Defects in TLR3 expression and RNase L activation lead to decreased MnSOD expression and insulin resistance in muscle cells of obese people

Lipotoxicity and immunometabolism in ischemic acute kidney injury: current perspectives and future directions

Dysregulated lipid metabolism is implicated in the pathophysiology of a range of kidney diseases. The specific mechanisms through which lipotoxicity contributes to acute kidney injury (AKI) remain poorly understood. Herein we review the cardinal features of lipotoxic injury in ischemic kidney injury; lipid accumulation and mitochondrial lipotoxicity. We then explore a new mechanism of lipotoxicity, what we define as "immunometabolic" lipotoxicity, and discuss the potential therapeutic implications of targeting this lipotoxicity using lipid lowering medications.

Diabetes diminishes muscle precursor cell-mediated microvascular angiogenesis

The skeletal muscles of Type II diabetic (T2D) patients can be characterized by a reduced vessel density, corresponding to deficiencies in microvascular angiogenesis. Interestingly, T2D also inhibits the function of many myogenic cells resident within skeletal muscle, including satellite cells, which are well-known for the role they play in maintaining homeostasis. The current study was undertaken to gain a better understanding of the mechanisms whereby satellite cell progeny, muscle precursor cells (MPCs), influence microvascular angiogenesis. Network growth and the expression of genes associated with angiogenesis were reduced when microvessels were treated with conditioned media generated by proliferating MPCs isolated from diabetic, as compared to control rat skeletal muscle, a phenomenon that was also observed when myoblasts from control or diabetic human skeletal muscle were used. When only exosomes derived from diabetic or control MPCs were used to treat microvessels, no differences in microvascular growth were observed. An evaluation of the angiogenesis factors in control and diabetic MPCs revealed differences in Leptin, vascular endothelial growth factor (VEGF), IL1-β, interleukin 10, and IP-10, and an evaluation of the MPC secretome revealed differences in interleukin 6, MCP-1, VEGF, and interleukin 4 exist. Angiogenesis was also reduced in tissue-engineered skeletal muscles (TE-SkM) containing microvessels when they were generated from MPCs isolated from diabetic as compared to control skeletal muscle. Lastly, the secretome of injured control, but not diabetic, TE-SkM was able to increase VEGF and increase microvascular angiogenesis. This comprehensive analysis of the interaction between MPCs and microvessels in the context of diabetes points to an area for alleviating the deleterious effects of diabetes on skeletal muscle.

Glucose Uptake Is Increased by Estradiol Dipropionate in L6 Skeletal Muscle Cells

GLUT4 is an important glucose transporter, which is closely related to insulin resistance and type 2 diabetes. In this study, we investigated the mechanism of Estradiol Dipropionate (EDP) on uptake of glucose in L6 skeletal muscle cells. In our study, we confirmed that EDP promoted uptake of glucose in L6 skeletal muscle cells in both normal and insulin resistant models. Western blot indicated that EDP accelerated GLUT4 expression and significantly activated AMPK and PKC phosphorylation; the expression of GLUT4 was significantly inhibited by AMPK inhibitor compound C and PKC inhibitor Gö6983, but not by Wortmannin (Akt inhibitor). Meanwhile, EDP boosted GLUT4 expression, and also increased intracellular Ca²⁺ levels. In the presence of 2 mM, 0 mM extracellular Ca²⁺ and 0 mM extracellular Ca²⁺ + BAPTA-AM, the involvement of intracellular Ca²⁺ levels contribute to EDP-induced GLUT4 expression and fusion with plasma membrane. Therefore, this study investigated whether EDP promoted GLUT4 expression through AMPK and PKC signaling pathways, thereby enhancing GLUT4 uptake of glucose and fusion into plasma membrane in L6 skeletal muscle cells. In addition, both EDP induced GLUT4 translocation and uptake of glucose were Ca²⁺ dependent. These findings suggested that EDP may be potential drug for the treatment of type 2 diabetes.

The Endometrial Transcriptome of Metabolic and Inflammatory Pathways During the Window of Implantation Is Deranged in Infertile Obese Polycystic Ovarian Syndrome Women

Introduction and Aim: Obese women with polycystic ovarian syndrome (PCOS) have a reduced rate of spontaneous conception even when their cycles are ovulatory. Endometrial receptivity is an important factor for poor implantation and increased miscarriage rates. Mechanisms in which both pathologies modify the endometrium are not fully clarified. The aim of our study was to compare the endometrial transcriptomic profiles between infertile obese PCOS (O-PCOS) women and infertile normal weight subjects during the window of implantation in ovulatory menstrual cycles. Methods: We conducted a prospective transcriptomic analysis of the endometrium using RNA sequencing. In this way, potential endometrial mechanisms leading to the poor reproductive outcome in O-PCOS patients could be characterized. Endometrial samples during days 21-23 of the menstrual cycle were collected from infertile O-PCOS women (n = 11) and normal weight controls (n = 10). Subgroups were defined according to the ovulatory/anovulatory status in the natural cycles, and O-PCOS women were grouped into the O-PCOS ovulatory (O-PCOS-ovul) subgroup. RNA isolation, sequencing with library reparation, and subsequent RNAseq data analysis were performed. Results: Infertile O-PCOS patients had 610 differentially expressed genes (DEGs), after adjustment for multiple comparisons with normal weight infertile controls, related to obesity (MXRA5 and ECM1), PCOS (ADAMTS19 and SLC18A2), and metabolism (VNN1 and PC). In the ovulatory subgroup, no DEGs were found, but significant differences in canonical pathways and the upstream regulator were revealed. According to functional and upstream analyses of ovulatory subgroup comparisons, the most important biological processes were related to inflammation (TNFR1 signaling), insulin signaling (insulin receptor signaling and PI3/AKT), fatty acid metabolism (stearate biosynthesis I and palmitate biosynthesis I), and lipotoxicity (unfolded protein response pathway). Conclusions: We demonstrated that endometrial transcription in ovulatory O-PCOS patients is deranged in comparison with the control ovulatory endometrium. The most important pathways of differentiation include metabolism and inflammation. These processes could also represent potential mechanisms for poor embryo implantation, which prevent the development of a successful pregnancy. ClinicalTrials.gov ID: NCT03353948.

Diabetic Conditions Confer Metabolic and Structural Modifications to Tissue-Engineered Skeletal Muscle

Skeletal muscle is a tissue that is directly involved in the progression and persistence of type 2 diabetes (T2D), a disease that is becoming increasingly common. Gaining better insight into the mechanisms that are affecting skeletal muscle dysfunction in the context of T2D has the potential to lead to novel treatments for a large number of patients. Through its ability to emulate skeletal muscle architecture while also incorporating aspects of disease, tissue-engineered skeletal muscle (TE-SkM) has the potential to provide a means for rapid high-throughput discovery of therapies to treat skeletal muscle dysfunction, to include that which occurs with T2D. Muscle precursor cells isolated from lean or obese male Zucker diabetic fatty rats were used to generate TE-SkM constructs. Some constructs were treated with adipogenic induction media to accentuate the presence of adipocytes that is a characteristic feature of T2D skeletal muscle. The maturity (compaction and creatine kinase activity), mechanical integrity (Young's modulus), organization (myotube orientation), and metabolic capacity (insulin-stimulated glucose uptake) were all reduced by diabetes. Treating constructs with adipogenic induction media increased the quantity of lipid within the diabetic TE-SkM constructs, and caused changes in construct compaction, cell orientation, and insulin-stimulated glucose uptake in both lean and diabetic samples. Collectively, the findings herein suggest that the recapitulation of structural and metabolic aspects of T2D can be accomplished by engineering skeletal muscle in vitro.

COVID-19: Underlying Adipokine Storm and Angiotensin 1-7 Umbrella

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the third coronavirus leading to a global health outbreak. Despite the high mortality rates from SARS-CoV-1 and Middle-East respiratory syndrome (MERS)-CoV infections, which both sparked the interest of the scientific community, the underlying physiopathology of the SARS-CoV-2 infection, remains partially unclear. SARS-CoV-2 shares similar features with SARS-CoV-1, notably the use of the angiotensin conversion enzyme 2 (ACE2) as a receptor to enter the host cells. However, some features of the SARS-CoV-2 pandemic are unique. In this work, we focus on the association between obesity, metabolic syndrome, and type 2 diabetes on the one hand, and the severity of COVID-19 infection on the other, as it seems greater in these patients. We discuss how adipocyte dysfunction leads to a specific immune environment that predisposes obese patients to respiratory failure during COVID-19. We also hypothesize that an ACE2-cleaved protein, angiotensin 1-7, has a beneficial action on immune deregulation and that its low expression during the SARS-CoV-2 infection could explain the severity of infection. This introduces angiotensin 1-7 as a potential candidate of interest in therapeutic research on CoV infections.

Pattern Recognition Receptor-Mediated Chronic Inflammation in the Development and Progression of Obesity-Related Metabolic Diseases

Obesity-induced chronic inflammation is known to promote the development of many metabolic diseases, especially insulin resistance, type 2 diabetes mellitus, nonalcoholic fatty liver disease, and atherosclerosis. Pattern recognition receptor-mediated inflammation is an important determinant for the initiation and progression of these metabolic diseases. Here, we review the major features of the current understanding with respect to obesity-related chronic inflammation in metabolic tissues, focus on Toll-like receptors and nucleotide-binding oligomerization domain-like receptors with an emphasis on how these receptors determine metabolic disease progression, and provide a summary on the development and progress of PRR antagonists for therapeutic intervention.

Oxidative stress pathways in pancreatic β-cells and insulin-sensitive cells and tissues: importance to cell metabolism, function, and dysfunction

It is now accepted that nutrient abundance in the blood, especially glucose, leads to the generation of reactive oxygen species (ROS), ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensatory response from antioxidant mechanisms, the cell, or indeed the tissue, becomes overwhelmed by oxidative stress, leading to the activation of intracellular stress-associated pathways. Activation of the same or similar pathways also appears to play a role in mediating insulin resistance, impaired insulin secretion, and late diabetic complications. The ability of antioxidants to protect against the oxidative stress induced by hyperglycemia and elevated free fatty acid (FFA) levels in vitro suggests a causative role of oxidative stress in mediating the latter clinical conditions. In this review, we describe common biochemical processes associated with oxidative stress driven by hyperglycemia and/or elevated FFA and the resulting clinical outcomes: β-cell dysfunction and peripheral tissue insulin resistance.

Panax notoginseng saponins alleviate skeletal muscle insulin resistance by regulating the IRS1-PI3K-AKT signaling pathway and GLUT4 expression

Panax notoginseng saponins (PNS) are a commonly used traditional medicine to treat diabetes in China. Recent studies have confirmed their anti-diabetic effects, but the underlying mechanisms have remained unclear. The present study was designed to explore whether PNS decrease hyperglycemia by improving insulin sensitivity in skeletal muscle and to elucidate the molecular mechanisms. The anti-diabetic effects of PNS were analyzed in a skeletal myoblast cell line, C2C12, and in high fat diet-induced diabetic KKAy mice. C2C12 cells were treated with PNS (50, 100, and 200 μg·L^-1 ) and examined for glucose uptake, cell viability and expression of components of the phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway. KKAy mice were intraperitoneally injected with PNS (200 mg·kg^-1 ) for 6 weeks. Body weight, blood glucose, serum insulin, serum lipid, glucose and insulin tolerance were measured to evaluate the anti-diabetic effects of PNS. Pathological changes, apoptosis and the PI3K-AKT signaling pathway were analyzed in KKAy skeletal muscle. PNS significantly increased insulin-induced glucose uptake, but did not affect the cell viability of C2C12 cells. In addition, PNS reduced blood glucose and serum insulin levels and improved glucose tolerance and insulin tolerance of KKAy mice. Pathological changes and apoptosis of skeletal muscle were relieved by PNS treatment. Moreover, PNS treatment enhanced expression of mRNA encoding IRS1 and GLUT4, as well as the protein expression of phosphorylated (p) -insulin receptor substrate 1 (IRS1), p-PI3K, p-AKT and glucose transporter type 4 (GLUT4) in C2C12 and KKAy mouse muscle. Collectively, these data indicate that PNS reduces hyperglycemia and insulin resistance through up-regulating GLUT4 expression and the IRS1-PI3K-AKT signaling pathway. Furthermore, PNS alleviated diabetes skeletal muscle pathological damage. Thus, our data suggest that PNS may be promising anti-diabetic compounds.

Identification of biomarkers and mechanisms of diabetic cardiomyopathy using microarray data

BACKGROUND

The study aimed to uncover the regulation mechanisms of diabetic cardiomyopathy (DCM) and provide novel prognostic biomarkers.

METHODS

The dataset GSE62203 downloaded from the Gene Expression Omnibus database was utilized in the present study. After pretreatment using the Affy package, differentially expressed genes (DEGs) were identified by the limma package, followed by functional enrichment analysis and protein- protein interaction (PPI) network analysis. Furthermore, module analysis was conducted using MCODE plug-in of Cytoscape, and functional enrichment analysis was also performed for genes in the modules.

RESULTS

A set of 560 DEGs were screened, mainly enriched in the metabolic process and cell cycle related process. Hub nodes in the PPI network were LDHA (lactate dehydrogenase A), ALDOC (aldolase C, fructose-bisphosphate) and ABCE1 (ATP Binding Cassette Subfamily E Member 1), which were also highlighted in Module 1 or Module 2 and predominantly enriched in the processes of glycolysis and ribosome biogenesis. Additionally, LDHA were linked with ALDOC in the PPI network. Besides, activating transcription factor 4 (ATF4) was prominent in Module 3; while myosin heavy chain 6 (MYH6) was highlighted in Module 4 and was mainly involved in muscle cells related biological processes.

CONCLUSIONS

Five potential biomarkers including LDHA, ALDOC, ABCE1, ATF4 and MYH6 were identified for DCM prognosis.

Decreased RNF41 expression leads to insulin resistance in skeletal muscle of obese women

CONTEXT

Toll-like receptor 4 (TLR4) activation contributes to obesity-associated insulin resistance in skeletal muscles (SM). TLR4 signaling involves two pathways: the myeloid differentiation primary response gene 88 (MyD88) leading to inflammatory cytokines production and the toll/interleukin-1 receptor domain-containing adapter-inducing interferon (IFN) I (TRIF)-dependent pathways leading to type 1 interferon (IFNI) and interferon stimulated genes (ISG) expression. The E3 ubiquitin ligase RNF41 allows the preferential activation of the TRIF-IFNI pathway; however, its role in insulin response has not been reported.

METHODS

We measured RNF41 level and IFNI pathway activation (ISG expression) in SM biopsies of obese insulin sensitive (OIS) and obese insulin resistant (OIR) women. Then we isolated and differentiated in myotubes, primary human SM cell progenitors from OIS and OIR SM biopsies. We modulated RNF41 and ISG expression in these myotubes and investigated their effects on insulin response.

RESULTS

RNF41 expression is down-regulated in vivo in OIR SM and myotubes compared to OIS SM and myotubes. TLR4 activation with palmitate induces TRIF-IFNI pathway and ISG in OIS myotubes but not in OIR myotubes. Inhibition of RNF41 expression with siRNF41 in OIS myotubes treated with palmitate attenuates insulin response, IFNI pathway activation and ISG induction, mimicking OIR phenotype. Further, overexpression of RNF41 in OIR myotubes increases insulin response and ISG expression. Exposure to IFNI or to its inducer polyinosinic-polycytidylic acid, restores ISG expression and insulin sensitivity in OIR myotubes and OIS myotubes transfected with siRNF41.

CONCLUSION

Our results identify RNF41 as essential to IFNI pathway activation in order to maintain muscle insulin sensitivity during human obesity.

No Additive Effects of Polyphenol Supplementation and Exercise Training on White Adiposity Determinants of High-Fat Diet-Induced Obese Insulin-Resistant Rats

One of the major insulin resistance instigators is excessive adiposity and visceral fat depots. Individually, exercise training and polyphenol intake are known to exert health benefits as improving insulin sensitivity. However, their combined curative effects on established obesity and insulin resistance need further investigation particularly on white adipose tissue alterations. Therefore, we compared the effects on different white adipose tissue depot alterations of a combination of exercise and grape polyphenol supplementation in obese insulin-resistant rats fed a high-fat diet to the effects of a high-fat diet alone or a nutritional supplementation of grape polyphenols (50 mg/kg/day) or exercise training (1 hr/day to 5 days/wk consisting of treadmill running at 32 m/min for a 10% slope), for a total duration of 8 weeks. Separately, polyphenol supplementation and exercise decreased the quantity of all adipose tissue depots and mesenteric inflammation. Exercise reduced adipocytes' size in all fat stores. Interestingly, combining exercise to polyphenol intake presents no more cumulative benefit on adipose tissue alterations than exercise alone. Insulin sensitivity was improved at systemic, epididymal, and inguinal adipose tissues levels in trained rats thus indicating that despite their effects on adipocyte morphological/metabolic changes, polyphenols at nutritional doses remain less effective than exercise in fighting insulin resistance.

Autophagy regulates apoptosis on the level of the death-inducing signalling complex

The interactions between apoptotic and autophagic proteins via the proteolytic systems are known mechanisms through which autophagy and apoptosis regulate each other. In this issue of The FEBS Journal, Gentle and colleagues propose a mechanism through which autophagy regulates the induction of apoptosis at the level of the TIR-domain-containing adaptor-inducing interferon-β (TRIF) in TLR signaling.

Poly (I:C) alleviates obesity related pro-inflammatory status and promotes glucose homeostasis

Obesity associated insulin resistance (IR) is implicated in chronic inflammation that mediated by the immune system. Imbalance between anti-inflammatory and pro-inflammatory response contributes to the origins and drivers of IR. However, cells of innate and adaptive immune system participate in the pathogenesis of IR, while glucose homeostasis related immune tolerance could be compromised high fat diet (HFD) reduced metabolic disorder. Although previous studies have demonstrated that anti-inflammatory therapy has a protective role in alleviating the pro-inflammatory status in HFD induced IR, the precise mechanism is still unclear. Ploy (I:C) is a synthetic double-stranded RNA that activates innate and/or adaptive immune response via retinoic acid-inducible gene-I (RIG-I), toll-like receptor 3 (TLR3) and melanoma differentiation-associated protein 5 (MDA5). In the present study, we initially perform a novel research on the relationship between Poly (I:C) preconditioning and improved glucose metabolism in obesity related IR. Interestingly, Poly (I:C) treatment has alleviated the pro-inflammatory status and promoted glucose homeostasis during a HFD feeding. Improved insulin sensitivity is consistent with enhanced immune tolerance, which accompanied with increased Foxp3⁺ regulatory T cells (Tregs). Of note, Tregs have a pivotal role in orchestrating the self-balance between autoimmunity and inflammation reaction. Thus, our findings reveal that Ploy (I:C) preconditioning prevents HFD induced glucose intolerance, which may be recognized as vaccination by the host. Overall, selectively targeting precise immune regulators may lead to new classes of potentially meaningful therapies for IR in the clinical trials.

Molecular mechanisms of ROS production and oxidative stress in diabetes

Oxidative stress and chronic inflammation are known to be associated with the development of metabolic diseases, including diabetes. Oxidative stress, an imbalance between oxidative and antioxidative systems of cells and tissues, is a result of over production of oxidative-free radicals and associated reactive oxygen species (ROS). One outcome of excessive levels of ROS is the modification of the structure and function of cellular proteins and lipids, leading to cellular dysfunction including impaired energy metabolism, altered cell signalling and cell cycle control, impaired cell transport mechanisms and overall dysfunctional biological activity, immune activation and inflammation. Nutritional stress, such as that caused by excess high-fat and/or carbohydrate diets, promotes oxidative stress as evident by increased lipid peroxidation products, protein carbonylation and decreased antioxidant status. In obesity, chronic oxidative stress and associated inflammation are the underlying factors that lead to the development of pathologies such as insulin resistance, dysregulated pathways of metabolism, diabetes and cardiovascular disease through impaired signalling and metabolism resulting in dysfunction to insulin secretion, insulin action and immune responses. However, exercise may counter excessive levels of oxidative stress and thus improve metabolic and inflammatory outcomes. In the present article, we review the cellular and molecular origins and significance of ROS production, the molecular targets and responses describing how oxidative stress affects cell function including mechanisms of insulin secretion and action, from the point of view of possible application of novel diabetic therapies based on redox regulation.

Human serum RNase-L level is inversely associated with metabolic syndrome and age

BACKGROUND

Ribonuclease-L (RNase-L) was known to be a ubiquitous enzyme involved in several cellular functions, especially innate immunity. It was recently shown to participate in adipogenesis in rodents. Here, we developed a method to measure serum levels of RNase-L and analyzed the relationship between RNase-L and metabolic syndrome (MetS).

METHODS

A total of 396 subjects were recruited from a health check-up program. An in-house RNase-L immunoassay was developed. The serum RNase-L levels of these subjects were measured, and the association of MetS-related factors with RNase-L levels was assessed.

RESULTS

The mean serum level of RNase-L of the subjects with MetS were lower than those without (16.5 ± 6.4 vs. 18.4 ± 8.0 μg/ml, P = 0.018). The subjects with central obesity, elevated blood pressure, or impaired fasting glucose also had lower serum RNase-L levels in comparison to those without. In multivariate linear regression analysis, diastolic blood pressure (β = -0.129, P = 0.024) and high-density lipoprotein cholesterol (HDL-C) (β = 0.127, P = 0.036) were related to serum RNase-L. For every 5 μg/ml increase in serum RNase-L levels, it is associated with a reduced risk of MetS (OR 0.83, 95% CI 0.71-0.98, P = 0.028), central obesity (OR 0.82, 95% CI 0.71-0.94, P = 0.005), or low HDL-C (OR 0.86, 95% CI 0.74-1.00, P = 0.042). Moreover, age is inversely related to serum RNase-L levels in various analyses.

CONCLUSIONS

The serum RNase-L levels were inversely associated with MetS, unfavorable metabolic profiles, and age.

Innate immune receptors in skeletal muscle metabolism

Recent decades have seen increasing evidence for a role for both innate and adaptive immunity in response to changes in and in the modulation of metabolic status. This new field of immunometabolism builds on evidence for activation of immune-derived signals in metabolically relevant tissues such as adipose tissue, liver, hypothalamus and skeletal muscle. Skeletal muscle is the primary site of dietary glucose disposal and therefore a key player in the development of diabetes, but studies on the role of inflammation in modulating skeletal muscle metabolism and its possible impact on whole body insulin sensitivity are scarce. This review describes the baseline mRNA expression of innate immune receptors (Toll- and NOD-like receptors) in human skeletal muscle and summarizes studies on putative role of these receptors in skeletal muscle in the context of diabetes, obesity and whole body metabolism.

Involvement of the FoxO1/MuRF1/Atrogin-1 Signaling Pathway in the Oxidative Stress-Induced Atrophy of Cultured Chronic Obstructive Pulmonary Disease Myotubes

Oxidative stress is thought to be one of the most important mechanisms implicated in the muscle wasting of chronic obstructive pulmonary disease (COPD) patients, but its role has never been demonstrated. We therefore assessed the effects of both pro-oxidant and antioxidant treatments on the oxidative stress levels and atrophic signaling pathway of cultured COPD myotubes. Treatment of cultured COPD myotubes with the pro-oxidant molecule H₂O₂ resulted in increased ROS production (P = 0.002) and protein carbonylation (P = 0.050), in association with a more pronounced atrophy of the myotubes, as reflected by a reduced diameter (P = 0.003), and the activated expression of atrophic markers MuRF1 and FoxO1 (P = 0.022 and P = 0.030, respectively). Conversely, the antioxidant molecule ascorbic acid induced a reduction in ROS production (P<0.001) and protein carbonylation (P = 0.019), and an increase in the myotube diameter (P<0.001) to a level similar to the diameter of healthy subject myotubes, in association with decreased expression levels of MuRF1, atrogin-1 and FoxO1 (P<0.001, P = 0.002 and P = 0.042, respectively). A significant negative correlation was observed between the variations in myotube diameter and the variations in the expression of MuRF1 after antioxidant treatment (P = 0.047). Moreover, ascorbic acid was able to prevent the H₂O₂-induced atrophy of COPD myotubes. Last, the proteasome inhibitor MG132 restored the basal atrophy level of the COPD myotubes and also suppressed the H₂O₂-induced myotube atrophy. These findings demonstrate for the first time the involvement of oxidative stress in the atrophy of COPD peripheral muscle cells in vitro, via the FoxO1/MuRF1/atrogin-1 signaling pathway of the ubiquitin/proteasome system.

RNase L and the NLRP3-inflammasome: An old merchant in a new trade

The type I/III interferon (IFN)-inducible 2'-5'- oligoadenylate synthetase (OAS)/endoribonuclease L (RNase L) is a classical innate immune pathway that has been implicated in antiviral and antibacterial defense and also in hereditary prostate cancer. The OAS/RNase L pathway is activated when OAS senses double-stranded RNA and catalyzes the synthesis of 2'-5' linked oligodenylates (2-5A) from ATP. 2-5A then binds and activates RNase L, resulting cleavage of single-stranded RNAs. RNase L cleavage products are capable of activating RIG-like receptors such as RIG-I and MDA5 that leads to IFN-β expression during viral infection. Our recent findings suggest that beside the RLR pathway, RNase L cleavage products can also activate the NLRP3-inflammasome pathway, which requires DHX33 (DExD/H-box helicase) and the mitochondrial adaptor protein MAVS. Here we discuss this newly identified role of OAS-RNase L pathway in regulation of inflammasome signaling as an alternative antimicrobial mechanism that has potential as a target for development of new broad-spectrum antimicrobial and anti-inflammatory therapies.

The Roles of RNase-L in Antimicrobial Immunity and the Cytoskeleton-Associated Innate Response

The interferon (IFN)-regulated endoribonuclease RNase-L is involved in multiple aspects of the antimicrobial innate immune response. It is the terminal component of an RNA cleavage pathway in which dsRNA induces the production of RNase-L-activating 2-5A by the 2′-5′-oligoadenylate synthetase. The active nuclease then cleaves ssRNAs, both cellular and viral, leading to downregulation of their expression and the generation of small RNAs capable of activating retinoic acid-inducible gene-I (RIG-I)-like receptors or the nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome. This leads to IFNβ expression and IL-1β activation respectively, in addition to broader effects on immune cell function. RNase-L is also one of a growing number of innate immune components that interact with the cell cytoskeleton. It can bind to several cytoskeletal proteins, including filamin A, an actin-binding protein that collaborates with RNase-L to maintain the cellular barrier to viral entry. This antiviral activity is independent of catalytic function, a unique mechanism for RNase-L. We also describe here the interaction of RNase-L with the E3 ubiquitin ligase and scaffolding protein, ligand of nump protein X (LNX), a regulator of tight junction proteins. In order to better understand the significance and context of these novel binding partners in the antimicrobial response, other innate immune protein interactions with the cytoskeleton are also discussed.

The interplay between inflammation and metabolism in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by extensive synovitis resulting in erosions of articular cartilage and marginal bone that lead to joint destruction. The autoimmune process in RA depends on the activation of immune cells, which use intracellular kinases to respond to external stimuli such as cytokines, immune complexes, and antigens. An intricate cytokine network participates in inflammation and in perpetuation of disease by positive feedback loops promoting systemic disorder. The widespread systemic effects mediated by pro-inflammatory cytokines in RA impact on metabolism and in particular in lymphocyte metabolism. Moreover, RA pathobiology seems to share some common pathways with atherosclerosis, including endothelial dysfunction that is related to underlying chronic inflammation. The extent of the metabolic changes and the types of metabolites seen may be good markers of cytokine-mediated inflammatory processes in RA. Altered metabolic fingerprints may be useful in predicting the development of RA in patients with early arthritis as well as in the evaluation of the treatment response. Evidence supports the role of metabolomic analysis as a novel and nontargeted approach for identifying potential biomarkers and for improving the clinical and therapeutical management of patients with chronic inflammatory diseases. Here, we review the metabolic changes occurring in the pathogenesis of RA as well as the implication of the metabolic features in the treatment response.

RNASET2 is required for ROS propagation during oxidative stress-mediated cell death

RNASET2 is a ubiquitously expressed acidic ribonuclease that has been implicated in diverse pathophysiological processes including tumorigeneis, vitiligo, asthenozoospermia, and neurodegeneration. Prior studies indicate that RNASET2 is induced in response to oxidative stress and that overexpression of RNASET2 sensitizes cells to reactive oxygen species (ROS)-induced cell death through a mechanism that is independent of catalytic activity. Herein, we report a loss-of-function genetic screen that identified RNASET2 as an essential gene for lipotoxic cell death. Haploinsufficiency of RNASET2 confers increased antioxidant capacity and generalized resistance to oxidative stress-mediated cell death in cultured cells. This function is critically dependent on catalytic activity. Furthermore, knockdown of RNASET2 in the Drosophila fat body confers increased survival in the setting of oxidative stress inducers. Together, these findings demonstrate that RNASET2 regulates antioxidant tone and is required for physiological ROS responses.

Koschei the immortal and anti-aging drugs

In Slavic folklore, Koschei the Immortal was bony, thin and lean. Was his condition caused by severe calorie restriction (CR)? CR deactivates the target of rapamycin pathway and slows down aging. But the life-extending effect of severe CR is limited by starvation. What if Koschei's anti-aging formula included rapamycin? And was rapamycin (or another rapalog) combined with commonly available drugs such as metformin, aspirin, propranolol, angiotensin II receptor blockers and angiotensin-converting enzyme inhibitors.

Identification of co-expression gene networks, regulatory genes and pathways for obesity based on adipose tissue RNA Sequencing in a porcine model

BACKGROUND

Obesity is a complex metabolic condition in strong association with various diseases, like type 2 diabetes, resulting in major public health and economic implications. Obesity is the result of environmental and genetic factors and their interactions, including genome-wide genetic interactions. Identification of co-expressed and regulatory genes in RNA extracted from relevant tissues representing lean and obese individuals provides an entry point for the identification of genes and pathways of importance to the development of obesity. The pig, an omnivorous animal, is an excellent model for human obesity, offering the possibility to study in-depth organ-level transcriptomic regulations of obesity, unfeasible in humans. Our aim was to reveal adipose tissue co-expression networks, pathways and transcriptional regulations of obesity using RNA Sequencing based systems biology approaches in a porcine model.

METHODS

We selected 36 animals for RNA Sequencing from a previously created F2 pig population representing three extreme groups based on their predicted genetic risks for obesity. We applied Weighted Gene Co-expression Network Analysis (WGCNA) to detect clusters of highly co-expressed genes (modules). Additionally, regulator genes were detected using Lemon-Tree algorithms.

RESULTS

WGCNA revealed five modules which were strongly correlated with at least one obesity-related phenotype (correlations ranging from -0.54 to 0.72, P < 0.001). Functional annotation identified pathways enlightening the association between obesity and other diseases, like osteoporosis (osteoclast differentiation, P = 1.4E-7), and immune-related complications (e.g. Natural killer cell mediated cytotoxity, P = 3.8E-5; B cell receptor signaling pathway, P = 7.2E-5). Lemon-Tree identified three potential regulator genes, using confident scores, for the WGCNA module which was associated with osteoclast differentiation: CCR1, MSR1 and SI1 (probability scores respectively 95.30, 62.28, and 34.58). Moreover, detection of differentially connected genes identified various genes previously identified to be associated with obesity in humans and rodents, e.g. CSF1R and MARC2.

CONCLUSIONS

To our knowledge, this is the first study to apply systems biology approaches using porcine adipose tissue RNA-Sequencing data in a genetically characterized porcine model for obesity. We revealed complex networks, pathways, candidate and regulatory genes related to obesity, confirming the complexity of obesity and its association with immune-related disorders and osteoporosis.