Ce myokine secretion. Cells were treated as described in Fig 2, but for 48 hr before assay. (A) Basal (open bars) and insulin-stimulated (hatched bars, 33 nM, 60 min) 2-deoxyglucose FPS-ZM1 msds AZD-8055 msds uptake. Results expressed relative to untreated control, either basal or insulin-stimulated, in each individual set of cells, average + SEM, n = 9 for ND, 8?0 for T2D. (B) Palmitate oxidation in ND (open bars, n = 3) and T2D (solid bars, n = 5?) hSMC. *p<0.05 vs paired control doi:10.1371/journal.pone.0158209.geffect in this cohort of T2D cells did not attain statistical significance (p = 0.115). Neither LPS nor oleate treatment caused significant changes in palmitate oxidation.Myokines and inflammatory signaling in myotubesThe impact of prolonged exposure of T2D myotubes to elevated levels of pro-inflammatory myokines was evaluated by following the expression and phosphorylation of key proteins involved in classic inflammatory signaling. IkBa protein expression did not differ between ND and T2D cells under control conditions (Fig 4B). Expression of the p65 subunit of NFkB also did not differ between ND and T2D myotubes: NFkB phosphorylation was not detectable. The expression of p44/42 MAPK was elevated in T2D hSMC (Fig 4B), while phosphorylation (Fig 4C) was similar in ND and T2D cells. Meanwhile, the protein expression (Fig 4B) and phosphorylation (Fig 4C) of both p38 MAPK and JNK were similar between ND and T2D myotubes under control conditions. Neither pro- (LPS) nor anti- (Pio) inflammatory treatments that induced changes in myokine secretion had consistent effects on IkBa expression in ND or T2D myotubes (Fig 5A). Treatment with palmitate and oleate also did not lead to consistent changes in IkBa protein expression. NFkB protein expression in both ND and T2D hSMCs was unaltered by any of the treatments (data not shown). None of these treatments displayed consistent or statistically significant effects on the extent of myotube differentiation, as indicated by expression of the myogenic determination factor MyoD (example in Fig 5A) (LPS--140 ?34 of paired control, palm?101 ?8 , oleate?88 ?21 , pio?95 ?31 , n = 7?). There were tendencies for Pio(p = 0.08) and oleate (p = 0.057) to down regulate p38 expression in ND but not T2D myotubes (Fig 4B) (p = 0.091 comparing the responses of ND vs T2D cells). There was a weak tendency for LPS (p = 0.082) to increase p38 phosphorylation in T2D hSMC but not ND cells (p = 0.053 comparing the responses between the groups). None of the treatments led to consistent effects on either the protein expression or phosphorylation of p44/ 42 (Fig 5C) or JNK (Fig 5D).DiscussionThe importance of skeletal muscle in locomotion and metabolism is undisputed. Over the last 10?5 years another function of skeletal muscle has been established, that of an endocrine tissue, secreting factors into the interstitial space and circulation [3]. Given their tissue of origin, such factors are termed "myokines", analogous to the adipokines produced in adipose tissuePLOS ONE | DOI:10.1371/journal.pone.0158209 July 25,8 /Myokine Secretion in Type 2 DiabetesFig 4. Impact of T2D on inflammatory signaling in hSMC. Proteins extracted from ND (open bars) and T2D (solid bars) hSMC under control conditions. (A) Representative western blots. (B) Quantification of protein expression normalized to loading control (?actin). Ave + SEM, n = 13?1 for ND, 10?6 for T2D. (C) Protein phosphorylation, expressed as ratio of phosphorylated to total protein. Ave + SEM,.Ce myokine secretion. Cells were treated as described in Fig 2, but for 48 hr before assay. (A) Basal (open bars) and insulin-stimulated (hatched bars, 33 nM, 60 min) 2-deoxyglucose uptake. Results expressed relative to untreated control, either basal or insulin-stimulated, in each individual set of cells, average + SEM, n = 9 for ND, 8?0 for T2D. (B) Palmitate oxidation in ND (open bars, n = 3) and T2D (solid bars, n = 5?) hSMC. *p<0.05 vs paired control doi:10.1371/journal.pone.0158209.geffect in this cohort of T2D cells did not attain statistical significance (p = 0.115). Neither LPS nor oleate treatment caused significant changes in palmitate oxidation.Myokines and inflammatory signaling in myotubesThe impact of prolonged exposure of T2D myotubes to elevated levels of pro-inflammatory myokines was evaluated by following the expression and phosphorylation of key proteins involved in classic inflammatory signaling. IkBa protein expression did not differ between ND and T2D cells under control conditions (Fig 4B). Expression of the p65 subunit of NFkB also did not differ between ND and T2D myotubes: NFkB phosphorylation was not detectable. The expression of p44/42 MAPK was elevated in T2D hSMC (Fig 4B), while phosphorylation (Fig 4C) was similar in ND and T2D cells. Meanwhile, the protein expression (Fig 4B) and phosphorylation (Fig 4C) of both p38 MAPK and JNK were similar between ND and T2D myotubes under control conditions. Neither pro- (LPS) nor anti- (Pio) inflammatory treatments that induced changes in myokine secretion had consistent effects on IkBa expression in ND or T2D myotubes (Fig 5A). Treatment with palmitate and oleate also did not lead to consistent changes in IkBa protein expression. NFkB protein expression in both ND and T2D hSMCs was unaltered by any of the treatments (data not shown). None of these treatments displayed consistent or statistically significant effects on the extent of myotube differentiation, as indicated by expression of the myogenic determination factor MyoD (example in Fig 5A) (LPS--140 ?34 of paired control, palm?101 ?8 , oleate?88 ?21 , pio?95 ?31 , n = 7?). There were tendencies for Pio(p = 0.08) and oleate (p = 0.057) to down regulate p38 expression in ND but not T2D myotubes (Fig 4B) (p = 0.091 comparing the responses of ND vs T2D cells). There was a weak tendency for LPS (p = 0.082) to increase p38 phosphorylation in T2D hSMC but not ND cells (p = 0.053 comparing the responses between the groups). None of the treatments led to consistent effects on either the protein expression or phosphorylation of p44/ 42 (Fig 5C) or JNK (Fig 5D).DiscussionThe importance of skeletal muscle in locomotion and metabolism is undisputed. Over the last 10?5 years another function of skeletal muscle has been established, that of an endocrine tissue, secreting factors into the interstitial space and circulation [3]. Given their tissue of origin, such factors are termed "myokines", analogous to the adipokines produced in adipose tissuePLOS ONE | DOI:10.1371/journal.pone.0158209 July 25,8 /Myokine Secretion in Type 2 DiabetesFig 4. Impact of T2D on inflammatory signaling in hSMC. Proteins extracted from ND (open bars) and T2D (solid bars) hSMC under control conditions. (A) Representative western blots. (B) Quantification of protein expression normalized to loading control (?actin). Ave + SEM, n = 13?1 for ND, 10?6 for T2D. (C) Protein phosphorylation, expressed as ratio of phosphorylated to total protein. Ave + SEM,.
