Increased global placental DNA methylation levels are associated with gestational diabetes

BACKGROUND: Gestational diabetes mellitus (GDM) is associated with adverse pregnancy outcomes. It is known that GDM is associated with an altered placental function and changes in placental gene regulation. More recent studies demonstrated an involvement of epigenetic mechanisms. So far, the focus regarding placental epigenetic changes in GDM was set on gene-specific DNA methylation analyses. Studies that robustly investigated placental global DNA methylation are lacking. However, several studies showed that tissue-specific alterations in global DNA methylation are independently associated with type 2 diabetes. Thus, the aim of this study was to characterize global placental DNA methylation by robustly measuring placental DNA 5-methylcytosine (5mC) content and to examine whether differences in placental global DNA methylation are associated with GDM. METHODS: Global DNA methylation was quantified by the current gold standard method, LC-MS/MS. In total, 1030 placental samples were analyzed in this single-center birth cohort study. RESULTS: Mothers with GDM displayed a significantly increased global placental DNA methylation (3.22 ± 0.63 vs. 3.00 ± 0.46 %; p = 0.013; ±SD). Bivariate logistic regression showed a highly significant positive correlation between global placental DNA methylation and the presence of GDM (p = 0.0009). Quintile stratification according to placental DNA 5mC levels revealed that the frequency of GDM was evenly distributed in quintiles 1-4 (2.9-5.3 %), whereas the frequency in the fifth quintile was significantly higher (10.7 %; p = 0.003). Bivariate logistic models adjusted for maternal age, BMI, ethnicity, recurrent miscarriages, and familiar diabetes predisposition clearly demonstrated an independent association between global placental DNA hypermethylation and GDM. Furthermore, an ANCOVA model considering known predictors of DNA methylation substantiated an independent association between GDM and placental DNA methylation. CONCLUSIONS: This is the first study that employed a robust quantitative assessment of placental global DNA methylation in over a thousand placental samples. The study provides large scale evidence that placental global DNA hypermethylation is associated with GDM, independent of established risk factors

Association between placental global DNA methylation and blood pressure during human pregnancy

Objective: Gene-specific placental DNA methylation patterns differ between normal pregnancies and pregnancies complicated by hypertension. However, whether global placental DNA methylation is associated with maternal blood pressure remains controversial. Methods: Using multiple linear regression models, we analysed the association between maternal mean arterial pressure (MAP) at the third trimester of pregnancy and global DNA methylation in the placenta in 922 mothers using LC-ESI-MS/MS. To better characterize the contribution of genetic or epigenetic mechanisms, we performed isolated analyses in mothers with and without a family history of hypertension. Results: Mean placental global DNA methylation was 3.00 ± 0.46%. A significant negative correlation between placental global DNA methylation and mean arterial blood pressure (MAP) in the third trimester could be observed (P = 0.023, r = –0.075). This association remained significant after adjusting for confounders. In placenta samples from mothers with a family history of hypertension, mean maternal MAP was higher (86.1 ± 8.1 vs. 84.6 ± 7.5, P < 0.01) and placental global DNA methylation was lower (2.94 ± 0.43 vs. 3.04 ± 0.47, P < 0.01) compared with samples without a family history of hypertension. Furthermore, the significant independent negative correlation between global placental DNA methylation and MAP was only found in mothers without a family history of hypertension. Conclusion: This study showed an independent negative correlation between placental global DNA methylation and maternal MAP in mothers without a family history of hypertension

Inhibition of acid sphingomyelinase increases regulatory T cells in humans

Genetic deficiency for acid sphingomyelinase or its pharmacological inhibition has been shown to increase Foxp3$^+$ regulatory T-cell frequencies among CD4$^+$ T cells in mice. We now investigated whether pharmacological targeting of the acid sphingomyelinase, which catalyzes the cleavage of sphingomyelin to ceramide and phosphorylcholine, also allows to manipulate relative CD4$^+$ Foxp3$^+$ regulatory T-cell frequencies in humans. Pharmacological acid sphingomyelinase inhibition with antidepressants like sertraline, but not those without an inhibitory effect on acid sphingomyelinase activity like citalopram, increased the frequency of Foxp3$^+$ regulatory T cell among human CD4$^+$ T cells in vitro. In an observational prospective clinical study with patients suffering from major depression, we observed that acid sphingomyelinase-inhibiting antidepressants induced a stronger relative increase in the frequency of CD4$^+$ Foxp3$^+$ regulatory T cells in peripheral blood than acid sphingomyelinase-non- or weakly inhibiting antidepressants. This was particularly true for CD45RA$^-$ CD25$^{high}$ effector CD4$^+$ Foxp3$^+$ regulatory T cells. Mechanistically, our data indicate that the positive effect of acid sphingomyelinase inhibition on CD4$^+$ Foxp3$^+$ regulatory T cells required CD28 co-stimulation, suggesting that enhanced CD28 co-stimulation was the driver of the observed increase in the frequency of Foxp3+ regulatory T cells among human CD4$^+$ T cells. In summary, the widely induced pharmacological inhibition of acid sphingomyelinase activity in patients leads to an increase in Foxp3+ regulatory T-cell frequencies among CD4$^+$ T cells in humans both in vivo and in vitro