The association between serum and tear plasminogen activator inhibitor-1 and tissue plasminogen activator in patients with diabetic retinopathy / Nurbadriah Jasmiad

Background : Diabetic retinopathy (DR) is a serious complication of longstanding type 2 diabetes mellitus (T2DM), which is the forerunner in causing blindness and visual disability in the world. The aim of this study was to investigate the relationship between the activity of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) in tears and serum of patients with DR and those without DR.
Method: T2DM patients with DR (n=26) were enrolled in this study and compared to those without DR (n= 29). Blood and tear samples were obtained from both groups. The level of PAI-1 and tPA were measured in both the serum and tears. Anthropometric measurements, HbA1c, renal and lipid profile were also obtained.
Results: Patients with DR had significantly longer disease duration and higher systolic blood pressure compared to those without DR. Serum PAI-1 level was significantly higher in patients with DR compared to those without DR, 32.72 (IQR 32.52) vs 21.37 (IQR 14.93) ng/mL, respectively (p<0.05). However, tear PAI-1 were comparable in both groups. Serum and tear tPA levels in both groups were also comparable (p>0.05). Among patients with DR, there were no significant correlations between tear and serum of both biomarkers. Patients without DR showed a moderate positive correlation between serum and tear tPA levels with a coefficient of 0.363, albeit no statistical significance. Patients with DR demonstrated a significant positive correlation between levels of tears PAI-1 and BMI (r=0.555, p=0.026). In the group without DR, there was a statistically significant positive correlation between serum level of PAI-1 with urine albumin creatinine ratio (UACR) (r=0.501, p=0.013).
Conclusion: This present study demonstrated significantly greater serum PAI-1 levels in patients with DR compared to those without DR. No significant correlations between tears and serum PAI-1 and tPA were observed. The tear PAI-1 levels positively correlated with BMI among patients with DR, whilst serum PAI-1 level positively correlated with UACR among patients without DR. Thus, the roles of tear biomarkers remain relevant for further investigations.