Pyruvate carboxylase deficiency An underestimated cause of lactic acidosis

Florence Habarou (1, 2) , Anaïs Brassier (2, 3) , M. Rio (4) , D. Chrétien (5) , S. Monnot (6, 4) , Valérie Barbier (2) , Robert Barouki (1, 2) , J.P. Bonnefont (5, 4) , N. Boddaert (7) , B. Chadefaux-Vekemans (1, 2) , Laurence Le Moyec (8) , J. Bastin (1) , Chris Ottolenghi (1, 2) , Pascale de Lonlay (5, 2, 3)

1 T3S - UMR_S 1124 - Toxicité environnementale, cibles thérapeutiques, signalisation cellulaire
2 MaMEA Necker - Centre Référence des Maladies Héréditaires du Métabolisme de l'Enfant et de l'Adulte [CHU Necker]
3 UPD5 - Université Paris Descartes - Paris 5
4 Hôpital Necker - Enfants Malades [AP-HP]
5 Inserm U781 - Génétique et épigénétique des maladies métaboliques, neurosensorielles et du développement
6 IMAGINE - U1163 - Imagine - Institut des maladies génétiques
7 Service de radiologie pédiatrique [CHU Necker]
8 UBIAE - Unité de biologie intégrative des adaptations à l'exercice

Pyruvate carboxylase (PC) is a biotin-containing mitochondrial enzyme that catalyzes the conversion of pyruvate to oxaloacetate, thereby being involved in gluconeogenesis and in energy production through replenishment of the tricarboxylic acid (TCA) cycle with oxaloacetate. PC deficiency is a very rare metabolic disorder. We report on a new patient affected by the moderate form (the American type A). Diagnosis was nearly fortuitous, resulting from the revision of an initial diagnosis of mitochondrial complex IV (C IV) defect. The patient presented with severe lactic acidosis and pronounced ketonuria, associated with lethargy at age 23 months. Intellectual disability was noted at this time. Amino acids in plasma and organic acids in urine did not show patterns of interest for the diagnostic work-up. In skin fibroblasts PC showed no detectable activity whereas biotinidase activity was normal. We had previously reported another patient with the severe form of PC deficiency and we show that she also had secondary C IV deficiency in fibroblasts. Different anaplerotic treatments in vivo and in vitro were tested using fibroblasts of both patients with 2 different types of PC deficiency, type A (patient 1) and type B (patient 2). Neither clinical nor biological effects in vivo and in vitro were observed using citrate, aspartate, oxoglutarate and bezafibrate. In conclusion, this case report suggests that the moderate form of PC deficiency may be underdiagnosed and illustrates the challenges raised by energetic disorders in terms of diagnostic work-up and therapeutical strategy even in a moderate form.

Keywords: Bezafibrate; defects; Lactic acidosis; PC deficiency; Secondary mitochondrial respiratory chain

Domains: Life Sciences [q-bio]

Florence Habarou, Anaïs Brassier, M. Rio, D. Chrétien, S. Monnot, et al.. Pyruvate carboxylase deficiency An underestimated cause of lactic acidosis. Molecular Genetics and Metabolism, 2015, 2, pp.25-31. ⟨10.1016/j.ymgmr.2014.11.001⟩. ⟨hal-02489932⟩