Glucocorticoids and thiazolidinediones interfere with adipocyte-mediated macrophage chemotaxis and recruitment

Glucocorticoids increase adiposity by stimulating Krüppel-like factor 9 expression in macrophages

The mechanisms underlying glucocorticoid (GC)-induced obesity are poorly understood. Macrophages are the primary targets by which GCs exert pharmacological effects and perform critical functions in adipose tissue homeostasis. Here, we show that macrophages are essential for GC-induced obesity. Dexamethasone (Dex) strongly induced Krüppel-like factor 9 (Klf9) expression in macrophages. Similar to Dex, lentivirus-mediated Klf9 overexpression inhibits M1 and M2a markers expression, causing macrophage deactivation. Furthermore, the myeloid-specific Klf9 transgene promotes obesity. Conversely, myeloid-specific Klf9-knockout (mKlf9KO) mice are lean. Moreover, myeloid Klf9 knockout largely blocks obesity induced by chronic GC treatment. Mechanistically, GC-inducible KLF9 recruits the SIN3A/HDAC complex to the promoter regions of Il6, Ptgs2, Il10, Arg1, and Chil3 to inhibit their expression, subsequently reducing thermogenesis and increasing lipid accumulation by inhibiting STAT3 signaling in adipocytes. Thus, KLF9 in macrophages integrates the beneficial anti-inflammatory and adverse metabolic effects of GCs and represents a potential target for therapeutic interventions.

Salicylate Sodium Suppresses Monocyte Chemoattractant Protein-1 Production by Directly Inhibiting Phosphodiesterase 3B in TNF-α-Stimulated Adipocytes

As a worldwide health issue, obesity is associated with the infiltration of monocytes/macrophages into the adipose tissue causing unresolved inflammation. Monocyte chemoattractant protein-1 (MCP-1) exerts a crucial effect on obesity-related monocytes/macrophages infiltration. Clinically, aspirin and salsalate are beneficial for the treatment of metabolic diseases in which adipose tissue inflammation plays an essential role. Herein, we investigated the effect and precise mechanism of their active metabolite salicylate on TNF-α-elevated MCP-1 in adipocytes. The results indicated that salicylate sodium (SAS) could lower the level of MCP-1 in TNF-α-stimulated adipocytes, which resulted from a previously unrecognized target phosphodiesterase (PDE), 3B (PDE3B), rather than its known targets IKKβ and AMPK. The SAS directly bound to the PDE3B to inactivate it, thus elevating the intracellular cAMP level and activating PKA. Subsequently, the expression of MKP-1 was increased, which led to the decrease in p-EKR and p-p38. Both PDE3B silencing and the pharmacological inhibition of cAMP/PKA compromised the suppressive effect of SAS on MCP-1. In addition to PDE3B, the PDE3A and PDE4B activity was also inhibited by SAS. Our findings identify a previously unrecognized pathway through which SAS is capable of attenuating the inflammation of adipocytes.

FK506 binding protein 51: Its role in the adipose organ and beyond

There is a great body of evidence that the adipose organ plays a central role in the control not only of energy balance, but importantly, in the maintenance of metabolic homeostasis. Interest in the study of different aspects of its physiology grew in the last decades due to the pandemic of obesity and the consequences of metabolic syndrome. It was not until recently that the first evidence for the role of the high molecular weight immunophilin FK506 binding protein (FKBP) 51 in the process of adipocyte differentiation have been described. Since then, many new facets have been discovered of this stress-responsive FKBP51 as a central node for precise coordination of many cell functions, as shown for nuclear steroid receptors, autophagy, signaling pathways as Akt, p38 MAPK, and GSK3, as well as for insulin signaling and the control of glucose homeostasis. Thus, the aim of this review is to integrate and discuss the recent advances in the understanding of the many roles of FKBP51 in the adipose organ.

Fresh insights into glucocorticoid-induced diabetes mellitus and new therapeutic directions

Glucocorticoid hormones were discovered to have use as potent anti-inflammatory and immunosuppressive therapeutics in the 1940s and their continued use and development have successfully revolutionized the management of acute and chronic inflammatory diseases. However, long-term use of glucocorticoids is severely hampered by undesirable metabolic complications, including the development of type 2 diabetes mellitus. These effects occur due to glucocorticoid receptor activation within multiple tissues, which results in inter-organ crosstalk that increases hepatic glucose production and inhibits peripheral glucose uptake. Despite the high prevalence of glucocorticoid-induced hyperglycaemia associated with their routine clinical use, treatment protocols for optimal management of the metabolic adverse effects are lacking or underutilized. The type, dose and potency of the glucocorticoid administered dictates the choice of hypoglycaemic intervention (non-insulin or insulin therapy) that should be provided to patients. The longstanding quest to identify dissociated glucocorticoid receptor agonists to separate the hyperglycaemic complications of glucocorticoids from their therapeutically beneficial anti-inflammatory effects is ongoing, with selective glucocorticoid receptor modulators in clinical testing. Promising areas of preclinical research include new mechanisms to disrupt glucocorticoid signalling in a tissue-selective manner and the identification of novel targets that can selectively dissociate the effects of glucocorticoids. These research arms share the ultimate goal of achieving the anti-inflammatory actions of glucocorticoids without the metabolic consequences.

Effects of Early-Life Stress, Postnatal Diet Modulation and Long-Term Western-Style Diet on Peripheral and Central Inflammatory Markers

Early-life stress (ES) exposure increases the risk of developing obesity. Breastfeeding can markedly decrease this risk, and it is thought that the physical properties of the lipid droplets in human milk contribute to this benefit. A concept infant milk formula (IMF) has been developed that mimics these physical properties of human milk (Nuturis®, N-IMF). Previously, we have shown that N-IMF reduces, while ES increases, western-style diet (WSD)-induced fat accumulation in mice. Peripheral and central inflammation are considered to be important for obesity development. We therefore set out to test the effects of ES, Nuturis® and WSD on adipose tissue inflammatory gene expression and microglia in the arcuate nucleus of the hypothalamus. ES was induced in mice by limiting the nesting and bedding material from postnatal day (P) 2 to P9. Mice were fed a standard IMF (S-IMF) or N-IMF from P16 to P42, followed by a standard diet (STD) or WSD until P230. ES modulated adipose tissue inflammatory gene expression early in life, while N-IMF had lasting effects into adulthood. Centrally, ES led to a higher microglia density and more amoeboid microglia at P9. In adulthood, WSD increased the number of amoeboid microglia, and while ES exposure increased microglia coverage, Nuturis® reduced the numbers of amoeboid microglia upon the WSD challenge. These results highlight the impact of the early environment on central and peripheral inflammatory profiles, which may be key in the vulnerability to develop metabolic derangements later in life.

Cardiovascular and metabolic risk factors in patients with subclinical Cushing

PURPOSE

Adrenal incidentalomas (AI) are discovered after work-up unrelated to adrenal gland diseases; up to 30% of AI show subclinical endogenous cortisol excess (SH), frequently associated to hypertension, obesity, metabolic disorders and increased incidence of cardiovascular events (CVEs).

METHODS

We analysed 628 AI patients divided into two groups: 471 non-functional adrenal adenoma (NFA) and 157 SH. All patients underwent complete examinations, 24-h ambulatory blood pressure monitoring, biohumoral parameters and vascular damage markers, such as c-IMT and ankle brachial index. After long-term follow-up, we registered newly onset of CVEs such as myocardial infarction (MI), percutaneous stenting and surgical bypass (PTA/CABG), stroke, overall/cardiovascular mortality. Moreover, SH patients underwent to surgical (SSH) or pharmacological treatment (MSH).

RESULTS

SH patients showed higher prevalence of metabolic syndrome, diabetes mellitus, and previous CVEs respect NFA at baseline. After follow-up MSH group showed higher recurrence of major CV events compared with NFA and SSH (RR 2.27 MSH vs NFA for MI; RR 2.30 MSH vs NFA for PTA/CABG; RR 2.41 MSH vs NFA for stroke). In SSH there was a significant reduction of the number of antihypertensive medications needed to reach target blood pressure levels (2.3 ± 1.0 to 1.5 ± 0.4 drugs). None differences were found in SH patients, distinguished in relation to cortisol plasma levels after dexamethasone suppression test (1.8-5 µg/dL, above 5 µg/dL).

CONCLUSIONS

SH is linked to relevant cardiovascular and metabolic alterations, leading to worsen clinical outcomes. In eligible patients, adrenalectomy is valid and safe option to treat SH, reducing cardiometabolic abnormalities.

Fibroblast growth factor 1 ameliorates adipose tissue inflammation and systemic insulin resistance via enhancing adipocyte mTORC2/Rictor signal

Obesity‐induced activation and proliferation of resident macrophages and infiltration of circulating monocytes in adipose tissues contribute to adipose tissue inflammation and insulin resistance. These effects further promote the development of metabolic syndromes, such as type 2 diabetes, which is one of the most prevalent health conditions severely threatening human health worldwide. Our study examined the potential molecular mechanism employed by fibroblast growth factor 1 (FGF1) to improve insulin sensitivity. The leptin receptor‐deficient obese mice (db/db) served as an insulin‐resistant model. Our results demonstrated that FGF1‐induced amelioration of insulin resistance in obese mice was related to the decreased levels of pro‐inflammatory adipose tissue macrophages (ATMs) and plasma inflammatory factors. We found that FGF1 enhanced the adipocyte mTORC2/Rictor signalling pathway to inhibit C‐C chemokine ligand 2 (CCL2) production, the major cause of circulating monocytes infiltration, activation and proliferation of resident macrophages in adipose tissues. Conversely, these alleviating effects of FGF1 were substantially abrogated in adipocytes with reduced expression of mTORC2/rictor. Furthermore, a model of adipocyte‐specific mTORC2/Rictor‐knockout (AdRiKO) obese mice was developed to further understand the in vitro result. Altogether, these results demonstrated adipocyte mTORC2/Rictor was a crucial target for FGF1 function on adipose tissue inflammation and insulin sensitivity.

α-Mangostin remodels visceral adipose tissue inflammation to ameliorate age-related metabolic disorders in mice

Low-grade chronic adipose tissue inflammation contributes to the onset and development of aging-related insulin resistance and type 2 diabetes. In the current study, α-mangostin, a xanthone isolated from mangosteen (Garcinia mangostana), was identified to ameliorate lipopolysaccharides-induced acute adipose tissue inflammation in mice, by reducing the expression of pro-inflammatory cytokines and chemokines. In a cohort of young (3 months) and old (18-20 months) mice, α-mangostin mitigated aging-associated adiposity, hyperlipidemia, and insulin resistance. Further study showed that α-mangostin alleviated aging-related adipose tissue inflammation by reducing macrophage content and shifting pro-inflammatory macrophage polarization. Moreover, α-mangostin protected the old mice against liver injury through suppressing the secretion of microRNA-155-5p from macrophages. The above results demonstrated that α-mangostin represents a new scaffold to alleviate adipose tissue inflammation, which might be a novel candidate to treat aging-related metabolic disorders.

Increased oxidative stress, inflammation and fibrosis in perirenal adipose tissue of patients with cortisol-producing adenoma

Although much is known about that corticosteroids affect the functions of adipose tissues, little genetic information is available for perirenal adipose tissue (peri-N) from patients with cortisol-producing adenoma (CPA). We conducted microarray analysis of peri-N from patients with CPA by using an Affymetrix human U133 plus 2.0 array. We also analysed the inflammation, fibrosis and oxidative stress in vitro. Compared with normotension (NT) group, CPA group has significantly higher protein levels of TNFα, IL-6, fibronectin (FN) and collagen I (COLI). The protein level of NADPH oxidase 4 (Nox4) significantly increased, while nuclear factor erythroid 2-related factor 2 (Nrf2) and hemeoxygenase-1 (HO-1) levels were significantly reduced in the CPA group. Dexamethasone markedly induced fibrosis and adipogenesis-related gene expression in predifferentiated stromal vascular fraction (SVF) cells, 3T3-L1 preadipocytes and brown preadipocytes. Chronic exposure to endogenous glucocorticoids due to CPA increases peri-N oxidative stress, inflammation and fibrosis, which may contribute to the metabolic disturbances associated with hypercortisolism in these patients.

The Therapeutic Role of Xenobiotic Nuclear Receptors Against Metabolic Syndrome

BACKGROUND

Diabetes, with an increased prevalence and various progressive complications, has become a significant global health challenge. The concrete mechanisms responsible for the development of diabetes still remain incompletely unknown, although substantial researches have been conducted to search for the effective therapeutic targets. This review aims to reveal the novel roles of Xenobiotic Nuclear Receptors (XNRs), including the Peroxisome Proliferator-Activated Receptor (PPAR), the Farnesoid X Receptor (FXR), the Liver X Receptor (LXR), the Pregnane X Receptor (PXR) and the Constitutive Androstane Receptor (CAR), in the development of diabetes and provide potential strategies for research and treatment of metabolic diseases.

METHODS

We retrieved a large number of original data about these five XNRs and organized to focus on their recently discovered functions in diabetes and its complications.

RESULTS

Increasing evidences have suggested that PPAR, FXR, LXR ,PXR and CAR are involved in the development of diabetes and its complications through different mechanisms, including the regulation of glucose and lipid metabolism, insulin and inflammation response and related others.

CONCLUSION

PPAR, FXR, LXR, PXR, and CAR, as the receptors for numerous natural or synthetic compounds, may be the most effective therapeutic targets in the treatment of metabolic diseases.

Chronodisruption, Metabolic Homeostasis, and the Regulation of Inflammation in Adipose Tissues

Molecular circadian clocks align daily behavioral and metabolic rhythms with the external day-night cycle. Priming energy metabolism for recurring changes on a 24-hour basis, these clocks are deeply interlinked with metabolic homeostasis and health. Circadian rhythm disruptions, as occurring in shift work or sleep disorders, are often accompanied by metabolic disturbances - from the promotion of overweight and type-2 diabetes to the development of the metabolic syndrome. An important indicator of the adverse outcomes of overweight seems to be a systemic low-grade inflammation which is initially observed in adipose tissues and is promoted by circadian misalignment. Interestingly, the genetic disruption of circadian clocks in rodents leads to metabolic dysregulations very comparable to what is observed in shift workers and with the development of tissue specific clock gene knockout mice, the importance of single-tissue clocks for the metabolic regulation was further deciphered. In this review, we summarize the current knowledge on the role of mistimed behavior in metabolic health and outline behavioral interventions aiming at reducing the metabolic ramifications of chronodisruption.

Adipose glucocorticoid action influences whole-body metabolism via modulation of hepatic insulin action

The connection between adipose glucocorticoid action and whole-body metabolism is incompletely understood. Thus, we generated adipose tissue-specific glucocorticoid receptor-knockout (Ad-GcR^-/-) mice to explore potential mechanisms. Ad-GcR^-/- mice had a lower concentration of fasting plasma nonesterified fatty acids and less hepatic steatosis. This was associated with increased protein kinase B phosphorylation and increased hepatic glycogen synthesis after an oral glucose challenge. High-fat diet (HFD)-fed Ad-GcR^-/- mice were protected against the development of hepatic steatosis and diacylglycerol-PKCε-induced impairments in hepatic insulin signaling. Under hyperinsulinemic-euglycemic conditions, hepatic insulin response was ∼10-fold higher in HFD-fed Ad-GcR^-/- mice. Insulin-mediated suppression of adipose lipolysis was improved by 40% in Ad-GcR^-/- mice. Adipose triglyceride lipase expression was decreased and insulin-mediated perilipin dephosphorylation was increased in Ad-GcR^-/- mice. In metabolic cages, food intake decreased by 3 kcal/kg per hour in Ad-GcR^-/- mice. Therefore, physiologic adipose glucocorticoid action appears to drive hepatic lipid accumulation during stressors such as fasting. The resultant hepatic insulin resistance prevents hepatic glycogen synthesis, preserving glucose for glucose-dependent organs. Absence of adipose glucocorticoid action attenuates HFD-induced hepatic insulin resistance; potential explanations for reduction in hepatic steatosis include reductions in adipose lipolysis and food intake.-Abulizi, A., Camporez, J.-P., Jurczak, M. J., Høyer, K. F., Zhang, D., Cline, G. W., Samuel, V. T., Shulman, G. I., Vatner, D. F. Adipose glucocorticoid action influences whole-body metabolism via modulation of hepatic insulin action.

Adipocyte Glucocorticoid Receptor Deficiency Promotes Adipose Tissue Expandability and Improves the Metabolic Profile Under Corticosterone Exposure

Widely used for their anti-inflammatory and immunosuppressive properties, glucocorticoids are nonetheless responsible for the development of diabetes and lipodystrophy. Despite an increasing number of studies focused on the adipocyte glucocorticoid receptor (GR), its precise role in the molecular mechanisms of these complications has not been elucidated. In keeping with this goal, we generated a conditional adipocyte-specific murine model of GR invalidation (AdipoGR knockout [KO] mice). Interestingly, when administered a corticosterone treatment to mimic hypercorticism conditions, AdipoGR-KO mice exhibited an improved glucose tolerance and insulin sensitivity. This was related to the adipose-specific activation of the insulin-signaling pathway, which contributed to fat mass expansion, as well as a shift toward an anti-inflammatory macrophage polarization in adipose tissue of AdipoGR-KO animals. Moreover, these mice were protected against ectopic lipid accumulation in the liver and displayed an improved lipid profile, contributing to their overall healthier phenotype. Altogether, our results indicate that adipocyte GR is a key factor of adipose tissue expansion and glucose and lipid metabolism control, which should be taken into account in the further design of adipocyte GR-selective modulators.

Glucocorticoid-induced insulin resistance is related to macrophage visceral adipose tissue infiltration

Insulin resistance is frequently present in patients with glucocorticoid (GC) excess (Cushing's syndrome) or treated with high doses of GCs. Furthermore, others similarities between metabolic syndrome (visceral obesity, elevated blood glucose levels, dyslipidemia) and Cushing's syndrome suggest that GCs could play a role in obesity-linked complications. Here we reported that long-term corticosterone (CORT) exposure in mice induced weight gain, dyslipidemia as well as hyperglycaemia and systemic insulin resistance. CORT-treated mice exhibited an increased 11β-Hsd1 expression and corticosterone levels in fat depots but a specific upregulation of glucocorticoid receptor (Gr) and hexose-6-phosphate dehydrogenase only in gonadal adipose tissue, suggesting that GC could act differentially on various fat depots. Despite fat accumulation in all depots, an increased expression of adipogenic (Pparγ, C/ebpα) and lipogenic (Acc, Fas) key genes was restricted to gonadal adipose tissue. Hypertrophied adipocytes observed in both visceral and subcutaneous depots also resulted from reduced lipolytic activity due to CORT treatment. Surprisingly, GC treatment promoted macrophage infiltration (F4/80, Cd68) within all adipose tissues along with predominant M2-like macrophage phenotype, and can directly act on macrophages to induce this phenotype. Moreover, macrophage infiltration preceded mass gain and adipocyte hypertrophy. Of note, specific macrophage depletion in gonadal fat preferentially reduced the M2-like macrophage content, and partially restored insulin sensitivity in mice with GC-induced obesity and insulin resistance. These data provide evidence that GCs act on adipose tissue in a depot-dependent manner and that gonadal adipose macrophages are key effectors of GC-associated insulin resistance.

Multigenerational effects of dietary macronutrient intake on the metabolic phenotype of male Wistar rats

OBJECTIVES

Gene-nutrient interactions are implicated in metabolic phenotypes like metabolic syndrome. The aim of this study was to examine the effects of diet-induced metabolic phenotypes in rats and investigate the effects of these phenotypes in three successive generations.

METHODS

Three generations of rats were fed on different diets and mated. Blood glucose, adiposity, lipid profile, insulin, adipocytokines, ghrelin, and corticosterone concentrations were determined in F0, F1, and F2 generations using standard methods.

RESULTS

In comparison with control across generations, glucose (32%), triacylglycerols (52%), and insulin (10%) were significantly elevated in the high-fat diet (HFD)-fed rats; total cholesterol was higher in HFD and high-carbohydrate diet (HCD)-fed groups; whereas high density lipoprotein was higher in the HFD rats but lower in the HPD rats. Adipocytokines were significantly higher in the HCD and HFD groups but lower in the high-protein diet group, whereas ghrelin only declined in HFD rats.

CONCLUSION

This study revealed that different dietary macronutrients induced distinctive metabolic phenotypes, which had variable effects in different generations.

Impact of MR on mature adipocytes in high-fat/high-sucrose diet-induced obesity

Active glucocorticoid levels are elevated in the adipose tissue of obesity due to the enzyme 11 beta-hydroxysteroid dehydrogenase type 1. Glucocorticoids can bind and activate both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), and pharmacological blockades of MR prevent high-fat diet-induced obesity and glucose intolerance. To determine the significance of MR in adipocytes, we generated adipocyte-specific MR-knockout mice (AdipoMR-KO) and fed them high-fat/high-sucrose diet. We found that adipocyte-specific deletion of MR did not affect the body weight, fat weight, glucose tolerance or insulin sensitivity. While liver weight was slightly reduced in AdipoMR-KO, there were no significant differences in the mRNA expression levels of genes associated with lipogenesis, lipolysis, adipocytokines and oxidative stress in adipose tissues between the control and AdipoMR-KO mice. The results indicated that MR in mature adipocytes plays a minor role in the regulation of insulin resistance and inflammation in high-fat/high-sucrose diet-induced obese mice.

Glucocorticoid Receptor and Adipocyte Biology

Glucocorticoids are steroid hormones that play a key role in metabolic adaptations during stress, such as fasting and starvation, in order to maintain plasma glucose levels. Excess and chronic glucocorticoid exposure, however, causes metabolic syndrome including insulin resistance, dyslipidemia, and hyperglycemia. Studies in animal models of metabolic disorders frequently demonstrate that suppressing glucocorticoid signaling improves insulin sensitivity and metabolic profiles. Glucocorticoids convey their signals through an intracellular glucocorticoid receptor (GR), which is a transcriptional regulator. The adipocyte is one cell type that contributes to whole body metabolic homeostasis under the influence of GR. Glucocorticoids' functions on adipose tissues are complex. Depending on various physiological or pathophysiological states as well as distinct fat depots, glucocorticoids can either increase or decrease lipid storage in adipose tissues. In rodents, glucocorticoids have been shown to reduce the thermogenic activity of brown adipocytes. However, in human acute glucocorticoid exposure, glucocorticoids act to promote thermogenesis. In this article, we will review the recent studies on the mechanisms underlying the complex metabolic functions of GR in adipocytes. These include studies of the metabolic outcomes of adipocyte specific GR knockout mice and identification of novel GR primary target genes that mediate glucocorticoid action in adipocytes.

Anti-angiogenesis effect of Neferine via regulating autophagy and polarization of tumor-associated macrophages in high-grade serous ovarian carcinoma

High-grade serous ovarian carcinoma (HGSOC) is one of the most lethal gynecologic malignancies. Currently, anti-angiogenesis therapy is the most promising strategy for the successful treatment of HGSOC. In this study, we found Neferine could inhibit the angiogenesis of ovarian cancer cells both in vitro and in vivo. Further analysis revealed that its suppressive effect on human umbilical vein endothelial cell (HUVEC) proliferation correlated with promoting cell cycle arrest and autophagy. The cell cycle genes were dose-dependently reduced and the level of LC3II/LC3I (microtubule associated protein 1 light chain 3) was increased. Using a specific marker for macrophages (CD206 and Mrc1), we indicated that Neferine could inhibit M2-macrophage in vivo. Finally, CD206 was stained in 150 HGSOC samples and its high expression predicted inferior overall survival. Our current study is the first to demonstrate the anti-angiogenesis mechanism of Neferine by inducing autophagy via mTOR/p70S6K pathway inhibition and suppressing M2-macrophage polarization. Our findings suggest that Neferine is an attractive reagent with great potential in HGSOC therapy, especially in standard-therapy resistant cases.

PPARγ activation mitigates glucocorticoid receptor-induced excessive lipolysis in adipocytes via homeostatic crosstalk

Proper balance between lipolysis and lipogenesis in adipocytes determines the release of free fatty acids (FFA) and glycerol, which is crucial for whole body lipid homeostasis. Although, dysregulation of lipid homeostasis contributes to various metabolic complications such as insulin resistance, the regulatory mechanism remains elusive. This study clarified the individual and combined roles for glucocorticoid receptor (GCR) and peroxisome proliferator-activated receptor (PPAR)γ pathways in lipid metabolism of adipocytes. In mature 3T3-L1 adipocytes, GCR activation using dexamethasone upregulated adipose triglyceride lipase (ATGL) and downregulated phosphoenolpyruvate carboxykinase (PEPCK), resulting in enhanced glycerol release into the medium. In contrast, PPARγ ligand pioglitazone modestly upregulated ATGL and hormone sensitive lipase (HSL), but markedly enhanced PEPCK and glycerol kinase (GK), thereby suppressed glycerol release. Dexamethasone showed permissive like effect on PPARγ target genes including perilipin A and aP2, therefore co-administration of dexamethasone and pioglitazone demonstrated synergistic upregulation of these enzymes excepting PEPCK, of which downregulation by dexamethasone was abolished by pioglitazone to the level above control. Thus, the excessive glycerol release was prevented as the net outcome of the co-administration. Consistently, the bodipy stain demonstrated that dexamethasone reduced the amount of cytosolic lipid, which was preserved in co-treated adipocytes. Moreover, silencing of PPARγ suppressed the synergistic effects of co-treatment on the lipolytic and lipogenic genes, and therefore the GCR pathway indeed involves PPARγ. In conclusion, crosstalk between GCR and PPARγ is largely synergistic but counter-regulatory in lipogenic genes, of which enhancement prevents excessive glycerol and possibly FFA release by glucocorticoids into the circulation.

Microenvironment of Immune Cells Within the Visceral Adipose Tissue Sensu Lato vs. Epicardial Adipose Tissue: What Do We Know?

The chronic low-grade inflammation of the visceral adipose tissue is now fully established as one of the main contributors to metabolic disorders such as insulin resistance, subsequently leading to metabolic syndrome and other associated cardiometabolic pathologies. The orchestration of immune response and the "ratio of responsibility" of different immune cell populations have been studied extensively over the last few years within the visceral adipose tissue in general sense (sensu lato). However, it is essential to clearly distinguish different types of visceral fat distribution. Visceral adipose tissue is not only the classical omental or epididymal depot, but includes also specific type of fat in the close vicinity to the myocardium-the epicardial adipose tissue. Disruption of this type of fat during obesity was found to have a unique and direct influence over the cardiovascular disease development. Therefore, epicardial adipose tissue and other types of visceral adipose tissue depots should be studied separately. The purpose of this review is to explore the present knowledge about the morphology and dynamics of individual populations of immune cells within the visceral adipose tissue sensu lato in comparison to the knowledge regarding the epicardial adipose tissue specifically.

Impact of Adrenal Steroids on Regulation of Adipose Tissue

Corticosteroids are secreted by the adrenal glands and control the functions of adipose tissue via the activation of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR). In turn, adipocytes release a large variety of adipokines into the bloodstream, regulating the function of several organs and tissues, including the adrenal glands, hereby controlling corticosteroid production. In adipose tissue, the activation of the MR by glucocorticoids (GC) and aldosterone affects important processes such as adipocyte differentiation, oxidative stress, autophagic flux, adipokine expression as well as local production of GC through upregulation of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Notably, the proinflammatory responses induced by the MR are counteracted by activation of the GR, whose activity inhibits the expression of inflammatory adipokines. Both GR and MR are deeply involved in adipogenesis and adipose expansion; hence pharmacological blockade of these two receptors has proven effective against adipose tissue dysfunction in experimental models of obesity and metabolic syndrome (MetS), suggesting a potential use for MR and GR antagonists in these clinical settings. Importantly, obesity and Cushing's syndrome (CS) share metabolic similarities and are characterized by high levels of circulating corticosteroids, which in turn are able to deeply affect adipose tissue. In addition, pharmacological approaches aimed at reducing aldosterone and GC levels, by means of the inhibition of CYP11B2 (aldosterone synthase) or 11β-HSD1, represent alternative strategies to counter the detrimental effects of excessive levels of corticosteroids, which are often observed in obesity and, more general, in MetS. © 2017 American Physiological Society. Compr Physiol 7:1425-1447, 2017.

The glucocorticoid-Angptl4-ceramide axis induces insulin resistance through PP2A and PKCζ

Chronic glucocorticoid exposure is associated with the development of insulin resistance. We showed that glucocorticoid-induced insulin resistance was attenuated upon ablation of Angptl4, a glucocorticoid target gene encoding the secreted protein angiopoietin-like 4, which mediates glucocorticoid-induced lipolysis in white adipose tissue. Through metabolomic profiling, we revealed that glucocorticoid treatment increased hepatic ceramide concentrations by inducing enzymes in the ceramide synthetic pathway in an Angptl4-dependent manner. Angptl4 was also required for glucocorticoids to stimulate the activities of the downstream effectors of ceramide, protein phosphatase 2A (PP2A) and protein kinase Cζ (PKCζ). We further showed that knockdown of PP2A or inhibition of PKCζ or ceramide synthesis prevented glucocorticoid-induced glucose intolerance in wild-type mice. Moreover, the inhibition of PKCζ or ceramide synthesis did not further improve glucose tolerance in Angptl4-/- mice, suggesting that these molecules were major downstream effectors of Angptl4. Overall, our study demonstrates the key role of Angptl4 in glucocorticoid-augmented hepatic ceramide production that induces whole-body insulin resistance.

Macrophage functions in lean and obese adipose tissue

Interactions between macrophages and adipocytes influence both metabolism and inflammation. Obesity-induced changes to macrophages and adipocytes lead to chronic inflammation and insulin resistance. This paper reviews the various functions of macrophages in lean and obese adipose tissue and how obesity alters adipose tissue macrophage phenotypes. Metabolic disease and insulin resistance shift the balance between numerous pro- and anti-inflammatory regulators of macrophages and create a feed-forward loop of increasing inflammatory macrophage activation and worsening adipocyte dysfunction. This ultimately leads to adipose tissue fibrosis and diabetes. The molecular mechanisms underlying these processes have therapeutic implications for obesity, metabolic syndrome, and diabetes.

Glucose Metabolism Abnormalities in Cushing Syndrome: From Molecular Basis to Clinical Management

An impaired glucose metabolism, which often leads to the onset of diabetes mellitus (DM), is a common complication of chronic exposure to exogenous and endogenous glucocorticoid (GC) excess and plays an important part in contributing to morbidity and mortality in patients with Cushing syndrome (CS). This article reviews the pathogenesis, epidemiology, diagnosis, and management of changes in glucose metabolism associated with hypercortisolism, addressing both the pathophysiological aspects and the clinical and therapeutic implications. Chronic hypercortisolism may have pleiotropic effects on all major peripheral tissues governing glucose homeostasis. Adding further complexity, both genomic and nongenomic mechanisms are directly induced by GCs in a context-specific and cell-/organ-dependent manner. In this paper, the discussion focuses on established and potential pathologic molecular mechanisms that are induced by chronically excessive circulating levels of GCs and affect glucose homeostasis in various tissues. The management of patients with CS and DM includes treating their hyperglycemia and correcting their GC excess. The effects on glycemic control of various medical therapies for CS are reviewed in this paper. The association between DM and subclinical CS and the role of screening for CS in diabetic patients are also discussed.

Circadian Rhythms in Adipose Tissue Physiology

The different types of adipose tissues fulfill a wide range of biological functions-from energy storage to hormone secretion and thermogenesis-many of which show pronounced variations over the course of the day. Such 24-h rhythms in physiology and behavior are coordinated by endogenous circadian clocks found in all tissues and cells, including adipocytes. At the molecular level, these clocks are based on interlocked transcriptional-translational feedback loops comprised of a set of clock genes/proteins. Tissue-specific clock-controlled transcriptional programs translate time-of-day information into physiologically relevant signals. In adipose tissues, clock gene control has been documented for adipocyte proliferation and differentiation, lipid metabolism as well as endocrine function and other adipose oscillations are under control of systemic signals tied to endocrine, neuronal, or behavioral rhythms. Circadian rhythm disruption, for example, by night shift work or through genetic alterations, is associated with changes in adipocyte metabolism and hormone secretion. At the same time, adipose metabolic state feeds back to central and peripheral clocks, adjusting behavioral and physiological rhythms. In this overview article, we summarize our current knowledge about the crosstalk between circadian clocks and energy metabolism with a focus on adipose physiology. © 2017 American Physiological Society. Compr Physiol 7:383-427, 2017.

Neuroendocrine Inflammatory Responses in Overweight/Obese Infants

Childhood obesity is related to a cascade of neuroendocrine inflammatory changes. However, there remains a gap in the current literature regarding the possible occurrence of these changes in overweight/obese infants. The objective of this study was to evaluate adipokines, cortisol, brain-derived neurotrophic factor (BDNF) and redox status in overweight/obese infants versus normal-weight peers. A cross-sectional study was conducted with 50 infants (25 in the overweight/obese group and 25 in the normal-weight group) between 6 and 24 months. Plasma levels of leptin, adiponectin, resistin, soluble tumor necrosis factor (TNF) receptors, chemokines, BDNF, serum cortisol and redox status were measured. Unpaired Student's t-test was used to analyze the results and a probability of p<0.05 was acceptable for rejection of the null hypothesis. The Pearson correlation was used to verify the association between the biomarkers analyzed in each group. Plasma levels of leptin (p = 0.0001), adiponectin (p = 0.0007) and BDNF (p = 0.003), and serum cortisol (p = 0.048) were significantly higher in overweight/obese infants than normal-weight infants. In contrast, the concentration of thiobarbituric acid reactive substances (TBARS) (p = 0.004), and catalase (p = 0.045) and superoxide dismutase activity (p = 0.02) were lower in overweight/obese infants than normal-weight peers. All the results together indicate neuroendocrine inflammatory response changes in overweight/obese infants between 6 and 24 months. Although there is already an environment that predisposes for a subsequent pro-inflammatory response, neuroendocrine secretion changes that permit the control of the inflammatory process in this age interval can be observed.

Adipocyte glucocorticoid receptor has a minor contribution in adipose tissue growth

The glucocorticoids bind and activate both the glucocorticoid receptor (GR) as well as the mineralocorticoid receptor in adipocytes. Despite several studies to determine the function of these two receptors in mediating glucocorticoids effects, their relative contribution in adipose tissue expansion and obesity is unclear. To investigate the effect of GR in adipose tissue function, we generated an adipocyte-specific Gr-knockout mouse model (Gr(ad-ko)). These mice were submitted either to a standard diet or a high-fat high sucrose diet. We found that adipocyte-specific deletion of Gr did not affect body weight gain or adipose tissue formation and distribution. However, the lack of Gr in adipocyte promotes a diet-induced inflammation determined by higher pro-inflammatory genes expression and macrophage infiltration in the fat pads. Surprisingly, the adipose tissue inflammation in Gr(ad-ko) mice was not correlated with insulin resistance or dyslipidemia, but with disturbed glucose tolerance. Our data demonstrate that adipocyte-specific ablation of Gr in vivo may affect the adipose tissue function but not its expansion during a high calorie diet.

Low expression of the GILZ may contribute to adipose inflammation and altered adipokine production in human obesity

The glucocorticoid-induced leucine zipper (GILZ), a primary target of glucocorticoids, is expressed in human adipocytes, but its importance in adipocyte function is unknown. Because TNFα is increased in obese adipose tissue and antagonizes a number of glucocorticoid actions, we investigated the interplay of these pathways. GILZ knockdown increased and GILZ overexpression decreased interleukin-6 (IL-6) and leptin mRNA and protein secretion. GILZ knockdown increased the magnitude of the glucocorticoid effect on leptin secretion, but did not affect the glucocorticoid suppression of IL-6. Although GILZ silencing decreased adiponectin mRNA levels, it did not affect the amount of adiponectin secreted. GILZ negatively modulated pro-inflammatory signaling pathways, blocking basal and TNFα-stimulated (1 h) p65 nuclear factor κB nuclear translocation and transcriptional activity by binding to p65 in the cytoplasm. GILZ silencing increased basal ERK1/2 and JNK phosphorylation, and decreased MAPK phosphatase-1 protein levels. Longer term TNFα (4 h or 24 h) treatment decreased GILZ expression in human adipocytes. Furthermore, adipose tissue GILZ mRNA levels were reduced in proportion to the degree of obesity and expression of inflammatory markers. Overall, these results suggest that GILZ antagonizes the pro-inflammatory effects of TNFα in human adipocytes, and its downregulation in obesity may contribute to adipose inflammation and dysregulated adipokine production, and thereby systemic metabolism.

Major role of adipocyte prostaglandin E2 in lipolysis-induced macrophage recruitment

Obesity induces accumulation of adipose tissue macrophages (ATMs), which contribute to both local and systemic inflammation and modulate insulin sensitivity. Adipocyte lipolysis during fasting and weight loss also leads to ATM accumulation, but without proinflammatory activation suggesting distinct mechanisms of ATM recruitment. We examined the possibility that specific lipid mediators with anti-inflammatory properties are released from adipocytes undergoing lipolysis to induce macrophage migration. In the present study, we showed that conditioned medium (CM) from adipocytes treated with forskolin to stimulate lipolysis can induce migration of RAW 264.7 macrophages. In addition to FFAs, lipolytic stimulation increased release of prostaglandin E2(PGE2) and prostaglandin D2(PGD2), reflecting cytosolic phospholipase A2α activation and enhanced cyclooxygenase (COX) 2 expression. Reconstituted medium with the anti-inflammatory PGE2potently induced macrophage migration while different FFAs and PGD2had modest effects. The ability of CM to induce macrophage migration was abolished by treating adipocytes with the COX2 inhibitor sc236 or by treating macrophages with the prostaglandin E receptor 4 antagonist AH23848. In fasted mice, macrophage accumulation in adipose tissue coincided with increases of PGE2levels and COX1 expression. Collectively, our data show that adipocyte-originated PGE2with inflammation suppressive properties plays a significant role in mediating ATM accumulation during lipolysis.

Regulation of metabolism by the innate immune system

Low-grade tissue inflammation induced by obesity can result in insulin resistance, which in turn is a key cause of type 2 diabetes mellitus. Cells of the innate immune system produce cytokines and other factors that impair insulin signalling, which contributes to the connection between obesity and the onset of type 2 diabetes mellitus. Here, we review the innate immune cells involved in secreting inflammatory factors in the obese state. In the adipose tissue, these cells include proinflammatory adipose tissue macrophages and natural killer cells. We also discuss the role of innate immune cells, such as anti-inflammatory adipose tissue macrophages, eosinophils, group 2 innate lymphoid cells and invariant natural killer T cells, in maintaining an anti-inflammatory and insulin-sensitive environment in the lean state. In the liver, both Kupffer cells and recruited hepatic macrophages can contribute to decreased hepatic insulin sensitivity. Proinflammatory macrophages might also adversely affect insulin sensitivity in the skeletal muscle and pancreatic β-cell function. Finally, this Review provides an overview of the mechanisms for regulating proinflammatory immune responses that could lead to future therapeutic opportunities to improve insulin sensitivity.

Adipogenesis is under surveillance of Hsp90 and the high molecular weight Immunophilin FKBP51

Adipose tissue plays a central role in the control of energy balance as well as in the maintenance of metabolic homeostasis. It was not until recently that the first evidences of the role of heat shock protein (Hsp) 90 and high molecular weight immunophilin FKBP51 have been described in the process of adipocyte differentiation. Recent reports describe their role in the regulation of PPARγ, a key transcription factor in the control of adipogenesis and the maintenance of the adipocyte phenotype. In addition, novel roles have been uncovered for FKBP51 in the organization of the architecture of the nucleus through its participation in the reorganization of the nuclear lamina. Therefore, the aim of this review is to integrate and discuss the recent advances in the field, with special emphasis on the roles of Hsp90 and FKBP51 in the process of adipocyte differentiation.

The new 4-O-methylhonokiol analog GS12021 inhibits inflammation and macrophage chemotaxis: role of AMP-activated protein kinase α activation

Preventing pathologic tissue inflammation is key to treating obesity-induced insulin resistance and type 2 diabetes. Previously, we synthesized a series of methylhonokiol analogs and reported that compounds with a carbamate structure had inhibitory function against cyclooxygenase-2 in a cell-free enzyme assay. However, whether these compounds could inhibit the expression of inflammatory genes in macrophages has not been investigated. Here, we found that a new 4-O-methylhonokiol analog, 3′,5-diallyl-4′-methoxy-[1,1′-biphenyl]-2-yl morpholine-4-carboxylate (GS12021) inhibited LPS- or TNFα-stimulated inflammation in macrophages and adipocytes, respectively. LPS-induced phosphorylation of nuclear factor-kappa B (NF-κB)/p65 was significantly decreased, whereas NF-κB luciferase activities were slightly inhibited, by GS12021 treatment in RAW 264.7 cells. Either mitogen-activated protein kinase phosphorylation or AP-1 luciferase activity was not altered by GS12021. GS12021 increased the phosphorylation of AMP-activated protein kinase (AMPK) α and the expression of sirtuin (SIRT) 1. Inhibition of mRNA expression of inflammatory genes by GS12021 was abolished in AMPKα1-knockdown cells, but not in SIRT1 knockout cells, demonstrating that GS12021 exerts anti-inflammatory effects through AMPKα activation. The transwell migration assay results showed that GS12021 treatment of macrophages prevented the cell migration promoted by incubation with conditioned medium obtained from adipocytes. GS12021 suppression of p65 phosphorylation and macrophage chemotaxis were preserved in AMPKα1-knockdown cells, indicating AMPK is not required for these functions of GS12021. Identification of this novel methylhonokiol analog could enable studies of the structure-activity relationship of this class of compounds and further evaluation of its in vivo potential for the treatment of insulin-resistant states and other chronic inflammatory diseases.

Coordinated regulation of adipose tissue macrophages by cellular and nutritional signals

The current epidemic of obesity is fueling a global rise in non-communicable diseases, including type 2 diabetes mellitus, atherothrombotic disease, and cancer. Obesity is associated with systemic inflammation, with various fat-derived inflammatory factors being implicated in the pathophysiology of insulin resistance. The infiltration of various types of inflammatory cells into adipose tissue seems to be an important mechanism whereby nutrient excess contributes to systemic insulin resistance. In particular, adipose tissue macrophages are abundant in obese adipose tissue, and may be the source of the majority of fat-derived circulating inflammatory factors. This review examines recent studies exploring mechanisms whereby cellular and nutritional signals mediate macrophage recruitment to adipose tissue and their pro-inflammatory activation.

Relationship between impaired adipogenesis of retroperitoneal adipose tissue and hypertrophic obesity: role of endogenous glucocorticoid excess

Although the pro-adipogenic effect of glucocorticoid (GC) on adipose tissue (AT) precursor cell differentiation is openly accepted, the effect of chronically high peripheral levels of GC on AT mass expansion is not fully understood. In the present study, we aim to assess the in vitro adipogenic capacity of AT precursor cells isolated from retroperitoneal (RP) AT pads of the hypercorticosteronaemic, adult neonatally treated monosodium L-glutamate (MSG) male rat. To ascertain this issue, we explored the in vitro adipogenic process of stromal-vascular fraction (SVF) cells isolated from RPAT pads of 60-day-old MSG rats. The data recorded indicated that RPAT-SVF cells from hypercorticosteronaemic MSG rats, although displaying an enhanced proliferation capacity, differentiated slower than normal cells. This dysfunction was associated with a reduction in key parameters indicative of precursor cell commitment, differentiation capacity and the percentage of fully differentiated adipocytes, with a retarded maturation process. The distorted adipogenic capacity was highly conditioned by RPAT-SVF cells displaying a low committed population and both excessive and reduced expression of anti- (Pref-1 and Wnt-10b) and pro-adipogenic (mineralocorticoid receptor) signals respectively. Notably, the normalization of peripheral corticosterone levels in MSG rats, as a result of bilateral adrenalectomy combined with GC replacement therapy, fully prevented reduced RPAT precursor cell commitment and overall impaired adipogenesis. Our study strongly supports that the impaired adipogenic process observed in the adult hypertrophic obese MSG male rat is a GC-dependent mechanism, thus explaining the unhealthy RPAT expansion observed in human hypertrophic obese phenotypes, such as in the Cushing's syndrome.

Oral administration of the milk casein-derived tripeptide Val-Pro-Pro attenuates high-fat diet-induced adipose tissue inflammation in mice

Inflammation of adipose tissue triggers the metabolic syndrome, atherosclerosis and CHD. In the present study, we investigated whether the milk casein-derived tripeptide valine-proline-proline (VPP) has an anti-inflammatory effect on the adipose tissue of high-fat diet (HFD)-fed mice. Male C57BL/6J mice (7 weeks of age) were fed ad libitum with either a HFD and plain tap water (HFD group) or a HFD and water containing 0·3 mg VPP/ml (HFD+VPP group) for 10 weeks. The results showed that the expression level of CD18 in the peripheral blood monocytes of the HFD+VPP group was significantly decreased compared with the level observed in those of the HFD group. Activated monocytes and pro-inflammatory macrophages were accumulated in the stromal vascular fractions of the adipose tissue from HFD-fed mice, which were significantly decreased in those supplemented with VPP. The formation of crown-like structures rich in pro-inflammatory macrophages was also significantly reduced in the adipose tissue of mice administered with VPP. Real-time PCR analysis revealed that the expression of monocyte chemoattractant protein-1 and that of the pro-inflammatory cytokine IL-6 in adipose tissue tend to be lower in the HFD+VPP group than in the HFD group. These observations indicate that oral administration of VPP exerts an anti-inflammatory effect on the adipose tissue of HFD-fed mice, which may eventually lead to the primary prevention of chronic inflammation-related diseases.

Endurance interval training in obese mice reduces muscle inflammation and macrophage content independently of weight loss

Obesity is associated with chronic low‐grade inflammation that involves infiltration of macrophages into metabolic organs such as skeletal muscle. Exercise enhances skeletal muscle insulin sensitivity independently of weight loss; but its role in regulating muscle inflammation is not fully understood. We hypothesized that exercise training would inhibit skeletal muscle inflammation and alter macrophage infiltration into muscle independently of weight loss. Wild type C57BL/6 male mice were fed a chow diet or a high‐fat diet (HFD, 45% calories fat) for 6 weeks. Then, mice maintained on the HFD either remained sedentary (HFD Sed) or exercised (HFD Ex) on a treadmill for another 6 weeks. The exercise training protocol involved conducting intervals of 2 min in duration followed by 2 min of rest for 60 min thrice weekly. Chow‐fed control mice remained sedentary for the entire 12 weeks. Muscle cytokine and macrophage gene expression analysis were conducted using qRT‐PCR, and muscle macrophage content was also measured using immunohistochemistry. Muscle cytokine protein content was quantified using a cytokine array. The HFD increased adiposity and weight gain compared to chow‐fed controls. HFD Sed and HFD Ex mice had similar body mass as well as total and visceral adiposity. However, despite similar adiposity, exercise reduced inflammation and muscle macrophage infiltration. We conclude that Endurance exercise training modulates the immune‐metabolic crosstalk in obesity independently of weight loss, and may have potential benefits in reducing obesity‐related muscle inflammation.

e12012

Obesity is associated with chronic low‐grade inflammation that involves infiltration of macrophages into metabolic organs such as skeletal muscle. Exercise enhances skeletal muscle insulin sensitivity independently of weight loss; but its role in regulating muscle inflammation is not fully understood. In this article, we show that endurance interval training inhibited skeletal muscle inflammation and reduced macrophage infiltration into muscle independently of weight loss in mice.

Fat storage-inducing transmembrane protein 2 is required for normal fat storage in adipose tissue

Triglycerides within the cytosol of cells are stored in a phylogenetically conserved organelle called the lipid droplet (LD). LDs can be formed at the endoplasmic reticulum, but mechanisms that regulate the formation of LDs are incompletely understood. Adipose tissue has a high capacity to form lipid droplets and store triglycerides. Fat storage-inducing transmembrane protein 2 (FITM2/FIT2) is highly expressed in adipocytes, and data indicate that FIT2 has an important role in the formation of LDs in cells, but whether FIT2 has a physiological role in triglyceride storage in adipose tissue remains unproven. Here we show that adipose-specific deficiency of FIT2 (AF2KO) in mice results in progressive lipodystrophy of white adipose depots and metabolic dysfunction. In contrast, interscapular brown adipose tissue of AF2KO mice accumulated few but large LDs without changes in cellular triglyceride levels. High fat feeding of AF2KO mice or AF2KO mice on the genetically obese ob/ob background accelerated the onset of lipodystrophy. At the cellular level, primary adipocyte precursors of white and brown adipose tissue differentiated in vitro produced fewer but larger LDs without changes in total cellular triglyceride or triglyceride biosynthesis. These data support the conclusion that FIT2 plays an essential, physiological role in fat storage in vivo.

Mono-allelic and bi-allelic ENPP1 deficiency promote post-injury neointimal hyperplasia associated with increased C/EBP homologous protein expression

OBJECTIVE

Bi-allelic function-inactivating ENPP1 mutations cause artery media calcification (AMC) with associated severe myointimal hyperplasia in generalized arterial calcification of infancy (GACI), whereas mono-allelic ENPP1 deficiency is phenotypically normal. Here, we tested if ENPP1 deficiency promotes abnormal vascular smooth muscle cell (VSMC)-driven responses to injury, with or without calcification. The ER stress mediator C/EBP homologous protein (CHOP) affects neointimal hyperplasia and atherosclerosis, and has paradoxical effects on bone formation. Hence, we assessed relationships between ENPP1 and CHOP in VSMCs.

METHODS

We studied ENPP1-deficient mice and control littermates subjected to left carotid artery ligation, and isolated and studied VSMCs from these and Chop-/- mice, or with CHOP siRNA treatment.

RESULTS

Normal Enpp1-/+ mice, in addition to Enpp1-/- mice prior to AMC development, had accelerated neointimal hyperplasia in response to carotid artery ligation at 7-8 weeks age. Neointimal hyperplasia was linked with robust artery media CHOP expression in situ, but with marked AMC only in injured Enpp1-/- arteries. Cultured, ENPP1-deficient and CHOP-deficient VSMCs had increased migration and proliferation to PDGF. Cultured Chop-/- VSMCs demonstrated increased Pi donor-induced calcification. CHOP was significantly increased in Pi donor treated Enpp1-/- and Enpp1-/+ cultured VSMCs. CHOP siRNA treatment of Enpp1-/- VSMCs increased calcification, associated with elevated expression of tissue nonspecific alkaline phosphatase and the master osteoblastic transcription factor RUNX2.

CONCLUSIONS

Both mono-allelic and bi-allelic ENPP1 deficiency promote dysregulated VSMC function, with robust lesion CHOP expression and enhanced neointimal hyperplasia after injury in vivo, but marked post-injury calcification limited to Enpp1-/- mice. Intimal hyperplasia in GACI appears regulated by biologic effects of ENPP1 deficiency other than calcification, including ER stress. VSMC CHOP excess in ENPP1 deficiency may primarily function to limit VSMC calcification.

The glucocorticoid receptor, not the mineralocorticoid receptor, plays the dominant role in adipogenesis and adipokine production in human adipocytes

Background

Both the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR) are expressed in adipose tissue and assumed to mediate cortisol actions on adipose tissue. The relative significance of the two receptors in mediating glucocorticoid regulation of adipogenesis and adipokine expression in human adipocytes has not been addressed.

Methods

We investigated the differential roles of the GR and MR in mediating glucocorticoid actions on adipogenesis and adipokine production using RNA interference in primary cultures of human preadipocytes and adipocytes.

RESULTS

Both types of receptors are expressed, but levels of GR were several hundred fold higher than MR in both human preadipocytes and adipocytes. As expected, cortisol added during adipogenesis increased the differentiation of human preadipocytes. Silencing of GR, but not MR, blocked these proadipogenic actions of cortisol. In differentiated human adipocytes, addition of cortisol increased leptin and adiponectin, while suppressing IL-6, mRNA levels and protein secretion. Knockdown of GR by 65% decreased leptin and adiponectin while increasing IL-6 production. In addition, GR silencing blocked the effects of cortisol on adipokine expression. In contrast, although MR knockdown increased leptin, it did not affect adiponectin and IL-6 expression.

Conclusion

Our data demonstrate that although both GR and MR have roles in regulating leptin expression, GR plays more important roles in mediating the actions of cortisol to regulate adipogenesis and adipokine production in human adipocytes.

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Very low density lipoprotein receptor (VLDLR) expression is a determinant factor in adipose tissue inflammation and adipocyte-macrophage interaction

Obesity is associated with adipose tissue remodeling, characterized by adipocyte hypertrophy and macrophage infiltration. Previously, we have shown that very low density lipoprotein receptor (VLDLR) is virtually absent in preadipocytes but is strongly induced during adipogenesis and actively participates in adipocyte hypertrophy. In this study, we investigated the role of VLDLR in adipose tissue inflammation and adipocyte-macrophage interactions in wild type and VLDLR-deficient mice fed a high fat diet. The results show that VLDLR deficiency reduced high fat diet-induced inflammation and endoplasmic reticulum (ER) stress in adipose tissue in conjunction with reduced macrophage infiltration, especially those expressing pro-inflammatory markers. In adipocyte culture, VLDLR deficiency prevented adipocyte hypertrophy and strongly reduced VLDL-induced ER stress and inflammation. Likewise, cultures of primary peritoneal macrophages show that VLDLR deficiency reduced lipid accumulation and inflammation but did not alter chemotactic response of macrophages to adipocyte signals. Moreover, VLDLR deficiency tempered the synergistic inflammatory interactions between adipocytes and macrophages in a co-culture system. Collectively, these results show that VLDLR contributes to adipose tissue inflammation and mediates VLDL-induced lipid accumulation and induction of inflammation and ER stress in adipocytes and macrophages.

Role of mineralocorticoid receptor and renin-angiotensin-aldosterone system in adipocyte dysfunction and obesity

The mineralocorticoid receptor (MR) classically mediates aldosterone effects on salt homeostasis and blood pressure regulation in epithelial target tissues. In recent years, functional MRs have been identified in non classical targets of aldosterone actions, in particular in adipose tissue, where they mediate the effects of aldosterone and glucocorticoids in the control of adipogenesis, adipose expansion and its pro-inflammatory capacity. In this context, inappropriate MR activation has been demonstrated to be a causal factor in several pathologic conditions such as vascular inflammation, endothelial dysfunction, insulin resistance and obesity. The aim of this review is to summarize the latest developments in this rapidly developing field, and will focus on the role of MR and renin-angiotensin-aldosterone system (RAAS) as potential leading characters in the early steps of adipocyte dysfunction and obesity. Indeed modulation of MR activity in adipose tissue has promise as a novel therapeutic approach to treat obesity and its related metabolic complications. This article is part of a Special Issue entitled 'CSR 2013'.

Coordinated regulation of adipose tissue macrophages by cellular and nutritional signals

The current epidemic of obesity is fueling a global rise in non-communicable diseases, including type 2 diabetes mellitus, atherothrombotic disease, and cancer. Obesity is associated with systemic inflammation, with various fat-derived inflammatory factors being implicated in the pathophysiology of insulin resistance. The infiltration of various types of inflammatory cells into adipose tissue seems to be an important mechanism whereby nutrient excess contributes to systemic insulin resistance. In particular, adipose tissue macrophages are abundant in obese adipose tissue, and may be the source of the majority of fat-derived circulating inflammatory factors. This review examines recent studies exploring mechanisms whereby cellular and nutritional signals mediate macrophage recruitment to adipose tissue and their pro-inflammatory activation.

Activation of adipose tissue macrophages in obese mice does not require lymphocytes

OBJECTIVE

Macrophages which infiltrate adipose tissue and secrete proinflammatory cytokines may be responsible for obesity-induced insulin resistance. However, the reason why macrophages migrate into adipose tissue and become activated remains unknown though some studies suggest that this may be regulated by T and B lymphocytes. In this study, it has been tested whether T and B lymphocytes and natural killer (NK) cells were necessary for the obesity-induced activation of macrophages in adipose tissue.

DESIGN AND METHODS

NOD/SCID/IL2-receptor gamma-chain knockout (NSG) mice, which lack mature T and B lymphocytes and NK cells, were made obese by selectively reducing litters and weaning onto a high-fat diet. Mice were then maintained on the diet for 10-11 weeks.

RESULTS

Adipose tissue from obese NSG mice had more activated macrophages than nonobese mice. These macrophages were found in "crown-like structures" surrounding adipocytes, and expressed higher levels of the inflammatory cytokine TNF-α. However, obesity did not impair glucose tolerance in the NSG mice.

CONCLUSIONS

These studies demonstrated that T and B lymphocytes and NK cells are not necessary for adipose tissue macrophage activation in obese mice. T and B lymphocytes and/or NK cells may be necessary for the development of obesity-induced impaired glucose tolerance.