Interaction of contractile activity and training history on mRNA abundance in skeletal muscle from trained athletes

Skeletal muscle displays enormous plasticity to respond to contractile activity with muscle from strength- (ST) and endurance-trained (ET) athletes representing diverse states of the adaptation continuum. Training adaptation can be viewed as the accumulation of specific proteins. Hence, the altered gene expression that allows for changes in protein concentration is of major importance for any training adaptation. Accordingly, the aim of the present study was to quantify acute subcellular responses in muscle to habitual and unfamiliar exercise. After 24-h diet/exercise control, 13 male subjects (7 ST and 6 ET) performed a random order of either resistance (8 × 5 maximal leg extensions) or endurance exercise (1 h of cycling at 70% peak O2 uptake). Muscle biopsies were taken from vastus lateralis at rest and 3 h after exercise. Gene expression was analyzed using real-time PCR with changes normalized relative to preexercise values. After cycling exercise, peroxisome proliferator-activated receptor-γ coactivator-1α (ET ∼8.5-fold, ST ∼10-fold, P < 0.001), pyruvate dehydrogenase kinase-4 (PDK-4; ET ∼26-fold, ST ∼39-fold), vascular endothelial growth factor (VEGF; ET ∼4.5-fold, ST ∼4-fold), and muscle atrophy F-box protein (MAFbx) (ET ∼2-fold, ST ∼0.4-fold) mRNA increased in both groups, whereas MyoD (∼3-fold), myogenin (∼0.9-fold), and myostatin (∼2-fold) mRNA increased in ET but not in ST (P < 0.05). After resistance exercise PDK-4 (∼7-fold, P < 0.01) and MyoD (∼0.7-fold) increased, whereas MAFbx (∼0.7-fold) and myostatin (∼0.6-fold) decreased in ET but not in ST. We conclude that prior training history can modify the acute gene responses in skeletal muscle to subsequent exercise.

Purification and characterization of heparan sulfate from human primary osteoblasts

Heparan sulfate (HS) is a linear, highly variable, highly sulfated glycosaminoglycan sugar whose biological activity largely depends on internal sulfated domains that mediate specific binding to an extensive range of proteins. In this study we employed anion exchange chromatography, molecular sieving and enzymatic cleavage on HS fractions purified from three compartments of cultured osteoblasts-soluble conditioned media, cell surface, and extracellular matrix (ECM). We demonstrate that the composition of HS chains purified from the different compartments is structurally non-identical by a number of parameters, and that these differences have significant ramifications for their ligand-binding properties. The HS chains purified of conditioned medium had twice the binding affinity for FGF2 when compared with either cell surface or ECM HS. In contrast, similar binding of BMP2 to the three types of HS was observed. These results suggest that different biological compartments of cultured cells have structurally and functionally distinct HS species that help to modulate the flow of HS-dependent factors between the ECM and the cell surface.