Abstract
Increasing evidence suggests thrombospondin-1 (TSP-1), a potent proatherogenic matricellular protein, as a putative link between hyperglycemia and atherosclerotic complications in diabetes. We previously reported that the micronutrient chromium picolinate (CrP), with long-standing cardiovascular benefits, inhibits TSP-1 expression in glucose-stimulated human aortic smooth muscle cells in vitro. Here, we investigated the atheroprotective action of orally administered CrP in type 1 diabetic apolipoprotein E-deficient (ApoE-/-) mice and elucidated the role of TSP-1 in this process. CrP decreased lipid burden and neointimal thickness in aortic root lesions of hyperglycemic ApoE-/- mice; also, smooth muscle cell (SMC), macrophage and leukocyte abundance was prevented coupled with reduced cell proliferation. Attenuated lesion progression was accompanied with inhibition of hyperglycemia-induced TSP-1 expression and reduced protein O-glycosylation following CrP treatment; also, PCNA and vimentin (SMC synthetic marker) expression were reduced while SM-MHC (SMC contractile marker) levels were increased. To confirm a direct role of TSP-1 in diabetic atherosclerosis, hyperglycemic TSP-1-/-/ApoE-/- double knockout mice were compared with age-matched hyperglycemic ApoE-/- littermates. Lack of TSP-1 prevented lesion formation in hyperglycemic ApoE-/- mice, mimicking the atheroprotective phenotype of CrP-treated mice. These results suggest that therapeutic TSP-1 inhibition may have important atheroprotective potential in diabetic vascular disease.