Lipoprotein(a) levels and apolipoprotein(a) polymorphism in type 1 diabetes mellitus: relationships to microvascular and neurological complications

To investigate plasma concentrations of lipoprotein(a) [Lp(a)] and apolipoprotein(a) [apo(a)] polymorphism in relation to the presence of microvascular and neurological complications in type I diabetes mellitus, 118 young diabetic patients and 127 age-matched controls were recruited. Lp(a) levels were higher in patients than in controls, but the apo(a) isoforms distribution did not differ between the two groups [higher prevalence of isoforms of high relative molecular mass (RMM) in both groups]. Microalbuminuric patients had Lp(a) levels significantly greater than normoalbuminuric patients, and normoalbuminuric patients showed higher Lp(a) levels than controls. Patients with retinopathy or neuropathy showed similar Lp(a) levels to those without retinopathy or neuropathy. No differences in apo(a) isoforms frequencies were observed between subgroups with and without complications (higher prevalence of isoforms of high RMM in every subgroup). However, among patients with retinopathy, those with proliferative retinopathy had higher Lp(a) levels and a different apo(a) isoforms distribution (higher prevalence of isoforms of low RMM) than those with non-proliferative and background retinopathy (higher prevalence of isoforms of high RMM). Our data suggest that young type 1 diabetic patients without microalbuminuria have Lp(a) levels higher than healthy subjects of the same age. Lp(a) levels are further increased in microalbuminuric patients. High Lp(a) levels and apo(a) isoforms of low RMM seem to be associated with the presence of proliferative retinopathy, but have no relation to neuropathy.