Vascular Calcification and Growth Arrest Specific Protein 6 Levels in Chronic Renal Disease

Abstract

Introduction: Cardiovascular disease is the main cause of mortality and morbidity in chronic renal failure. It’s known that vascular calcification (VC) and carotid intima media thickness (CIMT) are strongly associated with cardiovascular diseases. Growth arrest specific protein 6 (Gas6) is a vitamin K-dependent protein and regulates various processes such as proliferation, cell survival, migration and inflammation. Gas6 is known to protect endothelial cells and vascular smooth muscle cells against apoptosis by inhibiting Bcl-2 induced Caspase 3 activation. The relationship between Gas6 and cardiovascular diseases has been demonstrated in many mouse models and cell cultures. However, there are conflicting reports whether Gas6 levels are increasing or decreasing in human studies of diabetic and/or chronic renal failure. In present study the aim was to examine plasma Gas6 levels and its relation with CIMT and coronary artery calcification score (CACS) in chronic kidney disease (CKD) patients. Methods: Total of 137 patients of which 32 chronic hemodialysis and 105 predialysis patients as well as 73 healthy controls were enrolled in the study. Human Gas6 levels in serum samples were studied by ELISA method. CIMT was measured by ultrasonography. CACS was measured by multislice computed tomography. Results: The mean age was 54.37±16.61 years in dialysis group, 55.20±14.80 years in predialysis group and 53.26±9.04 years in control group. Serum creatinine was 0.78±0.16 mg/dl in the control group and 1.96±1.64 mg/dl in the predialysis and 5.94±1.55 mg/dl in the dialysis group. 24 hours urine protein levels were significally higher in the dialysis group than the predialysis and the control group. CIMT values were similar in predialysis and dialysis groups. These values were significantly higher than control group. Although CACS was higher in dialysis group than predialysis and control group, the results were not statistically significant since the distribution range was very wide. Gas6 was 98.84±53.32 ng/mL in the control group and statistically higher than dialysis (63.85±38.92 ng/mL) and predialysis groups (54.96±38.49 ng/mL) (p=0.001). Gas6 levels were lower in diabetic patients than non-diabetics (53.69±35.26 ng/mL, 69.26±47.50 ng/mL, p=0.023, respectively). Negative correlation was detected between Gas6 and age, BMI, CACS, carotid IMT and proteinuria. In the logistic regression analysis, Gas6 remained significantly associated with BMI, CIMT and proteinuria. Conclusion: In our study, a negative correlation of Gas6 with BMI, CACS, CIMT and proteinuria and lower Gas6 levels in diabetic patients support that decreased Gas6 levels in chronic renal failure may have a role in vascular calcification through altered glucose tolerance, chronic inflammation, endothelial dysfunction and increased apoptosis. Our study has an importance because it is the first study showing a relation between Gas6 and proteinuria, CACS and carotid IMT in patients with chronic renal failure. © 2019, Asociacion Regional de Dialisi y Transplantes Renales de Capital Federal y Provincia de Buenos Aires. All rights reserved.