Metabolic control of adult neural stem cell self-renewal by the mitochondrial protease YME1L

The transition between quiescence and activation in neural stem and progenitor cells (NSPCs) is coupled to reversible changes in energy metabolism with key implications for life-long NSPC self-renewal and neurogenesis. How this metabolic plasticity is ensured between NSPC activity states is unclear. We found that a state-dependent rewiring of the mitochondrial proteome by the peptidase YME1L is required to preserve NSPC self-renewal in the adult brain. YME1L-mediated proteome rewiring regulates the rate of fatty acid oxidation (FAO) for replenishing Krebs cycle intermediates and dNTP precursors, which are required to sustain NSPC amplification. Yme1l deletion irreversibly shifts the metabolic profile of NSPCs away from a FAO-dependent state resulting in defective self-renewal, premature differentiation and NSPC pool depletion. Our results disclose an important role for YME1L in coordinating the switch between metabolic states of NSPCs and suggest that NSPC fate is regulated by compartmentalized changes in protein network dynamics.

Metabolic Outcomes of Anaplerotic Dodecanedioic Acid Supplementation in Very Long Chain Acyl-CoA Dehydrogenase (VLCAD) Deficient Fibroblasts

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD, OMIM 609575) is associated with energy deficiency and mitochondrial dysfunction and may lead to rhabdomyolysis and cardiomyopathy. Under physiological conditions, there is a fine balance between the utilization of different carbon nutrients to maintain the Krebs cycle. The maintenance of steady pools of Krebs cycle intermediates is critical formitochondrial energy homeostasis especially in high-energy demanding organs such as muscle and heart. Even-chain dicarboxylic acids are established as alternative energy carbon sources that replenish the Krebs cycle by bypassing a defective β-oxidation pathway. Despite this, even-chain dicarboxylic acids are eliminated in the urine of VLCAD-affected individuals. In this study, we explore dodecanedioic acid (C12; DODA) supplementation and investigate its metabolic effect on Krebs cycle intermediates, glucose uptake, and acylcarnitine profiles in VLCAD-deficient fibroblasts. Our findings indicate that DODA supplementation replenishes the Krebs cycle by increasing the succinate pool, attenuates glycolytic flux, and reduces levels of toxic very long-chain acylcarnitines.

A multi-omics study to investigate tacrolimus nephrotoxicity mechanisms

Tacrolimus, prescribed to a majority of transplanted patients is associated with nephrotoxicity, the mechanism of which remains unclear. This study aims to evaluate the impact of tacrolimus on proximal tubular cells using a multi-omics approach. LLC-PK1 cells were exposed to 5 μM of tacrolimus for 24h. Intracellular proteins and metabolites, and extracellular metabolites were extracted and analysed by LC-MS/MS. The transcriptional expression of PCK-1, FBP1 and FBP2 was measured using RT-qPCR. In our cell model, tacrolimus impacted different metabolic pathways including urea cycle (e.g., citrulline, ornithine) (p < 0.0001), amino acid metabolism (e.g., valine, isoleucine, aspartic acid) (p < 0.0001) and pyrimidine metabolism (p<0.01). In addition, it induces oxidative stress (p < 0.01) shown by a decrease in total cell glutathione quantity and impacts cell energy through an increase in Krebs cycle intermediates (e.g., citrate, aconitate, fumarate) (p < 0.01) and a down-regulation of PCK-1 (p < 0.05) and FPB1 (p < 0.01), key enzymes in gluconeogenesis. Apart from glucose synthesis, gluconeogenesis is an important process in kidney mediated acid-base balance control. The observed variations found using this multi-omics approach clearly establish a dysregulation of energy production in epithelial cells of the renal tubule, and potentially of their functions, that can be implicated in tacrolimus chronic nephrotoxicity.

Dominant ACO2 mutations are a frequent cause of isolated optic atrophy

Biallelic mutations in ACO2, encoding the mitochondrial aconitase 2, have been identified in individuals with neurodegenerative syndromes, including infantile cerebellar retinal degeneration and recessive optic neuropathies (locus OPA9). By screening European cohorts of individuals with genetically unsolved inherited optic neuropathies, we identified 61 cases harboring variants in ACO2, among whom 50 carried dominant mutations, emphasizing for the first time the important contribution of ACO2 monoallelic pathogenic variants to dominant optic atrophy. Analysis of the ophthalmological and clinical data revealed that recessive cases are affected more severely than dominant cases, while not significantly earlier. In addition, 27% of the recessive cases and 11% of the dominant cases manifested with extraocular features in addition to optic atrophy. In silico analyses of ACO2 variants predicted their deleterious impacts on ACO2 biophysical properties. Skin derived fibroblasts from patients harboring dominant and recessive ACO2 mutations revealed a reduction of ACO2 abundance and enzymatic activity, and the impairment of the mitochondrial respiration using citrate and pyruvate as substrates, while the addition of other Krebs cycle intermediates restored a normal respiration, suggesting a possible short-cut adaptation of the tricarboxylic citric acid cycle. Analysis of the mitochondrial genome abundance disclosed a significant reduction of the mitochondrial DNA amount in all ACO2 fibroblasts. Overall, our data position ACO2 as the third most frequently mutated gene in autosomal inherited optic neuropathies, after OPA1 and WFS1, and emphasize the crucial involvement of the first steps of the Krebs cycle in the maintenance and survival of retinal ganglion cells. By screening European cohorts of individuals with genetically unsolved inherited optic neuropathies, Charif et al. report 61 new cases harboring variants in ACO2, among whom 50 with dominant mutations, emphasizing for the first time the important contribution of ACO2 monoallelic pathogenic variants to dominant optic atrophy.

Metabolic alterations in a rat model of takotsubo syndrome

Aims Cardiac energetic impairment is a major finding in takotsubo patients. We investigate specific metabolic adaptations to direct future therapies. Methods and results An isoprenaline-injection female rat model (vs. sham) was studied at Day 3; recovery assessed at Day 7. Substrate uptake, metabolism, inflammation, and remodelling were investigated by 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography, metabolomics, quantitative PCR, and western blot (WB). Isolated cardiomyocytes were patch-clamped during stress protocols for redox states of NAD(P)H/FAD or [Ca2+]c, [Ca2+]m, and sarcomere length. Mitochondrial respiration was assessed by seahorse/Clark electrode (glycolytic and β-oxidation substrates). Cardiac 18F-FDG metabolic rate was increased in takotsubo (P = 0.006), as was the expression of GLUT4-RNA/GLUT1/HK2-RNA and HK activity (all P &lt; 0.05), with concomitant accumulation of glucose- and fructose-6-phosphates (P &gt; 0.0001). Both lactate and pyruvate were lower (P &lt; 0.05) despite increases in LDH-RNA and PDH (P &lt; 0.05 both). β-Oxidation enzymes CPT1b-RNA and 3-ketoacyl-CoA thiolase were increased (P &lt; 0.01) but malonyl-CoA (CPT-1 regulator) was upregulated (P = 0.01) with decreased fatty acids and acyl-carnitines levels (P = 0.0001–0.02). Krebs cycle intermediates α-ketoglutarate and succinyl-carnitine were reduced (P &lt; 0.05) as was cellular ATP reporter dihydroorotate (P = 0.003). Mitochondrial Ca2+ uptake during high workload was impaired on Day 3 (P &lt; 0.0001), inducing the oxidation of NAD(P)H and FAD (P = 0.03) but resolved by Day 7. There were no differences in mitochondrial respiratory function, sarcomere shortening, or [Ca2+] transients of isolated cardiomyocytes, implying preserved integrity of both mitochondria and cardiomyocyte. Inflammation and remodelling were upregulated—increased CD68-RNA, collagen RNA/protein, and skeletal actin RNA (all P &lt; 0.05). Conclusion Dysregulation of glucose and lipid metabolic pathways with decreases in final glycolytic and β-oxidation metabolites and reduced availability of Krebs intermediates characterizes takotsubo myocardium. The energetic deficit accompanies defective Ca2+ handling, inflammation, and upregulation of remodelling pathways, with the preservation of sarcomeric and mitochondrial integrity.

Cytosolic Phosphoenolpyruvate Carboxykinase Deficiency: Cause of Hypoglycemia-Induced Seizure and Death

Cytosolic phosphoenolpyruvate carboxykinase (PEPCK) deficiency (MIM 261680, EC 4.1.1.32, encoded by PCK1) is a rare disorder of gluconeogenesis presenting with recurrent hypoglycemia, hepatic dysfunction, and lactic acidosis. We report on a previously healthy 3-year-old boy who was initially admitted under the suspicion of a febrile seizure during an upper airway infection. Diagnostic workup revealed hypoglycemia as well as a cerebral edema and ruled out an infection. After a complicated course with difficult to treat symptomatic seizures, the child died on the 5th day of admission due to progressive cerebral edema. The metabolic screening showed elevated urinary lactate and Krebs cycle intermediates in line with a primary or secondary energy deficit. Due to the unclear and fatal course, trio exome sequencing was initiated postmortem (“molecular autopsy”) and revealed the diagnosis of cytosolic PEPCK deficiency based on the compound heterozygosity of a known pathogenic (c.925G > A, p.(Gly309Arg)) and a previously unreported (c.724G > A, p.(Gly242Arg)) variant in PCK1 (NM_002591.3). Sanger sequencing ruled out the disease and carrier status in three older brothers. Molecular autopsy was performed due to the unclear and fatal course. The diagnosis of a cytosolic PEPCK deficiency not only helped the family to deal with the grief, but especially took away the fear that the siblings could be affected by an unknown disease in the same manner. In addition, this case increases the genetic and phenotypic spectrum of cytosolic PEPCK deficiency.

Identification of actoprotective compounds among Krebs cycle acid/aminoethanol derivatives

The screening study of the effects of several new diethylamino- and dimethylaminoethanol fumaric esters with Krebs cycle intermediates on the physical performance of male mice in the forced swimming test have been conducted. The compounds: Fumarate-DMAE-Fumarate at a dose of 75 mg/kg and Fumarate-DEAE-Succinate at a dose of 10 mg/kg, as well as Diethylaminoethanol (DEAE base) at a dose of 50 mg/kg. The study has shown that their effect on physical performance surpassed the comparison drug, deanol aceglumate, used at the optimal dose of 50 mg/kg. The latter provided a 74% increase in the maximum swimming time of animals, while the studied compounds showed +175%, +162%, +121% results compared to control. The actoprotective activity of the compounds Fumarate-DMAE-Fumarate (75 mg/kg dose) and Fumarate-DEAE-Succinate (FDES) (10 mg/kg dose) is comparable to the effect of ethylthiobenzimidazole hydrochloride (25 mg/kg dose).

Clinical Applications of Ketogenic Diet-Induced Ketosis in Neurodegenerative and Metabolism-Related Pathologies

Metabolic-based therapies such as nutritional ketosis have been proven effective for seizure disorders and various acute and chronic neurological pathologies. In a healthy brain, glucose is the primary metabolic fuel for cells. However, neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), seizure disorders, and traumatic brain injury (TBI) are associated with impaired glucose transport and metabolism and with mitochondrial dysfunction leading to energy deficit. Therapeutic ketosis can be considered as a form of metabolic therapy by providing alternative energy substrates. In addition, ketosis leads to metabolic adaptations that improve brain metabolism, restore mitochondrial ATP production, decrease reactive oxygen species production, reduce inflammation, and increase the activity of neurotrophic factors. Moreover, the synaptic activity between neurons is also stabilized through the increase of Szent-Györgyi–Krebs cycle intermediates, antioxidant effects, increased GABA-to-glutamate ratio, and activation of ATP-sensitive potassium channels.

Succination inactivates gasdermin D and blocks pyroptosis

Activated macrophages undergo a metabolic switch to aerobic glycolysis accumulating Krebs cycle intermediates that alter transcription of immune response genes. Here we extend these observations by defining fumarate as an inhibitor of pyroptotic cell death. We found that dimethyl fumarate (DMF) delivered to cells or endogenous fumarate reacts with gasdermin D (GSDMD) at critical cysteine residues to form S-(2-succinyl)-cysteine. GSDMD succination prevents its interaction with caspases, limiting its processing, oligomerization, and capacity to induce cell death. In mice, the administration of DMF protects against LPS shock and alleviates familial Mediterranean fever and experimental autoimmune encephalitis (EAE) by targeting GSDMD. Collectively, these findings identify GSDMD as a target of fumarate and reveal a mechanism of action for fumarate-based therapeutics including DMF used to treat multiple sclerosis.