Glucosaminyl N-deacetylase in cultured fibroblasts; comparison of patients with and without diabetic nephropathy, and identification of a possible mechanism for diabetes-induced N-deacetylase inhibition.
Impaired heparan sulphate biosynthesis through diabetes-induced inhibition of glucosaminyl N-deacetylase may have a central role in the development of diabetic nephropathy, and genetic differences in the vulnerability of the N-deacetylase could influence the risk of developing nephropathy. We studied N-deacetylase activity in fibroblast cultures from Type 1 (insulin-dependent) diabetic patients with (n = 14) or without (n = 13) diabetic nephropathy, together with non-diabetic control subjects (n = 7). No difference in N-deacetylase activity was found (p = 0.13), and no inhibition of N-deacetylase was found in cultures grown at 25 mmol/l glucose. N-deacetylase activity was inversely correlated to growth rate (r = -0.59, p = 0.0008), and in patients with nephropathy a negative correlation between HbA1C and fibroblast N-deacetylase activity (r = -0.72, p = 0.012) was found. Cell-cycle analysis revealed an increased fraction of S-phase cells in patients with nephropathy (28%(21-52%)) compared to healthy control subjects (17% (9-24%)), p = 0.0008, but not between patients with and without nephropathy (latter group 26%(11-43%)), p = 0.43. Forskolin, an activator of protein kinase A, specifically decreased N-deacetylase activity, whereas activation of protein kinase C produced a combined reduction in N-deacetylase activity and total protein synthesis. In conclusion, no constitutive defects in N-deacetylase activity were found in fibroblasts from these patients. Further studies should consider possible associations between fibroblast characteristics and pre-biopsy environmental parameters related to cellular memory phenomena. Finally, activation of protein kinase A provides a potential general pathway for regulating N-deacetylase activity.
Kofoed-Enevoldsen
A
A
Steno Diabetes Center, Gentofte, Denmark.
Petersen
J S
JS
Deckert
T
T
D000328:Adult; D000581:Amidohydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001706:Biopsy; D002453:Cell Cycle; D002455:Cell Division; D002478:Cells, Cultured; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology* / Q000473:pathology; D003928:Diabetic Nephropathies / Q000201:enzymology* / Q000473:pathology; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000473:pathology; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012867:Skin / Q000166:cytology / Q000201:enzymology* / Q000473:pathology
D000581:Amidohydrolases; C023079:N-acetylglucosamine deacetylase