Comparison of Albumin Depleted and Whole Serum Samples for Biomarker Identification

Abstract Text: Serum is a highly complex mixture of proteins with a vast range in concentrations. Ease and accessibility make serum an ideal fluid for biomarker identification. Eight proteins represent over 90% of the protein content of serum. Albumin alone often comprises over 50% of total protein content in serum. Presence of high abundance proteins like albumin has long been a hurdle to proteomic researchers in establishing suitable biomarkers for disease states and other biological statuses. Historically, albumin and other high abundance proteins have been removed from serum prior to biomarker studies. The purpose of this project was to investigate the impact of albumin removal on porcine serum protein profiles and protein spot abundance variation across samples. Serum samples from eight pigs were used; half of each sample was kept as whole serum while the other half was depleted of albumin using a commercially available kit designed to remove 95% of the albumin.  Depleted and whole serum samples, for a single pig, were then compared using two dimensional difference in gel electrophoresis for a total of eight comparisons run in duplicate. Among the 236 protein spots identified,  167 were changed in abundance (P ≤ 0.05) between depleted and whole serum. Of these differences, 87 protein spots were increased in the albumin depleted serum while 76 spots were increased in the whole serum. The 87 spots found to be increased are a result of a shift in protein profile due to the removal of albumin. While some of these changes in protein profile could be linked directly to the location of albumin on the gel, most spots were not co-localized with albumin. Albumin is known to interact with many proteins, thus albumin depletion procedures may alter abundance of such proteins and increase the overall variation within the serum. These data indicate that for serum protein biomarker discovery in animal production, it may be prudent to investigate technologies and methods that allow use of whole serum over depleted serum. These data also show that using gel based proteomic approaches may be one of the technologies that ameliorates the need to deplete high abundance proteins from serum. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2011-68004-30336 from the USDA National Institute of Food and Agriculture.

Keywords: Residual Feed Effciency, Serum, Albumin