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Circulation on the Run

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Mar 6, 2017

Dr. Carolyn Lam:               Welcome to Circulation on the Run. Your weekly podcast summary and [inaudible 00:00:06] of the journal and its editors. I'm Dr. Carolyn Lam, associate editor from the National Heart Center and Duke National University of Singapore. In just a moment we will be discussing really fascinating preclinical data to suggest that high fiber diet and acetate supplementation may change the gut microbiota and thereby prevent the development of hypertension and heart failure. But first here's your summary of this week's issue.

                                                The first paper describes the impact of heart transplantation on the functional status of children with end stage heart failure in the United States. First author, Dr. Peng, corresponding author Dr. Almond and colleagues from Stanford University, use the organ procurement and transplantation network to identify 1,633 US children age less than 21 years, and surviving one year or more post-heart transplant, from 2005 to 2014, with a functional status score available at three time points. Namely at listing, at transplant, and one year or more post-heart transplant. They found that at the one year assessment 64% were fully active with no limitations, or a functional status score of 10. 21% had minor limitations with strenuous activity, or a functional status score of 9. And 15% scored a functional status score lower than 9. Compared to the listing functional status, functional status at one year post-transplant increased in 91%, and declined or remain unchanged in 9%. Early rejection, older age, African-American race, chronic steroid use, hemodynamic support at heart transplantation, and being hospitalized at transplantation, were all associated with abnormal functional status post-transplant.

                                                These findings may be helpful to patients, families, and referring providers by providing a contemporary picture of the post-heart transplant life in children as they weigh the risks and benefits of transplantation.

                                                The next paper brings cardiac reprogramming one step closer to clinical translation. In this paper by first author Dr. Mohamed, corresponding author Dr. Srivastava, and colleagues from Gladstone Institute of Cardiovascular Disease in San Francisco, the authors used a high throughput chemical screen in post-natal mouse cardiac fibroblasts, and found that transforming growth factor beta, or TGF beta, and WNT, or wint inhibition, enhanced transcription factor based direct reprogramming of cardiac fibroblasts to induce cardiomyocyte like cells in vitro and in vivo. A combination of TGF beta and wint chemical inhibitors increased the quality, quantity, and speed of direct reprogramming, resulting in improved cardiac function after injury as early as one week after treatment. These chemical inhibitors enhanced human cardiac reprogramming and reduced the number of transcription factors needed for human cardiac reprogramming to just four factors. These findings if validated in large animals could facilitate a combined gene therapy and small molecule approach to heart failure.

                                                The next study is the first report of the risks of cardiac mortality among five year survivors of childhood cancer beyond 50 years of age. First author Dr. Fidler, corresponding author Dr. Hawkins, and colleagues from University of Birmingham in United Kingdom, looked at the British childhood cancer survivors study, a population based cohort of 34,489 five year survivors of childhood cancer that was diagnosed from 1940 to 2006 and followed up until February 28th in 2014. The authors quantify the cardiac mortality access risk. Overall 181 cardiac deaths were observed, which was 3.4 times that expected. Survivors were two and half times more at risk of ischemic heart disease, and almost six times more at risk of cardiomyopathy or heart failure at death than expected. Among those aged over 60 years, subsequent primary neoplasms, cardiac disease, and other circulatory conditions accounted for 31%, 22%, 15% of all deaths. Specifically for cardiomyopathy or heart failure deaths, survivors diagnosed between 1980 and 1989 had 29 times the excess number of deaths observed per survivors diagnosed either before 1970 or from 1990 onwards. Thus the authors concluded that excess cardio mortality among five year survivors of childhood cancer remains increased beyond 50 years of age, and has clear messages in terms of preventative strategies. However, the fact that the risk was greatest in those diagnosed in 1980 to 1989, suggests that initiatives to reduce cardio toxicity among those treated more recently may be have a measurable impact.

                                                The last study describes the 30 day results of the Source 3 Registry, that is the European Post Approval Registry of the latest generation of the Sapien 3 trans-catheter heart valve. Dr. Wendler and colleagues from King's Health Partners in London, describe that these 30 day results of the Source 3 Registry demonstrate that trans-catheter uratic valve implantation, or TAVI, using the Sapien 3 resulted in high procedural success with low procedural complications, and excellent post-implant hemodynamics. Moderate to severe paravalvular leakage appeared to be lower with the Sapien 3 than reported with prior versions of this trans-catheter heart valve. Rates of pacemaker implantation were higher with the Sapien 3 than in earlier generations of the valve. This, in combination with the growing experience of patient selection, procedure planning, execution, and post-operative care has led to one of the best short-term outcomes ever reported after TAVI. These results are discussed in an accompanying editorial by Dr. [Altassi 00:06:58], and Dr. [Urani 00:06:58], from the Emery Midtown Hospital in Atlanta, Georgia, where they say that these early results from Source 3 Registry are a source of encouragement with some caveats.

                                                Well, those were your summaries. Now for our feature discussion.

                                                I am so honored to have two lovely ladies join me today on the show. And they are the first author of a feature paper, Dr. Francine Marques from Baker Heart and Diabetes Institute in Melbourne, Australia, as well as Dr. Peipei Ping, associate editor from the David Geffen UCLA School of Medicine. Welcome ladies.

Dr. Peipei Ping:                 Hi, hello.

Dr. Francine Marques:   Hi, thank you for having us.

Dr. Carolyn Lam:               As a clinician, I have very very often advised my hypertensive patients to go on the dash diet. And you know, I have no had any trouble explaining the low salt bit, right? I understand it. But then I realize that I've always advocated as well the high fiber bit, not actually really understanding how high fiber directly impacts blood pressure. And I'm so excited because your paper, Francine, shed some light on this and it actually has something to do with the gut. So could you please explain what you did and what you found?

Dr. Francine Marques:   So we fed a mouse model called [adoca 00:08:25] model of habitation, that also developed heart failure, we fed them a high fiber diet for three weeks, and then after that we did a surgery to make them become [habitant 00:08:36] safe and we followed them up for six weeks. And what we observed through that trajectory is that mice that were fed a high fiber diet had significantly lower systolic and diastolic blood pressure, and also an improvement in the heart function, and also a decrease in both heart and brainal fibrosis. And the reason why the fiber is so important is because although we usually don't digest the fiber, the bacteria in our gut absolutely love it. And that allows the bacteria, good bacteria to grow. And with that growth we have release of the fermentation of the fiber, releases in short chain fatty acid. So these specific molecules can then be put back into our body and can help us in our health. So we also fed these mice acetate, which is one of the short chain fatty acids, directly and we also observed very good improvements in blood pressure and cardiovascular health.

Dr. Carolyn Lam:               It's just fascinating. So these are studies in mice. What do you think of clinical translational aspects of this?

Dr. Francine Marques:   Large epidemialogical studies have shown that there is an inverse correlation between fiber consumption and blood pressure. And they have seen this through very small clinical trials looking into the intake of fiber lowering blood pressure. But our study opens the possibility of new interventions using maybe short chain fatty acids specifically, but are also looking into a different type of fiber. So most studies would look into either soluble or insoluble fiber directly. Our study, the diet that we used, is mostly resistant starches. So these are their preferred type of fiber for bacteria growth in our gut. And maybe they use a [inaudible 00:10:32] type of fibers as well could be a new [inaudible 00:10:36] opportunity.

Dr. Carolyn Lam:               Peipei, I remember you discussing this paper at our editorial meetings and you so beautifully highlighted the novelty of this paper. Could you share this with our listeners?

Dr. Peipei Ping:                 Often within many complex studies trying to understand cellular pathways and mechanisms of cardio protection, it's a very important topic as we have had our research focus on in the pas t 25 years. What's very unique and provocative of this particular study is that it simply identified critical metabolic pathways that actually is underlying the protective effects. Many of us have wondered about with eating, for example vegetables or high fiber diet, it is examined specific molecules that have both a direct as well as an endocryne path that would circulate things back to the cardiac muscles, and having the muscles becoming more protective because of regulation of certain transcriptomic pathways to support cardiac muscle contraction. So we were very impressed by both the new concept as well as the state of the art technologies employed in this investigation.

Dr. Francine Marques:   Thank you, that's very nice.

Dr. Carolyn Lam:               I couldn't agree more, you put it so beautifully Peipei. I thought that it was really nice also linking pathways as well as linking several organ systems. Is there anything you might want to highlight about the renal effects, not just cardiac?

Dr. Francine Marques:   Yes. Many times investigations been focusing on if something went wrong how do we cure it? More precious is when we find novel results telling us the healthy individuals, what are the things we should be doing so our blood pressure would stay at the normal level, or our cardiac function is being protected if there's an insult or injury. And so in this situation, the examination of the entire renal transcriptomic do give us very valuable information on how the blood pressure regulation system that maybe actually protected by the short chain fatty acid acetate.

Dr. Carolyn Lam:               So true Francine. Anything else to add?

Dr. Francine Marques:   Just to say circulation, for giving the opportunity to submit this paper, and share it with the world. We're very very excited about the data.

Dr. Carolyn Lam:               Yeah we should be the ones to thank you. It's a beautiful paper. We're very privileged to publish it in circulation. May I ask what are next steps for you? What do you think needs to be done from here?

Dr. Francine Marques:   We're validating this in other models now. And we're also looking into the [inaudible 00:13:57] microbiome and how that's related to habitation. So trying to really pinpoint mechanisms and how we can move this forward into the clinic.

Dr. Carolyn Lam:               That's so great. And Peipei, do you think that there's certain gaps that urgently need to be addressed now?

Dr. Peipei Ping:                 Yes, I think one of the most beautiful thing that ... Concept, illustrated this investigation is we really couldn't be just focusing on one organ, our primary interest organ, heart, alone. What's demonstrated here is a beautiful link of both mechanism as well as governed by transforming parbolytes with endocryne effects. How the gut, the kidney, and the heart are all connected together in this process, achieving a better protective condition in the environment for the cardiac muscle.

Dr. Carolyn Lam:               Thank you listeners. You've been listening to Circulation on the Run. Tune in next week for even more news.

 

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