Heart disease in type 2 diabetes mellitus (T2DM) is directly related to the severity of coronary artery disease (CAD), which results in impaired coronary flow and increased risk of myocardial infarction (MI). This poses a very significant health and economic burden in the U.S. and worldwide since cardiovascular disease is the leading cause or mortality in T2DM, accounting for >65% of all deaths in diabetic patients. Moreover, diabetic patients are 2-4 times more likely to experience MI than non-diabetic patients. While atherosclerosis and endothelial dysfunction are known contributors to MI, the relative contribution of coronary resistance microvessel (CRM) remodeling versus macrovessel (conduit artery) remodeling to T2DM-induced cardiac disease remains largely unknown. We previously showed that CRMs isolated from either T2DM db/db mice or the pre-clinical Ossabaw porcine model of MetS undergo inward hypertrophic remodeling associated with reduced stiffness (novel and anti-dogmatic) in the face of increased macrovascular stiffness (dogmatic). CRM remodeling was accompanied by reduced coronary blood flow and was partially dependent upon vascular smooth muscle cell (VSMC) proliferation, increased expression of elastic extracellular matrix (ECM), and decreased expression of focal adhesion/cytoskeletal proteins. In contrast, focal adhesion/cytoskeletal and ECM protein expression were increased in macrovessels of T2DM db/db mice. These findings point to an intimate interaction between cellular stiffness and the ECM in macro- and coronary micro-vessels that dictates overall vascular stiffness in T2DM. We also observed that CRM VSMCs exhibit a proliferative phenotype that is associated with enhanced signaling by the advanced glycation end products (AGE)/RAGE pathway and decreased expression of cysteine rich-protein 2 (CRP2), which is a negative regulator of VSMC proliferation. There are currently no studies that have directly investigated the effect of stiffness on T2DM VSMC phenotype. Based on my preliminary data, a less stiff CRM wall promotes an in vivo proliferative VSMC phenotype, while the stiffer aortic (macrovascular) wall favors a synthetic VSMC phenotype. These data demonstrate that mechanisms underlying CRM remodeling are fundamentally different from those that regulate macrovascular remodeling and may represent pathologic mechanisms dictating VSMC phenotype, contributing to diabetic MI. Thus, my overall hypothesis is that alterations in macro- and coronary micro-vascular remodeling and stiffness reflect differential contributions of cellular and ECM stiffness that controls VSMC phenotype and may be dictated in part by AGE/RAGE and/or CRP2. The studies outlined in this proposal will investigate these mechanisms comprehensively utilizing a novel decellularization technique in aorta and CRMs, primary VSMC cultures, isolated coronary resistance microvessels, and in vivo analysis of vascular remodeling and blood flow in diabetic mice. During the mentored phase, we will determine the relative contribution of both the ECM and VSMCs to overall vascular stiffness further assess whether stiffness can modulate classical VSMC phenotypes in both macro-vessels and CRMs. The mentored studies will focus heavily on determining the cellular and biomechanical mechanisms underlying these alterations in primary VSMC cultures. During the independent phase, I will determine whether the interplay of stiffness, AGE/RAGE, and CRP2 modulates the phenotype of VSMCs isolated from both diabetic mice and pre-clinical pigs with MetS. Finally, I will evaluate the therapeutic potential of a novel RAGE antagonist, FPS-ZM1, in reducing adverse vascular remodeling in T2DM mice. This transition award will allow me access to additional mentoring necessary for future success as a competitive and successful independent investigator. This proposal includes a comprehensive training plan that will be overseen by members of a mentoring committee with expertise that encompasses vascular signaling and biomechanics, extracellular matrix, and coronary complications of diabetes and metabolic syndrome. Once complete, I will have gained additional expertise in hypothesis generation, experimental design, and data interpretation related to in vitro cellular signaling, vascular mechanics, ECM, and the coronary circulation that will enhance my already sound expertise in ex vivo and in vivo physiology. It will further provide a solid foundation for future studies in which I would like to investigate (1) the role of endothelial cells in adverse vascular remodeling in T2DM, and (2) the dynamic cross-talk between the coronary circulation and the diabetic heart, since the coronary circulation lies within a complex tissue that exhibits signs of diastolic dysfunction in metabolic conditions such as diabetes and metabolic syndrome. I am committed to maintaining extramural funding from sources such as the NIH to maintain an independent laboratory and training environment, while continuing to make inroads in the cardiovascular complications of metabolic diseases. My past performance is a testament to my excellent technical skills, problem-solving skills, work ethic, and drive that will collectively make me well poised for success.
Cardiovascular disease is the leading cause of death in type 2 diabetic patients, which is directly associated with the degree of coronary artery disease (CAD). CAD is characterized by impaired function, hardening of large arteries (atherosclerosis), and a narrowing of very small coronary blood vessels, which leads to increased heart attacks. While impaired coronary function and hardening of the arteries have been well studied, the impact of small coronary blood vessel versus large coronary artery remodeling to diabetes- and metabolic syndrome-induced heart disease remains unknown. New information about these processes may identify new treatments for diabetic and metabolic syndrome CAD.
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