Dose-dependent alteration in hepatic and cerebral glucose metabolism following exposure to polystyrene microplastic in Wistar rats

Background: Recently, microplastics (MPs) with dimensions less than 5 mm have gained more attention due to their adverse impact on the environment and living creatures. Polystyrene (PS) particle is a key element of primary microplastics, which are causing numerous health issues such as interruption of energy metabolism, oxidative stress, neurotoxicity, immunotoxicity, digestive gland disorders, reproductive disruption, and genotoxicity in marine living organisms. Method: Alteration in carbohydrate metabolism was evaluated in male Wistar rats (six weeks of age) after four weeks of oral exposure to polystyrene microplastic (PS-MP) at three different doses (0.5mg/L, 5mg/L and 50 mg/L via drinking water). Results: Polystyrene exposure caused a significant decrease in blood glucose, liver glycogen, and pyruvic acid content in liver and cerebral tissue. Free amino nitrogen content significantly altered in the liver and cerebrum in a dose-specific manner. The LDH activity was found to be decreased in the liver, whereas it increased in the cerebral cortex of rats in a dose-responsive fashion. Enzymes like glucose 6-phosphatase, GOT, GPT, and succinate dehydrogenase activities demonstrated differential effects on the liver and cerebrum of rats in terms of energy metabolism. Conclusion: It is suggested that sub-acute polystyrene exposure significantly perturbs glucose metabolism by inducing hypoglycemia associated with decreased glycolysis and increased TCA cycle enzyme function in rat liver in a dose-dependent manner. Gluconeogenesis is also affected differentially by metabolic adjustment in the studied organs.