| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 5925665 | Physiology & Behavior | 2011 | 7 Pages |
The aim of this study was to demonstrate differential effects of growth hormone (GH) on food intake in lean and obese rats and to investigate whether an anticipated anorectic response in obese rats might be associated with increased lipid oxidation and altered hypothalamic neuropeptide levels. GH (4 mg/kg/day) was administered during 5-21 days to non-obese and obese rats. Whereas GH stimulated food intake in the non-obese rats, the obese animals responded with a significantly (p < 0.05) suppressed food intake for 4-5 days. On day 4, the obese rats injected with GH and those injected with vehicle consumed 9.2 ± 0.66 g and 12.7 ± 1.05 g, respectively. The suppression of food intake was associated with significantly (p < 0.05) increased lipid oxidation. A similar, but statistically not verified, trend was seen in pair-fed rats not exposed to GH. However, while these animals appeared to economize their energy expenditure, the GH-exposed animals did not, thus creating a significant (p < 0.05) difference between these two groups. The increased lipid oxidation and energy expenditure observed in the rats exposed to GH were associated with significantly (p < 0.05) decreased levels of hypothalamic galanin (111 ± 33.2 pmol/g vs. those of the pair-fed controls: 228.5 ± 49.4 pmol/g). This difference was, however, not sustained. Thus, on day 21 both hypothalamic galanin and the food intake in the GH group were back to normal. Hypothalamic NPY remained unchanged by GH at all times. In conclusion, the present study suggests that increased lipid oxidation and decreased hypothalamic galanin are components in the mechanism by which GH inhibits food intake in an obese phenotype.
Research Highlights⺠Growth hormone stimulates food intake in lean growing rats while having the opposite effect in obese animals. ⺠Suppression of food intake is seen during the initial phase of GH exposure in obese rats. ⺠Lipid oxidation and energy expenditure are increased when food intake is maximally suppressed by GH. ⺠The supressed food intake is associated with reduced levels of hypothalamic galanin.
