Age influence on renalase and catecholamines concentration in hypertensive patients, including maintained dialysis

BACKGROUND: Hypertension in elderly patients is one of the main problems in cardiovascular diseases. The sympathetic nervous system hyperactivity seen in older patients is a known risk factor for hypertension and other cardiovascular events as well as chronic kidney disease. Renalase, secreted by the kidney and circulated in blood, may regulate the sympathetic tone by catecholamine degradation and in this way has an impact on cardiovascular and renal complications. OBJECTIVE: To assess the impact of age on renalase and catecholamine concentration in hypertensive patients, including those on dialyses and its possible relation to blood pressure control and cardiovascular disease. METHODS: The study cohort of 211 patients was divided into two groups according to age below 65 years (range 19–64) and above 65 years (range 65–86). The older group represented 38% of the whole studied population and 75% of them were dialyzed. The two groups of different ages were also divided into dialysis and nondialysis subgroups. The serum renalase, dopamine, and norepinephrine concentration together with blood pressure value and echocardiography were assessed. RESULTS: Patients aged 65 years and more had higher renalase (20.59 vs 13.14 µg/mL, P=0.02) and dopamine (41.71 vs 15.46 pg/mL, P<0.001) concentration as well as lower diastolic blood pressure (75.33 vs 85 mmHg, P=0.001), advanced abnormalities in echocardiography, and more often suffered from diabetes and coronary artery disease. The significant correlation between age and renalase (r=0.16; P=0.019), norepinephrine (r=0.179; P=0.013), and dopamine (r=0.21; P=0.003) was found in the whole study population. In the nondialysis subgroup, 44% had chronic kidney disease, mostly in the stage 2 (83%). There was a significantly higher norepinephrine concentration (1.21 vs 0.87 ng/mL; P=0.008) in older patients of that population. In the dialysis subgroup, there were no differences between renalase and catecholamine level but older participants had lower diastolic blood pressure (69 vs 78 mmHg, P=0.001) and ejection fraction (51% vs 56.8%, P=0.03). CONCLUSION: The elevated renalase level in older hypertensive patients is related rather to kidney function and cardiovascular diseases than to age itself. Thus, renalase appears to be the possible new marker of these indications in this special population.