EFFECTS OF HIGH GLUCOSE ON THE PRODUCTION OF HEPARAN-SULFATE PROTEOGLYCAN BY MESANGIAL AND EPITHELIAL-CELLS

Changes in heparan sulfate metabolism may be important in the pathogen esis of diabetic nephropathy. Recent studies performed on renal biopsi es from patients with diabetic nephropathy revealed a decrease in hepa ran sulfate glycosaminoglycan staining in the glomerular basement memb rane without changes in staining for heparan sulfate proteoglycan-core protein. To understand this phenomenon at the cellular level, we inve stigated the effect of high glucose conditions on the synthesis of hep aran sulfate proteoglycan by glomerular cells in vitro. Human adult me sangial and glomerular visceral epithelial cells were cultured under n ormal (5 mM) and high glucose (25 mM) conditions. Immunofluorescence p erformed on cells cultured in 25 mM glucose confirmed and extended the in vivo histological observations. Using metabolic labeling we observ ed an altered proteoglycan production under high glucose conditions, w ith predominantly a decrease in heparan sulfate compared to dermatan s ulfate or chondroitin sulfate proteoglycan. N-sulfalion analysis of he paran sulfate proteoglycan produced under high glucose conditions reve aled less di- and tetrasaccharides compared to larger oligosaccharides , indicating an altered sulfation pattern. Furthermore, with quantific ation of glomerular basement membrane heparan sulfate by ELISA, a sign ificant decrease was observed when mesangial and visceral epithelial c ells were cultured in high glucose conditions. We conclude that high g lucose concentration induces a significant alteration of heparan sulfa te production by mesangial cells and visceral epithelial cells. Change s in sulfation and changes in absolute quantities are both observed an d may explain the earlier in vivo observations. These changes may be o f importance for the altered integrity of the glomerular charge-depend ent filtration barrier and growth-factor matrix interactions in diabet ic nephropathy.