Abstract
Previous studies have shown that very lowdose infusions of leptin into the third or the fourth ventricle alone have little effect on energy balance, but simultaneous low-dose infusions cause rapid weight loss and increased phosphorylation of STAT3 (p-STAT3) in hypothalamic sites that express leptin receptors. Other studies show that injecting high doses of leptin into the fourth ventricle inhibits food intake and weight gain. Therefore, we tested whether fourth-ventricle leptin infusions that cause weight loss are associated with increased leptin signaling in the hypothalamus. In a dose response study 14-day infusions of increasing doses of leptin showed significant hypophagia, weight loss, and increased hypothalamic p-STAT3 in rats receiving at least 0.9 μg leptin/day. In a second study 0.6 μg leptin/day transiently inhibited food intake and reduced carcass fat, but had no significant effect on energy expenditure. In a final study, we identified the localization of STAT3 activation in the hypothalamus of rats receiving 0, 0.3, or 1.2 μg leptin/day. The high dose of leptin, which caused weight loss in the first experiment, increased p-STAT3 in the ventromedial, dorsomedial, and arcuate nuclei of the hypothalamus. The low dose that increased brown fat UCP1 but did not affect body composition in the first experiment had little effect on hypothalamic p-STAT3. We propose that hindbrain leptin increases the precision of control of energy balance by lowering the threshold for leptin signaling in the forebrain. Further studies are needed to directly test this hypothesis.
| Original language | English (US) |
|---|---|
| Pages (from-to) | E939-E948 |
| Journal | American Journal of Physiology - Endocrinology and Metabolism |
| Volume | 311 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jan 1 2016 |
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Keywords
- Body composition
- Energy expenditure
- Food intake
- Rats
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Physiology
- Physiology (medical)
Cite this
Fourth-ventricle leptin infusions dose-dependently activate hypothalamic signal transducer and activator of transcription 3. / Harris, Ruth B.S.; Desai, Bhavna N.
In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 311, No. 6, 01.01.2016, p. E939-E948.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Fourth-ventricle leptin infusions dose-dependently activate hypothalamic signal transducer and activator of transcription 3
AU - Harris, Ruth B.S.
AU - Desai, Bhavna N.
PY - 2016/1/1
Y1 - 2016/1/1
N2 - Previous studies have shown that very lowdose infusions of leptin into the third or the fourth ventricle alone have little effect on energy balance, but simultaneous low-dose infusions cause rapid weight loss and increased phosphorylation of STAT3 (p-STAT3) in hypothalamic sites that express leptin receptors. Other studies show that injecting high doses of leptin into the fourth ventricle inhibits food intake and weight gain. Therefore, we tested whether fourth-ventricle leptin infusions that cause weight loss are associated with increased leptin signaling in the hypothalamus. In a dose response study 14-day infusions of increasing doses of leptin showed significant hypophagia, weight loss, and increased hypothalamic p-STAT3 in rats receiving at least 0.9 μg leptin/day. In a second study 0.6 μg leptin/day transiently inhibited food intake and reduced carcass fat, but had no significant effect on energy expenditure. In a final study, we identified the localization of STAT3 activation in the hypothalamus of rats receiving 0, 0.3, or 1.2 μg leptin/day. The high dose of leptin, which caused weight loss in the first experiment, increased p-STAT3 in the ventromedial, dorsomedial, and arcuate nuclei of the hypothalamus. The low dose that increased brown fat UCP1 but did not affect body composition in the first experiment had little effect on hypothalamic p-STAT3. We propose that hindbrain leptin increases the precision of control of energy balance by lowering the threshold for leptin signaling in the forebrain. Further studies are needed to directly test this hypothesis.
AB - Previous studies have shown that very lowdose infusions of leptin into the third or the fourth ventricle alone have little effect on energy balance, but simultaneous low-dose infusions cause rapid weight loss and increased phosphorylation of STAT3 (p-STAT3) in hypothalamic sites that express leptin receptors. Other studies show that injecting high doses of leptin into the fourth ventricle inhibits food intake and weight gain. Therefore, we tested whether fourth-ventricle leptin infusions that cause weight loss are associated with increased leptin signaling in the hypothalamus. In a dose response study 14-day infusions of increasing doses of leptin showed significant hypophagia, weight loss, and increased hypothalamic p-STAT3 in rats receiving at least 0.9 μg leptin/day. In a second study 0.6 μg leptin/day transiently inhibited food intake and reduced carcass fat, but had no significant effect on energy expenditure. In a final study, we identified the localization of STAT3 activation in the hypothalamus of rats receiving 0, 0.3, or 1.2 μg leptin/day. The high dose of leptin, which caused weight loss in the first experiment, increased p-STAT3 in the ventromedial, dorsomedial, and arcuate nuclei of the hypothalamus. The low dose that increased brown fat UCP1 but did not affect body composition in the first experiment had little effect on hypothalamic p-STAT3. We propose that hindbrain leptin increases the precision of control of energy balance by lowering the threshold for leptin signaling in the forebrain. Further studies are needed to directly test this hypothesis.
KW - Body composition
KW - Energy expenditure
KW - Food intake
KW - Rats
UR - http://www.scopus.com/inward/record.url?scp=85006058994&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85006058994&partnerID=8YFLogxK
U2 - 10.1152/ajpendo.00343.2016
DO - 10.1152/ajpendo.00343.2016
M3 - Article
C2 - 27802966
AN - SCOPUS:85006058994
VL - 311
SP - E939-E948
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
SN - 0363-6135
IS - 6
ER -