Alteration of De Novo Glucose Production Contributes to Fasting Hypoglycaemia in Fyn Deficient Mice

Previous studies have demonstrated that glucose disposal is increased in the Fyn knockout (FynKO) mice due to increased insulin sensitivity. FynKO mice also display fasting hypoglycaemia despite decreased insulin levels, which suggested that hepatic glucose production was unable to compensate for the increased basal glucose utilization. The present study investigates the basis for the reduction in plasma glucose levels and the reduced ability for the liver to produce glucose in response to gluconeogenic substrates. FynKO mice had a 5-fold reduction in phosphoenolpyruvate carboxykinase (PEPCK) gene and protein expression and a marked reduction in pyruvate, pyruvate/lactate-stimulated glucose output. Remarkably, de novo glucose production was also blunted using gluconeogenic substrates that bypass the PEPCK step. Impaired conversion of glycerol to glucose was observed in both glycerol tolerance test and determination of the conversion of ¹³C-glycerol to glucose in the fasted state. α-glycerol phosphate levels were reduced but glycerol kinase protein expression levels were not changed. Fructose-driven glucose production was also diminished without alteration of fructokinase expression levels. The normal levels of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate observed in the FynKO liver extracts suggested normal triose kinase function. Fructose-bisphosphate aldolase (aldolase) mRNA or protein levels were normal in the Fyn-deficient livers, however, there was a large reduction in liver fructose-6-phosphate (30-fold) and fructose-1,6-bisphosphate (7-fold) levels as well as a reduction in glucose-6-phosphate (2-fold) levels. These data suggest a mechanistic defect in the allosteric regulation of aldolase activity.     

BRCT domains: Easy as one,two, three

BRCA1 C-terminal (BRCT) domains are integral signaling modules in the DNA damage response (DDR). Aside from their established roles as phospho-peptide binding modules, BRCT domains have been implicated in phosphorylation-independent protein interactions, DNA binding and poly(ADP-ribose) (PAR) binding. These numerous functions can be attributed to the diversity in BRCT domain structure and architecture, where domains can exist as isolated single domains or assemble into higher order homo- or hetero-domain complexes. In this review, we incorporate recent structural and biochemical studies to demonstrate how structural features allow single and tandem BRCT domains to attain a high degree of functional diversity.Key words: BRCT domain, DNA repair, phosphorylation, phospho-peptide interaction, protein interaction, DNA binding, DNA damage response     

CD36 mediates both cellular uptake of very long chain fatty acids and their intestinal absorption in mice

The intestine has an extraordinary capacity for fatty acid (FA) absorption. Numerous candidates for a protein-mediated mechanism of dietary FA absorption have been proposed, but firm evidence for this process has remained elusive. Here we show that the scavenger receptor CD36 is required both for the uptake of very long chain FAs (VLCFAs) in cultured cells and the absorption of dietary VLCFAs in mice. We found that the fraction of CD36-dependent saturated fatty acid association/absorption in these model systems is proportional to the FA chain length and specific for fatty acids and fatty alcohols containing very long saturated acyl chains. Moreover, intestinal VLCFA absorption is completely abolished in CD36-null mice fed a high fat diet, illustrating that the predominant mechanism for VLCFA absorption is CD36-dependent. Together, these findings represent the first direct evidence for protein-facilitated FA absorption in the intestine and identify a novel therapeutic target for the treatment of diseases characterized by elevated VLCFA levels.     

Le MorphoTEP au FDG est un examen utile dans les cancers différenciés de la thyroïde avec élévation des anticorps antithyroglobuline

AimAssessment of the clinical impact of a PET/CT with FDG for the follow-up of differentiated thyroid cancer (DTC) with rising or positive thyroglobulin autoantibodies (AbTg) level and negative or inconclusive conventional imaging work-up.MethodologyThis retrospective study involves 15 patients seen in follow-up with confirmed DTC primarily treated with total thyroidectomy and Iodine-131. Patients presenting increased AbTg and a negative or non informative conventional workout were included. The results of the PET/CT were correlated with histology and/or clinical follow-up. The clinical impact was determined on a change of intention to treat, which was decided upon in multidisciplinary meetings, based on the PET/CT result.ResultsWe observed 10 true positive exams confirmed via histology in seven patients and via clinical follow-up in three on the average 33 months (20–53 months), three real negative exams with negative follow up of on the average 39.5 months (30–47 months), one false positive and one false negative. The intention to treat was modified in 73.3 % (11/15 patients). PET/CT showed sensitivity, specificity, positive predictive value, negative predictive value and accurancy of 91, 75, 90, 75, 86.6% respectively. There was a large and comparable dispersion of the AbTg values in both the true positive and the true negative groups, the kinetic of AbTg evolution could have a predictive value of a positive PET.Discussion/ConclusionPET/CT with FDG seems to be very useful in the therapeutic management of DTC in the case of AbTg increased or positive, in particular for the patients with N1 in the initial staging. Further studies are suggested to confirm the very promising negative predictive value and specificity of this exam in a larger number of patients.     

Metabolic footprint of epiphytic bacteria on Arabidopsis thaliana leaves

The phyllosphere, which is defined as the parts of terrestrial plants above the ground, is a large habitat for different microorganisms that show a high extent of adaption to their environment. A number of hypotheses were generated by culture-independent functional genomics studies to explain the competitiveness of specialized bacteria in the phyllosphere. In contrast, in situ data at the metabolome level as a function of bacterial colonization are lacking. Here, we aimed to obtain new insights into the metabolic interplay between host and epiphytes upon colonization of Arabidopsis thaliana leaves in a controlled laboratory setting using environmental metabolomics approaches. Quantitative nuclear magnetic resonance (NMR) and imaging high-resolution mass spectrometry (IMS) methods were used to identify Arabidopsis leaf surface compounds and their possible involvement in the epiphytic lifestyle by relative changes in compound pools. The dominant carbohydrates on the leaf surfaces were sucrose, fructose and glucose. These sugars were significantly and specifically altered after epiphytic leaf colonization by the organoheterotroph Sphingomonas melonis or the phytopathogen Pseudomonas syringae pv. tomato, but only to a minor extent by the methylotroph Methylobacterium extorquens. In addition to carbohydrates, IMS revealed surprising alterations in arginine metabolism and phytoalexin biosynthesis that were dependent on the presence of bacteria, which might reflect the consequences of bacterial activity and the recognition of not only pathogens but also commensals by the plant. These results highlight the power of environmental metabolomics to aid in elucidating the molecular basis underlying plant–epiphyte interactions in situ.     

Inhibition of Akt activity and calcium channel function coordinately drive cell-cell fusion in the BeWO choriocarcinoma placental cell line

To establish a simple and quantitative live cell fusion assay for placental syncytialization, we generated stable GFP and dsRed expressing fusogenic BeWo cell lines. Fluorescent Activated Cell Sorting was shown to provide a quantitative determination of forskolin (cAMP-mediated) fusion in a time and concentration dependent manner consistent with the increased secretion of beta human chorionic gonadotrophin (β-HCG) and appearance of multi-nucleated cells. Analyses of the fusion process demonstrated that in addition to increased cAMP levels, simultaneous reduction of intracellular calcium and inhibition of Type 1 phosphatidylinositol 3 kinase (PI3K)/Akt signaling also resulted in cell fusion. Although individual blockade of calcium channel function or PI3K/Akt signaling was without effect, the combination with forskolin resulted in a potentiation of cell fusion. These data demonstrate syncytialization is a complex process that depends upon the regulation of distinct signaling inputs that function in concert with each other.     

Identification of genes differentially expressed in dorsal and ventral chick midbrain during early Development

Background  

During the development of the central nervous system (CNS), patterning processes along the dorsoventral (DV) axis of the neural tube generate different neuronal subtypes. As development progresses these neurons are arranged into functional units with varying cytoarchitecture, such as laminae or nuclei for efficient relaying of information. Early in development ventral and dorsal regions are similar in size and structure. Different proliferation rates and cell migration patterns are likely to result in the formation of laminae or nuclei, eventually. However, the underlying molecular mechanisms that establish these different structural arrangements are not well understood.