Immunoreactive and bioactive growth hormone responses to resistance exercise in men who are lean or obese

Abstract

The present study was designed to examine the effects of a highvolume, whole body acute resistance exercise (RE) protocol on immunoreactive GH (iGH), bioactive GH (bGH), and GH-binding protein (GHBP) in sedentary lean and obese men. Nine obese (mean Ϯ SD: 20.8 Ϯ 2.1 yr old, 177.0 Ϯ 4.1 cm height, 108.7 Ϯ 15.9 kg body mass, 37.6 Ϯ 5.29% body fat) and nine lean (20.1 Ϯ 2.1 yr old, 177.8 Ϯ 8.7 cm height, 71.7 Ϯ 5.8 kg body mass, 14.7 Ϯ 3.54% body fat) men completed an acute RE protocol (6 exercises, 3 sets of 10 repetitions at 85-95% of 10 repetitions maximum with 120-and 90-s rest periods), and blood samples were collected before, at the midpoint, and immediately after exercise and during recovery (ϩ50, ϩ70, and ϩ110). In contrast to prior studies, which examined acute responses to cardiovascular exercise protocols, groups did not differ in iGH response to the exercise stimulus. However, bGH concentrations overall were significantly lower in the obese than the lean participants (P Ͻ 0.001). Additionally, obese individuals had significantly higher GHBP concentrations (P Ͻ 0.001). Results suggest that obese and lean sedentary men performing a high-volume, whole body acute RE protocol demonstrate similar increases in iGH. Blunted bGH and elevated GHBP concentrations are indicative of altered GH activity associated with obesity. Prior research findings of blunted iGH response may be attributable to RE protocols not equated on relative intensity or volume. These results underscore the complexity of pituitary biology and its related mechanisms and may have implications for exercise prescription in the treatment of obesity.

Endocrine response to acute resistance exercise in obese versus lean physically active men

“…However, the overall GH response evaluated through the AUC analyses showed a dampened GH response; which is in agreement with previous studies (Ormsbee et al 2009;Thomas et al 2011). Excessive body fat and/or high insulin levels in obese could have contributed to the lower baseline GH concentration in this group by disrupting the GH signaling pathway (Ji et al 1999;Succurro et al 2009).…”

“…In previous studies evaluating GH response to RE, a lower GH response was observed in obese compared to lean sedentary men (Ormsbee et al 2009;Thomas et al 2011). However, these referenced studies did not include IGF-1.…”

“…However, these referenced studies did not include IGF-1. Interestingly, previous studies comparing hormonal responses to RE between lean and obese males did not include LH and testosterone (Ormsbee et al 2009;Thomas et al 2011). In such studies participants were sedentary rather than physically active adults.…”

Acute resistance exercise stimulates sex-specific dimeric immunoreactive growth hormone responses

“…Specifically, lower GH concentrations in men immediately after exercise might have resulted in a relatively higher growth hormone receptor (GHR) presence. Since growth hormone binding protein (GHBP) is thought to be produced from the proteolytic cleavage of GHRs [3,42], it is conceivable that an increase in GHRs could in turn increase GHBP concentrations, resulting in an extended biological half-life of GHBPbound GH [43]. This could then extend the biological half-life compared to free GH, resulting in the observation of a sustained GH increased at +30.…”

Interactive effects of an isocaloric high‐protein diet and resistance exercise on body composition, ghrelin, and metabolic and hormonal parameters in untrained young men: A randomized clinical trial

“…In addition, no change was observed in IGF-1, despite a higher GH during 12 weeks of resistance-exercise training in the HP group. Previous studies of the acute or chronic effect of exercise on circulating IGF-I have produced inconsistent results, with levels being reported to decline, to increase, or to remain unchanged after the onset of exercise 33,34 . Finally, data from the present study appear to support the importance of a fine balance between anabolism and catabolism during chronic moderate-high intensity resistance training with proper diet.…”