Aspartame-induced apoptosis in PC12 cells

Aspartame is an artificial sweetner added to many low-calorie foods. The safety of aspartame remains controversial even though there are many studies on its risks. In this study, to understand the physiological effects of trace amounts of artificial sweetners on cells, the effects of aspartame on apoptosis were investigated using a PC12 cell system. In addition, the mechanism of apoptosis induced by aspartame in PC12 cells and effects on apoptotic factors such as cytochrome c, apoptosis-inducing factor, and caspase family proteins were studied by Western blotting and RT-PCR.Aspartame-induced apoptosis in PC12 cells in a dose-dependent manner. In addition, aspartame exposure increased the expressions of caspases 8 and 9, and cytochrome c. These results indicate that aspartame induces apoptosis mainly via mitochondrial pathway involved in apoptosis due to oxigen toxicity.     

In vitro effect of aspartame in angiogenesis induction

Aspartame (APM) is the most widely used artificial sweetener and is added to a wide variety of foods, beverages, drugs, and hygiene products. In vitro and in vivo tests have reported contradictory data about APM genotoxicity. We evaluated the angiogenic effect of APM in an in vitro model using blood vessel development assay (Angio-Kit), cultured endothelial cells and fibroblasts. The release of IL-6, VEGF-A, and their soluble receptors sIL-R6 and sVEGFR-2 were determined over time in the conditioned medium of the Angio-Kit system, endothelial cells and cell lines with fibroblast properties after APM treatment. Reactive oxygen species (ROS) formation, cell viability, and stimulation of the extracellular signal-regulated kinases (erk1/2) and protein p38 were also evaluated. Exposure to APM induced blood vessel formation. ROS production was observed in endothelial cells after APM treatment, which was associated with a slight cell cytotoxicity. Neither intracellular ROS formation nor cell death was observed in fibroblasts. APM increases the levels of inflammatory mediator IL-6, VEGF and their soluble receptors released from endothelial cells into the medium. APM treatment induces VEGF-pathway activation by erk1/2 and p38 phosphorylation. APM at low doses is an angiogenic agent that induces regenerative cytokine production leading to the activation of MAPKs and resulting in the formation of new blood vessels.     

Acute effects of aspartame on systolic blood pressure in spontaneously hypertensive rats

Summary Exogenous tyrosine lowers blood pressure in spontaneously hypertensive rats (SHR). The artificial sweetener aspartame also elevates blood and brain tyrosine levels in rats by being hydrolyzed to phenylalanine, which is then rapidly hydroxylated to tyrosine in the liver. Hence we tested the ability of aspartame; its hydrolytic products phenylalanine, aspartic acid and methanol; and of tyrosine itself to lower blood pressure in SHR. For one week prior to experimentation rats were acclimated to the indirect blood pressure measurement technique; on the day of an experiment they received I.P. injections (mg/kg) of aspartame (12.5–200), tyrosine (25–200) or phenylalanine (100–200), or of aspartic acid or methanol in the doses theoretically contained within 200 mg/kg aspartame. Animals receiving 50, 100 or 200 mg/kg of aspartame exhibited maximum falls in blood pressure of 17.3, 24.2 and 19.3 mmHg, respectively. All changes were significant, as determined by ANOVA and the Newman-Keuls test (p<0.05). Tyrosine or phenylalanine also lowered blood pressure, but aspartic acid or methanol produced no significant effects. Co-administration of aspartame with valine, a large neutral amino acid that competes with phenylalanine or tyrosine for brain uptake, attenuated aspartame's hypotensive effect. These observations suggest that the neurochemical changes produced by aspartame lead to predicted tyrosine-induced changes in blood pressure.     

Caloric regulation in normal-weight men maintained on a palatable diet of concentional foods

The spontaneous food intake of six normal-weight male volunteers was measured for 24 days while the subjects were inpatients on a metabolic unit. They were fed a palatable diet of conventional foods and were kept unaware that their food intake was being measured. On days 7–18 the caloric content of their diet was covertly reduced by 25% by substituting aspartame-sweetened analogues for all menu items containing sucrose. Subjects did not alter their food intake for 3 days. Then between days 4–6 on the aspartame diet, they increased their intake to compensate for 40% of the missing calories. Food intake stabilized at 85% of baseline and remained the same for the rest of the 12-day dilution period. Subjects did not show a shift in either sweetened or unsweetened food choices while their diet was being diluted. In adjusting for the missing calories, they simply ate more of their customary diet. The replacement of sucrose by aspartame tended to curb the weight gain observed on the baseline diet.     

Taste responses to neohesperidin dihydrochalcone in rats and baboon monkeys

Preference-aversion behavior to solutions containing neohesperidin dihydrochalcone (NHDHC) was studied rats and baboon monkeys. Electrophysiological responses evoked by application of NHDHC solutions to taste receptors innervated by the chorda tympani and the glossopharyngeal nerves were also measured. As a group, rats were indifferent to solutions containing up to 1.2×10^?3 M NHDHC in short and long-term preference tests. A solution containing the very high concentration of 8.2×10^?3 M NHDHC was consumed less than water by all rats. The aversive behavior of rats to the 8.2×10^?3 M NHDHC solution appeared to be due to taste quality rather than olfaction. When percent preferences were calculated on an individual basis for the long-term preference tests, 59% of the rats were indifferent to solutions containing up to 1.2×10^?3 M NHDHC, 33% of the animals found this solution aversive and less than 8% showed preference. Behavioral responses to a solution of 3.4×10^?4 M aspartame also varied considerably among rats. The electrophysiological data were in line with the behavioral responses suggesting weak taste responses for NHDHC in rats. More pronounced responses observed in the glossopharyngeal nerve as compared to the chorda tympani. Baboon monkeys showed a strong preference for solutions containing 1.6×10^?5 M–1.6×10^?3 M NHDHC. A solution of 1.6×10^?2 M was consumed to a lesser extent than water. It is concluded that baboon monkeys present a better experimental model than rats for investigating the sweetness of NHDHC.     

Aspartame induced cardiac oxidative stress in Wistar albino rats

Aspartame (non-nutritive sweetener) is consumed by millions of people in products like beverages, instant breakfasts, desserts, breathe mints, sugar free chewing gum, vitamins, and pharmaceutical. On a weight basis, metabolism of aspartame generates approximately 50% phenylalanine, 40% aspartic acid and 10% methanol. The detailed mechanisms of their effects on cardiac tissue are still unclear. The present study aimed to clarify whether longer time aspartame consumption has any effect on heart of Wistar albino rats. Animals were randomly divided into 4 groups of 6 animals (group-1: control, group-2: folate deficient diet fed animals, group-3: control animals treated with aspartame, group-4: folate deficient diet fed animals treated with aspartame). Aspartame was given orally (40 mg/kg·bw/day), dissolved in normal saline and for 90 days. Since human beings have very low hepatic folate content, the folate deficient diet fed animals were used to mimic the human methanol metabolism. Aspartame consumption increased significantly plasma corticosterone level, suggesting that aspartame may act as a chemical stressor. There was a significant increase in lipid peroxidation, nitric oxide and protein carbonyl, and significant decrease in protein thiol, cardiac membrane bound ATPases (Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺), enzymatic (SOD, CAT, GPX, G6PD, GR) and non-enzymatic antioxidants (GSH, Vit-C, Vit-E) as well as a significant increase in heart rate and heart marker enzymes (CK and CK-MB). It may be due to excessive generation of free radicals, which impairs cardiac function. Aspartame metabolite methanol or formaldehyde may be the causative factors behind these changes. However, up regulation of Hsp70 in immunohistochemical analysis of cardiac tissue might be a protective response to oxidative stress induced by aspartame metabolites and structural damages in cardiac tissue.     

Towards internationally acceptable standards for food additives and contaminants based on the use of risk analysis

Internationally acceptable norms need to incorporate sound science and consistent risk management principles in an open and transparent manner, as set out in the Agreement on the Application of Sanitary and Phytosanitary Measures (the SPS Agreement). The process of risk analysis provides a procedure to reach these goals. The interaction between risk assessors and risk managers is considered vital to this procedure. This paper reports the outcome of a meeting of risk assessors and risk managers on specific aspects of risk analysis and its application to international standard setting for food additives and contaminants. Case studies on aflatoxins and aspartame were used to identify the key steps of the interaction process which ensure scientific justification for risk management decisions. A series of recommendations were proposed in order to enhance the scientific transparency in these critical phases of the standard setting procedure.     

α－L－天冬氨酰－L－苯丙氨酸甲酯的合成

以Ｎ－甲酰－Ｌ－天冬氨酸酐和Ｌ－苯丙氨酸为原料缩合成Ｎ－甲酰－ａ－Ｌ－天冬氨酰－Ｌ－苯丙氨酸，然后去保护基成ａ－Ｌ－天氨－Ｌ－苯丙氨酸，并酯化得ａ－Ｌ－天冬氨酰－Ｌ－苯丙氨酸甲酯产物昌形好，纯度高。     

Oral aspartame and plasma phenylalanine: pharmacokinetic difference between rodents and man,and relevance to CNS effects of phenylalanine

Summary The ingestion of aspartame, a phenylalanine-containing dipeptide, raises plasma phenylalanine levels. These increments are much greater in humans than rats, because the rat hydroxylates phenylalanine five times faster than man. Accordingly, dose comparisons of aspartame (or phenylalanine) between humans and rats have usually been corrected by a factor of five. Recently, a correction factor of sixty has been proposed (Wurtman and Maher, 1987); the rationale is based on a novel calculation of competitive phenylalanine transport into brain. An analysis of the logic behind this postulation reveals there to beno basis for accepting the higher dose conversion of 60 between rat and man.     

Artificial sweetener consumption and urinary tract tumors in Cordoba, Argentina

OBJECTIVE: To determine the role of the habitual use of the most common artificial sweeteners (AS) in the development of urinary tract tumors (UTT) in Argentina. METHODS: Case-control study of 197 patients with histologically confirmed UTT of transitional varieties, and 397 controls with acute, non-neoplastic, and non-urinary tract diseases, admitted to the same hospitals in Córdoba (Argentina) between 1999 and 2006. All subjects were interviewed about their use of AS and their exposure to other known or suspected risk factors for UTT. RESULTS: Fifty-one UTT patients (26%) and 87 controls (22%) used AS. The risk of UTT was significantly increased in long-term (> or =10 years) AS users compared with none-AS users. The OR (95% CI) for long-term consumers was 2.18 (1.22-3.89) and for short-term users was 1.10 (0.61-2.00) after adjustment for age, gender, BMI, social status. and years of tobacco use. CONCLUSION: Regular use of AS for 10 years or more was positively associated with UTT.