The effect of aspartame metabolites on human erythrocyte membrane acetylcholinesterase activity

Department of Experimental Physiology, Medical School, University of Athens, Greece.
Pharmacological Research (Impact Factor: 4.41). 02/2006; 53(1):1-5. DOI: 10.1016/j.phrs.2005.07.006
Source: PubMed


Studies have implicated aspartame (ASP) with neurological problems. The aim of this study was to evaluate acetylcholinesterase (AChE) activity in human erythrocyte membranes after incubation with the sum of ASP metabolites, phenylalanine (Phe), methanol (met) and aspartic acid (aspt), or with each one separately. Erythrocyte membranes were obtained from 12 healthy individuals and were incubated with ASP hydrolysis products for 1 h at 37 degrees C. AChE was measured spectrophotometrically. Incubation of membranes with ASP metabolites corresponding with 34 mg/kg, 150 mg/kg or 200 mg/kg of ASP consumption resulted in an enzyme activity reduction by -33%, -41%, and -57%, respectively. Met concentrations 0.14 mM, 0.60 mM, and 0.80 mM decreased the enzyme activity by -20%, -32% or -40%, respectively. Aspt concentrations 2.80 mM, 7.60 mM or 10.0 mM inhibited membrane AChE activity by -20%, -35%, and -47%, respectively. Phe concentrations 0.14 mM, 0.35 mM or 0.50mM reduced the enzyme activity by -11%, -33%, and -35%, respectively. Aspt or Phe concentrations 0.82 mM or 0.07 mM, respectively, did not alter the membrane AChE activity. It is concluded that low concentrations of ASP metabolites had no effect on the membrane enzyme activity, whereas high or toxic concentrations partially or remarkably decreased the membrane AChE activity, respectively. Additionally, neurological symptoms, including learning and memory processes, may be related to the high or toxic concentrations of the sweetener metabolites.

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    • "The erythrocytes were separated from plasma by bench centrifugation for 10 min. The harvested erythrocytes were washed by methods of Tsakiris et al.,[25] as described by Chikezie et al.,[26]. Within 2 h of collection of blood specimen, 1.0 mL of harvested erythrocyte was introduced into centrifuge test tubes containing 3.0 mL of buffer solution pH = 7.4: 250 mM tris (hydroxyl methyl) amino ethane–HCl (Tris–HCl)/140 mM NaCl/1.0 mM MgCl2/10 mM glucose). "
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    ABSTRACT: Background The present study sought to investigate erythrocyte glutathione S-transferases (GST), NADH-Methaemoglobin reductase (NADH-MR) and Na+/K+-ATPase activities of hypoglycemic rats treated with ethanol/water (1:2 v/v) extract of A. sativa as agent of glycemic control. Methods Hyperglycemia was induced by a single intra-peritoneal injection of 0.1 mol/L alloxan monohydrate in phosphate buffer saline (PBS) solution (pH = 7.4); dosage = 140 mg/kg. At the end of the experimental time (t = 76 h), erythrocyte GST, NADH-MR and Na+/K+-ATPase activities as well as serum fasting blood sugar (FBS) levels were measured by spectrophotometric methods. Results Serum FBS levels of control/normal (C/N) rats ranged between 72.93 ± 0.82–95.12 ± 0.92 mg/dL, whereas experimental rats without glycemic control gave: 249.41 ± 1.03–256.11 ± 1.23 mg/dL. Hyperglycemic rats treated with ethanol/water (1:2 v/v) extract of A. sativa exhibited comparative reduced serum levels of FBS alongside with erythrocyte GST, NADH-MR and Na+/K+-ATPase activities. The average relative activities of the three enzymes and corresponding order of enzyme activity in hyperglycemic rats treated with ethanol/water (1:2 v/v) extract of A. sativa was: NADH-MR = 60.99% > GST = 47.81% > Na+/K+-ATPase = 46.81%. In the same order, relative activities of the three enzymes in rats without glycemic control were: NADH-MR = 49.65% > GST = 23.69% > Na+/K+-ATPase = 17.02%. Conclusion Erythrocyte GST, NADH-MR and Na+/K+-ATPase activities gave insights into the pathophysiology of diabetic state and served as biomarkers for ascertaining therapeutic control in Type 1 diabetes mellitus.
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    • "In mice, aspartame has been reported to increase norepinephrine in several brain regions (Coulombe and Sharma 1986). In vitro, high concentrations of aspartame metabolites decreased erythrocyte membrane and hippocampal acetylcholinesterase activity (Tsakiris et al. 2006; Simintzi et al. 2007). Bacterial lipopolysaccharide (LPS) is a model widely used in experimental animals to study the effect of peripheral inflammatory stimuli on brain functions. "
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    ABSTRACT: This study aimed at investigating the effect of the sweetener aspartame on oxidative stress and brain monoamines in normal circumstances and after intraperitoneal (i.p.) administration of lipopolysaccharide (LPS; 100 μg/kg) in mice. Aspartame (0.625-45 mg/kg) was given via subcutaneous route at the time of endotoxin administration. Mice were euthanized 4 h later. Reduced glutathione (GSH), lipid peroxidation (thiobarbituric acid-reactive substances; TBARS), and nitrite concentrations were measured in brain and liver. Tumor necrosis factor-alpha (TNF-α) and glucose were determined in brain. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured in liver. The administration of only aspartame (22.5 and 45 mg/kg) increased brain TBARS by 17.7-32.8%, decreased GSH by 25.6-31.6%, and increased TNF-α by 16.7-44%. Aspartame caused dose-dependent inhibition of brain serotonin, noradrenaline, and dopamine. Aspartame did not alter liver TBARS, nitrite, GSH, AST, ALT, or ALP. The administration of LPS increased nitrite in brain and liver by 26.8 and 37.1%, respectively; decreased GSH in brain and liver by 21.6 and 31.1%, respectively; increased brain TNF-α by 340.4%, and glucose by 39.9%, and caused marked increase in brain monoamines. LPS increased AST, ALT, and ALP in liver tissue by 84.4, 173.7, and 258.9%, respectively. Aspartame given to LPS-treated mice at 11.25 and 22.5 mg/kg increased brain TBARS by 15.5-16.9%, nitrite by 12.6-20.1%, and mitigated the increase in monoamines. Aspartame did not alter liver TBARS, nitrite, GSH, ALT, AST, or ALP. Thus, the administration of aspartame alone or in the presence of mild systemic inflammatory response increases oxidative stress and inflammation in the brain, but not in the liver.
    No preview · Article · Aug 2011 · Neurotoxicity Research
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    • "This study was in accordance with the ethical principles that have their origins in the Declaration of Helsinki. The erythrocytes were washed by centrifugation methods as described by Tsakiris et al. (2005). Within 2 h of collection of blood samples, portions of 2.0 ml of the samples were introduced into centrifuge test tubes containing 4.0 ml of buffer solution pH = 7.4: 250 mM tris (hydroxyl methyl) amino ethane–HCl(Tris-HCl)/ 140 mM, NaCl/ 1.0 mM and MgCl2/ 10 mM glucose). "
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    Full-text · Article · May 2011
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