The Hepatoprotective Effect of Trigonelline in Diabetic Rat Through Insulin-related IRS1-GLUT2 Pathway: A Biochemical, Molecular, Histopathological, and Immunohistochemical 
Study

Abstract

Background: Diabetes significantly increases morbidity and mortality rates, causing complications such as cardiovascular disease, kidney failure, and blindness. Purpose: The aim of this study was to investigate the hepatoprotective effects of trigonelline (TRIG) in diabetic rats through the antioxidative, anti-inflammatory, and insulin-related IRS1-GLUT2 pathway. Methods: In this experimental investigation, sixty male Wistar rats (n = 10/group) were randomly divided into six groups: a healthy group (HEL), healthy rats treated with 1500 and 3000 mg/kg of TRIG, a diabetic (D), and diabetic rats treated with 1500 and 3000 mg/kg of TRIG (D+ TRIG). The effects of TRIG on rats with induced diabetes were evaluated by serum biochemical parameters, such as insulin, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), free fatty acids (FFA), nitric oxide, and adiponectin levels. The activities of hepatic carbohydrate metabolic enzymes (hepatic glucokinase, glucose 6-phosphatase, glycogen, and glucose-6-phosphate dehydrogenase) were also measured. Furthermore, the expression levels of genes and proteins associated with carbohydrate/lipid metabolism, including peroxisome proliferator-activated receptor gamma (PPARg), glucose transporter 2 (GLUT2), insulin receptor substrate 1 (IRS1), sterol regulatory element-binding protein 1c (SREBP-1c) were analyzed using real-time PCR and western blotting techniques, respectively. Liver sections were examined using H&E staining and immunohistochemistry targeting the p53 protein. Results: The results showed that 3000 mg/kg TRIG was able to suppress TNF-α, IL-6, and FFA by inhibiting inflammatory pathways along with increasing the activity of antioxidant enzymes. TRIG treatment regulated serum levels of insulin, adiponectin, and hepatic carbohydrate metabolic enzymes as well as glycogen content by regulation of the IRS1/ GLUT2- SREBP-1c/ PPARg pathway. Conclusion: These results provide evidence that TRIG has the potential to protect liver organs from oxidative damage in diabetic patients.