The perivascular Adipocyte: A Crooked Middleman In The Translation Of Metabolic challenge Into Early Vascular Dysfunction

Abstract

Cardiovascular disease is the leading cause of morbidity and mortality among diabetic patients. Although prolonger exposure to hyperglycemia is implicated in the pathogenesis of cardiovascular dysfunction, a significant proportion of patients display established diabetic microvascular complications at initial diagnosis of diabetes, before overt hyperglycemia. Moreover, recent studies from our laboratory have shown that cardiovascular dysfunction is evident in animal models of metabolic challenge before the onset of hyperglycemia and diabetes, thus placing the etiology of this early cardiovascular dysfunction in question.

Given the role of adipose tissue inflammation in the pathophysiology of metabolic syndrome, we hypothesized that interaction between perivascular adipose tissue and vascular smooth muscle cells may play a role in early cardiovascular dysfunction.

Phenotypic characteristics (migration, proliferation, metabolic activity, and protein marker expression) of primary aortic vascular smooth muscle cells (VSMCs) will be examined in control and prediabetic rats. The effect of exposure of control VSMCs to elevated insulin and free fatty acid (FFA) concentrations, mimicking the serum environment in prediabetic rats, will be assessed and compared to the observed phenotype of prediabetic VSMCs. To investigate the role of adipocytes in mediating VSMC dysfunction, 3T3-L1 cells will be differentiated to adipocyte-like cells and exposed to the above insulin and FFA treatment. The conditioned media from these cells will be used to treat control VSMCs to see if the prediabetic phenotype will be recapitulated. A human counterpart to this model will be used, as well, via the differentiation of human bone marrow mesenchymal stem cells into adipocyte-like cells, and challenging with insulin and FFAs. The conditioned medium will be used to treat human subcutaneous VSMCs, whose phenotype will be investigated. Control and challenged VSMC and adipocyte interaction with the immune system will be assessed through monocyte recruitment assays using THP-1. An attempt to resolve the identity and the effect of soluble mediators produced in the conditioned media will be made via western blotting and/or pharmacological blockers.

We expect that the metabolic challenge will alter VSMC phenotype indirectly via evoking pro-inflammatory changes in adipocytes. The latter, in turn, will produce soluble mediators that have direct effects on VSMCs.