The neuronal (pro)renin receptor and astrocyte inflammation in the central regulation of blood pressure and blood glucose in mice fed a high-fat diet

Abstract

We report here that the neuronal (pro)renin receptor (PRR), a key component of the brain renin-angiotensin system (RAS), plays a critical role in the central regulation of high-fat-diet (HFD)-induced metabolic pathophysiology. The neuronal PRR is known to mediate formation of the majority of angiotensin (ANG) II, a key bioactive peptide of the RAS, in the central nervous system and to regulate blood pressure and cardiovascular function. However, little is known about neuronal PRR function in overnutrition-related metabolic physiology. Here, we show that PRR deletion in neurons reduces blood pressure, neurogenic pressor activity, and fasting blood glucose and improves glucose tolerance without affecting food intake or body weight following a 16-wk HFD. Mechanistically, we found that a HFD increases levels of the PRR ligand (pro)renin in the circulation and hypothalamus and of ANG II in the hypothalamus, indicating activation of the brain RAS. Importantly, PRR deletion in neurons reduced astrogliosis and activation of the astrocytic NF-κB p65 (RelA) in the arcuate nucleus and the ventromedial nucleus of the hypothalamus. Collectively, our findings indicate that the neuronal PRR plays essential roles in overnutrition-related metabolic pathophysiology.

Keywords: (pro)renin receptor; astrocyte inflammation; diet-induced diabetes; neural mechanism; renin-angiotensin system.

Fig. 1.

(Pro)renin receptor (PRR) is expressed in neurons, but not astrocytes or microglia, in the arcuate nucleus (ARC). Representative microscopy images of no-primary antibody control (A), coimmunolabeling of the PRR with a neuronal marker (NeuN) and microglial marker (CX3CR1-GFP reporter mice) (B), and coimmunolabeling of the PRR with an astrocyte marker [glial fibrillary acidic protein (GFAP)] (C) in the ARC.

Fig. 2.

Neuron-specific (pro)renin receptor (PRR) knockout attenuates obesity-related hypertension. Mean arterial pressure (MAP; A), heart rate (HR; B), cardiac sympathetic tone (C), and neurogenic pressor activity (D) were measured in mice after a 16-wk of normal fat diet (NFD) or high-fat diet (HFD). PRRKO, PRR knockout. Data are presented as means ± SE [*P < 0.05, **P < 0.01, ****P < 0.0001 vs. wild-type (WT) NFD; #P < 0.05, ##P < 0.01, ###P < 0.001 vs. WT HFD; one-way ANOVA].

Fig. 3.

Neuronal (pro)renin receptor (PRR) knockout attenuates the development of high-fat diet (HFD)-induced diabetes. Summary data showing weekly food intake (A), caloric intake (B), body weight (C), fasting blood glucose (FBG) (D), glucose tolerance tests (GTTs) with AUC summary data (E and F), and insulin tolerance tests (ITTs), with area under the curve (AUC) summary data (G and H). Data are presented as means ± SE [*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 vs. wild-type (WT) normal fat diet (NFD); ^##P < 0.01, ^###P < 0.001, ^####P < 0.0001 vs. WT HFD; ^$P < 0.05, ^$$P < 0.01, ^$$$P < 0.001, ^$$$$P < 0.0001 vs. PRR knockout (KO) NFD; two-way ANOVA (A, B, E, and G) and one-way ANOVA (F and H)].

Fig. 4.

Neuronal (pro)renin receptor (PRR) deletion is associated with a reduction in high-fat diet (HFD)-induced pancreatic islet hypertrophy. Representative images show hematoxylin and eosin (H&E) staining (A) and fluorescence labeling (B) of insulin in pancreatic islets of HFD- and normal fat diet (NFD)-fed mice. PRRKO, PRR knockout. Quantitation of islet size (C), islet number (D), and plasma insulin (E). Data are presented as means ± SE [***P < 0.001 vs. wild-type (WT) NFD, 16-wk (16W); ^#P < 0.05, ^##P < 0.01 vs. WT HFD, 6-wk (6W); one-way ANOVA].

Fig. 5.

(Pro)renin receptor (PRR) deletion reduces hypothalamic ANG II levels in high-fat diet (HFD)-fed mice. (Pro)renin levels in the brain hypothalamus and plasma (A and B) and ANG II levels in the brain hypothalamus and plasma (C and D) of wild-type (WT) and PRR knockout (KO) mice after a 16-wk NFD or HFD. E: schematic Illustration of changes in prorenin, the PRR, and ANG II in NFD- and HFD-fed WT and PRR knockout (KO) mice. F: plasma leptin levels. Data are presented as means ± SE (*P < 0.05, **P < 0.01, ***P < 0.001 vs. WT NFD; ^##P < 0.01 vs. WT HFD; one-way ANOVA).

Fig. 6.

Neuronal (pro)renin receptor (PRR) knockdown regulates astrogliosis in the arcuate nucleus (ARC) of high-fat diet (HFD)-fed mice. Representative images and quantification of glial fibrillary acidic protein (GFAP) intensity in the subfornical organ (SFO) (A and B), paraventricular nucleus (PVN) (C and D), and ARC (E and F). PRRKO, PRR knockout; RFU, relative fluorescence units. Data are presented as means ± SE [*P < 0.05, **P < 0.01 vs. wild-type (WT) NFD; ^#P < 0.05 vs. WT HFD; one-way ANOVA].

Fig. 7.

Neuronal (pro)renin receptor (PRR) deletion reduces NF-κB p65 activation in the arcuate nucleus (ARC) of high-fat diet (HFD)-fed mice. Representative images and quantification of NF-κB p65 serine 536 phosphorylation in the ARC. PRRKO, PRR knockout; RFU, relative fluorescence units. Data are presented as means ± SE [*P < 0.05, ****P < 0.0001 vs. wild-type (WT) normal fat diet (NFD); ^###P < 0.001 vs. WT HFD; one-way ANOVA].

Fig. 8.

Neuronal (pro)renin receptor (PRR) deletion reduces astrocytic NF-κB p65 activation in the arcuate nucleus (ARC) of high-fat diet (HFD)-fed mice. Representative images and quantification of astrocyte-specific NF-κB p65 serine 536 phosphorylation in the ARC. PRRKO, PRR knockout; RFU, relative fluorescence units. Data are presented as means ± SE [****P < 0.0001 vs. wild-type (WT) normal fat diet (NFD); ^#P < 0.05 vs. WT HFD; one-way ANOVA].

Fig. 9.

Neuronal (pro)renin receptor (PRR) deletion reduces neuronal NF-κB p65 activation in the arcuate nucleus (ARC) of high-fat diet (HFD)-fed mice. Representative images and quantification of neuron-specific NF-κB p65 serine 536 phosphorylation in the ARC. PRRKO, PRR knockout; RFU, relative fluorescence units. Data are presented as means ± SE [***P < 0.001 vs. wild-type (WT) normal fat diet (NFD); ^##P < 0.01 vs. WT HFD; one-way ANOVA].

Fig. 10.

Neuronal (pro)renin receptor (PRR) deletion reduces astrocytic, but not neuronal, NF-κB p65 activation in the ventromedial nucleus (VMH) of high-fat diet (HFD)-fed mice. Representative images of neuron- and astrocyte-specific NF-κB p65 serine 536 phosphorylation in the arcuate nucleus (ARC) and quantification of neuronal and astrocytic NF-κB p65 serine 536 phosphorylation. PRRKO, PRR knockout; RFU, relative fluorescence units; GFAP, glial fibrillary acidic protein; NeuN, neuronal marker. Data are presented as means ± SE [****P < 0.0001 vs. wild-type (WT) normal fat diet (NFD); ^####P < 0.0001 vs. WT HFD; one-way ANOVA].

Fig. 11.

Proposed pathways for brain prorenin-angiotensin system in high-fat diet (HFD) induced cardiometabolic physiology and the role of astrocytes. During high-fat diet, elevation of circulating and brain prorenin, as well as other metabolic regulating factors cause activation of the (pro)renin receptor (PRR) and the prorenin-angiotensin system (RAS) activity in the central nervous system (CNS). The RAS activation in the CNS induces a feed-forward cycle of inflammation in the astrocytes leading to elevated autonomic dysfunction and blood pressure (BP) and hyperglycemia. AT₁R, ANG II type 1 receptor.