PLASMA-LIPOPROTEIN COMPOSITION, APOLIPOPROTEIN(A) CONCENTRATION AND ISOFORMS IN BETA-THALASSEMIA

Patients with homozygous beta-thalassemia show an abnormal lipoprotein profile. In asymptomatic heterozygotes the lipid pattern is less mark edly affected but interestingly related to a diminished cardiovascular risk. The extent and significance of these findings are still a matte r of debate and no data are available on lipoprotein(a) plasma levels. Seventy patients with homozygous beta-thalassemia (HT-P), 70 beta-tha lassemia trait carriers (TT-C) and 70 sex and age-matched controls wer e investigated and their plasma lipoprotein profile and apo(a) phenoty pes determined. In a subgroup of these same subjects (12 HT-P, 12 TT-C and 24 controls) and in 12 bone marrow-transplanted homozygous beta-t halassemic patients (BMT-P) plasma lipoprotein composition was assesse d. HT-P disclosed significantly lower total-cholesterol, LDL-cholester ol, HDL-cholesterol, apo A-I, apo B plasma levels and higher triglycer ide concentration than TT-C (-7, -11, -8, -8, -13 and +11%, respective ly) or controls (-39, -50, -46, -32, -30 and +35%, respectively). All lipoprotein subclasses were triglyceride-enriched, while LDLs were als o protein-enriched and HDLs protein-depleted. TT-C disclosed a small b ut significant reduction in apo A-I and apo B plasma levels but only m inor lipoprotein abnormalities with respect to the controls. BMT-P lip oprotein composition was intermediate between HT-P and normal subjects . Apo(a) plasma levels did not differ among the groups. A higher preva lence of 'small' apo(a) isoforms was present in HT-P. Within the same 'isoform group', apo(a) plasma levels were significantly lower in HT-P than in TT-C or controls. Since liver cirrhosis is almost always pres ent in HT-P, it is conceivable that an altered hepatic apo(a) synthesi s or catabolism due perhaps to diminished apolipoprotein glycation may be involved. In TT-C a partially improved cardiovascular risk profile was apparent (low hematocrit, low LDL-cholesterol and apo B), thus ju stifying the claim for a low prevalence of ischemic heart disease, but no Lp(a) plasma level modification could be detected. (C) 1997 Elsevi er Science Ireland Ltd.