Elevated glucose levels increase vascular calcification risk by disrupting extracellular pyrophosphate metabolism

Background Vascular calcification is a major contributor to cardiovascular disease, especially diabetes, whereit exacerbates morbidity and mortality. Although pyrophosphate is a recognized natural inhibitor of vascularcalcification, there have been no prior studies examining its specific deficiency in diabetic conditions. This study isthe first to analyze the direct link between elevated glucose levels and disruptions in extracellular pyrophosphatemetabolism.Methods Rat aortic smooth muscle cells, streptozotocin (STZ)-induced diabetic rats, and diabetic human aorticsmooth muscle cells were used to assess the effects of elevated glucose levels on pyrophosphate metabolismand vascular calcification. The techniques used include extracellular pyrophosphate metabolism assays, thin-layerchromatography, phosphate-induced calcification assays, BrdU incorporation for DNA synthesis, aortic smoothmuscle cell viability and proliferation assays, and quantitative PCR for enzyme expression analysis. Additionally,extracellular pyrophosphate metabolism was examined through the use of radiolabeled isotopes to track ATP andpyrophosphate transformations.Results Elevated glucose led to a significant reduction in extracellular pyrophosphate across all diabetic models. Thismetabolic disruption was marked by notable downregulation of both the expression and activity of ectonucleotidepyrophosphatase/phosphodiesterase 1, a key enzyme that converts ATP to pyrophosphate. We also observed anupregulation of ectonucleoside triphosphate diphosphohydrolase 1, which preferentially hydrolyzes ATP to inorganicphosphate rather than pyrophosphate. Moreover, tissue-nonspecific alkaline phosphatase activity was markedlyelevated across all diabetic models. This shift in enzyme activity significantly reduced the pyrophosphate/phosphateratio. In addition, we noted a marked downregulation of matrix Gla protein, another inhibitor of vascular calcification.The impaired pyrophosphate metabolism was further corroborated by calcification experiments across all threediabetic models, which demonstrated an increased propensity for vascular calcification.Conclusions This study demonstrated that diabetes-induced high glucose disrupts extracellular pyrophosphatemetabolism, compromising its protective role against vascular calcification. These findings identify pyrophosphatedeficiency as a potential mechanism in diabetic vascular calcification, highlighting a new therapeutic target.