The Protective Effects And The Molecular Mechanisms Of Dendrobium Officinale Kimura Et Migo Extract Against Diabetic Cardiomyopathy In Vitro And In Vivo

Diabetic cardiomyopathy(DCM)is a typical cardiovascular complications mediated by hyperglycemia,and it was first described by Rubler et al.in 1972.The main characters of diabetic cardiomyopathy are myocardial left ventricular dysfunction,cardiac injury,cardiomyocyte hypertrophy,cardiac cell apoptosis and microvascular abnormalities.Increasing evidence indicated that oxidative stress,cardiac fibrosis,lipid accumulation and inflammation play vital role in the development of diabetic cardiomyopathy.In recent years,researchers have done a lot of studies on diabetic cardiomyopathy,but its pathogenesis,early diagnosis and treatment are still remains unclear.And currently,there is still no specific treatment strategy to DCM.Dendrobium officinale Kimura et Migo,is one of the traditional Chinese medicinal herbs,which has been used as a herbal medicine in many Asian countries for thousands of years.Recent studies have shown that Dendrobium officinale possesses various pharmacological effects,including anti-oxidative,anti-cancer and immunomodulation effects.Polysaccharide is the major constituent of Dendrobium species.Increasing evidence also showed that Dendrobium officinale polysaccharide possesses the hypoglycemic effect.In addition,Dendrobium officinale polysaccharides inhibits the release of pro-inflammatory cytokines,such as tumor necrosis factor(TNF)-α,interleukin(IL)-1β and 6.However,no report was found about the cardio-protective effects of Dendrobium officinale.Consequently,we hypothesized that Dendrobium officinale may be possess the cardio-protective effect against diabetes-induced cardiomyopathy,thus,we explore the protective effect of Dendrobium officinale against DCM in vitro and in vivo.The total content of polysaccharide and species of monosaccharide in DOE were analyzed.As it showed in our results,the water extracts mainly consist of polysaccharide and the concentration of polysaccharide determined by phenol-sulfuric acid method was 72.10 %.According to the result of RP-HPLC,we found that DOE contains two main monosaccharides including mannose and glucose,and the content of mannose and glucose is 19.51 % and 14.03 % respectively.In the in vitro experiment,H9c2 cell models(high glucose induced oxidative stress model and LPS induced inflammation model)were established.Cells were cultured and divided into five groups: control group,DOE group(100 μg /m L,200 μg /mL and 400 μg /mL)and model group.In high glucose stimulation experiment,cells in DOE group were pretreated with different dose of DOE for 12 h,and then shifted into high glucose medium(50mM)for 6 h,the activities of LDH,MDA,T-SOD and ROS production in cells were measured.In LPS stimulation experiment,cells in DOE group were pretreated with different dose of DOE for 12 h,and then stimulated by LPS(1 μg/mL),cell apoptosis and ROS production were detected.Western blot technique was applied in this study to analysis the expression of inflammation associated proteins.The results indicated that pretreatment with DOE could significantly increase the cell viability in both HG and LPS stimulation experiments(P<0.01).An obvious decrease of LDH release and MDA level,increase of T-SOD were observed in HG stimulation experiment(P<0.01).DOE could also reduce the ROS production in both HG and LPS stimulation.In addition,DOE possesses the anti-apoptosis effects in LPS stimulation experiment.Moreover DOE could down-regulated the expression of inflammation associated proteins.In the In vivo experiment,the diabetic models were established by intraperitoneal injection of streptozotocin(50 mg/kg body weight)for 5 consecutive days.After treated with DOE for 8 weeks,mice were sacrificed,the blood samples and heart tissues were collected.The results indicated that the diabetic model was effectively achieved and the serum CK and LDH levels were obviously increased in model mice(P<0.01).After treatment with DOE,a significant decrease of the heart-to-body weight ratio and an evident hypoglycemic effect were found in mice(P<0.01).Our results also showed that DOE treatment could significantly decreased the levels of CK,LDH,TC and TG in serum,reduce the production of MDA and enhance the activity of T-SOD(P<0.01).The results of Oil red O staining and Sirius red staining showed that DOE could alleviate the cardiac injury,inhibit the lipid accumulation and decrease the deposition of collagen in heart tissues.Furthermore,Western blot technique was applied in this study to detect the expression of fibrosis and inflammation related proteins,the results demonstrated that DOE could significantly down-regulate the expression of TGF-β,collegan-1,fibronectin,NF-κB,TNF-α and IL-1β(P<0.01).In conclusion,the present study demonstrated that Dendrobium officinale may possess the protective effects against diabetic cardiomyopathy.The probable mechanism may be due to the inhibition of oxidative stress,down-regulation of pro-inflammatory cytokines and cardiac fibrosis.The present study firstly reported that DOE may possess the cardio-protective potential against DCM and can be a candidate for DCM treatment.However,our research is extremely limited,further studies still need to be carried out to reveal the specific molecular mechanisms.