Epinephrine-stimulated glycogen breakdown activates glycogen synthase and increases insulin-stimulated glucose uptake in epitrochlearis muscles.
نویسندگان
چکیده
Epinephrine increases glycogen synthase (GS) phosphorylation and decreases GS activity but also stimulates glycogen breakdown, and low glycogen content normally activates GS. To test the hypothesis that glycogen content directly regulates GS phosphorylation, glycogen breakdown was stimulated in condition with decreased GS activation. Saline or epinephrine (0.02 mg/100 g rat) was injected subcutaneously in Wistar rats (∼130 g) with low (24-h-fasted), normal (normal diet), and high glycogen content (fasted-refed), and epitrochlearis muscles were removed after 3 h and incubated ex vivo, eliminating epinephrine action. Epinephrine injection reduced glycogen content in epitrochlearis muscles with high (120.7 ± 17.8 vs. 204.6 ± 14.5 mmol/kg, P < 0.01) and normal glycogen (89.5 ± 7.6 vs. 152 ± 8.1 mmol/kg, P < 0.01), but not significantly in muscles with low glycogen (90.0 ± 5.0 vs. 102.8 ± 7.8 mmol/kg, P = 0.17). In saline-injected rats, GS phosphorylation at sites 2+2a, 3a+3b, and 1b was higher and GS activity lower in muscles with high compared with low glycogen. GS sites 2+2a and 3a+3b phosphorylation decreased and GS activity increased in muscles where epinephrine decreased glycogen content; these parameters were unchanged in epitrochlearis from fasted rats where epinephrine injection did not decrease glycogen content. Incubation with insulin decreased GS site 3a+3b phosphorylation independently of glycogen content. Insulin-stimulated glucose uptake was increased in muscles where epinephrine injection decreased glycogen content. In conclusion, epinephrine stimulates glycogenolysis in epitrochlearis muscles with normal and high, but not low, glycogen content. Epinephrine-stimulated glycogenolysis decreased GS phosphorylation and increased GS activity. These data for the first time document direct regulation of GS phosphorylation by glycogen content.
منابع مشابه
Adrenaline - stimulated glycogen breakdown activates glycogen synthase and 1 increases insulin - stimulated glucose uptake in epitrochlearis muscles
4 Department of Physical Performance, Norwegian School of Sports Sciences, P.O.Box 4014 11 Ullevål Stadion, Sognsveien 220, NO-0806 Oslo, Norway 12 13 Running Title: Cori cycle and insulin sensitivity in skeletal muscles 14 15 16 17 Corresponding Author: 18 Jørgen Jensen, Department of Physical Performance, Norwegian School of Sport Sciences, 19 Sognsvann 220, P.O.Box 4014 Ullevål Stadion, 0806...
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ورودعنوان ژورنال:
- American journal of physiology. Endocrinology and metabolism
دوره 308 3 شماره
صفحات -
تاریخ انتشار 2015