Adipose tissue macrophages

Adipose-tissue and intestinal inflammation - visceral obesity and creeping fat

Obesity has become one of the main threats to health worldwide and therefore gained increasing clinical and economic significance as well as scientific attention. General adipose-tissue accumulation in obesity is associated with systemically increased pro-inflammatory mediators and humoral and cellular changes within this compartment. These adipose-tissue changes and their systemic consequences led to the concept of obesity as a chronic inflammatory state. A pathognomonic feature of Crohn’s disease (CD) is creeping fat (CF), a locally restricted hyperplasia of the mesenteric fat adjacent to the inflamed segments of the intestine. The precise role of this adipose-tissue and its mediators remains controversial, and ongoing work will have to define whether this compartment is protecting from or contributing to disease activity. This review aims to outline specific cellular changes within the adipose-tissue, occurring in either obesity or CF. Hence the potential impact of adipocytes and resident immune cells from the innate and adaptive immune system will be discussed for both diseases. The second part focuses on the impact of generalized adipose-tissue accumulation in obesity, respectively on the locally restricted form in CD, on intestinal inflammation and on the closely related integrity of the mucosal barrier.

The role of obesity in the immune response during sepsis

Background/Objectives:

Sepsis is one of the most important causes of mortality in the developed world, where almost two-thirds of the population suffer from obesity. Therefore, the coexistence of both conditions has become frequent in clinical practice and a growing number of clinical studies attempts to examine the potential effect of obesity on sepsis with controversial results up to now. The present study investigates how obesity influences the immune response of septic patients, by assessing the number and activation state of adipose tissue macrophages, serum and adipose tissue tumor necrosis factor-alpha (TNFα) levels and plasma oxidative stress markers.

Subjects/methods:

The study included 106 patients, divided into four groups (control n=26, obesity n=27, sepsis n=27 and sepsis and obesity n=26). The number of macrophages in subcutaneous and visceral adipose tissue (SAT and VAT) and their subtypes (M1 and M2) were defined with immunohistochemical staining techniques under light microscopy. TNFα mRNA levels were determined in SAT and VAT using real-time reverse transcription-PCR. Serum levels of TNFα were determined with sandwich enzyme-linked immunosorbent assay. Plasma oxidative stress was evaluated using selective biomarkers (thiobarbituric acid-reactive substances (TBARS), protein carbonyls and total antioxidant capacity (TAC)).

Results:

Sepsis increased the total number of macrophages and their M2 subtype in (VAT), whereas obesity did not seem to affect the concentration of macrophages in fat. Obesity increased TNFα mRNA levels (P<0.05) in VAT as well as the plasma TBARS (P<0.001) and protein carbonyls (P<0.001) in septic patients. The plasma TAC levels were decreased and the serum TNFα levels were increased in sepsis although they were not influenced by obesity.

Conclusions:

Obesity is associated with elevated TNFα adipose tissue production and increased oxidative stress biomarkers, promoting the proinflammatory response in septic patients.

Elevated soluble CD163 in gestational diabetes mellitus: secretion from human placenta and adipose tissue

Recently soluble CD163 (sCD163), a cleaved form of the macrophage receptor CD163, was identified as a macrophage-specific risk-predictor for developing Type 2 Diabetes. Here, we investigate circulating levels of sCD163 in gestational diabetes mellitus (GDM). Furthermore, given the role of the placenta in the pathogenesis of GDM, we assessed placental contribution to sCD163 secretion. Paired maternal (venous) and umbilical vein blood samples from GDM (n = 18) and Body Mass Index (BMI) matched control women (n = 20) delivered by caesarean section at 39–40 week gestation were assessed for circulating levels of sCD163, Tumour necrosis factor alpha (TNF-α) and Interleukin 6 (IL-6). Media from explant culture of maternal subcutaneous fat and corresponding placental tissues were assayed for these same molecules. CD163 positive cell numbers were determined in placental and adipose tissues of GDM and control women. We found significantly elevated circulating sCD163 levels in GDM mothers (688.4±46.9 ng/ml vs. 505.6±38.6 ng/ml) and their offspring (418.2±26.6 ng/ml vs. 336.3±24.4 ng/ml [p<0.05 for both]) as compared to controls, together with elevated circulating TNF-α and IL-6 levels. Moreover, both GDM placentae (268.1±10.8 ng/ml/mg vs. 187.6±20.6 ng/ml/mg) and adipose explants (41.1±2.7 ng/ml/mg vs. 26.6±2.4 ng/ml/mg) released significantly more sCD163 than controls. Lastly, significantly more CD163 positive cells were observed in GDM placentae (25.7±1.1 vs. 22.1±1.2) and adipose tissue (19.1±1.1 vs 12.7±0.9) compared to controls. We describe elevated sCD163 levels in GDM and identify human placenta as a novel source of sCD163 suggesting that placental tissues might contribute to the increased levels of circulating sCD163 in GDM pregnancies.

Targeting macrophage subsets for infarct repair

Macrophages are involved in every cardiovascular disease and are an attractive therapeutic target. Macrophage activation is complex and can be either beneficial or deleterious, depending upon its mode of action, its timing, and its duration. An important macrophage characteristic is its plasticity, which enables it to switch from one subset to another. Macrophages, which regulate healing and repair after myocardial infarction, have become a major target for both treatment and diagnosis (theranostic). The aim of the present review is to describe the recent discoveries related to targeting and modulating of macrophage function to improve infarct repair. We will briefly review macrophage polarization, plasticity, heterogeneity, their role in infarct repair, regeneration, and cross talk with mesenchymal cells. Particularly, we will focus on the potential of macrophage targeting in situ by liposomes. The ability to modulate macrophage function could delineate pathways to reactivate the endogenous programs of myocardial regeneration. This will eventually lead to development of small molecules or biologics to enhance the endogenous programs of regeneration and repair.

MyD88-dependent interplay between myeloid and endothelial cells in the initiation and progression of obesity-associated inflammatory diseases

MyD88-dependent GM-CSF production by endothelial cells plays a role in the initiation of obesity-associated inflammation by promoting adipose macrophage recruitment and M1-like polarization.

Low-grade systemic inflammation is often associated with metabolic syndrome, which plays a critical role in the development of the obesity-associated inflammatory diseases, including insulin resistance and atherosclerosis. Here, we investigate how Toll-like receptor–MyD88 signaling in myeloid and endothelial cells coordinately participates in the initiation and progression of high fat diet–induced systemic inflammation and metabolic inflammatory diseases. MyD88 deficiency in myeloid cells inhibits macrophage recruitment to adipose tissue and their switch to an M1-like phenotype. This is accompanied by substantially reduced diet-induced systemic inflammation, insulin resistance, and atherosclerosis. MyD88 deficiency in endothelial cells results in a moderate reduction in diet-induced adipose macrophage infiltration and M1 polarization, selective insulin sensitivity in adipose tissue, and amelioration of spontaneous atherosclerosis. Both in vivo and ex vivo studies suggest that MyD88-dependent GM-CSF production from the endothelial cells might play a critical role in the initiation of obesity-associated inflammation and development of atherosclerosis by priming the monocytes in the adipose and arterial tissues to differentiate into M1-like inflammatory macrophages. Collectively, these results implicate a critical MyD88-dependent interplay between myeloid and endothelial cells in the initiation and progression of obesity-associated inflammatory diseases.

Growth hormone (GH) differentially regulates NF-kB activity in preadipocytes and macrophages: implications for GH's role in adipose tissue homeostasis in obesity

Adipose tissue remodeling in obesity involves macrophage infiltration and chronic inflammation. NF-kB-mediated chronic inflammation of the adipose tissue is directly implicated in obesity-associated insulin resistance. We have investigated the effect of growth hormone (GH) on NF-kB activity in preadipocytes (3T3-F442A) and macrophages (J774A.1). Our studies indicate that whereas GH increases NF-kB activity in preadipocytes, it decreases NF-kB activity in macrophages. This differential response of NF-kB activity to GH correlates with the GH-dependent expression of a cadre of NF-kB-activated cytokines in these two cell types. Activation of NF-kB by GH in preadipocytes heightens inflammatory response by stimulating production of multiple cytokines including TNF-α, IL-6, and MCP-1, the mediators of both local and systemic insulin resistance and chemokines that recruit macrophages. Our studies also suggest differential regulation of miR132 and SIRT1 expression as a mechanism underlying the observed variance in GH-dependent NF-kB activity and altered cytokine profile in preadipocytes and macrophages. These findings further our understanding of the complex actions of GH on adipocytes and insulin sensitivity.

Free fatty acids, lipopolysaccharide and IL-1α induce adipocyte manganese superoxide dismutase which is increased in visceral adipose tissues of obese rodents

Excess fat storage in adipocytes is associated with increased generation of reactive oxygen species (ROS) and impaired activity of antioxidant mechanisms. Manganese superoxide dismutase (MnSOD) is a mitochondrial enzyme involved in detoxification of ROS, and objective of the current study is to analyze expression and regulation of MnSOD in obesity. MnSOD is increased in visceral but not subcutaneous fat depots of rodents kept on high fat diets (HFD) and ob/ob mice. MnSOD is elevated in visceral adipocytes of fat fed mice and exposure of differentiating 3T3-L1 cells to lipopolysaccharide, IL-1α, saturated, monounsaturated and polyunsaturated free fatty acids (FFA) upregulates its level. FFA do not alter cytochrome oxidase 4 arguing against overall induction of mitochondrial enzymes. Upregulation of MnSOD in fat loaded cells is not mediated by IL-6, TNF or sterol regulatory element binding protein 2 which are induced in these cells. MnSOD is similarly abundant in perirenal fat of Zucker diabetic rats and non-diabetic animals with similar body weight and glucose has no effect on MnSOD in 3T3-L1 cells. To evaluate whether MnSOD affects adipocyte fat storage, MnSOD was knocked-down in adipocytes for the last three days of differentiation and in mature adipocytes. Knock-down of MnSOD does neither alter lipid storage nor viability of these cells. Heme oxygenase-1 which is induced upon oxidative stress is not altered while antioxidative capacity of the cells is modestly reduced. Current data show that inflammation and excess triglyceride storage raise adipocyte MnSOD which is induced in epididymal adipocytes in obesity.

TWEAK: A New Player in Obesity and Diabetes

Obesity and type 2 diabetes (T2D) are associated with chronic low-grade inflammation. Mounting evidence suggests the involvement of an inflammatory switch in adipose tissue, both in mature adipocytes and immune-competent cells from the stromal vascular compartment, in the progression of obesity and insulin resistance. Several inflammatory cytokines secreted by obese adipose tissue, including TNFα and IL-6 have been described as hallmark molecules involved in this process, impairing insulin signaling in insulin-responsive organs. An increasing number of new molecules affecting the local and systemic inflammatory imbalance in obesity and T2D have been identified. In this complex condition, some molecules may exhibit opposing actions, depending on the cell type and on systemic or local influences. Tumor necrosis factor weak inducer of apoptosis (TWEAK), a cytokine of the tumor necrosis (TNF) superfamily, is gaining attention as an important player in chronic inflammatory diseases. TWEAK can exist as a full-length membrane-associated (mTWEAK) form and as a soluble (sTWEAK) form and, by acting through its cognate receptor Fn14, can control many cellular activities including proliferation, migration, differentiation, apoptosis, angiogenesis, and inflammation. Notably, sTWEAK has been proposed as a biomarker of cardiovascular diseases. Here, we will review the recent findings relating to TWEAK and its receptor within the context of obesity and the associated disorder T2D.

Gut microbiota-based translational biomarkers to prevent metabolic syndrome via nutritional modulation

In the face of the global epidemic of metabolic syndrome (MetS) and its strong association with the increasing rate of cardiovascular morbidity and mortality, it is critical to detect MetS at an early stage in the clinical setting to implement preventive intervention long before the complications arise. Lipopolysaccharide, the cell wall component of Gram-negative bacteria produced from diet-disrupted gut microbiota, has been shown to induce metabolic endotoxemia, chronic low-grade inflammation, and ultimately insulin resistance. Therefore, ameliorating the inflammation and insulin resistance underlying MetS by gut microbiota-targeted, dietary intervention has gained increasing attention. In this review, we propose using dynamic monitoring of a set of translational biomarkers related with the etiological role of gut microbiota, including lipopolysaccharide binding protein (LBP), C-reactive protein (CRP), fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR), for early detection and prevention of MetS via nutritional modulation. LBP initiates the recognition and monomerization of lipopolysaccharide and amplifies host immune responses, linking the gut-derived antigen load and inflammation indicated by the plasma levels of CRP. Fasting plasma insulin and HOMA-IR are measured to evaluate insulin sensitivity that is damaged by pro-inflammatory cytokines. The dynamic monitoring of these biomarkers in high-risk populations may provide translational methods for the quantitative and dynamic evaluation of dysbiosis-induced insulin resistance and the effectiveness of dietary treatment for MetS.

Increased circulating CC chemokine levels in the metabolic syndrome are reduced by low-dose atorvastatin treatment: evidence from a randomized controlled trial

OBJECTIVE

Central obesity and insulin resistance are key components of the metabolic syndrome, which is associated with an increased risk of cardiovascular disease. In obesity, CC chemokines, such as monocyte chemotactic protein-1 (MCP-1), macrophage inhibitory protein-1β (MIP-1β) and eotaxin-1 and their respective receptors, are critically involved in peripheral monocyte activation and adipose tissue infiltration. The aim of the current study was to examine whether low-dose atorvastatin (10 mg/d) treatment modulated serum levels of CC chemokines in metabolic syndrome subjects.

MATERIALS AND METHODS

Serum levels of MCP-1, eotaxin-1, MIP-1β, C reactive protein (CRP) and interleukin-6 (IL-6) were measured in lean control and metabolic syndrome subjects at baseline, and following a 6-week randomized placebo-controlled clinical trial of atorvastatin (10 mg/d). Peripheral CD14(+) monocytes were isolated and mRNA levels of MCP-1, MIP-1 β and CCR5 determined.

RESULTS

Serum MCP-1 (P = 0·02), eotaxin-1 (P = 0·02) and MIP-1β (P = 0·03), CRP (P < 0·001) and IL-6 (P = 0·006) were significantly increased in metabolic syndrome in comparison with lean controls. Furthermore, CD14(+) peripheral monocyte mRNA expression of the chemokine receptor, CCR5, of which MIP-1β and eotaxin-1 are ligands, was increased two-fold in the metabolic syndrome group (P = 0·03). In addition to the expected improvements in lipid profile, atorvastatin treatment significantly reduced circulating eotaxin-1 (P < 0·05), MIP-1β (P < 0·05) levels and CD14(+) peripheral monocyte CCR5 mRNA expression (P = 0·02).

CONCLUSION

These results support a model whereby atorvastatin treatment, by inhibiting CD14(+) monocyte CCR5 expression, may inhibit monocyte trafficking, reduce chronic inflammation and, thus, lower circulating levels of CC chemokines.

Semaphorin3E-induced inflammation contributes to insulin resistance in dietary obesity

Semaphorins and their receptors (plexins) are axon-guiding molecules that regulate the development of the nervous system during embryogenesis. Here we describe a previously unknown role of class 3 semaphorin E (Sema3E) in adipose tissue inflammation and insulin resistance. Expression of Sema3E and its receptor plexinD1 was upregulated in the adipose tissue of a mouse model of dietary obesity. Inhibition of the Sema3E-plexinD1 axis markedly reduced adipose tissue inflammation and improved insulin resistance in this model. Conversely, overexpression of Sema3E in adipose tissue provoked inflammation and insulin resistance. Sema3E promoted infiltration of macrophages, and this effect was inhibited by disrupting plexinD1 expression in macrophages. Disruption of adipose tissue p53 expression led to downregulation of Sema3E expression and improved adipose tissue inflammation. These results indicate that Sema3E acts as a chemoattractant for macrophages, with p53-induced upregulation of Sema3E expression provoking adipose tissue inflammation and systemic insulin resistance in association with dietary obesity.

Activation and regulation of the pattern recognition receptors in obesity-induced adipose tissue inflammation and insulin resistance

Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor) family protein Radioprotective 105 (RP105)/myeloid differentiation protein-1 (MD-1).

Impaired local production of proresolving lipid mediators in obesity and 17-HDHA as a potential treatment for obesity-associated inflammation

Obesity-induced chronic low-grade inflammation originates from adipose tissue and is crucial for obesity-driven metabolic deterioration, including insulin resistance and type 2 diabetes. Chronic inflammation may be a consequence of a failure to actively resolve inflammation and could result from a lack of local specialized proresolving lipid mediators (SPMs), such as resolvins and protectins, which derive from the n-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). We assessed obesity-induced changes of n-3-derived SPMs in adipose tissue and the effects of dietary EPA/DHA thereon. Moreover, we treated obese mice with SPM precursors and investigated the effects on inflammation and metabolic dysregulation. Obesity significantly decreased DHA-derived 17-hydroxydocosahexaenoic acid (17-HDHA, resolvin D1 precursor) and protectin D1 (PD1) levels in murine adipose tissue. Dietary EPA/DHA treatment restored endogenous biosynthesis of n-3-derived lipid mediators in obesity while attenuating adipose tissue inflammation and improving insulin sensitivity. Notably, 17-HDHA treatment reduced adipose tissue expression of inflammatory cytokines, increased adiponectin expression, and improved glucose tolerance parallel to insulin sensitivity in obese mice. These findings indicate that impaired biosynthesis of certain SPM and SPM precursors, including 17-HDHA and PD1, contributes to adipose tissue inflammation in obesity and suggest 17-HDHA as a novel treatment option for obesity-associated complications.

The role of chronic inflammation in obesity-associated cancers

There is a strong relationship between metabolism and immunity, which can become deleterious under conditions of metabolic stress. Obesity, considered a chronic inflammatory disease, is one example of this link. Chronic inflammation is increasingly being recognized as an etiology in several cancers, particularly those of epithelial origin, and therefore a potential link between obesity and cancer. In this review, the connection between the different factors that can lead to the chronic inflammatory state in the obese individual, as well as their effect in tumorigenesis, is addressed. Furthermore, the association between obesity, inflammation, and esophageal, liver, colon, postmenopausal breast, and endometrial cancers is discussed.

Targeted deletion of growth hormone (GH) receptor in macrophage reveals novel osteopontin-mediated effects of GH on glucose homeostasis and insulin sensitivity in diet-induced obesity

We investigated GH action on macrophage (MΦ) by creating a MΦ-specific GH receptor-null mouse model (MacGHR KO). On a normal diet (10% fat), MacGHR KO and littermate controls exhibited similar growth profiles and glucose excursions on intraperitoneal glucose (ipGTT) and insulin tolerance (ITT) tests. However, when challenged with high fat diet (HFD, 45% fat) for 18 weeks, MacGHR KO mice exhibited impaired ipGTT and ITT compared with controls. In MacGHR KO, adipose-tissue (AT) MΦ abundance was increased with skewing toward M1 polarization. Expression of pro-inflammatory cytokines (IL1β, TNF-α, IL6, and osteopontin (OPN)) were increased in MacGHR KO AT stromal vascular fraction (SVF). In MacGHR KO AT, crown-like-structures were increased with decreased insulin-dependent Akt phosphorylation. The abundance of phosphorylated NF-κB and of OPN was increased in SVF and bone-marrow-derived MΦ in MacGHR KO. GH, acting via an NF-κB site in the distal OPN promoter, inhibited the OPN promoter. Thus in diet-induced obesity (DIO), lack of GH action on the MΦ exerts an unexpected deleterious effect on glucose homeostasis by accentuating AT inflammation and NF-κB-dependent activation of OPN expression. These novel results in mice support the possibility that administration of GH could have salutary effects on DIO-associated chronic inflammation and insulin resistance in humans.

Anti-inflammatory properties of a dual PPARgamma/alpha agonist muraglitazar in in vitro and in vivo models

Introduction

Peroxisome proliferator-activated receptor (PPAR) agonists are widely used drugs in the treatment of diabetes and dyslipidemia. In addition to their metabolic effects, PPAR isoforms PPARα and PPARγ are also involved in the regulation of immune responses and inflammation. In the present study, we investigated the effects of a dual PPARγ/α agonist muraglitazar on inflammatory gene expression in activated macrophages and on carrageenan-induced inflammation in the mouse.

Methods

J774 murine macrophages were activated by lipopolysaccharide (LPS) and treated with dual PPARγ/α agonist muraglitazar, PPARγ agonist GW1929 or PPARα agonist fenofibrate. The effects of PPAR agonists on cytokine production and the activation of inducible nitric oxide synthase (iNOS) pathway were investigated by ELISA, Griess method, Western blotting and quantitative RT-PCR. Nuclear translocation, DNA-binding activity and reporter gene assays were used to assess the activity of nuclear factor kappa B (NF-kB) transcription factor. Carrageenan-induced paw oedema was used as an in vivo model of acute inflammation.

Results

Muraglitazar as well as PPARγ agonist GW1929 and PPARα agonist fenofibrate inhibited LPS-induced iNOS expression and NO production in activated macrophages in a dose-dependent manner. Inhibition of iNOS expression by muraglitazar included both transcriptional and post-transcriptional components; the former being shared by GW1929 and the latter by fenofibrate. All tested PPAR agonists also inhibited IL-6 production, while TNFα production was reduced by muraglitazar and GW1929, but not by fenofibrate. Interestingly, the anti-inflammatory properties of muraglitazar were also translated in vivo. This was evidenced by the finding that muraglitazar inhibited carrageenan-induced paw inflammation in a dose-dependent manner in mice as did iNOS inhibitor L-NIL and anti-inflammatory steroid dexamethasone.

Conclusions

These results show that muraglitazar has anti-inflammatory properties both in vitro and in vivo and these effects reflect the agonistic action through both PPARα and PPARγ.

Roles of chemokine ligand-2 (CXCL2) and neutrophils in influencing endothelial cell function and inflammation of human adipose tissue

The hypertrophied white adipose tissue (WAT) during human obesity produces inflammatory mediators, including cytokines (IL-6 and TNFα) and chemokines ([C-C motif] chemokine ligand 2 and IL-8). These inflammatory factors are preferentially produced by the nonadipose cells, particularly the adipose tissue infiltrating macrophages. We identified the chemokine (C-X-C motif) ligand 2 (CXCL2) by a transcriptomic approach. Because CXCL2 could represent a WAT-produced chemokine, we explored its role in obesity-associated inflammation. CXCL2 levels in serum and mRNA in WAT were higher in obese subjects compared with lean ones. CXCL2 secretions were higher in sc and visceral (vis) WAT from obese compared with lean subjects. In vis WAT, CXCL2 mRNA expression was higher in macrophages compared with other WAT cells and positively correlated with the inflammatory macrophage markers TNFα and IL-6. CXCL2 triggered the in vitro adhesion of the neutrophils, its selective cell targets, to endothelial cells (ECs) of vis WAT (vis WAT-ECs). Immunohistological analysis indicated that activated neutrophils were adherent to the endothelium of vis WAT from human obese subjects. Blood neutrophils from obese subjects released high levels of proinflammatory mediators (IL-8, chemokine motif ligand 2 [CCL2], matrix metalloproteinase [MMP] 9, and myeloperoxidase [MPO]). Visceral WAT-ECs, treated by neutrophil-conditioned media prepared from obese subjects, displayed an increase of the expression of inflammatory molecules associated with senescence and angiogenic capacities. To conclude, CXCL2, a WAT-produced chemokine being up-regulated in obesity, stimulates neutrophil adhesion to vis WAT-ECs. Activated neutrophils in obesity may influence vis WAT-ECs functions and contribute to WAT inflammation.

Dual-energy computed tomography imaging of atherosclerotic plaques in a mouse model using a liposomal-iodine nanoparticle contrast agent

BACKGROUND

The accumulation of macrophages in inflamed atherosclerotic plaques has long been recognized. In an attempt to develop an imaging agent for detection of vulnerable plaques, we evaluated the feasibility of a liposomal-iodine nanoparticle contrast agent for computed tomography imaging of macrophage-rich atherosclerotic plaques in a mouse model.

METHODS AND RESULTS

Liposomal-iodine formulations varying in particle size and polyethylene glycol coating were fabricated and shown to stably encapsulate the iodine compound. In vitro uptake studies using optical and computed tomography imaging in the RAW 264.7 macrophage cell line identified the formulation that promoted maximal uptake. Dual-energy computed tomography imaging using this formulation in apolipoprotein E-deficient (ApoE(-/-)) mice (n=8) and control C57BL/6 mice (n=6) followed by spectral decomposition of the dual-energy images enabled imaging of the liposomes localized in the plaque. Imaging cytometry confirmed the presence of liposomes in the plaque and their colocalization with a small fraction (≈2%) of the macrophages in the plaque.

CONCLUSIONS

The results demonstrate the feasibility of imaging macrophage-rich atherosclerotic plaques using a liposomal-iodine nanoparticle contrast agent and dual-energy computed tomography.

Alternatively activated macrophages in types 1 and 2 diabetes

Macrophages are innate immune cells derived from monocytes, which, in turn, arise from myeloid precursor cells in the bone marrow. Macrophages have many important roles in the innate and adaptive immune response, as well as in tissue homeostasis. Two major populations have been defined: The classically activated macrophages that respond to intracellular pathogens by secreting proinflammatory cytokines and reactive oxygen species and alternatively activated macrophages which are induced during Th2 responses displaying anti-inflammatory activities. Both macrophage populations are central players in diabetes, the first one triggering inflammatory responses which initiates insulitis and pancreatic β cell death during type 1 diabetes, whereas the second population decreases hyperglycemia, insulitis, and inflammation in the pancreas, thereby negatively regulate type 1 diabetes. Obesity is an important factor in the development of type 2 diabetes; classically activated macrophages are a dominant cell population involved in the establishment of the inflammatory profile, insulin resistance, and activation of inflammatory signals during the development and progression of this disease. In contrast, alternatively activated macrophages regulate the release of proinflammatory cytokines, attenuating adipose tissue inflammation. Here, we review the advantages and disadvantages of these two macrophage populations with regard to their roles in types 1 and 2 diabetes.

The role of adipose tissue-associated macrophages and T lymphocytes in the pathogenesis of inflammatory bowel disease

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the gastrointestinal tract that affect more than 3 million people worldwide, but the pathological etiology is still unknown. The overall purpose of our investigations was to elucidate the possibility of pathological causes of IBD, and therefore, we determined the difference of inflammatory cytokine profiles in adipose tissue macrophages (ATMs) and T lymphocytes (ATTs) obtained near active lesions of IBD; investigated whether the alteration in ATM activation induces genes involved in collagen formation; and evaluated the effects of fatty acid oxidation inhibitors on factors involved in inflammation and collagen production by ATMs in IBD. Adipose tissues (ATs) were collected near active lesions and also at the margin of resected segments of the bowel from IBD patients with ulcerative colitis (UC) and CD (n=14/group). Normal appearing ATs from control subjects (n=14) who had colon resection for adenocarcinoma were collected as far away from the cancer lesion as possible to rule out possible changes. Compared with inactive disease lesions, ATMs and ATTs from active lesions released more IL-6, IL-4 and IL-13. Treatments of cytokine IL-4 and/or IL-13 to ATMs reduced iNOS expression but increased Arg-I expression which were exacerbated when treated with T cell- and adipocyte-conditioned medium. However, fatty acid oxidation inhibitors prevented the effects of cytokines IL-4 and/or IL-13 on iNOS and Arg-I expressions. This study was the first to show the effect of IL-4 and IL-13 on collagen formation, through iNOS and Arg-I expressions, that was exacerbated in a condition that mimics in vivo condition of active lesions. Moreover, our study was the first to provide potential benefits of fatty acid oxidation inhibitors to ATMs on preventing collagen formation; thus, providing therapeutic implications for individuals with intestinal fibrosis and stricture lesions, although future study should be guaranteed to elucidate the underlying mechanisms.

Mechanisms linking obesity, inflammation and altered metabolism to colon carcinogenesis

Due to its prevalence, obesity is now considered a global epidemic. It is linked to increased risk of colorectal cancer, the third most common cancer and the second leading cause of death among adults in Western countries. Obese adipose tissue differs from lean adipose tissue in its immunogenic profile, body fat distribution and metabolic profile. Obese adipose tissue releases free fatty acids, adipokines and many pro-inflammatory chemokines. These factors are known to play a key role in regulating malignant transformation and cancer progression. Obese adipose tissue is infiltrated by macrophages that participate in inflammatory pathways activated within the tissue. Adipose tissue macrophages consist of two different phenotypes. M1 macrophages reside in obese adipose tissue and produce pro-inflammatory cytokines, and M2 macrophages reside in lean adipose tissue and produce anti-inflammatory cytokines, such as interleukin-10 (IL-10). The metabolic networks that confer tumour cells with their oncogenic properties, such as increased proliferation and the ability to avoid apoptosis are still not well understood. We review the interactions between adipocytes and immune cells that may alter the metabolism towards promotion of colorectal cancer.

Obesity lowers the threshold of allergic sensitization and augments airway eosinophilia in a mouse model of asthma

BACKGROUND

Clinical and epidemiological studies show a close association between obesity and the risk of asthma development. The underlying cause-effect relationship between metabolism, innate and adaptive immunity, and inflammation remains to be elucidated.

METHODS

We developed an animal model to study the interaction between metabolic abnormalities and experimentally induced asthma. Obesity-susceptible AKR mice were fed with high-fat diet (HFD) or normal low-fat diet (LFD) and subjected to a protocol of ovalbumin (OVA) sensitization and airway allergen challenges followed by assessment of inflammation and lung function.

RESULTS

AKR mice developed obesity and a prestage of metabolic syndrome following HFD. This phenotype was associated with an increase in proinflammatory macrophages (CD11b+/CD11c+) together with higher serum levels of interleukin 6. Obese mice showed increased susceptibility to allergic sensitization as compared to LFD animals. Anti-ovalbumin IgE antibody titers correlated positively and anti-OVA IgG2a antibodies titers correlated negatively with body weight. Airway eosinophilia showed a positive correlation with body weight, whereas mucus production did not change with obesity.

CONCLUSIONS

This obesity model demonstrates that HFD-induced obesity lowers the sensitization threshold in a model of asthma. This finding helps to understand why, particularly during childhood, obesity is a risk factor for the development of allergic asthma.

Adipose tissue promotes a serum cytokine profile related to lower insulin sensitivity after chronic central leptin infusion

Obesity is an inflammatory state characterized by an augment in circulating inflammatory factors. Leptin may modulate the synthesis of these factors by white adipose tissue decreasing insulin sensitivity. We have examined the effect of chronic central administration of leptin on circulating levels of cytokines and the possible relationship with cytokine expression and protein content as well as with leptin and insulin signaling in subcutaneous and visceral adipose tissues. In addition, we analyzed the possible correlation between circulating levels of cytokines and peripheral insulin resistance. We studied 18 male Wistar rats divided into controls (C), those treated icv for 14 days with a daily dose of 12 μg of leptin (L) and a pair-fed group (PF) that received the same food amount consumed by the leptin group. Serum leptin and insulin were measured by ELISA, mRNA levels of interferon-γ (IFN-γ), interleukin-2 (IL-2), IL-4, IL-6, IL-10 and tumor necrosis factor-α (TNF-α) by real time PCR and serum and adipose tissue levels of these cytokines by multiplexed bead immunoassay. Serum leptin, IL-2, IL-4, IFN-γ and HOMA-IR were increased in L and TNF-α was decreased in PF and L. Serum leptin and IL-2 levels correlate positively with HOMA-IR index and negatively with serum glucose levels during an ip insulin tolerance test. In L, an increase in mRNA levels of IL-2 was found in both adipose depots and IFN-γ only in visceral tissue. Activation of leptin signaling was increased and insulin signaling decreased in subcutaneous fat of L. In conclusion, leptin mediates the production of inflammatory cytokines by adipose tissue independent of its effects on food intake, decreasing insulin sensitivity.

Effects of methotrexate on inflammatory alterations induced by obesity: an in vivo and in vitro study

Immunosuppressant drugs, such as methotrexate, are able to inhibit cytokine production and leukocyte migration to inflammatory foci; therefore, they could modify the establishment of inflammation in adipose tissue during obesity. Thus, we studied the effects of methotrexate in vivo on high-fat diet induced-obesity in mice and in vitro in isolated and co-cultured adipocytes and macrophages. Obese mice treated with methotrexate presented reduced serum levels of TNF-α, insulin and glucose, and an improvement of insulin sensitivity. Adipose tissue from these mice produced less proinflammatory (TNF-α, IL-6, leptin) and more anti-inflammatory adipokines (adiponectin and IL-10) associated with reduced macrophage infiltration and inflammation. Cytokine inhibition was also confirmed in isolated and co-cultured adipocytes and macrophages. Methotrexate presented anti-lipolytic effect in vivo and, in vitro through adenosine release. Drugs that combine anti-lipolytic effect and the ability to control inflammation in adipose tissue could play a role in the control of insulin resistance and other pathologies associated with obesity.

Phytochemicals and their impact on adipose tissue inflammation and diabetes

Type 2 diabetes mellitus is an inflammatory disease and the mechanisms that underlie this disease, although still incompletely understood, take place in the adipose tissue of obese subjects. Concurrently, the prevalence of obesity caused by Western diet's excessive energy intake and the lack of exercise escalates, and is believed to be causative for the chronic inflammatory state in adipose tissue. Overnutrition itself as an overload of energy may induce the adipocytes to secrete chemokines activating and attracting immune cells to adipose tissue. But also inflammation-mediating food ingredients like saturated fatty acids are believed to directly initiate the inflammatory cascade. In addition, hypoxia in adipose tissue as a direct consequence of obesity, and its effect on gene expression in adipocytes and surrounding cells in fat tissue of obese subjects appears to play a central role in this inflammatory response too. In contrast, revisiting diet all over the world, there are also some natural food products and beverages which are associated with curative effects on human health. Several natural compounds known as spices such as curcumin, capsaicin, and gingerol, or secondary plant metabolites catechin, resveratrol, genistein, and quercetin have been reported to provide an improved health status to their consumers, especially with regard to diabetes, and therefore have been investigated for their anti-inflammatory effect. In this review, we will give an overview about these phytochemicals and their role to interfere with inflammatory cascades in adipose tissue and their potential for fighting against inflammatory diseases like diabetes as investigated in vivo.

Characterizing and quantifying leukocyte populations in human adipose tissue: impact of enzymatic tissue processing

Adipose tissue inflammation is a major mechanistic link between obesity and chronic disease. To isolate and characterize specific leukocyte populations, e.g. by flow cytometry, tissue needs to be processed to digest the extracellular matrix. We have systematically compared the impact of different commonly used collagenase preparations, digestion times, and normalization strategies on the reproducibility of flow cytometric phenotyping of adipose tissue leukocyte populations. Subcutaneous adipose tissue was obtained from 11 anonymous donors undergoing elective procedures at a plastic surgery clinic in Seattle, WA. We found that collagenase alone consistently produced better cell yields (p=0.007) than when combined with additional proteases such as the commercially available liberases. Moreover, liberase significantly degraded the cell surface expression of CD4 (p<0.001) on T cells and to a lesser extent CD16 (p=0.058) on neutrophils. Extension of the digestion interval from 30 to 120 min did not significantly impact cell viability (p=0.319) or yield (p=0.247). Normalization by either 'live-gate' or percentage of CD45(pos) leukocytes exhibited the lowest coefficient of variation for tissue digests between 60 and 75 min, compared to normalization per gram of tissue, which consistently exhibited the greatest variability. Our data suggest that digestion of adipose tissue using pure collagenase for 60-75 min provides the best cell yield and viability, with minimal degradation of cell surface markers used to identify immune cell subpopulations, and best reproducibility independent of the normalization strategy.

Insights into the role of macrophage migration inhibitory factor in obesity and insulin resistance

High-fat diet (HFD)-induced obesity has emerged as a state of chronic low-grade inflammation characterised by a progressive infiltration of immune cells, particularly macrophages, into obese adipose tissue. Adipose tissue macrophages (ATM) present immense plasticity. In early obesity, M2 anti-inflammatory macrophages acquire an M1 pro-inflammatory phenotype. Pro-inflammatory cytokines including TNF-α, IL-6 and IL-1β produced by M1 ATM exacerbate local inflammation promoting insulin resistance (IR), which consequently, can lead to type-2 diabetes mellitus (T2DM). However, the triggers responsible for ATM recruitment and activation are not fully understood. Adipose tissue-derived chemokines are significant players in driving ATM recruitment during obesity. Macrophage migration inhibitory factor (MIF), a chemokine-like inflammatory regulator, is enhanced during obesity and is directly associated with the degree of peripheral IR. This review focuses on the functional role of macrophages in obesity-induced IR and highlights the importance of the unique inflammatory cytokine MIF in propagating obesity-induced inflammation and IR. Given MIF chemotactic properties, MIF may be a primary candidate promoting ATM recruitment during obesity. Manipulating MIF inflammatory activities in obesity, using pharmacological agents or functional foods, may be therapeutically beneficial for the treatment and prevention of obesity-related metabolic diseases.

Oxidized LDL/CD36 interaction induces loss of cell polarity and inhibits macrophage locomotion

Cell polarization is essential for migration and the exploratory function of leukocytes. However, the mechanism by which cells maintain polarity or how cells revert to the immobilized state by gaining cellular symmetry is not clear. Previously we showed that interaction between oxidized low-density lipoprotein (oxLDL) and CD36 inhibits macrophage migration; in the current study we tested the hypothesis that oxLDL/CD36-induced inhibition of migration is the result of intracellular signals that regulate cell polarity. Live cell imaging of macrophages showed that oxLDL actuated retraction of macrophage front end lamellipodia and induced loss of cell polarity. Cd36 null and macrophages null for Vav, a guanine nucleotide exchange factor (GEF), did not show this effect. These findings were caused by Rac-mediated inhibition of nonmuscle myosin II, a cell polarity determinant. OxLDL induced dephosphorylation of myosin regulatory light chain (MRLC) by increasing the activity of Rac. Six-thioguanine triphosphate (6-thio-GTP), which inhibits Vav-mediated activation of Rac, abrogated the effect of oxLDL. Activation of the Vav-Rac-myosin II pathway by oxidant stress may induce trapping of macrophages at sites of chronic inflammation such as atherosclerotic plaque.

Resolvin D1 and resolvin D2 govern local inflammatory tone in obese fat

The unprecedented increase in the prevalence of obesity and obesity-related disorders is causally linked to a chronic state of low-grade inflammation in adipose tissue. Timely resolution of inflammation and return of this tissue to homeostasis are key to reducing obesity-induced metabolic dysfunctions. In this study, with inflamed adipose, we investigated the biosynthesis, conversion, and actions of Resolvins D1 (RvD1, 7S,8R,17S-trihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid) and D2 (RvD2, 7S,16R,17S-trihydroxy-4Z,8E,10Z,12E,14E,19Z-docosahexaenoic acid), potent anti-inflammatory and proresolving lipid mediators (LMs), and their ability to regulate monocyte interactions with adipocytes. Lipid mediator-metabololipidomics identified RvD1 and RvD2 from endogenous sources in human and mouse adipose tissues. We also identified proresolving receptors (i.e., ALX/FPR2, ChemR23, and GPR32) in these tissues. Compared with lean tissue, obese adipose showed a deficit of these endogenous anti-inflammatory signals. With inflamed obese adipose tissue, RvD1 and RvD2 each rescued impaired expression and secretion of adiponectin in a time- and concentration-dependent manner as well as decreasing proinflammatory adipokine production including leptin, TNF-α, IL-6, and IL-1β. RvD1 and RvD2 each reduced MCP-1 and leukotriene B₄-stimulated monocyte adhesion to adipocytes and their transadipose migration. Adipose tissue rapidly converted both resolvins (Rvs) to novel oxo-Rvs. RvD2 was enzymatically converted to 7-oxo-RvD2 as its major metabolic route that retained adipose-directed RvD2 actions. These results indicate, in adipose, D-series Rvs (RvD1 and RvD2) are potent proresolving mediators that counteract both local adipokine production and monocyte accumulation in obesity-induced adipose inflammation.

A macrophage activation marker chitotriosidase in women with PCOS: does low-grade chronic inflammation in PCOS relate to PCOS itself or obesity?

OBJECTIVE

Polycystic ovary syndrome (PCOS) is described as a low-grade chronic inflammatory state where the macrophage infiltration increased in visceral fat play the major role. The aim of this study was to assess chitotriosidase (ChT) activity (an activated macrophage marker) in women with PCOS and controls and to evaluate its correlation with anthropometric and biochemical parameters.

STUDY DESIGN

Seventy-nine women with PCOS and 60 healthy controls were included in the study. PCOS and controls were divided into two subgroups according to body mass indexes (BMIs) as normoweight (<25 kg/m(2)) and overweight (≥25 kg/m(2)). ChT activity, biochemical (free testosterone, luteinizing hormone, insulin resistance index, etc.) and clinical parameters [BMI, waist-to-hip ratio, modified Ferriman-Gallwey scores (mFG)] were analyzed according to groups.

RESULTS

Serum ChT activity was significantly (p < 0.001) higher in women with PCOS than controls (normoweight, 87.1 ± 90.1 vs. 18.4 ± 9.0 nmol/ml/h; overweight, 92.0 ± 96.7 vs. 17.9 ± 12.1 nmol/ml/h PCOS and controls, respectively). No statistically significant difference was noted between ChT activity of normoweight and overweight PCOS subgroups. A positive correlation was found between ChT activity and PCOS status (r 0.598, p < 0.001), mFG scores (r 0.525, p < 0.001), free testosterone (r 0.402, p 0.001) and total testosterone (r 0.168, p 0.048) for the combined groups (PCOS + controls). In multivariant linear regression analysis participants' PCOS status (presence or absence) and LH levels were the main predictors of ChT activity in the whole study population (p 0.002 and p 0.041, respectively).

CONCLUSION

ChT activity elevates in PCOS independent of obesity. Our findings support the concept of PCOS is a state of low-grade chronic inflammation where the macrophages could play the major role. Hyperandrogenism might also be related to this inflammatory state and can be a subject of further trials.

Soluble CD163: a biomarker linking macrophages and insulin resistance

AIMS/HYPOTHESIS

Soluble CD163 (sCD163) was recently identified as a strong risk marker for developing type 2 diabetes. We hypothesised that sCD163 independently associates with insulin resistance.

METHODS

This cross-sectional study includes 234 participants: 96 with type 2 diabetes, 34 with impaired glucose tolerance (IGT) and 104 with normal glucose tolerance (NGT), matched for sex and BMI. Glucose-lowering medication was paused for 1 week before plasma samples were obtained for determination of sCD163 and other inflammatory and metabolic variables. Insulin resistance was estimated by homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Concentrations of sCD163 were 1.95 mg/l (0.63-6.97) in individuals with type 2 diabetes, 1.64 mg/l (0.58-4.19) in those with IGT, and 1.48 mg/l (0.48-4.11) (median [range]) in those with NGT (p < 0.0001). In univariate analyses, sCD163 correlated significantly with HOMA-IR (R = 0.44), insulin (R = 0.41), glucose (R = 0.30), triacylglycerol (R = 0.29) and HDL-cholesterol (R = -0.34) (all p < 0.0001). All but glucose remained significant when adjusting for age, sex, BMI and glycaemic group. In univariate regression analyses, HOMA-IR was associated with sCD163, C-reactive protein (CRP), TNF-α and IL-6 (all p ≤ 0.0001). An increase of 50% in sCD163 resulted in an estimated increase in HOMA-IR of 36% (95% CI 26, 48; p < 0.0001). In multiple linear regression analyses, sCD163 (p = 0.001) and CRP (p = 0.01) remained independent predictors of HOMA-IR, whereas TNF-α and IL-6 did not.

CONCLUSIONS/INTERPRETATION

Macrophage-specific sCD163 was strongly associated with insulin resistance independently of TNF-α and other predictors. Moreover, sCD163 was associated with well-known variables of the metabolic syndrome.

Relation of chemokines to BMI and insulin resistance at ages 18-21

OBJECTIVE

In obesity, adipose tissue becomes a significant source of chemokines and inflammatory cytokines that are associated with chronic systemic low-grade inflammation and may lead to insulin resistance. Studies in children have mainly focused on inflammatory cytokines and there are limited data for chemokines in adolescents and young adults. We studied the relation of chemokines to cardiovascular (CV)-risk factors, insulin resistance and adipocytokines in 18-21-year-old individuals.

SUBJECTS AND DESIGN

Cross-sectional data collected in a cohort originally enrolled at mean age 13, with data for the present study obtained from 252 examined at age 18.7±0.1 years.

METHODS

Multiple linear regression models were used to analyze the associations among chemokines (monocyte chemotactic protein-1, macrophage inflammatory protein-1β (MIP-1β), visfatin and interleukin-8 (IL-8)) and between chemokines and body mass index (BMI), glucose, lipids, blood pressure (BP), insulin resistance (euglycemic hyperinsulinemic clamp) and adipocytokines (IL-6, TNF-α and adiponectin).

RESULTS

Chemokine levels were significantly intercorrelated. Significant associations (P<0.05) with adjustment for age, race and sex included: MIP-1β with waist circumference and IL-6, IL-8 with systolic BP and visfatin with IL-6. No other significant relations were found between the chemokines and the other variables. Further adjustment for BMI did not alter these conclusions.

CONCLUSION

Considered in the context of prior studies in children and adults, these results suggest that in large part, the association between chemokines and CV risk or inflammatory factors does not appear to develop until adult life.

Surfactant protein d deficiency in mice is associated with hyperphagia, altered fat deposition, insulin resistance, and increased basal endotoxemia

Pulmonary surfactant protein D (SP-D) is a host defence lectin of the innate immune system that enhances clearance of pathogens and modulates inflammatory responses. Recently it has been found that systemic SP-D is associated with metabolic disturbances and that SP-D deficient mice are mildly obese. However, the mechanism behind SP-D's role in energy metabolism is not known.

Here we report that SP-D deficient mice had significantly higher ad libitum energy intake compared to wild-type mice and unchanged energy expenditure. This resulted in accumulation but also redistribution of fat tissue. Blood pressure was unchanged. The change in energy intake was unrelated to the basal levels of hypothalamic Pro-opiomelanocortin (POMC) and Agouti-related peptide (AgRP) gene expression. Neither short time systemic, nor intracereberoventricular SP-D treatment altered the hypothalamic signalling or body weight accumulation.

In ad libitum fed animals, serum leptin, insulin, and glucose were significantly increased in mice deficient in SP-D, and indicative of insulin resistance. However, restricted diets eliminated all metabolic differences except the distribution of body fat. SP-D deficiency was further associated with elevated levels of systemic bacterial lipopolysaccharide.

In conclusion, our findings suggest that lack of SP-D mediates modulation of food intake not directly involving hypothalamic regulatory pathways. The resulting accumulation of adipose tissue was associated with insulin resistance. The data suggest SP-D as a regulator of energy intake and body composition and an inhibitor of metabolic endotoxemia. SP-D may play a causal role at the crossroads of inflammation, obesity, and insulin resistance.

Macrophages in cancer and infectious diseases: the 'good' and the 'bad'

Macrophages are crucial orchestrators of host defence and tissue homeostasis. Macrophages are heterogeneous and plastic cells that in response to different microenvironmental signals can mount a broad spectrum of different programs of polarized activation. In different pathological contexts including cancer and infectious diseases, macrophages diversity and plasticity may act as a double-edged sword. The elucidation of the molecular mechanisms underlying macrophages recruitment and functional activation allows the identification of valuable targets for the development of innovative therapeutic approaches.

Relevance of the MEK/ERK signaling pathway in the metabolism of activated macrophages: a metabolomic approach

The activation of immune cells in response to a pathogen involves a succession of signaling events leading to gene and protein expression, which requires metabolic changes to match the energy demands. The metabolic profile associated with the MAPK cascade (ERK1/2, p38, and JNK) in macrophages was studied, and the effect of its inhibition on the specific metabolic pattern of LPS stimulation was characterized. A [1,2-[(13)C](2)]glucose tracer-based metabolomic approach was used to examine the metabolic flux distribution in these cells after MEK/ERK inhibition. Bioinformatic tools were used to analyze changes in mass isotopomer distribution and changes in glucose and glutamine consumption and lactate production in basal and LPS-stimulated conditions in the presence and absence of the selective inhibitor of the MEK/ERK cascade, PD325901. Results showed that PD325901-mediated ERK1/2 inhibition significantly decreased glucose consumption and lactate production but did not affect glutamine consumption. These changes were accompanied by a decrease in the glycolytic flux, consistent with the observed decrease in fructose-2,6-bisphosphate concentration. The oxidative and nonoxidative pentose phosphate pathways and the ratio between them also decreased. However, tricarboxylic acid cycle flux did not change significantly. LPS activation led to the opposite responses, although all of these were suppressed by PD325901. However, LPS also induced a small decrease in pentose phosphate pathway fluxes and an increase in glutamine consumption that were not affected by PD325901. We concluded that inhibition of the MEK/ERK cascade interferes with central metabolism, and this cross-talk between signal transduction and metabolism also occurs in the presence of LPS.

Macrophages, meta-inflammation, and immuno-metabolism

Current research depicts specific modes of immunity and energy metabolism as being interrelated at the molecular, cellular, organ and organism level. Hence, whereas M2 (alternatively-activated) macrophages dominate insulin-sensitive adipose tissue in the lean, M1-skewed (classically-activated) macrophages accumulate in parallel to adiposity in the obese, and promote inflammation and insulin resistance, that is, meta-inflammation. The latest frontier of immuno-metabolism explores the coregulation of energy metabolism and immune function within hematopoietic cells. M1-skewed macrophages are sustained in edematous, hypoxic tissues by anaerobic glycolysis, whereas mitochondrial biogenesis and respiration dominates in M2 cells. We review the underlying mechanisms and the consequences of the transition from M2 to M1 predominance in adipose tissue, as well as the extracellular signals and transcription factors that control macrophage phenotypes and impose distinct metabolic modes.

Soya protein hydrolysates modify the expression of various pro-inflammatory genes induced by fatty acids in ovine phagocytes

The objective of the present study was to test the hypothesis that fatty acids are the circulating mediators acting in a pro-inflammatory manner towards activated circulating ovine monocyte/macrophages and neutrophils. Furthermore, whether soya protein hydrolysates (SPH) inhibit the fatty acid-induced increase in the production of pro-inflammatory responses by ovine phagocytes was tested in vitro. All the fatty acids tested (myristic, palmitic, palmitoleic, stearic and oleic) increased (P < 0·01; C18>C16>C14) membrane-bound urokinase plasminogen activator (u-PA) and u-PA free binding sites in cell membranes of activated ovine blood monocytes/macrophages, but only the C18 fatty acids (stearic, oleic) were effective towards blood neutrophils. The C18 fatty acids up-regulated (P < 0·05) the gene expression of u-PA, u-PA receptor, intercellular adhesion molecule 1 and inducible NO synthase (in monocytes) but not that of cyclo-oxygenase-2, integrin α X and plasminogen activator inhibitor types 1 and 2 by ovine phagocytes. SPH blocked completely or partially all C18 fatty acid-induced changes in the expression of various pro-inflammatory genes. In conclusion, fatty acids selectively ‘activate’ ovine phagocytes, suggesting that these cells ‘sense’ metabolic signals derived from adipocytes. Soya protein peptides inhibit all changes in gene expression induced by fatty acids in ovine phagocytes in vitro. This constitutes a novel mechanism of action.

[Molecular mechanisms regulating the activity of macrophages]

This article reviews modern concepts of the most common types of macrophage activation: classical, alternative, and type II. Molecular mechanisms of induction and regulation of these three types of activation are discussed. Any population of macrophages was shown to change its properties depending on its microenvironment and concrete biological situation (the "functional plasticity of macrophages"). Many intermediate states of macrophages were described along with the most pronounced and well-known activation types (classical activation, alternative activation, and type II activation). These intermediate states are characterized by a variety of combinations of their biological properties, including elements of the three afore mentioned types of activation. Macrophage activity is regulated by a complex network of interrelated cascade mechanisms.

The macrophage at the intersection of immunity and metabolism in obesity

Obesity is a worldwide pandemic representing one of the major challenges that societies face around the globe. Identifying the mechanisms involved in its development and propagation will help the development of preventative and therapeutic strategies that may help control its rising rates.Obesity is associated with chronic low-grade inflammation, and this is believed to be one of the major contributors to the development of insulin resistance, which is an early event in obesity and leads to type 2 diabetes when the pancreas fails to keep up with increased demand for insulin. In this review, we discuss the role of macrophages in mediation of inflammation in obesity in metabolic organs including adipose tissue, skeletal muscle and liver. The presence of immune cells at the interface with metabolic organs modulates both metabolic function and inflammatory responses in these organs, and may provide a potential therapeutic target to modulate metabolic function in obesity.

Immunity as a link between obesity and insulin resistance

Obesity is a major public health problem in the United States and worldwide. Further, obesity is causally linked to the pathogenesis of insulin resistance, metabolic syndrome and type-2 diabetes (T2D). A chronic low-grade inflammation occurring in adipose tissue is at least in part responsible for the obesity-induced insulin resistance. This adipose tissue inflammation is characterized by changes in immune cell populations giving rise to altered adipo/cytokine profiles, which in turn induces skeletal muscle and hepatic insulin resistance. Detailed molecular mechanisms of insulin resistance, adipose tissue inflammation and the implications of these findings on therapeutic strategies are discussed in this review.

The use of THP-1 cells as a model for mimicking the function and regulation of monocytes and macrophages in the vasculature

Since their establishment thirty years ago, THP-1 cells have become one of most widely used cell lines to investigate the function and regulation of monocytes and macrophages in the cardiovascular system. However, because this cell line was derived from the blood of a patient with acute monocytic leukemia, the extent to which THP-1 cells mimic monocytes and macrophages in the vasculature is not entirely known. This article serves as a meaningful attempt to address this question by reviewing the recent publications. The interactions between THP-1 cells and various vascular cells (such as endothelial cells, smooth muscle cells, adipocytes, and T cells) provide insight into the roles of the interconnection of monocytes-macrophages with other vascular cells during vascular inflammation, particularly atherogenesis and obesity. Transcriptome, microRNA profile, and histone modifications of THP-1 cells shed new light on the regulatory mechanism of the monocytes-macrophages in response to various inflammatory mediators, such as oxidized low density lipoprotein, lipopolysaccharide, and glucose. These studies hint that under certain defined conditions, THP-1 cells not only resemble primary monocytes-macrophages isolated from healthy donors or donors with disease, such as diabetes mellitus, but also mimic the in situ alteration of macrophages in the adipose tissue of obese subjects and in atherosclerotic lesions. A potential trajectory is to use this cell line to study the novel molecular mechanisms in monocytes and macrophages in relation to the physiology and pathophysiology of the cardiovascular system, however, the conclusion of studies employing THP-1 cells requires further verification using primary cells and/or in vivo models to be generalized to monocytes and macrophages.

Redox balance in the pathogenesis of nonalcoholic fatty liver disease: mechanisms and therapeutic opportunities

Nonalcoholic fatty liver disease (NAFLD) is currently the most common liver disease in the world. It encompasses a histological spectrum, ranging from simple, nonprogressive steatosis to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis and hepatocellular carcinoma. While liver-related complications are confined to NASH, emerging evidence suggests both simple steatosis and NASH predispose to type 2 diabetes and cardiovascular disease. The pathogenesis of NAFLD is currently unknown, but accumulating data suggest that oxidative stress and altered redox balance play a crucial role in the pathogenesis of steatosis, steatohepatitis, and fibrosis. We will examine intracellular mechanisms, including mitochondrial dysfunction and impaired oxidative free fatty acid metabolism, leading to reactive oxygen species generation; additionally, the potential pathogenetic role of extracellular sources of reactive oxygen species in NAFLD, including increased myeloperoxidase activity and oxidized low density lipoprotein accumulation, will be reviewed. We will discuss how these mechanisms converge to determine the whole pathophysiological spectrum of NAFLD, including hepatocyte triglyceride accumulation, hepatocyte apoptosis, hepatic inflammation, hepatic stellate cell activation, and fibrogenesis. Finally, available animal and human data on treatment opportunities with older and newer antioxidant will be presented.

Molecular phenotype of monocytes at the maternal-fetal interface

OBJECTIVE

The purpose of this study was to gain insight into the pathways that are associated with inflammation at the maternal-fetal interface. This study examined the molecular characteristics of monocytes that were derived from the maternal circulation and the placenta of obese women.

STUDY DESIGN

Mononuclear cells were isolated from placenta, venous maternal, and umbilical cord blood at term delivery; activated monocytes were separated with CD14 immunoselection. The genotype and expression pattern of the monocytes were analyzed by microarray and real-time reverse transcriptase-polymerase chain reaction.

RESULTS

The transcriptome of the maternal blood and placental CD14 monocytes exhibited 73% homology, with 10% (1800 common genes) differentially expressed. Genes for immune sensing and regulation, matrix remodeling, and lipid metabolism were enhanced 2-2006 fold in placenta, compared with maternal monocytes. The CD14 placental monocytes exhibited a maternal genotype (9% DYS14 expression) as opposed to the fetal genotype (90% DYS14 expression) of the trophoblast cells.

CONCLUSION

CD14 monocytes from the maternal blood and the placenta share strong phenotypic and genotypic similarities with an enhanced inflammatory pattern in the placenta. The functional traits of the CD14 blood and placental monocytes suggest that they both contribute to propagation of inflammation at the maternal-fetal interface.