[The effects of aspartame exposure on the mechanical barrier of the mice colon].

Exploring the toxic effects of aspartame (APM) exposure on mice intestine and its potential mechanisms. Animal experimental research was conducted from July 2023 to May 2024 on the exposure omics platform of the School of Public Health at Capital Medical University. Using a random number table method, 6-8-week-old male C57BL/6J mice were divided into three groups: 0 mg/kg (control group), 150 mg/kg aspartame exposure group, and 500 mg/kg aspartame exposure group, once a day. After 8 weeks of gavage, intestinal permeability tests were performed, and serum was collected from the mice for biochemistry tests. Hematoxylin-eosin staining was used to evaluate the pathological phenotype of the mice's major organs and colorectal tissues. Transmission electron microscopy (TEM) was used to observe changes in the microscopic structure of the tight junctions in the colorectal epithelium. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunofluorescence (IF) were used to analyze the mRNA levels of tight junction-related genes ( and ) and the protein expression levels of tight junction-related proteins (Claudin-1, Occludin, and Tjp-1) in the colorectal tissues of the mice. Comparisons between data were performed using one-way analysis of variance (ANOVA). There were no statistically significant differences in the serum blood biochemistry indicators of mice in the 150 mg/kg and 500 mg/kg aspartame exposure groups compared to the control group. H&E staining showed no significant pathological changes in the major organs and colorectal tissues of mice in the aspartame exposure groups. The results of the intestinal permeability assay showed statistically significant differences in serum FITC-dextran content between groups. The serum FITC-dextran content of mice in the control group and aspartame low and high dose exposure groups were (286.9±33.26), (354.9±78.88) and (350.9±37.87) ng/ml, respectively, with statistically significant differences (=4.486, <0.05). Two-by-two comparisons revealed that the differences between the low or high dose groups and the control group were significant (=3.78,3.50,<0.05), but there was no statistically significant difference between the low and high dose groups (=0.23,>0.05).Transmission electron microscopy revealed disruption and blurred structure of tight junctions in the colorectal epithelium of mice in the low and high-dose aspartame exposure groups. The qRT-PCR results showed that the relative mRNA expression of and in mice colon was significantly lower in 150 mg/kg and 500 mg/kg exposed mice, but there was no significantly difference in the expression of the mRNA between the low and high dose groups. The qRT-PCR results showed that the relative mRNA expression levels of and in the colon of mice from the control group, 150 mg/kg, and 500 mg/kg aspartame exposure groups were (1.06±0.39, 0.44±0.16, 0.51±0.15) and (1.01±0.10, 0.32±0.17, 0.58±0.17), respectively. The differences were statistically significant (=10.26, 31.26, <0.05). The Tukey test results indicated that the mRNA levels of and in the colon of mice in the 150 mg/kg and 500 mg/kg aspartame exposure groups were significantly lower than those in the control group (=5.86, 5.18, 11.09, 6.78, <0.05), but there was no statistically significant difference between the low-dose and high-dose exposure groups (=0.68, 4.31, >0.05). There was no significantly difference in the mRNA expression of ene in the colon of mice in all groups (=1.18, >0.05). The protein levels of Claudin-1 and Occludin in the colorectal tissues of mice in the 150 mg/kg (=7.25, 5.62, <0.05) and 500 mg/kg (=5.35, 5.66, <0.05) aspartame exposure groups were significantly downregulated, however, there was no significantly difference in the 500 mg/kg compared to 150 mg/kg aspartame exposure group (=0.30, 1.64, >0.05). And the protein level of ZO-1 showed no significant differences between groups (=0.43, >0.05). Aspartame exposure may leads to decreased expression of colorectal tight junction genes and and intestinal mechanical barrier damage in mice.