title: The effect of dynamic knee-extension exercise on patellar tendon and quadriceps femoris muscle glucose uptake in humans studied by positron emission tomography.
abstract: Both tendon and peritendinous tissue show evidence of metabolic activity, but the effect of acute exercise on substrate turnover is unknown. We therefore examined the influence of acute exercise on glucose uptake in the patellar and quadriceps tendons during dynamic exercise in humans. Glucose uptake was measured in five healthy men in the patellar and quadriceps tendons and the quadriceps femoris muscle at rest and during dynamic knee-extension exercise (25 W) using positron emission tomography and [18F]-2-fluoro-2-deoxy-D-glucose ([18F]FDG). Glucose uptake index was calculated by dividing the tissue activity with blood activity of [18F]FDG. Exercise increased glucose uptake index by 77% in the patellar tendon (from 0.30 +/- 0.09 to 0.51 +/- 0.16, P = 0.03), by 106% in the quadriceps tendon (from 0.37 +/- 0.15 to 0.75 +/- 0.36, P = 0.02), and by 15-fold in the quadriceps femoris muscle (from 0.31 +/- 0.11 to 4.5 +/- 1.7, P = 0.005). The exercise-induced increase in the glucose uptake in neither tendon correlated with the increase in glucose uptake in the quadriceps muscle (r = -0.10, P = 0.87 for the patellar tendon and r = -0.30, P = 0.62 for the quadriceps tendon). These results show that tendon glucose uptake is increased during exercise. However, the increase in tendon glucose uptake is less pronounced than in muscle and the increases are uncorrelated. Thus tendon glucose uptake is likely to be regulated by mechanisms independently of those regulating skeletal muscle glucose uptake.
authors.affiliation: Copenhagen Muscle Research Centre, Institute of Sports Medicine, Bispebjerg Hospital, Denmark. kari.kalliokoski@tyks.fi
authors.forename: Kari K
authors.initials: KK
authors.lastname: Kalliokoski
authors.forename: Henning
authors.initials: H
authors.lastname: Langberg
authors.forename: Ann Kathrine
authors.initials: AK
authors.lastname: Ryberg
authors.forename: Celena
authors.initials: C
authors.lastname: Scheede-Bergdahl
authors.forename: Simon
authors.initials: S
authors.lastname: Doessing
authors.forename: Andreas
authors.initials: A
authors.lastname: Kjaer
authors.forename: Robert
authors.initials: R
authors.lastname: Boushel
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
mesh_terms: D000328:Adult; D005080:Exercise Test; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000378:metabolism*; D010329:Patella / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005082:Physical Exertion / Q000502:physiology*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005947:Glucose