Metabolic studies of a patient harbouring a novel S487L mutation in the catalytic subunit of AMPK.

AMP-activated protein kinase (AMPK) regulates many different metabolic pathways in eukaryote cells including mitochondria biogenesis and energy homeostasis. Here we identify a patient with hypotonia, weakness, delayed milestones and neurological impairment since birth harbouring a novel homozygous mutation in the AMPK catalytic α-subunit 1, encoded by the PRKAA1 gene. The homozygous mutation p.S487L in isoform 1 present in the patient is in a cryptic residue for AMPK activity. In the present study, we performed the characterization of mitochondrial respiratory properties of the patient, in comparison to healthy controls, through the culture of skin fibroblasts in order to understand some of the cellular consequences of the PRKAA1 mutation. In these assays, mitochondrial respiratory complex I showed lower activity, which was followed by a decrement in the mtDNA copy number, which is a probable consequence of the lower expression of PGC-1α and PRKAA1 itself as measured in our quantitative PCRs experiments. Confirming the effect of the patient mutation in respiration, transfection of patient fibroblasts with wild type PRKAA1 partially restore complex I level. The preliminary clinic evaluations of the patient suggested a metabolic defect related to the mitochondrial respiratory function, therefore treatment with CoQ10 supplementation dose started four years ago and a clear improvement in motor skills and strength has been achieved with this treatment.

Infantile encephaloneuromyopathy and defective mitochondrial translation are due to a homozygous RMND1 mutation.

Defects of mitochondrial protein synthesis are clinically and genetically heterogeneous. We previously described a male infant who was born to consanguineous parents and who presented with severe congenital encephalopathy, peripheral neuropathy, myopathy, and lactic acidosis associated with deficiencies of multiple mitochondrial respiratory-chain enzymes and defective mitochondrial translation. In this work, we have characterized four additional affected family members, performed homozygosity mapping, and identified a homozygous splicing mutation in the splice donor site of exon 2 (c.504+1G>A) of RMND1 (required for meiotic nuclear division-1) in the affected individuals. Fibroblasts from affected individuals expressed two aberrant transcripts and had decreased wild-type mRNA and deficiencies of mitochondrial respiratory-chain enzymes. The RMND1 mutation caused haploinsufficiency that was rescued by overexpression of the wild-type transcript in mutant fibroblasts; this overexpression increased the levels and activities of mitochondrial respiratory-chain proteins. Knockdown of RMND1 via shRNA recapitulated the biochemical defect of the mutant fibroblasts, further supporting a loss-of-function pathomechanism in this disease. RMND1 belongs to the sif2 family, an evolutionary conserved group of proteins that share the DUF155 domain, have unknown function, and have never been associated with human disease. We documented that the protein localizes to mitochondria in mammalian and yeast cells. Further studies are necessary for understanding the function of this protein in mitochondrial protein translation.

Determination of a method for extraction of coenzyme Q10 in human plasma: optimization of the use of surfactants and other variables.

OBJECTIVE: To establish a routine for the extraction of the total levels of CoQ10 in human plasma through the Ultra High Performance Liquid Chromatography (UHPLC). METHODS: Two extraction protocols were tested: a) methanol: hexane and b) 1-propanol. The following parameters were analyzed: extraction temperature (19ºC and 4ºC), extraction tubes (glass and polypropylene), and surfactants (SDS, Triton X-100, Tween-20) at different concentrations, i.e., 1%, 3%, 5% and 10%. RESULTS: The results showed that the method of extraction of CoQ10 in a sample of human plasma at 4ºC, using solvents methanol: hexane (85:15, v/v) in the presence of surfactant Tween-20 at 3% and polypropylene tubes showed better efficiency and reproducibility when compared to the method with 1-propanol. CONCLUSION: By the analyses performed, it was possible to observe that the addition of the surfactant Tween-20 promoted an increase in the recovery of CoQ10 by the methanol:hexane extraction method. This method showed good reproducibility, with a low coefficient of variation and high sensitivity, since CoQ10 was detected in samples of plasma of a control individual using a UV-type detector. The use of UHPLC equipment allowed a total analysis with total run time of 3.5 minutes, enabling the rapid achievement of results, considered mandatory for laboratory routines.

Determination of a method for extraction of coenzyme Q10 in human plasma: optimization of the use of surfactants and other variables / Determinação de um método de extração de coenzima Q10 em plasma humano: otimização do uso de surfactantes e outras variáveis

Objective: To establish a routine for the extraction of the total levels of CoQ10 in human plasma through the Ultra High Performance Liquid Chromatography (UHPLC). Methods: Two extraction protocols were tested: a) methanol: hexane and b) 1-propanol. The following parameters were analyzed: extraction temperature (19ºC and 4ºC), extraction tubes (glass and polypropylene), and surfactants (SDS, Triton X-100, Tween-20) at different concentrations, i.e., 1%, 3%, 5% and 10%. Results: The results showed that the method of extraction of CoQ10 in a sample of human plasma at 4ºC, using solvents methanol: hexane (85:15, v/v) in the presence of surfactant Tween-20 at 3% and polypropylene tubes showed better efficiency and reproducibility when compared to the method with 1-propanol. Conclusion: By the analyses performed, it was possible to observe that the addition of the surfactant Tween-20 promoted an increase in the recovery of CoQ10 by the methanol:hexane extraction method. This method showed good reproducibility, with a low coefficient of variation and high sensitivity, since CoQ10 was detected in samples of plasma of a control individual using a UV-type detector. The use of UHPLC equipment allowed a total analysis with total run time of 3.5 minutes, enabling the rapid achievement of results, considered mandatory for laboratory routines.

Objetivo: Estabelecer uma rotina de extração dos níveis totais de CoQ10 em plasma humano por meio da análise por Cromatografia Líquida de Ultra Alta Eficiência (UHPLC). Métodos: foram testados dois protocolos de extração: a) metanol:hexano e b) 1-propanol. Os seguintes parâmetros foram analisados: temperatura de extração (19ºC e 4ºC), tubos de extração (vidro e polipropileno), surfactantes (SDS, Triton X-100, Tween-20) em diferentes concentrações 1%, 3%, 5% e 10%. Resultados: Os resultados mostraram que o método de extração de CoQ10 em amostra de plasma humano, a 4ºC, utilizando-se os solventes metanol:hexano (85:15, v/v) na presença do surfactante Tween-20 a 3% e tubos de polipropileno apresentou melhor eficiência e reprodutibilidade quando comparado ao método com 1-propanol. Conclusão: A adição do surfactante Tween-20 no processo de preparação de amostra promoveu um aumento na recuperação da CoQ10 pelo método de extração metanol:hexano observada pela boa reprodutibilidade das prelicatas, pelo baixo coeficiente de variação e alta sensibilidade uma vez que a CoQ10 foi detectada em amostras de plasma de um indivíduo controle utilizando-se um detector do tipo UV. Além disso, a utilização de um equipamento de UHPLC proporcionou a obtenção de uma análise com tempo total de corrida de 3,5 minutos, o que viabiliza a obtenção rápida de resultados, considerado mandatório para rotinas laboratoriais.

Neonatal mitochondrial encephaloneuromyopathy due to a defect of mitochondrial protein synthesis.

Mitochondrial diseases are clinically and genetically heterogeneous disorders due to primary mutations in mitochondrial DNA (mtDNA) or nuclear DNA (nDNA). We studied a male infant with severe congenital encephalopathy, peripheral neuropathy, and myopathy. The patient's lactic acidosis and biochemical defects of respiratory chain complexes I, III, and IV in muscle indicated that he had a mitochondrial disorder while parental consanguinity suggested autosomal recessive inheritance. Cultured fibroblasts from the patient showed a generalized defect of mitochondrial protein synthesis. Fusion of cells from the patient with 143B206 rho(0) cells devoid of mtDNA restored cytochrome c oxidase activity confirming the nDNA origin of the disease. Our studies indicate that the patient has a novel autosomal recessive defect of mitochondrial protein synthesis.

Frequency of duplications in the D-loop in patients with mitochondrial DNA deletions.

Small duplications (miniduplications) of the D-loop of human mitochondrial DNA (mtDNA) have been described in patients with mtDNA deletions, mtDNA point mutations and in normal aged tissues. The origin of these miniduplications is still unknown but it is hypothesized that they could be formed after oxidative damage. The respiratory chain (RC) is the main source of free radicals in mitochondria and it is believed that a defect in RC increases free radical generation. If miniduplications are originated by oxidative damage, it is expected that they are more abundant in patients with a defect in the RC. We studied the frequency of miniduplications of D-loop in patients with a RC defect due to mtDNA deletions and in controls. We show that four types of miniduplications could be detected with a higher prevalence than in previous studies and that patients with mtDNA deletions did not have higher proportions or increased number of miniduplications, which is against the hypothesis that miniduplications are generated more abundantly in patients with RC defects. We also clearly demonstrate the age-related nature of these miniduplications by a carefully controlled study regarding the age of subjects, which was not considered in other studies on patients with a mitochondrial disease.