Elevated (Pro)renin Receptor Expression Contributes to Maintaining Aerobic Metabolism in Growth Hormone Deficiency

Soluble (Pro)Renin Receptor Level in Patients with Severe Obesity Is Associated with Visceral Adiposity and Is Involved with Insulin Resistance and Renal Injury

INTRODUCTION

High soluble (pro)renin receptor (s[P]RR) level in circulation is reported in obese patients; however, it is unclear which body composition components are responsible for it. In this study, the authors examined blood s(P)RR levels and ATP6AP2 gene expression levels in visceral and subcutaneous adipose tissue (VAT, SAT) in severely obese patients who underwent laparoscopic sleeve gastrectomy (LSG), with the aim of clarifying the relationship with body composition and metabolic factors.

METHODS

Seventy five cases who underwent LSG between 2011 and 2015 and were postoperatively followed-up for 12 months at the Toho University Sakura Medical Center were included in the analysis of the cross-sectional survey at baseline, and 33 cases were included in the analysis of the longitudinal survey during the 12 months after LSG. We evaluated body composition, glycolipid parameters, liver/renal function, as well as serum s(P)RR level and ATP6AP2 mRNA expression level in VAT and SAT.

RESULTS

The mean serum s(P)RR level at baseline was 26.1 ng/mL, this value was considered higher than values in healthy subjects. There was no significant difference in the expression level of ATP6AP2 mRNA between VAT and SAT. At baseline, multiple regression analysis for the association between s(P)RR and variables identified that visceral fat area, HOMA2-IR, and UACR showed the independent relationships with s(P)RR. During the 12 months after LSG, body weight, serum s(P)RR level showed a significant decrease (from 30.0 ± 7.0 to 21.9 ± 4.3). Multiple regression analysis for the association between the change in s(P)RR and variables showed that changes in visceral fat area, and alanine transaminase were independently related to the change in s(P)RR.

CONCLUSION

This study showed that blood s(P)RR level was high in severely obese patients, decreased with weight loss by LSG, and was associated with visceral fat area in both pre- and postoperative changes. The results suggest that blood s(P)RR levels in obese patients may reflect the involvement of visceral adipose (P)RR in insulin resistance and renal damage mechanisms associated with obesity.

Endothelin-1 production via placental (pro)renin receptor in a mouse model of preeclampsia

INTRODUCTION

Preeclampsia (PE) pathogenesis is explained by the two-stage disorder theory. However, mechanisms underlying hypertension and proteinuria in PE remain unclear. The role of (pro)renin receptor (PRR) in PE pathology has received special attention. We examined endothelin-1 (ET-1) production via placental PRR in a PE mouse model.

METHODS

At 14.5 day-post-coitum (DPC), we performed a reduced uterine perfusion pressure (RUPP) operation, ligating the uterine arteriovenous vessels in female mice. We also infused these mice with a PRR inhibitor, decoy peptide in the handle region of prorenin (HRP) for mice (NH2-RIPLKKMPSV-COOH). At 18.5 DPC, blood, urine, and placenta were collected; fetus and placenta were weighed. We evaluated placental hypoxia using quantitative polymerase chain reaction (PCR), with hypoxia-inducible factor-1α (HIF-1α) as index. We also evaluated PRR, transforming growth factor-β1 (TGF-β1), and ET-1 expression in the placenta using quantitative PCR and western blotting. ET-1 concentration in blood plasma was assessed using enzyme-linked immunosorbent assay.

RESULTS

Blood pressure and proteinuria significantly increased, and fetal and placental weights decreased in RUPP mice. HIF-1α, PRR, TGF-β1, and ET-1 expressions considerably increased in RUPP mice placentas. ET-1 concentration in RUPP mice blood plasma was markedly increased. PRR inhibitor suppressed these changes.

DISCUSSION

In PE model mice that underwent RUPP treatment, placental hypoxia increased PRR and ET-1 expression suggesting a causative relationship between ET-1 and intracellular PRR signaling. RUPP treatment, when combined with HRP, reversed the effect of elevated ET-1 levels in the model. This study may help to elucidate the pathogenesis of PE considering PRR and ET-1.

The Role of (Pro)Renin Receptor in the Metabolic Syndrome

The prorenin receptor (PRR) is a complex multi-functional single transmembrane protein receptor that is ubiquitously expressed in organs and tissues throughout the body. PRR is involved in different cellular mechanisms that comprise the generation of Angiotensin II, the activation of Wnt/β-catenin signaling, the stimulation of ERK 1/2 pathway, and the proper functioning of the vacuolar H+-ATPase. Evidence supports the role of PRR and its soluble form, sPRR, in the classical features of the metabolic syndrome, including obesity, hypertension, diabetes, and disruption of lipid homeostasis. This review summarizes our current knowledge and highlights new advances in the pathophysiological function of PRR and sPRR in adipogenesis, adipocyte differentiation, lipolysis, glucose and insulin resistance, lipid homeostasis, energy metabolism, and blood pressure regulation.

Urinary soluble (pro)renin receptor excretion is associated with urine pH in humans

The (pro)renin receptor [(P)RR] binds to renin and its precursor prorenin to activate the tissue renin-angiotensin system. It is cleaved to generate soluble (P)RR and M8–9, a residual hydrophobic truncated protein. The (pro)renin receptor also functions as an intracellular accessory protein of vacuolar-type H⁺-ATPase, which plays an essential role in controlling the intracellular vesicular acid environment. Thus, in the kidney, (P)RR may play a role in transporting H⁺ to urine in the collecting duct. Although blood soluble (P)RR has been recognized as a biomarker reflecting the status of the tissue renin-angiotensin system and/or tissue (P)RR, the significance of urinary soluble (P)RR excretion has not been determined. Therefore, this study aimed to investigate the characteristics of urinary soluble (P)RR excretion. Urinary soluble (P)RR excretion was measured, and its association with background factors was investigated in 441 patients. Relationships between changes in urine pH due to vitamin C treatment, which reduce urine pH, and urinary soluble (P)RR excretion were investigated in 10 healthy volunteers. Urinary soluble (P)RR excretion was 1.46 (0.44–2.92) ng/gCre. Urine pH showed a significantly positive association with urinary soluble (P)RR excretion, independent of other factors. Changes in urine pH and urinary soluble (P)RR excretion due to vitamin C treatment were significantly and positively correlated (ρ = 0.8182, p = 0.0038). These data showed an association between urinary soluble (P)RR excretion and urine pH in humans, suggesting that (P)RR in the kidney might play a role in urine pH regulation.

The (pro)renin receptor in health and disease

The (pro)renin receptor ((P)RR) was first identified as a single-transmembrane receptor in human kidneys and initially attracted attention owing to its potential role as a regulator of the tissue renin-angiotensin system (RAS). Subsequent studies found that the (P)RR is widely distributed in organs throughout the body, including the kidneys, heart, brain, eyes, placenta and the immune system, and has multifaceted functions in vivo. The (P)RR has roles in various physiological processes, such as the cell cycle, autophagy, acid-base balance, energy metabolism, embryonic development, T cell homeostasis, water balance, blood pressure regulation, cardiac remodelling and maintenance of podocyte structure. These roles of the (P)RR are mediated by its effects on important biological systems and pathways including the tissue RAS, vacuolar H⁺-ATPase, Wnt, partitioning defective homologue (Par) and tyrosine phosphorylation. In addition, the (P)RR has been reported to contribute to the pathogenesis of diseases such as fibrosis, hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer and obesity. Current evidence suggests that the (P)RR has key roles in the normal development and maintenance of vital organs and that dysfunction of the (P)RR is associated with diseases that are characterized by a disruption of the homeostasis of physiological functions.