Pyruvate dehydrogenase (PDH) deficiency is an uncommon condition responsible for primary refractory lactic acidosis, and PDH E1β (PDHB) subunit gene mutation rarely causes of PDH deficiency. We described a missense mutation of PDHB gene in a neonate with PDH deficiency, and verified the mutation damages PDH activity in vitro. Whole exome sequencing (WES) was used to discover the missense mutation. We constructed the recombinant eukaryotic recombinant expression vector, the phage-PDHB-wt/mut, containing human full-length wild-type (NM_000925.4) or mutant (c.575G > T) PDHB gene, and transfected vector into 293T cells. Western blot was performed to assess PDH protein stability, PDH activity was measured. A 37-week-gestation male infant was noted to have refractory lactic acidosis, growth retardation, and neurodevelopmental anomalies with abnormal brain magnetic resonance (MR) findings, starting with convulsive seizures at 3 months of age. WES analysis revealed the homozygous missense mutations in the PDHB gene, which was c.575G > T (p.Arg192Leu) in exon 6. This missense mutation of PDHB was predicted to be harmful by bioinformatics software including Sorting Intolerant From Tolerant (SIFT), Polyphen2, LRT, and Mutation Taster. Western blot showed that normal PDH protein expression was significantly decreased in the phage -PDHB-mut transfected cells than that in the phage -PDHB-wt transfected cells (P < 0.001). PDH activities analysis revealed that PDH activity was significantly decreased in the phage -PDHB-mut transfected cells than that in the phage -PDHB-wt transfected cells (P < 0.001). c.575G > T (p.Arg192Leu) in PDHB gene is a pathogenic missense mutation, which causes PDH deficiency in autosomal recessive inheritance mode.

A pyruvate dehydrogenase complex deficiency causes a reduction in adenosine triphosphate production and energy insufficiency, leading to neurological disorders. An abnormal E1-alpha protein originating from the PDHA1 gene with pathogenic variants is unable to communicate with E1-beta for the formation of the E1 enzyme, decreasing pyruvate dehydrogenase complex activity. In this study, we report a Vietnamese boy with lethargy, severe metabolic acidosis, increased serum lactate, hyperalaninemia, lactic acidosis, and globus pallidus lesions. Whole-exome sequencing and variant filtering identified a hemizygous missense variant NM000284.4 (PDHA1): c.479T>G (p.Phe160Cys) in the patient. The variant c.479T>G caused a single nucleotide substitution on exon 5 and was predicted to be a disease-causing variant in the in silico analyses. We present the first report with a genetic analysis of a Vietnamese patient with pyruvate dehydrogenase E1-alpha deficiency (PDHAD). Sanger sequencing demonstrated that the patient inherited the variant from his mother who harbored the variant in a heterozygous state, but no PDHAD symptoms were observed in her. In addition, a prenatal test of the patient's mother revealed a fetus with a normal genotype. Furthermore, the patient's father and sister both carried a normal allele. Based on the American College of Medical Genetics criteria, the variant c.479T>G was predicted to be a likely pathogenic variant. Using the combination of the patient's genotype and phenotype, he was definitively diagnosed with pyruvate dehydrogenase E1-alpha deficiency. Our findings expand the mutational spectrum of neurological disorders and provide the scientific basis for genetic counseling for the patient's family.

Pyruvate dehydrogenase complex deficiency (PDCD) is a common primary cause of defects in mitochondrial function and also can lead to peripheral neuropathy. Pyruvate dehydrogenase E1 component subunit beta (PDHB) is a subunit of pyruvate dehydrogenase E1, which is a well-known component of PDC. In Drosophila melanogaster, the CG11876 (dPDHB) gene is a homolog of human PDHB. In this study, we established a Drosophila model with neuron-specific knockdown of dPDHB to investigate its role in neuropathy pathogenesis. Knockdown of dPDHB in pan-neurons induced locomotor defects in both larval and adult stages, which were consistent with abnormal morphology of the motor neuron terminals at neuromuscular junctions and mitochondrial fragmentation in brains. Moreover, neuron-specific knockdown of dPDHB also shortened the lifespan of adult flies. In addition, flies with knockdown of dPDHB manifested a rough eye phenotype and aberrant photoreceptor axon targeting. These results with the Drosophila model suggest the involvement of PDHB in peripheral neuropathy.

Growth hormone deficiency (GHD) leads to obesity and may induce tissue hypoxia. As (pro)renin receptor [(P)RR] is reported to contribute to the aerobic metabolism by stabilizing pyruvate dehydrogenase (PDH), it may play a substantial role in GHD. We aimed to investigate serum soluble (P)RR [s(P)RR] concentration, the origin of s(P)RR, and significance of (P)RR in GHD. Serum s(P)RR concentration was examined in 72 patients with pituitary diseases, including 32 patients with severe GHD (SGHD) and after GH replacement in 16 SGHD patients. Leptin-deficient ob/ob obese mice were treated with pegvisomant, a GH receptor antagonist, to explore the source of elevated serum s(P)RR in GHD. Adipocytes were cultured with 5% O2 to examine the effects of hypoxia. Serum s(P)RR concentration was higher in patients with SGHD than in those without SGHD. Obesity was the important determinant of s(P)RR concentration. Serum s(P)RR concentration significantly decreased after GH replacement in SGHD patients. (P)RR mRNA expression was increased specifically in the adipose tissue (AT) of pegvisomant-treated obese mice compared with that of control obese mice. Hypoxia in cultured adipocytes increased (P)RR expression without affecting the PDH E1 β subunit (PDHB) expression; however, with (P)RR knockdown by small interfering RNA, hypoxia significantly decreased the expression of PDHB. GHD patients showed increased serum s(P)RR concentration, possibly caused by obesity and hypoxia. (P)RR expression in AT of GHD patients may be elevated to help maintain aerobic metabolism under hypoxia. Thus, the elevated serum s(P)RR level may reflect hypoxia in ATs.