The Effects of Long‐ or Medium‐Chain Fat Diets on Glucose Tolerance and Myocellular Content of Lipid Intermediates in Rats

Accumulation of triacylglycerols (TAGs) and acylcarnitines in skeletal muscle upon high‐fat (HF) feeding is the resultant of fatty acid uptake and oxidation and is associated with insulin resistance. As medium‐chain fatty acids (MCFAs) are preferentially β‐oxidized over long‐chain fatty acids, we examined the effects of medium‐chain TAGs (MCTs) and long‐chain TAGs (LCTs) on muscle lipid storage and whole‐body glucose tolerance. Rats fed a low‐fat (LF), HFLCT, or an isocaloric HFMCT diet displayed a similar body weight gain over 8 weeks of treatment. Only HFLCT increased myocellular TAG (42.3 ± 4.9, 71.9 ± 6.7, and 48.5 ± 6.5 µmol/g for LF, HFLCT, and HFMCT, respectively, P < 0.05) and long‐chain acylcarnitine content (P < 0.05). Neither HF diet increased myocellular diacylglycerol (DAG) content. Intraperitoneal (IP) glucose tolerance tests (1.5 g/kg) revealed a significantly decreased glucose tolerance in the HFMCT compared to the HFLCT‐fed rats (802 ± 40, 772 ± 18, and 886 ± 18 area under the curve for LF, HFLCT, and HFMCT, respectively, P < 0.05). Finally, no differences in myocellular insulin signaling after bolus insulin injection (10 U/kg) were observed between LF, HFLCT, or HFMCT‐fed rats. These results show that accumulation of TAGs and acylcarnitines in skeletal muscle in the absence of body weight gain do not impede myocellular insulin signaling or whole‐body glucose intolerance.     

Enhanced transmission of drug-resistant parasites to mosquitoes following drug treatment in rodent malaria

The evolution of drug resistant Plasmodium parasites is a major challenge to effective malaria control. In theory, competitive interactions between sensitive parasites and resistant parasites within infections are a major determinant of the rate at which parasite evolution undermines drug efficacy. Competitive suppression of resistant parasites in untreated hosts slows the spread of resistance; competitive release following treatment enhances it. Here we report that for the murine model Plasmodium chabaudi, co-infection with drug-sensitive parasites can prevent the transmission of initially rare resistant parasites to mosquitoes. Removal of drug-sensitive parasites following chemotherapy enabled resistant parasites to transmit to mosquitoes as successfully as sensitive parasites in the absence of treatment. We also show that the genetic composition of gametocyte populations in host venous blood accurately reflects the genetic composition of gametocytes taken up by mosquitoes. Our data demonstrate that, at least for this mouse model, aggressive chemotherapy leads to very effective transmission of highly resistant parasites that are present in an infection, the very parasites which undermine the long term efficacy of front-line drugs.     

Severe dengue is associated with consumption of von Willebrand factor and its cleaving enzyme ADAMTS-13

Background

Thrombocytopenia, bleeding and plasma leakage are cardinal features of severe dengue. Endothelial cell activation with exocytosis of Weibel-Palade bodies (WPBs) may play an etiological role in this condition.

Methods and Principal Findings

In a cohort of 73 Indonesian children with dengue hemorrhagic fever (DHF), of which 30 with dengue shock syndrome (DSS), we measured plasma levels of the WPB constituents von Willebrand factor antigen (VWF:Ag), VWF propeptide and osteoprotegerin (OPG), together with activity levels of the VWF-cleaving enzyme ADAMTS-13 and the amount of VWF in a platelet binding conformation (VWF activation factor). Compared with healthy controls (n = 17), children with DHF/DSS had significantly higher levels of VWF:Ag, VWF propeptide and OPG and decreased ADAMTS-13 activity. The VWF activation factor was also significantly higher in DHF/DSS and highest in children who died. There were significant differences in the kinetics of the various WPB constituents: VWF propeptide and OPG levels decreased toward discharge, while VWF:Ag levels were lower than expected at enrollment with plasma levels increasing toward discharge. Moreover, VWF propeptide levels correlated better with markers of disease severity (platelet count, liver enzymes, serum albumin and pleural effusion index) than corresponding VWF levels. Together, these findings suggest that there is consumption of VWF in DHF/DSS. In 4 out of 15 selected children with low ADAMTS-13 levels on admission, we found a remarkable reduction in the large and intermediate VWF multimers in the discharge blood samples, consistent with an acquired von Willebrand disease.

Conclusion

These findings suggest that severe dengue is associated with exocytosis of WPBs with increased circulating levels of VWF:Ag, VWF propeptide and OPG. High circulating levels of VWF in its active conformation, together with low ADAMTS-13 activity levels, are likely to contribute to the thrombocytopenia and complications of dengue. During the convalescence phase, qualitative defects in VWF with loss of larger VWF multimers may develop.     

A virosomal malaria peptide vaccine elicits a long-lasting sporozoite-inhibitory antibody response in a phase 1a clinical trial

Objectives

Peptides delivered on the surface of influenza virosomes have been shown to induce solid humoral immune responses in experimental animals. High titers of peptide-specific antibodies were also induced in a phase 1a clinical trial in volunteers immunized with virosomal formulations of two peptides derived from the circumsporozoite protein (CSP) and the apical membrane antigen 1 (AMA-1) of Plasmodium falciparum. The main objective of this study was to perform a detailed immunological and functional analysis of the CSP-specific antibodies elicited in this phase 1a trial.

Methodology/Principal Findings

46 healthy malaria-naïve adults were immunized with virosomal formulations of two peptide-phosphatidylethanolamine conjugates, one derived from the NANP repeat region of P. falciparum CSP (designated UK-39) the other from P. falciparum AMA-1 (designated AMA49-C1). The two antigens were delivered in two different concentrations, alone and in combination. One group was immunized with empty virosomes as control. In this report we show a detailed analysis of the antibody response against UK-39. Three vaccinations with a 10 µg dose of UK-39 induced high titers of sporozoite-binding antibodies in all volunteers. This IgG response was affinity maturated and long-lived. Co-administration of UK-39 and AMA49-C1 loaded virosomes did not interfere with the immunogenicity of UK-39. Purified total IgG from UK-39 immunized volunteers inhibited sporozoite migration and invasion of hepatocytes in vitro. Sporozoite inhibition closely correlated with titers measured in immunogenicity assays.

Conclusions

Virosomal delivery of a short, conformationally constrained peptide derived from P. falciparum CSP induced a long-lived parasite-inhibitory antibody response in humans. Combination with a second virosomally-formulated peptide derived from P. falciparum AMA-1 did not interfere with the immunogenicity of either peptide, demonstrating the potential of influenza virosomes as a versatile, human-compatible antigen delivery platform for the development of multivalent subunit vaccines.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00400101","term_id":"NCT00400101"}}NCT00400101     

Cloning and characterization of a gene cluster from Streptomyces cyanogenus S136 probably involved in landomycin biosynthesis

From a cosmid library of Streptomyces cyanogenus S136, DNA fragments encompassing approximately 35 kb of the presumed landomycin biosynthetic gene cluster were identified and sequenced, revealing 32 open reading frames most of which could be assigned through data base comparison.     

The parallel G-quadruplex structure of vertebrate telomeric repeat sequences is not the preferred folding topology under physiological conditions

G-quadruplex topologies of telomeric repeat sequences from vertebrates were investigated in the presence of molecular crowding (MC) mimetics, namely polyethylene glycol 200 (PEG), Ficoll 70 as well as Xenopus laevis egg extract by CD and NMR spectroscopy and native PAGE. Here, we show that the conformational behavior of the telomeric repeats in X. laevis egg extract or in Ficoll is notably different from that observed in the presence of PEG. While the behavior of the telomeric repeat in X. laevis egg extract or in Ficoll resembles results obtained under dilute conditions, PEG promotes the formation of high-order parallel topologies. Our data suggest that PEG should not be used as a MC mimetic.     

Paradoxical increase in TAG and DAG content parallel the insulin sensitizing effect of unilateral DGAT1 overexpression in rat skeletal muscle

Background

The involvement of muscle triacylglycerol (TAG) storage in the onset of insulin resistance is questioned and the attention has shifted towards inhibition of insulin signalling by the lipid intermediate diacylglycerol (DAG). The enzyme 1,2-acylCoA:diacylglyceroltransferase-1 (DGAT1) esterifies a fatty acyl-CoA on DAG to form TAG. Therefore, the aim of the present study was to investigate if unilateral overexpression of DGAT1 in adult rat Tibialis anterior (TA) muscle will increase conversion of the lipid intermediate DAG into TAG, thereby improving muscle insulin sensitivity.

Methodology/Principal Findings

The DGAT1 gene construct was injected in the left TA muscle of male rats on chow or high-fat (45% kcal) diet for three weeks, followed by application of one 800 V/cm and four 80 V/cm pulses, using the contralateral leg as sham-electroporated control. Seven days after electroporation, muscle specific insulin sensitivity was assessed with a hyperinsulinemic euglycemic clamp using 2-deoxy-[3H]glucose. Here, we provide evidence that unilateral overexpression of DGAT1 in TA muscle of male rats is associated with an increased rather than decreased DAG content. Strikingly, this increase in DAG content was accompanied by improved muscle insulin sensitivity. Interestingly, markers of muscle lipolysis and mitochondrial function were also increased in DGAT1 overexpressing muscle.

Conclusions/Significance

We conclude that unilateral DGAT1 overexpression can rescue insulin sensitivity, possibly by increasing DAG and TAG turnover in skeletal muscle. In case of a proper balance between the supply and oxidation of fatty acids in skeletal muscle, the lipid intermediate DAG may not exert harmful effects on insulin signalling.     

Calorie restriction-like effects of 30 days of resveratrol supplementation on energy metabolism and metabolic profile in obese humans

Resveratrol is a natural compound that affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here, we treated 11 healthy, obese men with placebo and 150?mg/day resveratrol (resVida) in a randomized double-blind crossover study for 30?days. Resveratrol significantly reduced sleeping and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1α protein levels, increased citrate synthase activity without change in mitochondrial content, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30?days of resveratrol supplementation induces metabolic changes in obese humans, mimicking the effects of calorie restriction.     

The Spatiotemporal Dynamics and Membranous Features of the Plasmodium Liver Stage Tubovesicular Network

For membrane‐bound intracellular pathogens, the surrounding vacuole is the portal of communication with the host cell. The parasitophorous vacuole (PV) harboring intrahepatocytic Plasmodium parasites satisfies the parasites' needs of nutrition and protection from host defenses to allow the rapid parasite growth that occurs during the liver stage of infection. In this study, we visualized the PV membrane (PVM) and the associated tubovesicular network (TVN) through fluorescent tagging of two PVM‐resident Plasmodium berghei proteins, UIS4 and IBIS1. This strategy revealed previously unrecognized dynamics with which these membranes extend throughout the host cell. We observed dynamic vesicles, elongated clusters of membranes and long tubules that rapidly extend and contract from the PVM in a microtubule‐dependent manner. Live microscopy, correlative light‐electron microscopy and fluorescent recovery after photobleaching enabled a detailed characterization of these membranous features, including velocities, the distribution of UIS4 and IBIS1, and the connectivity of PVM and TVN. Labeling of host cell compartments revealed association of late endosomes and lysosomes with the elongated membrane clusters. Moreover, the signature host autophagosome protein LC3 was recruited to the PVM and TVN and colocalized with UIS4. Together, our data demonstrate that the membranes surrounding intrahepatic Plasmodium are involved in active remodeling of host cells.