Licentiate of Medicine Timo Paavola
Faculty and research unit
University of Oulu Graduate School, Faculty of Medicine, Research Center for Internal Medicine
Field of study
Date and time of the thesis defence
Place of the thesis defence
Leena Palotie -auditorium, Aapistie 5 A
Topic of the dissertation
Associations of low HDL cholesterol level and premature coronary heart disease with functionality and phospholipid composition of HDL and with plasma oxLDL antibody levels
Professor Elina Ikonen, University of Helsinki
Adjunct professor Tuire Salonurmi, University of Oulu
Low HDL cholesterol level and premature coronary heart disease
Coronary heart disease (CHD) is a clinical manifestation of atherosclerosis. It is a major cause of mortality and morbidity both in Finland and globally. Even after the best known treatments a significant residual risk of CHD remains.
A low plasma HDL cholesterol level (HDL, high-density lipoprotein) is a common lipid abnormality in patients affected by premature CHD and also a component of the metabolic syndrome, a cluster of risk factors for atherosclerosis associated with central obesity. In this study, a phenotype of low HDL cholesterol level and premature CHD was investigated in two Northern Finnish family populations. The aim was to find new biological factors accounting for the elevated CHD risk in the phenotype.
In the subjects of family population I, plasma levels of antibodies (IgG, IgM, IgA) against experimental epitopes (malondialdehyde-acetaldehyde-modified, copper-oxidized) of oxidized LDL (low-density lipoprotein) particles were measured. In the subjects of family population II, capacity of HDL fractions (total HDL, HDL2 and HDL3) to accept cholesterol from a THP-1 experimental foam cell model was assayed (cholesterol efflux). In addition, a phospholipid composition of their HDL fractions (HDL2 and HDL3) was measured using liquid chromatography-mass spectrometry.
The antibody levels were not related to CHD or to HDL cholesterol level. Instead, the cholesterol efflux to HDL2 fraction was clearly impaired in CHD, which was associated with the low HDL cholesterol level of the patients. The impaired cholesterol efflux to HDL2 fraction was primarily in conjunction with the metabolic syndrome. The phospholipid composition of HDL fractions was different between the affected and the non-affected subjects. As an example, characteristic of the metabolic syndrome were elevated contents of palmitic, palmitoleic or oleic acids relative to linoleic acid in lysophosphatidylcholines and phosphatidylcholines.
In conclusion, the HDL fraction is both functionally and compositionally modified in the phenotype of low HDL cholesterol level and premature CHD. Especially the cholesterol efflux capacity of the HDL2 fraction and thus its many functional properties may be impaired. There are many characteristic features in the phospholipid composition of the HDL in the phenotype which were detected in HDL2 and HDL3 fractions.
Last updated: 10.10.2019