The risk factors that contribute to the development of vascular disease in diabetes are not fully defined. The overall objective of this proposal is to elucidate the cellular and molecular interactions between lipoproteins and connective tissue growth factor (CTGF) and their contributions to the development of vascular disease in type 1 diabetes, and to elucidate the underlying mechanisms involved in this process. Our findings in type 1 diabetic patients, demonstrate for the first time, an association between CTGF and vascular disease risk factors such as, hypertension, microalbuminuria and elevated lipids. In addition, we identified a novel polymorphism in the promoter region of the CTGF gene that associates with increased albuminuria. The relative risk to develop microalbuminuria in patients with the polymorphism is 3 times higher than patients without the polymorphism. At a cellular level, our data demonstrates that the expression of CTGF and collagens I and IV in human aortic endothelial cells and mesangial cells are induced by low density lipoproteins (LDL). This LDL-induced increase in CTGF and collagens was mediated via autocrine activation of TGF-P and members of the MARK pathway. In addition, stimulation of the MARK pathway by LDL is mediated via activation of sphingosine kinase. We hypothesize that in diabetes, increased levels of abnormal or modified lipoproteins leads to the induction of CTGF, which in turn plays a pivotal role in the initiation and progression of diabetic vascular complications.
Our specific aims are:1) Define the role and contribution of CTGF to the initiation and progression of vascular and renal disease in the DCCT/EDIC cohort of type 1 diabetic patients. We hypothesize that increases in the levels of CTGF leads to the development of diabetic vascular and renal disease. This will be demonstrated by determining whether type 1 diabetic patients who develop renal and vascular disease have prior increases in the levels of CTGF compared with type 1 diabetic patients who do not develop renal and vascular disease. 2) Elucidating the mechanisms through which lipoproteins modulate the production of biomarkers of vascular complications. We hypothesize that the cellular actions of lipoproteins to promote sclerosis of vascular and renal cells are mediated via increased expression of CTGF. The proposed studies bridge both clinical and basic research aimed at defining the risk factors and mechanisms of macrovascular disease in diabetes.
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