PLASMA APOLIPOPROTEIN(A) CONCENTRATION AND ISOFORMS IN SEVERE DIABETIC-RETINOPATHY

mie previously showed that patients with long-standing insulin-depende nt diabetes mellitus (IDDM) and severe diabetic retinopathy, resulting from widespread capillary occlusion, have higher circulating levels o f Lipoprotein(a) [Lp(a)] than IDDM patients without retinopathy or non -diabetic controls. This study was aimed at: 1) confirming and extendi ng that preliminary observation and 2) establishing whether heterogene ous frequency of phenotypes distribution contributes to increase apoli poprotein(a) [Apo(a)] concentrations in these patients. We studied 114 patients with IDDM of more than 15 years duration, of which 56 had se vere retinopathy (proliferative and/or ischemic maculopathy) (SR) and 58 had no retinopathy(NR) and 60 non-diabetic control subjects(C). Hig her Apo(a) levels were confirmed in patients with retinopathy but no d ifference for the frequency of smaller Apo(a) isoforms was evident amo ng the groups studied. However, among individuals with small isoforms, SR patients had higher plasma Apo(a) concentrations than NR patients and C group (p<0.05 for both). There was no relationship between the a pparent molecular weight of Apo(a) isoforms and plasma Apo(a) concentr ations within the three groups. These results suggest that Apo(a) poli morphism is not an important genetic risk factor for severe diabetic r etinopathy. If increased plasma Lp(a) plays a role in the pathogenesis of this complication, non-genetic factors are likely to contribute.