Independent Benefits of IV Iron: Beyond Raising Hgb Levels
A CME Symposium at the Renal Research Institute
7th International Conference on Dialysis: Advances in ESRD 2005
Our first speaker is Dr. Rajiv Agarwal. Dr. Agarwal's an Associate Professor of Medicine at Indiana University School of Medicine. He works predominantly at the Veteran's Administration Hospital there and is an expert in hypertension, anemia and in particular, iron utilization and administration in CKD and ESRD patients. And he will be talking on the independent benefits of IV iron, beyond raising hemoglobin levels. Rajiv?.
Thanks. I'm going to talk to you about the issue of the independent benefits of IV iron. We usually think about iron as a helper in raising hemoglobin when you're giving erythropoetin. Hopefully, at the end of the talk you will be convinced that we are using iron not simply to raise hemoglobin but also repleting an important element which is important for a lot of biological functions within the body.
Case study - 1
And, something that peaked my interest was this lady I took care of, and whom I still take care of. She is a patient on dialysis. She is several years older now, but at the time she was 41 years old - a Black lady. She had hypertension and glomerulonephritis, causing her kidney disease, and she has been on dialysis since a very young age; at about 15 years of age she was begun on dialysis. She had two previous transplants.
Her hemoglobin has been pretty stable, 15.4 g/dL for the last two years, and even now you see this erythrocytosis, and you wonder - Does she have a tumor causing EPO production? But she denies any fever, weight loss or hematuria, and she has been pretty stable for many years.
She takes oral iron, 200 milligrams per day. But she's not on EPO. She obviously doesn't need any EPO. And she complained of being sleepy and tired all the time, and she actually told me that she needs her iron. I looked at her monthly labs, and she had a transferrin saturation of 5% and a serum ferritin of 30 ng/mL.
Case study - 1 : Question
And then I had a question in my mind. Her hemoglobin is 15.4. But her labs look iron deficient. What should I do? What would you do in this patient?She has a normal hemoglobin and iron deficiency is not a cause of her symptoms. How many people would think that? I was one who was thinking that. I'll be honest. A patient is not on EPO, iron stores are immaterial. Well, in part, that's true, because if you look at the package insert for any of the intravenous iron products, they say the patient has to be on EPO to qualify for this therapy, at least in dialysis patients. Or, although there's no anemia, iron deficiency can cause symptoms, I would use IV iron. Hopefully you'll say "yes," at the end of the talk, but I was thinking more like, one, hemoglobin is normal. Iron doesn't matter.
Iron Deficiency in rats - 1
Well, I went back to the literature, and I found this study, and I'm going to share it with you. It's a very old study, it's more than 30 years old. It was done in Seattle by Dr. Finch, and Dr. Finch was expert on anemia, and he did some wonderful studies where he took animals and he made them iron deficient by simply giving them an iron deficient chow. So the rats were now being given a diet which didn't have any iron. So if you give no iron to this animal, then they get iron deficient, and they get anemic, and you can see a hemoglobin of 6.4. Then you can take this animal and you can either choose to treat it or leave it untreated. As controls, you can give it an iron deficient diet but inject it with iron, or, you can give it normal diet and continue to follow the "patient". In this case, these are rat doctors, for the patients are the rats.
At the end of a month, what he did was, he performed an exchange transfusion. He got the hemoglobin level to 6.4 in all the animals. What he is studying is iron deficiency with anemia, then. And every day a technician came in and transfused the animal to raise the hemoglobin somewhat. On day one, the hemoglobin was increased by one. On day two, by two. Three, four, seven, nine. Well, there's a Saturday and Sunday, so you don't see two days there. The technicians refused to do it every day. They wanted the weekend. What he did was, he simply put them on a treadmill. So this is an NIH funded study. This is 30 years ago. And he puts them on a treadmill, and sees, how far can they run before they fall off the treadmill? And he just takes a stop watch, and the technician has a stop watch, and just counting the number of minutes that rat runs before he falls off the treadmill.
Iron Deficiency in rats - 2
So here's the graph. And on the X axis, you have the number of days. It's not the days the rat is running. But it's the days that the experiment was performed. And on the Y axis, the running time in minutes. And you can see clearly that this graph, this curve is different from these curves. These curves are clearly different. These three curves look very similar, and this curve looks very different. So who are these animals who are falling off very early? These are the iron deficient, untreated animals. Look at this. At day ten, the hemoglobin is normal. The hemoglobin is 12. They are nonanemic, but still iron deficient. But they can't run. And if you treat this animal, they can run pretty well. They can run as much as a normal control rat. Remember, what you are seeing is the effect of anemia. If you're anemic, the rat can't run. If you are less anemic at the hemoglobin of 12, the rat can run pretty well. But a hemoglobin of 12, with iron deficiency, impairs the ability to perform physical activity here in the animal.
Iron Deficiency in rats - 3
Well, he wasn't satisfied. He said, well, we'll now do an experiment where we get the hemoglobin to 12 g/dL in all the animals. So first he does the experiment where he's producing iron deficiency. But he now maintains a hemoglobin of 12 in all the animals. So now the only factor that you are testing is iron deficiency. So you have iron deficiency, either for three weeks or four weeks, and you have animals which are either treated or untreated. At four weeks you have a treated iron deficiency or untreated iron deficiency. So if iron deficiency was the problem at three weeks, and four weeks, you would expect that the rats would fall off the treadmill pretty soon. Let's see if that happens.
Untreated iron deficiency
And you can see this curve, right at the bottom, that's untreated iron deficiency for four weeks. The rats can't run. They fall off the treadmill within three minutes, whereas a normal rat can run nearly 20 minutes. More than some people in the room can run. It is doing pretty good. Whereas the untreated iron deficiency is not doing too good. But you treat the iron deficiency and you maintain the hemoglobin, they can do pretty well.
Well, the conventional wisdom is that, oh, there's hemoglobin, there's myoglobin, there's cytochrome C, they must be playing a role. So that was the next step. Dr. Finch said, well, let's figure out what's causing the problem. It may be the myoglobin. And he did that. What you see is, here's the myoglobin. Muscle myoglobin. There's the control animal. Iron deficient, iron treated, doesn't make a difference. The animals who are iron treated can run pretty well, but their myoglobin levels remain low, so myoglobin levels are not the cause of them not being able to run. And here you see these three graphs look pretty same, and this looks very different. And what this is, is cytochrome A, B and C. And this is iron deficient and iron treated. And iron treated looks very similar to iron deficient, so this mustn't be the cause. It's not cytochromes, it's not myoglobin which is causing the inability to run.
Performance of oxidative phosphorylation
What they figured out is, there's an enzyme in the mitochondria which is a complicated name, alpha-glycerol phosphate in the skeletomuscle. It's a mitochondrial enzyme, which is important for the performance of oxidative phosphorylation. And in the iron deficient animals, it falls, and in the iron treated animals, it rises. So, iron is actually impacting mitochondrial function, which is then, in turn, impairing our physical performance. I haven't found this kind of a study in a human being. Otherwise, I would have shown it to you. Actually, I'm not a rat doctor. I'm a human doctor. But there isn't any such study in humans. But I think there's a very compelling evidence that iron deficiency itself can impair physical activity. In fact, there's an old paper in Scientific American. I read it about 20 years ago, and they looked at workers in Indonesia, and they supplemented them with oral iron, and their performance improved. When they have iron deficiency, they had less time off work, they could perform more work in the factory, and it improved their performance. It was like an anecdote that was published in Scientific American by this famous person who was an expert in iron metabolism. But they are anecdotes, but I think there's probably some truth behind it.
What we did in our patient was treat her with IV iron. Those days, we had iron dextran, and I gave her a gram of iron dextran over ten dialysis treatments. And within a week, she was feeling great. An iron deficiency without anemia could have caused the patient's symptoms. You might say that it was a placebo effect, but, even if it was a placebo, it worked for the patient.
I'm going to walk you through another scenario. We have heard about when we give intravenous iron, that it can cause infections. And there's this great controversy about iron causing infections. In fact, what I'm going to show you is quite the opposite. Here's a study which can be performed in iron deficient children. These are children with iron deficiency anemia, and they have a hemoglobin less than 10, and they have a bone marrow iron performed, and in all of these children, there's a hypochromic microcytic anemia, and these are all between one and eight years of age.
Measurement of neutrophil function
So the investigators, they had these children with moderate iron deficiency and severe iron deficiency, and they had a matched group of normal controls with no anemia or iron deficiency. And what they did was, they measured neutrophil function. And you can measure this by looking at the ability of neutrophils to kill bacteria. You expose the neutrophils to Staph. aureus, and then you look at how many Staph. aureus colonies are remaining at 20 minutes compared to at baseline. So that's a measure of intracellular bacterial killing. They also looked at the oxidative burst by looking at something called the nitroblue tetrazolium test. The way the neutrophils attack the bacteria is by mounting an oxidative response, and by doing that, you can look at not just the bacterial killing, but also the neutrophil function. And they did that at baseline, and then after giving them iron for about four to seven days. They treated them all with IV iron, or parenteral iron.
So you can see that in these two groups, bacterial killing was impaired; e.g., in children with moderate iron deficiency or those with severe iron deficiency. They have a lot of bacteria remaining at 20 minutes, compared to this control group of children. And when you treat them with IV iron, they have very few bacteria (remaining on the bacterial killing test) after a week of IV iron. The oxidative burst, which is a test of neutrophil function, is quite impaired at baseline, very low compared to the LD controls. But after you give them IV iron, neutrophil function is similar to that in controls. In other words, you need iron to have the adequate performance of neutrophil function. You have to mount a response to kill the bacteria and also to operate the oxidative machinery to do that. And here's a benefit of giving intravenous iron.
Brain iron deposition
Iron also is very important for brain function, and there's a very rich literature out there which suggests that it's important for neurotransmitter synthesis uptake and degradation. It's important for mitochondrial function, but I already told you about this for skeletal muscle. And the same mitochondria also exist in the brain, which is metabolically most active, in at least some of us. And there are issues with protein synthesis and brain iron deposition.
Effect of iron on the brain
If you talk to oncologists, they'll tell you best about the concept of pica. They'll tell you that this patient has pica, he or she came to my office. They were eating ice chips, and we gave them intravenous iron, and they threw the ice away, even before the anemia got corrected. You won't find published reports, but anybody who has treated these people with severe iron deficiency knows that this exists.
We'll also talk a little bit about the restless leg syndrome, about cognitive function and about thermoregulation.
Iron and cognitive function
First we'll talk about the cognitive function. Here's a study which was done in Baltimore on adolescent girls in four Baltimore high schools. The investigators went around and screenet for iron deficiency without anemia. The serum ferritin was less than 12 ng/mL. The hemoglobin was more than 11.5 g/dL for blacks, more than 12 g/dL for whites. Actually, these groups had iron deficiency without anemia, because the hemoglobin was in the normal range. But they're iron deficient. And 98 girls had nonanemic iron deficiency, about 15%. In other words, the hemoglobin was normal, but the iron was low. And then they randomly assigned these 98 girls to either ferrous sulfate by mouth or placebo, and they measured cognitive function by standard questionnaires at baseline and at eight weeks.
So here are the 98 girls that are identified, 17 refused participation. 81 enrolled. Forty were randomized to iron and 41 to placebo. A fair number of them, 90+ percent, completed the trial. They are teen age girls, 16 years, 50% are whites, and hemoglobins average 13 and the ferritins average 9. The maximum is 9.1. By anybody's definition, they're quite iron deficient, but they have a normal hemoglobin.
Changes in hematologic parameters
What they do then is look at recall of words. And first of all, they look at the hemoglobin performance. In the iron-treated girls the hemoglobin rises somewhat, by about 0.4 g/dL. In the control girls, it falls somewhat. Perhaps they were bleeding, these girls, also they had blood drawn to get the assays done for iron, and hemoglobin and all that. The ferritin goes up in the iron-treated girls, but doesn't change much in the controls.
Verbal learning and memory
But here's the actual meat. And you can see that these are all graphs which the lines are pointing up, but this red line is different from the other three. And what does this mean? Well, they're looking at simply, how many words you recall at the first try, at the second try, and the third try. So if I give you the same test three times, you're going to improve, right? That's what it shows. The first try, you don't do too well. The second try, you recall more words. And the third try, you recall even more. But if you are treated with iron, you recall more words at baseline, at the second trial, and the third trial, and that's statistically significant from if you got no iron at all. And so, this is the baseline iron group in the yellow, and the red one is after they have been treated with iron, and you can see there's a significant improvement at each of the three recalls. If you get placebo, you don't improve. So the ability to recall, which is a test of cognitive function, improves when you have had very little change in hemoglobin, but simply replacing iron in your brain, and perhaps this reflects mitochondrial function, as well as neurotransmitter function. Recall is a tough thing to define, but here's a statistically significant improvement in recall performance.
Restless leg syndrome (RLS)
What about restless leg syndrome? And here I show you data in normal people, normal controls, and patients with restless leg syndrome. And you might say, gee, have you labeled it wrong? Iron serum. Iron is higher. Ferritin is higher. It should be the other way around. The answer is, no, I haven't labeled it wrong. It just turns out that there's no statistical significance between these differences and the means. In other words, if you look at the serum parameters of iron, of ferritin and transferrin saturation, there are no differences between people who have restless leg syndrome versus who don't restless leg syndrome.
But if you sample their cerebrospinal fluid, and you measure the same parameters, you find that CSF iron in the restless leg syndrome is actually higher. The CSF ferritin is markedly lower. And the CSF transferrin saturation is also higher. So the saturation if you calculate the ratio, actually comes out low. And the ferritin is definitely low in the CSF of the patients with restless leg syndrome.
Brain iron by MRI in RLS
If you do even more sophisticated imaging studies in which you actually look at iron concentration in the substantia nigra, which is supposed to be the culprit that's supposed to be mediating movement disorders, you can see that there are a lot of white areas in the control, which tells you that there is a fair amount of iron. This is a specific test for iron imaging in the brain. Which lately has gotten a lot of interest in neurology. And you can see there's a lot of white out here in the control people, and in the patients with restless leg syndrome, there's actually reduced iron. Which suggests that it's really a state of regional iron deficiency. The fact that they don't have enough iron in the substantia nigra is the reason why they have restless leg syndrome.
Iron content in the substantia nigra
If you look at the actual numbers in these patients, you can see that the brain iron concentrations are much lower compared to the normal subjects. Even though they are only five and five. It seems like it's working out, at least for these investigators.
Improvement in the restless leg syndrome after IV iron
More recently, there was a trial done with IV iron in people with restless leg syndrome on hemodialysis. These are 14 people who get placebo, and they are looking at restless leg score at zero week, at one week, two week and four weeks. And you can see that restless legs continues pretty much the same throughout the four weeks of the trial when they're getting placebo. When they're getting IV iron, the restless leg score actually improves. And stays improved at least for the two weeks. It's kind of a proof of concept. These are not great numbers of patients here, there's 14 patients here, 11 patients here. Despite that, there's some improvement in the restless leg syndrome, suggesting that iron may actually be mediating some of the movement disorders that we see in our patients on hemodialysis.
Body temperature regulation and iron
Lastly, we want to talk about thermoregulation. So, often times, you'll hear your patient say, "Doc, I feel very cold." And you look at the hemoglobin, and it may be normal. And say, "No, no, you're not anemic, you're fine." But I'd like to tell you that maybe they are iron deficient, and that's why they are having an impaired ability to thermoregulate. And this is an experiment done in humans. It was done by Dr. Finch's group, the same person who did the rat study. He went to South America. And he took farmers, and he found farmers who were willing to volunteer to be submersed in a cold water bath and be studied for several hours there. And he found normal people, and he found people who had an iron-deficient, nonanemic state, so they had a hemoglobin which was pretty normal. But they were iron deficient. Or they had iron deficiency anemia. And he simply measured oral temperature, norepinephrine and oxygen consumption in these farmers.
You can see here the normal individuals and the iron-deficient, nonanemic individuals and anemic individuals. They're about the same age. Young people. Probably got paid a little bit to do the study. Hemoglobin is pretty low here. And these people are clearly iron deficient. Here the numbers look quite similar.
If you look at the oral temperature, the temperature drops, even in people who have normal hemoglobin. Drops a little bit. But, if you are nonanemic iron deficient; e.g., if you have a normal hemoglobin, but you are iron deficient, or you are anemic and iron deficient, it doesn't matter, your temperature drops much more than in the control patients.
Sympathetic activation in response to cold
If you look at these two graphs, you find that these two measures look very similar, while this one looks different. And that's the plasma norepinephrine. The epinephrine response is much more robust in iron-deficient, nonanemic and iron-deficient anemic individuals compared to normals. And you can see, this response and this response are no different, but this looks different, so they are having a much greater catecholamine response. And on this side, I've just shown you the time course at 15 minutes, 30 minutes, 45 minutes. One hour. Lastly, when they are taken out off this cold water baththey have quite a stimulated catecholamine release. In fact, it doesn't matter whether they are anemic or not anemic. If they are iron deficient, they have the same kind of an increased surge in catecholamines at one hour after cold exposure.
Oxygen consumption on exposure to cold
Same thing with oxygen consumption. It doesn't matter if you are anemic or nonanemic: You have very little change in oxygen consumption, but you increase your oxygen consumption quite a bit if you have iron deficiency with or without anemia. And you can see, it's much more in the iron deficient anemic individuals, but the iron deficient, nonanemic individuals also have quite an increase in oxygen consumption.
Conclusions: Temperature regulation and iron deficiency
What this means is, that if you have a falling body temperature, and you have an increase in metabolic activity, which means that you have an increase in oxygen consumption, it suggests there's heat loss with iron deficiency. So your temperature dropped despite an increase in metabolic activity. Your oxygen consumption had increased. That means you are losing heat. And you're not losing heat for any other reason. Probably it suggests that there's some defect in the mitochondria of these individuals by which there's uncoupling of oxidative phosphorylation. There's increase in catecholamines and oxygen consumption, which is similar in anemic or nonanemic individuals who have tissue iron deficiency, not just anemia. So you might say, okay, if you have anemia, then you are vasodilated and you'll dissipate heat. But that's not true. The nonanemic individuals are doing it as much. It seems like it might be a utilization of energy which might be at fault rather than anemia, as such.
Conclusion - 1
To conclude, iron is important for continued RBC production in patients treated with EPO. We know that quite well. Everybody in this room does. Dietary iron or oral iron is not enough to keep up with the ongoing iron loss, especially when you're treated with EPO. And we need maintenance IV iron therapy to maintain RBC production.
Conclusion - 2
Iron may be important for neutrophil and skeletal muscle function, and iron deficiency even without anemia may have clinically significant effects. I agree that the literature on this is not very intense. We don't have 100 studies like in ACE inhibitor use to control blood pressure, and you know, proteinuria, but I think that it's intriguing to understand that iron may have independent effects aside from hemoglobin. And iron deficiency, rather than low hemoglobin may contribute to clinical symptomatology that we have traditionally attributed to anemia. For example, feeling cold or having impaired cognitive function, or just forgetting things, or not feeling right. It might be not anemia, but iron deficiency which might be contributing. Thank you very much for your attention. I'd be glad to take a few questions.
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