Increased urinary protein excretion in the "normal" range is associated with increased renin-angiotensin system activity

Simultaneous angiotensin receptor blockade and glucagon-like peptide-1 receptor activation ameliorate albuminuria in obese insulin-resistant rats

Insulin resistance increases renal oxidant production by upregulating NADPH oxidase 4 (Nox4) expression contributing to oxidative damage and ultimately albuminuria. Inhibition of the renin-angiotensin system (RAS) and activation of glucagon-like peptide-1 (GLP-1) receptor signalling may reverse this effect. However, whether angiotensin receptor type 1 (AT1) blockade and GLP-1 receptor activation improve oxidative damage and albuminuria through different mechanisms is not known. Using insulin-resistant Otsuka Long-Evans Tokushima Fatty (OLETF) rats, we tested the hypothesis that simultaneous blockade of AT1 and activation of GLP-1r additively decrease oxidative damage and urinary albumin excretion (U_alb V) in the following groups: (a) untreated, lean LETO (n = 7), (b) untreated, obese OLETF (n = 9), (c) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg/d; n = 9), (d) OLETF + GLP-1 mimetic (EXE; 10 µg exenatide/kg/d; n = 7) and (e) OLETF + ARB +exenatide (Combo; n = 6). Mean kidney Nox4 protein expression and nitrotyrosine (NT) levels were 30% and 46% greater, respectively, in OLETF compared with LETO. Conversely, Nox4 protein expression and NT were reduced to LETO levels in ARB and EXE, and Combo reduced Nox4, NT and 4-hydroxy-2-nonenal levels by 21%, 27% and 27%, respectively. At baseline, U_alb V was nearly double in OLETF compared with LETO and increased to nearly 10-fold greater levels by the end of the study. Whereas ARB (45%) and EXE (55%) individually reduced U_alb V, the combination completely ameliorated the albuminuria. Collectively, these data suggest that AT1 blockade and GLP-1 receptor activation reduce renal oxidative damage similarly during insulin resistance, whereas targeting both signalling pathways provides added benefit in restoring and/or further ameliorating albuminuria in a model of diet-induced obesity.

Evidence of Augmented Intrarenal Angiotensinogen Associated With Glomerular Swelling in Gestational Hypertension and Preeclampsia: Clinical Implications

Background AGT (angiotensinogen) synthesis occurs in renal proximal tubular epithelial cells, independent from systemic AGT , as a component of the intrarenal renin-angiotensin system. We investigated urinary AGT , as a biomarker for renin-angiotensin system activation, and electrolyte concentrations, in relation to glomerular volume, as a proxy for glomerular endotheliosis in renal biopsy tissue from pregnant normotensive control and hypertensive women. Methods and Results Urine samples were collected from normotensive control (n=10), gestational hypertensive (n=6), and pre-eclamptic (n=16) women at the time a renal biopsy was obtained. Samples were collected from Lund University Hospital between November 1999 and June 2001. Urinary AGT , potassium, and sodium were measured, normalized to urinary creatinine. Mean glomerular volume was estimated from biopsy sections. AGT protein expression and localization were assessed in renal biopsies by immunohistochemistry. Urinary AGT concentrations were higher in hypertensive pregnancies (median, gestational hypertension: 11.3 ng/mmol [interquartile range: 2.8-13.6]; preeclampsia: 8.4 ng/mmol [interquartile range: 4.2-29.1]; normotensive control: 0.6 ng/mmol [interquartile range: 0.4-0.8]; P<0.0001) and showed a positive relationship with estimated mean glomerular volume. Urinary potassium strongly correlated with urinary AGT ( P<0.0001). Although numbers were small, AGT protein was found in both glomeruli and proximal tubules in normotensive control but was present only in proximal tubules in women with hypertensive pregnancy. Conclusions This study shows that pregnant women with gestational hypertension or preeclampsia have increased urinary AGT and potassium excretion associated with signs of glomerular swelling. Our data suggest that the kidneys of women with hypertensive pregnancies and endotheliosis have inappropriate intrarenal renin-angiotensin system activation, which may contribute toward the pathogenesis of hypertension and renal injury.

High-fat diet amplifies renal renin angiotensin system expression, blood pressure elevation, and renal dysfunction caused by Ceacam1 null deletion

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAMl), a substrate of the insulin receptor tyrosine kinase, regulates insulin action by promoting insulin clearance. Global null mutation of Ceacam1 gene (Cc1(-/-)) results in features of the metabolic syndrome, including insulin resistance, hyperinsulinemia, visceral adiposity, elevated blood pressure, and albuminuria. It also causes activation of the renal renin-angiotensin system (RAS). In the current study, we tested the hypothesis that high-fat diet enhances the expression of RAS components. Three-month-old wild-type (Cc1(+/+)) and Cc1(-/-) mice were fed either a regular or a high-fat diet for 8 wk. At baseline under regular feeding conditions, Cc1(-/-) mice exhibited higher blood pressure, urine albumin-to-creatinine ratio (UACR), and renal expression of angiotensinogen, renin/prorenin, angiotensin-converting enzyme, (pro)renin receptor, angiotensin subtype AT1 receptor, angiotensin II, and elevated PI3K phosphorylation, as detected by p85α (Tyr(508)) immunostaining, inflammatory response, and the expression of collagen I and collagen III. In Cc1(+/+) mice, high-fat diet increased blood pressure, UACR, the expression of angiotensin-converting enzyme and angiotensin II, PI3K phosphorylation, inflammatory response, and the expression of collagen I and collagen III. In Cc1(-/-) mice, high-fat intake further amplified these parameters. Immunohistochemical staining showed increased p-PI3K p85α (Tyr(508)) expression in renal glomeruli, proximal, distal, and collecting tubules of Cc1(-/-) mice fed a high-fat diet. Together, this demonstrates that high-fat diet amplifies the permissive effect of Ceacam1 deletion on renal expression of all RAS components, PI3K phosphorylation, inflammation, and fibrosis.

Normal range albuminuria and metabolic syndrome in South Korea: the 2011-2012 Korean National Health and Nutrition Examination Survey

Background

It is well-known that there is a close relationship between metabolic syndrome (MetS) and microalbuminuria. However, some recent studies have found that even normal range albuminuria was associated with MetS and cardiometabolic risk factors. The purpose of this study is to analyze the relationship between MetS and normal range albuminuria and to calculate the cutoff value for albuminuria that correlates with MetS in the representative fraction of Korean population.

Methods

Data were obtained from the 2011–2012 Korea National Health and Nutrition Examination Survey and included 9,650 subjects aged ≥19 years. We measured metabolic parameters: fasting blood glucose, waist circumference, blood pressure, and lipids, and albumin-to-creatinine ratio (ACR). The optimal ACR cutoff points for MetS were examined by the receiver operating characteristic curve. Multivariate logistic regression was used to obtain the prevalence of MetS and its components according to the ACR levels.

Results

The first cutoff value of ACR were 4.8 mg/g for subjects with ≥3 components of MetS. There was a graded association between ACR and prevalence of MetS and its components. If ACR was <4 mg/g, there was no significant increase in the prevalence of MetS or its components. From the ACR level of 4–5 mg/g, the prevalence of MetS significantly increased after adjusting for age, sex, body mass index, smoking, alcohol intake, exercise, and medications for diabetes mellitus and hypertension (odds ratio; 95% confidence intervals = 1.416; 1.041–1.926).

Conclusions

Albuminuria within the normal range (around 5 mg/g) was associated with prevalence of MetS in the Korean population.

IgA nephropathy with early kidney disease is associated with increased arterial stiffness and renin-angiotensin system activity

BACKGROUND

IgA nephropathy is associated with increased cardiovascular risk, though whether this is due to loss of kidney function or proteinuria is unclear.

METHODS

For this study 10 normotensive IgA nephropathy subjects with early kidney disease (41±5 yrs, glomerular filtration rate (GFR) 87±9 ml/min, proteinuria 720±300 mg/d) and 10 gender- and blood pressure-matched healthy controls (36±1 yrs, estimated GFR 102±5 ml/min, proteinuria 70±6 mg/d) were studied in high-salt balance. Blood pressure and arterial stiffness, expressed as pulse wave velocity and aortic augmentation index, were measured at baseline and in response to 60 min of angiotensin II (AngII) infusion.

RESULTS

At baseline, IgA nephropathy subjects demonstrated similar pulse wave velocity (8.6±0.7 vs. 8.0±0.4 m/s, p=0.5) but increased aortic augmentation index (12.6±3.1 vs. 1.8±4%, p=0.04) and a trend towards increased circulating renin-angiotensin system (RAS) components (plasma renin activity, 0.55±0.18 vs. 0.21±0.05 ng/l/s, p=0.08; angiotensin II, 25±5 vs. 16±1 ng/l, p=0.08) compared with controls. However, despite similar baseline blood pressure values (p=0.8), IgA nephropathy was associated with reduced arterial sensitivity to AngII challenge (Δmean arterial pressure: 19±4 vs. 29±1 mm Hg, p=0.05; Δpulse wave velocity: -0.06±0.6 vs. 1.5±0.3 m/s, p=0.07) compared with controls, even after multivariate analysis.

CONCLUSION

Even in the setting of early kidney disease, IgA nephropathy is associated with increased arterial stiffness and decreased angiotensin II responsiveness, a marker of increased RAS activity.

High normal urine albumin-to-creatinine ratio predicts development of hypertension in Korean men

BACKGROUND

Microalbuminuria is known as a risk factor for hypertension. Recently it was suggested that urine albumin-to-creatinine ratio (UACR), even within the normal range, can be associated with hypertension, but the temporal relationship between normal range UACR and hypertension was not confirmed. Therefore the aim of this study was to verify an association between normal range UACR and the development of hypertension in Korean men.

METHODS AND RESULTS

This prospective cohort study was performed on 1,284 initially non-hypertensive Korean men. The total follow-up period was 4,109.5 person-years and the mean follow-up period was 3.2±1.51 years. Cox proportional hazards model was used to estimate the hazard ratios (HR) for the risk of hypertension development. After adjusting for multiple covariates, the HR (95% confidence interval [CI]) for incident hypertension, comparing the second to the fourth quartiles of UACR level to the first quartile, were 1.35 (95% CI: 0.93-1.97), 1.55 (95% CI: 1.07-2.25) and 1.89 (95% CI: 1.31-2.71), respectively (P for trend=0.001).

CONCLUSIONS

High UACR within the normal range was significantly associated with hypertension development. Furthermore, this association remained significant after adjusting for multiple baseline covariates. 

High-normal albuminuria predicts metabolic syndrome in middle-aged Korean men: a prospective cohort study

OBJECTIVE

High-normal albuminuria has recently been associated with an elevated risk of cardiovascular disease. However, it is uncertain whether high-normal albuminuria is associated with metabolic syndrome (MetS). The objective of this prospective cohort study was to investigate whether a temporal relationship exists between a high-normal urine albumin-to-creatinine ratio (UACR) and the development of MetS.

STUDY DESIGN

A total of 4338 healthy Korean men who had their UACRs and MetS components assessed in 2005 were enrolled in the study. A MetS-free cohort of 1364 individuals, who did not have any conditions that would have excluded them from the study, was followed up until 2010.

MAIN OUTCOME MEASURE

MetS was defined according to the joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention.

RESULTS

Cox proportional hazards models were used to estimate the hazard ratio (HR) associated with normal UACR values stratified into following tertiles: <3.12 μg/mg, ≥3.12, <4.87 μg/mg, and ≥4.87 μg/mg. The UACR was categorised into the following tertiles. During 4470.6 person-years of follow-up, 247 incident cases of MetS developed between 2006 and 2010. The third UACR tertile was associated with the development of MetS after adjusting for multiple baseline covariates (HR 1.57; 95% confidence interval: 1.14-2.18).

CONCLUSIONS

On the basis of our 5-year follow-up study, a high-normal UACR predicts the development of MetS in Korean men.

25-Hydroxyvitamin D status, arterial stiffness and the renin-angiotensin system in healthy humans

Vitamin D deficiency is associated with increased arterial stiffness. We sought to clarify the influence of vitamin D in modulating angiotensin II-dependent arterial stiffness. Thirty-six healthy subjects (33 ± 2 years, 67% female, mean 25-hydroxyvitamin D 69 ± 4 nmol/L) were studied in high salt balance. Arterial stiffness, expressed as brachial pulse wave velocity (bPWV) and aortic augmentation index (AIx), was measured by tonometry at baseline and in response to angiotensin II infusion (3 ng/kg/min × 30 min then 6 ng/kg/min × 30 min). The primary outcome was change in bPWV after an angiotensin II challenge. Results were analyzed according to plasma 25-hydroxyvitamin D status: deficient (<50 nmol/L) and sufficient (≥ 50 nmol/L). There were no differences in baseline arterial stiffness between vitamin D deficient (25-hydroxyvitamin D 40 ± 2 nmol/L) and sufficient (25-hydroxyvitamin D 80 ± 4 nmol/L) groups. Compared with sufficient vitamin D status, vitamin D deficiency was associated with a decreased arterial response to angiotensin II challenge (Δbrachial pulse wave velocity: 0.48 ± 0.44 m/s versus 1.95 ± 0.22 m/s, p=0.004; Δaortic augmentation index: 9.4 ± 3.4% versus 14.2 ± 2.7%, p=0.3), which persisted for brachial pulse wave velocity response after adjustment for covariates (p=0.03). Vitamin D deficiency is associated with increased arterial stiffness in healthy humans, possibly through an angiotensin II-dependent mechanism.