Cardiac and placental mitochondrial characterization in a rabbit model of intrauterine growth restriction.

BACKGROUND: Intrauterine growth restriction (IUGR) is associated with cardiovascular remodeling persisting into adulthood. Mitochondrial bioenergetics, essential for embryonic development and cardiovascular function, are regulated by nuclear effectors as sirtuins. A rabbit model of IUGR and cardiovascular remodeling was generated, in which heart mitochondrial alterations were observed by microscopic and transcriptomic analysis. We aimed to evaluate if such alterations are translated at a functional mitochondrial level to establish the etiopathology and potential therapeutic targets for this obstetric complication. METHODS: Hearts and placentas from 16 IUGR-offspring and 14 controls were included to characterize mitochondrial function. RESULTS: Enzymatic activities of complexes II, IV and II + III in IUGR-hearts (-11.96 ±â€¯3.16%; -15.58 ±â€¯5.32%; -14.73 ±â€¯4.37%; p < 0.05) and II and II + III in IUGR-placentas (-17.22 ±â€¯3.46%; p < 0.005 and -29.64 ±â€¯4.43%; p < 0.001) significantly decreased. This was accompanied by a not significant reduction in CI-stimulated oxygen consumption and significantly decreased complex II SDHB subunit expression in placenta (-44.12 ±â€¯5.88%; p < 0.001). Levels of mitochondrial content, Coenzyme Q and cellular ATP were conserved. Lipid peroxidation significantly decreased in IUGR-hearts (-39.02 ±â€¯4.35%; p < 0.001), but not significantly increased in IUGR-placentas. Sirtuin3 protein expression significantly increased in IUGR-hearts (84.21 ±â€¯31.58%; p < 0.05) despite conserved anti-oxidant SOD2 protein expression and activity in both tissues. CONCLUSIONS: IUGR is associated with cardiac and placental mitochondrial CII dysfunction. Up-regulated expression of Sirtuin3 may explain attenuation of cardiac oxidative damage and preserved ATP levels under CII deficiency. GENERAL SIGNIFICANCE: These findings may allow the design of dietary interventions to modulate Sirtuin3 expression and consequent regulation of mitochondrial imbalance associated with IUGR and derived cardiovascular remodeling.

An incidental finding in newborn screening leading to the diagnosis of a patient with ECHS1 mutations.

Short-chain enoyl-CoA hydratase (ECHS1) is a mitochondrial beta-oxidation enzyme involved in the metabolism of acyl-CoA fatty acid esters, as well as in valine metabolism. ECHS1 deficiency has multiple manifestations, including Leigh syndrome early at birth or in childhood with poor prognosis, to cutis laxa, exercise-induced dystonia and congenital lactic acidosis. Here we describe the case of a newborn with mutations in ECHS1 that caught our attention after the incidental finding of 3-hydroxy-butyryl\3-hydroxy-isobutyryl\malonylcarnitine (C4OH\C3DC) and tiglylcarnitine (C5:1) on blood spot in the newborn screening (NBS) program. Diagnosis was suspected based on the analysis of organic acids on dried urine spot. A moderate increase of 2-methyl-2,3-dihydroxybutyric acid, was detected, which is a known marker of this disease. Exome analysis showed c.404A>G (p.Asn135Ser) mutation in homozygosis in the ECHS1 gene. The child was therefore admitted to the hospital. Initial examination showed little response to auditory stimuli and mild hypertonia of the extremities. Clinical deterioration was evident at 4 months of age, including neurological and cardiac involvement, and the patient died at 5 months of age. This case illustrates how an incidental detection in the NBS Program can lead to the diagnosis ECHS1 deficiency. Although it is a severe disease, with no treatment available, early detection would allow adequate genetic counseling avoiding the odyssey that suffered most of these families.