Raising Plasma Fatty Acids Reduces Baroreflex Sensitivity
We have shown that lipid abnormalities present in obese hypertensives could contribute to their enhanced α1-adrenoceptor sensitivity. In this study, we examined if changing lipids with an intralipid/heparin infusion could contribute to impaired baroreflex sensitivity (BRS). To test this hypothesis, we compared the dose of the α1-adrenoceptor agonist, phenylephrine, to raise MAP 20 mmHg (PD20) before and after an infusion of intralipid/heparin. Also, we determined BRS by the ratio of the change in heart rate recorded in msec over the change in systolic BP in mmHg. We studied six obese hypertensive subjects with a mean age of 40.6 ± 2 and % body fat by DEXA of 30 ± 4%. Raising plasma NEFA levels lowered the PD20 from a baseline of 1.21 to 0.8 μg/m2/min (p=0.05). With raising NEFAs, BRS was decreased from 6.3 ± 0.55 to 3.6 ± 0.42 msec/mmHg (p=0.02)(Δ = baseline measurements, ♦ = intralipid/heparin measurments). These data suggest that acute increases in plasma NEFAs enhance α1-adrenoceptor vascular reactivity and reduce BRS which may contribute to the maintenance of elevated BP in patients with obesity hypertension.