Fatty acids modulate protein kinase C activation in porcine vascular smooth muscle cells independently of their effect on de novo diacylglycerol synthesis.
OBJECTIVE
Diabetes-induced activation of protein kinase C has been associated with the development of vascular complications. Elevated de novo diacylglycerol synthesis has been postulated to underlie this protein kinase C activation. Diabetes also increases the circulating concentrations of non-esterified fatty acids, which are immediate precursors of diacylglycerol through the de novo pathway. We hypothesized that increased fatty acids contribute to de novo diacylglycerol synthesis and activation of protein kinase C in vascular cells.


METHODS
Primary cultures of porcine carotid smooth muscle cells were exposed to fatty acids, bound to albumin in physiologic ratios. Diacylglycerol and triacylglycerol were measured in extracts of these cells. Protein kinase C activation was measured as membrane translocation with isoform-specific antibodies.


RESULTS
Saturated fatty acids caused considerable accumulation of diacylglycerol through de novo synthesis. Unsaturated fatty acids increased triacylglycerol, but not diacylglycerol. Platelet-derived growth factor activated the alpha, epsilon and zeta protein kinase C isoforms. Activation of the alpha and zeta isoforms was amplified by oleate pretreatment but inhibited by palmitate. In the absence of growth factor stimulation, neither palmitate nor oleate had any effect on the membrane/cytosol distribution of any protein kinase C isoform.


CONCLUSIONS
Saturated fatty acids elicited de novo diacylglycerol synthesis in vascular smooth muscle cells without activating protein kinase C. Effects of fatty acids on protein kinase C activation by platelet-derived growth factor did not correlate with the effects on de novo diacylglycerol synthesis. These results indicate that de novo diacylglycerol synthesis is, by itself, insufficient to activate protein kinase C.
Lu
X
X
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, USA.
Yang
X Y
XY
Howard
R L
RL
Walsh
J P
JP
D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004075:Diglycerides / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000187:drug effects; D005227:Fatty Acids / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D019301:Oleic Acid / Q000494:pharmacology; D019308:Palmitic Acid / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D013552:Swine
D004075:Diglycerides; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D019301:Oleic Acid; D019308:Palmitic Acid; D011493:Protein Kinase C; C013102:margaric acid