Insulin-like growth factor-1 stimulates glycogen synthesis in the bovine uterine epithelium

Despite interventions and synchronization methods, early embryonic loss in cattle is 30-50%. Embryo development is dependent on proper secretion of glucose into the uterine lumen. Post-conception, the embryo primarily uses pyruvate and lactate. Too much glucose at this stage impairs development. At the morula stage, glucose uptake starts to increase dramatically. However, it is unclear how the bovine uterine epithelium meets the increasing glucose needs of the embryo. Research from our laboratory has found that the epithelial cells in the bovine uterus contain higher levels of glycogen, the storage form of glucose, on day 1 than day 11 of the cycle. During estrus, estradiol (E2) stimulates the production of insulin-like growth factor 1 (IGF-1) in the uterine stroma of other species, which mediates some of the effects of E2 on the uterine epithelium. Therefore, our objective was to evaluate the effect of E2 and IGF-1 on glycogenesis in immortalized bovine uterine epithelial (BUTE) cells. Treatment of BUTE cells with E2 (0.1-10 nM) did not stimulate glycogen synthesis. In contrast, treatment of BUTE cells with IGF-1 (50 or 100 ng/ml) resulted in a >2-fold increase in glycogen levels (P<0.01). When treated with both E2 (100 nM) and IGF-1 (50 ng/ml), only the main effect of IGF-1 was significant (P<0.0001). We next determined if bovine uterine fibroblast (BFIB) cells produced IGF-1 in response to E2. Treatment of BFIB cells with E2 increased IGF-1 production, and immunohistochemistry revealed that expression of IGF-1 in the stroma was higher on day 1 than on day 11. This agrees with higher levels of glycogen in the epithelium on Day 1. Elucidating the pathway by which IGF-1 increases glycogen synthesis, western blots revealed an increase of approximately 7-fold for phospho-AKT after IGF-1 treatment (P<0.05) and an increase of >2-fold for phospho-GSK3β (P<0.05). IGF-1 treatment also increased levels of hexokinase and glycogen synthase proteins (P<0.05). Metabolomics (GC-MS) showed that IGF-1 increased 3-phosphoglycerate, lactate, and N-acetyl-glucosamine in BUTE cells, suggesting increased glycolysis and hexosamine biosynthetic pathway activity. IGF-1 also resulted in increased levels of glycosylated proteins in BUTE cells (P<0.01). In conclusion, this study demonstrated that glycogen synthesis is the result of IGF-1 produced in the bovine endometrial stroma due to E2. IGF-1 stimulated glycogen synthesis via an AKT/GSK3β pathway and by increasing expression of glycogenic enzymes. Metabolomic (GC-MS) analysis indicated altered flux through glycolysis and the hexamine biosynthetic pathway. By increasing glycogen levels during estrus, the uterine epithelium may be better able to provide glucose to the developing blastocyst. Identifying mechanisms controlling glycogen synthesis and catabolism in the bovine uterus may enable further research toward decreasing early embryonic death in cattle and global revenue loss.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Gonzalez, Alexis

Contributors dc:contributor

• Dean, Matthew
• Wheeler, Matthew
• McCann, Joshua

• glucose
• endometrium
• stroma
• metabolism
• cow

Statement dc:rights

• Copyright 2022 Alexis Gonzalez

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/116175

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F116175