Endurance training increases gluconeogenesis during rest and exercise in men

The hypothesis that endurance training increases gluconeogenesis (GNG) duri ng rest and exercise was evaluated. We determined glucose turnover with [6, 6-H-2]glucose and lactate incorporation into glucose by use of [3-C-13]lact ate during 1 h of cycle ergometry at two intensities [45 and 65% peak O-2 c onsumption ((V) overdot O-2peak)] before and after training [65% pretrainin g (V) overdot O-2peak], same absolute workload (ABT), and 65% posttraining (V) overdot O-2peak, same relative intensity (RLT). Nine males (178.1 +/- 2 .5 cm, 81.8 +/- 3.3 kg, 27.4 +/- 2.0 yr) trained for 9 wk on a cycle ergome ter 5 times/wk for 1 h at 75% (V) overdot O-2peak. The power output that el icited 66.0 +/- 1.1% of (V) overdot O-2peak pretraining elicited 54.0 +/- 1 .7% posttraining. Rest and exercise arterial glucose concentrations were si milar before and after training, regardless of exercise intensity. Arterial lactate concentration during exercise was significantly greater than at re st before and after training. Compared with 65% pretraining, arterial lacta te concentration decreased at ABT (4.75 +/- 0.4 mM, 65% pretraining; 2.78 /- 0.3 mM, ABT) and RLT (3.76 +/- 0.46 mM) (P < 0.05). At rest alter traini ng, the percentage of glucose rate of appearance (R-a) from GNG more than d oubled(1.98 +/- 0.5% pretraining; 5.45 +/- 1.3% posttraining), as did the r ate of GNG (0.11 +/- 0.03 mg.kg(-1).min(-1) pretraining, 0.24 +/- 0.06 mg.k g(-1).min(-1) posttraining). During exercise after training, %glucose R-a f rom GNG increased significantly at ABT (2.3 +/- 0.8% at 65% pre- vs. 7.6 +/ - 2.1% posttraining) and RLT (6.1 +/- 1.5%), whereas GNG increased almost t hreefold (P < 0.05) at ABT(0.24 +/- 0.08 mg.kg(-1).min(-1) 65% pre-, and 0. 71 +/- 0.18 mg.kg(-1).min(-1) posttraining) and RLT (0.75 +/- 0.26 mg.kg(-1 ).min(-1)). We conclude that endurance training increases gluconeogenesis t wofold at rest and threefold during exercise at given absolute and relative exercise intensities.