1H NMR-Based Metabolic Signatures in the Liver and Brain in a Rat Model of Hepatic Encephalopathy

1H NMR-Based Metabolomic Signatures in Rodent Models of Sporadic Alzheimer's Disease and Metabolic Disorders

Alzheimer's disease (AD) is a chronic neurological disorder that impacts the elderly population all over the globe. Evidence suggests association between AD and metabolic disorders such as diabetes mellitus (DM) and obesity (OB). The present study is an attempt to evaluate metabolic alterations in the serum and brain through NMR spectroscopy with the aim to identify shared metabolic signatures. AD was induced in rats by stereotactic intracerebroventricular injection of oligomerized Aβ-42 peptide into the brain. DM and OB were induced by intraperitoneal injection of streptozotocin and feeding rats on a high-fat diet, respectively. The metabolic alterations obtained through 1H NMR spectroscopy were further subjected to multivariate analysis by principal component analysis and partial least-squares discrimination for identification of metabolic signatures. In the serum, the levels of lactate and betaine were increased in AD, DM, and OB rats. On the other hand, the metabolite profile of brain indicated increase in the levels of lactate, N-acetylaspartate, and creatinine in AD, DM, and OB rats. Additionally, the concentration of neurochemicals such as glutamate, GABA, N-acetylglutamate, and myo-inositol were also elevated. The alterations in neurotransmitters and cerebral energy metabolism were accompanied by deficits in cognition assessed by Morris water maze in AD, DM, and OB rats. The perturbed metabolic profiles were accompanied by the presence of pathogenic amyloid deposits visualized by Congo red stain in the brains of AD, DM, and OB rats. Overall, the study identifies common metabolic signatures in AD, DM, and OB that may be involved in etiopathogenesis and also suggests linkages between these three conditions.

Intestinal Dysbacteriosis Contributes to Persistent Cognitive Impairment after Resolution of Acute Liver Failure

Regulating the gut microbiota alleviates hepatic encephalopathy (HE). Whether it is imperative to withhold treatment for microbial imbalance after liver functional recovery remains unclear. The aim of this work was to elucidate the alterations in cognitive behavior, liver function, synaptic transmission, and brain metabolites in acute liver failure (ALF) mice before and after hepatic function recovery. Towards this end, thioacetamide was injected intraperitoneally to establish an ALF mouse model, which induced HE. Hierarchical clustering analysis indicated that while the liver functions normalized, cognitive dysfunction and intestinal dysbacteriosis occurred in the ALF mice 14 days after thioacetamide injection. In addition, fecal microbiota transplantation from the ALF mice with liver function recovery induced liver injury and cognitive impairment. Alterations in synaptic transmission were found in the ALF mice with liver function improvement, and the correlations between the gut bacteria and synaptic transmission in the cortex were significant. Finally, apparent alterations in the brain metabolic profiles of the ALF mice were detected after liver function improvement by performing 1H nuclear magnetic resonance spectroscopy, suggesting a risk of HE. These results showed that intestinal dysbacteriosis in ALF mice with liver function recovery is sufficient to induce liver injury and cognitive impairment. This indicates that continuous care may be necessary for monitoring microbial imbalance even in patients with ALF-induced HE whose liver function has recovered significantly.

Ferrous sulfate reverses cerebral metabolic abnormality induced by minimal hepatic encephalopathy

Orally administered ferrous iron was previously reported to significantly improve the cognition and locomotion of patients with minimal hepatic encephalopathy (MHE). However, the metabolic mechanisms of the therapeutic effect of ferrous iron are unknown. In this study, MHE was induced in rats by partial portal vein ligation (PPVL), and was treated with ferrous sulfate. The Morris water maze was used to evaluate the cognitive condition of the rats. The metabolites observed by NMR and validated by liquid chromatography-mass spectrometry were defined as the key affected metabolites. The enzyme activities and trace element contents in the rat brains were also investigated. The Mn content was found to be increased but the ferrous iron content decreased in the cortex and striatum in MHE. Decreased oxoglutarate dehydrogenase activity and increased glutamine synthetase (GS) and pyruvate carboxylase (PC) activity were observed in the cortex of MHE rats. Decreased pyruvate dehydrogenase activity and increased GS and PC activity were observed in the striatum of MHE rats. The levels of BCAAs and taurine were significantly decreased, and the contents of GABA, lactate, arginine, aspartate, carnosine, citrulline, cysteine, glutamate, glutamine, glycine, methionine, ornithine, proline, threonine and tyrosine were significantly increased. These metabolic abnormalities described above were restored after treatment with ferrous sulfate. Pathway enrichment analysis suggested that urea cycle, aspartate metabolism, arginine and proline metabolism, glycine and serine metabolism, and glutamate metabolism were the major metabolic abnormalities in MHE rats, but these processes could be restored and cognitive impairment could be improved by ferrous sulfate administration.

Metabolomics in the understanding and management of hepatic encephalopathy

Metabolomics refers to the study of biological components below 1000 Daltons (Da) involved in metabolic pathways as substrates, products or effectors. According to the interconnected metabolic disturbances that have been described in the pathophysiology of hepatic encephalopathy (HE), this technique appears to be well adapted to study and better delineate the disease. This review will focus on recent advances in metabolomics in the field of HE. Thus, after a brief overview of the general principles of metabolomics, we will discuss metabolomics as a potentially efficient tool for unraveling new HE pathophysiological insights, biomarkers identification, or as a predicting tool for treatment response or outcome prognosis. Finally, we will give our vision on the prospects offered by metabolomics for improving care of HE patients.

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.