Cinical, Metabolic, and Genetic Analysis and Follow-Up of Eight Patients With HIBCH Mutations Presenting With Leigh/Leigh-Like Syndrome

The burden of mitochondrial disease with associated seizures: systematic literature reviews of health-related quality of life, utilities, costs and healthcare resource use data

BACKGROUND

Mitochondrial disease is a degenerative, progressive, heterogeneous group of genetic disorders affecting children and adults. Mitochondrial disease is associated with morbidity and mortality, with predominantly neurological and neuromuscular symptoms including dystonia, weakness, encephalopathy, developmental delay and seizures. Seizures are one of the most common and severe manifestations of mitochondrial disease. These seizures are typically refractory to common anti-seizure therapies. There are no approved disease-modifying treatments for mitochondrial disease. Our objective was to conduct two systematic literature reviews to identify health-related quality of life (HRQoL), utilities, costs and healthcare resource use data in mitochondrial disease with associated seizures.

METHODS

A range of databases and information sources were searched up to July 2022 to identify eligible studies. Search strategies included a range of variant terms for mitochondrial disease and HRQoL, utilities, cost and healthcare resource use outcomes. Two reviewers independently assessed articles against the eligibility criteria; studies were extracted by one reviewer and checked by a second. Risk of bias was assessed for studies reporting HRQoL data. Results were narratively assessed.

RESULTS

Seven studies were eligible for the HRQoL and utilities review. The studies used different tools to report data, and despite the variability in methods, HRQoL scores across the studies showed moderate/severe disease in patients with mitochondrial disease with associated seizures. Parents of patients with mitochondrial disease with associated seizures were characterised by high total parenting stress. No studies reported utilities data. Two case reports and one retrospective review of medical records of children who died in hospital were eligible for the costs and resource use review. These provided limited information on the duration of hospital stay, in an intensive care unit (ICU), on mechanical ventilation. No studies reported costs data.

CONCLUSION

These reviews highlight the limited HRQoL, utilities, costs and resource use data and the variability of instruments used in mitochondrial disease with associated seizures. However, the data available indicate that mitochondrial disease with associated seizures affects patients' and caregivers' HRQoL alike. No robust conclusion can be drawn on the impact of mitochondrial disease with associated seizures on hospital or ICU length of stay. Trial registration PROSPERO: CRD42022345005.

Leigh-like syndrome with progressive cerebellar atrophy caused by novel HIBCH variants

Pathogenic variants in the HIBCH gene cause HIBCH deficiency, leading to mitochondrial disorders associated with valine metabolism. Patients typically present with symptoms such as developmental regression/delay, encephalopathy, hypotonia and dystonia. Brain magnetic resonance imaging (MRI) shows bilateral lesions in the basal ganglia with/without brainstem involvement. Here, we report a case of a Japanese patient with Leigh-like syndrome caused by novel HIBCH variants. Long-term follow-up MRI revealed progressive cerebellar atrophy, which expands the phenotypic spectrum of HIBCH deficiency.

Novel biallelic mutations in TMEM126B cause splicing defects and lead to Leigh-like syndrome with severe complex I deficiency

Leigh syndrome (LS)/Leigh-like syndrome (LLS) is one of the most common mitochondrial disease subtypes, caused by mutations in either the nuclear or mitochondrial genomes. Here, we identified a novel intronic mutation (c.82-2 A > G) and a novel exonic insertion mutation (c.290dupT) in TMEM126B from a Chinese patient with clinical manifestations of LLS. In silico predictions, minigene splicing assays and patients’ RNA analyses determined that the c.82-2 A > G mutation resulted in complete exon 2 skipping, and the c.290dupT mutation provoked partial and complete exon 3 skipping, leading to translational frameshifts and premature termination. Functional analysis revealed the impaired mitochondrial function in patient-derived lymphocytes due to severe complex I content and assembly defect. Altogether, this is the first report of LLS in a patient carrying mutations in TMEM126B. Our data uncovers the functional effect and the molecular mechanism of the pathogenic variants c.82-2 A > G and c.290dupT, which expands the gene mutation spectrum of LLS and clinical spectrum caused by TMEM126B mutations, and thus help to clinical diagnosis of TMEM126B mutation‐related mitochondrial diseases.

Identification of HIBCH as a Fatty Acid Metabolism-Related Biomarker in Aortic Valve Calcification Using Bioinformatics

Objective. To identify fatty acid metabolism-related biomarkers of aortic valve calcification (AVC) using bioinformatics and to research the role of immune cell infiltration for AVC. Methods. The AVC dataset was retrieved from the Gene Expression Omnibus database. R package is used for differential expression genes analysis and weighted gene coexpression analysis. The differentially coexpressed genes were identified by the Venn diagram, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of differentially coexpressed genes. Functions closely related to AVC were identified by GO and KEGG enrichment analyses of differentially coexpressed genes. Genes related to fatty acid metabolism were retrieved from the Molecular Signatures Database (MSigDB) database. After removing duplicate genes, least absolute shrinkage and selection operator (LASSO) regression analysis, support vector machine recursive feature elimination (SVM-RFE), and random forest were applied to recognize biomarkers related to fatty acid metabolism in AVC. The CIBERSORT tool was used to analyze infiltration of immune cells in normal and AVC samples. Correlations between biomarkers and immune cells were calculated. Finally, HIBCH-related pathway was predicted by single-gene gene set enrichment analysis (GSEA). Results. 2416 differentially expressed genes and one coexpression module were identified. A total of 1473 differentially coexpressed genes were acquired. GO and KEGG enrichment analyses demonstrated that differentially coexpressed genes were closely related to fatty acid metabolism. LASSO regression analysis, SVM-REF, and random forest revealed that 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) was a biomarker of fatty acid metabolism-related genes in AVC. Significant high levels of memory B cells were found in AVC than normal samples, while activated natural killer (NK) cells were significantly low in AVC than normal samples. A significantly positive relevance was observed between HIBCH and activated NK cells, regulatory T cells, monocytes, naïve B cells, activated dendritic cells, resting memory CD4 T cells, resting NK cells, and CD8 T cells. A significantly negative relevance was observed between HIBCH and activated memory CD4 T cells, memory B cells, neutrophils, gamma delta T cells, M0 macrophages, and plasma cells. The single-gene GSEA results suggest that HIBCH may work through the inhibition of multiple immune-related pathways. Conclusion. HIBCH is closely relevant to immune cell infiltration in AVC and could be applied as a diagnostic marker for AVC.