Increased Collagen Cross-Linkages in Experimental Diabetes: Reversal by β-Aminopropionitrile and D-Penicillamine

Abstract

The effects of diabetes on collagen cross-link formation and solubility were investigated in granulation tissue collagen induced by polyester fabric implanted subcutaneously in rats at the same time diabetes was produced by injection of streptozotocin. Thus, all the collagen analyzed was formed in a diabetic milieu. Ten days later the implants were removed and the total collagen content as well as the fraction soluble in 0.5 M acetic acid was determined. Predominantly type I collagen accumulated in the implants. Total collagen content was the same in diabetics and controls; however, the acid-soluble fraction in diabetic animals was only half that of controls (8.5% and 17.7%, respectively), and the ratio of beta chains to alpha chains in the acid-soluble fraction was higher in diabetics (0.89) than in controls (0.69). In animals treated with beta-aminopropionitrile or D-penicillamine the acid-soluble fraction of collagen from diabetics equaled that from controls. These observations indicate that both intramolecular and intermolecular cross-links are increased in type I collagen from diabetic animals. Since these cross-links interfere with degradation of collagen by collagenase, they may contribute to accelerated intimal sclerosis of arteries and to capillary basement membrane thickening in diabetes.

Galactose ingestion increases vascular permeability and collagen solubility in normal male rats.

“…The finding that collagen solubility was increased in new granulation tissue ofgalactose-fed rats sharply contrasts with the marked decrease observed in diabetic rats (28,29,31). On the other hand, net collagen accumulation is not affected by galactose ingestion or by diabetes (28, 29, 31).…”

“…Group I (controls) was fed ground rat chow mixed with equal parts by weight ofdextrin; group II was fed ground chow containing 10% (by weight) galactose; group III was fed 25% galactose; and group IV 50% galactose mixed with ground chow. The day before initiation of the diet, sterile preweighed polyester fabric was implanted subcutaneously over the dorsolateral aspect of the thigh, as described in previous publications (27,31), to induce angiogenesis and new granulation tissue formation. 3 wk later, '251-albumin permeation, collagen crosslinking, and levels ofpolyols and myo-inositol were assessed in the new granulation tissue.…”

“…Because solubility ofcollagen in neutral salt solutions and dilute acids is inversely related to the extent of intermolecular crosslinks (33), we have quantified collagen solubility in 0.5 M acetic acid as an index of collagen crosslinking (31). The implant tissue is first finely minced with scissors and a razor blade, and extracted with 0.15 M NaCl in 50 mM Tris (at neutral pH) at 4VC for 4-6 h to wash out plasma proteins and other soluble noncollagenous proteins.…”

“…We have recently reported that diabetes-induced increased vascular permeability and polyol levels in new tissue formed in diabetic rats (27) are prevented by castration (27) and by an inhibitor of aldose reductase (29,30). Diabetes-induced increases in collagen crosslinking, which appear to be mediated by lysyl oxidase (31), were prevented by castration (which did not affect plasma glucose levels) but were unaffected by the aldose reductase inhibitor.…”

Effects of age and diabetes mellitus on the solubility and nonenzymatic glucosylation of human skin collagen.

“…Two of the three JOD had less acid-soluble collagen compared with comparably aged nondiabetics. A similar decrease in the proportion of acid-soluble collagen extracted from dermal granulation tissue of streptozotocin-induced diabetic rats has been recently reported (31). The effect of diabetes on the reduced solubility of diabetic collagen was reversed by treatment ofthe diabetic rats with inhibitors oflysyl oxidase-dependent covalent cross-linking of collagen (31).…”