Impaired Transient Receptor Potential Vanilloid 1 In Streptozotocin Induced Diabetic Hearts

ObjectivesThis study was conducted to investigate the changes of transient receptor potential vanilloid 1 (TRPV1) and release of calcitonin gene related peptide (CGRP) in cardiac sensory nerves of diabetic mice in order to analyze the mechanism of myocardial ischemia during sensory neuropathy in diabetic hearts. We presume that the decrease of the expression of TRPV1 and release of CGRP in sensory nerves of diabetic hearts attenuate the self-protection of heart during myocardial ischemia, which result in or aggravate the myocardial infarction.MethodsFour weeks, weight 14-16 g, male C57BL/6J mice were divided into two groups: control(n=16) and diabetes mellitus(n=16). The mice were injected intraperitoneally with either streptozotocin(STZ) 150 mg/kg body weight or vehicle.Whole blood glucose were measured by nipping the distal part of the tail during fasting state after three days later and =16.7 mmol/L was our criterion for experimental diabetes mellitus. Then these animals were breed for another 8 weeks. All animals were sacrificed and hearts were dissected. The expression of TRPV1 and release of CGRP in sensory nerves of diabetic heart were measured by dint of Western blot and radioimmunoassay, respectively.Results1. Blood GlucoseThere was no difference of whole blood glucose level between control and diabetic mice before streptozotocin injection (6.25±0.57 mmol/L vs 6.73±0.84 mmol/L, P>0.05). Significant increase in whole blood glucose were observed in diabetic mice after 3 days post-streptozotocin injection (21.3±2.46 mmol/L vs 6.35±0.61 mmol/L,P<0.01).2. Expression of TRPV 1 proteinThe expression of TRPV1 protein were higher in diabetic mice than in control mice (0.44±0.11 vs 0.30±0.11, P<0.05).3. Release of CGRP in heartThe release of CGRP in hearts of diabetic mice were lower when compared with those in control mice (0.93±0.17 pg/mg vs 0.71±0.12 pg/mg, P<0.05).Conclusions1. The expression of TRPV1 and release of CGRP in sensory nerves of diabetic hearts were impaired.2. Impaired expression of TRPV1 and release of CGRP in sensory nerves of diabetic hearts attenuate the self-protection of heart during myocardial ischemia.