Abstract 428: Role of Thrombospondin-1 in Atherosclerotic Complications Associated With Metabolic Syndrome

Abstract

Atherosclerosis is the leading cause of increased morbidity and mortality in metabolic syndrome (MetS), a constellation of risk factors that include hyperglycemia and visceral obesity. Individuals with MetS have increased incidence of vascular smooth muscle cell (VSMC) migration and proliferation, a key characteristic of VSMC phenotypic transition. We previously reported that high glucose and high leptin, mimicking hyperglycemia and obesity, independently upregulate a potent proatherogenic matricellular protein, thrombospondin-1 (TSP-1), expression in VSMCs. The goal of the present study was to investigate the role of TSP-1 in development of atherosclerosis in MetS. We generated a mouse model of combined MetS and atherosclerosis ( KKAy +/- /ApoE -/- ) by crossing obese hyperglycemic agouti yellow KKAy +/- mice with atherosclerotic ApoE -/- mice. Upon weaning, yellow KKAy +/- /ApoE -/- mice and age-matched black KKAy -/- /ApoE -/- littermates were maintained on regular chow diet from 4-18 wks of age. Mice were euthanized after an overnight fasting; blood, aortae and heart were collected for lipid profiling, immunoblotting and atherosclerotic lesion studies. Yellow KKAy +/- /ApoE -/- mice showed significant increase in body weight, blood glucose and plasma lipid levels vs. black KKAy -/- /ApoE -/- littermates. Aortic root morphometry demonstrated increased lesion burden (Oil red O) and neointimal thickening (H & E) in MetS KKAy +/- /ApoE -/- vs. non-MetS KKAy -/- /ApoE -/- mice. Immunohistochemistry further revealed co-localization of α-SMA (SMC marker) and PCNA (proliferation marker) expression in aortic roots of KKAy +/- /ApoE -/- vs. KKAy -/- /ApoE -/- mice. Notably, lesion formation was associated with an increase in TSP-1 expression in aortic vessels. Consistently, TSP-1 and PCNA expression were elevated in aortic SMC (aSMC) primary cultures derived from obese diabetic KKAy +/- mice vs. lean non-diabetic KKAy -/- littermates. Finally, incubation of aSMC with a TSP-1 blocking peptide reduced PCNA and vimentin (SMC synthetic marker) expression coupled with attenuated SMC proliferation in obese diabetic KKAy +/- mice. Together, these results suggest a putative role of TSP-1 in accelerated atherosclerosis and VSMC phenotypic transition in MetS.