Midgestation Leptin Infusion Induces Characteristics of Clinical Preeclampsia in Mice, Which Is Ablated by Endothelial Mineralocorticoid Receptor Deletion

Abstract

Background: Patients with preeclampsia demonstrate increases in placental leptin production in midgestation, and an associated increase in late gestation plasma leptin levels. The consequences of mid-late gestation increases in leptin production in pregnancy is unknown. Our previous work indicates that leptin infusion induces endothelial dysfunction in nonpregnant female mice via leptin-mediated aldosterone production and endothelial mineralocorticoid receptor (ECMR) activation, which is ablated by ECMR deletion. Therefore, we hypothesized that leptin infusion in mid-gestation of pregnancy induces endothelial dysfunction and hypertension, hallmarks of clinical preeclampsia, which are prevented by ECMR deletion.

Methods: Leptin was infused via miniosmotic pump (0.9 mg/kg per day) into timed-pregnant ECMR-intact (WT) and littermate-mice with ECMR deletion (KO) on gestation day (GD)11-18.

Results: Leptin infusion decreased fetal weight and placental efficiency in WT mice compared with WT+vehicle. Radiotelemetry recording demonstrated that blood pressure increased in leptin-infused WT mice during infusion. Leptin infusion reduced endothelial-dependent relaxation responses to acetylcholine (ACh) in both resistance (second-order mesenteric) and conduit (aorta) vessels in WT pregnant mice. Leptin infusion increased placental ET-1 (endothelin-1) production evidenced by increased PPET-1 (preproendothelin-1) and ECE-1 (endothelin-converting enzyme-1) expressions in WT mice. Adrenal aldosterone synthase (CYP11B2) and angiotensin II type 1 receptor b (AT1Rb) expression increased with leptin infusion in pregnant WT mice. KO pregnant mice demonstrated protection from leptin-induced reductions in pup weight, placental efficiency, increased BP, and endothelial dysfunction.

Conclusions: Collectively, these data indicate that leptin infusion in midgestation induces endothelial dysfunction, hypertension, and fetal growth restriction in pregnant mice, which is ablated by ECMR deletion.

Keywords: endothelial function; hypertension; leptin; mice; preeclampsia.

Figure 1.. Leptin infusion induces fetal growth restriction in WT, but not KO, pregnant mice.

GD18 pup weights (A), average litter size by fetal number (B), placental efficiency (ratio of pup/placenta weight) (C), placental weights (D), reabsorbed pups (resorptions) per litter (E) in WT and KO pregnant mice with and without leptin infusion. 2-Way ANOVA with Tukey’s posthoc test for multiple comparisons. N=6 WT+Vehicle and WT+Leptin, N=7 KO+Vehicle, N=4 KO+Leptin. *P<0.05.

Figure 2.. Leptin infusion increases blood pressure in WT pregnant mice

Radiotelemetry recording and average blood pressures at GD11-18 of blood pressure prior to mating (prepregnancy), during GD 8-11 and following vehicle or leptin miniosmotic pump implantation in WT mice (GD11-18). Mean arterial pressure (MAP) (A), systolic blood pressure (SBP) (B), diastolic blood pressure (DBP) (C) and heart rate (D) are depicted across all time points and the summary data of average recording from GD11-18. 2-way ANOVA with repeated measures depicted below each phase of recording and results of student’s t-test in the average pressures at GD11-18. N=4 WT+vehicle, N=4 WT+leptin, *P<0.05.

Figure 3.. Leptin infusion reduces endothelial function in WT pregnant mice

Vascular relaxation responses in 2^nd order mesenteric arteries (Mesenteric) and thoracic aorta (aorta) in WT+vehicle and WT+leptin pregnant mice (GD 18). Leptin infusion decreased endothelial-dependent relaxation responses to acetylcholine (ACh) in both mesenteric arteries (A) and aorta (B) with and without LNAME preincubation. Leptin infusion did not reduce endothelial-independent relaxation responses to sodium nitroprusside (SNP) in either mesenteric arteries (C) or aorta (D) nor increase phenylephrine (Phe)-induced contraction in mesenteric arteries (E) or aorta (F). N=5 for both groups mesenteric arteries, N=5 WT+vehicle aorta, N=6 WT+leptin aorta. 2-way ANOVA with repeated measures.*P<0.05,

Figure 4.. Endothelial MR deletion prevented leptin-mediated increases in BP in pregnant mice

Radiotelemetry recording and average blood pressures at GD11-18 of blood pressure prior to mating (prepregnancy), during GD 8-11 and following vehicle or leptin miniosmotic pump implantation in KO mice (GD11-18). Mean arterial pressure (MAP) (A), systolic blood pressure (SBP) (B), diastolic blood pressure (DBP) (C) and heart rate (D) are depicted across all time points and the summary data of average recording from GD11-18. 2-way ANOVA with repeated measures depicted below each phase of recording and results of student’s t-test in the average pressures at GD11-18. N=5 KO+vehicle, N=4 KO+leptin, *P<0.05.

Figure 5.. Endothelial MR deletion prevented leptin-mediated reduction in endothelial relaxation in pregnant mice

Vascular relaxation responses in thoracic aorta of KO+vehicle and KO+leptin pregnant mice (GD 18). Leptin infusion did not reduce endothelial-dependent relaxation responses to ACh in KO pregnant mice in the absence of or presence of LNAME preincubation (A). Leptin did not reduce SNP-mediated endothelial-independent relaxation responses in KO pregnant mice (B). Leptin infusion also did not increase vascular constriction responses to phenylephrine (Phe) (C) or KCl (D) in KO pregnant mice. N=6 KO+vehicle, N=4 KO+leptin. 2-way ANOVA with repeated measures.*P<0.05.

Figure 6.. Leptin increases placental endothelin-1 production and increases adrenal CYP11B2 and AT1Rb expression in pregnant mice

Placental mRNA expression of prepro-endothelin-1 (PPET-1) (A) and endothelin converting enzyme-1 (ECE-1) increased with leptin infusion in WT pregnant mice (B). Adrenal protein expression of CYP11B2 increased in WT mice infused with leptin (C). Adrenal angiotensin II type 1 receptor a (AT1Ra) mRNA expression did not increase with leptin infusion in WT pregnant mice (D) in contrast to the leptin-induced increase in AT1Rb observed in leptin-infused WT pregnant mice (E). Placental N values: N=7 WT+Vehicle, N=9 WT+Leptin, N=4 KO+Vehicle, N=4 KO+Leptin. Protein expression data N=4 for all groups. Adrenal N values: N=5 WT+Vehicle, N=4 WT+Leptin, N=5 KO+Vehicle, N=4 KO+Leptin. Student’s unpaired t-test for paired comparisons to respective Vehicle, 2-way ANOVA with Tukey’s posthoc test for multiple comparisons for protein expression. *P<0.05.