Higher levels of physical activity is associated with lower arterial stiffness in patients with resistant hypertension

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Portuguese Foundation for Science and Technology (FCT) European Regional Development Fund – Operational Competitiveness Factors Program (COMPETE)

Background

 Physical activity has been associated with reduced arterial stiffness in patients with hypertension. However, in resistant hypertension, a specific population with an increased risk for target organ damage, cardiovascular morbidity, and mortality, the evidence is sparse. 

Purpose

 The present study aimed to determine the association between daily physical activity and arterial stiffness in patients with resistant hypertension.

Methods

 Fifty-seven patients with resistant hypertension were recruited. Physical activity was objectively assessed during 7 consecutive days with accelerometers. Arterial stiffness was evaluated using carotid-femoral pulse wave velocity (cf-PWV) . 

Results

 Participants (50.9% men), aged 58.8 ± 9.4 years, were mainly overweight and were taking in average 4.5 antihypertensive medications. The cf-PWV showed an inverse correlation with light-intensity physical activity (r = -0.290, p = 0.029) and total daily physical activity (r = -0.287, p = 0.030). Additionally, cf-PWV tended to be inversely associated with the number of steps per day (r = -0.242, p = 0.069). Patients with higher risk of cardiovascular events (cf-PWV ≥ 10 m/s) tended to spend less time in light-intensity physical activity (324.0 ± 129.4 vs. 380.5 ± 103.1 min/day, p = 0.090) and to perform less total daily physical activity (351.5 ± 141.7 vs. 411.7 ± 109.1 min/day, p = 0.091) than participants with cf-PWV below the risk threshold value.

Conclusions

 Higher levels of total physical activity and daily levels of light-intensity were associated to lower arterial stiffness. These results emphasize the importance of physical activity as a nonpharmacological tool for patients with resistant hypertension.

Irregular geometries in normal unmyelinated axons: a 3D serial EM analysis

Axons have generally been represented as straight cylinders. It is not at all uncommon for anatomists to take single cross-sections of an axonal bundle, and from the axonal diameter compute expected conduction velocities. This assumes that each cross-section represents a slice through a perfect cylinder. We have examined the three-dimensional geometry of 98 central and peripheral unmyelinated axons, using computer-assisted serial electron microscopy. These reconstructions reveal that virtually all unmyelinated axons have highly irregular axial shapes consisting of periodic varicosities. The varicosities were, without exception, filled with membranous organelles frequently including mitochondria, and have obligatory volumes similar to that described in other neurites. The mitochondria make contact with microtubules, while the other membraneous organelles were frequently found free floating in the cytoplasm. We conclude that unmyelinated axons are fundamentally varicose structures created by the presence of organelles, and that an axon's calibre is dynamic in both space and time. These irregular axonal geometries raise serious doubts about standard two dimensional morphometric analysis and suggest that electrical properties may be more heterogeneous than expected from single section data. These results also suggest that the total number of microtubules contained in an axon, rather than its single section diameter, may prove to be a more accurate predictor of properties such as conduction velocity. Finally, these results offer an explanation for a number of pathological changes that have been described in unmyelinated axons.