Changes in the cross-linking of collagen from rat tail tendons due to diabetes.
The acid solubility of Type I collagen from rat tail tendons decreases due to diabetes. This finding has been taken as evidence that collagen from diabetics may be more cross-linked than normal. We compared CNBr peptide maps prepared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for [3H] NaBH4-reduced tail tendons from streptozotocin-diabetic rats with maps from age-matched control rats. At least through 30 weeks of diabetes, the distribution of mass of both cross-linked and uncross-linked CNBr peptides was identical in diabetic and control tendons. Therefore, the number of cross-linked peptides did not increase due to diabetes. We analyzed the 3H-cross-linking compounds present on the CNBr peptides and found that the 3H content of peptides cross-linked in control tendons through the bivalent, reduced cross-links hydroxylysinonorleucine and lysinonorleucine was diminished on corresponding peptides from diabetic tendons as a function of duration of diabetes. The cross-linked peptides, however, persisted. Therefore, we conclude that a larger fraction of these bivalent cross-links is found in an unknown, non-reducible form in tendons from diabetic compared with control rats. This resembles a phenomenon normally associated with maturation and/or aging where the non-reducible form of the cross-links is acid-stable. An increase in the fraction of the cross-links that is non-reducible and acid-stable would explain, at least in part, the decrease in acid solubility of the collagen. Non-enzymatic glycation (NEG) was not very specific, since most CNBr peptides bound some glucose. However, peptides from the alpha 2-chain seemed to be preferential targets for NEG. While NEG clearly increased due to diabetes, we found no evidence that increased NEG led to an increased number of cross-links in tail tendon collagen from streptozotocin diabetic rats.
Brennan
M
M
Department of Fine Structure, Boston Biomedical Research Institute, Massachusetts 02114.
D000818:Animals; D003432:Cross-Linking Reagents; D003488:Cyanogen Bromide; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D051381:Rats; D011916:Rats, Inbred F344; D012995:Solubility; D013623:Tail; D013710:Tendons / Q000378:metabolism*
D003432:Cross-Linking Reagents; D010446:Peptide Fragments; D003488:Cyanogen Bromide