitophagy and improving mitochondrial function. Tissue-targeted manipulation of the NOV and/or PGC-1α signaling to reprogram white fat into brown fat may constitute a novel therapeutic strategy in the treatment of obesity-related cardiomyopathy.

A novel peroxisome proliferator-activated receptor gamma ligand improves insulin sensitivity and promotes browning of white adipose tissue in obese mice

ObjectiveNuclear receptor Peroxisome Proliferator-Activated Receptor γ (PPARγ) is a promising target for the treatment of type 2 diabetes. The antidiabetic drug thiazolidinediones (TZDs) are potent insulin sensitizers as full agonists of PPARγ, but cause unwanted side effects. Recent discoveries have shown that TZDs improve insulin sensitivity by blocking PPARγ phosphorylation at S273, which decouples the full agonism-associated side effects. PPARγ ligands that act through the blockage of PPARγ phosphorylation but lack the full agonist activity would be expected to improve insulin sensitivity without TZD-associated side effects, however, chemicals that carry such traits and bind to PPARγ with high-affinity are lacking. Moreover, TZDs are known to promote white-to-brown adipocyte conversion and energy expenditure and appear to require their full agonism on PPARγ for this activity. It is unknown whether a partial or non-TZD agonist of PPARγ is capable of promoting browning effect. In this study, we developed a novel non-TZD partial agonist of PPARγ and investigated its function on insulin sensitivity and white-to-brown conversion and energy expenditure in diet-induced obese mice. MethodsA novel indole-based chemical WO95E was designed via medicinal chemistry and tested for PPARγ binding and activity and for the effect on PPARγ phosphorylation. Diet-induced obese mice were administered with WO95E for 4 weeks. Insulin sensitivity, glucose tolerance, body weight, fat tissue weight, adipocyte size, morphology, energy expenditure, and expression levels of genes involved in PPARγ activity, thermogenesis/browning, and TZD-related side effects were evaluated. ResultsWO95E binds to PPARγ with high affinity and acts as a PPARγ partial agonist. WO95E inhibits PPARγ phosphorylation and regulates PPARγ phosphorylation-dependent genes. WO95E ameliorates insulin resistance and glucose tolerance in mice of diet-induced obesity, with minimal TZD use-associated side effects. We found that WO95E promotes white-to-brown adipocyte conversion and energy expenditure and hence protects against diet-induced obesity. WO95E decreases the size of adipocytes and suppresses adipose tissue inflammation. WO95E also suppresses obesity-associated liver steatosis. ConclusionsWO95E improves insulin sensitivity and glucose homeostasis and promotes browning and energy expenditure by acting as a novel PPARγ phosphorylation inhibitor/partial agonist. Our findings suggest the potential of this compound or its derivative for the therapeutic treatment of insulin resistance and obesity.

GPNMB protects against obesity-related metabolic disorders by attenuating macrophage-derived inflammation in white adipose tissue through CD44 receptor-dependent mechanism

Abstract Introduction Obesity is a worldwide health issue frequently linked to cardiovascular disease. Obesity is closely associated with chronic low-grade inflammation in adipose tissue caused by macrophage infiltration and activation, which leads to metabolic disorders. We discovered glycoprotein non-metastatic melanoma protein B (GPNMB) as a gene that is robustly expressed in white adipose tissue of obese mice. Purpose We aim to elucidate the role of GPNMB in obesity and its related metabolic disorders. Methods We generated GPNMB-knockout (KO) mice and assessed body weight, insulin sensitivity, and inflammation-related phenotypes after 12 weeks of high fat-diet (HFD) feeding. For in vitro experiment, we isolated peritoneal macrophages from wild-type (WT) and GPNMB-KO mice to explore their inflammatory phenotypes. Results After HFD feeding, obesity-related metabolic disorders were markedly worsened in GPNMB-KO mice, assessed by insulin and glucose tolerance test, although the weight gain and adiposity were similar between WT and GPNMB-KO mice. Expression of inflammatory cytokines was significantly increased in WAT of GPNMB-KO mice, in addition to a remarkable increase in crown-like structures. Peritoneal macrophages isolated from GPNMB-KO mice exhibited higher inflammatory cytokine levels, and significantly impaired the adipocytes insulin sensitivity in an endocrine manner. Recombinant soluble GPNMB attenuated the inflammatory capabilities in peritoneal macrophages isolated from GPNMB-KO mice. We identified that GPNMB inhibits the NF-κB signaling through binding to the CD44 receptor, and therefore negatively regulates inflammatory responses in macrophages. Conclusion Our study demonstrates GPNMB as an adipokine that protects against obesity-related metabolic disorders by reducing macrophage-derived inflammation, which in turn improves adipocytes functions and consequently preserves systemic metabolic health. Therefore, GPNMB is an attractive therapeutic target for the treatment of obesity-related metabolic disorders. Funding Acknowledgement Type of funding sources: None.

Adipose expression of CREB3L3 modulates body weight during obesity

We found the hepatic transcription factor Cyclic-AMP Responsive Element Binding Protein 3-like-3 (CREB3L3) to be expressed in adipose tissue, and selectively downregulated in the more metabolically protective subcutaneous adipose tissue in obese mice and humans. We sought to elucidate the specific role of this factor in adipose biology. CREB3L3 fat-specific knockout mice were fed a high-fat diet to induce obesity and metabolic dysfunction. Additionally, we injected a flip-excision adeno-associated virus directly into the subcutaneous inguinal adipose tissue of Adiponectin-Cre mice to create a depot-specific overexpression model for further assessment. Fat-specific ablation of CREB3L3 enhanced weight gain and insulin resistance following high-fat feeding, as fat-specific knockout mice expended less energy and possessed more inflammatory adipose tissue. Conversely, inguinal fat CREB3L3 overexpression deterred diet-induced obesity and ameliorated metabolic dysfunction. Together, this study highlights the relevance of CREB3L3 in obese adipose tissue and demonstrates its role as a powerful body weight modulator.

Abstract P158: Endothelin Inhibits Adiponectin Production Via ETB Receptor Activation On Adipocytes

Endothelin-1 has been implicated in obesity related insulin resistance. Our lab recently demonstrated that ET-1 is elevated in adipose tissue of obese mice, and blockade of ET-1 receptors improves insulin sensitivity in a mouse model of diet induced obesity. One potential mechanism by which ET-1 promotes insulin resistance is through activation of the ET-1 type B receptor (ET B ). Blockade of ET B receptors improves insulin sensitivity and increases circulating adiponectin, an adipokine only released by adipose tissue. Therefore, the current hypothesis is that ET-1 causes insulin resistance and inhibits adiponectin production by adipocytes. Primary mouse adipocytes were cultured and chronically treated with ET-1 for 3 days. ET-1 treated adipocytes had significantly lower peroxisome proliferator activator gamma, a transcription factor that drive adiponectin production, and adiponectin mRNA expression and release into media. This response was attenuated by co-treatment with an ET B receptor antagonist (BQ-788; 57.2±2.0 vehicle, 42.5±4.5 ET-1, 59.8±1.5 ET-1+BQ788, ng/ml; p<0.05) and in adipocytes from adipocyte ET B receptor knockout mice. Further, expression of several genes in the insulin signaling pathway, including Glut4 and insulin receptor substrates 1 and 2 were significantly reduced in adipocytes treated with ET-1, a response that was attenuated with ET B receptor blockade or knockout of the ET B receptor. These data suggest that increased ET-1 production in adipose tissue promotes insulin resistance on adipocytes and inhibits the release of insulin sensitizing adipokines such as adiponectin, a potential mechanism by which ET-1 receptor blockade improves insulin sensitivity in obese mice.

Oleanolic Acid Improves Obesity-Related Inflammation and Insulin Resistance by Regulating Macrophages Activation.

The chronic low-grade inflammation of adipose tissues, primarily mediated by adipose tissue macrophages (ATMs), is the key pathogenic link between obesity and metabolic disorders. Oleanolic acid (OA) is a natural triterpenoid possessing anti-diabetic and anti-inflammation effects, but the machinery is poorly understood. This study investigated the detailed mechanisms of OA on adipose tissue inflammation in obese mice. C57BL/6J mice were fed with high-fat diet (HFD) for 12 weeks, then daily intragastric administrated with vehicle, 25 and 50 mg/kg OA for 4 weeks. Comparing with vehicle, OA administration in obese mice greatly improved insulin resistance, and reduced adipose tissue hypertrophy, ATM infiltration as well as the M1/M2 ratio. The pro-inflammatory markers were significantly down-regulated by OA in both adipose tissue of obese mice and RAW264.7 macrophages treated with interferon gamma/lipopolysaccharide (IFN-γ/LPS). Furthermore, it was found that OA suppressed activation of mitogen-activated protein kinase (MAPK) signaling and NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome through decreasing voltage dependent anion channels (VDAC) expression and reactive oxygen species (ROS) production. This is the first report that oleanolic acid exerts its benefits by affecting mitochondrial function and macrophage activation.

Endothelin receptor antagonism improves glucose handling, dyslipidemia, and adipose tissue inflammation in obese mice.

Endothelin-1 (ET-1) is elevated in patients with obesity; however, its contribution to the pathophysiology related to obesity is not fully understood. We hypothesized that high ET-1 levels cause dyslipidemia, inflammation, and insulin resistance within the adipose tissue of obese mice. To test this hypothesis, male C57BL/6J mice were fed either normal diet (NMD) or high-fat diet (HFD) for 8 weeks followed by 2 weeks of treatment with either vehicle, atrasentan (ETA receptor antagonist, 10 mg/kg/day) or bosentan (ETA/ETB receptor antagonist, 100 mg/kg/day). Atrasentan and bosentan lowered circulating non-esterified free fatty acids and triglycerides seen in HFD mice, while atrasentan-treated mice had significantly lower liver triglycerides compared with non-treated HFD mice. ET-1 receptor blockade significantly improved insulin tolerance compared with insulin-resistant HFD mice and lowered expression of genes in epididymal white adipose tissue (eWAT) associated with insulin resistance and inflammation. Flow cytometric analyses of eWAT indicated that HFD mice had significantly higher percentages of both CD4+ and CD8+ T cells compared with NMD mice, which was attenuated by treatment with atrasentan or bosentan. Atrasentan treatment also abolished the decrease in eosinophils seen in HFD mice. Taken together, these data indicate that ETA and ETA/ETB receptor blockade improves peripheral glucose homeostasis, dyslipidemia and liver triglycerides, and also attenuates the pro-inflammatory immune profile in eWAT of mice fed HFD. These data suggest a potential use for ETA and ETA/ETB receptor blockers in the treatment of obesity-associated dyslipidemia and insulin resistance.

AB-Kefir Reduced Body Weight and Ameliorated Inflammation in Adipose Tissue of Obese Mice Fed a High-Fat Diet, but Not a High-Sucrose Diet.

Consumption of different types of high-calorie foods leads to the development of various metabolic disorders. However, the effects of multi-strain probiotics on different types of diet-induced obesity and intestinal dysbiosis remain unclear. In this study, mice were fed a control diet, high-fat diet (HFD; 60% kcal fat and 20% kcal carbohydrate), or western diet (WD; 40% kcal fat and 43% kcal carbohydrate) and administered with multi-strain AB-Kefir containing six strains of lactic acid bacteria and a Bifidobacterium strain, at 109 CFU per mouse for 10 weeks. Results demonstrated that AB-Kefir reduced body weight gain, glucose intolerance, and hepatic steatosis with a minor influence on gut microbiota composition in HFD-fed mice, but not in WD-fed mice. In addition, AB-Kefir significantly reduced the weight and size of adipose tissues by regulating the expression of CD36, Igf1, and Pgc1 in HFD-fed mice. Although AB-Kefir did not reduce the volume of white adipose tissue, it markedly regulated CD36, Dgat1 and Mogat1 mRNA expression. Moreover, the abundance of Eubacterium_coprostanoligenes_group and Ruminiclostridium significantly correlated with changes in body weight, liver weight, and fasting glucose in test mice. Overall, this study provides important evidence to understand the interactions between probiotics, gut microbiota, and diet in obesity treatment.