Circulating biomarkers as potential risk factors for inguinal hernia

Independent studies reported metabolic alterations in connective tissues of hernia patients, especially involving collagen fibers, compared to healthy controls. In the present work, we evaluated plasma concentrations of metalloproteinases (MMPs) and lysyl oxidase (LOX), enzymes involved in collagen metabolism, and peptides produced during collagen biosynthesis (PINP, PIIINP, and PIVNP) as potential biomarkers for the estimation of hernia risk. Zymography and ELISA assays were performed with plasma samples of 51 patients with primary or recurrent inguinal hernia and 42 healthy controls. A reduction in PINP (p = 0.007) and a concomitant increase in PIIINP (p < 0.001) were observed in patients. In controls, PINP levels were inversely related to age, whereas in patients PIIINP levels increased with age. Body mass index (BMI) showed a strong positive correlation with PIIINP plasma levels in controls but not in patients (p < 0.001). Moreover, patients with larger lesions had the lowest PINP/PIIINP ratio (p = 0.003). PIVNP collagen did not differ between controls and hernia patients. Plasma MMP-9 was reduced in patients (p = 0.015), while MMP-2 and LOX were unchanged. However, MMP-2 concentrations appeared lower in patients with familial history of hernia compared to those without. In regression analysis, the PINP/PIIINP ratio was inversely related to hernia risk, and a cut-off value of 0.948 was found by ROC analysis which classified hernia patients with a sensitivity of 82.9% and a specificity of 77.1%. In conclusion, our findings identified the PINP/PIIINP ratio as the most relevant molecular predictor of inguinal hernia risk.