L-ergothioneine and its combination with metformin attenuates renal dysfunction in type-2 diabetic rat model by activating Nrf2 antioxidant pathway

L-ergothioneine (L-egt) is a bioactive compound recently approved by the food and drug administration as a supplement. L-egt exerts potent cyto-protective, antioxidant and anti-inflammatory properties in tissues exposed to injury, while metformin is a first-line prescription in type-2 diabetes. Therefore, the present study investigated the protective effect of L-egt alone, or combined with metformin, on renal damage in a type-2 diabetic (T2D) rat model. T2D was induced in male Sprague-Dawley rats using the fructose-streptozotocin rat model. L-egt administration, alone or combined with metformin, began after confirming diabetes and was administered orally for seven weeks. After the experiment, all animals were euthanized by decapitation, blood samples were collected, and both kidneys were excised. Biochemical analysis, Enzyme-link Immunoassay (ELISA), Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR), western blotting, and histological analyses were done to evaluate various biomarkers and structural changes associated with renal damage. Untreated diabetic rats showed loss of kidney functions characterized by increased serum creatinine, blood urea nitrogen, proteinuria, triglycerides, lipid peroxidation, inflammation, and decreased antioxidant enzymes. Histological evaluation showed evidence of fibrosis, mesangial expansion, and damaged basement membrane in the nephrons. However, L-egt alleviates these functional and structural derangements in the kidney, while co-administration with metformin reduced hyperglycemia and improves therapeutic outcomes. Furthermore, L-egt treatment significantly increased the expression of major antioxidant transcription factors, cytoprotective genes and decreased the expression of inflammatory genes in the kidney. Thus, combining L-egt and metformin may improve therapeutic efficacy and be used as an adjuvant therapy to alleviate renal damage in type-2 diabetes.