Effects of biological sex and oral contraceptive pill use on cutaneous microvascular endothelial function and nitric oxide-dependent vasodilation in humans

Abstract

The purpose of this study was to evaluate in vivo endothelial function and nitric oxide (NO)-dependent vasodilation between women in either menstrual or placebo pill phases of their respective hormonal exposure [either naturally cycling (NC) or using oral contraceptive pills (OCP)] and men. A planned subgroup analysis was then completed to assess endothelial function and NO-dependent vasodilation between NC women, women using OCP, and men. Endothelium-dependent and NO-dependent vasodilation were assessed in the cutaneous microvasculature using laser-Doppler flowmetry, a rapid local heating protocol (39°C, 0.1°C/s), and pharmacological perfusion through intradermal microdialysis fibers. Data are mean ± standard deviation. Men displayed greater endothelium-dependent vasodilation (plateau, men: 71 ± 16 vs. women 52 ± 20 %CVCmax, p< 0.01), but lower NO-dependent vasodilation (men: 52 ± 11 vs. women 63 ± 17 %NO, p = 0.05), compared with all women. Subgroup analysis revealed NC women had lower endothelium-dependent vasodilation (plateau, NC women: 48 ± 21 %CVCmax, p = 0.01), but similar NO-dependent vasodilation (NC women: 52 ± 14 %NO, p > 0.99), compared with men. Endothelium-dependent vasodilation did not differ between women using OCP and men (p = 0.12) or NC women (p = 0.64), but NO-dependent vasodilation was significantly greater in women using OCP (74 ± 11 %NO) than both NC women and men (p < 0.01 for both). This study highlights the importance of directly quantifying NO-dependent vasodilation in cutaneous microvascular studies. This study also provides important implications for experimental design and data interpretation.

Reply to Letter to the Editor in response to: Microvascular endothelial function following cessation of long‐term oral contraceptive pill use

“…Although it is possible that endothelium-independent vasodilatation is augmented in women using OCP, it is important to highlight that endothelium-independent vasodilatation was not a primary outcome variable in either this case report or our other recent work (Turner, Stanhewicz, Nielsen, Otis et al, 2023). Therefore, we were not powered to accurately assess differences in endothelium-independent vasodilatation.…”

“…Black young adults (Turner, Hayat et al, 2023) or naturally cycling women during menstruation (Turner, Stanhewicz, Nielsen, Otis et al, 2023), suggesting that there is a complex interplay in mechanisms that result in a given percentage of maximal CVC in response to a local heat stimulus. For these reasons, we would suggest that it is important to assess a general measure of endothelial function (i.e., plateau) in addition to the NO contribution.…”

Inhibition of superoxide and iNOS augment cutaneous nitric oxide‐dependent vasodilation in non‐Hispanic black young adults

“…All participants had a fasting venous blood sample taken from a finger stick for analysis of blood lipids and glucose (Cholestech LDX, Abbott, Orlando, FL; Table 1). Participants were then instrumented with four intradermal microdialysis fibers (Custom CMA 31 probes with a 6 KDa molecular weight membrane; CMA Microdialysis, Harvard Apparatus, Hollister, MA) on the left dorsal forearm as described previously (Miller et al., 2021; Turner et al., 2020; Turner, Hayat, et al., 2023; Turner, Stanhewicz, et al., 2023; Wong et al., 2020). Microdialysis sites were assigned as: (1) lactated Ringer's (Baxter Healthcare, Deerfield, IL) to serve as a control, (2) 10 μM tempol (Sigma Aldrich, St. Louis, MO) to inhibit superoxide (Fujii et al., 2014), (3) 0.1 mM 1400 W (AdipoGen, San Diego, CA) to inhibit iNOS (Smith et al., 2011), and (4) combined tempol +1400 W (final concentrations of 10 μM and 1 mM, respectively).…”

“…A standardized local heating protocol was initiated to elicit cutaneous vasodilation. Local heaters at each microdialysis site were increased from 33°C to 39°C at a rate of 0.1°C per second (Choi et al., 2014; Miller et al., 2021; Turner, Hayat, et al., 2023; Turner, Stanhewicz, et al., 2023; Wong et al., 2020). Heaters were held at 39°C until a plateau in skin blood flow was achieved (approximately 30–40 min of heating) and then 20 mM L‐NAME (nonspecific NO synthase inhibitor) was infused through each microdialysis fiber to quantify NO‐dependent vasodilation at each site.…”

Letter to the Editor in response to: Microvascular endothelial function following the cessation of long‐term oral contraceptive pill use: A case report

“…The participant in this study was using a combined oral contraceptive containing drospirenone (0.02 mg ethinyl estradiol and 3.0 mg drospirenone), which Turner, Stanhewicz, Nielsen, Otis et al (2023) specify repeatedly throughout to add important context to their findings. Although this fourth-generation progestin has been associated with greater thromboembolic risk than other progestins, in vitro studies of drospirenone (Simoncini et al, 2007) and in vivo studies, whereby all (desogestrel or drospirenone; Thompson et al, 2011) or a considerable portion (∼40%; desogestrel or gestodene; John et al, 2000) of the women sampled were using pills containing third-and fourth-generation progestins, also collectively indicate that newer-generation progestins appear to enhance endothelial nitric oxide synthase expression and concurrently facilitate the beneficial effects of synthetic estradiol on endothelium-dependent vasodilatation.…”