Dichloroacetate improves systemic energy balance and feeding behavior during sepsis

NSUN3 Aggravates Sepsis-Associated Acute Kidney Injury by Stabilising TIFA mRNA Through m5C

BACKGROUND

Acute kidney injury (AKI) is a common complication of sepsis and also a risk factor for progression of chronic kidney disease. NOP2/Sun RNA methyltransferase 3 (NSUN3) is involved in the regulation of sepsis progression. However, the mechanism by which NSUN3 regulates sepsis-associated AKI (SA-AKI) remains unclear.

METHODS

SA-AKI mouse model and lipopolysaccharide (LPS)-induced injury model in HK-2 cells were constructed. Haematoxylin-eosin staining, quantitative polymerase chain reaction (qPCR), western blotting, cell counting kit 8, flow cytometry, 2',7'-dichlorofluorescein diacetate, enzyme-linked immunosorbent assay, methylation RNA immunoprecipitation-qPCR, actinomycin D and TdT-mediated dUTP Nick-End Labelling staining assays were utilised to explore the expression and related mechanism of NSUN3 in the SA-AKI models.

RESULTS

The expression of NSUN3 and tumour necrosis factor receptor-associated factor (TRAF)-interacting protein with forkhead-associated domain (TIFA) was upregulated in mice with SA-AKI and LPS-induced HK-2 cells. Knockdown of NSUN3 inhibited LPS-induced injury in HK-2 cells. Mechanically, NSUN3 increased TIFA mRNA stability and upregulated its expression through m5C modification. Moreover, knockdown of NSUN3 was found to alleviate LPS-induced HK-2 cell injury and SA-AKI in mice by reducing TIFA expression.

CONCLUSION

NSUN3 aggravates SA-AKI by stabilising TIFA mRNA through m5C, indicating that NSUN3 may be a biomarker for SA-AKI.

Comparative metabolomic analysis reveals shared and unique features of COVID-19 cytokine storm and surgical sepsis

The clinical manifestations of the cytokine storm (CS) associated with COVID-19 resemble the acute phase of sepsis. Metabolomics may contribute to understanding the specific pathobiology of these two syndromes. The aim of this study was to compare serum metabolomic profiles in CS associated with COVID-19 vs. septic surgery patients. In a retrospective cross-sectional study, serum samples from patients with CS associated with COVID-19, with and without comorbidity, as well as serum samples from patients with surgical sepsis were investigated. Targeted metabolomic analysis was performed on all samples using LC-MS/MS. Analysis revealed that similar alterations in the serum metabolome of patients with COVID-19 and surgical septic patients were associated with amino acid metabolism, nitrogen metabolism, inflammatory status, methionine cycle and glycolysis. The most significant difference was found for serum levels of metabolites of kynurenine synthesis, tricarboxylic acid cycle, gamma-aminobutyric acid and niacinamide. The metabolic pathway of cysteine and methionine metabolism was significantly disturbed in COVID-19 and surgical septic patients. For the first time, the similarities and differences between the serum metabolomic profiles of patients with CS associated with COVID-19 and patients with surgical sepsis were investigated for patients from the Northwest of the Russian Federation.

The pyruvate dehydrogenase kinase inhibitor dichloroacetate mitigates alcohol-induced hepatic inflammation and metabolic disturbances in mice

BACKGROUND

Dichloroacetate (DCA), a pan-pyruvate dehydrogenase kinase inhibitor, ameliorates multiple pathological conditions and tissue injury and shows strong potential for clinical applications. Here, we investigated the preventive effects of DCA in a murine model of alcohol-associated liver disease.

METHODS

C57BL/6J mice were subjected to the acute-on-chronic model of alcohol-associated liver disease and treated with DCA. Livers were assessed in liver histology, biochemistry, and gene expression. Mass spectrometry was used to compare protein expression and metabolite levels.

RESULTS

DCA inhibited hepatic expression of inflammatory genes but did not prevent steatosis and hepatocellular injury in ethanol-fed mice. Consistently, DCA repressed the expression of mRNAs for inflammatory genes in LPS-stimulated murine bone-marrow-derived macrophages and human monocytic THP-1 cells and inhibited both gene expression and protein release of interleukin-1 beta. DCA prevented hepatic accumulation of isovaleric acid in ethanol-fed mice, a short-chain fatty acid primarily produced by gut microbiota. In vitro, isovaleric acid potentiated LPS's effects, while DCA prevented this proinflammatory action. Ethanol feeding increased the expression of proteins involved in diverse metabolic pathways, including branched-chain amino acid (BCAA) degradation. In ethanol-fed mice, hepatic Fischer's ratio (the molar ratio of BCAAs to aromatic amino acids Phe and Tyr) and BTR (the molar ratio of BCAAs to Tyr) showed a decrease compared to pair-fed mice; however, this decrease was not observed in DCA-treated ethanol-fed mice. DCA blunted the ethanol-induced increase of BCKDHA, the rate-limiting enzyme in BCAA catabolism, and cytochrome P450 2E1.

CONCLUSIONS

Ethanol-induced hepatic inflammatory responses and metabolic disturbances were prevented by DCA in mice, indicating the potential to develop pyruvate dehydrogenase kinase inhibitors as an effective therapy to treat alcohol-associated liver disease.

Sepsis-induced changes in pyruvate metabolism: insights and potential therapeutic approaches

Sepsis is a heterogeneous syndrome resulting from a dysregulated host response to infection. It is considered as a global major health priority. Sepsis is characterized by significant metabolic perturbations, leading to increased circulating metabolites such as lactate. In mammals, pyruvate is the primary substrate for lactate production. It plays a critical role in metabolism by linking glycolysis, where it is produced, with the mitochondrial oxidative phosphorylation pathway, where it is oxidized. Here, we provide an overview of all cytosolic and mitochondrial enzymes involved in pyruvate metabolism and how their activities are disrupted in sepsis. Based on the available data, we also discuss potential therapeutic strategies targeting these pyruvate-related enzymes leading to enhanced survival.

Dichloroacetate attenuates brain injury through inhibiting neuroinflammation and mitochondrial fission in a rat model of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a severe complication of sepsis, characterized by neuroinflammation, mitochondrial dysfunction, and oxidative stress, leading to cognitive decline and high mortality. The effectiveness of dichloroacetate (DCA) in modulating mitochondrial function provides a novel therapeutic strategy for SAE. In this study, we evaluated the neuroprotective effects of DCA in a rat model of SAE induced by cecal ligation and puncture (CLP). Rats treated with DCA exhibited significant improvements in neurological function and survival, as evidenced by less neuron loss from histopathologic analysis, restored neurologic deficit scores, improved Y-maze alternation percentages, and enhanced recognition index performance. Biochemical analyses showed that DCA administration at 25 mg/kg and 100 mg/kg reduced astrocyte and microglial activation, indicating reduced neuroinflammation. Furthermore, DCA simultaneously reduced the production of circulating and cerebral inflammatory cytokines (including TNF-α, IL-1β, and IL-10), concomitant with mitigating oxidative stress through down-regulating expression of 8-Hydroxy-2'-deoxyguanosine (8-OHdG) and reactive oxygen species (ROS) in the brain. Mechanistically, DCA modulated mitochondrial dynamics by suppressing Drp1 and pDrp1 expression, which are indicators of mitochondrial fission. This was corroborated by transmission electron microscopy, quantification of mitochondrial area, and Western blot analyses. Furthermore, DCA treatment improved ATP levels, mitochondrial complex I activity, and NAD+/NADH ratio, indicating a significant attenuation of brain mitochondrial dysfunction. In conclusion, our findings suggest that DCA confers neuroprotection in SAE by curtailing neuroinflammation and mitochondrial fission, outlining a promising therapeutic strategy for treating SAE in critically ill patients.

The Values of PDK1 and LDH Levels in Patients with Sepsis and Septic Shock: A Prospective Observational Study

Background

Metabolic changing is the significant host stress response during sepsis, but there is increasing evidence that uncontrolled metabolic reprogramming is a contributing factor to sepsis. Nevertheless, its association with outcome in patients with sepsis has been poorly investigated. As the key enzyme of metabolic reprogramming, the clinical value of PDK1 and LDH in patients with sepsis will be investigated in this study.

Methods

We collected serum from 167 ICU patients within 24 hours of admission for a single-center prospective observational study. The levels of PDK1 and LDH were detected by enzyme-linked adsorption method. Pearson or Spearman coefficient for correlation analysis between PDK1, LDH and clinical indicators. Areas under the ROC curves for evaluation of mortality prediction. Kaplan-Meier survival curve analysis was performed, and Cox proportional hazards model was performed to determine the risk factors for 28-day mortality.

Results

The PDK1/LDH in the septic shock group was statistically different between both the sepsis group and ICU control group, and had good correlation with ScvO2 and lactate. In predicting 28-day mortality in patients with sepsis, the best AUC was observed for PDK1/LDH, and was higher than the AUC for PDK1, lactate, and SOFA. Additionally, patients with lower PDK1/LDH had markerablely higher 28-day mortality. The multivariate Cox proportional hazards model revealed that PDK1/LDH < 0.1808 were the independent risk factors for 28-day mortality in sepsis.

Conclusion

The level of PDK1/LDH at admission was markedly decreased in patients with septic shock, which can serve as a novel independent prognostic biomarker for predicting mortality.

Dichloroacetate Prevents Sepsis Associated Encephalopathy by Inhibiting Microglia Pyroptosis through PDK4/NLRP3

Dichloroacetate (DCA), a pyruvate dehydrogenase kinase inhibitor, is often used to treat lactic acidosis and malignant tumors. Increasing studies have shown that DCA has neuroprotective effects. Here, we explored the role and mechanism of DCA in Sepsis associated encephalopathy (SAE). Single-cell analysis was used to determine the important role of PDK4 in SAE and identify the cell type. GO and GSEA analysis were used to determine the correlation between DCA and pyroptosis. Through LPS + ATP stimulation, a microglia pyroptosis model was established to observe the expression level of intracellular pyroptosis-related proteins under DCA intervention, and further detect the changes in intracellular ROS and JC-1. Additionally, a co-culture environment of microglia and neuron was simply constructed to evaluate the effect of DCA on activated microglia-mediated neuronal apoptosis. Finally, Novel object recognition test and the Morris water maze were used to explore the effect of DCA on cognitive function in mice from different groups after intervention. Based on the above experiments, this study concludes that DCA can improve the ratio of peripheral and central M1 macrophages, inhibit NLRP3-mediated pyroptosis through ROS and mitochondrial membrane potential (MMP). DCA can reduce neuron death caused by SAE and improve cognitive function in LPS mice. In SAE, DCA may be a potential candidate drug for the treatment of microglia-mediated neuroinflammation.

Metabolic Regulation in the Induction of Trained Immunity

The innate immune system exhibits features of memory, termed trained immunity, which promote faster and more robust responsiveness to heterologous challenges. Innate immune memory is sustained through epigenetic modifications, affecting gene accessibility, and promoting a tailored gene transcription for an enhanced immune response. Alterations in the epigenetic landscape are intertwined with metabolic rewiring. Here, we review the metabolic pathways that underscore the induction and maintenance of trained immunity, including glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle, and amino acid and lipid metabolism. The intricate interplay of these pathways is pivotal for establishing innate immune memory in distinct cellular compartments. We explore in particular the case of resident lung alveolar macrophages. We propose that leveraging the memory of the innate immune system may present therapeutic potential. Specifically, targeting the metabolic programs of innate immune cells is an emerging strategy for clinical interventions, either to boost immune responses in immunosuppressed conditions or to mitigate maladaptive activation in hyperinflammatory diseases.

Itaconate stabilizes CPT1a to enhance lipid utilization during inflammation

One primary metabolic manifestation of inflammation is the diversion of cis-aconitate within the tricarboxylic acid (TCA) cycle to synthesize the immunometabolite itaconate. Itaconate is well established to possess immunomodulatory and metabolic effects within myeloid cells and lymphocytes, however, its effects in other organ systems during sepsis remain less clear. Utilizing Acod1 knockout mice that are deficient in synthesizing itaconate, we aimed to understand the metabolic role of itaconate in the liver and systemically during sepsis. We find itaconate aids in lipid metabolism during sepsis. Specifically, Acod1 KO mice develop a heightened level of hepatic steatosis when induced with polymicrobial sepsis. Proteomics analysis reveals enhanced expression of enzymes involved in fatty acid oxidation in following 4-octyl itaconate (4-OI) treatment in vitro. Downstream analysis reveals itaconate stabilizes the expression of the mitochondrial fatty acid uptake enzyme CPT1a, mediated by its hypoubiquitination. Chemoproteomic analysis revealed itaconate interacts with proteins involved in protein ubiquitination as a potential mechanism underlying its stabilizing effect on CPT1a. From a systemic perspective, we find itaconate deficiency triggers a hypothermic response following endotoxin stimulation, potentially mediated by brown adipose tissue (BAT) dysfunction. Finally, by use of metabolic cage studies, we demonstrate Acod1 KO mice rely more heavily on carbohydrates versus fatty acid sources for systemic fuel utilization in response to endotoxin treatment. Our data reveal a novel metabolic role of itaconate in modulating fatty acid oxidation during polymicrobial sepsis.

Regulating mitochondrial metabolism by targeting pyruvate dehydrogenase with dichloroacetate, a metabolic messenger

Dichloroacetate (DCA) is a naturally occurring xenobiotic that has been used as an investigational drug for over 50 years. Originally found to lower blood glucose levels and alter fat metabolism in diabetic rats, this small molecule was found to serve primarily as a pyruvate dehydrogenase kinase inhibitor. Pyruvate dehydrogenase kinase inhibits pyruvate dehydrogenase complex, the catalyst for oxidative decarboxylation of pyruvate to produce acetyl coenzyme A. Several congenital and acquired disease states share a similar pathobiology with respect to glucose homeostasis under distress that leads to a preferential shift from the more efficient oxidative phosphorylation to glycolysis. By reversing this process, DCA can increase available energy and reduce lactic acidosis. The purpose of this review is to examine the literature surrounding this metabolic messenger as it presents exciting opportunities for future investigation and clinical application in therapy including cancer, metabolic disorders, cerebral ischemia, trauma, and sepsis.

Glutathionylation of pyruvate dehydrogenase complex E2 and inflammatory cytokine production during acute inflammation are magnified by mitochondrial oxidative stress

Lipopolysaccharide (LPS) is a known inducer of inflammatory signaling which triggers generation of reactive oxygen species (ROS) and cell death in responsive cells like THP-1 promonocytes and freshly isolated human monocytes. A key LPS-responsive metabolic pivot point is the 9 MDa mitochondrial pyruvate dehydrogenase complex (PDC), which provides pyruvate dehydrogenase (E1), lipoamide-linked transacetylase (E2) and lipoamide dehydrogenase (E3) activities to produce acetyl-CoA from pyruvate. While phosphorylation-dependent decreases in PDC activity following LPS treatment or sepsis have been deeply investigated, redox-linked processes have received less attention. Data presented here demonstrate that LPS-induced reversible oxidation within PDC occurs in PDCE2 in both THP-1 cells and primary human monocytes. Knockout of PDCE2 by CRISPR and expression of FLAG-tagged PDCE2 in THP-1 cells demonstrated that LPS-induced glutathionylation is associated with wild type PDCE2 but not mutant protein lacking the lipoamide-linking lysine residues. Moreover, the mitochondrially-targeted electrophile MitoCDNB, which impairs both glutathione- and thioredoxin-based reductase systems, elevates ROS similar to LPS but does not cause PDCE2 glutathionylation. However, LPS and MitoCDNB together are highly synergistic for PDCE2 glutathionylation, ROS production, and cell death. Surprisingly, the two treatments together had differential effects on cytokine production; pro-inflammatory IL-1β production was enhanced by the co-treatment, while IL-10, an important anti-inflammatory cytokine, dropped precipitously compared to LPS treatment alone. This new information may expand opportunities to understand and modulate PDC redox status and activity and improve the outcomes of pathological inflammation.

Glutathionylation of Pyruvate Dehydrogenase Complex E2 and Inflammatory Cytokine Production During Acute Inflammation Are Magnified By Mitochondrial Oxidative Stress

Lipopolysaccharide (LPS) is a known inducer of inflammatory signaling which triggers generation of reactive oxygen species (ROS) and cell death in responsive cells like THP-1 promonocytes and freshly isolated human monocytes. A key LPS-responsive metabolic pivot point is the 9 megadalton mitochondrial pyruvate dehydrogenase complex (PDC), which provides pyruvate dehydrogenase (E1), lipoamide-linked transacetylase (E2) and lipoamide dehydrogenase (E3) activities to produce acetyl-CoA from pyruvate. While phosphorylation-dependent decreases in PDC activity following LPS treatment or sepsis have been deeply investigated, redox-linked processes have received less attention. Data presented here demonstrate that LPS-induced reversible oxidation within PDC occurs in PDCE2 in both THP-1 cells and primary human monocytes. Knockout of PDCE2 by CRISPR and expression of FLAG-tagged PDCE2 in THP-1 cells demonstrated that LPS-induced glutathionylation is associated with wild type PDCE2 but not mutant protein lacking the lipoamide-linking lysine residues. Moreover, the mitochondrially-targeted electrophile MitoCDNB, which impairs both glutathione- and thioredoxin-based reductase systems, elevates ROS similar to LPS but does not cause PDCE2 glutathionylation. However, LPS and MitoCDNB together are highly synergistic for PDCE2 glutathionylation, ROS production, and cell death. Surprisingly, the two treatments together had differential effects on cytokine production; pro-inflammatory IL-1β production was enhanced by the co-treatment, while IL-10, an important anti-inflammatory cytokine, dropped precipitously compared to LPS treatment alone. This new information may expand opportunities to understand and modulate PDC redox status and activity and improve the outcomes of pathological inflammation.

The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat

Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.

Pyruvate dehydrogenase kinase supports macrophage NLRP3 inflammasome activation during acute inflammation

Activating the macrophage NLRP3 inflammasome can promote excessive inflammation with severe cell and tissue damage and organ dysfunction. Here, we show that pharmacological or genetic inhibition of pyruvate dehydrogenase kinase (PDHK) significantly attenuates NLRP3 inflammasome activation in murine and human macrophages and septic mice by lowering caspase-1 cleavage and interleukin-1β (IL-1β) secretion. Inhibiting PDHK reverses NLRP3 inflammasome-induced metabolic reprogramming, enhances autophagy, promotes mitochondrial fusion over fission, preserves crista ultrastructure, and attenuates mitochondrial reactive oxygen species (ROS) production. The suppressive effect of PDHK inhibition on the NLRP3 inflammasome is independent of its canonical role as a pyruvate dehydrogenase regulator. Our study suggestsa non-canonical role of mitochondrial PDHK in promoting mitochondrial stress and supporting NLRP3 inflammasome activation during acute inflammation.