Hypergonadotrophic hypogonadism in a patient with transaldolase deficiency: novel mutation in the pentose phosphate pathway

Cell type-specific regulation of the pentose phosphate pathway during development and metabolic stress-driven autoimmune diseases: Relevance for inflammatory liver, renal, endocrine, cardiovascular and neurobehavioral comorbidities, carcinogenesis, and aging

The pathogenesis of autoimmunity is incompletely understood which limits the development of effective therapies. New compelling evidence indicates that the pentose phosphate pathway (PPP) profoundly regulate lineage development in the immune system that are influenced by genetic and environmental factors during metabolic stress underlying the development of autoimmunity. The PPP provides two unique metabolites, ribose 5-phosphate for nucleotide biosynthesis in support of cell proliferation and NADPH for protection against oxidative stress. The PPP operates two separate branches, oxidative (OxPPP) and non-oxidative (NOxPPP). While the OxPPP functions in all organisms, the NOxPPP reflects adaptation to niche-specific metabolic requirements. The OxPPP primarily depends on glucose 6-phosphate dehydrogenase (G6PD), whereas transaldolase (TAL) controls the rate and directionality of metabolic flux though the NOxPPP. G6PD is essential for normal development but its partial deficiency protects from malaria. Although men and mice lacking TAL develop normally, they exhibit liver cirrhosis progressing to hepatocellular carcinoma. Mechanistic target of rapamycin-dependent loss of paraoxonase 1 drives autoimmunity and cirrhosis in TAL deficiency, while hepatocarcinogenesis hinges on polyol pathway activation via aldose reductase (AR). Accumulated polyols, such as erythritol, xylitol, and sorbitol, which are commonly used as non-caloric sweeteners, may act as pro-inflammatory oncometabolites under metabolic stress, such as TAL deficiency. The TAL/AR axis is identified as a checkpoint of pathogenesis and target for treatment of metabolic stress-driven systemic autoimmunity with relevance for inflammatory liver, renal and cardiovascular disorders, diabetes, carcinogenesis, and aging.

Hypergonadotropic Hypogonadism Due to Transaldolase Deficiency: Two Cases and Literature Review

Transaldolase deficiency is a rare autosomal recessive inborn error of carbohydrate metabolism caused by pathogenic/likely pathogenic biallelic mutations in the TALDO1 gene. This disorder is characterized by multisystem involvement with variable phenotypes, including intrauterine growth restriction; dysmorphic features; abnormal skin; hepatosplenomegaly; cytopenia; and cardiac, renal, and endocrine abnormalities. Herein, we present two Emirati patients with hypergonadotropic hypogonadism due to transaldolase deficiency and variable phenotypes of systemic involvement.

Chances of Liver Transplantation in a Patient With Transaldolase Deficiency Complicated by Hepatopulmonary Syndrome

Eyaid's syndrome or Transaldolase Deficiency (TD) (OMIM 606003) is a rare autosomal recessive inborn error of metabolism. In this report, we describe the case of an eight-year-old Saudi girl with a history of hepatosplenomegaly since infancy, who presented to the emergency department for a short history of cough and worsening cyanosis. She had growth retardation, facial dysmorphia, cardiac defect, neutropenia, and thrombocytopenia, besides hepatosplenomegaly. A thorough investigation led to the diagnosis of hepatopulmonary syndrome and whole exome sequencing showed a homozygous frameshift variant in the TALDO1gene, c.793del, p.Gln265fs. Thus, the patient was diagnosed with TD complicated with hepatopulmonary syndrome, and the indication of liver transplantation was discussed.

Liver Disease and Risk of Hepatocellular Carcinoma in Children With Mutations in TALDO1

Mutations in the transaldolase 1 (TALDO1) gene have been described in a limited number of cases. Several organs can be affected and clinical manifestations are variable, but often include liver dysfunction and/or hepatosplenomegaly. We report 4 patients presenting with liver disease: 2 with early-onset hepatocellular carcinoma (HCC). Patients with cholestasis and mutations in TALDO1 were identified by next-generation sequencing. Clinical, laboratory, and histological data were collected. Four (1 male) patients were identified with variants predicted to be damaging in TALDO1. Three patients were homozygous (two protein truncating/one missense mutations), 1 one was compound heterozygous (two missense mutations). Median age at presentation was 4 months (range, 2-210 days) with jaundice (3), hepatosplenomegaly (3), and pancytopaenia (1). The diagnosis was corroborated by detection of minimal transaldolase enzyme activity in skin fibroblasts in two cases and raised urine polyols in the third. Three patients underwent liver transplantation (LT), 2 of whom had confirmed HCC on explanted liver. One patient suddenly died shortly after LT. The nontransplanted case has a chronic liver disease with multiple dysplastic liver nodules, but normal liver biochemistry and alpha-fetoprotein. Median follow-up was 4 years (range, 1-21). Conclusion: Transaldolase deficiency can include early-onset normal gamma-glutamyltransferase liver disease with multisystem involvement and variable progression. Patients with this disease are at risk of early-onset HCC and may require early LT.

Prenatal Diagnosis of Fetus With Transaldolase Deficiency Identifies Compound Heterozygous Variants: A Case Report

Transaldolase (TALDO) deficiency is a rare autosomal recessive disorder caused by variants in the TALDO1 gene that commonly results in multisystem dysfunction. Herein, we reported compound heterozygous variants in a Chinese prenatal case with TALDO deficiency using whole-exome sequencing (WES) for trios and Sanger sequencing. The heterozygous variants were located on the TALDO1 gene: NM_006755.2:c.574C > T(Chr11:g.763456C > T), a missense variant in exon 5 paternally inherited; NM_006755.2:c.462-2A > G(Chr11:g.763342A > G), a splicing aberration in intron 4 maternally inherited. The qualitative analysis of urinary polyols in neonatal urine indicated that xylitol + arabitol and ribitol in the proband’s urine were significantly increased. These findings expand the variation spectrum of the TALDO1 gene, provide solid evidence for the counseling of the family in regard to future pregnancies, strongly support the application of WES in prenatal diagnosis, and further prove that effective postpartum treatments could improve prognosis.

The Pentose Phosphate Pathway in Yeasts-More Than a Poor Cousin of Glycolysis

The pentose phosphate pathway (PPP) is a route that can work in parallel to glycolysis in glucose degradation in most living cells. It has a unidirectional oxidative part with glucose-6-phosphate dehydrogenase as a key enzyme generating NADPH, and a non-oxidative part involving the reversible transketolase and transaldolase reactions, which interchange PPP metabolites with glycolysis. While the oxidative branch is vital to cope with oxidative stress, the non-oxidative branch provides precursors for the synthesis of nucleic, fatty and aromatic amino acids. For glucose catabolism in the baker’s yeast Saccharomyces cerevisiae, where its components were first discovered and extensively studied, the PPP plays only a minor role. In contrast, PPP and glycolysis contribute almost equally to glucose degradation in other yeasts. We here summarize the data available for the PPP enzymes focusing on S. cerevisiae and Kluyveromyces lactis, and describe the phenotypes of gene deletions and the benefits of their overproduction and modification. Reference to other yeasts and to the importance of the PPP in their biotechnological and medical applications is briefly being included. We propose future studies on the PPP in K. lactis to be of special interest for basic science and as a host for the expression of human disease genes.