Hyperhomocysteinemia induced by methionine dietary nutritional overload modulates acetylcholinesterase activity in the rat brain Dragan Hrnc ˇic ´ • Aleksandra Ras ˇic ´ -Markovic ´ • Tihomir Stojkovic ´ • Milica Velimirovic ´ • Nela Pus ˇkas ˇ • Radmila Obrenovic ´ • Djuro Macut • Veselinka S ˇ us ˇic ´ • Vladimir Jakovljevic ´ • Dragan Djuric • Natas ˇa Petronijevic ´ • Olivera Stanojlovic ´ Received: 25 February 2014 / Accepted: 11 July 2014 / Published online: 23 July 2014 Ó Springer Science+Business Media New York 2014 Abstract Methionine is the only endogenous precursor of homocysteine, sulfur—containing amino acid and well known as risk factor for various brain disorders. Acetyl- cholinesterase is a serine protease that rapidly hydrolyzes neurotransmitter acetylcholine. It is widely distributed in different brain regions. The aim of this study was to eluci- date the effects of methionine nutritional overload on ace- tylcholinesterase activity in the rat brain. Males of Wistar rats were randomly divided into control and experimental group, fed from 30th to 60th postnatal day with standard or methionine-enriched diet (double content comparing to standard, 7.7 g/kg), respectively. On the 61st postnatal day, total homocysteine concentration was determined and showed that animals fed with methionine-enriched diet had significantly higher serum total homocysteine concentra- tions comparing to control rats (p \ 0.01). Acetylcholines- terase activity has been determined spectrophotometrically in homogenates of the cerebral cortex, hippocampus, thal- amus, and nc. caudatus. Acetylcholinesterase activity showed tendency to decrease in all examined brain struc- tures in experimental comparing to control rats, while sta- tistical significance of this reduction was achieved in the cerebral cortex (p \ 0.05). Brain slices were stained with haematoxylin and eosin (H&E) and observed under light microscopy. Histological analysis of H&E-stained brain slices showed that there were no changes in the brain tissue of rats which were on methionine-enriched diet compared to control rats. Results of this study showed selective vulner- ability of different brain regions on reduction of acetyl- cholinesterase activity induced by methionine-enriched diet and consecutive hyperhomocysteinemia. Keywords Methionine Á Homocysteine Á Acetylcholinesterase Á Brain Á Rats Introduction Together with cysteine, homocysteine, and taurine, methi- onine belongs to a group of sulfur-containing amino acids. Among other roles, it should be point out that methionine is (a) crucial for a variety of methyltransferase reactions as a precursor of S-adenosyl-methionine (SAM), a main methyl donor in mammals [1, 2] and (b) is a precursor in biosynthesis of homocysteine, non-protein thiol-containing amino acid [3]. Metabolic relation of methionine—homocysteine is of particular importance, since homocysteine could not be obtained from diet [2]. D. Hrnc ˇic ´ Á A. Ras ˇic ´ -Markovic ´ Á D. Djuric Á O. Stanojlovic ´(&) Institute of Medical Physiology ‘‘Richard Burian’’, Belgrade University Faculty of Medicine, Vis ˇegradska 26/II, 11000 Belgrade, Serbia e-mail: solja@afrodita.rcub.bg.ac.rs T. Stojkovic ´ Á M. Velimirovic ´ Á N. Petronijevic ´ Institute of Clinical and Medical Biochemistry, Belgrade University Faculty of Medicine, Belgrade, Serbia N. Pus ˇkas ˇ Institute of Histology and Embryology ‘‘Aleksandar Dj. Kostic’’, Belgrade University Faculty of Medicine, Belgrade, Serbia R. Obrenovic ´ Á D. Macut CCS, Faculty of Medicine, University of Belgrade, Belgrade, Serbia V. S ˇ us ˇic ´ Serbian Academy of Sciences and Arts, Belgrade, Serbia V. Jakovljevic ´ Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia 123 Mol Cell Biochem (2014) 396:99–105 DOI 10.1007/s11010-014-2146-8