Diabetes causes marked inhibition of mitochondrial metabolism in pancreatic β-cells

Diabetes is a global health problem caused primarily by the inability of pancreatic β-cells to secrete adequate levels of insulin. The molecular mechanisms underlying the progressive failure of β-cells to respond to glucose in type-2 diabetes remain unresolved. Using a combination of transcriptomics and proteomics, we find significant dysregulation of major metabolic pathways in islets of diabetic βV59M mice, a non-obese, eulipidaemic diabetes model. Multiple genes/proteins involved in glycolysis/gluconeogenesis are upregulated, whereas those involved in oxidative phosphorylation are downregulated. In isolated islets, glucose-induced increases in NADH and ATP are impaired and both oxidative and glycolytic glucose metabolism are reduced. INS-1 β-cells cultured chronically at high glucose show similar changes in protein expression and reduced glucose-stimulated oxygen consumption: targeted metabolomics reveals impaired metabolism. These data indicate hyperglycaemia induces metabolic changes in β-cells that markedly reduce mitochondrial metabolism and ATP synthesis. We propose this underlies the progressive failure of β-cells in diabetes.Peer reviewe

Expression profiling in transgenic FVB/N embryonic stem cells overexpressing STAT3

BACKGROUND: The transcription factor STAT3 is a downstream target of the LIF signalling cascade. LIF signalling or activation is sufficient to maintain embryonic stem (ES) cells in an undifferentiated and pluripotent state. To further investigate the importance of STAT3 in the establishment of ES cells we have in a first step derived stable pluripotent embryonic stem cells from transgenic FVB mice expressing a conditional tamoxifen dependent STAT3-MER fusion protein. In a second step, STAT3-MER overexpressing cells were used to identify STAT3 pathway-related genes by expression profiling in order to identify new key-players involved in maintenance of pluripotency in ES cells. RESULTS: Transgenic STAT3-MER blastocysts yielded pluripotent germline-competent ES cells at a high frequency in the absence of LIF when established in tamoxifen-containing medium. Expression profiling of tamoxifen-induced transgenic FVB ES cell lines revealed a set of 26 genes that were markedly up- or down-regulated when compared with wild type cells. The expression of four of the up-regulated genes (Hexokinase II, Lefty2, Pramel7, PP1rs15B) was shown to be restricted to the inner cell mass (ICM) of the blastocysts. These differentially expressed genes represent potential candidates for the maintenance of pluripotency of ES cells. We finally overexpressed two candidate genes, Pem/Rhox5 and Pramel7, in ES cells and demonstrated that their overexpression is sufficient for the maintenance of expression of ES cell markers as well as of the typical morphology of pluripotent ES cells in absence of LIF. CONCLUSION: Overexpression of STAT3-MER in the inner cell mass of blastocyst facilitates the establishment of ES cells and induces the upregulation of potential candidate genes involved in the maintenance of pluripotency. Two of them, Pem/Rhox5 and Pramel7, when overexpressed in ES cells are able to maintain the embryonic stem cells in a pluripotent state in a LIF independent manner as STAT3 or Nanog

T-cell recognition of chemicals, protein allergens and drugs: towards the development of in vitro assays

Chemicals can elicit T-cell-mediated diseases such as allergic contact dermatitis and adverse drug reactions. Therefore, testing of chemicals, drugs and protein allergens for hazard identification and risk assessment is essential in regulatory toxicology. The seventh amendment of the EU Cosmetics Directive now prohibits the testing of cosmetic ingredients in mice, guinea pigs and other animal species to assess their sensitizing potential. In addition, the EU Chemicals Directive REACh requires the retesting of more than 30,000 chemicals for different toxicological endpoints, including sensitization, requiring vast numbers of animals. Therefore, alternative methods are urgently needed to eventually replace animal testing. Here, we summarize the outcome of an expert meeting in Rome on 7 November 2009 on the development of T-cell-based in vitro assays as tools in immunotoxicology to identify hazardous chemicals and drugs. In addition, we provide an overview of the development of the field over the last two decades

The carbon source governs the population dynamics of phosphate accumulating organisms in aerobic granules

Aerobic granules are quasi-spherical biofilms mainly composed of self-immobilized mixed microbial communities. The application of aerobic granules to treat domestic and low-strength industrial wastewaters is gaining attention because granules can accommodate high biomass concentrations and this translates into small foot-print treatment reactors. For robust application of this novel treatment technology, aerobic granules should be physically stable, and to account for the removal of the desired contaminants, should contain an appropriate microbial assembly. One main challenge is to engineer and control the granules microbial assembly. This requires a good understanding of the microbial composition and dynamics in relation to process parameters and process performance; and the incorporation of this knowledge as feedback tool for optimized reactors operation. For the removal of phosphorus, phosphate accumulating organisms (PAO) are crucial players. Hence their abundance is desirable and the recognition of key operational parameters that guarantee their population stability is important. In this study we developed aerobic granules using two different carbon sources and through this process we determined their microbial composition and dynamics and its association to reactor functionality. To assess temporal changes in bacterial and in PAO community structures, 16S rRNA gene- and polyphosphate kinase (ppk1) gene-based community fingerprint patterns were assessed via terminal restriction fragment length polymorphism (T-RFLP), respectively. Analysis of the community dynamics showed that during granules development, the microbial richness dropped considerably suggesting that granulation is a very selective process. Propionate favored the establishment of PAO populations as compared to acetate. Based on ppk1 gene community fingerprint analysis, the carbon source selected for different PAO strains in the two systems and resulted in an excellent phosphorus removal capacity in the propionate fed reactor while phosphorus removal upsets were observed in the acetate fed reactor despite the presence of PAO

High-resolution mapping and modeling of anammox recovery from recurrent oxygen exposure

Oxygen inhibits anammox, a bioconversion executed by anoxic ammonium oxidizing bacteria (AnAOB). Nonetheless, oxygen is mostly found in the proximity of AnAOB in nitrogen removal applications, being a substrate for nitritation. The experiments performed to date were mostly limited to batch activity tests where AnAOB activity is estimated during oxygen exposure. However, little attention has been paid to the recovery and reversibility of activity following aerobic conditions, of direct relevance for bioreactor operation. In this work, anoxic and autotrophic reactor cultivation at 20 degrees C yielded an enriched microbial community in AnAOB, consisting for 75% of a member of the genus Brocadia. High-resolution kinetic data were obtained with online ammonium measurements and further processed with a newly developed Python data pipeline. The experimentally obtained AnAOB response showed complete inhibition until micro-aerobic conditions were reached again (<0.02 mg O-2 L-1). After oxygen inhibition, AnAOB recovered gradually, with recovery times of 5-37 h to reach a steady-state activity, dependent on the perceived inhibition. The recovery immediately after inhibition was lowest when exposed to higher oxygen concentrations (range: 0.5-8 mg O-2 L-1) with long contact times (range: 9-24 h). The experimental data did not fit well with a conventional 'instant recovery' Monod-type inhibition model. Yet, the fit greatly improved by incorporating a dynamic growth rate formula accurately describing gradual activity recovery. With the upgraded model, long-term kinetic simulations for partial nitritation/anammox (PN/A) with intermittent aeration showed a decrease in growth rate compared to the instant recovery mode. These results indicate that recovery of AnAOB after oxygen exposure was previously overlooked. It is recommended to account for this effect in the intensification of partial nitritation/anammox. (C) 2018 Elsevier Ltd. All rights reserved

Decentralized Control for Swarm Flocking in 3D Space

Second International Conference on Intelligent Robotics and Applications, Singapore, 16-18 December 2009This paper presents a decentralized control strategy for a robot swarm where each robot tries to form a regular tetrahedron with its three neighbors. The proposed method is based on virtual spring. Robots can form regular tetrahedron regardless of their initial positions and they require minimum amount of information about their neighbors. The control strategy is made scalable by integrating a neighbor selection procedure so that it can be expanded to large swarms easily. In addition, an obstacle avoidance mechanism, based on artificial physics, is also introduced. By utilizing this control strategy, basic swarm behaviors such as aggregation, flocking and obstacle avoidance are demonstrated through simulations in an unknown three dimensional environment.Department of Electrical EngineeringRefereed conference pape