Cortisol and IGF‐1 synergistically up‐regulate taurine transport by the rat skeletal muscle cell line, L6

Abstract

This study was undertaken to evaluate effects of exercise-induced hormones, cortisol, IGF-1, and beta-endorphin, on the regulation of taurine transport activity in rat skeletal myoblasts, L6 cells. Challenge of L6 cells with cortisol (100 nM) for 24 hrs resulted in a 165% increase in taurine transport activity, 220% increase in Vmax of the taurine transporter, and 55% increase in taurine transporter/ beta-actin mRNA level compared with untreated control cells. Neither IGF-1 (1 approximately 100 nM) nor beta-endorphin (1 approximately 20 nM), added in the incubation medium separately for 24 hrs, affected taurine uptake by L6 cells. However, when cells were co-treated with IGF-1 (10 nM) plus cortisol (100 nM), taurine transport activity (37% increase, p < 0.05), Vmax of the transporter (54%, p < 0.05), and taurine transporter/ beta-actin mRNA level were further increased compared to the value for cells treated with cortisol alone. These results suggest that taurine transport by skeletal muscle cells appear to be synergistically up-regulated during a prolonged exercise via elevated levels of cortisol and IGF-1 in muscle.

Taurine deficiency, synthesis and transport in the mdx mouse model for Duchenne Muscular Dystrophy

“…In vitro studies point to alternate mechanisms of regulating levels of TauT. In rat (L6) myoblasts, TauT activity and mRNA expression is increased in response to exposure to cortisol and IGF1 (Park et al, 2004), and TauT mRNA expression is upregulated during myogenesis in mouse (C2C12) myotubes (Uozumi et al, 2006).…”

Taurine: A Maternally Derived Nutrient Linking Mother and Offspring

“…Severe social stress and chronic hypertension can act in combination to increase the risk of PE [ 54 ]. However, as described, TNF-α was observed to enhance taurine transport by TauT in the study using TR-TBT cells [ 30 ], and cortisol enhances TauT activity in a muscle cell line [ 36 ]. These in vitro observations are not apparently consistent with reduced TauT activity in the placenta in both obesity and PE.…”

“…Cell swelling induced by hypoosmotic conditions results in reactive oxygen species production, which accounts for reduced taurine uptake under low-sodium/hypo-osmotic conditions by the direct modulation of TauT in NIH3T3 mouse fibroblasts [ 35 ]. Elevated levels of cortisol and IGF-1 also upregulate taurine transport in L6, a rat skeletal muscle cell line [ 36 ].…”

“…The ratio of taurine concentration in breast milk to its concentration in maternal plasma was significantly increased in the restraint stress group, suggesting that maternal stress promoted taurine transportation from maternal blood into milk [ 73 ]. Although the detailed molecular mechanisms underlying this phenomenon remain to be elucidated, the enhanced transport of taurine into milk under maternal stress conditions may be associated with the upregulation of the activity of TauT by the stress hormone, cortisol, at the cellular level as described above [ 36 ].…”