Mécanisme(s) d'action de l'insuline dans la prévention de l'hypertension et la progression de la tubulopathie dans le diabète : rôle de hnRNP F, Nrf2 et Bmf

Le diabète sucré est un trouble métabolique complexe qui se caractérise par une homéostasie anormale du glucose résultant en une concentration plasmatique trop élevée en glucose et due à un déficit absolu ou relatif de la production de l’insuline ou de son action. Les patients souffrant de diabète sont plus à risque de développer diverses complications comme la néphropathie diabétique (DN), qui demeure la principale cause de maladie rénale en phase terminale (ESRD) et est associée à une morbidité et mortalité cardiovasculaire accrue. Bien que les diabètes de type I et de type II (T1D et T2D) se développent par le biais de mécanismes différents, il n’existe pas de différences pathophysiologiques majeures entre la progression de la DN et ESRD pour les deux types de diabète. La tubulopathie, qui comprend à la fois l’apoptose/atrophie tubulaire et la fibrose tubulo-interstitielle, est déjà bien acceptée comme marqueur final de la progression de la DN. Et quoique l’hyperglycémie et le stress oxydant soient tous deux associés à l’hypertension et aux lésions tubulaires, leurs mécanismes moléculaires précis d’action demeurent incertains. Pour les patients T1D, le traitement intensif à l’insuline par le biais d’injections quotidiennes demeure la thérapie la plus efficace mais est associé à de nombreux inconvénients, dont l’hypoglycémie. Le but de cette thèse est d’identifier des gènes ou molécules en aval de l’action de l’insuline comme nouvelles cibles thérapeutiques pour contrer la progression de la DN. Dans un premier temps, nous avons examiné si l’insuline peut affecter l’expression rénale de Nrf2 dans le T1D et étudié les mécanismes sous-jacents. Le traitement avec l’insuline chez les souris Akita a permis de normaliser l’hyperglycémie, l’hypertension, le stress oxydant et les dommages rénaux; l’inhibition de l’expression rénale de Nrf2 et Agt et l’augmentation de l’expression de hnRNP F/K (ribonucléoprotéines nucléaires hétérogènes F et K) ont également été demontrées. In vitro en condition HG, l’insuline réprime la transcription de Nrf2 et Agt, mais stimule celle de hnRNP F/K via la signalisation p44/42 MAPK (p44/42 mitogen-activated protein kinase) dans les RPTCs. L’inhibition de p44/42 MAPK, hnRNP F ou hnRNP K au moyen de siRNA permet de renverser l’inhibition de la transcription de Nrf2 par l’insuline. Un élément de réponse a l’insuline (IRE) a également été identifié dans le promoteur du gène Nrf2 de rat auquel peuvent se lier hnRNP F/K. Dans des études réalisées sur des souris hyperinsulinémiques-euglycémiques, l’expression de Nrf2 et Agt était diminuée alors que celle de hnRNP F/K était augmentée, indiquant que les effets de l’insuline sur l’expression de Nrf2 et Agt le sont principalement indépendamment de son effet hypoglycémiant. Finalement, les mécanismes sous-jacents de l’action de l’insuline sur la prévention de l’apoptose des RPTCs ont été élucidés. Nous avons créé une souris Tg surexprimant le gène Bcl2-modifying factor (Bmf) humain, spécifiquement dans les RPTCs, et caractérisé ce modèle. Les mécanismes moléculaires de l’action de l’insuline dans la prévention de l’apoptose des RPTCs induite par Bmf et la perte des RPTCs dans des souris diabétiques ont également été étudiés. Afin de démontrer l’effet de l’insuline sur l’expression de Bmf, des souris Akita traitées avec des implants d’insuline, ainsi que des souris surexprimant hnRNP F spécifiquement au niveau des RPTCs ont été utilisées. Les souris Bmf-Tg présentent une augmentation de la pression systolique (SBP), du ratio albumine-créatinine urinaire (ACR), de l’apoptose des RPTCs et un plus grand nombre de RPTCs urinaires que les souris non-Tg. Le traitement avec l’insuline et la surexpression de hnRNP F dans les souris Akita permet de supprimer l’expression de Bmf des RPTCs et leur apoptose. In vitro dans les RPTCs en culture, l’insuline inhibe l’expression du gène Bmf induite par le HG via la voie de signalisation p44/42 MAPK. La transfection de siRNA contre hnRNP F prévient l’inhibition de la transcription de Bmf par l’insuline. HnRNP F inhibe la transcription de Bmf via un élément sensible à hnRNP F localisé dans le promoteur du gène Bmf. En résumé, ces études ont permis de démontrer que l’activation chronique de Nrf2 par l’hyperglycémie aggrave la dysfonction rénale par le biais de l’augmentation de l’expression intrarénale de l’Agt et l’activation du système rénine-angiotensine dans le diabète. Nous avons montré que l’insuline stimule l’expression de hnRNP F et hnRNP K dans les RPTCs afin d’inhiber l’expression de Agt, Nrf2 et Bmf, et ultérieurement atténue l’hypertension et les dommages rénaux chez les souris diabétiques Akita. Les travaux présentés dans cette thèse ont donc permis d’identifier hnRNP F/K, Nrf2 et Bmf comme cibles potentielles pour le traitement de l’hypertension et de la maladie rénale dans le diabète.Diabetes mellitus is a complex metabolic disorder characterized by abnormal glucose homeostasis, resulting in higher plasma glucose due to an absolute or relative deficit in insulin production or action. People with diabetes have an increased risk of developing complications including diabetic nephropathy (DN), which is the major cause of developing end stage renal disease (ESRD) and is associated with increased cardiovascular morbidity and mortality. Although, type I and type II diabetes (T1D and T2D) are developed by different mechanisms, there is no major pathophysiological difference between nephropathy progression and ESRD in both diabetes. Tubulopathy including tubular apoptosis/atrophy and tubule-interstitial fibrosis is known to be final marker for DN progression. Hyperglycemia and oxidative stress are associated with hypertension and tubular injury; their precise molecular mechanisms remain unclear. Intensive insulin treatment for T1D patients, including daily insulin injections is the most effective therapy but is associated with drawbacks such as hypoglycemia. The aim of this thesis is to identify downstream target genes or molecules of insulin action as potential therapeutic targets to counter DN progression. Firstly, we investigated whether insulin affects renal Nrf2 expression in T1D and studied its underlying mechanism and reported that insulin treatment normalized hyperglycemia, hypertension, oxidative stress, and renal injury; inhibited renal Nrf2 and Agt gene expression; and upregulated heterogeneous nuclear ribonucleoprotein F and K (hnRNP F/K) expression in Akita mice. In vitro, insulin suppressed Nrf2 and Agt but stimulated hnRNP F/K gene transcription in HG via p44/42 mitogen-activated protein kinase (p44/42 MAPK) signalling in RPTCs. Inhibition with siRNAs of p44/42 MAPK, hnRNP F, or hnRNP K, reversed insulin inhibition of Nrf2 gene transcription. We further identified an insulin-responsive element (IRE) in rat Nrf2 promoter that binds to hnRNP F/K. In hyperinsulinemic-euglycemic clamp studies, renal Nrf2 and Agt expression were downregulated, whereas hnRNP F/K expression was upregulated, indicating insulin-mediated effects on Nrf2 and Agt expression largely occur independently of its glucose-lowering effect. Secondly, the underlying mechanism of insulin action on preventing RPTC apoptosis was studied. In the present study, a Tg mouse overexpressing human Bcl2-modifying factor (Bmf) in RPTs was created and characterized. Furthermore, the molecular mechanism(s) of insulin action on preventing Bmf-induced RPTC apoptosis and loss in diabetic mice were investigated. To study the effect of insulin on Bmf expression, Akita mice implanted with insulin, specifically those overexpressing hnRNP F in their RPTCs, were used. Bmf-Tg mice exhibited higher systolic blood pressure (SBP), urinary albumin-creatinine ratio (ACR), RPTC apoptosis and more urinary RPTCs than non-Tg mice. Insulin treatment and hnRNP F-overexpression in Akita mice suppressed RPTC Bmf expression and apoptosis. In vitro, insulin inhibited HG-induced Bmf gene expression in RPTCs via p44/42 MAPK signaling. Transfection of hnRNP F siRNA prevented insulin inhibition of Bmf transcription. HnRNP F inhibited Bmf transcription via hnRNP F-responsive element in the Bmf promoter. In summary, this thesis demonstrated that chronic Nrf2 activation by hyperglycemia aggravates renal dysfunction via enhanced intrarenal Agt expression and RAS activation in diabetes. It was demonstrated that insulin inhibits Agt, Nrf2, and Bmf expression in RPTCs via hnRNP F and hnRNP K expression and, subsequently, attenuates hypertension and kidney injury in Akita mice. This study identifies renal hnRNP F/K, Nrf2 and Bmf as potential targets for the treatment of hypertension and kidney injury in diabetes

Not Quite up to Scratch: An Examination of Failure, Persistence, and ‘Living Dead’ Outcomes for Wireless Start-Ups

This dissertation analyzes why some VC-funded high-tech firms do not generate harvesting events for investors through a lucrative sale, either to another company or on the stock exchange. I investigate the effects of three signals of quality on failure and persistence. In the first essay, hypotheses are developed on the unintended consequences of patenting. Disclosure, through patents, exposes new firms to undesired spillovers. The second essay exploits asymmetric effects on success and failure to expose start-up persistence. It analyzes another signal of quality—technology breadth, the applicability across domains—and suggests that hazards of disclosure also varies with this breadth. Finally, the third essay examines the effects of signals related to founding team on a third outcome, ‘living dead’—a transitory state to which a start-up shifts when it persists beyond the norm without harvest or failure. I tested these hypotheses on a longitudinal dataset of 428 US VC-backed wireless firms founded between 1990 and 2009 using event history analysis and matched case-control study. I find that a start-up’s failure rate increases as its inventions are cited at a higher rate by others; in addition failure rate increases when the citing firms have a reputation of litigiousness. I show that the effect of signaling a specific technology while experiencing high rate of knowledge diffusion diminishes both the likelihood of failure and success—uncovering persistence. Loss of members in founding teams comprised of entrepreneurs with prior founding experience is found to be a shock that increases the odds of marginal performance

When Difference Hurts: Technology Space Activity and Failure

This paper investigates failure of startups due to their accumulation of intellectual property rights (IPR) in the context of the wireless telecommunication industry, here framed as their technology space - a space that we constructed through shared technology. Obtaining intellectual property rights forms an important signal for startup viability but only to a limited degree, compelling us to posit a U shape relationship between failure rate and IPR flow. The location of startups in the technology space, and the associated signals that come with that location presents powerful information regarding their failure rates. Disclosing intellectual properties erodes the benefits of secrecy and innovative lead time as deference (as proxied by patent citations) by peer to new firms increases their hazard of failure due potential competition and harmful spillover effects - particularly if the sector manifests a weak appropriability regime. Technology concentration of the deference is also found to be harmful; however the interaction of the two is positive. This leads us to infer that startups with specific and focused technology acknowledged many other firms or those with general but deferred to by few others have better possibility of stemming the rot

Mastocytosis: a mutated KIT receptor induced myeloproliferative disorder

Although more than 90% systemic mastocytosis (SM) patients express gain of function mutations in the KIT receptor, recent next generation sequencing has revealed the presence of several additional genetic and epigenetic mutations in a subset of these patients, which confer poor prognosis and inferior overall survival. A clear understanding of how genetic and epigenetic mutations cooperate in regulating the tremendous heterogeneity observed in these patients will be essential for designing effective treatment strategies for this complex disease. In this review, we describe the clinical heterogeneity observed in patients with mastocytosis, the nature of relatively novel mutations identified in these patients, therapeutic strategies to target molecules downstream from activating KIT receptor and finally we speculate on potential novel strategies to interfere with the function of not only the oncogenic KIT receptor but also epigenetic mutations seen in these patients

Bandwidth Optimization of Microstrip Patch Antenna- A Basic Overview

An antenna is a very important device in wireless applications. It converts the electrical energy into RF signal at the transmitter and RF signal into electrical energy at the receiver side. A micro strip antenna consists of a rectangular patch on a ground plane separated by dielectric substrate. The patch in the antenna is made of a conducting material Cu (Copper) or Au (Gold) and this can be in any shape of rectangular, circular, triangular, elliptical or some other common shape. Researches of past few year shows that, various work on Microstrip Patch Antenna is attentive on designing compact sized Microstrip Antenna with efficiency and bandwidth optimized. But inherently Microstrip Patch Antenna have narrow bandwidth so to enhance bandwidth various techniques are engaged. Today’s Communication devices need several applications which require higher bandwidth; such as mobile phones these days are getting thinner and smarter but many applications supported by them require higher bandwidth, so microstrip antenna used for performing this operation should provide wider bandwidth as well as their shape should be more efficient and size should be compact so that it should occupy less space while keeping the size of device as small as possible. In this review paper, a review of different techniques used for bandwidth optimization & various shapes of compact and broadband microstrip patch antenna is given

Effect of spinning process parameters on mélange yarn quality by Taguchi experimental design

The important yarn quality parameters, like evenness, imperfection, hairiness, strength and breaking elongation percentage, of blow-room blended cotton mélange yarn have been studied using Taguchi experimental design. The impacts of process parameters, such as shade depth (%), twist multiplier and ring frame spindle speed, have been studied in presence of two unavoidable and uncontrolled noise parameters. The experimental results show that the mélange yarn quality parameters are significantly affected by shade depth and ring frame spindle speed. A ranking of the three controlled parameters and the percentage contribution of each of these parameters have also been evaluated. The shade depth is found most dominating factor affecting cotton mélange yarn quality. The set of optimum parameters that correspond to the highest S/N ratio of evenness, imperfections, hairiness, strength and breaking elongation percentage have also been determined