Hepatic gluconeogenesis and Krebs cycle fluxes in a CCl4 model of acute liver failure

IDH1/MDH1 deacetylation promotes acute liver failure by regulating NETosis

BACKGROUND

Acute liver failure (ALF) is a life-threatening disease, but its pathogenesis is not fully understood. NETosis is a novel mode of cell death. Although the formation of neutrophil extracellular traps (NETs) has been found in various liver diseases, the specific mechanism by which NETosis regulates the development of ALF is unclear. In this article, we explore the role and mechanism of NETosis in the pathogenesis of ALF.

METHODS

Clinically, we evaluated NETs-related markers in the liver and peripheral neutrophils of patients with ALF. In in vitro experiments, HL-60 cells were first induced to differentiate into neutrophil-like cells (dHL-60 cells) with dimethyl sulfoxide (DMSO). NETs were formed by inducing dHL-60 cells with PMA. In in vivo experiments, the ALF model in mice was established with LPS/D-gal, and the release of NETs was detected by immunofluorescence staining and western blotting. Finally, the acetylation levels of IDH1 and MDH1 were detected in dHL-60 cells and liver samples by immunoprecipitation.

RESULTS

Clinically, increased release of NETs in liver tissue was observed in patients with ALF, and NETs formation was detected in neutrophils from patients with liver failure. In dHL-60 cells, mutations at IDH1-K93 and MDH1-K118 deacetylate IDH1 and MDH1, which promotes the formation of NETs. In a mouse model of ALF, deacetylation of IDH1 and MDH1 resulted in NETosis and promoted the progression of acute liver failure.

CONCLUSIONS

Deacetylation of IDH1 and MDH1 reduces their activity and promotes the formation of NETs. This change aggravates the progression of acute liver failure.

Mahuang Decoction Antagonizes Acute Liver Failure via Modulating Tricarboxylic Acid Cycle and Amino Acids Metabolism

Acute liver failure (ALF) is a serious clinical disorder with high fatality rates. Mahuang decoction (MHD), a well-known traditional Chinese medicine, has multiple pharmacological effects, such as anti-inflammation, anti-allergy, anti-asthma, and anti-hyperglycemia. In this study, we investigated the protective effect of MHD against ALF. In the lipopolysaccharide and D-galactosamine (LPS/D-GalN)-induced ALF mouse model, the elevated activities of the serum alanine and aspartate transaminases as well as the liver pathological damage were markedly alleviated by MHD. Subsequently, a metabolomics study based on the ultrahigh performance liquid chromatograph coupled with Q Exactive Orbitrap mass spectrometry was carried to clarify the therapeutic mechanisms of MHD against ALF. A total of 36 metabolites contributing to LPS/D-GalN-induced ALF were identified in the serum samples, among which the abnormalities of 27 metabolites were ameliorated by MHD. The analysis of metabolic pathways revealed that the therapeutic effects of MHD are likely due to the modulation of the metabolic disorders of tricarboxylic acid (TCA) cycle, retinol metabolism, tryptophan metabolism, arginine and proline metabolism, nicotinate and nicotinamide metabolism, phenylalanine metabolism, phenylalanine, tyrosine and tryptophan synthesis, as well as cysteine and methionine metabolism. This study demonstrated for the first time that MHD exerted an obvious protective effect against ALF mainly through the regulation of TCA cycle and amino acid metabolism, highlighting the importance of metabolomics to investigate the drug-targeted metabolic pathways.

Dietary supplementation of Pleurotus tuber regium in rat feed ameliorates metabolic and hematotoxicity induced by carbon tetrachloride

Pleurotus tuber regium, a wild edible mushroom can reduce free radical-mediated injury and oxidative stress induced by carbon tetrachloride (CCl4) via improvement of antioxidant capacity. This work evaluates the protective effects of this mushroom against the metabolic and hematological toxicity induced by CCl4. Sixty male Sprague Dawley rats were divided into six groups (n = 10). Group I received olive oil (3 mL/kg) i.p. twice weekly for 13 weeks, while maintaining free access to food and water ad libitum (negative control). Group II received 3 mL/kg (30% CCl4 in olive oil) injected i.p. twice weekly, while Groups III, IV, and V received 100, 200, and 500 mg wild edible P. tuber regium (33.3% in feed) daily in addition to 3 mL/kg CCl4 in olive oil injected twice weekly i.p. Group VI received olive oil (3 mL/kg) i.p. twice weekly for 13 weeks in addition to 500 mg P. tuber regium (33.3% in feed) daily. The body weight (b.w.), feed intake (FI), and water intake (WI) were obtained weekly, while the hematological indices and oxidative stress parameters were carried out shortly after necropsy on days 30, 60, and 90. Treatment with CCl4 significantly (p < 0.05) decreased the b.w., FI and WI, feed efficiency, ascorbic acid, α-tocopherol, and antioxidant enzymes, superoxide dismutase, catalase, total glutathione, and peroxidase, while increasing the oxidative stress as measured by malondialdehyde in CCl4 only group when compared with control. Supplementation of feed with P. tuber regium reversed the effects of CCl4. Pleurotus tuber regium ameliorated the CCl4-induced metabolic and hematotoxicity by improving the antioxidant capacity.

Salivary gland metabolism in an animal model of chronic kidney disease

OBJECTIVE

The aim of this study was to determine the effects of experimental CKD into the metabolism of parotid and submandibular glands of rats. CKD was induced by 5/6 nephrectomy.

DESIGN

Serum analyses of BUN (Blood Urea Nitrogen) and creatinine concentrations were performed. Major salivary glands metabolism was investigated in vivo, both at rest and during salivary stimulation conditions by NMR isotopomer analysis, using [U-¹³C]glucose as metabolic tracer.

RESULTS

CKD increases BUN and serum creatinine concentrations (p < 0.001). Multiple metabolic alterations were detected in the parotid glands of this animal model, including decreased concentrations of alanine (p < 0.05) and creatine (p < 0.05) and increased lactate/alanine ratios (p < 0.05). The salivary stimulus fostered accumulations of acetate at both analyzed glands of the CKD model (p < 0.05), indicative of disruption of the oxidative metabolic process.

CONCLUSIONS

Experimental CKD induced by 5/6 nephrectomy altered the parotid salivary gland function, since glucose metabolism is clearly affected after stimulation for salivation in this gland.

Inter-relations between 3-hydroxypropionate and propionate metabolism in rat liver: relevance to disorders of propionyl-CoA metabolism

Propionate, 3-hydroxypropionate (3HP), methylcitrate, related compounds, and ammonium accumulate in body fluids of patients with disorders of propionyl-CoA metabolism, such as propionic acidemia. Although liver transplantation alleviates hyperammonemia, high concentrations of propionate, 3HP, and methylcitrate persist in body fluids. We hypothesized that conserved metabolic perturbations occurring in transplanted patients result from the simultaneous presence of propionate and 3HP in body fluids. We investigated the inter-relations of propionate and 3HP metabolism in perfused livers from normal rats using metabolomic and stable isotopic technologies. In the presence of propionate, 3HP, or both, we observed the following metabolic perturbations. First, the citric acid cycle (CAC) is overloaded but does not provide sufficient reducing equivalents to the respiratory chain to maintain the homeostasis of adenine nucleotides. Second, there is major CoA trapping in the propionyl-CoA pathway and a tripling of liver total CoA within 1 h. Third, liver proteolysis is stimulated. Fourth, propionate inhibits the conversion of 3HP to acetyl-CoA and its oxidation in the CAC. Fifth, some propionate and some 3HP are converted to nephrotoxic maleate by different processes. Our data have implications for the clinical management of propionic acidemia. They also emphasize the perturbations of the liver intermediary metabolism induced by supraphysiological, i.e., millimolar, concentrations of labeled propionate used to trace the intermediary metabolism, in particular, inhibition of CAC flux and major decreases in the [ATP]/[ADP] and [ATP]/[AMP] ratios.

Impaired gluconeogenesis in a porcine model of paracetamol induced acute liver failure

AIM: To investigate glucose homeostasis and in particular gluconeogenesis in a large animal model of acute liver failure (ALF).

METHODS: Six pigs with paracetamol induced ALF under general anaesthesia were studied over 25 h. Plasma samples were withdrawn every five hours from a central vein. Three animals were used as controls and were maintained under anaesthesia only. Using ¹H NMR spectroscopy we identified most gluconeogenic amino acids along with lactate and pyruvate in the animal plasma samples.

RESULTS: No significant changes were observed in the concentrations of the amino acids studied in the animals maintained under anaesthesia only. If we look at the ALF animals, we observed a statistically significant rise of lactate (P < 0.003) and pyruvate (P < 0.018) at the end of the experiments. We also observed statistically significant rises in the concentrations of alanine (P < 0.002), glycine (P < 0.005), threonine (P < 0.048), tyrosine (P < 0.000), phenylalanine (P < 0.000) and isoleucine (P < 0.01). Valine levels decreased significantly (P < 0.05).

CONCLUSION: Our pig model of ALF is characterized by an altered gluconeogenetic capacity, an impaired tricarboxylic acid (TCA) cycle and a glycolytic state.

A biochemical prognostic model of outcome in paracetamol-induced acute liver injury

BACKGROUND

The aim of this study was to develop a prognostic model of outcome for patients with paracetamol induced acute liver injury based on admission parameters

METHODS

We used a cohort of 97 patients admitted to the Scottish Liver Transplant Unit between 1997 and 1998 to identify biochemical prognostic markers of outcome and thus create a prognostic model. Blood samples were taken on admission for analysis. The model was subsequently validated by testing it on a second cohort of 86 patients admitted between 1999 and 2000.

RESULTS

The following were identified as independent variables of poor prognosis (death/ transplant); phenylalanine, pyruvate, alanine, acetate, calcium, haemoglobin and lactate. A prognostic model was then constructed by stepwise forward logistic regression analysis: (400xPyruvate mmols/L)+(50xPhenylalanine (mmols/L)-(4 x Hemoglobin (g/dL). A value of <16 had an accuracy of 93% in predicting death correctly. When applied to the validation cohort this model had a positive predictive value of 91%, a negative predictive value of 94%, a sensitivity of 91%, and a specificity of 94%. On the same population overall, the positive and negative predictive value of the King's criteria were 94% and 93% respectively, whereas their sensitivity and specificity were 88% and 96% respectively.

CONCLUSIONS

Using admission characteristics our model is able to identify patients who die from paracetamol overdose fulminant hepatic failure as accurately as King's College criteria, but at a much earlier stage in their condition.

Metabolic engineering: advances in modeling and intervention in health and disease

The field of metabolic engineering encompasses a powerful set of tools that can be divided into (a) methods to model complex metabolic pathways and (b) techniques to manipulate these pathways for a desired metabolic outcome. These tools have recently seen increased utility in the medical arena, and this paper aims to review significant accomplishments made using these approaches. The modeling of metabolic pathways has been applied to better understand disease-state physiology in a variety of cellar, subcellular, and organ systems, including the liver, heart, mitochondria, and cancerous cells. Metabolic pathway engineering has been used to generate cells with novel biochemical functions for therapeutic use, and specific examples are provided in the areas of glycosylation engineering and dopamine-replacement therapy. In order to document the potential of applying both metabolic modeling and pathway manipulation, we describe pertinent advances in the field of diabetes research. Undoubtedly, as the field of metabolic engineering matures and is applied to a wider array of problems, new advances and therapeutic strategies will follow.

Measuring in-vivo metabolism using nuclear magnetic resonance

PURPOSE OF REVIEW

This review introduces physiologists and clinical investigators to an ever-widening array of nuclear magnetic resonance applications. In particular, it highlights a multiple tracer technique that provides a comprehensive picture of metabolic processes within human liver.

RECENT FINDINGS

Magnetic resonance spectroscopy is an important technique for studying metabolism in the brain, liver, heart and skeletal muscle. One fundamental advantage is that the studies are inherently noninvasive, so time-dependent information can be obtained. For example, 31P nuclear magnetic resonance investigations indicate that greater maximal oxygen uptake and oxidative capacity in trained athletes can be partially attributed to adaptations enhancing the rates at which phosphocreatine and inorganic phosphate recover during stress. In-vivo measurements of lipids and glycogen by 1H and 13C spectroscopy demonstrate that accumulation of intracellular lipids and impaired rates of glycogen synthesis contribute to insulin resistance and type 2 diabetes mellitus. Similar techniques can be used to analyze blood and urine samples obtained during administration of 2H or 13C tracers to yield information that cannot be easily obtained by mass spectrometry. Additional information available from nuclear magnetic resonance yields a comprehensive picture of liver metabolic pathways from a single clinical study.

SUMMARY

A variety of magnetic resonance spectroscopy protocols have been validated and exploited for clinical studies, but relatively few investigators are comfortable with technical aspects of these protocols and utilize them for clinical research. Increased interaction between spectroscopists and other investigators is needed if the potential of nuclear magnetic resonance for studying in-vivo metabolism is to be fully realized.