Circ-PNPT1 contributes to gestational diabetes mellitus (GDM) by regulating the function of trophoblast cells through miR-889-3p/PAK1 axis

BACKGROUND: Gestational diabetes mellitus (GDM) is the most common medical complication of pregnancy. CircRNA polyribonucleotide nucleotidyltransferase 1 (circ-PNPT1) has been found to be abnormally expressed in GDM patients. However, function and mechanism of circ-PNPT1 in GDM remain largely undefined. METHODS: Levels of circ-PNPT1, microRNA (miR)-889-3p and PAK1 (p21 (RAC1) activated kinase 1) were detected using quantitative real-time polymerase chain reaction and Western blot assays. Cell viability, apoptosis, migration and invasion were determined using cell counting kit-8 assay, flow cytometry, transwell and wound healing assays, respectively. The binding interaction between miR-889-3p and circ-PNPT1 or PAK1 was verified using dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays. Exosomes were obtained from culture media by the use of commercial kits and qualified by transmission electron microscopy (TEM). RESULTS: Circ-PNPT1 was highly expressed in the placental tissues of GDM and high glucose (HG)-induced trophoblast cells. Knockdown of circ-PNPT1 reversed HG-induced arrest of trophoblast cell viability, migration, invasion and the promotion of cell apoptosis. Mechanistically, we confirmed circ-PNPT1 could promote the expression of PAK1, the target of miR-889-3p, by directly sponging miR-889-3p, and circ-PNPT1 regulated HG-induced trophoblast cell dysfunction by miR-889-3p/PAK1 axis. Further studies showed circ-PNPT1 was packaged into exosomes and could be internalized by surrounding trophoblast cells. CONCLUSION: Circ-PNPT1 promoted HG-induced trophoblast cell biological dysfunction through miR-889-3p/PAK1 axis. Meanwhile, it could be transferred from HG-induced trophoblast cells to surrounding untreated cells via exosomes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13098-021-00678-9.