Faculty of Health Sciences
School of Medicine
Department of Paediatrics
Selected Highlights from Research Findings
The aim of this study was to identify a metabolite fingerprint in the urine of patients with possible mitochondrial disorders in order to simplify the very tedious and expensive methods currently used. The first phase was to do stability tests to assess the influence of storage conditions and time. For urine metabolite stability analyses, a total of 1 231 metabolites (features) were extracted. Given the different levels of the analysis scenarios (factors), a data matrix of 54 (cases) and 1 231 variables was produced. The researchers also received 24 positive control urine samples from The Netherlands, which proved to be extremely important to this investigation. The metabolite stability study has progressed up to the sixth month and preliminary data presented has shown that creatinine remains stable under the conditions investigated. The metabolomic analysis, however, shows that time of storage and temperature have an effect on the data. The further analysis, interpretation and implementation of this information will be crucial in further urine analyses
Contact person: Prof I Smuts.
Children with neuromuscular disorders impose a diagnostic challenge to the clinician. Molecular genetics or enzyme deficiencies are the gold standards for the confirmation of myopathies, and immuno-histochemistry is a diagnostic option for specific conditions, but not readily available. The contribution of oxidative phosphorylation (OXPHOS) and Pyruvate dehydrogenase complex (PDHc) analyses to the diagnosis of children with myopathies were assessed. The researchers tested 77 patients with possible neuromuscular disorders between 2004 and 2007. Diagnoses were confirmed in 49 (64%) patients. Molecular genetics were done for 30 patients and diagnoses were confirmed in 17 (22%). Spinal muscular atrophy was the most common genetically confirmed diagnosis (12/17). Muscle biopsies were performed on 47 patients. Five biopsies were only sent for histology, and dermatomyositis was confirmed in four cases, while 42 biopsies were sent for histology and enzyme analyses, and an additional 28 diagnoses were made on the basis of the OXPHOS and PDHc results. The confirmation of neuromuscular disorders remains a challenge. Thorough clinical assessment remains the cornerstone in the initial assessment and the appropriate investigations must be selected accordingly. The researchers found that although molecular genetics is valuable, it only has a limited number of available investigations. Histology is useful to confirm inflammatory disorders. The availability of PSPHOS and PDHc analyses contributed 37% additional diagnoses in a previously undiagnosed population. In addition, the researchers found that OXPHOS and PDHc analyses should be done routinely on muscle biopsies of children with a suspected neuromuscular disorder
Contact person: Prof I Smuts.
Deficiencies of enzymes in the mitochondrial oxidative phosphorylation (OXPHOS or energy producing) system are of the most frequently encountered inherited metabolic diseases and are often collectively referred to as mitochondrial disorders. Diagnosis of these disorders is complicated and requires a combination of clinical, histochemical and biochemical assessment of respiratory chain function and molecular genetic studies. The objective of this study was to perform respiration analyses, in addition to single enzyme assays, on freshly prepared mitochondria of patients with possible mitochondrial disorders in order to improve the diagnostic yield of mitochondrial disorders in muscle specimens. The researcher found that of the 18 controls and 26 possible patients, 19 patients (73%) were identified with either OXPHOS and or PDHc complex deficiencies. The respiration analyses supported the diagnoses of a mitochondrial disorder in only four (15%) cases. No additional patients were identified through respiration analyses only. The researcher concluded that single enzyme analyses remain the gold standard for the diagnosis of mitochondrial disorders. It was postulated that respiration analyses may contribute to the diagnostic yield, but it only supported the diagnosis in 15% of cases. In addition, the researcher found that respiration can still be normal in the presence of enzyme deficiencies and it did not contribute significantly to the diagnoses of patients with mitochondrial disorders
Contact person: Prof I Smuts.
The aim of this study was to find ways to diagnose disorders in the ethnic diverse paediatric population in South Africa caused by deficiencies in the oxidative phosphorylation system (OXPHOS) and Pyruvate dehydrogenase complex (PDHc). The strategy, competencies and logistics to provide the basic diagnostic capability, however, have only been established in recent years. The researchers identified 28 patients with mostly combined deficiencies of the respiratory chain and/or PDHc enzymes. The protocols for biochemical analyses were modified over time to increase sensitivities and allow changes in strategy. The researchers used 600xg supernatants for enzyme analyses that allow the use of frozen biopsies and have thus excluded respiration analysis. The patients had mostly combined enzyme deficiencies, but complex I (CI) deficiency was the most prevalent, followed by the combined deficiency of complex II + III (CII + III). The researchers found that, as has been the norm worldwide, the age of onset and phenotypes was diverse. The phenotypes differed in the different ethnic groupings. African patients had predominant early onset with mainly myopathic presentation in contrast to Caucasian patients that had a group with early onset central nervous system (CNS) involvement and a group with later onset in the second or later decade with predominant exercise intolerance as one of the presenting features. The researchers concluded that this investigation provides the first clinical and biochemical data on a cohort of South African paediatric patients suspected to have a mitochondrial disorder. It has also provided a basis for reviewing the strategy of diagnosis and research of mitochondrial disorders in a developing country. Considering the demands on health care facilities in southern Africa, future diagnosis and research on mitochondrial disorders will require optimisation through a constant review of strategy and ethical considerations
Contact person: Prof I Smuts.
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