Regulation of vascular proteoglycan synthesis by metabolic factors associated with diabetes.
BACKGROUND
Diabetes is associated with accelerated atherosclerosis, but the mechanisms responsible for this are not known. Proteoglycans have been shown to play a critical role in the initiation of atherosclerosis owing to their ability to bind and retain atherogenic lipoproteins in the artery wall. Proteoglycan structure and composition are altered in atherosclerotic lesions compared with adjacent normal regions of the artery wall, and this is exaggerated in diabetes. The purpose of this study was to determine if metabolic factors associated with diabetes lead to altered proteoglycan structure and composition.


METHODS
Vascular smooth muscle cells, endothelial cells, and macrophages were exposed to normal (5.6 mmol/L) or high (25 mmol/L) glucose levels, various insulin and free fatty acid levels, and the cytokines transforming growth factor beta (TGF-beta1) and platelet-derived growth factor, alone or in combination, and proteoglycan synthesis was determined.


RESULTS
Glucose concentrations, insulin, and free fatty acids did not alter proteoglycan synthesis, size, or relative distribution. The effect of TGF-beta to increase biglycan and versican synthesis, increase sulfate incorporation, and increase the size of the secreted proteoglycans was not altered by the ambient glucose level in the culture medium, nor did high glucose increase levels of active TGF-beta.


CONCLUSIONS
Vascular proteoglycan synthesis is not affected by metabolic factors associated with diabetes. We suggest that elevated TGF-beta levels in diabetes are responsible for the altered proteoglycan synthesis observed in diabetes.
Wilson
Patricia
P
Division of Endocrinology and Molecular Medicine, Department of Medicine, University of Kentucky, Lexington, KY 40536-0200, USA.
Drennon
Katherine
K
Tannock
Lisa R
LR
D000818:Animals; D002478:Cells, Cultured; D003920:Diabetes Mellitus / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D008254:Macaca nemestrina; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011509:Proteoglycans / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
D004338:Drug Combinations; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D011509:Proteoglycans; D053773:Transforming Growth Factor beta1; D005947:Glucose