A comparison of different methods of assessing free radical activity in type 2 diabetes and peripheral vascular disease.

Increased free radical activity in diabetes mellitus may contribute to the higher prevalence and mortality from macrovascular disease in diabetic patients. To investigate this, levels of plasma antioxidants (superoxide dismutase, caeruloplasmin, plasma, and lysate thiol), diene conjugates, lipid peroxides, and chemiluminescence were measured in diabetic and non-diabetic patients with peripheral vascular disease compared with healthy control subjects. Caeruloplasmin, diene conjugate ratio, and lipid peroxides were significantly increased in patients with vascular disease but there was no difference between diabetic and non-diabetic patients. Conjugated diene ratio correlated with caeruloplasmin (r = 0.40, p < 0.02) and inversely with superoxide dismutase level (r = 0.36, p < 0.05) but there was no significant correlation between other antioxidants and diene conjugates, lipid peroxides or chemiluminescence. The relationship between different indirect measurements of free radical activity is variable but there appears to be no additive effect of diabetes on the increased free radical activity associated with vascular disease.