Growth hormone-releasing hormone (GHRH) promotes the differentiation of myoblasts and white adipocytes into brown/beige adipocytes

Obesity and its associated metabolic disorders represent a major global health challenge, underscoring the need for novel therapeutic strategies aimed at enhancing energy expenditure and improving lipid metabolism. Adipose tissue plasticity, particularly the acquisition of thermogenic features by myogenic precursor cells and the browning of white adipocytes, has emerged as a promising target for counteracting metabolic dysregulations. While adrenergic and endocrine pathways governing brown and beige adipocyte differentiation and activation are well established, the contribution of hypothalamic-releasing hormones remains poorly understood. Growth hormone-releasing hormone (GHRH), an hypothalamic neuropeptide classically known for regulating growth hormone (GH) synthesis and secretion, has recently been implicated in extra-pituitary functions; however, its role in adipogenesis, browning, and thermogenic reprogramming has not yet been elucidated. This study investigated the ability of GHRH to enhance thermogenic reprogramming in three cellular models: C2C12 murine myoblasts and human skeletal myoblasts differentiated into brown adipocytes, and 3T3-L1 white adipocytes transdifferentiatiated into beige adipocytes. Cells were differentiated in the absence or presence of GHRH, and thermogenic activation was assessed through gene and protein expression analyses, lipid metabolism assays, immunofluorescence, mitochondrial activity measurements, and oxygen consumption rate profiling. GHRH significantly enhanced the acquisition of thermogenic features in all models tested. Specifically, GHRH upregulated key thermogenic markers (Ucp1, Pgc-1α, Prdm16), increased the expression of brown/beige-specific genes (Cidea, Dio2, Tmem26, Tnfrsf9), and promoted a metabolic shift from lipid storage toward lipid mobilization and oxidation by suppressing lipogenic regulators (Srebp1, Acaca, Fasn), increasing ATGL expression and glycerol release, and inducing mitochondrial and peroxisomal β-oxidation genes (Cpt1b, Acox). Morphologically, GHRH-treated cells exhibited characteristics of brown adipocytes, including a higher number of small lipid droplets. GHRH also stimulated mitochondrial biogenesis and function, as demonstrated by enhanced MitoTracker and UCP1 staining, upregulation of Nrf1 and Tfam, and improved oxygen consumption parameters. These effects were conserved in human myoblast-derived brown adipocytes, supporting the translational relevance of our findings. Mechanistically, GHRH exerted it thermogenic and metabolic actions through activation of the AMPK/SIRT1 and PKA/CREB signaling pathways, two central regulators of cellular energy homeostasis and thermogenic gene expression. Importantly, pharmacological inhibition of either GHRH receptor signaling or the downstream AMPK and PKA pathways abolished all GHRHdependent effects, confirming the specificity of GHRH-mediated mechanisms. Collectively, this study provides comprehensive evidence that GHRH acts as a peripheral metabolic regulator capable of enhancing thermogenic reprogramming in both myogenic and adipogenic lineages. By coordinating the activation of thermogenic genes, mitochondrial biogenesis, and lipid catabolism, the GHRH/GHRH-R axis emerges as a promising therapeutic target for obesity and metabolic disorders characterized by impaired adipose tissue function and lipid dysregulation.