PET-kuvantamisen menetelmät yleistajuisesti

Positroniemissiotomografia (PET) on kliinisessä lääketieteessä nopeasti yleistynyt isotooppikuvausmenetelmä, joka antaa tarkkaa tietoa elimistön toiminnasta, aineenvaihdunnasta ja biologiasta lyhytikäisten säteilevien merkkiaineiden avulla. Nykyisin kaikki kuvaukset tehdään yhdistelmälaitteella, jossa PET-kuvauslaitteeseen on yhdistetty joko tietokonetomografia- (TT) tai magneettikuvauslaite (MK), joka antaa samanaikaisesti tarkan kuvan elimistön rakenteesta. Kliinisistä PET-TT-kuvauksista jopa yli kaksi kolmasosaa liittyy syöpätautien diagnostiikkaan ja hoitoon. Lisäksi PET-kuvantamista käytetään muun muassa infektioiden ja tulehduksellisten tilojen selvittelyssä sekä neurologisissa ja kardiologisissa aiheissa. PET-kuvantaminen vaatii onnistuakseen tarkkaa esivalmistelua, josta on laadittu kirjalliset ohjeet hoitohenkilökunnalle ja potilaille

Effect of pravastatin on plasma sterols and oxysterols in men

Objectives: The HMG-CoA reductase inhibitors, or statins, are well established in the prevention and treatment of coronary artery disease, mainly by lowering low-density lipoprotein (LDL) cholesterol levels. These compounds are structurally similar, but differ in their lipophilicity. Several studies have indicated a link between cholesterol and Alzheimer's disease (AD), and there is also epidemiological evidence that statin treatment may decrease the prevalence of dementias. In the present study we wanted to investigate whether pravastatin treatment affects brain cholesterol metabolism. Methods: A post hoc analysis was performed with plasma material from a clinical trial where 51 healthy men (35±4 years) were randomly assigned to receive either pravastatin (40 mg/day) or placebo for 6 months. Cholesterol, its precursor lathosterol, its brain-specific metabolite 24(S)-hydroxycholesterol (24S-OH-chol) and 27-hydroxycholesterol (27-OH-chol) were determined in plasma samples before and after treatment by using gas-liquid chromatography (GC)-flame ionization detection (GC-FID) and GC mass spectrometry (GC-MS). Results: Besides reducing total cholesterol (-20%, P<0.001) and LDL cholesterol (LDL-C; -33%, P<0.001) concentrations, pravastatin treatment resulted in a decrease of the ratio of lathosterol to cholesterol, a surrogate marker of endogenous cholesterol synthesis, by 20% (P<0.05). Absolute concentrations of 24S-OH-chol were not altered, but its ratio to cholesterol slightly increased by 15% (P<0.05). 27-OH-chol concentrations as well as its ratio to cholesterol were both significantly altered due to pravastatin treatment (-7% and +14%, P<0.05 for both, respectively). Conclusions: The treatment with pravastatin 40 mg once a day for 6 months does not affect brain cholesterol metabolism as judged by plasma concentrations of 24(S)-hydroxycholesterol. © Springer-Verlag 2005.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Genetic variant of the SREBF-1 gene is significantly related to cholesterol synthesis in man

Sterol regulatory element binding proteins-1 and -2 (SREBPs) are transcription factors controlling lipid homeostasis in human cells. The G-allele carriers of the SREBF-1 gene C-G polymorphism in exon 18c and coding for glycine at the protein level (G952G) have shown to associate more frequently with obesity and type 2 diabetes than the C-allele carriers. However, the C-allele has suggested to be linked to dyslipidemia. Thus, our aim was to study effect of the SREBF-1 gene polymorphism (G952G) on sterol metabolism in man. Ninety-five subjects with moderate hypercholesterolemia participated in this study and 14 homozygous CC carriers of the SREBF-1 (G952G) gene were found. Plasma lathosterol concentration and lathosterol-to-cholesterol ratio, markers of endogenous cholesterol synthesis, were significantly higher in CC homozygous subject compared to others. Similarly muscle cholesterol (p = 0.045) and lathosterol (p = 0.054) concentrations were elevated in the CC homozygotes supporting the view that endogenous cholesterol synthesis rate is SREBF-1 genotype-dependent. © 2005 Elsevier Ireland Ltd. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Increased physical activity decreases hepatic free fatty acid uptake: a study in human monozygotic twins

Exercise is considered to be beneficial for free fatty acid (FFA) metabolism, although reports of the effects of increased physical activity on FFA uptake and oxidation in different tissues in vivo in humans have been inconsistent. To investigate the heredity-independent effects of physical activity and fitness on FFA uptake in skeletal muscle, the myocardium, and liver we used positron emission tomography (PET) in nine healthy young male monozygotic twin pairs discordant for physical activity and fitness. The cotwins with higher physical activity constituting the more active group had a similar body mass index but less body fat and 18 ± 10% higher V˙O2,max (P < 0.001) compared to the less active brothers with lower physical activity. Low-intensity knee-extension exercise increased skeletal muscle FFA and oxygen uptake six to 10 times compared to resting values but no differences were observed between the groups at rest or during exercise. At rest the more active group had lower hepatic FFA uptake compared to the less active group (5.5 ± 4.3 versus 9.0 ± 6.1 μmol (100 ml)−1 min−1, P = 0.04). Hepatic FFA uptake associated significantly with body fat percentage (P = 0.05). Myocardial FFA uptake was similar between the groups. In conclusion, in the absence of the confounding effects of genetic factors, moderately increased physical activity and aerobic fitness decrease body adiposity even in normal-weighted healthy young adult men. Further, increased physical activity together with decreased intra-abdominal adiposity seems to decrease hepatic FFA uptake but has no effects on skeletal muscle or myocardial FFA uptake