BACKGROUND: Compared with normal postmenopausal women, estrogen deficiency and hyperglycemia in postmenopausal women with type 2 diabetes (T2DM) lead to more severe bone property degradation. Liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, has been reported to improve bone condition among people with T2DM but the precise mechanisms remain unclear. Exosomes work as mediators in cell-to-cell communication, delivering functional miRNAs between cells. We aimed to explore the role of exosomes in T2DM-related bone metabolic disorders and the bone protective mechanisms of liraglutide.

MATERIAL AND METHODS: We made comparative analyses of bone marrow-derived exosomal miRNAs from ovariectomized (OVX) control rats, OVX + T2DM rats, and OVX + T2DM + liraglutide-treated rats. miRNA profiles were generated using high-throughput sequencing. Target gene prediction and pathway analysis were performed to investigate the signal pathway alterations. Three miRNAs were randomly chosen to validate their absolute expression levels by real-time quantitative PCR.

RESULTS: Bone marrow-derived exosomal miRNAs were different with respect to miRNA numbers, species, and expression levels. miRNA spectra varied under T2DM condition and after liraglutide treatment. By bioinformatics analysis, we found T2DM and liraglutide administration lead to significant changes in exosomal miRNAs which targeted to insulin secretion and insulin-signaling pathway. Wnt signaling pathway alteration was the critical point regarding bone metabolism.

CONCLUSIONS: Our findings show the selective packaging of functional miRNA cargoes into exosomes due to T2DM and liraglutide treatment. Bone marrow exosome-mediated Wnt signaling pathway alteration may play a part in the bone protective effect of liraglutide.

Keywords: Diabetes Mellitus, Type 2, exosomes, Glucagon-Like Peptide 1, Postmenopause