Nod1-mediated lipolysis promotes diacylglycerol accumulation and successive inflammation via PKCδ-IRAK axis in adipocytes

Chronic inflammation contributes to obesity mediated metabolic disturbances, including insulin resistance. Obesity is associated with altered microbial load in metabolic tissues that can contribute to metabolic inflammation. Different bacterial components such as, LPS, peptidoglycans have been shown to underpin metabolic disturbances through interaction with host innate immune receptors. Activation of Nucleotide-binding oligomerization domain-containing protein 1 (Nod1) with specific peptidoglycan moieties promotes insulin resistance, inflammation and lipolysis in adipocytes. However, it was not clear how Nod1-mediated lipolysis and inflammation is linked. Here, we tested if Nod1-mediated lipolysis caused accumulation of lipid intermediates and promoted cell autonomous inflammation in adipocytes. We showed that Nod1-mediated lipolysis caused accumulation of diacylglycerol (DAG) and activation of PKCδ in 3T3-L1 adipocytes, which was prevented with a Nod1 inhibitor. Nod1-activated PKCδ caused downstream stimulation of IRAK1/4 and was associated with increased expression of proinflammatory cytokines such as, IL-1β, IL-18, IL-6, TNFα and MCP-1. Pharmacological inhibition or siRNA mediated knockdown of IRAK1/4 attenuated Nod1-mediated activation of NF-κB, JNK, and the expression of proinflammatory cytokines. These results reveal that Nod1-mediated lipolysis promoted accumulation of DAG, which engaged PKCδ and IRAK1/4 to augment inflammation in 3T3-L1 adipocytes.     

Prognostic molecular markers in pediatric liver disease – Are there any?

Pediatric liver disease (PLD) is a major cause of severe morbidity and prolonged hospitalizations in children. Stratifying patients in terms of prognosis remains challenging. The limited knowledge about molecular mechanisms causing and accompanying PLD remains the main obstacle in a search for reliable prognostic biomarkers. A systematic search of MEDLINE via PubMed and Embase via OVID was conducted on studies published between August 2007 and August 2017. Molecular markers with a prognostic potential in terms of survival, need for liver transplantation or disease progression/regression were selected. In general, identified studies were single center smaller case-control studies or case series with a low level of evidence and a high risk of bias. Only 23 studies comprising 898 patients could be included, mostly focusing on biliary atresia, non-alcoholic fatty liver disease, viral hepatitis, and LT; and markers related to morphogenesis and fibrosis. Furthermore, molecular markers in metabolic pathways and inflammation shown to be relevant, however requiring further validation. Hence, further biological and clinical studies are needed to gain greater molecular insight into PLD.     

Hymenolepis diminuta: Action of worm RNase against RNA

Hymenolepis diminuta possesses a tegumental ribonuclease (RNase) which hydrolyzes rat liver and degraded yeast RNA. Polyacrylamide gel electrophoresis and gel chromatography of rat liver RNA after incubation with intact worms demonstrated significant hydrolysis of the high molecular weight RNA fractions (28 S and 18 S), with the appearance of fractions of intermediate molecular weight (i.e., between 18 S and 4 S), as well as ethanol-soluble fractions. Hydrolysis of degraded yeast RNA (with a molecular weight of approximately 25,000) yielded a single ethanol-precipitable hydrolysis product, as well as ethanol-soluble hydrolysis products.     

Metabolic Reconfiguration in C. elegans Suggests a Pathway for Widespread Sterol Auxotrophy in the Animal Kingdom

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Cryo-EM structures of cardiac thin filaments reveal the 3D architecture of troponin

Troponin is an essential component of striated muscle and it regulates the sliding of actomyosin system in a calcium-dependent manner. Despite its importance, the structure of troponin has been elusive due to its high structural heterogeneity. In this study, we analyzed the 3D structures of murine cardiac thin filaments using a cryo-electron microscope equipped with a Volta phase plate (VPP). Contrast enhancement by a VPP enabled us to reconstruct the entire repeat of the thin filament. We determined the orientation of troponin relative to F-actin and tropomyosin, and characterized the interactions between troponin and tropomyosin. This study provides a structural basis for understanding the molecular mechanism of actomyosin system.     

Signal transduction in blue light‐induced oxygen uptake in Chlorella cells

In DCMU‐poisoned wild‐type and in non‐photosynthetic pigment mutant cells of Chlorella kessleri , grown heterotrophically with glucose as a carbon source and with nitrate as sole nitrogen source, the known blue light‐enhanced uptake of oxygen and breakdown of starch were reduced by staurosporine and K252a, both potent inhibitors of protein kinase C. This corresponded to sensitivity to these inhibitors of blue light‐induced uptake of nitrate of such organisms. Cells grown with ammonia as sole nitrogen source responded to short wavelength visible irradiation with an increase in oxygen uptake, and this, too, was inhibited by staurosporine and K252a. However, these cells did not show any blue light‐enhanced uptake of nitrate. From these results, enhanced consumption of oxygen under blue light cannot be a consequence of blue light‐induced protein phosphorylation involved in the light‐dependent uptake of nitrate. However, existence of a specific protein phosphorylation within the process of enhancement of oxygen uptake under blue light is not yet proven by the data. There might be a master reaction that induces both processes independently, or there may be influences of other light‐induced processes which lead to enhanced starch breakdown, thereby supplying the glucose for oxidative degradation.     

Identification and in silico prediction of metabolites of tebufenozide derivatives by major human cytochrome P450 isoforms

Cytochrome P450 (CYP) enzymes constitute a superfamily of heme-containing monooxygenases. CYPs are involved in the metabolism of many chemicals such as drugs and agrochemicals. Therefore, examining the metabolic reactions by each CYP isoform is important to elucidate their substrate recognition mechanisms. The clarification of these mechanisms may be useful not only for the development of new drugs and agrochemicals, but also for risk assessment of chemicals. In our previous study, we identified the metabolites of tebufenozide, an insect growth regulator, formed by two human CYP isoforms: CYP3A4 and CYP2C19. The accessibility of each site of tebufenozide to the reaction center of CYP enzymes and the susceptibility of each hydrogen atom for metabolism by CYP enzymes were evaluated by a docking simulation and hydrogen atom abstraction energy estimation at the density functional theory level, respectively. In this study, the same in silico prediction method was applied to the metabolites of tebufenozide derivatives by major human CYPs (CYP1A2, 2C9, 2C19, 2D6, and 3A4). In addition, the production rate of the metabolites by CYP3A4 was quantitively analyzed by frequency based on docking simulation and hydrogen atom abstraction energy using the classical QSAR approach. Then, the obtained QSAR model was applied to predict the sites of metabolism and the metabolite production order by each CYP isoform.     

Anaphase-promoting complex/cyclosome-dependent proteolysis of human cyclin A starts at the beginning of mitosis and is not subject to the spindle assembly checkpoint

Cyclin A is a stable protein in S and G2 phases, but is destabilized when cells enter mitosis and is almost completely degraded before the metaphase to anaphase transition. Microinjection of antibodies against subunits of the anaphase-promoting complex/cyclosome (APC/C) or against human Cdc20 (fizzy) arrested cells at metaphase and stabilized both cyclins A and B1. Cyclin A was efficiently polyubiquitylated by Cdc20 or Cdh1-activated APC/C in vitro, but in contrast to cyclin B1, the proteolysis of cyclin A was not delayed by the spindle assembly checkpoint. The degradation of cyclin B1 was accelerated by inhibition of the spindle assembly checkpoint. These data suggest that the APC/C is activated as cells enter mitosis and immediately targets cyclin A for degradation, whereas the spindle assembly checkpoint delays the degradation of cyclin B1 until the metaphase to anaphase transition. The "destruction box" (D-box) of cyclin A is 10-20 residues longer than that of cyclin B. Overexpression of wild-type cyclin A delayed the metaphase to anaphase transition, whereas expression of cyclin A mutants lacking a D-box arrested cells in anaphase.