Saturated fatty acid-induced CSF3 expression via Toll-like receptors. (A) CSF3 mRNA expression was measured in human myotubes pretreated for 6 h with TAK-242 (1 μg/mL) prior to 24-hour treatment with palmitate (0.5 mmol/L). (B) Human myotubes were pretreated for 24 h with siRNA for TLR2 or TLR4, respectively, prior to 24-hour treatment with palmitate (0.5 mmol/L), and TLR2, TLR4, and CSF3 mRNA contents were quantified. Data are given as means ± SEM. Two-group comparisons were performed using matched-pairs Student's t-test (N ≥ 3; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). (C and D) Myotube cultures derived from 33 human donors were treated for 24 h with stearate (0.5 mmol/L), stearate-stimulated induction rates (fold-changes) of CSF3, TLR2, and TLR4 mRNA expression were determined, and their inter-relationships were analyzed by simple linear regression analysis.