The metabolic response of human trophoblasts derived from term placentas to metformin.

AIMS/HYPOTHESIS: Metformin is increasingly used therapeutically during pregnancy worldwide, particularly in the treatment of gestational diabetes, which affects a substantial proportion of pregnant women globally. However, the impact on placental metabolism remains unclear. In view of the association between metformin use in pregnancy and decreased birthweight, it is essential to understand how metformin modulates the bioenergetic and anabolic functions of the placenta. METHODS: A cohort of 55 placentas delivered by elective Caesarean section at term was collected from consenting participants. Trophoblasts were isolated from the placental samples and treated in vitro with clinically relevant doses of metformin (0.01 mmol/l or 0.1 mmol/l) or vehicle. Respiratory function was assayed using high-resolution respirometry to measure oxygen concentration and calculated [Formula: see text]. Glycolytic rate and glycolytic stress assays were performed using Agilent Seahorse XF assays. Fatty acid uptake and oxidation measurements were conducted using radioisotope-labelled assays. Lipidomic analysis was conducted using LC-MS. Gene expression and protein analysis were performed using RT-PCR and western blotting, respectively. RESULTS: Complex I-supported oxidative phosphorylation was lower in metformin-treated trophoblasts (0.01 mmol/l metformin, 61.7% of control, p<0.05; 0.1 mmol/l metformin, 43.1% of control, p<0.001). The proton efflux rate arising from glycolysis under physiological conditions was increased following metformin treatment, up to 23±5% above control conditions following treatment with 0.1 mmol/l metformin (p<0.01). There was a significant increase in triglyceride concentrations in trophoblasts treated with 0.1 mmol/l metformin (p<0.05), particularly those of esters of long-chain polyunsaturated fatty acids. Fatty acid oxidation was reduced by ~50% in trophoblasts treated with 0.1 mmol/l metformin compared with controls (p<0.001), with no difference in uptake between treatment groups. CONCLUSIONS/INTERPRETATION: In primary trophoblasts derived from term placentas metformin treatment caused a reduction in oxidative phosphorylation through partial inactivation of complex I and potentially by other mechanisms. Metformin-treated trophoblasts accumulate lipids, particularly long- and very-long-chain polyunsaturated fatty acids. Our findings raise clinically important questions about the balance of risk of metformin use during pregnancy, particularly in situations where the benefits are not clear-cut and alternative therapies are available.

PLK1 inhibition dampens NLRP3 inflammasome-elicited response in inflammatory disease models.

Unabated activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome is linked with the pathogenesis of various inflammatory disorders. Polo-like kinase 1 (PLK1) has been widely studied for its role in mitosis. Here, using both pharmacological and genetic approaches, we demonstrate that PLK1 promoted NLRP3 inflammasome activation at cell interphase. Using an unbiased proximity-dependent biotin identification (Bio-ID) screen for the PLK1 interactome in macrophages, we show an enhanced proximal association of NLRP3 with PLK1 upon NLRP3 inflammasome activation. We further confirmed the interaction between PLK1 and NLRP3 and identified the interacting domains. Mechanistically, we show that PLK1 orchestrated the microtubule-organizing center (MTOC) structure and NLRP3 subcellular positioning upon inflammasome activation. Treatment with a selective PLK1 kinase inhibitor suppressed IL-1ß production in in vivo inflammatory models, including LPS-induced endotoxemia and monosodium urate-induced peritonitis in mice. Our results uncover a role of PLK1 in regulating NLRP3 inflammasome activation during interphase and identify pharmacological inhibition of PLK1 as a potential therapeutic strategy for inflammatory diseases with excessive NLRP3 inflammasome activation.