title: Increased physical activity decreases hepatic free fatty acid uptake: a study in human monozygotic twins.
abstract: 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 (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 micromol (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.
authors.affiliation: Turku PET Centre, University of Turku, Turku, Finland. jarna.hannukainen@tyks.fi
authors.forename: Jarna C
authors.initials: JC
authors.lastname: Hannukainen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.forename: Ronald
authors.initials: R
authors.lastname: Borra
authors.forename: Borra
authors.initials: B
authors.lastname: Ronald
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Urho M
authors.initials: UM
authors.lastname: Kujala
authors.forename: Tuula
authors.initials: T
authors.lastname: Janatuinen
authors.forename: Olli J
authors.initials: OJ
authors.lastname: Heinonen
authors.forename: Jukka
authors.initials: J
authors.lastname: Kapanen
authors.forename: Tapio
authors.initials: T
authors.lastname: Viljanen
authors.forename: Merja
authors.initials: M
authors.lastname: Haaparanta
authors.forename: Tapani
authors.initials: T
authors.lastname: Rönnemaa
authors.forename: Riitta
authors.initials: R
authors.lastname: Parkkola
authors.forename: Juhani
authors.initials: J
authors.lastname: Knuuti
authors.forename: Kari K
authors.initials: KK
authors.lastname: Kalliokoski
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D015308:Anaerobic Threshold / Q000502:physiology; D000886:Anthropometry; D001823:Body Composition / Q000502:physiology; D015331:Cohort Studies; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014430:Twins, Monozygotic
chemical_list: D005230:Fatty Acids, Nonesterified; D019275:Radiopharmaceuticals