Visit-to-visit and 24-h blood pressure variability: association with endothelial and smooth muscle function in African Americans.

The purpose of this study was to investigate the association of visit-to-visit and 24-h blood pressure (BP) variability with markers of endothelial injury and vascular function. We recruited 72 African Americans who were non-diabetic, non-smoking and free of cardiovascular (CV) and renal disease. Office BP was measured at three visits and 24-h ambulatory BP monitoring was conducted to measure visit-to-visit and 24-h BP variability, respectively. The 5-min time-course of brachial artery flow-mediated dilation and nitroglycerin-mediated dilation were assessed as measures of endothelial and smooth muscle function. Fasted blood samples were analyzed for circulating endothelial microparticles (EMPs). Significantly lower CD31+CD42- EMPs were found in participants with high visit-to-visit systolic blood pressure (SBP) variability or high 24-h diastolic blood pressure (DBP) variability. Participants with high visit-to-visit DBP variability had significantly lower flow-mediated dilation and higher nitroglycerin-mediated dilation at multiple time-points. When analyzed as continuous variables, 24-h mean arterial pressure variability was inversely associated with CD62+ EMPs; visit-to-visit DBP variability was inversely associated with flow-mediated dilation normalized by smooth muscle function and was positively associated with nitroglycerin-mediated dilation; and 24-h DBP variability was positively associated with nitroglycerin-mediated dilation. All associations were independent of age, gender, body mass index and mean BP. In conclusion, in this cohort of African Americans visit-to-visit and 24-h BP variability were associated with measures of endothelial injury, endothelial function and smooth muscle function. These results suggest that BP variability may influence the pathogenesis of CV disease, in part, through influences on vascular health.

Effects of oestrogen deficiency on rat mandibular and tibial microarchitecture.

OBJECTIVES: To investigate the effects of oestrogen deficiency on the microarchitecture of trabecular bone in the mandible and the tibia and to test whether they are correlated. METHODS: Twenty-four age-matched Lewis-Brown-Norway female rats underwent surgical intervention either to remove ovaries (ovariectomy, n=12) or to create a complementary control group (sham-operated, n=12). Sixteen weeks later, the animals were sacrificed and the left side of the mandibles and the tibias were scanned with high resolution micro-CT (15 micro m). Multiple morphological measures including the ratio of bone volume/tissue volume, trabecular thickness, trabecular separation and structure model index were obtained from the experimental and control groups. RESULTS: Ovariectomy significantly decreased the ratio of bone volume/soft tissue volume and trabecular thickness, whilst significantly increasing trabecular separation and structure model index in the mandible (P<0.005) and the tibia (P<0.005). There were significant positive correlations between the mandible and the tibia for trabecular separation (r=0.68, P<0.01) and structure model index (r=0.60, P<0.01). CONCLUSIONS: Oestrogen deficiency results in microarchitectural alterations of trabecular bone in both the mandible and the tibia within 16 weeks. The size of marrow spaces and the shape of trabeculae in the mandible correlate with osteoporotic changes in the long bone.