Increased non-enzymatic glycosylation and reduced solubility of skin collagen in insulin-dependent diabetic patients.

Abstract

The solubility of skin collagen into acetic acid and by pepsin digestion and the degree of non-enzymatic glycosylation of collagen (ketoamine linkage) in these fractions was determined in skin specimens from 27 insulin-dependent diabetic subjects and from 17 age-matched controls. Glycosylation in acid soluble collagen specimen was significantly increased in the diabetics, 1.9 +/- 1.8 (SD)ng of hexose/micrograms of hydroxyproline in comparison to the controls. 0.9 +/- 0.8 ng of hexose/micrograms of hydroxyproline. No significant difference in this respect was noted in pepsin soluble collagen specimens. The solubility of collagen into acetic acid and by pepsin digestion were significantly reduced in the diabetics. No clear relationships between non-enzymatic glycosylation or collagen solubility and diabetic late complications (nephropathy, retinopathy or limited joint mobility) were noted. We suggest (a) that equilibrium levels of early glycosylation products are different in acid and pepsin soluble collagen specimens. (b) ketoamine linkage glycosylation products by themselves are not directly involved in diabetic late complications and (c) the solubility in acid and digestibility of collagen by pepsin may be an indicator, even though nonspecific, of increased amounts of advanced glycosylation end products.