Thyroid hormone receptor-α deletion decreases heart function and exercise performance in apolipoprotein E-deficient mice.

The deletion of thyroid hormone receptor-α (TRα) in atherosclerosis-prone apolipoprotein E-deficient (ApoE−/−) mice (ApoE−/−TRα0/0) accelerates the formation of atherosclerotic plaques without aggravation of hypercholesterolemia. To evaluate other predisposition risk factors to atherosclerosis in this model, we studied blood pressure (BP) and cardiac and vascular functions, as well as exercise tolerance in young adult ApoE−/−TRα0/0 mice before the development of atherosclerotic plaques. Telemetric BP recorded for 4 consecutive days showed that the spontaneous systolic BP was slightly decreased in ApoE−/−TRα0/0 compared with ApoE−/− mice associated with a reduced locomotor activity. The percentage of animals that completed endurance (57% vs. 89%) and maximal running (0% vs. 89% at 46 cm/s speed in ApoE−/−TRα0/0 and ApoE−/− mice, respectively) tests was lower in ApoE−/−TRα0/0 mice. Moreover, during the maximal running test, both maximal running speed and running distance were significantly reduced in ApoE−/...