Acute growth hormone administration causes exaggerated increases in plasma lactate and glycerol during moderate to high intensity bicycling in trained young men

TY - JOUR

T1 - Acute growth hormone administration causes exaggerated increases in plasma lactate and glycerol during moderate to high intensity bicycling in trained young men

AU - Lange, Kai Henrik Wiborg

AU - Larsson, Benny

AU - Flyvbjerg, Allan

AU - Dall, Rolf

AU - Bennekou, Morten

AU - Rasmussen, Michael Højby

AU - Ørskov, Hans

AU - Kjaer, Michael

PY - 2002/11

Y1 - 2002/11

N2 - We studied the acute effects of a single, sc GH dose on exercise performance and metabolism during bicycling. Seven highly trained men [age, 26 +/- 1 yr (mean +/- SEM); weight, 77 +/- 3 kg; maximal oxygen uptake, 65 +/- 1 ml O(2).min(-1).kg(-1)] performed 90 min of bicycling 4 h after receiving 7.5 IU (2.5 mg) GH or placebo in a randomized, double-blinded, cross-over design trial. A standardized pre-exercise meal was given 2 h before exercise. Blood was sampled at rest and during exercise and analyzed for GH, IGF-I, glucose, lactate, insulin, glycerol, and nonesterified fatty acids (NEFA). In the placebo trial, all subjects completed the exercise protocol without any difficulties. In contrast, two subjects were not able to complete the exercise protocol in the GH trial, and one subject barely managed to complete the protocol. In addition, GH administration resulted in exaggerated increases in plasma lactate concentrations during exercise (P < 0.0001). The combined lipolytic effect of GH and exercise, evidenced by increased plasma glycerol and serum NEFA concentrations, was 3-fold greater than the effect of exercise alone (P < 0.0001), but this increased substrate availability did not result in increased whole body fat oxidation (indirect calorimetry). Plasma glucose was, on average, 9% higher during exercise after GH administration compared with placebo (P < 0.0001). We conclude that a single, relevant GH dose causes exaggerated increases in plasma lactate and glycerol as well as serum NEFA during 90 min of subsequent bicycling at moderate to high intensity. The exaggerated increase in plasma lactate may be associated with substantially decreased exercise performance.

AB - We studied the acute effects of a single, sc GH dose on exercise performance and metabolism during bicycling. Seven highly trained men [age, 26 +/- 1 yr (mean +/- SEM); weight, 77 +/- 3 kg; maximal oxygen uptake, 65 +/- 1 ml O(2).min(-1).kg(-1)] performed 90 min of bicycling 4 h after receiving 7.5 IU (2.5 mg) GH or placebo in a randomized, double-blinded, cross-over design trial. A standardized pre-exercise meal was given 2 h before exercise. Blood was sampled at rest and during exercise and analyzed for GH, IGF-I, glucose, lactate, insulin, glycerol, and nonesterified fatty acids (NEFA). In the placebo trial, all subjects completed the exercise protocol without any difficulties. In contrast, two subjects were not able to complete the exercise protocol in the GH trial, and one subject barely managed to complete the protocol. In addition, GH administration resulted in exaggerated increases in plasma lactate concentrations during exercise (P < 0.0001). The combined lipolytic effect of GH and exercise, evidenced by increased plasma glycerol and serum NEFA concentrations, was 3-fold greater than the effect of exercise alone (P < 0.0001), but this increased substrate availability did not result in increased whole body fat oxidation (indirect calorimetry). Plasma glucose was, on average, 9% higher during exercise after GH administration compared with placebo (P < 0.0001). We conclude that a single, relevant GH dose causes exaggerated increases in plasma lactate and glycerol as well as serum NEFA during 90 min of subsequent bicycling at moderate to high intensity. The exaggerated increase in plasma lactate may be associated with substantially decreased exercise performance.

KW - Adult

KW - Bicycling

KW - Blood Glucose/analysis

KW - Cross-Over Studies

KW - Double-Blind Method

KW - Exercise

KW - Fatty Acids, Nonesterified/blood

KW - Glycerol/blood

KW - Heart Rate

KW - Hematocrit

KW - Human Growth Hormone/administration & dosage

KW - Humans

KW - Insulin/blood

KW - Insulin-Like Growth Factor I/analysis

KW - Lactic Acid/blood

KW - Male

KW - Oxygen Consumption

KW - Physical Endurance

KW - Placebos

U2 - 10.1210/jc.2001-011797

DO - 10.1210/jc.2001-011797

M3 - Journal article

C2 - 12414860

SN - 0021-972X

VL - 87

SP - 4966

EP - 4975

JO - The Journal of clinical endocrinology and metabolism

JF - The Journal of clinical endocrinology and metabolism

IS - 11

ER -