Effects of iridoid total glycoside from Cornus officinalis on prevention of glomerular overexpression of transforming growth factor beta 1 and matrixes in an experimental diabetes model

The present study was conducted to determine whether iridoid total glycoside from Cornus officinalis was effective in regulating expression of transforming growth factor beta 1 (TGF-beta1) and preventing overdeposition of extracellular matrix (ECM) in a diabetes state. An experimental rat model of diabetic nephropathy (DN) was successfully induced by one intraperitoneal injection of streptozotocin at a dose of 60 mg(.)kg(-1) and maintained for 12 weeks. All rats had free access to standard chow and water. Four groups: normal control, diabetic control, diabetic rats with aminoguanidine treatment and diabetic rats with iridoid total glycoside treatment were used in this experiment. All treatments were administered by intragastric gavage (ig). At the end of the experiment, serum was collected for ELISA determination of TGF-beta1 protein level; renal cortex was dissected for reverse transcription polymerase chain reaction (RT-PCR) analysis of its mRNA expression; and immunohistochemistry was introduced to observe ECM deposition. A significantly higher level of protein and mRNA expression of TGF-beta1, and also overdeposition of fibronectin and laminin was found in diabetic rats. Both iridoid total glycoside and aminoguanidine were effective in decreasing serum protein level and glomerular mRNA expression of TGF-beta1, and in preventing renal overdeposition of fibronectin and laminin. This study suggests that iridoid total glycoside is a beneficial agent for prevention and therapy of DN.