Dose-dependent effects of neotame on hepatic Th and Cyp1a2 mRNA expression, dopamine level, and hepatic histopathology in male rats

Document Type : Research Paper

Authors

1 College of Science, Al-Qasim Green University, 51013, Babylon, Iraq.

2 College of Science, Al-Qasim Green University, 51013, Babylon, Iraq

Abstract

Objective
Neotame is a high-intensity, non-caloric dipeptide sweetener structurally related to aspartame that is approved for use in foods and beverages. Because it is metabolized in the liver and shares structural features with compounds shown to disturb hepatic drug-metabolizing enzymes and catecholaminergic signaling, concerns persist regarding its dose-dependent effects on hepatic gene expression and dopaminergic-related systemic function. This study was designed to evaluate the dose-dependent effects of orally administered neotame on the hepatic expression of tyrosine hydroxylase (TH) and cytochrome P450 1A2 (CYP1A2) genes, serum dopamine concentration, liver function biomarkers, and hepatic histoarchitecture in adult male albino rats.
Material and methods
Four groups of ten adult male Wistar rats (forty rats in total) were randomly selected. One group of animals was a control group treated with solvent and the other three groups were treated with neotame for 60 consecutive days. The doses used were 250, 500, or 750 mg/kg body weight per day, administered by oral gavage. Hepatic TH and CYP1A2 mRNA expression was quantified by quantitative real-time reverse-transcription PCR (qRT-PCR) with normalization to validated reference gene. Serum dopamine was measured by ELISA; liver function was assessed via ALT, AST, ALP, total protein, and total bilirubin; and liver sections were examined histopathologically. Data were analyzed by one-way ANOVA with Duncan's and Tukey's post-hoc test, and Pearson correlation coefficients were calculated between gene expression and biochemical/histological markers.

Results
Neotame produced a dose-dependent downregulation of hepatic TH mRNA and a concomitant reduction in serum dopamine, together with dose-dependent upregulation of hepatic CYP1A2 mRNA and elevation of ALT and AST activities, accompanied by progressively more severe periportal inflammation, hepatocellular vacuolation, and mild fibrosis at the highest dose. TH expression correlated positively with serum dopamine and negatively with CYP1A2 expression and liver enzyme activities.
Conclusion
This study suggests that dose-dependent changes in hepatic Th and Cyp1a2 mRNA expression, serum dopamine concentration, liver biochemical markers, and liver histopathology in male rats may be due to the fact that these animals were chronically exposed to high doses of neotame. These results confirm the need for further studies to use more reference genes, perform protein level measurements, and evaluate the mechanism of the relevant signaling pathways.

Keywords

References

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Agricultural Biotechnology Journal
Volume 18, Issue 4
August 2026
Pages 629-648

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