Pelnena 2016 Abstract MitoFit Science Camp 2016

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OXPHOS enzyme activity measurements in mitochondria isolated from peripheral blood leukocytes in control group and patients with suspected mitochondrial disease.

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Pelnena D, Lace B, Micule I, Grinfelde I, Inaskina I (2016)

Event: MitoFit Science Camp 2016 Kuehtai AT

Mitochondrial disorders are a heterogeneous group of diseases usually caused by defects in the mitochondrial oxidative phosphorylation system (OXPHOS). Diagnosis is often challenging and includes both clinical observations and biochemical analysis followed by molecular genetic testing. OXPHOS enzyme activity measurements in muscle biopsies are considered as cornerstone for diagnostic of mitochondrial diseases [1]. As in Latvia diagnosing of mitochondrial diseases has been based so far only on clinical phenotype, metabolite analysis and mtDNA sequencing, we aimed to introduce measurement of OXPHOS enzyme activity in peripheral leukocytes as a routine diagnostic method.

Respiratory Complex I (CI) and citrate synthase (CS) activities in mitochondria isolated from peripheral blood leukocytes were measured. Ten to twenty ml of peripheral blood were collected from 9 healthy persons and 3 patients with suspected mitochondrial diseases. Leukocytes were isolated by centrifugation in RBC lysis buffer in 600 g 10 min 4 °C and after washed with PBS. Isolated leukocytes were disrupted by homogenization with Dounce homogenizer in medium that contained 0.1 mg/ml digitonin as described before [2]. Obtained mitochondria were suspended in buffer with 25 mM KH2PO4 and 5 mM MgCl2, pH 7.2. CI and CS activities were measured spectrophotometrically as previously described [3] with modifications. The results were expressed as ratio between CI and CS activities in order to compare patients and control group.

Mean CI activity in control group was 25.59 ± 8.25 mU/mg protein, mean CS activity was 196.59 ± 56.57 mU/mg protein and mean CI/CS ratio was 0.14 ± 0.06. One of the examined patients had lower CI activity and all three patients had increased CS activities compared to control group. All three examined patients had decreased CI/CS ratio (Fig 1).

OXPHOS enzyme activity measurements in peripheral leukocytes is fast robust method for routine diagnosis of patients with suspected mitochondrial disease as it is less traumatic than comprehensive biopsy. The limitation of this method is relatively large volume of blood that is essential to measure activities of all OXPHOS enzymes and citrate synthase spectrophotometrically. Therefore, more sensitive and reliable method as high-resolution respirometry would be required for this approach.


Labels: MiParea: mt-Medicine, Patients 

Stress:Mitochondrial disease  Organism: Human  Tissue;cell: Blood cells, Macrophage-derived  Preparation: Isolated mitochondria  Enzyme: TCA cycle and matrix dehydrogenases 


Pathway:

Event: B1, Poster  MitoFit Science Camp 2016 

Affiliations

1-Latvian Biomedical Research Study Centre, Latvia; 2-Laval Univ; 3-Centre hospitalier univ Québec, Canada; 4-Children's Clin Univ Hosp, Latvia. – dita@biomed.lu.lv

References

  1. Rodenburg RJ (2011) Biochemical diagnosis of mitochondrial disorders. J Inherit Metab Dis 34:283-92.
  2. Ma YY, Zhang XL, Wu TF, Liu YP, Wang Q, Zhang Y, Song JQ, Wang YJ, Yang YL (2011) Analysis of the mitochondrial complex I-V enzyme activities of peripheral leukocytes in oxidative phosphorylation disorders. J Child Neurol 26:974-9.
  3. Feichtinger RG, Zimmermann F, Mayr JA, Neureiter D, Hauser-Kronberger C, Schilling FH, Jones N, Sperl W, Kofler B (2010) Low aerobic mitochondrial energy metabolism in poorly- or undifferentiated neuroblastoma. BMC Cancer 10:149.

Figure 1

MitoFit Training Camp 2016 Pelnena Figure.jpg
Figure 1. Ratio between complex I and citrate synthase activities of peripheral blood leukocytes in control group and patients.