Cardioprotective effect of Linagliptin on diabetic Wistar rats

Diabetic cardiomyopathy(DCM)is an important cardiovascular complication of diabetes mellitus,while the pathogenesis of DCM has not been fully elucidated.In the present study,we aimed to investigate the effect of Linagliptin on cardiomyocytes of diabetic rats and its mechanism.Cardiac function was evaluated by two-dimensional ultrasound at different time points for each group.HE staining was used to evaluate myocardial injury and inflammatory condition.Sirius-red staining was used to observe the degree of myocardial fibrosis under optical microscope.TUNEL staining was used to investigate the degree of cardiomyocyte apoptosis in four groups.The expressions of m RNAs in relevant cells,including Bcl-2,Bax,TNF-α,PAI-1,CTGF and TGF-β1,were measured by reverse transcription polymerase chain reaction(RT-PCR)and Western blotting analysis in different groups.The expression and transcriptional function of Nrf2 in myocardium activated by Lingliptin were determined using RT-PCR,Western blotting analysis and immunofluorescence.The results showed that the left ventricular volume(LV),left ventricular thickness(LT),fasting blood glucose(FBG)and heart weight/body weight(HW/BW)in diabetes and Linagliptin CO treatment group were significantly lower compared with diabetic group(P<0.05),while the ejection fraction(EF)was higher compared with diabetic group(P<0.05).From HE staining,the treatment of Linagliptin made the arrangement of myocardial fibers more regular,and the striation of myocardial cells became clearer.The Sirus-red staining showed that there was significant accumulation of collagen in the diabetic group rats,indicating that the rats in diabetic group had cardiac fibrosis.The phenomenon in diabetes and Linagliptin CO treatment group was alleviated.TUNEL staining showed that at time point of 4 weeks,the degree of cardiomyocyte apoptosis in diabetes and Linagliptin CO treatment group was lower compared with diabetic group(P<0.01).The expressions of cleaved-caspase-3,TNF-α,PAI-1,CTGF and TGF-β1 proteins in diabetic rats were significantly decreased by Linagliptin,and the difference was statistically significant(cleaved-caspase-3:P<0.01;TNF-α:P<0.01;PAI-1:P<0.05;CTGF:P<0.05;TGF-β1:P<0.05).Compared with the diabetic group,the ratio of Bcl-2/Bax was inecreased in diabetes and Linagliptin CO treatment group,and the difference was statistically significant(P<0.05).From Nrf2 expression in the nucleus and cytosol by RT-PCR,Western blotting analysis and immunofluorescence test,the results showed that Linagliptin promoted the Nrf2 nuclear translocation in myocardial tissue cells.The expression of Nrf2 was significantly down-regulated in the heart of diabetic rats(P<0.01),while this phenomenon in diabetes and Linagliptin CO treatment group was greatly ameliorated.This paper studied the effect of Linagliptin on diabetic myocardial injur and found that the protective mechanism might be related to Nrf2 signaling pathway of antioxidant stress.Collectively,our finding provided new ideas and therapeutic targets for the prevention and treatment of DCM.