Biochemical studies on glomerular basement membrane in human diabetic microangiopathy

Biochemical modifications of glomerular basement membrane (GBM) in diabetes mellitus have been investigated in human subjects. Amino acid analysis and electrophoretic study of unfractioned GBM from diabetic and non diabetic kidneys showed an increase in hydroxylysine, hydroxyproline and glycine and in the glycosylgalactosyl-hydroxylysine (G-G-H) content of diabetic GBM. A decrease in 1/2 cystine was also demonstrated in diabetes. Fractionation of GBM showed the increase in G-G-H observed on unfractioned GBM to reflect a quantitative increase of the "collagen" fraction in diabetes, the amino acid composition of this fraction remaining unchanged. The decrease in 1/2 cystine demonstrated on unfractioned GBM was located in the non collagenous fractions of this structure.