A predisposing factor for development of the hyperglycaemic state of gestational diabetes mellitus (GDM) is obesity. We previously showed that increasing maternal obesity is associated with significant reductions in placental mitochondrial respiration. MicroRNA (miR)-143 has been previously shown to regulate the metabolic switch from oxidative phosphorylation to aerobic glycolysis in cancer tissues. We hypothesized that mitochondrial respiration is reduced and aerobic glycolysis is up-regulated via changes in miR-143 expression in the placenta of women with GDM. Placental tissue was collected at term from women with A1GDM (controlled by diet), A2GDM (controlled by medication) and body mass index (BMI)-matched controls (CTRL). miR-143 expression was measured by RT-PCR. Expression of mitochondrial complexes, transcription factors peroxisome proliferator-activated receptor-γ co-activator 1α (PGC1α) and peroxisome proliferator-activated receptor γ (PPARγ), components of mammalian target of rapamycin (mTOR) signalling, glucose transporter GLUT1 and glycolytic enzymes [hexokinase-2 (HK-2), phosphofructokinase (PFK) and lactate dehydrogenase (LDH)] were measured by Western blot. Trophoblast respiration was measured by XF24 Analyser. Expression of miR-143, mitochondrial complexes, and PPARγ and PGC1α, which act downstream of miR-143, were significantly decreased in A2GDM placentae compared with A1GDM and CTRL (P<0.01). Placental hPL (human placental lactogen) levels, expression of glycolytic enzymes, GLUT1 and mTOR signalling were also significantly increased by more than 2-fold in A2GDM compared with A1GDM and CTRL (P<0.05). There was a 50% reduction in mitochondrial respiration in trophoblast cells isolated from A2GDM placentae. Overexpression of miR-143 was able to increase mitochondrial respiration, increase protein expression of mitochondrial complexes and decrease expression of glycolytic enzymes by 40% compared with A2GDM. Down-regulation of miR-143 mediates the metabolic switch from oxidative phosphorylation to aerobic glycolysis in placenta of women with A2GDM.

The inflammatory and metabolic derangements of obesity in pregnant women generate an adverse intrauterine environment, increase pregnancy complications and adverse fetal outcomes and program the fetus for obesity and metabolic syndrome in later life. We hypothesized that epigenetic modifications in placenta including altered DNA methylation/hydroxymethylation may mediate these effects. Term placental villous tissue was collected following cesarean section from lean (prepregnancy BMI30) women. Genomic DNA was isolated, methylated and hydroxymethylated DNA immunoprecipitated and hybridized to the NimbleGen 2.1M human DNA methylation array. Intermediate metabolites in placental tissues were measured by HPLC-ESI-MS, ascorbate levels by reverse phase HPLC and gene expression by RT-PCR. Differentially methylated and hydroxymethylated regions occurred across the genome, with a 21% increase in methylated but a 31% decrease in hydroxymethylated regions in obese vs lean groups. Whereas increased methylation and decreased methylation was evident around transcription start sites of multiple genes in the GH/CSH and PSG gene clusters on chromosomes 17 and 19 in other areas there was no relationship. Increased methylation was associated with decreased expression only for some genes in these clusters. Biological pathway analysis revealed the 262 genes which showed reciprocal differential methylation/ hydroxymethylation were enriched for pregnancy, immune response and cell adhesion-linked processes. We found a negative relationship for maternal BMI but a positive relationship for ascorbate with α-ketoglutarate a metabolite that regulates ten eleven translocase (TET) which mediates DNA methylation. We provide evidence for the obese maternal metabolic milieu being linked to an altered DNA methylome that may affect placental gene expression in relation to adverse outcomes.

Objective: Maternal obesity and gestational diabetes mellitus (GDM) are associated with adverse outcomes, particularly with a male fetus. The composition and amount of substrate supplied to the placenta are altered in these conditions. We hypothesized that there are sexually dimorphic differences in utilization of glucose, fatty acids, and glutamine between trophoblast of lean women, women with obesity, and women with GDM.Design: Trophoblasts were isolated from term male or female placentas from lean women, women with obesity, or women with GDM (n = 4 to 6 per group), and syncytiotrophoblast formed during 72 hours before measuring mitochondrial respiration by a fuel flex assay (Seahorse XF96 analyzer). Dependency, capacity, and flexibility for use of glucose, glutamine, and fatty acids were measured with western blot of glucose transporter GLUT1, glutaminase, and carnitine palmitoyltransferase 1A.Results: Sexual dimorphism in syncytiotrophoblast fuel utilization was seen in women with GDM vs lean women with a significant increase in glucose dependency in males and glucose capacity in females, whereas for glutamine, capacity was significantly decreased in males and females but dependency significantly decreased only in females. Fatty acid dependency and capacity significantly increased in male trophoblast and capacity in female trophoblast of women with GDM vs either lean women or women with obesity. In male but not female trophoblast, flexibility to use all three fuels significantly decreased from lean women to women with obesity and women with GDM. In male trophoblast there were significant associations between GLUT1 and glucose dependency (positive) and flexibility (negative).Conclusions: Human syncytiotrophoblast utilizes glutamine for mitochondrial respiration. Utilization of glucose, fatty acids, and glutamine changes in a sexually dimorphic manner with obesity and GDM, predominantly with a male placenta.