En funksjonell studie av det essensielle amidotransferasekomplekset MurT/CobQ i Streptococcus pneumoniae

The bacterial cell wall is responsible for maintaining cell shape and gives protection from osmotic lysis caused by turgor pressure. The major component of the cell wall in Gram-positive bacteria is the structurally complex biopolymer peptidoglycan. Streptococcus pneumoniae (Pneumococcus) is a Gram-positive human pathogen responsible for an estimated 1-2 million deaths annually worldwide. Studies of its cell wall synthesis machinery are of high academic interest and it can contribute to drug target discoveries, which have the potential to improve treatments in the future. The recently discovered essential amidotransferase complex MurT/CobQ, encoded by the operon murTcobQ, is in S. pneumoniae responsible for the amidation the peptidoglycan precursor lipid II. The amidation of the second residue γ-glutamate to isoglutamine in lipid II has previously been shown to be necessary for the transpeptidase activity of the peptidoglycan synthesising proteins, known as penicillin binding proteins (PBPs). What biological role this amidation plays is currently not known. In the present work depletion of MurT/CobQ expression has been used extensively to study how low levels of amidated lipid II affects the phenotype of S. pneumoniae. The sensitivity against the β−lactam antibiotics cefotaxime and ampicillin did not appear to be significantly affected by MurT/CobQ depletion, and neither did lysozyme resistance. The non-essential PBP1a is the only PBP to have reported residual transpeptidase activity with non-amidated lipid II in vitro. This proved difficult to demonstrate in vivo, and as such the results of these experiments were inconclusive. It was shown that depletion of MurT/CobQ severely affected the pneumococcal cells ability to properly divide, with septal cell wall synthesis being inhibited. The cells were still able to synthesize cell wall peripherally, strongly indicating that there is a difference between the septal and peripheral cell wall synthesising machineries in their ability to utilize non-amidated lipid II as substrate. The depletion of MurT/CobQ also affected the ability of the muralytic fratricide protein CbpD to successfully lyse cells, further strengthening the existing theory that this enzyme attacks the septal region of dividing cells. Furthermore this work demonstrated that in vivo, the PBPs are able to cross-link the stem peptides of the cell wall using non-amidated lipid II as substrate. Here it was shown that while the cell walls of normal pneumococcal cells contained a small amount of non-amidated stem-peptide dimers, cells depleted of MurT/CobQ contained significantly higher amounts of non-amidated stem-peptide dimers. Den bakterielle cellveggen gir bakteriecellene sin form og beskytter dem fra osmotisk lysis. Hovedkomponenten i celleveggen hos grampositive bakterier den komplekse biopolymeren peptidoglykan. Streptococcus pneumoniae er en grampositiv, humanpatogen bakterie som er ansvarlig for mellom 1-2 millioner dødsfall årlig på verdensbasis, og studier av celleveggssyntesen kan potensielt lede til forbedrede behandlingsmetoder i fremtiden. Det nylig oppdagede essensielle amidotransferasekomplekset MurT/CobQ, kodet av operonet murTcobQ, er ansvarlig for amideringen av peptidoglykanforløperen lipid II i S. pneumoniae. Amideringen av aminosyren γ−glutamat til isoglutamin i lipid II er tidligere vist å være nødvendig for transpeptidaseaktiviteten til de peptidoglykansyntetiserende enzymene (PBPer). Hvilken biologisk rolle denne amideringen spiller er for øyeblikket ukjent. I dette arbeidet har depletion (underuttrykk) av MurT/CobQ uttrykk blitt brukt for å studere hvordan lave konsentrasjoner av amidert lipid II påvirker fenotype hos S. pneumoniae. Sensitiviteten mot β−laktam antibiotikaene cefotaxim og ampicillin, samt lysozym ble ikke signifikant påvirket av MurT/CobQ depletion. Det ikke-essensielle enzymet PBP1a er det eneste som tidligere har vist en viss aktivitet med uamidert lipid II in vitro. Dette viste seg å være vanskelig å demonstrere in vivo, og resultatene fra disse forsøkene var mangelfulle. Arbeidet har vist at depletion av MurT/CobQ påvirker streptokokk-cellenes evne til å dele seg ved at den septale celleveggssyntesen blir inhibert. Cellene evnet fremdeles å syntetisere ny cellevegg i lengderetningen, noe som indikerer at der er en forskjell mellom de septale og perifere celleveggssyntesemaskinerienes evne til å bruke uamidert lipid II. Depletion av MurT/CobQ førte også til at det muralytiske fratricidproteinet CbpD ikke klarer å lysere celler, noe som bidrar til å styrke den rådende teorien om at dette proteinet angriper septum hos pneumokokker i delingsfasen. Videre viser denne studien at in vivo så evner PBPene å inkorporere og kryssbinde uamidert lipid II til en viss grad i celleveggen. Det ble vist at mens celleveggen til normale celler inneholdt en liten mengde uamiderte peptid-dimerer, så inneholdt MurTCobQ-depleted celler et signifikant høyere nivå av uamiderte peptid-dimerer.M-M

Postoperative Osteoporosis in Subjects with Morbid Obesity Undergoing Bariatric Surgery with Gastric Bypass or Sleeve Gastrectomy

Obesity has become a worldwide epidemic accompanied by adverse health effects. The limited efficiency of traditional weight reduction regimens has led to a substantial increase in the use of bariatric surgery. Today, sleeve gastrectomy (SG) and Roux-en-Y-gastric bypass (RYGB) are the most used procedures. The present narrative review focuses on the risk of developing postoperative osteoporosis and summarizes some of the most relevant micronutrient deficiencies associated with RYGB and SG. Preoperatively, the dietary habits of obese individuals might lead to precipitated deficiencies in vitamin D and other nutrients affecting bone mineral metabolism. Bariatric surgery with SG or RYGB can aggravate these deficiencies. The various surgical procedures appear to affect nutrient absorption differently. Being purely restrictive, SG may particularly affect the absorption of vitamin B12 and also vitamin D. In contrast, RYGB has a more profound impact on the absorption of fat-soluble vitamins and other nutrients, although both surgical methods induce only a mild protein deficiency. Despite adequate supplementation of calcium and vitamin D, osteoporosis may still occur after the surgery. This might be due to deficiencies in other micronutrients, e.g., vitamin K and zinc. Regular follow-ups with individual assessments and nutritional advice are indispensable to prevent osteoporosis and other adverse postoperative issues.publishedVersio

Molecular mechanisms of in vivo metal chelation: implications for clinical treatment of metal intoxications.

Successful in vivo chelation treatment of metal intoxication requires that a significant fraction of the administered chelator in fact chelate the toxic metal. This depends on metal, chelator, and organism-related factors (e.g., ionic diameter, ring size and deformability, hardness/softness of electron donors and acceptors, route of administration, bioavailability, metabolism, organ and intra/extracellular compartmentalization, and excretion). In vivo chelation is not necessarily an equilibrium reaction, determined by the standard stability constant, because rate effects and ligand exchange reactions considerably influence complex formation. Hydrophilic chelators most effectively promote renal metal excretion, but they complex intracellular metal deposits inefficiently. Lipophilic chelators can decrease intracellular stores but may redistribute toxic metals to, for example, the brain. In chronic metal-induced disease, where life-long chelation may be necessary, possible toxicity or side effects of the administered chelator may be limiting. The metal selectivity of chelators is important because of the risk of depletion of the patient's stores of essential metals. Dimercaptosuccinic acid and dimercaptopropionic sulfonate have gained more general acceptance among clinicians, undoubtedly improving the management of many human metal intoxications, including lead, arsenic, and mercury compounds. Still, development of new safer chelators suited for long-term oral administration for chelation of metal deposits (mainly iron), is an important research challenge for the future

Medical Therapy of Patients Contaminated with Radioactive Cesium or Iodine

Follow-up studies after the Chernobyl and Fukushima accidents have shown that137Cs and131I made up the major amount of harmful contaminants in the atmospheric dispersion and fallout. Other potential sources for such radionuclide exposure may be terrorist attacks, e.g., via contamination of drinking water reservoirs. A primary purpose of radionuclide mobilization is to minimize the radiation dose. Rapid initiation of treatment of poisoned patients is imperative after a contaminating event. Internal contamination with radioactive material can expose patients to prolonged radiation, thus leading to short-and long-term clinical consequences. After the patient’s emergency conditions are addressed, the treating physicians and assisting experts should assess the amount of radioactive material that has been internalized. This evaluation should include estimation of the radiation dose that is delivered and the specific radionuclides inside the body. These complex assessments warrant the reliance on a multidisciplinary approach that incorporates regional experts in radiation medicine and emergencies. Regional hospitals should have elaborated strategies for the handling of radiation emergencies. If radioactive cesium is a significant pollutant, Prussian blue is the approved antidote for internal detoxification. Upon risks of radioiodine exposure, prophylactic or immediate treatment with potassium iodide tablets is recommended. Chelators developed from calcium salts have been studied for gastrointestinal trapping and enhanced mobilization after strontium exposure

Chelation Combination - A Strategy to Mitigate the Neurotoxicity of Manganese, Iron, and Copper?

The chelating thiol dimercaptosuccinate (DMSA) and the traditional agent D-penicillamine (PSH) are effective in enhancing the urinary excretion of copper (Cu) and lead (Pb) in poisoned individuals. However, DMSA, PSH, EDTA (ethylenediamine tetraacetate), and deferoxamine (DFOA) are water-soluble agents with limited access to the central nervous system (CNS). Strategies for mobilization of metals such as manganese (Mn), iron (Fe), and Cu from brain deposits may require the combined use of two agents: one water-soluble agent to remove circulating metal into urine, in addition to an adjuvant shuttler to facilitate the brain-to-blood mobilization. The present review discusses the chemical basis of metal chelation and the ligand exchange of metal ions. To obtain increased excretion of Mn, Cu, and Fe, early experiences showed promising results for CaEDTA, PSH, and DFOA, respectively. Recent experiments have indicated that p-amino salicylate (PAS) plus CaEDTA may be a useful combination to remove Mn from binding sites in CNS, while the deferasirox-DFOA and the tetrathiomolybdate-DMSA combinations may be preferable to promote mobilization of Fe and Cu, respectively, from the CNS. Further research is requested to explore benefits of chelator combinations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Chelation Combination - A Strategy to Mitigate the Neurotoxicity of Manganese, Iron, and Copper?publishedVersio

How may increased physical activity in primary school prevent the development of overweight in children?

Bacheloroppgave folkehelse, 2018Problemstilling: «Hvordan kan økt fysisk aktivitet i grunnskolen forebygge utvikling av overvekt hos barn?». Teori: Omhandler overvekt- og fedmeutviklingen i dagens samfunn, årsaker til at barn utvikler overvekt og fedme, konsekvenser dette kan ha og om hvordan utviklingen kan forebygges med skolen som arena for det forebyggende arbeidet. Metode: Litteraturstudie. Resultat og diskusjon: Resultater fra seks ulike forskningsstudier, der forskerne har sett på hvordan overvekt og fedme kan forebygges ved hjelp av tiltak i grunnskolen som fremmer fysisk aktivitet. Konklusjon: For å forsøke å forebygge overvekt blant barn i grunnskolen ved å øke den fysiske aktiviteten kan det se ut som, ut i fra gjennomgått teori og diskusjon, at en har mest hell med å øke fysisk aktivitetsnivået i den ordinære klasseromundervisningen, i friminuttene, i korte pauser mellom undervisningstimer, i lunsjpauser og i skolefritidsordningen, kombinert med livsstilsundervisning for både elever og foreldre. Samtidig som det legges til rette for et skolemiljø der det er lett å holde på med fysisk aktivitet i. Det kan være enklere for mange barn å redusere stillesittende aktiviteter, enn det å øke det fysiske aktivitetsnivået i seg selv. Det kan dermed være gunstig å tilrettelegge og tilpasse tiltakene som fremmer fysisk aktivitet etter bestemte målgrupper, med tanke på alder og kjønn, for å få størst mulig effekt av de forebyggende tiltakene mot overvekt. Det viktigste er at barna finner aktiviteter som de selv liker å holde på med, slik at de kan opprettholde et høyere fysisk aktivitetsnivå også på fritiden

The Role of Tryptophan Dysmetabolism and Quinolinic Acid in Depressive and Neurodegenerative Diseases

Emerging evidence suggests that neuroinflammation is involved in both depression and neurodegenerative diseases. The kynurenine pathway, generating metabolites which may play a role in pathogenesis, is one of several competing pathways of tryptophan metabolism. The present article is a narrative review of tryptophan metabolism, neuroinflammation, depression, and neurodegeneration. A disturbed tryptophan metabolism with increased activity of the kynurenine pathway and production of quinolinic acid may result in deficiencies in tryptophan and derived neurotransmit ters. Quinolinic acid is an N-methyl-D-aspartate receptor agonist, and raised levels in CSF, together with increased levels of inflammatory cytokines, have been reported in mood disorders. Increased quinolinic acid has also been observed in neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis, and HIV-related cognitive decline. Oxidative stress in connection with increased indole-dioxygenase (IDO) activity and kynurenine formation may contribute to inflammatory responses and the production of cytokines. Increased formation of quinolinic acid may occur at the expense of kynurenic acid and neuroprotective picolinic acid. While awaiting ongoing research on potential pharmacological interventions on tryptophan metabolism, ad equate protein intake with appropriate amounts of tryptophan and antioxidants may offer protection against oxidative stress and provide a balanced set of physiological receptor ligands.publishedVersio

Xenobiotics, trace metals and genetics in the pathogenesis of tauopathies

Tauopathies are a disease group characterized by either pathological accumulation or release of fragments of hyperphosphorylated tau proteins originating from the central nervous system. The tau hypotheses of Parkinson’s and Alzheimer’s diseases contain a clinically diverse spectrum of tauopathies. Studies of case records of various tauopathies may reveal clinical phenotype characteristics of the disease. In addition, improved understanding of different tauopathies would disclose environmental factors, such as xenobiotics and trace metals, that can precipitate or modify the progression of the disorder. Important for diagnostics and monitoring of these disorders is a further development of adequate biomarkers, including refined neuroimaging, or proteomics. Our goal is to provide an in-depth review of the current literature regarding the pathophysiological roles of tau proteins and the pathogenic factors leading to various tauopathies, with the perspective of future advances in potential therapeutic strategies

Gadolinium in Medical Imaging - Usefulness, Toxic Reactions and Possible Countermeasures - A Review

Gadolinium (Gd) is one of the rare-earth elements. The properties of its trivalent cation (Gd3+) make it suitable to serve as the central ion in chelates administered intravenously to patients as a contrast agent in magnetic resonance imaging. Such Gd-chelates have been used for more than thirty years. During the past decades, knowledge has increased about potential harmful effects of Gd-chelates in patients with severe renal dysfunction. In such patients, there is a risk for a potentially disabling and lethal disease, nephrogenic systemic fibrosis. Restricting the use of Gd-chelates in persons with severely impaired renal function has decreased the occurrence of this toxic effect in the last decade. There has also been an increasing awareness of Gd-retention in the body, even in patients without renal dysfunction. The cumulative number of doses given, and the chemical structure of the chelate given, are factors of importance for retention in tissues. This review describes the chemical properties of Gd and its medically used chelates, as well as its toxicity and potential side effects related to injection of Gd-chelates. Keywords: chelates; contrast induced nephropathy; gadolinium; gadolinium induced respiratory distress syndrome; gadolinium kinetics; gadolinium toxicity; nephrogenic systemic fibrosis; side effects of gadolinium chelates; treatment of gadolinium toxicity. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/ 4.0/).Gadolinium in Medical Imaging - Usefulness, Toxic Reactions and Possible Countermeasures - A ReviewpublishedVersio