Cholesterol metabolism in rabbit blastocysts under maternal diabetes.

In the rabbit reproductive model, maternal experimentally induced insulin-dependent diabetes mellitus (expIDD) leads to accumulation of lipid droplets in blastocysts. Cholesterol metabolism is a likely candidate to explain such metabolic changes. Therefore, in the present study we analysed maternal and embryonic cholesterol concentrations and expression of related genes in vivo (diabetic model) and in vitro (embryo culture in hyperglycaemic medium). In pregnant expIDD rabbits, the serum composition of lipoprotein subfractions was changed, with a decrease in high-density lipoprotein cholesterol and an increase in very low-density lipoprotein cholesterol; in uterine fluid, total cholesterol concentrations were elevated. Expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), very low-density lipoprotein receptor (VLDLR), sterol regulatory element binding transcription factor 2 (SREBF2), insulin-induced gene-1 (INSIG1) and cholesterol 7α-hydroxylase (CYP7A1) mRNA was decreased in the liver and low-density lipoprotein receptor (LDLR) mRNA expression was decreased in the adipose tissue of diabetic rabbits. In embryos from diabetic rabbits, the mean (±s.e.m.) ratio of cholesterol concentrations in trophoblasts to embryoblasts was changed from 1.27±2.34 (control) to 0.88±3.85 (expIDD). Rabbit blastocysts expressed HMGCR, LDLR, VLDLR, SREBF2 and INSIG1 but not CYP7A1, without any impairment of expression as a result of maternal diabetes. In vitro hyperglycaemia decreased embryonic HMGCR and SREBF2 transcription in rabbit blastocysts. The findings of the present study show that a diabetic pregnancy leads to distinct changes in maternal cholesterol metabolism with a minor effect on embryo cholesterol metabolism.

Induction of G protein-coupled estrogen receptor (GPER) and nuclear steroid hormone receptors by gonadotropins in human granulosa cells.

Estradiol and progesterone mediate their actions by binding to classical nuclear receptors, estrogen receptor α (ERα) and estrogen receptor ß (ERß) and progesterone receptor A and B (PR-A and PR-B) and the non-classical G protein-coupled estrogen receptor (GPER). Several animal knock-out models have shown the importance of the receptors for growth of the oocyte and ovulation. The aim of our study was to identify GPER in human granulosa cells (GC) for the first time. Moreover, the effect of different doses of gonadotropins on estrogen and progesterone receptors in the human ovary should be investigated as follicle stimulating hormone (FSH) and luteinizing hormone (LH) are also responsible for numerous mechanisms in the ovary like induction of the steroid biosynthesis. Human GC were cultured in vitro and stimulated with different doses of recombinant human FSH or LH. Receptor expression was analyzed by immunocytochemistry and quantitative real-time RT-PCR. GPER could be identified for the first time in human GC. It could be shown that high concentrations of LH increase GPER protein expression. Furthermore FSH and LH increased ERß, PR-A and PR-B significantly on protein level. These findings were verified for high doses of FSH and LH on mRNA level. ERα was not affected with FSH or LH. We assume that gonadotropins induce GPER, ERß and PR in luteinized granulosa cells.