PVN Orexin Receptor 1 Knockdown Effect on Metabolism and Fluid Homeostasis
Previous research has shown the importance of orexin, a neuropeptide, in the regulation of appetite, sleep, and arousal. However, limited research has been done on the impact of orexin in the hypothalamic paraventricular nucleus (PVN) on the control of metabolism and body fluid homeostasis. In this...
Saved in:
| Published in: | The FASEB journal Vol. 32; no. S1; p. lb465 |
|---|---|
| Main Authors: | , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
The Federation of American Societies for Experimental Biology
01-04-2018
|
| Online Access: | Get full text |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Previous research has shown the importance of orexin, a neuropeptide, in the regulation of appetite, sleep, and arousal. However, limited research has been done on the impact of orexin in the hypothalamic paraventricular nucleus (PVN) on the control of metabolism and body fluid homeostasis. In this study, we investigated the role of PVN orexin signaling on metabolism through chronic knockdown of orexin 1 receptor (OX1R) using AAV1‐OX1R‐shRNA. Seven‐week‐old male Dahl Salt sensitive rats were divided into two groups and were microinjected with either AAV2‐scembled‐shRNA (n=6) or AAV2‐OX1R‐shRNA (n=5) into the PVN. After one week recovery from the surgery, all rat baseline body weights were measured. There was no significant difference found between the groups. The rats were then fed with a high salt diet (HS, 4% NaCl) for 5 consecutive weeks, after which body weights were once again measured and the rats were then transferred into individual metabolic cages. Rats were given 24 hours to get accustomed to the new environment and their food intake, water intake, urine excretion, and fecal output were measured for 24 hours. The results showed that PVN OX1R knockdown rats had a lower body weight when compared to control rats after the 5 weeks of high salt intake (Control: 336.6±9.10, vs. OX1R‐shRNA: 299.8±14.62 g P<0.05). In addition, chronic knockdown of PVN OX1R showed a significant decrease in water intake (Control: 43.67±3.72, vs. OX1R‐shRNA: 24.96±5.16 mL P<0.05), urine output (Control: 27.0±3.32, vs. OX1R‐shRNA: 14.04±2.75 mL P<0.05), and food intake (Control: 20.85±2.16, vs. OX1R‐shRNA: 13.68±1.84 g P≤0.05), but there was no fecal output alteration observed between PVN OX1R knockdown rats and control rats. At the end of this protocol, rats were euthanized and their brains were removed and subjected to either real time PCR or immunostaining to test mRNA or protein expression of the genes of interest in the PVN. Real time PCR showed that AAV2‐OX1R‐shRNA injection decreased OX1R mRNA level by 41%, and melanocortin‐4 receptor (MC4R) mRNA by 68% compared to control vector injection group. Immunostaining showed that both vasopressin immunoreactivity and positive vasopressin expressing cells are dramatically decreased in the PVN of AAV2‐OX1R‐shRNA rats as well. These observations coupled with the importance of MC4R in controlling satiety, and vasopressin in controlling urine water excretion, suggest that orexin plays a large and complex regulatory role in fluid homeostasis within the body as well as in appetite, through direct mediation by the PVN.
Support or Funding Information
NIHR15 HL129213 (Shan) and Michigan Tech and Portage Health Foundation Research Excellent Fund (Shan).
This is from the Experimental Biology 2018 Meeting. There is no full text article associated with this published in The FASEB Journal. |
|---|---|
| ISSN: | 0892-6638 1530-6860 |
| DOI: | 10.1096/fasebj.2018.32.1_supplement.lb465 |