UNDERSTANDING THE EFFECT OF MONOSODIUM GLUTAMATE ON GROWTH, OBESITY AND SUGAR LEVEL IN ZEBRAFISH MODEL

Abstract

Monosodium glutamate (MSG), a popular flavor enhancer found in many processed foods, has raised growing concerns due to its possible role in driving metabolic disorders. This study aimed to investigate both the immediate and long term effects of MSG on growth patterns, fat build up, blood sugar, cholesterol and lipid level, and gene expression in zebrafish (Danio rerio) model. For the acute exposure phase, zebrafish embryos (24 hours post fertilization) were exposed to varying MSG concentrations (0 to 400 mg/L) for 72 hours. Along with other physiological data (hatching rate, mortality and developmental deformities), the expression of IL-1β and P53 was analyzed in these embryos through semi-quantitative PCR. In the chronic exposure phase, zebrafish larvae were exposed to sub lethal concentrations (0, 6, 60 and 100 mg/L) for 3 months. Histological changes, total lipids and sugar levels were analyzed in fish from the exposed and control groups. Statistical analysis was performed through one way ANOVA and Tukey’s post hoc tests. Results revealed a concentration dependent increase in morphological deformities during early developmental phases of embryos. These deformities included bent tail (95% at 350mg/L), yolk sac edema (90% at 150 and 180 mg/L), and heart edema (95% at 100, 140 and 200mg/L), with significant embryo lethality (100%) at concentrations above 250 mg/L. At the molecular level, increased expression of IL-1β (2 fold) and altered expression of P53 gene were observed in these embryos. These data suggest increased inflammation and oxidative stress responses triggered by MSG. Phenotypic assessment of the chronically exposed groups showed significant increase in body weight (20% at 60mg/L compared to the control), Body mass index (BMI) increases  (45% at 60 mg/L as compared to control and condition factor (100% increase) at 60 mg/L as compared to control. These are indicative of excessive fat accumulation and accelerated physical development. Biochemical assays of homogenized whole body tissues showed elevated levels of triglycerides (11.12 ± 0.48 in the control vs 16.00 ± 0.57 mg/g in the MSG group) and cholesterol levels (from 2.9 ± 0.21 to 7.24 ± 0.38mg/g) in MSG treated groups, but there was no significant increase in sugar levels. Histological examination of preserved tissues samples stained with hematoxylin and eosin highlighted tissues vacuolization and structural disorganization, showed that MSG induced structural damage. Overall, the study confirms MSG as a potent obesogenic and metabolic disruptor, causing developmental toxicity and long term metabolic disturbances, and validates zebrafish as a potent model for assessing metabolic syndrome, gene expression and toxicological risks.