Endothelial heparanase secretion after acute hypoinsulinemia is regulated by glucose and fatty acid.
Following diabetes, the heart increases its lipoprotein lipase (LPL) at the coronary lumen by transferring LPL from the cardiomyocyte to the endothelial lumen. We examined how hyperglycemia controls secretion of heparanase, the enzyme that cleaves myocyte heparan sulphate proteoglycan to initiate this movement. Diazoxide (DZ) was used to decrease serum insulin and generate hyperglycemia. A modified Langendorff technique was used to separate coronary from interstitial effluent, which were assayed for heparanase and LPL. Within 30 min of DZ, interstitial heparanase increased, an effect that closely mirrored an augmentation in interstitial LPL. Endothelial cells were incubated with palmitic acid (PA) or glucose, and heparanase secretion was determined. PA increased intracellular heparanase, with no effect on secretion of this enzyme. Unlike PA, glucose dose-dependently lowered endothelial intracellular heparanase, which was strongly associated with increased heparanase activity in the incubation medium. Preincubation with cytochalasin D or nocodazole prevented the high glucose-induced depletion of intracellular heparanase. Our data suggest that following hyperglycemia, translocation of LPL from the cardiomyocyte cell surface to the apical side of endothelial cells is dependent on the ability of the fatty acid to increase endothelial intracellular heparanase followed by rapid secretion of this enzyme by glucose, which requires an intact microtubule and actin cytoskeleton.
Wang
Fang
F
Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The Univ. of British Columbia, 2146 East Mall, Vancouver, BC, Canada V6T 1Z3. rodrigue@interchange.ubc.ca
Kim
Min Suk
MS
Puthanveetil
Prasanth
P
Kewalramani
Girish
G
Deppe
Sylvia
S
Ghosh
Sanjoy
S
Abrahani
Ashraf
A
Rodrigues
Brian
B
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects; D003981:Diazoxide; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005227:Fatty Acids / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D005966:Glucuronidase / Q000378:metabolism*; D006943:Hyperglycemia / Q000139:chemically induced / Q000378:metabolism*; D007328:Insulin / Q000097:blood*; D008071:Lipoprotein Lipase / Q000378:metabolism; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D019308:Palmitic Acid / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D050257:Tubulin Modulators / Q000494:pharmacology; D000099175:Heparanase
D015638:Cytochalasin D; D003981:Diazoxide; D004791:Enzyme Inhibitors; D005227:Fatty Acids; D005947:Glucose; D005966:Glucuronidase; D007328:Insulin; D008071:Lipoprotein Lipase; D015739:Nocodazole; D019308:Palmitic Acid; D050257:Tubulin Modulators; D000099175:Heparanase