Apolipoprotein C-II deficiency

ApoB-containing lipoproteins regulate angiogenesis by modulating expression of VEGF receptor 1

Despite the clear major contribution of hyperlipidemia to the prevalence of cardiovascular disease in the developed world, the direct effects of lipoproteins on endothelial cells have remained obscure and are under debate. Here we report a previously uncharacterized mechanism of vessel growth modulation by lipoprotein availability. Using a genetic screen for vascular defects in zebrafish, we initially identified a mutation, stalactite (stl), in the gene encoding microsomal triglyceride transfer protein (mtp), which is involved in the biosynthesis of apolipoprotein B (ApoB)-containing lipoproteins. By manipulating lipoprotein concentrations in zebrafish, we found that ApoB negatively regulates angiogenesis and that it is the ApoB protein particle, rather than lipid moieties within ApoB-containing lipoproteins, that is primarily responsible for this effect. Mechanistically, we identified downregulation of vascular endothelial growth factor receptor 1 (VEGFR1), which acts as a decoy receptor for VEGF, as a key mediator of the endothelial response to lipoproteins, and we observed VEGFR1 downregulation in hyperlipidemic mice. These findings may open new avenues for the treatment of lipoprotein-related vascular disorders.

A neonatal case of apolipoprotein C-II deficiency

A neonatal case of apo C-II deficiency with hypertriglyceridaemia and xanthomas is presented. The patient responded well to a special diet formula containing medium-chain triglycerides (MCT). This is the first case of apo C-II deficiency to be discovered during the neonatal period.

Apolipoprotein CIISt. Michael. Familial apolipoprotein CII deficiency associated with premature vascular disease

A 60-yr-old woman and her brother, products of a consanquinous mating, were chylomicronemic. The chylomicronemia in both subjects was found to be due to the absence of functional apoCII. A mutant form, designated apoCIISt. Michael (apoCIIs), was identified by two-dimensional electrophoresis and Western blot using anti-apoCII antiserum. The isoelectric point of apoCIIs was similar to that of normal apoCII, but its apparent molecular weight was 3,000 greater. Tryptic peptides of apoCIIs were identified that had retention times in reverse-phase high pressure liquid chromatography and amino acid compositions indistinguishable from that of residues 1 to 48 and 51 to 55 of normal apoCII. The complete sequence of apoCIIs was deduced from a combination of the sequence analysis of tryptic peptides corresponding to residues 56 through 96 and the known sequence of the apoCII gene. ApoCIIs differed from apoCII at residue 70 where Gln70 was replaced by Pro70 and the sequence terminated with Pro96. This is consistent with a base insertion in the codon for Asp69 or Gln70 in the apoCII gene and a subsequent translation reading frame shift. Both patients were homozygous for apoE-4. This and the absence of normal apoCII is consistent with homozygozity at the apoE-CII gene locus on chromosome 19. Both siblings and several relatives had premature ischemic vascular disease, in contrast with its apparent absence in other apoCII-deficient families.