Role of galectin-9 in the development of gestational diabetes mellitus.

Galectin-9 (Gal-9) is highly expressed in trophoblasts in placenta. Interaction between Gal-9 and T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) is important for the differentiation of tissue resident natural killer (trNK) cells in placenta and maintenance of normal pregnancy. Furthermore, the enhanced maternal systemic inflammation associated with increased proinflammatory cytokines in preeclampsia is mediated by enhanced interaction between Gal-9 and Tim-3. However, the role of Gal-9 in gestational diabetes (GDM) remains unexplored. Plasma Gal-9 levels were elevated at 3rd trimester in pregnant women with GDM and positively correlated with placenta and newborn weight. Lgals9 knockout pregnant mice fed with high fat diet (HFD KO) demonstrated maternal glucose intolerance and fetus macrosomia compared with controls (HFD WT). In HFD KO, increased proliferating cells, reduced apoptosis, and autophagy impairment were observed in junctional zones. The number of trNK cells and percentage of Tim-3 + trNK increased, while early apoptosis percentage in Tim-3 + trNK was reduced in placenta of HFD KO. The elevation of plasma Gal-9 may be a biomarker for prediction of maternal glucose intolerance and fetal macrosomia in pregnant women with GDM and Gal-9 functions as a compensation factor for GDM by inducing apoptosis in Tim-3 + trNK cells.