As we’ve been enjoying the World Cup and the Commonwealth Games my latest cheesecake appeared in print online. The topic once more is Kidney Attack biomarkers – those pesky little proteins in the urine that appear when your kidney is injured. This time I have been getting stuck into some math (sorry) to try and understand what it is that affects when these biomarkers appear in the urine after injury. I call this a biomarker time-course. A “Pee Profile” may be a better term but it would never get past the editor. What I care about is whether the type of biomarker and/or extent of injury, affects the pee profiles.
There are three basic types of biomarkers. First are those that are filtered from the blood by the two million odd filters in the kidney. Often they are then reabsorbed back into the blood in the little tubules where the pee is produced – that is, they don’t appear in the urine. Think of it like a stadium with many entrances. People (biomarkers) come in and sit down (are reabsorbed). If, though, a section of the stadium has been fenced off because of broken seating from the previous game (the injury), then some of those entering the stadium may end up exiting it again (the pee biomarkers). The numbers being reabsorbed and exiting will also depend on whether all the entrances are open – if some are closed then this will have a flow on affect on the rate of people leaving the stadium.
The second are preformed biomarkers. If we change the analogy slightly, imagine these as people already in the stadium (if the analogy was accurate they would have been born there!). If some terrible injury happens (like the 4th, 5th, 6th and 7th goals of a now famous football match) some of those people would get up and exit quickly. The overall rate of exit would reflect on the extent of the injury.
The third, are induced biomarkers. These are ones that don’t already exist, but are produced in response to an “injury.” Instead of being biomarkers, let us think of the spectators as produces of these biomarkers and let noise be the biomarker. There is some background noise of course, but when an “injury” (goal, gold medal performance etc) occurs there is a sudden increase in noise which slowly dies down. Depending on the team and the number of supporters this will be softer or loader and will carry on for shorter or longer periods (Goooooooooooaaaaaaaaaaaa……lllllllllllll).
The upshot of it all were many coloured graphs and a step towards understanding how we may better make use of the various types of novel biomarkers of kidney injury that have been recently discovered.
Pickering, J. W., & Endre, Z. H. (2014). Acute kidney injury urinary biomarker time-courses. PloS One. doi:10.1371/journal.pone.0101288