Endocrine Abstracts

Obesity is associated with increased and dysfunctional white adipose tissue (WAT). Pharmacological approaches of obesity are still far from obtaining a stable weight loss. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have been proposed as anti-obesity drugs due to their effects on weight loss. Furthermore, dual agonists engaging both GLP-1 and glucagon are currently under investigation for their marked effects on weight loss, although their mechanisms of action is still unclear. Compared to WAT, brown adipose tissue (BAT) is specialized in energy dissipation by heat production resulting from the specific expression of the mitochondrial enzyme uncoupling protein-1 (UCP-1). There is growing interest for new therapeutic strategies aimed at stimulating BAT to increase energy expenditure and counteract the dysfunctional expansion of WAT in obesity. Our group has previously demonstrated that liraglutide, GLP-1 and glucagon impair the proliferative and differentiation ability of an in vitro-model of primary human adipose-derived stem cells (ASCs), supporting a peripheral action of GLP-1RAs on weight loss. In this study, we compared the effect of these three molecules in reshaping adipogenesis toward brown adipogenesis by stimulating the “browning process” in ASCs. Glucagon, liraglutide and GLP-1 (10nM) added during in vitro-stimulated adipogenesis significantly reduced intracellular triglyceride accumulation evaluated by Adipored staining (-24%,-40%,-23%, P<0.001) associated with a decreased expression in the white-adipocyte marker FABP4 (-48%,-94%,-78%, P<0.05), while the functional marker adiponectin was upregulated (+34%,65%,72%, P<0.05). These findings suggest a differentiation reshape towards a more functional adipocyte phenotype. Moreover, adipogenesis in the presence of the three molecules resulted in a significant upregulation of the brown phenotype marker UCP-1 (fold-increase 2.13, 2.48, 2.14-fold versus adipogenesis alone, P<0.05). Mitochondrial functional analysis through Seahorse technology of the adipocytes differentiated in the presence glucagon, liraglutide and GLP-1 revealed a significant increase in the maximal respiration (+15%,25%,29%, P<0.05) and a similar reduction (-17%,-14%,-18%, P<0.001) in ATP production, supporting a stimulation of the browning process. Finally, morphological analysis of the differentiated adipocytes revealed that liraglutide, GLP-1 and glucagon addition to the adipogenic media associated with an increase in the number and surface of mitochondria and an increase in the number of lipid droplets with decreased diameter, coherently with the typical feature of brown adipocytes. In conclusion, we demonstrated a direct effect of glucagon and GLP1RAs in inducing a significant improvement of the in vitro-derived adipocytes, determining a metabolic shift towards the brown phenotype, coherently with a peripherical action exerted by these molecules directly on the adipose tissue.