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Vitamin D binding protein and endothelial injury after hematopoietic stem cell transplantation: an actin scavenger with a lipid-bound character
In a recent issue of Haematologica, Luebbering et al. described an association between filamentous-actin (F-actin), a mediator of endothelial damage, and vitamin D binding protein (VDBP), an actin scavenger, as modi- fiers of risk of clinical consequences of endothelial injury.1 As mentioned by the authors, the amount of actin-VDBP complexes present differed among the individuals and was influenced by several factors. Besides the variables described in the manuscript, one should take into account the partly lipid-bound character of VDBP. More specifically, the transport of the macromolecular bound VDBP-actin complexes is partly carried out by very low- density lipoprotein (VLDL) particles. VLDL carry 90% of the serum triglycerides in the fasting state. In our previ- ous work2 investigating the evolution of the serum VDBP concentration in cardiac surgery patients, the delta serum VDBP concentrations correlated significantly with the delta serum triglyceride concentrations. The relationship between the serum concentrations of this 52-59 kDa a2-globulin and a number of lipid-related parameters (serum total cholesterol, LDL-cholesterol, triglycerides) was demonstrated.3 In addition, a partial coprecipitation of actin, VDBP, very low-density lipoprotein (VLDL) plus low-density lipoprotein (LDL) particles was observed using precipitation experiments, high-pressure gel perme- ation chromatography and ultracentrifugation.2 Being
part of the VLDL, VDBP associates with globular actin (G-actin) in VLDL particles and acts as a transport pro- tein.2-4 So based on these findings, the difference in serum actin-VDBP complexes following hematopoietic stem cell transplantation might be partly explained by the interac- tions between VDBP, actin and lipids.
Marijn M. Speeckaert1,2 and Joris. R. Delanghe3
1Department of Nephrology, Ghent University Hospital and 2Research Foundation Flanders, Brussels and 3Department of Diagnostic Sciences, Ghent University, Ghent, Belgium
Correspondence:
MARIJN SPEECKAERT - marijn.speeckaert@ugent.be
doi:10.3324/haematol.2020.256131 Disclosures: no conflicts of interest to disclose. Contributions: MS and JD wrote the manuscript.
References
1. Luebbering N, Abdullah S, Lounder D, et al. Endothelial injury, F- actin and vitamin-D binding protein after hematopoietic stem cell transplant and association with clinical outcomes. Haematologica. 2020; 2 [Epub ahead of print].
2. SpeeckaertMM,TaesYE,DeBuyzereML,etal.Investigationofthe potential association of vitamin D binding protein with lipoproteins. Ann Clin Biochem. 2010;47(Pt 2):143-150.
3. SpeeckaertMM,WehlouC,VandewalleS,etal.VitaminDbinding protein, a new nutritional marker in cystic fibrosis patients. Clin Chem Lab Med. 2008;46(3):365-370.
4. Speeckaert M, Huang G, Delanghe JR, et al. Biological and clinical aspects of the vitamin D binding protein (Gc-globulin) and its poly- morphism. Clin Chim Acta. 2006;372(1-2):33-42.
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