4-HIL mitigates type-2 diabetic complications through inhibiting inflammation and Nrf2 mediated oxidative stress in rats

Abstract Background Hyperglycemia induced diabetic complications as well as dysfunction of multiple organs is closely related to the increased inflammation and oxidative stress (OS). 4-hydroxyisoleucine (4-HIL), a major constituent of Trigonella foenum-graecum L. shown to have anti-diabetic effects. However, its potential mechanism against diabetic complications in the model of metabolic syndrome have not yet been characterized. Purpose The present study aimed to investigate the ameliorative effects of 4-HIL in rat model of metabolic syndrome and to explore the possible mechanism of action. Methods Male Sprague dawley rat of 6 -7 weeks were administrated with 4-HIL by oral gavage from 12 to 20 weeks after development of complications. At the end of the study, all animals were sacrificed. Tissues and blood samples were collected for histopathologic and biochemical analysis. Serum metabolic parameters, level of triglycerides, glycated hemoglobin, activities of antioxidant enzymes were estimated. Pathological changes in the tissues were assessed by Hematoxylin – Eosin (H & E), Masson's trichrome and Periodic Acid - Schiff (PAS) staining. In vivo gene expressions were demonstrated by Western blotting. Results Oral administration of 4-HIL (200 mg kg−1) reduced the body hyperglycemia, glycated hemoglobin (HbA1c), creatinine, blood urea nitrogen (BUN), triglyceride and restored the histopathological indices when compared with the diabetic control group. The 4-HIL increased the activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) in tissues samples. It down-regulate the expression of vascular endothelial growth factor (VEGF), tissue injury molecule-1 (TIM-1), insulin receptor (INSULIN R) and transforming growth factor beta 1 (TGF-β1) mediated inflammatory response in all the tissues. Moreover, it exhibits protective effect against oxidative stress by activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway-related proteins in the tissues. Conclusion The findings highlight the beneficial role of 4-HIL in diabetic complications by decreasing inflammatory response and oxidative stress through TGF-β1 signaling pathway and activation of Nrf2 gene expression respectively in addition to its effect on glycemic control.