The relation between the PST1 restriction fragment length polymorphism at the APO-AI locus and plasma APO-AI concentrations in marathon runners.

A PST1 restriction fragment length polymorphism (RFLP), located close to the apolipoprotein AI (apo-AI) gene on chromosome 11, is associated with elevated levels of apo-AI in normal healthy individuals and with depressed levels in patients with coronary heart disease. In both cases the association is with the P2 allele (the allele not containing the PST1 cutting site). Prolonged exercise is known to increase steady-state plasma apo-AI concentrations. We investigated the effect of adaptation to endurance exercise on the association of the PST1 marker with plasma apo-AI levels. Eighty-two male subjects between the ages of 20 and 50 years were randomly selected from a group of local marathon runners. The frequency of the P2 allele was 14% in this group. This was similar to the frequency reported for this RFLP in other population groups of healthy men. Plasma levels of apo-AI were elevated in the marathon runners compared with randomly selected healthy South African men in the same age group. There was, however, no association between the PST1 RFLP and the plasma high-density lipoprotein cholesterol and/or apo-AI concentrations in this group. The elevated apo-AI levels in marathon runners therefore bear no relation to differences associated with the PST1 RFLP at the apo-AI gene locus.

Selected risk factors for coronary heart disease in male scholars from the major South African population groups.

A number of risk factors for coronary heart disease (CHD) in 7 groups of South African male scholars aged between 15 and 20 years were surveyed. Selection of the groups was based on socioeconomic status and comprised urban and rural blacks, Indians of higher and lower socio-economic status, coloureds of higher and lower socioeconomic status, and middle-class whites. Both Indian groups, both coloured groups and the whites had a much greater prevalence and severity of CHD risk factors than the two black groups. This held for total cholesterol, low-density lipoprotein cholesterol (LDLC), high-density lipoprotein cholesterol (HDLC), the HDLC/LDLC ratio, apolipoprotein B, apolipoprotein A-I, insulin, fibrinogen and mass. One exception was lipoprotein a, levels of which were higher in both black groups. In general the CHD risk factor profile was worse in the higher socio-economic groups, and it also tended to be worse in urban than in rural blacks. These findings stress the need to reduce CHD risk factors in our developed populations and to prevent their emergence in our developing peoples.

A common Lithuanian mutation causing familial hypercholesterolemia in Ashkenazi Jews.

Familial hypercholesterolemia (FH) is an autosomal dominant disease caused by mutations in the low-density-lipoprotein (LDL) receptor. Here we characterize an LDL-receptor founder mutation that is associated with a distinct LDL-receptor haplotype and is responsible for FH in 35% of 71 Jewish-Ashkenazi FH families in Israel. Sixty four percent (16/25) of the Ashkenazi patients who carry this mutant allele were of Lithuanian origin. The mutation was not found in 47 non-Ashkenazi FH families. This mutation was prevalent (8/10 FH cases) in the Jewish community in South Africa, which originated mainly from Lithuania. The mutation, a 3-bp in-frame deletion that would result in the elimination of Gly197, has been previously designated FH-Piscataway. PCR amplification of a DNA fragment that includes the mutation in heterozygous individuals results in the formation of a heteroduplex that can be demonstrated by PAGE and used for molecular diagnosis.

Neutrophil association and degradation of normal and acute-phase high-density lipoprotein 3.

The interaction of normal and acute-phase high-density lipoproteins of the subclass 3 (N-HDL3 and AP-HDL3) with human neutrophils and the accompanying degradation of HDL3 apolipoproteins have been studied in vitro. The chemical composition of normal and acute-phase HDL3 was similar except that serum amyloid A protein (apo-SAA) was a major apolipoprotein in AP-HDL3 (approx. 30% of total apolipoproteins). 125I-labelled AP-HDL3 was degraded 5-10 times faster than 125I-labelled N-HDL3 during incubation with neutrophils or neutrophil-conditioned medium. Apo-SAA, like apolipoprotein A-II (apo-A-II), was more susceptible than apolipoprotein A-I (apo-A-I) to the action of proteases released from the cells. The amounts of cell-associated AP-HDL3 apolipoproteins at saturation were up to 2.8 times greater than N-HDL3 apolipoproteins; while apo-A-I was the major cell-associated apolipoprotein when N-HDL3 was bound, apo-SAA constituted 80% of the apolipoproteins bound in the case of AP-HDL3. The associated intact apo-SAA was mostly surface-bound as it was accessible to the action of exogenous trypsin. alpha 1-Antitrypsin-resistant (alpha 1-AT-resistant) cellular degradation of AP-HDL3 apolipoproteins also occurred; experiments in which pulse-chase labelling was performed or lysosomotropic agents were used indicated that insignificant intracellular degradation occurred which points to the involvement of cell-surface proteases in this degradation.

Serum amyloid A-containing human high density lipoprotein 3. Density, size, and apolipoprotein composition.

Serum amyloid A protein (apo-SAA), an acute phase reactant, is an apolipoprotein of high density lipoproteins (HDL), in particular the denser subpopulation HDL3. The structure of HDL3 isolated from humans affected by a variety of severe disease states was investigated with respect to density, size, and apolipoprotein composition, using density gradient ultracentrifugation, gradient gel electrophoresis, gel filtration, and solid phase immunoadsorption. Apo-SAA was present in HDL particles in increasing amounts as particle density increased. Apo-SAA-containing HDL3 had bigger radii than normal HDL3 of comparable density. Purified apo-SAA associated readily with normal HDL3 in vitro, giving rise to particles containing up to 80% of their apoproteins as apo-SAA. The addition of apo-SAA resulted in a displacement of apo-A-I and an increase in particle size. Acute phase HDL3 represented a mixture of particles, polydisperse with respect to apolipoprotein content; for example, some particles were isolated that contained apo-A-I, apo-A-II, and apo-SAA, whereas others contained apo-A-I and apo-SAA but no apo-A-II. We conclude that apo-SAA probably associates in the circulation of acute phase patients with existing HDL particles, causing the remodeling of the HDL shell to yield particles of bigger size and higher density that are relatively depleted of apo-A-I.

Standardisation of the quantitation of serum amyloid A protein (SAA) in human serum.

An adequate method for standardising the quantitation of serum amyloid A protein (SAA) in human serum was developed. Acute phase high density lipoprotein3 (HDL3) was used as a standard. The concentration of the SAA in the standard was determined by the use of purified SAA. After protein determination, various concentrations of purified SAA were run on SDS-polyacrylamide gel together with the HDL3 standard containing an unknown amount of SAA amongst the apolipoproteins. From the standard curve obtained by pyridine extraction (Coomassie blue colour yield at A605 nm) the concentration of SAA in the HDL3 standard was determined. An established immunoradiometric assay (IRMA) for SAA was standardised with the HDL3. SAA concentrations in normal and acute phase sera were determined.

The conversion of sterigmatocystin to O-methylsterigmatocystin and aflatoxin B1 by a cell-free preparation.

A cell-free system derived from a versicolorin A-accumulating mutant of Aspergillus parasiticus was found to convert sterigmatocystin to both O-methylsterigmatocystin and aflatoxin B1. It is suggested that the similarity in the chromatographic properties of these two metabolites has caused erroneous conclusions to be made with regards to the biosynthesis of aflatoxin B1.