The in vitro effect of leptin on growth hormone secretion from primary cultured ovine somatotrophs.
Chen. C C; Roh. S G SG; Nie. G Y GY; Loneragan. K K; Xu. R W RW; Ruan. M M; Clarke. L J LJ; Goding. J W JW; Gertler. A A
Key Findings
- Short‑term (30 min) leptin exposure (10⁻⁹‑10⁻⁷ M) does not affect basal, GHRH‑ or GHRP‑2‑stimulated GH secretion.
- After 1‑3 days of leptin treatment, GHRH‑stimulated GH release is reduced, while GHRP‑2‑stimulated GH release is increased.
- Leptin decreases GHRH receptor mRNA and increases GHRP‑2 receptor mRNA in somatotrophs after 3 days.
Practical Outcomes
- For biohackers using GHRP‑2, the study suggests that higher leptin levels (e.g., from excess body fat or leptin supplementation) might enhance the peptide's ability to boost GH after several days. Conversely, leptin may blunt the effect of GHRH‑based strategies. While the work is in sheep cells and not directly tested in humans, it hints that managing leptin (through diet, weight, or timing) could influence how well GHRP‑2 works for growth‑hormone related goals.
Summary
In sheep pituitary cells, leptin didn't change growth hormone (GH) release right away, but after a few days it lowered the response to the natural hormone GHRH and boosted the response to the peptide GHRP‑2. This shift happened because leptin reduced the number of GHRH receptors and increased the number of GHRP‑2 receptors on the cells.
Abstract
Although existing data suggest an influence of leptin on circulating levels of growth hormone (GH), the action site and properties of leptin are still controversial. Using primary cultured ovine pituitary cells, we studied the direct effect of leptin on the secretion of GH. Pituitary cells were dissociated by collagenase and subjected to Percoll gradient centrifugation to enrich the somatotroph population to 60-80% of cells. Treatment of primary cultured ovine somatotrophs with leptin (10(-9)-10(-7) M) for 30 min did not affect basal, GH-releasing hormone (GHRH) (10(-7) M)- or GH-releasing peptide-2 (GHRP-2)(10(-7) M)-stimulated GH secretion. Following treatment of cells for 1-3 d with leptin, GHRH-stimulated GH secretion was reduced and GHRP-2-stimulated GH secretion increased. The combined effect of GHRH and GHRP-2 on GH secretion was not altered by the treatment of cells with leptin for 3 d. GHRH receptor mRNA levels in cultured somatotrophs were decreased but GHRP receptor mRNA levels were increased by 3-d leptin treatment. These results suggest that leptin has a long-term effect on somatotrophs to reduce GHRH receptor synthesis leading to a decrease in GHRH-stimulated GH secretion. Leptin appears, however, to have an opposite effect on GHRP receptor synthesis leading to an increase in GHRP-stimulated GH secretion.
Study Information
pubmed
2001
10.1385/endo:14:1:073