Inverse correlation between plasma pyrophosphate hydrolysis and early growth of abdominal aortic aneurysm: a pilot study

Abdominal aortic aneurysm (AAA) is often associated with vascular calcification, the calcium-phosphate crystal depositionin the aortic wall, which could impact aneurysm progression and/or stability. Tissue-nonspecific alkaline phosphatase (TNAP)hydrolyzes pyrophosphate—a natural inhibitor of calcification—thereby promoting calcium deposition. This study analyzesphosphatase activity and pyrophosphate dynamics in the plasma of AAA patients, randomly selected from the whole VIVAcohort, including controls (n = 48, aortic diameter in < 30 mm) and small AAA patients (n = 96, aortic diameter 30–55 mm),which were stratified by growth rate (low < 2 mm/year or high > 2 mm/year, n = 48 in each group), initially adjusted by aorticdiameter. The phosphatase activity was assessed at physiological (7.4) and optimal (10.5) pH levels. Phosphatase activitywas significantly higher in AAA patients at physiological pH, a pattern absent at optimal pH, suggesting disease-specificalterations. Small AAA patients showed notably higher phosphatase activity and pyrophosphate hydrolysis than controls atphysiological pH. An inverse correlation was also observed between phosphatase activity and aortic growth rate.