Anemia of chronic diseases in the early stages of chronic kidney disease as a risk factor for cardiovascular complications in patients with glomerulonephritis

Aim. To determine biomarkers of anemia of chronic disease (ACD) in patients with glomerulonephritis (GN) in the early stages of CKD, to assess their role as risk factors for cardiovascular complications (CVС).

Materials and methods. Seventy nine patients with GN were studied, among them: 40 with primary сhronic GN (CGN), 39 with secondary forms:19 – GN with ANCA-associated systemic vasculitis, 20 – GN with systemic lupus erythematosus (SLE) at early (all I–II) CKD stages. In all patients, the level of serum C-reactive protein (CRP), hepcidin, interferon γ, and the circulating form of protein Klotho (s-Klotho) were determined. When a relative iron deficiency was detected [transferrin iron saturation coefficient (TSAT) <20%], patients were administered parenterally iron [III] sucrose hydroxide complex (Venofer).

Results. The frequency of anemia among patients with systemic diseases is 3.2 times higher than among patients with primary CGN. Patients with anemia (group I; n=43) had higher rates of daily proteinuria (p<0.001), systolic blood pressure (p<0.05), serum levels of interferon γ (p<0.001) and hepcidin (p<0.001) and lower values of eGFR (p<0.05) than patients without anemia (group II; n=36). A strong inverse correlation was noted between the level of hepcidin and the content of iron in serum (r=-0.856; p<0.001), between the level of hemoglobin and the level of interferon γ (r=-0.447; p<0.05), hepcidin (r=-0.459; p<0.05) and CRP (r=-0.453; p<0.05). A significant inverse correlation was found between the level of hemoglobin and CVC risk factors – the value of systolic blood pressure (r=-0.512; p<0.05) and the mass index of the left ventricular myocardium (r=-0.619; p<0.01). At the same time, the contribution of 2 from 6 analyzed factors, hepcidin and eGFR, to the development of ACD was 92.5%, of which 86.6% accounted for hepcidin. A strong direct correlation was also found between a decrease in hemoglobin level and a decrease in the level of s-Klotho protein (r=0.645; p<0.001), a decrease in the level of s-Klotho and an increase in the level of serum hepcidin (r=-0.541; p<0.05). The leading value of anemia (beta -0,29; p=0,04) and depression of the s-Klotho level (beta -0,44; p=0,02) as independent cardiovascular risk factors in this group of patients was confirmed by multivariate analysis. In patients with identified deficiency of iron (n=40), after 3–4 weeks of intravenous administration of venofer, the target level of hemoglobin (Нb>120 g/l) and transferrin saturation with iron (TSAT>20%) were achieved.

Conclusion. Among the biomarkers of ACD in patients with immunoinflammatory diseases of the kidneys (primary and secondary СGN), the increase in the serum level of hepcidin is greatest importance. The concomitant to anemia decrease in s-Klotho is a leading risk factor for CVС in CKD. Early correction of ACD with iron supplements makes it possible to achieve target levels of Hb and TSAT and have subsequently a positive effect on the production of s-Klotho and the severity of left ventricular hypertrophia.