Background: Multiple human and animal studies have reviewed the (non-)actin scavenger functions of vitamin D binding protein (DBP). Recently, we demonstrated the partially lipid bound character of DBP. The purpose of the present study was to explore the link between actin, lipids and DBP in a cohort of patients undergoing cardiac surgery.
Methods: The interplay between DBP, actin and lipids was investigated in a cohort study of 35 Caucasian patients who underwent cardiac surgery. Total and actin-free DBP concentrations were assessed by immunonephelometry and ELISA. Total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase (-MB) and C-reactive protein (CRP) were measured using routine methods. Low-density lipoprotein cholesterol was calculated according to the Friedewald formula. The DBP phenotypes and the macromolecular bound DBP fractions were determined by polyacrylamide gel electrophoresis (PAGE) and confirmed by Western blotting.
Results: Using PAGE and Western blotting with an anti-human DBP polyclonal antibody, the actin-bound DBP complex was identified in serum. Following cardiac surgery, total serum DBP concentrations were characterized by a two phased course. This was paralleled by a similar pattern in serum total cholesterol, HDL-cholesterol and triglyceride concentrations. Good correlation was found between total and actin free serum DBP concentrations (r=0.69, p<0.0001). The serum actin free DBP/total DBP ratio remained stable throughout the study period. Although no significant correlation between cumulative CK-MB enzyme release and delta serum total DBP concentration was observed (p=NS), the latter value correlated significantly with delta serum triglyceride concentrations (r=0.37, p<0.05).
Conclusions: The lipid bound character is an underestimated property of DBP in the extracellular actin-scavenger system.