Current Trainees

Olukemi Akintewe, Ph.D

Development of 3-D Cardiac Tissues for Regenerative Therapies

contact: olukemi@mail.usf.edu

(June 30, 2015 – present, Joyce Wong, PhD, mentor)akinewate

Mortality rates due to congenital heart defects (HD) may have declined in the United States, but the burden of the disease still remains high. Regeneration of these cardiac tissues is challenging due to its complex three-dimensional (3D) architecture and pertinent electrophysiological function. Current regenerative therapies (cell transplantation and biodegradable scaffolds) have shown limited inherent regenerative capacity due to poor integration and inflammatory response. Therefore, there is a need for an alternative approach to organ transplantation that can induce proper cardiovascular permanency to prevent early deaths, arrhythmias or heart failures. We aim to improve the wellness of pediatric patients suffering from congenital HD by developing a cardiac patch. Dynamic surfaces will be employed to generate contractile and conductive tissue engineered 3-D cardiac patches that will aid the regenerative repairs after transplantation. This study investigates the attachment, organization and interaction of human induced pluripotent stem cells (iPS) derived cardiomyocytes using a photo-sensitive tunable substrate for preparation of three-dimensional (3-D) cardiac tissues that can promote normal electrophysiological functions of the heart and ultimately neovascularization, and angiogenesis upon implantation.

 

Deepa M. Gopal, MD., MS

Contact: dmgopal@bu.edu

(July 2015 – present; Wilson S. Colucci, M.D., F.A.C.C., F.A.H.A, mentor)

deepagopalMetabolic disease and obesity prevalence rates are rapidly increasing in the United States. Metabolic syndrome is an entity shown to confer increased risk of incident heart failure; individual components of the syndrome are well linked to heart failure with preserved ejection fraction. The relationship of metabolic dysfunction to abnormal cardiac structure and function is termed metabolic heart disease (MHD). Early and subclinical identification of MHD may help lead to prevention and early intervention for heart failure in these patients.

Over the last four years, the Boston University Cardiovascular Proteomics Center (Co-PI’s: Costello / Cohen / Colucci) collected 350 subjects with metabolic syndrome (including healthy controls) that were well phenotyped with regards to cardiac function (2D and Doppler echocardiography) and arterial stiffness. Blood was banked for future biomarker studies and proteomic analysis to identify novel circulating biomarkers based on protein modifications. Dr. Gopal participated in the analysis of the echocardiographic data, developing methods to evaluate pulmonary hypertension and RV function with her work published in the Journal of the American Heart Association in March 2015. Dr. Gopal’s research plans during her research fellowship are to explore relationships of biomarkers, specifically galectin-3, a putative marker of interstitial fibrosis, and follistastin-like 3, a cardiac myokine, with abnormal cardiac function (LV diastolic dysfunction, hypertrophy, and subclinical pulmonary hypertension) as well as with insulin resistance in this cohort. She will also direct the collection of a second observation in matched subjects based on the presence or absence of diastolic dysfunction and pulmonary hypertension allowing observation of interval changes in cardiac function and biomarkers and to test putative relationships in a more controlled manner. Her second line of investigation is to extend her echocardiographic skillset in humans to both a diet-induced mouse model of MHD as well as a second model of MHD in which a transgenic myocyte-specific expression of catalase prevents LV diastolic dysfunction and hypertrophy but spares metabolic syndrome. She plans to work with these model systems to investigate and compare abnormal LV diastolic function, pulmonary hemodynamics, and RV function in relation to metabolic disease and insulin resistance.

Publications Related to this Research

Wang YC, Liang CS, Gopal DM, Ayalon N, Donohue C, Santhanakrishnan R, Sandhu H, Perez AJ, Downing J, Gokce N, Colucci WS, Ho JE. Preclinical Systolic and Diastolic Dysfunction in Metabolically Healthy and Unhealthy Obese Individuals. Circ Heart Failure. 2015 Jul 14. PMID: 26175540.

Gopal DM, Wang YC, Ayalon N, Donohue C, Santhanakrishnan R, Rahban Y, Gokce N, Perez AJ, Downing J, Liang CS, Colucci W, Ho, JE. Impaired Right Ventricular Hemodynamics Suggest Preclinical Pulmonary Hypertension in Patients with Metabolic Syndrome. JAHA. 2015 March 10; e001597. PMID: 25758604.

Ayalon N, Gopal DM, Mooney DM, Simonetti JS, Grossman JR, Dwivedi A, Donohue C, Perez AJ, Downing J, Gokce N, Miller EJ, Liang CS, Apovian CM, Colucci WS, Ho JE. Preclinical left ventricular diastolic dysfunction in metabolic syndrome. Am J Cardiol. 2014 Sep 15; 114. PMID: 25084691.

Shakuntala Karki, Ph.D.

Karki

Contact: shakunk@bu.edu

Obesity-related diseases including diabetes and cardiovascular disease have risen to epidemic proportions in the US and worldwide. Dysregulation of adipose tissue metabolism, particularly associated with accumulation of visceral fat, has been linked to mechanisms of insulin resistance and cardiometabolic disease. The vascular endothelium plays a critical role in the regulation of arterial homeostasis, and its dysfunction leads to cardiovascular disease. While endothelial phenotype serves as a barometer of vascular health, it displays impairment in obesity-related insulin resistant states and specific pathogenic mechanisms leading to vascular dysfunction are incompletely understood.

Insulin regulates whole body glucose uptake and enhances blood flow in part by regulating endothelial nitric oxide synthase (eNOS) through the PI3K-Akt pathway. Transcription factor forkhead box O1 (FOXO1) represents a key downstream target of Akt in both adipose tissue and vascular endothelium. In recent years, FOXO1 has been implicated in modulating adipogenesis and hepatic glucose metabolism, however its potential role in vascular pathogenesis is unknown. Dr. Karki’s current translational project investigates mechanisms of vascular endothelial dysfunction within fat tissue microenvironments by studying depot-specific adipose phenotypes in obese humans. Her current work focuses on isolating and characterizing endothelial cells from different human fat depots and probing the role of FOXO1 on eNOS activation and endothelial function. Preliminary data have demonstrated that insulin signaling and endothelium-dependent responses are severely impaired in visceral fat depots, and provide novel evidence that altered functionality of FOXO1 may play a key role in vascular insulin resistance.  Dr. Karki’s work was recently accepted for presentation at the American Heart Association 2013 Scientific Sessions. Dr. Karki’s projects studying endothelial insulin resistance in the adipose microenvironment may provide clues to mechanisms of systemic insulin resistance in human obesity.

 

Darae Ko, M.D.

Darae Ko T32 photo

Contact: daraeko@bu.edu

Mentor: Elaine Hylek

Atrial fibrillation (AF) poses significant health risks. Its most devastating outcome, stroke, is associated with high morbidity and mortality and substantial health care costs. As the population ages, the health care burden from AF is expected to in

crease. Therefore, there is a critical need to identify modifiable risk factors that affect stroke severity in AF. We now have a database consisting of 1017 ischemic stroke events in patients with AF collected across three large medical centers:  Boston Medical Center, University of Alabama, and Geisinger Health Systems. Stroke events were rigorously validated through medical record review and adjudicated by a stroke neurologist. The database includes a wide range of information including but not limited to basic patient characteristics, cardiovascular co-morbidities, types of AF, medication use, vital, imaging findings, laboratory values, and 30-day mortality.  Stroke severity was assigned in a blinded manner according to the modified Rankin Scale by a stroke neurologist. We aim to use this database to investigate relationship between various proinflammatory triggers such as hyperglycemia, arterial hypertension, hypoxia, infection, heart failure, and stroke severity in AF. Our study will not only broaden our understanding of AF stroke but also help identify strategies to mitigate stroke severity in AF

 

 

Nicole L. Spartano, Ph.D.Spartano_image

Impact of physical activity on biomarkers of cardiovascular and metabolic health

Contact: spartano@bu.edu

(June 2014 – present, Vasan Ramachandran, MD, mentor)

Physical activity reduces the risk of developing metabolic and cardiovascular diseases. Current national guidelines for physical activity are based on research from self-report questionnaires, which may be unreliable. Dr. Spartano’s research will focus on objective physical activity monitoring using accelerometry to examine the link between physical activity and metabolic and cardiovascular health. She will explore mechanisms involving inflammatory cytokines, vascular function, lipoprotein metabolism and other metabolites and biomarkers which may be elevated or suppressed in individuals who do not achieve adequate levels of physical activity.

A second line of research involves the cardiovascular response to stressors (such as mental stress or exercise). The stress response causes a rise in heart rate and blood pressure, which, repeated over decades, can be damaging to the arteries and target organs such as the heart and brain. Dr. Spartano’s previous research has identified an association between elevated systolic blood pressure in the carotid artery in response to mental stress and carotid artery intima-media thickness. She will continue this line of research by examining the association between the cardiovascular response to exercise and later-life morphology of another target organ which is susceptible to damage, the brain. This research may shed light on the involvement in stress-reactivity in disease development. Together, Dr. Spartano’s research projects may also reveal some of the mechanisms by which physical activity and cardiovascular fitness prevent metabolic and cardiovascular disease progression.

 

Tathagat Dutta Ray, Ph.D

tathagatduttaray

Contact: tdray@bu.edu

Dr. Tathagat Dutta Ray is a post doctoral fellow in the laboratory of Dr. Robin Ingalls in Division of Infectious Diseases, BUMC. He is interested in studying the cross regulation of the complement system and other innate immune signaling pathways in regulating chronic inflammation. Obesity is a chronic inflammatory disorder that poses a very strong risk factor for development of insulin resistance and Type 2 Diabetes Mellitus (T2DM). However, the molecular mechanisms underlying this strong link between obesity and T2DM is not clearly understood. The development of obesity induced T2DM is regulated by several adipokines secreted by the adipose tissue. Complement proteins like C3/Acylation stimulating protein is one such adipokine with a strong association with obesity, lipid dysregulation, insulin resistance syndrome and T2DM. However, most of these studies have linked the level of complement proteins like C3 or the complement activation in plasma with obesity or Type 2 diabetes independently. In this study Dr. Dutta Ray is addressing two broad questions. First, what is the role of complement cascade in development of insulin resistance and T2DM due to obesity. Although, obesity is strongly related to Type 2 diabetes, some obese individuals do not develop diabetes or insulin resistance. It is possible that activation of the complement cascade plays a role in development of insulin resistance during obesity leading to T2DM. Complement proteins are present in abundance and form a cascade of proteases that is very tightly regulated by several complement regulators like factor H, factor D and properidin. A few reports so far have looked at the correlation of insulin sensitivity and glucose metabolism markers with different complement activation products like C3a/ASP or the complement regulators independently of each other. In this study, Dr. Dutta Ray wants to simultaneously determine the correlation of circulating and adipose tissue specific levels of complement C3, its downstream activation products like C3a/ASP and C5b-9 and the complement regulators with insulin resistance syndrome during obesity. In addition, the molecular mechanism of complement protein induction in adipose tissue during diet induced obesity is unknown. Data from the Ingalls lab shows a role of the intracellular danger signal receptor NOD2 in induction of C3 in macrophages. Intracellular innate immune receptors like NOD1 and NOD2 have been implicated in insulin resistance. Dr. Dutta Ray is investigating the role of NOD2 in complement C3 induction its possible implication towards development of a chronic inflammatory state that leads to insulin resistance and type 2 diabetes.

 

 

Simon Shim, Ph.D

Sympathoinhibitory signaling through brain-kidney interaction in hypertension

simonshim(July 2015 – present, Richard D. Wainford, PhD, Mentor)

My research interest is pathophysiology of hypertension along brain and kidney signaling pathways. Hypertension is a critical public health issue as 1:3 US adults and 1:56 billion population worldwide having this condition. We are aiming at increasing our understanding of the interactions between cerebral neural control centers and the kidney that evoke impaired regulation of fluid and electrolyte homeostasis and systemic blood pressure regulation in the pathophysiology of hypertension. Our studies center on the role of hypothalamic G proteins called, PVN Gαi2, in regulating sympathetic outflow, particularly to the kidney, in response to increased salt-intake to maintain a salt-resistant phenotype. The critical importance of continuing our investigations in the area of the centrally regulated renal mechanisms underlying the pathophysiology of hypertension is highlighted by 1) the conflicting results of the recent clinical trials in which renal nerve ablation produced both persistent blood pressure reduction (trial 1 & 2) and a lack of effect versus placebo (recent trial 3) and, 2) the latest studies which suggest the renal sympathetic nerves influence the expression and function of renal sodium transporters to influence blood pressure, yet failed to investigate the central mechanisms regulating renal nerve traffic. The overall hypothesis I will be addressing is do sodium-sensitive renal afferent nerves evoke suppression of sympathetic outflow to the kidneys, via an endogenous PVN Gαi2 protein mediated signal transduction pathway, to facilitate sodium balance and maintain a salt-resistant phenotype? We will address these questions using a combined basic science and translational approach. By increasing understanding of the mechanisms regulating blood pressure we will augment development of new anti-hypertensive target in sympathoinhibitory signaling of the nervous system.

Publications

Shim JW, Carmichael CY, Wainford RD. Renal Afferent Nervous System in Hypertension. Current Hypertension Reports (invited review), Submission due Dec. 2015

Walsh KR, Shim JW, Kuwabara JT, Wainford RD. Norepinephrine-evoked salt-sensitive hypertension requires impaired renal sodium chloride co-transporter (NCC) activity in Sprague-Dawley rats. American Journal of Physiology Regulatory, Integrative and Comparative Physiology (in revision) due Feb. 2016

Shim JW, Territo PR, Maue E, Ahmed S, Watson JC, Fulkerson D, Blazer-Yost BL. Neurological consequences of a TMEM67 mutation in the Wistar polycystic kidney rat model of Meckel-Gruber Syndrome. J. Neurosci. 2015 (in revision) due Sep. 2015

Shim JW, Wainford RD. Hypothalamic PVN Gαi2 protein-mediated renal nerve dependent sympathoinhibition facilitates suppression of NCC activity and a salt-resistant phenotype (In Preparation).

 

 

Karen Weikel, Ph.D

Contact:kaweikel@bu.edu

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Management of diabetes and cardiovascular disease has been improved in recent years by drugs such as metformin and various statins that activate AMP-activated protein kinase (AMPK). AMPK regulates key events in energy metabolism and cellular stress responses that are thought to contribute to atherogenesis. Unfortunately, these treatments do not prevent heart attacks in all patients. This is likely due to an incomplete understanding of how diabetes affects cardiovascular health and why current drug targets respond differently in diabetic patients than in healthy adults.

To address the long-term objective of improving these therapies, my work focuses on how diabetes damages the aorta, a large blood vessel near the heart where most heart attacks begin. One of the ways in which high amounts of sugar and fat (which are often observed in diabetic patients), can damage blood vessels and increase risk for heart attacks is by impairing “autophagy”, a process in which damaged cellular material is discarded. In healthy blood vessels, drugs that target and activate AMPK increase autophagy, but this does not happen in blood vessels exposed to excessive sugar and fat. My goal is to determine how and why the cardioprotective actions of AMPK are attenuated by diabetic conditions, with a specific focus on cellular autophagy. I predict that increased activity of another protein, glycogen synthase kinase 3β (GSK3β), may be interfering with the beneficial effects of AMPK activation. These mechanistic studies will first be carried out in primary human aortic endothelial cells cultured in diabetic conditions. Future studies in mouse models of metabolic disease can then be used to determine how AMPK affects the cardioprotective effects of GSK3β inhibitors. This work will enhance the understanding of how regulation of AMPK changes in patients that have diabetes and may help develop combination therapies that target molecules in addition to AMPK. Such therapies may improve not only the efficacy of cardiovascular and diabetes treatments, but also impact patients with other diseases in which AMPK plays a role.

 

Relevant Publications (the first was published before becoming a CVI fellow)

  1. Weikel, K. A., Cacicedo, J. M., Ruderman, N. B. and Ido, Y. (2015) Glucose and palmitate uncouple AMPK from autophagy in human aortic endothelial cells. American journal of physiology. Cell physiology. 308, C249-263.
  1. Weikel, K.A., Ruderman, N.B. and Cacicedo, J.M.   (2015) Unraveling the actions of AMP-activated protein kinase in metabolic diseases: systemic to molecular insights. Submitted to Metabolism.