Mesenteric adipose tissue-derived monocyte chemoattractant protein-1 plays a crucial role in adipose tissue macrophage migration and activation in obese mice

Interrelation of adipose tissue macrophages and fibrosis in obesity

Obesity is characterized by adipose tissue expansion, extracellular matrix remodelling and unresolved inflammation that contribute to insulin resistance and fibrosis. Adipose tissue macrophages represent the most abundant class of immune cells in adipose tissue inflammation and could be key mediators of adipocyte dysfunction and fibrosis in obesity. Although macrophage activation states are classically defined by the M1/M2 polarization nomenclature, novel studies have revealed a more complex range of macrophage phenotypes in response to external condition or the surrounding microenvironment. Here, we discuss the plasticity of adipose tissue macrophages (ATMs) in response to their microenvironment in obesity, with special focus on macrophage infiltration and polarization, and their contribution to adipose tissue fibrosis. A better understanding of the role of ATMs as regulators of adipose tissue remodelling may provide novel therapeutic strategies against obesity and associated metabolic diseases.

Overview of Natural Supplements for the Management of Diabetes and Obesity

Bioactive compounds found in various natural sources, such as fruits, vegetables, and herbs, have been studied for their potential benefits in managing obesity and diabetes. These compounds include polyphenols, flavonoids, other antioxidants, fiber, and certain fatty acids. Studies have found that these compounds may improve insulin sensitivity, regulate blood sugar levels, and promote weight loss. However, the effects of these compounds can vary depending on the type and amount consumed, as well as individual factors, such as genetics and lifestyle. Nutraceutical substances have multifaceted therapeutic advantages, and they have been reported to have disease-prevention and health-promoting properties. Several clinically used nutraceuticals have been shown to target the pathogenesis of diabetes mellitus, obesity, and metabolic syndrome and their complications and modulate various clinical outcomes favorably. This review aims to highlight and comment on some of the most prominent natural components used as antidiabetics and in managing obesity.

Docosapentaenoic acid-rich oil lowers plasma glucose and lipids in a mouse model of diabetes and mild obesity

Many studies have investigated the beneficial effects of n-3 polyunsaturated fatty acids, such as their potential for lowering lipid levels and reducing diabetes risk. However, few studies have specifically examined docosapentaenoic acid (DPA), an n-3 polyunsaturated fatty acid with limited availability in its pure form. We hypothesized that DPA would have lipid-lowering effects and improve insulin resistance in KK/Ta mice. To test our hypothesis, 7-week-old KK/Ta mice were fed a high-fat diet for 12 weeks to induce obesity before being divided into 3 groups and fed an experimental diet for 10 weeks. The experimental diets were: LSO, using lard and safflower oil as fat sources; SO, in which lard in the LSO diet was replaced with safflower oil; and DPA, in which lard in the LSO diet was replaced with DPA oil. After 10 weeks, plasma triglyceride and total cholesterol concentrations were significantly decreased in the DPA group, but not in the SO group. Sterol regulatory element-binding protein-1 and stearoyl-CoA desaturase-1 gene expressions involved in fatty acid synthesis in the liver were significantly lower in the DPA group compared with the LSO group. Plasma glucose concentrations were significantly decreased in both the SO group and the DPA group compared with the LSO group, whereas plasma insulin concentrations were significantly decreased in the DPA group alone. These results indicate that DPA has plasma lipid-lowering and hypoglycemic effects, possibly from suppression of fatty acid synthesis in the liver.

Adipose tissue macrophages as potential targets for obesity and metabolic diseases

Macrophage infiltration into adipose tissue is a key pathological factor inducing adipose tissue dysfunction and contributing to obesity-induced inflammation and metabolic disorders. In this review, we aim to present the most recent research on macrophage heterogeneity in adipose tissue, with a focus on the molecular targets applied to macrophages as potential therapeutics for metabolic diseases. We begin by discussing the recruitment of macrophages and their roles in adipose tissue. While resident adipose tissue macrophages display an anti-inflammatory phenotype and promote the development of metabolically favorable beige adipose tissue, an increase in pro-inflammatory macrophages in adipose tissue has negative effects on adipose tissue function, including inhibition of adipogenesis, promotion of inflammation, insulin resistance, and fibrosis. Then, we presented the identities of the newly discovered adipose tissue macrophage subtypes (e.g. metabolically activated macrophages, CD9+ macrophages, lipid-associated macrophages, DARC+ macrophages, and MFehi macrophages), the majority of which are located in crown-like structures within adipose tissue during obesity. Finally, we discussed macrophage-targeting strategies to ameliorate obesity-related inflammation and metabolic abnormalities, with a focus on transcriptional factors such as PPARγ, KLF4, NFATc3, and HoxA5, which promote macrophage anti-inflammatory M2 polarization, as well as TLR4/NF-κB-mediated inflammatory pathways that activate pro-inflammatory M1 macrophages. In addition, a number of intracellular metabolic pathways closely associated with glucose metabolism, oxidative stress, nutrient sensing, and circadian clock regulation were examined. Understanding the complexities of macrophage plasticity and functionality may open up new avenues for the development of macrophage-based treatments for obesity and other metabolic diseases.

Adipose tissue metabolic changes in chronic kidney disease

Adipose tissue is a complex organ whose functions go beyond being an energy reservoir to sustain proper body energy homeostasis. Functioning as an endocrine organ, the adipose tissue has an active role in the body's metabolic balance regulation through several secreted factors generally termed as adipokines. Thus, adipose tissue dysregulation in chronic kidney disease (CKD) can have a deep impact in the pathophysiology of diseases associated with metabolic dysregulation including metabolic syndrome, insulin resistance (IR), atherosclerosis, and even cachexia. CKD is a progressive disorder linked to increased morbidity and mortality. Despite being characterized by renal function loss, CKD is accompanied by metabolic disturbances such as dyslipidemia, protein energy wasting, chronic low-grade inflammation, IR, and lipid redistribution. Thus far, the mechanisms by which these changes occur and the role of adipose tissue in CKD development and progression are unclear. Further understanding of how these factors develop could have implications for the management of CKD by helping identify pharmacological targets to improve CKD outcomes.

Obesity in HIV infection: host-pathogen interaction

OBJECTIVE

Both obesity and HIV infection are characterized by a state of chronic inflammation associated with increased morbidity and mortality. This review aims to assess the available literature on immune dysregulation in obesity and people with HIV infection (PWH).

DESIGN

A systematic review of peer-reviewed literature.

METHODS

We conducted a systematic literature search of PubMed, Embase, Scopus, and international conference abstracts for articles on the epidemiology of obesity in the general population and in PWH and the pathogenesis of obesity with a focus on inflammation and immune activation.

RESULTS

Of the 631 articles selected after title review, 490 met the inclusion criteria and 90 were included in the final selection. The selected studies highlight the increasing prevalence of obesity in PWH and a substantial role for antiretroviral treatment (ART) in its development. Pathogenesis of obesity and its associated inflammation derives from disturbances in adipose tissue (AT) immune function, focused on T-cell and macrophage function, with a switch to pro-inflammatory immune phenotype and resulting increases in pro-inflammatory chemokines, which contribute to the development of metabolic syndrome. Although dysregulation of these pathways is seen in both obesity and HIV, there remains a lack of human studies on AT inflammation in HIV.

CONCLUSION

Obesity is an emerging comorbidity in PWH, with a substantial overlap in immune dysregulation patterns seen in both conditions. How this immune dysfunction impacts on development of metabolic complications for both obesity and HIV infection, and whether targeting of AT-derived inflammation will improve outcomes in PWH requires further study.

Effects of obesity on neuroinflammatory and neurochemical parameters in an animal model of reserpine-induced Parkinson's disease

Obesity is associated with low-grade chronic inflammation and oxidative stress, affecting the brain's reward system by decreasing dopaminergic neurotransmission. It is known that dopaminergic neurotransmission is also reduced in Parkinson's disease (PD), and high adiposity is considered a risk factor for the development of several neurodegenerative diseases, including PD. This study aimed to assess the effects of obesity on neuroinflammatory and neurochemical parameters in an animal model of reserpine-induced PD. The obese group showed increased inflammation and oxidative damage as well as inhibition of mitochondrial respiratory chain complexes I and II and DNA damage in the evaluated structures. The PD group did not show inflammation or mitochondrial dysfunction but exhibited oxidative damage in the hippocampus. The combination group (obesity + PD) showed reduced inflammation and oxidative stress and increased activity of complexes I and II of the mitochondrial respiratory chain in most of the analyzed structures. On the other hand, obesity + PD caused oxidative damage to proteins in the liver, prefrontal cortex, striatum, and cerebral cortex and oxidative stress in the hypothalamus, resulting in reduced catalase activity. Furthermore, the combination group showed DNA damage in blood, liver, and cerebral cortex. In conclusion, it was observed that the association of obesity and PD did not increase inflammation, oxidative stress, or mitochondrial dysfunction in most of the evaluated structures but increased oxidative damage and induced mechanisms that led to DNA damage in peripheral tissues and brain structures.

Pyroptosis: A possible link between obesity-related inflammation and inflammatory diseases

The main manifestation of obesity is persistent low-level inflammation and insulin resistance, which is an important factor inducing or promoting other obesity-related diseases. As a proinflammatory programmed cell death, pyroptosis plays an important role, especially in the activation and regulation of the NLRP3 inflammasome pathway. Pyroptosis is associated with the pathogenesis of many chronic inflammatory diseases and is characterized by the formation of micropores in the plasma membrane and the release of a large number of proinflammatory cytokines. This article mainly introduces the main pathways and key molecules of pyroptosis and focuses on the phenomenon of pyroptosis in obesity. It is suggested that the regulation of pyroptosis-related targets may become a new potential therapy for the prevention and treatment of systemic inflammatory response caused by obesity, and we summarize the potential molecular substances that may be beneficial to obesity-related inflammatory diseases through target pyroptosis.

Fetuin-A secretion from β-cells leads to accumulation of macrophages in islets, aggravates inflammation and impairs insulin secretion

Elevated fetuin-A levels, chemokines and islet-resident macrophages are crucial factors associated with obesity-mediated type 2 diabetes (T2D). Here, the aim of the study was to investigate the effect of MIN6 (a mouse insulinoma cell line)-derived fetuin-A (also known as AHSG) in macrophage polarization and decipher the effect of M1 type pro-inflammatory macrophages in commanding over insulin secretion. MIN6 and islet-derived fetuin-A induced expression of the M1 type macrophage markers Emr1 (also known as Adgre1), Cd68 and CD11c (Itgax) (∼1.8 fold) along with increased cytokine secretion. Interestingly, suppression of fetuin-A in MIN6 successfully reduced M1 markers by ∼1.5 fold. MIN6-derived fetuin-A also induced chemotaxis of macrophages in a Boyden chamber chemotaxis assay. Furthermore, high-fat feeding in mice showed elevated cytokine and fetuin-A content in serum and islets, and also migration and polarization of macrophages to the islets, while β-cells failed to meet the increased insulin demand. Moreover, in MIN6 culture, M1 macrophages sharply decreased insulin secretion by ∼2.8 fold. Altogether our results support an association of fetuin-A with islet inflammation and β-cell dysfunction, owing to its role as a key chemoattractant and macrophage polarizing factor.

Improvement Effect of Sweet Basil (Ocimum basilicum L.) Powder Intake on Obese Mice Fed a High-fat and High-sucrose Diet

This study aimed to determine if there are anti-inflammatory and anti-obesity effects of sweet basil, an herb, in mice. Sweet basil was administered as a powder to male C57BL/6JJcl mice, which were divided into three groups: the (control [C], high-fat and high-sucrose diet [H], and high-fat and high-sucrose diet plus sweet basil powder [HB]) groups. The mice were fed for 12 weeks and the dry sweet basil powder comprised 1% per kg of the diet. From experiment third week, the average body weight was significantly higher in the H group than in the C group. The average body weight was significantly lower in the HB group than in the H group, but food intake did not significantly differ between the H and HB groups. Liver weight was drastically lower in the HB group than in the H group. Perirenal fat weight and epididymal fat weight were not significantly different between the H and HB groups. Therefore, we assumed that body-weight reduction caused by sweet basil powder intake depended on inhibition of liver enlargement. We then examined lipid metabolism-related gene expression in the mice livers. Expression of the sterol response element binding protein 1-c gene tended to be lower in the HB group than in the H group (p=0.056). We speculated that sweet basil inhibited liver enlargement by suppressing fatty acid synthesis. Moreover, expression of the monocyte chemoattractant protein-1 gene in epididymal fat was significantly lower in the HB group than in the H group. Sweet basil powder appears to have a potent anti-inflammatory effect in the adipose tissue of mice fed a high-fat and high-sucrose diet.

Effect of δ-Tocopherol on Mice Adipose Tissues and Mice Adipocytes Induced Inflammation

The study aim was to evaluate the potential anti-inflammatory effects of vitamin E analogs, especially α-tocopherol and δ-tocopherol. We used male C57BL/6JJcl mice, which were divided into four groups: the control (C), high-fat and high-sucrose diet (H), high-fat and high-sucrose diet+α-tocopherol (Ha) and high-fat and high-sucrose diet+δ-tocopherol (Hd) groups. The mice were fed for 16 weeks. To the high-fat and high-sucrose diet, 800 mg/kg of α-tocopherol or δ-tocopherol was added more. The final body weight was significantly higher in the H group than in the C group. On the other hand, the final body weight was drastically lower in the Ha group and Hd group than in the H group. However, the energy intake was not significantly different among all groups. Therefore, we assumed that α-tocopherol and δ-tocopherol have potential anti-obesity effect. Besides, inflammatory cytokine gene expression was significantly higher in the epididymal fat of the H group than in the C group. These results showed that inflammation was induced by epididymal fat of mice fed a high-fat and high-sucrose diet for 16 weeks. Unfortunately, addition of α-tocopherol or δ-tocopherol to the diet did not restrain inflammation of epididymal fat. Investigation of the anti-inflammatory effects of α-tocopherol or δ-tocopherol in co-cultured 3T3-L1 cells and RAW264.7 cells showed that δ-tocopherol inhibited increased gene expression of the inflammatory cytokines, IL-1β, IL-6, and iNOS. These results suggest that an anti-inflammatory effect in the δ-tocopherol is stronger than that in the α-tocopherol in vitro. We intend to perform an experiment by in vivo sequentially in the future.

Role of the Endocannabinoid System in the Adipose Tissue with Focus on Energy Metabolism

The endocannabinoid system is involved in a wide range of processes including the control of energy acquisition and expenditure. Endocannabinoids and their receptors are present in the central nervous system but also in peripheral tissues, notably the adipose tissues. The endocannabinoid system interacts with two main hormones regulating appetite, namely leptin and ghrelin. The inhibitory effect of the cannabinoid receptor 1 (CB₁) antagonist rimonabant on fat mass suggested that the endocannabinoid system can also have a peripheral action in addition to its effect on appetite reduction. Thus, several investigations have focused on the peripheral role of the endocannabinoid system in the regulation of metabolism. The white adipose tissue stores energy as triglycerides while the brown adipose tissue helps to dissipate energy as heat. The endocannabinoid system regulates several functions of the adipose tissues to favor energy accumulation. In this review we will describe the presence of the endocannabinoid system in the adipose tissue. We will survey the role of the endocannabinoid system in the regulation of white and brown adipose tissue metabolism and how the eCB system participates in obesity and metabolic diseases.

Advanced-glycation end-products axis: A contributor to the risk of severe illness from COVID-19 in diabetes patients

Compelling pieces of evidence derived from both clinical and experimental research has demonstrated the crucial role of the receptor for advanced-glycation end-products (RAGE) in orchestrating a plethora of proinflammatory cellular responses leading to many of the complications and end-organ damages reported in patients with diabetes mellitus (DM). During the coronavirus disease 2019 (COVID-19) pandemic, many clinical reports have pointed out that DM increases the risk of COVID-19 complications, hospitalization requirements, as well as the overall severe acute respiratory syndrome coronavirus 2 case-fatality rate. In the present review, we intend to focus on how the basal activation state of the RAGE axis in common preexisting conditions in DM patients such as endothelial dysfunction and hyperglycemia-related prothrombotic phenotype, as well as the contribution of RAGE signaling in lung inflammation, may then lead to the increased mortality risk of COVID-19 in these patients. Additionally, the cross-talk between the RAGE axis with either another severe acute respiratory syndrome coronavirus 2 receptor molecule different of angiotensin-converting enzyme 2 or the renin-angiotensin system imbalance produced by viral infection, as well as the role of this multi-ligand receptor on the obesity-associated low-grade inflammation in the higher risk for severe illness reported in diabetes patients with COVID-19, are also discussed.

Contribution of RAGE axis activation to the association between metabolic syndrome and cancer

Far beyond the compelling proofs supporting that the metabolic syndrome represents a risk factor for diabetes and cardiovascular diseases, a growing body of evidence suggests that it is also a risk factor for different types of cancer. However, the involved molecular mechanisms underlying this association are not fully understood, and they have been mainly focused on the individual contributions of each component of the metabolic syndrome such as obesity, hyperglycemia, and high blood pressure to the development of cancer. The Receptor for Advanced Glycation End-products (RAGE) axis activation has emerged as an important contributor to the pathophysiology of many clinical entities, by fueling a chronic inflammatory milieu, and thus supporting an optimal microenvironment to promote tumor growth and progression. In the present review, we intend to highlight that RAGE axis activation is a crosswise element on the potential mechanistic contributions of some relevant components of metabolic syndrome into the association with cancer.

Fucoxanthin inhibits lipopolysaccharide-induced inflammation and oxidative stress by activating nuclear factor E2-related factor 2 via the phosphatidylinositol 3-kinase/AKT pathway in macrophages

PURPOSE

Anti-inflammatory and antioxidant effects of fucoxanthin (FCX), a xanthophyll carotenoid, have been suggested. However, underlying mechanisms are elusive. The objective of this study was to elucidate the mechanisms by which FCX and its metabolites inhibit lipopolysaccharide (LPS)-induced inflammation and oxidative stress in macrophages.

METHODS

The effects of the FCX on mRNA and protein expression of pro-inflammatory cytokines and antioxidant genes, and reactive oxygen species (ROS) accumulation were determined in RAW 264.7 macrophages. A potential role of FCX in the modulation of phosphatidylinositol 3-kinase (PI3K)/AKT/nuclear E2-related factor 2 (NRF2) axis was evaluated.

RESULTS

FCX significantly decreased LPS-induced interleukin (Il)6, Il1b, and tumor necrosis factor α (Tnf) mRNA abundance and TNFα secretion. FCX attenuated LPS or tert-butyl-hydroperoxide-induced ROS accumulation with concomitant increases in the expression of antioxidant enzymes. Also, trolox equivalent antioxidant capacity assay demonstrated that FCX had a potent free radical scavenging property. FCX markedly increased nuclear translocation of NRF2 in LPS-treated macrophages, consequently inducing its target gene expression. Interestingly, the effect of FCX on NRF2 nuclear translocation was noticeably diminished by LY294002, an inhibitor of PI3K, but not by inhibitors of mitogen-activated protein kinases. Phosphorylation of AKT, a downstream element of PI3K, was also markedly increased by FCX. FCX metabolites, such as fucoxanthinol and amarouciaxanthin A, significantly attenuated LPS-induced ROS accumulation and pro-inflammatory cytokine expression.

CONCLUSION

FCX exerts anti-inflammatory and antioxidant effects by the activation of NRF2 in the macrophages activated by LPS, which is mediated, at least in part, through the PI3K/AKT pathway.

Macrophage and adipocyte interaction as a source of inflammation in kidney disease

In obesity, adipose tissue derived inflammation is associated with unfavorable metabolic consequences. Uremic inflammation is prevalent and contributes to detrimental outcomes. However, the contribution of adipose tissue inflammation in uremia has not been characterized. We studied the contribution of adipose tissue to uremic inflammation in-vitro, in-vivo and in human samples. Exposure to uremic serum resulted in activation of inflammatory pathways including NFκB and HIF1, upregulation of inflammatory cytokines/chemokines and catabolism with lipolysis, and lactate production. Also, co-culture of adipocytes with macrophages primed by uremic serum resulted in higher inflammatory cytokine expression than adipocytes exposed only to uremic serum. Adipose tissue of end stage renal disease subjects revealed increased macrophage infiltration compared to controls after BMI stratification. Similarly, mice with kidney disease recapitulated the inflammatory state observed in uremic patients and additionally demonstrated increased peripheral monocytes and inflammatory polarization of adipose tissue macrophages (ATMS). In contrast, adipose tissue in uremic IL-6 knock out mice showed reduced ATMS density compared to uremic wild-type controls. Differences in ATMS density highlight the necessary role of IL-6 in macrophage infiltration in uremia. Uremia promotes changes in adipocytes and macrophages enhancing production of inflammatory cytokines. We demonstrate an interaction between uremic activated macrophages and adipose tissue that augments inflammation in uremia.

Erucic Acid-Rich Yellow Mustard Oil Improves Insulin Resistance in KK-Ay Mice

Obesity is a major risk factor for some metabolic disorders including type 2 diabetes. Enhancement of peroxisome proliferator-activated receptor (PPAR) γ, a master regulator of adipocyte differentiation, is known to increase insulin-sensitive small adipocytes. In contrast, decreased PPARγ activity is also reported to improve insulin resistance. We have previously identified erucic acid as a novel natural component suppressing PPARγ transcriptional activity. In this study, we investigated the effect of erucic acid-rich yellow mustard oil (YMO) on obese/diabetic KK-A^y mice. An in vitro luciferase reporter assay and mesenchymal stem cell (MSC) differentiation assay revealed that 25 µg/mL YMO significantly inhibited PPARγ transcriptional activity and differentiation of MSCs into adipocytes but promoted their differentiation into osteoblasts. In KK-A^y mice, dietary intake of 7.0% (w/w) YMO significantly decreased the surrogate indexes for insulin resistance and the infiltration of macrophages into adipose tissue. Furthermore, 7.0% YMO increased bone mineral density. These results suggest that YMO can ameliorate obesity-induced metabolic disorders.

Adipose Tissue Immunomodulation: A Novel Therapeutic Approach in Cardiovascular and Metabolic Diseases

Adipose tissue is a critical regulator of systemic metabolism and bodily homeostasis as it secretes a myriad of adipokines, including inflammatory and anti-inflammatory cytokines. As the main storage pool of lipids, subcutaneous and visceral adipose tissues undergo marked hypertrophy and hyperplasia in response to nutritional excess leading to hypoxia, adipokine dysregulation, and subsequent low-grade inflammation that is characterized by increased infiltration and activation of innate and adaptive immune cells. The specific localization, physiology, susceptibility to inflammation and the heterogeneity of the inflammatory cell population of each adipose depot are unique and thus dictate the possible complications of adipose tissue chronic inflammation. Several lines of evidence link visceral and particularly perivascular, pericardial, and perirenal adipose tissue inflammation to the development of metabolic syndrome, insulin resistance, type 2 diabetes and cardiovascular diseases. In addition to the implication of the immune system in the regulation of adipose tissue function, adipose tissue immune components are pivotal in detrimental or otherwise favorable adipose tissue remodeling and thermogenesis. Adipose tissue resident and infiltrating immune cells undergo metabolic and morphological adaptation based on the systemic energy status and thus a better comprehension of the metabolic regulation of immune cells in adipose tissues is pivotal to address complications of chronic adipose tissue inflammation. In this review, we discuss the role of adipose innate and adaptive immune cells across various physiological and pathophysiological states that pertain to the development or progression of cardiovascular diseases associated with metabolic disorders. Understanding such mechanisms allows for the exploitation of the adipose tissue-immune system crosstalk, exploring how the adipose immune system might be targeted as a strategy to treat cardiovascular derangements associated with metabolic dysfunctions.

Role of Flavonoids in The Interactions among Obesity, Inflammation, and Autophagy

Nowadays, obesity is considered as one of the main concerns for public health worldwide, since it encompasses up to 39% of overweight and 13% obese (WHO) adults. It develops because of the imbalance in the energy intake/expenditure ratio, which leads to excess nutrients and results in dysfunction of adipose tissue. The hypertrophy of adipocytes and the nutrients excess trigger the induction of inflammatory signaling through various pathways, among others, an increase in the expression of pro-inflammatory adipocytokines, and stress of the endoplasmic reticulum (ER). A better understanding of obesity and preventing its complications are beneficial for obese patients on two facets: treating obesity, and treating and preventing the pathologies associated with it. Hitherto, therapeutic itineraries in most cases are based on lifestyle modifications, bariatric surgery, and pharmacotherapy despite none of them have achieved optimal results. Therefore, diet can play an important role in the prevention of adiposity, as well as the associated disorders. Recent results have shown that flavonoids intake have an essential role in protecting against oxidative damage phenomena, and presents biochemical and pharmacological functions beneficial to human health. This review summarizes the current knowledge of the anti-inflammatory actions and autophagic flux of natural flavonoids, and their molecular mechanisms for preventing and/or treating obesity.

The Absence of Adiponectin Alters Niacin's Effects on Adipose Tissue Inflammation in Mice

Obesity is an immunometabolic disease associated with chronic inflammation and the dysregulation of pro- and anti-inflammatory cytokines. One hallmark of obesity is reduced concentrations of the anti-inflammatory adipokine, adiponectin. Pharmacologic doses of niacin produce multiple metabolic benefits, including attenuating high-fat diet (HFD)-induced adipose tissue inflammation and increasing adiponectin concentrations. To determine if adiponectin mediates the anti-inflammatory effects of niacin, male C57BL/6J (WT) and adiponectin null (Adipoq^-/-) mice were maintained on a low-fat diet (LFD) or HFD for 6 weeks, before being administered either vehicle or niacin (360 mg/kg/day) for 5 weeks. HFD-fed mice had increased expression of genes associated with macrophage recruitment (Ccl2) and number (Cd68), and increased crown-like structure (CLS) number in adipose tissue. While niacin attenuated Ccl2 expression, there were no effects on Cd68 or CLS number. The absence of adiponectin did not hinder the ability of niacin to reduce Ccl2 expression. HFD feeding increased gene expression of inflammatory markers in the adipose tissue of WT and Adipoq^-/- mice. While niacin tended to decrease the expression of inflammatory markers in WT mice, niacin increased their expression in HFD-fed Adipoq^-/- mice. Therefore, our results indicate that the absence of adiponectin alters the effects of niacin on markers of adipose tissue inflammation in HFD-fed mice, suggesting that the effects of niacin on tissue cytokines may involve adiponectin.

High-Fat Diet Alters Immunogenic Properties of Circulating and Adipose Tissue-Associated Myeloid-Derived CD45+DDR2+ Cells

Chronic inflammation is evident in the adipose tissue and periphery of patients with obesity, as well as mouse models of obesity. T cell subsets in obese adipose tissue are skewed towards Th1- and Th17-associated phenotypes and their secreted cytokines contribute to obesity-associated inflammation. Our lab recently identified a novel, myeloid-derived CD45⁺DDR2⁺ cell subset that modulates T cell activity. The current study sought to determine how these myeloid-derived CD45⁺DDR2⁺ cells are altered in the adipose tissue and peripheral blood of preobese mice and how this population modulates T cell activity. C57BL/6 mice were fed with a diet high in milkfat (60%·kcal, HFD) ad libitum until a 20% increase in total body weight was reached, and myeloid-derived CD45⁺DDR2⁺ cells and CD4⁺ T cells in visceral adipose tissue (VAT), mammary gland-associated adipose tissue (MGAT), and peripheral blood (PB) were phenotypically analyzed. Also analyzed was whether mediators from MGAT-primed myeloid-derived CD45⁺DDR2⁺ cells stimulate normal CD4⁺ T cell cytokine production. A higher percentage of myeloid-derived CD45⁺DDR2⁺ cells expressed the activation markers MHC II and CD80 in both VAT and MGAT of preobese mice. CD4⁺ T cells were preferentially skewed towards Th1- and Th17-associated phenotypes in the adipose tissue and periphery of preobese mice. In vitro, MGAT from HFD-fed mice triggered myeloid-derived CD45⁺DDR2⁺ cells to induce CD4⁺ T cell IFN-γ and TNF-α production. Taken together, this study shows that myeloid-derived CD45⁺DDR2⁺ cells express markers of immune activation and suggests that they play an immune modulatory role in the adipose tissue of preobese mice.

Beneficial effects of thyroid hormone on adipose inflammation and insulin sensitivity of obese Wistar rats

Thyroid hormones play an important role in glucose metabolism and there is evidence of increased prevalence of thyroid dysfunction in obese and diabetic patients. This study aimed at evaluating the thyroid function and the effects of the triiodothyronine (T3) treatment on glycemia control, insulin sensitivity and subclinical inflammation in cafeteria‐diet‐induced obesity in rats. Obesity was induced in male Wistar rats by offering a cafeteria diet and a subset of the obese rats was treated with T3 (1.5 μg per 100 g of body weight) for a 28‐day period. The pituitary‐thyroid axis was evaluated by molecular and biochemical parameters. Cytokine content was measured in the serum as well as in the mesenteric and epididymal white adipose tissue. Obese rats exhibited impairment of glycemia control, increased content of inflammatory cytokines in mesenteric white adipose tissue, decreased serum thyrotropin (TSH) concentration and increased sodium/iodide symporter (NIS) and TSH receptor (TSHR) protein content in thyroid gland. T3 treatment improved insulin sensitivity, glucose tolerance, and reduced inflammatory cytokine content in mesenteric white adipose tissue. In the thyroid gland NIS, TSHR, and thyroperoxidase (TPO) content were reduced while thyroglobulin (TG) content was increased by T3. The thyrotrophic response to negative feedback exerted by T3 was preserved in obese rats. The present data reinforce the beneficial effects of T3 treatment of obese rats on the improvement of insulin sensitivity and on the negative modulation of inflammatory cytokine expression in adipose tissue. Moreover, we have evidenced that the pituitary‐thyroid axis is affected in obese rats, as illustrated by the impaired TSH secretion.

The effect of mesenchymal stem cells on chemotaxis of osteoclast precursor cells

Regeneration of tissue, including bone, using mesenchymal stem cells (MSCs) has been progressing rapidly. Regeneration of bone requires the presence of an appropriate environment and efficient chemotaxis of cells to the target site. Differentiation of MSCs into mesenchymal cells has received considerable attention, but the effect of MSCs on chemotaxis is not well understood. In this study, we investigated the effect of MSCs on chemotaxis of RAW264 cells via C-C motif chemokine ligand 2 (CCL2). Balb/c mouse bone marrow-derived MSCs and RAW264 cells, which are osteoclast precursor cells, were co-cultured without cell contact. The gene expression of CCL2 in MSCs and CC-chemokine receptor 2 (CCR2) in RAW264 cells was determined using quantitative real-time PCR. Analysis of RAW264 cell chemotaxis was performed using the Boyden chamber assay. mRNAs for CCL2 and CCR2 were significantly upregulated upon co-culture in comparison to culture of either cell type alone, and the number of chemotactic RAW264 cells was significantly increased by co-culture. MSCs enhanced the chemotaxis of RAW264 cells, possibly via CCL2-CCR2 interaction, suggesting the potential utility of MSCs for tissue regeneration.

The Role of Leukocytes in Diabetic Cardiomyopathy

Diabetes is predominant risk factor for cardiovascular diseases such as myocardial infarction and heart failure. Recently, leukocytes, particularly neutrophils, macrophages, and lymphocytes, have become targets of investigation for their potential role in a number of chronic inflammatory diseases such as diabetes and heart failure. While leukocytes contribute significantly to the progression of diabetes and heart failure individually, understanding their participation in the pathogenesis of diabetic heart failure is much less understood. The present review summarizes the role of leukocytes in the complex interplay between diabetes and heart failure, which is critical to the discovery of new targeted therapies for diabetic cardiomyopathy.

Altered expression of inflammation-associated genes in the hypothalamus of obesity mouse models

Metabolic inflammation is a distinct feature of obesity. Increased inflammation in the adipose tissue and the liver has been so far implicated to affect metabolic homeostasis, mainly insulin resistance. In addition to the peripherals, the inflammation in the hypothalamus which governs systemic metabolism by linking neuronal and endocrine signals has been suggested to be linked to the metabolic disease. However, the underlying molecular mechanisms are poorly understood. We hypothesized that a high-fat diet (HFD) led to central metabolic inflammation via transcriptional changes in the hypothalamus. To address the hypothesis, we characterized obesity-related hypothalamic, transcriptional alterations, and their effects on functional networks. Male C57BL/6J mice were fed with either a control diet (CD) or an HFD for 20 weeks. Microarray and gene ontology analyses of the hypothalamus demonstrated that immune-related pathways, including inflammatory and cytokine signaling, were overrepresented in the hypothalamus of HFD-fed mice compared to that of CD mice. In addition, through secondary analysis of leptin-deficient obese (ob/ob) mouse hypothalamus, we found that enriched gene sets for tumor necrosis factor-α signaling pathways and cancer pathways were common in both the obese mouse models. The results suggest that inflammatory pathway is transcriptionally enriched in the hypothalamus in obesity models and is related with hyperadiposity rather than the primary causes of obesity including the dietary fat and the genetic mutation.

Food-derived regulatory factors against obesity and metabolic syndrome

Obesity is a key factor in metabolic syndrome. The study of metabolic syndrome focuses on the anti-weight gain properties of physiological mechanisms and food components. Abnormal energy metabolism is a major risk factor of metabolic syndrome. Chronic inflammation is a feature of obesity; cytokines from hypertrophied adipocytes cause inflammation in both adipose tissue and blood vessels, resulting in symptoms of metabolic syndrome. Tumor necrosis factor-α causes insulin resistance in adipocytes and regression of brown adipocytes, resulting in abnormal energy metabolism. Functional foods can serve as a strategy for prevention and treatment of obesity linked with metabolic processes in white and brown adipose tissues. Diet-induced thermogenesis caused by certain food components stimulates burning of stored fat within adipose tissues. A mechanistic understanding of dietary thermogenesis via the sympathetic nerve system will prove valuable for the development of precise strategies for the practical prevention of metabolic syndrome.

Diet-induced obesity causes visceral, but not subcutaneous, lymph node hyperplasia via increases in specific immune cell populations

OBJECTIVES

The spatial proximity of adipose depots to secondary lymph nodes allows a unique relation between the two systems. Obesity, predominately visceral adiposity, links to numerous diseases; hence, we postulate that secondary lymphatics within this region contributes to disease risk.

MATERIAL AND METHODS

Male C57BL/6 mice were fed standard CHOW (18% kcal fat) or Western diet (45% kcal fat) for 7 weeks. Visceral and subcutaneous lymph nodes and associated adipose depots they occupy were excised. Lymph node morphology and resident immune cell populations were characterized via histopathology, immunofluorescence and flow cytometry. Adipose tissue immune cell populations were also characterized.

RESULTS

Obesity caused lymph node expansion, increased viable cell number and deviations in immune cell populations. These alterations were exclusive to visceral lymph nodes. Notably, pro-inflammatory antigen presenting cells and regulatory T cells increased in number in the visceral lymph node. Obesity, however, reduced T regulatory cells in visceral lymph nodes. The visceral adipose depot also had greater reactivity towards HFD than subcutaneous, with a greater percent of macrophages, dendritic and CD8⁺ T cells. Immune cell number, in both the visceral and subcutaneous, however decreased as adipose depots enlarged.

CONCLUSION

Overall, HFD has a greater influence on visceral cavity than the subcutaneous. In the visceral lymph node, but not subcutaneous, HFD-induced obesity decreased cell populations that suppressed immune function while increasing those that regulate/activate immune response.

Quercetin Protects Obesity-Induced Hypothalamic Inflammation by Reducing Microglia-Mediated Inflammatory Responses via HO-1 Induction

Obesity-induced hypothalamic inflammation is characterized by activation of microglia, which are resident macrophages of the central nervous system, and is implicated in the derangement of energy homeostasis, metabolic complications, and neurodegenerative diseases. Quercetin, a naturally occurring flavonoid, is known to protect against oxidative stress and inflammation-related metabolic complications. Here, we demonstrate that quercetin reduces obesity-induced hypothalamic inflammation by inhibiting microglia-mediated inflammatory responses, and the beneficial action of quercetin is associated with heme oxygenase (HO-1) induction. Quercetin markedly reduced the production of inflammatory mediators (monocyte chemoattractant protein (MCP)-1, interleukin (IL-6), IL-1β, nitric oxide) by microglia stimulated with saturated fatty acid palmitate and/or lipid-laden microglia-conditioned medium. Quercetin also upregulated the expression of HO-1 in palmitate-treated lipid-laden microglia, and the actions of quercetin against microglia activation accompanied by IκBα degradation were abolished by a HO-1 inhibitor. Moreover, quercetin supplementation reduced the levels of inflammatory cytokines and microglia activation markers in the hypothalamus of high fat diet (HFD)-fed obese mice, which was accompanied by upregulation of HO-1. These findings indicate that quercetin suppresses microglia-mediated inflammatory responses via the induction of HO-1, and hence protects against obesity-induced hypothalamic inflammation.

Impact of the cardiovascular system-associated adipose tissue on atherosclerotic pathology

Cardiac obesity makes an important contribution to the pathogenesis of cardiovascular disease. One of the important pathways of this contribution is the inflammatory process that takes place in the adipose tissue. In this review, we consider the role of the cardiovascular system-associated fat in atherosclerotic cardiovascular pathology and a non-atherosclerotic cause of coronary artery disease, such as atrial fibrillation. Cardiovascular system-associated fat not only serves as the energy store, but also releases adipokines that control local and systemic metabolism, heart/vascular function and vessel tone, and a number of vasodilating and anti-inflammatory substances. Adipokine appears to play an important protective role in cardiovascular system. Under chronic inflammation conditions, the repertoire of signaling molecules secreted by cardiac fat can be altered, leading to a higher amount of pro-inflammatory messengers, vasoconstrictors, profibrotic modulators. This further aggravates cardiovascular inflammation and leads to hypertension, induction of the pathological tissue remodeling and cardiac fibrosis. Contemporary imaging techniques showed that epicardial fat thickness correlates with the visceral fat mass, which is an established risk factor and predictor of cardiovascular disease in obese subjects. However, this correlation is no longer present after adjustment for other covariates. Nevertheless, recent studies showed that pericardial fat volume and epicardial fat thickness can probably serve as a better indicator for atrial fibrillation.

Hypothalamic lipid-laden astrocytes induce microglia migration and activation

Obesity-induced hypothalamic inflammation is closely associated with various metabolic complications and neurodegenerative disorders. Astrocytes, the most abundant glial cells in the central nervous system, play a crucial role in pathological hypothalamic inflammatory processes. Here, we demonstrate that hypothalamic astrocytes accumulate lipid droplets under saturated fatty acid-rich conditions, such as obese environment, and that the lipid-laden astrocytes increase astrogliosis markers and inflammatory cytokines (TNFα, IL-1β, IL-6, MCP-1) at the transcript and/or protein level. Medium conditioned by the lipid-laden astrocytes stimulate microglial chemotactic activity and upregulate transcripts of the microglia activation marker Iba-1 and inflammatory cytokines. These findings indicate that the lipid-laden astrocytes formed in free fatty acid-rich obese condition may participate in obesity-induced hypothalamic inflammation through promoting microglia migration and activation.

The Potential Role of Aerobic Exercise-Induced Pentraxin 3 on Obesity-Related Inflammation and Metabolic Dysregulation

Obesity is defined as the excess accumulation of intra-abdominal body fat, resulting in a state of chronic, low-grade proinflammation that can directly contribute to the development of insulin resistance. Pentraxin 3 (PTX3) is an acute-phase protein that is expressed by a variety of tissue and cell sources and provides an anti-inflammatory property to downregulate the production of proinflammatory cytokines, in particular interleukin-1 beta and tumor necrosis factor alpha. Although PTX3 may therapeutically aid in altering the proinflammatory milieu in obese individuals, and despite elevated expression of PTX3 mRNA observed in adipose tissue, the circulating level of PTX3 is reduced with obesity. Interestingly, aerobic activity has been demonstrated to elevate PTX3 levels. Therefore, the purpose of this review is to discuss the therapeutic potential of PTX3 to positively regulate obesity-related inflammation and discuss the proposition for utilizing aerobic exercise as a nonpharmacological anti-inflammatory treatment strategy to enhance circulating PTX3 concentrations in obese individuals.

L-4F Inhibits Oxidized Low-density Lipoprotein-induced Inflammatory Adipokine Secretion via Cyclic AMP/Protein Kinase A-CCAAT/Enhancer Binding Protein β Signaling Pathway in 3T3-L1 Adipocytes

Background:

Adipocytes behave like a rich source of pro-inflammatory cytokines including monocyte chemoattractant protein-1 (MCP-1). Oxidized low-density lipoprotein (oxLDL) participates in the local chronic inflammatory response, and high-density lipoprotein could counterbalance the proinflammatory function of oxLDL, but the underlying mechanism is not completely understood. This study aimed to evaluate the effect of apolipoprotein A-I mimetic peptide L-4F on the secretion and expression of MCP-1 in fully differentiated 3T3-L1 adipocytes induced by oxLDL and to elucidate the possible mechanisms.

Methods:

Fully differentiated 3T3-L1 adipocytes were incubated in the medium containing various concentration of L-4F (0–50 μg/ml) with oxLDL (50 μg/ml) stimulated, with/without protein kinase A (PKA) inhibitor H-89 (10 μmol/L) preincubated. The concentrations of MCP-1 in the supernatant, the mRNA expression of MCP-1, the levels of CCAAT/enhancer binding protein α (C/EBPα), and CCAAT/enhancer binding protein β (C/EBPβ) were evaluated. The monocyte chemotaxis assay was performed by micropore filter method using a modified Boyden chamber.

Results:

OxLDL stimulation induced a significant increase of MCP-1 expression and secretion in 3T3-L1 adipocytes, which were inhibited by L-4F preincubation in a dose-dependent manner. PKA inhibitor H-89 markedly reduced the oxLDL-induced MCP-1 expression, but no further decrease was observed when H-89 was used in combination with L-4F (50 μg/ml) (P > 0.05). OxLDL stimulation showed no significant effect on C/EBPα protein level but increased C/EBPβ protein level in a time-dependent manner. H-89 and L-4F both attenuated C/EBPβ protein level in oxLDL-induced 3T3-L1 adipocytes.

Conclusions:

OxLDL induces C/EBPβ protein synthesis in a time-dependent manner and enhances MCP-1 secretion and expression in 3T3-L1 adipocytes. L-4F dose-dependently counterbalances the pro-inflammatory effect of oxLDL, and cyclic AMP/PKA-C/EBPβ signaling pathway may participate in it.

Circulating cytokines as determinants of weight loss-induced improvements in insulin sensitivity

Dietary calorie restriction and exercise promote weight loss and may have additive effects for improving insulin sensitivity, independent of weight loss. It is not known if these effects are attributable to changes in circulating cytokines. We evaluated the hypothesis that modest, matched weight loss induced by calorie restriction and exercise have additive effects on circulating cytokines and these changes correlate with improvements in insulin sensitivity. Overweight and sedentary women and men (n = 52, 45-65 years) were randomized to undergo 7 % weight loss by using 3-6 months of calorie restriction, exercise, or a combination of both calorie restriction and exercise. Concentrations of cytokines and hormones were measured in fasting and oral glucose tolerance test blood samples. Insulin sensitivity was estimated based on oral glucose tolerance test for glucose and insulin. With all groups combined, fasting leptin (p < 0.0001) and high molecular weight adiponectin (p = 0.04) decreased and pentraxin-3 increased (p < 0.0001), in a manner that correlated with improvements in insulin sensitivity (all p ≤ 0.0002). These changes, combined with decreases in glucose-dependent insulinotropic polypeptide from the oral glucose tolerance test, explained 63 % of the variance (p < 0.0001) in insulin sensitivity improvements. Exercise and calorie restriction had additive effects on leptin, with a similar trend for high molecular weight adiponectin. Monocyte chemoattractant protein-1 and C-reactive protein concentrations did not change. Calorie restriction and exercise had opposite effects on soluble tumor necrosis factor receptor-1. Modest weight loss in overweight adults decreases serum leptin and high molecular weight adiponectin, and increases pentraxin-3 concentrations in a manner that correlates with increased insulin sensitivity. Exercise has additive effects to those induced by calorie restriction for reductions in leptin and possibly adiponectin. These changes may contribute to the additive effects of calorie restriction and exercise for improving insulin sensitivity.

Gender Differences in Adipocyte Metabolism and Liver Cancer Progression

Liver cancer is the third most common cancer type and the second leading cause of deaths in men. Large population studies have demonstrated remarkable gender disparities in the incidence and the cumulative risk of liver cancer. A number of emerging risk factors regarding metabolic alterations associated with obesity, diabetes and dyslipidemia have been ascribed to the progression of non-alcoholic fatty liver diseases (NAFLD) and ultimately liver cancer. The deregulation of fat metabolism derived from excessive insulin, glucose, and lipid promotes cancer-causing inflammatory signaling and oxidative stress, which eventually triggers the uncontrolled hepatocellular proliferation. This review presents the current standing on the gender differences in body fat compositions and their mechanistic linkage with the development of NAFLD-related liver cancer, with an emphasis on genetic, epigenetic and microRNA control. The potential roles of sex hormones in instructing adipocyte metabolic programs may help unravel the mechanisms underlying gender dimorphism in liver cancer and identify the metabolic targets for disease management.

The Soy Peptide Phe-Leu-Val Reduces TNFα-Induced Inflammatory Response and Insulin Resistance in Adipocytes

Obesity-induced adipose inflammation plays a crucial role in the development of obesity-induced metabolic disorders such as insulin resistance and type 2 diabetes. In the presence of obesity, hypertrophic adipocytes release inflammatory mediators, including tumor necrosis factor-alpha (TNFα) and monocyte chemoattractant protein-1 (MCP-1), which enhance the recruitment and activation of macrophages, and in turn augment adipose inflammation. We demonstrate that the soy peptide Phe-Leu-Val (FLV) reduces inflammatory responses and insulin resistance in mature adipocytes. Specifically, the soy peptide FLV inhibits the release of inflammatory cytokines (TNFα, MCP-1, and IL-6) from both TNFα-stimulated adipocytes and cocultured adipocytes/macrophages. This inhibition is mediated by the inactivation of the inflammatory signaling molecules c-Jun N-terminal kinase (JNK) and IκB kinase (IKK), and the downregulation of IκBα in the adipocytes. In addition, soy peptide FLV enhances insulin responsiveness and increases glucose uptake in adipocytes. More importantly, we, for the first time, found that adipocytes express peptide transporter 2 (PepT2) protein, and the beneficial action of the soy peptide FLV was disrupted by the peptide transporter inhibitor GlySar. These findings suggest that soy peptide FLV is transported into adipocytes by PepT2 and then downregulates TNFα-induced inflammatory signaling, thereby increasing insulin responsiveness in the cells. The soy peptide FLV, therefore, has the potential to prevent obesity-induced adipose inflammation and insulin resistance.

Exercise Prevents Diet-Induced Cellular Senescence in Adipose Tissue

Considerable evidence implicates cellular senescence in the biology of aging and chronic disease. Diet and exercise are determinants of healthy aging; however, the extent to which they affect the behavior and accretion of senescent cells within distinct tissues is not clear. Here we tested the hypothesis that exercise prevents premature senescent cell accumulation and systemic metabolic dysfunction induced by a fast-food diet (FFD). Using transgenic mice that express EGFP in response to activation of the senescence-associated p16(INK4a) promoter, we demonstrate that FFD consumption causes deleterious changes in body weight and composition as well as in measures of physical, cardiac, and metabolic health. The harmful effects of the FFD were associated with dramatic increases in several markers of senescence, including p16, EGFP, senescence-associated β-galactosidase, and the senescence-associated secretory phenotype (SASP) specifically in visceral adipose tissue. We show that exercise prevents the accumulation of senescent cells and the expression of the SASP while nullifying the damaging effects of the FFD on parameters of health. We also demonstrate that exercise initiated after long-term FFD feeding reduces senescent phenotype markers in visceral adipose tissue while attenuating physical impairments, suggesting that exercise may provide restorative benefit by mitigating accrued senescent burden. These findings highlight a novel mechanism by which exercise mediates its beneficial effects and reinforces the effect of modifiable lifestyle choices on health span.

Piceatannol exhibits anti-inflammatory effects on macrophages interacting with adipocytes

Piceatannol (PIC), a natural analog of resveratrol (RES), is a phytochemical found in passion fruit seeds. To clarify the effects of PIC on obesity‐induced inflammation in adipose tissue, we investigated the anti‐inflammatory activity of PIC‐related compounds (PIC, RES, and metabolites from PIC) in culture models of obese adipose tissue. Lipopolysaccharide (LPS) and conditioned medium from 3T3‐L1 adipocytes (3T3‐L1‐CM) enhanced proinflammatory gene expression and synthesis of nitric oxide (NO), tumor necrosis factor‐α (TNF‐α), and interleukin‐6 (IL‐6) in RAW264.7 macrophages. Although each compound inhibited the mRNA expression of iNOS (inducible NO synthase), TNF‐α, and IL‐6, PIC potently inhibited them, and 30 μmol/L PIC suppressed the LPS‐ and 3T3‐L1‐CM‐induced mRNA expression of iNOS (70.4% and 69.2% suppression, respectively), TNF‐α (42.6% and 47.0% suppression), and IL‐6 (27.3% and 42.1% suppression). PIC also significantly suppressed production of NO (80.3% suppression) and inflammatory cytokines (TNF‐α; 33.7% suppression, IL‐6; 66.5% suppression). Furthermore, PIC was found to rescue the uncoupling protein 1 mRNA expression induced by isoproterenol in 10T1/2 adipocytes, which was suppressed by LPS‐activated macrophages. These results suggest that PIC may attenuate the pathologic inflammation triggered by adipose tissues.

Citrus flavanones prevent systemic inflammation and ameliorate oxidative stress in C57BL/6J mice fed high-fat diet

The flavanones hesperidin, eriocitrin and eriodictyol were investigated for their prevention of the oxidative stress and systemic inflammation caused by high-fat diet in C57BL/6J mice. The mice received a standard diet (9.5% kcal from fat), high-fat diet (45% kcal from fat) or high-fat diet supplemented with hesperidin, eriocitrin or eriodictyol for a period of four weeks. Hesperidin, eriocitrin and eriodictyol increased the serum total antioxidant capacity, and restrained the elevation of interleukin-6 (IL-6), macrophage chemoattractant protein-1 (MCP-1), and C-reactive protein (hs-CRP). In addition, the liver TBARS levels and spleen mass (g per kg body weight) were lower for the flavanone-treated mice than in the unsupplemented mice. Eriocitrin and eriodictyol reduced TBARS levels in the blood serum, and hesperidin and eriodictyol also reduced fat accumulation and liver damage. The results showed that hesperidin, eriocitrin and eriodictyol had protective effects against inflammation and oxidative stress caused by high-fat diet in mice, and may therefore prevent metabolic alterations associated with the development of cardiovascular diseases in other animals.

Molecular Mechanisms of the Anti-Obesity and Anti-Diabetic Properties of Flavonoids

Obesity and diabetes are the most prevailing health concerns worldwide and their incidence is increasing at a high rate, resulting in enormous social costs. Obesity is a complex disease commonly accompanied by insulin resistance and increases in oxidative stress and inflammatory marker expression, leading to augmented fat mass in the body. Diabetes mellitus (DM) is a metabolic disorder characterized by the destruction of pancreatic β cells or diminished insulin secretion and action insulin. Obesity causes the development of metabolic disorders such as DM, hypertension, cardiovascular diseases, and inflammation-based pathologies. Flavonoids are the secondary metabolites of plants and have 15-carbon skeleton structures containing two phenyl rings and a heterocyclic ring. More than 5000 naturally occurring flavonoids have been reported from various plants and have been found to possess many beneficial effects with advantages over chemical treatments. A number of studies have demonstrated the potential health benefits of natural flavonoids in treating obesity and DM, and show increased bioavailability and action on multiple molecular targets. This review summarizes the current progress in our understanding of the anti-obesity and anti-diabetic potential of natural flavonoids and their molecular mechanisms for preventing and/or treating obesity and diabetes.

A role for novel adipose tissue-secreted factors in obesity-related carcinogenesis

Obesity, a pandemic disease, is caused by an excessive accumulation of fat that can have detrimental effects on health. Adipose tissue plays a very important endocrine role, secreting different molecules that affect body physiology. In obesity, this function is altered, leading to a dysfunctional production of several factors, known as adipocytokines. This process has been linked to various comorbidities associated with obesity, such as carcinogenesis. In fact, several classical adipocytokines with increased levels in obesity have been demonstrated to exert a pro-carcinogenic role, including leptin, TNF-α, IL-6 and resistin, whereas others like adiponectin, with decreased levels in obesity, might have an anti-carcinogenic function. In this expanding field, new proteomic techniques and approaches have allowed the identification of novel adipocytokines, a number of which exhibit an altered production in obesity and type 2 diabetes and thus are related to adiposity. Many of these novel adipocytokines have also been identified in various tumour types, such as that of the breast, liver or endometrium, thereby increasing the list of potential contributors to carcinogenesis. This review is focused on the regulation of these novel adipocytokines by obesity, including apelin, endotrophin, FABP4, lipocalin 2, omentin-1, visfatin, chemerin, ANGPTL2 or osteopontin, emphasizing its involvement in tumorigenesis.

Inhibitory Effect of Serotonin Antagonist on Leukocyte-Endothelial Interactions In Vivo and In Vitro

Background

Although 5-HT_2A serotonergic antagonists have been used to treat vascular disease in patients with diabetes mellitus or obesity, their effects on leukocyte-endothelial interactions have not been fully investigated. In this study, we assessed the effects of sarpogrelate hydrochloride (SRPO), a 5-HT_2A receptor inverse agonist, on leukocyte-endothelial cell interactions in obesity both in vivo and in vitro.

Methods and Findings

In the in vivo experiment, C57BL/6 mice were fed a high-fat high-fructose diet (HFFD), comprising 20% fat and 30% fructose, with or without intraperitoneal injection of 5 mg/kg/day SRPO for 4 weeks. The body weight, visceral fat weight, and serum monocyte chemoattractant protein-1 levels in the mice increased significantly with the HFFD, but these effects were prevented by chronic injections of SRPO. Intravital microscopy of the femoral artery detected significant leukocyte-endothelial interactions after treatment with HFFD, but these leukocyte-endothelial interactions were reduced in the mice injected with SRPO. In the in vitro experiment, pre-incubation of activated human umbilical vein endothelial cells (HUVECs) with platelet-rich plasma (PRP) induced THP-1 cell adhesion under physiological flow conditions, but the adhesion was reduced by pretreatment of PRP with SRPO. A fluorescent immunobinding assay showed that PRP induced significant upregulation of E-selectin in HUVECs, but this upregulation was reduced by pretreatment of PRP with SRPO. In other in vitro conditions, pre-incubation of THP-1 cells with phorbol 12-myristate 13-acetate increased the adhesion of THP-1 cells to activated HUVECs under rotational conditions, but this adhesion was reduced by pretreatment with SRPO. Western blotting analysis showed that protein kinase C α activation in THP-1 cells was inhibited by SRPO.

Conclusion

Our findings indicated that SRPO inhibits vascular inflammation in obesity via inactivation of platelets and leukocytes, and improvement of obese.

Adipose Tissue Remodeling: Its Role in Energy Metabolism and Metabolic Disorders

The adipose tissue is a central metabolic organ in the regulation of whole-body energy homeostasis. The white adipose tissue functions as a key energy reservoir for other organs, whereas the brown adipose tissue accumulates lipids for cold-induced adaptive thermogenesis. Adipose tissues secrete various hormones, cytokines, and metabolites (termed as adipokines) that control systemic energy balance by regulating appetitive signals from the central nerve system as well as metabolic activity in peripheral tissues. In response to changes in the nutritional status, the adipose tissue undergoes dynamic remodeling, including quantitative and qualitative alterations in adipose tissue-resident cells. A growing body of evidence indicates that adipose tissue remodeling in obesity is closely associated with adipose tissue function. Changes in the number and size of the adipocytes affect the microenvironment of expanded fat tissues, accompanied by alterations in adipokine secretion, adipocyte death, local hypoxia, and fatty acid fluxes. Concurrently, stromal vascular cells in the adipose tissue, including immune cells, are involved in numerous adaptive processes, such as dead adipocyte clearance, adipogenesis, and angiogenesis, all of which are dysregulated in obese adipose tissue remodeling. Chronic overnutrition triggers uncontrolled inflammatory responses, leading to systemic low-grade inflammation and metabolic disorders, such as insulin resistance. This review will discuss current mechanistic understandings of adipose tissue remodeling processes in adaptive energy homeostasis and pathological remodeling of adipose tissue in connection with immune response.

Bardoxolone Methyl Prevents Mesenteric Fat Deposition and Inflammation in High-Fat Diet Mice

Mesenteric fat belongs to visceral fat. An increased deposition of mesenteric fat contributes to obesity associated complications such as type 2 diabetes and cardiovascular diseases. We have investigated the therapeutic effects of bardoxolone methyl (BARD) on mesenteric adipose tissue of mice fed a high-fat diet (HFD). Male C57BL/6J mice were administered oral BARD during HFD feeding (HFD/BARD), only fed a high-fat diet (HFD), or fed low-fat diet (LFD) for 21 weeks. Histology and immunohistochemistry were used to analyse mesenteric morphology and macrophages, while Western blot was used to assess the expression of inflammatory, oxidative stress, and energy expenditure proteins. Supplementation of drinking water with BARD prevented mesenteric fat deposition, as determined by a reduction in large adipocytes. BARD prevented inflammation as there were fewer inflammatory macrophages and reduced proinflammatory cytokines (interleukin-1 beta and tumour necrosis factor alpha). BARD reduced the activation of extracellular signal-regulated kinase (ERK) and Akt, suggesting an antioxidative stress effect. BARD upregulates energy expenditure proteins, judged by the increased activity of tyrosine hydroxylase (TH) and AMP-activated protein kinase (AMPK) and increased peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and uncoupling protein 2 (UCP2) proteins. Overall, BARD induces preventive effect in HFD mice through regulation of mesenteric adipose tissue.

Adipocyte progenitor cells initiate monocyte chemoattractant protein-1-mediated macrophage accumulation in visceral adipose tissue

OBJECTIVE

Macrophages are important producers of obesity-induced MCP-1; however, initial obesity-induced increases in MCP-1 production precede M1 macrophage accumulation in visceral adipose tissue (VAT). The initial cellular source of obesity-induced MCP-1 in vivo is currently unknown. Preliminary reports based on in vitro studies of preadipocyte cell lines and adherent stroma-vascular fraction cells suggest that resident stromal cells express MCP-1. In the past several years, elegant methods of identifying adipocyte progenitor cells (AdPCs) have become available, making it possible to study these cells in vivo. We have previously published that global deletion of transcription factor Inhibitor of Differentiation 3 (Id3) attenuates high fat diet-induced obesity, but it is unclear if Id3 plays a role in diet-induced MCP-1 production. We sought to determine the initial cellular source of MCP-1 and identify molecular regulators mediating MCP-1 production.

METHODS

Id3 (+/+) and Id3 (-/-) mice were fed either a standard chow or HFD for varying lengths of time. Flow cytometry, semi-quantitative real-time PCR, ELISAs and adoptive transfers were used to assess the importance of AdPCs during diet-induced obesity. Flow cytometry was also performed on a cohort of 14 patients undergoing bariatric surgery.

RESULTS

Flow cytometry identified committed CD45(-)CD31 (-) Ter119(-)CD29(+)CD34(+)Sca-1(+)CD24(-) adipocyte progenitor cells as producers of high levels of MCP-1 in VAT. High-fat diet increased AdPC numbers, an effect dependent on Id3. Loss of Id3 increased p21(Cip1) levels and attenuated AdPC proliferation, resulting in reduced MCP-1 and M1 macrophage accumulation in VAT, compared to Id3 (+/+) littermate controls. AdPC rescue by adoptive transfer of 50,000 Id3 (+/+) AdPCs into Id3 (-/-) recipient mice increased MCP-1 levels and M1 macrophage number in VAT. Additionally, flow cytometry identified MCP-1-producing CD45(-)CD31(-)CD34(+)CD44(+)CD90(+) AdPCs in human omental and subcutaneous adipose tissue, with a higher percentage in omental adipose. Furthermore, high surface expression of CD44 marked abundant MCP-1 producers, only in visceral adipose tissue.

CONCLUSIONS

This study provides the first in vivo evidence, to our knowledge, that committed AdPCs in VAT are the initial source of obesity-induced MCP-1 and identifies the helix-loop-helix transcription factor Id3 as a critical regulator of p21(Cip1) expression, AdPC proliferation, MCP-1 expression and M1 macrophage accumulation in VAT. Inhibition of Id3 and AdPC expansion, as well as CD44 expression in human AdPCs, may serve as unique therapeutic targets for the regulation of adipose tissue inflammation.

Tomato extract suppresses the production of proinflammatory mediators induced by interaction between adipocytes and macrophages

Obese adipose tissue is characterized by enhanced macrophage infiltration. A loop involving monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNFα) between adipocytes and macrophages establishes a vicious cycle that augments inflammatory changes and insulin resistance in obese adipose tissue. Tomatoes, one of the most popular crops worldwide, contain many beneficial phytochemicals that improve obesity-related diseases such as diabetes. Some of them have also been reported to have anti-inflammatory properties. In this study, we focused on the potential protective effects of phytochemicals in tomatoes on inflammation. We screened fractions of tomato extract using nitric oxide (NO) assay in lipopolysaccharide (LPS)-stimulated RAW264 macrophages. One fraction, RF52, significantly inhibited NO production in LPS-stimulated RAW264 macrophages. Furthermore, RF52 significantly decreased MCP-1 and TNFα productions. The coculture of 3T3-L1 adipocytes and RAW264 macrophages markedly enhanced MCP-1, TNFα, and NO productions compared with the control cultures; however, the treatment with RF52 inhibited the production of these proinflammatory mediators. These results suggest that RF52 from tomatoes may have the potential to suppress inflammation by inhibiting the production of NO or proinflammatory cytokines during the interaction between adipocytes and macrophages.