Carnosine supplementation and retinal oxidative parameters in a high-calorie diet rat model

Abstract

Background: To assess oxidative effects induced by a high-calorie diet on the retina of Wistar rats and test the antioxidative effects of carnosine supplementation.

Methods: Wistar rats were randomly divided into the following groups: standard diet (SD), high-calorie diet (HcD), standard diet + carnosine (SD + Car), and high-calorie diet + carnosine (HcD + Car). The body weight, adiposity index, plasma glucose, total lipids, high-density lipoprotein (HDL), low-density lipoprotein (LDL), uric acid, creatinine, and triglycerides of the animals were evaluated. The retinas were analyzed for markers of oxidative stress. Hydrogen peroxide production was assessed by 2',7'-dichlorodihydrofluorescein diacetate (DCF) oxidation. The total glutathione (tGSH), total antioxidant capacity (TAC), protein carbonyl, and sulfhydryl groups of the antioxidant system were analyzed.

Results: TAC levels increased in the retinas of the SD + Car group compared to the SD group (p < 0.05) and in the HcD + Car group compared to the HcD group (p < 0.05). The levels of GSH and the GSSH:GSSG ratio were increased in the HcD + Car group compared to the SD + Car group (p < 0.05). An increase in the retinal carbonyl content was observed in the HcD group compared to the SD group (p < 0.05) and in the HcD + Car group compared to the SD + Car group (p < 0.05). A high-calorie diet (HcD) was also associated with a decrease in retinal sulfhydryl-type levels compared to the SD group (p < 0.05).

Conclusion: The results suggest that feeding a high-calorie diet to rats can promote an increase in carbonyl content and a reduction in sulfhydryl groups in their retinas. The administration of carnosine was not effective in attenuating these oxidative markers.

Trial registration: Animal Ethics Committee of Botucatu Medical School - Certificate number 1292/2019.

Keywords: Antioxidant; Carnosine; High-calorie diet; Retina.

Fig. 1

Carnosine supplementation effects on hydrogen peroxide production in animals fed a high caloric diet. Values are means + \- standard error of the mean (SEM); groups: SD, standard diet; SD + Car, standard diet + carnosine; HcD, high-calorie diet; HcD + Car, high-calorie diet + carnosine. Carnosine 250 mg / (Kg body wt /day) or saline IP for 4 wks; DCF, formation of the fluorescent derivative of oxidized DCFH-DA (oxidation of 2 ', 7'-dichlorodihydrofluorescein diacetate); One-way ANOVA, followed by the Newman-Keuls test, used to analyze the treatment effects

Fig. 2

Effect of carnosine supplementation on antioxidant system in retinas from animals undergoing a high-calorie diet. Values are means + \- standard error of the mean (SEM); groups: SD, standard diet; SD + Car, standard diet + carnosine; HcD, high-calorie diet; HcD + Car, high high-calorie diet + carnosine. Carnosine 250 mg / (Kg body wt /day) or saline IP for 4 wks; Total antioxidant capacity (TAC) (a), total GSH activity (b), and glutathione (GSH)/oxidized glutathione (GSSG) ratio (c). One-way ANOVA, followed by the Newman-Keuls test, used to analyze the treatment effects (p < 0.05)

Fig. 3

Effects of carnosine supplementation on carbonyl contents and sulfhydryl levels in the retina. Values are means + \- standard error of the mean (SEM); groups: SD, standard diet; SD + Car, standard diet + carnosine; HcD, high-calorie diet; HcD + Car, high-calorie diet + carnosine. Carnosine 250 mg / (Kg body wt /day) or saline IP for 4 wks; Carbonyl contents, a, sulfhydryl type levels, b; One-way ANOVA, followed by the Newman-Keuls test, used to analyze the treatment effects (p < 0.05)

Fig. 4

Effects of high-calorie diet and carnosine supplementation on metabolic parameters and retinal oxidation