Abstract: Objective To investigate the protective effect of fucoxanthin (FX) against diabetic cardiomyopathy and explore the underlying mechanism. Methods Rat models of diabetes mellitus (DM) induced by intraperitoneal injection of streptozotocin (60 mg/kg) were randomized into DM model group, fucoxanthin treatment (DM+FX) group and metformin treatment (DM+Met) group, and normal rats with normal feeding served as the control group. In the two treatment groups, fucoxanthin and metformin were administered after modeling by gavage at the daily dose of 200 mg/kg and 230 mg/kg, respectively for 12 weeks, and the rats in the DM model group were given saline only. HE staining was used to examine the area of cardiac myocyte hypertrophy in each group. The expression levels of fibrotic proteins TGF-β1 and FN proteins in rat hearts were detected with Western blotting. In the cell experiment, the effect of 1 μmol/L FX on H9C2 cell hypertrophy induced by exposure to high glucose (HG, 45 mmol/L) was evaluated using FITC-labeled phalloidin. The mRNA expression levels of the hypertrophic factors ANP, BNP and β-MHC in H9C2 cells were detected using qRT-PCR. The protein expressions of Nrf2, Keap1, HO-1 and SOD1 proteins in rat heart tissues and H9C2 cells were determined using Western blotting. The DCFH-DA probe was used to detect the intracellular production of reactive oxygen species (ROS). Results In the diabetic rats, fucoxanthin treatment obviously alleviated cardiomyocyte hypertrophy and myocardial fibrosis, increased the protein expressions of Nrf2 and HO-1, and decreased the protein expressions of Keap1 in the heart tissue (P<0.05). In H9C2 cells with HG exposure, fucoxanthin significantly inhibited the enlargement of cell surface area, lowered the mRNA expression levels of ANP, BNP and β-MHC (P<0.05), promoted Nrf2 translocation from the cytoplasm to the nucleus, and up-regulated the protein expressions its downstream targets SOD1 and HO-1 (P<0.05) to enhance cellular antioxidant capacity and reduce intracellular ROS production. Conclusion Fucoxanthin possesses strong inhibitory activities against diabetic cardiomyocyte hypertrophy and myocardial fibrosis and is capable of up-regulating Nrf2 signaling to promote the expression of its downstream antioxidant proteins SOD1 and HO-1 to reduce the level of ROS.

Key words: fucoxanthin; diabetic cardiomyopathy; Nrf2/Keap1; oxidative stress