AJP-Heart and Circulatory Physiology Podcast

Attenuation of Coronary Adenosine Dilation by Aldosterone

High plasma aldosterone is an independent risk factor for cardiac mortality, but what is known about the underlying mechanisms linking high levels of aldosterone to cardiac ischemic events? Listen as Consulting Editor Donal O’Leary (Wayne State University) interviews lead author Shawn Bender (University of Missouri & Truman VA) and expert Judy Muller-Delp (Florida State University) about the work led by motivated undergraduate Maloree Khan, which tested the hypothesis that increased plasma aldosterone impairs adenosine-mediated coronary vasodilation. Bender and co-authors found that high plasma aldosterone levels impaired adenosine A2A receptor-mediated dilation, but not adenosine A2B receptor-mediated vasodilation. Using a dose of aldosterone that does not significantly elevate blood pressure, Khan et al observed aldosterone-mediated changes in coronary dilation to adenosine via downregulation of calcium-activated potassium channels. Listen as these experts discuss the role of aldosterone and the mineralocorticoid receptor in ion channel expression in the vasculature, as well as future next steps related to sex differences and cell-specific knockout models.

 

Maloree Khan, Alex I. Meuth, Scott M. Brown, Bysani Chandrasekar, Douglas K. Bowles, and Shawn B. Bender Aldosterone impairs coronary adenosine-mediated vasodilation via reduced functional expression of Ca2+-activated K+ channels  Am J Physiol Heart Circ Physiol, published June 14, 2019. DOI: doi.org/10.1152/ajpheart.00081.2019

Total Sleep Deprivation and MSNA in Older Adults

Does 24 hours of total sleep deprivation affect older women and older men differently? Associate Editor Nisha Charkoudian (U.S. Army Research Institute for Environmental Medicine) interviews lead author Jason Carter (Michigan Technological University) and expert Nina Stachenfeld (Yale University School of Medicine) about the innovative study by Carter and co-authors, who found a sympatho-excitatory response to the sleep deprivation protocol in older women, but not in older men. The work by Carter et al suggests that the autonomic nervous system may have a larger role in older women who are sleep deprived, which is particularly important given that older women are at higher risk of developing hypertension than their age-matched male counterparts. Carter and colleagues conclude that "the association between sleep deprivation and hypertension is real." Will this new research kickstart a push for sleep as medicine for cardiometabolic diseases? Listen and find out.

 

Jason R. Carter, Ida T. Fonkoue, Ian M. Greenlund, Christopher E. Schwartz, Babak Mokhlesi, Carl A. Smoot Sympathetic Neural Responsiveness to Sleep Deprivation in Older Adults: Sex Differences Am J Physiol Heart Circ Physiol, published July 29, 2019. DOI: doi.org/10.1152/ajpheart.00232.2019

Heat Therapy vs. Exercise in Peripheral Arterial Disease

Can heat therapy improve exercise tolerance in peripheral arterial disease patients? Associate Editor Nisha Charkoudian (U.S. Army Research Institute of Environmental Medicine) interviews lead author Ashley Akerman (University of Ottawa) and content expert Zachary Schlader (Indiana University) about the novel passive heat training study by Akerman and co-authors. While exercise is the gold standard for conservative management of peripheral arterial disease (PAD), patients often struggle to comply with exercise treatment guidelines due to painful atherosclerotic plaque build-up in their arteries. Aimed at breaking the vicious cycle of needing to exercise but failing to do so because of pain, Akerman and collaborators designed a 12-week intervention study to compare exercise to heat therapy in older PAD patients. While functional walking improved for both groups, systolic blood pressure was markedly reduced in the heat therapy group. Surprisingly, other measures such as blood volume and flow mediated dilation were largely unchanged in both groups. Could these results have a wider impact on other patient populations, such as younger individuals recovering from an injury or diabetes patients?

 

Ashley P. Akerman, Kate N. Thomas, Andre M. van Rij, E. Dianne Body, Mesfer Alfadhel, James D. Cotter Heat therapy vs. supervised exercise therapy for peripheral arterial disease: a 12-wk randomized, controlled trial Am J Physiol Heart Circ Physiol, published June 5, 2019. DOI: doi.org/10.1152/ajpheart.00151.2019

Dietary Calanus Oil, Energy Metabolism, and Cardiac Function

How can a minute crustacean found in the Norwegian seas help to normalize cardiac metabolism in obese subjects? Associate Editor Fabio Recchia (Temple University and Scuola Superiore Sant'Anna) interviews first author Kirsten Jansen (UiT The Arctic University of Norway) and expert Luc Bertrand (Université Catholique de Louvain) about the innovative new study by Jansen and co-authors. Using a mouse model of high fat diet-induced obesity, Jansen and collaborators showed that 8 weeks of food supplementation with a small amount (just 2%) of dietary Calanus oil, which is derived from the marine zooplankton Calanus finmarchicus, improved cardiac function after 20 minutes of global ischemia. The unique fatty acid composition of the wax esters in Calanus oil is expected to activate GPR 120 (an omega-3 fatty acid receptor) in the gut, causing secretion of GLP-1 and release of insulin from pancreatic beta-cells. What is the link between Calanus oil and a decrease in intra-abdominal fat deposition, glucose metabolism recovery in the heart, and calcium handling? Listen now.

 

Kirsten Maria Jansen, Sonia Moreno, Pablo M. Garcia-Roves PhD, and Terje S. Larsen Dietary Calanus oil recovers metabolic flexibility and rescues post-ischemic cardiac function in obese female mice Am J Physiol Heart Circ Physiol, published May 24, 2019. DOI: doi.org/10.1152/ajpheart.00191.2019

Effector CD8 T Cells Seed Atherogenic Foci

Do T cells directly contribute to the inflammatory response and progression of atherosclerosis? Guest Editor Kristine DeLeon-Pennell (Medical University of South Carolina) interviews lead author Anthony Vella (University of Connecticut Health) and content expert Shyam Bansal (The Ohio State University) about the new study by Xu et al published as part of the AJP-Heart and Circulatory Physiology Call for Papers on Adaptive Immunity in Cardiovascular Disease. By activating T cells via the 4-1BB pathway, also known as the common potent anti-tumor biologic CD137, Vella and co-authors found that the T cells were attracted to sites of inflammation. Using sophisticated T cell isolation techniques to analyze the T cells within the plaque, Vella and collaborators determined that co-stimulated T cells penetrated deep into the plaque and perpetuated inflammation. Does this study suggest that there is a dynamic cross-talk between immune cells, and that inhibiting infiltration by T cells into plaques could alter the cascade and inhibit the progression of atherosclerosis? How do auto-immune disease and sex differences fit into this picture? Listen and find out.

Maria Mei Xu, Antoine Ménoret, Sarah-Anne E. Nicholas, Sebastian Günther, Eric J. Sundberg, Beiyan Zhou, Annabelle Rodriguez, Patrick A. Murphy, and Anthony T. Vella Direct CD137 costimulation of CD8 T cells promotes retention and innate-like function within nascent atherogenic foci Am J Physiol Heart Circ Physiol, published April 12, 2019. DOI: 10.1152/ajpheart.00088.2019

Dietary Sodium, Oxidative Stress and Microvascular Function

How does dietary sodium affect cardiovascular health beyond its influence on blood pressure? In this lively podcast, Associate Editor Nisha Charkoudian (U.S. Army Research Institute of Environmental Medicine) interviews lead author David G. Edwards (University of Delaware) and R. Matthew Brothers (University of Texas at Arlington) about the innovative study by Ramick et al examining the mechanisms by which high dietary sodium may impair vascular function. The authors used 24-hour blood pressure monitoring to identify blood pressure-independent effects of a high salt diet for salt-resistant individuals, compared to salt-sensitive individuals. Using a 7-day randomized high and low salt diet protocol, as well as intradermal microdialysis, the authors built on previous work to investigate specific mechanisms of oxidative stress in the microvasculature with a high-salt diet. Was the source of reactive oxygen species superoxide? From a public health perspective, does this study suggest that we need to shift focus from sodium and blood pressure, to sodium and overall cardiovascular health? Listen and find out.

 

Meghan G. Ramick, Michael S. Brian, Evan L. Matthews, Jordan C. Patik, Douglas R. Seals, Shannon L. Lennon, William B. Farquhar, and David G. Edwards Apocynin and Tempol Ameliorate Dietary Sodium-Induced Declines in Cutaneous Microvascular Function in Salt Resistant Humans Am J Physiol Heart Circ Physiol, published May 10, 2019. DOI: 10.1152/ajpheart.00786.2018

Maternal Obesity Induces Transgenerational Cardiac Mitochondrial Dysfunction

Does maternal obesity have transgenerational effects on the cardiovascular health of offspring? Listen as Deputy Editor Merry Lindsey (University of Nebraska Medical Center) interviews authors Kelle Moley and Abhinav Diwan (both at Washington University in St. Louis), along with content expert Linda May (East Carolina University) about the unique study by Ferey and colleagues. In this elegantly designed study, the authors fed female C57 black mice a high fat-high sucrose diet for 9 weeks before mating with male mice on a normal diet. The female mice remained on the high fat-high sucrose diet for the duration of their pregnancies, and after birth, pups were weaned to a normal diet. Ferey et al showed that the offspring, despite not being obese, demonstrated cardiac mitochondrial abnormalities and reduced oxygen consumption. In addition, increased left ventricular mass persisted three generations. What are the potential public health implications of this work? Listen now.

 

Jeremie L. A. Ferey, Anna L. Boudoures, Michaela Reid, Andrea Drury, Suzanne Scheaffer, Zeel Modi, Attila Kovacs, Terri Pietka, Brian J. DeBosch, Michael D. Thompson, Abhinav Diwan, and Kelle H. Moley A maternal high-fat, high-sucrose diet induces transgenerational cardiac mitochondrial dysfunction independently of maternal mitochondrial inheritance Am J Physiol Heart Circ Physiol, published May 2, 2019. DOI: 10.1152/ajpheart.00013.2019

Proteostasis in Senescent Endothelial Cells

Do senescent primary human coronary artery endothelial cells have a diminished heat shock response and/or impaired proteostasis? Listen as Editor in Chief Irving H. Zucker (University of Nebraska Medical Center) interviews lead author Aldrin Gomes (University of California Davis) and content expert Cameron McCarthy (University of Toledo) about this novel new study by Hwang et al, which determines that estrogen did not decrease protein aggregation nor improve the heat shock response in senescent vascular endothelial cells. As the current study was performed using all female donor coronary artery endothelial cells, the authors suspect sex differences play a key role in estrogen and heat shock response. How might the regulation of anti-oxidant enzymes and the pro- anti-oxidant transcription factor Nrf-2 play a role in reducing oxidative stress and proteolysis? Does a so-called Mediterranean diet show promise in reducing levels of oxidative stress biomarkers? Listen and learn more.

 

HyunTae V. Hwang, Yun Lin, Michelle N. Rebuffatti, Darlene T. Tran, Lily Lee, Aldrin V. Gomes, Chin-Shang Li, and Anne A. Knowlton Impaired proteostasis in senescent vascular endothelial cells: a perspective on estrogen and oxidative stress in the aging vasculature Am J Physiol Heart Circ Physiol, published February 1, 2019. DOI: 10.1152/ajpheart.00318.2018

K+ Channel Isoforms Regulate Human Atrial Arrhythmogenesis

Can small changes in action potential duration have a major impact in human atrial electrophysiology? Listen as Associate Editor Mario Delmar (New York University) interviews authors Wayne Giles (University of Calgary) and Sanjiv Narayan (Stanford University) along with content expert Brian Delisle (University of Kentucky) about the new study by Ni et al. Combining mathematical modeling and clinical observations, Ni et al found that alternans could be strongly influenced by the types of potassium currents expressed in atrial myocytes, and that some potassium channel isoform switches occurring in atrial fibrillation may affect atrial physiology. The current study takes a reductionist approach to compare a single atrial control myocyte and a single myocyte in a-fib. What might the authors find if they replicate the isoform switch and study the conducted action potential in a 2-dimensional “sausage” of hundreds of myocytes? Listen and learn more.

 

Haibo Ni, Henggui Zhang, Eleonora Grandi, Sanjiv M. Narayan, and Wayne R. Giles Transient outward K+ current can strongly modulate action potential duration and initiate alternans in the human atrium Am J Physiol Heart Circ Physiol, published February 20, 2019. DOI: 10.1152/ajpheart.00251.2018

Heterogeneous Sodium in Ventricular Myocytes

Is sodium evenly or unevenly distributed in the subsarcolemmal space? Intracellular sodium is an important regulator of cardiac contractility and plays a role in cardiac arrythmias. Therefore, understanding how and why sodium may be differentially distributed in the subsarcolemmal space is critically important. Associate Editor Mario Delmar (New York University) interviews lead author Jonas Skogestad (University of Oslo) and content expert Sand Despa (University of Kentucky) about the novel studies by Skogestad et al. Using both patch-clamping and mathematical modeling, Skogestad and co-authors challenge the current paradigm by suggesting that subsarcolemmal sodium may exist in not just one, but rather many, compartments. The authors found that, after activating the sodium channel for a short amount of time, the sodium released into the subsarcolemmal space did not affect Na+/K+-ATPase (NKA) activity. Did the same hold true for longer activation times, and what does this indicate about the possible interaction between the sodium pump and sodium channels? Listen now.

 

Jonas Skogestad, Glenn Terje Lines, William E. Louch, Ole M. Sejersted, Ivar Sjaastad, and Jan Magnus Aronsen Evidence for heterogeneous subsarcolemmal Na+ levels in rat ventricular myocytes Am J Physiol Heart Circ Physiol, published January 18, 2019. DOI: 10.1152/ajpheart.00637.2018