Novel African trypanocidal agents: membrane rigidifying peptides

The bloodstream developmental forms of pathogenic African trypanosomes are uniquely susceptible to killing by small hydrophobic peptides. Trypanocidal activity is conferred by peptide hydrophobicity and charge distribution and results from increased rigidity of the plasma membrane. Structural analysis of lipid-associated peptide suggests a mechanism of phospholipid clamping in which an internal hydrophobic bulge anchors the peptide in the membrane and positively charged moieties at the termini coordinate phosphates of the polar lipid headgroups. This mechanism reveals a necessary phenotype in bloodstream form African trypanosomes, high membrane fluidity, and we suggest that targeting the plasma membrane lipid bilayer as a whole may be a novel strategy for the development of new pharmaceutical agents. Additionally, the peptides we have described may be valuable tools for probing the biosynthetic machinery responsible for the unique composition and characteristics of African trypanosome plasma membranes

Telomerecat: A ploidy-agnostic method for estimating telomere length from whole genome sequencing data.

Telomere length is a risk factor in disease and the dynamics of telomere length are crucial to our understanding of cell replication and vitality. The proliferation of whole genome sequencing represents an unprecedented opportunity to glean new insights into telomere biology on a previously unimaginable scale. To this end, a number of approaches for estimating telomere length from whole-genome sequencing data have been proposed. Here we present Telomerecat, a novel approach to the estimation of telomere length. Previous methods have been dependent on the number of telomeres present in a cell being known, which may be problematic when analysing aneuploid cancer data and non-human samples. Telomerecat is designed to be agnostic to the number of telomeres present, making it suited for the purpose of estimating telomere length in cancer studies. Telomerecat also accounts for interstitial telomeric reads and presents a novel approach to dealing with sequencing errors. We show that Telomerecat performs well at telomere length estimation when compared to leading experimental and computational methods. Furthermore, we show that it detects expected patterns in longitudinal data, repeated measurements, and cross-species comparisons. We also apply the method to a cancer cell data, uncovering an interesting relationship with the underlying telomerase genotype

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GWAS meta-analysis of intrahepatic cholestasis of pregnancy implicates multiple hepatic genes and regulatory elements

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder affecting 0.5–2% of pregnancies. The majority of cases present in the third trimester with pruritus, elevated serum bile acids and abnormal serum liver tests. ICP is associated with an increased risk of adverse outcomes, including spontaneous preterm birth and stillbirth. Whilst rare mutations affecting hepatobiliary transporters contribute to the aetiology of ICP, the role of common genetic variation in ICP has not been systematically characterised to date. Here, we perform genome-wide association studies (GWAS) and meta-analyses for ICP across three studies including 1138 cases and 153,642 controls. Eleven loci achieve genome-wide significance and have been further investigated and fine-mapped using functional genomics approaches. Our results pinpoint common sequence variation in liver-enriched genes and liver-specific cis-regulatory elements as contributing mechanisms to ICP susceptibility

Small hydrophobic peptide mediated killing of African trypanosomes.

<p>(<b>a</b>) The metacyclic developmental form (the developmental stage injected during a tsetse fly bite) of <i>T. b. brucei</i> was assayed for susceptibility to SHP-1 in 2 h <i>in vitro</i> killing assays (green ⧫, metacyclic; orange ▪, BSF). (<b>b</b>) The veterinary pathogenic African trypanosomes, <i>T. vivax</i> (red ▪, SHP-1; red-open □, DMSO) and <i>T. congolense</i> (blue ▴, SHP-1; blue-open ▵, DMSO), were assayed for susceptibility to SHP-1 in 2 h <i>in vitro</i> killing assays. (<b>c</b>) The sequences of trypanolytic and non-trypanolytic SHP are shown from N- to C-terminus and aligned to the C-terminus in order to emphasize the identity of the amino acid at position -5 relative to the putative signal peptidase cleavage site. Positively charged amino acids are in red, negatively charged amino acids are in green and non-polar amino acids are underlined. (<b>d</b>) The SHP listed in (c) were tested against BSF <i>T. b. brucei</i> in 2 h killing assays (blue •, SHP-1; red ▪, SHP-3; green ▴, SHP-3ΔR; purple ▪, SHP-3ΔK; orange ▴, SHP-3ΔE; black •, SHP-1swap). Colors correspond to the peptide names in (c).</p

Membrane rigidity changes and physiological consequences of SHP.

<p>The rigidity of the interior (<b>a</b>) or interfacial (<b>b</b>) region of the plasma membrane of BSF <i>T. b. brucei</i> treated with increasing concentrations of SHP-1 (blue •), SHP-2 (grey ⧫), SHP-3 (red ▪), SHP-3ΔR (green ▴), SHP-3ΔK (purple ▴), SHP-3ΔE (orange-open ▵), SHP-1swap (black-open ○) or solvent alone (DMSO, black ×) was determined by measuring the fluorescence depolarization of DPH or TMA-DPH respectively. (<b>c</b>) FRAP analysis of the mobile fraction of BSF <i>T. b. brucei</i> VSG in the presence (red ▪) or absence (black ▪) of 8 µM SHP-1. (<b>d</b>) Live BSF <i>T. b. brucei</i> treated with equivolume DMSO (grey), 40 µM SHP-1 (blue), SHP-3 (red) or SHP-3ΔR (green) were visualized by DIC microscopy and scored for normal, hyperactivated and constricted motility as well as death at the indicated timepoints (see Movies S1, S2, S3 and S4 for examples of the normal, hyperactivated and constricted motilities respectively).</p

Orientation and structure of SHP in lipid bilayers.

<p>(<b>a</b>) The depth of peptide penetration into the hydrocarbon region of model liposomes was determined via parallax analysis. Assuming a hydrocarbon bilayer thickness of 29 Å, the depths of tryptophans spanning SHP-1 (blue •) and SHP-3 (red ▪) are plotted against a background of the outer leaflet of a POPC bilayer. (<b>b</b>) Circular dichroism spectroscopy of SHP-1 in aqueous buffer (green •) and in the presence of egg phosphatidylcholine liposomes (blue •). (<b>c</b>) Molecular dynamic modeling of SHP-1 in a lipid environment. The backbone trace (top) illustrates a predominantly α-helical structure with disordered termini and an internal disordered region. Surface potential representations (N to C terminal, middle; C to N terminal, bottom) indicate positively charged patches (blue) formed by the N-terminal amino acid and the arginine at position 14. Non-polar and negatively charged regions are shown in white and red, respectively.</p

Improved hepatic lipid composition following short-term exercise in nonalcoholic fatty liver disease

CONTEXT: Hepatic steatosis, insulin resistance, inflammation, low levels of polyunsaturated lipids, and adiponectin are implicated in the development and progression of nonalcoholic fatty liver disease (NAFLD). OBJECTIVE: We examined the effects of short-term aerobic exercise on these metabolic risk factors. DESIGN AND PARTICIPANTS: Obese individuals (N = 17, 34.3 ± 1.0 kg/m(2)) with clinically confirmed NAFLD were enrolled in a short-term aerobic exercise program that consisted of 7 consecutive days of treadmill walking at ∼85% of maximal heart rate for 60 minutes per day. Preintervention and postintervention measures included hepatic triglyceride content, and a lipid saturation index and polyunsaturated lipid index (PUI) of the liver, obtained by (1)H magnetic resonance spectroscopy (N = 14). Insulin sensitivity was estimated from an oral glucose tolerance test (OGTT), and mononuclear cells were isolated to assess reactive oxygen species production during the OGTT. Circulating glucose, insulin, and high molecular weight (HMW) adiponectin were determined from plasma. MAIN OUTCOME: Short-term aerobic exercise training improved hepatic lipid composition in patients with NAFLD. RESULTS: Exercise training resulted in an increase in liver PUI (P < .05), increased insulin sensitivity (Matsuda Index: P < .05), HMW adiponectin (P < .05), and maximal oxygen consumption (P < .05). Reactive oxygen species production during the OGTT was reduced following exercise training (P < .05). HMW adiponectin was increased after the exercise program and the increase was positively correlated with the increase in liver PUI (r = 0.52, P = .05). Body weight remained stable during the program (P > .05). CONCLUSION: Short-term exercise can target hepatic lipid composition, which may reduce the risk of NAFLD progression. The improvement in hepatic lipid composition may be driven by adiponectin