Catatonia and glucose-6-phosphate dehydrogenase deficiency: a report of two cases and a review

Glucose-6-phosphate dehydrogenase deficiency and psychotic disorders: A systematic review

OBJECTIVES

Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD) is the most common enzymopathy globally. Early studies suggested an association with severe psychotic illness; however, changes to laboratory testing and diagnostic classification renders the association unclear. This study aims to explore the interaction between G6PD deficiency and psychotic symptoms, in particular to identify specific patterns of presentation or impact on outcomes.

METHODS

Pubmed, Embase, and PsycInfo databases were searched from inception to May 2023. Descriptive statistics and narrative review of were used to synthesise data on demographics, mental and physical health diagnoses, investigations, treatment, and outcomes.

RESULTS

No clear link was found in published data (eight case reports, case series of n = 29) with a high rate (63%) of haemolytic crisis at the time of psychiatric presentation suggested delirium as an alternative diagnosis. Four case control studies found no significant difference in the prevalence of G6PD deficiency. However, catatonic presentation was reported in 40% of the case series and a higher prevalence of G6PD deficiency in catatonic schizophrenia was noted in case control studies.

CONCLUSIONS

Based on the information available there was no clear association between G6PD deficiency and psychotic illness or treatment resistance, although paucity of studies and risk of bias limit strong conclusions.

Glucose-6-phosphate dehydrogenase activity in bipolar disorder and schizophrenia: Relationship to mitochondrial impairment

Glucose-6-phosphate dehydrogenase (G6PD) is the first and rate-limiting enzyme of the pentose phosphate pathway that is essential to maintaining cellular redox balance. G6PD is especially plentiful in brain, and its deficiency has been linked to mood and psychotic disorders. We measured G6PD activity spectrophotometrically in four groups of 15 parietal somatosensory association cortex [Brodmann area (BA) 7] tissue samples (N = 60) from individuals with bipolar disorder (BPD); nonpsychotic unipolar major depression (UPD); schizophrenia (SCZ), and controls without psychiatric illness (CON). We report for the first time brain G6PD activity levels in these disorders. G6PD activity did not differ by brain group. In BPD and SCZ brains, however, it correlated significantly and inversely with percent of hexokinase 1 (HK1) in the tissue homogenate mitochondrial fraction as determined previously in another set of tissue samples obtained from the same brains and brain region. The correlation in SCZ brains lost statistical significance after controlling for brain pH. This finding indicates a positive relationship in BPD brains between G6PD activity and HK1 mitochondrial detachment, an indicator of mitochondrial impairment associated with increased mitochondrial generation of reactive oxygen species. We speculate that this relationship could be evidence that G6PD activity is proportionate to and may be a compensatory response to oxidative stress in the BA7 region of BPD brains. Future research should focus on clarifying the relationships among G6PD activity, markers of oxidative stress, brain pH, and evidence of mitochondrial impairment, particularly HK1 mitochondrial detachment, in brains of individuals with G6PD deficiency, BPD and SCZ.

Coupling between Protein Stability and Catalytic Activity Determines Pathogenicity of G6PD Variants

G6PD deficiency, an enzymopathy affecting 7% of the world population, is caused by over 160 identified amino acid variants in glucose-6-phosphate dehydrogenase (G6PD). The clinical presentation of G6PD deficiency is diverse, likely due to the broad distribution of variants across the protein and the potential for multidimensional biochemical effects. In this study, we use bioinformatic and biochemical analyses to interpret the relationship between G6PD variants and their clinical phenotype. Using structural information and statistical analyses of known G6PD variants, we predict the molecular phenotype of five uncharacterized variants from a reference population database. Through multidimensional analysis of biochemical data, we demonstrate that the clinical phenotypes of G6PD variants are largely determined by a trade-off between protein stability and catalytic activity. This work expands the current understanding of the biochemical underpinnings of G6PD variant pathogenicity and suggests a promising avenue for correcting G6PD deficiency by targeting essential structural features of G6PD.