Lipopolysaccharide (LPS)-induced septic shock causes profound changes in myocardial energy metabolites in pigs

Norepinephrine Infusion and the Central Venous Waveform in a Porcine Model of Endotoxemic Hypotension with Resuscitation: A Large Animal Study

BACKGROUND

Venous waveform analysis is an emerging technique to estimate intravascular fluid status by fast Fourier transform deconvolution. Fluid status has been shown proportional to f0, the amplitude of the fundamental frequency of the waveform's cardiac wave upon deconvolution. Using a porcine model of distributive shock and fluid resuscitation, we sought to determine the influence of norepinephrine on f0 of the central venous waveform.

METHODS

Eight pigs were anesthetized, catheterized and treated with norepinephrine after precipitation of endotoxemic hypotension, and subsequent fluid resuscitation to mimic sepsis physiology. Hemodynamic parameters and central venous waveforms were continually transduced throughout the protocol for post-hoc analysis. Central venous waveform f0 before, during and after norepinephrine administration were determined using Fourier analysis.

RESULTS

Heart rate increased, while central venous pressure, pulmonary capillary wedge pressure and stroke volume decreased throughout norepinephrine administration (p < 0.05). Mean f0 at pre-norepinephrine, and doses 0.05, 0.10, 0.15, 0.20 and 0.25 mcg/kg/min, were 2.5, 1.4, 1.7, 1.7, 1.6 and 1.4 mmHg2, respectively (repeated measures ANOVA; p < 0.001). On post-hoc comparison to pre-norepinephrine, f0 at 0.05 mcg/kg/min was decreased (p = 0.04).

CONCLUSIONS

As the performance of f0 was previously characterized during fluid administration, these data offer novel insight into the performance of f0 during vasopressor delivery. Central venous waveform f0 is a decreased with norepinephrine, in concordance with pulmonary capillary wedge pressure. This allows contextualization of the novel, venous-derived signal f0 during vasopressor administration, a finding that must be understood prior to clinical translation.

Increase in plasma succinate is associated with aerobic lactate production in a model of endotoxic shock

The Krebs or tricarboxylic acid (TCA) cycle plays a key role in the regulation of immune responses and adaptations to hypoxia that occur during sepsis. Although the concentrations of some of these intermediates have been reported to be increased in large cohorts of septic patients, a detailed analysis of their changes during sepsis is still lacking. Here, we investigated the plasma concentrations of several TCA intermediates in a swine model of endotoxic shock and the relationship between these TCA cycle intermediates and lactate production. Nine female swine were administered lipopolysaccharide to induce endotoxic shock, while four females served as controls. Plasma samples were collected at three time points: baseline, 3 and 6 h after lipopolysaccharide administration. Control samples were collected at parallel time points. Quantification of TCA intermediates, lactate and pyruvate was performed by high-performance liquid chromatography. Oxygen-derived variables were obtained by gas analysis of arterial and venous samples. The endotoxic shock group showed a significant increase in lactate, accompanied by stability of oxygen-derived variables and a low lactate:pyruvate ratio, indicative of aerobic conditions. Of all the TCA intermediates analysed, only citrate and succinate showed significant increases compared with controls. Furthermore, the changes in lactate were determined, in part, by the changes in succinate concentration. The increase in succinate concentrations was associated with the increase in lactate in global aerobic conditions. Our results suggest a potential role for succinate as a biomarker of aerobic lactate production.

Nucleolin myocardial-specific knockout exacerbates glucose metabolism disorder in endotoxemia-induced myocardial injury

Background

Sepsis-induced myocardial injury, as one of the important complications of sepsis, can significantly increase the mortality of septic patients. Our previous study found that nucleolin affected mitochondrial function in energy synthesis and had a protective effect on septic cardiomyopathy in mice. During sepsis, glucose metabolism disorders aggravated myocardial injury and had a negative effect on septic patients.

Objectives

We investigated whether nucleolin could regulate glucose metabolism during endotoxemia-induced myocardial injury.

Methods

The study tested whether the nucleolin cardiac-specific knockout in the mice could affect glucose metabolism through untargeted metabolomics, and the results of metabolomics were verified experimentally in H9C2 cells. The ATP content, lactate production, and oxygen consumption rate (OCR) were evaluated.

Results

The metabolomics results suggested that glycolytic products were increased in endotoxemia-induced myocardial injury, and that nucleolin myocardial-specific knockout altered oxidative phosphorylation-related pathways. The experiment data showed that TNF-α combined with LPS stimulation could increase the lactate content and the OCR values by about 25%, and decrease the ATP content by about 25%. However, interference with nucleolin expression could further decrease ATP content and OCR values by about 10-20% and partially increase the lactate level in the presence of TNF-α and LPS. However, nucleolin overexpression had the opposite protective effect, which partially reversed the decrease in ATP content and the increase in lactate level.

Conclusion

Down-regulation of nucleolin can exacerbate glucose metabolism disorders in endotoxemia-induced myocardial injury. Improving glucose metabolism by regulating nucleolin was expected to provide new therapeutic ideas for patients with septic cardiomyopathy.

Dexmedetomidine post-treatment exacerbates metabolic disturbances in septic cardiomyopathy via α2A-adrenoceptor

Cardiomyopathy is a common complication and significantly increases the risk of death in septic patients. Our previous study demonstrated that post-treatment with dexmedetomidine (DEX) aggravates septic cardiomyopathy. However, the mechanisms for the side effect of DEX post-treatment on septic cardiomyopathy are not well-defined. Here we employed a cecal ligation and puncture (CLP) model and α2A-adrenoceptor deficient (Adra2a-/-) mice to observe the effects of DEX post-treatment on myocardial metabolic disturbances in sepsis. CLP mice displayed significant cardiac dysfunction, altered mitochondrial dynamics, reduced cardiac lipid and glucose uptake, impaired fatty acid and glucose oxidation, enhanced glycolysis and decreased ATP production in the myocardium, almost all of which were dramatically enhanced by DEX post-treatment in septic mice. In Adra2a-/- mice, DEX post-treatment did not affect cardiac dysfunction and metabolic disruptions in CLP-induced sepsis. Additionally, Adra2a-/- mice exhibited impaired cardiac function, damaged myocardial mitochondrial structures, and disturbed fatty acid metabolism and glucose oxidation. In sum, DEX post-treatment exacerbates metabolic disturbances in septic cardiomyopathy in a α2A-adrenoceptor dependent manner.

The effects of polyethylene microplastics on the growth, reproduction, metabolic enzymes, and metabolomics of earthworms Eisenia fetida

The existing data regarding the effects of polyethylene (PE) microplastics (MPs) smaller than 5 mm in size on earthworms are insufficient to fully comprehend their toxicity. In this study, earthworms Eisenia fetida were exposed to artificially added PE at a concentration ranging from 0.05 to 20 g/kg soil (0.005%-2%) for 60 days to determine the concentration range causing negative effects on earthworms and to uncover the potential toxic mechanisms. The individual growth, reproduction, and metabolic enzyme activities, including phase I enzymes (cytochrome P450 [CYP] 1A2, 2B6, 2C9, and 3A4), and phase II metabolic enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione sulfotransferase (GST)), and metabolomics were measured. The observed variations in responses of multiple cross-scale endpoints indicated that individual indices are less responsive to PE MPs than metabolic enzymes or metabolomics. Despite the absence of significant alterations in growth inhibition based on body weight, PE MPs at concentrations equal to or exceeding 2.5 g/kg were found to exert a toxic effect on earthworms, which was evidenced by significant changes in metabolic enzyme activities (CYP1A2, 2B6, 2C9, and 3A4, SOD, CAT, and GST) and important small molecule metabolites screened based on metabolomics, likely due to the bioaccumulation of PE. The toxicity of PE MPs to earthworms is inferred to be associated with neurotoxicity, oxidative damage, decreased detoxification capacity, energy metabolism imbalance, and impaired amino acid and purine metabolism due to bioaccumulation. The findings of this study will enhance our understanding of the molecular toxicity mechanisms of PE MPs and contribute to a more accurate assessment of the ecological risks posed by PE MPs in soil.

The Effect of Fluid Pre-loading on Vital Signs and Hemodynamic Parameters in a Porcine Model of Lipopolysaccharide-Induced Endotoxemia

Background Animal models of distributive hypotension and resuscitation allow the assessment of hemodynamic monitoring modalities and resuscitation strategies. The fluid-first paradigm for resuscitation is currently being challenged with clinical trials. In this investigation, venous return and perfusion are assessed, and full hemodynamics are characterized, in a porcine model of endotoxemic hypotension with and without fluid pre-loading. Methods Two groups of six pigs had the induction of standardized endotoxemic hypotension ("critical hypotension"). Group 1 underwent four 10 cc/kg crystalloid boluses, and Group 2 was not fluid pre-resuscitated. Both groups underwent progressive norepinephrine (NE) up-titration to 0.25 mcg/kg/minute over 30 minutes. Vital signs, central parameters, and laboratory values were obtained at baseline, "critical hypotension," after each bolus and during NE administration. Results Endotoxemia decreased the systemic vascular resistance (SVR) in Group 1 (1031±106 dyn/s/cm-5 versus 738±258 dyn/s/cm-5; P=0.03) and Group 2 (1121±196 dyn/s/cm-5 versus 759±342 dyn/s/cm-5; P=0.003). In Group 1, the four fluid boluses decreased heart rate (HR), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) (P<0.05). No changes were observed in blood pressure, cardiac output (CO), or lactate. NE up-titration increased HR in Group 1 and decreased CVP in both groups. Higher final CVP (11 {3} versus 4 {4} mmHg; P=0.01) and PCWP (5 {1} versus 2 {2} mmHg; P=0.005) values were observed in Group 1 relative to Group 2, reflecting increased venous return. Conclusions Porcine endotoxemic hypotension and resuscitation were robustly characterized. In this model, fluid loading improved venous return with NE, though perfusion (CO) was preserved by increased NE-induced chronotropy.

Predictive value of presepsin and acylcarnitines for severity and biliary drainage in acute cholangitis

BACKGROUND

Bacteremia, which is a major cause of mortality in patients with acute cholangitis, induces hyperactive immune response and mitochondrial dysfunction. Presepsin is responsible for pathogen recognition by innate immunity. Acylcarnitines are established mitochondrial biomarkers.

AIM

To clarify the early predictive value of presepsin and acylcarnitines as biomarkers of severity of acute cholangitis and the need for biliary drainage.

METHODS

Of 280 patients with acute cholangitis were included and the severity was stratified according to the Tokyo Guidelines 2018. Blood presepsin and plasma acylcarnitines were tested at enrollment by chemiluminescent enzyme immunoassay and ultra-high-performance liquid chromatography-mass spectrometry, respectively.

RESULTS

The concentrations of presepsin, procalcitonin, short- and medium-chain acylcarnitines increased, while long-chain acylcarnitines decreased with the severity of acute cholangitis. The areas under the receiver operating characteristic curves (AUC) of presepsin for diagnosing moderate/severe and severe cholangitis (0.823 and 0.801, respectively) were greater than those of conventional markers. The combination of presepsin, direct bilirubin, alanine aminotransferase, temperature, and butyryl-L-carnitine showed good predictive ability for biliary drainage (AUC: 0.723). Presepsin, procalcitonin, acetyl-L-carnitine, hydroxydodecenoyl-L-carnitine, and temperature were independent predictors of bloodstream infection. After adjusting for severity classification, acetyl-L-carnitine was the only acylcarnitine independently associated with 28-d mortality (hazard ratio 14.396; P < 0.001) (AUC: 0.880). Presepsin concentration showed positive correlation with direct bilirubin or acetyl-L-carnitine.

CONCLUSION

Presepsin could serve as a specific biomarker to predict the severity of acute cholangitis and need for biliary drainage. Acetyl-L-carnitine is a potential prognostic factor for patients with acute cholangitis. Innate immune response was associated with mitochondrial metabolic dysfunction in acute cholangitis.

Parecoxib attenuates inflammation injury in septic H9c2 cells by regulating the MAPK signaling pathway

Parecoxib, a non-steroidal anti-inflammatory drug, has been reported to possess protective effects against sepsis. However, its detailed role and underlying mechanisms in septic cardiomyopathy remain unclear. Therefore, the goal of the present study was to clarify the function and to investigate the mechanisms of parecoxib in lipopolysaccharide (LPS)-treated H9c2 rat cardiomyocytes. TNF-α, IL-1β and IL-6 expression levels in parecoxib-treated H9c2 cells stimulated with LPS were assessed using ELISA. Parecoxib-treated H9c2 cells stimulated with LPS were tested for viability using the Cell Counting Kit-8 assay. Western blotting analysis and 5-ethynyl-2'-deoxyuridine were used to evaluate cell proliferation. Apoptosis was assessed using TUNEL and western blotting. To assess the protein expression of the MAPK signaling pathway, western blotting was performed. The data showed that parecoxib significantly and dose-dependently reduced the inflammatory responses of LPS-treated H9c2 cells. Parecoxib also significantly and dose-dependently increased the proliferation and inhibited the apoptosis of LPS-treated H9c2 cells. In addition, parecoxib significantly suppressed the activation of the MAPK (p38, JNK and ERK) signaling pathway. The current study indicated that parecoxib could be a viable therapeutic option for septic cardiomyopathy.

Mitochondrial Dysfunction in Intensive Care Unit-Acquired Weakness and Critical Illness Myopathy: A Narrative Review

Mitochondria are key structures providing most of the energy needed to maintain homeostasis. They are the main source of adenosine triphosphate (ATP), participate in glucose, lipid and amino acid metabolism, store calcium and are integral components in various intracellular signaling cascades. However, due to their crucial role in cellular integrity, mitochondrial damage and dysregulation in the context of critical illness can severely impair organ function, leading to energetic crisis and organ failure. Skeletal muscle tissue is rich in mitochondria and, therefore, particularly vulnerable to mitochondrial dysfunction. Intensive care unit-acquired weakness (ICUAW) and critical illness myopathy (CIM) are phenomena of generalized weakness and atrophying skeletal muscle wasting, including preferential myosin breakdown in critical illness, which has also been linked to mitochondrial failure. Hence, imbalanced mitochondrial dynamics, dysregulation of the respiratory chain complexes, alterations in gene expression, disturbed signal transduction as well as impaired nutrient utilization have been proposed as underlying mechanisms. This narrative review aims to highlight the current known molecular mechanisms immanent in mitochondrial dysfunction of patients suffering from ICUAW and CIM, as well as to discuss possible implications for muscle phenotype, function and therapeutic approaches.

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.

LncRNA-mRNA expression profile and functional network of vascular dysfunction in septic rats

BACKGROUND

We used microarrays to analyse the changes in long non-coding RNAs (lncRNAs) and mRNAs in aorta tissue in model rats with lipopolysaccharide-induced sepsis and determined the lncRNA-mRNA and lncRNA-miRNA-mRNA functional networks.

METHODS

Wistar rats were intraperitoneally injected with lipopolysaccharide, and the lncRNA and mRNA expression profiles in the aorta were evaluated using microarrays. The functions of the differentially expressed mRNAs were analysed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. We then constructed coding/non-coding co-expression and competing endogenous RNA networks to study the mechanisms related to sepsis in rats.

RESULTS

We identified 503 differentially expressed lncRNAs and 2479 differentially expressed mRNAs in the model rats with lipopolysaccharide-induced sepsis. Mitochondrial fission process 1 (MTFP1) was the most significantly down-regulated mRNA. Bioinformatics analysis showed that the significantly down-regulated mRNAs in the sepsis models were in pathways related to mitochondrial structure, function, and energy metabolism. Coding/non-coding co-expression and competing endogenous RNA analyses were conducted using 12 validated lncRNAs in combination with all mRNAs. The coding/non-coding co-expression analysis showed that the 12 validated lncRNAs were mainly regulatory factors for abnormal energy metabolism, including mitochondrial structure damage and aberrant mitochondrial dynamics. The competing endogenous RNA analysis revealed that the potential functions of these 12 lncRNAs might be related to the inflammatory response.

CONCLUSION

We determined the differentially expressed lncRNAs and mRNAs in the aorta of septic rats using microarrays. Further studies on these lncRNAs will help elucidate the mechanism of sepsis at the genetic level and may identify potential therapeutic targets.

Lipopolysaccharide sensitizes the therapeutic response of breast cancer to IAP antagonist

Inhibitor of apoptosis protein (IAP) is a class of E3 ubiquitin ligases functioning to support cancer survival and growth. Many small-molecule IAP antagonists have been developed, aiming to degrade IAP proteins to kill cancer. We have evaluated the effect of lipopolysaccharide (LPS), a component of the bacterial outer membrane, on IAP antagonists in treating breast cancer in a mouse model to guide future clinical trials. We show that LPS promotes IAP antagonist-induced regression of triple-negative breast cancer (TNBC) from MDA-MB-231 cells in immunodeficient mice. IAP antagonists such as SM-164, AT-406, and BV6, do not kill MDA-MB-231 cells alone, but allow LPS to induce cancer cell apoptosis rapidly. The apoptosis caused by LPS plus SM-164 is blocked by toll-like receptor 4 (TLR4) or MyD88 inhibitor, which inhibits LPS-induced TNFα production by the cancer cells. Consistent with this, MDA-MB-231 cell apoptosis induced by LPS plus SM-164 is also blocked by the TNF inhibitor. LPS alone does not kill MDA-MB-231 cells because it markedly increases the protein level of cIAP1/2, which is directly associated with and stabilized by MyD88, an adaptor protein of TLR4. ER⁺ MCF7 breast cancer cells expressing low levels of cIAP1/2 undergo apoptosis in response to SM-164 combined with TNFα but not with LPS. Furthermore, TNFα but not LPS alone inhibits MCF7 cell growth in vitro. Consistent with these, LPS combined with SM-164, but not either of them alone, causes regression of ER⁺ breast cancer from MCF7 cells in immunodeficient mice. In summary, LPS sensitizes the therapeutic response of both triple-negative and ER⁺ breast cancer to IAP antagonist therapy by inducing rapid apoptosis of the cancer cells through TLR4- and MyD88-mediated production of TNFα. We conclude that antibiotics that can reduce microbiota-derived LPS should not be used together with an IAP antagonist for cancer therapy.

Influence of Microbial Metabolites and Itaconic Acid Involved in Bacterial Inflammation on the Activity of Mitochondrial Enzymes and the Protective Role of Alkalization

Human microbiota produces metabolites that may enter the bloodstream and exert systemic influence on various functions including mitochondrial. Mitochondria are not only a target for microbial metabolites, but also themselves, due to the inhibition of several enzymes, produce metabolites involved in infectious processes and immune response. The influence of indolic acids, microbial derivatives of tryptophan, as well as itaconic acid, formed in the tricarboxylic acid cycle under the action of bacterial lipopolysaccharides, on the activity of mitochondrial enzymes was studied by methyl thiazolyl tetrazolium (MTT), dichlorophenolindophenol (DCPIP) and pyridine nucleotide fluorescence assays. Thus, it was found that indolic acids suppressed succinate and glutamate oxidation, shifting the redox potential of pyridine nucleotides to a more oxidized state. Itaconic acid, in addition to the well-known inhibition of succinate oxidation, also decreased NAD reduction in reactions with glutamate as a substrate. Unlike itaconic acid, indolic acids are not direct inhibitors of succinate dehydrogenase and glutamate dehydrogenase as their effects could be partially eliminated by the thiol antioxidant dithiothreitol (DTT) and the scavenger of lipid radicals butyl-hydroxytoluene (BHT). Alkalization turned out to be the most effective means to decrease the action of these metabolites, including itaconic acid, which is due to the protective influence on redox-dependent processes. Thus, among mitochondrial oxidative enzymes, the most accessible targets of these microbial-related metabolites are succinate dehydrogenase and glutamate dehydrogenase. These are important in the context of the shifting of metabolic pathways involved in bacterial inflammation and sepsis as well as the detection of new markers of these pathologies.

Effect of Dihydroquercetin on Energy Metabolism in LPS-Induced Inflammatory Mice

This study investigated the effects and alterations of dihydroquercetin on the growth performance, nutriment metabolism, antioxidant and immune function, and energy substrate utilization in lipopolysaccharide-challenged mice. A total of 0, 50, and 200 mg/kg of dihydroquercetin were intragastrically administered once a day for 21 days. After the pretreatment with dihydroquercetin, each group was subjected to a lipopolysaccharide challenge (except for the control group). After lipopolysaccharide injection, food intake, body weight, metabolic indexes of blood and liver nutrients, blood inflammatory factors, and liver oxidative stress indexes were measured at 6, 12, 24, and 48 h, respectively. Indirect calorimetry analysis was performed by respiratory gas analysis for 48 h to calculate the energy substrate metabolism of carbohydrate, fat, and protein. Urinary nitrogen excretion was measured to evaluate the urinary protein metabolism to calculate the substrate utilization. The results showed that dihydroquercetin pretreatment can significantly increase the weight gain and average food intake and decrease the mortality rate in lipopolysaccharide-induced inflammation mice. Furthermore, dihydroquercetin pretreatment can alleviate the negative effects of lipopolysaccharides by increasing levels of superoxide dismutase and glutathione peroxidase and by decreasing the malondialdehyde and serum inflammatory cytokines (interleukin-1β, nuclear factor κB, and interleukin-6). Dihydroquercetin pretreatment also can relieve nutrient metabolic disorder by increasing blood glucose, serum total protein, and liver glycogen levels and reducing serum and liver triglycerides, serum cholesterol, serum lactate dehydrogenase, and serum urea nitrogen levels. Meanwhile, it increases the relative utilization of carbohydrate, reducing relative utilization of protein and lipid, alleviating the change in energy metabolism pattern from glucose-predominant to lipid-predominant caused by lipopolysaccharide stimulation. In addition, the degree of metabolic pattern transformation depends on the dose of dihydroquercetin supplement. Finally, according to principal component analysis, we found that the inflammation was strongest in the mice at 24 h and was subsequently relieved in the LPS-stimulated group, whereas in the dihydroquercetin-pretreated group, the inflammation was initially relieved. To summarize, dihydroquercetin pretreatment can improve energy metabolism disorder and attenuate the negative effects of lipopolysaccharide challenge in mice from the initial stage of inflammation.

Pyruvate-Driven Oxidative Phosphorylation is Downregulated in Sepsis-Induced Cardiomyopathy: A Study of Mitochondrial Proteome

BACKGROUND

Sepsis-induced cardiomyopathy (SIC) is a major contributing factor for morbidity and mortality in sepsis. Accumulative evidence has suggested that cardiac mitochondrial oxidative phosphorylation is attenuated in sepsis, but the underlying molecular mechanisms remain incompletely understood.

METHODS

Adult male mice of 9 to 12 weeks old were subjected to sham or cecal ligation and puncture procedure. Echocardiography in vivo and Langendorff-perfused hearts were used to assess cardiac function 24 h after the procedures. Unbiased proteomics analysis was performed to profile mitochondrial proteins in the hearts of both sham and SIC mice. Seahorse respirator technology was used to evaluate oxygen consumption in purified mitochondria.

RESULTS

Of the 665 mitochondrial proteins identified in the proteomics assay, 35 were altered in septic mice. The mitochondrial remodeling involved various energy metabolism pathways including subunits of the electron transport chain, fatty acid catabolism, and carbohydrate oxidative metabolism. We also identified a significant increase of pyruvate dehydrogenase (PDH) kinase 4 (PDK4) and inhibition of PDH activity in septic hearts. Furthermore, compared to sham mice, mitochondrial oxygen consumption of septic mice was significantly reduced when pyruvate was provided as a substrate. However, it was unchanged when PDH was bypassed by directly supplying the Complex I substrate NADH, or by using the Complex II substrate succinate, or using Complex IV substrate, or by providing the beta-oxidation substrate palmitoylcarnitine, neither of which require PDH for mitochondrial oxygen consumption.

CONCLUSIONS

These data demonstrate a broad mitochondrial protein remodeling, PDH inactivation and impaired pyruvate-fueled oxidative phosphorylation during SIC, and provide a molecular framework for further exploration.

Orexins: A promising target to digestive cancers, inflammation, obesity and metabolism dysfunctions

Hypothalamic neuropeptides named hypocretin/orexins which were identified in 1998 regulate critical functions such as wakefulness in the central nervous system. These past 20 years had revealed that orexins/receptors system was also present in the peripheral nervous system where they participated to the regulation of multiple functions including blood pressure regulation, intestinal motility, hormone secretion, lipolyze and reproduction functions. Associated to these peripheral functions, it was found that orexins and their receptors were involved in various diseases such as acute/chronic inflammation, metabolic syndrome and cancers. The present review suggests that orexins or the orexin neural circuitry represent potential therapeutic targets for the treatment of multiple pathologies related to inflammation including intestinal bowel disease, multiple sclerosis and septic shock, obesity and digestive cancers.

Energetic dysfunction in sepsis: a narrative review

Background

Growing evidence associates organ dysfunction(s) with impaired metabolism in sepsis. Recent research has increased our understanding of the role of substrate utilization and mitochondrial dysfunction in the pathophysiology of sepsis-related organ dysfunction. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Main text

Sepsis is characterized by systemic and organ-specific changes in metabolism. Alterations of oxygen consumption, increased levels of circulating substrates, impaired glucose and lipid oxidation, and mitochondrial dysfunction are all associated with organ dysfunction and poor outcomes in both animal models and patients. The pathophysiological relevance of bioenergetics and metabolism in the specific examples of sepsis-related immunodeficiency, cerebral dysfunction, cardiomyopathy, acute kidney injury and diaphragmatic failure is also described.

Conclusions

Recent understandings in substrate utilization and mitochondrial dysfunction may pave the way for new diagnostic and therapeutic approaches. These findings could help physicians to identify distinct subgroups of sepsis and to develop personalized treatment strategies. Implications for their use as bioenergetic targets to identify metabolism- and mitochondria-targeted treatments need to be evaluated in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00893-7.

A 1H-NMR approach to myocardial energetics

Understanding the energetic state of the heart is essential for unraveling the central tenets of cardiac physiology. The heart uses a tremendous amount of energy and reductions in that energy supply can have lethal consequences. While ischemic events clearly result in significant metabolic perturbations, heart failure with both preserved and reduced ejection fraction display reductions in energetic status. To date, most cardiac energetics have been performed using ³¹P-NMR, which requires dedicated access to a specialized NMR spectrometer. This has limited the availability of this method to a handful of centers around the world. Here we present a method of assessing myocardial energetics in the isolated mouse heart using ¹H-NMR spectrometers that are widely available in NMR core facilities. In addition, this methodology provides information on many other important metabolites within the heart, including unique metabolic differences between the hypoxic and ischemic hearts. Furthermore, we demonstrate the correlation between myocardial energetics and measures of contractile function in the mouse heart. These methods will allow a broader examination of myocardial energetics providing a valuable tool to aid in the understanding of the nature of these energetic deficits and to develop therapies directed at improving myocardial energetics in failing hearts.

Non-thyroidal illness syndrome, the hidden player in the septic shock induced myocardial contractile depression

Septic shock causes high mortality in hospitalized patients, especially in those that develop myocardial dysfunction as an early complication. The myocardial dysfunction of septic shock is characterized by a decrease in ventricular relaxation (diastolic dysfunction) and reduced ventricular ejection fraction (systolic dysfunction). Most patients with septic shock have low serum thyroid hormone levels, a condition known as non-thyroidal illness syndrome. Thyroid hormones sustain myocardial contractility and energy metabolism. Septic shock non-thyroidal illness syndrome causes myocardial hypothyroidism, and hypothyroidism causes myocardial dysfunction that resembles the myocardial depression of septic shock. We hypothesize that the myocardial hypothyroidism that occurs during septic shock has a causal role in the pathogenesis of septic shock-induced myocardial dysfunction. Thyroid hormones regulate the calcium cycle, the phenotype of contractile proteins, adrenergic response, and fatty acid transport and oxidation in the cardiomyocytes. Therefore, the administration of levothyroxine and liothyronine to normalize thyroid hormones level within the myocardium will improve the myocardial function. The hypothesis will be tested in humans with septic shock by performing a prospective, randomized, placebo-controlled study to compare the effect of thyroid hormone administration with placebo on myocardial function. The proposed hypothesis challenges the idea that non-thyroidal illness syndrome is a beneficial response of the thyroid hormone axis to illness and that thyroid hormone replacement is detrimental. The administration of thyroid hormone in order to prevent and reverse myocardial hypothyroidism during septic shock is a new theoretical concept on thyroid hormone metabolism and action at the tissue level during non-thyroidal illness syndrome. If the hypothesis is correct, clinicians should consider cardiac hypothyroidism as a central player in myocardial dysfunction caused by sepsis. Thyroid hormone replacement should be incorporated into the armamentarium of septic shock treatment.