Increased activity of serum amine oxidases in granuloma annulare, necrobiosis lipoidica and diabetes

SUMMARY Serum monoamine oxidase, diamine oxidase and lysyl oxidase-like activity were measured in patients with granuloma annulare (GA), necrobiosis lipoidica (NL) and diabetes mellitus. In diabetes, all enzyme measurements were raised by a factor of about 2.2, and in NL by a factor of about 1.5. The rise in patients with GA was small and only significant in the case of benzylamine monoamine oxidase. ‘Stiff’ collagen would seem to link these three disorders and the present results suggest that these amine oxidases could be useful in monitoring collagen abnormality in diabetes and diabetes-associated disorders, particularly in the absence of chronic liver disease. A negative correlation was found between enzyme activity and blood glucose levels, thus collagen changes in these conditions may occur independently of elevated blood glucose levels. Possible involvement of these enzymes in angiopathy remains to be elucidated.