c-Jun N-terminal kinase is involved in the suppression of adiponectin expression by TNF-alpha in 3T3-L1 adipocytes

Hydroxychloroquine and Cardiovascular Events in Patients with Rheumatoid Arthritis

INTRODUCTION

Cardiovascular disease (CVD) is the leading cause of mortality in patients with rheumatoid arthritis (RA). Some studies have reported a decrease in CVD in patients with RA using hydroxychloroquine (HCQ). Most of these have had fewer participants and have analyzed only composite outcomes. We aimed to identify the association between the use of HCQ in patients with RA and the incidence of major adverse cardiac events (MACEs), cerebral infarction, and AMI.

METHODS

This was a retrospective observational study using the TriNetX Diamond Network. Propensity score matching (PSM) was used to equilibrate the cohorts. The dependent variables in our study were MACE, cerebral infarction, and AMI.

RESULTS

A total of 2,261,643 patients with RA were identified. Approximately 6% had been prescribed HCQ. Of those prescribed HCQ, 80% (112,743) were females, while of those not prescribed HCQ, 72.5% (1,536,937) were females. HCQ was associated with lower rates of MACE (HR 0.827, 95%CI 0.8,0.86), cerebral infarction (HR 0.824, 95% CI 0.78,0.87), and AMI (HR 0.9, 95% CI 0.85,0.96). These associations were not seen in patients taking biologics. HCQ was associated with lower MACE in all other subgroups.

CONCLUSION

In conclusion, HCQ was slightly beneficial in decreasing MACE and cerebral infarction in patients with RA. These associations were significantly lower in patients taking methotrexate or biologics. Although there was a significant decrease in the risk of AMI in all patients with RA, these results were not replicated in subgroup analyses, and there was an apparent increased risk of AMI with the use of HCQ in patients using biologics.

Metabolic Syndrome: A Narrative Review from the Oxidative Stress to the Management of Related Diseases

Metabolic syndrome (MS) is a growing disorder affecting thousands of people worldwide, especially in industrialised countries, increasing mortality. Oxidative stress, hyperglycaemia, insulin resistance, inflammation, dysbiosis, abdominal obesity, atherogenic dyslipidaemia and hypertension are important factors linked to MS clusters of different pathologies, such as diabesity, cardiovascular diseases and neurological disorders. All biochemical changes observed in MS, such as dysregulation in the glucose and lipid metabolism, immune response, endothelial cell function and intestinal microbiota, promote pathological bridges between metabolic syndrome, diabesity and cardiovascular and neurodegenerative disorders. This review aims to summarise metabolic syndrome's involvement in diabesity and highlight the link between MS and cardiovascular and neurological diseases. A better understanding of MS could promote a novel strategic approach to reduce MS comorbidities.

Adipokines and Bacterial Metabolites: A Pivotal Molecular Bridge Linking Obesity and Gut Microbiota Dysbiosis to Target

Adipokines are essential mediators produced by adipose tissue and exert multiple biological functions. In particular, adiponectin, leptin, resistin, IL-6, MCP-1 and PAI-1 play specific roles in the crosstalk between adipose tissue and other organs involved in metabolic, immune and vascular health. During obesity, adipokine imbalance occurs and leads to a low-grade pro-inflammatory status, promoting insulin resistance-related diabetes and its vascular complications. A causal link between obesity and gut microbiota dysbiosis has been demonstrated. The deregulation of gut bacteria communities characterizing this dysbiosis influences the synthesis of bacterial substances including lipopolysaccharides and specific metabolites, generated via the degradation of dietary components, such as short-chain fatty acids, trimethylamine metabolized into trimethylamine-oxide in the liver and indole derivatives. Emerging evidence suggests that these bacterial metabolites modulate signaling pathways involved in adipokine production and action. This review summarizes the current knowledge about the molecular links between gut bacteria-derived metabolites and adipokine imbalance in obesity, and emphasizes their roles in key pathological mechanisms related to oxidative stress, inflammation, insulin resistance and vascular disorder. Given this interaction between adipokines and bacterial metabolites, the review highlights their relevance (i) as complementary clinical biomarkers to better explore the metabolic, inflammatory and vascular complications during obesity and gut microbiota dysbiosis, and (ii) as targets for new antioxidant, anti-inflammatory and prebiotic triple action strategies.

The locoregional adiponectin and its synergistic antitumor effect with HIF-1α blockade in TSCC

Adiponectin (APN) is a kind of endogenous anti-tumor adipocytokine, which exerts its function by binding to its receptors (AdipoR1 and AdipoR2). However, hyperadiponectinemia is found in some pathophysiological processes without significant protective effect, which indicates the existence of APN resistance. Here, we aimed to investigate the locoregional expression of APN in tongue squamous cell carcinoma (TSCC) tissues, and to explore the potential regulatory mechanism of APN resistance under hypoxia. Consequently, we found that the protein expression of APN and AdipoR1, but not AdipoR2, was upregulated in the early stage of TSCC and after hypoxic treatment ex vivo and in vitro. Knockdown of HIF-1α decreased the level of APN and AdipoR1, and simultaneously, HIF-1α was identified as transcriptor of the APN. Intriguingly, a regenerative feedback of HIF-1α was unexpectedly detected after application of recombinant globular APN (gAPN), which most likely contributed to the APN resistance. Furthermore, HIF-1α blockade combined with gAPN has a prominent synergistic antitumor effect, which suggested an effective amelioration in APN resistance. In all, our study revealed the possible mechanism of APN resistance under hypoxia and provides a promising strategy of bi-target treatment with APN and HIF-1α for TSCC therapy.

Distribution, composition, and activity of airway-associated adipose tissue in the porcine lung

Patients with comorbid asthma-obesity experience greater disease severity and are less responsive to therapy. We have previously reported adipose tissue within the airway wall that positively correlated with body mass index. Accumulation of biologically active adipose tissue may result in the local release of adipokines and disrupt large and small airway function depending on its anatomical distribution. This study therefore characterized airway-associated adipose tissue distribution, lipid composition, and adipokine activity in a porcine model. Airway segments were systematically dissected from different locations of the bronchial tree in inflation-fixed lungs. Cryosections were stained with hematoxylin and eosin (H&E) for airway morphology, oil red O to distinguish adipose tissue, and Nile blue A for lipid subtype delineation. Excised airway-associated adipose tissue was cultured for 72 h to quantify adipokine release using immunoassays. Results showed that airway-associated adipose tissue extended throughout the bronchial tree and occupied an area proportionally similar to airway smooth muscle within the wall area. Lipid composition consisted of pure neutral lipids (61.7 ± 3.5%), a mixture of neutral and acidic lipids (36.3 ± 3.4%), or pure acidic lipids (2.0 ± 0.8%). Following tissue culture, there was rapid release of IFN-γ, IL-1β, and TNF-α at 12 h. Maximum IL-4 and IL-10 release was at 24 and 48 h, and peak leptin release occurred between 48 and 72 h. These data extend previous findings and demonstrate that airway-associated adipose tissue is prevalent and biologically active within the bronchial tree, providing a local source of adipokines that may be a contributing factor in airway disease.

KRAS Affects Adipogenic Differentiation by Regulating Autophagy and MAPK Activation in 3T3-L1 and C2C12 Cells

Kirsten rat sarcoma 2 viral oncogene homolog (Kras) is a proto-oncogene that encodes the small GTPase transductor protein KRAS, which has previously been found to promote cytokine secretion, cell survival, and chemotaxis. However, its effects on preadipocyte differentiation and lipid accumulation are unclear. In this study, the effects of KRAS inhibition on proliferation, autophagy, and adipogenic differentiation as well as its potential mechanisms were analyzed in the 3T3-L1 and C2C12 cell lines. The results showed that KRAS was localized mainly in the nuclei of 3T3-L1 and C2C12 cells. Inhibition of KRAS altered mammalian target of rapamycin (Mtor), proliferating cell nuclear antigen (Pcna), Myc, peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein beta (C/ebp-β), diacylglycerol O-acyltransferase 1 (Dgat1), and stearoyl-coenzyme A desaturase 1 (Scd1) expression, thereby reducing cell proliferation capacity while inducing autophagy, enhancing differentiation of 3T3-L1 and C2C12 cells into mature adipocytes, and increasing adipogenesis and the capacity to store lipids. Moreover, during differentiation, KRAS inhibition reduced the levels of extracellular regulated protein kinases (ERK), c-Jun N-terminal kinase (JNK), p38, and phosphatidylinositol 3 kinase (PI3K) activation. These results show that KRAS has unique regulatory effects on cell proliferation, autophagy, adipogenic differentiation, and lipid accumulation.

Nutritional Contributions and Health Associations of Traditional Fermented Foods

The growing interest in the consumption and study of traditionally fermented food worldwide has led to the development of numerous scientific investigations that have focused on analyzing the microbial and nutritional composition and the health effects derived from the consumption of these foods. Traditionally fermented foods and beverages are a significant source of nutrients, including proteins, essential fatty acids, soluble fiber, minerals, vitamins, and some essential amino acids. Additionally, fermented foods have been considered functional due to their prebiotic content, and the presence of specific lactic acid bacterial strains (LAB), which have shown positive effects on the balance of the intestinal microbiota, providing a beneficial impact in the treatment of diseases. This review presents a bibliographic compilation of scientific studies assessing the effect of the nutritional content and LAB profile of traditional fermented foods on different conditions such as obesity, diabetes, and gastrointestinal disorders.

Coffee Bioactive N-Methylpyridinium Attenuates Tumor Necrosis Factor (TNF)-α-Mediated Insulin Resistance and Inflammation in Human Adipocytes

Although coffee consumption has been historically associated with negative health outcomes, recent evidence suggests a lower risk of metabolic syndrome, obesity and diabetes among regular coffee drinkers. Among the plethora of minor organic compounds assessed as potential mediators of coffee health benefits, trigonelline and its pyrolysis product N-methylpyridinium (NMP) were preliminary shown to promote glucose uptake and exert anti-adipogenic properties. Against this background, we aimed at characterizing the effects of trigonelline and NMP in inflamed and dysfunctional human adipocytes. Human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes were treated with NMP or, for comparison, trigonelline, for 5 h before stimulation with tumor necrosis factor (TNF)-α. NMP at concentrations as low as 1 µmol/L reduced the stimulated expression of several pro-inflammatory mediators, including C-C Motif chemokine ligand (CCL)-2, C-X-C Motif chemokine ligand (CXCL)-10, and intercellular adhesion Molecule (ICAM)-1, but left the induction of prostaglandin G/H synthase (PTGS)2, interleukin (IL)-1β, and colony stimulating factor (CSF)1 unaffected. Furthermore, NMP restored the downregulated expression of adiponectin (ADIPOQ). These effects were functionally associated with downregulation of the adhesion of monocytes to inflamed adipocytes. Under the same conditions, NMP also reversed the TNF-α-mediated suppression of insulin-stimulated Ser473 Akt phosphorylation and attenuated the induction of TNF-α-stimulated lipolysis restoring cell fat content. In an attempt to preliminarily explore the underlying mechanisms of its action, we show that NMP restores the expression of the master regulator of adipocyte differentiation peroxisome proliferator-activated receptor (PPAR)γ and downregulates activation of the pro-inflammatory mitogen-activated protein jun N-terminal kinase (JNK). In conclusion, NMP reduces adipose dysfunction in pro-inflammatory activated adipocytes. These data suggest that bioactive NMP in coffee may improve the inflammatory and dysmetabolic milieu associated with obesity.

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

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

The Effects of Adipocytes on the Regulation of Breast Cancer in the Tumor Microenvironment: An Update

Obesity is a global pandemic and it is well evident that obesity is associated with the development of many disorders including many cancer types. Breast cancer is one of that associated with a high mortality rate. Adipocytes, a major cellular component in adipose tissue, are dysfunctional during obesity and also known to promote breast cancer development both in vitro and in vivo. Dysfunctional adipocytes can release metabolic substrates, adipokines, and cytokines, which promote proliferation, progression, invasion, and migration of breast cancer cells. The secretion of adipocytes can alter gene expression profile, induce inflammation and hypoxia, as well as inhibit apoptosis. It is known that excessive free fatty acids, cholesterol, triglycerides, hormones, leptin, interleukins, and chemokines upregulate breast cancer development. Interestingly, adiponectin is the only adipokine that has anti-tumor properties. Moreover, adipocytes are also related to chemotherapeutic resistance, resulting in the poorer outcome of treatment and advanced stages in breast cancer. Evaluation of the adipocyte secretion levels in the circulation can be useful for prognosis and evaluation of the effectiveness of cancer therapy in the patients. Therefore, understanding about functions of adipocytes as well as obesity in breast cancer may reveal novel targets that support the development of new anti-tumor therapy. In this systemic review, we summarize and update the effects of secreted factors by adipocytes on the regulation of breast cancer in the tumor microenvironment.

Deficiency of mitophagy receptor FUNDC1 impairs mitochondrial quality and aggravates dietary-induced obesity and metabolic syndrome

There is overwhelming evidence for an association between impaired mitochondrial function and metabolic syndrome. Mitophagy, a process that selectively removes damaged mitochondria via a specialized form of autophagy, is essential for mitochondrial quality control (mitochondrial QC) and metabolic homeostasis. We thus addressed the potential role of defective mitophagy in the pathogenesis of metabolic disorders. Mice lacking Fundc1, a newly characterized mitophagy receptor, develop more severe obesity and insulin resistance when fed a high-fat diet (HFD). Ablation of Fundc1 results in defective mitophagy and impaired mitochondrial QC in vitro and in white adipose tissue (WAT). In addition, there is more pronounced WAT remodeling with more adipose tissue-associated macrophages infiltration, more M1 macrophage polarization and thus an elevated inflammatory response. Mechanistically, hyperactivation of MAPK/JNK leads to insulin insensitivity, which can be inhibited by knocking out Mapk8/Jnk1 in fundc1 KO mice. Our results demonstrate that dysregulated mitochondrial QC due to defective mitophagy receptor FUNDC1 links with metabolic disorders via MAPK signaling and inflammatory responses. Abbreviations: ATMs: adipose tissue macrophages; BAT: brown adipose tissue; BMDMs: bone marrow-derived macrophages; GOT1/AST: glutamic-oxaloacetic transaminase 1, soluble; GPT/ALT: glutamic pyruvic transaminase, soluble; H&E staining: hematoxylin and eosin staining; HFD: high-fat diet; LIR: LC3-interacting region; mitochondrial QC: mitochondrial quality control; mito-ROS: mitochondrial ROS; mtDNA: mitochondrial DNA; RT-PCR: real-time-PCR; T2D: type 2 diabetes; WAT: white adipose tissue.

New insights into oxidative stress and inflammation during diabetes mellitus-accelerated atherosclerosis

Oxidative stress and inflammation interact in the development of diabetic atherosclerosis. Intracellular hyperglycemia promotes production of mitochondrial reactive oxygen species (ROS), increased formation of intracellular advanced glycation end-products, activation of protein kinase C, and increased polyol pathway flux. ROS directly increase the expression of inflammatory and adhesion factors, formation of oxidized-low density lipoprotein, and insulin resistance. They activate the ubiquitin pathway, inhibit the activation of AMP-protein kinase and adiponectin, decrease endothelial nitric oxide synthase activity, all of which accelerate atherosclerosis. Changes in the composition of the gut microbiota and changes in microRNA expression that influence the regulation of target genes that occur in diabetes interact with increased ROS and inflammation to promote atherosclerosis. This review highlights the consequences of the sustained increase of ROS production and inflammation that influence the acceleration of atherosclerosis by diabetes. The potential contributions of changes in the gut microbiota and microRNA expression are discussed.

Pro-inflammatory cytokines: The link between obesity and osteoarthritis

Osteoarthritis (OA), characterized by joint malfunction and chronic disability, is the most common form of arthritis. Clinical and animal experiments reveal that age-related OA is associated with many factors such as age, sex, trauma, and obesity. One of the most influential and modifiable risk factors is obesity. Obesity not only increases mechanical stress on the tibiofemoral cartilage, but also leads to a higher prevalence of OA in non-weight-bearing areas. There is a link between obesity and inflammation. Adipose tissues play a crucial role in this context because they are the major source of cytokines, chemokines, and metabolically-active mediators named adipokines. The adipokines, including adiponectin and leptin, have been demonstrated to regulate inflammatory immune responses in cartilage. Obese people and animals show a higher level of serum tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL)-1β and IL-6, all of which are produced by macrophages derived from adipose tissue. These pro-inflammatory cytokines regulate the proliferation and apoptosis of adipocytes, promote lipolysis, inhibit lipid synthesis and decrease blood lipids through autocrine and paracrine mechanisms. Elevated levels of TNF-α, IL-1 and IL-6 have been found in the synovial fluid, synovial membrane, subchondral bone and cartilage of OA patients, confirming their important roles in OA pathogenesis. TNF-α, IL-6 and IL-1 are the factors released by fat to negatively regulate cartilage directly. Moreover, TNF-α, IL-1 and IL-6 can induce the production of other cytokines, matrix metalloproteinases (MMPs) and prostaglandins and inhibit the synthesis of proteoglycans and type II collagen; thus, they play a pivotal role in cartilage matrix degradation and bone resorption in OA. Activated chondrocytes also produce MMP-1, MMP-3, MMP-13, and aggrecanase 1 and 2 (ADAMTS-4, ADAMTS-5). In addition, IL-1, TNF-α and IL-6 may cause OA indirectly by regulating release of adiponectin and leptin from adipocytes. In this review, we first summarize the relationship between obesity and inflammation. Then we summarize the roles of IL-1, TNF-α and IL-6 in OA. We further discuss how IL-1, TNF-α and IL-6 regulate the communication between fat and OA, and their pathological roles in obesity-related OA. Lastly, we discuss the possibility of using the pro-inflammatory signaling pathway as a therapeutic target to develop drugs for obesity-related OA.

miR-876-3p regulates glucose homeostasis and insulin sensitivity by targeting adiponectin

miRNA has been known to regulate diverse cellular and molecular functions. In the earlier study, we have reported that adipocytes differentiated from human mesenchymal stem cells (hMSC) on 72-h chronic insulin (CI) treatment exhibit insulin resistance (IR). Present study has further explored above model to investigate the role of early expressed miRNAs within human adipocytes to modulate differential adipokine expression as observed during IR. Our results highlight that miR-876-3p regulate glucose homeostasis and its dysregulation leads to IR. We found that miR-876-3p level is a critical determinant of adiponectin expression by virtue of its target within adiponectin 3′UTR. Regulatory effect of miR-876-3p impacts crosstalk between adiponectin and insulin signaling. Rosiglitazone treatment in CI-induced IR adipocytes drastically reduced miR-876-3p expression and increased adiponectin level. In line with this, lentiviral-mediated inhibition of miR-876-3p expression ameliorated CI and high-fat diet (HFD)-induced IR in adipocytes differentiated from hMSC and C57BL/6 mice, respectively. Our findings thus suggest that modulating miR-876-3p expression could provide novel opportunities for therapeutic intervention of obesity-associated metabolic syndrome.

Adiponectin and Inflammation in Health and Disease: An Update

Adiponectin, a protein secreted by adipocytes, gained a special medical attention in the past two decades mostly due to its relation to obesity, a major health problem worldwide. Moreover, adiponectin has shown to have a preventive effect on insulin resistance, diabetes and cardiovascular diseases. Lately, obesity has been classified as a chronic inflammatory state, whereby dysregulated adipocytes and high infiltration of macrophages shift toward the production of pro-inflammatory cytokines like TNF-α and IL-6 among others. This status contributes to a decrease in adiponectin levels, thus leading to the emergence of obesity related complications. This review will focus on the hormone adiponectin and its mechanisms of action in relation to insulin resistance, diabetes, cardiovascular effect and atherosclerosis. It will also cover the various therapeutic approaches aiming to increase the levels of this important cytokine, and to highlight the promising role of AdipoRon, an adiponectin receptor agonist, and of diet.

Integrated Immunomodulatory Mechanisms through which Long-Chain n-3 Polyunsaturated Fatty Acids Attenuate Obese Adipose Tissue Dysfunction

Obesity is a global health concern with rising prevalence that increases the risk of developing other chronic diseases. A causal link connecting overnutrition, the development of obesity and obesity-associated co-morbidities is visceral adipose tissue (AT) dysfunction, characterized by changes in the cellularity of various immune cell populations, altered production of inflammatory adipokines that sustain a chronic state of low-grade inflammation and, ultimately, dysregulated AT metabolic function. Therefore, dietary intervention strategies aimed to halt the progression of obese AT dysfunction through any of the aforementioned processes represent an important active area of research. In this connection, fish oil-derived dietary long-chain n-3 polyunsaturated fatty acids (PUFA) in the form of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to attenuate obese AT dysfunction through multiple mechanisms, ultimately affecting AT immune cellularity and function, adipokine production, and metabolic signaling pathways, all of which will be discussed herein.

11β-Hydroxysteroid Dehydrogenase Type 1(11β-HSD1) mediates insulin resistance through JNK activation in adipocytes

Glucocorticoids are used to treat a number of human diseases but often lead to insulin resistance and metabolic syndrome. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is a key enzyme that catalyzes the intracellular conversion of cortisone to physiologically active cortisol. Despite the known role of 11β-HSD1 and active glucocorticoid in causing insulin resistance, the molecular mechanisms by which insulin resistance is induced remain elusive. The aim of this study is to identify these mechanisms in high fat diet (HFD) experimental models. Mice on a HFD were treated with 11β-HSD1 inhibitor as well as a JNK inhibitor. We then treated 3T3-L1-derived adipocytes with prednisone, a synthetic glucocorticoid, and cells with 11β-HSD1 overexpression to study insulin resistance. Our results show that 11β-HSD1 and JNK inhibition mitigated insulin resistance in HFD mice. Prednisone stimulation or overexpression of 11β-HSD1 also caused JNK activation in cultured adipocytes. Inhibition of 11β-HSD1 blocked the activation of JNK in adipose tissue of HFD mice as well as in cultured adipocytes. Furthermore, prednisone significantly impaired the insulin signaling pathway, and these effects were reversed by 11β-HSD1 and JNK inhibition. Our study demonstrates that glucocorticoid-induced insulin resistance was dependent on 11β-HSD1, resulting in the critical activation of JNK signaling in adipocytes.

Infliximab therapy restores adiponectin expression in perivascular adipose tissue and improves endothelial nitric oxide-mediated vasodilation in mice with type 1 diabetes

Increased TNFα-mediated JNK signaling in the perivascular adipose tissue (PVAT) may contribute to the pathogenesis of vascular complications in T1DM by reducing adiponectin (Ad) synthesis and therefore impairing Ad-mediated activity in the contiguous blood vessel system. We evaluated whether in vivo treatment with the TNFα blocking antibody infliximab normalized expression of Ad and Ad receptors in various fat depots, and whether this effect correlated with improved endothelial activity and vasodilator function in streptozotocin (STZ)-induced diabetic mice. STZ mice were studied at 1 and 2weeks after diabetes onset, and compared to age-matched infliximab-treated diabetic (I-STZ) and control animals (CTRL) (n=10 each group). In STZ mice, activation of pro-inflammatory JNK signaling was faster in PVAT (P<0.01) than in visceral (VAT), epididymal (EAT) and subcutaneous (SAT) adipose depots, and associated with decreased Ad synthesis and dysregulated AdipoR1/R2 levels. In parallel, activation of JNK in aortic endothelial cells and mesenteric arteries was associated with decreased expression/phosphorylation of eNOS and impaired ACh-mediated vasodilation (P<0.05 vs. CTRL). Treatment with infliximab abrogated JNK activation, ameliorated Ad protein expression, and normalized expression of both AdipoR1 and AdipoR2 in PVAT, concomitantly improving eNOS expression and vessel relaxation in mesenteric arteries from I-STZ mice (P<0.01 vs. STZ). These observations underline the early susceptibility of PVAT to activation of pro-inflammatory JNK signaling, and highlight its potential importance in early vascular changes of T1DM. Further elucidation of the role of PVAT in cardiovascular complications may allow for the design of novel therapeutic strategies directly addressing PVAT pathophysiology.

The multimerization and secretion of adiponectin are regulated by TNF-alpha

Obesity is often associated with insulin resistance, mild systemic inflammation, and decreased blood adiponectin. However, some adipokines are increased in the adipose tissue of obese individuals, and whether these adipokines are directly related to the reductions in serum adiponectin levels in an autocrine or paracrine manner remains unknown. This study indicates that the tumor necrosis factor alpha (TNF-α) suppresses the multimerization and secretion of adiponectin both in vitro and in vivo. Additionally, TNF-α remarkably suppressed the expression of the ER-resident chaperone proteins ERO1-La, DsbA-L, and ERp44. Overexpression of the transcription factor PPARγ antagonized the suppressive effect of TNF-α on ERO1-La and DsbA-L expressions. Further study revealed that PPARγ enhanced the transcription of ERO1-La and DsbA-L by directly binding to the PPRE element of ERO1-La and DsbA-L promoters. TNF-α treatment decreased this binding activity. Furthermore, TNF-α treatment enhanced the interaction between adiponectin and ERp44. In this study, we show that TNF-α impairs adiponectin multimerization and consequently decreases adiponectin secretion by altering disulfide bond modification in the endoplasmic reticulum. Altered adiponectin multimerization could explain declined adiponectin levels and altered distribution of adiponectin complexes in the plasma of obese insulin-resistant individuals.

Adiponectin downregulation is associated with volume overload-induced myocyte dysfunction in rats

AIM

Adiponectin has been reported to exert protective effects during pathological ventricular remodeling, but the role of adiponectin in volume overload-induced heart failure remains unclear. In this study we investigated the effect of adiponectin on cardiac myocyte contractile dysfunction following volume overload in rats.

METHODS

Volume overload was surgically induced in rats by infrarenal aorta-vena cava fistula. The rats were intravenously administered adenoviral adiponectin at 2-, 6- and 9-weeks following fistula. The protein expression of adiponectin, adiponectin receptors (AdipoR1/R2 and T-cadherin) and AMPK activity were measured using Western blot analyses. Isolated ventricular myocytes were prepared at 12 weeks post-fistula to examine the contractile performance of myocytes and intracellular Ca(2+) transient.

RESULTS

A-V fistula resulted in significant reductions in serum and myocardial adiponectin levels, myocardial adiponectin receptor (AdipoR1/R2 and T-cadherin) levels, as well as myocardial AMPK activity. Consistent with these changes, the isolated myocytes exhibited significant depression in cell shortening and intracellular Ca(2+) transient. Administration of adenoviral adiponectin significantly increased serum adiponectin levels and prevented myocyte contractile dysfunction in fistula rats. Furthermore, pretreatment of isolated myocytes with recombinant adiponectin (2.5 μg/mL) significantly improved their contractile performance in fistula rats, but had no effects in control or adenoviral adiponectin-administered rats.

CONCLUSION

These results demonstrate a positive correlation between adiponectin downregulation and volume overload-induced ventricular remodeling. Adiponectin plays a protective role in volume overload-induced heart failure.

Adiponectin as an anti-fibrotic and anti-inflammatory adipokine in the liver

Hepatic fibrosis is a dynamic process resulting from excessive deposition of extracellular matrix in the liver; uncontrolled progression of fibrosis can eventually lead to liver cirrhosis and/or hepatocellular carcinoma. The fibrogenic process is complex and modulated by a number of both hepatic and extra-hepatic biological factors. Growing evidence indicates that adipokines, a group of cytokines produced by adipose tissue, impart dynamic functions in liver and are involved in modulation of hepatic fibrosis. In particular, two key adipokines, adiponectin and leptin, directly regulate many biological responses closely associated with development and progression of hepatic fibrosis. Leptin acts as a pro-fibrogenic cytokine, while adiponectin possesses anti-fibrogenic and anti-inflammatory properties. Adiponectin, acting via its cognate receptors, adiponectin receptors 1 and 2, potently suppresses fibrosis and inflammation in liver via multiple mechanisms. This review summarizes recent findings concerning the role of adiponectin in fibrogenic process in liver and addresses the underlying molecular mechanisms in modulation of fibrosis.

Additive regulation of adiponectin expression by the mediterranean diet olive oil components oleic Acid and hydroxytyrosol in human adipocytes

Adiponectin, an adipocyte-derived insulin-sensitizing and anti-inflammatory hormone, is suppressed in obesity through mechanisms involving chronic inflammation and oxidative stress. Olive oil consumption is associated with beneficial cardiometabolic actions, with possible contributions from the antioxidant phenol hydroxytyrosol (HT) and the monounsaturated fatty acid oleic acid (OA, 18:1n-9 cis), both possessing anti-inflammatory and vasculo-protective properties. We determined the effects of HT and OA, alone and in combination, on adiponectin expression in human and murine adipocytes under pro-inflammatory conditions induced by the cytokine tumor necrosis factor(TNF)-α. We used human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes and murine 3T3-L1 adipocytes as cell model systems, and pretreated them with 1-100 μmol/L OA, 0.1-20 μmol/L HT or OA plus HT combination before stimulation with 10 ng/mL TNF-α. OA or HT significantly (P<0.05) prevented TNF-α-induced suppression of total adiponectin secretion (by 42% compared with TNF-α alone) as well as mRNA levels (by 30% compared with TNF-α alone). HT and OA also prevented-by 35%-TNF-α-induced downregulation of peroxisome proliferator-activated receptor PPARγ. Co-treatment with HT and OA restored adiponectin and PPARγ expression in an additive manner compared with single treatments. Exploring the activation of JNK, which is crucial for both adiponectin and PPARγ suppression by TNF-α, we found that HT and OA additively attenuated TNF-α-stimulated JNK phosphorylation (up to 55% inhibition). In conclusion, the virgin olive oil components OA and HT, at nutritionally relevant concentrations, have additive effects in preventing adiponectin downregulation in inflamed adipocytes through an attenuation of JNK-mediated PPARγ suppression.

Inhibitory effects of Doenjang, Korean traditional fermented soybean paste, on oxidative stress and inflammation in adipose tissue of mice fed a high-fat diet

BACKGROUND/OBJECTIVES

Doenjang, Korean traditional fermented soybean paste has been reported to have an anti-obesity effect. Because adipose tissue is considered a major source of inflammatory signals, we investigated the protective effects of Doenjang and steamed soybean on oxidative stress and inflammation in adipose tissue of diet-induced obese mice.

MATERIALS/METHODS

Male C57BL/6J mice were fed a low fat diet (LF), a high-fat diet (HF), or a high-fat containing Doenjang diet (DJ) or a high-fat containing steamed soybean diet (SS) for 11 weeks.

RESULTS

Mice fed a DJ diet showed significantly lower body and adipose tissue weights than those in the HF group. Although no significant differences in adipocyte size and number were observed among the HF diet-fed groups, consumption of Doenjang alleviated the incidence of crown-like structures in adipose tissue. Consistently, we observed significantly reduced mRNA levels of oxidative stress markers (heme oxygenase-1 and p40^phox), pro-inflammatory adipokines (tumor necrosis factor alpha and macrophage chemoattractant protein-1), macrophage markers (CD68 and CD11c), and a fibrosis marker (transforming growth factor beta 1) by Doenjang consumption. Gene expression of anti-inflammatory adipokine, adiponectin was significantly induced in the DJ group and the SS group compared to the HF group. The anti-oxidative stress and anti-inflammatory effects observed in mice fed an SS diet were not as effective as those in mice fed a DJ diet, suggesting that the bioactive compounds produced during fermentation and aging may be involved in the observed health-beneficial effects of Doenjang.

CONCLUSIONS

Doenjang alleviated oxidative stress and restored the dysregulated expression of adipokine genes caused by excess adiposity. Therefore, Doenjang may ameliorate systemic inflammation and oxidative stress in obesity via inhibition of inflammatory signals of adipose tissue.

Metabolic obesity, adipocytokines, and inflammatory markers in Asian Indians--CURES-124

AIM

This study looked at the association of adipokines, inflammatory and oxidative stress markers in subjects with the following phenotypes: metabolically healthy, nonobese (MHNO), metabolically healthy, obese (MHO), metabolically obese, nonobese (MONO), and metabolically obese, obese (MOO).

MATERIALS AND METHODS

Subjects with MHNO (n=462), MHO (n=192), MONO (n=315), and MOO (n=335) were randomly selected from the Chennai Urban Rural Epidemiology Study. Adiponectin, visfatin, resistin, high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), oxidized low-density lipoprotein (LDL), and monocyte chemoattractant protein-1 (MCP-1) were measured by enzyme-linked immunosorbent assay.

RESULTS

Levels of adiponectin were lowest in the MOO group, followed by the MONO, MHO, and the MHNO groups (P=0.042), whereas the levels of visfatin (P=0.042) and resistin (P=0.043) were highest in the MOO group, followed by the MONO, MHO, and the MHNO groups. Levels of hs-CRP (P=0.029), TNF-α (P=0.036), IL-6 (P=0.042), oxidized LDL (P=0.036), and MCP-1 (P=0.039) increased from the MHNO to MHO to MONO to MOO phenotypes. Linear regression analysis of the parameters with body mass index (BMI) and metabolic syndrome components showed that adiponectin is negatively associated with abdominal obesity (β=-0.060; P=0.039) and BMI (β=-0.076; P=0.009) and that TNF-α is negatively associated with high-density lipoprotein levels (β=0.114, P=0.049) even after adjusting for age and gender. hs-CRP (β=0.112, P=0.020) and oxidized LDL (β=0.114, P=0.050) showed a positive association with systolic blood pressure even after adjusting for age and gender.

CONCLUSIONS

The metabolically obese phenotype is characterized by altered adipokine and inflammatory profiles, which could make this phenotype at high risk for type 2 diabetes mellitus and cardiovascular diseases.

Effect of periodontal treatment on adipokines in type 2 diabetes

The association between adipokines and inflammatory periodontal diseases has been studied over the last two decades. This review was intended to explore the observation that periodontal therapy may lead to an improvement of adipokines in diabetic patients. In summary, substantial evidence suggests that diabetes is associated with increased prevalence, extent and severity of periodontitis. Numerous mechanisms have been elucidated to explain the impact of diabetes on the periodontium. However, current knowledge concerning the role of major adipokines indicates only some of their associations with the pathogenesis of periodontitis in type 2 diabetes. Conversely, treatment of periodontal disease and reduction of oral inflammation may have positive effects on the diabetic condition, although evidence for this remains somewhat equivocal.

Role of adiponectin system in insulin resistance

The knowledge of the pathogenesis of obesity and its metabolic sequelae has significantly advanced over the last few decades and adipose tissue is now considered a link between obesity and insulin resistance. Adiponectin, one of the major adipocyte-secreted proteins, has attracted scientific interest in recent years and has been extensively studied both in human and animal models. Adiponectin exerts insulin-sensitizing effects through binding to its receptors, leading to activation of AMPK, PPAR-α, and potentially other unknown molecular pathways. In obesity-linked insulin resistance, both adiponectin and adiponectin receptors are downregulated, leading to activation of signaling pathways involved in metabolism regulation. Up-regulation of adiponectin/adiponectin receptors or enhancing adiponectin receptor function may be an interesting therapeutic strategy for obesity-linked insulin resistance. In this review we will focus on the recent research related to the relationship between the adiponectin system and insulin resistance. The potential use of adiponectin or its receptor for therapeutic intervention will be also discussed.

Back to the heart: the protective role of adiponectin

Cardiovascular disease (CVD) is the leading cause of death worldwide and the prevalence of obesity and diabetes are increasing. In obesity, adipose tissue increases the secretion of bioactive mediators (adipokines) that may represent a key mechanism linking obesity to CVD. Adiponectin, extensively studied in metabolic diseases, exerts anti-diabetic, anti-atherogenic and anti-inflammatory activities. Due to these positive actions, the role of adiponectin in cardiovascular protection has been evaluated in recent years. In particular, for its potential therapeutic benefits in humans, adiponectin has become the subject of intense preclinical research. In the cardiovascular context, understanding of the cellular and molecular mechanisms underlying the adiponectin system, throughout its secretion, regulation and signaling, is critical for designing new drugs that target adiponectin system molecules. This review focused on recent advances regarding molecular mechanisms related to protective effects of the adiponectin system on both cardiac and vascular compartments and its potential use as a target for therapeutic intervention of CVD.

Adipokines and melanocortins in the hepatic manifestation of metabolic syndrome: nonalcoholic fatty liver disease

Metabolic syndrome is associated with nonalcoholic fatty liver disease and its more aggressive form, nonalcoholic steatohepatitis. Adipokines produced by white adipose tissue possess broad physiological activity and play an important autocrine role in obesity-associated complications, including metabolic syndrome, nonalcoholic fatty liver disease and cardiovascular disease. Various adipokines may have beneficial or harmful effects. Other tissues, particularly stomach and intestine, produce active molecules that can influence the function of adipocytes and, possibly, the levels of adipokine secretion. In some cases, the production sites of these molecules remain unknown. The review focuses on our current understanding of the disease-related effects of the adipokines and the melanocortins on various peripheral tissues, and discusses some of their potential interactions with each other. Potential therapeutic applications are also considered.

Potential Roles of Stevia rebaudiana Bertoni in Abrogating Insulin Resistance and Diabetes: A Review

Insulin resistance is a key factor in metabolic disorders like hyperglycemia and hyperinsulinemia, which are promoted by obesity and may later lead to Type II diabetes mellitus. In recent years, researchers have identified links between insulin resistance and many noncommunicable illnesses other than diabetes. Hence, studying insulin resistance is of particular importance in unravelling the pathways employed by such diseases. In this review, mechanisms involving free fatty acids, adipocytokines such as TNFα and PPARγ and serine kinases like JNK and IKKβ, asserted to be responsible in the development of insulin resistance, will be discussed. Suggested mechanisms for actions in normal and disrupted states were also visualised in several manually constructed diagrams to capture an overall view of the insulin-signalling pathway and its related components. The underlying constituents of medicinal significance found in the Stevia rebaudiana Bertoni plant (among other plants that potentiate antihyperglycemic activities) were explored in further depth. Understanding these factors and their mechanisms may be essential for comprehending the progression of insulin resistance towards the development of diabetes mellitus.

Role of adipokines and cytokines in obesity-associated breast cancer: therapeutic targets

Obesity is the cause of a large proportion of breast cancer incidences and mortality in post-menopausal women. In obese people, elevated levels of various growth factors such as insulin and insulin-like growth factors (IGFs) are found. Elevated insulin level leads to increased secretion of estrogen by binding to the circulating sex hormone binding globulin (SHBG). The increased estrogen-mediated downstream signaling favors breast carcinogenesis. Obesity leads to altered expression profiles of various adipokines and cytokines including leptin, adiponectin, IL-6, TNF-α and IL-1β. The increased levels of leptin and decreased adiponectin secretion are directly associated with breast cancer development. Increased levels of pro-inflammatory cytokines within the tumor microenvironment promote tumor development. Efficacy of available breast cancer drugs against obesity-associated breast cancer is yet to be confirmed. In this review, we will discuss different adipokine- and cytokine-mediated molecular signaling pathways involved in obesity-associated breast cancer, available therapeutic strategies and potential therapeutic targets for obesity-associated breast cancer.

Genistein and daidzein, typical soy isoflavones, inhibit TNF-α-mediated downregulation of adiponectin expression via different mechanisms in 3T3-L1 adipocytes

SCOPE

Previous reports suggest that soy isoflavones have multiple biological functions and may help to restore adiponectin expression and insulin sensitivity. However, little is known about whether soy isoflavones can inhibit the downregulation of adiponectin and their molecular mechanisms. In the present study, we demonstrate that genistein (Gen) or daidzein (Dai) can significantly inhibit the downregulation of adiponectin expression via unique and different molecular mechanisms.

METHODS AND RESULTS

Pretreatment with Gen or Dai significantly inhibited the tumor necrosis factor-alpha (TNF-α)-mediated downregulation of adiponectin expression in 3T3-L1 adipocytes. Gen inhibited the TNF-α-induced c-Jun-NH(2) -terminal kinase (JNK) signaling that is involved in adiponectin expression. Molecular docking studies based on JNK1 with Gen or Dai clearly supported our experimental results. However, Dai did not significantly inhibit JNK signaling. Dai did, however, inhibit the TNF-α-induced downregulation of forkhead box-containg protein O1, which is also involved in adiponectin expression.

CONCLUSION

These data demonstrate that: (i) both Gen and Dai significantly inhibit the TNF-α-mediated downregulation of adiponectin in adipocytes; (ii) Gen is an effective inhibitor of JNK activation, thus inhibiting the TNF-α-mediated downregulation of adiponectin; and (iii) Dai can inhibit the downregulation of adiponectin by restoring the TNF-α-mediated reduction of forkhead box-containg protein O1 protein expression.

Cellular cross-talk between epicardial adipose tissue and myocardium in relation to the pathogenesis of cardiovascular disease

Epicardial and perivascular fat depot size is considered an index of cardiac and visceral obesity. The functional and anatomic proximity of epicardial adipose tissue (EAT) to myocardium has drawn increasing attention in recent years among researchers attempting to elucidate its putative role as an endocrine organ. This includes the role of EAT as a lipid storing depot and as an inflammatory tissue secreting cytokines and chemokines under pathogenic conditions such as cardiovascular diseases. In this review, we discuss the current state of knowledge regarding the potential EAT mediators of inflammation and the paracrine cross-talk between EAT and the underlying myocardium. We also highlight the most recent findings on the causes and correlates of myocardial steatosis/cardiac lipotoxicity and its association with cardiac dysfunction.

Hypoadiponectinaemia in diabetes mellitus type 2: molecular mechanisms and clinical significance

1. This review focuses on the regulatory mechanisms of adiponectin (APN) gene expression during physiologic conditions and both the clinical significance and underlying molecular mechanisms of hypoadiponectinaemia during pathologic conditions. 2. Adiponectin is a versatile cardiovascular protective factor. It plays an important role in regulating insulin sensitivity and energy homeostasis, with anti-inflammatory and anti-atherosclerotic properties. 3. Adiponectin gene expression is downregulated in both obesity and diabetes mellitus type 2. Hypoadiponectinaemia is an independent risk factor for coronary artery disease in type 2 diabetic patients. 4. Exogenous supplementation of recombinant APN attenuates insulin resistance, improving metabolic disorders. Therefore, APN-targeted pharmaceutical strategies increasing circulating APN levels may be therapeutic against type 2 diabetes. 5. There is great value in elucidating the regulatory mechanisms of APN gene expression during physiologic and pathologic conditions. APN biosynthesis regulation includes transcriptional expression and post-translational modification, oligomerization, and secretion. Under pathological conditions, including obesity and diabetes mellitus type 2, hypoxia, oxidative stress, and inflammation suppress APN mRNA levels and its secretion.

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.

γ-Tocotrienol attenuates TNF-α-induced changes in secretion and gene expression of MCP-1, IL-6 and adiponectin in 3T3-L1 adipocytes

Tocotrienols, members of the vitamin E family, have been shown to possess anti-inflammatory properties and display activity against a variety of chronic diseases, such as cancer, cardiovascular and neurological diseases. However, whether tocotrienols contribute to the prevention of inflammatory responses in adipose tissue remains to be elucidated. In this study, we examined the effects of γ-tocotrienol, the most common tocotrienol isomer, on tumor necrosis factor-α (TNF-α)-induced inflammatory responses by measuring the expression of the adipokines, monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and adiponectin in 3T3-L1 adipocytes. Exposure to TNF-α (10 ng/ml) for 24 h increased MCP-1 and IL-6 secretion, and decreased adiponectin secretion and peroxisome proliferator-activated receptor-γ (PPARγ) mRNA expression. γ-tocotrienol effectively improved the TNF-α-induced adverse changes in MCP-1, IL-6 and adiponectin secretion, and in MCP-1, IL-6, adiponectin and PPARγ mRNA expression. Furthermore, TNF-α-mediated IκB-α phosphorylation and nuclear factor-κB (NF-κB) activation were significantly suppressed by the γ-tocotrienol treatment. Our results suggest that γ-tocotrienol may improve obesity-related functional abnormalities in adipocytes by attenuating NF-κB activation and the expression of inflammatory adipokines.

Screening for adiponectin secretion regulators

Adiponectin is an adipokine secreted from adipocytes and plays important roles in the suppression of metabolic syndromes that can result in type 2 diabetes, obesity, and atherosclerosis. Adiponectin is a promising drug target because a number of studies have shown that upregulation of adiponectin has a number of therapeutic benefits. Extensive efforts have revealed various adiponectin regulators, such as cytokines, transcription factors, and drugs. Cytokines, such as tumor necrosis factor α, IL-6, and IL-18, downregulate adiponectin production. On the other hand, transcription factors such as peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT-enhancer-binding protein α, and forkhead box O1 (FoxO1) upregulate adiponectin expression, although the activating transcription factor 3 and cAMP response element-binding protein downregulate it. Although a number of therapeutic drugs have been reported as adiponectin secretion regulators, most of them act through PPARγ-dependent mechanisms, leaving PPARγ-derived side effects as a concern. Using high-throughput screening, we have identified PPARγ-independent adiponectin secretion regulators as potential drug candidates with a novel mechanism of action.

Adiponectin and PPARγ: cooperative and interdependent actions of two key regulators of metabolism

The recent advances in the understanding of adiponectin and other adipokines have highlighted the role of adipose tissue as an active endocrine organ. One of the central regulators of adipocyte biology is peroxisome proliferator-activated receptor gamma (PPARγ), a transcription factor that induces the adipogenic gene expression program during development, promotes adipose remodeling, and regulates the functions of adipocytes in lipid storage, adipokine secretion, and energy homeostasis. Activation of PPARγ results in increased insulin sensitivity in skeletal muscle and liver and improves the secretory profile of adipose tissue, favoring release of insulin-sensitizing adipokines, such as adiponectin, and reducing inflammatory cytokines. Increased adiponectin production is likely a significant mediator of the systemic effects of PPARγ activation. This chapter will review the interplay between PPARγ and adiponectin in regulating metabolism, presenting evidence that PPARγ regulates adiponectin gene expression, processing, and secretion and that the two proteins have overlapping effects on downstream metabolic pathways.

Clodronate liposomes improve metabolic profile and reduce visceral adipose macrophage content in diet-induced obese mice

Background

Obesity-related adipose inflammation has been thought to be a causal factor for the development of insulin resistance and type 2 diabetes. Infiltrated macrophages in adipose tissue of obese animals and humans are an important source for inflammatory cytokines. Clodronate liposomes can ablate macrophages by inducing apoptosis. In this study, we aim to determine whether peritoneal injection of clodronate liposomes has any beneficial effect on systemic glucose homeostasis/insulin sensitivity and whether macrophage content in visceral adipose tissue will be reduced in diet-induced obese (DIO) mice.

Methodology/Principal Findings

Clodronate liposomes were used to deplete macrophages in lean and DIO mice. Macrophage content in visceral adipose tissue, metabolic parameters, glucose and insulin tolerance, adipose and liver histology, adipokine and cytokine production were examined. Hyperinsulinemic-euglycemic clamp study was also performed to assess systemic insulin sensitivity. Peritoneal injection of clodronate liposomes significantly reduced blood glucose and insulin levels in DIO mice. Systemic glucose tolerance and insulin sensitivity were mildly improved in both lean and DIO mice treated with clodronate liposomes by intraperitoneal (ip) injection. Hepatosteatosis was dramatically alleviated and suppression of hepatic glucose output was markedly increased in DIO mice treated with clodronate liposomes. Macrophage content in visceral adipose tissue of DIO mice was effectively decreased without affecting subcutaneous adipose tissue. Interestingly, levels of insulin sensitizing hormone adiponectin, including the high molecular weight form, were significantly elevated in circulation.

Conclusions/Significance

Intraperitoneal injection of clodronate liposomes reduces visceral adipose tissue macrophages, improves systemic glucose homeostasis and insulin sensitivity in DIO mice, which can be partially attributable to increased adiponectin levels.

Pentamethylquercetin improves adiponectin expression in differentiated 3T3-L1 cells via a mechanism that implicates PPARγ together with TNF-α and IL-6

Adiponectin is an adipocyte-derived hormone that plays a pivotal role in the regulation of lipid and glucose metabolism. Up-regulation of adiponectin expression and production has been shown to benefit for metabolic disorders, including type 2 diabetes, hyperlipidemia, etc. The present study investigated whether the novel polymethoxylated flavonoid pentamethylquercetin (PMQ), a member of polymethoxylated flavonoids family which is present in seabuckthorn (Hippophae L.) would affect adiponectin production in differentiated 3T3-L1 adipocytes. It was found that PMQ increased the adiponectin mRNA and protein expressions in adipocytes in time- and concentration-dependent manners. The PPARγ pathway plays a important roles in this effect of PMQ because blockade of PPARγ by GW9662 eliminates the PMQ-induced up-regulation of adiponectin expression. Furthermore, significant decreases of mRNA expression and secretion of TNF-α and IL-6 were also observed in PMQ-treated cells. Taken together, our study demonstrated that PMQ up-regulates adiponectin expression via a mechanism that implicates PPARγ together with TNF-α and IL-6, suggesting that PMQ might be a potential candidate for the treatment of metabolic diseases.

Brazilian propolis-derived components inhibit TNF-α-mediated downregulation of adiponectin expression via different mechanisms in 3T3-L1 adipocytes

BACKGROUND

Previous reports suggest that Brazilian propolis has multiple biological functions and may help to restore adiponectin expression and insulin sensitivity. However, little is known about the molecular mechanisms by which these compounds inhibit the downregulation of adiponectin.

METHODS

The effect of various Brazilian propolis-derived components on inhibition of tumor necrosis factor-α (TNF-α)-mediated downregulation of adiponectin expression in 3T3-L1 adipocytes and molecular mechanism was investigated.

RESULTS AND CONCLUSIONS

Pretreatment with either artepillin C (C3) or its derivative (C4) significantly inhibited TNF-α-mediated downregulation of adiponectin expression in 3T3-L1 adipocytes. Interestingly, C3 strongly activated peroxisome proliferator-activated receptor γ (PPARγ) transcriptional activity. Treatment of adipocytes with C3 resulted in the upregulation of adiponectin and fatty acid-binding protein 4 expression, but C4 did not significantly induce PPARγ transactivation. C4 did, however, inhibit the TNF-α-induced c-Jun-NH(2)-terminal kinase (JNK) signaling that is involved in adiponectin expression. Molecular docking studies based on hPPARγ with C3 and JNK1 with C4 clearly supported our experimental results. These data demonstrate that 1) both C3 and C4 significantly inhibit the TNF-α-mediated downregulation of adiponectin in adipocytes, 2) C3 functions as a PPARγ agonist, and its inhibition of the effect of TNF-α is due to this PPARγ transactivation, and 3) C4 is an effective inhibitor of JNK activation, thus inhibiting the TNF-α-mediated downregulation of adiponectin.

GENERAL SIGNIFICANCE

Brazilian propolis-derived components (C3 and C4) can significantly inhibit TNF-α-mediated downregulation of adiponectin in adipocytes, although they do so via different mechanisms.

Reduced plasma adiponectin levels relative to oxidized low density lipoprotein and nitric oxide in coronary artery disease patients

INTRODUCTION

Adiponectin is a circulating hormone that is produced exclusively by adipocytes and has antiinflammatory and anti-atherogenic properties. The hypothesis that there are differences in adiponectin levels between stable and unstable coronary-artery disease patients remains controversial. Furthermore, the potential relationships between the plasma adiponectin level and the inflammatory and non-inflammatory markers (oxidized low density lipoprotein and nitric oxide) in patients with stable and unstable coronary-artery disease relative to normal subjects have not been assessed.

OBJECTIVES

To assess whether plasma adiponectin levels differ among patients with stable and unstable coronary-artery disease and among control subjects, and to correlate plasma adiponectin level with inflammatory and clinical risk factors (such as oxidized-LDL and nitric oxide) in these patients.

METHODS

This study included 50 control subjects, 50 stable angina patients and 50 unstable angina patients with angiographically documented coronary-artery disease. Plasma adiponectin and oxidized-LDL levels were determined using an enzyme immunoassay. Plasma nitric oxide, high sensitivity C-reactive protein and lipid profile levels were also measured.

RESULTS

Plasma adiponectin levels were lower in the unstable angina patients (4.9 ± 1.30 µg/mL) than in the stable angina patients (6.34 ± 1.0 µg/mL) or in the controls (9.25 ± 1.8 µg/mL); these levels were also significantly lower in stable angina patients versus controls (p<0.001). Plasma adiponectin levels were negatively correlated with oxidized-LDL, high sensitivity C-reactive protein, lipid profile and other clinical risk factors but positively correlated with nitric oxide.

CONCLUSION

Plasma adiponectin levels were found to be lower in both stable and unstable angina patients relative to control subjects, and the correlation between plasma adiponectin and cardiovascular markers is weakened in these patients.

The effect of hypoxia mimetic cobalt chloride on the expression of EC-SOD in 3T3-L1 adipocytes

It is well known that adipose tissue is not only a passive reservoir for energy storage but also produces and secretes a variety of bioactive molecules called adipocytokines, including adiponectin and tumor necrosis factor-alpha (TNF-alpha). Recently, it has been reported that adipose tissue can suffer a chronic hypoxic condition during hypertrophy of adipocytes, and this condition leads to the dysregulation of adipocytokines. Further, hypoxic adipocytes are in an increased oxidative stress. Extracellular-superoxide dismutase (EC-SOD) is an anti-inflammatory enzyme that protects cells from reactive oxygen species (ROS) by scavenging superoxide anion. Previous reports showed that plasma EC-SOD levels in type 2 diabetes patients were significantly and inversely related to the body mass index, homeostasis model assessment-insulin resistance index; however, the mechanisms of EC-SOD and adiponectin reductions during hypoxia remain poorly understood. Here, we demonstrate that cobalt chloride (CoCl(2)), a hypoxia mimetic, decreases EC-SOD and adiponectin in 3T3-L1 adipocytes by intracellular ROS-independent, but TNF-alpha and c-jun N-terminal kinase (JNK)-dependent mechanisms. From these results, it is possible that TNF-alpha is a key regulator of the reduction of EC-SOD and adiponectin in CoCl(2)-treated 3T3-L1 adipocytes, and we speculated that the reduction of EC-SOD and adiponectin would lead to and/or promote metabolic disorders.

Coronary and aortic endothelial function affected by feedback between adiponectin and tumor necrosis factor α in type 2 diabetic mice

OBJECTIVE

To verify that adiponectin and tumor necrosis factor (TNF)-α reciprocally regulate their expression, thereby synergistically affecting both coronary and aortic endothelial dysfunction in type 2 diabetic mice.

METHODS AND RESULTS

We examined endothelium-dependent and endothelium-independent vasodilation/vasorelaxation of coronary arterioles and aortas in control mice, diabetic mice (Lepr(db)), and Lepr(db) treated with adiponectin or neutralizing antibody to TNF-α (anti-TNF-α). Endothelium-dependent vasodilation to acetylcholine in both coronary arterioles and aortas was blunted in Lepr(db) compared with control mice. Endothelium-independent vasodilation to sodium nitroprusside was comparable. Adiponectin and anti-TNF-α improved acetylcholine-induced vasodilation of coronary arterioles and aortas in Lepr(db) without affecting dilator response to sodium nitroprusside. Adiponectin protein expression was significantly reduced, and TNF-α protein expression was significantly greater, in coronary arterioles and aortas of Lepr(db) compared with control mice. Immunofluorescence staining results indicate that adiponectin was colocalized with endothelial cells. Anti-TNF-α treatment upregulated adiponectin protein expression in Lepr(db) coronary arterioles and aortas. Adiponectin administration reduced TNF-α protein expression in Lepr(db). Although adiponectin receptor 1 protein expression in coronary arterioles and aortas was similar between control and diabetic mice, adiponectin receptor 2 protein expression was significantly reduced in Lepr(db). Both adiponectin and anti-TNF-α inhibited IκBα phosphorylation and nuclear factor κB protein expression in Lepr(db), suggesting that adiponectin and TNF-α signaling may converge on nuclear factor κB to reciprocally regulate their expression.

CONCLUSIONS

A reciprocal suppression occurs between adiponectin and TNF-α that fundamentally affects the regulation of coronary and aortic endothelial function in type 2 diabetic mice.

Adiponectin and breast cancer

Adiponectin, an adipose tissue-derived hormone, has been studied intensively for the past decade because of its anti-inflammatory, anti-atherogenic, and anti-diabetic properties. Recent advances suggest that adiponectin also plays an important role in the development and progression of various cancers, especially obesity-related cancers. In this review, the authors focus on the potential role of adiponectin in breast cancer, an obesity- and endocrine-associated tumor. Epidemiological studies have shown that plasma adiponectin level is a risk factor for breast cancer in post-menopausal women. Adiponectin and its receptors are expressed on both breast cancer line cells and tumor tissues. Furthermore, exogenous adiponectin has exhibited therapeutic potential in animal models. Underlying mechanisms include the inhibition of cell proliferation and promotion of apoptosis, the regulation of tumorigenic-related factors, and the suppression of angiogenesis. The signaling pathways linking adiponectin with tumorigenesis might provide potential drug targets for the future. However, more convincing evidence is needed to fully elucidate the exact role of adiponectin in breast cancer, since both its beneficial effects and possible mechanisms remain controversial.