Mechanistic insights into the role of USP14 in adipose tissue macrophage recruitment and insulin resistance in obesity.

Diet-induced obesity can cause metabolic syndromes. The critical link in disease progression is adipose tissue macrophage (ATM) recruitment, which drives low-level inflammation, triggering adipocyte dysfunction. It is unclear whether ubiquitin-specific proteinase 14 (USP14) affects metabolic disorders by mediating adipose tissue inflammation. In the present study, we showed that USP14 is highly expressed in ATMs of obese human patients and diet-induced obese mice. Mouse USP14 overexpression aggravated obesity-related insulin resistance by increasing the levels of pro-inflammatory ATMs, leading to adipose tissue inflammation, excessive lipid accumulation, and hepatic steatosis. In contrast, USP14 knockdown in adipose tissues alleviated the phenotypes induced by a high-fat diet. Co-culture experiments showed that USP14 deficiency in macrophages led to decreased adipocyte lipid deposition and enhanced insulin sensitivity, suggesting that USP14 plays an important role in ATMs. Mechanistically, USP14 interacted with TNF receptor-associated 6, preventing K48-linked ubiquitination as well as proteasome degradation, leading to increased pro-inflammatory polarization of macrophages. In contrast, the pharmacological inhibition of USP14 significantly ameliorated diet-induced hyperlipidemia and insulin resistance in mice. Our results demonstrated that macrophage USP14 restriction constitutes a key constraint on the pro-inflammatory M1 phenotype, thereby inhibiting obesity-related metabolic diseases.

History and future perspectives of adipose tissue macrophage biology.

Macrophages contribute to adipose tissue homeostasis; however, they are also thought to be responsible for insulin resistance in obesity. Macrophages, which were oversimplified in past methodologies, have become rather difficult to understand comprehensively as recent developments in research methodology have revealed their diversity. This review highlights recent studies on adipose tissue macrophages, identifies controversial issues that need to be resolved and proposes a scenario for further development of adipose tissue macrophage biology.

Chondroitin Sulfate-Derived Micelles for Adipose Tissue-Targeted Delivery of Celastrol and Phenformin to Enhance Obesity Treatment.

Adipose tissue macrophages (ATMs) are crucial in maintaining a low-grade inflammatory microenvironment in adipose tissues (ATs). Modulating ATM polarization to attenuate inflammation represents a potential strategy for treating obesity with insulin resistance. This study develops a combination therapy of celastrol (CLT) and phenformin (PHE) using chondroitin sulfate-derived micelles. Specifically, CLT-loaded 4-aminophenylboronic acid pinacol ester-modified chondroitin sulfate micelle (CS-PBE/CLT) and chondroitin sulfate-phenformin conjugate micelles (CS-PHE) were synthesized, which were shown to actively target ATs through CD44-mediated pathways. Furthermore, the dual micellar systems significantly reduced inflammation and lipid accumulation via protein quantification and Oil Red O staining. In preliminary in vivo studies, we performed H&E staining, immunohistochemical staining, insulin tolerance test, and glucose tolerance test, and the results showed that the combination therapy using CS-PBE/CLT and CS-PHE micelles significantly reduced the average body weight, white adipose tissue mass, and liver mass of high-fat diet-fed mice while improving their systemic glucose homeostasis. Overall, this combination therapy presents a promising alternative to current treatment options for diet-induced obesity.

Macrophage CREBZF Orchestrates Inflammatory Response to Potentiate Insulin Resistance and Type 2 Diabetes.

Chronic adipose tissue inflammation accompanied by macrophage accumulation and activation is implicated in the pathogenesis of insulin resistance and type 2 diabetes in humans. The transcriptional coregulator CREBZF is a key factor in hepatic metabolism, yet its role in modulating adipose tissue inflammation and type 2 diabetes remains elusive. The present study demonstrates that overnutrition-induced CREBZF links adipose tissue macrophage (ATM) proinflammatory activation to insulin resistance. CREBZF deficiency in macrophages, not in neutrophils, attenuates macrophage infiltration in adipose, proinflammatory activation, and hyperglycemia in diet-induced insulin-resistant mice. The coculture assays show that macrophage CREBZF deficiency improves insulin sensitivity in primary adipocytes and adipose tissue. Mechanistically, CREBZF competitively inhibits the binding of IκBα to p65, resulting in enhanced NF-κB activity. In addition, bromocriptine is identified as a small molecule inhibitor of CREBZF in macrophages, which suppresses the proinflammatory phenotype and improves metabolic dysfunction. Furthermore, CREBZF is highly expressed in ATM of obese humans and mice, which is positively correlated with proinflammatory genes and insulin resistance in humans. This study identifies a previously unknown role of CREBZF coupling ATM activation to systemic insulin resistance and type 2 diabetes.

The miR-23-27-24 clusters drive lipid-associated macrophage proliferation in obese adipose tissue.

Identifying molecular circuits that control adipose tissue macrophage (ATM) function is necessary to understand how ATMs contribute to tissue homeostasis and obesity-induced insulin resistance. In this study, we find that mice with a myeloid-specific knockout of the miR-23-27-24 clusters of microRNAs (miRNAs) gain less weight on a high-fat diet but exhibit worsened glucose and insulin tolerance. Analysis of ATMs from these mice shows selectively reduced numbers and proliferation of a recently reported subset of lipid-associated CD9+Trem2+ ATMs (lipid-associated macrophages [LAMs]). Leveraging the role of miRNAs to control networks of genes, we use RNA sequencing (RNA-seq), functional screens, and biochemical assays to identify candidate target transcripts that regulate proliferation-associated signaling. We determine that miR-23 directly targets the mRNA of Eif4ebp2, a gene that restricts protein synthesis and proliferation in macrophages. Altogether, our study demonstrates that control of proliferation of a protective subset of LAMs by noncoding RNAs contributes to protection against diet-induced obesity metabolic dysfunction.

The GDF3-ALK7 signaling axis in adipose tissue: a possible therapeutic target for obesity and associated diabetes?

ALK7, a type I receptor for the transforming growth factor-ß superfamily, is known to be predominantly expressed in adipocytes in both mice and humans. The present review describes recent findings suggesting that ALK7 plays a major role in regulating lipid metabolism and fat mass. Furthermore, the ligands and upstream regulators that activate ALK7 signaling are discussed. The focus is on findings in mice and their derivative tissues and cells that harbor the mutations of ALK7 and related molecules. Particular attention is paid to the contradictory nature of the current literature about the loss-of-function phenotypes and the relationship with insulin secretion and sensitivity. Additional attention is paid to the ALK7 gene variants found in humans and their associated traits. The goal is to seek a parsimonious, and preferably singular and unified, description of the underlying mechanism. This review also introduces recent promising findings about ALK7 neutralizing treatment to obese mice.

San-wei-tan-xiang capsule attenuates atherosclerosis by increasing lysosomal activity in adipose tissue macrophages.

ETHNOPHARMACOLOGICAL RELEVANCE: Dyslipidemia is the leading risk factor of atherosclerosis (AS). Adipose tissue macrophages (ATMs) can regulate postprandial cholesterol levels via uptake and hydrolyzation of lipids and regulation of macrophage cholesterol efflux (MCE). San-wei-tan-xiang (SWTX) capsule, a Traditional Chinese medicine, exerts clinical benefits in patients with atherosclerotic cardiovascular diseases. AIM OF THE STUDY: This work is aimed to evaluate the chemical ingredients and mechanisms of SWTX in anti-AS. MATERIALS AND METHODS: The chemical ingredients of SWTX identified by liquid chromatography coupled with tandem mass spectrometry were used for network pharmacological analysis. The atheroprotective function of SWTX was evaluated in ApoE-/- mice fed a cholesterol-enriched diet. RESULTS: The chemical ingredients identified in SWTX were predicated to be important for lipid metabolism and AS. Animals studies suggested that SWTX effectively attenuated the atherosclerotic plaque growth, elevated postprandial HDL cholesterol levels, elevated the proportion of Tim4 and CD36-expressed ATMs, and upregulated the uptake of lipid and lysosomal activity in ATMs. SWTX-induced elevation of postprandial HDL cholesterol levels was dependent on increased lysosomal activity, since chloroquine, an inhibitor of lysosomal function, blocked the effect of SWTX. Lastly, some predicated bioactive compounds in SWTX can elevate lysosomal activity in vitro. CONCLUSION: SWTX could attenuate atherosclerotic plaque formation by elevating lysosomal activity and enhancing MCE in ATMs.

Thromboxane A2-TP axis promotes adipose tissue macrophages M1 polarization leading to insulin resistance in obesity.

Aberrant arachidonic acid metabolism has been implicated in multiple pathophysiological conditions, and the downstream prostanoids levels are associated with adipocyte dysfunction in obesity. However, the role of thromboxane A2 (TXA2) in obesity remains unclear. We observed that TXA2, through its receptor TP, is a candidate mediator in obesity and metabolic disorders. Obese mice with upregulated TXA2 biosynthesis (TBXAS1) and TXA2 receptor (TP) expression in caused insulin resistance and macrophage M1 polarization in white adipose tissue (WAT), which can be prevented by treatment with aspirin. Mechanistically, the activation of TXA2-TP signaling axis leads to accumulation of protein kinase Cɛ (PKCɛ), thereby enhancing free fat acid (FFA) induced Toll-like receptor4 (TLR4) proinflammatory macrophage activation and the tumor necrosis factor-a (TNF-a) production in adipose tissues. Importantly, TP knockout mice reduced the accumulation of proinflammatory macrophages and adipocyte hypertrophy in WAT. Thus, our findings demonstrate that TXA2-TP axis plays a crucial role in obesity-induced adipose macrophage dysfunction, and rational targeting TXA2 pathway may improve obesity and its associated metabolic disorders in future. In this work, we establish previously unknown role of TXA2-TP axis in WAT. These findings might provide new insight into the molecular pathogenesis of insulin resistance, and indicate rational targeting TXA2 pathway to improve obesity and its associated metabolic disorders in future.

Reciprocal signaling between adipose tissue depots and the central nervous system.

In humans, various dietary and social factors led to the development of increased brain sizes alongside large adipose tissue stores. Complex reciprocal signaling mechanisms allow for a fine-tuned interaction between the two organs to regulate energy homeostasis of the organism. As an endocrine organ, adipose tissue secretes various hormones, cytokines, and metabolites that signal energy availability to the central nervous system (CNS). Vice versa, the CNS is a critical regulator of adipose tissue function through neural networks that integrate information from the periphery and regulate sympathetic nerve outflow. This review discusses the various reciprocal signaling mechanisms in the CNS and adipose tissue to maintain organismal energy homeostasis. We are focusing on the integration of afferent signals from the periphery in neuronal populations of the mediobasal hypothalamus as well as the efferent signals from the CNS to adipose tissue and its implications for adipose tissue function. Furthermore, we are discussing central mechanisms that fine-tune the immune system in adipose tissue depots and contribute to organ homeostasis. Elucidating this complex signaling network that integrates peripheral signals to generate physiological outputs to maintain the optimal energy balance of the organism is crucial for understanding the pathophysiology of obesity and metabolic diseases such as type 2 diabetes.

Adipose tissue macrophage in obesity-associated metabolic diseases.

Adipose tissue macrophage (ATM) has been appreciated for its critical contribution to obesity-associated metabolic diseases in recent years. Here, we discuss the regulation of ATM on both metabolic homeostatsis and dysfunction. In particular, the macrophage polarization and recruitment as well as the crosstalk between ATM and adipocyte in thermogenesis, obesity, insulin resistance and adipose tissue fibrosis have been reviewed. A better understanding of how ATM regulates adipose tissue remodeling may provide novel therapeutic strategies against obesity and associated metabolic diseases.

Cellular and Molecular Mechanisms and Effects of Berberine on Obesity-Induced Inflammation.

Obesity represents chronic low-grade inflammation that precipitates type 2 diabetes, cardiovascular disease, and cancer. Berberine (BBR) has been reported to exert anti-obesity and anti-inflammatory benefits. We aimed to demonstrate the underlying immune-modulating mechanisms of anti-obesity effects of BBR. First, we performed in silico study to identify therapeutic targets, describe potential pathways, and simulate BBR docking at M1 and M2 adipose tissue macrophages (ATMs), tumor necrosis factor-α (TNF-α), C-C motif chemokine ligand 2 (CCL2), CCL4, CCL5, and C-X-C motif chemokine receptor 4 (CXCR4). Next, in vivo, we divided 20 C58BL/6 mice into four groups: normal chow, control (high fat diet (HFD)), HFD + BBR 100 mg/kg, and HFD + metformin (MET) 200 mg/kg. We evaluated body weight, organ weight, fat area in tissues, oral glucose and fat tolerance tests, HOMA-IR, serum lipids levels, population changes in ATMs, M1 and M2 subsets, and gene expression of TNF-α, CCL2, CCL3, CCL5, and CXCR4. BBR significantly reduced body weight, adipocyte size, fat deposition in the liver, HOMA-IR, triglycerides, free fatty acids, ATM infiltration, all assessed gene expression, and enhanced the CD206+ M2 ATMs population. In conclusion, BBR treats obesity and its associated metabolic dysfunctions, by modulating ATM recruitment and polarization via chemotaxis inhibition.

An Iron Refractory Phenotype in Obese Adipose Tissue Macrophages Leads to Adipocyte Iron Overload.

Adipocyte iron overload is a maladaptation associated with obesity and insulin resistance. The objective of the current study was to determine whether and how adipose tissue macrophages (ATMs) regulate adipocyte iron concentrations and whether this is impacted by obesity. Using bone marrow-derived macrophages (BMDMs) polarized to M0, M1, M2, or metabolically activated (MMe) phenotypes, we showed that MMe BMDMs and ATMs from obese mice have reduced expression of several iron-related proteins. Furthermore, the bioenergetic response to iron in obese ATMs was hampered. ATMs from iron-injected lean mice increased their glycolytic and respiratory capacities, thus maintaining metabolic flexibility, while ATMs from obese mice did not. Using an isotope-based system, we found that iron exchange between BMDMs and adipocytes was regulated by macrophage phenotype. At the end of the co-culture, MMe macrophages transferred and received more iron from adipocytes than M0, M1, and M2 macrophages. This culminated in a decrease in total iron in MMe macrophages and an increase in total iron in adipocytes compared with M2 macrophages. Taken together, in the MMe condition, the redistribution of iron is biased toward macrophage iron deficiency and simultaneous adipocyte iron overload. These data suggest that obesity changes the communication of iron between adipocytes and macrophages and that rectifying this iron communication channel may be a novel therapeutic target to alleviate insulin resistance.

The Adipose Tissue Macrophages Central to Adaptive Thermoregulation.

White fat stores excess energy, and thus its excessive expansion causes obesity. However, brown and beige fat, known as adaptive thermogenic fat, dissipates energy in the form of heat and offers a therapeutic potential to counteract obesity and metabolic disorders. The fat type-specific biological function is directed by its unique tissue microenvironment composed of immune cells, endothelial cells, pericytes and neuronal cells. Macrophages are major immune cells resident in adipose tissues and gained particular attention due to their accumulation in obesity as the primary source of inflammation. However, recent studies identified macrophages' unique role and regulation in thermogenic adipose tissues to regulate energy expenditure and systemic energy homeostasis. This review presents the current understanding of macrophages in thermogenic fat niches with an emphasis on discrete macrophage subpopulations central to adaptive thermoregulation.

Lactiplantibacillus plantarum K8-based paraprobiotics prevents obesity and obesity-induced inflammatory responses in high fat diet-fed mice.

This study was conducted to investigate the effect of the paraprobiotics, lactic acid bacteria lysates (LAB-P) prepared from Lactiplantibacillus plantarum K8, on obesity and obesity-induced inflammatory responses in high-fat diet (HFD)-fed mice. LAB-P (100 mg/kg) significantly decreased the HFD-induced increase in weight by approximately 20% compared to that in the HFD control. This result was accompanied by a decrease in adipose weight/size. The white adipose tissue weight of epididymis, subcutaneous inguinal region, and mesentery were decreased by 36%, 20%, and 40%, respectively, in LAB-P (100 mg/kg)-administered mice. The size of the epididymal white adipose tissue-derived adipocytes was reduced by 41%. The LAB-P-mediated reduction in adipose tissues was associated with downregulation of adipogenic factors, such as peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα). In addition, LAB-P administration reduced total cholesterol and low-density lipoprotein levels by 23% and 42%, respectively, with a 55% reduction in lactate dehydrogenase levels. Stromal vascular fraction-derived adipose tissue macrophages were favorably regulated by LAB-P administration; the expression of CD11c, an inflammatory marker, was reduced by 30%, and that of CD206, an anti-inflammatory marker, was increased by 9-fold. These results were shown to correlated with the inhibition of proinflammatory cytokines (IL-1ß and IL-6) and downregulation of NF-κB expression. Furthermore, LAB-P administration suppressed HFD-induced fatty liver by activating AMPKα, an energy metabolic sensor. This study indicates that LAB-P effectively prevents HFD-induced obesity and obesity-induced inflammatory responses and serves a valuable basic work for utilizing LAB-P as functional food ingredient to preventing obesity and treating obesity-associated inflammatory diseases.

Subtype-Specific Surface Proteins on Adipose Tissue Macrophages and Their Association to Obesity-Induced Insulin Resistance.

A chronic low-grade inflammation, originating in the adipose tissue, is considered a driver of obesity-associated insulin resistance. Macrophage composition in white adipose tissue is believed to contribute to the pathogenesis of metabolic diseases, but a detailed characterization of pro- and anti-inflammatory adipose tissue macrophages (ATMs) in human obesity and how they are distributed in visceral- and subcutaneous adipose depots is lacking. In this study, we performed a surface proteome screening of pro- and anti-inflammatory ATMs in both subcutaneous- (SAT) and visceral adipose tissue (VAT) and evaluated their relationship with systemic insulin resistance. From the proteomics screen we found novel surface proteins specific to M1-like- and M2-like macrophages, and we identified depot-specific immunophenotypes in SAT and VAT. Furthermore, we found that insulin resistance, assessed by HOMA-IR, was positively associated with a relative increase in pro-inflammatory M1-like macrophages in both SAT and VAT.

High Hydrostatic Pressure Extract of Mulberry Leaf Attenuated Obesity-Induced Inflammation in Rats.

Low-grade inflammation might be a link between obesity and obesity-associated metabolic dysfunction, including diabetes, hepatic steatosis, and other health complications. This study investigated whether the supplementation of high hydrostatic pressure extract of mulberry (Morus alba L.) leaves (HML) to obese rats could counteract obesity-related inflammation. Three-week-old male Sprague-Dawley rats were separated into three groups as follows: (a) a normal diet, (b) 45% high-fat (HF) diet, and HF diet containing 0.4% HML (c) or 0.8% HML (d) (IACUC No. 17-033). After 14 weeks of HML supplementation, adipose tissue mass, mRNA expression of adipogenic genes, such as aP2, peroxisome proliferator-activated receptor γ (PPARγ), and sterol regulatory element binding protein 1c (SREBP1c), and macrophage recruitment were significantly decreased in HF-fed obese rats. Serum concentrations of nitric oxide and mRNA levels of arginase1 (Arg1), CD11c, and inducible nitric oxide synthase (iNOS) involved in adipose tissue macrophage M1 polarization were also significantly reduced by HML. Moreover, HML alleviated the serum and hepatic lipid profiles and reduced hepatic lipogenic gene expression of acetyl-CoA carboxylase (ACC), cluster of differentiation 36 (CD36), CPT1, fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD1), and SREBP1c, and inflammation-associated genes, including IL1ß, interleukin 6 (IL6), and tumor necrosis factor α (TNFα). Serum IL6 and TNFα levels were remarkedly suppressed in the 0.8% HML group. These results suggested that the favorable effect of HML on obesity-associated inflammation might be related in part to the decrease in adipose tissue and hepatic fat deposition and inflammation.

Adipose tissue macrophage-derived exosomes induce ferroptosis via glutathione synthesis inhibition by targeting SLC7A11 in obesity-induced cardiac injury.

Ferroptosis is an iron-dependent programmed cell death characterized by the accumulation of reactive oxygen species (ROS). Long-term high fat diet (HFD) was found to be associated with ferroptosis and cardiac injury. HFD-induced obesity is characterized by sustained, low-grade inflammation in adipose tissue, while macrophage infiltration plays a crucial role in inflammation. Exosomes (Exos) derived from adipose tissue macrophages (ATMs) participate in the physiological processes of recipient cells. In this study, we investigated the role of ATM-Exos in obesity-induced ferroptosis and cardiac injury. We found that HFD-induced obesity resulted in higher mRNA expression levels of specific markers, e.g., prostaglandin endoperoxide synthase 2 (PTGS2), and increased the levels of lipid peroxides, including malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Macrophages infiltrated the adipose tissues, as examined by flow cytometry. Exosomes derived from ATM-Exos were analyzed using transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Obese ATM-Exos administration induced higher levels of PTGS2, MDA, 4-HNE, lipid ROS, and mitochondrial injury. Obese ATM-Exos further provoked obvious cardiac injury, demonstrated by abnormal levels of cardiac enzymes and inflammatory factors. Systolic left ventricle (LV) function anomalies were induced by ATM-Exos in obese mice. miR-140-5p is abundant in obese ATM-Exos and promotes ferroptosis in cardiomyocytes. Solute carrier family 7 member 11 (SLC7A11) is a downstream target of miR-140-5p, which induces ferroptosis via inhibition of GSH synthesis by targeting SLC7A11. Attenuating exosomal-miR-140-5p expression alleviates ferroptosis and cardiac injury induced by obese ATM exosomes by alleviating GSH inhibition. In summary, the current study provides evidence that obese ATM-exosomal miR-140-5p promotes ferroptosis by regulating GSH synthesis and provides a novel therapeutic strategy for targeting obese ATM-Exos in obesity-induced cardiac injury.

Moderate l-lactate administration suppresses adipose tissue macrophage M1 polarization to alleviate obesity-associated insulin resistance.

As a crucial metabolic intermediate, l-lactate is involved in redox balance, energy balance, and acid-base balance in organisms. Moderate exercise training transiently elevates plasma l-lactate levels and ameliorates obesity-associated type 2 diabetes. However, whether moderate l-lactate administration improves obesity-associated insulin resistance remains unclear. In this study, we defined 800 mg/kg/day as the dose of moderate l-lactate administration. In mice fed with a high-fat diet (HFD), moderate l-lactate administration for 12 weeks was shown to alleviate weight gain, fat accumulation, and insulin resistance. Along with the phenotype alterations, white adipose tissue thermogenesis was also found to be elevated in HFD-fed mice. Meanwhile, moderate l-lactate administration suppressed the infiltration and proinflammatory M1 polarization of adipose tissue macrophages (ATMs) in HFD-fed mice. Furthermore, l-lactate treatment suppressed the lipopolysaccharide-induced M1 polarization of bone marrow-derived macrophages (BMDMs). l-lactate can bind to the surface receptor GPR132, which typically drives the downstream cAMP-PKA signaling. As a nutrient sensor, AMP-activated protein kinase (AMPK) critically controls macrophage inflammatory signaling and phenotype. Thus, utilizing inhibitors of the kinases PKA and AMPK as well as siRNA against GPR132, we demonstrated that GPR132-PKA-AMPKα1 signaling mediated the suppression caused by l-lactate treatment on BMDM M1 polarization. Finally, l-lactate addition remarkably resisted the impairment of lipopolysaccharide-treated BMDM conditional media on adipocyte insulin sensitivity. In summary, moderate l-lactate administration suppresses ATM proinflammatory M1 polarization through activation of the GPR132-PKA-AMPKα1 signaling pathway to improve insulin resistance in HFD-fed mice, suggesting a new therapeutic and interventional approach to obesity-associated type 2 diabetes.

Puerarin Attenuates Obesity-Induced Inflammation and Dyslipidemia by Regulating Macrophages and TNF-Alpha in Obese Mice.

Obesity causes low-grade inflammation that results in dyslipidemia and insulin resistance. We evaluated the effect of puerarin on obesity and metabolic complications both in silico and in vivo and investigated the underlying immunological mechanisms. Twenty C57BL/6 mice were divided into four groups: normal chow, control (HFD), HFD + puerarin (PUE) 200 mg/kg, and HFD + atorvastatin (ATO) 10 mg/kg groups. We examined bodyweight, oral glucose tolerance test, serum insulin, oral fat tolerance test, serum lipids, and adipocyte size. We also analyzed the percentage of total, M1, and M2 adipose tissue macrophages (ATMs) and the expression of F4/80, tumor necrosis factor-α (TNF-α), C-C motif chemokine ligand 2 (CCL2), CCL4, CCL5, and C-X-C motif chemokine receptor 4. In silico, we identified the treatment-targeted genes of puerarin and simulated molecular docking with puerarin and TNF, M1, and M2 macrophages based on functionally enriched pathways. Puerarin did not significantly change bodyweight but significantly improved fat pad weight, adipocyte size, fat area in the liver, free fatty acids, triglycerides, total cholesterol, and HDL-cholesterol in vivo. In addition, puerarin significantly decreased the ATM population and TNF-α expression. Therefore, puerarin is a potential anti-obesity treatment based on its anti-inflammatory effects in adipose tissue.

Fetuin-A regulates adipose tissue macrophage content and activation in insulin resistant mice through MCP-1 and iNOS: involvement of IFNγ-JAK2-STAT1 pathway.

In the context of obesity-induced adipose tissue (AT) inflammation, migration of macrophages and their polarization from predominantly anti-inflammatory to proinflammatory subtype is considered a pivotal event in the loss of adipose insulin sensitivity. Two major chemoattractants, monocyte chemoattractant protein-1 (MCP-1) and Fetuin-A (FetA), have been reported to stimulate macrophage migration into inflamed AT instigating inflammation. Moreover, FetA could notably modulate macrophage polarization, yet the mechanism(s) is unknown. The present study was undertaken to elucidate the mechanistic pathway involved in the actions of FetA and MCP-1 in obese AT. We found that FetA knockdown in high fat diet (HFD) fed mice could significantly subdue the augmented MCP-1 expression and reduce adipose tissue macrophage (ATM) content thereby indicating that MCP-1 is being regulated by FetA. Additionally, knockdown of FetA in HFD mice impeded the expression of inducible nitric oxide synthase (iNOS) reverting macrophage activation from mostly proinflammatory to anti-inflammatory state. It was observed that the stimulating effect of FetA on MCP-1 and iNOS was mediated through interferon γ (IFNγ) induced activation of JAK2-STAT1-NOX4 pathway. Furthermore, we detected that the enhanced IFNγ expression was accounted by the stimulatory effect of FetA upon the activities of both cJun and JNK. Taken together, our findings revealed that obesity-induced FetA acts as a master upstream regulator of AT inflammation by regulating MCP-1 and iNOS expression through JNK-cJun-IFNγ-JAK2-STAT1 signaling pathway. This study opened a new horizon in understanding the regulation of ATM content and activation in conditions of obesity-induced insulin resistance.