We have previously demonstrated that aging reduces the compensatory vasodilator response during hypoxic exercise due to blunted nitric oxide (NO) signaling. Recent evidence suggests that NO bioavailability can be augmented by dietary nitrate through the nitrate-nitrite pathway. Thus we tested the hypothesis that acute dietary nitrate supplementation increases the compensatory vasodilator response to hypoxic exercise, particularly in older adults. Thirteen young (25 ± 1 yr) and 12 older (64 ± 2 yr) adults performed rhythmic forearm exercise at 20% of maximum voluntary contraction during normoxia and hypoxia (∼80% O2 saturation); both before (control) and 3 h after beetroot juice (BR) consumption. Forearm vascular conductance (FVC; ml·min(-1)·100 mmHg(-1)) was calculated from forearm blood flow (ml/min) and blood pressure (mmHg). Compensatory vasodilation was defined as the relative increase in FVC due to hypoxic exercise (i.e., % increase compared with respective normoxic exercise trial). Plasma nitrite was determined from venous blood samples obtained before the control trials and each of the exercise trials (normoxia and hypoxia) after BR. Consumption of BR increased plasma nitrite in both young and older adults (P < 0.001). During the control condition, the compensatory vasodilator response to hypoxic exercise was attenuated in older compared with young adults (3.8 ± 1.7% vs. 14.2 ± 1.2%, P < 0.001). Following BR consumption, compensatory vasodilation did not change in young (13.7 ± 3.3%, P = 0.81) adults but was substantially augmented in older adults (11.4 ± 2.1%, P < 0.01). Our data suggest that acute dietary nitrate supplementation increases the compensatory vasodilator response to hypoxic exercise in older but not young adults.

Aging is associated with increased peripheral chemoreceptor activity, reduced nitric oxide (NO) bioavailability, and attenuation of cardiovagal baroreflex sensitivity (BRS), collectively increasing the risk of cardiovascular disease. Evidence suggests that NO may attenuate peripheral chemoreflex sensitivity and increase BRS. Exogenous inorganic nitrate ([Formula: see text]) increases NO bioavailability via the [Formula: see text]-[Formula: see text]-NO pathway. Our hypothesis was that inorganic [Formula: see text] supplementation would attenuate peripheral chemoreflex sensitivity and enhance spontaneous cardiovagal BRS in older adults. We used a randomized, placebo-controlled crossover design in which 13 older (67 ± 3 yr old) adults ingested beetroot powder containing (BR) or devoid of (BR) [Formula: see text] and [Formula: see text] daily over 4 wk. Spontaneous cardiovagal BRS was assessed over 15 min of rest and was quantified using the sequence method. Chemoreflex sensitivity was assessed via ~5 min of hypoxia (10% fraction of inspired O) and reported as the slope of the relationship between O saturation (%[Formula: see text]) and minute ventilation (in l/min) or heart rate (in beats/min). Ventilatory responsiveness to hypoxia was reduced after BR (from -0.14 ± 0.04 to -0.05 ± 0.02 l·min·%[Formula: see text], P = 0.01) versus BR (from -0.10 ± 0.05 to -0.11 ± 0.05 l·min·%[Formula: see text], P = 0.80), with no differences in heart rate responsiveness (BR: from -0.47 ± 0.06 to -0.33 ± 0.04 beats·min·%[Formula: see text], BR: from -0.48 ± 0.07 to -0.42 ± 0.06 beats·min·%[Formula: see text]) between conditions (interaction effect, P = 0.41). Spontaneous cardiovagal BRS was unchanged after BR and BR (interaction effects, P = 0.69, 0.94, and 0.39 for all, up, and down sequences, respectively), despite a reduction in resting systolic and mean arterial blood pressure in the experimental (BR) group ( P < 0.01 for both). These findings illustrate that inorganic [Formula: see text] supplementation attenuates peripheral chemoreflex sensitivity without concomitant change in spontaneous cardiovagal BRS in older adults. NEW & NOTEWORTHY Exogenous inorganic nitrate supplementation attenuates ventilatory, but not heart rate, responsiveness to abbreviated hypoxic exposure in older adults. Additionally, inorganic nitrate reduces systolic and mean arterial blood pressure without affecting spontaneous cardiovagal baroreflex sensitivity. These findings suggest that inorganic nitrate may attenuate sympathetically oriented pathologies associated with aging.

Sleep may play a role in overweight and obesity in adolescents. the objective of this study is to investigate the relationships between sleep duration and timing and overweight and obesity status in adolescents, with a special emphasis on weekday-weekend difference in sleep characteristics as well as sex-specific relationships. We examined 1,254 U.S. adolescents (12-17 years) self-reported sleep duration, timing, weekday-weekend differences in duration and timing in relation to overweight and obesity. We found an inverse association between sleep duration and overweight and obesity. Compared to 8-9 h of sleep, short sleep (< 7 h) on weekdays was associated with higher odds of overweight and obesity [Odds ratio (95% confidence interval), 1.73 (1.00, 2.97)] in the overall population, while long sleep (10+ h) on weekends was associated with lower odds, but only in males [0.56 (0.34, 0.92)]. We also found that a larger weekday-weekend difference in sleep duration was associated with overweight and obesity in females, but not in males. Specifically, the odds of overweight and obesity were significantly higher among females reporting longer sleep on weekends than weekdays by ≥ 2 h [2.31 (1.15, 4.63)] when compared to those reporting little weekday-weekend differences. Sleep timing, or weekday-weekend differences in sleep timing, were not associated with overweight and obesity in the overall population, although we found suggestive evidence linking later weekend sleep with overweight and obesity in females. Our findings support a role of sleep in adolescent obesity and suggest sex-differences in this relationship that warrant future studies. Adolescents who are overweight and obese are at a greater risk of developing a wide range of health conditions in adulthood, including high blood pressure, heart disease and strokes, certain types of cancer, kidney disease, and type II diabetes 1. Emerging evidence suggests that sleep deficiency may be an important risk factor for overweight and obesity in childhood and adolescence. However, findings from previous studies are mixed, with some reporting negative associations between sleep duration and body-mass index (BMI) 2-5 , others reporting U-shaped associations similar to findings in adults 6 , and some reporting no associations at all 7. Recent studies suggested that later sleep timing and propensity of eveningness may also be associated with higher BMI 8-12. This may be due to more severe misalignment between the internal circadian cycles and the behavioral sleep-wake cycles that are partially influenced by social and environmental factors such as school schedules and social obligations 13,14. It has been well documented that chronotype shifts later during adolescent years 14. Many middle and high schools have a relatively early start time, and this mismatch between school schedules and chronotype-determined sleep window may lead to sleep deficiency on weekdays among adolescents. Moreover, sex-differences in chronotype and sleep patterns have been reported among adolescents, ...

Purpose With aging, there tends to be an increase in retrograde and oscillatory shear in peripheral conduit arteries of humans. Whether the increase in shear rate is due to the aging process or an effect of a less active lifestyle that often accompanies aging is unknown. Therefore, we examined whether chronic endurance exercise training attenuates conduit artery retrograde and oscillatory shear in older adults. Methods Brachial and common femoral artery mean blood velocities and diameter were determined via Doppler ultrasound under resting conditions, and shear rate was calculated in 13 young (24 ± 2 years), 17 older untrained (66 ± 3 years), and 16 older endurance exercise-trained adults (66 ± 7 years). Results Brachial artery retrograde (−9.1 ± 6.4 vs. −12.6 ± 9.4 s−1; P = 0.35) and oscillatory (0.14 ± 0.08 vs. 0.14 ± 0.08 arbitrary units; P = 0.99) shear were similar between the older trained and untrained groups, whereas brachial artery retrograde and oscillatory shear were greater in older untrained compared to young adults (−5.0 ± 3.4, 0.08 ± 0.05 s−1 arbitrary units, P = 0.017 and 0.048, respectively). There was no difference between the young and older trained brachial retrograde (P = 0.29) and oscillatory (P = 0.07) shear. Common femoral artery retrograde (−6.3 ± 2.9 s−1) and oscillatory (0.21 ± 0.08 arbitrary units) shear were reduced in older trained compared to the older untrained group (−10.4 ± 4.1 and 0.30 ± 0.09 s−1 arbitrary units, both P = 0.005 and 0.006, respectively), yet similar to young adults (−7.1 ± 3.5 and 0.19 ± 0.06 s−1 arbitrary units, P = 0.81 and 0.87, respectively). Conclusion Our results suggest that chronic endurance exercise training in older adults ameliorates retrograde and oscillatory shear rate patterns, particularly in the common femoral artery.

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