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This Article Full Text Full Text (PDF) All Versions of this Article: 578/1/347    most recent jphysiol.2006.121368v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hannukainen, J. C. Articles by Kalliokoski, K. K. Search for Related Content PubMed PubMed Citation Articles by Hannukainen, J. C. Articles by Kalliokoski, K. K. Related Collections Integrative

¹ Turku PET Centre
² Department of Medicine
³ Department of Clinical Physiology
⁴ Paavo Nurmi Centre, Department of Physiology
⁵ Department of Radiology, University of Turku, Turku, Finland
⁶ Department of Public Health, University of Helsinki, Helsinki, Finland
⁷ Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland
⁸ Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland

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 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.

(Received 18 September 2006; accepted after revision 10 October 2006; first published online 19 October 2006)
Corresponding author J. Hannukainen, Turku PET Centre, PO Box 52, FIN-20521 Turku, Finland. Email: jarna.hannukainen{at}tyks.fi

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