Figure 7.

Glucose and oleic acid metabolism after culturing myotubes in cell media where glucose was replaced by lactic acid or removed. Myotubes were cultured in regular cell media (basal, 5.5 mM glucose), cell media containing no glucose (0 mM glucose) or cell media where glucose were replaced with lactic acid (5 mM) for the whole proliferation and differentiation period. Oxidation was measured as CO₂ trapped in a filter and counted by liquid scintillation. Uptake was assessed as the sum of oxidized (trapped CO₂) lactic acid and remaining cell-associated (CA) radioactivity. (a,b) Uptake and oxidation of [¹⁴C(U)]glucose (1 µCi/ml, 200 µM). (c,d) Uptake and oxidation of [¹⁴C]oleic acid (OA, 1 µCi/ml, 100 µM). Absolute values (means ± SEM) representing 100%: glucose uptake; 16.7 ± 2.6 nmol/mg protein, glucose oxidation; 8.3 ± 0.8 nmol/mg protein, oleic acid (OA) uptake; 77.8 ± 12.9 nmol/mg protein and oleic acid (OA) oxidation; 7.1 ± 1.8 nmol/mg protein. Data are presented as means ± SEM relative to basal (n = 11). *Statistically significant vs. basal (p < 0.05, paired Student’s t-test).