Preventive Effect Of Sulforaphane On Type 2 Diabetes-induced Cardiomyopathy

Background:Type 2 diabetes mellitus(T2DM) is the most widespread metabolic disease in the world. Cardiovascular disease is the major cause of mortality in diabetic patients. T2DM-induced cardiomyopathy is associated with cardiac oxidative stress, inflammation, and remodeling, all of which may be related to cardiac lipid metabolic disorders which induce cardiac lipid accumulation and lipotoxicity. Sulforaphane(SFN), an isothiocyanate naturally presenting in widely Cruciferae vegetables, particularly broccoli, plays an important role in cardiac protection from diabetes. Several studies indicate that SFN prevents diabetes-induced cardiac and aortic damage. It was found that SFN activates nuclear factor erythroid-2 related factor 2(Nrf2) to upregulate cellular antioxidants against oxidative stress and damage. Reccently, it is reported that Nrf2 plays an important role in lipid metabolism. In the present study, therefore, we used an animal model of T2 DM to determine whether and how SFN prevents T2DM-induced cardiac lipotoxicity. Methods:Male C57BL/6J mice were fed with a high-fat diet for 3 months to induce insulin resistance, followed by a treatment with 100 mg/kg body-weight streptozotocin to induce hyperglycemia, as a T2 DM mouse model. Other age-matched mice were fed with normal diet as control. The T2 DM and control mice were treated with or without SFN of 0.5 mg/kg daily, five days a week for 4 months. At the study's end, the cardiac function was assessed. The indices of cardiac inflammation(PAI-1 and TNF-?), fibrosis(CTGF and TGF-?1), oxidative damage(3-NT and 4-HNE), Nrf2, lipid metabolic regular(LKB1/AMPK and its downstream proteins) and autophagy markers LC3 II by Western blot were observed. Lipid acuumulation was detected by oil red O staining. Cardic fibrosis was detected by Sirius red staining. Nrf2 expression and transcription were detected with real-time PCR method. At last 4-HNE-LKB1 adducts were measured by immunoprecipitation assay. Results:The cardiac remodeling and dysfunction induced by T2 DM were significantly attenuated with SFN treatment, the cardiac lipid accumulation measured by oil red O staining also was significantly inhibited, and the cardiac inflammation oxidative stress and fibrosis shown by down-regulating diabetes-induced PAI-1, TNF-?, CTGF, TGF-?, 3-NT and 4-HNE expressions were improved. Elevated 4-HNE resulted in the increase of 4-HNE-LKB1 adducts that should inhibit LKB1 and subsequent AMPK activity. SFN upregulated the expressions of Nrf2 and its downstream genes, NQO1 and HO-1, decreased the levels of 4-HNE-LKB1 adducts and then reversed diabetes-induced inhibition of LKB1/AMPK and its downstream targets, including sirtuin 1, PGC-1?, phosphorylated acetyl-Co A carboxylase, carnitine palmitoyl transferase-1, ULK1 and light chain-3 II. Conclusin:These results suggest that SFN treatment to T2 DM mice may attenuate the cardiac oxidative stress-induced inhibition of LKB1/AMPK signaling pathway, thereby preventing T2DM-induced lipotoxicity and cardiomyopathy.