Growth hormone releasing factor decreases long form leptin receptor expression in porcine anterior pituitary cells.
Lin. J J; Barb. C R CR; Kraeling. R R RR; Rampacek. G B GB
Key Findings
- GRF at concentrations from 10⁻⁸ to 10⁻⁶ M increased GH secretion by 20‑50% after 4 hours.
- The same GRF treatments reduced expression of the long form leptin receptor (Ob‑Rl) by 32‑50% in the same cells.
- The effect was observed in primary cultures from six pigs, indicating a direct pituitary-level action of GRF on leptin signaling.
Practical Outcomes
- For biohackers using sermorelin to raise GH, this study hints that higher GH may come with reduced pituitary leptin sensitivity, potentially influencing hunger or metabolic signaling. However, because the work is in vitro and in pigs, it does not provide concrete dosing or safety guidance for humans. It’s a modest piece of evidence that GRF can modulate leptin pathways, but more human research is needed before changing protocols.
Summary
In pig pituitary cells, the growth hormone releasing factor (GRF, the same peptide used in sermorelin) boosted growth hormone release and lowered the amount of the long form leptin receptor. This suggests GRF can directly affect how the pituitary responds to leptin, a hormone that regulates appetite and metabolism.
Abstract
Pituitary cells from six pigs, 180-200 days of age, were studied in primary culture to determine if growth hormone releasing factor (GRF) affects long form leptin receptor (Ob-Rl) expression. On Day 4 of culture, 10(5) live cells per well were challenged with either 0, 10(-6), 10(-7) or 10(-8)M [Ala15]-hGRF-(1-29)NH(2) (3 wells per treatment per pig). Secretion of growth hormone (GH) into the media and pituitary Ob-Rl mRNA expression were determined at 4 h after treatment. Media were analyzed for GH by radioimmunoassay, and total RNA was isolated from cells for determination of Ob-Rl expression by semi quantitative reverse transcription PCR. Basal GH concentration was 32+/-2 ng per 10(5) cells per well (n=18 wells) for 4 h. Relative to control at 4 h, 10(-6),10(-7) and 10(-8)M GRF increased (P<0.01) GH secretion by 151, 129 and 120%, but decreased (P<0.05) Ob-Rl expression by 32, 50 and 38%, respectively. These results indicate that GRF directly modulates Ob-Rl expression at the level of the pituitary, and thereby playing a role in regulating pituitary sensitivity to leptin.
Study Information
pubmed
2003
10.1016/s0739-7240(02)00209-6