Molecular mechanisms of the antiglycative and cardioprotective activities of Psidium guajava leaves in the rat diabetic myocardium.

CONTEXT: Antiglycative potential of Psidium guajava L. (Myrtaceae) leaves has been established. However, the molecular basis of its antiglycative potential remains unknown.

OBJECTIVE: The ethyl acetate fraction of P. guajava leaves (PGEt) was evaluated to determine the cardioprotective effect and its mechanism of action compared to quercetin.

MATERIALS AND METHODS: After the induction of diabetes by streptozotocin (55 mg/kg body weight), PGEt and quercetin (50 mg/kg body weight) was administered for 60 days. Rats were grouped as follows: Group C: Control, Group D: Diabetic, Group D + E: Diabetic rats treated with PGEt, Group D + Q: Diabetic rats treated with quercetin. The antiglycative potential was evaluated by assaying glycosylated haemoglobin, serum fructosamine and advanced glycation end product levels. The differential receptor for advanced glycation end products and nuclear factor kappa B (NFκB) protein levels was determined by western blot and the transcript level changes of connective tissue growth factor (CTGF), brain natriuretic peptide (BNP) and TGF-β1 in heart tissue were assessed by RT-PCR analysis.

RESULTS: Glycated haemoglobin and serum fructosamine levels were found to be enhanced in diabetic rats when compared with control. Administration of PGEt significantly reduced the glycated haemoglobin and fructosamine levels to a larger extent than quercetin treated diabetic rats. PGEt reduced the translocation of NFκB from cytosol to nucleus when compared with diabetic rats. Expression of TGF-β1, CTGF and BNP was downregulated in PGEt treated groups compared with diabetic controls.

DISCUSSION AND CONCLUSION: Administration of PGEt ameliorated diabetes associated changes in the myocardium to a greater extent than quercetin.