Because various fetal anomalies are seen in diabetic offspring, we examined the effects of sugars on proteoglycans (PGs): extracellular matrix (ECM) macromolecules modulating morphogenesis. 13-d-old mouse metanephric kidney explants were exposed to mannose for 7 d and labeled with [35S]sulfate, [35S]-methionine, or [3H]thymidine. Mannose exposure caused reduction in kidney size and disorganization of ureteric bud branches with inhibition of glomerulogenesis. Tissue autoradiographic and immunofluorescence studies indicated decreased expression of sulfated PGs in ECMs. Helix pomatia lectin binding to D-GalNAc residues of glomerular epithelial cells was also reduced. Biochemical studies revealed decreased synthesis of sulfated PGs. PGs were of lower molecular weight with reduced charge density and increased chondroitin/heparan sulfate ratio. Immunoprecipitation of [35S]methionine-labeled proteins confirmed the reduction of PG core peptides. Intracellular ATP levels were reduced. The addition of 0.1 mM ATP to culture media restored kidney size, the population of glomeruli, and the synthesis and characteristics of PGs to almost normal, with no detectable effect on the replication of cells as determined by [3H]thymidine incorporation. The effect of ATP could be partially blocked by the P2y-purinoreceptor, i.e., reactive blue-2. Data suggest that mannose causes energy depletion by cellular ATP consumption and thus selectively alters the synthesis of heavily glycosylated proteins with rapid turnover, such as PGs, resulting in renal dysmorphogenesis.
Z Z Liu, F A Carone, T M Dalecki, B Lelongt, E I Wallner, Y S Kanwar