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.

The Effect of Non-Nutritive Sweetened Beverages on Postprandial Glycemic and Endocrine Responses: A Systematic Review and Network Meta-Analysis.

Background: There has been an emerging concern that non-nutritive sweeteners (NNS) can increase the risk of cardiometabolic disease. Much of the attention has focused on acute metabolic and endocrine responses to NNS. To examine whether these mechanisms are operational under real-world scenarios, we conducted a systematic review and network meta-analysis of acute trials comparing the effects of non-nutritive sweetened beverages (NNS beverages) with water and sugar-sweetened beverages (SSBs) in humans. Methods: MEDLINE, EMBASE, and The Cochrane Library were searched through to January 15, 2022. We included acute, single-exposure, randomized, and non-randomized, clinical trials in humans, regardless of health status. Three patterns of intake were examined: (1) uncoupling interventions, where NNS beverages were consumed alone without added energy or nutrients; (2) coupling interventions, where NNS beverages were consumed together with added energy and nutrients as carbohydrates; and (3) delayed coupling interventions, where NNS beverages were consumed as a preload prior to added energy and nutrients as carbohydrates. The primary outcome was a 2 h incremental area under the curve (iAUC) for blood glucose concentration. Secondary outcomes included 2 h iAUC for insulin, glucagon-like peptide 1 (GLP-1), gastric inhibitory polypeptide (GIP), peptide YY (PYY), ghrelin, leptin, and glucagon concentrations. Network meta-analysis and confidence in the network meta-analysis (CINeMA) were conducted in R-studio and CINeMA, respectively. Results: Thirty-six trials involving 472 predominantly healthy participants were included. Trials examined a variety of single NNS (acesulfame potassium, aspartame, cyclamate, saccharin, stevia, and sucralose) and NNS blends (acesulfame potassium + aspartame, acesulfame potassium + sucralose, acesulfame potassium + aspartame + cyclamate, and acesulfame potassium + aspartame + sucralose), along with matched water/unsweetened controls and SSBs sweetened with various caloric sugars (glucose, sucrose, and fructose). In uncoupling interventions, NNS beverages (single or blends) had no effect on postprandial glucose, insulin, GLP-1, GIP, PYY, ghrelin, and glucagon responses similar to water controls (generally, low to moderate confidence), whereas SSBs sweetened with caloric sugars (glucose and sucrose) increased postprandial glucose, insulin, GLP-1, and GIP responses with no differences in postprandial ghrelin and glucagon responses (generally, low to moderate confidence). In coupling and delayed coupling interventions, NNS beverages had no postprandial glucose and endocrine effects similar to controls (generally, low to moderate confidence). Conclusions: The available evidence suggests that NNS beverages sweetened with single or blends of NNS have no acute metabolic and endocrine effects, similar to water. These findings provide support for NNS beverages as an alternative replacement strategy for SSBs in the acute postprandial setting.

Effect of continuous sweet gustatory stimulation on salivary flow rate over time.

OBJECTIVE: This study aimed to determine changes in saliva secretion and subjective taste intensity during a sustained period with continuous gustatory stimulation. DESIGN: Twenty-two healthy adults participated in this study. The selected taste solutions were aspartame, sucralose, and acesulfame potassium, which are nonnutritive sweeteners. The concentrations of sucralose1 and acesulfame potassium were set to show the same sweetness intensity as aspartame. Sucralose2 was twice the concentration of sucralose1. The solution was continuously fed into the oral cavity at a flow rate of 0.04 mL / min through a neck-worn precise infusion system. The salivary flow rate (g/min) after 10 min of intraoral water supply from the device was used as the baseline. Salivary flow rate, subjective taste intensity evaluated by the visual analog scale (VAS), and salivary flow rate relative to the baseline were recorded at 10, 30, 60, and 120 min after the start of the test. RESULTS: In the aspartame, sucralose1, and sucralose2 groups, the salivary flow rate increased significantly from 10 min to 120 min after the start of the test when compared to the rate at baseline (p < 0.05). The relative salivary flow rate increased and the VAS value decreased significantly over time and were affected by the time factor (p < 0.001, p = 0.013, respectively) but not by the sweetener-group factor and the interaction effects. CONCLUSIONS: Continuous gustatory stimulation may maintain increased salivary production for a sustained period.

Metformin induces mitochondrial remodeling and differentiation of pancreatic progenitor cells into beta-cells by a potential mechanism including suppression of the T1R3, PLCß2, cytoplasmic Ca+2, and AKT.

The main goal of this study was to investigate the molecular changes in pancreatic progenitor cells subject to high glucose, aspartame, and metformin in vitro. This scope of work glucose, aspartame, and metformin were exposed to pancreatic islet derived progenitor cells (PID-PCs) for 10 days. GLUT1's role in beta-cell differentiation was examined by using GLUT1 inhibitor WZB117. Insulin+ cell ratio was measured by flow cytometry; the expression of beta-cell differentiation related genes was shown by RT-PCR; mitochondrial mass, mitochondrial ROS level, cytoplasmic Ca2+, glucose uptake, and metabolite analysis were made fluorometrically and spectrophotometrically; and proteins involved in related molecular pathways were determined by western blotting. Findings showed that glucose or aspartame exposed cells had similar metabolic and gene expression profile to control PID-PCs. Furthermore, relatively few insulin+ cells in aspartame treated cells were determined. Aspartame signal is transmitted through PLCß2, CAMKK2 and LKB1 in PID-PCs. The most obvious finding of this study is that metformin significantly increased beta-cell differentiation. The mechanism involves suppression of the sweet taste signal's molecules T1R3, PLCß2, cytoplasmic Ca+2, and AKT in addition to the direct effect of metformin on mitochondria and AMPK, and the energy metabolism of PID-PCs is remodelled in the direction of oxidative phosphorylation. These findings are very important in terms of determining that metformin stimulates the mitochondrial remodeling and the differentiation of PID-PCs to beta-cells and thus it may contribute to the compensation step, which is the first stage of diabetes development.

Aspartame induces cancer stem cell enrichment through p21, NICD and GLI1 in human PANC-1 pancreas adenocarcinoma cells.

This study aimed to investigate the molecular effects of the common natural sugar glucose and artificial sweetener aspartame on cancer stem cell (CSC) population and cancer aggressiveness of PANC-1 human pancreas adenocarcinoma cells. According to our findings while aspartame exposure significantly increased the CSC population, high glucose had no effect on it. The epithelial-mesenchymal transition marker N-cadherin increased only in the aspartame group. The findings indicate that a high level of glucose exposure does not effect the invasion and migration of PANC-1 cells, while aspartame increases both of these aggressiveness criteria. The findings also suggest that a high concentration of glucose maintains CSC population through induction of nuclear Oct3/4 and differentiation to parental cells via increasing cytoplasmic c-myc. Aspartame exposure to PANC-1 cells activated AKT and deactivated GSK3ß by increasing levels of ROS and cytoplasmic Ca+2, respectively, through T1R2/T1R3 stimulation. Then p-GSK3ß(Ser9) boosted the CSC population by increasing pluripotency factors Oct3/4 and c-myc via NICD, GLI1 and p21. In the aspartame group, T1R1 silencing further increased the CSC population but decreased cell viability and suppressed the p21, NICD and GLI activation. The presence and amount of T1R subunits in the membrane fraction of PANC-1 cells are demonstrated for the first time in this study, as is the regulatory effect of T1R1's on CSC population. In conclusion, the present study demonstrated that long-term aspartame exposure increases CSC population and tumor cell aggressiveness through p21, NICD, GLI1. Moreover, while aspartame had no tumorigenic effect, it could potentially advance an existing tumor.

High Concentrations of Aspartame Induce Pro-Angiogenic Effects in Ovo and Cytotoxic Effects in HT-29 Human Colorectal Carcinoma Cells.

Aspartame (ASP), an artificial sweetener abundantly consumed in recent years in an array of dietary products, has raised some concerns in terms of toxicity, and it was even suggested a link with the risk of carcinogenesis (colorectal cancer), though the present scientific data are rather inconclusive. This study aims at investigating the potential role of aspartame in colorectal cancer by suggesting two experimental approaches: (i) an in vitro cytotoxicity screening in HT-29 human colorectal carcinoma cells based on cell viability (Alamar blue assay), cell morphology and cell migration (scratch assay) assessment and (ii) an in ovo evaluation in terms of angiogenic and irritant potential by means of the chorioallantoic membrane method (CAM). The in vitro results showed a dose-dependent cytotoxic effect, with a significant decrease of viable cells at the highest concentrations tested (15, 30 and 50 mM) and morphological cellular changes. In ovo, aspartame (15 and 30 mM) proved to have a pro-angiogenic effect and a weak irritant potential at the vascular level. These data suggest new directions of research regarding aspartame's role in colorectal cancer.

Effects of Dietary Glucose and Fructose on Copper, Iron, and Zinc Metabolism Parameters in Humans.

Alterations of transition metal levels have been associated with obesity, hepatic steatosis, and metabolic syndrome in humans. Studies in animals indicate an association between dietary sugars and copper metabolism. Our group has conducted a study in which young adults consumed beverages sweetened with glucose, fructose, high fructose corn syrup (HFCS), or aspartame for two weeks and has reported that consumption of both fructose- and HFCS-sweetened beverages increased cardiovascular disease risk factors. Baseline and intervention serum samples from 107 participants of this study were measured for copper metabolism (copper, ceruloplasmin ferroxidase activity, ceruloplasmin protein), zinc levels, and iron metabolism (iron, ferritin, and transferrin) parameters. Fructose and/or glucose consumption were associated with decreased ceruloplasmin ferroxidase activity and serum copper and zinc concentrations. Ceruloplasmin protein levels did not change in response to intervention. The changes in copper concentrations were correlated with zinc, but not with iron. The decreases in copper, ceruloplasmin ferroxidase activity, ferritin, and transferrin were inversely associated with the increases in metabolic risk factors associated with sugar consumption, specifically, apolipoprotein CIII, triglycerides, or post-meal glucose, insulin, and lactate responses. These findings are the first evidence that consumption of sugar-sweetened beverages can alter clinical parameters of transition metal metabolism in healthy subjects.

Identification of aspartame-induced haematopoietic and lymphoid tumours in rats after lifetime treatment.

Lymphomas and leukaemias involving the lung have in some cases been hard to distinguish from respiratory tract infection in Sprague-Dawley (SD) rats from long-term bioassays. In order to differentiate between tumours and immune cell infiltrates, updated pathological criteria and nomenclature were used and immunohistochemistry (IHC) was applied to haematopoietic and lymphoid tissue tumours (HLTs) in the original prenatal long-term Aspartame (APM) study performed by the Ramazzini Institute (RI). All 78 cases of HLTs from treated and control groups were re-examined based on light microscopic morphological characteristics and subjected to a panel of IHC markers including Ki67, CD3, PAX5, CD20, CD68, TdT, CD45, CD14 and CD33. The analysis confirmed the diagnoses of HLTs in 72 cases, identified 3 cases of preneoplastic lesions (lymphoid hyperplasia), and categorized 3 cases as inflammatory lesions. A statistically significant increase in total HLTs (p = 0.006), total lymphomas (p = 0.032) and total leukaemias (p = 0.031) in treated female rats was confirmed (high dose vs control), and a statistically significant linear trend for each HLT type was also observed. After the HLT cases re-evaluation, the results obtained are consistent with those reported in the previous RI publication and reinforce the hypothesis that APM has a leukaemogenic and lymphomatogenic effect.

Identify old drugs as selective bacterial ß-GUS inhibitors by structural-based virtual screening and bio-evaluations.

Irinotecan (CPT-11) is a cytotoxic drug that has wide applicability and usage in cancer treatment. Despite its success, patients suffer dose-dependent diarrhea, limiting the drug's efficacy. No effective therapy is available for this unmet medical need. The bacterial ß-glucuronidase (ß-GUS) plays pivotal role in CPT-11-induced diarrhea (CID) via activating the non-toxic SN-38G to toxic SN-38 inside intestine. By using structural-based virtual screening, three old drugs (N-Desmethylclozapine, Aspartame, and Gemifloxacin) were firstly identified as selective bacterial ß-GUS inhibitors. The IC50 values of the compounds in the enzyme-based and cell-based assays range from 0.0389 to 3.6040 and 0.0105 to 5.3730 µM, respectively. The compounds also showed good selectivity against mammalian ß-GUS and no significant cytotoxicity in bacteria. Molecular docking and molecular dynamics simulations were performed to further investigate the binding modes of compounds with bacterial ß-GUS. Binding free energy decomposition revealed that the compounds formed strong interactions with E413 in catalytic trail from primary monomer and F365' on the bacterial loop from the other monomer of bacterial ß-GUS, explaining the selectivity against mammalian ß-GUS. The old drugs identified here may be used as bacterial ß-GUS inhibitors for CID or other bacterial ß-GUS-related disorders.

Aspartame supplementation in starter accelerates small intestinal epithelial cell cycle and stimulates secretion of glucagon-like peptide-2 in pre-weaned lambs.

The objective of this study was to test the hypothesis that aspartame supplementation in starter diet accelerates small intestinal cell cycle by stimulating secretion and expression of glucagon-like peptide -2 (GLP-2) in pre-weaned lambs using animal and cell culture experiments. In vivo, twelve 14-day-old lambs were selected and allocated randomly to two groups; one was treated with plain starter diet (Con, n = 6) and the other was treated with starter supplemented with 200 mg of aspartame/kg starter (APM, n = 6). Results showed that the lambs received APM treatment for 35 d had higher (p < .05) GLP-2 concentration in the plasma and greater jejunum weight/live body weight (BW) and jejunal crypt depth. Furthermore, APM treatment significantly upregulated (p < .05) the mRNA expression of cyclin D1 in duodenum; and cyclin A2, cyclin D1, cyclin-dependent kinases 6 (CDK6) in jejunum; and cyclin A2, cyclin D1, CDK4 in ileum. Moreover, APM treatment increased (p < .05) the mRNA expression of glucagon (GCG), insulin-like growth factor 1 (IGF-1) in the jejunum and ileum and mRNA expression of GLP-2 receptor (GLP-2R) in the jejunum. In vitro, when jejunal cells were treated with GLP-2 for 2 hr, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) OD, IGF-1 concentration, and the mRNA expression of IGF-1, cyclin D1 and CDK6 were increased (p < .05). Furthermore, IGF-1 receptor (IGF-1R) inhibitor decreased (p < .05) the mRNA expression of IGF-1, cyclin A2, cyclin D1 and CDK6 in GLP-2 treatment jejunal cells. These results suggest that aspartame supplementation in starter accelerates small intestinal cell cycle that may, in part, be related to stimulate secretion and expression of GLP-2 in pre-weaning lambs. Furthermore, GLP-2 can indirectly promote the proliferation of jejunal cells mainly through the IGF-1 pathway. These findings provide new insights into nutritional interventions that promote the development of small intestines in young ruminants.

Recent evidence for the effects of nonnutritive sweeteners on glycaemic control.

PURPOSE OF REVIEW: By replacing sugar, nonnutritive sweeteners (NNSs) are thought to aid in weight management and decrease insulin resistance. We reviewed the latest randomized clinical trials (RCTs) investigating the effects NNSs on glycaemic control. RECENT FINDINGS: Six RCTs addressed this topic between 2017 and 2018; the majority tested artificial NNS (sucralose or aspartame), with only one testing natural NNS (stevia and monk fruit extract). Most found no effect of NNS on blood glucose, insulin, gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels; however, two trials showed an effect of sucralose on the acute insulin response. SUMMARY: We are still incapable of reaching a definite judgement on which types of NNS, if any, impact glycaemic control. There is a need for more research to overcome the limitations of recent RCTs, related to sample size, intervention duration, dose, form of NNSs used, and inclusion of males or female participants only. Future studies should also compare different NNS types with each other, and include the increasingly popular 'natural' NNS.

Synergistic Effects of The Enhancements to Mitochondrial ROS, p53 Activation and Apoptosis Generated by Aspartame and Potassium Sorbate in HepG2 Cells.

The safety of food additives has been widely concerned. Using single additives in the provisions of scope is safe, but the combination of additives, may induce additive, synergy, antagonism and other joint effects. This study investigated the cytotoxicity of aspartame (AT) together with potassium sorbate (PS). Thiazolyl Blue Tetrazolium Bromide (MTT) assay indicated that AT and PS had IC50 values of 0.48 g/L and 1.25 g/L at 24 h, respectively. High content analysis (HCA) showed that both AT and PS had a negative effect on mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and DNA damage while the joint group behaved more obviously. The biochemical assays revealed typical cell morphological changes and the activation of cytochrome c and caspase-3 verified apoptosis induced by AT together with PS. With dissipation of MMP and increase of cell membrane permeability (CMP), it indicated AT together with PS-induced apoptosis was mediated by mitochondrial pathway. Meanwhile, p53 were involved in DNA damage, and the ratio of Bax/Bcl-2 was increased. Moreover, excessive ROS induced by AT together with PS is a key initiating factor for apoptosis. All these results proved that p53 was involved in apoptosis via mitochondria-mediated pathway and the process was regulated by ROS.

Aspartame Consumption for 12 Weeks Does Not Affect Glycemia, Appetite, or Body Weight of Healthy, Lean Adults in a Randomized Controlled Trial.

Background: Low-calorie sweeteners are often used to moderate energy intake and postprandial glycemia, but some evidence indicates that they may exacerbate these aims. Objective: The trial's primary aim was to assess the effect of daily aspartame ingestion for 12 wk on glycemia. Effects on appetite and body weight were secondary aims. Methods: One hundred lean [body mass index (kg/m2): 18-25] adults aged 18-60 y were randomly assigned to consume 0, 350, or 1050 mg aspartame/d (ASP groups) in a beverage for 12 wk in a parallel-arm design. At baseline, body weight and composition were determined, a 240-min oral-glucose-tolerance test (OGTT) was administered, and measurements were made of appetite and selected hormones. Participants also collected a 24-h urine sample. During the intervention, the 0-mg/d ASP group consumed capsules containing 680 mg dextrose and 80 mg para-amino benzoic acid. For the 350-mg/d ASP group, the beverage contained 350 mg aspartame and the 1050-mg/d ASP group consumed the same beverage plus capsules containing 680 mg dextrose and 700 mg aspartame. Body weight, blood pressure, heart rate, and waist circumference were measured weekly. At weeks 4, 8, and 12, participants collected 24-h urine samples and kept appetite logs. Baseline measurements were repeated at week 12. Results: With the exception of the baseline OGTT glucose concentration at 60 min (and resulting area under the curve value), there were no group differences for glucose, insulin, resting leptin, glucagon-like peptide 1, or gastric inhibitory peptide at baseline or week 12. There also were no effects of aspartame ingestion on appetite, body weight, or body composition. Compliance with the beverage intervention was ∼95%. Conclusions: Aspartame ingested at 2 doses for 12 wk had no effect on glycemia, appetite, or body weight among healthy, lean adults. These data do not support the view that aspartame is problematic for the management of glycemia, appetite, or body weight. This trial was registered at www.clinicaltrials.gov as NCT02999321.

Oxidative stress evoked damages on rat sperm and attenuated antioxidant status on consumption of aspartame.

Although several studies on toxic effect of aspartame metabolite have been studied, controversial reports over the use of aspartame owing to the fact that it releases methanol as one of its metabolite during metabolism exist. This present study is proposed to investigate whether aspartame (40 mg kg-1 b.wt) administration for 90 days could induce oxidative stress and alter antioxidant status of epididymal sperm in Wistar strain male albino rats. To mimic the human methanol metabolism, methotrexate (MTX)-treated rats were included to study the effects of aspartame. Oral intubations of FDA approved 40 mg kg-1 b.wt aspartame were given daily for 90 days to Wistar strain male albino rats and studied along with controls and MTX-treated controls. Sperm count, viability, morphology, morphometry and motility were assessed. A significant decrease in sperm function of aspartame treated animals was observed when compared with the control and MTX control. The free radical generation were observed in epididymal sperm by assessing the scavenging enzymes, enzymatic and non-enzymatic antioxidants. Result suggest that there was a significant increase glutathione-s-transferase (GST), with a significant decrease in reduced glutathione (GSH), superoxide dismutase activity (SOD), glutathione peroxidase levels (GPx), catalase activity (CAT) and glutathione reductase concentration. The increase in free radicals generation could have ultimately caused the lipid peroxidation mediated damages on the testis. Aspartame treated animals also revealed the reduced space in seminiferous tubules, which resulted in reduced Leydig cells when compared with control in histopathology. These findings demonstrate that aspartame metabolites could be a contributing factor for development of oxidative stress in the epididymal sperm.

"Aspartame: A review of genotoxicity data".

Aspartame is a methyl ester of a dipeptide of aspartic acid and phenylalanine. It is 200× sweeter than sucrose and is approved for use in food products in more than 90 countries around the world. Aspartame has been evaluated for genotoxic effects in microbial, cell culture and animal models, and has been subjected to a number of carcinogenicity studies. The in vitro and in vivo genotoxicity data available on aspartame are considered sufficient for a thorough evaluation. There is no evidence of induction of gene mutations in a series of bacterial mutation tests. There is some evidence of induction of chromosomal damage in vitro, but this may be an indirect consequence of cytotoxicity. The weight of evidence from in vivo bone marrow micronucleus, chromosomal aberration and Comet assays is that aspartame is not genotoxic in somatic cells in vivo. The results of germ cell assays are difficult to evaluate considering limited data available and deviations from standard protocols. The available data therefore support the conclusions of the European Food Safety Authority (EFSA) that aspartame is non-genotoxic.

Impact of aspartame and saccharin on the rat liver: Biochemical, molecular, and histological approach.

The current work was undertaken to settle the debate about the toxicity of artificial sweeteners (AS), particularly aspartame and saccharin. Twenty-five, 7-week-old male Wistar albino rats with an average body weight of 101 ± 4.8 g were divided into a control group and four experimental groups (n = 5 rats). The first and second experimental groups received daily doses equivalent to the acceptable daily intake (ADI) of aspartame (250 mg/Kg BW) and four-fold ADI of aspartame (1000 mg/Kg BW). The third and fourth experimental groups received daily doses equivalent to ADI of saccharin (25 mg/Kg BW) and four-fold ADI of saccharin (100 mg/Kg BW). The experimental groups received the corresponding sweetener dissolved in water by oral route for 8 weeks. The activities of enzymes relevant to liver functions and antioxidants were measured in the blood plasma. Histological studies were used for the evaluation of the changes in the hepatic tissues. The gene expression levels of the key oncogene (h-Ras) and the tumor suppressor gene (P27) were also evaluated. In addition to a significant reduction in the body weight, the AS-treated groups displayed elevated enzymes activities, lowered antioxidants values, and histological changes reflecting the hepatotoxic effect of aspartame and saccharin. Moreover, the overexpression of the key oncogene (h-Ras) and the downregulation of the tumor suppressor gene (P27) in all treated rat groups may indicate a potential risk of liver carcinogenesis, particularly on long-term exposure.

Longer period of oral administration of aspartame on cytokine response in Wistar albino rats.

INTRODUCTION: Aspartame is a non-nutritive sweetener particularly used in 'diet' and 'low calorie' products and also in a variety of foods, drugs and hygiene products. Aspartame is metabolized by gut esterases and peptidases to three common chemicals: the amino acids, aspartic acid and phenylalanine, and small amounts of methanol. The aim of the present study was to assess potential changes in molecular mediators of aspartame as a chemical stressor in rats. MATERIALS AND METHODS: The effects of long-term administration of aspartame (40 mg/kg body weight/day) were tested in Wistar Albino rats. The treatment effects were assessed in different conditions, including control groups. After 90 days of treatment, circulating concentrations of different parameters were assessed: corticosterone, lipid peroxidation, antioxidant activity, nitric oxide, reduced glutathione and cytokines (interleukin 2, interleukin 4, tumor necrosis factor-α and interferon-γ). RESULTS: The results show that there was a significant increase in plasma corticosterone, serum lipid peroxidation and nitric oxide level along with a decrease in enzymatic and non-enzymatic antioxidant as well as significant decrease in interleukin 2, tumor necrosis factor-α and interferon-γ. There was also a significant increase in interleukin 4 irrespective of whether the animals were immunized or not. CONCLUSION: The findings clearly point out that aspartame acts as a chemical stressor because of increased corticosterone level and increased lipid peroxidation and nitric oxide level induce generation of free radicals in serum which may be the reason for variation of cytokine level and finally results in alteration of immune function. Aspartame metabolite methanol or formaldehyde may be the causative factors behind the changes observed.

The in vitro effects of artificial and natural sweeteners on the immune system using whole blood culture assays.

This article investigates the effects of commercially available artificial (aspartame, saccharin, sucralose) and natural sweeteners (brown sugar, white sugar, molasses) on the immune system. Human whole blood cultures were incubated with various sweeteners and stimulated in vitro with either phytohemagglutinin or endotoxin. Harvested supernatants were screened for cytotoxicity and cytokine release. Results showed that none of the artificial or natural sweeteners proved to be cytotoxic, indicating that no cell death was induced in vitro. The natural sweetener, sugar cane molasses (10 ug/mL), enhanced levels of the inflammatory biomarker IL-6 while all artificial sweeteners (10 ug/mL) revealed a suppressive effect on IL-6 secretion (P < 0.001). Exposure of blood cells to sucralose-containing sweeteners under stimulatory conditions reduced levels of the biomarker of humoral immunity, Interleukin-10 (P < 0.001). The cumulative suppression of Interleukin-6 and Interleukin-10 levels induced by sucralose may contribute to the inability in mounting an effective humoral response when posed with an exogenous threat.

Effects of artificial sweeteners on the AhR- and GR-dependent CYP1A1 expression in primary human hepatocytes and human cancer cells.

Food constituents may cause a phenomenon of food-drug interactions. In the current study, we examined the effects of artificial sweeteners (aspartame, acesulfame, cyclamate, saccharin) on the aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR)-dependent expression of CYP1A1 in human hepatocytes, hepatic HepG2 and intestinal LS174T cancer cell lines. Sweeteners were tested in concentrations up to those occurring in non-alcoholic beverages. Basal and ligand-inducible AhR- and GR-dependent reporter gene activation in stably transfected HepG2 and HeLa cells, respectively, were not affected by either of the sweeteners tested after 24h of incubation. The expression of CYP1A1 mRNA and protein in primary cultures of human hepatocytes and in LS174T and HepG2 cells was not induced by any of the tested sweeteners. Overall, aspartame, acesulfame, saccharin and cyclamate had no effects on CYP1A1 expression and transcriptional activities of AhR and GR. These data imply the safety of artificial sweeteners in terms of interference with AhR, GR and CYP1A1.

Effect of chronic exposure to aspartame on oxidative stress in the brain of albino rats.

This study was aimed at investigating the chronic effect of the artificial sweetener aspartame on oxidative stress in brain regions of Wistar strain albino rats. Many controversial reports are available on the use of aspartame as it releases methanol as one of its metabolite during metabolism. The present study proposed to investigate whether chronic aspartame (75 mg/kg) administration could release methanol and induce oxidative stress in the rat brain. To mimic the human methanol metabolism, methotrexate (MTX)-treated rats were included to study the aspartame effects. Wistar strain male albino rats were administered with aspartame orally and studied along with controls and MTX-treated controls. The blood methanol level was estimated, the animal was sacrificed and the free radical changes were 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, superoxide dismutase (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 in detectable methanol in blood. Methanol per se and its metabolites may be responsible for the generation of oxidative stress in brain regions.