Diabetes is a worldwide health problem with increasing prevalence. Some reports indicate the interplay between bone and glucose metabolism. The imbalance between bone resorption and formation resulted in the structural integrity and strength of bone. Glucagon-like peptide-1 (GLP-1) and its agonists (Liraglutide) have an anabolic action on bone remodeling by stimulating osteoblast differentiation as well as increasing osteoblast longevity. However, the underlying mechanisms remain elusive. We detected the presence of GLP-1 receptor (GLP-1R) in MC3T3-E1 cells via immunocytochemistry assay. Alkaline phosphatase activity assay, alizarin red stain, quantitative real-time polymerase chain reaction, and western blot were employed to detect the effect of Liraglutide on osteogenic differentiation. Liraglutide promoted the expression of GLP-1R in a dosage- and time-dependent manner, and it enhanced the osteogenic differentiation in MC3T3-E1 cells. Liraglutide application improved the levels of Smad2/3 and p-Smad2/3; however, the silencing of Smad2/3 blocked the osteogenic differentiation induced by Liraglutide. What is more, the application of PI3K and Wnt inhibitors inhibited the upregulation of Akt, p-Akt, β-catenin, Smad2/3, and p-Smad2/3 induced by Liraglutide. Liraglutide facilitated the osteogenic differentiation via the regulation of Smad2/3 via PI3K/AKT and Wnt/β-catenin pathways. These data revealed a new mechanism of Liraglutide inducing osteogenic differentiation and provided theory evidence to maintain normal bone metabolism during diabetes therapy.
Keywords: Liraglutide; Smad2/3; glucagon-like peptide-1 receptor; osteoblast differentiation; β-catenin.