Preventing declines in cerebral blood flow is important for maintaining optimal brain health with aging. We compared the effects of a morning bout of moderate-intensity exercise, with and without subsequent light-intensity walking breaks from sitting, on cerebral blood velocity over 8 h in older adults. In a randomized crossover trial, overweight/obese older adults ( n = 12, 70 ± 7 yr; 30.4 ± 4.3 kg/m2), completed three acute conditions (6-day washout); SIT: prolonged sitting (8 h, control); EX+SIT: sitting (1 h), moderate-intensity walking (30 min), followed by uninterrupted sitting (6.5 h); and EX + BR: sitting (1 h), moderate-intensity walking (30 min), followed by sitting (6.5 h) interrupted with 3 min of light-intensity walking every 30 min. Bilateral middle cerebral artery velocities (MCAv) were determined using transcranial Doppler at 13 time points across the day. The temporal pattern and average MCAv over 8 h was determined. The pattern of MCAv over 8 h was a negative linear trend in SIT ( P < 0.001), but a positive quadratic trend in EX + SIT ( P < 0.001) and EX + BR ( P < 0.01). Afternoon time points in SIT were lower than baseline within condition ( P ≤ 0.001 for all). A morning dip in MCAv was observed in EX + SIT and EX + BR ( P < 0.05 relative to baseline), but afternoon time points were not significantly lower than baseline. The average MCAv over 8 h was higher in EX + SIT than SIT ( P = 0.007) or EX + BR ( P = 0.024). Uninterrupted sitting should be avoided, and moderate-intensity exercise should be encouraged for the daily maintenance of cerebral blood flow in older adults. The clinical implications of maintaining adequate cerebral blood flow include the delivery of vital oxygen and nutrients to the brain. NEW & NOTEWORTHY This is the first study to measure the combined effects of an exercise bout with breaks in sitting on cerebral blood velocity in older adults. Using frequent recordings over an 8-h period, we have performed a novel analysis of the pattern of cerebral blood velocity, adjusting for concurrent measures of mean arterial pressure and other potential confounders in a linear mixed effects regression.
This study examines the effect of dexamethasone (Dex), a phospholipase A2 inhibitor, on the reversal of 1-kidney, 1-clip (1K,1C) hypertension and the synthesis of phospholipase A2-dependent products. Male Sprague-Dawley 1K,1C hypertensive rats [blood pressure (BP) greater than 190 mmHg] were allocated to three groups: two groups were given daily oral doses of Dex (0.142 mg/kg in water) for 72 h, whereas the third group was given water only (controls). One of the Dex-treated groups was then sham unclipped (n = 9), while the other Dex-treated group (n = 8) and the control group (n = 8) were unclipped. Dex attenuated the BP fall in the unclipped (223 +/- 8-148 +/- 9 mmHg) compared with the control unclipped (226 +/- 9-114 +/- 5 mmHg) animals (P less than 0.005). Aortic 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) was reduced in unclipped Dex-treated rats (13.4 +/- 1.2 ng/mg) compared with unclipped control rats (16.3 +/- 1.4 ng/mg; P less than 0.05) but was higher than in the sham-unclipped Dex group (11.5 +/- 1.2 ng/mg; P less than 0.05). Serum thromboxane B2 (TxB2) in the unclipped Dex-treated group was lower than in the unclipped control rats (P less than 0.05) but higher than in sham-unclipped rats (P less than 0.05). Dex significantly increased urinary prostaglandin E2 (PGE2) excretion, whereas urinary 6-keto-PGF1 alpha was unaltered. After unclipping, both urinary PGE2 and 6-keto-PGF1 alpha increased significantly, although there was no obvious difference between Dex-treated and control animals. These findings demonstrate opposite effects of Dex on renal compared with extrarenal prostanoid synthesis and support the hypothesis that attenuation of aortic 6-keto-PGF1 alpha synthesis may be responsible for the smaller fall in BP after unclipping in Dex-treated rats.
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