Oleate and linoleate enhance the growth-promoting effects of insulin-like growth factor-I through a phospholipase D-dependent pathway in arterial smooth muscle cells.
Diabetes causes accelerated atherosclerosis and subsequent cardiovascular disease through mechanisms that are poorly understood. We have previously shown, using a porcine model of diabetes-accelerated atherosclerosis, that diabetes leads to an increased accumulation and proliferation of arterial smooth muscle cells in atherosclerotic lesions and that this is associated with elevated levels of plasma triglycerides. We therefore used the same model to investigate the mechanism whereby diabetes may stimulate smooth muscle cell proliferation. We show that lesions from diabetic pigs fed a cholesterol-rich diet contain abundant insulin-like growth factor-I (IGF-I), in contrast to lesions from non-diabetic pigs. Furthermore, two fatty acids common in triglycerides, oleate and linoleate, enhance the growth-promoting effects of IGF-I in smooth muscle cells isolated from these animals. These fatty acids accumulate predominantly in the membrane phospholipid pool; oleate accumulates preferentially in phosphatidylcholine and phosphatidylethanolamine, whereas linoleate is found mainly in phosphatidylethanolamine. The growth-promoting effects of oleate and linoleate depend on phospholipid hydrolysis by phospholipase D and subsequent generation of diacylglycerol. Thus, concurrent increases in levels of IGF-I and triglyceride-derived oleate and linoleate in lesions may contribute to accumulation and proliferation of smooth muscle cells and lesion progression in diabetes-accelerated atherosclerosis.
Askari
Bardia
B
Department of Pathology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
Carroll
Mairead A
MA
Capparelli
Maria
M
Kramer
Farah
F
Gerrity
Ross G
RG
Bornfeldt
Karin E
KE
D000818:Animals; D001158:Arteries / Q000166:cytology*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental; D004730:Endothelium, Vascular / Q000166:cytology*; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D019787:Linoleic Acid / Q000494:pharmacology*; D008041:Linoleic Acids / Q000378:metabolism; D050356:Lipid Metabolism; D008954:Models, Biological; D009130:Muscle, Smooth / Q000166:cytology*; D019301:Oleic Acid / Q000494:pharmacology*; D010739:Phospholipase D / Q000378:metabolism*; D010766:Phosphorylation; D013552:Swine; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
D008041:Linoleic Acids; D014280:Triglycerides; D019301:Oleic Acid; C024348:13-hydroxy-9,11-octadecadienoic acid; D007334:Insulin-Like Growth Factor I; D004247:DNA; D019787:Linoleic Acid; D010739:Phospholipase D; D013936:Thymidine