Effects of methylation and hydroxylation of sphingomyelins on their biophysical properties and interactions with cholesterol

Sfingomyeliner är viktiga sphingolipidmolekyler som finns i cellmembranets exoplastiska monolager. Sfingomyeliner är sällsynta i växter och mikroorganismer. Den enigmatiska sfingomelinmolekylen som Thudicum isolerade från hjärnvävnad i slutet på 1800-talet fick sitt namn på basen av det grekiska ordet”sfinx”. Sfingomyeliner återfinns speciallt rikligt i myelinskidorna i nervvävnad, var de sfingomyelinrika membranen bildar ett isolerande lager runt nervcellernas axoner. De polära sfingomyelinerna är viktiga beståndsdelar av ägg, mjölk och kött, och betraktas som viktiga näringsämnen speciellt för spädbarn. Det finns ett flertal sjukdomar uppstår på grund av defekter i sfingomyelinmetabolismen., t.ex. Niemann-Picks sjukdom, som är en obotlig ärftlig metabolisk sjukdom. Nyligen har det rapporterats att sfingomyelin tillsammans med kolesterol och specifika proteiner bildar funtionella domäner, s.k. membranflottar, i cellers membran. Membranflottar anses delta i många viktiga biologiska processer som t.ex. signalöverföring, lipid- och proteinsortering, apoptos, celladhesion, cellmigration och synapsers signalöverföring. Därför är det ytterst viktigt att förstå samverkan mellan sfingomyelin och kolesterol och hur denna samverkan påverkar bildandet membranflottar. I avhandlingen presenteras data från våra studier av sfingomyelin samverkan med kolesterol. För avhandlingen syntetiserade vi unika sfingomyelin molekyler genom att införa metyl- och hydroxylgrupper i olika positioner i sphingomyelinmolekylerna, med målet att lära oss mera om sphingomyelinets membranegenskaper och samverkan med kolesterol. Alla sfingomyelin molekyler som användes i avhandlingsarbetet är biologiskt relevanta. I studierna fann vi att hydroxyl- och amidgrupperna i sfingomyelin är viktiga i vätebindningar mellan sfingomyelinmolekyler samt mellan sfingomyelin och kolesterol. Vi upptäckte ytterligare att substition av metylgrupper i acylkedjan eller i interfasregionen hos sfingomyelinmolekyler signifikant destabiliserade sphingomyelin bilagret och försvagade/upphävde molekylernas samverkan med kolesterol. Hur sfingomyelinbilagrens stabilitet och sfingomyelinen-koleterol samverkan påverkades av hydroxylgrupper var beroende av hydrohygruppens position. Förekomst av en extra hydroxylgrupp i sfingomyelionmolekylens sfingoidbasen ökade stabilitetnen hos sfingomyelinbilagren samt stabiliserade sfingomyelinets samverkan med kolesterol.

Promoting Healthy Lifestyles with Personalized, APOE Genotype Based Health Information: The Effects on Psychological-, Health Behavioral and Clinical Factors

There is an increasing demand for individualized, genotype-based health advice. The general population-based dietary recommendations do not always motivate people to change their life-style, and partly following this, cardiovascular diseases (CVD) are a major cause of death in worldwide. Using genotype-based nutrition and health information (e.g. nutrigenetics) in health education is a relatively new approach, although genetic variation is known to cause individual differences in response to dietary factors. Response to changes in dietary fat quality varies, for example, among different APOE genotypes. Research in this field is challenging, because several non-modifiable (genetic, age, sex) and modifiable (e.g. lifestyle, dietary, physical activity) factors together and with interaction affect the risk of life-style related diseases (e.g. CVD). The other challenge is the psychological factors (e.g. anxiety, threat, stress, motivation, attitude), which also have an effect on health behavior. The genotype-based information is always a very sensitive topic, because it can also cause some negative consequences and feelings (e.g. depression, increased anxiety). The aim of this series of studies was firstly to study how individual, genotype-based health information affects an individual’s health form three aspects, and secondly whether this could be one method in the future to prevent lifestyle-related diseases, such as CVD. The first study concentrated on the psychological effects; the focus of the second study was on health behavior effects, and the third study concentrated on clinical effects. In the fourth study of this series, the focus was on all these three aspects and their associations with each other. The genetic risk and health information was the APOE gene and its effects on CVD. To study the effect of APOE genotype-based health information in prevention of CVD, a total of 151 volunteers attended the baseline assessments (T0), of which 122 healthy adults (aged 20 – 67 y) passed the inclusion criteria and started the one-year intervention. The participants (n = 122) were randomized into a control group (n = 61) and an intervention group (n = 61). There were 21 participants in the intervention Ɛ4+ group (including APOE genotypes 3/4 and 4/4) and 40 participants in the intervention Ɛ4- group (including APOE genotypes 2/3 and 3/3). The control group included 61 participants (including APOE genotypes 3/4, 4/4, 2/3, 3/3 and 2/2). The baseline (T0) and follow-up assessments (T1, T2, T3) included detailed measurements of psychological (threat and anxiety experience, stage of change), and behavioral (dietary fat quality, consumption of vegetables, - high fat/sugar foods and –alcohol, physical activity and health and taste attitudes) and clinical factors (total-, LDL- HDL cholesterol, triglycerides, blood pressure, blood glucose (0h and 2h), body mass index, waist circumference and body fat percentage). During the intervention six different communication sessions (lectures on healthy lifestyle and nutrigenomics, health messages by mail, and personal discussion with the doctor) were arranged. The intervention groups (Ɛ4+ and Ɛ4-) received their APOE genotype information and health message at the beginning of the intervention. The control group received their APOE genotype information after the intervention. For the analyses in this dissertation, the results for 106/107 participants were analyzed. In the intervention, there were 16 participants in the high-risk (Ɛ4+) group and 35 in the low-risk (Ɛ4-) group. The control group had 55 participants in studies III-IV and 56 participants in studies I-II. The intervention had both short-term (≤ 6 months) and long-term (12 months) effects on health behavior and clinical factors. The short-term effects were found in dietary fat quality and waist circumference. Dietary fat quality improved more in the Ɛ4+ group than the Ɛ4- and the control groups as the personal, genotype-based health information and waist circumference lowered more in the Ɛ4+ group compared with the control group. Both these changes differed significantly between the Ɛ4+ and control groups (p<0.05). A long-term effect was found in triglyceride values (p<0.05), which lowered more in Ɛ4+ compared with the control group during the intervention. Short-term effects were also found in the threat experience, which increased mostly in the Ɛ4+ group after the genetic feedback (p<0.05), but it decreased after 12 months, although remaining at a higher level compared to the baseline (T0). In addition, Study IV found that changes in the psychological factors (anxiety and threat experience, motivation), health and taste attitudes, and health behaviors (dietary, alcohol consumption, and physical activity) did not directly explain the changes in triglyceride values and waist circumference. However, change caused by a threat experience may have affected the change in triglycerides through total- and HDL cholesterol. In conclusion, this dissertation study has given some indications that individual, genotypebased health information could be one potential option in the future to prevent lifestyle-related diseases in public health care. The results of this study imply that personal genetic information, based on APOE, may have positive effects on dietary fat quality and some cardiovascular risk markers (e.g., improvement in triglyceride values and waist circumference). This study also suggests that psychological factors (e.g. anxiety and threat experience) may not be an obstacle for healthy people to use genotype-based health information to promote healthy lifestyles. However, even in the case of very personal health information, in order to achieve a permanent health behavior change, it is important to include attitudes and other psychological factors (e.g. motivation), as well as intensive repetition and a longer intervention duration. This research will serve as a basis for future studies and its information can be used to develop targeted interventions, including health information based on genotyping that would aim at preventing lifestyle diseases. People’s interest in personalized health advices has increased, while also the costs of genetic screening have decreased. Therefore, generally speaking, it can be assumed that genetic screening as a part of the prevention of lifestyle-related diseases may become more common in the future. In consequence, more research is required about how to make genetic screening a practical tool in public health care, and how to efficiently achieve long-term changes.

Cholesterol, cardiovascular disease and statin use in older persons

Older age increases the risk of developing a chronic atherosclerotic cardiovascular disease (CVD), such as coronary heart disease. Complications of CVDs, myocardial infarction or stroke often lead to loss of functional capacity or premature death. Dyslipidemia, high serum levels of total or low-density lipoprotein cholesterol (LDL-c) and low levels of high-density lipoprotein cholesterol (HDL-c), is among the most important modifiable risk factors for CVDs; it can be treated with lifestyle modifications, and with lipid-lowering drugs, primarily statins. In older persons, however, the association of cholesterol levels with cardiovascular and all-cause mortality has been inconsistent in previous studies. Furthermore, the beneficial effects of statins in older persons without previous CVD are still somewhat unclear, and older persons are more prone to adverse effects from statins. This thesis presents a prospective cohort study (TUVA), exploring associations of cholesterol levels with mortality and the changes in cholesterol levels of a 70-year-old population in long-term follow-up. Further, prevalence of CVDs, risk factors and preventive medication use in the TUVA cohort is compared with respective prevalences in another age-matched cohort (UTUVA) 20 years later in order to examine the changes in cardiovascular risk over time. Additionally, to evaluate statin use patterns among older persons, an observational register study was conducted covering the total Finnish population aged 70 and older during 2000-2008. Based on individual-level data retrieved from national health registries, the population was classified into low, moderate and high risk groups according to estimated CVD risk. The prevalence, incidence and persistence of statin use among the risk groups was then evaluated based upon yearly statin purchases tracked from the Prescription Register. The prospective cohort study demonstrated that low total cholesterol, LDL-c and HDL-c were associated with higher mortality in a cohort of home-dwelling 70-year-olds. However, after adjusting for traditional cardiovascular risk factors and cancer this association disappeared. Further, low total cholesterol seemed to be protective, whereas low HDL-c strongly predicted increased risk of CVD death. Cholesterol levels of those elderly who remained available for follow-up and were still home-dwelling at the age of 85 seemed to improve with advancing age. Compared to the TUVA cohort, the later born UTUVA cohort had less CVDs and their risk factors were better controlled, which was reflected in the higher use of preventive medications such as statins and antihypertensives. The register studies confirmed that statin use has increased significantly during 2000-2008 among older persons, especially among the oldest (80+) age groups and among those at high risk for cardiovascular events. Two-thirds of new statin users persisted with their use during the four years of follow-up; the most discontinuations were made during the first year of use. In conclusion, statins are commonly used among older age groups in Finland. Most of the older statin users had a high cardiovascular event risk, indicating that the treatment is well directed towards those who are likely to benefit from it the most. No age-limits should be put on the screening and treatment of dyslipidemia in older persons, but the benefits and adverse effects of statin treatment should be carefully weighed based on an individual assessment of the person’s general health status and functional capacity. Physicians should pay more attention to medication adherence, especially when prescribing preventive medications.

Common dyslipidemias, high lipoprotein(a) concentrations and endothelial function in the children of the STRIP study families

Extreme lipid values predisposing on illnesses are dyslipidemias. Dyslipidemias evolve in early childhood, but their significance or persistency is not well known. Common dyslipidemias may aggregate in the same families. This thesis is a part of the longitudinal randomized Special Turku coronary Risk factor Intervention Project STRIP, in which 1054 families with six months old children were randomized to a control or to an intervention group. The family lipid data from the first 11 years was used. Fasting samples at the age of five years defined the lipid phenotypes. The dyslipidemias coexisting in the parent and the child were studied. At the age of 11 years 402 children participated artery ultrasound studies. The significance of the childhood dyslipidemias and lipoprotein(a) concentration on endothelial function was evaluated with the flow mediated arterial dilatation test. Frequently elevated non-HDL cholesterol concentration from one to seven-year-old children associated to similar parental dyslipidemia that improved the predictive value of the childhood sample. The familial combinations were hypercholesterolemia (2.3%), hypertriglyceridemia (2.0%), familial combined hyperlipidemia (1.8%), and isolated low HDL-cholesterol concentration (1.4%). Combined hyperlipidemia in a parent predicted most frequently the child’s hyperlipidemia. High lipoprotein(a) concentration aggregated in some families and associated to childhood attenuated brachial artery dilatation. Hypercholesterolemia and high lipoprotein(a) concentration at five years of age predicted attenuated dilatation. This study demonstrated that parental dyslipidemias and high lipoprotein(a) concentration help to find early childhood dyslipidemias. The association of hypercholesterolemia and lipoprotein(a) concentration with endothelial function emphasizes the importance of the early recognition of the dyslipidemias.