Urinary angiotensinogen as a marker of intrarenal angiotensin II activity in adolescents with primary hypertension

Urinary excretion of renin and angiotensinogen in hypertensive children and adolescents

INTRODUCTION

In recent years hypertension has become an emerging condition in the young population. It has been proposed that the renin-angiotensin system plays an important role in regulation of blood pressure. We assessed whether activation of the intrarenal renin-angiotensin system occurs in hypertensive children and adolescents and what better reflects its activity: urine angiotensinogen (AGT) or urine renin (REN).

MATERIAL AND METHODS

The study was conducted on a sample of 58 subjects with primary hypertension (HT) and 29 normotensive children and adolescents. We measured urine REN and AGT excretion and assessed the values in relation to blood pressure (BP) and other clinical parameters. Both REN and AGT values were calculated by urine creatinine: REN/cr. and AGT/cr., respectively.

RESULTS

We observed higher urine REN/cr. values in hypertensive subjects in comparison to the reference group (6.99 vs. 2.93, p = 0.003). Hypertensive participants showed positive correlations between urine REN/cr. and diastolic 24-hour BP (r = 0.42, p = 0.002) as well as between urine REN/cr. and urine AGT/cr. (r = 0.266, p = 0.044, respectively).

CONCLUSIONS

Increased urine REN/cr. in hypertensive children and adolescents and its positive correlation with BP may indicate its important role in the pathogenesis of HT. Perhaps urine REN/cr. could be a marker of intrarenal renin-angiotensin system activity. Nevertheless, further research should be undertaken to confirm this observation.

Severe Hypouricemia Impairs Endothelium-Dependent Vasodilatation and Reduces Blood Pressure in Healthy Young Men: A Randomized, Placebo-Controlled, and Crossover Study

Background

Uric acid (UA) is a plasmatic antioxidant that has possible effects on blood pressure. The effects of UA on endothelial function are unclear. We hypothesize that endothelial function is not impaired unless significant UA depletion is achieved through selective xanthine oxidase inhibition with febuxostat and recombinant uricase (rasburicase).

Methods and Results

Microvascular hyperemia, induced by iontophoresis of acetylcholine and sodium nitroprusside, and heating‐induced local hyperemia after iontophoresis of saline and a specific nitric oxide synthase inhibitor were assessed by laser Doppler imaging. Blood pressure and renin‐angiotensin system markers were measured, and arterial stiffness was assessed. CRP (C‐reactive protein), allantoin, chlorotyrosine/tyrosine ratio, homocitrulline/lysine ratio, myeloperoxidase activity, malondialdehyde, and interleukin‐8 were used to characterize inflammation and oxidative stress. Seventeen young healthy men were enrolled in a randomized, double‐blind, placebo‐controlled, 3‐way crossover study. The 3 compared conditions were placebo, febuxostat alone, and febuxostat together with rasburicase. The allantoin (μmol/L)/UA (μmol/L) ratio differed between sessions (P<0.0001). During the febuxostat‐rasburicase session, heating‐induced hyperemia became altered in the presence of nitric oxide synthase inhibition; and systolic blood pressure, angiotensin II, and myeloperoxidase activity decreased (P≤0.03 versus febuxostat). The aldosterone concentration decreased in the febuxostat‐rasburicase group (P=0.01). Malondialdehyde increased when UA concentration decreased (both P<0.01 for febuxostat and febuxostat‐rasburicase versus placebo). Other parameters remained unchanged.

Conclusions

A large and short‐term decrease in UA in humans alters heat‐induced endothelium‐dependent microvascular vasodilation, slightly reduces systolic blood pressure through renin‐angiotensin system activity reduction, and markedly reduces myeloperoxidase activity when compared with moderate UA reduction. A moderate or severe hypouricemia leads to an increase in lipid peroxidation through loss of antioxidant capacity of plasma.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT03395977.

Longer duration of obesity is associated with a reduction in urinary angiotensinogen in prepubertal children

BACKGROUND

We aimed to study the impact of obesity on urinary excretion of angiotensinogen (U-AGT) in prepubertal children, focusing on the duration of obesity and gender. Also, we aimed to evaluate whether plasma angiotensinogen (P-AGT) and hydrogen peroxide (H₂O₂) play a role in the putative association.

METHODS

Cross-sectional evaluation of 305 children aged 8-9 years (160 normal weight, 86 overweight, and 59 obese). Anthropometric measurements and 24-h ambulatory blood pressure monitoring were performed. Angiotensinogen (AGT) was determined by a commercial enzyme-linked immunosorbent assay (ELISA) kit and H₂O₂ by a microplate fluorometric assay.

RESULTS

U-AGT and P-AGT levels were similar across body mass index (BMI) groups and between sexes. However, boys who were overweight/obese since the age of 4 years presented lower levels of U-AGT compared with those of normal weight at the same age. In children who were overweight/obese since the age of 4, urinary H₂O₂ decreased with P-AGT.

CONCLUSIONS

A higher duration of obesity was associated with decreased U-AGT in boys, thus reflecting decreased intrarenal activity of the renin-angiotensin system. Also, children with a longer duration of obesity showed an inverse association between urinary H₂O₂ and P-AGT. Future studies should address whether these results reflect an early compensatory mechanism to limit obesity-triggered renal dysfunction.

Angiotensinogen and Interleukin-18 as Markers of Chronic Kidney Damage in Children With a History of Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is a type of thrombotic microangiopathy, in the course of which some patients may develop chronic kidney disease (CKD). It is clinically important to investigate the markers of a poor prognosis. The levels of angiotensinogen (AGT) and interleukin-18 (IL-18) in serum and urine were evaluated. Study was conducted in 29 children with a history of HUS. Serum and urine AGT concentration was significantly higher in children after HUS as compared to the control group. No differences depending on the type of HUS and gender were noted. The serum concentration of IL-18 in children after HUS was significantly lower, whereas in urine did not differ significantly between the sick and healthy children. A negative correlation between the concentration of AGT in serum and albuminuria in patients after HUS was detected. The results indicate that the concentration of AGT in serum and urine in children after HUS increases, which may indicate the activation of the intrarenal renin-angiotensin-aldosterone system. The statement, that AGT may be a good biomarker of CKD after acute kidney injury due to HUS requires prospective studies with follow-up from the acute phase of the disease on a larger group of patients. Reduced IL-18 serum concentration in children after HUS with no difference in its urine concentration may indicate a loss of the protective effects of this cytokine on renal function due to previously occurred HUS.

The Specific α1-Adrenergic Receptor Antagonist Prazosin Influences the Urine Proteome

Urine, reflecting many changes in the body, is a better source than blood for biomarker discovery. However, even under physiological conditions, the urine proteome often varies. Understanding how various regulating factors affect urine proteome helps link changes to urine proteome with urinary biomarkers of physiological conditions as well as corresponding diseases. To evaluate the possible impact of α1-adrenergic receptor on urine proteome, this study investigated effects of the specific inhibitor prazosin on the urine proteome in a rat model by using tandem mass tagging and two-dimensional liquid chromatography-tandem mass spectrometry. A total of 775 proteins were identified, approximately half of which were influenced by prazosin treatment, indicating that the sympathetic nervous system exerts a significant impact on urine proteome. Eight significantly changed proteins were previously annotated as urinary candidate biomarkers. Angiotensinogen, haptoglobin, and beta-2 microglobulin, which were reported to be associated with blood pressure, were validated via Western blot. Prazosin is widely used in clinical practice; thus, these protein changes should be considered when studying corresponding diseases such as hypertension, post-traumatic stress disorder and benign prostatic hyperplasia. The related physiological activities of α1-receptors, controlling blood pressure and fear response might significantly affect the urine proteome and warrant further biomarker studies.

Early urinary angiotensinogen excretion in critically ill neonates

INTRODUCTION

Urinary angiotensinogen is considered a reliable biomarker for intrarenal renin-angiotensin system activity. The aims of this study were to assess the urinary angiotensinogen level during the first day of life and to evaluate its correlation with renal function in critically ill neonates.

METHODS

Urinary angiotensinogen concentration during the first 24 hours of life was measured in 98 critically ill neonates. Neonatal renal function was assessed by urinary levels of cystatin-C, albumin and α1-microglobulin and urinary electrolyte excretion.

RESULTS

Urinary angiotensinogen level decreased with increasing gestational age and body weight in critically ill neonates (P<0.001). After adjustment for gestational age, urinary angiotensinogen level correlated with urinary fractional excretion of sodium and urinary levels of cystatin-C and α1-microglobulin. Multivariate linear regression identified a significant impact of urinary cystatin-C on urinary angiotensinogen level (P<0.001). Furthermore, urinary angiotensinogen was significantly increased in neonates with a urinary cystatin-C-to-creatinine ratio ⩾2500 ng/mg, which was the optimal cut-off value to predict acute kidney injury in our previous study.

CONCLUSIONS

The urinary angiotensinogen level correlates with the overall maturity of renal function during the early postnatal period in critically ill neonates and an increased urinary angiotensinogen level might reflect renal injury in immature neonates.

Urinary angiotensinogen as a potential biomarker of intrarenal renin-angiotensin system activity in Chinese chronic kidney disease patients

BACKGROUND

Urinary angiotensinogen (AGT) mainly derives from the AGT produced in proximal tubular cells. Evidence exists that supports the correlation between urinary AGT and circulating AGT.

AIM

To investigate the role of urinary AGT as a potential biomarker of intrarenal renin-angiotensin system activity in Chinese chronic kidney disease (CKD) patients.

METHODS

ELISA-based method used to quantify urinary AGT. Analyzed the relationship between urinary AGT and intrarenal angiotensin II (Ang II) activity in 128 CKD patients. ELISA was applied to measure the urinary and plasma renin activity, AGT, Ang II and aldosterone. Furthermore expression levels of intrarenal renin, AGT, Ang II and Ang II receptor were examined by immunohistochemistry staining (IHCS) in 72 CKD patients undergoing renal biopsy.

RESULTS

The logarithmic transformation Log(urinary AGT/UCre) levels showed a normal distribution. Therefore, Log(urinary AGT/UCre) levels were used for the analyses. Average urinary AGT was 2.02 ± 0.55 ng/(mg Cr). Hypertension, urinary protein, urinary Ang II and urinary type IV collagen (Col IV) positively correlated with urinary AGT. Estimated glomerular filtration rate (eGFR), urinary sodium and serum AGT negatively correlated with urinary AGT. Multiple regression analysis indicated that low serum AGT, high urinary protein, urinary Ang II and urinary Col IV correlated significantly with high urinary AGT.

CONCLUSIONS

We observed positive correlation between urinary AGT and positive IHCS area of AGT, Ang II and Ang II type 1 receptor in renal tissue. These data suggest that urinary AGT might be a potential biomarker of intrarenal Ang II activity in CKD patients.

Serum uric acid level in newly diagnosed essential hypertension in a Nepalese population: a hospital based cross sectional study

OBJECTIVE

To develop the missing link between hyperuricemia and hypertension.

METHODS

The study was conducted in Department of Biochemistry in collaboration with Nephrology Unit of Internal Medicine Department. Hypertension was defined according to blood pressure readings by definitions of the Seventh Report of the Joint National Committee. Totally 205 newly diagnosed and untreated essential hypertensive cases and age-sex matched normotensive controls were enrolled in the study. The potential confounding factors of hyperuricemia and hypertension in both cases and controls were controlled. Uric acid levels in all participants were analyzed.

RESULTS

Renal function between newly diagnosed hypertensive cases and normotensive healthy controls were adjusted. The mean serum uric acid observed in newly diagnosed hypertensive cases and in normotensive healthy controls were (290.05±87.05) μmol/L and (245.24±99.38) μmol/L respectively. A total of 59 (28.8%) participants of cases and 28 (13.7%) participants of controls had hyperuricemia (odds ratio 2.555 (95% CI: 1.549-4.213), P<0.001).

CONCLUSIONS

The mean serum uric acid levels and number of hyperuricemic subjects were found to be significantly higher in cases when compared to controls.

Urinary angiotensinogen and urinary sodium are associated with blood pressure in normoalbuminuric children with diabetes

BACKGROUND

The aim of this study was to evaluate the association between blood pressure (BP) and urinary angiotensinogen excretion (uAGT) and renal sodium excretion (uNa) in children with type 1 diabetes mellitus (DM1).

METHODS

The study group consisted of 52 children with DM1 (28 males and 24 females) with albumin/creatinine ratio (ACR) below 30 mg/g and glomerular filtration rate (eGFR) above 90 ml/min/1.73 m(2). BP was assessed by 24-h ambulatory blood pressure monitoring (ABPM).

RESULTS

The patients showed significantly increased uAGT values with respect to controls (median 0.00 and range 1.76 vs. 0.00 and 0.00 ng/mg, respectively). The significant increase of uAGT was observed even in prehypertensive patients. uAGT concentrations showed positive correlation with systolic and diastolic 24-h BP and with mean arterial pressure (MAP) (r = 0.594). uNa values were negatively correlated with BP parameters, uAGT, ACR and eGFR.

CONCLUSIONS

An increase in uAGT precedes hypertension (HTN) in normoalbuminuric children with DM1 and may be considered as a new marker of HTN. Decreased sodium excretion seems to be involved in the development of HTN and early renal injury. Both uAGT and uNa are associated with BP in normoalbuminuric diabetic children.