This study presents three feature selection methods for identifying the metabolite features in nuclear magnetic resonance spectra that contribute to the distinction of samples among varying nutritional conditions. Principal component analysis, Fisher discriminant analysis, and Partial Least Square Discriminant Analysis (PLS-DA) were used to calculate the importance of individual metabolite feature in spectra. Moreover, an Orthogonal Signal Correction (OSC) filter was used to eliminate unnecessary variations in spectra. We evaluated the presented methods by comparing the ability of classification based on the features selected by each method. The result showed that the best classification was achieved from an OSC-PLS-DA model.
Background:Nutritional deficiencies are common following Roux-en-Y Gastric Bypass (RYGB). Aetiology is diverse; including non-compliance, altered diet, unresolved preoperative deficiency and differential degrees of post-operative malabsorption occurring as function of length of bypassed intestine. Iron and calcium/vitamin D deficiency occur in up to 50% of patients following RYGB. Currently, treatment strategies recommend the prescription of oral supplements for those who become deficient. Meanwhile, debate exists regarding the absorption capacity of these post-operatively and their efficacy in treating deficiency.Objective:To examine the disposition of oral iron and calcium/vitamin D supplementation following RYGB. Methods: A literature review was carried out using PubMed and Embase. Data from the key interventional studies investigating iron and calcium/vitamin D oral supplement absorption and efficacy following RYGB was summarized.Results:Absorption of both iron and vitamin D/calcium is adversely affected following RYGB. Distribution and metabolism may be altered by the predominance of paracellular absorption pathways which promote unregulated influx into the circulatory system. Overall, studies indicate that current supplementation strategies are efficacious to a degree in treating deficiency following RYGB, generally restoration of optimal status is not achieved.Conclusion:Oral supplement disposition is altered following RYGB. As a result, patients are required to take regimens of oral supplementation indefinitely. The dosage which confers optimum health benefit while avoiding potential toxicity and tolerability issues remains unknown. Novel preparations with improved disposition could help limit the extent of post-RYGB nutritional deficiencies.
Background Oxidative stress occurs through free radical- and non-radical-mediated oxidative mechanisms, but these are poorly discriminated by most assays. A convenient assay for oxidants in human serum is based upon the Fe2+-dependent decomposition of peroxides to oxidize N,N′-diethyl-1,4-phenylenediamine (DEPPD) to a stable radical cation which can be measured spectrophotometrically. Methods We investigated modification of the DEPPD oxidation assay to discriminate color formation due to non-radical oxidants, including hydroperoxides and endoperoxides, which are sensitive to ebselen. Results Use of serum, which has been pretreated with ebselen as a reference, provides a quantitative assay for non-radical, reactive oxidant species in serum, including hydroperoxides, endoperoxides and epoxides. In a set of 35 human serum samples, non-radical oxidants largely accounted for DEPPD oxidation in 86% of the samples while the remaining 14% had considerable contribution from other redox-active chemicals. Conclusions The simple modification in which ebselen-pretreated sample is used as a reference provides means to quantify non-radical oxidants in human serum. Application of this approach could enhance understanding of the contribution of different types of oxidative stress to disease.
Objective This pilot study was designed to determine if metabolic effects in different brain regions (left and right parietal lobes, midbrain) due to 3 days of food consumption without methionine or cysteine could be detected by proton magnetic resonance spectroscopy (MRS). Research Methods & Procedures Healthy individuals aged 18-36 y (n=8) were studied by MRS after receiving diet with adequate sulfur amino acids (SAA) or with zero SAA for 3 days. Pulse sequences were used to selectively measure glutathione (GSH) and linear combination modeling (LCM) of spectra was used to measure other high abundance brain metabolites, and expressed relative to creatine (Cr). Results Although dietary SAA are required to maintain glutathione (GSH), the 3-d SAA insufficiency resulted in no significant change in GSH/Cr in the three brain regions. Principal component analysis of 16 metabolites measured by LCM showed that the metabolic pattern in the midbrain, but not the parietal lobes, was distinguished according to the dietary SAA. Multivariate statistical analysis showed that the major discriminating factors were signals of glutamate/Cr, (glutamate+glutamine)/Cr, and myo-inositiol/Cr. Correlation analyses between midbrain metabolites and GSH-related metabolites in plasma showed that midbrain glutamate/Cr had an inverse correlation with plasma cystine. Conclusion The data show that MRS is a non-invasive tool suitable for nutritional assessment and suggest that nutritional imbalance caused by 3-d of sulfur amino acid-free food more selectively affects midbrain than the parietal lobes.
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