Glyoxalase 1 expression is downregulated in preimplantation blastocysts of diabetic rabbits

Advanced maternal age leads to changes within the insulin/IGF system and lipid metabolism in the reproductive tract and preimplantation embryo: insights from the rabbit model

Reproductive potential in women declines with age. The impact of ageing on embryo-maternal interactions is still unclear. Rabbits were used as a reproductive model to investigate maternal age-related alterations in reproductive organs and embryos on Day 6 of pregnancy. Blood, ovaries, endometrium, and blastocysts from young (16-20 weeks) and advanced maternal age phase (>108 weeks, old) rabbits were analysed at the mRNA and protein levels to investigate the insulin-like growth factor (IGF) system, lipid metabolism, and stress defence system. Older rabbits had lower numbers of embryos at Day 6 of pregnancy. Plasma insulin and IGF levels were reduced, which was accompanied by paracrine regulation of IGFs and their receptors in ovaries and endometrium. Embryos adapted to hormonal changes as indicated by reduced embryonic IGF1 and 2 levels. Aged reproductive organs increased energy generation from the degradation of fatty acids, leading to higher oxidative stress. Stress markers, including catalase, superoxide dismutase 2, and receptor for advanced glycation end products were elevated in ovaries and endometrium from aged rabbits. Embryonic fatty acid uptake and β-oxidation were increased in both embryonic compartments (embryoblast and trophoblast) in old rabbits, associated with minor changes in the oxidative and glycative stress defence systems. In summary, the insulin/IGF system, lipid metabolism, and stress defence were dysregulated in reproductive tissues of older rabbits, which is consistent with changes in embryonic metabolism and stress defence. These data highlight the crucial influence of maternal age on uterine adaptability and embryo development.

Ectopic Lipid Accumulation Correlates with Cellular Stress in Rabbit Blastocysts from Diabetic Mothers

Maternal diabetes mellitus in early pregnancy leads to hyperlipidemia in reproductive tract organs and an altered embryonic environment. To investigate the consequences on embryonic metabolism, the effect of high environmental-lipid levels was studied in rabbit blastocysts cultured with a lipid mixture in vitro and in blastocysts from diabetic, hyperlipidemic rabbits in vivo. The gene and protein expression of marker molecules involved in lipid metabolism and stress response were analyzed. In diabetic rabbits, the expression of embryoblast genes encoding carnitine palmityl transferase 1 and peroxisome proliferator-activated receptors α and γ increased, whereas trophoblast genes encoding for proteins associated with fatty acid synthesis and β-oxidation decreased. Markers for endoplasmic (activating transcription factor 4) and oxidative stress (nuclear factor erythroid 2-related factor 2) were increased in embryoblasts, while markers for cellular redox status (superoxide dismutase 2) and stress (heat shock protein 70) were increased in trophoblasts from diabetic rabbits. The observed regulation pattern in vivo was consistent with an adaptation response to the hyperlipidemic environment, suggesting that maternal lipids have an impact on the intracellular metabolism of the preimplantation embryo in diabetic pregnancy and that embryoblasts are particularly vulnerable to metabolic stress.