The Future Role of the United States in Global Health: Emphasis on Cardiovascular Disease

U.S. global health investment has focused on detection, treatment, and eradication of infectious diseases such as tuberculosis, malaria, and human immunodeficiency virus/acquired immunodeficiency syndrome, with significant results. Although efforts should be maintained and expanded to provide ongoing therapy for chronic infectious disease, there is a pressing need to meet the challenge of noncommunicable diseases, which constitute the highest burden of diseases globally. A Committee of the National Academies of Sciences, Engineering, and Medicine has made 14 recommendations that require ongoing commitments to eradication of infectious disease and increase the emphasis on chronic diseases such as cardiovascular disease. These include improving early detection and treatment, mitigating disease risk factors, shifting global health infrastructure to include management of cardiovascular disease, developing global partners and private-public ventures to meet infrastructure and funding challenges, streamlining medical product development and supply, increasing research and development capacity, and addressing gaps in global political and institutional leadership to meet the shifting challenge.

Abstract 153: Using Enzyme-Catalyzed Proximity Labeling to Define the Interactome of the Insulin-like Growth Factor-1 Receptor

Introduction: Manipulation of I nsulin-like G rowth F actor- 1 R eceptor (IGF1R) signaling has been proposed to be an important therapeutic for the treatment of heart failure and myocardial infarction. However, activation of this receptor has, under certain conditions, been shown to result in deleterious side-effects such as pathological hypertrophy. Development of therapeutic strategies that avoid these side-effects requires a more comprehensive understanding of the proteins involved in the IGF1R signaling axis. To this end, we have made use of the enzyme-catalyzed proximity labeling technique called BioID.

Objective: To comprehensively define the interactome of the activated IGF1R.

Methods and Results: Briefly, BioID makes use of a biotin protein ligase called BirA* that promiscuously biotinylates neighboring proteins. The protein of interest is fused with BirA* and is then expressed in a particular cell line. Following administration of an excess amount of biotin, BirA* will biotinylate those proteins that are adjacent to or interact with the protein of interest. Interacting proteins are identified by tandem mass spectrometry (MS/MS). We have made a HEK 293T cell line that stably expresses the BirA* biotin ligase fused to the C-terminus of IGF1R. We performed BioID using this cell line (N=3) to identify a set of proteins that bind to the IGF1R following stimulation by IGF1. This set included many known interactors of the IGF1R, such as IRS2 and SHC1, thereby validating this technique. Of the many interesting novel interactors, we chose to pursue validation of sorting nexin 6 (SNX6) as some SNX proteins have been shown to be involved in receptor recycling to the plasma membrane following stimulation. We have found that SNX6 knockdown results in a dramatic diminution of IGF1-mediated ERK phosphorylation (2-fold; N=4; p <0.05). However, there was no effect on IGF1-mediated Akt phosphorylation (N=4). We are currently assessing the role of SNX6 in IGF1R-mediated function and recycling of this receptor.

Conclusion: We have demonstrated the ability of the BioID technique to identify a set of proteins that can interact with the activated IGF1R. Moreover, BioID has identified a number of novel interactors that further define IGF1R signaling and function.

The Cardiovascular Continuum extended: Aging effects on the aorta and microvasculature

The ‘Cardiovascular Continuum’ was described by Dzau and colleagues in 2006 to explain the development over many years of coronary disease with its complications, then end-stage heart failure. The Continuum identified different points along the way where the process could be interrupted by drug therapies or interventions, then described the trials that have been undertaken over the last three decades to establish their value. The approach summarized the major steps in cardiology through modern times, but it had an emphasis on coronary atherosclerosis in prosperous nations, and did not account fully for the problems of aging, which occur in all societies. Aging of the aorta and elastic arteries causes arterial stiffening and leads to development of cardiac failure and microvascular disease in highly perfused organs such as the brain and kidneys. The ‘Vascular Aging Continuum’ which we introduce, dovetails with the late phases of the Cardiovascular Continuum and provides a more comprehensive explanation, especially for vascular diseases in nations with little atherosclerosis. It will become more common in the Western World where attention to risk factors and widespread use of statins are responsible for a decrease in atherosclerotic disease, prolongation of life, and dominance of macrovascular and microvascular arterial disease, as well as of cardiac failure.

Secreted frizzled related protein 2 (Sfrp2) is the key Akt-mesenchymal stem cell-released paracrine factor mediating myocardial survival and repair

Stem cell therapy has emerged as a promising tool for the treatment of a variety of diseases. Previously, we have shown that Akt-modified mesenchymal stem cells mediate tissue repair through paracrine mechanisms. Using a comprehensive functional genomic strategy, we show that secreted frizzled related protein 2 (Sfrp2) is the key stem cell paracrine factor that mediates myocardial survival and repair after ischemic injury. Sfrp2 is known to modulate Wnt signaling, and we demonstrate that cardiomyocytes treated with secreted frizzled related protein increase cellular beta-catenin and up-regulate expression of antiapoptotic genes. These findings reveal the key role played by Sfrp2 in mediating the paracrine effects of Akt-mesenchymal stem cells on tissue repair and identify modulation of Wnt signaling as a therapeutic target for heart disease.

The cardiovascular continuum and renin-angiotensin-aldosterone system blockade

A progressive chain of pathophysiological events links cardiovascular risk factors to clinical manifestations of disease and life-threatening cardiovascular events. This chain--the cardiovascular continuum--underlies cardiovascular disease and holds the key to its prevention and treatment. Progressive tissue damage can result in morbidity from congestive heart failure, end-stage heart disease, nephrotic proteinuria and dementia and, eventually, death from cardio- or cerebrovascular causes. The renin-angiotensin-aldosterone system (RAAS) is involved at all stages of the cardiovascular continuum, because the effector molecules of the RAAS, angiotensin II in particular, have direct pathobiological effects on a variety of tissues, including the endothelium, vascular smooth muscle and the renal mesangium. Clinical trials of angiotensin II receptor blockers (ARBs) and angiotensin-converting enzyme (ACE) inhibitors have demonstrated the essential validity of this hypothesis. Interruption of the RAAS has been shown to reduce cardiovascular morbidity and mortality in patients with left ventricular hypertrophy, heart failure and post-myocardial infarction, as well as renal disease in patients with type 2 diabetes. Key questions remain, however. What are the clinical effects of combination ARB and ACE inhibitor treatment? How will combinations of RAAS blockade with other agents, such as statins, affect the cardiovascular continuum? Answers to these questions will require well-planned, adequately powered clinical trials, such as the Programme of Research tO evaluate Telmisartan End-organ proteCTION (PROTECTION) and the ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET) programmes. However, it is already clear that RAAS blockade is an essential part of blocking progression along the cardiovascular continuum.

Integration of an academic medical center and a community hospital: the Brigham and Women's/Faulkner hospital experience

Brigham and Women's Hospital (BWH), a major academic tertiary medical center, and Faulkner Hospital (Faulkner), a nearby community teaching hospital, both in the Boston, Massachusetts area, have established a close affiliation relationship under a common corporate parent that achieves a variety of synergistic benefits. Formed under the pressures of limited capacity at BWH and excess capacity at Faulkner, and the need for lower-cost clinical space in an era of provider risk-sharing, BWH and Faulkner entered into a comprehensive affiliation agreement. Over the past seven years, the relationship has enhanced overall volume, broadened training programs, lowered the cost of resources for secondary care, and improved financial performance for both institutions. The lessons of this relationship, both in terms of success factors and ongoing challenges for the hospitals, medical staffs, and a large multispecialty referring physician group, are reviewed. The key factors for success of the relationship have been integration of training programs and some clinical services, provision of complementary clinical capabilities, geographic proximity, clear role definition of each institution, commitment and flexibility of leadership and medical staff, active and responsive communication, and the support of a large referring physician group that embraced the affiliation concept. Principal challenges have been maintaining the community hospital's cost structure, addressing cultural differences, avoiding competition among professional staff, anticipating the pace of patient migration, choosing a name for the new affiliation, and adapting to a changing payer environment.

A genome scan for hypertension susceptibility loci in populations of Chinese and Japanese origins

BACKGROUND

Our understanding of genes that predispose to essential hypertension is poor.

METHODS

A genome-wide scan for linkage at approximately 10 cM resolution was done on 1425 sibpairs of Chinese and Japanese origins that were concordant for hypertension (N = 661), low-normal blood pressure (BP) (N = 184), or discordant for BP (N = 580).

RESULTS

There was no significant evidence of linkage to a single locus in the genome. There was suggestive evidence of linkage to chromosome 10p, with a LOD score of 2.5.

CONCLUSIONS

We can exclude the possibility that a single gene accounts for at least 15% of the variance in hypertension in this population.

Genetic variation in aldosterone synthase predicts plasma glucose levels

The mineralocorticoid hormone, aldosterone, is known to play a role in sodium homeostasis. We serendipitously found, however, highly significant association between single-nucleotide polymorphisms in the aldosterone synthase gene and plasma glucose levels in a large population of Chinese and Japanese origin. Two polymorphisms--one in the putative promoter (T-344C) and another resulting in a lysine/arginine substitution at amino acid 173, which are in complete linkage disequilibrium in this population--were associated with fasting plasma glucose levels (P = 0.000017) and those 60 (P = 0.017) and 120 (P = 0.0019) min after an oral glucose challenge. A C/T variant in intron 1, between these polymorphisms, was not associated with glucose levels. Arg-173 and -344C homozygotes were most likely to be diabetic [odds ratio 2.51; 95% confidence interval (C.I.) 1.39-3.92; P = 0.0015] and have impaired fasting glucose levels (odds ratio 3.53; 95% C.I. 2.02-5.5; P = 0.0000036). These results suggest a new role for aldosterone in glucose homeostasis.

Lack of evidence for an association between alpha-adducin and blood pressure regulation in Asian populations

Recent studies have found the tryptophan allele of a glycine to tryptophan polymorphism at position 460 (G460W) of the alpha-adducin protein to be associated with essential hypertension in European populations. We examined whether the tryptophan allele is associated with hypertension in a different population, comprised of subjects of Chinese origin from Taiwan, and Chinese and Japanese origin from the San Francisco Bay area and Hawaii. We adapted the 5' allelic discrimination assay or TaqMan to type individuals for the G460W polymorphism, and using this method we typed more than 1000 individuals. The frequency of the W allele was slightly increased in the treated subjects in the Chinese population (0.458 v 0.423) but not the Japanese population (0.549 v 0.558). We considered dominant, recessive, and additive models in our analysis. There was a significant result for a recessive model for systolic blood pressure in the Chinese population (chi2 6.84, df = 2, P < .05), but only suggestive evidence for diastolic blood pressure (chi2 3.30). In contrast, in the Japanese population, there was no evidence for a positive association under any model. For the combined Chinese and Japanese samples, the evidence for association with alpha-adducin was not significant.

Measuring contributions to the research mission of medical schools

The authors of this article, who were the members and staff of a research panel formed by the AAMC as part of its mission-based management initiative, reflect on the growing interest in quantitative information in the management of the research mission of medical schools. They note the serious limitations of any such system of measures for research, particularly its inability to represent directly the quality of the research effort. Despite these concerns, the authors acknowledge that leaders in academic medicine have always used quantitative measures in one form or another to compare performance or assess progress. Two factors appear to be driving increases in this practice: (1) the need to demonstrate to institutional stakeholders that resources are being used wisely and that the school's performance justifies continued investment in the research mission; and (2) the need to fashion an economic strategy to manage precious institutional resources, particularly research space. Given these realities, the authors offer guidelines for the proper development and use of measures to assess contributions by faculty, departments, and institutions to the research mission. They also comment on the measures most commonly used in four areas: grants and other revenue-generating activities; publications; faculty members' research reputation and contributions to the national research enterprise; and support to the general research mission of the school. The authors conclude that quantitative information can help institutional leaders in important management decisions. However, the potential for misuse is great. The key is always to regard this information as an aid to judgment, not a substitute for it.

Complete reversal of ischemic wall motion abnormalities by combined use of gene therapy with transmyocardial laser revascularization

INTRODUCTION

Transmyocardial laser revascularization is believed to induce an angiogenic response within ischemic myocardium. We evaluated transgene expression in the setting of transmyocardial laser revascularization and hypothesized that intramyocardial injection of plasmid DNA encoding the gene for vascular endothelial growth factor could enhance the revascularization achieved by transmyocardial laser revascularization, resulting in improved cardiac function.

METHODS

Ten Yorkshire pigs had carbon dioxide-transmyocardial laser revascularization or acupuncture sites with injections of an expression plasmid encoding the gene for beta-galactosidase with or without HVJ-liposomes. Three days after transduction, transgene expression was determined by enzyme-linked immunosorbent assay. Six weeks after placement of a constrictor on the left circumflex artery, 29 pigs were randomized to ischemic controls (n = 5), transmyocardial laser revascularization (n = 4), transmyocardial laser revascularization with expression plasmid beta-galactosidase injections (n = 5), expression plasmid-vascular endothelial growth factor injections (n = 4), or transmyocardial laser revascularization with expression plasmid-vascular endothelial growth factor (n = 5) and harvested 6 weeks after therapy. Six transmyocardial laser revascularization pigs had either expression plasmid beta-galactosidase or expression plasmid-vascular endothelial growth factor injections and were harvested at 2 weeks. Normal pigs (n = 5) were included for comparison. Left ventricular free wall motion was assessed by a cardiologist in a blinded manner.

RESULTS

Transgene expression did not vary significantly with or without HVJ-liposomes in transfected transmyocardial laser revascularization myocardium. However, expression was detected in 56 of 60 (93%) transmyocardial laser revascularization-transfected sites, but in only 10 of 20 (50%) non-transmyocardial laser revascularization sites (P < .001). All (5 of 5 hearts) of the transmyocardial laser revascularization-vascular endothelial growth factor treated hearts displayed no evidence of wall motion abnormalities. Only these hearts had a statistically significantly different rate of wall motion abnormality compared with ischemic controls (P = .004).

CONCLUSION

Transfection efficiency was improved with the use of transmyocardial laser revascularization. Wall motion abnormalities were completely reversed within 6 weeks after transmyocardial laser revascularization with the direct injection of an expression plasmid encoding vascular endothelial growth factor.

Resolved and unresolved issues in the prevention and treatment of coronary artery disease: a workshop consensus statement

Advances in cardiovascular research during the past two decades have resulted in an improved understanding of the chain of events that lead to end-stage coronary artery disease. These developments have been paralleled by therapeutic advances that now make it possible to intervene at virtually every stage in the development of advanced cardiac disease, from asymptomatic persons at risk of developing coronary atherosclerosis to patients with end-stage heart failure. By interrupting this chain of events, perhaps at multiple sites, it may be possible to prevent or slow the development of symptomatic heart disease and hopefully prolong life. Many opportunities exist for obtaining further information regarding the underlying pathophysiology, the fundamental mechanisms of action of interventions designed to prevent and/or treat the development of myocardial ischemia and cardiac failure and for effecting favorably the natural history of various forms of heart disease.

Acute thrombosis of a composite ascending aortic conduit containing a Bjork-Shiley valve during pregnancy: successful emergency cesarean section and operative repair

A 31-year-old female had an ascending aortic conduit with a Bjork-Shiley valve placed for an aortic dissection. A year later she became pregnant and was placed on heparin instead of coumadin therapy. She then developed a distal aortic dissection and was hospitalized for close medical monitoring of fetal status and maturity. At 33 weeks of gestation the aortic valve thrombosed, resulting in pulmonary edema and cardiac arrest. Emergency cesarean section and replacement of the aortic valve and ascending aortic conduit was successful in salvaging mother and child. Both are well at 2 years followup. The case illustrates the hazards of prosthetic valves in pregnant patients and cardiac surgery during pregnancy. These issues are reviewed along with the details leading to successful surgical management.

Renin synthesis by canine aortic smooth muscle cells in culture

Angiotensin-I generating activity has been detected in homogenates of arterial tissue but it remains unclear whether this enzymatic activity results from the presence of renin itself or from the action of other proteases such as cathepsin D. In an assay system employing anephric dog plasma as substrate and buffered to pH 7.4, we detected angiotensin-I generating activity in homogenates of canine aortic smooth muscle cells. This enzymatic activity was in large part inhibitable by renin-specific antisera raised to pure canine renal renin. Immunofluorescent study of cultured arterial smooth muscle cells was also performed using renin specific antiserum. Granular cytoplasmic immunofluorescence was detected when specific antirenin serum was used but not when preimmune serum was employed. The addition of pure canine renin to the renin antiserum during staining suppressed the granular immunofluorescence confirming the specificity of staining. Finally, biosynthetic radiolabelling studies were performed. Immunoprecipitation of newly synthesized proteins with antirenin serum and staphylococcal protein A followed by gel electrophoresis and autoradiography demonstrated the synthesis of an immunoreactive protein with the molecular weight of renin. Pretreatment of the antirenin serum with pure canine renin resulted in the disappearance of this immunoreactive protein band. Thus these studies provide multiple lines of evidence to indicate the in situ synthesis of renin by vascular smooth muscle cells.

Monoclonal antibodies binding renal renin

Somatic-cell fusion of normal antibody-producing spleen cells with cells from a plasmacytoma culture results in a culture of hybrid cells from which a monoclonal line may be selected. These lines are immortal and may be amplified as tumors in syngeneic animals to produce large quantities of antibodies characterized by molecular homogeneity. We report the application of this technique to the production of antibodies binding canine renin. Balb/c mice were immunized with pure canine renal renin and their spleen cells fused with the NS-1 myeloma line. In two separate fusions, nine clones of cells were isolated that bound canine renal renin but did not cross-react with a number of protein antigens tested. One of these antibodies cross-reacted with renins of several different species, including human renin. Binding inhibition studies carried out with one of these monoclonal antibodies demonstrated a dissociation constant for renin of 10(-7) M. These monoclonal antibodies have great potential in answering significant questions concerning the structure, biosynthesis, tissue localization, and physiologic actions of renin.

A trial of two strategies to modify the test-ordering behavior of medical residents

We studied two methods to reduce the ordering of laboratory and radiologic tests by medical residents in their first postgraduate year. Dividing the residents into three groups, we compared the effect of concurrent chart review and discussion in one group with the effect of a moderate financial incentive for limited ordering of tests in a second group. The third group of residents served as a concurrent control, and data on the testing patterns of residents at the same hospital during the year before the study provided a retrospective control.