Cardiorespiratory Fitness And The Cerebrovascular Response To A Metabolic Stimulus Following Cyclooxygenase Inhibition

Abstract

Cardiorespiratory fitness (CRF) is positively associated with cerebrovascular function and cognition. We have previously shown that prostaglandins play an important role in regulating the cerebral vasodilator response to hypercapnia, and that the magnitude of change in cerebral vasodilator responses during cyclooxygenase (COX) inhibition is associated with CRF in older adults. However, it is unknown if CRF also influences the cerebrovascular response to a metabolic stimulus in older adults. PURPOSE: To determine the effects of CRF on the cerebrovascular response to a metabolic stimulus before and during COX inhibition in older adults. METHODS: Thirty-five participants completed a maximal exercise test on a cycle ergometer. Participants were split into two groups, High CRF (10 men, 8 women, age = 62 ± 5y) or Low CRF (7 men, 10 women, age = 66 ± 7y), based on the median VO2max (ml/kg/min). All participants completed two levels of the Stroop Color Word Test. Beat-to-beat mean arterial pressure (MAP) and middle cerebral artery velocity (MCAv) were measured at baseline and in response to each level of the Stroop test before and after administration of the COX inhibitor Indomethacin (INDO). The maximum MAP, MCAv, and cerebral pulsatility index (PI) responses were calculated as the highest 3-beat average during each cognitive challenge. RESULTS: There were no differences between high and low CRF groups in MCAv at rest or in response to the metabolic stimulus. There was a trend for lower PI at rest (p = 0.09) and in response to the Stroop test (p = 0.09) in the high CRF group compared with the low CRF group. During INDO, MCAv decreased (Low CRF: -29 ± 4%, High CRF: -27 ± 3%; p < 0.01) and PI increased (Low CRF: 22 ± 3%, High CRF: 17 ± 3%; p < 0.01). During INDO, MCAv at rest was not different between groups; however, PI was lower in the high CRF compared to low CRF group (Low CRF: 0.98 ± 0.05, High CRF: 0.87 ± 0.03; p < 0.05). Lastly, the change in MCAv and PI in response to the metabolic stimulus did not differ between groups. CONCLUSION: In older adults, elevated levels of CRF may lead to a lower PI at rest and in response to a metabolic stimulus. Additionally, COX inhibition did not alter the cerebrovascular response to a metabolic stimulus. Supported by NIH Grant HL118154.