Acute Exercise Reduces Intranasal Insulin-Mediated Elevations in Blood Pressure in Aging Adults with Cardiometabolic Risk

Background: Insulin contributes to blood pressure (BP) regulation through, in part, effects on the brain. Whether exercise impacts brain insulin action in parallel with alterations in BP is unclear. Purpose: Examine if an acute exercise lowers BP after intranasal insulin (INI) and increases cerebral blood flow (CBF) in aging adults with cardiometabolic risk. Methods: In a counter-balanced design, 15 cognitively unimpaired (MoCA: 28.2±1.3 a.u.) adults (56.7±2.1 yr; VO 2 max: 23.9±0.9 ml/kg/min) with obesity (BMI 31.8±1.3 kg/m 2 ) were randomized to a rest or acute treadmill exercise bout (70% VO 2 max for 60 minutes) in the evening. The next morning, participants arrived fasted and BP, heart rate, glucose and insulin were assessed. Brainstem and hypothalamus CBF were then tested via pseudo-Continuous Arterial Spin Labeling (pCASL) MRI. INI (40 IU) was administered and 30 as well as 90 minutes later, BP, heart rate, glucose, and insulin were measured. Then a 75g oral glucose tolerance test (OGTT) was provided, and outcomes were obtained again every 30 minutes up to 120 minutes. Results: Exercise had no effect on glucose following INI, although insulin was reduced during the OGTT ( P<0.05). Exercise blunted the rise in systolic BP after INI as well as during the entire protocol (both P<0.05), independent of heart rate. Exercise raised CBF in the brainstem ( P<0.05) but not the hypothalamus. However, the increase in fasting hypothalamus CBF correlated with reductions in INI-mediated systolic BP (r=-0.51, P=0.05). Conclusion: In adults with cardiometabolic risk, an acute exercise bout blunted systolic BP rises after INI in parallel with increased fasting brainstem and hypothalamic CBF.