Local endothelin-1 receptor type A antagonism improves cutaneous microvascular function in women with a history of gestational diabetes mellitus

Abstract

Women with a history of gestational diabetes mellitus (GDM) are at a greater risk of developing cardiovascular disease (CVD) compared to women who had an uncomplicated pregnancy. Microvascular endothelial dysfunction, mediated in part by reduced nitric oxide (NO)-dependent mechanisms, persists after GDM and contributes to vascular disease progression. Endothelin-1 (ET-1), a potent vasoconstrictor, contributes to vascular dysfunction in diabetes and may similarly contribute to vascular dysfunction after GDM. We hypothesized that local ET-1 receptor type A (ET_AR) antagonism would improve endothelium- and NO-dependent dilation in the cutaneous microvasculature of women with a history of GDM. Two intradermal microdialysis fibers were placed in the skin of the ventral forearm of 12 healthy controls (HC, 35 ± 3 years) and 12 women with a history of GDM (34 ± 4 years) for the local delivery of lactated Ringer’s (control) or 500nmol/L BQ-123 (ET_AR antagonist) during a standard local heating protocol (42°C; 0.1°C·s⁻¹). After full expression of the local heating response, 15mmol/L N^G-nitro-L-arginine methyl ester (NO synthase inhibitor) was perfused. Red blood cell flux was measured by laser-Doppler flowmetry (LDF) and cutaneous vascular conductance was calculated (CVC=LDF/mean arterial pressure) and normalized to maximum (28mmol/L sodium nitroprusside + 43°C). Endothelium- (p=0.04) and NO-dependent (p=0.03) dilation were attenuated at the Ringer’s site in GDM compared with HC women. In GDM women, ET_AR antagonism increased endothelium- (vs. Ringer’s; p=0.03) and NO-dependent (vs. Ringer’s; p=0.01) dilation but had no effect in HC (p>0.05). These data suggest that ET-1 contributes to microvascular dysfunction following pregnancy complicated by GDM.

Graphical Abstract

INTRODUCTION

Gestational diabetes mellitus (GDM) is a pregnancy complication characterized by the new onset of glucose intolerance during gestation in women who previously had normal glucose tolerance(1). Approximately 10% of women in the United States experience GDM and prevalence has been rising steadily over the past decades with no indication of a plateau (2). In most cases, GDM-associated glucose intolerance resolves after delivery and clinical markers of metabolic health normalize after pregnancy(3). However, women with a history of GDM are twice as likely to develop cardiovascular disease (CVD), and do so at an earlier age compared to women who had an uncomplicated pregnancy(4, 5). This accelerated chronic disease trajectory of women with a history of GDM highlights the need to identify the underlying mechanisms by which these diseases progress.

One putative mechanism that may link a history of GDM to increased CVD risk is vascular dysfunction. Microvascular endothelial dysfunction, mediated in part by reduced nitric oxide (NO)-dependent vasodilatory mechanisms, precedes and contributes to the development of CVD(6–9). We have demonstrated that women with a history of GDM exhibit reductions in cutaneous microvascular endothelium-dependent responses to physiological (i.e. local heating(10)) and pharmacological (i.e. insulin and acetylcholine(11, 12)) stimuli even in the absence of overt cardiovascular or metabolic disease mediated, in part, by oxidative stress and reduced NO-dependent dilation. Importantly, early reductions in endothelial function are reversible with lifestyle or pharmacological interventions(13–19), underscoring the need to identify mechanisms driving this dysfunction that can be targeted to improve function and delay or prevent the progression of chronic disease in this cohort at high risk.

Endothelin-1 (ET-1), a potent vasoconstrictor peptide that is primarily produced and released by endothelial cells(20), contributes to the development and progression of vascular dysfunction in CVD(21, 22) and metabolic(23, 24) disease (21, 25, 26), and may similarly contribute to long-term vascular risk after GDM. Notably, ET-1 activity is modulated by NO(27), where NO tonically inhibits ET-1 and imbalances in NO lead to excessive ET-1 activity. Furthermore, ET-1 can stimulate the production of superoxide, and at the same time, reactive oxygen species appear to stimulate ET-1 production(28). As such, the ET-1 system is currently a target for therapeutic intervention in numerous disease conditions(29) and may specifically contribute to exaggerated vascular oxidative stress and microvascular endothelial dysfunction in women with a history of GDM. However, whether ET-1 contributes to microvascular dysfunction in the microvasculature after pregnancy complicated by GDM has not been explored.

ET-1 exerts its vascular actions via two receptor subtypes. ET-1 acts as a vasoconstrictor when it binds to ET-1 type A receptors (ET_AR) and ET-1 type B receptors (ET_BR) located on vascular smooth muscle cells. ET-1 can also cause vasodilation when it binds to ET_BR localized on vascular endothelial cells. Nonselective ET-1 receptor blockade improves endothelium-dependent vasodilation in atherosclerotic patients and patients with essential hypertension(30, 31). However, nonselective ET-1 receptor blockade may potentially mask the benefits elicited by the inhibition of ET-1-induced vasoconstriction alone. Importantly, selective ET_AR blockade improves endothelium-dependent dilation in overweight and obese adults(32) and attenuates vascular dysfunction in patients with T2DM(33) and coronary artery disease(34). Additionally, chronic ET_AR antagonism with atrasentan attenuates vascular dysfunction in mildly hyperglycemic, normotensive, nonobese murine models of type 2 diabetes (35). Identifying whether ET_AR antagonism can improve microvascular function in women with a history of GDM could provide rationale for future clinical trials specifically designed to reduce CVD risk in these women.

The purpose of this study was to identify whether ET-1 contributes to attenuated microvascular endothelial function in otherwise healthy women with a history of GDM. Using the cutaneous circulation as an in vivo model, we assessed microvascular vasodilation responses to a physiological stimulus (standardized local heating protocol) in women with a history of GDM and healthy control (HC) women with a history of uncomplicated pregnancy who were within 5 years of pregnancy and free of cardiovascular and metabolic disease. We hypothesized that local ET_AR antagonism with BQ-123 would improve endothelium- and NO-dependent dilation in the cutaneous microvasculature of women with a history of GDM.

METHODS

Ethical Approval

Experimental protocols were approved by the University of Iowa Institutional Review Board (IRB# 202405720) and the United States Food and Drug Administration (IND no. 153,527). Written and verbal consent were obtained voluntarily from all participants prior to enrollment according to the Declaration of Helsinki and the U.S. Code of Federal Regulations, Part 46, and registered on ClinicalTrials.gov (NCT06547619).

Study Population

A total of 24 women who had been pregnant within the past 5 years participated in the study. Of these, 12 had a history of GDM during their most recent pregnancy, diagnosed by their obstetrician in accordance with criteria set by the American College of Obstetrics and Gynecologists(1). The other 12 women had a history of a healthy pregnancy, confirmed by medical chart review, and served as age-matched healthy controls (HC). The effect of ET_AR antagonism on the cutaneous local heating vasodilation response has not been assessed or published previously in this population.

Participants were screened for CVD and metabolic diseases and underwent a complete medical screening that included a physical examination, lipid profile, and blood chemistry. All participants were not diabetic or prediabetic, non-smokers, who were not taking medications with primary or secondary vascular effects. Exclusion criteria included: history of preeclampsia, history of gestational hypertension, and history of hypertension or diabetes before pregnancy. Race and ethnicity were self-reported. The homeostatic model assessment of insulin resistance (HOMA-IR: fasting plasma glucose mg/dL x fasting plasma insulin μU/mL / 22.5) was used to assess insulin sensitivity(36).

Experimental procedure: cutaneous vasodilator responsiveness to local heat

Participants completed one laboratory visit and were instructed to fast for 8 hours, avoid caffeine for 8 hours, and abstain from alcohol and strenuous physical activity for 24 hours prior to the visit. A fasted blood sample was taken at the beginning of the experimental visit. Two intradermal microdialysis fibers (CMA31, Harvard Apparatus, Holliston, MA, USA) were placed into the dermal layer of the ventral forearm for the local delivery of lactated Ringer’s solution (control) or 500nmol/L BQ-123 for the local inhibition of ET_AR(37–39). Pharmacological agents were weighed just before use, dissolved in lactated Ringer’s solution, sterilized using syringe microfilters (Acrodisc; Pall, Ann Arbor, MI, USA), wrapped in foil to prevent degradation due to light exposure, and perfused through the microdialysis fiber at a rate of 2 μl∙ min⁻¹ (Bee Hive controller and Baby Bee microinfusion pumps; Bioanalytical Systems, West Lafayette, IN, USA). The experimental protocol commenced after an initial hyperemia-resolution period (~60 minutes). Cutaneous red blood cell flux was continually measured directly over each microdialysis site with a laser-Doppler flowmetry (VMS-LDF2) probe placed in a local heating unit (VMS-HEAT, Moor Instruments, Wilmington, DE, USA) for the control of local skin temperature. Automated brachial blood pressure (Philips Medical Systems, SureSigns VS2+, Andover, MA, USA) was measured every 5 minutes on the contralateral arm throughout the protocol.

Local heating protocol

During baseline measurements, the local heaters were set to thermoneutral (33°C). Following stable baseline measurements (~10 min), the temperature of the local heaters was raised to 42°C (0.1°C ∙s⁻¹) following a standardized local skin heating protocol(40, 41) and remained at 42°C until skin blood flow reached a stable plateau (~40 min, endothelium-dependent plateau). Next, the sites were perfused with 15mmol/L N^G-nitro-l-arginine methyl ester (L-NAME, endothelial NO-synthase inhibitor) until skin blood flow reached a stable plateau (~40 minutes, L-NAME plateau) to determine NO-dependent dilation. At the end of the experimental protocol, 28mmol/L sodium nitroprusside (United States Pharmacopeia) was perfused, and local temperature was increased to 43°C to elicit maximal dilation(39, 41). Figure 1 depicts a representative tracing of the skin blood flow response to local heating in Ringer’s (control) and BQ-123 sites in a participant with a history of GDM.

Figure 1. Representative tracing of cutaneous local heating response in a participant with a history of gestational diabetes mellitus.

Individual tracing showing representative endothelium-dependent plateau responses in the cutaneous microvasculature at a control (Lactated Ringer’s, gray) site and an endothelin-1 receptor type A antagonized site (500nmol/L BQ-123, gold) during standardized local heating of the skin to 42°C. 15 mmol/L L^G-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor) was perfused to quantify nitric-oxide dependent dilation and maximal dilation was elicited by perfusing 28 mmol/L sodium nitroprusside and increasing local temperature to 43°C.

Enzyme-linked immunosorbent assay (ELISA)

The concentration of circulating ET-1 was measured in plasma collected at the beginning of the microdialysis experimental visit. Plasma concentrations of ET-1 were measured using the Human Endothelin-1 ELISA kit (R&D Systems, Minneapolis, MN, USA) according to the manufacturer’s instructions.

Data and statistical analysis

All data collection and analysis procedures were standardized before testing. Skin blood flow data were digitized at 40 Hz, recorded, and stored for offline analysis (PowerLab and LabChart, ADInstruments, Sydney, Australia). Cutaneous vascular conductance was calculated (CVC = laser-Doppler flux/mean arterial pressure) and normalized to a percentage of site-specific maximum (%CVC_max). NO-dependent dilation was calculated as the difference between the endothelium-dependent plateau and the L-NAME plateau (Δ%CVCmax).

Sample size (n=12 per group) was determined a priori by power analysis (power=0.08, α=0.05) based on prior studies comparing similar outcomes between HC and GDM women (CVC %maximum endothelium-dependent dilation: mean difference between groups = 19%, Cohen’s d=1.3; %NO-dependent dilation: mean difference between groups = 15%, Cohen’s d = 1.1) and utilizing ET-1-antagonists in a similar approach (CVC %maximum endothelium-dependent dilation: mean difference with ET-1 antagonist treatment = 5%, Cohen’s d = 0.7) (39). Student’s unpaired t-tests were used to compare subject characteristics. Absolute CVC, %CVCmax, and NO-dependent dilation data were analyzed using a 2-way repeated measures ANOVA (group*pharmacological site; SAS 9.4, Cary, IN) with post hoc Tukey corrections applied for specific planned comparisons when appropriate. Values are presented as mean ± SEM.

RESULTS

Participant characteristics are presented in Table 1. There were no differences in age, parity, time postpartum, blood pressure, cholesterol, high-density or low-density lipoprotein, triglycerides, fasting plasma glucose, fasting plasma insulin, or HOMA-IR between groups (all p>0.05). BMI (p=0.02) and HbA1c (p=0.009) were higher in the GDM group compared to HC. Circulating plasma ET-1 concentrations were not different between groups (p=0.42). Three HC participants and two GDM participants were actively breastfeeding during study enrollment. Nine HC (two oral pill, seven intrauterine device) and six GDM (all intrauterine device) participants were using a form of hormonal contraceptive. Baseline and maximal CVC values are presented in Table 2. There were no group or site differences in baseline or maximal CVC responses (all p>0.05).

Table 1.

Participant Characteristics

	HC (n=12)	GDM (n=12)	p-value
Age (years)	35 ± 3	34 ± 4	0.19
Parity (number)	2 ± 1	2 ± 1	0.28
Race, n (%)
White	12 (100)	12 (100)
Black or African American	0 (0)	0 (0)
Asian	0 (0)	0 (0)
Unknown/not reported	0 (0)	0 (0)
Ethnicity, n (%)
Not Hispanic or Latino	11 (92)	11 (92)
Hispanic or Latino	1 (8)	1 (8)
Time post-partum (months)	29 ± 18	25 ± 16	0.41
Glucose management during pregnancy (n)
Diet	--	11
Insulin Injection	--	1
FDR with type 2 diabetes mellitus, n (%)	0 (0)	4 (33)
SDR with type 2 diabetes mellitus, n (%)	3 (25)	3 (25)
MAP (mmHg)	80 ± 7	82 ± 6	0.61
SBP (mmHg)	110 ± 9	112 ± 11	0.61
DBP (mmHg)	70 ± 6	72 ± 7	0.45
BMI (kg·m−2)	26.9 ± 3.7	31.7 ± 5.2	0.02
Total cholesterol (mg·dl−1)	168 ± 21	183 ± 37	0.23
HDL (mg ·dl−1)	56 ± 11	58 ± 13	0.72
LDL (mg·dl−1)	98 ± 26	108 ± 29	0.41
Triglycerides (mg·dl−1)	66 ± 24	87 ± 38	0.14
Fasting glucose (mg·dl−1)	81 ± 6	86 ± 9	0.08
Fasting insulin (μU·ml−1)	7 ± 4	11 ± 8	0.13
HOMA-IR	1.4 ± 0.7	2.5 ± 2.0	0.09
HbA1c (%)	5.1 ± 0.2	5.3 ± 0.3	0.009
Contraceptive use (n)
Oral pill	2	0
Implant	0	0
Intrauterine device	7	6
Plasma endothelin-1 (pg/mL)	0.77 ± 0.47	0.63 ± 0.31	0.42

Values are mean ± SD. HC, history of healthy pregnancy; GDM, history of gestational diabetes mellitus; FDR, 1^st-degree relative; SDR, 2^nd-degree relative; MAP, mean arterial pressure; SBP, systolic blood pressure; DBP, diastolic blood pressure; BMI, body mass index; HDL, high-density lipoprotein; LDL, low-density lipoprotein; Hba1c, glycated hemoglobin; HOMA-IR, homeostatic model assessment of insulin resistance. Statistical comparisons and P-values presented from Student’s t test. P-values indicated in boldface are considered significant.

Table 2.

Cutaneous Vascular Conductance

Microdialysis Site	HC	GDM	p-value
Lactated Ringer’s
Baseline	0.23 ± 0.14	0.24 ± 0.13	0.95
Maximum	2.2 ± 0.92	2.6 ± 0.89	0.37
BQ-123
Baseline	0.23 ± 0.13	0.21 ± 0.11	0.69
Maximum	2.16 ± 1.0	2.2 ± 0.60	0.84

Values are mean ± SD. Cutaneous vascular conductance (flux·mmHg⁻¹) = laser-Doppler flux /mean arterial pressure; BQ-123 (500nmol/L), endothelin-1 receptor type A antagonist; HC, history of uncomplicated pregnancy (n=12); GDM, history of gestational diabetes mellitus (n=12).

Cutaneous local heating response

Figure 2 presents the endothelium-dependent plateau phase of the local heating response (Figure 2A) and the NO-dependent contribution to the plateau (Figure 2B). The endothelium-dependent local heating plateau (GDM: 78 ± 11 vs. HC: 88 ± 8 %CVCmax; p=0.04) and the NO-dependent portion of the plateau (GDM: 63 ± 11 vs. HC: 73 ± 8 Δ%CVCmax; p=0.03) were attenuated at the Ringer’s site in GDM compared with HC women. ET_AR antagonism with BQ-123 increased the endothelium-dependent local heating plateau (89 ± 7 vs. Ringer’s 78 ± 11 %CVCmax; p=0.03) and NO contribution to the plateau (75 ± 11 vs. Ringer’s 63 ± 11 Δ%CVCmax; p=0.01) in GDM women, but had no effect on the plateau (83 ± 17 vs. Ringer’s 88 ± 8 %CVCmax, p=0.27) or NO contribution to the plateau (70 ± 15 vs. Ringer’s 73 ± 8 Δ%CVCmax, p=0.39) in HC women.

Figure 2. Microvascular endothelium-dependent and nitric oxide-dependent dilation.

Mean ± SEM cutaneous vascular conductance (CVC %max) response to local heating. Endothelium-dependent dilation (Figure 2A) and nitric oxide (NO)-dependent dilation (Figure 2B) were attenuated at the control (Ringer’s) site in women with a history of gestational diabetes mellitus (GDM, n=12, gold) compared with healthy control (HC, n=12, white) women. Endothelin-1 receptor type A antagonism (500nmol/L BQ-123) increased endothelium-dependent dilation and nitric oxide-dependent dilation in GDM but not in HC.

DISCUSSION

The primary finding of this study suggests that women with a history of GDM exhibit reductions in microvascular function, mediated in part by ET-1, compared to HC women who had an uncomplicated pregnancy. Using the human cutaneous circulation as an in vivo bioassay to examine mechanisms of microvascular function(42), we provide the first, direct, in vivo evidence that selective ET_AR antagonism improves endothelium- and NO-dependent vasodilation in the microvasculature of otherwise healthy women with a history of GDM. These findings provide mechanistic insight regarding the influence of the ET-1 system on reduced microvascular function in otherwise healthy women with a history of GDM.

The overall prevalence of CVD in women is projected to increase over the next 30 years, with rising rates of adverse events in pregnancy contributing to this rise(43). Women with a history of GDM are also seven times more likely to develop type 2 diabetes mellitus (T2DM)(44) and while subsequent development of T2DM elevates CVD risk, prior GDM is an independent risk factor for CVD morbidity, particularly within the first decade postpartum(4, 5, 45–47). Our prior work has demonstrated that reductions in microvascular endothelium- and NO-dependent dilation observed in women after a pregnancy complicated by GDM are mediated in part by increased vascular oxidative stress(10, 12), and that nonspecific antioxidant perfusion with ascorbic acid(10) and targeted nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibition with apocynin(12) improve microvascular function in women with a history of GDM. Prior to the current study, no one has examined the influence of the ET system on microvascular function in women with a history of GDM, highlighting a biomedically relevant research gap with the potential to inform future work designed to delay or prevent vascular disease progression in these women.

ET-1 activates proinflammatory and profibrotic pathways, ultimately leading to the induction of superoxide production via NADPH oxidase activation (28, 48). Interestingly, NADPH oxidase inhibition with apocynin has been shown to prevent ET-1-mediated increases in superoxide production in pulmonary arterial smooth muscle cells(49), highlighting the interconnected nature of oxidative stress and the ET-1 system. Given that ET-1 contributes to endothelial dysfunction in patients at high risk for, or who currently have, T2DM(33), and that ET-1 may be an upstream mechanism contributing to vascular oxidative stress and reduced endothelial reactivity in overt cardiovascular disease, we hypothesized that it may be a mechanism driving endothelial dysfunction in women with a history of GDM, representing a molecular target to improve vascular function in women with a history of GDM.

In the current study, we demonstrate that acute, local ET_AR antagonism with BQ-123 improves both endothelium- and NO-dependent vasodilation in otherwise healthy women with a history of GDM. ET-1 activity has been linked to the development and progression of several cardiovascular pathologies(24) including hypertension, atherosclerosis, coronary artery disease, congestive heart failure, pulmonary arterial hypertension, cerebrovascular disease, chronic kidney disease, and preeclampsia(21, 22). ET-1 has also been implicated in the development and progression of metabolic disorders such as T2DM(23, 24). ET-1 contributes to both cardiovascular and metabolic disorders by inducing vascular endothelial dysfunction(26), in part by reducing NO bioavailability, which is a potent predictor of future CVD risk(7, 9, 50). In addition to eliciting vasodilation, a key function of NO is to inhibit the production, release, and vasoconstrictor capacity of ET-1(27, 51). Importantly, significant crosstalk exists between the ET and NO systems within the vasculature(27) and an imbalance between ET-1 and NO has been implicated in a number of vascular pathologies(52). Our results suggest that women with a history of GDM exhibit attenuated vascular function, due in part to local ET_AR action and reduced NO-dependent mechanisms. Importantly, enhanced ET-1 is associated with an increased risk of T2DM in women(53), which may partially explain why women with a history of GDM are at a much higher risk of developing T2DM compared to women who had uncomplicated pregnancies. Collectively, optimal vascular endothelial function and NO bioavailability are essential for cardiovascular health and our results suggest that ET-1 may be driving reductions in these measures in women with a history of GDM. Targeting the ET-1 pathway may be a clinically relevant therapeutic strategy for the management of elevated CVD risk in this population of women.

By design, we chose to specifically examine the ET_AR because it is localized on vascular smooth muscle cells and solely elicits vasoconstriction. Furthermore, ET_AR-specific antagonism has been demonstrated to improve vascular endothelial function in individuals with T2DM(33, 35), coronary artery disease(34), and obesity(32). The clinical utility of ET-1 antagonists is being examined in the context of CVD treatments and shows promise when combined with renin angiotensin aldosterone system antagonists in the context of renal diseases specifically (54) and when combined with sodium-glucose cotransporter-2 channel inhibitors more broadly(55). Our data suggest that treatments including ET-1 antagonists may similarly improve endothelial function in women with a history of GDM. Larger studies utilizing orally available antagonists to the ET system are required to explore this potential.

ET-1 production is elicited by several stimuli including inflammation, insulin, cortisol, hypoxia, and shear stress(56). Findings regarding maternal plasma ET-1 concentrations during pregnancy complicated by GDM remain mixed, despite the fact that women with GDM exhibit reductions in vascular endothelial function (assessed via brachial artery flow mediated dilation) during pregnancy compared to women who have an uncomplicated pregnancy(57). Some studies have identified increased circulating ET-1 in maternal blood(57), whereas others have not identified significant differences in circulating ET-1 in excised omental arteries from HC women and women with a history of GDM (58). Interestingly, mRNA expression of ET_AR does not differ during pregnancy between women with GDM and HC women with uncomplicated pregnancies(58). Despite our results indicating that the ET-1 system is involved in GDM-associated vascular dysfunction, we did not detect differences in plasma ET-1 between our cohorts of women who were within 5 years postpartum. However, the autocrine and paracrine nature of ET-1 make determining tissue specific origins and interpreting circulating concentrations difficult. The majority of ET-1 is released abluminally; therefore, circulating ET-1 may be a poor indicator of overall ET-1 production and its effects on the vasculature. Therefore, our results suggest that plasma concentrations of ET-1 likely do not reflect ET-1-mediated vasoconstrictor tone at the vessel wall. Future work distinguishing between the increased production or reduced clearance of ET-1, and well as ET-1 receptor sensitivity and subtype density, is warranted to more fully describe the physiology of the ET-1 system in the vasculature of women with history of GDM.

LIMITATIONS

Our cohort of women with a history of GDM had higher HbA1c and BMI compared to the HC group. However, the HbA1c values were within clinically normal ranges(59) and participants with CVD or metabolic diseases were excluded from both groups. Both groups included women with BMI in the overweight and obese categories, and the GDM group had statistically higher BMI compared to HC. We have previously shown that these statistical, but not clinical, differences in HbA1c and BMI do not explain the differences in our in vivo measures of microvascular function(10). However, we cannot rule out the possibility that higher HbA1c and/or BMI may contribute to the reductions in microvascular function and the role of ET-1-dependent mechanisms in the dysfunction that we observed, independent of GDM history.

We also acknowledge that our study involved a relatively small sample size (n=12/group), which may limit the translatability of these results. It is plausible that a larger sample size may have detected additional differences in other markers of baseline cardiovascular health, such as HOMA-IR and fasting plasma glucose, and allowed for statistical adjustments to explore the role of these markers in the dysfunction we detected.

We did not examine the ET_BR, which is located on vascular smooth muscle where it elicits vasoconstriction, and on the vascular endothelium where it elicits vasodilation(60). In healthy premenopausal women, ET_BR-mediated dilation responses serve as a counterbalance to ET_AR-mediated constriction, attenuating the overall vascular constrictor response to ET-1(61). However, it is possible that the ET_BR may contribute to vascular endothelial dysfunction in women with a history of GDM. ET_BR blockade has been examined in other groups of women at high risk for CVD, including women with a history of preeclampsia and postmenopausal women(38, 62), and ET_BR blockade improves vascular endothelial function in these populations. Future studies designed to explore the role of ET_BR could provide further insight into therapeutic targets to delay or prevent disease progression in women with a history of GDM.

Pharmacological inhibition of ET-1 receptors is used in several cardiovascular diseases(63). Selective ET_AR antagonism with ambrisentan (64) and dual ET_AR and ET_BR antagonism with macitentan (65) treat pulmonary arterial hypertension by reducing ET-mediated vasoconstriction. Additionally, dual blockade of ET_A and ET_B receptors improves endothelium-dependent vasodilation in individuals with insulin resistance(66), essential hypertension(30), and atherosclerosis(31). As recently as 2024, the dual ET-1 receptor antagonist aprocitentan was approved to manage treatment resistant hypertension(67). Although we did not evaluate the effect of ET_BR antagonism on endothelium- or NO-dependent dilation, it is plausible that dual ET_AR and ET_BR blockade may be a more effective method to improve vascular function in this cohort than ET_AR antagonism alone.

Although our results regarding ET_AR antagonism suggest that pharmacotherapies that block ET-1 receptors may improve endothelial function in women with a history of GDM, we acknowledge that the clinical utility of ET-1 receptor antagonists faces significant challenges in this otherwise healthy population of women. ET-1 receptor antagonists are highly teratogenic and are contraindicated during pregnancy and lactation(68). Furthermore, the teratogenicity of these drugs, coupled with their side effect profiles, make them unlikely candidates for prophylactic treatment in otherwise healthy women of childbearing age. Although we did not give ET_AR antagonists systemically, our data suggest that women with a history of GDM may benefit from treatment with ET-1 antagonists. Clinical studies exploring the utility of orally available ET-1 receptor antagonists to improve endothelial function in these women are warranted.

CLINICAL PERSPECTIVE

A history of GDM is a potent risk factor for CVD development. Although women with a history of GDM re-establish normoglycemia after delivery, our data suggest that these women exhibit ET-1-related impairments in microvascular endothelial function. Microvascular dysfunction precedes and predicts the development of CVD, and our data suggest that the ET_AR contributes to vascular endothelial dysfunction after pregnancy complicated by GDM.

CONCLUSION

Local, acute ET_AR antagonism improved cutaneous microvascular endothelium-dependent dilation, mediated in part by NO-dependent mechanisms, in women with a history of GDM. These data suggest that ET-1 contributes to microvascular dysfunction following pregnancy complicated by GDM. Future work investigating the clinical utility of ET receptor antagonism after GDM and before CVD development is warranted.

NEW & NOTEWORTHY.

Women who experienced gestational diabetes are at a high risk of developing cardiovascular disease later in life. This risk may be mediated, in part, by endothelial dysfunction after pregnancy. We demonstrate that endothelin-1 receptor type A antagonism with BQ-123 improves microvascular endothelial responses to local heating in otherwise healthy women with a history of gestational diabetes. These findings suggest that ET-1 contributes to microvascular endothelial dysfunction after gestational diabetes.

DATA AVAILABILITY

Data supporting these findings are available from the corresponding author upon reasonable request and under a Data Use Agreement with the University of Iowa.