The modern interleukin-1 superfamily: Divergent roles in obesity

Revisiting the role of IL-27 in obesity-related metabolic diseases: safeguard or perturbation?

The prevalence of metabolic diseases, such as obesity, has been steadily increasing in recent years, posing a significant threat to public health. Therefore, early identification and intervention play a crucial role. With the deepening understanding of the etiology of metabolic diseases, novel therapeutic targets are emerging for the treatment of obesity, lipid metabolism disorders, cardiovascular and cerebrovascular diseases, glucose metabolism disorders, and other related metabolic conditions. IL-27, as a multi-potent cytokine, holds great promise as a potential candidate target in this regard. This article provides a comprehensive review of the latest findings on IL-27 expression and signal transduction in the regulation of immune inflammatory cells, as well as its implications in obesity and other related metabolic diseases. Furthermore, it explores the potential of IL-27 as a novel therapeutic target for the treatment of obesity and metabolic disorders. Finally, an overview is presented on both the opportunities and challenges associated with targeting IL-27 for therapeutic interventions.

Interleukin-33: Expression, regulation and function in adipose tissues

Interleukin-33 (IL-33) is a pleiotropic cytokine of the IL-1 family that plays a key role in innate and adaptive immune responses and contributes to tissue homeostasis. Its role in adipose tissue function has been extensively studied, as adipose tissue serves as an important mediator of metabolic dysfunction. In adipose tissue, IL-33 is primarily produced by stromal cells. Its production is regulated by factors, such as androgens, aging, sympathetic innervation, and various inflammatory stimuli that affect the proliferation and differentiation of IL-33-producing stromal cells. Many studies have elucidated the mechanisms by which IL-33 interacts with the immune system components, local nerve fibers, and adipocytes to influence energy balance, with important consequences in obesity, cold-induced thermogenesis, and aging-related metabolic dysfunction. Here, we detail our current understanding of the molecular events that regulate the production of IL-33 within adipose tissue and discuss its role in regulating adipose function.

Exploring the multifaceted effects of Interleukin-1 in lung cancer: From tumor development to immune modulation

Lung cancer, acknowledged as one of the most fatal cancers globally, faces limited treatment options on an international scale. The success of clinical treatment is impeded by challenges such as late diagnosis, restricted treatment alternatives, relapse, and the emergence of drug resistance. This predicament has led to a saturation point in lung cancer treatment, prompting a rapid shift in focus towards the tumor microenvironment (TME) as a pivotal area in cancer research. Within the TME, Interleukin-1 (IL-1) is abundantly present, originating from immune cells, tissue stromal cells, and tumor cells. IL-1's induction of pro-inflammatory mediators and chemokines establishes an inflammatory milieu influencing tumor occurrence, development, and the interaction between tumors and the host immune system. Notably, IL-1 expression in the TME exhibits characteristics such as staging, tissue specificity, and functional pluripotency. This comprehensive review aims to delve into the impact of IL-1 on lung cancer, encompassing aspects of occurrence, invasion, metastasis, immunosuppression, and immune surveillance. The ultimate goal is to propose a novel treatment approach, considering the intricate dynamics of IL-1 within the TME.

AMPK Activation as a Protective Mechanism to Restrain Oxidative Stress in the Insulin-Resistant State in Skeletal Muscle of Rat Model of PCOS Subjected to Postnatal Overfeeding

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women of reproductive age, often associated with obesity and insulin resistance. Childhood obesity is an important predisposing factor for the development of PCOS later in life. Being particularly interested in the interplay between prepubertal obesity and hyperandrogenemia, we investigated the effects of early postnatal overfeeding, accomplished by reducing litter size during the period of suckling, on energy sensing and insulin signaling pathways in the gastrocnemius muscle of a rat model of PCOS-induced by 5α-dihydrotestosterone (DHT). The combination of overfeeding and DHT treatment caused hyperinsulinemia and decreased systemic insulin sensitivity. Early postnatal overfeeding induced defects at critical nodes of the insulin signaling pathway in skeletal muscle, which was associated with reduced glucose uptake in the presence of hyperandrogenemia. In this setting, under a combination of overfeeding and DHT treatment, skeletal muscle switched to mitochondrial β-oxidation of fatty acids, resulting in oxidative stress and inflammation that stimulated AMP-activated protein kinase (AMPK) activity and its downstream targets involved in mitochondrial biogenesis and antioxidant protection. Overall, a combination of overfeeding and hyperandrogenemia resulted in a prooxidative and insulin-resistant state in skeletal muscle. This was accompanied by the activation of AMPK, which could represent a potential therapeutic target in insulin-resistant PCOS patients.

Celastrol: A Promising Agent Fighting against Cardiovascular Diseases

Cardiovascular diseases (CVD) are leading causes of morbidity and mortality worldwide; therefore, seeking effective therapeutics to reduce the global burden of CVD has become increasingly urgent. Celastrol, a bioactive compound isolated from the roots of the plant Tripterygium wilfordii (TW), has been attracting increasing research attention in recent years, as it exerts cardiovascular treatment benefits targeting both CVD and their associated risk factors. Substantial evidence has revealed a protective role of celastrol against a broad spectrum of CVD including obesity, diabetes, atherosclerosis, cerebrovascular injury, calcific aortic valve disease and heart failure through complicated and interlinked mechanisms such as direct protection against cardiomyocyte hypertrophy and death, and indirect action on oxidation and inflammation. This review will mainly summarize the beneficial effects of celastrol against CVD, largely based on in vitro and in vivo preclinical studies, and the potential underlying mechanisms. We will also briefly discuss celastrol’s pharmacokinetic limitations, which hamper its further clinical applications, and prospective future directions.

The emerging roles of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications

Diabetes mellitus is a metabolic disease caused by a combination of genetics and environmental factors. The importance of the inflammatory response occurring in the pancreas and adipose tissue in the occurrence and progression of diabetes has been gradually accepted. Excess blood glucose and free fatty acids produce large amounts of inflammatory cytokines and chemokines through oxidative stress and endoplasmic reticulum stress. There is sufficient evidence that proinflammatory mediators, such as interleukin (IL)-1β, IL-6, macrophage chemotactic protein-1, and tumor necrosis factor-α, are engaged in the insulin resistance in peripheral adipose tissue and the apoptosis of pancreatic β-cells. IL-36, IL-37, and IL-38, as new members of the IL-1 family, play an indispensable effect in the regulation of immune system homeostasis and are involved in the pathogenesis of inflammatory and autoimmune diseases. Recently, the abnormal expression of IL-36, IL-37, and IL-38 in diabetes has been reported. In this review, we discuss the emerging functions, potential mechanisms, and future research directions on the role of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications.

Decreased serum profile of the interleukin-36α in polycystic ovary syndrome

OBJECTIVE

The aim of this study was to determine the serum adiponectin and interleukin-36 alpha (IL-36α) levels in polycystic ovary syndrome (PCOS), and their relationship with obesity.

MATERIALS AND METHODS

This observatory study included 80 PCOS patients and 58 controls. The clinical, biochemical, and hormonal parameters, and serum adiponectin and IL-36α levels of the patients were evaluated.

RESULTS

The serum IL-36α levels of the PCOS patients were significantly lower when compared to the control group, despite a similar mean body mass index (BMI) (P = 0.000). The adiponectin levels were significantly lower in the obese PCOS group when compared to the obese control group (P = 0.03). The plasma IL-36α level was positively correlated with adiponectin level, but negatively correlated with the serum LH level (P = 0.000 and P = 0.004, respectively). Using receiver operating characteristic analysis, the cut-off value of IL-36α was calculated as 0.815 for PCOS. In the multiple binary logistic regression analysis, IL-36α (OR [95% CI] 0.432 [0.303, 0.616], P < 0.001) and adiponectin (OR [95% CI] 1.044 [1.005, 1.084], P = 0.028) were determined to be significantly associated with PCOS.

CONCLUSION

A reduced IL-36α level may play a role in the pathogenesis of ovulatory disfunction and insulin resistance in PCOS patients. Further studies are needed to understand the pathogenic and clinical significance of the IL-36 system in PCOS.

Obesity-related IL-18 Impairs Treg Function and Promotes Lung Ischemia-reperfusion Injury

RATIONALE

Primary graft dysfunction (PGD) is a severe form of acute lung injury, leading to increased early morbidity and mortality after lung transplantation. Obesity is a major health problem, and recipient obesity is one of the most significant risk factors for developing PGD.

OBJECTIVES

We hypothesized that T-regulatory (Treg) cells are able to dampen early ischemia/reperfusion events and thereby decrease risk of PGD, whereas that action is impaired in obese recipients.

METHODS

We evaluated Treg, T cells and inflammatory markers, plus clinical data, in 79 lung and 41 liver or kidney transplant recipients and studied two groups of mice on high fat diet (HFD), who developed ("inflammatory" HFD) or not ("healthy" HFD) low-grade inflammation with decreased Treg function.

RESULTS

We identified increased levels of IL-18 as a previously unrecognized mechanism that impairs Treg suppressive function in obese individuals. IL-18 decreases levels of FOXP3, the key Treg transcription factor, decreases FOXP3 di- and oligomerization and increases the ubiquitination and proteasomal degradation of FOXP3. IL-18-treated Tregs or Treg from obese mice fail to control PGD, while IL-18 inhibition ameliorates lung inflammation. The IL-18 driven impairment in Treg suppressive function pre-transplant was associated with increased risk and severity of PGD in clinical lung transplant recipients.

CONCLUSION

Obesity-related IL-18 induces Treg dysfunction that may contribute to the pathogenesis of PGD. Evaluation of Treg suppressive function along with IL-18 levels may serve as screening tools to identify pre-transplant obese recipients with increased risk of PGD.

The Peculiar Trialogue between Pediatric Obesity, Systemic Inflammatory Status, and Immunity

Pediatric obesity is not only an energetic imbalance, but also a chronic complex multisystem disorder that might impair both the life length and quality. Its pandemic status should increase worldwide awareness regarding the long-term life-threatening associated complications. Obesity related complications, such as cardiovascular, metabolic, or hepatic ones, affect both short and long-term wellbeing, and they do not spare pediatric subjects, defined as life-threatening consequences of the systemic inflammatory status triggered by the adipose tissue. The energetic imbalance of obesity clearly results in adipocytes hypertrophy and hyperplasia expressing different degrees of chronic inflammation. Adipose tissue might be considered an immune organ due to its rich content in a complex array of immune cells, among which the formerly mentioned macrophages, neutrophils, mast cells, but also eosinophils along with T and B cells, acting together to maintain the tissue homeostasis in normal weight individuals. Adipokines belong to the class of innate immunity humoral effectors, and they play a crucial role in amplifying the immune responses with a subsequent trigger effect on leukocyte activation. The usefulness of complete cellular blood count parameters, such as leukocytes, lymphocytes, neutrophils, erythrocytes, and platelets as predictors of obesity-triggered inflammation, was also proved in pediatric patients with overweight or obesity. The dogma that adipose tissue is a simple energy storage tissue is no longer accepted since it has been proved that it also has an incontestable multifunctional role acting like a true standalone organ resembling to endocrine or immune organs.

Waist to height ratio is associated with an increased risk of mortality in Chinese patients with heart failure with preserved ejection fraction

Background

Abdominal obesity as a predominant comorbidity has played a key role in the incidence and worsening of heart failure with preserved ejection fraction (HFpEF), and waist-to-height ratio (WHtR) behaves better than waist circumference or body mass index in evaluating abdominal obesity. While the association between WHtR and all-cause death in Chinese patients with HFpEF remains unclear.

Methods

Patients with stable HFpEF (N = 2041) who presented to our hospital from January 2008 to July 2019 were divided into low-WHtR (< 0.5, N = 378) and high-WHtR (≥ 0.5, N = 1663). Multivariable Cox proportional-hazard models were used to examine the association of WHtR with all-cause death.

Results

The average age was 76.63 ± 11.44 years, and the mean follow-up was 4.53 years. During follow-up, 185 patients (9.06%) reached the primary outcome of all-cause death. As for the secondary outcome, 79 patients (3.87%) experienced cardiovascular death, 106 (5.19%) had non-cardiovascular death, and 94 (4.61%) had heart failure rehospitalization. After multivariable adjustment, a higher WHtR was significantly associated with the increased risks of all-cause death [adjusted hazard ratios (HR) 1.91, 95% confidence interval (CI) 1.06–3.45, p = 0.032], cardiovascular death (adjusted HR 2.58; 95% CI 1.01–6.67, p = 0.048), and HF rehospitalization (adjusted HR 3.04; 95% CI 1.26–7.31, p = 0.013).

Conclusions

Higher WHtR is an independent risk factor for all-cause death in Chinese patients with HFpEF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02080-9.

Use of a Highly Antioxidant Diet in the Regulation of Adipose Tissue Secretion in Patients after the BIB Procedure

Obesity is a global problem. The secretory activity of adipose tissue causes inflammation and disturbs metabolic parameters. Low-invasive bariatric procedures are an alternative to surgical treatment, especially in individuals who do not qualify for surgery or in whom conservative treatment does not bring the expected results. The diets designed for bariatric patients contained an increased proportion of bioflavonoids. The dietary components were carefully selected to provide anti-inflammatory effects. The experimental diets showed an antioxidant capacity (TEAC) of 433–969 µM TE/100 g or 100 mL, reducing ability (FRAP) of 13–58 µM TE/100 g or 100 mL, and total polyphenol content of 80–250 mg catechins/100 g or 100 mL. Lower levels of adipocytokines were obtained in the blood of patients following the diet. The results of the present study showed the participation of some adipocytokines in the regulation of energy homeostasis, lipid metabolism, glucose level, blood pressure and inflammation. Diet therapy should yield positive results in the long term, with the possibility of using immune modulation in personalized therapy for metabolic syndrome.

A matter of time: Circadian clocks in osteoarthritis and the potential of chronotherapy

Osteoarthritis (OA) is a common and debilitating joint disease which develops and progresses with age. Despite extensive research into the disease, potent disease-modifying drugs remain elusive. Changes to the character and function of chondrocytes of the articular cartilage underly the pathogenesis of OA. A recently emerging facet of chondrocyte biology that has been implicated in OA pathogenesis is the role of circadian rhythms, and the cellular clock which governs rhythmic gene transcription. Here, we review the role of the chondrocyte's cellular clock in governing normal homeostasis, and explore the wide range of consequences that contribute to OA development when the clock is dysregulated by aging and other factors. Finally, we explore how harnessing this understanding of clock mechanics in aging and OA can be translated into novel treatment strategies, or 'chronotherapies', for patients.

Postprandial Glucose Spikes, an Important Contributor to Cardiovascular Disease in Diabetes?

Clinical trials investigating whether glucose lowering treatment reduces the risk of CVD in diabetes have thus far yielded mixed results. However, this doesn't rule out the possibility of hyperglycemia playing a major causal role in promoting CVD or elevating CVD risk. In fact, lowering glucose appears to promote some beneficial long-term effects, and continuous glucose monitoring devices have revealed that postprandial spikes of hyperglycemia occur frequently, and may be an important determinant of CVD risk. It is proposed that these short, intermittent bursts of hyperglycemia may have detrimental effects on several organ systems including the vasculature and the hematopoietic system collectively contributing to the state of elevated CVD risk in diabetes. In this review, we summarize the potential mechanisms through which hyperglycemic spikes may increase atherosclerosis and how new and emerging interventions may combat this.

Ghrelin protects against obesity-induced myocardial injury by regulating the lncRNA H19/miR-29a/IGF-1 signalling axis

BACKGROUND

Obesity is associated with the impairment of cardiac fitness and consequent ventricular dysfunction and heart failure. Ghrelin has been largely documented to be cardioprotective against ischaemia/reperfusion injury. However, the role of ghrelin in obesity-induced myocardial injury is largely unknown. This study sought to determine the cardiac effect of ghrelin against obesity-induced injury and the underlying mechanisms.

METHODS

The effect of ghrelin was evaluated in a mouse model of obesity and a palmitic acid (PA)-treated cardiomyocyte cell line with or without ghrelin transfection. Gene and protein expression levels were determined by real-time PCR and western blot, respectively. Cell apoptosis was measured by flow cytometry analysis.

RESULTS

In the present study, we found that both a high-fat diet (HFD) and PA treatment caused myocardial injury by increasing apoptosis and the expression of inflammatory cytokines. Overexpression of ghrelin reversed the effects induced by HFD or PA treatment. Knockdown of lncRNA H19 or overexpression of miR-29a abrogated the cardioprotective effects of ghrelin against apoptosis and inflammation. We also found that IGF-1 was a target gene of miR-29a and that H19 regulated IGF-1 expression via miR-29a. Overexpression of IGF-1 partially reversed the apoptosis and inflammation promoting effects of miR-29a.

CONCLUSIONS

Our findings suggested that ghrelin protected against obesity-induced myocardial injury by regulating the H19/miR-29a/IGF-1 signalling axis, providing further evidence for the clinical application of ghrelin.

Hydroxytyrosol Modulates Adipocyte Gene and miRNA Expression Under Inflammatory Condition

Chronic inflammation of the adipose tissue (AT) is a major contributor to obesity-associated cardiometabolic complications. The olive oil polyphenol hydroxytyrosol (HT) contributes to Mediterranean diet cardiometabolic benefits through mechanisms still partially unknown. We investigated HT (1 and 10 μmol/L) effects on gene expression (mRNA and microRNA) related to inflammation induced by 10 ng/mL tumor necrosis factor (TNF)-α in human Simpson–Golabi–Behmel Syndrome (SGBS) adipocytes. At real-time PCR, HT significantly inhibited TNF-α-induced mRNA levels, of monocyte chemoattractant protein-1, C-X-C Motif Ligand-10, interleukin (IL)-1β, IL-6, vascular endothelial growth factor, plasminogen activator inhibitor-1, cyclooxygenase-2, macrophage colony-stimulating factor, matrix metalloproteinase-2, Cu/Zn superoxide dismutase-1, and glutathione peroxidase, as well as surface expression of intercellular adhesion molecule-1, and reverted the TNF-α-mediated inhibition of endothelial nitric oxide synthase, peroxisome proliferator-activated receptor coactivator-1α, and glucose transporter-4. We found similar effects in adipocytes stimulated by macrophage-conditioned media. Accordingly, HT significantly counteracted miR-155-5p, miR-34a-5p, and let-7c-5p expression in both cells and exosomes, and prevented NF-κB activation and production of reactive oxygen species. HT can therefore modulate adipocyte gene expression profile through mechanisms involving a reduction of oxidative stress and NF-κB inhibition. By such mechanisms, HT may blunt macrophage recruitment and improve AT inflammation, preventing the deregulation of pathways involved in obesity-related diseases.

Aerobic Exercise Ameliorates Myocardial Inflammation, Fibrosis and Apoptosis in High-Fat-Diet Rats by Inhibiting P2X7 Purinergic Receptors

Background

High-fat-diet (HFD) is associated with chronic low-grade inflammation. P2X7 purinergic receptors (P2X7R) are key regulators of inflammasome activation. The benefits of exercise are partly attributed to its anti-inflammatory effect, but whether it regulates P2X7R expression to improve remodeling in cardiac myocytes treated by HFD is not completely clarified.

Methods

Three groups of Sprague-Dawley (SD) rats were studied: (1) control group (fed a normal chow diet), (2) HFD group, and (3) HFD+ exercise group. H9c2 myocytes were pretreated with or without A438079 (a P2X7R inhibitor) and then exposed to 200 μM palmitic acid (PA) for 24 h. The levels of mRNA and protein were measured by real-time PCR and Western blot, respectively. Masson staining and hematoxylin-eosin (HE) staining were used to identify remodeling of the heart. The concentration of IL-1β in serum or supernatants were measured by ELISA.

Results

In vivo, collagen deposition and the number of disordered cells significantly increased in the hearts of the HFD group compared to the control group. However, exercise markedly reversed these changes in the myocardium, and the same trends were observed in the expression of MMP9, collagen I and TGF-β. Notably, the expression of P2X7R, NLRP3, caspase-1 in the hearts, and serum IL-1β level were also greatly upregulated in the heart of the HFD diet rats, and all these changes were ameliorated in the HFD + EX group. As expected, exercise also reduced the number of TUNEL-positive cells, which was consistent with the caspase-3, Bax, and Bcl-2 results. Moreover, exercise reduced body weight and blood lipid concentrations in the HFD diet rats. In vitro, we observed that the hallmark of fibrosis, inflammation and apoptosis in H9c2 myocytes enhanced by PA, and the P2X7R inhibitor treatment significantly reduced the expression of the NLRP3, caspase-1, suppressed the secretion of IL-1β of H9c2 cells, inhibited collagen I, TGF-β, MMP9, Bax, caspase-3 levels and increased the expression of Bcl-2, compared with the PA group. In addition, a decrease of the number of TUNEL-positive cells used by A438079 further support that cardiomyocytes apoptosis could be inhibited.

Conclusion

Aerobic exercise reversed the cardiac remodeling via the reduction of inflammation, fibrosis and apoptosis in HFD rats, at least in part through inhibiting P2X7R expression in cardiomyocytes.

Interleukin-36 cytokines alter the intestinal microbiome and can protect against obesity and metabolic dysfunction

Members of the interleukin-1 (IL-1) family are important mediators of obesity and metabolic disease and have been described to often play opposing roles. Here we report that the interleukin-36 (IL-36) subfamily can play a protective role against the development of disease. Elevated IL-36 cytokine expression is found in the serum of obese patients and negatively correlates with blood glucose levels among those presenting with type 2 diabetes. Mice lacking IL-36Ra, an IL-36 family signalling antagonist, develop less diet-induced weight gain, hyperglycemia and insulin resistance. These protective effects correlate with increased abundance of the metabolically protective bacteria Akkermansia muciniphila in the intestinal microbiome. IL-36 cytokines promote its outgrowth as well as increased colonic mucus secretion. These findings identify a protective role for IL-36 cytokines in obesity and metabolic disease, adding to the current understanding of the role the broader IL-1 family plays in regulating disease pathogenesis.

IL-36α,β and ɣ are IL-1-related cytokines promoting inflammation in the skin and intestine. Here the authors show they are elevated in individuals with obesity, and that mice lacking the IL-36 receptor antagonist are more resistant to diet-induced obesity and metabolic dysfunction, which depends on intestinal microbiota.

Macrophage Origin, Metabolic Reprogramming and IL-1 Signaling: Promises and Pitfalls in Lung Cancer

Macrophages are tissue-resident cells that act as immune sentinels to maintain tissue integrity, preserve self-tolerance and protect against invading pathogens. Lung macrophages within the distal airways face around 8000⁻9000 L of air every day and for that reason are continuously exposed to a variety of inhaled particles, allergens or airborne microbes. Chronic exposure to irritant particles can prime macrophages to mediate a smoldering inflammatory response creating a mutagenic environment and favoring cancer initiation. Tumor-associated macrophages (TAMs) represent the majority of the tumor stroma and maintain intricate interactions with malignant cells within the tumor microenvironment (TME) largely influencing the outcome of cancer growth and metastasis. A number of macrophage-centered approaches have been investigated as potential cancer therapy and include strategies to limit their infiltration or exploit their antitumor effector functions. Recently, strategies aimed at targeting IL-1 signaling pathway using a blocking antibody have unexpectedly shown great promise on incident lung cancer. Here, we review the current understanding of the bridge between TAM metabolism, IL-1 signaling, and effector functions in lung adenocarcinoma and address the challenges to successfully incorporating these pathways into current anticancer regimens.

Interleukin (IL)-33 and the IL-1 Family of Cytokines-Regulators of Inflammation and Tissue Homeostasis

Cytokines play an integral role in shaping innate and adaptive immune responses. Members of the interleukin (IL)-1 family regulate a plethora of immune-cell-mediated processes, which include pathogen defense and tissue homeostasis. Notably, the IL-1 family cytokine IL-33 promotes adaptive and innate type 2 immune responses, confers viral protection and facilitates glucose metabolism and tissue repair. At the cellular level, IL-33 stimulates differentiation, maintenance, and function of various immune cell types, including regulatory T cells, effector CD4⁺ and CD8⁺ T cells, macrophages, and type 2 innate lymphoid cells (ILC2s). Other IL-1 family members, such as IL-1β and IL-18 promote type 1 responses, while IL-37 limits immune activation. Although IL-1 cytokines play critical roles in immunity and tissue repair, their deregulated expression is often linked to autoimmune and inflammatory diseases. Therefore, IL-1 cytokines are regulated tightly by posttranscriptional mechanisms and decoy receptors. In this review, we discuss the biology and function of IL-1 family cytokines, with a specific focus on regulation and function of IL-33 in immune and tissue homeostasis.

Obesity-Induced TNFα and IL-6 Signaling: The Missing Link between Obesity and Inflammation-Driven Liver and Colorectal Cancers

Obesity promotes the development of numerous cancers, such as liver and colorectal cancers, which is at least partly due to obesity-induced, chronic, low-grade inflammation. In particular, the recruitment and activation of immune cell subsets in the white adipose tissue systemically increase proinflammatory cytokines, such as tumor necrosis factor α (TNFα) and interleukin-6 (IL-6). These proinflammatory cytokines not only impair insulin action in metabolic tissues, but also favor cancer development. Here, we review the current state of knowledge on how obesity affects inflammatory TNFα and IL-6 signaling in hepatocellular carcinoma and colorectal cancers.

Regulation of IL-1 signaling by the decoy receptor IL-1R2

The pleiotropic cytokine IL-1 mediates its biological functions via association with the signaling receptor IL-1R1. Despite an apparent simplicity in IL-1 signaling activation, multiple negative regulators have been identified. The decoy receptor IL-1R2 (also known as CD121b) can suppress IL-1 maturation, sequester its active forms or hinder the signaling complex assembly. IL-1R2 is differentially expressed among numerous cell types and displays cis- and trans- modes of action. In this review, we link different forms of IL-1R2 (membrane-bound (mIL-1R2), secreted (sIL-1R2), shedded (shIL-1R2), cytoplasmic, and intracellular domain (IL-1R2^ICD) restricted) with their ability to interfere with IL-1, thereby regulating immune responses. We also discuss the intriguing possible function of IL-1R2 as a transcriptional regulator. Finally, we summarize the known impact of IL-1R2 in disease pathogenesis and discuss its potential role in treatment of inflammatory conditions.

Hand of FATe: lipid metabolism in hematopoietic stem cells

PURPOSE OF REVIEW

Hematopoietic stem cells (HSCs) reside in the bone marrow and are important in replenishing all cells in the blood through a process termed hematopoiesis. One of the defining characteristics of HSCs is that they must be able to balance their self-renewal capacity with their differentiation into committed blood cells in various blood lineages. For these events to occur, HSCs must be tightly regulated in the bone marrow by intrinsic and extrinsic factors to maintain steady hematopoiesis.

RECENT FINDINGS

Recently, the effect on how metabolism regulates HSC function has received a great amount of attention. In particular, lipids have been found to participate in mitochondrial activity to maintain HSCs, a role previously overlooked due to HSCs being thought of as mostly glycolytic. Moreover, there has been a re-emergence of how adipocytes in the bone marrow can regulate HSCs.

SUMMARY

As these areas evolve, more studies are required to determine the exact contribution of lipids toward HSC maintenance. These studies will allow newer therapeutic targets to help reduce abnormal hematopoiesis such as myelopoiesis, which contributes to many metabolic diseases.

Low expression of IL-18 and IL-18 receptor in human skeletal muscle is associated with systemic and intramuscular lipid metabolism-Role of HIV lipodystrophy

Introduction

Interleukin (IL)-18 is involved in regulation of lipid and glucose metabolism. Mice lacking whole-body IL-18 signalling are prone to develop weight gain and insulin resistance, a phenotype which is associated with impaired fat oxidation and ectopic skeletal muscle lipid deposition. IL-18 mRNA is expressed in human skeletal muscle but a role for IL-18 in muscle has not been identified. Patients with HIV-infection and lipodystrophy (LD) are characterized by lipid and glucose disturbances and increased levels of circulating IL-18. We hypothesized that skeletal muscle IL-18 and IL-18 receptor (R) expression would be altered in patients with HIV-lipodystrophy.

Design and methods

Twenty-three HIV-infected patients with LD and 15 age-matched healthy controls were included in a cross-sectional study. Biopsies from the vastus lateralis muscle were obtained and IL-18 and IL-18R mRNA expression were measured by real-time PCR and sphingolipids (ceramides, sphingosine, sphingosine-1-Phosphate, sphinganine) were measured by HPLC. Insulin resistance was assessed by HOMA and the insulin response during an OGTT.

Results

Patients with HIV-LD had a 60% and 54% lower level of muscular IL-18 and IL-18R mRNA expression, respectively, compared to age-matched healthy controls. Patients with HIV-LD had a trend towards increased levels of ceramide (18.3±4.7 versus 14.8±3.0,p = 0.06) and sphingosine (0.41±0.13 versus 0.32±0.07, and lower level of sphinganine (p = 0.06). Low levels of muscle IL-18 mRNA correlated to high levels of ceramides (r = -0.31, p = 0.038) and sphingosine-1P (r = -0.29, p = 0.046) in skeletal muscle, whereas such a correlation was not found in healthy controls. Low expression of IL-18 mRNA in skeletal muscle correlated to elevated concentration of circulating triglycerides (R_p = -0.73, p<0.0001). Neither muscle expression of IL-18 mRNA or ceramide correlated to parameters of insulin resistance.

Conclusion

IL-18 (mRNA) in skeletal muscle appears to be involved in the regulation of intramuscular lipid metabolism and hypertriglyceridemia.

Treatment of obesity-associated overactive bladder by the phosphodiesterase type-4 inhibitor roflumilast

PURPOSE

To prove that phosphodiesterase type-4 inhibitors could potentially treat obesity-associated overactive bladder through modulation of the systemic inflammatory response.

METHODS

In this 12-week study, 90 female Sprague-Dawley rats were divided into three groups: (1) vehicle-treated normal diet (ND)-fed rats; (2) vehicle-treated high-fat diet (HFD)-fed rats; and (3) roflumilast-treated HFD-fed rats. Oral roflumilast (5 mg/kg/day) was administered during the last 4 weeks of HFD feeding in the test group. At 12 weeks, a urodynamic study was performed in ten rats of each group. Bladder tissue was extracted, the bladder mucosa was separated under microscopy, and bladder detrusor smooth muscle (DSM) expression of TNF-α, interleukin (IL)-6, IL-1β, and nuclear factor kappa B (NF-κB) were analyzed using Western blotting and quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

Bodyweights of the HFD-fed rats significantly increased and were not ameliorated by roflumilast treatment. Cystometry evidenced augmented frequency and non-void contractions in obese rats that were also prevented by roflumilast. These alterations were accompanied by a markedly increased expression of TNF-α, IL-6, IL-1β, and NF-κB in DSM of obese rats. Furthermore, roflumilast decreased expression of inflammatory factors in DSM.

CONCLUSIONS

Oral treatment with roflumilast in rats fed an HFD restores normal bladder function and downregulates expression of inflammatory factors in the bladder.