205588760-aspartam

Effect of chronic exposure to aspartame on oxidative stress in the

ASHOK IYYASWAMY and SHEELADEVI RATHINASAMY*Department of Physiology, Dr. ALM PG Institute of Basic Medical Sciences,University of Madras, Sekkizhar campus, Taramani, Chennai 600 113, India

*Corresponding author (Fax, +91-44-24540709; Email, [email protected])

This study was aimed at investigating the chronic effect of the artificial sweetener aspartame on oxidative stress inbrain regions of Wistar strain albino rats. Many controversial reports are available on the use of aspartame as itreleases methanol as one of its metabolite during metabolism. The present study proposed to investigate whetherchronic aspartame (75 mg/kg) administration could release methanol and induce oxidative stress in the rat brain. Tomimic the human methanol metabolism, methotrexate (MTX)-treated rats were included to study the aspartameeffects. Wistar strain male albino rats were administered with aspartame orally and studied along with controls andMTX-treated controls. The blood methanol level was estimated, the animal was sacrificed and the free radical changeswere observed in brain discrete regions by assessing the scavenging enzymes, reduced glutathione, lipid peroxidation(LPO) and protein thiol levels. It was observed that there was a significant increase in LPO levels, superoxidedismutase (SOD) activity, GPx levels and CAT activity with a significant decrease in GSH and protein thiol.Moreover, the increases in some of these enzymes were region specific. Chronic exposure of aspartame resulted indetectable methanol in blood. Methanol per se and its metabolites may be responsible for the generation of oxidativestress in brain regions.

[Iyyaswamy A and Rathinasamy S 2012 Effect of chronic exposure to aspartame on oxidative stress in the brain of albino rats. J. Biosci.37 679–688] DOI 10.1007/s12038-012-9236-0

1. Introduction

Aspartame (L-aspartyl-L-phenylalanine methyl ester), a low-calorie sweetener, is about 180 times sweeter than normalsugar and is used in over 5000 foods and beverages intoday’s market. The use of aspartame by diabetic individualsis increasing; it is widely used in the weight loss regime, andapproximately 200 million people consume aspartameworldwide (Shapiro 1988). In 1965 aspartame was discov-ered by James Schlatter of the G.D. Searle Company(Garriga and Metcalfe 1988). Aspartame has a biologicaleffect even at the recommended daily dose (Gombos et al.2007). Approximately 50% of the aspartame molecule isphenylalanine, 40% is aspartic acid and 10% is methanol(Newsome 1986). Aspartic acid is a metabolite of aspartamethat is an excitatory amino acid and is normally found inhigh levels in the brain. These levels are controlled by the

blood–brain barrier, which protects the brain from largefluctuations in plasma aspartate (Maher and Wurtman1987). Phenylalanine is an amino acid essential to the pro-duction of monoamines in the brain and is found in nearly allprotein foods (Fernstrom et al. 1983). On the other hand, dueto the high levels of phenylalanine in blood, consumption ofaspartame may cause brain damage (Haschemeyer andHaschemeyer 1973). Certain brain amino acid levels havebeen shown to be increased after aspartame consumption(Dailey et al. 1991; Diomede et al. 1991; Yokogoshi et al.1984). Although methanol is released during aspartame di-gestion, it only accounts for 10% of the aspartame molecule(Stegink et al. 1983), and among the metabolites, methanolis a toxicant that causes systemic toxicity (Kruse 1992).

Various neurochemical effects due to aspartame con-sumption have been reported (Coulombe and Sharma 1986;Pan-Hou et al. 1990; Goerss et al. 2000). Their adverse

http://www.ias.ac.in/jbiosci J. Biosci. 37(4), September 2012, 679–688, * Indian Academy of Sciences 679

Keywords. Aspartame; blood methanol; oxidative stress; rat folate-deficient model; free radical

Published online: 3 August 2012

brain of albino rats

neurological effects include headache (Johns 1986), insom-nia and seizures after ingestion of aspartame, which are alsoaccompanied by the alterations in regional concentrations ofcatecholamine (Coulombe and Sharma 1986). Previous find-ing have shown that aspartate may lead to neurotoxicitythrough sustained contact with the receptors, such as gluta-mate producing an excitotoxic effect (Olney et al. 1980).Large doses of both aspartame as well as these individualmetabolites have been tested in humans and other animals,with controversial reports. It has been reported that not onlythe metabolites of methanol, but methanol per se as well, istoxic to the brain (Jeganathan and Namasivayam 1998). Theprimary metabolic fate of methanol is the direct oxidation toformaldehyde and then into formate. The toxic effects ofmethanol in humans are due to the accumulation of itsmetabolite formate (Tephly and McMartin 1984; Tephly1991). The severity of clinical findings in methanol intoxi-cation correlated better with formate levels (Osterloh et al.1986). Formate is metabolized twice as fast in rat as inmonkey (McMartin et al. 1978). The metabolism of formateis mediated through a tetra-hydro-folate-dependent pathway(Eells et al. 1982). Humans and non-human primates areuniquely sensitive to methanol poisoning because of theirlow liver folate content (Johlin et al. 1987). There are pro-found differences in the rate of formate oxidation in differentspecies which determine their sensitivity to methanol(Mcmartin et al. 1978; Eells et al. 1983). In non-humanprimates and humans, alcohol dehydrogenase mediates thisreaction (Makar et al. 1990). In rats and other non-primatespecies, this reaction is mediated by catalase. Microsomaloxidizing system is reported to be responsible for free radicalgeneration. In addition to that, inhibition of cytochromeoxidase by formate leads to the generation of superoxide,peroxyl and hydroxyl radicals. Tephly (1991) also provedthat a catalase system is also one of the major pathways ofmethanol oxidation in rat hepatocytes. Free methanol iscreated from aspartame when it is heated to above 86°F(30°C). This would occur when an aspartame-containing prod-uct is improperly stored or when it is heated (e.g. as part of a‘food’ product such as Jello). Methanol is gradually released inthe small intestine when the methyl group of aspartameencounters the enzyme chymotrypsin. Methanol breaks downinto formic acid and formaldehyde in the body. Formaldehydeis a deadly neurotoxin (Lee et al. 1994; Eells et al. 2000).Rodents do not develop metabolic acidosis during methanolpoisoning, owing to their high liver folate content, and inorder to create similar results in human beings, only folate-deficient rodents are required to accumulate formate in orderto develop acidosis in methanol poisoning (Lee et al. 1994;Eells et al. 2000).

Hence, in this study, in order to mimic the humansituation, a folate deficiency status was induced by ad-ministering methotrexate (MTX). The focus of this study

is to investigate whether the chronic oral administrationof aspartame (75 mg/kg) can release methanol as a by-productafter metabolism and whether it induces oxidative stress in therat brain regions after aspartame administration.

2. Materials and methods

2.1 Animals

Wistar strain male albino rats (200–220 gm) were main-tained under standard laboratory conditions with water andfood. For the folate-deficient group, folate-deficient diet wasprovided for 45 days prior to the experiment and MTX wasadministered for a week before the experiment. The animalswere handled according to the principles of laboratory careframed by the committee for the purpose of Control andSupervision of Experiments on Animals (CPCSEA),Government of India. Prior to the experimentation, properapproval was obtained from the Institutional Animal EthicalCommittee (No: 01/032/2010).

2.2 Chemicals

Aspartame, methotrexate and malondialdehyde were pur-chased from Sigma-Aldrich.Co., St. Louis, USA. All theother chemicals were of analytical grade obtained fromSisco research laboratory, Mumbai, India.

2.3 Experimental design

The rats were divided in to three groups, namely, salinecontrol, MTX-treated control, and MTX-treated aspartame-administered groups. Each group consisted of six animals.Aspartame mixed in sterile saline was administered orally(75 mg/kg body weight), based on the earlier report (Leonet al. 1989). However, early reports on aspartame of higherdoses included two different authors, namely, Labra-Ruiz etal. (2007) and Leon et al. (1989), and the reports are con-troversial. This provided additional interest to use this dos-age in our study. In order to confine within the humanexposure limit, this dose was selected. A 1 L (approx. 1quart) aspartame-sweetened beverage contains about 56 mgof methanol was used. Heavy users of aspartame-containingproducts consume as much as 250 mg of methanol daily, or32 times the EPA limit.

MTX in sterile saline was administered (0.2 mg/kg/day)subcutaneously for 7 days to folate-deficient treated as wellas to folate-treated aspartame groups (Gonzalez-Quevedoet al. 2002). One week after treatment with MTX, folatedeficiency was confirmed by estimating the urinary excretionof formaminoglutamic acid (FIGLU) (Tabor and Wyngarden1962). From the eighth day, only the MTX-treated aspartame

680 Ashok Iyyaswamy and Sheeladevi Rathinasamy

J. Biosci. 37(4), September 2012

group received the aspartame, whereas the other two groupsreceived equivalent volumes of saline as an oral dose and allanimals were handled similarly. The chronic dose of aspar-tame was given for 90 days and all the animals were fedfolate-deficient diet except the control animals till 90 days.

2.4 Sample collections

The blood samples and isolation of brain was performedbetween 8 and 10 a.m. to avoid circadian rhythm inducedchanges. Stress-free blood samples were collected as per thetechnique described by Feldman and Conforti (1980).

2.5 Brain dissection

The animals were sacrificed and the brain was immediatelyremoved and washed with ice-cold phosphate buffered saline(PBS). To expose the brain, the tip of curved scissors wasinserted into the foramen magnum and a single lateral cutwas made into the skull extending forward on the left andright side. With a bone cutter, the dorsal portion of craniumwas peeled off, and using a blunt forceps, the brain wasdropped onto the ice-cold glass plate, leaving the olfactorybulbs behind. The whole process of removing brain took lessthan 2 min. After removing the brain, it was blotted andchilled. Further dissection was made on ice-cold glass plate.The discrete regions of brain (cerebral cortex, cerebellum,midbrain, pons medulla, hippocampus and hypothalamus)were dissected according the method given by Glowinskiand Iverson (1996). The homogenate (10%w/v) of the indi-vidual regions were prepared in a Teflon-glass tissue ho-mogenizer, using ice-cold Tris HCl (100 mm, pH 7.4) bufferand centrifuged separately in refrigerated centrifuge at 300gfor 15 min. The supernatant was used for analysing theparameters in this study.

2.6 Blood methanol measurement

100 mL plasma was deproteinized with equal volume ofacetonitrile and centrifuged for 7 min at 4°C (Dorman et al.1994). The supernatant (20 mL) was analysed for bloodmethanol and formate using a HPLC refractive index detec-tor system (Shimadzu RID, Japan) (equipped with RezexROA-organic acid column 300 mm×7.5 mm I.D.,Phenomenex) with the security guard cartridge (AJO 4490Phenomenex). Column oven was used to maintain the tem-perature at 60°C. The mobile phase was 0.026 N sulphuricacid (Pecina et al. 1984). By using methanol as an externalstandard, the recovery of methanol (HPLC grade) fromblood was found to be 92–96%. Linearity for methanolwas found to be 5–500 mg/100 mL. The detector sensitivity

for methanol was found to be 5 mg/100 mL and reproduc-ibility was>93%.

2.7 Plasma corticosterone

Plasma corticosterone level was estimated according to themethod described earlier by (Mattingly 1962) using excita-tion at 470 nm and emission at 530 nm in fluorescencespectrophotometer.

2.8 Lipid peroxidation

15 gm trichloro acetic acid was added to 100 mL of 0.25 Nhydrochloric acid. 15 mg of thio barbituric acid was dissolvedin 4 mL of trichloro acetic acid in HCl mixture. To 0.1 mL ofhomogenate, 0.4 mL trichloro acetic acid–thio barbituric acid–hydrochloric acid mixture was added and kept in a boilingwater bath for 20min. Then, it was cooled to room temperaturegradually, followed by addition of 1 mL of n-butanol, vor-texed well and centrifuged for 10 min. The supernatant wastaken and was read at 532 nm in spectrophotometer. Thelevel of LPO was expressed as nanomoles of malondialde-hyde (an intermediary product of lipid peroxidation, usingthio barbituric acid)/mg protein (Ohkawa et al. 1970).

2.9 Superoxide dismutase (EC 1.15.1.1) (SOD)

0.5 mL of homogenate was mixed with 0.5 mL of ethanolchloroform mixture; the content was shaken well for 15 minand the centrifuged for 10 min. To 0.5 mL of supernatanttaken, 2 mL of Tris-HCl buffer (pH 8.2) was added. Finally,0.5 mL of freshly prepared pyrogallol solution was addedand read at 470 nm in 0, 1, 2 and 3 min intervals. Theactivity was expressed as Units/min/mg protein (Marklundand Marklund 1974).

2.10 Catalase (EC.1.11.1.6)(CAT)

Four sets of 0.1 mL of homogenate was mixed with 1 mL ofphosphate buffer and 0.5 mL of H2O2, and this reaction wasarrested by addition of 2 mL potassium dichromate aceticacid reagent at various intervals of 0, 15, 30 and 60 s. Thenall the samples were kept in a boiling water bath for 10 minand were cooled gradually. The developed green colour wasread at 610 nm. The activity was expressed amount of H2O2

utilized/min/mg protein (Sinha 1972).

2.11 Glutathione peroxidase (EC.1.11.1.9) (GPx)

To three sets of test tubes 0.4 mL of phosphate buffer,0.1 mL of sodium azide, 0.2 mL of standard GSH solution

Effect of aspartame on oxidative stress 681


and 1 mL of H2O were sequentially mixed. To this 0.1 mL ofH2O2 was added and the reaction in individual set wasarrested with 1 mL of 10% TCA at 0, 1.5, 3 min intervalsand then centrifuged for 10 min. To the 0.2 mL of superna-tant 1.8 mL of H2O followed by 1 mL of 5% TCA wereadded and allowed to stand at room temperature for 20 min.Then 4 mL of phosphate solution was added, followed by0.5 mL of DTNB. The optical density was taken at 412 nmwithin 5 min. The GPx activity is expressed as units/min/mgprotein (Rotruck et al. 1973).

2.12 Reduced glutathione

To 0.2 mL of homogenate, 1.8 mL of H2O, 1 mL of 5%TCA were sequentially added and kept at room temperaturefor 20 min. Then, 4 mL of 0.3 M phosphate solution fol-lowed by 0.5 mL of DTNB was added and mixed well. Theoptical density was taken at 412 nm within 5 min. from theaddition of DTNB. Reduced glutathione (GSH) was mea-sured by its reaction with 5.5- dithiobis 2 nitro benzoic acid(DTNB), to form a compound that absorbs at 412 nm(Moron et al. 1979). The level of GSH is expressed as μgof GSH/mg of protein.

2.13 Protein thiol

To 1 mL of homogenate was added 1.5 mL of Tris-hydrochloric acid buffer (pH 8.2) which contained 0.02ethylene di-amine tetra acetic acid . This was followed bythe addition of 0.1 mL of DTNB solution and 7.5 mL meth-anol. The contents were mixed well in a vortex mixture andthan centrifuged at 3000g for 10 min. The colour developedwas read at 412 nm. The level of thiol was expressed asμg/mg protein. Tissues were analysed for protein andsulfhydryl concentration (Sedlack and Lindsay 1968).

2.14 Statistical analysis

Statistical analysis was carried out using the SPSS statisticalpackage version 17.0. The results are expressed as mean ± STDand the data were analysed by the one-way analysis of variance(ANOVA) followed by Turkey’s multiple comparison tests

when there was a significant ‘F’ test ratio. The level of signif-icance was fixed at p≤0.05.

3. Results

The data from various groups for the individual parametersare presented as bar diagram with mean ± STD.

3.1 Blood methanol level and plasma corticosterone level

The data for the blood methanol level and plasma cortico-sterone level after chronic exposure to aspartame adminis-tration are given in figure 1. Even after chronic exposure, theaspartame-treated MTX animals showed marked increase inthe blood methanol level (df 2, F=2789) and plasma corti-costerone level (df 2, F=874.6) from controls as well as fromthe MTX-treated group.

3.2 Lipid peroxidation, superoxide dismutaseand catalase levels

The results are given in figure 2. The LPO levels in thelipid peroxidation (LPO) MTX-treated animals did not differfrom those in the controls. However, the aspartame-treatedMTX animals showed a marked increase in the LPO level inthe entire brain regions studied, which included cerebralcortex (df 2, F=182), cerebellum (df 2, F=125.8), midbrain(df 2, F=272.2), pons-medulla (df 2,F=206.5), hippocampus(df 2, F=187.4) and hypothalamus (df 2, F=235.7) from thecontrol as well as from the MTX-treated animals.

The results are given in figure 3. The superoxide dismu-tase (SOD) activity in the MTX-treated animals did notdiffer from those in the controls. However, the aspartame-treated MTX animals showed a marked increase in the SODactivity as compared to control and MTX-treated animals, inthe cerebral cortex (df 2, F=50.5), cerebellum (df 2, F=19.2), midbrain (df 2, F=46.5), pons-medulla (df 2, F=90.3) hippocampus (df 2, F=106) and hypothalamus(df 2,F=84.8) from. The results are given in figure 4. The CATactivity in the MTX-treated animals did not differ from thecontrols. However, the aspartame-treated MTX animalsshowed a marked increase in the CAT activity as compared

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Figure 1. Methanol level (mM) in rat blood upon aspartame administration (75 mg/kg) using HPLC and plasma corticosterone level.



to control and MTX treated animals, in the cerebral cortex(df 2, F=130.2), pons-medulla (df 2, F=51), hippocampus(df 2, F=169) and hypothalamus (df 2, F=289.8). In themidbrain (df 2, F=196.7) and cerebellum (df 2, F =126),only a marked increase in CAT activity as compared tocontrol was seen and this remained similar to MTX-treatedanimals.

3.3 Glutathione peroxidase, reduced glutathioneand protein thiol levels

The results are given in figure 5. The GPx activity in theMTX-treated animals did not differ from the controls.However, the aspartame-treated MTX animals showed amarked increase in the GPx activity as compared tocontrol and MTX-treated animals, in tge cerebral cortex

(df 2, F=35.4) and midbrain (df 2, F=89.9). In the cerebellum(df 2, F=83.6), pons-medulla (df 2, F=67.7), hippocampus (df2, F=81.7) and hypothalamus (df 2, F =136.9), a markedincrease in GPx activity as compared control was seen, andthis remained similar to MTX-treated animals. The results aregiven in figure 6.The GSH levels in the MTX-treated animalsdid not differ from the controls. However, the aspartame-treated MTX animals showed a marked decrease in the GSHlevels as compared to control and MTX-treated animals, inthe cerebral cortex (df 2, F =21.4), midbrain (df 2, F=28.7),pons-medulla (df 2, F=23.1) and hippocampus (df 2, F=14.62). However, in the hypothalamus (df 2, F=19.4) theGSH level showed marked decrease as compared to controlsbut not the MTX-treated group. Moreover, in the cerebellum,the GSH level remained similar to that in control and MTX-treated animals. The results are given in figure 7. The proteinthiol levels in the MTX-treated animals did not differ from

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Figure 2. Effect of aspartame (75 mg/kg body weight) on LPO activity (mmol/mg tissue) in rat brain discrete regions.

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Figure 3. Effect of aspartame (75 mg/kg body weight) on SOD activity (units/mg tissue) in rat brain discrete regions.



those in the controls. However, the aspartame-treated MTXanimals showed a marked decrease in the protein thiol levelsas compared to control and MTX-treated animals, in theentire brain regions studied such as the cerebral cortex (df2, F=114.7), cerebellum (df 2, F=158.9), midbrain (df 2, F=83.7), pons-medulla (df 2, F=37.1), hippocampus (df 2, F=68.6) and hypothalamus (df 2, F=119.3).

4. Discussion

This study deals with strengthening the toxic metabolitemethanol released in the body after the consumption ofaspartame. The alteration in the free-radical-scavengingenzymes in the aspartame-administered animals clearly indi-cates that free radical generation may be due to the methanolwhich is one of the metabolic products of aspartame. Evenafter chronic aspartame administration, there was detectable

blood methanol in the aspartame-treated animals. Methanolis metabolized by three enzyme systems, namely, the alcoholdehydrogenase system, the catalase peroxidative pathwayand the microsomal oxidizing systems. Among these, themicrosomal oxidizing system is reported to be responsiblefor free radical generation (Goodman and Tephly 1968).Exposure to methanol causes oxidative stress by alteringthe oxidant/antioxidant balance in lymphoid organs of rat(Parthasarathy et al. 2006). The condition could also beassociated with the abundance of redox active transitionmetal ions, and the relative death of antioxidant defencesystem (Samuel et al. 2005). In addition to that, oxidativestress may lead to the generation of superoxide, peroxyl andhydroxyl radicals (Keyhani and Keyhani 1980).The increasein free radicals could not be ignored as cells can be injured orkilled when the ROS generation overwhelms the cellularant ioxidant capaci ty (Oberly and Oberly 1986).Particularly, the brain is more vulnerable to oxidative

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Figure 4. Effect of aspartame (75 mg/kg body weight) catalase activity (units/mg tissue) in rat brain discrete regions.

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Figure 5. Effect of aspartame (75 mg/kg body weight) on GPx activity (units/mg tissue) in rat brain discrete regions.



damage due its high oxygen consumption and due to thepresence of high levels of polyunsaturated fatty acids (Floydand Carney 1992).

SOD converts superoxide anion (O2−) to hydrogen per-

oxide (H2O2) (Akyol et al. 2002), which are subsequentlyconverted to water and molecular oxygen by glutathioneperoxidase or catalase (Dringen 2000). GPx is a major anti-oxidant enzyme in many tissues and has been speculated tobe a major antioxidative mechanism in the brain (Barlow-Walden et al. 1995). In this study there was a significantincrease in the SOD activity after chronic aspartame inges-tion with an associated increase in the catalase activity. Ascatalase is the main scavenger of H2O2 at high concentration(Kono and Fridorich 1982), that indicates the accumulationof H2O2 as a result of increased SOD activity. It has beenfound that consumption of methanol provokes changes in theactivity of antioxidant enzymes with an increase in theactivity of catalase (Skrzydlewska et al. 1998). Hence, theincrease in this enzyme activity may also be due to the freeradicals generated. According to Yu (1994), free radicalsmay also induce the expression of antioxidant enzymes,thereby enhancing the neuronal resistance to subsequentoxidative challenges.

LPO is a free-radical-mediated process. In the entire ratbrain regions after aspartame consumption, a marked in-crease in LPO was noted, which also supports the generationof free radicals. Generally, when the generation of reactivefree radicals overwhelms the antioxidant defense, LPO of thecell membrane occurs. In spite of the increase in the SOD,CAT and GPx enzyme system in order to prevent the accu-mulation of free radical, a marked increase in the LPO in theentire brain regions indicated this result and possible loss ofmembrane integrity. Moreover, reactive-oxygen-mediateddamage could not be overlooked particularly to proteins,which has been shown to deleteriously affect cellular func-tions (Sohal et al. 2002).

GSH is considered to be one of the most important com-ponents of the antioxidant defense of living cells. The re-duced tri-peptide GSH is a hydroxyl radical and singletoxygen scavenger, and participates in a wide range of cellu-lar functions. Since GSH is present in high intracellularconcentrations, there is a high probability that reactiveoxygen species (such as superoxide, singlet oxygen andhydrogen peroxide) is to be quenched by reaction withGSH before they can initiate their chain reaction-damaging effects (Jones et al. 1981). The depletion of

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Figure 6. Effect of aspartame (75 mg/kg body weight) on GSH concentration (mmol/mg tissue) in rat brain discrete regions.

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Figure 7. Effect of aspartame (75 mg/kg body weight) on protein thiol levels (mmol/mg tissue) in rat brain discrete regions. CC, cerebral cortex;CB, cerebellum; MB, mid brain; PM, pons medulla; HI, hippocampus; HY, hypothalamus. The level of significance was fixed at p≤0.05 (n= 6).



GSH may be one of the reasons for the increase in thevulnerability added to free-radical-induced damage. In addi-tion, the decrease in GSH concentration is quite possiblebecause the methanol metabolism also depends upon GSH(Pankow and Jagielki 1993).

The significant decrease in the protein thiols observed inthis study may be due to the oxidation of proteins in oxida-tive process, and it is also justified by the decreased level ofone of the major thiol substance GSH. Similarly decreasedprotein thiols in brain due to oxidative damage was reportedby Patsoukis et al. (2004), and Nikolaos et al. (2004) supportthe present findings.

From the foregoing it is clear that the methanol,which is a by-product of aspartame, may be responsiblefor the alteration observed in the free-radical-scavengingsystem. Since methanol is freely permeable throughmembranes and lipids, it also gets distributed in thebrain tissues and may cause the damage. Increased pro-duction of free radicals and increased oxidative damageto proteins in distinct brain regions, retina and optic nerveafter methanol administration (Rajamani et al. 2006) was alsoreported earlier lending support to the present findings. Thescientific reports on aspartame also revealed that aspartameconsumption affects the brain. The aspartame intake hasbeen reported to be responsible for neurological and behav-ioural disturbances in sensitive individuals (Johns 1986).Moreover, Mourad and Noor (2011) have observed that thedaily ingestion of aspartame for 4 weeks induces significantincrease in the LPO levels in the cerebral cortex, which isaccompanied by significant decrease in GSH content and asignificant increase in SOD activity, which is also in agree-ment with this study. According to them, the decrease inGSH content and increase in SOD activity persisted untilafter 6 weeks of aspartame treatment. Moreover, they addthat aspartame-induced oxidative stress may depend on theduration of aspartame administration even within the accept-able daily intake dose. The present study reveals that aspar-tame administration in the body system persists for longerduration, which indicates the possible accumulation of meth-anol and its metabolite. Since it is consumed more by dia-betic people whose metabolism is already altered, it isessential to do more work on these lines and create aware-ness regarding the usage of this artificial sweetener.

5. Conclusion

After chronic exposure of aspartame, detectable methanol con-tinues to circulate in the blood; methanol per se and its metab-olites may be responsible for the generation of oxidative stress inbrain regions. This study confirms the presence of toxic metab-olite after aspartame administration and it emphasises the needto caution the people who are using aspartame routinely.

Acknowledgements

The author is grateful for the valuable suggestion offered byDr NJ Parthasarathy and Dapkupar Wankhar. The financialassistance provided by the University of Madras is gratefullyacknowledged.

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MS received 18 April 2012; accepted 06 June 2012

Corresponding editor: INDRANEEL MITTRA



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