A brief note on diabetes cures
I friend pointed me to a Danish article talking about this. I pointed out a few problems and reasons to be skeptical to my friend, and I figured I might as well share a few thoughts on these matters here as well. I do not have access to my library at the present point in time, so this post will be less well sourced than most posts I’ve written on related topics in the past.
i. I’ve had diabetes for over 25 years. A cure for type 1 diabetes has been just around the corner for decades. This is not a great argument for assuming that a cure will not be developed in a few years’ time, but you do at some point become a bit skeptical.
ii. The type of ‘mouse diabetes’ people use when they’re doing research on animal models such as e.g. NOD mice, from which many such ‘breakthroughs’ are derived, is different from ‘human diabetes’. As pointed out in the reddit thread, “Doug’s group alone has cured diabetes in mice nearly a dozen times”. This may or may not be true, but I’m pretty sure that at the present point in time my probability of being cured of diabetes would be significantly higher if I happened to be one of those lab mice.
iii. A major related point often overlooked in contexts like these is that type 1 diabetes is not one disease – it is a group of different disorders all sharing the feature that the disease process involved leads to destruction of the pancreatic beta-cells. At least this is not a bad way to think about it. This potentially important neglected heterogeneity is worth mentioning when we’re talking about cures. To talk about ‘type 1 diabetes’ as if it’s just one disease is a gross simplification, as multiple different, if similar, disease processes are at work in different patients; some people with ‘the disease’ get sick in days or weeks, in others it takes years to get to the point where symptoms develop. Multiple different gene complexes are involved. Prognosis – both regarding the risk of diabetes-related organ damage and the risk of developing ‘other’ autoimmune conditions (‘other’ because it may be the same disease process causing the ‘other’ diseases as well), such as Hashimoto’s thyroiditis – depends to some extent on the mutations involved. This stuff relates also to the question of what we mean by the word ‘cure’ – more on this below. You might argue that although diabetics are different from each other and vary in a lot of ways, the same thing could be said about the sufferers of all kinds of other diseases, such as, say, prostate cancer. So maybe heterogeneity within this particular patient population is not that important. But the point remains that we don’t treat all prostate cancer patients the same way, and that some are much easier to cure than others.
iv. The distinction between types (type 1, type 2) makes it easy to overlook the fact that there are significant within-group heterogeneities, as mentioned above. But the complexity of the processes involved are perhaps even better illustrated by pointing out that even between-group distinctions can also sometimes be quite complicated. The distinction between type 1 and type 2 diabetes is a case in point; usually people say only type 1 is auto-immune, but it was made clear in Sperling et al.’s textbook that that’s not really true; in a minority of type 2 diabetics autoimmune processes are also clearly involved – and this is actually highly relevant as these subgroups of patients have a much worse prognosis than the type 2 diabetics without autoantibody markers, as they’ll on average progress to insulin-dependent disease (uncontrollable by e.g. insulin-sensitizers) much faster than people without an auto-immune disease process. In my experience most people who talk about diabetes online, also well-informed people e.g. in reddit/askscience threads, are not (even?) aware of this. I mention it because it’s one obvious example of how within-group hidden heterogeneities can have huge relevance for which treatment modalities are desirable or useful. You’d expect type 2’s with auto-immune processes involved would need a different sort of ‘cure’ than ‘ordinary type 2’s’. For a little more on different ‘varieties’ of diabetes, see also this and this.
There are as already mentioned also big differences in outcomes between subgroups within the type 1 group; some people with type 1 diabetes will end up with three or four ‘different'(?) auto-immune diseases, whereas others will get lucky and ‘only’ ever get type 1 diabetes. Not only that, we also know that glycemic control differences between those groups do not account for all the variation in between-group differences in outcomes in terms of diabetes-related complications; type 1 diabetics hit by ‘other’ auto-immune processes (e.g. Graves’ disease) tend to be more likely to develop complications to their diabetes than the rest, regardless of glycemic control. Would successful beta-cell transplants, assuming these at some point become feasible, and achieved euglycemia in that patient population still prevent thyroid failure later on? Would the people more severely affected, e.g. people with multiple autoimmune conditions, still develop some of the diabetes-related complications, such as cardiovascular complications, even if they had functional beta cells and were to achieve euglycemia, because those problems may be caused by disease aspects like accelerated atherosclerosis to some extent perhaps unrelated to glycemic control? These are things we really don’t know. It’s very important in that context to note that most diabetics, both type 1 and type 2, die from cardiovascular disease, and that the link between glycemic control and cardiovascular outcomes is much weaker than the one between glycemic control and microvascular complications (e.g., eye disease, kidney disease). There may be reasons why we do not yet have a good picture of just how important euglycemia really is, e.g. because glucose variability and not just average glucose levels may be important in terms of outcomes (I recall seeing this emphasized recently in a paper, but I’m not going to look for a source) – and Hba1c only account for the latter. So maybe it does all come back to glycemic control, it’s just that we don’t have the full picture yet. Maybe. But to the extent that e.g. cardiovascular outcomes – or other complications in diabetics – are unrelated to glycemic control, beta-cell transplants may not improve cardiovascular outcomes at all. One potential cure might be one where diabetics get beta-cell transplants, achieve euglycemia and are able to drop the insulin injections – yet they still die too soon from heart disease because other aspects of the disease process has not been addressed by the ‘cure’. I don’t think at the current point in time that we really know enough about these diseases to really judge if a hypothetical diabetic with functional transplanted beta-cells may not still to some extent be ‘sick’.
v. If your cure requires active suppression of the immune system, not much will really be gained. A to some people perhaps surprising fact is that we already know how to do ‘curative’ pancreas transplants in diabetics, and these are sometimes done in diabetic patients with kidney failure (“In most cases, pancreas transplantation is performed on individuals with type 1 diabetes with end-stage renal disease, brittle diabetes [poor glycemic control, US] and hypoglycaemia unawareness. The majority of pancreas transplantation (>90%) are simultaneous pancreas-kidney transplantation.” – link) – these people would usually be dead without a kidney transplant and as they already have to suffer through all the negative transplant-related effects of immune suppression and so on, the idea is that you might as well switch both defective organs now you’re at it, if they’re both available. But immune suppression sucks and these patients do not have great prognoses so this is not a good way to deal with diabetes in a ‘healthy diabetic’; if rejection problems are not addressed in a much better manner than the ones currently available in whole-organ-transplant cases, the attractiveness of any such type of intervention/’cure’ goes down a lot. In the study they tried to engineer their way around this issue, but whether they’ve been successful in any meaningful way is subject to discussion – I share ‘SirT6”s skepticism at the original reddit link. I’d have to see something like this working in humans for some years before I get too optimistic.
vi. One final aspect is perhaps noting. Even a Complete and Ideal Cure involving beta-cell transplants in a setting where it turns out that everything that goes wrong with all diabetics is really blood-glucose related, is not going to repair the damage that’s already been done. Such aspects will of course matter much more to some people than to others.
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