Maternal high-fat diet changes DNA methylation in the early embryo by disrupting the TCA cycle intermediary alpha ketoglutarate

Abstract

Maternal obesity can impair offspring metabolic health, however the precise mechanism underpinning programming is unknown. Ten-Eleven translocase (TET) enzymes demethylate DNA using the TCA cycle intermediary α-ketoglutarate and may be involved in programming offspring health. Whether TETs are disrupted by maternal obesity is unknown. 5-6 week old C57Bl/6 female mice were fed a control diet (CD; 6% fat, n=175) or a high-fat diet (HFD; 21% fat, n=158) for six weeks. After superovulation oocytes were collected for metabolic assessment, or females were mated and zygotes cultured for embryo development, foetal growth, and assessment of global DNA methylation (5mC, 5hmC, 5fC and 5caC) in the 2-cell embryo. Zygotes collected from superovulated CBAF1 females were cultured in media containing α-ketoglutarate (0mM, 1.4mM, 3.5mM, or 14.0mM) or with 2-hydroxyglutarate (2HG) (0mM or 20mM), a competitive inhibitor of α-ketoglutarate, with methylation and blastocyst differentiation assessed. After HFD, oocytes showed increased pyruvate oxidation and intracellular ROS, with no changes in Tet3 expression, while 2-cell embryo global 5hmC DNA methylation was reduced and 5fC increased. Embryos cultured with 1.4 mM α-ketoglutarate had decreased 2-cell 5mC, whilst 14.0mM α-ketoglutarate increased the 5hmC:5mC ratio. In contrast supplementation with 20 mM 2HG increased 5mC and decreased the 5fC:5mC and 5caC:5mC ratios. α-ketoglutarate up to 3.5mM did not alter embryo development, whilst culturing in 14.0mM α-ketoglutarate blocked development at the 2-cell. Culture with 2HG delayed embryo development past the 4-cell and decreased blastocyst total cell number. In conclusion, disruptions in metabolic intermediates in the preimplantation embryo may provide a link between maternal obesity and programming offspring for ill health.

Dilemma of Epigenetic Changes Causing or Reducing Metabolic Disorders in Offsprings of Obese Mothers

“…Moody et al, demonstrated that offspring born to HF dams were able to remodel hepatic epigenome when subjected to a postweaning control diet [19]. It has been reported that a paternal high-fat diet (PHFD) and MHFD comprising 62 % fat resulted in the downregulation of adiponectin and upregulation of leptin gene in offspring along with weight gain, increased blood pressure, glucose, insulin, total triglyceride level thus predisposing the offspring towards the development of metabolic syndrome including T2D [13,14,20,21]. The differential expression of adiponectin and leptin was associated with the decreased level of acetyl H3K9 and increased expression of dimethyl H3K9 in the promoter region of the adiponectin gene and increased monomethyl H4K20 levels in the promoter region of the leptin gene suggesting HFD influence epigenetic markers.…”

“…Recently, Penn et al showed that MHFD resulted in a decrease in the 5hmC DNA methylation and an increase in 5-formyl cytosine (5fC) in two cell-stage embryos. They observed that 1.4 mM α-ketoglutarate resulted in a decrease in 5mC level in two cell embryos while 14.0 mM α-ketoglutarate led to an increased 5hmC:5mC ratio suggesting a link between metabolic intermediate and MHFD as well as indicating that MHFD might be influencing offspring metabolic state during early development [14].…”

“…The differential expression of adiponectin and leptin was associated with the decreased level of acetyl H3K9 and increased expression of dimethyl H3K9 in the promoter region of the adiponectin gene and increased monomethyl H4K20 levels in the promoter region of the leptin gene suggesting HFD influence epigenetic markers. However, they found that control diet (CD) (12 % fat) consumption for two to three generation was able to abolish the epigenetic effect caused by PHFD and MHFD indicating epigenetic reversal using a control diet is a slow process [13,14,20,21]. A study revealed that 5hmC modification on hypothalamic anorexigenic neuropeptide proopiomelanocortin (POMC) negatively correlates while 5mC modification positively correlates with the body weight of offspring born from HFD and control-fed dams.…”

Epigenetic implications in maternal diabetes and metabolic syndrome‐associated risk of orofacial clefts

“…Histone H3 Lysine 4 dimethylation (H3K4me2) was reduced in the embryos of obese mice (Pan et al, 2020), which may alter signaling gene activities critical for orofacial development. A more recent animal study demonstrates that maternal high‐fat diet changes DNA methylation in early embryos by disrupting the TCA cycle intermediary α‐ketoglutarate, which is necessary for DNA demethylation by TET enzymes (Penn et al, 2023). These studies suggest that maternal obesity may alter DNA and histone methylation at OFC‐associated genes, and provide new directions for related mechanistic studies.…”