[Pancreatic panniculitis with polyarthritis: PPP syndrome]. / Polyartritis, panniculitis en pancreatitis.

BACKGROUND: Diseases of the pancreas may present with extrapancreatic symptoms, such as (poly)arthritis or necrosis of subcutaneous fat. A combination of pancreatitis, panniculitis and (poly)arthritis is referred to as the PPP syndrome, which is associated with acute and chronic pancreatitis, as well as pancreatic malignancies. CASE DESCRIPTION: This article describes a patient which was admitted to our hospital with severe polyarthritis and panniculitis. A meticulous work-up revealed an underlying focal alcoholic pancreatitis. The clinical course in our patient illustrates the severity of the PPP syndrome and emphasizes the need of a multidisciplinary approach. CONCLUSION: Panniculitis and/or (poly)arthritis may be the first symptom of underlying pancreatic disease. Timely recognition and diagnosis is imperative for successful treatment and outcome. The multi-organ involvement in the PPP syndrome requires close collaboration across different medical departments.

Gab2 deficiency suppresses high-fat diet-induced obesity by reducing adipose tissue inflammation and increasing brown adipose function in mice.

Obesity is caused by a long-term imbalance between energy intake and consumption and is regulated by multiple signals. This study investigated the effect of signaling scaffolding protein Gab2 on obesity and its relevant regulation mechanism. Gab2 knockout (KO) and wild-type (WT) mice were fed with a standard diet (SD) or high-fat diet (HFD) for 12 weeks. The results showed that the a high-fat diet-induced Gab2 expression in adipose tissues, but deletion of Gab2 attenuated weight gain and improved glucose tolerance in mice fed with a high-fat diet. White adipose tissue and systemic inflammations were reduced in HFD-fed Gab2 deficiency mice. Gab2 deficiency increased the expression of Ucp1 and other thermogenic genes in brown adipose tissue. Furthermore, the regulation of Gab2 on the mature differentiation and function of adipocytes was investigated in vitro using primary or immortalized brown preadipocytes. The expression of brown fat-selective genes was found to be elevated in differentiated adipocytes without Gab2. The mechanism of Gab2 regulating Ucp1 expression in brown adipocytes involved with its downstream PI3K (p85)-Akt-FoxO1 signaling pathway. Our research suggests that deletion of Gab2 suppresses diet-induced obesity by multiple pathways and Gab2 may be a novel therapeutic target for the treatment of obesity and associated complications.

Celastrol attenuates inflammatory responses in adipose tissues and improves skeletal muscle mitochondrial functions in high fat diet-induced obese rats via upregulation of AMPK/SIRT1 signaling pathways.

Accumulating evidence indicates that adipose tissue inflammation and mitochondrial dysfunction in skeletal muscle are inextricably linked to obesity and insulin resistance. Celastrol, a bioactive compound derived from the root of Tripterygium wilfordii exhibits a number of attributive properties to attenuate metabolic dysfunction in various cellular and animal disease models. However, the underlying therapeutic mechanisms of celastrol in the obesogenic environment in vivo remain elusive. Therefore, the current study investigated the metabolic effects of celastrol on insulin sensitivity, inflammatory response in adipose tissue and mitochondrial functions in skeletal muscle of the high fat diet (HFD)-induced obese rats. Our study revealed that celastrol supplementation at 3 mg/kg/day for 8 weeks significantly reduced the final body weight and enhanced insulin sensitivity of the HFD-fed rats. Celastrol noticeably improved insulin-stimulated glucose uptake activity and increased expression of plasma membrane GLUT4 protein in skeletal muscle. Moreover, celastrol-treated HFD-fed rats showed attenuated inflammatory responses via decreased NF-κB activity and diminished mRNA expression responsible for classically activated macrophage (M1) polarization in adipose tissues. Significant improvement of muscle mitochondrial functions and enhanced antioxidant defense machinery via restoration of mitochondrial complexes I + III linked activity were effectively exhibited by celastrol treatment. Mechanistically, celastrol stimulated mitochondrial biogenesis attributed by upregulation of the adenosine monophosphate-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) signaling pathways. Together, these results further demonstrate heretofore the conceivable therapeutic mechanisms of celastrol in vivo against HFD-induced obesity mediated through attenuation of inflammatory response in adipose tissue and enhanced mitochondrial functions in skeletal muscle.

Role of adipose tissue inflammation in fat pad loss induced by fasting in lean and mildly obese mice.

Inflammation induced by obesity contributes to insulin resistance and atherosclerosis. Indeed, high levels of proinflammatory cytokines trigger chronic low-grade inflammation and promote detrimental metabolic effects in the adipose tissue. On the other hand, inflammation seems to control fat pad expansion and to have important functions on lipolysis and glucose metabolism. Thus, it is possible that inflammation may also drive fat pad loss, as seen during long-fast periods. Herein, we have used fasting as a strategy to induce weight loss and evaluate the possible role of inflammation on adipose tissue remodeling. Male BALB-c mice were fed with chow diet (lean mice) or with high-carbohydrate refined diet (mildly obese mice) for 8 weeks. After that, animals were subjected to 24 h of fasting. There was a 63% reduction of adiposity in lean mice following fasting. Furthermore, the adipose tissue was enriched of immune cells and had a higher content of IL-6, TNF-alpha, IL-10, TGF-ß and CXCL-1. Interestingly, mildly obese mice, subjected to the same 24-h fasting period, lost only 33% of their adiposity. Following fasting, these mice did not show any increment in leukocyte recruitment and cytokine levels, as did lean mice. Our findings indicate that inflammation participates in fat mass loss induced by fasting. Although the chronic low-grade inflammation seen in obesity is associated with metabolic diseases, a lower inflammatory response triggered by fasting in mildly obese mice impairs fat pad mobilization.

Panniculitis in the setting of dermato/rheumatologic diseases.

Panniculitides represent a heterogeneous group of inflammatory diseases that are traditionally considered one of the most difficult challenge for clinicians and pathologists. They may occur in a variety of dermato/rheumatologic diseases and are of particular relevance for clinicians dealing with such pathologies, including immune-mediated/autoimmune and autoinflammatory disorders. In fact, panniculitides can be the initial sign of presentation of a dermato/rheumatologic disease, thereby providing the physician with important clues to the correct diagnosis. Then, panniculitides may serve as an easy-to-access indicator of both systemic involvement and prognostic outcome in dermato/rheumatologic disorders. This review will focus on clinical and histopathological findings of panniculitides in the setting of dermato/rheumatologic disorders and discusses the value of skin biopsies and consequent histopathological examination in the diagnosis of these disorders with the help of a logarithmic table.

Obesity and malnutrition similarly alter the renin-angiotensin system and inflammation in mice and human adipose.

The main goal of the present study was to evaluate the metabolic profile, inflammatory markers and the gene expression of the renin-angiotensin system (RAS) components in the visceral adipose tissue of eutrophic, obese and malnourished individuals and mice models of obesity and food restriction. Male Swiss mice were divided into eight groups and fed different levels of food restriction (20%, 40%, or 60%) using standard or high-fat diet. Metabolic profile and adipose tissues were assessed. The expression of AGT (Angiotensinogen), ACE (Angiotensin-converting enzyme), ACE2 (Angiotensin-converting enzyme 2), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in the mice epididymal adipose tissue and the human visceral adipose tissue was assessed. The main findings showed reduced body weight, improved metabolism, decreased adipose tissues weight and reduced adipocyte area in mice submitted to food restriction. Diminished expression of IL-6, TNF-α, AGT, AT1 and ACE was detected in the 20% and 40% food restriction animal groups, although they were increased in the 60% malnourished group. Increased expression of IL-6, TNF-α, AGT and ACE in obese and malnourished individuals was observed. Adipocytes size was increased in obese individuals and reduced in malnutrition. In conclusion, we found that food restriction of 20% and 40% improved the metabolic profile, ameliorated the inflammatory status and down-regulated the RAS in mice. Severe 60% food restriction (malnutrition), however, stimulated a proinflammatory state and increased AGT and ACE expression in the adipose tissue of mice. A similar profile was observed in the adipose tissue of obese and malnourished humans, supporting the critical role of inflammation and RAS as mediators of metabolic disorders.

Pancreatic Panniculitis and Polyarthritis.

PURPOSE OF REVIEW: Polyarthritis can have numerous reasons and may thus constitute a challenge for differential diagnosis. One rare potential reason for sterile polyarthritis is underlying pancreatic disease with systemic hyperlipasemia, most often accompanied by painful skin lesions caused by a subcutaneous inflammatory process known as panniculitis. Systematic evidence on pancreatic panniculitis and polyarthritis is limited, particularly regarding its feature as facultative paraneoplasia with underlying intra- or even extra-pancreatic malignancy. Therefore, we will summarize the current knowledge about this orphan disease including epidemiological, pathophysiological, diagnostic, and treatment aspects in the present review. RECENT FINDINGS: Although direct evidence is lacking, it is highly probable that pancreatic polyarthritis and panniculitis are caused by peripheral lipolytic activity of lipase systemically circulating due to benign (e.g., acute or chronic pancreatitis) or malign (e.g., acinar cell carcinoma (ACC) or adenocarcinoma) pancreatic disease. In the latter case, pancreatic polyarthritis and panniculitis are associated with poor outcome. Pancreatic polyarthritis and panniculitis should always be included into diagnostic considerations, and once suspected, a thorough work-up to identify the underlying disease has to be performed.

Chronic kidney disease promotes chronic inflammation in visceral white adipose tissue.

White adipose tissue plays an important role in the development of metabolic disturbance, which is a common feature in patients with chronic kidney disease (CKD). The effect of CKD on white adipose tissue remains poorly appreciated. Here, we evaluated the inflammatory potential of visceral white adipose tissue in a rat model of CKD. The results showed that production of proinflammatory cytokines and infiltration of macrophage in the tissue were increased significantly in CKD rats compared with sham rats. Moreover, the primary adipocytes and stromal vascular fraction under the condition of CKD could trigger the inflammatory response in each other. Free fatty acid induced robust inflammatory response in ex vivo peritoneal-derived macrophages from CKD rats, which was associated with reduced activity of silent information regulator T1 (SIRT1). Improvement of SIRT1 activity by an activator could alleviate free fatty acid-induced inflammatory response in the macrophages and inflammation in the white adipose tissue. Moreover, oxidative stress occurred in the tissue and linked with the reduced activity of SIRT1 in macrophages and enhanced release of free fatty acid in the tissue. We thus identified CKD as a risk factor for chronic inflammation in white adipose tissue. These observations might open up new therapeutic strategies for metabolic disturbance in CKD via the modulation of adipose tissue-related pathways.

α1-Antitrypsin Deficiency.

α1-Antitrypsin deficiency is an autosomal codominant condition that predisposes to emphysema and cirrhosis. The condition is common but grossly under-recognized. Identifying patients' α1-antitrypsin deficiency has important management implications (ie, smoking cessation, genetic and occupational counseling, and specific treatment with the infusion of pooled human plasma α1-antitrypsin). The weight of evidence suggests that augmentation therapy slows the progression of emphysema in individuals with severe α1-antitrypsin deficiency.

Ablation of eNOS does not promote adipose tissue inflammation.

Adipose tissue (AT) inflammation is a hallmark characteristic of obesity and an important determinant of insulin resistance and cardiovascular disease; therefore, a better understanding of factors regulating AT inflammation is critical. It is well established that reduced vascular endothelial nitric oxide (NO) bioavailability promotes arterial inflammation; however, the role of NO in modulating inflammation in AT remains disputed. In the present study, 10-wk-old C57BL6 wild-type and endothelial nitric oxide synthase (eNOS) knockout male mice were randomized to either a control diet (10% kcal from fat) or a Western diet (44.9% kcal from fat, 17% sucrose, and 1% cholesterol) for 18 wk (n= 7 or 8/group). In wild-type mice, Western diet-induced obesity led to increased visceral white AT expression of inflammatory genes (e.g., MCP1, TNF-α, and CCL5 mRNAs) and markers of macrophage infiltration (e.g., CD68, ITGAM, EMR1, CD11C mRNAs, and Mac-2 protein), as well as reduced markers of mitochondrial content (e.g., OXPHOS complex I and IV protein). Unexpectedly, these effects of Western diet on visceral white AT were not accompanied by decreases in eNOS phosphorylation at Ser-1177 or increases in eNOS phosphorylation at Thr-495. Also counter to expectations, eNOS knockout mice, independent of the diet, were leaner and did not exhibit greater white or brown AT inflammation compared with wild-type mice. Collectively, these findings do not support the hypothesis that reduced NO production from eNOS contributes to obesity-related AT inflammation.

Obesity-Associated Adipose Tissue Inflammation and Transplantation.

Obesity is often associated with the development of adipose tissue (AT) inflammation, resulting in metabolic dysfunction and an increased risk for developing type 2 diabetes. It is also associated with multiple chronic diseases, including cardiovascular, liver, and kidney disease, and thus can contribute to organ failure. Several studies have investigated whether there is a correlation between obesity and outcomes in transplantation, but there is currently very limited information on the specific role of AT inflammation in the rejection process or on the overall function of the transplanted organ. Here, we provide a brief review of the current understanding of the cellular mechanisms that control obesity-associated AT inflammation and summarize knowledge about how obesity affects clinical outcomes following solid organ or hematopoietic stem cell transplantation. We also highlight opportunities for more research to better understand how obesity affects outcomes of transplantation.

Pathological aspects of bovine focal fibrogranulomatous proliferative panniculitis (Lechiguana).

Lechiguana is a disease of cattle caused by an interaction between Dermatobia hominis warble and the bacteria Manheimia granulomatis. It is characterized by subcutaneous swellings that grow rapidly and result in death after 3 to 8 months. The objective of this paper was to investigate some vascular and fibrogenic changes of the disease at different lesion stages by histochemical and immunohistochemical techniques. A peculiar histopathological aspect observed during a proliferative phase (before treatment) was the intense vasculitis, described as degenerative and fibro-proliferative, expressed by the oncogene p53, possibly caused by the presence of bacteria in close contact with enthotelial cells, along with dense accumulations of lymphoid cells around venules. The synthesis of collagen fibers during the development of Lechiguana lesions assume a structural aspect of star arrangement with fiber radiation centers that gradually interconnect to design the Extracellular Matrix (ECM) framework, seen by Confocal Laser Scanning Microscopy (CSLM). Angiogenesis was the most characteristic finding in both proliferative and regressive stages as seen by the immunohistochemical expression of cytoskeleton proteins and von Willebrand (Factor VIII-Related Antigen). Additionally, in all tissues samples, active ECM elements like Metalloproteinases (MMPs), Tissue Inhibitors Metalloproteinases (TIMP) and Fibronectin (FN) were mainly associated to vessels structures. The extraordinary regression of exuberant granulation tissue after treatment is undoubtedly associated to the maintenance of the vascular components observed during the regressive phase.

Infectious panniculitides: an update.

Very few areas in the realm of diagnostic dermatopathology may be so challenging both for the dermatologist and the histopathologist as are those related to panniculitis, because of their frequent overlapping microscopical patterns and uncertain etiology. Classically, a dicotomic taxonomy key has been proposed according the prevalent involvement of subcutaneous septa or lobules of the inflammation, presence or absence of vasculitis and type of vessel involved, but exceptions to this approach do occur and overlapping forms are sometimes encountered. Infectious panniculitides have also been traditionally approached according to this schema, and their microscopic diagnosis may be even more complex when the causative agent is unknown and underrepresented in the specimen. Many types of pathogens are capable to evoke protean clinical manifestations, which range from organism-specific to aspecific pictures. For this reason a tissue biopsy is always mandatory to ascertain the type of lesion and differentiate an infectious process from its many other mimickers essentially represented by reactive-based panniculitides. Recognition of morphologic changes which characterize distinct infections in the subcutis often needs a complete clinical history, physical examination and laboratory studies, especially when few microorganisms if any are found. This review will be focussed on the pathophysiology of the adipose tissue in relation to immunity and mechanisms of host reaction. The most frequent infectious panniculitides will then be discussed with special reference to their microscopic pictures, to provide clues to their specific diagnosis and the use of immunohistochemistry and molecular biology techniques as ancillary techniques.

TNF-α impairs endothelial function in adipose tissue resistance arteries of mice with diet-induced obesity.

We tested the hypothesis that high fat (HF) feeding results in endothelial dysfunction in resistance arteries of epididymal white adipose tissue (eWAT) and is mediated by adipose tissue inflammation. When compared with normal chow (NC)-fed mice (n = 17), HF-fed male B6D2F1 mice were glucose intolerant and insulin resistant as assessed by glucose tolerance test (area under the curve; HF, 18,174 ± 1,889 vs. NC, 15,814 ± 666 mg·dl(-1)·min(-1); P < 0.05) and the homeostatic model assessment (HF, 64.1 ± 4.3 vs. NC, 85.7 ± 6.4; P = 0.05). HF diet-induced metabolic dysfunction was concomitant with a proinflammatory eWAT phenotype characterized by greater macrophage infiltration (HF, 3.9 ± 0.8 vs. NC, 0.8 ± 0.4%; P = 0.01) and TNF-α (HF, 22.6 ± 4.3 vs. NC, 11.4 ± 2.5 pg/dl; P < 0.05) and was associated with resistance artery dysfunction, evidenced by impaired endothelium-dependent dilation (EDD) (maximal dilation; HF, 49.2 ± 10.7 vs. NC, 92.4 ± 1.4%; P < 0.01). Inhibition of nitric oxide (NO) synthase by N(ω)-nitro-L-arginine methyl ester (L-NAME) reduced dilation in NC (28.9 ± 6.3%; P < 0.01)- and tended to reduce dilation in HF (29.8 ± 9.9%; P = 0.07)-fed mice, eliminating the differences in eWAT artery EDD between NC- and HF-fed mice, indicative of reduced NO bioavailability in eWAT resistance arteries after HF feeding. In vitro treatment of excised eWAT arteries with recombinant TNF-α (rTNF) impaired EDD (P < 0.01) in NC (59.7 ± 10.9%)- but not HF (59.0 ± 9.3%)-fed mice. L-NAME reduced EDD in rTNF-treated arteries from both NC (21.9 ± 6.4%)- and HF (29.1 ± 9.2%)-fed mice (both P < 0.01). In vitro treatment of arteries with a neutralizing antibody against TNF-α (abTNF) improved EDD in HF (88.2 ± 4.6%; P = 0.05)-fed mice but was without effect on maximal dilation in NC (89.0 ± 5.1%)-fed mice. L-NAME reduced EDD in abTNF-treated arteries from both NC (25.4 ± 7.5%)- and HF (27.1 ± 16.8%)-fed mice (both P < 0.01). These results demonstrate that inflammation in the visceral adipose tissue resulting from diet-induced obesity impairs endothelial function and NO bioavailability in the associated resistance arteries. This dysfunction may have important implications for adipose tissue blood flow and appropriate tissue function.

Loss of Pdk1-Foxo1 signaling in myeloid cells predisposes to adipose tissue inflammation and insulin resistance.

Chronic inflammation in adipose tissue contributes to obesity-related insulin resistance. The 3-phosphoinositide-dependent protein kinase 1 (Pdk1)/forkhead transcription factor (Foxo1) pathway is important in regulating glucose and energy homeostasis, but little is known about this pathway in adipose tissue macrophages (ATMs). To investigate this, we generated transgenic mice that carried macrophage/granulocyte-specific mutations, including a Pdk1 knockout (LysMPdk1(-/-)), a Pdk1 knockout with transactivation-defective Foxo1 (Δ256LysMPdk1(-/-)), a constitutively active nuclear (CN) Foxo1 (CNFoxo1(LysM)), or a transactivation-defective Foxo1 (Δ256Foxo1(LysM)). We analyzed glucose metabolism and gene expression in ATM populations isolated with fluorescence-activated cell sorting. The LysMPdk1(-/-) mice exhibited elevated M1 macrophages in adipose tissue and insulin resistance. Overexpression of transactivation-defective Foxo1 rescued these phenotypes. CNFoxo1(LysM) promoted transcription of the C-C motif chemokine receptor 2 (Ccr2) in ATMs and increased M1 macrophages in adipose tissue. On a high-fat diet, CNFoxo1(LysM) mice exhibited insulin resistance. Pdk1 deletion or Foxo1 activation in bone marrow-derived macrophages abolished insulin and interleukin-4 induction of genes involved in alternative macrophage activation. Thus, Pdk1 regulated macrophage infiltration by inhibiting Foxo1-induced Ccr2 expression. This shows that the macrophage Pdk1/Foxo1 pathway is important in regulating insulin sensitivity in vivo.

Lipoatrophic panniculitis: case report and review of the literature.

BACKGROUND: Lipoatrophic panniculitis (LP) is a rare disease of childhood characterized by eruption of tender erythematous nodules and plaques followed by circumferential bands of lipoatrophy often seen on the arms and legs. This condition has also been known as lipophagic panniculitis of childhood, annular atrophy of the ankles, and partial lipodystrophy. OBSERVATIONS: A previously healthy 8-year-old boy was evaluated for tender, raised plaques on the ankles, which progressed to circumferential atrophy of the distal lower extremities. Biopsy specimen analysis revealed a dense mixed infiltrate extending into the subcutaneous tissue as well as lipophages within the fatty lobules. A diagnosis of LP was made, and the patient began treatment with prednisone and hydroxychloroquine. Methotrexate was added later to the regimen as a steroid-sparing agent, and the dose was increased over the course of 3 months, by which time the cutaneous disease progression was nearly halted. However, the patient continued to have lower leg pain with bone changes demonstrated on magnetic resonance imaging. CONCLUSIONS: We report this case and review of the literature to call attention to the clinical features of LP and its association with skeletal changes. Our patient's response to combination therapy is of interest and contributes to the limited literature about management of this disease.

Subcutaneous lymphoma and related conditions.

A variety of lymphoma entities can involve the subcutaneous tissue. The term subcutaneous panniculitis-like T cell lymphoma is now solely utilized for primary cutaneous CD8+ lymphomas expressing the alphabeta T cell receptor heterodimer. This condition is generally responsive to treatment; however, the development of the hemophagocytic syndrome is a poor prognostic indicator. Overlapping features with lupus panniculitis has been observed, and cases with ambiguous pathology may be classified as atypical lobular lymphocytic panniculitis. These ambiguous cases often respond to systemic steroids or methotrexate. Overall, this condition follows an indolent course; however, evolution into frank lymphomas in some cases reflects the diagnostic difficulties of these conditions. Gamma-delta lymphomas have a poor prognosis regardless of the presence or absence of a hemophagocytic syndrome. Treatment options are limited because of lack of large studies and the rarity of this condition. Prolonged remission may be achieved with allogeneic stem cell transplantation.

Cytophagic histiocytic panniculitis and hemophagocytic lymphohistiocytosis: an overview.

Cytophagic histiocytic panniculitis (CHP) is a rare panniculitis that is associated with systemic features including fevers, hepatosplenomegaly, lymphadenopathy, pancytopenia, hepatic abnormalities, hypertriglyceridemia, and coagulopathy without an elevated erythrocyte sedimentation rate. The panniculitis lesions show adipose tissue lymphocytic and histiocytic infiltration along with hemophagocytosis, which may also appear in bone marrow, spleen, lymph nodes, and liver. Patients may have a rapidly fatal disease course, a longer disease course with intermittent remissions and exacerbations for many years prior to death, or a nonfatal acute or intermittent course responsive to treatment. The cytophagocytic disorder in these patients is a hemophagocytic lymphohistiocytosis (HLH), similar to the infection-activated reaction associated with perforin mutations found in familial hemophagocytic lymphohistiocytosis. HLH is a group of autoinflammatory disorders, which include macrophage activation syndrome and infection-associated hemophagocytic syndrome, which if not treated rapidly, can be fatal. The relationship of CHP and HLH is discussed. CHP associated diseases include: subcutaneous panniculitis-like T cell lymphomas; infections, connective tissue diseases, other malignancies, and the molecular disorders that cause HLH. Treatment of CHP includes: glucocorticoids in combination with cyclosporine, combined chemotherapeutic medications and most recently, anakinra, an Interleukin-1 receptor antagonist; along with supportive care, search for underlying malignancies and treatment thereof, and control of associated infections.

Interleukin-33 induces protective effects in adipose tissue inflammation during obesity in mice.

RATIONALE: Chronic low-grade inflammation involving adipose tissue likely contributes to the metabolic consequences of obesity. The cytokine interleukin (IL)-33 and its receptor ST2 are expressed in adipose tissue, but their role in adipose tissue inflammation during obesity is unclear. OBJECTIVE: To examine the functional role of IL-33 in adipose tissues and investigate the effects on adipose tissue inflammation and obesity in vivo. METHODS AND RESULTS: We demonstrate that treatment of adipose tissue cultures in vitro with IL-33 induced production of Th2 cytokines (IL-5, IL-13, IL-10) and reduced expression of adipogenic and metabolic genes. Administration of recombinant IL-33 to genetically obese diabetic (ob/ob) mice led to reduced adiposity, reduced fasting glucose and improved glucose and insulin tolerance. IL-33 also induced accumulation of Th2 cells in adipose tissue and polarization of adipose tissue macrophages toward an M2 alternatively activated phenotype (CD206(+)), a lineage associated with protection against obesity-related metabolic events. Furthermore, mice lacking endogenous ST2 fed high-fat diet had increased body weight and fat mass and impaired insulin secretion and glucose regulation compared to WT controls fed high-fat diet. CONCLUSIONS: In conclusion, IL-33 may play a protective role in the development of adipose tissue inflammation during obesity.