"Aspartame: A review of genotoxicity data"

Syntheses and Applications of Coumarin-Derived Fluorescent Probes for Real-Time Monitoring of NAD(P)H Dynamics in Living Cells across Diverse Chemical Environments

Fluorescent probes play a crucial role in elucidating cellular processes, with NAD(P)H sensing being pivotal in understanding cellular metabolism and redox biology. Here, the development and characterization of three fluorescent probes, A, B, and C, based on the coumarin platform for monitoring of NAD(P)H levels in living cells are described. Probes A and B incorporate a coumarin-cyanine hybrid structure with vinyl and thiophene connection bridges to 3-quinolinium acceptors, respectively, while probe C introduces a dicyano moiety for replacement of the lactone carbonyl group of probe A which increases the reaction rate of the probe with NAD(P)H. Initially, all probes exhibit subdued fluorescence due to intramolecular charge transfer (ICT) quenching. However, upon hydride transfer by NAD(P)H, fluorescence activation is triggered through enhanced ICT. Theoretical calculations confirm that the electronic absorption changes upon the addition of hydride to originate from the quinoline moiety instead of the coumarin section and end up in the middle section, illustrating how the addition of hydride affects the nature of this absorption. Control and dose-response experiments provide conclusive evidence of probe C's specificity and reliability in identifying intracellular NAD(P)H levels within HeLa cells. Furthermore, colocalization studies indicate probe C's selective targeting of mitochondria. Investigation into metabolic substrates reveals the influence of glucose, maltose, pyruvate, lactate, acesulfame potassium, and aspartame on NAD(P)H levels, shedding light on cellular responses to nutrient availability and artificial sweeteners. Additionally, we explore the consequence of oxaliplatin on cellular NAD(P)H levels, revealing complex interplays between DNA damage repair, metabolic reprogramming, and enzyme activities. In vivo studies utilizing starved fruit fly larvae underscore probe C's efficacy in monitoring NAD(P)H dynamics in response to external compounds. These findings highlight probe C's utility as a versatile tool for investigating NAD(P)H signaling pathways in biomedical research contexts, offering insights into cellular metabolism, stress responses, and disease mechanisms.

Non-sugar sweeteners and cancer: Toxicological and epidemiological evidence

Several toxicological and epidemiological studies were published during the last five decades on non-sugar sweeteners (NSS) and cancer. Despite the large amount of research, the issue still continues to be of interest. In this review, we provided a comprehensive quantitative review of the toxicological and epidemiological evidence on the possible relation between NSS and cancer. The toxicological section includes the evaluation of genotoxicity and carcinogenicity data for acesulfame K, advantame, aspartame, cyclamates, saccharin, steviol glycosides and sucralose. The epidemiological section includes the results of a systematic search of cohort and case-control studies. The majority of the 22 cohort studies and 46 case-control studies showed no associations. Some risks for bladder, pancreas and hematopoietic cancers found in a few studies were not confirmed in other studies. Based on the review of both the experimental data on genotoxicity or carcinogenicity of the specific NSS evaluated, and the epidemiological studies it can be concluded that there is no evidence of cancer risk associated to NSS consumption.

Updated systematic assessment of human, animal and mechanistic evidence demonstrates lack of human carcinogenicity with consumption of aspartame

Aspartame has been studied extensively and evaluated for its safety in foods and beverages yet concerns for its potential carcinogenicity have persisted, driven primarily by animal studies conducted at the Ramazzini Institute (RI). To address this controversy, an updated systematic review of available human, animal, and mechanistic data was conducted leveraging critical assessment tools to consider the quality and reliability of data. The evidence base includes 12 animal studies and >40 epidemiological studies reviewed by the World Health Organization which collectively demonstrate a lack of carcinogenic effect. Assessment of >1360 mechanistic endpoints, including many guideline-based genotoxicity studies, demonstrate a lack of activity associated with endpoints grouped to key characteristics of carcinogens. Other non-specific mechanistic data (e.g., mixed findings of oxidative stress across study models, tissues, and species) do not provide evidence of a biologically plausible carcinogenic pathway associated with aspartame. Taken together, available evidence supports that aspartame consumption is not carcinogenic in humans and that the inconsistent findings of the RI studies may be explained by flaws in study design and conduct (despite additional analyses to address study limitations), as acknowledged by authoritative bodies.

Zebrafish Behavioral Phenomics Links Artificial Sweetener Aspartame to Behavioral Toxicity and Neurotransmitter Homeostasis

Artificial sweeteners (ASs) are extensively used as food additives in drinks and beverages to lower calorie intake and prevent lifestyle diseases such as obesity. Although clinical and epidemiological data revealed the link between the chronic overconsumption of ASs and adverse health effects, there still exist controversies over the potential adverse neural toxic effect of ASs such as aspartame (APM), with acceptable daily intake (ADI) for a long time, on human health. In addition, whether APM and its metabolites are neurotoxic remains debatable due to a lack of data from an animal experiment or clinical investigation. Herein, to fully describe the potential neurological effect of APM, adult zebrafish served as the animal model to assess neurophysiological alteration induced by APM exposure within the range of the ADI (1, 10, and 100 mg/L) for 2 months. A cohort of standardized neurobehavioral phenotyping assays was conducted, including light/dark preference tests (LDP), novel tank diving tests, novel object recognition tests, social interaction tests, and color preference tests. For instance, in the LDP test, saccharin remarkably decreased the swimming time of zebrafish in the DARK part from 111 ± 10.8 (control group) to 72.2 ± 11.4 (100 mg/L groups). Besides, brain chemistry involved in the alteration of total neurotransmitters was determined by LC-MS/MS to confirm the behavioral results. Overall, current research studies revealed that APM within the range of the ADI altered the total behavioral profiles of zebrafish and disturbed the homeostasis of neurotransmitters in the brain. The present study has established a set of experimental paradigms, revealing the standardized procedure of using adult zebrafish to determine the neural activity or toxicity of AS molecules phenotypically. Zebrafish behavioral phenotyping methods, which were characterized by a cohort of behavioral fingerprints, can link the phenotypical alteration to changes in neurotransmitters in the brain, so as to provide a predictive reference for the further exploration of the molecular mechanism of phenotypic changes induced by ASs.

Aspartame-True or False? Narrative Review of Safety Analysis of General Use in Products

Aspartame is a sweetener introduced to replace the commonly used sucrose. It was discovered by James M. Schlatter in 1965. Being 180-200 times sweeter than sucrose, its intake was expected to reduce obesity rates in developing countries and help those struggling with diabetes. It is mainly used as a sweetener for soft drinks, confectionery, and medicines. Despite its widespread use, its safety remains controversial. This narrative review investigates the existing literature on the use of aspartame and its possible effects on the human body to refine current knowledge. Taking to account that aspartame is a widely used artificial sweetener, it seems appropriate to continue research on safety. Studies mentioned in this article have produced very interesting results overall, the current review highlights the social problem of providing visible and detailed information about the presence of aspartame in products. The studies involving the impact of aspartame on obesity, diabetes mellitus, children and fetus, autism, neurodegeneration, phenylketonuria, allergies and skin problems, its cancer properties and its genotoxicity were analyzed. Further research should be conducted to ensure clear information about the impact of aspartame on health.

Soft drinks and sweeteners intake: Possible contribution to the development of metabolic syndrome and cardiovascular diseases. Beneficial or detrimental action of alternative sweeteners?

The rapid increase in obesity, metabolic syndrome, and cardiovascular diseases (CVDs) has been related to the rise in sugar-added foods and sweetened beverages consumption. An interesting approach has been to replace sugar with alternative sweeteners (AS), due to their impact on public health. Preclinical and clinical studies, which analyze the safety of AS intake, are still limited. Major pathogenic mechanisms of these substances include ROS and AGEs formation. Indeed, endothelial dysfunction involving in the pathogenesis of micro- and macro-vascular diseases is mitochondrial dysfunction dependent. Hyperglycemia and endoplasmic reticulum stress together produce ROS, contributing to the development and progression of cardiovascular complications during type 2 diabetes (T2D), thus causing oxidative changes and direct damage of lipids, proteins, and DNA. Epidemiological studies in healthy subjects have suggested that the consumption of artificial AS can promote CV complications, such as glucose intolerance and predisposition to the onset of T2D, whereas natural AS could reduce hyperglycemia, improve lipid metabolism and have antioxidant effects. Long-term prospective clinical randomized studies are needed to evaluate precisely whether exposure to alternative sugars can have clinical implications on natural history and clinical outcomes, especially in children or during the gestational period through breast milk.

A fluorescent probe based on cucurbit[7]uril for the selective recognition of phenylalanine

Herein we describe a simple fluorescence quenching method for the selective recognition and determination of the amino acid phenylalanine (Phe). The use of ¹H NMR spectroscopy revealed that the alkaloid palmatine (PAL) can encapsulated partially into the cavity of cucurbit[7]uril (Q[7]) in aqueous solution to form a stable 1:1 host-guest inclusion complex. This host-guest complex exhibits fluorescence of moderate intensity. Interestingly, the addition of the Phe results in a dramatic quenching of the fluorescence intensity associated with the inclusion complex. By contrast, the addition of other natural amino acids resulted in no change in the fluorescence. Based on the linear relationship between the fluorescence intensity and the concentration of Phe, the detection of the concentration of Phe in aqueous solution is facile. Thus, a new fluorescence quenching method for the recognition and determination of the Phe has established herein.

Anticlastogenic, antimutagenic, and cytoprotective properties of Orthosiphon stamineus ethanolic leaves extract

Orthosiphon stamineus (O.S) is widely consumed for its medidcinal value including anti-inflammatory, anti-infective, and diuretic properties. The present study evaluates the cytoprotective, anti-mutagenic, and anticlastogenic efficacies of standardized extract of Orthosiphon stamineus. Normal liver cell line (WRL68) exposed to hydrogen peroxide and serum-deprived media as insults to evaluate cytoprotective and glutathione activation activities of (Et. O. s). Salmonella typhimurium TA98 and TA100 exposed to different concentrations of (Et. O. s). The influence of Et. O. s on mitotic, replicative indices as well as chromosomal aberration (CA) and sister chromatid exchange (SCE) induced in human peripheral blood lymphocytes by mitomycin C (MMC). The Et. O.s proved to be a potent scavenger for hydrogen peroxide and other free radicals in serum-depraved media, which showed to stimulate glutathione production in liver cells line. Moreover, it did not induce mutations in S. typhimurium subspecies TA98 and TA100. The standardized extract exhibited powerful antimutagenic activities as verified against both 2-nitrofluorene and sodium azide in S. typhimurium TA98 and TA100 cells, respectively. Cytogenetic tests showed high concentrations of Et. O. s to reduce the values of mitotic and replicative indices without any accompanying side effects, such as chromosomal abnormalities or SCE. To ameliorate MMC effects, pretreatment with the extract proofed to be efficient protocol. These data suggests that O. stamineus extract could be useful as cytoprotective, antimutagenic, and anticlastogenic efficacies, which owes to its potent chemoprevention, antioxidant, and glutathione activation properties.

The in vitro cytotoxic, genotoxic, and oxidative damage potentials of the oral artificial sweetener aspartame on cultured human blood cells

Background/aim

Aspartame (APM, L-aspartyl-L-phenylalanine methylester) is a low-calorie, nonsaccharide artificial sweetener widely used in foods and beverages. When metabolized by the body, APM is broken down into aspartic acid, phenylalanine amino acids, and a third substance, methanol. Since the amino acid phenylalanine serves as a neurotransmitter building block affecting the brain, and methanol is converted into toxic formaldehyde, APM has deleterious effects on the body and brain. Thus, its safety and, toxicity have been the subjects of concern ever since it was first discovered. Although many studies have been performed on it, due to the presence of conflicting data in the literature, there are still numerous question marks concerning APM.Therefore, the safety of aspartame was tested using in vitro methods.

Materials and methods

We aimed to evaluate the in vitro cytotoxic effects by using 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase release tests, genotoxic damage potential by using chromosome aberration (CA) assay, and antioxidant/oxidant activity by using total antioxidant capacity (TAC) and total oxidative stress (TOS) analysis in primary human whole blood cell cultures.

Results

The results of the MTT test showed that APM led to significant decreases in cell viability in a clear concentration-dependent manner. Moreover, an increase in CA frequency was found in the cells treated with APM. However, APM treatments did not cause any significant changes in TAC and TOS levels in whole blood cultures.

Conclusion

Overall, the obtained results showed that APM had genotoxicity potential and a concentration-dependent cytotoxic activity in human blood cells.

Self-Assembly of Artificial Sweetener Aspartame Yields Amyloid-like Cytotoxic Nanostructures

Recent reports have revealed the intrinsic propensity of single aromatic metabolites to undergo self-assembly and form nanostructures of amyloid nature. Hence, identifying whether aspartame, a universally consumed artificial sweetener, is inherently aggregation prone becomes an important area of investigation. Although the reports on aspartame-linked side effects describe a multitude of metabolic disorders, the mechanistic understanding of such destructive effects is largely mysterious. Since aromaticity, an aggregation-promoting factor, is intrinsic to aspartame's chemistry, it is important to know whether aspartame can undergo self-association and if such a property can predispose any cytotoxicity to biological systems. Our study finds that aspartame molecules, under mimicked physiological conditions, undergo a spontaneous self-assembly process yielding regular β-sheet-like cytotoxic nanofibrils of amyloid nature. The resultant aspartame fibrils were found to trigger amyloid cross-seeding and become a toxic aggregation trap for globular proteins, Aβ peptides, and aromatic metabolites that convert native structures to β-sheet-like fibrils. Aspartame fibrils were also found to induce hemolysis, causing DNA damage resulting in both apoptosis and necrosis-mediated cell death. Specific spatial arrangement between aspartame molecules is predicted to form a regular amyloid-like architecture with a sticky exterior that is capable of promoting viable H-bonds, electrostatic interactions, and hydrophobic contacts with biomolecules, leading to the onset of protein aggregation and cell death. Results reveal that the aspartame molecule is inherently amyloidogenic, and the self-assembly of aspartame becomes a toxic trap for proteins and cells, exposing the bitter side of such a ubiquitously used artificial sweetener.

Measuring Artificial Sweeteners Toxicity Using a Bioluminescent Bacterial Panel

Artificial sweeteners have become increasingly controversial due to their questionable influence on consumers' health. They are introduced in most foods and many consume this added ingredient without their knowledge. Currently, there is still no consensus regarding the health consequences of artificial sweeteners intake as they have not been fully investigated. Consumption of artificial sweeteners has been linked with adverse effects such as cancer, weight gain, metabolic disorders, type-2 diabetes and alteration of gut microbiota activity. Moreover, artificial sweeteners have been identified as emerging environmental pollutants, and can be found in receiving waters, i.e., surface waters, groundwater aquifers and drinking waters. In this study, the relative toxicity of six FDA-approved artificial sweeteners (aspartame, sucralose, saccharine, neotame, advantame and acesulfame potassium-k (ace-k)) and that of ten sport supplements containing these artificial sweeteners, were tested using genetically modified bioluminescent bacteria from E. coli. The bioluminescent bacteria, which luminesce when they detect toxicants, act as a sensing model representative of the complex microbial system. Both induced luminescent signals and bacterial growth were measured. Toxic effects were found when the bacteria were exposed to certain concentrations of the artificial sweeteners. In the bioluminescence activity assay, two toxicity response patterns were observed, namely, the induction and inhibition of the bioluminescent signal. An inhibition response pattern may be observed in the response of sucralose in all the tested strains: TV1061 (MLIC = 1 mg/mL), DPD2544 (MLIC = 50 mg/mL) and DPD2794 (MLIC = 100 mg/mL). It is also observed in neotame in the DPD2544 (MLIC = 2 mg/mL) strain. On the other hand, the induction response pattern may be observed in its response in saccharin in TV1061 (MLIndC = 5 mg/mL) and DPD2794 (MLIndC = 5 mg/mL) strains, aspartame in DPD2794 (MLIndC = 4 mg/mL) strain, and ace-k in DPD2794 (MLIndC = 10 mg/mL) strain. The results of this study may help in understanding the relative toxicity of artificial sweeteners on E. coli, a sensing model representative of the gut bacteria. Furthermore, the tested bioluminescent bacterial panel can potentially be used for detecting artificial sweeteners in the environment, using a specific mode-of-action pattern.

Mutagenicity and genotoxicity studies of aspartame

Two studies were conducted to further assess its mutagenic and genotoxic potential. In a bacterial reverse mutation pre-incubation study, Salmonella typhimurium strains TA100, TA1535, TA98, and TA1537 and Escherichia coli WP2 uvrA were treated with aspartame at concentrations of up to 5000 μg/plate with or without metabolic activation and showed no mutagenic potential. Similarly, in vivo micronucleus testing of aspartame following gavage administration (500-2000 mg/kg body weight) to Crlj:CD1(ICR) strain SPF male mice showed no increase in the proportion of micronucleated polychromatic erythrocytes in bone marrow cells collected and evaluated 24 or 48 h post administration. Overall, aspartame had no potential for mutagenic or genotoxic activity.

Noncaloric Sweeteners in Children: A Controversial Theme

Noncaloric sweeteners (NCS) are food additives used to provide sweetness without adding calories. Their consumption has become more widespread around the world in all age groups, including children. The aim of this study is to show the state of the art about the intake of noncaloric sweeteners in children, as well as their benefits and consumption risk. Scientific searchers were used (PUBMED, Scopus, and Scielo) to analyze articles that included keywords (noncaloric sweeteners/saccharin/cyclamate/acesulfame potassium/aspartame/sucralose/stevia/children) in English, Spanish, and Portuguese. Authors conclude that it is imperative that health professionals judiciously and individually evaluate the overall benefits and risks of NCS use in consumers before recommending their use. Different subgroups of the population incorporate products containing NCS in their diet with different objectives, which should be considered when recommending a diet plan for the consumer. In childhood, in earlier age groups, this type of additives should be used as a dietary alternative when other forms of prevention in obesity are not sufficient.