Showing papers by "John W. Newman published in 2011"

The Human Serum Metabolome

Abstract: Continuing improvements in analytical technology along with an increased interest in performing comprehensive, quantitative metabolic profiling, is leading to increased interest pressures within the metabolomics community to develop centralized metabolite reference resources for certain clinically important biofluids, such as cerebrospinal fluid, urine and blood. As part of an ongoing effort to systematically characterize the human metabolome through the Human Metabolome Project, we have undertaken the task of characterizing the human serum metabolome. In doing so, we have combined targeted and non-targeted NMR, GC-MS and LC-MS methods with computer-aided literature mining to identify and quantify a comprehensive, if not absolutely complete, set of metabolites commonly detected and quantified (with today's technology) in the human serum metabolome. Our use of multiple metabolomics platforms and technologies allowed us to substantially enhance the level of metabolome coverage while critically assessing the relative strengths and weaknesses of these platforms or technologies. Tables containing the complete set of 4229 confirmed and highly probable human serum compounds, their concentrations, related literature references and links to their known disease associations are freely available at http://www.serummetabolome.ca.

Genetic contribution of the leukotriene pathway to coronary artery disease.

Abstract: We evaluated the genetic contribution of the leukotriene (LT) pathway to risk of coronary artery disease (CAD) in 4,512 Caucasian and African American subjects ascertained through elective cardiac evaluation. Of the three previously associated variants, the shorter “3” and “4” alleles of a promoter repeat polymorphism in ALOX5 increased risk of CAD in African Americans (OR = 1.4, 95% CI 1.0–1.9; p = 0.04), whereas a haplotype of LTA4H (HapK) was associated with CAD in Caucasians (OR = 1.2, 95% CI 1.01–1.4; p = 0.03). In Caucasians, first-stage analysis of 254 haplotype-tagging SNPs in 15 LT pathway genes with follow-up of 19 variants in stage 2 revealed an LTA4H SNP (rs2540477) that increased risk of CAD (OR = 1.2, 95% CI 1.1–1.5; p = 0.003) and a PLA2G4A SNP (rs12746200) that decreased risk of CAD (OR = 0.7, 95% CI 0.6–0.9; p = 0.0007). The PLA2G4A rs12746200 variant also decreased risk of experiencing a major adverse cardiac event (MACE = myocardial infarction, stroke, or death) over 3 years of follow-up (HR = 0.7, 95% CI 0.5–0.9; p = 0.01), consistent with its cardioprotective effect. Functional experiments demonstrated that stimulated monocytes from carriers of LTA4H variants HapK or rs2540477 had 50% (p = 0.002) and 33% (p = 0.03) higher LTB4 production, respectively, compared to non-carriers. These ex vivo results are consistent with LTB4 being the direct product of the reaction catalyzed by LTA4H and its role in promoting monocyte chemotaxis to sites of inflammation, including the artery wall of atherosclerotic lesions. Taken together, this study provides additional evidence that functional genetic variation of the LT pathway can mediate atherogenic processes and the risk of CAD in humans.

Effect of trans fatty acid intake on abdominal and liver fat deposition and blood lipids: a randomized trial in overweight postmenopausal women.

Abstract: Intake of industrially produced trans fatty acids (TFAs) is, according to observational studies, associated with an increased risk of cardiovascular disease, but the causal mechanisms have not been fully elucidated. Besides inducing dyslipidemia, TFA intake is suspected to promote abdominal and liver fat deposition. We examined the effect of a high intake of TFA as part of an isocaloric diet on whole-body, abdominal and hepatic fat deposition, and blood lipids in postmenopausal women. In a 16-week double-blind parallel intervention study, 52 healthy overweight postmenopausal women were randomized to receive either partially hydrogenated soybean oil providing 15.7 g day−1 of TFA or a control oil with mainly oleic and palmitic acid. Before and after the intervention, body composition was assessed by dual-energy X-ray absorptiometry, abdominal fat by magnetic resonance (MR) imaging, and liver fat by 1H MR spectroscopy. Compared with the control fat, TFA intake decreased plasma high-density lipoprotein (HDL)-cholesterol by 10%, increased low-density lipoprotein (LDL)-cholesterol by 18% and resulted in an increased LDL/HDL-cholesterol ratio (baseline adjusted mean (95% CI) difference between diet groups 0.41 (0.22; 0.60); P<0.001). TFA tended to increase the body fat (0.46 (−0.20; 1.17) kg; P=0.16) and waist circumference (1.1 (−0.1; 2.4) cm; P=0.08) more than the control fat, whereas neither abdominal nor liver fat deposition was affected by TFA. The adverse effect of dietary TFA on cardiovascular disease risk involves induction of dyslipidemia, and perhaps body fat, whereas weight gain-independent accumulation of ectopic fat could not be identified as a contributory factor during short-term intake.

Modelling the Delta1/Notch1 pathway: in search of the mediator(s) of neural stem cell differentiation.

Abstract: The Notch1 signalling pathway has been shown to control neural stem cell fate through lateral inhibition of mash1, a key promoter of neuronal differentiation. Interaction between the Delta1 ligand of a differentiating cell and the Notch1 protein of a neighbouring cell results in cleavage of the trans-membrane protein, releasing the intracellular domain (NICD) leading to the up regulation of hes1. Hes1 homodimerisation leads to down regulation of mash1. Most mathematical models currently represent this pathway up to the formation of the HES1 dimer. Herein, we present a detailed model ranging from the cleavage of the NICD and how this signal propagates through the Delta1/Notch1 pathway to repress the expression of the proneural genes. Consistent with the current literature, we assume that cells at the self renewal state are represented by a stable limit cycle and through in silico experimentation we conclude that a drastic change in the main pathway is required in order for the transition from self-renewal to differentiation to take place. Specifically, a model analysis based approach is utilised in order to generate hypotheses regarding potential mediators of this change. Through this process of model based hypotheses generation and testing, the degradation rates of Hes1 and Mash1 mRNA and the dissociation constant of Mash1-E47 heterodimers are identified as the most potent mediators of the transition towards neural differentiation.

Effects of Dynamic Exercise on Plasma Arachidonic Acid Epoxides and Diols in Human Volunteers

Abstract: Metabolites of the cytochrome P450 (CYP) pathway may contribute to vasodilation of the vasculature. However, it is not known whether exercise affects their circulating concentrations. The authors determined effects of exercise intensity and duration on plasma concentrations of epoxy and dihydroxy metabolites of arachidonic acid. Their goal was to delineate the threshold workload, optimal workload, and duration required to produce increases in plasma concentrations of these vasoactive substances. Healthy volunteers (N = 14) performed maximal exercise testing on a bicycle ergometer during Visit 1. On separate days, subjects cycled for 20 min at 30%, 60%, and 80% of their maximal exercise intensity. The last day consisted of 40 min of exercise at 60% of maximal exercise intensity. Venous blood was obtained before, during, and after exercise for analysis. Compared with rest, increases were observed during the 80% workload at 20 min postexercise —14,15-DHET (0.77 ± 0.21 vs. 0.93 ± 0.27 nM)—and at 2 min postexe...

Resveratrol given intraperitoneally does not inhibit the growth of high-risk t(4;11) acute lymphoblastic leukemia cells in a NOD/SCID mouse model

Abstract: The efficacy of resveratrol as a preventive agent against the growth of t(4;11) acute lymphoblastic leukemia (ALL) was evaluated in NOD.CB17-Prkdcscid/J mice engrafted with the human t(4;11) ALL SEM cell line. SEM cells were injected into the tail vein and engraftment was monitored by flow cytometry. Once engraftment was observed, mice were injected intraperitoneally with resveratrol (10 mg/kg body weight) dissolved in dimethylsulfoxide (DMSO) or DMSO alone (control) every other day, or vincristine (0.5 mg/kg body weight) 3 times per week for 4 weeks (n=16 per group). Comparisons of the percent of human leukemia cells in blood and survival curves showed resveratrol did not inhibit progression of the disease. Liquid chromatography-tandem mass spectrometry analyses of mouse sera showed resveratrol was rapidly metabolized to glucuronidated and sulfated forms 1 h post-injection, with low to no resveratrol or metabolites observed in sera by 24-48 h. These data indicate that in contrast to findings in in vitro models, parenterally administered resveratrol does not have potential as a preventive agent against high risk t(4;11) ALL.