BackgroundCoronary artery disease is 2-3 times more common in diabetic individuals.
Dietary nitrate/nitrite has beneficial effects in both diabetes and
cardiovascular disease. It also has protective effects against myocardial
ischemia-reperfusion (IR) injury in healthy animals. However, the effects of
nitrate on myocardial IR injury in diabetic rats have not yet been
investigated.ObjectiveWe examined the effects of dietary nitrate on myocardial IR injury in
streptozotocin-nicotinamide-induced diabetic rats.MethodRats were divided into four groups (n=7 in each group): control,
control+nitrate, diabetes, and diabetes+nitrate. Type 2 diabetes was induced
by injection of streptozotocin and nicotinamide. Nitrate (sodium nitrate)
was added to drinking water (100 mg/L) for 2 months. The hearts were
perfused in a Langendorff apparatus at 2 months and assessed before
(baseline) and after myocardial IR for the following parameters: left
ventricular developed pressure (LVDP), minimum and maximum rates of pressure
change in the left ventricle (±dP/dt), endothelial nitric oxide (NO)
synthase (eNOS) and inducible NO synthase (iNOS) mRNA expression, and levels
of malondialdehyde (MDA) and NO metabolites (NOx).ResultsRecovery of LVDP and ±dP/dt was lower in diabetic rats versus
controls, but almost normalized after nitrate intake. Diabetic rats had
lower eNOS and higher iNOS expression both at baseline and after IR, and
dietary nitrate restored these parameters to normal values after IR.
Compared with controls, heart NOx level was lower in diabetic rats at
baseline but was higher after IR. Diabetic rats had higher MDA levels both
at baseline and after IR, which along with heart NOx levels decreased
following nitrate intake.ConclusionDietary nitrate in diabetic rats provides cardioprotection against IR injury
by regulating eNOS and iNOS expression and inhibiting lipid peroxidation in
the heart.