Researchers at the University of Copenhagen and Rigshospitalet in Denmark have for the first time developed an accurate method to measure apolipoprotein M (apoM), a protein that is involved in several diseases like diabetes but also arteriosclerosis and sclerosis, disorders characterized by the stiffening of structures usually by replacement of the normal tissue by connective tissue. The study is entitled “Protein unfolding allows use of commercial antibodies in an apolipoprotein M sandwich ELISA” and was recently published in the Journal of Lipid Research.
The protein apoM circulates in the plasma attached to high-density lipoprotein (HDL) particles. ApoM is important for cholesterol metabolism and has been recently shown to transport the signaling lipid sphingosine-1-phosphate (S1P), which has been implicated in various inflammatory diseases such as rheumatoid arthritis and multiple sclerosis.
“We know that apoM is of importance to the development of arteriosclerosis and cardiovascular diseases. Previously, we have discovered that apoM carries a small fatty molecule, S1P, which plays a part in both diabetes and sclerosis. Whether or not apoM is of importance, remains to be seen, however, our new and secure measuring methods open up completely new perspectives on the research being conducted in these areas” said the study’s senior author Dr. Christina Christoffersen in a news release.
To establish an accurate, reliable and efficient method to measure apoM has been a challenge for researchers worldwide. “The protein is attached to the good cholesterol, HDL, which makes measuring it difficult. It is folded like a small funnel, but expressed in popular terms, we have managed to unfold it, which makes it much easier to identify” explained Dr. Christoffersen.
Danish researchers have developed a method that specifically recognizes the human apoM in plasma using commercially available apoM antibodies and a “sandwich” ELISA-based assay (an enzyme-linked immunosorbent assay to detect sample antigens through antibodies). The antibodies were carefully selected and the method was found to have a high degree of specificity, sensitivity and precision.
Although it took several years to reach this technique, it is relatively simple and can be easily performed by researchers worldwide. “These antibodies are actually commercially available, so all you have to do is order them and start measuring” concluded Dr. Christoffersen.
The research team believes this method can be implemented in every laboratory and that the ability to accurately measure apoM will allow further studies focused on its biological functions and eventual clinical implications in several diseases such as multiple sclerosis.