Adipocyte deficiency of ACE2 increases systolic blood pressures of obese female C57BL/6 mice

Abstract

Background: Obesity increases the risk for hypertension in both sexes, but the prevalence of hypertension is lower in females than in males until menopause, despite a higher prevalence of obesity in females. We previously demonstrated that angiotensin-converting enzyme 2 (ACE2), which cleaves the vasoconstrictor, angiotensin II (AngII), to generate the vasodilator, angiotensin-(1-7) (Ang-(1-7)), contributes to sex differences in obesity-hypertension. ACE2 expression in adipose tissue was influenced by obesity in a sex-specific manner, with elevated ACE2 expression in obese female mice. Moreover, estrogen stimulated adipose ACE2 expression and reduced obesity-hypertension in females. In this study, we hypothesized that deficiency of adipocyte ACE2 contributes to obesity-hypertension of females.

Methods: We generated a mouse model of adipocyte ACE2 deficiency. Male and female mice with adipocyte ACE2 deficiency or littermate controls were fed a low (LF) or a high fat (HF) diet for 16 weeks and blood pressure was quantified by radiotelemetry. HF-fed mice of each sex and genotype were challenged by an acute AngII injection, and blood pressure response was quantified. To translate these findings to humans, we performed a proof-of-principle study in obese transwomen in which systemic angiotensin peptides and blood pressure were quantified prior to and after 12 weeks of gender-affirming 17β-estradiol hormone therapy.

Results: Adipocyte ACE2 deficiency had no effect on the development of obesity in either sex. HF feeding increased systolic blood pressures (SBP) of wild-type male and female mice compared to LF-fed controls. Adipocyte ACE2 deficiency augmented obesity-induced elevations in SBP in females, but not in males. Obese female, but not obese male mice with adipocyte ACE2 deficiency, had an augmented SBP response to acute AngII challenge. In humans, plasma 17β-estradiol concentrations increased in obese transwomen administered 17β-estradiol and correlated positively with plasma Ang-(1-7)/AngII balance, and negatively to SBP after 12 weeks of 17β-estradiol administration.

Conclusions: Adipocyte ACE2 protects female mice from obesity-hypertension, and reduces the blood pressure response to systemic AngII. In obese transwomen undergoing gender-affirming hormone therapy, 17β-estradiol administration may regulate blood pressure via the Ang-(1-7)/AngII balance.

Keywords: Angiotensin-(1-7); Angiotensin-converting enzyme 2; Blood pressure; Obesity; Transgender.

Fig. 1

Development of a mouse model of adipocyte ACE2 deficiency. a Schematic representation depicting the loxP-flanked ACE2 allele before (a) and after successive recombination with Flp (b) and transgenic adiponectin-driven Cre expression (c). The disrupted allele is shown in c, indicating deletion of exon 4 of the ACE2 gene. b Tissue characterization demonstrating reduced ACE2 mRNA abundance is specific to adipose tissues (subcutaneous, SubQ; retroperitoneal, RPF) (n = 4–8 male mice/genotype). Data are mean + SEM; P < 0.05 compared to Ace2^fl/y using t test. c PCR reactions were performed with DNA extracted from RPF (n = 3 female mice/genotype). Primers amplify a 923 base pair product for the disrupted portion of the ACE2 gene

Fig. 2

Deficiency of ACE2 in adipocytes has no effect on the development of obesity in male or female mice. Body weights (weekly) of female Ace2^fl/fl (a) or male Ace2^fl/y (b) and Ace2^Adipo mice fed a low fat (LF) or high fat (HF) diet. Lean mass (c) and fat mass (d) (as % body weight) of female or male mice from each genotype fed the LF or HF diet. Data are mean + SEM from n = 6–13 mice/genotype/diet. *p < 0.05 compared to LF within sex using two-way ANOVA followed by Holm-Sidak pairwise analysis; @p < 0.01 compared to female within diet group using two-way ANOVA followed by Holm-Sidak pairwise analysis

Fig. 3

ACE2 deficiency in adipocytes increases blood pressures of obese female, but not obese male mice. Systolic blood pressures (SBP, 24-h average) (a) of female Ace2^fl/fl and male Ace2^fl/y and Ace2^Adipo mice fed a LF or HF diet for 4 months. Diastolic blood pressures (DBP) (b) of female and male mice of each genotype fed the LF or HF diet for 4 months. Data are mean + SEM from 4–5 mice/genotype/diet. *p < 0.01 compared to LF within sex using two-way ANOVA followed by Holm-Sidak pairwise analysis; #p < 0.05 compared to Ace2^fl/fl within sex group using two-way ANOVA followed by Holm-Sidak pairwise analysis; @p < 0.01 compared to female within diet group using two-way ANOVA followed by Holm-Sidak pairwise analysis

Fig. 4

Systolic blood pressure (SBP) response to acute AngII challenge is augmented in obese female, but not obese male mice with adipocyte-ACE2 deficiency. At 4 months of HF feeding, the time course of SBP following an acute injection (sc) of AngII (20 μg/kg) to female Ace2^fl/fl (a) or male Ace2^fl/y (b) and Ace2^Adipo mice. Data are reported as the average blood pressure per minute at each time point. Integrated area under the curve (AUC) corresponding to the time course of SBP response to AngII for HF-fed female Ace2^fl/fl (c) or HF-fed male Ace2^fl/y (d) and Ace2^Adipo mice. Data are mean + SEM for n = 4 mice/genotype. #p < 0.05 compared to Ace2^fl/fl at each time point using repeated measures (RM) two-way ANOVA; *p < 0.05 compared to Ace2^fl/fl using t test

Fig. 5

Administration of 17β-estradiol to obese transwomen initiating gender-affirming hormone therapy increases plasma concentrations of 17β-estradiol, which correlates positively to plasma Ang-(1-7)/AngII balance and negatively to systolic blood pressures (SBP). a Plasma 17β-estradiol concentrations before (baseline) and after administration of 17β-estradiol to obese transwomen for 12 weeks. b Scatterplot showing the correlation between the ratio of Ang-(1-7) to AngII concentrations in plasma to plasma 17β-estradiol concentrations after 12 weeks of 17β-estradiol administration. c Scatterplot showing correlation between change in SBP and the ratio of Ang-(1-7) to AngII in plasma following 12 weeks 17β-estradiol administration. N = 4 subjects. *p < 0.05 compared to baseline