Reduction of Arterial Stiffness by Exercise Training Is Associated with Increasing Plasma Apelin Level in Middle-Aged and Older Adults

Abstract

Aging-induced deterioration of arterial stiffness is decreased by regular exercise, and increased nitric oxide (NO) production participates in this effect. Apelin regulates endothelial NO synthase in endothelial cells, promoting NO production. However, the effect of aerobic exercise training on circulating apelin levels in healthy middle-aged and older adults remains unknown. Accordingly, this study aimed to clarify the effects of regular aerobic exercise on apelin concentrations in middle-aged and older adults. Thirty-four healthy middle-aged and older subjects (67.0 ± 1.3 years) were randomly divided into two groups: exercise intervention and sedentary controls. Subjects in the training group completed 8-week of aerobic exercise training (60–70% peak oxygen uptake [VO2peak] for 45 min, 3 days/week). Before and after the intervention, we evaluated plasma apelin and nitrite/nitrate (NOx) concentrations, VO2peak, and arterial stiffness index. In the training group, VO2peak was significantly increased, and carotid β-stiffness was significantly decreased, after the intervention (P<0.05). Moreover, plasma apelin and NOx levels were significantly increased in the training group after the intervention (P<0.05). Additionally, there was a correlation between the training effects of plasma apelin levels and carotidβ-stiffness (r = −0.508, P = 0.032) and plasma NOx levels (r = 0.494, P = 0.037). By contrast, none of these parameters changed significantly in the control group. These results suggest that the increased in plasma apelin levels may be associated with exercise training-induced alternation of arterial stiffness in middle-aged and older adults.

Aerobic exercise training-induced changes in serum adropin level are associated with reduced arterial stiffness in middle-aged and older adults

“…V O2 peak was measured during breath-bybreath assessment using an incremental cycle exercise test on a cycle ergometer (MINATO, AE-310SRD, Osaka, Japan). Incremental cycle exercise began at a work rate of 60 W (30 -90 W) for men and 30 W (0 -60 W) for women, and power output was increased by 15 W/min until the subjects could not maintain a fixed pedaling frequency of 60 rpm (10,22). During the ergometer test, the subjects were encouraged to exercise at maximum intensity.…”

“…Carotid ␤-stiffness was examined as an indicator of arterial stiffness. A combination of ultrasound imaging of the pulsatile common carotid artery and simultaneous applanation of tonometrically obtained arterial pressure from the contralateral carotid artery allowed noninvasive determination of arterial compliance (10,15). The carotid artery diameter was measured from images obtained using an ultrasound system equipped with a high-resolution linear array transducer (15).…”

“…Pressure waveforms and amplitudes were obtained from the common carotid artery using a pencil-shaped probe with a high-fidelity strain gauge transducer [SPT-301; Millar Instruments; Houston, TX (10,15)]. Because baseline blood pressure levels are dependent on hold-down pressure, the pressure signal obtained via tonometry was calibrated by equating the carotid mean arterial blood pressure and DBP to brachial artery values (10,15).…”

“…A cross-sectional study revealed that arterial stiffness was lower in individuals with higher levels of cardiorespiratory fitness (23,28). Furthermore, habitual aerobic exercise reduces arterial stiffness (10,28).…”

“…Recent work showed that adropin is expressed in vascular endothelial cells and promotes nitric oxide (NO) release by regulating endothelial nitric oxide synthase (eNOS) expression via vascular endothelial growth factor receptor 2 (VEGFR2), suggesting that adropin might be involved in endothelial function (20). Aerobic exercise training reduces arterial stiffness, concomitant with the elevation of plasma nitrite/nitrate (NOx) level, in middle-aged and older adults (10), and plasma NOx level is higher in athletes than in sedentary individuals with lower cardiorespiratory fitness (9). Moreover, aging-induced impairment of arterial eNOS protein and mRNA expression is increased by aerobic exercise training in aged rats (27).…”