On the TRAIL of obesity and diabetes

TNF-Related Apoptosis-Inducing Ligand: Non-Apoptotic Signalling

TNF-related apoptosis-inducing ligand (TRAIL or Apo2 or TNFSF10) belongs to the TNF superfamily. When bound to its agonistic receptors, TRAIL can induce apoptosis in tumour cells, while sparing healthy cells. Over the last three decades, this tumour selectivity has prompted many studies aiming at evaluating the anti-tumoral potential of TRAIL or its derivatives. Although most of these attempts have failed, so far, novel formulations are still being evaluated. However, emerging evidence indicates that TRAIL can also trigger a non-canonical signal transduction pathway that is likely to be detrimental for its use in oncology. Likewise, an increasing number of studies suggest that in some circumstances TRAIL can induce, via Death receptor 5 (DR5), tumour cell motility, potentially leading to and contributing to tumour metastasis. While the pro-apoptotic signal transduction machinery of TRAIL is well known from a mechanistic point of view, that of the non-canonical pathway is less understood. In this study, we the current state of knowledge of TRAIL non-canonical signalling.

Genetic Investigation of the Trail Mechanism in Diabetic and Non-diabetic Obese Patients

Obesity is an important healthcare issue caused by abnormally increased adipose tissue because of energy-intake overcoming energy expenditure. Disturbances in the physiological function of adipose tissue mediate the development of diabetes. It is a metabolic disease that results from decreased insulin-levels and/or changes in the insulin action mechanism. Tumor Necrosis Factor-Associated Apoptosis-Inducing Ligand(TRAIL), which is a member of the Tumor Necrosis Factor(TNF)-family with an important role in adipose tissue biology, is included in many studies with its ability to induce apoptosis in cancer cells, but the number of human-studies conducted on the gene related to its protective-role against diabetes and obesity at this level is insufficient. Our study was carried out as a case and control and included three groups (80 diabetic obese, 80 non-diabetic obese, and 80 healthy individuals as the control group). The Real-Time-PZR(RT-qPZR), and DNA Sanger-Sequencing Methods were used for gene expression and gene squences. As a result of the analyses, TRAIL gene expression level was found to be higher in the controls than in the diabetic-obese and non-diabetic-obese group. This change in TRAIL gene expression suggests that TRAIL maybe a protective factor against diabetes. The presence of rs781673405, rs143353036, rs1244378045, rs767450259, rs759369504, rs750556128, and rs369143448 mutations, which was determined with the Sequencing-Method, was shown for the first time in the present study. In addition, it is the first study in which human TRAIL gene-expression and sequencing were performed together. We believe that these data will make an important contribution to the literature.

Approximate estimation of cell-type resolution transcriptome in bulk tissue through matrix completion

Single-cell RNA sequencing (scRNA-seq) has emerged as a powerful tool for uncovering cellular heterogeneity. However, the high costs associated with this technique have rendered it impractical for studying large patient cohorts. We introduce ENIGMA (Deconvolution based on Regularized Matrix Completion), a method that addresses this limitation through accurately deconvoluting bulk tissue RNA-seq data into a readout with cell-type resolution by leveraging information from scRNA-seq data. By employing a matrix completion strategy, ENIGMA minimizes the distance between the mixture transcriptome obtained with bulk sequencing and a weighted combination of cell-type-specific expression. This allows the quantification of cell-type proportions and reconstruction of cell-type-specific transcriptomes. To validate its performance, ENIGMA was tested on both simulated and real datasets, including disease-related tissues, demonstrating its ability in uncovering novel biological insights.

Imatinib prevents dexamethasone-induced pancreatic β-cell apoptosis via decreased TRAIL and DR5

Prolonged administration of dexamethasone, a potent anti-inflammatory drug, can lead to steroid-induced diabetes. Imatinib, a medication commonly prescribed for chronic myeloid leukemia (CML), has been shown to improve diabetes in CML patients. Our recent study demonstrated that dexamethasone induces pancreatic β-cell apoptosis by upregulating the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptor, death receptor 5 (DR5). We hypothesized that imatinib may protect against dexamethasone-induced pancreatic β-cell apoptosis by reducing the expression of TRAIL and DR5, thereby favorably modulating downstream effectors in apoptotic pathways. We test this hypothesis by assessing the effects of imatinib on dexamethasone-induced apoptosis in rat insulinoma cell line cells. As anticipated, dexamethasone treatment led to increased TRAIL and DR5 expression, as well as an elevation in superoxide production. Conversely, expression of the TRAIL decoy receptor (DcR1) was decreased. Moreover, key effectors in the extrinsic and intrinsic apoptosis pathways, such as B-cell lymphoma 2 (BCL-2) associated X (BAX), nuclear factor kappa B (NF-κb), P73, caspase 8, and caspase 9, were upregulated, while the antiapoptotic protein BCL-2 was downregulated. Interestingly and importantly, imatinib at a concentration of 10 µM reversed the effect of dexamethasone on TRAIL, DR5, DcR1, superoxide production, BAX, BCL-2, NF-κB, P73, caspase 3, caspase 8, and caspase 9. Similar effects of imatinib on dexamethasone-induced TRAIL and DR5 expression were also observed in isolated mouse islets. Taken together, our findings suggest that imatinib protects against dexamethasone-induced pancreatic β-cell apoptosis by reducing TRAIL and DR5 expression and modulating downstream effectors in the extrinsic and intrinsic apoptosis pathways.

Anti-Diabetic and Anti-Adipogenic Effect of Harmine in High-Fat-Diet-Induced Diabetes in Mice

One of the most important health issues facing the world today is obesity. It is an important independent risk factor for developing type 2 diabetes. Harmine offers various pharmacological effects, such as anti-inflammatory and anti-tumor effects. The current study aims to investigate Harmine's anti-diabetic and anti-adipogenic properties in albino mice after inducing low-grade inflammation with a high-fat diet (HFD). About forty-eight male albino mice were divided into four groups. Group 1: control mice were injected with daily saline and fed a normal chow diet of 21% protein for 5 months. Group 2: mice were treated daily with IP-injected Harmine (30 mg/kg body weight) and were fed a normal chow diet for 5 months. Group 3: mice were fed HFD to induce type 2 Diabetes Mellitus (T2DM) for 5 months. Group 4: mice were fed HFD for 14 weeks and treated with Harmine for the last 6 weeks. A figh-fat diet caused a significant increase in body and organ weight, lipid profiles, and destructive changes within the pancreas, kidney, and liver tissue. The administration of Harmine led to a remarkable improvement in the histological and ultrastructural changes induced by HFD. The findings indicate that mice cured using Harmine had lower oxidative stress, a higher total antioxidant capacity, and a reduced lipid profile compared to HFD mice. Harmine led to the hepatocytes partly restoring their ordinary configuration. Furthermore, it was noticed that the pathological incidence of damage in the structure of both the kidney and pancreas sections reduced in comparison with the diabetic group. Additional research will be required to fully understand Harmine and its preventive effects on the two forms of diabetes.

Expression-based Genome-wide Association Study Links OPN and IL1-RA With Newly Diagnosed Type 1 Diabetes in Children

CONTEXT

Islet autoantibodies (IAbs) are currently the most reliable indicators of islet autoimmunity. However, IAbs do not fully meet the need for the prediction and intervention of type 1 diabetes (T1D). Serological proteins should be great sources for biomarkers.

OBJECTIVE

This work aimed to identify new proteomic biomarkers with the technology of an expression-based genome-wide association study (eGWAS) in children newly diagnosed with T1D.

METHODS

In an attempt to identify additional biomarkers, we performed an eGWAS using microarray data from 169 arrays of the pancreatic islets of T1D rodents (78 T1D cases and 91 controls). We ranked all 16 099 protein-coding genes by the likelihood of differential expression in the pancreatic islets. Our top 20 secreted proteins were screened in 170 children including 100 newly diagnosed T1D, and 50 type 2 diabetes (T2D) and 20 age-matched healthy children. With 6 proteins showing significance, we further conducted a validation study using the second independent set of 400 samples from children including 200 newly diagnosed with T1D, 100 T2D, and 100 age-matched controls.

RESULTS

We identified 2 serum proteins that were significantly changed in T1D vs both control and T2D, and 5 serum proteins were significantly changed both in T1D and T2D vs control. Serum osteopontin (OPN) levels were uniquely higher in T1D (T1D vs controls, P = 1.29E-13 ~ 9.38E-7, T1D vs T2D, P = 2.65E-8 ~ 1.58E-7) with no difference between T2D and healthy control individuals. Serum interleukin 1 receptor antagonist (IL-1RA) levels were lower in T1D compared both with T2D (P = 3.36E-9~0.0236) and healthy participants (P = 1.09E-79 ~ 2.00E-12).

CONCLUSION

Our results suggest that OPN and IL1-RA could be candidates for useful biomarkers for T1D in children.

Unspecific CTL Killing Is Enhanced by High Glucose via TNF-Related Apoptosis-Inducing Ligand

TNF-related apoptosis inducing ligand (TRAIL) is expressed on cytotoxic T lymphocytes (CTLs) and TRAIL is linked to progression of diabetes. However, the impact of high glucose on TRAIL expression and its related killing function in CTLs still remains largely elusive. Here, we report that TRAIL is substantially up-regulated in CTLs in environments with high glucose (HG) both in vitro and in vivo. Non-mitochondrial reactive oxygen species, NFκB and PI3K/Akt are essential in HG-induced TRAIL upregulation in CTLs. TRAIL^high CTLs induce apoptosis of pancreatic beta cell line 1.4E7. Treatment with metformin and vitamin D reduces HG-enhanced expression of TRAIL in CTLs and coherently protects 1.4E7 cells from TRAIL-mediated apoptosis. Our work suggests that HG-induced TRAIL^high CTLs might contribute to the destruction of pancreatic beta cells in a hyperglycemia condition.

Repositioning the Role of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) on the TRAIL to the Development of Diabetes Mellitus: An Update of Experimental and Clinical Evidence

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF protein superfamily, represents a multifaceted cytokine with unique biological features including both proapoptotic and pro-survival effects in different cell types depending on receptor interactions and local stimuli. Beyond its extensively studied anti-tumor and immunomodulatory properties, a growing body of experimental and clinical evidence over the past two decades suggests a protective role of TRAIL in the development of type 1 (T1DM) and type 2 (T2DM) diabetes mellitus. This evidence can be briefly summarized by the following observations: (i) acceleration and exacerbation of T1DM and T2DM by TRAIL blockade or genetic deficiency in animal models, (ii) prevention and amelioration of T1DM and T2DM with recombinant TRAIL treatment or systemic TRAIL gene delivery in animal models, (iii) significantly reduced circulating soluble TRAIL levels in patients with T1DM and T2DM both at disease onset and in more advanced stages of diabetes-related complications such as cardiovascular disease and diabetic nephropathy, (iv) increase of serum TRAIL levels in diabetic patients after initiation of antidiabetic treatment and metabolic improvement. To explore the underlying mechanisms and provide mechanistic links between TRAIL and diabetes, a number of animal and in vitro studies have reported direct effects of TRAIL on several tissues involved in diabetes pathophysiology such as pancreatic islets, skeletal muscle, adipose tissue, liver, kidney, and immune and vascular cells. Residual controversy remains regarding the effects of TRAIL on adipose tissue homeostasis. Although the existing evidence is encouraging and paves the way for investigating TRAIL-related interventions in diabetic patients with cardiometabolic abnormalities, caution is warranted in the extrapolation of animal and in vitro data to the clinical setting, and further research in humans is imperative in order to uncover all aspects of the TRAIL-diabetes relationship and delineate its therapeutic implications in metabolic disease.

ER stress-induced cell death proceeds independently of the TRAIL-R2 signaling axis in pancreatic β cells

Prolonged ER stress and the associated unfolded protein response (UPR) can trigger programmed cell death. Studies in cancer cell lines demonstrated that the intracellular accumulation of TRAIL receptor-2 (TRAIL-R2) and the subsequent activation of caspase-8 contribute significantly to apoptosis induction upon ER stress. While this might motivate therapeutic strategies that promote cancer cell death through ER stress-induced caspase-8 activation, it could also support the unwanted demise of non-cancer cells. Here, we therefore investigated if TRAIL-R2 dependent signaling towards apoptosis can be induced in pancreatic β cells, whose loss by prolonged ER stress is associated with the onset of diabetes. Interestingly, we found that elevated ER stress in these cells does not result in TRAIL-R2 transcriptional induction or elevated protein levels, and that the barely detectable expression of TRAIL-R2 is insufficient to allow TRAIL-induced apoptosis to proceed. Overall, this indicates that apoptotic cell death upon ER stress most likely proceeds independent of TRAIL-R2 in pancreatic β cells. Our findings therefore point to differences in ER stress response and death decision-making between cancer cells and pancreatic β cells and also have implications for future targeted treatment strategies that need to differentiate between ER stress susceptibility of cancer cells and pancreatic β cells.

TRAIL/DR5 pathway promotes AKT phosphorylation, skeletal muscle differentiation, and glucose uptake

TNF-related apoptosis-inducing ligand (TRAIL) is a protein that induces apoptosis in cancer cells but not in normal ones, where its effects remain to be fully understood. Previous studies have shown that in high-fat diet (HFD)-fed mice, TRAIL treatment reduced body weight gain, insulin resistance, and inflammation. TRAIL was also able to increase skeletal muscle free fatty acid oxidation. The aim of the present work was to evaluate TRAIL actions on skeletal muscle. Our in vitro data on C2C12 cells showed that TRAIL treatment significantly increased myogenin and MyHC and other hallmarks of myogenic differentiation, which were reduced by Dr5 (TRAIL receptor) silencing. In addition, TRAIL treatment significantly increased AKT phosphorylation, which was reduced by Dr5 silencing, as well as glucose uptake (alone and in combination with insulin). Our in vivo data showed that TRAIL increased myofiber size in HFD-fed mice as well as in db/db mice. This was associated with increased myogenin and PCG1α expression. In conclusion, TRAIL/DR5 pathway promotes AKT phosphorylation, skeletal muscle differentiation, and glucose uptake. These data shed light onto a pathway that might hold therapeutic potential not only for the metabolic disturbances but also for the muscle mass loss that are associated with diabetes.

Biochemical and immunological changes in obesity

Obesity is a syndemia that promotes high expenditures for public health, and is defined by the excess of adipose tissue that is classified according to its function and anatomical distribution. In obese people, this tissue generates oxidative stress associated with a chronic inflammatory response, in which there is an imbalance in relation to the release of hormones and adipokines that cause loss of body homeostasis and predisposition to the development of some comorbidities. The purpose of this review is to summarize the main events that occur during the onset and progression of obesity with a special focus on biochemical and immunological changes. Hypertrophied and hyperplasia adipocytes have biomarkers and release adipokines capable of regulating pathways and expressing genes that culminate in the development of metabolic changes, such as changes in energy balance and intestinal microbiota, and the development of some comorbidities, diabetes mellitus, dyslipidemias, arterial hypertension, liver disease, cancer, allergies, osteoporosis, sarcopenia and obstructive sleep apnea. Thus, it is necessary to treat and/or prevent pathology, using traditional methods based on healthy eating, and regular physical and leisure activities.

TRAIL treatment prevents renal morphological changes and TGF-β-induced mesenchymal transition associated with diabetic nephropathy

BACKGROUND

TNF-related apoptosis-inducing ligand (TRAIL) has attracted attention not only as an anti-cancer agent, but also as a potential treatment for diabetes. Animal studies have shown that TRAIL delivery ameliorated glucose control in type 1 and type 2 diabetes. It is currently unknown whether TRAIL positive effects are maintained in more severe forms of type 2 diabetes, and whether they include renoprotection. Our study aimed at evaluating TRAIL effects in a severe form of type 2 diabetes with nephropathy.

MATERIALS AND METHODS

A total of 20 db/db mice were treated with saline or TRAIL twice per week for 12 weeks. In parallel, renal tubular epithelial cells were cultured with TGF-β1 in the presence and absence of TRAIL, with and without silencing TRAIL-specific receptor (DR5) and leptin receptor.

RESULTS

TRAIL did not improve glucose control, but it significantly reduced circulating interleukin (IL)-6 and resistin. In the kidney, TRAIL treatment significantly ameliorated glomerular and tubular morphology with an improvement in kidney function, but no effect on proteinuria. Our in vitro studies on TGF-β1-treated cells, showed that by binding to DR5, TRAIL rescued normal tubular cell morphology, increasing E-cadherin and reducing α-smooth muscle actin (SMA) expression, with no effects on cell viability. Interestingly, both in vivo and in vitro, TRAIL reduced the accumulation of the autophagy substrate p62.

CONCLUSIONS

Our data confirm TRAIL protective effects against organ damage and shed light on to promising anti-fibrotic actions, which are independent of glucose control. TRAIL anti-fibrotic actions might be due to the rescue of autophagy in diabetes.

The Role of Inflammatory Cytokines as Intermediates in the Pathway from Increased Adiposity to Disease

OBJECTIVE

This study aimed to investigate the role of cytokines as intermediates in the pathway from increased adiposity to disease.

METHODS

BMI and circulating levels of up to 41 cytokines were measured in individuals from three Finnish cohort studies (n = 8,293). Mendelian randomization (MR) was used to assess the impact of BMI on circulating cytokines and the impact of BMI-driven cytokines on risk of obesity-related diseases.

RESULTS

Observationally, BMI was associated with 19 cytokines. For every SD increase in BMI, causal effect estimates were strongest for hepatocyte growth factor, monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and were as ratios of geometric means 1.13 (95% CI: 1.08-1.19), 1.08 (95% CI: 1.04-1.14), and 1.13 (95% CI: 1.04-1.21), respectively. TRAIL was associated with a small increase in the odds of coronary artery disease (odds ratio: 1.03; 95% CI: 1.00-1.06). There was inconsistent evidence for a protective role of MCP-1 against inflammatory bowel diseases.

CONCLUSIONS

Observational and MR estimates of the effect of BMI on cytokine levels were generally concordant. There was little evidence for an effect of raised levels of BMI-driven cytokines on disease. These findings illustrate the challenges of MR when applied in the context of molecular mediation.

A TRAIL-TL1A Paracrine Network Involving Adipocytes, Macrophages, and Lymphocytes Induces Adipose Tissue Dysfunction Downstream of E2F1 in Human Obesity

Elevated expression of E2F1 in adipocyte fraction of human visceral adipose tissue (hVAT) associates with a poor cardiometabolic profile. We hypothesized that beyond directly activating autophagy and MAP3K5 (ASK)-MAP kinase signaling, E2F1 governs a distinct transcriptome that contributes to adipose tissue and metabolic dysfunction in obesity. We performed RNA sequencing of hVAT samples from age-, sex-, and BMI-matched patients, all obese, whose visceral E2F1 protein expression was either high (E2F1^high) or low (E2F1^low). Tumor necrosis factor superfamily (TNFSF) members, including TRAIL (TNFSF10), TL1A (TNFSF15), and their receptors, were enriched in E2F1^high While TRAIL was equally expressed in adipocytes and stromal vascular fraction (SVF), TL1A was mainly expressed in SVF, and TRAIL-induced TL1A was attributed to CD4⁺ and CD8⁺ subclasses of hVAT T cells. In human adipocytes, TL1A enhanced basal and impaired insulin-inhibitable lipolysis and altered adipokine secretion, and in human macrophages it induced foam cell biogenesis and M1 polarization. Two independent human cohorts confirmed associations between TL1A and TRAIL expression in hVAT and higher leptin and IL6 serum concentrations, diabetes status, and hVAT-macrophage lipid content. Jointly, we propose an intra-adipose tissue E2F1-associated TNFSF paracrine loop engaging lymphocytes, macrophages, and adipocytes, ultimately contributing to adipose tissue dysfunction in obesity.

Vascular transcriptome landscape of Trail-/- mice: Implications and therapeutic strategies for diabetic vascular disease

Circulating plasma TRAIL levels are suppressed in patients with cardiovascular and diabetic diseases. To identify novel targets in vascular metabolic diseases, genome-wide transcriptome of aortic tissue from Trail^-/- versus Trail^+/+ mice were interrogated. We found 861 genes differentially expressed with TRAIL deletion. Gene enrichment analyses showed many of these genes were related to inflammation, cell-to-cell cytoskeletal interactions, and transcriptional modulation. We identified vascular protective and pathological gene clusters, with Ifi205 as the most significantly reduced vascular protective gene, whereas Glut1, the most significantly increased pathological gene with TRAIL deletion. We hypothesized that therapeutic targets could be devised from such integrated analysis and validated our findings from vascular tissues of diabetic mice. From the differentially expressed gene targets, enriched transcription factor (TF) and microRNA binding motifs were identified. The top two TFs were Elk1 and Sp1, with enrichment to eight gene targets common to both. miR-520d-3p and miR-377-3p were the top enriched microRNAs with TRAIL deletion; with four overlapping genes enriched for both microRNAs. Our findings offer an alternate in silico approach for therapeutic target identification and present a deeper understanding of gene signatures and pathways altered with TRAIL suppression in the vasculature.

Effect of inactivated Bifidobacterium longum intake on obese diabetes model mice (TSOD)

Obesity and diabetes have been increasing at an alarming rate worldwide. Studies have shown the futility of chemical drugs in the treatment of obesity and diabetes. Bifidobacterium longum (BL), a common member of the gut microbiota throughout the human lifespan, has been widely reported to play a role in host health and disease. Here, we evaluated the effects of inactivated cells of BL (IBL) on obesity and blood glucose levels in TSOD mice by administering IBL orally for 5 weeks. The treated mice showed a significant decrease of body weight gain, adipose tissue mass and blood glucose levels, as well as a significant reduction in blood glucose during an oral glucose tolerance test. The treatment also resulted in reduced levels of cholesterol, triglycerides, and NEFA. Moreover, serum and urine analysis showed low creatinine levels in IBL-treated mice. These data demonstrate that IBL may have the potential to prevent obesity and diabetes.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

Cathepsin D improves the prediction of undetected diabetes in patients with myocardial infarction

Background: Newer therapeutic agents for type 2 diabetes mellitus can improve cardiovascular outcomes, but diabetes remains underdiagnosed in patients with myocardial infarction (MI). We sought to identify proteomic markers of undetected dysglycaemia (impaired fasting glucose, impaired glucose tolerance, or diabetes mellitus) to improve the identification of patients at highest risk for diabetes. Materials and methods: In this prospective cohort, 626 patients without known diabetes underwent oral glucose tolerance testing (OGTT) during admission for MI. Proximity extension assay was used to measure 81 biomarkers. Multivariable logistic regression, adjusting for risk factors, was used to evaluate the association of biomarkers with dysglycaemia. Subsequently, lasso regression was performed in a 2/3 training set to identify proteomic biomarkers with prognostic value for dysglycaemia, when added to risk factors, fasting plasma glucose, and glycated haemoglobin A1c. Determination of discriminatory ability was performed in a 1/3 test set. Results: In total, 401/626 patients (64.1%) met the criteria for dysglycaemia. Using multivariable logistic regression, cathepsin D had the strongest association with dysglycaemia. Lasso regression selected seven markers, including cathepsin D, that improved prediction of dysglycaemia (area under the receiver operator curve [AUC] 0.848 increased to 0.863). In patients with normal fasting plasma glucose, only cathepsin D was selected (AUC 0.699 increased to 0.704). Conclusions: Newly detected dysglycaemia, including manifest diabetes, is common in patients with acute MI. Cathepsin D improved the prediction of dysglycaemia, which may be helpful in the a priori risk determination of diabetes as a motivation for confirmatory OGTT.

A comprehensive evaluation of anti-diabetic drugs on nuclear receptor PXR platform

Pregnane & Xenobiotic Receptor (PXR), one of the members of nuclear receptor superfamily, acts as a 'master-regulator' of drug metabolism and disposition machinery (DMD). Activation of PXR enables detoxification and elimination of toxic xenobiotics/endobiotics, and defends our body against chemical insults. On the contrary, PXR activation also imposes a serious concern for drug-drug interactions (DDIs). Such DDIs could either decrease the efficacy or lead to accumulation of co-administered drugs at toxic level. Therefore, it is desirable that during drug development process the small drug molecules are screened on PXR-platform prior to their clinical trial and prevent late stage failures. In view of this, we have selected a group of anti-diabetic drug molecules to examine if the success and potential failure of small molecule modulators can be pre-assessed and judiciously correlated on PXR platform. For this purpose, we have examined the PXR activation potential of the selected anti-diabetic drugs. Subsequent to screening of these anti-diabetic drugs, we elaborated the study further with rosiglitazone and pioglitazone (thiazolidinediones, TZDs) which are oral anti-diabetic formulations and have been in controversy owing to their association with cardiotoxicity and bladder cancer respectively. Our study revealed that some of the selected anti-diabetic drugs possess PXR activation potential, implying that these can up-regulate the expression of CYP3A4, UGT1A1, MDR1 and thereby can be predicted to inflict undesirable consequences.

Targeted proteomic response to coffee consumption

PURPOSE

Coffee is widely consumed and implicated in numerous health outcomes but the mechanisms by which coffee contributes to health is unclear. The purpose of this study was to test the effect of coffee drinking on candidate proteins involved in cardiovascular, immuno-oncological and neurological pathways.

METHODS

We examined fasting serum samples collected from a previously reported single blinded, three-stage clinical trial. Forty-seven habitual coffee consumers refrained from drinking coffee for 1 month, consumed 4 cups of coffee/day in the second month and 8 cups/day in the third month. Samples collected after each coffee stage were analyzed using three multiplex proximity extension assays that, after quality control, measured a total of 247 proteins implicated in cardiovascular, immuno-oncological and neurological pathways and of which 59 were previously linked to coffee exposure. Repeated measures ANOVA was used to test the relationship between coffee treatment and each protein.

RESULTS

Two neurology-related proteins including carboxypeptidase M (CPM) and neutral ceramidase (N-CDase or ASAH2), significantly increased after coffee intake (P < 0.05 and Q < 0.05). An additional 46 proteins were nominally associated with coffee intake (P < 0.05 and Q > 0.05); 9, 8 and 29 of these proteins related to cardiovascular, immuno-oncological and neurological pathways, respectively, and the levels of 41 increased with coffee intake.

CONCLUSIONS

CPM and N-CDase levels increased in response to coffee intake. These proteins have not previously been linked to coffee and are thus novel markers of coffee response worthy of further study. CLINICAL TRIAL REGISTRY: http://www.isrctn.com/ISRCTN12547806.

TRAIL-Expressing Monocyte/Macrophages Are Critical for Reducing Inflammation and Atherosclerosis

Circulating tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) levels are reduced in patients with cardiovascular disease, and TRAIL gene deletion in mice exacerbates atherosclerosis and inflammation. How TRAIL protects against atherosclerosis and why levels are reduced in disease is unknown. Here, multiple strategies were used to identify the protective source of TRAIL and its mechanism(s) of action. Samples from patients with coronary artery disease and bone-marrow transplantation experiments in mice lacking TRAIL revealed monocytes/macrophages as the main protective source. Accordingly, deletion of TRAIL caused a more inflammatory macrophage with reduced migration, displaying impaired reverse cholesterol efflux and efferocytosis. Furthermore, interleukin (IL)-18, commonly increased in plasma of patients with cardiovascular disease, negatively regulated TRAIL transcription and gene expression, revealing an IL-18-TRAIL axis. These findings demonstrate that TRAIL is protective of atherosclerosis by modulating monocyte/macrophage phenotype and function. Manipulating TRAIL levels in these cells highlights a different therapeutic avenue in the treatment of cardiovascular disease.

Visceral white adipose tissue and serum proteomic alternations in metabolically healthy obese patients undergoing bariatric surgery

Metabolically healthy obesity is characterized as a comorbidity-free obesity status, however the exact pathogenetic mechanisms implicated in its transition to unhealthy obesity have not yet been unveiled. Our aim was to investigate the effect of metabolic health on the proteomic profile both in serum and visceral fat of morbidly obese subjects. 28 patients undergoing bariatric surgery were prospectively enrolled. They were divided into two groups: metabolically healthy (MHO, n = 18) and unhealthy (MUO, n = 10) obese patients. 30 biomarkers were measured in serum and visceral adipose tissue with the use of targeted proteomic analysis (Luminex assays). TNF weak inducer of apoptosis (TWEAK) (p = 0.043), TNF related apoptosis inducing ligand (TRAIL) (p = 0.037), Growth differentiation factor-15 (GDF-15) (p = 0.04), Resistin (RETN) (p = 0.047), Matrix metalloproteinase-9 (MMP-9) (p = 0.011) and C-terminal telopeptide (ICTP) (p = 0.022) were up-regulated in the MUO group in the visceral white adipose tissue. Moreover, C-C motif ligand-3 (CCL-3) (p = 0.056), Interleukin-20 (IL-20) (p = 0.04), Prokineticin-1 (PROK-1) (p = 0.028) and TWEAK (p = 0.016) were found to be suppressed in the serum of MHO group. Significant correlations between serum and adipose tissue levels of certain cytokines were also observed, while 16 biomarkers were associated with BMI. Our results indicate metabolic health substantially attenuates the expression of TWEAK, TRAIL, GDF-15, RETN, MMP-9 and ICTP expression locally, in the visceral white adipose tissue, and the expression of CCL-3, IL-20, PROK-1 and TWEAK in the peripheral blood. Intriguingly, different cytokines -except for TWEAK- are up-regulated in each site, suggesting that obesity is not a homogenous but a multi-dimensional disease.

TRAIL reduces impaired glucose tolerance and NAFLD in the high-fat diet fed mouse

Recent studies suggest that a circulating protein called TRAIL (TNF-related apoptosis inducing ligand) may have an important role in the treatment of type 2 diabetes. It has been shown that TRAIL deficiency worsens diabetes and that TRAIL delivery, when it is given before disease onset, slows down its development. The present study aimed at evaluating whether TRAIL had the potential not only to prevent, but also to treat type 2 diabetes. Thirty male C57BL/6J mice were randomized to a standard or a high-fat diet (HFD). After 4 weeks of HFD, mice were further randomized to receive either placebo or TRAIL, which was delivered weekly for 8 weeks. Body weight, food intake, fasting glucose, and insulin were measured at baseline and every 4 weeks. Tolerance tests were performed before drug randomization and at the end of the study. Tissues were collected for further analyses. Parallel in vitro studies were conducted on HepG2 cells and mouse primary hepatocytes. TRAIL significantly reduced body weight, adipocyte hypertrophy, free fatty acid levels, and inflammation. Moreover, it significantly improved impaired glucose tolerance, and ameliorated non-alcoholic fatty liver disease (NAFLD). TRAIL treatment reduced liver fat content by 47% in vivo as well as by 45% in HepG2 cells and by 39% in primary hepatocytes. This was associated with a significant increase in liver peroxisome proliferator-activated receptor (PPAR) γ (PPARγ) co-activator-1 α (PGC-1α) expression both in vivo and in vitro, pointing to a direct protective effect of TRAIL on the liver. The present study confirms the ability of TRAIL to significantly attenuate diet-induced metabolic abnormalities, and it shows for the first time that TRAIL is effective also when administered after disease onset. In addition, our data shed light on TRAIL therapeutic potential not only against impaired glucose tolerance, but also against NAFLD.

TRAIL attenuates RANKL-mediated osteoblastic signalling in vascular cell mono-culture and co-culture models

Background and objectives

Vascular calcification (VC) is a major risk factor for elevated cardiovascular morbidity/mortality. Underlying this process is osteoblastic signalling within the vessel wall involving complex and interlinked roles for receptor-activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). RANKL promotes vascular cell osteoblastic differentiation, whilst OPG acts as a neutralizing decoy receptor for RANKL (and TRAIL). With respect to TRAIL, much recent evidence points to a vasoprotective role for this ligand, albeit via unknown mechanisms. In order to shed more light on TRAILs vasoprotective role therefore, we employed in vitro cell models to test the hypothesis that TRAIL can counteract the RANKL-mediated signalling that occurs between the vascular cells that comprise the vessel wall.

Methods and results

Human aortic endothelial and smooth muscle cell mono-cultures (HAECs, HASMCs) were treated with RANKL (0–25 ng/mL ± 5 ng/mL TRAIL) for 72 hr. Furthermore, to better recapitulate the paracrine signalling that exists between endothelial and smooth muscle cells within the vessel wall, non-contact transwell HAEC:HASMC co-cultures were also employed and involved RANKL treatment of HAECs (±TRAIL), subsequently followed by analysis of pro-calcific markers in the underlying subluminal HASMCs. RANKL elicited robust osteoblastic signalling across both mono- and co-culture models (e.g. increased BMP-2, alkaline phosphatase/ALP, Runx2, and Sox9, in conjunction with decreased OPG). Importantly, several RANKL actions (e.g. increased BMP-2 release from mono-cultured HAECs or increased ALP/Sox9 levels in co-cultured HASMCs) could be strongly blocked by co-incubation with TRAIL. In summary, this paper clearly demonstrates that RANKL can elicit pro-osteoblastic signalling in HAECs and HASMCs both directly and across paracrine signalling axes. Moreover, within these contexts we present clear evidence that TRAIL can block several key signalling actions of RANKL in vascular cells, providing further evidence of its vasoprotective potential.

Low Circulating TRAIL Levels Are Associated with Increase of Resistin and Lipocalin-2/ngal Adipokines in Postmenopausal Women

Objective

Tumor necrosis factor- (TNF-) related apoptosis-inducing ligand (TRAIL) is attracting attention for its role in the physiopathology of metabolic disease/diabetes. Evidence suggests that it might protect against metabolic abnormalities driven by obesity-induced dysregulated secretion of adipokines, but this role of TRAIL has not yet been fully established. On this basis, we aimed to investigate the potential association between TRAIL and adipokine levels in a cohort of subjects in which age/gender/hormonal interferences were excluded.

Methods

Serum levels of TRAIL and a panel of adipokines were measured in postmenopausal women (n = 147) stratified according to waist circumference measures as normal, overweight, or obese. The panel of adipokines included interleukin- (IL-) 6, IL-8, IL-1β, adipsin, lipocalin-2/neutrophil gelatinase-associated lipocalin (ngal), TNF-alpha, monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, hepatocyte growth factor, resistin, leptin, adiponectin, and nerve growth factor.

Results

Low serum TRAIL concentration (deciles I–IV) was significantly and inversely correlated with resistin and lipocalin 2/ngal levels (r = −0.502 and p < 0.001 and r = −0.360 and p < 0.01, resp.). Both associations retained their statistical significance after adjustment for confounding factors, such as waist circumference and age.

Conclusions

Our data indicate a link between low circulating levels of TRAIL and markers of obesity-induced diseases (resistin and lipocalin-2/ngal), highlighting a new potential axis of TRAIL functions.

Association between thyroid hormones and TRAIL

INTRODUCTION

Recent studies suggest that a circulating protein called TRAIL (TNF-related apoptosis-inducing ligand) might have a role in the regulation of body weight and metabolism. Interestingly, thyroid hormones seem to increase TRAIL tissue expression. This study aimed at evaluating whether overt thyroid disorders affected circulating TRAIL levels.

METHODS

TRAIL circulating levels were measured in euthyroid, hyperthyroid, and hypothyroid patients before and after thyroid function normalization. Univariate and multivariate analyses were performed to evaluate the correlation between thyroid hormones and TRAIL. Then, the stimulatory effect of both triiodothyronine (T3) and thyroxine (T4) on TRAIL was evaluated in vitro on peripheral blood mononuclear cells.

RESULTS

Circulating levels of TRAIL significantly increased in hyperthyroid and decreased in hypothyroid patients as compared to controls. Once thyroid function was restored, TRAIL levels normalized. There was an independent association between TRAIL and both fT3 and fT4. Consistent with these findings, T3 and T4 stimulated TRAIL release in vitro.

CONCLUSION

Here we show that thyroid hormones are associated with TRAIL expression in vivo and stimulate TRAIL expression in vitro. Given the overlap between the metabolic effects of thyroid hormones and TRAIL, this work sheds light on the possibility that TRAIL might be one of the molecules mediating thyroid hormones peripheral effects.

Non-alcoholic fatty liver disease, vascular inflammation and insulin resistance are exacerbated by TRAIL deletion in mice

Non-alcoholic fatty liver disease (NAFLD) incorporates steatosis, non-alcoholic steato-hepatitis (NASH) and liver cirrhosis, associating with diabetes and cardiovascular disease (CVD). TNF-related apoptosis-inducing ligand (TRAIL) is protective of CVD. We aimed to determine whether TRAIL protects against insulin resistance, NAFLD and vascular injury. Twelve-week high fat diet (HFD)-fed Trail^−/− mice had increased plasma cholesterol, insulin and glucose compared to wildtype. Insulin tolerance was impaired with TRAIL-deletion, with reduced p-Akt, GLUT4 expression and glucose uptake in skeletal muscle. Hepatic triglyceride content, inflammation and fibrosis were increased with TRAIL-deletion, with elevated expression of genes regulating lipogenesis and gluconeogenesis. Moreover, Trail^−/− mice exhibited reduced aortic vasorelaxation, impaired insulin signaling, and >20-fold increased mRNA expression for IL-1β, IL-6, and TNF-α. In vitro, palmitate treatment of hepatocytes increased lipid accumulation, inflammation and fibrosis, with TRAIL mRNA significantly reduced. TRAIL administration inhibited palmitate-induced hepatocyte lipid uptake. Finally, patients with NASH had significantly reduced plasma TRAIL compared to control, simple steatosis or obese individuals. These findings suggest that TRAIL protects against insulin resistance, NAFLD and vascular inflammation. Increasing TRAIL levels may be an attractive therapeutic strategy, to reduce features of diabetes, as well as liver and vascular injury, so commonly observed in individuals with NAFLD.

Intracellular localization of DR5 and related regulatory pathways as a mechanism of resistance to TRAIL in cancer

TNF-related apoptosis-inducing ligand (TRAIL) is a prominent cytokine capable of inducing apoptosis. It can bind to five different cognate receptors, through which diverse intracellular pathways can be activated. TRAIL's ability to preferentially kill transformed cells makes it a promising potential weapon for targeted tumor therapy. However, recognition of several resistance mechanisms to TRAIL-induced apoptosis has indicated that a thorough understanding of the details of TRAIL biology is still essential before this weapon can be confidently unleashed. Critical to this aim is revealing the functions and regulation mechanisms of TRAIL's potent death receptor DR5. Although expression and signaling mechanisms of DR5 have been extensively studied, other aspects, such as its subcellular localization, non-signaling functions, and regulation of its membrane transport, have only recently attracted attention. Here, we discuss different aspects of TRAIL/DR5 biology, with a particular emphasis on the factors that seem to influence the cell surface expression pattern of DR5, along with factors that lead to its nuclear localization. Disturbance of this balance apparently affects the sensitivity of cancer cells to TRAIL-mediated apoptosis, thus constituting an eligible target for potential new therapeutic agents.

Analysis of TNF-related apoptosis-inducing ligand and receptors and implications in thymus biology and myasthenia gravis

Myasthenia Gravis is an autoantibody-mediated, neuromuscular junction disease, and is usually associated with thymic abnormalities presented as thymic tumors (~10%) or hyperplastic thymus (~65%). The exact role of thymus in Myasthenia Gravis development is not clear, yet many patients benefit from thymectomy. The apoptotic ligand TNF-Related Apoptosis-Inducing Ligand is thought to be involved in the regulation of thymocyte counts, although conflicting results are reported. We investigated differential expression profiles of TNF-Related Apoptosis-Inducing Ligand and its transmembrane receptors, Nuclear Factor-kB activation status, and apoptotic cell counts in healthy thymic tissue and pathological thymus from Myasthenia Gravis patients. All tissues expressed TNF-Related Apoptosis-Inducing Ligand and its receptors, with hyperplastic tissue having the highest expression levels of death receptors DR4 and DR5. No detectable Nuclear Factor-kB activation, at least via the canonical Protein Kinase A-mediated p65 Ser276 phosphorylation, was evident in any of the tissues studied. Apoptotic cell counts were higher in MG-associated tissue compared to the normal thymus. Possible use of the TNF-Related Apoptosis-Inducing Ligand within the concept of an apoptotic ligand-mediated medical thymectomy in thymoma- or thymic hyperplasia-associated Myasthenia Gravis is also discussed.

TRAIL (TNF-related apoptosis-inducing ligand) inhibits human adipocyte differentiation via caspase-mediated downregulation of adipogenic transcription factors

Tumor necrosis factor-α (TNFα) and other ligands of the TNF superfamily are potent regulators of adipose tissue metabolism and play a crucial role in the obesity-induced inflammation of adipose tissue. Adipose tissue expression levels of TRAIL (TNF-related apoptosis-inducing ligand) and its receptor were shown to be upregulated by overfeeding and decreased by fasting in mice. In the present study we aimed to elucidate the impact of TRAIL on adipogenesis. To this end, human Simpson-Golabi-Behmel syndrome (SGBS) preadipocytes as well as stromal-vascular cells isolated from human white adipose tissue were used as model systems. Human recombinant TRAIL inhibited adipogenic differentiation in a dose-dependent manner. It activated the cleavage of caspase-8 and -3, which in turn resulted in a downregulation of the key adipogenic transcription factors C/EBPα, C/EBPδ, and PPARγ. The effect was completely blocked by pharmacological or genetic inhibition of caspases. Taken together we discovered a so far unrecognized function of TRAIL in the regulation of adipogenesis. Targeting the TRAIL/TRAIL receptor system might provide a novel strategy to interfere with adipose tissue homeostasis.

Nrf2 signaling and redox homeostasis in the aging heart: A potential target to prevent cardiovascular diseases?

Aging process is often accompanied with a high incidence of cardiovascular diseases (CVD) due to the synergistic effects of age-related changes in heart morphology/function and prolonged exposure to injurious effects of CVD risk factors. Oxidative stress, considered a hallmark of aging, is also an important feature in pathologies that predispose to CVD development, like hypertension, diabetes and obesity. Approaches directed to prevent the occurrence of CVD during aging have been explored both in experimental models and in controlled clinical trials, in order to improve health span, reduce hospitalizations and increase life quality during elderly. In this review we discuss oxidative stress role as a main risk factor that relates CVD with aging. As well as interventions that aim to reduce oxidative stress by supplementing with exogenous antioxidants. In particular, strategies of improving the endogenous antioxidant defenses through activating the nuclear factor related-2 factor (Nrf2) pathway; one of the best studied molecules in cellular redox homeostasis and a master regulator of the antioxidant and phase II detoxification response.

Soluble TRAIL Concentration in Serum Is Elevated in People with Hypercholesterolemia

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a multi-functional cytokine, which is involved in the pathophysiological processes of cardiovascular and metabolic diseases. Previously, we demonstrated that TRAIL stimulated lipid uptake and foam cell formation in macrophages in vitro. Several clinical studies have suggested that the serum concentration of TRAIL may be increased in humans with elevated blood cholesterol; however, the current data appear to be inconclusive in this regard. In the present study, we examined the relationships between the serum TRAIL concentration and cholesterol levels in 352 generally healthy subjects undergoing the routine annual health check. We showed that there were significant correlations between TRAIL concentration and levels of total and low-density lipoprotein cholesterols. The level of TRAIL was significantly elevated in subjects with hypercholesterolemia, although this relationship might be also associated with changes of other metabolic factors. Moreover, we showed that the level of blood cholesterol was significantly higher in subjects in the upper quartile of serum TRAIL. In conclusion, our data demonstrate that the serum TRAIL concentration is elevated in people with hypercholesterolemia.

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) Promotes Angiogenesis and Ischemia-Induced Neovascularization Via NADPH Oxidase 4 (NOX4) and Nitric Oxide-Dependent Mechanisms

BACKGROUND

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has the ability to inhibit angiogenesis by inducing endothelial cell death, as well as being able to promote pro-angiogenic activity in vitro. These seemingly opposite effects make its role in ischemic disease unclear. Using Trail(-/-) and wildtype mice, we sought to determine the role of TRAIL in angiogenesis and neovascularization following hindlimb ischemia.

METHODS AND RESULTS

Reduced vascularization assessed by real-time 3-dimensional Vevo ultrasound imaging and CD31 staining was evident in Trail(-/-) mice after ischemia, and associated with reduced capillary formation and increased apoptosis. Notably, adenoviral TRAIL administration significantly improved limb perfusion, capillary density, and vascular smooth-muscle cell content in both Trail(-/-) and wildtype mice. Fibroblast growth factor-2, a potent angiogenic factor, increased TRAIL expression in human microvascular endothelial cell-1, with fibroblast growth factor-2-mediated proliferation, migration, and tubule formation inhibited with TRAIL siRNA. Both fibroblast growth factor-2 and TRAIL significantly increased NADPH oxidase 4 (NOX4) expression. TRAIL-inducible angiogenic activity in vitro was inhibited with siRNAs targeting NOX4, and consistent with this, NOX4 mRNA was reduced in 3-day ischemic hindlimbs of Trail(-/-) mice. Furthermore, TRAIL-induced proliferation, migration, and tubule formation was blocked by scavenging H2O2, or by inhibiting nitric oxide synthase activity. Importantly, TRAIL-inducible endothelial nitric oxide synthase phosphorylation at Ser-1177 and intracellular human microvascular endothelial cell-1 cell nitric oxide levels were NOX4 dependent.

CONCLUSIONS

This is the first report demonstrating that TRAIL can promote angiogenesis following hindlimb ischemia in vivo. The angiogenic effect of TRAIL on human microvascular endothelial cell-1 cells is downstream of fibroblast growth factor-2, involving NOX4 and nitric oxide signaling. These data have significant therapeutic implications, such that TRAIL may improve the angiogenic response to ischemia and increase perfusion recovery in patients with cardiovascular disease and diabetes.

Elevation of circulating TNF receptors 1 and 2 increases the risk of end-stage renal disease in American Indians with type 2 diabetes

In Caucasians with type 2 diabetes, circulating TNF receptors 1 (TNFR1) and 2 (TNFR2) predict end-stage renal disease (ESRD). Here we examined this relationship in a longitudinal cohort study of American Indians with type 2 diabetes with measured glomerular filtration rate (mGFR, iothalamate) and urinary albumin-to-creatinine ratio (ACR). ESRD was defined as dialysis, kidney transplant, or death attributed to diabetic kidney disease. Age-gender-adjusted incidence rates and incidence rate ratios of ESRD were computed by Mantel-Haenszel stratification. The hazard ratio of ESRD was assessed per interquartile range increase in the distribution of each TNFR after adjusting for baseline age, gender, mean blood pressure, HbA1c, ACR, and mGFR. Among the 193 participants, 62 developed ESRD and 25 died without ESRD during a median follow-up of 9.5 years. The age-gender-adjusted incidence rate ratio of ESRD was higher among participants in the highest versus lowest quartile for TNFR1 (6.6, 95% confidence interval (CI) 3.3-13.3) or TNFR2 (8.8, 95% CI 4.3-18.0). In the fully adjusted model, the risk of ESRD per interquartile range increase was 1.6 times (95% CI 1.1-2.2) as high for TNFR1 and 1.7 times (95% CI 1.2-2.3) as high for TNFR2. Thus, elevated serum concentrations of TNFR1 or TNFR2 are associated with increased risk of ESRD in American Indians with type 2 diabetes after accounting for traditional risk factors including ACR and mGFR.

TRAIL modulates the immune system and protects against the development of diabetes

TRAIL or tumor necrosis factor (TNF) related apoptosis-inducing ligand is a member of the TNF superfamily of proteins, whose best characterized function is the induction of apoptosis in tumor, infected, or transformed cells through activation of specific receptors. In nontransformed cells, however, the actions of TRAIL are less well characterized. Recent studies suggest that TRAIL may be implicated in the development and progression of diabetes. Here we review TRAIL biological actions, its effects on the immune system, and how and to what extent it has been shown to protect against diabetes.

IRF5 deficiency ameliorates lupus but promotes atherosclerosis and metabolic dysfunction in a mouse model of lupus-associated atherosclerosis

Premature atherosclerosis is a severe complication of lupus and other systemic autoimmune disorders. Gain-of-function polymorphisms in IFN regulatory factor 5 (IRF5) are associated with an increased risk of developing lupus, and IRF5 deficiency in lupus mouse models ameliorates disease. However, whether IRF5 deficiency also protects against atherosclerosis development in lupus is not known. In this study, we addressed this question using the gld.apoE(-/-) mouse model. IRF5 deficiency markedly reduced lupus disease severity. Unexpectedly, despite the reduction in systemic immune activation, IRF5-deficient mice developed increased atherosclerosis and also exhibited metabolic dysregulation characterized by hyperlipidemia, increased adiposity, and insulin resistance. Levels of the atheroprotective cytokine IL-10 were reduced in aortae of IRF5-deficient mice, and in vitro studies demonstrated that IRF5 is required for IL-10 production downstream of TLR7 and TLR9 signaling in multiple immune cell types. Chimera studies showed that IRF5 deficiency in bone marrow-derived cells prevents lupus development and contributes in part to the increased atherosclerosis. Notably, IRF5 deficiency in non-bone marrow-derived cells also contributes to the increased atherosclerosis through the generation of hyperlipidemia and increased adiposity. Together, our results reveal a protective role for IRF5 in lupus-associated atherosclerosis that is mediated through the effects of IRF5 in both immune and nonimmune cells. These findings have implications for the proposed targeting of IRF5 in the treatment of autoimmune disease as global IRF5 inhibition may exacerbate cardiovascular disease in these patients.

Impaired adipose tissue expandability and lipogenic capacities as ones of the main causes of metabolic disorders

Obesity is considered a major health problem. However, mechanisms involved and its comorbidities are not elucidated. Recent theories concerning the causes of obesity have focused on a limit to the functional capacity of adipose tissue, comparing it with other vital organs. This assumption has been the central point of interest in our laboratory. We proposed that the failure of adipose tissue is initiated by the difficulty of this tissue to increase its cellularity due to excess in fat contribution, owing to genetic or environmental factors. Nevertheless, why the adipose tissue reduces its capacity to make new adipocytes via mesenchymal cells of the stroma has not yet been elucidated. Thus, we suggest that this tissue ceases fulfilling its main function, the storage of excess fat, thereby affecting some of the key factors involved in lipogenesis, some of which are reviewed in this paper (PPARγ, ROR1, FASN, SCD1, Rab18, BrCa1, ZAG, and FABP4). On the other hand, mechanisms involved in adipose tissue expandability are also impaired, predominating hypertrophy via an increase in apoptosis and a decrease in adipogenesis and angiogenesis. However, adipose tissue failure is only part of this great orchestra, only a chapter of this nightmare.

Osteoprotegerin increases in metabolic syndrome and promotes adipose tissue proinflammatory changes

BACKGROUND

Inflammation is believed to link obesity to insulin resistance, as in the setting of metabolic syndrome (MetS). Osteoprotegerin (OPG) is a soluble protein that seems to exert proatherogenic and prodiabetogenic effects. This study aims at determining OPG levels in MetS and whether OPG might contribute to MetS development and progression.

METHODOLOGY/PRINCIPAL FINDINGS

Circulating OPG was measured in 46 patients with MetS and 63 controls, and was found significantly elevated in those with MetS. In addition, circulating and tissue OPG was significantly increased in high-fat diet (HFD) fed C57BL6 mice, which is one of the animal models for the study of MetS. To evaluate the consequences of OPG elevation, we delivered this protein to C57BL6 mice, finding that it promoted systemic and adipose tissue proinflammatory changes in association with metabolic abnormalities.

CONCLUSIONS/SIGNIFICANCE

These data suggest that OPG may trigger adipose tissue proinflammatory changes in MetS/HFD-induced obesity.