AB0490 FIBROBLAST GROWTH FACTOR-23 IN SYSTEMIC LUPUS ERYTHEMATOSUSPATIENTS
Authors: Dina Abdul Azim, Nahla Eesa, Mahmoud Sarraya, Marwa El Sharkawy, Ahmed Fayed, Somaya Anwar Hussein, Usama Sharaf El Din
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Systemic lupus erythematosus (SLE) is a chronic inflammatory disease that affects multiple organs including the kidneys and the heart. Chronic kidney disease (CKD) is common among SLE patients. SLE is also associated with increased left ventricular (LV) mass. LV hypertrophy (LVH) may have an additional role in the increased morbidity and mortality among in SLE patients. Fibroblast growth factor 23 (FGF23) is a phosphatonin that steadily increases in serum of CKD patients. High FGF23 is associated with inflammation, CKD progression, and LVH. <h3>Objectives</h3> The aim of this study is to determine the serum level of FGF23 in SLE patients with and without lupus nephritis looking for its possible association with the inflammatory and cardiovascular manifestations encountered in this disease. <h3>Methods</h3> Sixty SLE patient were recruited and appointed into 2 groups based on renal function; group I composed of thirty patients that had normal kidney functions or stage 1 CKD (eGFR&gt;90 ml/min/1.73m<sup>2</sup>) and group II of thirty cases with significant renal involvement defined as stage 2 to 4 CKD (eGFR &lt;90 - &gt;15 ml/min/1.73m<sup>2</sup>). After history taking and complete clinical examination of every patient, we measured body weight, height, Systemic lupus erythematosus disease activity index (SLEDAI), Systemic lupus erythematosus International Collaborating Clinics (SLICC), serum level of creatinine, calcium, phosphorus, albumin, complement 3 (C3), complement 4 (C4), interleukin 6 (IL6), fibroblast growth factor 23 (FGF23), estimated glomerular filtration rate (eGFR), 24 hour urine protein, complete blood count, erythrocyte sedimentation rate (ESR), antinuclear antibody (ANA), and left ventricular mass index (LVMI). Sixty normal healthy adults were included as control group. They were tested for serum FGF23 level. <h3>Results</h3> Serum level of FGF23 in SLE patients was comparable to normal control subjects (99.6±79.86 vs. 139±12.3 pg/mL,P&gt;0.05). In addition, there was no significant difference in FGF23 between the two studied groups (106.49± 88.2 vs. 93.84± 74.67 pg/mL,P&gt;0.05). In addition, there was no significant difference in serum IL6 between the two groups (58.6 ± 63.69 vs 55.9 ± 47.97 ng/L, P=085). On the other hand, LVMI was significantly higher in Group II(138.6 ± 36.59 vs. 187.6 ± 81.7 gm/m<sup>2</sup> in group I vs. group II respectively, P=0.0045). FGF23 showed significant positive correlation with IL6 (r= 0.776, P&lt;0.001) and failed to show significant correlation with LVMI, serum creatinine, eGFR or serum phosphorus. <h3>Conclusion</h3> FGF23 behaves differently in SLE patients; in spite of significant increase in inflammation and the frequent renal involvement, FGF23 level remains normal in SLE patients. There is a possible existence of an inhibitor to FGF23 production in SLE. This possibility should trigger further studies. <h3>References</h3> [1] Podolska MJ, et al., Inflammatory etiopathogenesis of systemic lupus erythematosus: an update. J Inflamm Res. 2015 Aug 20;8:161-71 [2] Pieretti J1, et al., Systemic lupus erythematosus predicts increased left ventricular mass. Circulation. 2007 Jul 24;116(4):419-26. [3] Liu S, et al., How Fibroblast Growth Factor 23 Works. J Am Soc Nephrol. 2007 Jun;18(6):1637-47. [4] Lai CC, et al., Increased serum fibroblast growth factor-23 and decreased bone turnover in patients with systemic lupus erythematosus under treatment with cyclosporine and steroid but not steroid only. Osteoporos Int. 2015 Feb; 26(2):601-10. [5] Durlacher-Betzer K, et al., Interleukin-6 contributes to the increase in fibroblast growth factor 23 expression in acute and chronic kidney disease. Kidney Int., 2018 Aug; 94(2):315-325. [6] Faul C, et al. FGF23 induces left ventricular hypertrophy. J Clin Invest., 2011 121:4393–4408. <h3>Disclosure of Interests</h3> None declared