[Methods of biochemical diagnosis of connective tissue involvement in diabetes]

During the course of diabetes mellitus, several lines of evidence demonstrate that connective matrix is involved. This relationship is still ambiguous and the biological techniques of study are more related to research than to routine. Skin biopsy followed by cultivation of the fibroblasts permits to demonstrate that the diabetic cells divide more slowly than the normal ones. The collagens of the diabetic patients do not seem to be modified according to any genetical abnormality. The evaluation of serum collagens and procollagens by radioimmunological techniques recently showed that the type IV collagen, which derivates from basement membranes, should be in increased amount. In the case of experimental diabetes, in animals, the skin collagen concentration is decreased whereas the amount of intermediate degradation products increases. The method of skin collagen evaluation is not used for clinical purposes and the degradation products found in human diabetic urine are not in increased amounts. The thickening of basement membrane is a well established phenomenon in the diabetes mellitus patients, but the chemical nature of the lesions is not well understood. A non-enzymatic hyperglycosylation of collagen and the other molecules of the basement membrane is possible but does not explain completely this thickening on a quantitative basis, inasmuch that hemoglobin glycosylation, that serves as a model for all the nonenzymatic glycosylations, is presently under discussion as regards its mechanism and seems more complicated than previously suggested.(ABSTRACT TRUNCATED AT 250 WORDS)