Plasma growth hormone secretion is impaired in obesity-prone rats before onset of diet-induced obesity.
Sprague-Dawley rats, which become obese (obesity prone) when fed a moderately high-fat (MHF; 32.5% of kcal as fat) diet, have decreased growth hormone (GH) concentrations compared with obesity-resistant rats fed the same diet. To determine whether plasma GH concentrations are different in obesity-prone rats compared with obesity-resistant rats before diet-induced obesity occurs, total integrated GH concentrations were determined in male Sprague-Dawley rats before exposure to the MHF diet. After initial blood sampling, rats were fed an MHF diet for 15 wk, over which time the animals were separated into two discrete populations based on body weight gain. Analysis of GH in episodic blood samples showed that the obesity-prone group had a GH secretion deficit before the onset of obesity (115.2 +/- 12.9 ng . ml-1 . 200 min-1) compared with obesity-resistant rats (237.2 +/- 47.1 ng . ml-1 . 200 min-1). The GH concentration difference was due to a decrease in mean GH peak height in rats that later became obese (34.8 ng/ml) compared with rats that remained lean (74.2 ng/ml). The results suggest that GH secretion impairment exists before dietary challenge or onset of obesity and may contribute to the susceptibility to obesity observed in these animals.
Department of Physiology, Eastern Virginia Medical School, Norfolk, Virginia 23501, USA.
T J
TJ
Lauterio
A
A
Barkan
M
M
DeAngelo
R
R
DeMott-Friberg
R
R
Ramirez
D000818:Animals; D001835:Body Weight; D004041:Dietary Fats; D004198:Disease Susceptibility; D002149:Energy Intake; D004734:Energy Metabolism; D013006:Growth Hormone / Q000097:blood* / Q000378:metabolism; D008297:Male; D009765:Obesity / Q000209:etiology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D004041:Dietary Fats; D013006:Growth Hormone