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  • Bioenergetic cues shift FXR splicing towards FXR alpha 2 to modulate hepatic lipolysis and fatty acid metabolism
    Publication . Correia, Jorge; Massart, Julie; de Boer, Jan Freark; Porsmyr-Palmertz, Margareta; Martinez-Redondo, Vicente; Agudelo, Leandro Z.; Sinha, Indranil; Meierhofer, David; Ribeiro, Vera; Bjornholm, Marie; Sauer, Sascha; Dahlman-Wright, Karin; Zierath, Juleen R.; Groen, Albert K.; Ruas, Jorge L.
    Objective: Farnesoid X receptor (FXR) plays a prominent role in hepatic lipid metabolism. The FXR gene encodes four proteins with structural differences suggestive of discrete biological functions about which little is known. Methods: We expressed each FXR variant in primary hepatocytes and evaluated global gene expression, lipid profile, and metabolic fluxes. Gene delivery of FXR variants to Fxr(-/-) mouse liver was performed to evaluate their role in vivo. The effects of fasting and physical exercise on hepatic Fxr splicing were determined. Results: We show that FXR splice isoforms regulate largely different gene sets and have specific effects on hepatic metabolism. FXR alpha 2 (but not alpha 1) activates a broad transcriptional program in hepatocytes conducive to lipolysis, fatty acid oxidation, and ketogenesis. Consequently, FXR alpha 2 decreases cellular lipid accumulation and improves cellular insulin signaling to AKT. FXR alpha 2 expression in Fxr(-/-) mouse liver activates a similar gene program and robustly decreases hepatic triglyceride levels. On the other hand, FXRa1 reduces hepatic triglyceride content to a lesser extent and does so through regulation of lipogenic gene expression. Bioenergetic cues, such as fasting and exercise, dynamically regulate Fxr splicing in mouse liver to increase Fxr alpha 2 expression. Conclusions: Our results show that the main FXR variants in human liver (alpha 1 and alpha 2) reduce hepatic lipid accumulation through distinct mechanisms and to different degrees. Taking this novel mechanism into account could greatly improve the pharmacological targeting and therapeutic efficacy of FXR agonists. (C) 2015 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).
  • Plasmodium infection alters Anopheles gambiae detoxification gene expression
    Publication . Felix, Rute C.; Mueller, Pie; Ribeiro, Vera; Ranson, Hilary; Silveira, Henrique
    Background: Anopheles gambiae has been shown to change its global gene expression patterns upon Plasmodium infection. While many alterations are directly related to the mosquito's innate immune response, parasite invasion is also expected to generate toxic by-products such as free radicals. The current study aimed at identifying which loci coding for detoxification enzymes are differentially expressed as a function of Plasmodium berghei infection in midgut and fat body tissues. Results: Using a custom-made DNA microarray, transcript levels of 254 loci primarily belonging to three major detoxification enzyme families (glutathione S-transferases, cytochrome P450 monooxygenases and esterases) were compared in infected and uninfected mosquitoes both during ookinete invasion and the release of sporozoites into the hemocoel. The greatest changes in gene expression were observed in the midgut in response to ookinete invasion. Interestingly, many detoxification genes including a large number of P450s were down-regulated at this stage. In the fat body, while less dramatic, gene expression alterations were also observed and occurred during the ookinete invasion and during the release of sporozoites into the hemocoel. While most gene expression changes were tissue-related, CYP6M2, a CYP previously associated with insecticide resistance, was over-expressed both in the midgut and fat body during ookinete invasion. Conclusions: Most toxicity-related reactions occur in the midgut shortly after the ingestion of an infected blood meal. Strong up-regulation of CYP6M2 in the midgut and the fat body as well as its previous association with insecticide resistance shows its broad role in metabolic detoxification.
  • Cucurbiturils as supramolecular inhibitors of DNA restriction by type II endonucleases
    Publication . Parente Carvalho, Catia; Norouzy, Amir; Ribeiro, Vera; Nau, Werner M.; Pischel, Uwe
    Cucurbiturils (CB6 and CB7) were shown to inhibit the enzymatically catalyzed restriction of plasmids and linear DNA. This effect can be inverted by supramolecular masking of the macrocycles through competitive complexation with polyamines. These experiments provide supramolecular control of biocatalytic processes.