Dec 17, 2018
Dr Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. I'm Dr Carolyn Lam, associate editor from the National Heart Center and Duke National University of Singapore.
In today's feature discussion, we will be doing a deep dive into the LEADER trial results, looking at new results of liraglutide and its effects in patients with type two diabetes, with or without a history of myocardial infarction or stroke. All of that coming right up after these summaries.
In today's issue, five groups of investigators in two original basic research articles and three research letters tackled the same biological question, and all reached the same conclusion that cells in the heart expressing the SCA-1 cell surface antigen do not become cardiomyocytes to any meaningful degree, and instead become endothelial cells. Among the original basic papers, first author Dr Vagnozzi, corresponding author Dr Molkentin from Howard Hughes Medical Institute and Cincinnati Children's Hospital Medical Center, and their colleagues use the inducible recombinase method and generated a constitutive recombinase at the SCA-1 locus. They found that cardiac resident SCA-1 positive cells were not significant contributors to cardiomyocyte renewal in vivo. Instead, SCA-1 positive cells generated cardiac vasculature throughout development, during aging, and following injury with trivial contribution to the cardiomyocyte population.
In the second paper from co-first authors, Drs Zhang and Sultana, with corresponding author Dr Cai from Indiana University School of Medicine and colleagues, these authors engineered a series of genetically altered mice to identify and track SCA-1 positive cells in the heart, and found that SCA-1 positive cells were purely of the endothelial lineage. Together with three research letters, these five papers add to the growing body of evidence that in adult mammals, our new cardiomyocytes arise from preexisting cardiomyocytes and rarely, if at all, from adult cardiac stem cells.
Could metformin be cardioprotective in patients with type one diabetes? Co-first authors Drs Bjornstad and Schafer, corresponding author Dr Nadeau from University of Colorado School of Medicine, and their colleagues hypothesized that adolescents with type one diabetes have impaired vascular function, and that metformin may improve insulin resistance and vascular dysfunction.
To test this hypothesis, they studied 48 adolescents with type one diabetes and 24 non-diabetic controls using MRI of the ascending and descending aorta, as well as assessment of carotid intima-medial thickness by ultrasound, brachial distance ability by DynaPulse, fat and lean mass by DXA, fasting labs following overnight glycemic control, and insulin sensitivity by hyperinsulinemic euglycemic clamp. The adolescents with type one diabetes were randomized one as to one to three months of 2000 milligrams metformin or placebo daily, after which the baseline measures were repeated.
The authors detected early signs of cardiovascular disease with MRI in these adolescents with type one diabetes compared to controls. They further found that three months of metformin therapy improved insulin sensitivity as assessed by gold standard hyperinsulinemic euglycemic clamp, both in normal weight and obese adolescents with type one diabetes. Moreover, metformin improved carotid intima-medial thickness and aortic wall shear stress and stiffness. Thus, metformin may hold promise as a cardioprotective intervention in type one diabetes.
What are the clinical genetic and environmental determinants of varicose vein formation? Co-first authors Drs Fukaya and Flores, corresponding author Dr Leeper from Stanford University, and colleagues applied machine learning to agnostically search for risk factors of varicose veins in nearly half a million individuals in the UK bio bank. They found that greater height appeared as a novel predictor of varicose vein disease in machine learning analyses, and was independently associated in multi-variable adjusted Cox regression. Using Mendelian randomization, they demonstrated that greater height had a causal role in varicose vein development. A genome-wide association study identified 30 new genome-wide significant loci, identifying pathways involved in vascular development, and skeletal/limb biology, and discovering a strong genetic correlation between varicose veins and deep vein thrombosis. The knowledge greatly expands our understanding of disease pathophysiology, and may help future improvements in the management of varicose veins and their associated complications.
The final original paper describes the effect of glucagon-like peptide-1 receptor agonist liraglutide on cardiovascular events, and all-cause mortality in patients with type two diabetes and chronic kidney disease. First and corresponding author Dr Mann from Friedrich Alexander University of Erlangen in Germany and their colleagues performed a post hoc analysis of the LEADER trial comparing the liraglutide's treatment effects in patients with and without kidney disease.
As a reminder, LEADER was designed to recruit a subgroup of at least 660 patients with an estimated glomerular filtration rate, or eGFR, less than 60, approximately 220 patients with severe renal impairment, eGFR less than 30, and at least 440 patients with moderate renal impairment with an eGFR of 30 to 60. The authors found that the liraglutide reduced the risk of major adverse cardiovascular events, and all-cause mortality compared with placebo in patients with chronic kidney disease defined as an eGFR less than 60, and also in patients with albuminuria defined as a urinary albumin to creatinine ratio above 30.
The overall risk of adverse events did not differ between the liraglutide and placebo treated patients either with or without chronic kidney disease in the LEADER trial. In summary, these results show that liraglutide added to standard of care reduced the risk of major cardiovascular events and all-cause mortality in patients with type two diabetes and chronic kidney disease. Furthermore, these results appear to apply across the chronic kidney disease spectrum that was enrolled.
And that brings us to the end of our summaries. Now for this week's feature discussion.
Cardiovascular outcome trials have transformed the world of treating patients with diabetes. And for our feature discussion today, we're going to be talking about a new analysis from a very important trial, the LEADER trial of GLP-1 receptor agonists, and that's the liraglutide. I'm very proud to have the corresponding author of this paper with us, Dr Subodh Verma, and he's from St Michael's Hospital and University of Toronto, and our senior associate editor, Dr Gabriel Steg, from University of Paris. Actually, Gabriel, I'm actually going to start with you for once because I recall perhaps something you may have written about cardiovascular outcome trials.
Dr Gabriel Steg: Yeah, it's really funny. I'll try to take it graciously. You know, I wrote a frame of reference in Circulation a few years ago, wondering whether we were doing good by doing all these large outcome trials for safety with new anti-diabetic drugs, because there had been not one but two, three, four, five, six trials that were essentially neutral, enrolling more than 107 patients and participants at the expense of millions of dollars, and not much came out of it. And this was published in circulation. I was very happy until the next trial comes up, and this is EMPA-REG. And the next one is LEADER. And we have two trials that literally transform our vision of anti-diabetic agents as major agents for cardiovascular prevention. The trial we're going to discuss today, which you wrote about, is one of these trials. And I think I have to revisit my own writings and probably eat my hat.
Dr Carolyn Lam: So indeed, that's a great segue. Thank you, Gabriel. And Subodh, tell us then, what did you look at this time in LEADER? And maybe start by saying a little bit about LEADER, and the rationale for doing this particular sub analysis.
Dr Subodh Verma: Right. So, as Dr Steg mentioned, these were FDA-mandated studies to look at safety and potential efficacy of newer antihyperglycemic agents. The entire premise was that cardiologists and cardiovascular specialists were not really getting that excited about antihyperglycemic therapies in people with diabetes, because there was no data that they did much. And as Dr Steg mentioned, even the data leading up to some of these trials were disappointing, suggesting that they're safe, but they neither reduce nor increase events.
So, I think EMPA-REG and LEADER really changed the calculus in many ways of how we look at cardiovascular risk reduction with antihyperglycemic agents. LEADER was a trial that was 9,340 patients. These are patients that were at high cardiovascular risk, but unlike EMPA-REG that only enrolled people with prior to ischemic cardiovascular events ICAD, PAD, and CVD, LEADER took a position of enriching the population with this spectrum of patients with cardiovascular disease and risk factors.
So, some were in so-called high risk primary prevention who had not had established ASCVD, but had multiple risk factors such as uncontrolled hypertension or chronic kidney disease. Some had evidence of ASCVD, but had not had a prior myocardial infarction. And some, in fact, had had a prior MI stroke or PAD. So, it was a broad population of patients that was enrolled. And the primary result, again, for the primary outcome of MACE, demonstrated a significant reduction in favor of liraglutide versus placebo. And then for the individual components of that primary outcome, they were all statistically significant, or at least went in the right direction. Importantly, CV death was reduced by 22% with liraglutide versus placebo.
I would like to emphasize that in this day and age, and Dr Steg has nicely set the stage, we have started thinking about how do we think about cardiovascular phenotypes of patients. You know, is a drug more likely to reduce heart failure? More likely to reduce ischemic events? And with LEADER, we found that in fact the trial actually reduced mostly ischemic events, and was really not that beneficial on heart failure related outcomes.
So, that was the broad positive outcome from LEADER. They've led to guideline changes worldwide that patients with diabetes should be prioritized to receive an agent that has shown benefit, particularly if they have cardiovascular disease. And one of those agents was empagliflozin. The other was liraglutide. But, secondary prevention is a pretty crowded space, and not everybody can get everything, and not everybody should get everything, and not everybody can afford everything. So, I think leaders like the two of you here are often thinking about, how do you risk-stratify these populations, and how do we start thinking about people who are at greater risk, people who can actually derive benefit? And I think that's the smart and thoughtful way of doing this. And is there a certain threshold at which point the therapy loses its ability to reduce cardiovascular events, at least in the short term?
So, in that theme, in that vein, what we looked at here was an analysis of people in LEADER who truly had a prior ischemic event. And the work that Dr Steg and others have done in REACH registries, etc. clearly establish that that's a population of patients, type two diabetes and a prior ischemic event. You don't really need many more calculators beyond that. That's the highest risk population. And then, the next level is really type two diabetes with a ASCVD. And we know that from REACH as well, that that's the next level of risk. And then, what about people who have type two diabetes just by itself? Which certainly are much higher risk than people who don't have diabetes, but we didn't have a non-diabetic group to compare to.
And what we find is that the higher the baseline risk defined by this, the greater is the absolute risk reduction. The P value is consistent for ... You know, this is non-significant for heterogeneity. but specifically, people with a prior ischemic event derive benefit. People without a prior ischemic event who've had ASCVD derive significant benefit. But, in fact, we found that the curves were almost superimposable for people who did not have prior ASCVD. And that's not to say the GLP-1 receptor agonists should not be used in diabetes in the absence of cardiovascular disease, because they're great glucose lowering agents. They cause hypoglycemia, they cause weight loss. And potentially, within longer exposure times, cardiovascular benefit may actually emerge. And we've heard data from Dr Gerstein's study called Rewind that is positive, that will be presented next year. Harmony Outcomes was a study that was presented recently that also showed a benefit. So, whether in the primary prevention group we see a benefit in the future remains to be seen.
Dr Carolyn Lam: Oh, that's a great, great summary. But Subodh, you know, it's become a bit of what do we define as a primary and secondary prevention anymore, you know? And the patient that already got type two diabetes. Now, in this paper, it's very nice. As you said, has a history of myocardial infarction and stroke. And maybe I could just clarify to the audience, you couldn't just pick up the primary paper and see that because the way the inclusion exclusion criteria were designed in LEADER, you can't just pick up the sub-groups. So, this specific analysis, so carefully and wonderfully done, was absolutely needed. But then you know, what do you think? What's primary and what's secondary prevention anymore?
Dr Gabriel Steg: Well, I want to commend the authors for doing the careful stratification of diabetic patients they've done in the paper, and particularly for pointing out that it's one thing to have had an event where you actually ruptured a plaque and had a traumatic event. And it's very different from merely having plaque in one of your carotids or your arteries, and which is, of course, in turn very different from the majority of diabetic patients who have neither an event, nor diagnosed plaque or established plaque. And when we think about preventing cardiovascular and diabetes, we have to remember that the outer circle, the broader circle of diabetic patients who haven't had disease is the largest component.
Dr Subodh Verma: True.
Dr Gabriel Steg: And these are the patients whom we treat every day with the hope of eventually keeping them from harm, safe from harm, or with therapies that are new and potentially beneficial. And I think your research very clearly shows that there's a gradient of benefit. The sicker the patient, the greater the benefit in preventing MACE. And as long as you get to more healthier phenotypes of diabetes, then there is less of a benefit. Which doesn't mean that we shouldn't use these agents. As you point out, they're very convenient and effective agents for glucose control. But then, their cardiovascular benefits are more uncertain. And I think this is the key message from this analysis, and it's a great analysis.
Dr Subodh Verma: Thank you. I appreciate that. I totally agree that for the doctor in the trenches, particularly the cardiologist who's just trying to get their feet wet with antihyperglycemic therapy, you know? Cardiologists will embrace PCSK9 inhibitors and rivaroxaban at low dose, and maybe a new way of doing surgery or putting an LVAD. But it's very hard to get their attention when it comes to antihyperglycemic therapy. So, defining for them the population that matters the most, where the greatest risk and risk reduction can be achieved, I think is quite important from a clinical standpoint. And I think most cardiologists will agree that type two diabetes and a prior ischemic event is a high-risk population. Type two diabetes in a prior ASCVD is a high-risk population, and the magnitude of CV death reduction here is something meaningful for them to pay attention to.
Dr Carolyn Lam: Yeah, indeed. That's what I love best about this paper. It's actually asking the question the way a cardiologist would, exactly like you had both put. So, what do you think is the next step now? Do you think we need to look at this primary prevention type two diabetics with no established cardiovascular disease? Do we really need to? Is it that we need a method analysis, which you can talk about? Or, is it that we need longer follow up? Or, what next?
Dr Subodh Verma: I think that first of all, we have to get rid of the terminology, and maybe as a heart surgeon, I can be a little bit provocative and just say it. I wrote an editorial to the Declare Study that was just published yesterday in The Lancet called "Pumps, Pipes, and Filter: Do SGLT2 inhibitors cover it all?" Then I made a strong statement there that this nomenclature of primary and secondary really is artificial because it only captures ischemic risk, and does not capture risk of heart failure or renal disease. So, in a patient, as you've asked, Carolyn, who has type two diabetes, whose renal function is 54 or GFR is 55, who's not had a prior MI ... Is that patient primary prevention? Maybe from an ischemic standpoint, but he's clearly secondary prevention from a renal standpoint.
Dr Subodh Verma: So, I think we need to just think about all disease as a spectrum, and not as an artificial cutoff that, if you've had an ischemic event, suddenly the world changes for you there. Because, that gradient I think is probably what we need to somehow appreciate as to where that risk lies. The patient who's 40 who's had no risk factors, you know? The Rashami paper from the New England Journal that looks at risk factor control and diabetes make a very compelling story that if you control your five risk factors, you actually don't have an excess risk of cardiovascular events in diabetes, at least from MACE. The story is whether anybody can have those five risk factors controlled. But, early on in diabetes, with diabetes duration not being that significant, with risk factors not being that significant, I think maybe that's not the population to go after. But certainly, waiting for ASCVD to develop and then start therapy is also not the right way of doing it, so ...
Dr Carolyn Lam: Interesting. I really wonder what new guidelines are gonna show. Gabriel, any other perspective?
Dr Gabriel Steg: Well, first of all, I love the editorial. I thought the title was fantastic, and you summarize here what we need to think about when we think about diabetes; not solely the pipes. As an interventional cardiologist, I'm very interested in the pipes.
Dr Subodh Verma: Me, too.
Dr Gabriel Steg: Not solely the pump, but also the filter. And there's more than the heart and vessels in the complications of diabetes. So I thought it was a great, great title. My view is that we still need to remember that if we take the lifetime perspective, a healthy youngster with type one diabetes, a relatively healthy patient in his fifties with type two diabetes, their probability of dying from cardiovascular disease is enormous. Even though risk calculators will give them a relatively low probability over the 5 year or 10 year term, eventually that's what's gonna get them. And therefore, we still have progress to make. We are fortunate to have lived an incredible period in the past few years where we've had emergence of new risk preventive therapies in diabetes. That's incredible. It's an epiphany. But, it's not over. We need more information, more trials in other populations. We need to look at renal function and heart failure. So, it's a great time to be doing clinical trials in diabetes.
Dr Subodh Verma: Right.
Dr Carolyn Lam: And indeed, a great time to be publishing in circulation. We've been really doing a lot of publications in the cardiovascular outcome trials in diabetes here.
Dr Subodh Verma: And it's being noticed. There's no doubt about it.
Dr Carolyn Lam: I hope so. And, maybe a time for a new frame of reference, because what you just said was diametrically sort of in contrast.
Dr Subodh Verma: I would emphasize one more point, and that is, you know in atherosclerosis, the dominant mechanism has been LDL, right? And Dr Steg here is changing the landscape of that with Odyssey Outcomes and many other strategies. But again, in Circulation, Dr Bhatt, and I, along with the LEADER investigators, recently presented and published a paper showing that liraglutide's benefit is seen independent of LDL cholesterol, and all the way down to people with LDLs of below .5. So, the point is that this mechanism of benefit of GLP-1 seems to be complimentary to LDL lowering. And therefore, I think it offers great hope that you can actually reduce the ischemic burden in diabetes, not just by ultra-low LDL, but by potentially additional mechanisms as well.
Dr Carolyn Lam: Absolutely. And then now, because I have to have the last word here on this show, let's not forget heart failure outcomes in diabetes. I think it's underestimated. I think it's really important. Okay, and with that, thank you gentlemen for joining me today.
You've been listening to Circulation on the Run. Don't forget to tune in again next week.
This program is copyright American Heart Association, 2018.