Identification and characterization of novel MPC1 gene variants causing mitochondrial pyruvate carrier deficiency

Pyruvate, the end product of glycolysis, is a key metabolic molecule enabling mitochondrial adenosine triphosphate synthesis and takes part in multiple biosynthetic pathways within mitochondria. The mitochondrial pyruvate carrier (MPC) plays a vital role in transporting pyruvate from the cytosol into the organelle. In humans, MPC is a hetero-oligomeric complex formed by the MPC1 and MPC2 paralogs that are both necessary to stabilize each other and form a functional MPC. MPC deficiency (OMIM#614741) due to pathogenic MPC1 variants is a rare autosomal recessive disease involving developmental delay, microcephaly, growth failure, and increased serum lactate and pyruvate. To date, two MPC1 variants in four cases have been reported, though only one with a detailed clinical description. Herein, we report three novel pathogenic MPC1 variants in six patients from three unrelated families, identified within European, Kuwaiti, and Chinese mitochondrial disease patient cohorts, one of whom presented as a Leigh-like syndrome. Functional analysis in primary fibroblasts from the patients revealed decreased expression of MPC1 and MPC2. We rescued pyruvate-driven oxygen consumption rate in patient's fibroblasts by reconstituting with wild-type MPC1. Complementing homozygous MPC1 mutant cDNA with CRISPR-deleted MPC1 C2C12 cells verified the mechanism of variants: unstable MPC complex or ablated pyruvate uptake activity. Furthermore, we showed that glutamine and beta-hydroxybutyrate were alternative substrates to maintain mitochondrial respiration when cells lack pyruvate. In conclusion, we expand the clinical phenotypes and genotypes associated with MPC deficiency, with our studies revealing glutamine as a potential therapy for MPC deficiency.

[Interventional radiology, angioplasty and TIPS in Budd-Chiari syndrome]

INTRODUCTION

Budd-Chiari syndrome consists of complete or partial obstruction of the hepatic veins. Many treatment options are available; new interventional radiology techniques may play an important role as an alternative to surgical shunting.

PATIENTS AND METHOD

Of 11 patients diagnosed with Budd-Chiari syndrome, 7 were treated with percutaneous balloon angioplasty or transjugular intrahepatic portosystemic shunt (TIPS) (2 and 5 patients, respectively). The efficacy of both techniques in the treatment of this syndrome was evaluated.

RESULTS

Two patients presented significant isolated stenosis of a suprahepatic vein and underwent percutaneous balloon angioplasty. In both patients outcome was favorable with resolution of ascites. Five patients underwent TIPS and four showed clinical improvement with significant reduction in Child-Pugh score (p < 0.05) and resolution of ascites. No shunt malfunction was detected during follow-up. One patient showed no improvement after placement of TIPS and died soon after the procedure and a further two died from their underlying disease during follow-up.

CONCLUSIONS

Treatment of Budd-Chiari syndrome requires multidisciplinary evaluation and should be individualized. In patients with Budd-Chiari syndrome uncontrolled by medical therapy, TIPS may become the decompressive method of choice as an alternative to surgical shunting. Liver transplantation may be reserved to patients in whom these techniques are ineffective.

[Leishmaniasis in a patient with liver cirrhosis]

We present a 35 years-old man with fever related leishmania infection as the first complication of a previously undiagnosed cirrhosis. Diagnosis of leishmaniasis is often complicated. Clinical and therapeutical aspects are commented.