19 февраля 2016г.
Introduction. Chronic renal failure (chronic kidney disease - CKD stages 3-5D) spreads widely in the population (10-15% of the population), is characterized by a high rate of cardiovascular events (CVE) [1,4,7], the risk of which, including young people, increases 100 and more times [5].
In the genesis of CVE in CKD many mechanisms have a value. Among them, in recent years the dysfunction of morphogenetic proteins (FGF-23 and Klotho) plays а growing role. According to Gutierrez O.M. et al. [2], high levels of FGF-23 correlate with an increase in the left ventricular mass index (LVMI). Klotho gene damage in experimental mice causes ectopic calcification, pathological fractures, premature aging [6]. On the other hand, the circulating form of Klotho protein can function as a humoral factor that protects the cardiovascular system [9]. Overexpression of the protein Klotho provides both renal and cardiovascular protection [9, 10]. Furthermore, recently has been identified a new factor secreted by osteocytes - glicoprotein sclerostin which involved in the regulation of bone formation and osteoblastogenesis [11]. At the same time in the literature, there is a hypothesis, about its impact on the process of arteries and heart valves calcification in patients with CKD [5].
Most studies of morphogenetic proteins were carried out on a dialysis population and in world literature to date, no conclusive data about the role of FGF-23 and Klotho in cardiorenal relationships in patients with early stages of CKD. As for sclerostin, with regard to this biomarker are only a few reports
The aim of the study was to investigate the relationships between FGF-23, Klotho, Sclerostin serum concentration changes and diffuse arterial stiffness and calcification intensity in patients with Chronic Kidney Disease (CKD) different stages.
Methods. 65 patients with CKD 1-5D stage were included in the study: 25 - with chronic glomerulonephritis, 20 - tubulointerstitial nephritis 20 - hypertensive nephrosclerosis (33 men and 32 women, 20-65 years old, mean age at enrollment was 41 ± 6,7 years).The control group consisted of 15 volunteers the same average age and sex. Serum FGF- 23 levels (Human FGF-23 ELISA kit using monoclonal antibodies to the full FGF-23 molecule), Klotho (Human alpha-Kl ELISA using anti-Klotho antibodies) and Sclerostin (Human Sclerostin ELISA kit) were applied in these patients. Blood pressure (BP) was measured in all study patients. Echocardiography was performed to patients with arterial hypertension and left ventricular mass index (LVMI) was calculated. The state of blood flow in the heart and large vessels (Doppler ultrasound Echocardiography), pulse wave velocity (Sphigmokor), calcifications presence (echocardiography, radiography of abdominal aorta by Kauppila method) and vascular wall functional ability (augmentation indices by SphigmokorAtcor) were studed. Among 49 hypertensive patients in 29 (59.1%) from them it was able to maintain target BP-130/80-140/80 mm Hg., the remaining 20 (40.7%) patients took antihypertensive medications irregularly. At the start of screening they remained hypertensive (BP 150/90-165/100 mm Hg.).
Results. Strong direct correlation [r=0,731, p<0,01] was established between stage of CKD by MDRD and serum FGF-23 concentration (fig.1), inverse correlations [r= - 0,489, p <0,01] and [r=-0,510, p<0,01] were established between stage of CKD and Klotho(fig.2) and stage of CKD and Sclerostin (fig.3) concentrations respectively.
Fig.1. Change in FGF-23 serum levels depending on CKD stage.
Fig.2. Change in Klotho serum levels depending on CKD stage
Fig.3. Change in Sclerostin serum levels depending on CKD stage
When comparing serum FGF-23 levels in patients with different CKD stages was found FGF-23 levels increases with decreasing GFR ahead of serum phosphorus and PTH levels elevating, starting at CKD 3a stage, whereas hyperphosphatemia and increased PTH levels were started in CKD-4 -5 stage.
Fig.4. Dynamics of inorganic phosphorus serum levels as CKD progression
Fig.5. Dynamics of PTH serum levels as CKD progression
We assessed the serum morphogenetic proteins changes depending on BP levels. The degree of increasing blood pressure correlated positively with FGF-23 serum concentrations (r = 0,452; p <0,01) and inversely with Klotho concentrations (r = - 0,687; p <0,01).Significant correlation of the sklerostin levels with the degree of hypertension has not been received.
Fig.6. Dynamics of BP values depending on FGF-23 serum levels in CKD patients (n = 49)
Fig.7. Dynamics of BP values depending on Klotho serum levels in CKD patients (n = 49)
We also established the strong straight relationship of FGF-23 serum concentrations [r =0,492,p<0,01] and the reverse relationship of serum Klotho levels [r = -0,537; p<0,01] and Sclerostin serum levels [r=-0,541,p<0,05] respectively with time of pulse valve reflection (Sphigmokor)
Fig.8. Changing of the pulse wave velocity in patients with CKD according to the serum levels of Klotho.
Fig.9. Changing of the pulse wave velocity in patients with CKD according to the serum levels of Sclerostin.
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Fig.10. Changing of the pulse wave velocity in patients with CKD according to the serum levels of FGF-23.
In addition, it was found the feedback between enhanced FGF-23 levels with increased left ventricular mass ( r=0,452; p <0,05).
In hypertensive patients (n = 20) this connection was extremely expressed ( r=0,850 p<0,05).
Fig.11. LVMM depending on the serum levels of FGF-23 in CKD patients with hypertension who have failed to achieve adequate correction of blood pressure (n = 22)
In studied patients reduced serum Klotho and Sclerostin levels have been clearly associated with a higher frequency of stiffness and calcificat identification in the heart valves ( Echocardiography) [ mitral valve r=-0,492 p<0,01 and r=- 0,487 p<0,01, respectively ] and large arteries (abdominal aorta) [Kloto r =-0,525;p<0,01.]
Fig.12. The relation of low Klotho and Sclerostin serum levels with the detection rate of heart valve calcification (mitral valve) in CKD patients with hypertension (n = 49)
Fig.14. The relation of low Klotho and Sclerostin serum levels with the detection rate of heart valve (aortic valve) calcification in CKD patients with hypertension (n = 49
Fig.15. Association of low Klotho serum levels with the frequency of abdominal aortic calcification in CKD patients with hypertension (n = 49)
Reduced serum Klotho and Sclerostin levels have been also associated with a concentric remodeling of the myocardium [r =-0,445 p<0,01 and r= -0,567 p<0.01].
Fig.16. Reduced serum Klotho and Sclerostin levels have been associated with a concentric remodeling of the myocardium
Conclusion. It was found the clear link between increased serum FGF-23 and decreased Klotho as increasing CKD severity, and diffuse arterial stiffness and calcification, myocardial remodelling independent of traditional risk factors. To clarify the role of Sclerostin more exactly further researches are required.
Acknowledgments: This work was supported by the Russian Science Foundation (grant № 14-15-00947 2014 year)
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