The effect of aspartame on acetylcholinesterase activity in hippocampal homogenates of suckling rats

Aspartame-induced cognitive dysfunction: Unveiling role of microglia-mediated neuroinflammation and molecular remediation

Aspartame, an artificial sweetener, is consumed by millions of people globally. There are multiple reports of aspartame and its metabolites affecting cognitive functions in animal models and humans, which include learning problems, headaches, seizures, migraines, irritable moods, anxiety, depression, and insomnia. These cognitive deficits and associated symptoms are partly attributed to dysregulated excitatory and inhibitory neurotransmitter balance due to aspartate released from aspartame, resulting in an excitotoxic effect in neurons, leading to neuronal damage. However, microglia, a central immunocompetent cell type in brain tissue and a significant player in inflammation can contribute to the impact. Microglia rapidly respond to changes in CNS homeostasis. Aspartame consumption might affect the microglia phenotype directly via methanol-induced toxic effects and indirectly via aspartic acid-mediated excitotoxicity, exacerbating symptoms of cognitive decline. Long-term oral consumption of aspartame thus might change microglia's phenotype from ramified to activated, resulting in chronic or sustained activation, releasing excess pro-inflammatory molecules. This pro-inflammatory surge might lead to the degeneration of healthy neurons and other glial cells, impairing cognition. This review will deliberate on possible links and research gaps that need to be explored concerning aspartame consumption, ecotoxicity and microglia-mediated inflammatory cognitive impairment. The study covers a comprehensive analysis of the impact of aspartame consumption on cognitive function, considering both direct and indirect effects, including the involvement of microglia-mediated neuroinflammation. We also propose a novel intervention strategy involving tryptophan supplementation to mitigate cognitive decline symptoms in individuals with prolonged aspartame consumption, providing a potential solution to address the adverse effects of aspartame on cognitive function.

Aspartame Safety as a Food Sweetener and Related Health Hazards

Aspartame is the methyl-ester of the aspartate-phenylalanine dipeptide. Over time, it has become a very popular artificial sweetener. However, since its approval by the main food safety agencies, several concerns have been raised related to neuropsychiatric effects and neurotoxicity due to its ability to activate glutamate receptors, as well as carcinogenic risks due to the increased production of reactive oxygen species. Within this review, we critically evaluate reports concerning the safety of aspartame. Some studies evidenced subtle mood and behavioral changes upon daily high-dose intake below the admitted limit. Epidemiology studies also evidenced associations between daily aspartame intake and a higher predisposition for malignant diseases, like non-Hodgkin lymphomas and multiple myelomas, particularly in males, but an association by chance still could not be excluded. While the debate over the carcinogenic risk of aspartame is ongoing, it is clear that its use may pose some dangers in peculiar cases, such as patients with seizures or other neurological diseases; it should be totally forbidden for patients with phenylketonuria, and reduced doses or complete avoidance are advisable during pregnancy. It would be also highly desirable for every product containing aspartame to clearly indicate on the label the exact amount of the substance and some risk warnings.

The consumption pattern and perception of using artificial sweeteners among the public in Tabuk region, Saudi Arabia

Background

Obesity and weight gain have become major problems worldwide. Thus, several forms of alternative intense sweeteners are extensively used, offering a non-caloric sweet taste. To the best of our knowledge, no research has studied either the consumption pattern or the perception of using artificial sweeteners in Saudi Arabia.

Objectives

Our research aimed to study the usage pattern of such artificial sweeteners in the Tabuk region and estimate the knowledge of and attitudes toward their usage among the population.

Methods

A cross-sectional study promoted on multiple social media platforms and face-to-face interviews in different malls and hospitals in the Tabuk region. We grouped the participants into two major groups: the users and the non-users of artificial sweeteners. Each group has been subdivided into a healthy subgroup and those with a medical record subgroup. Participants' characteristics and their choice of sweeteners were analyzed using bivariate analysis. The age, gender, and education level of the participants were adjusted using binary logistic regression in order to adjust for potential confounders.

Results

A total of 2,760 participants were included in our study. We found that more than 59% of the participants that were over 45 years old were non-hospitalized non-hospitalized diseased irrespective of their usage of artificial sweeteners. Furthermore, females, graduates, diabetics were significantly high irrespective of their subgroup. Moreover, Steviana^® is the most commonly used artificial sweetener. In addition, healthy participants showed a greater perception of the usage and adverse effects of artificial sweeteners. Furthermore, bivariate analysis using logistic regression revealed significant associations (p < 0.05) with confounders such as gender, age, and education level.

Conclusion

Educational programs and nutritional advice for the safe consumption and the daily permissible doses of artificial sweeteners are essential and should be directed specifically at females.

Aspartame and Its Metabolites Cause Oxidative Stress and Mitochondrial and Lipid Alterations in SH-SY5Y Cells

Due to a worldwide increase in obesity and metabolic disorders such as type 2 diabetes, synthetic sweeteners such as aspartame are frequently used to substitute sugar in the diet. Possible uncertainties regarding aspartame's ability to induce oxidative stress, amongst others, has led to the recommendation of a daily maximum dose of 40 to 50 mg per kg. To date, little is known about the effects of this non-nutritive sweetener on cellular lipid homeostasis, which, besides elevated oxidative stress, plays an important role in the pathogenesis of various diseases, including neurodegenerative diseases such as Alzheimer's disease. In the present study, treatment of the human neuroblastoma cell line SH-SY5Y with aspartame (271.7 µM) or its three metabolites (aspartic acid, phenylalanine, and methanol (271.7 µM)), generated after digestion of aspartame in the human intestinal tract, resulted in significantly elevated oxidative stress associated with mitochondrial damage, which was illustrated with reduced cardiolipin levels, increased gene expression of SOD1/2, PINK1, and FIS1, and an increase in APF fluorescence. In addition, treatment of SH-SY5Y cells with aspartame or aspartame metabolites led to a significant increase in triacylglycerides and phospholipids, especially phosphatidylcholines and phosphatidylethanolamines, accompanied by an accumulation of lipid droplets inside neuronal cells. Due to these lipid-mediating properties, the use of aspartame as a sugar substitute should be reconsidered and the effects of aspartame on the brain metabolism should be addressed in vivo.

Toxicological and Nutraceutical Screening Assays of Some Artificial Sweeteners

Artificial sweeteners are food additives worldwide used instead of fructose or glucose in many diet beverages. Furthermore, diet beverages intake has been increasing every year. Thus, some food agencies should regulate it based on toxicological studies. Debates and controversial results are demonstrated, and authority can revise its decision on the basis of new data reporting toxicological effects since cyclamate has been forbidden in some countries. Therefore, the aim of this study was to report new data about the toxicity of acesulfame-k, aspartame, and cyclamate, which are useful for authority agencies, determining the toxic potential and nutraceutical capabilities of these compounds. The toxicity, antitoxicity, genotoxicity, antigenotoxicity, and life expectancy assays were carried out in Drosophila as an in vivo model. In addition, in vitro HL-60 line cell was used to evaluate the chemopreventive activity determining the cytotoxic effect and the capability of producing DNA damage due to internucleosomal fragmentation or DNA strand breaks. Furthermore, the methylated status of these cancer cells treated with the tested compounds was assayed as a cancer therapy. Our results demonstrated that all tested compounds were neither toxic nor genotoxic, whereas these compounds resulted in antigenotoxic and cytotoxic substances, except for cyclamate. Aspartame showed antitoxic effects in Drosophila. All tested compounds decreased the quality of life of this in vivo organism model. Acesulfame-k, aspartame, and cyclamate induced DNA damage in the HL-60 cell line in the comet assay, and acesulfame-k generally increased the methylation status. In conclusion, all tested artificial sweeteners were safe compounds at assayed concentrations since toxicity and genotoxicity were not significantly induced in flies. Moreover, Aspartame and Cyclamate showed protective activity against a genotoxin in Drosophila Regarding nutraceutical potential, acesulfame-k and aspartame could be demonstrated to be chemopreventive due to the cytotoxicity activity shown by these compounds. According to DNA fragmentation and comet assays, a necrotic way could be the main mechanism of death cells induced by acesulfame-k and aspartame. Finally, Acesulfame-K hypermethylated repetitive elements, which are hypomethylated in cancer cells resulting in a benefit to humans.

Oxidative stress evoked damages leading to attenuated memory and inhibition of NMDAR–CaMKII–ERK/CREB signalling on consumption of aspartame in rat model

Many controversial reports are available on the use of aspartame as it releases methanol as one of its metabolite during metabolism. The present study proposes to investigate whether long term (90 days) aspartame (40 mg/kg b.wt) administration could induce oxidative stress and alter the memory in Wistar strain male albino rats. To mimic the human methanol metabolism, methotrexate (MTX)-treated rats were included as a model to study the effects of aspartame. Wistar strain albino rats were administered with aspartame (40 mg/kg b.wt) orally and studied along with controls and MTX-treated controls. Aspartame interfered in the body weight and corticosterone levels in the rats. A marked increase in the mRNA and protein expression of neuronal nitric oxide synthase (nNOS) and induced nitric oxide synthase (iNOS) which resulted in the increased nitric oxide radical’s level indicating that aspartame is a stressor. These reactive nitrogen species could be responsible for the altered cell membrane integrity and even cause death of neurons by necrosis or apoptosis. The animals showed a marked decrease in learning, spatial working and spatial recognition memory deficit in the Morris water maze and Y-maze performance task which could have resulted due to reduced hippocampal acetylcholine esterase (AChE) activity. The animal brain homogenate also revealed the decrease in the phosphorylation of NMDAR1–CaMKII–ERK/CREB signalling pathway, which well documents the inhibition of phosphorylation leads to the excitotoxicity of the neurons and memory decline. This effect may be due to methanol which may also activate the NOS levels, microglia and astrocytes, inducing neurodegeneration in brain. Neuronal shrinkage of hippocampal layer due to degeneration of pyramidal cells revealed the abnormal neuronal morphology of pyramidal cell layers in the aspartame treated animals. These findings demonstrate that aspartame metabolites could be a contributing factor for the development of oxidative stress in the brain.

Revisiting the safety of aspartame

Aspartame is a synthetic dipeptide artificial sweetener, frequently used in foods, medications, and beverages, notably carbonated and powdered soft drinks. Since 1981, when aspartame was first approved by the US Food and Drug Administration, researchers have debated both its recommended safe dosage (40 mg/kg/d) and its general safety to organ systems. This review examines papers published between 2000 and 2016 on both the safe dosage and higher-than-recommended dosages and presents a concise synthesis of current trends. Data on the safe aspartame dosage are controversial, and the literature suggests there are potential side effects associated with aspartame consumption. Since aspartame consumption is on the rise, the safety of this sweetener should be revisited. Most of the literature available on the safety of aspartame is included in this review. Safety studies are based primarily on animal models, as data from human studies are limited. The existing animal studies and the limited human studies suggest that aspartame and its metabolites, whether consumed in quantities significantly higher than the recommended safe dosage or within recommended safe levels, may disrupt the oxidant/antioxidant balance, induce oxidative stress, and damage cell membrane integrity, potentially affecting a variety of cells and tissues and causing a deregulation of cellular function, ultimately leading to systemic inflammation.

Vitamin E can improve behavioral tests impairment, cell loss, and dendrite changes in rats' medial prefrontal cortex induced by acceptable daily dose of aspartame

Aspartame is an artificial sweetener used in about 6000 sugar-free products. Aspartame consumption could be associated with various neurological disorders. This study aimed to evaluate the effect of aspartame onmedial Prefrontal Cortex (mPFC) as well as neuroprotective effects of vitamin E. The rats were divided into seven groups, including distilled water, corn oil, vitamin E (100mg/kg/day), and low (acceptable daily dose) and high doses of aspartame (40 and 200mg/kg/day) respectively, with or without vitamin E consumption, for 8 weeks. Behavioral tests were recorded and the brain was prepared for stereological assessments. Novel objects test and eight-arm radial maze showed impairmentoflong- and short-termmemoriesin aspartame groups. Besides, mPFC volume, infralimbic volume, neurons number, glial cells number, dendrites length per neuron,and number of spines per dendrite length were decreased by 7-61% in the rats treated with aspartame. However, neurons' number, glial cells number, and rats' performance in eight-arm radial mazes were improved by concomitant consumption of vitamin E and aspartame. Yet, the mPFC volume and infralimbic cortex were protected only in the rats receiving the low dose of aspartame+vitamin E. On the other hand, dendrites length, spines number,and novel object recognition were not protected by treatment with vitamin E+aspartame. The acceptable daily dose or higher doses of aspartame could induce memory impairments and cortical cells loss in mPFC. However, vitamin E could ameliorate some of these changes.

Alterations in behaviour, cerebral cortical morphology and cerebral oxidative stress markers following aspartame ingestion

OBJECTIVE

The study evaluated changes in open field behaviours, cerebral cortical histomorphology and biochemical markers of oxidative stress following repeated administration of aspartame in mice.

METHODOLOGY

Adult mice were assigned into five groups of twelve each. Vehicle (distilled water), or aspartame (20, 40, 80 and 160mg/kg body weight) were administered orally for 28days. Horizontal locomotion, rearing and grooming were assessed after the first and last dose of aspartame. Sections of the cerebral cortex were processed and stained for general histology, and also examined for neuritic plaques using the Bielschwosky's protocol. Glial fibrillary acidic protein (GFAP) and neuron specific enolase (NSE) immunoreactivity were assessed using appropriate antibodies. Aspartate and antioxidant levels were also assayed from cerebral cortex homogenates. Data obtained were analysed using descriptive and inferential statistics.

RESULTS

Body weight and food consumption decreased significantly with aspartame consumption. Locomotion, rearing and grooming increased significantly after first dose, and with repeated administration of aspartame. Histological changes consistent with neuronal damage were seen at 40, 80 and 160mg/kg. Neuritic plaque formation was not evident; while GFAP-reactive astrocytes and NSE-reactive neurons increased at 40 and 80mg/kg but decreased at 160mg/kg. Superoxide dismutase and nitric oxide increased with increasing doses of aspartame, while aspartate levels showed no significant difference.

CONCLUSION

The study showed morphological alterations consistent with neuronal injury and biochemical changes of oxidative stress. These data therefore supports the need for caution in the indiscriminate use of aspartame as a non-nutritive sweetener.

Effect of long term-administration of aspartame on the ultrastructure of sciatic nerve

Aspartame is the most widely used artificial sweetener worldwide. There is much controversy about the effect of aspartame on different cells in the body. The aim of this study was to evaluate the effect of aspartame on the structure of the sciatic nerve. Thirty adult male albino rats were divided into three groups. Group I served as control; Group II received aspartame orally in a dose of 250 mg/kg/d for 3 months; Group III received aspartame at the same dose and for the same period, and was allowed to recover for 1 month. Specimens of sciatic nerve were processed, and semithin and ultrathin sections were examined by light and electron microscopy. A morphometric study was done to evaluate the g-ratio, which is the ratio between the axon diameter and total fiber diameter. Long-term aspartame administration resulted in many degenerative changes affecting mainly the myelin sheath, in the form of focal and extensive demyelination; disruption and splitting of myelin lamellae with loss of compact lamellar structure; and excessive enfolding with irregular thickening of myelin sheaths. Less frequent than those observed in the myelin sheath, some axonal changes were detected, such as compression and distortion. Dilated rough endoplasmic reticulum and vacuolation of the cytoplasm of Schwann cells were also detected. Partial improvement was observed in the recovery group. It was concluded that long-term administration of aspartame had a harmful effect on the structure of sciatic nerve and 1 month stoppage of aspartame was not enough to achieve complete recovery.

Inhibition of Na(+),K(+)-ATPase in the hypothalamus, pons and cerebellum of the offspring rat due to experimentally-induced maternal hypothyroidism

Neurodevelopment is known to be particularly susceptible to thyroid hormone insufficiency and can result in extensive structural and functional deficits within the central nervous system (CNS), subsequently leading to the establishment of cognitive impairment and neuropsychiatric symptomatology. The current study evaluated the effects of gestational and/or lactational maternal exposure to propylthiouracil (PTU)-induced hypothyroidism (as a suggestive multilevel experimental approach to the study of hypothyroidism-induced changes that has been developed and characterized by the authors) on crucial brain enzyme activities of 21-day-old Wistar rat offspring in a CNS region-specific manner. The activities of acetylcholinesterase (AChE), Na(+),K(+)-ATPase and Mg(2+)-ATPase in the offspring hypothalamus, cerebellum and pons were assessed. The study demonstrated that maternal exposure to PTU (0.05% w/v in the drinking water) during the critical periods of neurodevelopment can result in an inhibition of hypothalamic, pontine and cerebellar Na(+),K(+)-ATPase; a major marker of neuronal excitability and metabolic energy production as well as an important regulator of important systems of neurotransmission. On the other hand, no significant changes in the activities of the herein offspring CNS regions' AChE and Mg(2+)-ATPase were recorded. The observed Na(+),K(+)-ATPase inhibition: (i) is region-specific (and non-detectable in whole brain homogenetes), (ii) could constitute a central event in the pathophysiology of clinically-relevant hypothyroidism-associated developmental neurotoxicity, (iii) occurs under all examined experimental schemes, and (iv) certainly deserves further clarification at a molecular and histopathological level. As these findings are analyzed and compared to the available literature, they also underline the need for the adoption and further study of Na(+),K(+)-ATPase activity as a consistent neurochemical marker within the context of a systematic comparative study of existing (and novel) simulation approaches to congenital and early age hypothyroidism.

Chronic Effect of Aspartame on Ionic Homeostasis and Monoamine Neurotransmitters in the Rat Brain

Aspartame is one of the most widely used artificial sweeteners globally. Data concerning acute neurotoxicity of aspartame is controversial, and knowledge on its chronic effect is limited. In the current study, we investigated the chronic effects of aspartame on ionic homeostasis and regional monoamine neurotransmitter concentrations in the brain. Our results showed that aspartame at high dose caused a disturbance in ionic homeostasis and induced apoptosis in the brain. We also investigated the effects of aspartame on brain regional monoamine synthesis, and the results revealed that there was a significant decrease of dopamine in corpus striatum and cerebral cortex and of serotonin in corpus striatum. Moreover, aspartame treatment significantly alters the tyrosine hydroxylase activity and amino acids levels in the brain. Our data suggest that chronic use of aspartame may affect electrolyte homeostasis and monoamine neurotransmitter synthesis dose dependently, and this might have a possible effect on cognitive functions.

Assessment of exposure of Korean consumers to acesulfame K and sucralose using a stepwise approach

Using a stepwise assessment of the exposure of Korean consumers to acesulfame K and sucralose, theoretical maximum daily intakes of the sweeteners were calculated using the Budget screening method, which resulted in values greater than the acceptable daily intakes (ADIs). Accordingly, the daily intakes of the sweeteners based on food consumption data and concentrations determined by instrumental analysis of 605 food samples were estimated for the more refined approach. The estimated daily intakes (EDIs) of all ordinary consumers were lower than the ADI, which was considered safe. However, for infants and 95th percentile high-level consumers (especially those who choose sucralose-containing foods), the EDIs of sucralose were very close to and higher than the ADI. Therefore, the sucralose concentration in sweetened beverages should be reduced; this would benefit the health of both high-level consumers and infants.

Cytotoxic effect of aspartame (diet sweet) on the histological and genetic structures of female albino rats and their offspring

The present study evaluated the effect of aspartame intake on the histological and genetic structures of mother albino rats and their offspring. Sixty adult female albino rats and 180 of their offspring were equally divided into two groups (control and treated), each group divided into three subgroups. Each subgroup consisted of 10 pregnant rats and 30 of their offspring. The experimental design divided into three periods: (1) the gestation period (subgroup one), (2) the gestation period and three weeks after delivery (subgroup two) and (3) animals in the third subgroup treated as subgroup two then left till the end of the ninth week after delivery. Each pregnant rat in the treated subgroups was given a single daily dose of 1 mL aspartame solution (50.4 mg) by gastric gavage throughout the time intervals of experimental design. At the end of each experimental period for control and treated subgroups, the liver of half of both control and treated groups were subjected for histological study while the liver and bone marrow of the other halves were subjected for cytogenetic studies. Body weight of both groups were recorded individually twice weekly in the morning before offering the diet. The results revealed that the rats and their offspring in the subgroups of control animals showed increases in body weight, normal histological sections, low chromosomal aberration and low DNA fragmentation. The treated animals in the three subgroups rats and their offspring revealed decreases in body weight, high histological lesions, increases in the chromosomal aberration and DNA fragmentation compared with control groups. In conclusion, the consumption of aspartame leads to histopathological lesions in the liver and alterations of the genetic system in the liver and bone marrow of mother albino rats and their offspring. These toxicological changes were directly proportional to the duration of its administration and improved after its withdrawal.

Effect of long term intake of aspartame on antioxidant defense status in liver

The present study evaluates the effect of long term intake of aspartame, the artificial sweetener, on liver antioxidant system and hepatocellular injury in animal model. Eighteen adult male Wistar rats, weighing 150-175 g, were randomly divided into three groups as follows: first group was given aspartame dissolved in water in a dose of 500 mg/kg b.wt.; the second group was given a dose of 1000 mg/kg b.wt.; and controls were given water freely. Rats that had received aspartame (1000 mg/kg b.wt.) in the drinking water for 180 days showed a significant increase in activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and γ-glutamyl transferase (GGT). The concentration of reduced glutathione (GSH) and the activity of glutathione peroxidase (GPx), and glutathione reductase (GR) were significantly reduced in the liver of rats that had received aspartame (1000 mg/kg b.wt.). Glutathione was significantly decreased in both the experimental groups. Histopathological examination revealed leukocyte infiltration in aspartame-treated rats (1000 mg/kg b.wt.). It can be concluded from these observations that long term consumption of aspartame leads to hepatocellular injury and alterations in liver antioxidant status mainly through glutathione dependent system.