Effects of Litchi chinensis subproducts on metabolic parameters and antioxidant defense in adult zebrafish

Abstract

Obesity is a complex and multifactorial disease, often associated with excessive increase of adiposity and considered a health risk. Parallelly, the agro-food industry generates many residues that contain bioactive compounds with antioxidant properties, useful in areas such as food, health, pharmacy, cosmetics and environment. Thus, the objectives of the present study were to evaluate the impact of lychee peel and seed flour on biochemical parameters and oxidative stress in adult zebrafish. In the first experiment, 225 zebrafish were used. The animals were fed a high-carbohydrate diet supplemented with different concentrations of lychee peel flour (2, 4 and 6%), being divided into five groups (Control, High Carbohydrate (HC), HC2%, HC4% and HC6%). During the first four weeks, freeze-dried artemia was provided once a day and in the last four weeks freeze-dried artemia with glucose, except for the control group. At the end of the feeding trial, the levels of glucose, triglycerides, total cholesterol, HDL, lactate, creatinine, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined. The activity of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), and the concentration of glutathione (GSH) and lipid peroxidation were also evaluated. The results showed that the HC6% group presented a significant decrease in glucose and triglyceride levels compared to the HC group. In addition, the HC6% group presented increased activities of the antioxidant enzymes CAT and SOD, along with reduced levels of malondialdehyde (MDA). These findings suggest that dietary supplementation with 6% lychee peel flour can significantly modulate glucose homeostasis and lipid metabolism in zebrafish. In the second experiment, 200 adult zebrafish were used. The animals were fed a high-fat diet supplemented with different concentrations of lychee seed flour (2, 4 and 6%) for 12 weeks. The animals were divided into five groups, namely: control, High Fat Diet (HFD), HFD2%, HFD4% and HFD6%. At the end of the 12 weeks, the biochemical parameters (glycemia, triglycerides, total cholesterol, HDL, ALT, AST and cortisol) were evaluated. The oxidative stress biomarkers evaluated were CAT, SOD, glutathione S-transferase (GST), GSH and reactive oxygen species (ROS). In addition, the average diameter of visceral adipose tissue and the histopathological analysis of liver tissue were evaluated. The results showed that the HFD6% group presented the lowest final weight and the lowest weight gain. The feed containing 6% of lychee seed flour resulted in the reduction of glycemia and increase of HDL. Lower activity of CAT and GST were observed in the HFD4% group, in addition, the decrease of ROS occurred in the HFD4% and HFD6% groups. The long-term intake of the flour showed a decrease in visceral adipose tissue of the HFD4% group and mild steatosis in the HFD6% group. It is concluded that lychee seed flour may have beneficial effects on biochemical parameters and oxidative stress markers, suggesting potential applications in food and supplements.