Gestational Intermittent Hypoxia Impairs AT2R-Mediated Vascular Protection in Female Offspring on a High-Fat, High-Sucrose Diet

Abstract

Background: Gestational intermittent hypoxia (GIH), a hallmark of maternal obstructive sleep apnea, sex-differentially causes hypertension and endothelial dysfunction in adult male offspring but not in females. This study investigated whether the GIH-exposed female offspring, a "protected" group against the hypertensive effects of maternal GIH exposure, exhibit increased susceptibility to hypertension and cardiovascular dysfunction when fed a high-fat high-sucrose (HFHS) diet and whether this effect could be reversed by pharmacological intervention activating the angiotensin II type 2 receptor (AT₂R).

Methods: Female offspring of control and GIH-exposed (10.5% O₂, 8 h/d, E10-21) dams were assigned either an HFHS diet or a standard diet from 12 weeks of age. Blood pressure was monitored. At 28 weeks, a systemic CGP42112 (AT₂R agonist) or saline infusion was administered through the osmotic pump. At 30 weeks, the heart was weighed and collected for H&E staining, mesenteric arteries for vascular reactivity assessment and protein analysis, and plasma for ELISA.

Results: The HFHS diet induced similar increases in body weight gain and blood pressure in control and GIH female offspring. HFHS feeding did not affect heart structure, but impaired endothelial-dependent vascular relaxation with associated decreased AT₂R and eNOS expression and reduced plasma bradykinin levels in both control and GIH offspring. CGP42112 administration effectively mitigated HFHS-induced hypertension and endothelial dysfunction only in control offspring, accompanied by restored AT₂R, eNOS, and bradykinin levels, but not in the GIH counterparts.

Conclusion: These findings suggest that GIH induces endothelial dysfunction and AT₂R insensitivity in female offspring exposed to an HFHS diet.

Keywords: AT2R; Blood pressure; Endothelium; Intermittent hypoxia; Offspring; high-fat diet.

Figure 1:

Body weight and feed intake. Female offspring rats exposed to gestational normoxia (Control) or intermittent hypoxia (GIH) exposures were randomly assigned to a standard diet (STD) or a high-fat high-sucrose diet (HFHS) starting 12 weeks of age. Both control- and GIH-exposed female offspring rats with or without HFHS were treated with saline (VEH) or CGP42112 (CGP) from 28 to 30 weeks of age. (A) Percent body weight increase measured on a bi-weekly basis. (B) Percent body weight change at 30 weeks with and without CGP treatment. (C) Average daily feed intake measured on a bi-weekly basis. (D) Average daily feed intake with and without CGP treatment. Data are presented as means ± SEM of 12 rats per group before, and 6 rats per group after VEH or CGP treatment. *P<0.05 HFHS vs. STD counterparts.

Figure 2:

Effect of HFHS and AT₂R agonist CGP421112 treatment on blood pressure. Mean arterial blood pressure was measured non-invasively using the CODA system. (A) Mean arterial blood pressure measured on a bi-weekly basis. (B) Mean arterial blood pressure measured after VEH or CGP treatment in control offspring. (C) Mean arterial blood pressure measured after VEH or CGP treatment in GIH offspring. Data are presented as means ± SEM of 12 rats per group before, and 6 rats per group after VEH or CGP treatment. ^#P<0.05 GIH vs. control counterparts; *P<0.05 HFHS vs. STD counterparts; ^xP<0.05 CGP vs. VEH counterparts.

Figure 3:

Effect of HFHS and AT₂R agonist CGP421112 treatment on heart structure. (A) Heart weight normalized to tibia length, and (B) ventricle weight normalized to whole heart weight were measured. (C) Left ventricular wall thickness was analyzed with H&E staining. Data are presented as means ± SEM of 6 rats per group.

Figure 4:

Effect of HFHS and AT₂R agonist CGP421112 treatment on endothelium-dependent vascular relaxation responses. At 30 weeks of age, mesenteric artery rings isolated from control- and GIH-exposed female offspring, with or without HFHS and CGP treatment, were precontracted with submaximal phenylephrine. The relaxation responses to incremental doses of acetylcholine (ACh) were examined. Data are presented as means ± SEM of 6 rats per group.

Figure 5:

Effect of HFHS and AT₂R agonist CGP421112 treatment on endothelium-independent vascular relaxation responses. Endothelium-denuded mesenteric artery rings were precontracted with submaximal phenylephrine, and subsequently challenged with incremental doses of sodium nitroprusside (SNP). Data are presented as means ± SEM of 6 rats per group.

Figure 6:

Effect of HFHS and AT₂R agonist CGP421112 treatment on plasma angiotensin II (Ang II), nitrate/nitrite (NO_X), and bradykinin levels. At 30 weeks of age, blood was collected from control- and GIH-exposed female offspring rats via cardiac puncture. (A) Ang II, (B) NO_X, and (C) bradykinin levels were measured using ELISA kits. Data are presented as means ± SEM of 6 rats per group. *P<0.05 HFHS vs. STD counterparts.

Figure 7:

Effect of HFHS and AT₂R agonist CGP421112 treatment on protein expression of angiotensin II receptors, eNOS, and bradykinin receptors in the mesenteric arteries. Protein expression of (A) AT₁R, (B) B₁R, (C) B₂R, (D) AT₂R, and (E) eNOS, in week 30 mesenteric artery samples from control- and GIH-exposed female offspring rats were analyzed using Western blotting. The left panel displays representative bands, while the right panel shows normalized densitometry data. Data are presented as means ± SEM of 6 rats per group. *P<0.05 HFHS vs. STD counterparts; ^xP<0.05 CGP vs. VEH counterparts.