miR-709 Blocks Growth Hormone Production Stimulated by GHRP6 in Pituitary Cells

The pituitary gland is crucial for producing Growth Hormone (GH), a peptide hormone vital for growth, metabolism, and body composition. Growth Hormone Releasing Peptide 6 (GHRP6) is a synthetic compound known to potently stimulate GH release, often used in research to understand GH regulation. While the mechanisms of GHRP6 action are well-studied, the precise role of microRNAs (miRNAs)—small non-coding RNA molecules that regulate gene expression—in modulating GHRP6-induced GH synthesis remains largely unexplored. This study aimed to uncover if and how miR-709, a specific microRNA, influences GHRP6-stimulated GH production and identify its molecular targets within pituitary cells.

The study revealed that GHRP6 treatment significantly increased GH synthesis, showing a 2.3-fold increase in GH mRNA levels compared to untreated controls (p<0.01). When miR-709 was overexpressed in these cells, it potently inhibited this GHRP6-induced GH production. > miR-709 overexpression led to a 43% reduction in GHRP6-stimulated GH mRNA levels and a 35% decrease in GH protein secretion compared to cells treated with GHRP6 alone (p<0.001). Further mechanistic investigations confirmed that miR-709 directly targets the 3'-UTR (untranslated region) of the PRKCA gene, leading to a significant 30% decrease in PRKCA protein expression. Importantly, knocking down PRKCA using siRNA (small interfering RNA) alone resulted in a 38% reduction in basal GH synthesis and a 40% attenuation of GHRP6-induced GH production, effectively mimicking the inhibitory effects of miR-709.