Table 2.

Human studies investigating epigenetic alterations in pregnant women with hyperglicemia and in their offspring.

Author Year [Reference]	Study Design	Sample size	Hyperglicemia criteria	Tissue	Method	Main finding
Bouchard 2010 [95]	Case-control	48 (23 IGT)	2-h 75 g OGTT, IGT glucose ≥7.8 mmol/L at 2-h	Placenta (foetal and maternal) UCB	Bisulfite pyrosequencing	Correlation between LEP DNA methylation and 2h glucose levels in IGT women
Bouchard 2012 [96]	Cohort	98 (31 IGT)	2-h 75 g OGTT, IGT glucose ≥7.8 mmol/L at 2-h according to WHO	Placenta (foetal and maternal) UCB MBS	Bisulfite pyrosequencing	Inverse correlation between ADIPOQ DNA methylation on the foetal side and 2h glucose levels in IGT women
Houde 2013 [97]	Cohort	100 (26 IGT)	2-h 75 g OGTT, IGT glucose ≥7.8 mmol/L at 2-h according to WHO	Placenta (foetal and maternal) UCB MBS	Bisulfite pyrosequencing qRT-PCR	Positive correlation between ABCA1 DNA methylation on the maternal side and HDL-C and 2h glucose levels in IGT women correlation between DNA methylation on the fetal side and TGs in UCB Negative correlation between ABCA1 DNA methylation in UCB and 2h glucose levels
El Hajj 2013 [103]	Cohort	251 offspring (88 OD-GDM 98 OI-GDM 65 O non-GDM)	2-h 75 g OGTT, GDM glucose >180 mg/dL at 1 h and/or >155 mg/dL at 2 h	Placenta UCB	Bisulfite pyrosequencing	Decreased methylation of MEST, NR3C1, and ALUs in O-GDM
Ruchat 2013 [100]	Case-control	44 offspring (30 O-GDM)	2-h 75 g OGTT, GDM glucose ≥7.8 mmol/L at 2 h according to WHO	Placenta (foetal) UCB	Infinium HumanMethylation450 array	Number of genes potentially differentially methylated in the placenta and UCB in O-GDM
Quilter 2014 [87]	Cohort	C-HAPO cohort (n = 36) I-CBGS cohort [n = 96 (16 GDM)]	WHO criteria	UCB	Human Methylation27 BeadChip	Different methylation of some loci related to growth and diabetes
Houde 2014 [99]	Cohort	126 (27 GDM)	2-h 75 g OGTT, GDM glucose ≥7.8 mmol/L according to WHO criteria	Placenta (foetal)	Bisulfite pyrosequencing qRT-PCR	Lower LPL DNA methylation levels in GDM. Negative correlation between LPL DNA methylation levels in GDM and maternal 2h glucose levels/HDL-C
Desgagne 2014 [101]	Cohort	140 (IGT 34)	2-h 75 g OGTT, IGT glucose ≥7.8 mmol/L at 2 h according to WHO criteria	Placenta (foetal)	Bisulfite pyrosequencing qRT-PCR	Lower IGF1R and IGFBP3 DNA methylation levels and correlation with maternal 2h glucose levels Association between IGF1R mRNA levels and newborns’ growth markers
Petropoulos 2015 [102]	Case control	14 (7 mild hyperglicemia)	GCT or a OGTT (1 week after GCT)	Placenta	Infinium HumanMethylation450 array	Different methylation of some loci involved in endocrine function, metabolism, and insulin responses
Reichetzeder 2016 [94]	Cohort	1030 (56 GDM)	GDA and DGGG 2014	Placenta (maternal)	LC-MS/MS	Increased global methylation in GDM
Côté 2016 [105]	Cohort	E-21 birth cohort (n = 133, 33 GDM) Gen3G birth cohort (n = 172, all controls)	E-21: 2h OGTT, GDM glucose ≥7.8 mmol/L according to WHO criteria Gen3G: 2h OGTT according to IADPSG 2010	Placenta (foetal)	E-21: bisulfite pyrosequencing Gen3G: HumanMethylation450 array	Inverse correlation between PRDM16, BMP7 and PPARGC1A DNA methylation levels and maternal glycemia at the 2nd and 3rd trimester
Gagné-Ouellet 2017 [17]	Prospective birth cohort	66 offspring (24 O-GDM)	2-h 75 g OGTT, GDM glucose ≥7.8 mmol/L according to WHO criteria	Placenta (foetal) Offspring’s whole blood at 5 years	Bisulfite pyrosequencing qRT-PCR	Negative correlation between LPL DNA methylation and mRNA levels in placenta Positive correlation between LPL DNA methylation levels and anthropometric profile at 5 years of age
Chen 2017 [53]	Cohort	388 Pima Indian offspring (187 O-T2DM, 201 O-BP)	2-h 75 g OGTT, T2DM FBG≥7 mmol/L or 2-h glucose ≥11.1 mmol/L according to WHO criteria	blood samples	Illumina HumanMethylation450 K	Different methylation at multiple genomic sites
Houshmand-Oeregaard 2017 [106]	Cohort	206 adult offspring (82 O-GDM, 67 O-T1DM, 57 O-BP)	Mother = 3-h 50g OGTT in women at risk with two consecutive FBG ≥4.1 mmol/l Offspring = 2-h 75g OGTT according to WHO 2006 criteria	SAT plasma	Bisulfite pyrosequencing qRT-PCR	Increased ADIPOQ methylation levels and decreased ADIPOQ and RETN gene expression in SAT of O-GDM
Ott 2018 [107]	prospective observational cohort	55 mother-child dyads (25 GDM)	National Germany guidelines	SAT VAT UCB blood samples	Bisulfite pyrosequencing qRT-PCR	Alteration of ADIPOQ DNA methylation profiles in CB cells of O-GDM Reduction of mRNA adiponectin levels in SAT and VAT of GDM women
Ott 2019 [108]	Prospective observational	55 mother-child dyads (25 GDM)	National Germany guidelines	SAT VAT UCB blood samples	Bisulfite pyrosequencing qRT-PCR	Similar DNA methylation patterns across tissues Reduction of IR mRNA/protein expressions in SAT and VAT of GDM women

IGT, Impaired Glucose Tolerance; OGTT, oral glucose tolerance test; UCB, umbilical cord blood; MBS, Maternal blood samples; qRT-PCR, quantitative Real-Time PCR; HDL-C, high-density lipoprotein cholesterol; TGs, triglycerides; OD-GDM, offspring of mother with dietetically treated gestational diabetes, OI-GDM offspring of mother with insulin-dependent GDM; C-HAPO, children from Hyperglicemia and Adverse Pregnancy Outcome; I-CBGS, infants from Cambridge Baby Growth Study; WHO, World Health Organization; GCT, Glucose Challenge Test; GDA, German Diabetes Association; DGGG, German Association for Gynaecology and Obstetrics; LC-MS/MS, Liquid Chromatography tandem Mass Spectrometry; E-21, ECOGENE-21; Gen3G, Genetics of Glucose regulation in Gestation and Growth; IADPSG, International Association of the Diabetes and Pregnancy Study Groups; O-GDM, offspring of women with GDM; O-T2DM, offspring of women with T2DM during pregnancy, O-BP, offspring of women from the background population; FBG, fasting blood glucose; O-T1DM, offspring of women with T1DM during pregnancy; SAT, subcutaneous adipose tissue; VAT, visceral adipose tissue;