Apolipoprotein A-V (apoA-V) is a recently discovered apolipoprotein that appears to have a role in plasma triglyceride (TG) transport. We have developed an ELISA for apoA-V using monoclonal antibodies that has a lower limit of detection of 0.3 ng/ml and linearity up to 20 ng/ml. The ELISA was then used to quantify plasma apoA-V in 196 healthy subjects and 106 patients with insulin-resistant diabetes mellitus. In the healthy subjects, total apoA-V concentration was 179.2 ؎ 74.8 ng/ml, and it was greater in females than in males ( P Ͻ 0.005). It was correlated positively with the plasma HDL cholesterol ( r ‫؍‬ 0.32, P Ͻ 0.0001), apoA-I ( r ‫؍‬ 0.27, P ‫؍‬ 0.0001), and apoE ( r ‫؍‬ 0.18, P ‫؍‬ 0.011) concentrations and negatively with plasma TG concentration ( r ‫؍‬ ؊ 0.22, P ‫؍‬ 0.021). In relation to single nucleotide polymorphism 3 ( ؊ 1131C/T) of the apoA-V gene, apoA-V concentration was higher in the T/T type than in the C/C type ( P Ͻ 0.01). Plasma TG concentration was lower in the T/T type than in the C/C or C/T type ( P Ͻ 0.05). ApoA-V concentration was lower in the diabetic patients (69.4 ؎ 44.3 ng/ml; P Ͻ 0.01) than in the healthy controls. Plasma triglyceride (TG) levels are influenced by both genetic and environmental factors and are a major independent risk factor for coronary heart disease (1, 2). Plasma TG concentration is influenced by many factors. These include apolipoproteins A-I, A-IV, C-II, and C-III, LPL, LCAT, cholesteryl ester transfer protein, and phospholipid transfer protein (3-11). These factors and their associated gene-environment interactions are of importance in the pathogenesis of coronary heart disease.Apolipoprotein A-V (apoA-V) has recently been identified by comparative sequencing of human and mouse DNA and is located ‫ف‬ 27 kb distal to the apoA-IV gene in the APOA1/C3/A4 gene cluster on chromosome 11q23 (12). ApoA-V, shown to be expressed mostly in liver and independently named regeneration-associated protein 3, is upregulated after the early phase of liver regeneration after hepatectomy in rat (13). In mice overexpressing the human apoA-V gene, TG concentrations decreased by 50-70%, and in apoA-V gene knockout mice, plasma TG concentrations increased ‫ف‬ 4-fold (12-14). These results suggest that apoA-V expression may strongly influence, and be negatively associated with, plasma TG concentrations. ApoA-V both enhances lipoprotein lipase-mediated hydrolysis of plasma TG and inhibits hepatic VLDL-TG production (15). ApoA-V also stimulates the efflux of cholesterol from cells by a mechanism independent on the ABCA1 protein, as do other exchangeable apolipoproteins, such as apoA-I and apoA-IV (16). It was recently described that apoA-V mRNA is regulated by peroxisome proliferator-activated receptor ␣ agonists (17,18) and that the liver X receptor ligand T0901317 decreases apoA-V mRNA through the activation of sterol-regulatory element binding protein 1c (SREBP-1c) (19). These results raise the possibility that some TG-lowering agents, such as fenofibrate, may act by alte...

Plasma cholesteryl ester transfer protein (CETP) facilitates the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to apolipoprotein

Plasma lipoprotein-associated phospholipase A2 (Lp-PLA2), also known as platelet-activating factor (PAF) acetylhydrolase (PAF-AH), is a member of the serine-dependent class of A2 phospholipases that hydrolyze sn2-ester bonds of fragmented or oxidized phospholipids at sites where atherosclerotic plaques are forming. Most circulating Lp-PLA2 is bound to lowdensity lipoprotein (LDL) particles in plasma and the rest to high-density lipoprotein (HDL). Deficiency of Lp-PLA2 is a predisposing factor for cardiovascular diseases in the Japanese population. We describe here two novel mutations of the gene encoding Lp-PLA2, InsA191 and I317N in Japanese subjects. The first patient, with partial Lp-PLA2 deficiency, was heterozygous for the InsA191 mutation; macrophages from this patient secreted only half the normal amount of Lp-PLA2 in vitro. The other patient, who showed complete Lp-PLA2 deficiency, was a compound heterozygote for the novel I317N mutation and a common V279F mutation; macrophages from that patient failed to secrete any Lp-PLA2. Measurement of Lp-PLA2 mass, activity and Western blotting verified impaired production and secretion of the enzyme after transfection of mutant construct into COS-7 cells. These results indicated that both novel mutants, InsA191 and I317N, impair function of the Lp-PLA2 gene.

No abstract

The bifunctional autolysin gene (all) of Staphylococcus aureus was transcribed into a 4.1-kb transcript. The transcription initiation site was located at an adenine residue 33-nt upstream from the putative atl start codon. Analysis using a promoter-reporter plasmid showed that promoter activity increased during the exponential growth phase. The Tn551 insertion site of the autolysis-deficient mutant S. aureus RUSAL2 was located in the putative catalytic region of the glucosaminidase domain.