Integrated multi-omics reveals anaplerotic rewiring in methylmalonyl-CoA mutase deficiency

Evidence for interaction of 5,10-methylenetetrahydrofolate reductase (MTHFR) with methylenetetrahydrofolate dehydrogenase (MTHFD1) and general control nonderepressible 1 (GCN1)

5,10-Methylenetetrahydrofolate reductase (MTHFR) is a folate cycle enzyme required for the intracellular synthesis of methionine. MTHFR was previously shown to be partially phosphorylated at 16 residues, which was abrogated by conversion of threonine 34 to alanine (T34A) or truncation of the first 37 amino acids (i.e. expression of amino acids 38-656), and promoted by methionine supplementation. Here, we over-expressed wild-type MTHFR (MTFHRWT), as well as the variants MTHFRT34A and MTHFR38-656 in 293T cells to provide further insights into these mechanisms. We demonstrate that following incubation in high methionine conditions (100-1000 μM) MTHFRWT is almost completely phosphorylated, but in methionine restricted conditions (0-10 μM) phosphorylation is reduced, while MTHFRT34A always remains unphosphorylated. Following affinity purification coupled mass spectrometry of an empty vector, MTHFRWT, MTHFRT34A and MTHFR38-656 in three separate experiments, we identified 134 proteins consistently pulled-down by all three MTHFR protein variants, of which 5 were indicated to be likely true interactors (SAINT prediction threshold of 0.95 and 2 fold-change). Amongst these were the folate cycle enzyme methylenetetrahydrofolate dehydrogenase (MTHFD1) and the amino acid starvation sensor general control nonderepressible 1 (GCN1). Immunoprecipitation-immunoblotting of MTHFRWT replicated interaction with both proteins. An AlphaFold 3 generated model of the MTHFR-MTHFD1 interaction places the MTHFD1 dehydrogenase/cyclohydrolase domain in direct contact with the MTHFR catalytic domain, suggesting their interaction may facilitate direct delivery of methylenetetrahydrofolate. Overall, we confirm methionine availability increases MTHFR phosphorylation, and identified potential interaction of MTHFR with MTHFD1 and GCN1.

Characterizing circulating biomarkers for childhood dementia disorders: A scoping review of clinical trials

Childhood dementias, a group of neurological disorders are characterised by neurocognitive decline, with physical and psychosocial impacts for individuals. With therapy available for <5 ​% of childhood dementias, there is a high level of unmet need. Integration of biomarkers in clinical trials are important to characterize distinctive biological activities and interrogate targets for therapeutic development. This study reviewed four clinical trial registries to examine circulating biomarkers in childhood dementias. Findings from 262 studies were synthesized across 49/72 (68 ​%) childhood dementia disorders. Disease-related biomarkers were associated with 1) the primary pathophysiology 2) downstream pathogenic events 3) drug-related pharmacokinetics, safety and/or tolerability. The predominant biological measures were metabolites linked to the primary pathophysiological pathway (102 measures, 185 studies), while use of cytoskeletal proteins (3 measures, 15 studies), inflammatory mediators (19 measures, 24 studies), oxidative stress-related analytes (15 measures, 8 studies), neurotransmitters or related neuro-metabolites (3 measures, 5 studies) were limited. A range of potential biomarkers are used in clinical trials; however, their use is inconsistent and under utilised among conditions. Development of a panel of biomarkers has potential to interrogate and link shared biological pathways across the heterogeneity of childhood dementias to exert a significant impact for the development of disease-modifying therapies.

Methylmalonic acid at the serum level in the elderly contributes to cell growth via mitochondrial dysfunction in colorectal cancer cell spheroids

Methylmalonic acid (MMA) is a small molecule produced during the metabolism of propionate and branched-chain amino acids. Recently, it has been reported that the blood concentration of MMA increases with age and promotes lung cancer metastasis. However, little is known regarding its effects on cancers other than lung cancer. In the present study, we examined the effects of MMA on colorectal cancer cell spheroids. We found that MMA promoted the proliferation of colorectal cancer spheroids at physiological concentrations that can be exhibited by the elderly and induced mitochondrial reactive oxygen species generation, which in turn affected the promotion of cell growth. MMA treatment also induces a metabolic shift in the glycolytic system. These results suggest that MMA may promote cancer cell proliferation by decreasing mitochondrial function, inducing a metabolic shift, and provide new insights into the effects of aging on cancer.

Chemical Tomography of Cancer Organoids and Cyto-Proteo-Genomic Development Stages Through Chemical Communication Signals

Organoids mimic human organ function, offering insights into development and disease. However, non-destructive, real-time monitoring is lacking, as traditional methods are often costly, destructive, and low-throughput. In this article, a non-destructive chemical tomographic strategy is presented for decoding cyto-proteo-genomics of organoid using volatile signaling molecules, hereby, Volatile Organic Compounds (VOCs), to indicate metabolic activity and development of organoids. Combining a hierarchical design of graphene-based sensor arrays with AI-driven analysis, this method maps VOC spatiotemporal distribution and generate detailed digital profiles of organoid morphology and proteo-genomic features. Lens- and label-free, it avoids phototoxicity, distortion, and environmental disruption. Results from testing organoids with the reported chemical tomography approach demonstrate effective differentiation between cyto-proteo-genomic profiles of normal and diseased states, particularly during dynamic transitions such as epithelial-mesenchymal transition (EMT). Additionally, the reported approach identifies key VOC-related biochemical pathways, metabolic markers, and pathways associated with cancerous transformations such as aromatic acid degradation and lipid metabolism. This real-time, non-destructive approach captures subtle genetic and structural variations with high sensitivity and specificity, providing a robust platform for multi-omics integration and advancing cancer biomarker discovery.

Anaplerotic filling in heart failure: a review of mechanism and potential therapeutics

Heart failure (HF) is a complex syndrome and a leading cause of mortality worldwide. While current medical treatment is based on known pathophysiology and is effective for many patients, the underlying cellular mechanisms are poorly understood. Energy deficiency is a characteristic of HF, marked by complex alterations in metabolism. Within the tricarboxylic acid cycle, anaplerosis emerges as an essential metabolic process responsible for replenishing lost intermediates, thereby playing a crucial role in sustaining energy metabolism and consequently cardiac function. Alterations in cardiac anaplerosis are commonly observed in HF, demonstrating potential for therapeutic intervention. This review discusses recent advances in understanding the anaplerotic adaptations that occur in HF. We also explore therapeutics that can directly modulate anaplerosis or are likely to confer cardioprotective effects through anaplerosis, which could potentially be implemented to rescue the failing heart.

Paediatric Personalized Research Network Switzerland (SwissPedHealth): a joint paediatric national data stream

INTRODUCTION

Children represent a large and vulnerable patient group. However, the evidence base for most paediatric diagnostic and therapeutic procedures remains limited or is often inferred from adults. There is an urgency to improve paediatric healthcare provision based on real-world evidence generation. Digital transformation is a unique opportunity to shape a data-driven, agile, learning healthcare system and deliver more efficient and personalised care to children and their families. The goal of Paediatric Personalized Research Network Switzerland (SwissPedHealth) is to build a sustainable and scalable infrastructure to make routine clinical data from paediatric hospitals in Switzerland interoperable, standardised, quality-controlled, and ready for observational research, quality assurance, trials and health-policy creation. This study describes the design, aims and current achievements of SwissPedHealth.

METHODS AND ANALYSIS

SwissPedHealth was started in September 2022 as one of four national data streams co-funded by the Swiss Personalized Health Network (SPHN) and the Personalized Health and Related Technologies (PHRT). SwissPedHealth develops modular governance and regulatory strategies and harnesses SPHN automatisation procedures in collaboration with clinical data warehouses, the Data Coordination Center, Biomedical Information Technology Network, and other SPHN institutions and funded projects. The SwissPedHealth consortium is led by a multisite, multidisciplinary Steering Committee, incorporating patient and family representatives. The data stream contains work packages focusing on (1) governance and implementation of standardised data collection, (2) nested projects to test the feasibility of the data stream, (3) a lighthouse project that enriches the data stream by integrating multi-omics data, aiming to improve diagnoses of rare diseases and 4) engagement with families through patient and public involvement activities and bioethics interviews.

ETHICS AND DISSEMINATION

The health database regulation of SwissPedHealth was approved by the ethics committee (AO_2022-00018). Research findings will be disseminated through national and international conferences and publications in peer-reviewed journals, and in lay language via online media and podcasts.

Renal phenotyping in a hypomorphic murine model of propionic aciduria reveals common pathomechanisms in organic acidurias

Mutations in the mitochondrial enzyme propionyl-CoA carboxylase (PCC) cause propionic aciduria (PA). Chronic kidney disease (CKD) is a known long-term complication. However, good metabolic control and standard therapy fail to prevent CKD. The pathophysiological mechanisms of CKD are unclear. We investigated the renal phenotype of a hypomorphic murine PA model (Pcca-/-(A138T)) to identify CKD-driving mechanisms. Pcca-/-(A138T) mice show elevated retention parameters and express markers of kidney damage progressing with time. Morphological assessment of the Pcca-/-(A138T) mouse kidneys indicated partial flattening of tubular epithelial cells and focal tubular-cystic dilation. We observed altered renal mitochondrial ultrastructure and mechanisms acting against oxidative stress were active. LC-MS/MS analysis confirmed disease-specific metabolic signatures and revealed disturbances in mitochondrial energy generation via the TCA cycle. Our investigations revealed altered mitochondrial networks shifted towards fission and a marked reduction of mitophagy. We observed a steep reduction of PGC-1-α, the key mediator modulating mitochondrial functions and a counter actor of mitochondrial fission. Our results suggest that impairment of mitochondrial homeostasis and quality control are involved in CKD development in PA. Therapeutic targeting of the identified pathways might help to ameliorate CKD in addition to the current treatment strategies.

GLUD1 determines murine muscle stem cell fate by controlling mitochondrial glutamate levels

Muscle stem cells (MuSCs) enable muscle growth and regeneration after exercise or injury, but how metabolism controls their regenerative potential is poorly understood. We describe that primary metabolic changes can determine murine MuSC fate decisions. We found that glutamine anaplerosis into the tricarboxylic acid (TCA) cycle decreases during MuSC differentiation and coincides with decreased expression of the mitochondrial glutamate deaminase GLUD1. Deletion of Glud1 in proliferating MuSCs resulted in precocious differentiation and fusion, combined with loss of self-renewal in vitro and in vivo. Mechanistically, deleting Glud1 caused mitochondrial glutamate accumulation and inhibited the malate-aspartate shuttle (MAS). The resulting defect in transporting NADH-reducing equivalents into the mitochondria induced compartment-specific NAD+/NADH ratio shifts. MAS activity restoration or directly altering NAD+/NADH ratios normalized myogenesis. In conclusion, GLUD1 prevents deleterious mitochondrial glutamate accumulation and inactivation of the MAS in proliferating MuSCs. It thereby acts as a compartment-specific metabolic brake on MuSC differentiation.

Single-cell landscape of innate and acquired drug resistance in acute myeloid leukemia

Deep single-cell multi-omic profiling offers a promising approach to understand and overcome drug resistance in relapsed or refractory (rr) acute myeloid leukemia (AML). Here, we combine single-cell ex vivo drug profiling (pharmacoscopy) with single-cell and bulk DNA, RNA, and protein analyses, alongside clinical data from 21 rrAML patients. Unsupervised data integration reveals reduced ex vivo response to the Bcl-2 inhibitor venetoclax (VEN) in patients treated with both a hypomethylating agent (HMA) and VEN, compared to those pre-exposed to chemotherapy or HMA alone. Integrative analysis identifies both known and unreported mechanisms of innate and treatment-related VEN resistance and suggests alternative treatments, like targeting increased proliferation with the PLK inhibitor volasertib. Additionally, high CD36 expression in VEN-resistant blasts associates with sensitivity to CD36-targeted antibody treatment ex vivo. This study demonstrates how single-cell multi-omic profiling can uncover drug resistance mechanisms and treatment vulnerabilities, providing a valuable resource for future AML research.

Propionic Acidemia, Methylmalonic Acidemia, and Cobalamin C Deficiency: Comparison of Untargeted Metabolomic Profiles

Methylmalonic acidemia (MMA), propionic acidemia (PA), and cobalamin C deficiency (cblC) share a defect in propionic acid metabolism. In addition, cblC is also involved in the process of homocysteine remethylation. These three diseases produce various phenotypes and complex downstream metabolic effects. In this study, we used an untargeted metabolomics approach to investigate the biochemical differences and the possible connections among the pathophysiology of each disease. The significantly changed metabolites in the untargeted urine metabolomic profiles of 21 patients (seven MMA, seven PA, seven cblC) were identified through statistical analysis (p < 0.05; log2FC > |1|) and then used for annotation. Annotated features were associated with different metabolic pathways potentially involved in the disease's development. Comparative statistics showed markedly different metabolomic profiles between MMA, PA, and cblC, highlighting the characteristic species for each disease. The most affected pathways were related to the metabolism of organic acids (all diseases), amino acids (all diseases), and glycine and its conjugates (in PA); the transsulfuration pathway; oxidative processes; and neurosteroid hormones (in cblC). The untargeted metabolomics study highlighted the presence of significant differences between the three diseases, pointing to the most relevant contrast in the cblC profile compared to MMA and PA. Some new biomarkers were proposed for PA, while novel data regarding the alterations of steroid hormone profiles and biomarkers of oxidative stress were obtained for cblC disease. The elevation of neurosteroids in cblC may indicate a potential connection with the development of ocular and neuronal deterioration.

mRNA therapies: Pioneering a new era in rare genetic disease treatment

Rare genetic diseases, often referred to as orphan diseases due to their low prevalence and limited treatment options, have long posed significant challenges to our medical system. In recent years, Messenger RNA (mRNA) therapy has emerged as a highly promising treatment approach for various diseases caused by genetic mutations. Chemically modified mRNA is introduced into cells using carriers like lipid-based nanoparticles (LNPs), producing functional proteins that compensate for genetic deficiencies. Given the advantages of precise dosing, biocompatibility, transient expression, and minimal risk of genomic integration, mRNA therapies can safely and effectively correct genetic defects in rare diseases and improve symptoms. Currently, dozens of mRNA drugs targeting rare diseases are undergoing clinical trials. This comprehensive review summarizes the progress of mRNA therapy in treating rare genetic diseases. It introduces the development, molecular design, and delivery systems of mRNA therapy, highlighting their research progress in rare genetic diseases based on protein replacement and gene editing. The review also summarizes research progress in various rare disease models and clinical trials. Additionally, it discusses the challenges and future prospects of mRNA therapy. Researchers are encouraged to join this field and collaborate to advance the clinical translation of mRNA therapy, bringing hope to patients with rare genetic diseases.

Towards personalized genome-scale modeling of inborn errors of metabolism for systems medicine applications

Inborn errors of metabolism (IEMs) are a group of more than 1000 inherited diseases that are individually rare but have a cumulative global prevalence of 50 per 100,000 births. Recently, it has been recognized that like common diseases, patients with rare diseases can greatly vary in the manifestation and severity of symptoms. Here, we review omics-driven approaches that enable an integrated, holistic view of metabolic phenotypes in IEM patients. We focus on applications of Constraint-based Reconstruction and Analysis (COBRA), a widely used mechanistic systems biology approach, to model the effects of inherited diseases. Moreover, we review evidence that the gut microbiome is also altered in rare diseases. Finally, we outline an approach using personalized metabolic models of IEM patients for the prediction of biomarkers and tailored therapeutic or dietary interventions. Such applications could pave the way towards personalized medicine not just for common, but also for rare diseases.

Multiomic analysis in fibroblasts of patients with inborn errors of cobalamin metabolism reveals concordance with clinical and metabolic variability

BACKGROUND

The high variability in clinical and metabolic presentations of inborn errors of cobalamin (cbl) metabolism (IECM), such as the cblC/epicblC types with combined deficits in methylmalonyl-coA mutase (MUT) and methionine synthase (MS), are not well understood. They could be explained by the impaired expression/activity of enzymes from other metabolic pathways.

METHODS

We performed metabolomic, genomic, proteomic, and post-translational modification (PTM) analyses in fibroblasts from three cblC cases and one epi-cblC case compared with three cblG cases with specific MS deficits and control fibroblasts.

FINDINGS

CblC patients had metabolic profilings consistent with altered urea cycle, glycine, and energy mitochondrial metabolism. Metabolomic analysis showed partial disruption and increased glutamate/ketoglutarate anaplerotic pathway of the tricarboxylic acid cycle (TCA), in patient fibroblasts. RNA-seq analysis showed decreased expression of MT-TT (mitochondrial tRNA threonine), MT-TP (mitochondrial tRNA proline), OXCT1 (succinyl CoA:3-oxoacid CoA transferase deficiency), and MT-CO1 (cytochrome C oxidase subunit 1). Proteomic changes were observed for key mitochondrial enzymes, including NADH:ubiquinone oxidoreductase subunit A8 (NDUFA8), carnitine palmitoyltransferase 2 (CPT2), and ubiquinol-cytochrome C reductase, complex III subunit X (UQCR10). Propionaldehyde addition in ornithine aminotransferase was the predominant PTM in cblC cells and could be related with the dramatic cellular increase in propionate and methylglyoxalate. It is consistent with the decreased concentration of ornithine reported in 3 cblC cases. Whether the changes detected after multi-omic analyses underlies clinical features in cblC and cblG types of IECM, such as peripheral and central neuropathy, cardiomyopathy, pulmonary hypertension, development delay, remains to be investigated.

INTERPRETATION

The omics-related effects of IECM on other enzymes and metabolic pathways are consistent with the diversity and variability of their age-related metabolic and clinical manifestations. PTMs are expected to produce cumulative effects, which could explain the influence of age on neurological manifestations.

FUNDING

French Agence Nationale de la Recherche (Projects PREDICTS and EpiGONE) and Inserm.

Integrative omics approaches to advance rare disease diagnostics

Over the past decade high-throughput DNA sequencing approaches, namely whole exome and whole genome sequencing became a standard procedure in Mendelian disease diagnostics. Implementation of these technologies greatly facilitated diagnostics and shifted the analysis paradigm from variant identification to prioritisation and evaluation. The diagnostic rates vary widely depending on the cohort size, heterogeneity and disease and range from around 30% to 50% leaving the majority of patients undiagnosed. Advances in omics technologies and computational analysis provide an opportunity to increase these unfavourable rates by providing evidence for disease-causing variant validation and prioritisation. This review aims to provide an overview of the current application of several omics technologies including RNA-sequencing, proteomics, metabolomics and DNA-methylation profiling for diagnostics of rare genetic diseases in general and inborn errors of metabolism in particular.

Insights into energy balance dysregulation from a mouse model of methylmalonic aciduria

Inherited disorders of mitochondrial metabolism, including isolated methylmalonic aciduria, present unique challenges to energetic homeostasis by disrupting energy-producing pathways. To better understand global responses to energy shortage, we investigated a hemizygous mouse model of methylmalonyl-CoA mutase (Mmut)-type methylmalonic aciduria. We found Mmut mutant mice to have reduced appetite, energy expenditure and body mass compared with littermate controls, along with a relative reduction in lean mass but increase in fat mass. Brown adipose tissue showed a process of whitening, in line with lower body surface temperature and lesser ability to cope with cold challenge. Mutant mice had dysregulated plasma glucose, delayed glucose clearance and a lesser ability to regulate energy sources when switching from the fed to fasted state, while liver investigations indicated metabolite accumulation and altered expression of peroxisome proliferator-activated receptor and Fgf21-controlled pathways. Together, these shed light on the mechanisms and adaptations behind energy imbalance in methylmalonic aciduria and provide insight into metabolic responses to chronic energy shortage, which may have important implications for disease understanding and patient management.

Architecture of the human G-protein-methylmalonyl-CoA mutase nanoassembly for B12 delivery and repair

G-proteins function as molecular switches to power cofactor translocation and confer fidelity in metal trafficking. The G-protein, MMAA, together with MMAB, an adenosyltransferase, orchestrate cofactor delivery and repair of B12-dependent human methylmalonyl-CoA mutase (MMUT). The mechanism by which the complex assembles and moves a >1300 Da cargo, or fails in disease, are poorly understood. Herein, we report the crystal structure of the human MMUT-MMAA nano-assembly, which reveals a dramatic 180° rotation of the B12 domain, exposing it to solvent. The complex, stabilized by MMAA wedging between two MMUT domains, leads to ordering of the switch I and III loops, revealing the molecular basis of mutase-dependent GTPase activation. The structure explains the biochemical penalties incurred by methylmalonic aciduria-causing mutations that reside at the MMAA-MMUT interfaces we identify here.

Biomarkers to predict disease progression and therapeutic response in isolated methylmalonic acidemia

Methylmalonic Acidemia (MMA) is a heterogenous group of inborn errors of metabolism caused by a defect in the methylmalonyl-CoA mutase (MMUT) enzyme or the synthesis and transport of its cofactor, 5'-deoxy-adenosylcobalamin. It is characterized by life-threatening episodes of ketoacidosis, chronic kidney disease, and other multiorgan complications. Liver transplantation can improve patient stability and survival and thus provides clinical and biochemical benchmarks for the development of hepatocyte-targeted genomic therapies. Data are presented from a US natural history protocol that evaluated subjects with different types of MMA including mut-type (N = 91), cblB-type (15), and cblA-type MMA (17), as well as from an Italian cohort of mut-type (N = 19) and cblB-type MMA (N = 2) subjects, including data before and after organ transplantation in both cohorts. Canonical metabolic markers, such as serum methylmalonic acid and propionylcarnitine, are variable and affected by dietary intake and renal function. We have therefore explored the use of the 1-13 C-propionate oxidation breath test (POBT) to measure metabolic capacity and the changes in circulating proteins to assess mitochondrial dysfunction (fibroblast growth factor 21 [FGF21] and growth differentiation factor 15 [GDF15]) and kidney injury (lipocalin-2 [LCN2]). Biomarker concentrations are higher in patients with the severe mut0 -type and cblB-type MMA, correlate with a decreased POBT, and show a significant response postliver transplant. Additional circulating and imaging markers to assess disease burden are necessary to monitor disease progression. A combination of biomarkers reflecting disease severity and multisystem involvement will be needed to help stratify patients for clinical trials and assess the efficacy of new therapies for MMA.

Architecture of the human G-protein-methylmalonyl-CoA mutase nanoassembly for B 12 delivery and repair

G-proteins function as molecular switches to power cofactor translocation and confer fidelity in metal trafficking. MMAA, a G-protein motor, together with MMAB, an adenosyltransferase, orchestrate cofactor delivery and repair of B ₁₂ -dependent human methylmalonyl-CoA mutase (MMUT). The mechanism by which the motor assembles and moves a >1300 Da cargo, or fails in disease, are poorly understood. Herein, we report the crystal structure of the human MMUT-MMAA nanomotor assembly, which reveals a dramatic 180° rotation of the B ₁₂ domain, exposing it to solvent. The nanomotor complex, stabilized by MMAA wedging between two MMUT domains, leads to ordering of the switch I and III loops, revealing the molecular basis of mutase-dependent GTPase activation. The structure explains the biochemical penalties incurred by methylmalonic aciduria-causing mutations that reside at the newly identified MMAA-MMUT interfaces.

Anaplerosis in action

Investigation of multi-omic changes and their effects on regulation of metabolic pathways confirm anaplerotic deficiencies in methylmalonic acidaemia, strengthening the need for future therapies aimed at replenishing intermediates of the tricarboxylic acid cycle.