Aerobic training reverses high-fat diet-induced pro-inflammatory signalling in rat skeletal muscle

Abstract

High-fat feeding activates components of the pro-inflammatory pathway and increases co-immunoprecipitation of suppressor of cytokine signalling (SOCS)-3 with both the insulin receptor (IR)-β subunit and IRS-1, which together contribute to keeping PI-3 kinase from being fully activated. However, whether aerobic training reverses these impairments is unknown. Sprague-Dawley rats were fed a chow (CON, n = 8) or saturated high-fat (n = 16) diets for 4 weeks. High-fat-fed rats were then allocated (n = 8/group) to either sedentary (HF) or aerobic exercise training (HFX) for an additional 4 weeks after which all animals underwent hind limb perfusions. Insulin-stimulated red quadriceps 3-O-methylglucose transport rates and PI-3 kinase activity were greater (p < 0.05) in CON and HFX compared to HF. IRS-1 tyrosine phosphorylation was increased (p < 0.05) and IRS-1 serine 307 phosphorylation was decreased (p < 0.05) in HFX compared to HF. IR-β subunit co-immunoprecipitation with IRS-1 was increased in HFX compared to HF. SOCS-3 co-immunoprecipitation with both the IR-β subunit and IRS-1 was decreased (p < 0.05) in HFX compared to HF. IKKα/β serine phosphorylation, and IκBα serine phosphorylation were decreased (p < 0.05) while IκBα protein concentration was increased in HFX compared to HF. By decreasing the association of SOCS-3 with both the IR-β subunit and IRS-1 the interaction between IRS-1 and the IR-β subunit was normalized in the HFX, and may have contributed to skeletal muscle PI-3 kinase being fully activated by insulin. Additionally, the reduction in IKKα/β serine phosphorylation in HFX may have contributed to decreasing IRS-1 serine phosphorylation, and in turn, promoted the normalization of insulin-stimulated activation of PI-3 kinase.

Fig. 1

Insulin receptor beta (IR-β) subunit protein concentration and IR-β tyrosine phosphorylation (pY) in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercise trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin

Fig. 2

IRS-1 protein concentration, IRS-1 tyrosine phosphorylation (pY) and IRS-1 serine 307 phosphorylation (pS) in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercise trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)

Fig. 3

Co-immunoprecipitation of IR-β subunit with IRS-1 in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercise trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)

Fig. 4

Insulin-stimulated IRS-1 associated Phosphoinositol 3-kinase (PI3-K) activity in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercise trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)

Fig. 5

IKKα, IKKβ protein concentration and IKK α/β serine phosphorylation (pS) in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercise trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. Values are mean ± SE. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)

Fig. 6

IκBα protein concentration and IκBα serine phosphorylation (pS) in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercise trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. Values are mean ± SE. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)

Fig. 7

SOCS3 protein concentration in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercised trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. Values are mean ± SE. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)

Fig. 8

SOCS3 co-immunoprecipitation with IR-β and SOCS3 coimmunoprecipitation with IRS-1 in skeletal muscle obtained from control (CON), high-fat fed (HF) and high fat exercised trained (HFX) animals perfused in the presence of 500 μU ml⁻¹ insulin. Values are mean ± SE. *Significantly different from CON group (p < 0.05). ^#Significantly different from HFX group (p < 0.05)