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Hepatic Encephalopathy (HE) is a debilitating neuropsychiatric complication associated with acute and chronic liver failure. It is characterized by diverse symptoms with variable severity that includes cognitive and motor deficits. The aim of the study is to assess metabolic alterations in brain and liver using nuclear magnetic resonance (NMR) spectroscopy and subsequent multivariate analyses to characterize metabolic signatures associated with HE. HE was developed by bile duct ligation (BDL) that resulted in hepatic dysfunctions and cirrhosis as shown by liver function tests. Metabolic profiles from control and BDL rats indicated increased levels of lactate, branched chain amino acids (BCAAs), glutamate and choline in liver, whereas levels of glucose, phenylalanine and pyridoxine were decreased. In case of brain, the levels of lactate, acetate, succinate, citrate and malate were increased, while glucose, creatine, isoleucine, leucine and proline levels were decreased.Furthermore, neurotransmitters such as glutamate and GABA were increased, whereas choline and myo-inositol were decreased. The alterations in neurotransmitter levels resulted in cognitive and motor defects in BDL rats. A significant correlation was found between alterations in NAA/choline, choline/creatine and NAA/creatine with behavioural deficits.Thus, the data suggests impairment in metabolic pathways such as tricarboxylic acid (TCA) cycle, glycolysis and ketogenesis in liver and brain of animals with HE. The study highlights that metabolic signatures could be potential marker to monitor HE progression and to assess therapeutic interventions.

Parkinson’s disease is a multiplexed disease involving diverse symptoms and progression rate. Heterogenous diseases need an efficient animal model to enhance the understanding of the underlying mechanism. MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), a neurotoxin, has been widely used to replicate the pathophysiology of PD in rodents, but its effect on energy metabolic perturbation is limited. Moreover, susceptibility to different dosage regime of MPTP varies among mice strains. Thus, herein the present study compares the effect of acute and sub-acute MPTP dosage regimes on mitochondrial functions in terms of mitochondrial respiratory chain enzymes, mitochondrial swelling and membrane potential in C57BL/6 and Balb/c mice. In addition, activities of enzymes involved in energy metabolic pathways were also studied along with behaviour and neurochemical alterations. The results showed that acute dose of MPTP in C57BL/6 mice had more profound effect on the enzyme activities of electron transport chain complexes. Further, the activity of MAO-A and MAO-B was increased following acute and sub-acute MPTP administration in C57BL/6 mice. However, no significant change was observed in Balb/c strain. Acute MPTP treatment resulted in decreased mitochondrial membrane potential along with swelling of mitochondria in C57BL/6 mice. In addition, perturbations were observed in hexokinase and pyruvate dehydrogenase of glycolysis pathway and citrate synthase, aconitase, isocitrate dehydrogenase and fumarase of TCA cycle. Moreover, acute MPTP led to pronounced depletion in neostriatal dopamine levels in C57BL/6 than in Balb/c mice. Behavioral tests such as open field, Narrow beam walk test and footprint test showed that locomotor activity was drastically reduced as an acute effect of MPTP in C57BL/6 mice strain. Therefore, these results consistently showed that acute MPTP treatment in C57BL/6 strain had severe mitochondrial dysfunctions, perturbed energy metabolic pathways, altered neurotransmission and motor defects as compared to Balb/c strain. Thus, the findings suggest that the dose and strain of mice need to consider for pre-clinical studies targeting mitochondrial dysfunctions in MPTP-induced Parkinson’s disease model.

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