Liquid Chromatography to Analyze Vitamin D Proteins in Psoriasis Patients

A recent study by scientists at the National Institutes of Health (Bethesda, Maryland) and the University of Kentucky sought to compare whether high density lipoproteins (HDL)-associated Vitamin D binding protein (DBP) or total serum DBP (S-DBP) could serve as useful biomarkers for assessing disease severity in psoriasis (PSO) and cardiovascular disease. PSO patients and non-PSO control subjects underwent blood collection for HDL purification by liquid chromatography (LC) and coronary computed tomography angiography (CCTA) scans to assess coronary plaque burden. A paper based on this research was published in Atherosclerosis Plus (1).

HDLs interact with a heterogeneous set of proteins that have been proposed to exert numerous antiatherogenic properties, including the passage of cholesterol from the arterial wall to the liver for excretion, termed reverse cholesterol transport (RCT) (2). A major protein component of HDL is Apolipoprotein A1 (ApoA1) , the component which facilitates RCT via interactions with ATP-binding cassette transporter (ABC)-A1, G1 or by the scavenger receptor SR-B1 (2). The authors of the paper report that there are now nearly 50 studies that have reported more than 200 proteins HDL-interacting proteins, and the possible roles of these proteins in HDL functions that are independent of lipid transport have been the subject of intense investigation (2,3).

A highly polymorphic protein that is found in serum at high concentrations (approximately 5 μM), numerous studies have established that DBP interacts with actin, fatty acids, and both active 1,25 dihyroxyvitamin D (1,25(OH)₂D) and inactive 25-hydroxyvitamin D (25OHD) metabolites, admittingly showing a stronger affinity for the latter (4,5). DBP is the primary transport protein for vitamin D metabolites with approximately 85% of 25OHD complexed with DBP in the blood (4,5).

For the study, 318 participants were recruited in an ongoing cohort study to understand the association between psoriasis and cardiometabolic disease. Of the pool of potential participants, 83 consecutive psoriasis patients were included in the analyses who had a combination of available CCTA, sufficient blood volume, and one year’s worth of follow-up visits. In addition, a cohort of healthy volunteers in an ongoing longitudinal prospective study (ICKD; NCT01934660) from December 2013 to March 2020 was included as controls. Strengthening the reporting of observational studies in epidemiology guidelines were followed for reporting the findings. All patients provided informed consent before study participation. Detailed inclusion and exclusion criteria of psoriasis participants are previously described (6).

By using chromatography to separate HDL from serum, the researchers confirmed the presence of DBP in the HDL molecule (3,7). Furthermore, they were surprised to note a decrease in DBP contained within the HDL molecule in their psoriasis cohort. Therefore, the authors of the paper concluded that HDL-DBP levels may better capture the severity of psoriatic disease and association with cardiovascular risk factors than S-DBP, and, due to the protein’s potential to bind lipids, actin and vitamin D, each of which have a role in CVD, makes it a compelling biomarker warranting further investigation (1).

Tertiary structure of human vitamin D binding protein. © Walter_D - stock.adobe.com

References

1. Playford, M. P.; Li, H.; Dey, A. K.; Florida, E. M.; Teague, H. L.; Gordon, S. M.; Mehta, N. N. HDL-Associated Vitamin D Binding Protein Levels Are Inversely Associated with Necrotic Plaque Burden in Psoriasis. Atheroscler. Plus. 2024, 59, 32-38. DOI: 10.1016/j.athplu.2024.12.002

2. von Eckardstein, A.; Nordestgaard, B. G.; Remaley, A. T.; Catapano, A. L. High-Density Lipoprotein Revisited: Biological Functions and Clinical Relevance, Eur. Heart J. 2023, 44 (16), 1394-1407.DOI: 10.1093/eurheartj/ehac605

3. Davidson, W. S.; Shah, A. S.; Sexmith, H.; Gordon, S. M. (2022). The HDL Proteome Watch: Compilation of Studies Leads to New Insights on HDL Function. Biochimica et Biophysica Acta (BBA)-Molecular and Cell Biology of Lipids 2022, 1867 (2), 159072. DOI: 10.1016/j.bbalip.2021.159072

4. Bouillon, R.; Schuit, F.; Antonio, L.; Rastinejad, F. (2020). Vitamin D Binding Protein: A Historic Overview. Front. Endocrinol.2020, 10, 910. DOI: 10.3389/fendo.2019.00910

5. Chun, R. F.; Shieh, A.; Gottlieb, C.; Yacoubian, V.; Wang, J.; Hewison, M.; Adams, J. S. Vitamin D Binding Protein and the Biological Activity of Vitamin D. Front. Endocrinol 2019, 10, 718. DOI: 10.3389/fendo.2019.00718

6. Playford, M. P.; Dey, A. K.; Zierold, C.; Joshi, A. A.; Blocki, F.; Bonelli, F.: Rodante, J. A.; Harrington, C. L.; Rivers, J. P.; Elnabawi, Y. A.; Chen, M. Y.; Ahlman, M. A.; Teague, H. L.; Mehta, N. N. Serum Active 1,25(OH)2D, but Not Inactive 25(OH)D Vitamin D Levels are Associated with Cardiometabolic and Cardiovascular Disease Risk in Psoriasis. Atherosclerosis 2019, 289, 44-50. DOI: 10.1016/j.atherosclerosis.2019.08.006

7. Gordon, S. M.; Deng, J.; Lu, L. J.; Davidson, W. S. Proteomic Characterization of Human Plasma High Density Lipoprotein Fractionated by Gel Filtration Chromatography. J. Proteome Res. 2010, 9 (10), 5239-5249. DOI: 10.1021/pr100520x