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BACKGROUND AND OBJECTIVE: Studies have shown that the increase in urotensin – II is associated with diabetes disorders. Considering that using herbal medicines for the treatment of diseases leads to fewer complications compared to most chemical drugs, the present study was conducted to investigate the effect of silymarin on glucose, and insulin levels and the expression of urotensin – II (U–II) and urotensin – II receptor (U–II R) genes in the liver tissue of type 2 diabetic male rats. METHODS: In this experimental study, 36 male albino Wistar rats were randomly divided into 6 groups (n=6): 1. Control group; 2 and 3. Control groups treated with 60 and 120 mg / kg / day silymarin; 4. Type 2 diabetic group which received an intraperitoneal (i.p.) injection of 60 mg / kg streptozotocin and 120 mg / kg nicotinamide; 5 and 6. Diabetic rats treated with 60 and 120 mg/kg/day silymarin. After 60 days of treatment, serum and liver tissue samples were collected. Glucose, insulin, HOMA-IR index and liver enzymes were evaluated by spectrophotometry and ELISA methods, while gene expression in liver tissue was analyzed by Real-time PCR method. FINDINGS: Insulin levels increased significantly in diabetic groups treated with silymarin (60 and 120 mg/kg) (9.6±1.11 and 9.8±0.96, respectively) in comparison with the diabetic control group (7.10±1.06) (p

Urotensin II (U-II) is a disulfide bridged peptide hormone identified as the ligand of a G-protein-coupled receptor. Human U-II (H-Glu-Thr-Pro-Asp-c[Cys-Phe-Trp-Lys-Tyr-Cys]-Val-OH) has been described as the most potent vasoconstrictor compound identified to date. We have recently identified both a superagonist of human U-II termed P5U (H-Asp-c[Pen-Phe-Trp-Lys-Tyr-Cys]-Val-OH) and the compound termed urantide (H-Asp-c[Pen-Phe- d-Trp-Orn-Tyr-Cys]-Val-OH), which is the most potent UT receptor peptide antagonist described to date. In the present study, we have synthesized four analogues of P5U and urantide in which the Trp7 residue was replaced by the highly constrained l-Tpi and d-Tpi residues. The replacement of the Trp7 by Tpi led to active analogues. Solution NMR analysis allowed improving the knowledge on conformation-activity relationships previously reported on UT receptor ligands. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]