Exercise-induced changes in expression and activity of proteins involved in insulin signal transduction in skeletal muscle: Differential effects on insulin-receptor substrates 1 and 2

Level of physical activity is linked to improved glucose homeostasis. We determined whether exercise alters the expression and/or activity of proteins involved in insulin-signal transduction in skeletal muscle. Wistar rats swam 6 h per day for 1 or 5 days. Epitrochlearis muscles were excised 16 h after the last exercise bout, and were incubated with or without insulin (120 nM). Insulin-stimulated glucose transport increased 30% and 50% after 1 and 5 days of exercise, respectively. Glycogen content increased 2- and 4-fold after 1 and 5 days of exercise, with no change in glycogen synthase expression. Protein expression of the glucose transporter GLUT4 and the insulin receptor increased 2-fold after 1 day, with no further change after 5 days of exercise. Insulin-stimulated receptor tyrosine phosphorylation increased 2-fold after 5 days of exercise. Insulin-stimulated tyrosine phosphorylation of insulin-receptor substrate (IRS) 1 and associated phosphatidylinositol (PI) 3-kinase activity increased 2.5- and 3.5-fold after 1 and 5 days of exercise, despite reduced (50%) IRS-1 protein content after 5 days of exercise. After 1 day of exercise, IRS-2 protein expression increased 2.6-fold and basal and insulin-stimulated IRS-2 associated PI 3-kinase activity increased 2.8-fold and 9-fold, respectively. In contrast to IRS-1, IRS-2 expression and associated PI 3-kinase activity normalized to sedentary levels after 5 days of exercise. Insulin-stimulated Akt phosphorylation increased 5-fold after 5 days of exercise. In conclusion, increased insulin-stimulated glucose transport after exercise is not limited to increased GLUT4 expression. Exercise leads to increased expression and function of several proteins involved in insulin-signal transduction. Furthermore, the differential response of IRS-1 and IRS-2 to exercise suggests that these molecules have specialized, rather than redundant, roles in insulin signaling in skeletal muscle.

Letters on the Irish question /

"Letters are ... from the Freeman's Journal."--p. iv.

The effects of fatigue and alcohol on highway safety. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Essays,

A Jesuit reformer and poet [F. [Spee] (19th cent., August, 1885)--Revelations of the after-world (19th cent., February, 1887)--Savonarola (The Weekly register, September, 1899)--M. Emery, superior of St. Sulpice (1789-1811) (Dub. R., October, 1887)--Auricular confession.--The pope and the Anglican archbishops (19th cent., July, 1897)--Ritualism, Roman Catholicism, and converts (Contemp., February, 1879)--On certain ecclesiastical miracles (19th cent., August 1891)--Irresponsible opinion (Macmil., March, 1885)--The ethics of war (19th cent., May 1899)--The passion of the past (Macmil., September, 1887)--Some memories of a prison chaplain (Macmil., February, 1898)--Purcell's life of Cardinal Manning.--Appendix: Some notes on Fr. Ryder's controversy with Dr. Ward.

Memoirs of a Magdalen or The history of Louisa Mildway : now first published from a series of original letters, in two volumes ; vol.I [-II]

Mode of access: Internet.

Report of the ... annual meeting of the American Association for the Advancement of Physical Education.

Imprint varies: 1894, New Haven, Conn. : Clarence H. Ryder; 1895, Concord, N.H. : Republican Press Assn.

The Merrill story : (being a record of the life and achievements of Charles Washington Merrill, and a history of the Merrill Company and subsidiaries) /

Mode of access: Internet.

Skin friction, heat transfer, and pressure measurements on hypersonic inlet compression surfaces in the Mach number range 7.5 to 16.

Cornell Aeronautical Laboratory, Inc., Buffalo. Report no. AA-1948-Y-3

Go right on, girls! : Develop your bodies, your minds, your characters /

Mode of access: Internet.

Live stock in the east,

Mode of access: Internet.

They wouldn't take ashes for an answer.

Mode of access: Internet.

Galloping Dick /

Sequel: The king's highway.

Report on aging out.

"May 1987."

Harry and Lucy : complete in three volumes ... /

Cf. Osborne Coll., p. 247-248; 879.