Naringin Attenuates the Diabetic Neuropathy in STZ-Induced Type 2 Diabetic Wistar Rats

Abstract

The application of traditional medicines for the treatment of diseases, including diabetic neuropathy (DN), has received great attention. The aim of this study was to investigate the ameliorative potential of naringin, a flavanone, to treat streptozotocin-induced DN in rat models. After the successful induction of diabetes, DN complications were measured by various behavioral tests after 4 weeks of post-induction of diabetes with or without treatment with naringin. Serum biochemical assays such as fasting blood glucose, HbA1c%, insulin, lipid profile, and oxidative stress parameters were determined. Proinflammatory cytokines such as TNF-α and IL-6, and neuron-specific markers such as BDNF and NGF, were also assessed. In addition, pancreatic and brain tissues were subjected to histopathology to analyze structural alterations. The diabetic rats exhibited increased paw withdrawal frequencies for the acetone drop test and decreased frequencies for the plantar test, hot plate test, and tail flick test. The diabetic rats also showed an altered level of proinflammatory cytokines and oxidative stress parameters, as well as altered levels of proinflammatory cytokines and oxidative stress parameters. Naringin treatment significantly improved these parameters and helped in restoring the normal architecture of the brain and pancreatic tissues. The findings show that naringin's neuroprotective properties may be linked to its ability to suppress the overactivation of inflammatory molecules and mediators of oxidative stress.

Keywords: diabetes mellitus; diabetic neuropathy; histopathology; naringin; neuronal specific markers; proinflammatory cytokines; streptozotocin.

Figure 1

Structure of naringin.

Figure 2

Effects of naringin on behavioral parameters: (A) acetone drop test, (B) plantar test, (C) hot plate test, and (D) tail flick test. Data are expressed as mean ± SEM (n = 6) and analyzed using one-way ANOVA and Kruskal–Wallis test, followed by Dunn’s test. NC, Normal control; DC, Diabetic control; Std, Standard; NR-1, Naringin 10 mg/kg bw. po; NR-2, Naringin 20 mg/kg bw. po; NR-3, Naringin 40 mg/kg bw. po (* p < 0.05).

Figure 3

Estimation of serum biochemical levels in diabetic neuropathy rats and potential of naringin on (A) fasting blood glucose level (FBG) (B) insulin level, and (C) glycated hemoglobin % (HbA1c%). Data are expressed as the mean ± SEM (n = 6) and were analyzed using one-way ANOVA and Kruskal–Wallis test, followed by Dunn’s test. NC, Normal control; DC, Diabetic control; Std, Standard, NR-1, Naringin 10 mg/kg bw. po; NR-2, Naringin 20 mg/kg bw. po; NR-3, Naringin 40 mg/kg bw. po (* p < 0.05).

Figure 4

Estimation of lipid profile of diabetic neuropathy rats and potential of naringin on (A) total cholesterol (TC) level, (B) triglyceride (TG) level, (C) high-density lipid-cholesterol (HDL-C) level, and (D) low-density lipid-cholesterol (LDL-C). Data are expressed as the mean ± standard error of the mean (n = 6) and were analyzed using one-way ANOVA and Kruskal–Wallis test, followed by Dunn’s test. NC, Normal control; DC, Diabetic control; Std, Standard, NR-1, Naringin 10 mg/kg bw. po; NR-2, Naringin 20 mg/kg bw. po; NR-3, Naringin 40 mg/kg bw. po. (* p < 0.05).

Figure 5

Estimation of oxidative stress in diabetic neuropathy rats and their attenuation by naringin on (A) lipid peroxidation (LPO) assay, (B) glutathione (GSH) activity assay, (C) SOD activity, and (D) catalase (CAT) activity. Data are expressed as the mean ± standard error of the mean (n = 6) and were analyzed using one-way ANOVA and Kruskal–Wallis test, followed by Dunn’s test. NC, Normal control; DC, Diabetic control; Std, Standard, NR-1, Naringin 10 mg/kg bw. po; NR-2, Naringin 20 mg/kg bw. po; NR-3, Naringin 40 mg/kg bw. po (* p < 0.05).

Figure 6

Effects of naringin on proinflammatory cytokines (A) IL-6 and (B) TNF-α protein expression. Data are expressed as the mean ± standard error of the mean (n = 6) and were analyzed using one-way ANOVA and Kruskal–Wallis test, followed by Dunn’s test. NC, Normal control; DC, Diabetic control; Std, Standard, NR-1, Naringin 10 mg/kg bw. po; NR-2, Naringin 20 mg/kg bw. po; NR-3, Naringin 40 mg/kg bw. po (* p < 0.05).

Figure 7

Effects of naringin on neuronal specific markers (A) BDNF and (B) NGF protein expression. Data are expressed as the mean ± standard error of the mean (n = 6) and were analyzed using one-way ANOVA and Kruskal–Wallis test, followed by Dunn’s test. NC, Normal control; DC, Diabetic control; Std, Standard, NR-1, Naringin 10 mg/kg bw. po; NR-2, Naringin 20 mg/kg bw. po; NR-3, Naringin 40 mg/kg bw. po (* p < 0.05).

Figure 8

Representative hematoxylin and eosin (H&E) stained brain sections from neuropathic rats (n = 6) treated with (A) normal saline and diet (NC), (B) diabetic rats (DC), (C) rats treated with standard drug (Std), and (D) animal treated with highest dose of NR for a period of 4 weeks treatment (40× × 10× = 400×).

Figure 9

Representative hematoxylin and eosin (H&E) stained pancreas sections from neuropathic rats (n = 6) treated with (A) normal saline and diet (NC), (B) diabetic rats (DC), (C) rats treated with standard drug (Std), and (D). rats treated with highest dose of NR for a period of 4 weeks treatment (40× × 10× = 400×).