Characterization of glycosaminoglycans in urine from patients with nephrotic syndrome and control subjects, and their effects on lipoprotein lipase.

Previously we found that alpha 2-acid glycoprotein fraction from urine of patients with the nephrotic syndrome stimulated the lipoprotein lipase reaction in vivo and in vitro. The activator was separated from the alpha 1-acid glycoprotein and identified as a glycosaminoglycan. The studies reported here were undertaken to characterize and quantify the glycosaminoglycans contained in urine of patients with the nephrotic syndrome and to compare these to the glycosaminoglycans in urine of the control subjects. We found that free low molecular weight glycosaminoglycans, heparan sulfate and chondroitin 4-sulfate, are excreted in both patients with the nephrotic syndrome and controls however, patients with the nephrotic syndrome excreted much less of both glycosaminoglycans. The free form of heparan sulfate was found to be the activator which stimulated the lipoprotein lipase reaction in vitro in the presence of apolipoprotein CII. In addition, the urine from patients with the nephrotic syndrome contained a protein-glycosaminoglycan complex which was absent in control urine. Glycosaminoglycans in the complex could be released by papain digestion or by trichloroacetic acid. Our evidence indicates that this glycosaminoglycans fraction is a law charge form of chondroitin sulfate.