Background:
Maternal dietary modifications alter the nutrient composition of the preimplantation embryonic environment. This can stimulate persistent metabolic and epigenetic adaptations in the embryo that program development, ultimately affecting child and adult health. The ketogenic diet (KD), which is increasingly popular amongst sub-fertile women trying to conceive, induces elevated maternal ketone levels, including beta-hydroxybutyrate (ßOHB). ßOHB has a known ability to modulate metabolic and epigenetic regulation, however, the impact of elevated ßOHB exposure on embryonic viability and developmental programming remains unknown.
Aim:
To assess the impact of ßOHB on preimplantation mouse embryo development, metabolism, epigenetic state, and post-transfer viability.
Method:
Preimplantation mouse embryos were cultured in vitro with or without 2 mM ßOHB, representing serum concentrations with KD consumption. Day 5 blastocyst cell number and lineage allocation was assessed via differential nuclear stain, metabolism of ßOHB and carbohydrates was assessed by ultramicrofluorescence, and acetylation of histone 3 lysine 9 (H3K9ac) and lysine 27 (H3K27ac) were assessed by immunofluorescence. Day 4 blastocysts were transferred to pseudo-pregnant females for analysis of embryonic day 14.5 placental and fetal development.
Results:
A reduction in total and trophectoderm cell number (P<0.05) was observed following 96 h exposure to 2 mM ßOHB, indicating reduced viability. Blastocysts were shown to consume ßOHB in vitro, with uptake increasing with ßOHB concentration. Further, ßOHB increased blastocyst glycolytic rate (P<0.01), while epigenetic analyses revealed H3K9ac and H3K27ac were unaffected. Of significance, post-transfer implantation rates were reduced (P<0.05), concurrent with smaller placental diameter (P<0.01) and fetal crown-rump length (P<0.05), indicating alterations in developmental programming.
Conclusion:
Preimplantation ßOHB exposure induces negative developmental programming effects that are mediated by metabolic aberrations, and plausibly incorporate epigenetic components other than H3K9ac or H3K27ac. There may therefore be negative impacts on the long-term viability and health of offspring exposed to a maternal KD during early pregnancy.