Browsing by Subject "Atherosclerosis"

Coronary heart disease is a number one killer in westernized countries and the costs from it will continue to grow in the future. It is caused by atherosclerosis, build-up of plaque and chronic inflammation in the arteries of heart, and endogenous lipoproteins have a special role in its development. Among other atheroprotective properties, High density lipoproteins (HDL) have a role in intrinsic mechanism of the reverse cholesterol transport (RCT), of gathering and removing excess cholesterol from peripheral tissues. There have been several HDL raising strategies in the past for the treatment of atherosclerosis, but their success has been modest. Synthetic HDL (sHDL), comprising of various types of phospholipids and proteins or peptides, have been developed to mimic the properties of endogenous HDL. Despite some success in animal studies, failures in clinical studies have turned the focus on the HDL’s interaction with a specific enzyme lecithin:cholesterol acyl transferase (LCAT), responsible for cholesterol esterification, a key step in RCT. ApoA-I, the most abundant protein component of HDL, acts as LCAT cofactor in cholesterol esterification, and many LCAT activating peptides have been developed to mimic the features of apoA-I. The molecular level understanding behind LCAT activation is however still foggy. During enzymatic activation, LCAT goes through conformational changes specific regions, which are generated by interactions with apoA-I or synthetic peptides. These mechanisms have been studied widely with molecular dynamic simulations, in vitro experiments, and imaging. In this study, we investigated 22A (PVLDLFRELLNELLEALKQKLK), apoA-I mimetic peptide known for its as good LCAT activation potency as apoA-I, and four variations of it (21A, 22A-P, 22A-K22Q, and 22A-R7Q), and combined them with phospholipid DPPC to create sHDL nanodiscs by thermal cycling method. We examined the effect of small changes in peptide sequence on LCAT-sHDL binding strength with quartz crystal microbalance with dissipation (QCM-D). The interest was to further test the suitability of thermal cycling method on nanodisc assembly, test the binding strengths against the hypothesis of the role of salt-bridge forming amino acids R7 and K22 in peptide dimerization and its effect on LCAT binding and activation, and to see if QCM could act as a suitable method for the research of sHDL-LCAT interactions. All peptides formed similar sized sHDL particles with diameter of ~10 nm with thermal cycling method. As expected, the LCAT binding tendency of 22A-sHDL was highest, about double compared to four other peptide nanodiscs with almost identical results. The QCM results suggest that binding tendency between LCAT and sHDL is affected by small, one amino acid change in peptide sequence, but it does not necessarily have a big impact on LCAT’s esterification activity, but based on this experiment alone, we cannot make any further conclusions. Electron microscopy revealed exceptional breakdown of 21A-sHDL incubated with LCAT compared to 22A-sHDL. This phenomenon could indicate high lipolytic rate of LCAT but needs further investigation. There were some challenges with the measurement parameters in the beginning, and the variability between parallel measurements with QCM-D was high, which cause a little doubt about the method’s suitability for these kinds of precise measurements. More research for revealing the molecular mechanism behind LCAT activation is needed for the development of more effective treatments.

Faculty: Faculty of Biological and Environmental Sciences Degree programme: Master’s Programme in Neuroscience Study track: Cell and Systems Physiology Author: Mélina GUILLON Title: Inflammatory activation of Macrophages by Triglyceride-Rich Lipoproteins in Atherosclerosis Level: Master’s thesis Month and year: August 2023 Number of pages: 38 Keywords: Atherosclerosis, Inflammation, Triglycerides-Rich Lipoproteins, Emulsion Particles Supervisor or supervisors: Dr. Katariina Öörni Where deposited: Helsinki University Library Additional information: Background: Inflammation is a key factor in atherosclerotic cardiovascular disease (ASCVD) and is present at all phases. It has been shown that reducing inflammation by blocking cytokine pathways diminishes the risk of stroke and myocardial infarction. Despite the well-established linked between lipoproteins and atherosclerosis, little is known on the specific effect of lipids on inflammation. In this study, we investigated the impact of triglycerides-rich lipoproteins’ (TRLs) lipids on inflammation in the context of atherosclerosis. Methods: TRLs were isolated and purified from pooled plasma of healthy volunteers, and emulsion particles (EPs) generated by sonication using lipids extracted from TRLs. TRLs and EPs were characterized in size, triglycerides, and cholesterol content. THP-1 cells were treated with EPs, TRLs, and modified EPs (oxidation, vortexed, and lipolysis with PLA2), and the release of pro-inflammatory cytokines (IL-1β and TNF-α) was detected with ELISA. Results: EPs were successfully synthesized by sonication using an ultrasonic probe. EPs induced cytokine secretion from THP-1 cells (N=4). Modified EPs (Oxidized EPs, vortexed EPs, and PLA2-treated EPs) did not increase cytokine secretion (N=4). Conclusion: Our findings suggest that TRLs’ lipids contribute to inflammation and that TRLs may play a crucial role in the pathogenesis and pathophysiology of ASCVD. Inflammatory properties of TRLs should be extensively investigated in the future for the development of preventive and curative strategies.

Lipoproteins are biochemical carriers of the insoluble lipids. They are complexes combining lipids and proteins for the transport of lipids. Amongst the type of lipoproteins are low-density lipoproteins (LDL) which are prevalent in various diseases such as obesity, diabetes, atherosclerosis, and other cardiovascular diseases (CVD). Omega-3 fatty acids are polyunsaturated fatty acids (PUFA) that are essential components of lipid metabolism and play a significant role in the human diet. Omega-3 PUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are derived from fish and are necessary for proper cardiovascular functioning. Because the human body is unable to produce enough quantities of some omega-3, diet is an important source for its availability. When a diet is rich in saturated fats, the above-mentioned diseases transpire. This study investigated how consumption of two fish diets, Lean fish and Fatty fish, influence the lipid species of human LDL particles. The lipid species analysed in this study are phospholipids such as phosphatidylcholine (PC), sphingomyelin (SM), and lysophosphatidylcholine (LPC), and cholesteryl esters (CE), and triacylglycerols (TAG). A total of 42 volunteers with a history of impaired fasting glucose had randomly been divided into two groups: fatty fish (4 fish meals/week) and lean fish (4 fish meals/week) for 12 weeks. Blood samples had been collected from the volunteers before and after consumption of the fish meals and LDL particles had been isolated from the blood samples by ultracentrifugation. In this study, the lipids were extracted by Folch method, and the extracted lipids were analysed using Triple quadrupole mass spectrometry. The lipid class profile did not change due to the two fish type diets. However, the consumption of fatty fish diet increased the levels of lipid species of PC, LPC, and CE containing EPA and DHA acyl chains, while decreasing levels of several TAG species. Lean fish induced minor changes in the lipid composition of LDL particles. Based on these results, fatty fish diet alters the plasma LDL lipidome profile with changes induced to both the surface and the core composition of the LDL particles in a positive way regarding cardiovascular health.

Tässä syventävässä tutkielmassa selvitettiin tilastollisen analyysin avulla lapsuudessa sairastettujen suusairauksien korrelaatiota aikuisuudessa havaittaviin valtimokovettumataudin riskitekijöihin ja sen vaikeusasteeseen. Tutkielma tehtiin osana lasten ja nuorten sepelvaltimotaudin riskitekijät (LASERI) -tutkimusta. Suusairauksien ja sydäntautien yhteyttä on tutkittu runsaasti ja etenkin parodontiitin on osoitettu lisäävän riskiä valtimokovettumatautiin. Tämä pitkittäistutkimus on kuitenkin ensimmäisiä, jossa tutkitaan lapsuusiän suusairauksien vaikutusta valtimokovettumataudin kehittymiseen. Tärkeimpiä sairauksien välistä yhteyttä selittäviä tekijöitä ovat infektio, inflammaatio ja elimistön immuunijärjestelmän säätelyn häiriintyminen. Käyttämässäni aineistossa 755 lapselle ja nuorelle oli tehty suun terveystarkastus, josta tilastoitiin karies, parodontiitti, gingiviitti, plakin ja hammaskiven määrä sekä hampaiden harjaustiheys. Näitä verrattiin 27 vuotta myöhemmin mitattuihin kaulavaltimon seinämän paksuuteen ja joustavuuteen, olkavarren valtimon virtausvälitteiseen vasodilataatioon, verenpaineeseen, kolesteroliarvoihin, glukoosipitoisuuteen ja painoindeksiin. Korrelaation ja p-arvot saatiin SPSS-ohjelman ANOVA-testin avulla. Gingiviitti korreloi korkean carotiksen intima-media-paksuuden (cIMT), systolisen ja diastolisen verenpaineiden sekä matalan carotiksen komplianssin (cDC) kanssa. Parodontiitti korreloi korkean cIMT:n ja cDC:n kanssa. Karieksella oli tilastollista merkitystä korkeiden systolisen ja diastolisen verenpaineiden kanssa. Plakki korreloi suuren painoindeksin (BMI) sekä korkean systolisen ja diastolisen verenpaineen kanssa. Matala hampaiden harjaustiheys yhdistyi korkeaan diastoliseen verenpaineeseen. Tämän tutkimuksen tulokset viittaavat, että lapsuuden ja nuoruuden aikana sairastetuista suusairauksista parodontaalisairaudet ja karies korreloivat aikuisiällä mitattavan valtimokovettumataudin riskitekijöiden kanssa. (190 sanaa)

Cardiovascular diseases (CVDs) are the leading cause of death worldwide and the major cause for them is atherosclerosis. Atherosclerosis is a state of chronic inflammation of the arterial wall, which slowly progresses to form plaques that can eventually obstruct blood flow. The resulting hypoxia in the tissues affected by the ischemia manifests as clinical symptoms such as chest pain. All this begins with chronically high LDL-C concentrations in the blood. LDL-C is transported into the intima of the arterial wall where it is modified with for example oxidizing enzymes. Intimal macrophages remove oxidized LDL via phagocytosis, which leads to lipid accumulation that turns macrophages into foam cells. At first, foam cells die via apoptosis as they are removed by other macrophages. At some point, macrophages cannot remove all the apoptotic material, which leads to a necrotic release of the cell contents. This creates a necrotic core in the center of the atherosclerotic plaque. The inflammatory environment makes vascular smooth muscle cells proliferate and form a fibrous cap to protect the prothrombotic necrotic core. Eventually the plaque can rupture, which leads to the formation of a thrombus and possibly even thrombosis. To prevent this, drugs including statins, ezetimibe and PCSK9 inhibitors are widely used along with certain dietary modifications. More options for diagnosing, preventing, and treating atherosclerosis are still needed to decrease the burden of atherosclerosis and CVDs on both the individual and healthcare systems. A potential example of such methods is presented in this review. This method utilizes synthetic LDL receptors to isolate LDL from the blood, which is needed for determining the quality of LDL particles. The knowledge of LDL quality helps predict the individual risk for developing atherosclerosis.