Caspase-1 deficiency in mice reduces intestinal triglyceride absorption and hepatic triglyceride secretion

Caspase-1 is known to activate the proinflammatory cytokines IL-1β and IL-18. Additionally, it can cleave other substrates, including proteins involved in metabolism. Recently, we showed that caspase-1 deficiency in mice strongly reduces high-fat diet-induced weight gain, at least partly caused by an increased energy production. Increased feces secretion by caspase-1-deficient mice suggests that lipid malabsorption possibly further reduces adipose tissue mass. In this study we investigated whether caspase-1 plays a role in triglyceride-(TG)-rich lipoprotein metabolism using caspase-1-deficient and wild-type mice. Caspase-1 deficiency reduced the postprandial TG response to an oral lipid load, whereas TG-derived fatty acid (FA) uptake by peripheral tissues was not affected, demonstrated by unaltered kinetics of [³H]TG-labeled very low-density lipoprotein (VLDL)-like emulsion particles. An oral gavage of [³H]TG-containing olive oil revealed that caspase-1 deficiency reduced TG absorption and subsequent uptake of TG-derived FA in liver, muscle, and adipose tissue. Similarly, despite an elevated hepatic TG content, caspase-1 deficiency reduced hepatic VLDL-TG production. Intestinal and hepatic gene expression analysis revealed that caspase-1 deficiency did not affect FA oxidation or FA uptake but rather reduced intracellular FA transport, thereby limiting lipid availability for the assembly and secretion of TG-rich lipoproteins. The current study reveals a novel function for caspase-1, or caspase-1-cleaved substrates, in controlling intestinal TG absorption and hepatic TG secretion.     

The Impact of Healthcare-Associated Infection on Mortality: Failure in Clinical Recognition Is Related with Inadequate Antibiotic Therapy

Purpose

To understand if clinicians can tell apart patients with healthcare-associated infections (HCAI) from those with community-acquired infections (CAI) and to determine the impact of HCAI in the adequacy of initial antibiotic therapy and hospital mortality.

Methods

One-year prospective cohort study including all consecutive infected patients admitted to a large university tertiary care hospital.

Results

A total of 1035 patients were included in this study. There were 718 patients admitted from the community: 225 (31%) with HCAI and 493 (69%) with CAI. Total microbiologic documentation rate of infection was 68% (n = 703): 56% in CAI, 73% in HCAI and 83% in hospital-acquired infections (HAI). Antibiotic therapy was inadequate in 27% of patients with HCAI vs. 14% of patients with CAI (p<0.001). Among patients with HCAI, 47% received antibiotic therapy in accordance with international recommendations for treatment of CAI. Antibiotic therapy was inadequate in 36% of patients with HCAI whose treatment followed international recommendations for CAI vs. 19% in the group of HCAI patients whose treatment did not follow these guidelines (p = 0.014). Variables independently associated with inadequate antibiotic therapy were: decreased functional capacity (adjusted OR = 2.24), HCAI (adjusted OR = 2.09) and HAI (adjusted OR = 2.24). Variables independently associated with higher hospital mortality were: age (adjusted OR = 1.05, per year), severe sepsis (adjusted OR = 1.92), septic shock (adjusted OR = 8.13) and inadequate antibiotic therapy (adjusted OR = 1.99).

Conclusions

HCAI was associated with an increased rate of inadequate antibiotic therapy but not with a significant increase in hospital mortality. Clinicians need to be aware of healthcare-associated infections among the group of infected patients arriving from the community since the existing guidelines regarding antibiotic therapy do not apply to this group and they will otherwise receive inadequate antibiotic therapy which will have a negative impact on hospital outcome.     

A Dual Tracer 18F-FCH/18F-FDG PET Imaging of an Orthotopic Brain Tumor Xenograft Model

Early diagnosis of low grade glioma has been a challenge to clinicians. Positron Emission Tomography (PET) using ¹⁸F-FDG as a radio-tracer has limited utility in this area because of the high background in normal brain tissue. Other radiotracers such as ¹⁸F-Fluorocholine (¹⁸F-FCH) could provide better contrast between tumor and normal brain tissue but with high incidence of false positives. In this study, the potential application of a dual tracer ¹⁸F-FCH/¹⁸F-FDG-PET is investigated in order to improve the sensitivity of PET imaging for low grade glioma diagnosis based on a mouse orthotopic xenograft model. BALB/c nude mice with and without orthotopic glioma xenografts from U87 MG-luc2 glioma cell line are used for the study. The animals are subjected to ¹⁸F-FCH and ¹⁸F-FDG PET imaging, and images acquired from two separate scans are superimposed for analysis. The ¹⁸F-FCH counts are subtracted from the merged images to identify the tumor. Micro-CT, bioluminescence imaging (BLI), histology and measurement of the tumor diameter are also conducted for comparison. Results show that there is a significant contrast in ¹⁸F-FCH uptake between tumor and normal brain tissue (2.65 ± 0.98), but with a high false positive rate of 28.6%. The difficulty of identifying the tumor by ¹⁸F-FDG only is also proved in this study. All the tumors can be detected based on the dual tracer technique of ¹⁸F-FCH/ ¹⁸F-FDG-PET imaging in this study, while the false-positive caused by ¹⁸F-FCH can be eliminated. Dual tracer ¹⁸F-FCH/¹⁸F-FDG PET imaging has the potential to improve the visualization of low grade glioma. ¹⁸F-FCH delineates tumor areas and the tumor can be identified by subtracting the ¹⁸F-FCH counts. The sensitivity was over 95%. Further studies are required to evaluate the possibility of applying this technique in clinical trials.     

KU0063794, a Dual mTORC1 and mTORC2 Inhibitor,Reduces Neural Tissue Damage and Locomotor Impairment After Spinal Cord Injury in Mice

Autophagy is an intracellular catabolic mechanism for the degradation of cytoplasmic constituents in the autophagosomal–lysosomal pathway. This mechanism plays an important role in homeostasis and it is defective in certain diseases. Preceding studies have revealed that autophagy is developing as an important moderator of pathological responses associated to spinal cord injury (SCI) and plays a crucial role in secondary injury initiating a progressive degeneration of the spinal cord. Thus, based on this evidence in this study, we used two different selective inhibitors of mTOR activity to explore the functional role of autophagy in an in vivo model of SCI as well as to determine whether the autophagic process is involved in spinal cord tissue damage. We treated animals with a novel synthetic inhibitor temsirolimus and with a dual mTORC1 and mTORC2 inhibitor KU0063794 matched all with the well-known inhibitor of mTOR the rapamycin. Our results demonstrated that mTOR inhibitors could regulate the neuroinflammation associated to SCI and the results that we obtained evidently demonstrated that rapamycin and temsirolimus significantly diminished the expression of iNOS, COX2, GFAP, and re-established nNOS levels, but the administration of KU0063794 is able to blunt the neuroinflammation better than rapamycin and temsirolimus. In addition, neuronal loss and cell mortality in the spinal cord after injury were considerably reduced in the KU0063794-treated mice. Accordingly, taken together our results denote that the administration of KU0063794 produced a neuroprotective function at the lesion site following SCI, representing a novel therapeutic approach after SCI.     

Efficacy of Various Pasteurization Time-Temperature Conditions in Combination with Homogenization on Inactivation of Mycobacterium avium subsp. paratuberculosis in Milk

The effect of various pasteurization time-temperature conditions with and without homogenization on the viability of Mycobacterium avium subsp. paratuberculosis was investigated using a pilot-scale commercial high-temperature, short-time (HTST) pasteurizer and raw milk spiked with 10¹ to 10⁵ M. avium subsp. paratuberculosis cells/ml. Viable M. avium subsp. paratuberculosis was cultured from 27 (3.3%) of 816 pasteurized milk samples overall, 5 on Herrold's egg yolk medium and 22 by BACTEC culture. Therefore, in 96.7% of samples, M. avium subsp. paratuberculosis had been completely inactivated by HTST pasteurization, alone or in combination with homogenization. Heat treatments incorporating homogenization at 2,500 lb/in², applied upstream (as a separate process) or in hold (at the start of a holding section), resulted in significantly fewer culture-positive samples than pasteurization treatments without homogenization (P < 0.001 for those in hold and P < 0.05 for those upstream). Where colony counts were obtained, the number of surviving M. avium subsp. paratuberculosis cells was estimated to be 10 to 20 CFU/150 ml, and the reduction in numbers achieved by HTST pasteurization with or without homogenization was estimated to be 4.0 to 5.2 log₁₀. The impact of homogenization on clump size distribution in M. avium subsp. paratuberculosis broth suspensions was subsequently assessed using a Mastersizer X spectrometer. These experiments demonstrated that large clumps of M. avium subsp. paratuberculosis cells were reduced to single-cell or “miniclump” status by homogenization at 2,500 lb/in². Consequently, when HTST pasteurization was being applied to homogenized milk, the M. avium subsp. paratuberculosis cells would have been present as predominantly declumped cells, which may possibly explain the greater inactivation achieved by the combination of pasteurization and homogenization.     

Chemosynthetic endosymbioses: adaptations to oxic-anoxic interfaces

Chemosynthetic endosymbioses occur ubiquitously at oxic-anoxic interfaces in marine environments. In these mutualisms, bacteria living directly within the cell of a eukaryotic host oxidize reduced chemicals (sulfur or methane), fueling their own energetic and biosynthetic needs, in addition to those of their host. In habitats such as deep-sea hydrothermal vents, chemosynthetic symbioses dominate the biomass, contributing substantially to primary production. Although these symbionts have yet to be cultured, physiological, biochemical and molecular approaches have provided insights into symbiont genetics and metabolism, as well as into symbiont-host interactions, adaptations and ecology. Recent studies of endosymbiont biology are reviewed, with emphasis on a conceptual model of thioautotrophic metabolism and studies linking symbiont physiology with the geochemical environment. We also discuss current and future research directions, focusing on the use of genome analyses to reveal mechanisms that initiate and sustain the symbiont-host interaction.     

Unphysical nucleation of diamond in the extended cutoff Tersoff potential

In simulations of carbon materials it is common practice to view the coefficients of the cutoff function as free parameters which can be optimised according to the system of interest. This work examines a common modification to the widely used Tersoff potential in which the coefficient of the upper cutoff is increased to improve the properties of amorphous carbon. Using molecular dynamics simulations, we show that this so-called extended cutoff Tersoff model leads to nucleation of diamond nanocrystals during annealing of amorphous carbon. By varying the density of the system, and examining the radial distribution function in conjunction with the modified cutoff function, we demonstrate that this behaviour is unphysical, and does not represent a new pathway for synthesising diamond. Viewed from a broader perspective, this observation provides a cautionary tale against altering the parameters of empirical potentials without fully considering the wider implications.     

Orexin A/Hypocretin Modulates Leptin Receptor-Mediated Signaling by Allosteric Modulations Mediated by the Ghrelin GHS-R1A Receptor in Hypothalamic Neurons

The hypothalamus is a key integrator of nutrient-seeking signals in the form of hormones and metabolites originated in both the central nervous system and the periphery. The main autocrine and paracrine target of orexinergic-related hormones such as leptin, orexin/hypocretin, and ghrelin are neuropeptide Y neurons located in the arcuate nucleus of the hypothalamus. The aim of this study was to investigate the expression and the molecular and functional relationships between leptin, orexin/hypocretin and ghrelin receptors. Biophysical studies in a heterologous system showed physical interactions between them, with potential formation of heterotrimeric complexes. Functional assays showed robust allosteric interactions particularly different when the three receptors are expressed together. Further biochemical and pharmacological assays provided evidence of heterotrimer functional expression in primary cultures of hypothalamic neurons. These findings constitute evidence of close relationships in the action of the three hormones already starting at the receptor level in hypothalamic cells.     

VIP and CRF reduce ADAMTS expression and function in osteoarthritis synovial fibroblasts

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family is known to play an important role in the pathogenesis of osteoarthritis (OA), working on aggrecan degradation or altering the integrity of extracellular matrix (ECM). Thus, the main purpose of our study was to define the role of vasoactive intestinal peptide (VIP) and corticotrophin‐releasing factor (CRF), as immunoregulatory neuropeptides, on ADAMTS production in synovial fibroblasts (SF) from OA patients and healthy donors (HD). OA‐ and HD‐SF were stimulated with pro‐inflammatory mediators and treated with VIP or CRF. Both neuropeptides decreased ADAMTS‐4, ‐5, ‐7 and ‐12 expressions, aggrecanase activity, glycosaminoglycans (GAG), and cartilage oligomeric matrix protein (COMP) degradation after stimulation with fibronectin fragments (Fn‐fs) in OA‐SF. After stimulation with interleukin‐1β, VIP reduced ADAMTS‐4 and ‐5, and both neuropeptides decreased ADAMTS‐7 production and COMP degradation. Moreover, VIP and CRF reduced Runx2 and β‐catenin activation in OA‐SF. Our data suggest that the role of VIP and CRF on ADAMTS expression and cartilage degradation could be related to the OA pathology since scarce effects were produced in HD‐SF. In addition, their effects might be greater when a degradation loop has been established, given that they were higher after stimulation with Fn‐fs. Our results point to novel OA therapies based on the use of neuropeptides, since VIP and CRF are able to stop the first critical step, the loss of cartilage aggrecan and the ECM destabilization during joint degradation.