Long Chain fatty Acids Analysis in Egyptian Patients with Inherited Peroxisomal Disorders

Abstract

Peroxisomal disorders are a group of genetically heterogeneous metabolic diseases that share dysfunction of peroxisomes. More than 50 enzymes have been discovered in mammalian peroxisomes that participate in various metabolic pathways. β-oxidation of very long chain fatty acid (VLCFA) is one of the most important functions of the peroxisome. Peroxisomes work in conjunction with mitochondria to shorten the VLCFA by β-oxidation, which are in turn degraded to completion in mitochondria. The end result is formation of acetyl-CoA units, which are degraded in the Krebs cycle to produce energy (ATP). Disorders of peroxisome function are divided into two major categories. This first one is named Peroxisome Biogenesis Disorders (PBDs) because it is a result of defect in peroxisome formation, which can be divided into two subtypes, including: (1) the Zellweger spectrum disorders (ZSDs) and (2) the rhizomelic chondrodysplasia punctate (RCDP) type 1. The second category includes the disorders, which result from the deficiency of a single peroxisomal enzyme or transporter (e.g. X-ALD, NALD, IRD and RCDP). Abnormal accumulation of VLCFAs (C24 & C26) is the hallmark of peroxisomal disorders. VLCFA have deleterious effect on RBC membranes and impairing the adrenal cells to respond to adrenocorticotropic hormone (ACTH). In the CNS, VLCFA accumulation may cause demyelination associated with an intense inflammatory response in the white matter, with increased levels of leukotrienes due to β-oxidation deficiency. Most peroxisomal disorders are inherited autosomal recessive diseases. They are extremely rare, with frequencies reported at one in 30,000 to one in 150,000, although these numbers are only estimates. X-ALD is the most common of the peroxisomal disorders, affecting about one in 20,000 males. The accumulation of VLCFA due to β-oxidation defect is the main cause for X-ALD. Developmental delay, mental retardation, vision and hearing impairment are common among those who have these disorders. Peroxisomal disorders are also associated with facial abnormalities, including high forehead, frontal bossing (swelling), small face, lowest ears and slanted eyes. There is no standard course of treatment for PDs. Therapies include supplementation of the diet with antioxidant vitamins or limitation of intake of fatty acids, especially VLCFAs. Lorenzo’s oil known as a good treatment for decreasing X-ALD symptoms. In this study which includes 50 cases clinically diagnosed as peroxisomal disorders and 25 control samples, it is proved that using ESI/MS/MS for the determination of VLCFA is sensitive, reliable, effective and time consuming method. In this method we used plasma samples and blood spots on the Guthrie cards. The results indicatedan elevation in C24:0, C26:0, C24:0/C22:0 & C26:0/C22 concentration for 6 patients in both plasma and filter paper samples, which proved the clinical diagnosis for X-ALD disorder. It also proved that Guthrie cared can be used for saving the expensive plasma samples collection and shipping. The study proved that using labeled internal standard is important for the sensitivity and accuracy. For measuring phytanic and pristanic acid, chromatographic separation with the ESI/MS/MS method has been used. The method was sensitive and precise but time consuming and need double sample volume.