Disturbances in Glomerular Basement Membrane Glycosaminoglycans in Experimental Diabetes

Abstract

Glycosaminoglycans (GAGs) were purified from basement membranes isolated from glomeruli of control and streptozocin-induced diabetic rats and were quantitatively analyzed with a recently described competitive binding assay that is specific for and sensitive to microgram amounts of chondroitin and heparan sulfate. Total GAG content in glomeruli from diabetic rats and in the basement membranes prepared from these samples (17.22 +/- 1.45 and 6.56 +/- 0.49 micrograms/10(5) glomeruli, respectively was significantly less than that found in comparable control preparations (43.71 +/- 3.35 and 16.05 +/- 1.41 micrograms/10(5) glomeruli, respectively). The portion of total GAG in the water-soluble fraction recovered after osmotic lysis of isolated glomeruli was also markedly decreased in diabetic samples (26.11 +/- 4.55 vs. 3.30 +/- 0.32 micrograms/10(5) glomeruli, control vs. diabetic). Treatment of lysed glomeruli with the ionic detergent deoxycholate, required for liberation of the extracellular matrix from plasma membrane lipoproteins and purification of the insoluble glomerular basement membrane (GBM), resulted in solubilization of approximately 10% of the water-insoluble GAG in control samples but greater than 50% in diabetic membranes. Heparan sulfate comprised greater than 90% of the GAGs in both control and diabetic GBM, defined as the water- and detergent-insoluble matrix. The findings clearly demonstrate that the GAG content of GBM is diminished in experimental diabetes and provide evidence that the reduction in GBM anionic sites associated with diabetes derives from a decrease in the constituent GAGs of this extracellular matrix. The results further suggest that the interaction between GBM and populations of GAG associated with the surface of plasma membranes of adjacent cells is disturbed in diabetes.

Basement membrane abnormalities in diabetes mellitus: Relationship to clinical microangiopathy

“…The content of heparan sulfate proteoglycans, and the extent to which they are sulfated, are reported to be decreased in glomerular basement membranes isolated from human diabetic^'^^,"^ and diabetic rats. 278 Shimomura and SpiroZ6 reported that the heparan sulfate proteoglycan content of glomerular basement membrane isolated from diabetic humans was reduced by 70%. Several investigators have reported that incorporation of [35S] sulfate into glomerular basement membrane proteoglycans is decreased during in vitro incubation of isolated glomeruli from diabetic rats .21,43,129 Coh en and S~r m a~~ were unable to demonstrate any effect of insulin or glucose levels on 35S incorporation.…”

Charge Selectivity of Proteinuria in Type I Diabetes Explored by Ig Subclass Clearance

“…A decrease in kidney fixed anionic charges is assumed to occur in diabetes mainly as a consequence of the decrease in sialic acid and heparan sulfate content (12)(13)(14)(15). Furthermore, nonenzymic glycosylation may modify the net charge of both circulating and tissue proteins at all levels of the kidney filter (16)(17)(18).…”

Reduced negative surface charge on arterial endothelium of diabetic rats

“…Glycosoaminoglycans of the renal glomerular basement membrane contain anionic sites that regulate the charge-selective nature of the glomerular filtration barrier [7,8]. These glycosaminoglycans are reduced in glomeruli of diabetic rats which may account for the defective function in their glomerular filtration barrier [9]. The erythrocyte surface concentration of sialic residues and, therefore, their surface negative charge is also significantly lower in diabetic patients than in healthy subjects [10,11].…”