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Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy.

ABSTRACT: We have determined uterine glycogen content, metabolizing enzyme expression and activity in the mink, a species that exhibits obligatory embryonic diapause, resulting in delayed implantation. Gross uterine glycogen concentrations were highest in estrus, decreased 50% by diapause and 90% in pregnancy (P ? 0.05). Endometrial glycogen deposits, which localized primarily to glandular and luminal epithelia, decreased 99% between estrus and diapause (P ? 0.05) and were nearly undetectable in pregnancy. Glycogen synthase and phosphorylase proteins were most abundant in the glandular epithelia. Glycogen phosphorylase activity (total) in uterine homogenates was higher during estrus and diapause, than pregnancy. While glycogen phosphorylase protein was detected during estrus and diapause, glycogen synthase was almost undetectable after estrus, which probably contributed to a higher glycogenolysis/glycogenesis ratio during diapause. Uterine glucose-6-phosphatase 3 gene expression was greater during diapause, when compared to estrus (P ? 0.05) and supports the hypothesis that glucose-6-phosphate resulting from phosphorylase activity was dephosphorylated in preparation for export into the uterine lumen. The relatively high amount of hexokinase-1 protein detected in the luminal epithelia during estrus and diapause may have contributed to glucose trapping after endometrial glycogen reserves were depleted. Collectively, our findings suggest to us that endometrial glycogen reserves may be an important source of energy, supporting uterine and conceptus metabolism up to the diapausing blastocyst stage. As a result, the size of uterine glycogen reserves accumulated prior to mating may in part, determine the number of embryos that survive to the blastocyst stage, and ultimately litter size.

SUBMITTER: Dean M

PROVIDER: S-EPMC4284318 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy.

Dean Matthew M Hunt Jason J McDougall Lisa L Rose Jack J

The Journal of reproduction and development 20140915 6

We have determined uterine glycogen content, metabolizing enzyme expression and activity in the mink, a species that exhibits obligatory embryonic diapause, resulting in delayed implantation. Gross uterine glycogen concentrations were highest in estrus, decreased 50% by diapause and 90% in pregnancy (P ≤ 0.05). Endometrial glycogen deposits, which localized primarily to glandular and luminal epithelia, decreased 99% between estrus and diapause (P ≤ 0.05) and were nearly undetectable in pregnancy ...[more]

PMID: 25225159

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Project description:Glycogen content in mink uterine glandular and luminal epithelia (GE and LE) is maximal during estrus and is depleted before implantation while embryos are in diapause. Uterine glycogen synthesis in vivo is stimulated by estradiol (E2) while its mobilization is induced by progesterone (P4). Nevertheless, treatment of an immortalized mink uterine epithelial cell line (GMMe) with E2 did not affect glycogen production. Interestingly, insulin alone significantly increased synthesis of the nutrient and glycogen content in response to insulin + E2 was greater than for insulin alone. Our objectives were to determine: 1) If insulin receptor protein (INSR) is expressed by mink uterine GE and LE in vivo and if the amount differs between estrus, diapause and pregnancy; 2) if E2, P4 or insulin regulate insulin receptor gene (Insr) expression by GMMe cells, and 3) if E2 and P4 act independently to regulate glycogen metabolism by GMMe cells and/or if their effects are mediated in part through the actions of insulin. The mean (±S.E.) percent INSR content of uterine epithelia was greatest during diapause (GE: 15.65 ± 0.06, LE:16.56 ± 1.25), much less during pregnancy (GE: 2.53 ± 0.60, LE:2.25 ± 0.32) and barely detectable in estrus (GE: 0.03 ± 0.01, LE:0.02 ± 0.01). Glycogen concentrations in GMMe cells increased 10-fold in response to insulin and 20-fold with insulin + E2 when compared to controls. Expression of Insr was increased 2-fold by insulin and insulin + E2 when compared to controls and there was no difference between the two hormone treatments, indicating that E2 does not increase Insr expression in insulin-treated cells. To simulate E2-priming, cells were treated with Insulin + E2 for 24 h, followed by the same hormones + P4 for the second 24 h (Insulin + E2 → P4) which resulted in Insr and glycogen levels not different from controls. Similarly, cells treated with Insulin + P4 resulted in glycogen concentrations not different from controls. We conclude that the glycogenic actions of E2 on GMMe cells are due to increased responsiveness of the cells to insulin, but not as a result of up-regulation of the insulin receptor. Glycogen mobilization in response to P4 was the result of decreased glycogenesis and increased glycogenolysis occurring concomitantly with reduced Insr expression. Mink uterine glycogen metabolism appears to be regulated in a reproductive cycle-dependent manner in part as a result of the actions of E2 and P4 on cellular responsiveness to insulin.

Dataset Information

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy.

Publications

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy.

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