THBS1 and atherosclerosis: Several mechanisms of action have been implicated in the potential antiatherosclerotic effects of vitamin D, including a downregulation of the renin-angiotensin system, and a reduced expression of mRNA and protein levels of plasminogen activator inhibitor-1 (PAI-1) and thrombospondin-1 (THBS1) which are known to be involved in the development of atherosclerosis [35, 36].