Factors influencing nocturnal blood pressure dipping in patients with metabolic syndrome
Creators: name: Stewart, Nathan
Publisher: name: No Publisher Supplied
Year: 2021

description: BACKGROUND: Blunted dips in nocturnal systolic blood pressure (SBP) are independently related to cardiovascular disease (CVD). While alterations in insulin sensitivity, endothelial function and sympathovagal balance have been suggested to explain dysregulated nocturnal SBP, few studies have systematically assessed these factors in patients with metabolic syndrome (MetS). We hypothesized that insulin sensitivity, vascular function, and autonomic function significantly associate with AMBP in patients with MetS. We further hypothesize that patients who experience a &gt;10% drop in their SBP at night will have more favorable outcomes compared to those who do not experience this dip. METHODS: Twenty-eight adults with MetS (ATP III criteria) (53.2±6.5 y; BMI 35.8±4.5 kgm2) were categorized as “dippers” (≥10% change in SBP; n=4M/6F) or “non-dippers” (&lt;10%; n=5M/13F). Twenty-four hour ambulatory blood pressure monitoring was recorded to assess SBP dipping. Participants were fed isocaloric mixed meals for the 24-hr blood pressure monitoring period. A 2-hr euglycemic-hyperinsulinemic clamp (40 mUm2min, 90 mgdl-1) was performed the next day to test metabolic (glucose infusion rate/insulin) and vascular (brachial artery diameter and %FMD) insulin sensitivity. Augmentation index (AIx@75; arterial waveforms) and post-ischemic flow velocity (PIFV) were measured pre and post the clamp procedure to estimate arterial stiffness and endothelial function respectively. A graded, incremental exercise test (VO2peak) was conducted on a separate day to assess SBPslope and HRslope response during exercise to estimate sympathetic activity. Heart rate recovery (HRR) (peak–post exercise) at 1- and 2-min post exercise was then used to determine parasympathetic activity. Metabolic panels (e.g., estimated glomerular filtration rate (eGFR), circulating sodium and potassium, etc.) were also tested. Three-day food logs were collected in a subgroup (n=16) to estimate habitual diet. RESULTS: Insulin sensitivity, fasted and insulin-stimulated FMD/PIFV, fasted and insulin-stimulated AIx@75 did not differ between groups. Non-dippers had significantly higher LDL concentrations compared to dippers (146.39±28.56 vs. 110.20±21.11 mgdl-1, P=0.002). During exercise, non-dippers experienced a steeper rise in SBPslope compared to dippers (8.0±2.7 vs. 4.9±2.0, P=0.04) but HRR did not differ between dippers and non-dippers at 1-min (17.4±4.8 vs. 21.3±6.3 bpm, P=0.23) or 2-min after exercise (35.4±6.9 vs. 35.8±8.5 bpm, P=0.58). SBP dipping correlated with greater lean body mass (r=0.44, P&lt;0.01), lower LDL cholesterol (r=-0.59, P=0.01), and elevated fasting insulin levels (r=0.61, P=0.01). CONCLUSION: People with MetS who dipped ≥10% in nocturnal SBP experienced a more gradual rise in SBP compared to non-dippers, suggesting that dippers have less sympathetic overactivation compared to non-dippers. Additionally, dippers had significantly lower LDL concentrations and tended to be leaner and more aerobically fit despite lower metabolic insulin sensitivity and no difference in clinic blood pressure, endothelial function or aortic waveforms.Keywords: blood pressure, metabolic syndrome, insulin sensitivity, vascular function