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Tuesday, November 2, 2010
Okay, so I’m going to start posting some of the little “tricks” I’ve learned over the years for running with diabetes … and getting the most I can out of it. I don’t have a list of things and some stuff has just gotten to be second nature over the years, but as I think of something here and there, I’ll post a “tricks” column.
So, what I’ll talk about today is choosing the best insulin regimen for you. So, you think they’re all the same with the exception of how fast and how long the action of each kind is. Well, that’s not true. For example, Humalog, Novolog, and Apidra have two amino acids changed at the end of the insulin chain. It makes the insulin chain degrade faster in your blood stream so that it becomes active quickly. So, the activity profile is not due to how it’s absorbed as much as what happens once it is absorbed. Lantus, on the other hand, has a lower pH (technically it’s called the isoelectric point). Most insulins have a pH of 5 or so and Lantus is closer to 4, maybe 4.2 or 4.3. Our body’s normal pH is around 4.7, so Lantus is acidic. Once it’s injected, the body tries to convert the pH (because it’s acidic – duh) and that conversion process follows the same cascade that our bodies use to convert lactic acid. Do you see where I’m going with this yet? So, the action of Lantus is dependent on how it’s absorbed.
Okay, so let’s say that you’re training for long distance running events. Let’s say that you are on a pump and you’re using one of the rapid-acting insulin analogs in your pump. Let’s also say that you either turn down your basal rate or you disconnect from your pump when you run. So far, so good, right? Um, not so much. The insulin analogs are being abosrbed from the infusion set site very, very quickly once you start to run. Remember back to the insulin 101 chemistry stuff back a paragraph or so ago (which, by the way, was so oversimplified that it’s almost wrong). Those rapid acting insulins will start working as soon as they hit the bloodstream (a pH of 4.7 will degrade them and voila, they work). The faster they’re abosorbed, the MORE insulin you have on board basically. Even the small amount that was dripping out of your infusion set can be activated.
Okay, another problem is that the analogs will be cleared out really fast too. So, you have bigtime, somewhat unpredictable insulin acitivity shortly after starting to run and then it’s gone fast. The insulin will be used and cleared faster than usual. Wham bam!
Before I move on to discuss Lantus, I want to mention something here about Regular insulin. While Regular will be absorbed more quickly in the context of running (just like the rapid analogs), its activity profile stays more constant. Regular is in a zinc suspension that has to be “broken down” to work, so it doesn’t start working the second it hits the bloodstream – essentially, it has another step to go. So, even though you may have the physiological equivalent of “more on board” you don’t also have the “wham bam” problem too.
Now, Lantus is absorbed at the rate that your body can convert pH. The rate of pH conversion does not change immediately with exercise. Rather, it’s a training effect. So, let’s say your body can convert X amount of lactate in 2 seconds right now. After you have been trained for better aerobic capacity, in about 4 or 5 months your body may be able to convert X plus 2 amount of lactate in 2 seconds. So, the difference in how quickly Lantus is converted is dependent more on your level of fitness than on what you are doing at any given moment. Again, this is so way oversimplified that some chemist is probably cringing right now.
One more thing to add before I discuss the choices that I have made for insulin. There is also the issue of affinity to certain receptor sites called IGF-1, or insulin-like growth factor. Regular is a little bit over normal physiology; the analogs are about the same as normal or maybe even a little less (except lispro which is about 1.5 times more); and Lantus can have as much as a 6 to 8 fold increase in IGF-1 receptor affinity (not for everyone and not all day long, but it can get that high).
Okay, so let’s put this in terms you can understand. People with Type 1 diabetes often complain about the difficulty in gaining weight, that is lean muscle mass (we all gain fat pretty easily). This also affects how quickly our bodies can recover from strenuous exercise; if you can’t gain lean muscle mass, you probably can’t repair it well either. The rapid-acting analogs don’t help you with that problem (except Lispro … a little bit). But, Regular insulin helps more. And, Lantus helps so much that many endos who work with pregnant women will not let them use Lantus during their pregnancies because they can grow some big babies!
So, based on all this, what insulin regimen do I use? I tried an insulin pump as my sole method of insulin delivery. That didn’t last long. I had lows all the time, I lost leg strength, and I could not recover from my workouts. I added Lantus, but continued to use the pump for boluses and to correct for dawn phenomenon if I wanted to sleep in. That worked pretty well, but I was also using Regular in the mornings before running because the action worked better for runs over an hour (which was like always for me back then). Finally, I decided that if I was doing all that, why was I using a pump? So, I disconnected one day and now I don’t even know where the batteries are.
I use Lantus for my basal coverage. The amount and the timing of injections depends on my level of fitness. I use Humalog or Novolog with meals or to correct a high blood sugar. I use 1-2 units of Regular every morning for puttering around, drinking coffee, and then finally getting out the door to run. The difference in how well I can recover from hard training (I say “hard” almost tongue-in-cheek now as I’m so much slower than I was in my prime) is absolutely measurable. My blood sugars in general are more even with this regimen than anything I could work out with a pump. I can run farther/longer without blood sugar problems, upset stomach, muscle pain and fatigue, or cramping than what I could manage during my brief analog-only phase. I would get these horrible cramps in my large muscles, particularly my glutes, so bad that I would get stopped in my tracks (and it would hurt the rest of the day).
Well, does this mean that this is the solution to everyone’s problems with running in the context of Type 1 diabetes? Oh, no way. But, it does mean that you should really think through any problems you have with your training and talk to your doctor about the different profiles, actions, absorption rates, and kinetics of the various insulins and see if you really are using the best insulin regimen for you. You know, like they always say, everyone is different… It’s true, though. And, if things aren’t working, you might actually be able to do something about it.
So, that’s my diabetes trick of the trade for today. I’m not a physician, nor am I a chemist or pharmacist. But, this is what has worked for me. I would happily trade all that in, though, to be boringly normal and have no need to think like a pancreas!