الفهرس 
PeroxisomesOnly 14 pages are availabe for public view
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Abstract
Peroxisomal disorders (PDs) are a group of genetically heterogeneous metabolic diseases that share dysfunction of peroxisomes. Developmental delay, mental retardation, vision, hearing impairment, hypotonia and failure to thrive along with an enlarged liver due to abnormality in liver enzymes function are common on those who have these disorders. PDs are divided into two major categories. The 1st is Peroxisome Biogenesis Disorders (PBD) which results from a failure in organelle formation includes (Zellweger spectrum disorders (ZSDs) and the rhizomelic chondrodysplasia punctata (RCDP) type 1). The 2nd category includes the disorders, which result from the deficiency of a single peroxisomal enzyme or transporter (e.g. X-ALD/AMN, RCDP and Refsum disease) (Poll-The and Gartner, 2012.
Mammalian peroxisome is a cellular organelle has more than 50 enzymes participate in various metabolic pathways including β-oxidation of very long chain fatty acid (VLCFA). It works in conjunction with mitochondria to shorten the VLCFA by β-oxidation (Ferdinandusse et al., 2002).
Peroxisomal are extremely rare, with frequencies reported at one in 30,000 to one in 150,000, although these numbers are only estimates. X- Adrenoleukodystrophy (X-ALD) is the most common of the peroxisomal disorders, affecting about one in 20,000 males. There is no standard course of treatment. In general therapies include supplementation of the diet with antioxidant vitamins or limitation of intake of fatty acids, especially VLCFAs.
The goal of this work was to establish a rapid, reliable, less expensive and sensitive procedure for the diagnosis of peroxisomal disorders by using Electro Spray Triple Quadruple Mass Spectrometry (ESI-MS/MS) for the quantification of VLCFAs in plasma and dried blood spot. To compare the results of the labeled and non-labeled fatty acid standards to evaluate a reliable, rapid method versus the cost. Also, to validate and endorse a rapid and accurate procedure for measuring phytanic and pristanic acids.
50 patients (GII) clinically suspicious to have peroxisomal disorders and 25 control samples (GI) from the same age were included in this study. Their ages ranged from 2 to 10 years. The patients were classified as follow: 45 (90%) male and 5 (10) female. Positive consanguinity was present in 32 (64%) cases, while the percent was 83% among the positive cases.
Level of ALT and γGT was measured for all patients Justify suffering from liver dysfunction. The results of ALT & γGT indicated that their concentrations were above the normal range of the control samples. This confirms the clinical diagnosis of peroxisomal disorders. 6 X-ALD diagnosed patients (GIIb) (12%) exhibited higher ALT and γGT compared to the rest (44 patients) from the study group (GIIa), due to the accumulation of the VLCFAs in the liver tissue.
VLCFAs quantification using Triple Quadruple Mass Spectrometry was done using dimethylaminoethyl esters for plasma and dried blood spots samples derived from patients and controls using deuterated internal standard. Comparison between the means of (C24:0, C26:0, and C24:0/C22:0 & C26:0/C22:0 ratio) (GIIb) with the means of (GI) showed a high significant increase in both plasma and filter paper analysis, which prove the clinical X-ALD diagnosis. On the other hand, the results for the (GIIa) were within the normal range and the comparison with the control means was non-significant. This conclusion verifies that they are not suffering from X-ALD disorder. Comparing the mean results of the filter paper samples with the plasma samples ascertained a highly significant difference due to the presence of VLCFAs in wax of the filter paper and in the red blood cells.
The same analysis for the plasma samples was repeated without using deuterated internal standards but with using external undeuterated standards. Comparing the means for (GIIb) group with the means of (GI) group revealed a high significant increase, which assure the X-ALD diagnosis. The difference between means of (GIIa) with the means of (GI) group was non-significant. This indicates that they are not suffering from X-ALD disorder. Also, comparing the results for the samples using undeuterated internal standards with those of the labeled internal standards showed a highly significant decrease except C24:0/C22:0 which was slightly higher, which may be due to the absence of the internal labeled standards which make correction for concentration loss.
Phytanic and pristanic acids were estimated quantitatively using electro spray ionization tandem mass spectrometry (ESI-MS/MS), by the trimethylaminoethyl (TMAE) ester iodide derivative with a liquid chromatography separation step and using internal labeled standers for the same (GI) control group and (GII) patient’s plasma samples group. The difference between the means of (GII) group with (GI) group was non-significant, which certifies that these patients don’t have Refsum disease or Rhizomelic Chondrodysplasia Punctata (phytanic elevation) or peroxisomal 3-oxoacyl-CoA thiolase deficiency (pristanic elevation).