Insulin resistance dysregulates CYP7B1 leading to oxysterol accumulation: a pathway for NAFL to NASH transition

NAFLD is an important public health issue closely associated with the pervasive epidemics of diabetes and obesity. Yet, despite NAFLD being among the most common of chronic liver diseases, the biological factors responsible for its transition from benign nonalcoholic fatty liver (NAFL) to NASH remain unclear. This lack of knowledge leads to a decreased ability to find relevant animal models, predict disease progression, or develop clinical treatments. In the current study, we used multiple mouse models of NAFLD, human correlation data, and selective gene overexpression of steroidogenic acute regulatory protein (StarD1) in mice to elucidate a plausible mechanistic pathway for promoting the transition from NAFL to NASH. We show that oxysterol 7α-hydroxylase (CYP7B1) controls the levels of intracellular regulatory oxysterols generated by the “acidic/alternative” pathway of cholesterol metabolism. Specifically, we report data showing that an inability to upregulate CYP7B1, in the setting of insulin resistance, results in the accumulation of toxic intracellular cholesterol metabolites that promote inflammation and hepatocyte injury. This metabolic pathway, initiated and exacerbated by insulin resistance, offers insight into approaches for the treatment of NAFLD.     

Floral fragrances in two closely related fruit fly orchids,Bulbophyllum hortorum and B. macranthoides (Orchidaceae): assortments of phenylbutanoids to attract tephritid fruit fly males

Floral chemical components are important cues used by plants to attract pollinators. One outstanding case is “fruit fly orchids” in the genus of Bulbophyllum to attract their pollinators by releasing characteristic fragrances. Dacini fruit flies are main or exclusive pollinators which are strongly attracted to certain natural chemicals, either methyl eugenol (ME: a phenylpropanoid) or raspberry ketone (RK: a phenylbutanoid). Furthermore, zingerone (ZN: a phenylbutanoid) has been characterized as the attractant for both ME- and RK-sensitive fruit fly species. In the present study, we examined chemical profiles of two closely related Bulbophyllum orchids—B. hortorum, and B. macranthoides subsp. tollenoniferum—distributed in Papua New Guinea and the Southeast Asian countries, respectively. We first observed that RK-sensitive flies were attracted to these orchids by ex situ cultivation in Penang, Malaysia. These Bulbophyllum orchids contained RK and/or ZN as their main floral components. Other than these attractants, multiple phenylbutanoids including potential attractants for RK-sensitive species were identified from these orchids. Therefore, we examined attractiveness of potential phenylbutanoid attractants to an RK-sensitive melon fly, Zeugodacus cucurbitae, using laboratory-reared flies. Furthermore, we analyzed molecular phylogenetic relationships among phenylpropanoid- or phenylbutanoid-producing orchids to see a relation between chemical profiles and phylogenetic classification in the related species.     

Amino acid sequence variations of signaling lymphocyte activation molecule and mortality caused by morbillivirus infection in cetaceans

Morbillivirus infection is a severe threat to marine mammals. Mass die‐offs caused by this infection have repeatedly occurred in bottlenose dolphins (Turiops truncatus) and striped dolphins (Stenella coeruleoalba), both of which belong to the family Delphinidae, but not in other cetaceans. However, it is unknown whether sensitivity to the virus varies among cetacean species. The signaling lymphocyte activation molecule (SLAM) is a receptor on host cells that allows morbillivirus invasion and propagation. Its immunoguloblin variable domain‐like (V) region provides an interface for the virus hemagglutinin (H) protein. In this study, variations in the amino acid residues of the V region of 26 cetacean species, covering almost all cetacean genera, were examined. Three‐dimensional (3D) models of them were generated in a homology model using the crystal structure of the marmoset SLAM and measles virus H protein complex as a template. The 3D models showed 32 amino acid residues on the interface that possibly bind the morbillivirus. Among the cetacean species studied, variations were found at six of the residues. Bottlenose and striped dolphins have substitutions at five positions (E68G, I74V, R90H, V126I, and Q130H) compared with those of baleen whales. Three residues (at positions 68, 90 and 130) were found to alternate electric charges, possibly causing changes in affinity for the virus. This study shows a new approach based on receptor structure for assessing potential vulnerability to viral infection. This method may be useful for assessing the risk of morbillivirus infection in wildlife.     

Molecular Dynamics Calculations of Wild Type vs. Mutant Protein C: Relationship Between Binding Affinity to Endothelial Cell Protein C Receptor and Hereditary Disease

Abstract

Molecular dynamics simulations of the protein C γ-carboxyglutamic acid (Gla) domain and endothelial cell protein C receptor (EPCR) complex were performed to determine the effect of a hereditary disease, which results in a mutation (Gla 25 → Lys) in the protein C Gla domain. Our results suggest that the Gla 25 → Lys mutation causes a significant reduction in the binding force between protein C Gla domain and EPCR due to destabilization of the helix structure of EPCR and displacement of a Ca²⁺ ion.     

Role of galactolipid biosynthesis in coordinated development of photosynthetic complexes and thylakoid membranes during chloroplast biogenesis in Arabidopsis

The galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the predominant lipids in thylakoid membranes and indispensable for photosynthesis. Among the three isoforms that catalyze MGDG synthesis in Arabidopsis thaliana, MGD1 is responsible for most galactolipid synthesis in chloroplasts, whereas MGD2 and MGD3 are required for DGDG accumulation during phosphate (Pi) starvation. A null mutant of Arabidopsis MGD1 (mgd1‐2), which lacks both galactolipids and shows a severe defect in chloroplast biogenesis under nutrient‐sufficient conditions, accumulated large amounts of DGDG, with a strong induction of MGD2/3 expression, during Pi starvation. In plastids of Pi‐starved mgd1‐2 leaves, biogenesis of thylakoid‐like internal membranes, occasionally associated with invagination of the inner envelope, was observed, together with chlorophyll accumulation. Moreover, the mutant accumulated photosynthetic membrane proteins upon Pi starvation, indicating a compensation for MGD1 deficiency by Pi stress‐induced galactolipid biosynthesis. However, photosynthetic activity in the mutant was still abolished, and light‐harvesting/photosystem core complexes were improperly formed, suggesting a requirement for MGDG for proper assembly of these complexes. During Pi starvation, distribution of plastid nucleoids changed concomitantly with internal membrane biogenesis in the mgd1‐2 mutant. Moreover, the reduced expression of nuclear‐ and plastid‐encoded photosynthetic genes observed in the mgd1‐2 mutant under Pi‐sufficient conditions was restored after Pi starvation. In contrast, Pi starvation had no such positive effects in mutants lacking chlorophyll biosynthesis. These observations demonstrate that galactolipid biosynthesis and subsequent membrane biogenesis inside the plastid strongly influence nucleoid distribution and the expression of both plastid‐ and nuclear‐encoded photosynthetic genes, independently of photosynthesis.     

Excitotoxicity-induced immediate surge in hippocampal prostanoid production has latent effects that promote chronic progressive neuronal death

Excitotoxicity is involved in neurodegenerative conditions. We investigated the pathological significance of a surge in prostaglandin production immediately after kainic acid (KA) administration [initial phase], followed by a sustained moderate elevation in prostaglandin level [late phase] in the hippocampus of juvenile rats. Numerous pyknotic hippocampal neurons were observed 72 h after KA treatment; this number remained elevated on days 10 and 30. Gross hippocampal atrophy was observed on days 10 and 30. Pre-treatment with indomethacin ameliorated neuronal death on days 10 and 30, and prevented hippocampal atrophy on day 30. Microglial response was moderated by the indomethacin pre-treatment. Blockade of only late-phase prostaglandin production by post-treatment with indomethacin ameliorated neuronal death on day 30. These findings suggest a role for initial-phase prostaglandin production in chronic progressive neuronal death, which is exacerbated by late-phase prostaglandin production. Blockade of prostaglandin production has therapeutic implications in preventing long-term neurological sequelae following excitotoxic brain damage.     

Phytuberol,from Japanese Domestic Tobacco,Nicotiana tabacum cv. Suifu

Carcinogenesis is believed to be induced through the oxidative damage of DNA, and antioxidants are expected to suppress it. So, the polyphenolic antioxidants in daily foods were investigated to see whether they protect against genetic damage by active oxygen. In the evaluation, we used a bioassay and a chemical determination, a Salmonella mutagenicity test for mutation by a N-hydroxyl radical from one of the dietary carcinogens 3-amino-1-methyl-5H-pyrido[4,3-b]indole and the formation of 8-hydroxyl (8-OHdG) from 2′-deoxyguanosine (2′-dG) in a Fenton OH-radical generating system. Thirty-one antioxidants including flavonoids were compared in terms of radical-trapping activity with bacterial DNA and 2′-dG. Antioxidants inhibited the mutation but the IC₅₀ values were in the mM order. Against 8-OHdG formation, only α-tocopherol had a suppressive effect with an IC₅₀ of 1.5 μM. Thus, except α-tocopherol, the dietary antioxidants did not scavenge the biological radicals faster than bacterial DNA and intact 2′-dG, indicating that they failed to prevent oxidative gene damage and probably carcinogenesis.     

Development of a Host-vector System for Gluconobacter suboxydans

A shuttle vector for Gluconobacter suboxydans and Escherichia coli was constructed by ligation of a cryptic plasmid, pMV201, found in G. suboxydans IFO 3130 to E. coli plasmid pACYC177. The chimeric plasmid named pMGlOl carries the ampicillin resistance gene derived from pACYC177 and transforms G. suboxydans var. α IFO 3254 as well as E. coli. The transformation conditions for G. suboxydansvar. α IFO 3254 were examined using pMGlOl DNA. Competent cells were induced efficiently by treatment with LiCl or RbCl CaCl₂ which induced the competency of Acetobacter was much less effective. Addition of polyethylene glycol enhanced the transformation efficiency significantly. An efficiency of approximately 10² transformants per μg DNA was finally obtained.     

Cold Shock of Germinating Bacillus subtilis Spores

Susceptibility of germinating spores of Bacillus subtilis to a rapid chilling was examined by viable countings. Dormant spores were quite resistant to the cold shock but the spores, immediately upon germination, lose viability almost completely by the same treatment. The presence of divalent cation, magnesium, calcium or manganese, in a buffer to which the germinating spores were suspended, markedly protected the cells from the death by the cold shock effect. When the shocked cells were incubated in the buffer containing casein acid hydrolyzate, glucose and magnesium ion for short period of time, a remarkable increase in viable counts was observed. The existence of two critical temperature zones, which were determined by the initial temperature of cell suspension, was confirmed in the cold shock of germinating spores.