Prognostic importance of hemoglobin in hypertensive patients with electrocardiographic left ventricular hypertrophy: the Losartan Intervention For End point reduction in hypertension (LIFE) study

Erythropoietin Regulation by Angiotensin II

The renin-angiotensin system (RAS) is a key regulator of blood pressure and blood volume homeostasis. The RAS is primarily comprised of the precursor protein angiotensinogen and the two proteases, renin and angiotensin-converting enzyme (ACE). Angiotensin I (Ang I) is derived from angiotensinogen by renin, but appears to have no biological activity. In contrast, angiotensin II (Ang II) that has a variety of biological functions in the cells is converted from Ang I through removal of two-C-terminal residues by ACE. The physiological effects of Ang II are due to Ang II signaling through specific receptor binding, resulting in muscle contraction leading to increased blood pressure and volume. To modulate RAS, three classes of drugs have been developed: (1) renin inhibitors to prevent angiotensinogen conversion to Ang I, (2) ACE inhibitors, to prevent Ang I processing to Ang II and (3) angiotensin receptor blockers, to inhibit Ang II signaling through its receptor. Studies using the RAS inhibitors and Ang II demonstrated that RAS signaling mediates actions of Ang II in the regulation of proliferation and differentiation of specific hematopoietic cell types, especially in the red blood cell lineage. Accumulating evidence indicates that RAS regulates EPO, an essential mediator of red cell production, for human anemia and erythropoiesis in vivo and in vitro. The regulation of EPO expression by Ang II may be responsible for maintaining red blood cell homeostasis. This review highlights the biological roles of RAS for blood cell and EPO homeostasis through Ang II signaling. The molecular mechanism for Ang II-induced EPO production of the cell or tissue type-specific expression is discussed.

Association of hemoglobin with ankle-brachial index in general population

OBJECTIVES

Previous studies have demonstrated that both low and high hemoglobin concentrations are predictive of adverse cardiovascular outcomes in various populations. However, an association of hemoglobin with the ankle-brachial index, which is widely used as a screening test for peripheral arterial disease, has not yet been identified.

METHODS

We examined 786 subjects (236 women and 550 men) who received routine physical check-ups. The ankle-brachial index and several hematological parameters, including the hemoglobin level, hematocrit and red blood cell count and other demographic and biochemical characteristics were collected. Univariate and multivariate linear regression analyses were performed to assess the relationships between the ankle-brachial index and the independent determinants. Receiver operating characteristic curve analysis was conducted to calculate the cut-off level of hemoglobin for detecting a relatively low ankle-brachial index (less than 20% of all subjects, which was 1.02).

RESULTS

The hemoglobin level, hematocrit and red blood cell count were correlated with the ankle-brachial index in the males (r=-0.274, r=-0.224 and r=-0.273, respectively, p<0.001 for all), but these associations were not significant in the females. Multivariate linear regression analysis revealed that the independent determinants of the ankle-brachial index included age, total cholesterol, high-density lipoprotein cholesterol and the white blood cell count for the females and age, hypertension, total cholesterol and hemoglobin (β=-0.001, p<0.001) for the males after adjusting for confounding factors. Receiver operating characteristic curve analysis revealed that the cut-off level of hemoglobin for predicting a low ankle-brachial index was 156.5 g/L in the males.

CONCLUSIONS

A high hemoglobin concentration was independently correlated with a low ankle-brachial index in the healthy males, indicating that an elevation in this level may be associated with an increased atherosclerosis risk.

Assessment of left ventricular myocardial performance by tissue Doppler echocardiography in patients with polycythemia vera

AIMS

The aim of this study was to evaluate myocardial performance index (MPI) which reflects the combined systolic and diastolic performance of the ventricles by tissue Doppler imaging (TDI) in patients with polycythemia vera (PV).

METHOD AND MATERIALS

Twenty-eight patients with PV (17 men; mean age 60±9 years) and 30 age-matched healthy subjects were prospectively evaluated. The diagnosis of PV was performed according to the World Health Organization (WHO) criteria. Left ventricular (LV) systolic and diastolic functions were assessed by conventional echocardiography and TDI. MPI of both the LV and right ventricles (RV) were measured by TDI method.

RESULTS

The LV MPI was significantly higher in PV group than in the controls (0.61±0.16 vs. 0.49±0.05; P=0.001). Also, the RV MPI was impaired in patients with PV compared to the control subjects (0.51±0.11 vs. 0.43±0.09; P=0.005). RV late A filling velocity (Am) and RV isovolumetric relaxation time were significantly higher in the PV group compared to healthy subjects (P=0.03 and 0.05, respectively). In logistic regression models, PV was determined as an independent predictor of impaired MPI (odds ratio: 3.7; CI 95%, 1.2-7.5). In addition, pulmonary arterial pressure was significantly elevated in patients with PV compared to the controls (P=0.02).

CONCLUSION

This study demonstrated that biventricular MPI is impaired in patients with PV.

Autosomal dominant mutation in the signal peptide of renin in a kindred with anemia, hyperuricemia, and CKD

Homozygous or compound heterozygous mutations in renin (REN) cause renal tubular dysgenesis, which is characterized by death in utero due to kidney failure and pulmonary hypoplasia. The phenotype resembles the fetopathy caused by angiotensin-converting enzyme inhibitor or angiotensin receptor blocker intake during pregnancy. Recently, heterozygous REN mutations were shown to result in early-onset hyperuricemia, anemia, and chronic kidney disease (CKD). To date, only 3 different heterozygous REN mutations have been published. We report mutation analysis of the REN gene in 39 kindreds with hyperuricemia and CKD who previously tested negative for mutations in the UMOD (uromodulin) and HNF1B (hepatocyte nuclear factor 1β) genes. We identified one kindred with a novel thymidine to cytosine mutation at position 28 in the REN complementary DNA, corresponding to a tryptophan to arginine substitution at amino acid 10, which is found within the signal sequence (c.28T>C; p.W10R). On this basis, we conclude that REN mutations are rare events in patients with CKD. Within the kindred, we found affected individuals over 4 generations who carried the novel REN mutation and were characterized by significant anemia, hyperuricemia, and CKD. Anemia was severe and disproportional to the degree of decreased kidney function. Because all heterozygous REN mutations that have been described are localized in the signal sequence, screening of the REN gene for patients with CKD with hyperuricemia and anemia may best be focused on sequencing of exon 1, which encodes the signal peptide.

Association of hemoglobin with ambulatory arterial stiffness index in untreated essential hypertensive patients without anemia

OBJECTIVE

Increased hemoglobin (Hb) levels are known to be associated with increased cardiovascular events and mortality in hypertensive patients, but the underlying mechanism remains unclear. However, an increased Ambulatory Arterial Stiffness Index (AASI), the surrogate maker of arterial stiffness, has been proven to be an independent predictor of cardiovascular disease. This pilot study evaluated the association between Hb and AASI in untreated essential hypertensive patients without anemia.

METHODS

A total of 566 untreated essential hypertensive patients without anemia were divided into Normal-Hb and High-Hb groups according to their Hb levels. The AASI and its symmetric calculation (Sym_AASI) were derived from 24h-Ambulatory Blood Pressure Monitoring (24h-ABPM). A multivariable linear regression analysis was performed to determine the relationship between Hb and AASI, Sym_AASI.

RESULTS

High-Hb group (n=127) showed higher AASI and Sym_AASI (0.51±0.11 vs 0.43±0.12, p<0.001; 0.33±0.10 vs 0.27±0.08, p<0.001) compared to Normal-Hb group (n=439). Univariate correlation analysis showed that Hb levels were positively related to AASI and Sym_AASI values (r=0.459, p<0.001; r=0.353, p<0.001). After adjustment for age, sex, BMI, current smoker, eGFR, uric acid, total cholesterol, high-density lipoprotein, 24h-SBP, 24h-PP and dipper status, Hb persisted as a independent determinant of AASI and Sym_AASI (β=0.402, p<0.001 and β=0.298, p<0.001, respectively).

CONCLUSION

High hemoglobin seems be to associated with increased AASI in untreated essential hypertensive patients without anemia.

Relation of anemia to echocardiographically estimated left ventricular filling pressure in hypertensive patients over 50 year-old

BACKGROUND

Anemia is associated with worse long term outcomes in heart failure. However, there is little evidence on the effect of low hemoglobin level to the left ventricular (LV) structure and diastolic function in hypertensive patients. This study assessed the relationship of hemoglobin level to LV filling pressure in elderly hypertensive patients.

METHODS

From January 2005 to January 2009, 200 newly diagnosed hypertensive patients over 50 years old (mean age 60 ± 6 years, 116 women) were analyzed. The clinical parameters and comprehensive echocardiographic data were obtained. The patients with and without anemia were compared.

RESULTS

There were significant differences between the anemic and non-anemic groups in the LV mass index (115.27 ± 34.95 vs. 103.75 ± 28.21 g/m(2)), left atrial (LA) volume index (29.31 ± 10.74 vs. 24.99 ± 7.43 mL/m(2)), and E/E' (11.92 ± 4.34 vs. 9.37 ± 2.51). Chronic renal failure was more prevalent in anemic group. On multivariate logistic analysis, anemia was significantly correlated with high LV filling pressure, reflected by E/E', even after controlling for LV mass index and LA volume index. Furthermore, E/E' was significantly correlated with the hemoglobin level (R(2) = 0.093, p < 0.001).

CONCLUSION

In newly-diagnosed hypertensive patients over 50 years old, the presence of anemia was significantly associated with elevated LV filling pressure and LV structural changes. And the hemoglobin level was negatively correlated with noninvasively estimated LV filling pressure.

The role of the renin-angiotensin system in the regulation of erythropoiesis

The renin-angiotensin system is the major regulator of blood pressure by virtue of controlling vascular resistance and plasma volume. Much less recognition exists for the role of the renin-angiotensin system in regulating erythropoiesis, a biological function critical for oxygen delivery to tissues. In this review, we present evidence that angiotensin II (Ang II) is a physiologically important regulator of erythropoiesis with 2 key actions. First, Ang II is a growth factor of erythroid progenitors and, in cooperation with erythropoietin, increases red blood cell mass. Second, Ang II acts as an erythropoietin secretagogue to maintain increased erythropoietin levels despite increments in hematocrit. Among a multitude of physiologic and pathophysiologic implications, these lines of evidence provide an explanation for the effect of angiotensin-converting enzyme inhibitors and Ang II type 1 receptor blockers to decrease hematocrit or cause anemia in various clinical conditions.