Adipocyte-derived Th2 cytokines and myeloid PPARdelta regulate macrophage polarization and insulin sensitivity

Nitrate Esters Alleviated Coronary Atherosclerosis Through Inhibition of NF-κB-Regulated Macrophage Polarization Shift in Epicardial Adipose Tissue

Nitrate esters have been used in clinical practice for more than one century for the treatment of angina. Their clinical effectiveness is due to vasodilator activity in arteries through a method of delivering nitric oxide or a nitric oxide-like compound. Recently, an increasing numbers of functions of this molecule in biology and pathophysiology have been discovered. Macrophage polarization shift in epicardial adipose tissue (EAT) has been demonstrated to be correlated with the severity of coronary artery disease (CAD). In this study, we aimed to investigate whether nitrate esters could improve coronary atherosclerosis through inhibition of macrophage polarization shift in EAT. A case-control study enrolled 48 subjects in 2 groups: CAD patients with or without nitrate esters treatment. Infiltration of M1/M2 macrophages and the expressions of pro-inflammatory and anti-inflammatory cytokines in EAT and subcutaneous white adipose tissue were investigated by immunohistochemical stain among subjects undergoing coronary artery bypass graft surgery. The expression levels of metabolic genes were investigated by real-time reverse transcription-polymerase chain reaction (RT-PCR). We found that nitrate ester treatment significantly inhibited NF-кB activity and decreased macrophage infiltration and M1/M2 macrophage ratio in EAT in patients with CAD. The expressions of pro-inflammatory cytokines were significantly decreased, along with significantly elevated expressions of anti-inflammatory cytokines in CAD patients with nitrate ester treatment, corresponding EAT dysfunction was ameliorated and the severity of patients with CAD (Gensini score) was significantly decreased. The protective effects on macrophage polarization and EAT function through NF-кB activity inhibition suggested a potential mechanism of nitrate esters in alleviating the severity of CAD.

Regulation of lipid-induced macrophage polarization through modulating peroxisome proliferator-activated receptor-gamma activity affects hepatic lipid metabolism via a Toll-like receptor 4/NF-κB signaling pathway

BACKGROUND AND AIM

Chronic inflammation links closely to insulin resistance and lipid metabolism in nonalcoholic fatty liver disease (NAFLD). Macrophage M1 activation plays an important role in the initiation and continuing of pro-inflammatory response of NAFLD. Our study was to investigate whether macrophage M1/M2 polarization switching would affect hepatic inflammation and lipid metabolism through modulation of peroxisome proliferator-activated receptor-gamma (PPAR-γ) activity in vivo and in vitro.

METHODS

RAW264.7 macrophages were treated with different fatty acids, and cell culture supernatants were collected to prepare conditioned media (CM). Different co-culture systems between primary hepatocytes and CM from macrophages were established. A PPAR-γ agonist or antagonist was administered to regulate PPAR-γ activity and macrophage polarization. M1/M2 phenotype markers, inflammatory signaling pathway, and lipid-related genes expression were determined. Wild-type C57BL/6 mice were fed a high-fat diet to induce NAFLD and given rosiglitazone to regulate PPAR-γ activity in vivo.

RESULTS

Saturated fatty acids induced M1-polarized macrophages while polyunsaturated fatty acids induced M2-polarized macrophages. M1-polarized macrophages significantly promoted lipid synthesis and accumulation in primary hepatocytes through upregulation of a toll-like receptor 4 (TLR4)/NF-κB signaling pathway. The PPAR-γ agonist made lipid-induced M1-polarized macrophages switch to an M2-predominant phenotype, while PPAR-γ antagonist had the opposite effect. Macrophage polarization shifting subsequently affected lipid metabolism in primary hepatocytes. Administration of rosiglitazone improved high-fat diet induced hepatic steatosis and lipid metabolism through reducing hepatic TLR4/NF-κB expression and M1-polarized Kupffer cells.

CONCLUSIONS

Lipid-induced macrophage M1 polarization promoted hepatic lipid metabolism. Modulation of PPAR-γ activity could shift macrophage polarization and subsequently affect lipid metabolism. Upregulation of the TLR4/NF-κB signaling pathway is closely linked to dysregulated lipid metabolism in NAFLD.

Implications of metabolism-driven myeloid dysfunctions in cancer therapy

Immune homeostasis is maintained by an adequate balance of myeloid and lymphoid responses. In chronic inflammatory states, including cancer, this balance is lost due to dramatic expansion of myeloid progenitors that fail to mature to functional inflammatory neutrophils, macrophages, and dendritic cells (DCs), thus giving rise to a decline in the antitumor effector lymphoid response. Cancer-related inflammation orchestrates the production of hematopoietic growth factors and cytokines that perpetuate recruitment and activation of myeloid precursors, resulting in unresolved and chronic inflammation. This pathologic inflammation creates profound alterations in the intrinsic cellular metabolism of the myeloid progenitor pool, which is amplified by competition for essential nutrients and by hypoxia-induced metabolic rewiring at the tumor site. Therefore, persistent myelopoiesis and metabolic dysfunctions contribute to the development of cancer, as well as to the severity of a broad range of diseases, including metabolic syndrome and autoimmune and infectious diseases. The aims of this review are to (1) define the metabolic networks implicated in aberrant myelopoiesis observed in cancer patients, (2) discuss the mechanisms underlying these clinical manifestations and the impact of metabolic perturbations on clinical outcomes, and (3) explore new biomarkers and therapeutic strategies to restore immunometabolism and differentiation of myeloid cells towards an effector phenotype to increase host antitumor immunity. We propose that the profound metabolic alterations and associated transcriptional changes triggered by chronic and overactivated immune responses in myeloid cells represent critical factors influencing the balance between therapeutic efficacy and immune-related adverse effects (irAEs) for current therapeutic strategies, including immune checkpoint inhibitor (ICI) therapy.

Gut Microbiota as a Trigger for Metabolic Inflammation in Obesity and Type 2 Diabetes

The gut microbiota has been linked to the development of obesity and type 2 diabetes (T2D). The underlying mechanisms as to how intestinal microbiota may contribute to T2D are only partly understood. It becomes progressively clear that T2D is characterized by a chronic state of low-grade inflammation, which has been linked to the development of insulin resistance. Here, we review the current evidence that intestinal microbiota, and the metabolites they produce, could drive the development of insulin resistance in obesity and T2D, possibly by initiating an inflammatory response. First, we will summarize major findings about immunological and gut microbial changes in these metabolic diseases. Next, we will give a detailed view on how gut microbial changes have been implicated in low-grade inflammation. Lastly, we will critically discuss clinical studies that focus on the interaction between gut microbiota and the immune system in metabolic disease. Overall, there is strong evidence that the tripartite interaction between gut microbiota, host immune system and metabolism is a critical partaker in the pathophysiology of obesity and T2D.

Differential effects of selective- and pan-PPAR agonists on experimental steatohepatitis and hepatic macrophages☆

BACKGROUND & AIMS

Peroxisome proliferator-activated receptors (PPARs) are essential regulators of whole-body metabolism, but also modulate inflammation in immune cells, notably macrophages. We compared the effects of selective PPAR agonists to those of the pan-PPAR agonist lanifibranor in non-alcoholic fatty liver disease (NAFLD), and studied isoform-specific effects on hepatic macrophage biology.

METHODS

Lanifibranor or selective PPARα (fenofibrate), PPARγ (pioglitazone) and PPARδ (GW501516) agonists were therapeutically administered in choline-deficient, amino acid-defined high-fat diet (CDAA-HFD)- and Western diet (WD)-fed mouse models of NAFLD. Acute liver injury was induced by carbon tetrachloride (CCl4). The role of PPARs on macrophage functionality was studied in isolated hepatic macrophages, bone marrow-derived macrophages stimulated with palmitic acid, and circulating monocytes from patients with NAFLD.

RESULTS

Lanifibranor improved all histological features of steatohepatitis in CDAA-HFD-fed mice, including liver fibrosis, thereby combining and exceeding specific effects of the single PPAR agonists. Its potent anti-steatotic efficacy was confirmed in a 3D liver biochip model with primary cells. Infiltrating hepatic monocyte-derived macrophages were reduced following PPAR agonist administration, especially with lanifibranor, even after short-term treatment, paralleling improved steatosis and hepatitis. Lanifibranor similarly decreased steatosis, liver injury and monocyte infiltration in the WD model. In the acute CCl4 model, neither single nor pan-PPAR agonists directly affected monocyte recruitment. Hepatic macrophages isolated from WD-fed mice displayed a metabolically activated phenotype. Lanifibranor attenuated the accompanying inflammatory activation in both murine palmitic acid-stimulated bone marrow-derived macrophages, as well as patient-derived circulating monocytes, in a PPARδ-dependent fashion.

CONCLUSION

Pan-PPAR agonists combine the beneficial effects of selective PPAR agonists and may counteract inflammation and disease progression more potently. PPARδ agonism and lanifibranor directly modulate macrophage activation, but not infiltration, thereby synergizing with beneficial metabolic effects of PPARα/γ agonists.

LAY SUMMARY

Peroxisome proliferated-activated receptors (PPARs) are essential regulators of metabolism and inflammation. We demonstrated that the pan-PPAR agonist lanifibranor ameliorated all aspects of non-alcoholic fatty liver disease in independent experimental mouse models. Non-alcoholic fatty liver disease and fatty acids induce a specific polarization status in macrophages, which was altered by lanifibranor to increase expression of lipid handling genes, thereby decreasing inflammation. PPAR isoforms have differential therapeutic effects on fat-laden hepatocytes, activated hepatic stellate cells and inflammatory macrophages, supporting the clinical development of pan-PPAR agonists.

Natural polymorphism of Ym1 regulates pneumonitis through alternative activation of macrophages

We have positionally cloned the Ym1 gene, with a duplication and a promoter polymorphism, as a major regulator of inflammation. Mice with the RIIIS/J haplotype, with the absence of Ym1 expression, showed reduced susceptibility to mannan-enhanced collagen antibody-induced arthritis and to chronic arthritis induced by intranasal exposure of mannan. Depletion of lung macrophages alleviated arthritis, whereas intranasal supplement of Ym1 protein to Ym1-deficient mice reversed the disease, suggesting a key role of Ym1 for inflammatory activity by lung macrophages. Ym1-deficient mice with pneumonitis had less eosinophil infiltration, reduced production of type II cytokines and IgG1, and skewing of macrophages toward alternative activation due to enhanced STAT6 activation. Proteomics analysis connected Ym1 polymorphism with changed lipid metabolism. Induced PPAR-γ and lipid metabolism in Ym1-deficient macrophages contributed to cellular polarization. In conclusion, the natural polymorphism of Ym1 regulates alternative activation of macrophages associated with pulmonary inflammation.

Indole Alleviates Diet-Induced Hepatic Steatosis and Inflammation in a Manner Involving Myeloid Cell 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 3

BACKGROUND AND AIMS

Indole is a microbiota metabolite that exerts anti-inflammatory responses. However, the relevance of indole to human non-alcoholic fatty liver disease (NAFLD) is not clear. It also remains largely unknown whether and how indole acts to protect against NAFLD. The present study sought to examine the association between the circulating levels of indole and liver fat content in human subjects and explore the mechanisms underlying indole actions in mice with diet-induced NAFLD.

APPROACH AND RESULTS

In a cohort of 137 subjects, the circulating levels of indole were reversely correlated with body mass index. In addition, the circulating levels of indole in obese subjects were significantly lower than those in lean subjects and were accompanied with increased liver fat content. At the whole-animal level, treatment of high-fat diet (HFD)-fed C57BL/6J mice with indole caused significant decreases in the severity of hepatic steatosis and inflammation. In cultured cells, indole treatment stimulated the expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), a master regulatory gene of glycolysis, and suppressed macrophage proinflammatory activation in a PFKFB3-dependent manner. Moreover, myeloid cell-specific PFKFB3 disruption exacerbated the severity of HFD-induced hepatic steatosis and inflammation and blunted the effect of indole on alleviating diet-induced NAFLD phenotype.

CONCLUSIONS

Taken together, our results demonstrate that indole is relevant to human NAFLD and capable of alleviating diet-induced NAFLD phenotypes in mice in a myeloid cell PFKFB3-dependent manner. Therefore, indole mimetic and/or macrophage-specific PFKFB3 activation may be the viable preventive and/or therapeutic approaches for inflammation-associated diseases including NAFLD.

Differential Effects of Myeloid Cell PPARδ and IL-10 in Regulating Macrophage Recruitment, Phenotype, and Regeneration following Acute Muscle Injury

Changes in macrophage phenotype in injured muscle profoundly influence regeneration. In particular, the shift of macrophages from a proinflammatory (M1 biased) phenotype to a proregenerative (M2 biased) phenotype characterized by expression of CD206 and CD163 is essential for normal repair. According to the current canonical mechanism regulating for M1/M2 phenotype transition, signaling through PPARδ is necessary for obtaining the M2-biased phenotype. Our findings confirm that the murine myeloid cell-targeted deletion of Ppard reduces expression in vitro of genes that are activated in M2-biased macrophages; however, the mutation in mice in vivo increased numbers of CD206+ M2-biased macrophages and did not reduce the expression of phenotypic markers of M2-biased macrophages in regenerating muscle. Nevertheless, the mutation impaired CCL2-mediated chemotaxis of macrophages and slowed revascularization of injured muscle. In contrast, null mutation of IL-10 diminished M2-biased macrophages but produced no defects in muscle revascularization. Our results provide two significant findings. First, they illustrate that mechanisms that regulate macrophage phenotype transitions in vitro are not always predictive of mechanisms that are most important in vivo. Second, they show that mechanisms that regulate macrophage phenotype transitions differ in different in vivo environments.

Berberine as a Potential Multi-Target Agent for Metabolic Diseases: A Review of Investigations for Berberine

Berberine (BBR) is a botanic alkaloid extracted from Coptis chinensis (Huanglian), which has various properties, compassing anti-hyperglycemia, anti-obesity, anti-inflammation, and improves insulin resistance, etc. Several researches have confirmed that BBR has effective actions in treating glycolipid metabolic abnormalities. BBR is also beneficial in regulating intestinal flora. Metabolic diseases are strongly associated with metabolic disorders, which are growing in the population and dramatically impacting human health, which also have been considered as a leading cause of diseases and death globally. This review is to evaluate the metabolic properties of BBR, and its potential application to the treatment of metabolic diseases by its effective actions on metabolic disorders.

EB virus-induced ATR activation accelerates nasopharyngeal carcinoma growth via M2-type macrophages polarization

Chronic inflammation induced by persistent viruses infection plays an essential role in tumor progression, which influenced on the interaction between the tumor cells and the tumor microenvironment. Our earlier study showed that ATR, a key kinase participant in single-stranded DNA damage response (DDR), was obviously activated by Epstein-Barr virus (EBV) in nasopharyngeal carcinoma (NPC). However, how EBV-induced ATR activation promotes NPC by influencing inflammatory microenvironment, such as tumor-associated macrophages (TAMs), remains elusive. In this study, we showed that EBV could promote the expression of p-ATR and M2-type TAMs transformation in clinical NPC specimens. The expression of p-ATR and M2-type TAMs were closely correlated each other and involved in TNM stage, lymph node metastasis and poor prognosis of the patients. In addition, the expression levels of CD68⁺CD206⁺, Arg1, VEGF, and CCL22 were increased in EB⁺ CNE1 cells, and decreased when ATR was inhibited. In the nude mice, EBV-induced ATR activation promoted subcutaneous transplanted tumor growth, higher expression of Ki67 and lung metastasis via M2-type TAMs recruitment. Experimental data also showed that the polarization of M2, the declined tumor necrosis factor-α (TNF-α) and increased transforming growth factor-β (TGF-β) were associated with ATR. Meanwhile, ATR activation could promote PPAR-δ and inhibited c-Jun and p-JNK expression, then downregulate JNK pathway. Collectively, our current study demonstrated the EBV infection could activate the ATR pathway to accelerate the transition of TAMs to M2, suggesting ATR knockdown could be a potential effective treatment strategy for EBV-positive NPC.

Mechanisms Underlying Biological Effects of Cruciferous Glucosinolate-Derived Isothiocyanates/Indoles: A Focus on Metabolic Syndrome

An inverse correlation between vegetable consumption and the incidence of cancer has long been described. This protective effect is stronger when cruciferous vegetables are specifically consumed. The beneficial properties of vegetables are attributed to their bioactive components like fiber, antioxidants vitamins, antioxidants, minerals, and phenolic compounds. Cruciferous vegetables contain all these molecules; however, what makes them different are their sulfurous components, called glucosinolates, responsible for their special smell and taste. Glucosinolates are inactive biologically in the organism but are hydrolyzed by the enzyme myrosinase released as a result of chewing, leading to the formation of active derivatives such as isothiocyanates and indoles. A considerable number of in vitro and in vivo studies have reported that isothiocyanates and indoles elicit chemopreventive potency through multiple mechanisms that include modulation of phases I and II detoxification pathway enzymes, regulation of cell cycle arrest, and control of cell growth, induction of apoptosis, antioxidant activity, anti-angiogenic effects, and epigenetic regulation. Nuclear erythroid 2-related factor 2 (Nrf2) and Nuclear factor-κB (NF-κB) are key and central regulators in all these processes with a main role in oxidative stress and inflammation control. It has been described that isothiocyanates and indoles regulate their activity directly and indirectly. Today, the metabolic syndrome (central obesity, insulin resistance, hyperlipidemia, and hypertension) is responsible for a majority of deaths worldwide. All components of metabolic syndrome are characterized by chronic inflammation with deregulation of the PI3K/AKT/mTOR, MAPK/EKR/JNK, Nrf2, and NF-κB signaling pathways. The effects of GLSs derivatives controlling these pathways have been widely described in relation to cancer. Changes in food consumption patterns observed in the last decades to higher consumption of ultra-processed foods, with elevation in simple sugar and saturated fat contents and lower consumption of vegetables and fruits have been directly correlated with metabolic syndrome prevalence. In this review, it is summarized the knowledge regarding the mechanisms by which cruciferous glucosinolate derivatives (isothiocyanates and indoles) directly and indirectly regulate these pathways. However, the review places a special focus on the knowledge of the effects of glucosinolates derivatives in metabolic syndrome, since this has not been reviewed before.

Adoptive transfer of Pfkfb3-disrupted hematopoietic cells to wild-type mice exacerbates diet-induced hepatic steatosis and inflammation

BACKGROUND AND OBJECTIVES

Hepatic steatosis and inflammation are key characteristics of non-alcoholic fatty liver disease (NAFLD). However, whether and how hepatic steatosis and liver inflammation are differentially regulated remains to be elucidated. Considering that disruption of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (Pfkfb3/iPfk2) dissociates fat deposition and inflammation, the present study examined a role for Pfkfb3/iPfk2 in hematopoietic cells in regulating hepatic steatosis and inflammation in mice.

METHODS

Pfkfb3-disrupted (Pfkfb3 ^+/-) mice and wild-type (WT) littermates were fed a high-fat diet (HFD) and examined for NAFLD phenotype. Also, bone marrow cells isolated from Pfkfb3 ^+/- mice and WT mice were differentiated into macrophages for analysis of macrophage activation status and for bone marrow transplantation (BMT) to generate chimeric (WT/BMT- Pfkfb3 ^+/-) mice in which Pfkfb3 was disrupted only in hematopoietic cells and control chimeric (WT/BMT-WT) mice. The latter were also fed an HFD and examined for NAFLD phenotype. In vitro, hepatocytes were co-cultured with bone marrow-derived macrophages and examined for hepatocyte fat deposition and proinflammatory responses.

RESULTS

After the feeding period, HFD-fed Pfkfb3 ^+/- mice displayed increased severity of liver inflammation in the absence of hepatic steatosis compared with HFD-fed WT mice. When inflammatory activation was analyzed, Pfkfb3 ^+/- macrophages revealed increased proinflammatory activation and decreased anti-proinflammatory activation. When NAFLD phenotype was analyzed in the chimeric mice, WT/BMT-Pfkfb3 ^+/- mice displayed increases in the severity of HFD-induced hepatic steatosis and inflammation compared with WT/BMT-WT mice. At the cellular level, hepatocytes co-cultured with Pfkfb3 ^+/- macrophages revealed increased fat deposition and proinflammatory responses compared with hepatocytes co-cultured with WT macrophages.

CONCLUSIONS

Pfkfb3 disruption only in hematopoietic cells exacerbates HFD-induced hepatic steatosis and inflammation whereas the Pfkfb3/iPfk2 in nonhematopoietic cells appeared to be needed for HFD feeding to induce hepatic steatosis. As such, the Pfkfb3/iPfk2 plays a unique role in regulating NAFLD pathophysiology.

Metabolic and Molecular Mechanisms of Macrophage Polarisation and Adipose Tissue Insulin Resistance

Inflammation plays a key role in the development and progression of type-2 diabetes (T2D), a disease characterised by peripheral insulin resistance and systemic glucolipotoxicity. Visceral adipose tissue (AT) is the main source of inflammation early in the disease course. Macrophages are innate immune cells that populate all peripheral tissues, including AT. Dysregulated AT macrophage (ATM) responses to microenvironmental changes are at the root of aberrant inflammation and development of insulin resistance, locally and systemically. The inflammatory activation of macrophages is regulated at multiple levels: cell surface receptor stimulation, intracellular signalling, transcriptional and metabolic levels. This review will cover the main mechanisms involved in AT inflammation and insulin resistance in T2D. First, we will describe the physiological and pathological changes in AT that lead to inflammation and insulin resistance. We will next focus on the transcriptional and metabolic mechanisms described that lead to the activation of ATMs. We will discuss more novel metabolic mechanisms that influence macrophage polarisation in other disease or tissue contexts that may be relevant to future work in insulin resistance and T2D.

Peroxisome Proliferator-Activated Receptor Beta/Delta Agonist Suppresses Inflammation and Promotes Neovascularization

The effects of peroxisome proliferator-activated receptor (PPAR)β/δ ophthalmic solution were investigated in a rat corneal alkali burn model. After alkali injury, GW501516 (PPARβ/δ agonist) or vehicle ophthalmic solution was topically instilled onto the rat’s cornea twice a day until day 7. Pathological findings were evaluated, and real-time reverse transcription polymerase chain reaction was performed. GW501516 strongly suppressed infiltration of neutrophils and pan-macrophages, and reduced the mRNA expression of interleukin-6, interleukin-1β, tumor necrosis factor alpha, and nuclear factor-kappa B. On the other hand, GW501516 promoted infiltration of M2 macrophages, infiltration of vascular endothelial cells associated with neovascularization in the wounded area, and expression of vascular endothelial growth factor A mRNA. However, 7-day administration of GW501516 did not promote neovascularization in uninjured normal corneas. Thus, the PPARβ/δ ligand suppressed inflammation and promoted neovascularization in the corneal wound healing process. These results will help to elucidate the role of PPARβ/δ in the field of ophthalmology.

PPARβ/δ-dependent MSC metabolism determines their immunoregulatory properties

Mesenchymal stem cell (MSC)-based therapy is being increasingly considered a powerful opportunity for several disorders based on MSC immunoregulatory properties. Nonetheless, MSC are versatile and plastic cells that require an efficient control of their features and functions for their optimal use in clinic. Recently, we have shown that PPARβ/δ is pivotal for MSC immunoregulatory and therapeutic functions. However, the role of PPARβ/δ on MSC metabolic activity and the relevance of PPARβ/δ metabolic control on MSC immunosuppressive properties have never been addressed. Here, we demonstrate that PPARβ/δ deficiency forces MSC metabolic adaptation increasing their glycolytic activity required for their immunoregulatory functions on Th1 and Th17 cells. Additionally, we show that the inhibition of the mitochondrial production of ATP in MSC expressing PPARβ/δ, promotes their metabolic switch towards aerobic glycolysis to stably enhance their immunosuppressive capacities significantly. Altogether, these data demonstrate that PPARβ/δ governs the immunoregulatory potential of MSC by dictating their metabolic reprogramming and pave the way for enhancing MSC immunoregulatory properties and counteracting their versatility.

Polarization of M2 Macrophages by Interaction between Prostate Cancer Cells Treated with Trichomonas vaginalis and Adipocytes

Trichomonas vaginalis causes inflammation of the prostate and has been detected in tissues of prostate cancers (PCa), prostatitis and benign prostatic hyperplasia. Obesity is a risk factor for PCa and causes a chronic subclinical inflammation. This chronic inflammation further exacerbates adipose tissue inflammation as results of migration and activation of macrophages. Macrophages are the most abundant immune cells in the PCa microenvironment. M2 macrophages, known as Tumor-Associated Macrophages, are involved in increasing cancer malignancy. In this study, conditioned medium (TCM) of PCa cells infected with live trichomonads contained chemokines that stimulated migration of the mouse preadipocytes (3T3-L1 cells). Conditioned medium of adipocytes incubated with TCM (ATCM) contained Th2 cytokines (IL-4, IL-13). Macrophage migration was stimulated by ATCM. In macrophages treated with ATCM, expression of M2 markers increased, while M1 markers decreased. Therefore, it is suggested that ATCM induces polarization of M0 to M2 macrophages. In addition, conditioned medium from the macrophages incubated with ATCM stimulates the proliferation and invasiveness of PCa. Our findings suggest that interaction between inflamed PCa treated with T. vaginalis and adipocytes causes M2 macrophage polarization, so contributing to the progression of PCa.

Intervention of resistant starch 3 on type 2 diabetes mellitus and its mechanism based on urine metabonomics by liquid chromatography-tandem mass spectrometry

As a severe metabolic disease, type 2 diabetes mellitus (T2DM) has aroused increasing public attentions. Resistant starch 3 (RS3), as a starch resistant to enzymatic hydrolysis owing to its special structure, has a good effect on improving insulin resistance and reducing blood sugar in T2DM patients. However, the possible mechanisms were barely interpreted yet. In our research, we aimed to evaluate the effects and the possible mechanisms of RS3 on the treatment of T2DM. ICR mice treated with high-fat diet (HFD) for eight weeks, and then injected with streptozotocin (STZ) (100 mg/kg) to establish the T2DM. We choose the mice with the fast blood glucose (FBG) more than 11 mmol/L as T2DM. After treated for 11 weeks the relevant data was analyzed. According to the results, the FBG was dramatically reduced (p < 0.05), which also downregulated triglyceride (p < 0.01) and total cholesterol (p < 0.01). Additionally, the insulin resistance indexes were significantly reduced (p < 0.01), the homeostasis model assessment-β and insulin-sensitive index were significantly improved (p < 0.01) in RS3 group. Meanwhile, the metabolic profiles of urine were analyzed and 29 potential biomarkers were screened out, including amino acids and lipids. In conclusion, we speculated that the tricarboxylic acid cycle, amino acid metabolism and lipid metabolism played roles in the therapeutic mechanisms of RS3 on T2DM.

GRP94 regulates M1 macrophage polarization and insulin resistance

Macrophage polarization contributes to obesity-induced insulin resistance. Glucose-regulated protein 94 (GRP94) is an endoplasmic reticulum (ER) chaperone specialized for folding and quality control of secreted and membrane proteins. To determine the role of GRP94 in macrophage polarization and insulin resistance, macrophage-specific GRP94 conditional knockout (KO) mice were challenged with a high-fat diet (HFD). Glucose tolerance, insulin sensitivity, and macrophage composition were compared with control mice. KO mice showed better glucose tolerance and increased insulin sensitivity. Adipose tissues from HFD-KO mice contained lower numbers of M1 macrophages, with lower expression of M1 macrophage markers, than wild-type (WT) mice. In vitro, WT adipocytes cocultured with KO macrophages retained insulin sensitivity, whereas those cultured with WT macrophages did not. In addition, compared with WT bone marrow-derived macrophages (BMDMs), BMDMs from GRP94 KO mice exhibited lower expression of M1 macrophage marker genes following stimulation with LPS or IFN-γ, and exhibited partially increased expression of M2 macrophage marker genes following stimulation with interleukin-4. These findings identify GRP94 as a novel regulator of M1 macrophage polarization and insulin resistance and inflammation.

Mitochondrial function in immune cells in health and disease

One of the main functions of mitochondria is production of ATP for cellular energy needs, however, it becomes more recognized that mitochondria are involved in differentiation and activation processes of immune cells. Upon activation, immune cells have a high need for energy. Immune cells have different strategies to generate this energy. In pro-inflammatory cells, such as activated monocytes and activated T and B cells, the energy is generated by increasing glycolysis, while in regulatory cells, such as regulatory T cells or M2 macrophages, energy is generated by increasing mitochondrial function and beta-oxidation. Except for being important for energy supply during activation, mitochondria also induce immune responses. During an infection, they release mitochondrial danger associated molecules (DAMPs) that resemble structures of bacterial derived pathogen associated molecular patterns (PAMPs). Such mitochondrial DAMPS are for instance mitochondrial DNA with hypomethylated CpG motifs or a specific lipid that is only present in prokaryotic bacteria and mitochondria, i.e. cardiolipin. Via release of such DAMPs, mitochondria guide the immune response towards an inflammatory response against pathogens. This is an important mechanism in early detection of an infection and in stimulating and sustaining immune responses to fight infections. However, mitochondrial DAMPs may also have a negative impact. If mitochondrial DAMPs are released by damaged cells, without the presence of an infection, such as after a trauma, mitochondrial DAMPs may induce an undesired inflammatory response, resulting in tissue damage and organ dysfunction. Thus, immune cells have developed mechanisms to prevent such undesired immune activation by mitochondrial components. In the present narrative review, we will describe the current view of mitochondria in regulation of immune responses. We will also discuss the current knowledge on disturbed mitochondrial function in immune cells in various immunological diseases.

The Targeted Impact of Flavones on Obesity-Induced Inflammation and the Potential Synergistic Role in Cancer and the Gut Microbiota

Obesity is an inflammatory disease that is approaching pandemic levels, affecting nearly 30% of the world's total population. Obesity increases the risk of diabetes, cardiovascular disorders, and cancer, consequentially impacting the quality of life and imposing a serious socioeconomic burden. Hence, reducing obesity and related life-threatening conditions has become a paramount health challenge. The chronic systemic inflammation characteristic of obesity promotes adipose tissue remodeling and metabolic changes. Macrophages, the major culprits in obesity-induced inflammation, contribute to sustaining a dysregulated immune function, which creates a vicious adipocyte-macrophage crosstalk, leading to insulin resistance and metabolic disorders. Therefore, targeting regulatory inflammatory pathways has attracted great attention to overcome obesity and its related conditions. However, the lack of clinical efficacy and the undesirable side-effects of available therapeutic options for obesity provide compelling reasons for the need to identify additional approaches for the prevention and treatment of obesity-induced inflammation. Plant-based active metabolites or nutraceuticals and diets with an increased content of these compounds are emerging as subjects of intense scientific investigation, due to their ability to ameliorate inflammatory conditions and offer safe and cost-effective opportunities to improve health. Flavones are a class of flavonoids with anti-obesogenic, anti-inflammatory and anti-carcinogenic properties. Preclinical studies have laid foundations by establishing the potential role of flavones in suppressing adipogenesis, inducing browning, modulating immune responses in the adipose tissues, and hindering obesity-induced inflammation. Nonetheless, the understanding of the molecular mechanisms responsible for the anti-obesogenic activity of flavones remains scarce and requires further investigations. This review recapitulates the molecular aspects of obesity-induced inflammation and the crosstalk between adipocytes and macrophages, while focusing on the current evidence on the health benefits of flavones against obesity and chronic inflammation, which has been positively correlated with an enhanced cancer incidence. We conclude the review by highlighting the areas of research warranting a deeper investigation, with an emphasis on flavones and their potential impact on the crosstalk between adipocytes, the immune system, the gut microbiome, and their role in the regulation of obesity.

Bmal1 integrates mitochondrial metabolism and macrophage activation

Metabolic pathways and inflammatory processes are under circadian regulation. Rhythmic immune cell recruitment is known to impact infection outcomes, but whether the circadian clock modulates immunometabolism remains unclear. We find that the molecular clock Bmal1 is induced by inflammatory stimulants, including Ifn-γ/lipopolysaccharide (M1) and tumor-conditioned medium, to maintain mitochondrial metabolism under metabolically stressed conditions in mouse macrophages. Upon M1 stimulation, myeloid-specific Bmal1 knockout (M-BKO) renders macrophages unable to sustain mitochondrial function, enhancing succinate dehydrogenase (SDH)-mediated mitochondrial production of reactive oxygen species as well as Hif-1α-dependent metabolic reprogramming and inflammatory damage. In tumor-associated macrophages, aberrant Hif-1α activation and metabolic dysregulation by M-BKO contribute to an immunosuppressive tumor microenvironment. Consequently, M-BKO increases melanoma tumor burden, whereas administering the SDH inhibitor dimethyl malonate suppresses tumor growth. Therefore, Bmal1 functions as a metabolic checkpoint that integrates macrophage mitochondrial metabolism, redox homeostasis and effector functions. This Bmal1-Hif-1α regulatory loop may provide therapeutic opportunities for inflammatory diseases and immunotherapy.

PPAR Beta/Delta and the Hallmarks of Cancer

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor family. Three different isoforms, PPAR alpha, PPAR beta/delta and PPAR gamma have been identified. They all form heterodimers with retinoic X receptors to activate or repress downstream target genes dependent on the presence/absence of ligands and coactivators or corepressors. PPARs differ in their tissue expression profile, ligands and specific agonists and antagonists. PPARs attract attention as potential therapeutic targets for a variety of diseases. PPAR alpha and gamma agonists are in clinical use for the treatment of dyslipidemias and diabetes. For both receptors, several clinical trials as potential therapeutic targets for cancer are ongoing. In contrast, PPAR beta/delta has been suggested as a therapeutic target for metabolic syndrome. However, potential risks in the settings of cancer are less clear. A variety of studies have investigated PPAR beta/delta expression or activation/inhibition in different cancer cell models in vitro, but the relevance for cancer growth in vivo is less well documented and controversial. In this review, we summarize critically the knowledge of PPAR beta/delta functions for the different hallmarks of cancer biological capabilities, which interplay to determine cancer growth.

Adipose tissue macrophages: Unique polarization and bioenergetics in obesity

Macrophages comprise a majority of the resident immune cells in adipose tissue (AT) and regulate both tissue homeostasis in the lean state and metabolic dysregulation in obesity. Since the AT environment rapidly changes based upon systemic energy status, AT macrophages (ATMs) must adapt phenotypically and metabolically. There is a distinct dichotomy in the polarization and bioenergetics of in vitro models, with M2 macrophages utilizing oxidative phosphorylation (OX PHOS) and M1 macrophages utilizing glycolysis. Early studies suggested differential polarization of ATMs, with M2-like macrophages predominant in lean AT and M1-like macrophages in obese AT. However, recent studies show that the phenotypic plasticity of ATMs is far more complicated, which is also reflected in their bioenergetics. Multiple ATM populations exist along the M2 to M1 continuum and appear to utilize both glycolysis and OX PHOS in obesity. The significance of the dual fuel bioenergetics is unclear and may be related to an intermediate polarization, their buffering capacity, or the result of a mixed population of distinct polarized ATMs. Recent evidence also suggests that ATMs of lean mice serve as a substrate buffer or reservoir to modulate lipid, catecholamine, and iron availability. Furthermore, recent models of weight loss and weight cycling reveal additional roles for ATMs in systemic metabolism. Evaluating ATM phenotype and intracellular metabolism together may more accurately illuminate the consequences of ATM accumulation in obese AT, lending further insight into obesity-related comorbidities in humans.

Gut Microbiome, Intestinal Permeability, and Tissue Bacteria in Metabolic Disease: Perpetrators or Bystanders?

The emerging evidence on the interconnectedness between the gut microbiome and host metabolism has led to a paradigm shift in the study of metabolic diseases such as obesity and type 2 diabetes with implications on both underlying pathophysiology and potential treatment. Mounting preclinical and clinical evidence of gut microbiota shifts, increased intestinal permeability in metabolic disease, and the critical positioning of the intestinal barrier at the interface between environment and internal milieu have led to the rekindling of the "leaky gut" concept. Although increased circulation of surrogate markers and directly measurable intestinal permeability have been linked to increased systemic inflammation in metabolic disease, mechanistic models behind this phenomenon are underdeveloped. Given repeated observations of microorganisms in several tissues with congruent phylogenetic findings, we review current evidence on these unanticipated niches, focusing specifically on the interaction between gut permeability and intestinal as well as extra-intestinal bacteria and their joint contributions to systemic inflammation and metabolism. We further address limitations of current studies and suggest strategies drawing on standard techniques for permeability measurement, recent advancements in microbial culture independent techniques and computational methodologies to robustly develop these concepts, which may be of considerable value for the development of prevention and treatment strategies.

CD137 signaling induces macrophage M2 polarization in atherosclerosis through STAT6/PPARδ pathway

CD137 signaling plays an important role in the formation and development of atherosclerotic plaques. The purpose of the present study was to investigate the effects of CD137 signaling on macrophage polarization during atherosclerosis and to explore the underlying mechanisms. The effect of CD137 signaling on macrophage phenotype in atherosclerotic plaques was determined by intraperitoneal injection of agonist-CD137 recombinant protein in apolipoprotein E-deficient (ApoE-/-) mice, an established in vivo model of atherosclerosis. Murine peritoneal macrophages and RAW 264.7 cells were treated with AS1517499 and siPPARδ (peroxisome proliferator-activated receptor δ) to study the role of STAT6 (signal transducers and activators of transcription 6)/PPARδ signaling in CD137-induced M2 macrophage polarization in vitro. Results from both in vivo and in vitro experiments showed that CD137 signaling can transform macrophages into the M2 phenotype during the process of atherosclerotic plaque formation and regulate the angiogenic features of M2 macrophages. Furthermore, activation of the CD137 signaling pathway induces phosphorylation of STAT6 and enhances the expression of PPARδ. We further found that macrophage M2 polarization is reduced when the STAT6/PPARδ pathway is inhibited. Together, these data show a role for the STAT6/PPARδ signaling pathway in the CD137 signaling-induced M2 macrophage polarization pathway.

Molecular mechanism of obesity-induced adipose tissue inflammation; the role of Mincle in adipose tissue fibrosis and ectopic lipid accumulation

Metabolic syndrome is a common metabolic disorder that involves multiple organs and is predominantly influenced by obesity, especially the accumulation of visceral fat. It is also known that macrophages that infiltrate obese adipose tissue play an important role in inflammation of the adipose tissue. Macrophage-inducible C-type lectin (Mincle), a new inflammatory regulator found in obese adipose tissue, is expressed in pro-inflammatory M1 macrophages in adipose tissue. In addition, Mincle is expressed in macrophages that form a crown-like structure, where dead or dying adipocytes are surrounded by pro-inflammatory M1 macrophages; within this crown-like structure, adipocyte-macrophage crosstalk may occur in close proximity. Although there is no significant difference in body weight between Mincle-deficient and wild-type mice under high-fat diet, the epididymal fat weight is significantly higher and the liver weight is significantly lower in Mincle-deficient mice than those in wild-type mice. It has been shown that adipose tissue inflammation and fibrosis are attenuated in Mincle-deficient mice when compared with wild-type mice. In addition, Mincle-deficient mice have reduced hepatic lipid accumulation and better glucose metabolism. These results suggest that Mincle signaling in adipose tissue macrophages activates adipose tissue fibroblasts, which leads to adipose tissue fibrosis.

Catestatin improves insulin sensitivity by attenuating endoplasmic reticulum stress: In vivo and in silico validation

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An endogenous peptide catestatin alleviates obesity-induced ER stress.

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Alleviation of ER stress by catestatin improves insulin sensitivity.

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PID controller based model of ER stress is supported by experimental findings.

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It predicts AKT phosphorylation achieves insulin sensitivity overcoming ER stress.

Obesity is characterized by a state of chronic, unresolved inflammation in insulin-targeted tissues. Obesity-induced inflammation causes accumulation of proinflammatory macrophages in adipose tissue and liver. Proinflammatory cytokines released from tissue macrophages inhibits insulin sensitivity. Obesity also leads to inflammation-induced endoplasmic reticulum (ER) stress and insulin resistance. In this scenario, based on the data (specifically patterns) generated by our in vivo experiments on both diet-induced obese (DIO) and normal chow diet (NCD) mice, we developed an in silico state space model to integrate ER stress and insulin signaling pathways. Computational results successfully followed the experimental results for both DIO and NCD conditions. Chromogranin A (CgA) peptide catestatin (CST: hCgA352-372) improves obesity-induced hepatic insulin resistance by reducing inflammation and inhibiting proinflammatory macrophage infiltration. We reasoned that the anti-inflammatory effects of CST would alleviate ER stress. CST decreased obesity-induced ER dilation in hepatocytes and macrophages. On application of Proportional-Integral-Derivative (PID) controllers on the in silico model, we checked whether the reduction of phosphorylated PERK resulting in attenuation of ER stress, resembling CST effect, could enhance insulin sensitivity. The simulation results clearly pointed out that CST not only decreased ER stress but also enhanced insulin sensitivity in mammalian cells. In vivo experiment validated the simulation results by depicting that CST caused decrease in phosphorylation of UPR signaling molecules and increased phosphorylation of insulin signaling molecules. Besides simulation results predicted that enhancement of AKT phosphorylation helps in both overcoming ER stress and achieving insulin sensitivity. These effects of CST were verified in hepatocyte culture model.

Fumarate and oxidative stress synergize to promote stability of C/EBP homologous protein in the adipocyte

C/EBP homologous protein (CHOP) is a transcription factor that is elevated in adipose tissue across many models of diabetes and metabolic stress. Although increased CHOP levels are associated with the terminal response to endoplasmic reticulum stress and apoptosis, there is no evidence for CHOP mediated apoptosis in the adipose tissue during diabetes. CHOP protein levels increase in parallel with protein succination, a fumarate derived cysteine modification, in the adipocyte during metabolic stress. We investigated the factors contributing to sustained CHOP proteins levels in the adipocyte, with an emphasis on the regulation of CHOP protein turnover by metabolite-driven modification of Keap1 cysteines. CHOP protein stability was investigated in conditions of nutrient stress due to high glucose or elevated fumarate (fumarase knockdown model); where cysteine succination is specifically elevated. CHOP protein turnover is significantly reduced in models of elevated glucose and fumarate with a ~30% increase in CHOP stability (p > 0.01), in part due to decreased CHOP phosphorylation. Sustained CHOP levels occur in parallel with elevated heme-oxygenase-1, a production of increased Nrf2 transcriptional activity and Keap1 modification. While Keap1 is directly succinated in the presence of excess fumarate derived from genetic knockdown of fumarase (fumarate levels are elevated >20-fold), it is the oxidative modification of Keap1 that predominates in adipocytes matured in high glucose (fumarate increases 4-5 fold). Elevated fumarate indirectly regulates CHOP stability through the induction of oxidative stress. The antioxidant N-acetylcysteine (NAC) reduces fumarate levels, protein succination and CHOP levels in adipocytes matured in high glucose. Elevated CHOP does not contribute elevated apoptosis in adipocytes, but plays a redox-dependent role in decreasing the adipocyte secretion of interleukin-13, an anti-inflammatory chemokine. NAC treatment restores adipocyte IL-13 secretion, confirming the redox-dependent regulation of a potent anti-inflammatory eotaxin. This study demonstrates that physiological increases in the metabolite fumarate during high glucose exposure contributes to the presence of oxidative stress and sustained CHOP levels in the adipocyte during diabetes. The results reveal a novel metabolic link between mitochondrial metabolic stress and reduced anti-inflammatory adipocyte signaling as a consequence of reduced CHOP protein turnover.

Mechanisms of Macrophage Polarization in Insulin Signaling and Sensitivity

Type-2 diabetes (T2D) is a disease of two etiologies: metabolic and inflammatory. At the cross-section of these etiologies lays the phenomenon of metabolic inflammation. Whilst metabolic inflammation is characterized as systemic, a common starting point is the tissue-resident macrophage, who's successful physiological or aberrant pathological adaptation to its microenvironment determines disease course and severity. This review will highlight the key mechanisms in macrophage polarization, inflammatory and non-inflammatory signaling that dictates the development and progression of insulin resistance and T2D. We first describe the known homeostatic functions of tissue macrophages in insulin secreting and major insulin sensitive tissues. Importantly we highlight the known mechanisms of aberrant macrophage activation in these tissues and the ways in which this leads to impairment of insulin sensitivity/secretion and the development of T2D. We next describe the cellular mechanisms that are known to dictate macrophage polarization. We review recent progress in macrophage bio-energetics, an emerging field of research that places cellular metabolism at the center of immune-effector function. Importantly, following the advent of the metabolically-activated macrophage, we cover the known transcriptional and epigenetic factors that canonically and non-canonically dictate macrophage differentiation and inflammatory polarization. In closing perspectives, we discuss emerging research themes and highlight novel non-inflammatory or non-immune roles that tissue macrophages have in maintaining microenvironmental and systemic homeostasis.

The Interplay Between Tissue Niche and Macrophage Cellular Metabolism in Obesity

Obesity is associated with the development of metabolic diseases such as type 2 diabetes and non-alcoholic fatty liver disease. The presence of chronic, low-grade inflammation appears to be an important mechanistic link between excess nutrients and clinical disease. The onset of these metabolic disorders coincides with changes in the number and phenotype of macrophages in peripheral organs, particularly in the liver and adipose tissue. Macrophage accumulation in these tissues has been implicated in tissue inflammation and fibrosis, contributing to metabolic disease progression. Recently, the concept has emerged that changes in macrophage metabolism affects their functional phenotype, possibly triggered by distinct environmental metabolic cues. This may be of particular importance in the setting of obesity, where both liver and adipose tissue are faced with a high metabolic burden. In the first part of this review we will discuss current knowledge regarding macrophage dynamics in both adipose tissue and liver in obesity. Then in the second part, we will highlight data linking macrophage metabolism to functional phenotype with an emphasis on macrophage activation in metabolic disease. The importance of understanding how tissue niche influences macrophage function in obesity will be highlighted. In addition, we will identify important knowledge gaps and outstanding questions that are relevant for future research in this area and will facilitate the identification of novel targets for therapeutic intervention in associated metabolic diseases.

Deletion of Ppard in CD11c+ cells attenuates atherosclerosis in ApoE knockout mice

Ppardδ, one of the lipid-activated nuclear receptor expressed in many cell types to activate gene transcription, also regulates cellular functions other than lipid metabolism. The mechanism regulating the function of antigen-presenting cells during the development of atherosclerosis is not fully understood. Here we aimed to study the involvement of PPARδ in CD11c⁺ cells in atherosclerosis. We used the Cre-loxP approach to make conditional deletion of Ppard in CD11c⁺ cells in mice on Apoe^-/- background, which were fed with high cholesterol diet to develop atherosclerosis. Ppard deficiency in CD11c⁺ cells attenuated atherosclerotic plaque formation and infiltration of myeloid-derived dendritic cells (DCs) and T lymphocytes. Reduced lesion was accompanied by reduced activation of dendritic cells, and also a reduction of activation and differentiation of T cells to Th1 cells. In addition, DC migration to lymph node was also attenuated with Ppard deletion. In bone marrow-derived DCs, Ppard deficiency reduced palmitic acid-induced upregulation of co-stimulatory molecules and pro-inflammatory cytokine IL12 and TNFα. Our results indicated PPARδ activation by fatty acid resulted in the activation of myeloid DCs and subsequent polarization of T lymphocytes, which contributed to atherosclerosis in Apoe^-/- mice. These findings also reveal the potential regulatory role of PPARδ in antigen presentation to orchestrate the immune responses during atherosclerosis.

Antiobesity Effect of Biochanin-A: Effect on Trace Element Metabolism in High Fat Diet-Induced Obesity in Rats

BACKGROUND

Imbalanced diets have contributed to the increased prevalence of obesity and other metabolic disorders in the modern world including trace element metabolism. However, the underlying mechanisms are not fully understood.

AIM AND OBJECTIVES

The present study investigated the effects of Biochanin A (BCA) on the changes in element metabolism induced by HFD-induced obese rats.

METHODS

BCA was administered orally for 30 days to experimental obese rats. Changes in body weight, glucose, insulin resistance and lipid profiles of plasma, as well as the level of trace elements (Fe, Zn, Mg and Cu) in various tissues (liver, kidney, heart and pancreas) and hepsidine and heme oxygenase, were observed in experimental rats.

RESULTS

The administration of BCA elicited a significant (p<0.05) reduction in, glucose, insulin, ferritin, total cholesterol, phospholipids, free fatty acids, VLDL-C, LDL-C, triglycerides and hepsidin. Significant alterations were observed in trace elements level, HDL-C, transferrin, bilirubin and HO - 1 level.

CONCLUSION

These findings suggested that HFD results in derangement of trace elements in the tissues of rats fed with HFD. BCA may alleviate the derangement of HFD induced trace elements metabolism by modulating hyperglycemic and insulin resistance status and altering hepcidin and HO-1.

Obesity: a neuroimmunometabolic perspective

Neuroimmunology and immunometabolism are burgeoning topics of study, but the intersection of these two fields is scarcely considered. This interplay is particularly prevalent within adipose tissue, where immune cells and the sympathetic nervous system (SNS) have an important role in metabolic homeostasis and pathology, namely in obesity. In the present Review, we first outline the established reciprocal adipose-SNS relationship comprising the neuroendocrine loop facilitated primarily by adipose tissue-derived leptin and SNS-derived noradrenaline. Next, we review the extensive crosstalk between adipocytes and resident innate immune cells as well as the changes that occur in these secretory and signalling pathways in obesity. Finally, we discuss the effect of SNS adrenergic signalling in immune cells and conclude with exciting new research demonstrating an immutable role for SNS-resident macrophages in modulating SNS-adipose crosstalk. We posit that the latter point constitutes the existence of a new field - neuroimmunometabolism.

Macrophage Function in the Pathogenesis of Non-alcoholic Fatty Liver Disease: The Mac Attack

Obesity is a prevalent predisposing factor to non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in the developed world. NAFLD spectrum of disease involves progression from steatosis (NAFL), to steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). Despite clinical and public health significance, current FDA approved therapies for NAFLD are lacking in part due to insufficient understanding of pathogenic mechanisms driving disease progression. The etiology of NAFLD is multifactorial. The induction of both systemic and tissue inflammation consequential of skewed immune cell metabolic state, polarization, tissue recruitment, and activation are central to NAFLD progression. Here, we review the current understanding of the above stated cellular and molecular processes that govern macrophage contribution to NAFLD pathogenesis and how adipose tissue and liver crosstalk modulates macrophage function. Notably, the manipulation of such events may lead to the development of new therapies for NAFLD.

Leptin induces TNFα-dependent inflammation in acquired generalized lipodystrophy and combined Crohn's disease

Leptin has been shown to modulate intestinal inflammation in mice. However, clinical evidence regarding its immune-stimulatory potential in human Crohn’s disease remains sparse. We here describe a patient with the unique combination of acquired generalized lipodystrophy and Crohn’s disease (AGLCD) featuring a lack of adipose tissue, leptin deficiency and intestinal inflammation. Using mass and flow cytometry, immunohistochemistry and functional metabolic analyses, the AGLCD patient was compared to healthy individuals and Crohn’s disease patients regarding immune cell composition, function and metabolism and the effects of recombinant N-methionylleptin (rLeptin) were evaluated. We provide evidence that rLeptin exerts diverse pro-inflammatory effects on immune cell differentiation and function, including the metabolic reprogramming of immune cells and the induction of TNFα, ultimately aggravating Crohn’s disease in the AGLCD patient, which can be reversed by anti-TNFα therapy. Our results indicate that leptin is required for human immune homeostasis and contributes to autoimmunity in a TNFα-dependent manner.

The adipokine leptin modulates intestinal inflammation in mice. Here the authors describe a patient with inflammatory bowel disease and lipodystrophy, providing evidence that leptin aggravates intestinal inflammation with proinflammatory effects on leukocytes that are reversible by TNFα blockade.

Skewed macrophage polarization in aging skeletal muscle

Skeletal muscle aging is a major cause of disability and frailty in the elderly. The progressive impairment of skeletal muscle function with aging was recently linked to a disequilibrium between damage and repair. Macrophages participate in muscle tissue repair, first as pro-inflammatory M1 subtype and then as anti-inflammatory M2 subtype. However, information on the presence of macrophages in skeletal muscle is still sporadic and the effect of aging on macrophage phenotype remains unknown. In this study, we sought to characterize the polarization status of macrophages in skeletal muscle of persons across a wide range of ages. We found that most macrophages in human skeletal muscle are M2, and that this number increased with advancing age. On the contrary, M1 macrophages declined with aging, making the total number of macrophages invariant with older age. Notably, M2 macrophages colocalized with increasing intermuscular adipose tissue (IMAT) in aging skeletal muscle. Similarly, aged BALB/c mice showed increased IMAT and M2 macrophages in skeletal muscle, accompanied by slightly increased collagen protein production. Collectively, we report that polarization of macrophages to the major M2 subtype is associated with IMAT and propose that increased M2 in aged skeletal muscle may impact upon muscle metabolism associated with aging.

Interleukin-4 Promotes Myogenesis and Boosts Myocyte Insulin Efficacy

Anti-inflammatory cytokine interleukin-4 (IL-4) promotes glucose tolerance and insulin sensitivity while reduces lipid deposits. However, the effects of IL-4 on energy metabolism in muscle, the largest insulin-targeting organ, remain obscure. The study aimed at addressing the roles of IL-4 in myocyte differentiation (myogenesis) and energy metabolism of muscle cells. Effects of IL-4 on myogenesis, and interaction between IL-4 and insulin on glucose metabolism of C2C12 myoblasts and the terminal differentiated myocytes were analyzed. IL-4 improved GLUT4 translocation and tended to elevate glucose uptake by boosting insulin signaling. In diabetic mice, transient and long-term IL-4 showed differential effects on insulin signaling and efficacy. The study provides evidence to address the roles of IL-4 in mediating whole-body muscle reservoir and glucose metabolism, as well as the interaction between immune responses and energy homeostasis. IL-4 has dual potential to act as an adjuvant therapeutic target for sarcopenia to preserve muscle mass and insulin resistance to improve insulin sensitivity, which implicates the regulation of immune system to the muscle differentiation and exercise performance.

Oncolytic virotherapy in glioblastoma patients induces a tumor macrophage phenotypic shift leading to an altered glioblastoma microenvironment

Background

Immunosuppressive protumoral M2 macrophages are important in pathogenesis, progression, and therapy resistance in glioblastoma (GBM) and provide a target for therapy. Recently oncolytic virotherapy in murine models was shown to change these M2 macrophages toward the pro-inflammatory and antitumoral M1 phenotype. Here we study the effects of the oncolytic virotherapy Delta24-RGD in humans, using both in vitro models and patient material.

Methods

Human monocyte-derived macrophages were co-cultured with Delta24-RGD-infected primary glioma stem-like cells (GSCs) and were analyzed for their immunophenotype, cytokine expression, and secretion profiles. Cerebrospinal fluid (CSF) from 18 Delta24-RGD-treated patients was analyzed for inflammatory cytokine levels, and the effects of these CSF samples on macrophage phenotype in vitro were determined. In addition, tumor macrophages in resected material from a Delta24-RGD-treated GBM patient were compared with 5 control GBM patient samples by flow cytometry.

Results

Human monocyte-derived M2 macrophages co-cultured with Delta24-RGD-infected GSCs shifted toward an M1-immunophenotype, coinciding with pro-inflammatory gene expression and cytokine production. This phenotypic switch was induced by the concerted effects of a change in tumor-produced soluble factors and the presence of viral particles. CSF samples from Delta24-RGD-treated GBM patients revealed cytokine levels indicative of a pro-inflammatory microenvironment. Furthermore, tumoral macrophages in a Delta24-RGD-treated patient showed significantly greater M1 characteristics than in control GBM tissue.

Conclusion

Together these in vitro and patient studies demonstrate that local Delta24-RGD therapy may provide a therapeutic tool to promote a prolonged shift in the protumoral M2 macrophages toward M1 in human GBM, inducing a pro-inflammatory and potentially tumor-detrimental microenvironment.

Peroxisome Proliferator-Activated Receptor-δ Acts within Peripheral Myeloid Cells to Limit Th Cell Priming during Experimental Autoimmune Encephalomyelitis

Peroxisome proliferator-activated receptor (PPAR)-δ is a fatty acid-activated transcription factor that regulates metabolic homeostasis, cell growth, and differentiation. Previously, we reported that mice with a global deficiency of PPAR-δ develop an exacerbated course of experimental autoimmune encephalomyelitis (EAE), highlighting a role for this nuclear receptor in limiting the development of CNS inflammation. However, the cell-specific contribution of PPAR-δ to the more severe CNS inflammatory response remained unclear. In this study, we studied the specific involvement of PPAR-δ in myeloid cells during EAE using mice that had Cre-mediated excision of floxed Ppard driven by the lysozyme M (LysM) promoter (LysM ^Cre :Ppard ^fl/fl). We observed that LysM ^Cre :Ppard ^fl/fl mice were more susceptible to EAE and developed a more severe course of this disease compared with Ppard ^fl/fl controls. The more severe EAE in LysM ^Cre :Ppard ^fl/fl mice was associated with an increased accumulation of pathogenic CD4⁺ T cells in the CNS and enhanced myelin-specific Th1 and Th17 responses in the periphery. Adoptive transfer EAE studies linked this EAE phenotype in LysM ^Cre :Ppard ^fl/fl mice to heightened Th responses. Furthermore, studies using an in vitro CD11b⁺ cell:Th cell coculture system revealed that CD11b⁺CD11c⁺ dendritic cells (DC) from LysM ^Cre :Ppard ^fl/fl mice had a heightened capacity to prime myelin oligodendrocyte glycoprotein (MOG)-specific Th cells compared with Ppard ^fl/fl counterparts; the effects of DC on Th1 cytokine production were mediated through production of the IL-12p40 homodimer. These studies revealed a role for PPAR-δ in DC in limiting Th cell priming during EAE.

Regulation of Systemic Glucose Homeostasis by T Helper Type 2 Cytokines

Obesity results in an inflammatory microenvironment in adipose tissue, leading to the deterioration of tissue protective mechanisms. Although recent studies suggested the importance of type 2 immunity in an anti-inflammatory microenvironment in adipose tissue, the regulatory effects of T helper 2 (Th2) cytokines on systemic metabolic regulation are not fully understood. Recently, we identified the roles of the Th2 cytokine (interleukin 4 [IL-4] and IL-13)-induced adipokine, growth differentiation factor 15 (GDF15), in adipose tissue in regulating systemic glucose metabolism via signal transducer and activator of transcription 6 (STAT6) activation. Moreover, we showed that mitochondrial oxidative phosphorylation is required to maintain these macrophage-regulating autocrine and paracrine signaling pathways via Th2 cytokine-induced secretion of GDF15. In this review, we discuss how the type 2 immune response and Th2 cytokines regulate metabolism in adipose tissue. Specifically, we review the systemic regulatory roles of Th2 cytokines in metabolic disease and the role of mitochondria in maintenance of type 2 responses in adipose tissue homeostasis.

Understanding the glucoregulatory mechanisms of metformin in type 2 diabetes mellitus

Despite its position as the first-line drug for treatment of type 2 diabetes mellitus, the mechanisms underlying the plasma glucose level-lowering effects of metformin (1,1-dimethylbiguanide) still remain incompletely understood. Metformin is thought to exert its primary antidiabetic action through the suppression of hepatic glucose production. In addition, the discovery that metformin inhibits the mitochondrial respiratory chain complex 1 has placed energy metabolism and activation of AMP-activated protein kinase (AMPK) at the centre of its proposed mechanism of action. However, the role of AMPK has been challenged and might only account for indirect changes in hepatic insulin sensitivity. Various mechanisms involving alterations in cellular energy charge, AMP-mediated inhibition of adenylate cyclase or fructose-1,6-bisphosphatase 1 and modulation of the cellular redox state through direct inhibition of mitochondrial glycerol-3-phosphate dehydrogenase have been proposed for the acute inhibition of gluconeogenesis by metformin. Emerging evidence suggests that metformin could improve obesity-induced meta-inflammation via direct and indirect effects on tissue-resident immune cells in metabolic organs (that is, adipose tissue, the gastrointestinal tract and the liver). Furthermore, the gastrointestinal tract also has a major role in metformin action through modulation of glucose-lowering hormone glucagon-like peptide 1 and the intestinal bile acid pool and alterations in gut microbiota composition.

Contributions of innate type 2 inflammation to adipose function

A critical contributor to the health consequences of the obesity epidemic is dysregulated adipose tissue (AT) homeostasis. While white, brown, and beige AT function is altered in obesity-related disease, white AT is marked by progressive inflammation and adipocyte dysfunction and has been the focus of extensive "immunometabolism" research in the past decade. The exact triggering events initiating and sustaining AT inflammation are still under study, but it has been shown that reducing inflammation improves insulin action in AT. Scientific efforts seeking interventions to mitigate obesity-associated AT inflammation continue, and many groups are now determining how lean healthy AT homeostasis is maintained in order to leverage these mechanisms as therapeutic targets. Such studies have revealed that an elaborate network of immune cells, cytokines, and other cellular mediators coordinate AT function. Recent studies elucidated the involvement of the innate immune system in AT homeostasis (e.g., beiging and insulin sensitivity), including M2-like macrophages, eosinophils, innate lymphoid type 2 cells, and several others. In this review, we summarize the existing literature on innate type 2 inflammation in AT; additionally, we draw attention to areas of debate where seemingly conflicting data promises to yield more surprising and elegant biology as studies continue to dissect AT physiology.

Mice lacking adenosine 2A receptor reveal increased severity of MCD-induced NASH

Adenosine 2A receptor (A2AR) exerts a protective role in obesity-related non-alcoholic fatty liver disease. Here, we examined whether A2AR protects against non-alcoholic steatohepatitis (NASH). In C57BL/6J mice, feeding a methionine- and choline-deficient diet (MCD) resulted in significant weight loss, overt hepatic steatosis, and massive aggregation of macrophages in the liver compared with mice fed a chow diet. MCD feeding also significantly increased the numbers of A2AR-positive macrophages/Kupffer cells in liver sections although decreasing A2AR amount in liver lysates compared with chow diet feeding. Next, MCD-induced NASH phenotype was examined in A2AR-disrupted mice and control mice. Upon MCD feeding, A2AR-disruptd mice and control mice displayed comparable decreases in body weight and fat mass. However, MCD-fed A2AR-disrupted mice revealed greater liver weight and increased severity of hepatic steatosis compared with MCD-fed control mice. Moreover, A2AR-disupted mice displayed increased severity of MCD-induced liver inflammation, indicated by massive aggregation of macrophages and increased phosphorylation states of Jun-N terminal kinase (JNK) p46 and nuclear factor kappa B (NFκB) p65 and mRNA levels of tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6. In vitro, incubation with MCD-mimicking media increased lipopolysaccharide (LPS)-induced phosphorylation states of JNK p46 and/or NFκB p65 and cytokine mRNAs in control macrophages and RAW264.7 cells, but not primary hepatocytes. Additionally, MCD-mimicking media significantly increased lipopolysaccharide-induced phosphorylation states of p38 and NFκB p65 in A2AR-deficient macrophages, but insignificantly decreased lipopolysaccharide-induced phosphorylation states of JNK p46 and NFκB p65 in A2AR-deficient hepatocytes. Collectively, these results suggest that A2AR disruption exacerbates MCD-induced NASH, which is attributable to, in large part, increased inflammatory responses in macrophages.

Extrinsic and Intrinsic Immunometabolism Converge: Perspectives on Future Research and Therapeutic Development for Obesity

PURPOSE OF REVIEW

Research over the past decade has shown that immunologic and metabolic pathways are intricately linked. This burgeoning field of immunometabolism includes intrinsic and extrinsic pathways and is known to be associated with obesity-accelerated metabolic disease. Intrinsic immunometabolism includes the study of fuel utilization and bioenergetic pathways that influence immune cell function. Extrinsic immunometabolism includes the study of immune cells and products that influence systemic metabolism.

RECENT FINDINGS

Th2 immunity, macrophage iron handling, adaptive immune memory, and epigenetic regulation of immunity, which all require intrinsic metabolic changes, play a role in systemic metabolism and metabolic function, linking the two arms of immunometabolism. Together, this suggests that targeting intrinsic immunometabolism can directly affect immune function and ultimately systemic metabolism. We highlight important questions for future basic research that will help improve translational research and provide therapeutic targets to help establish new treatments for obesity and associated metabolic disorders.

Mechanism of Interleukin-4 Reducing Lipid Deposit by Regulating Hormone-Sensitive Lipase

Accumulating evidence indicates that inflammation participates in the pathophysiological progress from insulin resistance, obesity, metabolic abnormalities, and type 2 diabetes mellitus. Our previous study reveals that interleukin-4 (IL-4) inhibits adipogenesis and promotes lipolysis to decrease lipid deposits by enhancing the activity of hormone sensitive lipase (HSL). The present study further dissects and characterizes the molecular mechanism of IL-4 in regulating HSL expression and lipolytic activity in the terminal differentiated 3T3-L1 mature adipocytes. Our results showed that IL-4 increased cAMP which then enhanced PKA activity and subsequent phosphorylation of HSL and perilipin. The phosphorylated HSL (p-HSL) translocated from cytoplasm to the surface of lipid droplets and exhibited lipolytic function. After being phosphorylated, p-perilipin also facilitated lipolysis through interacting with p-HSL. The in vitro findings were further verified by in vivo study in which IL-4 exhibited pro-lipolytic activity and enhanced HSL activity. In summary, the net outcome of IL-4 treatment is to reduce lipid storage by promoting lipolysis through enhancing HSL activity via cAMP/PKA pathway, the major route leading to lipolysis.

Bidirectional crosstalk between neutrophils and adipocytes promotes adipose tissue inflammation

Chronic activation of the IL-1β system in adipose tissue on metabolic disorders is well demonstrated. However, a mechanism for its expression and activation in the tissue has remained unexplored. Here, we demonstrate that IL-1β transcript was enriched in neutrophils of white adipose tissue (WAT) from lean mice. Mechanistically, the interaction of neutrophils with adipocytes induced IL-1β expression via NF-κB pathway. Lipolysis of adipocytes accumulated neutrophils prior to macrophages in WAT and produced high levels of IL-1β via an inflammasome pathway. Leukotriene B₄ (LTB₄) production in WAT also contributed to neutrophil accumulation. Furthermore, an LTB₄-inflammasome axis contributed to the expression of chemotactic molecules involved in high-fat diet-induced macrophage infiltration into WAT. We have identified previously unappreciated roles for neutrophils in the development of adipose tissue inflammation: robust IL-1β production and infiltration of macrophages to initiate chronic inflammation.-Watanabe, Y., Nagai, Y., Honda, H., Okamoto, N., Yanagibashi, T., Ogasawara, M., Yamamoto, S., Imamura, R., Takasaki, I., Hara, H., Sasahara, M., Arita, M., Hida, S., Taniguchi, S., Suda, T., Takatsu, K. Bidirectional crosstalk between neutrophils and adipocytes promotes adipose tissue inflammation.

The role of pro-inflammatory cytokines in lipid metabolism of metabolic diseases

Adipose tissue has been considered as a crucial source of certain pro-inflammatory cytokines; conversely, these pro-inflammatory cytokines are involved in regulating the proliferation and apoptosis of adipocytes, promoting lipolysis, inhibiting lipid synthesis and decreasing blood lipids, etc. In recent decades, extensive studies have indicated that pro-inflammatory cytokines play important roles in the development of lipid metabolism of metabolic diseases, including obesity, atherosclerosis, steatohepatitis and hyperlipoproteinemia. However, the involved pro-inflammatory cytokines types and the underlying mechanisms remain largely unknown. The "re-discovery" of cancer as a metabolic disorder largely occurred in the last five years. Although pro-inflammatory cytokines have been intensively investigated in cancer research, there are very few studies about the roles of pro-inflammatory cytokines in the lipid metabolism of cancer. In the current review, we provide an overview of the progress that has been made in the roles of different pro-inflammatory cytokines in lipid metabolism of metabolic diseases including cancer.

Association between Type 2 Diabetes, Obesity and Key Immunological Components of IgE-mediated Inflammation

BACKGROUND

Changes in lifestyle and obesity in recent decades have brought about a dramatic increase in type 2 diabetes mellitus (DM2) and allergic diseases. Clinical and epidemiological studies associate obesity with epidemics of allergic diseases. The link between obesity and DM2 with immunological components of IgE-mediated allergic inflammation is not yet conclusively established.

AIM

To examine the key immunological components of IgE-mediated allergic inflammation in patients with DM2 and their relationship with glycemic control and anthropometric indicators.

MATERIALS AND METHODS

Fifty-five patients with DM2 and 32 healthy controls with normal weight and body mass index (BMI) of 18-24.9 kg/m2 were included in the study. Th2-cytokine profile (serum levels of IL-4 and IL-5, pg/ml) and total serum IgE IU/ml were assessed in all participants in the study using ELISA. In patients with DM2, levels of glycated hemoglobin (HbA1c%) in the blood were also measured.

RESULTS

Serum levels of IL-4 and IL-5 are significantly higher in patients with DM2 compared to the control group. Serum levels of IL-4 and IL-5 positively correlated with BMI as well as serum levels of IL-4 with waist circumference. Total serum IgE positively correlated with HbA1c.

CONCLUSION

Obesity and poor glycemic control in patients with DM2 affect key immunological components of IgE-mediated allergic inflammation and possibly alter the immune response to allergens and antigens.

Macrophage Polarization in the Development and Progression of Ovarian Cancers: An Overview

Ovarian cancer is the most lethal gynecological malignancy worldwide. Most patients are diagnosed at late stages because of atypical symptoms and the lack of effective early diagnostic measures. The mechanisms underlying the oncogenesis and development of ovarian cancer are not clear. Macrophages, immune cells derived from the innate immune system, have two states of polarization (M1 and M2) that develop in response to different stimuli. The polarization and differentiation of macrophages into the cancer-inhibiting M1 and cancer-promoting M2 types represent the two states of macrophages in the tumor microenvironment. The interaction of polarized macrophages with cancer cells plays a crucial role in a variety of cancers. However, the effects of macrophage M1/M2 polarization on ovarian cancer have not yet been systematically and fully discussed. In this review, we discuss not only the occurrence, development and influences of macrophage polarization but also the association between macrophage polarization and ovarian cancer. The polarization of macrophages into the M1 and M2 phenotypes plays a pivotal role in ovarian cancer initiation, progression, and metastasis, and provides targets for macrophage-centered treatment in the cancer microenvironment for ovarian cancer therapy. We also addressed the regulation of macrophage polarization in ovarian cancer via noncoding RNAs, exosomes, and epigenetics.