Endocrine Abstracts

Aim: Traumatic brain injury (TBI) is known to be associated with pituitary insufficiency (PI). We have recently shown that there was a relationship between miR-126-3p, miR-3610 and PI developing in follow up of patients with TBI. In this study, we aimed to test the effects of miR-126-3p on hypothalamus pituitary-adrenal (HPA) and Growth hormone-Insulin like growth factor (GH-IGF-1) axes.

Materials and methods: miR126-3p microinjection was performed to mouse embryos and mild-TBI was applied to these mice at 2 months of age. Tissue expression levels of corticotrophin releasing hormone (CRH), propiomelanocortin (POMC), corticosterone (CORT), GH genes and serum levels of CRH, corticotrophin (ACTH), CORT, GH and IGF-1 were determined in acute (24 hours after trauma) and chronic (a month after trauma) periods of TBI.

Results: miR126-3p microinjected mice had similar hypothalamic CRH, higher pituitary POMC and higher adrenal CORT expression; similar serum CRH, higher ACTH and similar CORT levels compared to controls. In acute TBI, miR126-3p microinjected mice had similar hypothalamic CRH, higher pituitary POMC and similar adrenal CORT expression; higher serum CRH, ACTH and CORT levels than controls with acute TBI. In chronic TBI, miR126-3p microinjected mice had similar hypothalamic CRH, similar pituitary POMC and higher adrenal CORT expression; similar serum CRH, ACTH and CORT levels compared to controls with chronic TBI. miR126-3p microinjected mice had higher pituitary GH expression, higher serum GH and similar serum IGF-1 levels compared to controls. In acute TBI, miR126-3p microinjected mice had higher pituitary GH expression, higher serum GH and similar serum IGF-1 levels compared to controls with acute TBI. In chronic TBI, miR126-3p microinjected mice had higher pituitary GH expression, higher serum GH and similar serum IGF-1 levels compared to controls with chronic TBI.

Conclusion: miR126-3p may have a protective role in HPA axis functions after acute TBI, but this protective effect is not seen in chronic TBI. miR126-3p is associated with higher GH levels in mice with acute and chronic trauma and without trauma. Similar IGF levels despite higher GH levels may show a state of GH resistance in miR126-3p microinjected mice.