Aerobic Swim Training Restores Aortic Endothelial Function by Decreasing Superoxide Levels in Spontaneously Hypertensive Rats

OBJECTIVE:

We aimed to determine whether aerobic training decreases superoxide levels, increases nitric oxide levels, and improves endothelium-dependent vasodilation in the aortas of spontaneously hypertensive rats.

METHODS:

Spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were distributed into 2 groups: sedentary (SHRsd and WKYsd, n=10 each) and swimming-trained (SHRtr, n=10 and WKYtr, n=10, respectively). The trained group participated in training sessions 5 days/week for 1 h/day with an additional work load of 4% of the animal's body weight. After a 10-week sedentary or aerobic training period, the rats were euthanized. The thoracic aortas were removed to evaluate the vasodilator response to acetylcholine (10-10 to 10-4 M) with or without preincubation with L-NG-nitro-L-arginine methyl ester hydrochloride (L-NAME; 10-4 M) in vitro. The aortic tissue was also used to assess the levels of the endothelial nitric oxide synthase and nicotinamide adenine dinucleotide oxidase subunit isoforms 1 and 4 proteins, as well as the superoxide and nitrite contents. Blood pressure was measured using a computerized tail-cuff system.

RESULTS:

Aerobic training significantly increased the acetylcholine-induced maximum vasodilation observed in the SHRtr group compared with the SHRsd group (85.9±4.3 vs. 71.6±5.2%). Additionally, in the SHRtr group, superoxide levels were significantly decreased, nitric oxide bioavailability was improved, and the levels of the nicotinamide adenine dinucleotide oxidase subunit isoform 4 protein were decreased compared to the SHRsd group. Moreover, after training, the blood pressure of the SHRtr group decreased compared to the SHRsd group. Exercise training had no effect on the blood pressure of the WKYtr group.

CONCLUSIONS:

In SHR, aerobic swim training decreased vascular superoxide generation by nicotinamide adenine dinucleotide oxidase subunit isoform 4 and increased nitric oxide bioavailability, thereby improving endothelial function.

Skeletal myopathy in heart failure: effects of aerobic exercise training

Reduced aerobic capacity, as measured by maximal oxygen uptake, is a hallmark in cardiovascular diseases and strongly predicts poor prognosis and higher mortality rates in heart failure patients. While exercise capacity is poorly correlated with cardiac function in this population, skeletal muscle abnormalities present a striking association with maximal oxygen uptake. This fact draws substantial attention to the clinical relevance of targeting skeletal myopathy in heart failure. Considering that skeletal muscle is highly responsive to aerobic exercise training, we addressed the benefits of aerobic exercise training to combat skeletal myopathy in heart failure, focusing on the mechanisms by which aerobic exercise training counteracts skeletal muscle atrophy.

Lack of β2-AR improves exercise capacity and skeletal muscle oxidative phenotype in mice

β(2)-adrenergic receptor (β(2)-AR) agonists have been used as ergogenics by athletes involved in training for strength and power in order to increase the muscle mass. Even though anabolic effects of β(2)-AR activation are highly recognized, less is known about the impact of β(2)-AR in endurance capacity. We presently used mice lacking β(2)-AR [β(2)-knockout (β(2) KO)] to investigate the role of β(2)-AR on exercise capacity and skeletal muscle metabolism and phenotype. β(2) KO mice and their wild-type controls (WT) were studied. Exercise tolerance, skeletal muscle fiber typing, capillary-to-fiber ratio, citrate synthase activity and glycogen content were evaluated. When compared with WT, β(2) KO mice displayed increased exercise capacity (61%) associated with higher percentage of oxidative fibers (21% and 129% of increase in soleus and plantaris muscles, respectively) and capillarity (31% and 20% of increase in soleus and plantaris muscles, respectively). In addition, β(2) KO mice presented increased skeletal muscle citrate synthase activity (10%) and succinate dehydrogenase staining. Likewise, glycogen content (53%) and periodic acid-Schiff staining (glycogen staining) were also increased in β(2) KO skeletal muscle. Altogether, these data provide evidence that disruption of β(2)-AR improves oxidative metabolism in skeletal muscle of β(2) KO mice and this is associated with increased exercise capacity.