Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Bidasee, K.R. et al.

Keshore R. Bidasee, Hong Zheng, Chun-Hong Shao, Sheeva K. Parbhu, George J. Rozanski, Kaushik P. Patel,

Exercise training initiated after the onset of diabetes preserves myocardial function: effects on expression of beta-adrenoceptors.

The present study was undertaken to assess cardiac function and characterize beta-adrenoceptor subtypes in hearts of diabetic rats that underwent exercise training (ExT) after the onset of diabetes. Type 1 diabetes was induced in male Sprague-Dawley rats using streptozotocin. Four weeks after induction, rats were randomly divided into two groups. One group was exercised trained for 3 wk while the other group remained sedentary. At the end of the protocol, cardiac parameters were assessed using M-mode echocardiography. A Millar catheter was also used to assess left ventricular hemodynamics with and without isoproterenol stimulation. beta-Adrenoceptors were assessed using Western blots and [(3)H]dihydroalprenolol binding. After 7 wk of diabetes, heart rate decreased by 21%, fractional shortening by 20%, ejection fraction by 9%, and basal and isoproterenol-induced dP/dt by 35%. beta(1)- and beta(2)-adrenoceptor proteins were reduced by 60% and 40%, respectively, while beta(3)-adrenoceptor protein increased by 125%. Ventricular homogenates from diabetic rats bound 52% less [(3)H]dihydroalprenolol, consistent with reductions in beta(1)- and beta(2)-adrenoceptors. Three weeks of ExT initiated 4 wk after the onset of diabetes minimized cardiac function loss. ExT also blunted loss of beta(1)-adrenoceptor expression. Interestingly, ExT did not prevent diabetes-induced reduction in beta(2)-adrenoceptor or the increase of beta(3)-adrenoceptor expression. ExT also increased [(3)H]dihydroalprenolol binding, consistent with increased beta(1)-adrenoceptor expression. These findings demonstrate for the first time that ExT initiated after the onset of diabetes blunts primarily beta(1)-adrenoceptor expression loss, providing mechanistic insights for exercise-induced improvements in cardiac function.[1]

References

Exercise training initiated after the onset of diabetes preserves myocardial function: effects on expression of beta-adrenoceptors. Bidasee, K.R., Zheng, H., Shao, C.H., Parbhu, S.K., Rozanski, G.J., Patel, K.P. J. Appl. Physiol. (2008) [Pubmed]

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