Endometrial glycogen metabolism during early pregnancy in mice

The protective effect of curcumin on the diabetic uterus: Quantitative and qualitative evaluation

BACKGROUND

The objective of this study was to examine the impact of diabetes on the rat uterus and to assess the potential therapeutic benefits of curcumin in a diabetic uterus.

MATERIALS AND METHODS

A total of thirty-eight female Wistar albino rats were randomly assigned to seven experimental groups. The control group (Cont) was not subjected to any treatment. The sham group (Sham) was administered corn oil, while the curcumin group (Curc) received 30 mg/kg curcumin. A single dose of 50 mg/kg streptozotocin (STZ) was administered to induce experimental diabetes. The diabetic animals were then divided into four groups: a group with diabetes mellitus (DM), a group administered curcumin after seven days of diabetes induced (DC1) and 21 days (DC2) after the onset of diabetes, and a group that received curcumin simultaneously with STZ (DC3). The Cavalieri's method was used to estimate the volume ratios of the uterine epithelium, layers, and blood vessels.

RESULTS

The volume ratio of the myometrium was observed to be higher in the DC2 group than in the Cont and DM groups. Conversely, the endometrial volume ratio was found to be lower in the DC2 group than in the Cont group. The cell borders and basement membranes of the epithelial and gland cells were well preserved in the curcumin treatment groups, despite the obvious damage observed in the DM group. Similar findings were also observed in the electron microscopic sections, with collagen fibers, which were arranged in thick bands in the DM group and were unable to maintain their ultrastructure, were well organized in the DC1, DC2, and DC3.

CONCLUSION

Considering that it improves the endometrial structure and reduces degeneration in the surface and gland epithelium, it can be said that curcumin is an effective agent in reducing and preventing complications associated with DM in the uterus.

Glucose uptake is essential for Brucella abortus growth in the extracellular space of the murine placenta

Brucella abortus infects the placenta of its natural bovine host, which results in abortion and transmission of infection to other cattle and to humans. While the metabolism of B. abortus during chronic infection of the mononuclear phagocyte system has been studied, the nutrients fueling growth of B. abortus in the placenta are unknown. We found that in mice, glucose is an important carbon source for B. abortus in the placenta. A gluP mutant lacking a major facilitator superfamily protein required for glucose uptake had diminished growth in the placenta of pregnant mice and caused reduced inflammatory pathology and fetal demise. The gluP mutant was able to replicate intracellularly in a trophoblast cellular model and to cause trophoblast cell death in infected placentas. Attenuated growth of the gluP mutant was maintained in mice conditionally deficient for peroxisome proliferator-activated receptor γ in macrophages, suggesting that M2-like macrophages were not the major site for glucose-dependent growth of B. abortus in the placenta. Our results show that the infected placenta contains multiple distinct nutrient niches and that glucose utilization within the interstitial space of the placenta is an important process contributing to bacterial growth and fetal demise during placental B. abortus infection.

Methimazole-Induced Hypothyroidism Increases the Content of Glycogen and Changes the Expression of LDH, GLUT4, and Aromatase in the Pregnant Uterus of Rabbits

Objective: To determine the impact of hypothyroidism on uterine glycogen accumulation during pregnancy. Methods: Non-pregnant and pregnant (days 5, 10, and 20) rabbits were grouped into control and methimazole (MMI) groups. In rabbits, serum concentrations of thyroxine (T4), triiodothyronine, glucose, insulin, progesterone, and estradiol were quantified. In uterine inter- and implantation sites, the glycogen content and expression of lactate dehydrogenase (LDH), GLUT4, and aromatase were quantified via Western blot. Fetuses' characteristics at 20 days of pregnancy were analyzed. Two-way ANOVA was used to compare variables between groups. Results: Pregnancy reduced T4 concentrations but not T3. In virgin groups, MMI treatment significantly reduced the concentrations of T4 and T3 and increased the expression of GLUT4 and aromatase in the uterus compared to the control group. In pregnant groups, T4, T3, glucose, insulin, progesterone, and estradiol levels were similar between control and MMI-treated rabbits. Compared to controls, MMI treatment in pregnant rabbits (a) reduced GLUT4 expression on inter-implantation sites on day 5; (b) increased glycogen content on implantation sites but reduced GLUT4 expression on inter-and implantation sites on day 10; (c) increased glycogen content and LDH and aromatase expression but reduced GLUT4 on inter-implantation sites; and (d) increased glycogen content and the expression of LDH, GLUT4, and aromatase on day 20 on implantation sites. Moreover, the fetus characteristics were similar between groups. Conclusions: MMI-induced hypothyroidism is associated with changes in the uterine content of glycogen and the expression of LDH, GLUT4, and aromatase during pregnancy.

Membrane progesterone receptors mediate progesterone-stimulated glycogenolysis in the bovine uterine epithelium

In livestock, the amount of glucose needed by the endometrium and embryo increases during early pregnancy. Yet, how glucose concentrations in the endometrium are regulated remains unclear. The bovine uterine epithelium can store glucose as glycogen, and glycogen content decreases in the luteal phase. Our objective was to elucidate the role of progesterone in glycogen breakdown in immortalized bovine uterine epithelial (BUTE) cells. After 48 h of treatment, progesterone decreased glycogen abundance in BUTE cells (P < 0.001) but did not alter glycogen phosphorylase levels. RU486, a nuclear progesterone receptor (nPR; part of the PAQR family) antagonist, did not block progesterone's effect, suggesting that progesterone acted through membrane progesterone receptors (mPRs). RT-PCR confirmed that BUTE cells express all five mPRs, and immunohistochemistry showed that the bovine uterine epithelium expresses mPRs in vivo. An mPRα agonist (Org OD 02-0) reduced glycogen abundance in BUTE cells (P < 0.001). Progesterone nor Org OD 02-0 affected cAMP concentrations. Progesterone increased phosphorylated AMP-activated protein kinase (pAMPK) levels (P < 0.001), indicating that progesterone increases intracellular AMP concentrations. However, AMPK did not mediate the effect of progesterone. AMP allosterically activates glycogen phosphorylase, and D942 (which increases intracellular AMP concentrations) decreased glycogen abundance in BUTE cells. A glycogen phosphorylase inhibitor partially blocked the effect of progesterone (P < 0.05). Progesterone and Org OD 02-0 had similar effects in Ishikawa cells (P < 0.01), a human cell line that lacks nPRs. In conclusion, progesterone stimulates glycogen breakdown in the uterine epithelium via mPR/AMP signaling. Glucose released from glycogen could support embryonic development or be metabolized by the uterine epithelium.

Progesterone increases metabolism via the pentose phosphate pathway in bovine uterine epithelial cells

BACKGROUND

During early pregnancy, glucose is essential for the uterine epithelium and the developing embryo. In cows, progesterone increases the secretion of glucose into the uterine lumen. The uterine epithelium can convert glucose to fructose, but other fates of glucose in the uterine epithelium have been sparsely investigated. Therefore, our objective was to investigate how progesterone influences glucose metabolism in immortalized bovine uterine epithelial (BUTE) cells.

METHODS

BUTE cells were grown to 80% confluence and treated with vehicle (DMSO) or 10 µM progesterone for 24 h. Cells were collected and analyzed. Immunohistochemistry was performed on endometrial samples collected from the bovine endometrium on days 1 and 11 of the reproductive cycle.

RESULTS

Progesterone treatment increased glucose consumption of BUTE cells. RNAseq identified 3,072 genes regulated by progesterone. KEGG analysis indicated that progesterone altered genes associated with metabolic pathways and glutathione metabolism. Manually examining genes unique to specific glucose metabolic pathways identified an increase in the rate-limiting enzyme in the pentose phosphate pathway-glucose-6-phosphate dehydrogenase. Functionally, a major product of the pentose phosphate pathway is NADPH, and progesterone treatment increased NADPH levels in BUTE cells. In cows, immunohistochemistry confirmed that glucose-6-phosphate dehydrogenase levels were higher in the uterine epithelium in the luteal phase when progesterone concentrations are high.

CONCLUSIONS

Progesterone increased glucose-6-phosphate dehydrogenase expression and metabolism via the pentose phosphate pathway in the bovine uterine epithelium. This metabolism could provide substrates for cell proliferation, molecules to be secreted into the uterine lumen, or maintain reduction/oxidation balance in the uterine epithelium.

The glycogenolytic enzyme acid α-glucosidase is expressed in the bovine uterine endometrium

Progesterone has been shown to stimulate glycogen catabolism in uterine epithelial cells. Acid α-glucosidase (GAA) is an enzyme that breaks down glycogen within lysosomes. We hypothesized that progesterone may stimulate glycogenolysis in the uterine epithelium via GAA. We found that GAA was more highly expressed in the stroma on Day 1 than on Day 11. However, GAA did not appear to differ in the epithelium on Days 1 and 11. Progesterone (0-10 μM) had no effect on the levels of the full-length inactive protein (110 kDa) or the cleaved (active) peptides present inside the lysosome (70 and 76 kDa) in immortalized bovine uterine epithelial (BUTE) cells. Furthermore, the activity of GAA did not differ between the BUTE cells treated with 10 μM progesterone or control. Overall, we confirmed that GAA is present in the cow endometrium and BUTE cells. However, progesterone did not affect protein levels or enzyme activity.

gys1 regulates maternal glycogen reserve essential for embryonic development in zebrafish

The reserve of glycogen is essential for embryonic development. In oviparous fish, egg is an isolated system after egg laying with all the required energy deposits by their mothers. However, the key regulated factor mediates the storage of maternal glycogen reserve which support for embryogenesis in the offspring is largely unknown. Glycogen synthase (GYS) is a central enzyme for glycogen synthesis. In our previous study, we generated a gys1 knockout zebrafish line, showed an embryonic developmental defect in F3 generation. In this study, firstly we determined that the gys1 was maternal origin by backcrossing the F2 mutant with wildtype lines. PAS staining and glycogen content measurement showed that glycogen reserve was reduced both in ovaries and embryos in the mutant group compared to wildtypes. Free glucose measurement analysis showed a 50 % of reduction in gys1 mutant embryos compared to wildtype embryos at 24 hpf; showed an approximal 50 % of reduction in gys1 mutant adults compared to wildtypes. Microinjection of 2-NBDG in embryos and comparison of fluorescent signal demonstrated that glucose uptake ability was decreased in the mutant embryos, indicating an impaired glucose metabolism. Untargeted metabolomics analysis then was employed and revealed that key modified metabolites enriched into vitamin B pathway, carbohydrate and unsaturated fatty acid pathways. These results demonstrated that gys1 played a role on glycogen metabolism, involved into the maternal glycogen reserve which essentially contribute to embryonic development.

Endometrial Glucose Metabolism During Early Pregnancy

Approximately 50% of human pregnancies humans fail, most before or during implantation. One factor contributing to pregnancy loss is abnormal glucose metabolism in the endometrium. Glucose contributes to preimplantation embryo development, uterine receptivity, and attachment of the embryo. Across multiple species, the epithelium stores glucose as the macromolecule glycogen at estrus. This reserve is mobilized during the preimplantation period. Glucose from circulation or glycogenolysis can be secreted into the uterine lumen for use by the embryo or metabolized via glycolysis, producing ATP for the cell. The resulting pyruvate could be converted to lactate, another important nutrient for the embryo. Fructose is an important nutrient for early embryos, and the epithelium and placenta can convert glucose to fructose via the polyol pathway. The epithelium also uses glucose to glycosylate proteins, which regulates embryo attachment. In some species, decidualization of the stroma is critical to successful implantation. Formation of the decidua requires increased glucose metabolism via the pentose phosphate pathway and glycolysis. After decidualization, the cells switch to aerobic glycolysis to produce ATP. Paradoxically, the decidua also stores large amounts of glucose as glycogen. Too little glucose or an inability to take up glucose impairs embryo development and decidualization. Conversely, too much glucose inhibits these same processes. This likely contributes to the reduced pregnancy rates associated with conditions like obesity and diabetes. Collectively, precise control of glucose metabolism is important for several endometrial processes required to establish a successful pregnancy. The factors regulating these metabolic processes remain poorly understood.

Energy metabolism and maternal-fetal tolerance working in decidualization

One pivotal aspect of early pregnancy is decidualization. The decidualization process includes two components: the differentiation of endometrial stromal cells to decidual stromal cells (DSCs), as well as the recruitment and education of decidual immune cells (DICs). At the maternal-fetal interface, stromal cells undergo morphological and phenotypic changes and interact with trophoblasts and DICs to provide an appropriate decidual bed and tolerogenic immune environment to maintain the survival of the semi-allogeneic fetus without causing immunological rejection. Despite classic endocrine mechanism by 17 β-estradiol and progesterone, metabolic regulations do take part in this process according to recent studies. And based on our previous research in maternal-fetal crosstalk, in this review, we elaborate mechanisms of decidualization, with a special focus on DSC profiles from aspects of metabolism and maternal-fetal tolerance to provide some new insights into endometrial decidualization in early pregnancy.