The Effect of a High Fat Meal on Cerebral Vascular Function

It is well known that a single high fat meal (HFM) causes a robust and transient elevation in serum triglycerides (TG). This elevation in serum TG is a primary contributor to the post-prandial attenuation of peripheral vascular endothelial function, as assessed by flow-mediated dilation in the brachial artery. Whether a similar impairment in vascular reactivity can be observed in the cerebral circulation remains unknown, and was the focus of this investigation. PURPOSE: To test the hypothesis that cerebral vascular function is impaired following a HFM. METHODS: End-tidal carbon dioxide partial pressure (PETCO2), middle cerebral artery blood velocity (MCAVmean), calculated cerebral vascular conductance index (CVCI; MCAVmean/mean arterial pressure) and cerebral vasodilator response to rebreathing induced hypercapnia (% increase in CVC from baseline at common maximal ΔPETCO2) were assessed in 6 healthy young men (27 ±5 years). Measures were assessed during fasted baseline and again at 2 and 4 h post meal consumption (HFM day) or at a similar time point in the fasted state (TC day). The two visits were separated by 2-7 days and were conducted in a randomized order. Blood lipids were assessed at baseline and at the 2 h time point into each respective condition. RESULTS: As expected, consumption of the HFM significantly elevated serum TG concentrations relative to TC at 2 h (HFM: 101±38 to 169±77mg/dl, TC: 107±32 to 92±31mg/dl, P=0.007). However, the HFM had no effect of cerebral vasodilator capacity during rebreathing induced hypercapnia. The maximal increase in %CVC achieved at the highest common ΔPETCO2 during all conditions within each subject was unchanged during 2hr and 4hr post HFM or TC (condition x time interaction: P=0.96). Similarly, the slope of the change in %CVC per change in ΔPETCO2 was unaffected by HFM across time (P=0.49). CONCLUSION: Contrary to our hypothesis, and unlike the peripheral vasculature, our preliminary data suggest that the cerebral circulation appears to be protected from the acute negative effects of a high fat meal

Effect of Acute Antioxidant Consumption on Cardiac Baroreflex Sensitivity in Young Healthy Adults

There is an emerging body of evidence in animals indicating that elevated oxidative stress impairs baroreflex sensitivity (BRS) function, however studies in healthy humans have yielded equivocal results. One potential reason for this discrepancy is that previous studies have used individual antioxidant treatments (e.g., Vitamin C only) to investigate the effect of oxidative stress on BRS. Recent studies in healthy humans have demonstrated significant reductions in reactive oxygen species using an antioxidant cocktail (AOC; Vitamin C, Vitamin E, and Co-enzyme Q10) suggesting the effectiveness of this treatment. Whether this AOC induced reduction in oxidative species affects BRS in young, healthy adults remains unknown. PURPOSE: We tested the hypothesis that AOC will improve cardiac BRS in young healthy adults. METHODS: Five young men were studied on two separate days: placebo (sugar pills) and AOC (2000 mg Vitamin C, 150 IU Vitamin E and 100 mg Co-enzyme Q10) performed in random order. Resting heart rate (ECG) and arterial blood pressure (automated sphygmomanometer and finger photoplethysmography) were measured 90 minutes after AOC or placebo (a time period this AOC has been shown to have peak effects on oxidative stress). Spontaneous cardiac BRS was determined for all sequences combined (overall BRS), and also separately for up (increase systolic blood pressure: increase R-R interval) and down (decrease systolic blood pressure: decrease R-R interval) sequences. RESULTS: Systolic blood pressure on AOC day tended to be lower relative to the placebo day (127 ± 4 vs. 131 ± 5; p=0.098). However, no differences in overall cardiac BRS were found between placebo and AOC (18.0 ± 2.7 vs.17.3 ± 2.6 ms/mmHg; p=0.59). Likewise, up sequences (17.02 ± 2.9 vs 14.04 ± 4.0 ms/mmHg; p=0.51) and down sequences (18.0 ± 2.7 placebo vs. 18.0 ± 2.6 ms/mmHg AOC; p=0.98) were not different between conditions. Equal number of sequences were found between the placebo and AOC days. CONCLUSION: These preliminary data suggest that antioxidant treatment does not affect resting cardiac BRS in young, healthy men

The Effects of Elevated Sodium on Mitochondrial Function in Peripheral Blood Mononuclear Cells

See Attached Abstrac

Inverse Salt Sensitivity in Normotensive Adults: Role of Demographic Factors

See Attached Abstrac

Exaggerated Vasoconstriction to Spontaneous Bursts of Muscle Sympathetic Nerve Actviity in Healthy Young Black Men

Blacks have the highest prevalence of hypertension, putting them at greater risk of cardiovascular disease and death. Previous studies have reported that, relative to whites, healthy black men have augmented pressor responses to sympathoexcitatory stressors. Although important, these studies do not inform about the resting state and the influence of spontaneous changes in resting muscle sympathetic nerve activity (MSNA). Likewise, little is known about the transduction of MSNA into a vascular response at rest on a beat-to-beat basis. Accordingly, we tested the hypothesis that relative to whites, blacks would exhibit greater vasoconstriction and pressor responses following spontaneous bursts of MSNA. Mean arterial pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 minutes of supine rest in 35 young healthy men (17 blacks and 18 whites). Signal averaging was used to characterize changes in leg vascular conductance, total vascular conductance, and mean arterial pressure following spontaneous MSNA bursts. Blacks demonstrated significantly greater decreases in leg vascular conductance (blacks: −15.0±1.0%; whites: −11.5±1.2%; P=0.042) and total vascular conductance (blacks: −8.6±0.9%; whites: −5.1±0.4%; P=0.001) following MSNA bursts, which resulted in greater mean arterial pressure increases (blacks: +5.2±0.6 mm Hg; whites: +3.9±0.3 mm Hg; P=0.04). These exaggerated responses in blacks compared with whites were present whether MSNA bursts occurred in isolation (singles) or in combination (multiples) and were graded with increases in burst height. Collectively, these findings suggest that healthy young black men exhibit augmented sympathetic vascular transduction at rest and provide novel insight into potential mechanism(s) by which this population may develop hypertension later in life.(Hypertension. 2018;71:192-198. DOI:10.1161/HYPERTENSIONAHA.117.10229.

Exaggerated Vasoconstriction to Spontaneous Bursts of Muscle Sympathetic Nerve Activity in Healthy Young Black Men

Blacks have the highest prevalence of hypertension, putting them at greater risk of cardiovascular disease and death. Previous studies have reported that, relative to whites, healthy black men have augmented pressor responses to sympathoexcitatory stressors. Although important, these studies do not inform about the resting state and the influence of spontaneous changes in resting muscle sympathetic nerve activity (MSNA). Likewise, little is known about the transduction of MSNA into a vascular response at rest on a beat-to-beat basis. Accordingly, we tested the hypothesis that relative to whites, blacks would exhibit greater vasoconstriction and pressor responses following spontaneous bursts of MSNA. Mean arterial pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 minutes of supine rest in 35 young healthy men (17 blacks and 18 whites). Signal averaging was used to characterize changes in leg vascular conductance, total vascular conductance, and mean arterial pressure following spontaneous MSNA bursts. Blacks demonstrated significantly greater decreases in leg vascular conductance (blacks: −15.0±1.0%; whites: −11.5±1.2%; P=0.042) and total vascular conductance (blacks: −8.6±0.9%; whites: −5.1±0.4%; P=0.001) following MSNA bursts, which resulted in greater mean arterial pressure increases (blacks: +5.2±0.6 mm Hg; whites: +3.9±0.3 mm Hg; P=0.04). These exaggerated responses in blacks compared with whites were present whether MSNA bursts occurred in isolation (singles) or in combination (multiples) and were graded with increases in burst height. Collectively, these findings suggest that healthy young black men exhibit augmented sympathetic vascular transduction at rest and provide novel insight into potential mechanism(s) by which this population may develop hypertension later in life.(Hypertension. 2018;71:192-198. DOI:10.1161/HYPERTENSIONAHA.117.10229.