Regulation of arterial phenotype by perivascular adipose tissue in cardiometabolic disease

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Obesity and metabolic disease are risk factors for cardiovascular diseases, and their increasing prevalence has led to increased rates of vascular pathology in our population. Adipocytes have functional specificity based on their molecular phenotype; white adipocytes store energy in the form of lipids (white adipose tissue), and thermogenic adipocytes burn calories and generate heat (beige and brown adipose tissue). Within the vascular microenvironment, blood vessels are surrounded by perivascular adipose tissue (PVAT) that impacts vascular function. In the mouse, PVAT surrounding the thoracic aorta are brown-like, with high levels of thermogenic markers, and a clear association with vascular reactivity and vascular disease progression. In humans, aortic PVAT appears similar to human subcutaneous white adipose tissue, with unilocular adipocytes displaying a lipid storage phenotype. However, we identified thermogenic markers within human aortic PVAT, and molecular differences are established between human PVAT from healthy versus diseased vasculature. The ability to increase the proportion of thermogenic versus white adipose tissue in the body has been suggested to be an anti-obesity therapeutic strategy, and increasing thermogenesis of PVAT is predicted to be protective against vascular disease. Thus, it is critical to understand molecular determinants of adipocyte thermogenesis in humans. In collaborative work, we recently defined novel lineages of thermogenic adipocytes that were functionally tested in mice. These lineages, interestingly, included a smooth muscle cell (SMC) like adipocyte lineage, which is relevant to PVAT, which is directly adjacent to the vessel wall. We hypothesize that the smooth muscle cell-like adipocyte lineage in human PVAT contributes directly to the thermogenic adipocyte lineage in humans, and that the functional activity of this lineage inversely correlates to vascular disease progression. This is a translational study with the following specific aims: Aim 1. Define the molecular identity of the adipocyte progenitor cells in human PVAT, and cellular PVAT composition in vascular pathology. We will perform molecular studies to identify sub-populations of adipocyte progenitors and overall cellular composition in human PVAT, and identify associations with clinical and physiological measures of health and disease. Aim 2. Identify the mechanisms driving functional capacity thermogenic adipocyte differentiation in human adipocyte progenitors, and impact on vascular smooth muscle cell physiology. Differentiation capacity will be tested in the fibroblast progenitor population and the SMC-like progenitor population, and paracrine signaling from adipocytes will be evaluated using human vascular SMC. Novel pathways identified from molecular studies will inform studies to determine drivers of thermogenic differentiation. Our results are expected to identify for the first time molecular signatures of PVAT corresponding to different vascular pathologies, and characterize critical adipocyte progenitor populations related to the differentiation of thermogenic adipocytes in human progenitor cells.