Sept. 12, 2022
This week, please join authors Svati Shah and Senthil Selvaraj as well as Guest Editor and Editorialist Manuel Mayr as they discuss the article "Metabolomic Profiling of the Effects of Dapagliflozin in Heart Failure With Reduced Ejection Fraction: DEFINE-HF" and the editorial "SGLT2 Inhibitors in Heart Failure: Targeted Metabolomics and Energetic Metabolism."
Dr. Carolyn Lam:
Welcome to Circulation On Run, your weekly podcast summary and backstage pass to the journal and its editors. We're your co-hosts, I'm Dr. Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.
Dr. Greg Hundley:
And I'm Dr. Greg Hundley, Associate Editor, Director of the Pauley Heart Center at VCU Health Richmond, Virginia.
Dr. Carolyn Lam:
In today's feature paper, we will be talking about the metabolomic profiling of the effects of dapagliflozin in heart failure, and this is from the DEFINE-HF trial. It's just such a cool paper with a lot of insights you have to hear from the authors. But, before we get there, let's talk about some of the other papers in today's issue. Shall we, Greg?
Dr. Greg Hundley:
You bet, Carolyn. Well, how about if I go first?
Dr. Carolyn Lam:
Please.
Dr. Greg Hundley:
Thank you, Carolyn. My first paper comes to us from Professor Paulus Kirchhof from the Universitäres Herzzentrum in Hamburg. Carolyn, in the randomized EAST-AFNET 4 study, so the early treatment of atrial fibrillation for stroke prevention, these trial investigators demonstrated that systematic initiation of early rhythm control reduced adverse cardiovascular outcomes in patients with recently diagnosed atrial fibrillation and stroke risk factors. However, the effectiveness and safety of early rhythm control in patients with multiple cardiovascular comorbidities is not known. Carolyn, in this study, it was a prespecified sub-analysis of the EAST-AFNET 4 trial and it compared the effectiveness and safety of early rhythm control with usual care stratified into patients with high CHA2DS2-VASc scores of greater than or equal to 4.
Dr. Carolyn Lam:
Nice. Okay. Important question, what did they find?
Dr. Greg Hundley:
Right, Carolyn. Quite a bit of data in this study, so let's walk through it carefully. First, in regards to the study population, the EAST-AFNET 4 randomized 1093 patients with CHA2DS2-VASc scores of greater than or equal to 4, these were predominantly women, 61% female, and then also 1,696 patients with CHA2DS2-VASc of less than four, and these were predominantly men, so only 37% women.
Now let's get to the date. Early rhythm control reduced the composite primary efficacy outcome of cardiovascular death, stroke, or hospitalization for worsening heart failure or for acute coronary syndrome in patients with high CHA2DS2-VASc scores of greater than 4, but not in patients with CHA2DS2-VASc scores of less than 4. Second, now Carolyn, the primary safety outcome, so death, stroke, or serious adverse events of rhythm control therapy, was not different between study groups in patients with high CHA2DS2-VASc scores of greater than 4, but occurred more often in patients with low CHA2DS2-VASc scores randomized to early rhythm control. Now Carolyn, life threatening events or death were not different between the groups. When female sex was ignored for the creation of high and lower groups, the interaction P was not significant for the primary efficacy outcome, but remained significant for the primary safety outcome.
Dr. Carolyn Lam:
Oh, you are right. A lot of interesting data here. What's a take home message?
Dr. Greg Hundley:
Right, Carolyn. So the take home message is the following. Patients with recently diagnosed atrial fibrillation and multiple cardiovascular comorbidities should be considered to have priority access to early rhythm control to reduce cardiovascular outcomes, and a specific trial of early rhythm control in these patients is really needed as a next step.
Dr. Carolyn Lam:
Oh, thank you, Greg. The next paper focuses on arrhythmogenic right ventricular cardiomyopathy, which we know is characterized by a high propensity to life threatening arrhythmias and progressive loss of heart muscle. More than 40% of reported genetic variants linked to arrhythmogenic right ventricular cardiomyopathy, or ARVC, reside in a gene called plakophilin-2, or PKP2. In today's paper, Dr. Delmar and Lundby from NYU Grossman School of Medicine and University of Copenhagen, respectively, and their colleagues, described a comprehensive characterization of the ARVC molecular landscape using a multidisciplinary approach including human samples from ARVC patients with PKP2 mutations and left ventricular ejection fraction above 45%, as well as PKP2-deficient murine and human induced pluripotent stem cell-derived cardiomyocytes. They studied all of these with comprehensive proteomics and functional analysis.
Dr. Greg Hundley:
Wow, Carolyn, another great study in circulation combining both preclinical murine models as well as data from human subjects. So, what did they find?
Dr. Carolyn Lam:
Precisely, Greg. Here's what they found. Loss of nuclear envelope integrity and subsequent DNA damage is a key substrate in the molecular pathology of AR VC. The authors further showed transcriptional down regulation of proteins of the electron transcript chain as an early event in the molecular pathophysiology of the disease prior to an ejection fraction falling below 45%. This associates with increased oxidant production, with the clinical message being, therefore, that the authors propose therapies that limit oxidant formation may be a possible intervention to restrict DNA damage in ARVC.
Dr. Greg Hundley:
Very nice, Carolyn. Okay, our next paper comes from Dr. Donald Lloyd-Jones from Northwestern University, the Feinberg School of Medicine. Carolyn, you can tell the change in inflection of my voice because it's time for another Carolyn's quiz. Carolyn, open-ended question. Can you remind us of life's essential eight?
Dr. Carolyn Lam:
Oh boy, Greg. It's like asking me to name the dwarfs. I know I'm going to forget one, but here you go. Diet, exercise, cholesterol, weight, smoking, sugar must be there, diabetes, blood pressure. You see, I got seven. What's the eighth?
Dr. Greg Hundley:
Yeah. Remember seven dwarfs, Sleepy.
Dr. Carolyn Lam:
Sleep.
Dr. Greg Hundley:
Very good. Great job, Carolyn.
Dr. Carolyn Lam:
Thank you.
Dr. Greg Hundley:
Recently, the American Heart Association recently published an updated algorithm for quantifying cardiovascular health, the Life's Essential 8 score. In this study, the investigative team quantified US levels of cardiovascular health using the new score. They included non-pregnant, non-institutionalized individuals aged 2 through 79 years who were free of cardiovascular disease from the National Health and Nutrition Examination Surveys that were conducted between 2013 and 2018.
Now, for all participants, they calculated the overall cardiovascular health score, and it ranged from 0, which is really low, to 100, which is the highest, as well as the score for each component. And Carolyn, yes, you are very close. Remember the eight? Diet, physical activity, nicotine exposure, sleep duration, body mass index, blood lipids, blood glucose, and blood pressure, and they used published American Heart Association definitions of these. The cardiovascular health scores were assessed across strata of age, sex, race, ethnicity, family income, and depression.
Dr. Carolyn Lam:
Okay, Greg. What did they find?
Dr. Greg Hundley:
Right, Carolyn. There were 23,400 plus participants, representing 201,728,000 adults and 74 million children. The overall mean cardiovascular health score was 64.7 among adults using all eight metrics, and it was 65.5 for the three metrics available of diet, physical activity, and BMI among the children and adolescents that were aged 2 through 19 years.
Now, for the adults there were significant differences in mean cardiovascular health scores by sex, age, and racial ethnic group. Mean scores were lowest for diet, physical activity, and the BMI metrics. There were large differences in mean scores across demographic groups for diet, nicotine exposure, blood glucose, and blood pressure. In children, diet scores were low, 40.6, and were progressively lower in higher age groups. Large differences were also noted in mean physical activity and BMI by sociodemographic group.
Carolyn, this study basically identifies wide ranges of scores across multiple domains of the essential eight, and thus, this new Life's Essential 8 score helps identify large group and individual differences in cardiovascular health. Additionally, overall, cardiovascular health in the US population remains well below optimal levels, and there are both broad and targeted opportunities to monitor, preserve, and improve cardiovascular health across the life course in both individuals, as well as the population at large.
Dr. Carolyn Lam:
Wow. Thanks, Greg. Truly really interesting. Everyone's going to have to pick up that paper and all the other papers in this issue, because there's also an In Depth paper by Dr. Whelton on “Harmonization of the ACC/AHA and ESC/ESH Blood Pressure Hypertension Guidelines, Comparisons, Reflections, and Recommendations. There's a Research Letter by Dr. Munshi on the accurate classification of cardiomyopathy etiology by chromatin accessibility.
Dr. Greg Hundley:
Carolyn, I have got to report an exchange of letters from Professor Sun and Weng regarding the article, “Legumain Is an Endogenous Modulator of Integrin αvβ3 Triggering Vascular Degeneration, Dissection, and Rupture.” And then Carolyn, lastly, there's a Perspective piece from Professor Vidal-Petiot entitled, “Thresholds for Hypertension Definition, Treatment Initiation, and Treatment Targets: Recent Guidelines at a Glance.” Well, Carolyn, how about we get on to that feature discussion?
Dr. Carolyn Lam:
Yes, let's go Greg.
Wow, we have a star stud cast for today's feature discussion, and on a star studied topic, if I may. It's on the SGLT2 inhibitors, this time in the DEFINE-HF study and really going into the mechanism of action of SGLT2 inhibitors. Now, that's one question I personally get all the time. How do these things work? Today's paper brings us one step closer, for sure, in the understanding. I'm so grateful to have the first author, Dr. Senthil Selvaraj from University of Pennsylvania, as well as the corresponding author of the paper, Dr. Svati Shah, associate editor, as well as the corresponding author from Duke Molecular Physiology Institute. We also have Dr. Manuel Mayr who was both the guest editor and editorialist for this paper, and Dr. Mayr is from Kings College London, British Heart Foundation Center. Welcome, everyone. Senthil, get us started here. The DEFINE-HF study, just a quick summary, what that was about and then what you did, what you found.
Dr. Senthil Selvaraj:
Absolutely. Good morning, everyone, or maybe good evening for your time, Carolyn, but we were very excited about this study and the ability to do targeted metabolomic profiling in DEFINE. This audience is well familiar with the fact that SGLT2 inhibitors are foundational therapy in heart failure reduced ejection fraction, and the interesting thing is, despite a lot of literature, we still don't know why. Whether it relates to change in inflammation or endothelial function, but given the mechanism of action, metabolism is sort of at its core. So in this study we sought to identify metabolic pathways that were associated with dapagliflozin treatment using this targeted metabolomics platform in which we assayed 63 metabolites, acylcarnitine, which are markers of fatty acid oxidation, several amino acids, and ketone-related metabolites.
To do this, we studied 234 participants from DEFINE, which is a 12-week placebo-controlled trial of dapagliflozin in this population, and we perform principal components analysis for dimensionality reduction techniques. In this study, briefly we found that, first, our principal components analysis yielded 13 different factors that accounted for the substantial proportion in the variation of the data, and that two in particular, ketone-related metabolites and short acylcarnitines in factor 6, as well as medium-chain acylcarnitines in factor 7 were differentially associated with dapagliflozin treatment. Specifically, there were increases in several ketone-related metabolites and short acylcarnitines, as well as several medium-chain acylcarnitines, really speaking to, potentially, changes in fatty acid as well as ketone biology with dapagliflozin treatment.
The second aim of our study was to look at changes in metabolites and changes in endpoint studying DEFINE, which included NT-proBNP as well as KCCQ scores. We found that dicarboxylate long-chain acylcarnitines and aromatic amino acids really related to worsening heart failure endpoints there. So, a lot to impact, a lot that we found, and appreciative about the opportunity.
Dr. Carolyn Lam:
Oh, wow. Thank you so much for that amazing summary. Svati, I've heard you speak so many times on metabolomics on our calls, but this is really so important. First, I think the question is, congratulations for thinking ahead of time to collect the samples and to do all of this. Congratulations on that. Could I ask if you went in with any specific hypothesis or were you surprised by these findings, Svati?
Dr. Svati Shah:
Yeah, Carolyn, thank you so much. It was such a pleasure to work with Senthil on this and I really want to highlight what an incredible early career investigator he is. He's really going to set the metabolism world on fire. I also wanted to say thank you to the PI of the clinical trial, the parent clinical trial DEFINE-HF Mikhail Kosiborod, who did the really hard work of collecting the samples along with the clinical trial itself.
To me, what's really cool is to be able to take a clinical trial like this with really important clinical outcomes well adjudicated and to be able to dig into the mechanism at a metabolic level of what might be going on with SGLT2 inhibitors. Going into this, Carolyn, we suspected that ketone-related biology was at play. There have been studies in other populations, non-HFrEF populations, that have shown that SGLT2 inhibitors have what appears to be beneficial impacts on ketone biology and induced ketosis. So, going into this, we suspected that this ketone pathway was going to come up. I think what's exciting is, not only did we find that the ketone pathway was differential modified by dapagliflozin, but that it wasn't at the level of severe ketosis that we would be concerned about. And then secondly, we found pathways of fatty acid oxidation. Some related to the effects of the medication and some related to changes in functional outcome. So it really enhanced beyond what we already knew about ketone biology, expanded our understanding of potential mechanisms of SGLT2 inhibitors, and expanded this into the HFrEF space, Carolyn.
Dr. Carolyn Lam:
Oh, that's so nice. I'm bursting with questions, but I really, really have to ask Dr. Manuel Mayr, first, could you put these findings into context for us and tell us what they mean clinically?
Dr. Manuel Mayr:
Yeah, Carolyn. First of all, I want to join you in congratulating the authors to this important study. As Svati mentioned, previous studies have reported effects of SGLT2 inhibitors on ketone bodies, but the present study really adds to the literature because it uses the state of the art metabolomic techniques. It uses a technique called mass spectrometry, but they also have a rating of, I think, in total, 63 metabolites in over 200 patients. Mass spectrometry is becoming increasingly important for cardiovascular precision medicine because we can use it in clinical trials to provide an unbiased assessment of metabolites and proteins. So it's a very versatile technology. I think this study really adds to the rapidly growing literature that SGLT2 inhibition is a principle of unloading the failing heart from metabolic stress.
Dr. Carolyn Lam:
Wow, I really like that and your editorial is just beautiful. I love that you say, "After the serendipitous findings of improved heart failure outcomes with SGLT2 inhibitors, mechanisms were postulated, but studies, such as the one we're discussing, are needed to really uncover what's the real thing." Now, I know this may sound really oversimplified and so on, but I'd really love for Senthil or Svati to just bear with me as I ask, what are you going to say to people who go, "Okay, then we should just be downing ketones," Or, "We should be Working on the fatty acid parts of it," Or taking conclusions like that. What would you say to something like that?
Dr. Senthil Selvaraj:
I'm happy to go first. It's a really wonderful question and I do think that this study raises the question of whether we should be exogenously increasing ketone levels to provide some sort of benefit. I would say the jury's still out there. I think it's a hot topic right now. But there are also differences between how we raise key tone levels, whether you do that endogenously in the body, or whether you give something like a ketone supplement, so exogenous ketone supplementation. And I think that there are completely different physiologies there. So more to come. I think there are a lot of studies in this space.
The ketogenic diet is something that I'm often asked as well, whether that might provide benefit to heart failure. There are a lot of ways that I can, but one thing that we need to be mindful of is the fact that it will reduce glycogen stores as well, which may impact exercise capacity. So, we need more data. I would say the other thing that we found in our studies, while they were increased in ketone levels and markers of fatty acid oxidation with dapagliflozin treatment, we aren't necessarily sure that those mediate the benefits of SGLT2 inhibitors. DEFINE has important clinically relevant endpoints, but it is not an event-based trial. And so we don't know and we can't link the changes in metabolites with changes in outcomes quite yet.
Dr. Svati Shah:
Carolyn, just to add to the wonderful response that Senthil just gave, I think we do have to be careful. We don't know whether these are direct effects of SGLT2 inhibitors or whether these are related to the caloric loss that we know happens with these medications. I think it's important to point out that we're looking in the blood, we don't actually know what's happening at the tissue level, so we do have to be a little bit careful. We have made inferences that this is reporting on substrate fuel selection in the heart, but we also suspect that skeletal muscle and other organs are heavily involved in some of the pathways we're seeing. So I just wanted to make those important caveat to the epidemiologic work that we do.
Dr. Carolyn Lam:
And those are so important, so thank you Senthil and Svati. Manuel, I'd love to invite your thoughts because you did sort of point out some of these points in your editorial. Could you maybe discuss a bit of those and raise any questions, perhaps?
Dr. Manuel Mayr:
Yes. I think Svati and Senthil have nicely mentioned already that these measurements are performed in plasma. So the changes in plasma could be due to, for example, increased production in the liver due to decreased consumption in other tissues. So I guess the next step would be, and I would be really interested on what the authors want to pursue, is to provide direct evidence for the energetic hypothesis, that really the heart is consuming these keto bodies and what type of measurements could be performed to provide direct evidence in humans for these metabolic hypothesis.
Dr. Senthil Selvaraj:
That's a really great question, Manuel. There was a really nice study that was published about a year or two ago in Science in which the authors did coronary sinus sampling. So really to get arterial venous gradients, measure substances in the arterial system as well as the coronary sinus venous system and get extraction. I think that that study would be very interesting to understand. You take patients on SGLT2 inhibitors, those who are not, and to understand what is the heart chewing on. Obviously more invasive than some other approaches, but other studies that I think would be really interesting in those space would be flux studies and stable isotope studies. Again, as Svati really nicely mentioned, these are systemic physiology snapshots whenever we do less localized techniques like that, but they're still very important because heart failure is a systemic process.
Dr. Carolyn Lam:
Anything to add, Svati?
Dr. Svati Shah:
No, I think you said it beautifully. I'll just say on the sort of epidemiologic side, to be able to link this to harder outcomes, DEFINE-HF wasn't really designed to be able to do that. So as we expand our understanding of SGLT2 inhibitors, understand different populations, and to link these pathways to more objective outcomes, I think, will be really useful, also.
Dr. Carolyn Lam:
Indeed. Manual, in your editorial, you actually discuss some of your own work, which may be the ones that Senthil is actually talking about. What is your view?
Dr. Manuel Mayr:
Well, I think I'm very excited that beyond fatty acid metabolism and glucose metabolism, ketones have extracted increasing attention. Ketone body metabolism, I think, has long been underappreciated. We still need to understand to what extent it really acts as a fuel and that it can help to overcome the energy deficit that creates heart failure. I think, as mentioned by Svati and Senthil, we need more studies in this area, and of course other trials are ongoing where they're going to measure, for example, the phosphocreatine to ATP ratio by using phosphor-NMR spectroscopy. So we get direct evidence whether there really is an energetic improvement upon SGLT2 inhibition. I think this will be studies to look forward to and to add to the growing literature that metabolism is important as a therapeutic target for heart failure.
Dr. Carolyn Lam:
Oh, such exciting times. You mentioned the EMPA-VISION trial in your editorial. I think I'm trying to tell everybody, you have to pick up the paper and the editorial. You're going to learn so much. This is so cool. Thank you so, so much all of you for being on this podcast, for sharing your thoughts. I'm sure everyone has learned a lot and enjoyed it just as I have. On behalf of Greg and I, thank you for being here, thank you for joining us today, and don't forget to tune in again next week. Thank you.
Dr. Greg Hundley:
This program is copyright of the American Heart Association 2022. The opinions expressed by speakers in this podcast are their own and not necessarily those of the editors or of the American Heart Association. For more, please visit ahajournals.org.
