Endogenous erythropoietin correlates with blood pressure in essential hypertension

Epidemiologic and Genetic Associations of Erythropoietin With Blood Pressure, Hypertension, and Coronary Artery Disease

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Recombinant erythropoietin acutely decreases renal perfusion and decouples the renin-angiotensin-aldosterone system

The effect of recombinant erythropoietin (rhEPO) on renal and systemic hemodynamics was evaluated in a randomized double-blinded, cross-over study. Sixteen healthy subjects were tested with placebo, or low-dose rhEPO for 2 weeks, or high-dose rhEPO for 3 days. Subjects refrained from excessive salt intake, according to instructions from a dietitian. Renal clearance studies were done for measurements of renal plasma flow, glomerular filtration rate (GFR) and the segmentel tubular handling of sodium and water (lithium clearance). rhEPO increased arterial blood pressure, total peripheral resistance, and renal vascular resistance, and decreased renal plasma flow in the high-dose rhEPO intervention and tended to decrease GFR. In spite of the decrease in renal perfusion, rhEPO tended to decrease reabsorption of sodium and water in the proximal tubule and induced a prompt decrease in circulating levels of renin and aldosterone, independent of changes in red blood cell mass, blood volumes, and blood pressure. We also found changes in biomarkers showing evidence that rhEPO induced a prothrombotic state. Our results suggest that rhEPO causes a direct downregulation in proximal tubular reabsorption that seems to decouple the activity of the renin-angiotensin-aldosterone system from changes in renal hemodynamics. This may serve as a negative feed-back mechanism on endogenous synthesis of EPO when circulating levels of EPO are high. These results demonstrates for the first time in humans a direct effect of rhEPO on renal hemodynamics and a decoupling of the renin-angiotensin-aldosterone system.

Erythropoietin and glucose homeostasis in women at varying degrees of future diabetic risk

AIMS/BACKGROUND

Recently, there has been considerable interest in the potential anti-diabetic effects of erythropoietin in animal models. It is not known, however, whether endogenous erythropoietin is associated with glucose regulation in humans.

METHODS

We evaluated the longitudinal relationship between endogenous erythropoietin at 3-months postpartum and glucose homeostasis at 12-months postpartum in a cohort of 229 women with varying degrees of glucose intolerance in their recent pregnancy, a model of the early natural history of pre-diabetes/diabetes. The women reflected the full spectrum of glucose tolerance in pregnancy from normal (n=63) to mildly abnormal (n=65) to gestational impaired glucose tolerance (n=46) to gestational diabetes (n=55), and hence a broad range of future diabetic risk.

RESULTS

At 3-months postpartum, there was no difference in serum erythropoietin between these 4 groups (p=0.22). After covariate adjustment, erythropoietin was not associated with beta-cell function, insulin sensitivity, or glycemia at either 3- or 12-months postpartum. On multiple linear regression analyses, however, erythropoietin at 3-months emerged as an independent predictor of both systolic (beta=0.51326, p=0.003) and diastolic blood pressure (beta=0.3321, p=0.01) at 12-months.

CONCLUSION

Endogenous erythropoietin is not associated with glucose homeostasis early in the natural history of metabolic disease, but may be relevant to vascular health.

Association of hemoglobin levels with blood pressure and hypertension in a large population-based study: the Korea National Health and Nutrition Examination Surveys 2008-2011

BACKGROUND

We investigated the association of hemoglobin (Hb) concentrations with blood pressure (BP) and hypertension in the full range of Hb concentrations, after adjusting for other hypertension risk factors.

METHODS

The study population consisted of a total of 20,076 subjects (8721 men, 11,355 women) aged ≥20 y who participated in the Korea National Health and Nutrition Examination Surveys conducted between 2008 and 2011.

RESULTS

The systolic BP (SBP) and diastolic BP (DBP) increased by 2.6mmHg and 3.2mmHg with 1mmol/l increase in the Hb concentration, respectively, after adjusting for age, body mass index, total cholesterol, alcohol drinking, current smoking, mild renal dysfunction, and diabetes mellitus both in men with Hb concentrations of ≥8.1mmol/l (13.0g/dl) and women with a hemoglobin concentration ≥6.8mmol/l (11.0g/dl). In the multiple logistic regression analysis, the Hb concentration showed significant positive association with hypertension independently of other confounding factors both in men and women.

CONCLUSIONS

Hb concentration was positively associated with SBP and DBP in men with Hb concentrations ≥8.1mmol/l (13.0g/dl) and women with Hb concentrations ≥6.8mmol/l (11.0g/dl) in the general Korean population.

Interdialytic hypertension-an update

The reference standard for diagnosing hypertension among hemodialysis patients is 44-hour interdialytic ambulatory blood pressure (BP) recording. However, a more practical way to diagnose and manage hypertension is to measure home BP over the interdialytic interval. In contrast to pre- and postdialysis BP recordings, measurements of BP performed outside the dialysis unit correlate with the presence of left ventricular hypertrophy and directly and strongly with all-cause mortality. Hypervolemia that is not clinically obvious is the most common treatable cause of hypertension among patients with end-stage renal disease; thus, volume control should be the initial therapy to treat hypertension in most hemodialysis patients. To diagnose hypervolemia, continuous blood volume monitoring is emerging as an effective and simple technique. Reducing dietary and dialysate sodium is an often overlooked strategy to improve BP control. Although definitive randomized trials that show cardiovascular benefits of BP lowering among hypertensive hemodialysis have not been performed, emerging evidence suggests that lowering BP might reduce cardiovascular events. The treatment should be guided by BP obtained outside the dialysis unit because predialysis and postdialysis BP are quite variable and agree poorly with measurements obtained outside the dialysis unit. Although the appropriate level to which BP should be lowered remains elusive, current data suggest that interdialytic ambulatory systolic BP should be lowered to <130 mm Hg and averaged home systolic BP to <140 mm Hg. Antihypertensive drugs will be required by most patients receiving thrice weekly dialysis for 4 hours. Beta blockers, dihydropyridine calcium blockers, and agents that block the renin-angiotensin system appear to be effective in lowering BP in these patients.

Antihypertensive agents and arterial stiffness: relevance to reducing cardiovascular risk in the chronic kidney disease patient

PURPOSE OF REVIEW

Arterial stiffness is a sign of diffuse adventitial macrovascular disease. The purpose of the present review is to discuss, in patients with chronic kidney disease, the pathophysiology of increased arterial stiffness, the role of antihypertensive therapy on reduction of arterial stiffness, and the clinical ways by which the prognostication of cardiovascular disease in patients with chronic kidney disease can be refined using arterial stiffness monitoring.

RECENT FINDINGS

Arterial stiffness is increased with increasing prevalence of traditional cardiovascular risk factors. In patients with chronic kidney disease some unique factors further increase the risk of arterial stiffness, and include volume overload, activation of the renin-angiotensin system, anemia, and dysregulated mineral metabolism. Arterial stiffness is increased even in patients with early-stage chronic kidney disease. Blood pressure reduction when accompanied by a reduction in arterial stiffness is associated with improved prognosis. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers can preferentially improve arterial stiffness, which may be an additional mechanism of cardiovascular protection with these agents.

SUMMARY

The impact of improvement in arterial stiffness with antihypertensive agents on cardiovascular outcomes needs well designed clinical trials.

Overcoming barriers that inhibit proper treatment of anemia

Intravenous (i.v.) iron and recombinant human erythropoietin (EPO), like all other medications, are associated with the risk of adverse events. Historically, the primary concern with iron therapy has been the possibility of iron overload, which exposes the individual to the effects associated with nontransferrin-bound iron. Experience with EPO use has demonstrated an association with hypertension and with the upregulation of a number of markers of inflammation. The impact of these potential adverse effects merits careful analysis, given that both i.v. iron and EPO are designed for long-term use in a patient population at high risk for infection and cardiovascular disease. However, the incidence of iron overload and the risks associated with nontransferrin-bound iron have dramatically been reduced since the introduction of EPO therapy, and no data exist that demonstrate a definitive association between i.v. iron and an increased risk of morbidity related to infection or cardiovascular disease. On the other hand, EPO use is associated with hypertension, endothelial dysfunction, and prothrombotic and inflammatory states in hemodialysis patients. Risks associated with hypertension can be minimized by using the lowest effective EPO dose, which may be achieved through the regular use of i.v. iron. Judicious use of both i.v. iron and EPO may optimize cardiovascular outcomes.

Hypertension in Chronic Kidney Disease and Dialysis: Pathophysiology and Management

Hypertension affects 24% of the adult US population. In the United States, 3% of the adult population has an elevated serum creatinine level, and 70% of these patients have hypertension. The prevalence of hypertension in chronic kidney disease (CKD) depends on the patient's age and the severity of renal failure, proteinuria, and underlying renal disease. As patients with CKD progress to end-stage renal disease (ESRD), 86% are diagnosed with hypertension. It has long been recognized that kidney function affects and is affected by hypertension. This article discusses the pathophysiology and management of hypertension in patients with CKD.

Etiology and management of hypertension in chronic kidney disease

The kidneys are vital in the pathogenesis of hypertension and are also pathologically affected by the presence of hypertension. The prevalence of hypertension in chronic kidney disease (CKD) depends on age, the severity of renal failure, and proteinuria. The intricate and inextricable relationship between CKD and hypertension seems to cause cardiovascular disease that has assumed epidemic proportions. This article discusses the etiology and treatment of hypertension in CKD so that it can be better controlled.

A comparison of the bioequivalence of two formulations of epoetin alfa after subcutaneous injection

BACKGROUND

The previous formulation of epoetin alfa in Japan was a citrate-buffered protein solution containing gelatin hydrolysate as the protein protective agent. To eliminate pain at injection sites, and the risks of anaphylactic shock and unknown infections by gelatin we have developed a new formulation of phosphate-buffered epoetin alfa, which does not contain gelatin hydrolysate.

AIM

To compare the bioequivalence of two formulations of epoetin alfa administered by the subcutaneous route.

METHODS

Four separate studies were performed to assess the bioequivalence of two epoetin alfa formulations using different strength and doses, i.e. 750 IU per 0.5 ml x 0.5 ml (= 750 IU per subject), 750 IU per 0.5 ml x 4 ml (= 6000 IU per subject), 6000 IU per 0.5 ml x 0.5 ml (= 6000 IU per subject) and 24,000 IU per 0.5 ml x 0.125 ml (= 6000 IU per subject). Each study was a single-centre, open-label, randomized, two-treatment, two-period, crossover study for which healthy volunteers were enrolled. Bioequivalence was assessed using the confidence interval (CI) of the ratios for the log-transformed, baseline-corrected Cmax and AUC(0,t). Baseline-corrected AUC(0,t) was calculated using the following equation: AUC(0,t) = AUC(0,t), uncorrected -- predose level x observation period.

RESULTS

The ratios (gelatin-free/gelatin-containing) for the log-transformed Cmax and AUC(0,t) after 6000 IU per subject injection of three different concentrations of epoetin alfa were well within the usual range for bioequivalence (90% CI 0.8, 1.25). The 90% CI of the ratio for Cmax after 750 IU per subject injection was 0.906, 1.24, which was within the bioequivalence range. However, the ratio for AUC(0,t) was not determined in this lowest dose because of negative AUC(0,t) values obtained in 12/60 cases. The overall safety data were consistent with those expected for a healthy study population, and did not present any concerns suggestive of adverse effects due to either formulation.

CONCLUSIONS

The point estimates and 90% CIs of the ratios of Cmax and AUC(0,t) for the gelatin-free/gelatin-containing formulations indicated that the two formulations are bioequivalent.

Elevated erythropoietin receptor and transforming growth factor-beta1 expression in stenotic arteriovenous fistulae used for hemodialysis

The issue of whether recombinant human erythropoietin (rhEPO) increases thrombosis of arteriovenous (AV) fistulae used for hemodialysis remains unclear. Thrombosis often occurs at stenotic segments of fistulae where there is marked intimal hyperplasia and extracellular matrix accumulation. Increased expression of transforming growth factor-beta1 (TGF-beta1) has been shown to be involved in the development of atherosclerotic lesions by promoting intimal hyperplasia and extracellular matrix accumulation. To clarify the role of rhEPO in the development of stenosis of AV fistulae, this study examined expression of the erythropoietin receptor (EPO-R), TGF-beta1, plasminogen activator inhibitor type 1 (PAI-1), cellular fibronectin containing an extra domain A (EDA+), and TGF-beta1 mRNA, and assessed in situ rhEPO binding in tissue specimens from seven cutaneous veins and eight patent and seven stenosed portions of AV fistulae of patients undergoing dialysis. Prominent intimal hyperplasia was evident in the stenosed segments. Significant elevation in expression of EPO-R and TGF-beta1 was noted in patent AV fistulae compared to the cutaneous veins. Significant enhancement of EPO-R and TGF-beta expression was detected in the stenotic fistulae. Fibronectin EDA+ and PAI-1 expression was increased in intimal hyperplasia compared to patent fistulae and cutaneous veins. Elevated EPO-R expression was further confirmed by in situ binding of biotin-labeled rhEPO in stenosed tissue specimens. It is hypothesized that increased rhEPO binding due to elevated EPO-R expression contributes to the development of AV fistula stenosis caused by intimal hyperplasia and extracellular matrix accumulation in response to increased TGF-beta1 expression in patients receiving hemodialysis.