Leucine Mitigates Diabetic Nephropathy via Its Antioxidant Effect and Modulation of TGF-β/SMAD-3 Signalling Pathway in Streptozotocin-Induced Diabetic Rats

Zekrayat JH Merdas,1 Mahmoud A Bekhit,2 Reem M Hazem,3 Enas S Gad,4,5 Nuseibah Al Qtaish,1 Alanoud F Alsumait,6 Norhan M El-Sayed31Department of Pharmacology & Toxicology, College of Pharmacy, Amman Arab University, Amman, Jordan; 2Egypt Healthcare Authority, Comprehensive Health Insurance, Ismailia, Egypt; 3Department of Pharmacology & Toxicology, Faculty of Pharmacy, Suez Canal University, Ismailia, 41522, Egypt; 4Department of Pharmaceutical Sciences, College of Clinical Pharmacy, King Faisal University, Al-Ahsaa, Saudi Arabia; 5Department of Pharmacology and Toxicology, Faculty of Pharmacy, Sinai University, Kantara Branch, Ismailia, Egypt; 6Clinical Nutrition Department, Kuwait Cancer Control Center, Ministry of Health, Kuwait City, KuwaitCorrespondence: Norhan M El-Sayed, Email Norhan.ms@pharm.suez.edu.egBackground/Objectives: Diabetic nephropathy (DN) is the main contributor to the incidence of end-stage renal disease and kidney failure. This research aims to explore the curative effect of leucine in the DN rat model.Methods: 40 male rats were sorted into four equal groups. Group I acted as the control group. Group II was given leucine (1.35g/kg orally, once daily) for 8 weeks. Group III administered a single intraperitoneal injection of Streptozotocin (STZ) (45 mg/kg, i.p.). Group IV was administered leucine following the diagnosis of diabetes for a duration of 8 weeks. In this study, samples were obtained from blood and renal tissue for biochemical assessments, evaluation of redox state, real-time polymerase chain reaction (RT-PCR) analysis of L-type amino acid transporter 1 (LAT1) and suppressor of Mothers against Decapentaplegic (SMAD3) genes, as well as histological examination.Results: Leucine supplementation to diabetic rats markedly reduced alterations in markers of kidney function. Furthermore, a reduction in redox markers and inflammatory cytokines was observed in tissues isolated from the leucine-treated diabetic group compared with diabetic rats. Additionally, the expression of the SMAD3 gene, mTOR, and c-JNK protein in renal tissue was significantly reduced in the leucine-diabetic group compared with the diseased group. Conversely, LAT1 tissue expression was upregulated in the leucine-diabetic group.Conclusion: The administration of leucine inhibited renal damage by reducing activation of the profibrotic transforming growth factor beta-1 TGF-β/Smad3 signalling pathway.Keywords: diabetic nephropathy, SMAD3, oxidative stress, inflammation, LAT-1, leucine