Metabolomic study of altered energy metabolism during global forebrain ischemia and ischemic precoditioning in blood plasma in homocysteine treated rats

Abstract

Elevated homocysteine (Hcy) level is a well known risk factor for cardiovascular and neuropsychiatric diseases. In this study, we investigated metabolic changes in blood plasma in Hcy-treated rats. In combination with Hcy injections to induce hyperhomocysteinemia-like state, we used an animal model of global cerebral ischemia to investigate metabolic changes after 24 h reperfusion in rats. We also focused on the endogenous phenomenon known as ischemic tolerance induced by the preischemic treatment. The experiments were carried out on blood plasma samples as they are easily available and metabolically reflect the overall changes in injured organism. We observed significant changes in plasma metabolite levels of: pyruvate, citrate, acetate implicating alterations in energy metabolism, and increase in triacylglycerols, arginine and lysine, in Hcy-treated rats compared with naive animals. Ischemic insult with 24 reperfusion in Hcy-treated rats led to increase in plasma lactate, and decrease in plasma glucose, pyruvate, citrate and acetate. Complementary, an increase in ketone body 3-hydroxybutyrate was observed. The plasma metabolites: alanine, lactate, valine, glucose, leucine, isoleucine, acetate, citrate and 3-hydroxybutyrate were considered to reflect the response induced by ischemic preconditioning in Hcy rats, where the extent of postischemic damage was not as high as in the non-preconditioned rats. Our results provide evidence that nuclear magnetic resonance (NMR) spectra analysis can identify a specific group of metabolites present in plasma with the capability of discriminating between individual groups of animals. Regarding the effect of elevated Hcy level on plasma metabolome, we showed, that acetate, pyruvate and glucose had the excellent discriminatory power between Hcy-treated and naive rats plasma. Concerning ischemic insult in Hcy-treated animals, we also document the ideal discrimination of ischemic from non-ischemic rats by various groups of metabolites, that can be considered as a potential plasma biomarkers.