ANGPTL8 regulates glucose metabolism in gestational diabetes mellitus mice, and proteomic analysis reveals the PI3K/Akt pathway plays its role in insulin-resistance HepG

backgroundInsulin resistance (IR) is a pivotal determinant in the pathophysiological processes underlying gestational diabetes mellitus (GDM). Angiopoietin-like protein 8 (ANGPTL8) exhibits an ambiguous influence on glucose metabolism in the onset and progression of GDM. However, the functions of ANGPTL8 in the metabolic profiles of insulin-resistant (IR) HepG2 cells, glucose tolerance in GDM mice, and the possible underlying mechanisms require further exploration.

methodsANGPTL8 knockout and over-expressing HepG2 cell lines were established. Glucose uptake capacity in three clones (wild-type, ANGPTL8 knockout, and over-expressing) of insulin-resistant HepG2 cells was detected. Proteomic analysis of the IR HepG2 cells identified a cluster of relevant signaling pathways, and the effect of ANGPTL8 on metabolomic changes was evaluated. The GDM model was induced by a high-fat diet (HFD) and intraperitoneal injection of Streptozotocin (STZ) in pregnant mice. An oral glucose tolerance test (OGTT) was performed in both GDM mice and ANGPTL8 over-expressing GDM mice.

resultsThe PI3K/Akt signaling cascade was stimulated by insulin resistance, and this activation could be effectively suppressed by inhibitors targeting PI3K, Akt, and GSK-3β. HepG2 cells over-expressing ANGPTL8 and exposed to high insulin concentrations demonstrated a marked enhancement in glucose uptake capacity, as opposed to their wild-type counterparts or ANGPTL8 knockout cells under IR conditions. The most substantial down-regulation was observed in lactate and branched-chain amino acids (BCAAs), which exhibited a positive correlation with IR. Promoted translation of ANGPTL8 was found in the liver, pancreas, and placental tissues of GDM mice. Significantly better glucose tolerance was observed in GDM mice transfected with m-ANGPTL8 compared with those that were not. Furthermore, the activation of Akt was observed in the primary hepatocytes of ANGPTL8 over-expressing GDM mice.

conclusionOver-expression of ANGPTL8 may increase glucose uptake capacity and influence the metabolic profiles in IR HepG2 cells, enhancing the insulin-mediated activation of the PI3K/Akt/GSK-3β pathway. ANGPTL8 may improve glucose tolerance in GDM mice. These findings might contribute to a new understanding of the roles of ANGPTL8 in glucose metabolism during the onset and progression of insulin resistance, providing novel insights for the clinical therapy of GDM.