Presentation Title

Lipid metabolism genes are differentially expressed during photostimulated ovarian recrudescence in Siberian hamsters (Phodopus sungorus).

Faculty Mentor

Kelly A. Young

Start Date

23-11-2019 10:00 AM

End Date

23-11-2019 10:45 AM

Location

71

Session

poster 3

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

Photoperiod, or the number of hours of light per day, regulates reproductive function in a seasonally-dependent manner in many vertebrates, including Siberian hamsters (Phodopus sungorus). Exposing female Siberian hamsters to long days (LD;16h light: 8h dark) maintains ovarian cyclicity, whereas exposure to inhibitory short days (SD; 8L:16D) induces declines in ovarian function which can be reversed with transfer back to LD (post transfer, PT). The changes observed in photo-stimulated recrudescence, or the return of ovarian function in PT groups, are associated with upregulation of intra-ovarian factors involved in follicle development. However, the impact of photoperiod on aspects of ovarian metabolism has not been investigated. While lipid metabolism involves multiple pathways, liver receptor homolog-1 (Lhr-1) is important in the ovary as it functions in the regulation of cholesterol homeostasis, a key aspect of production of sex steroid hormones. The proteins encoded by the liver X receptor (Lxr) gene are involved in lipid metabolism through their function as nuclear receptors to phospholipids, and may play a role in oocyte maturation. We hypothesized that exposing female Siberian hamsters (n=32) to different photoperiod regimes to induce cyclicity (LD), regression (SD), or recrudescence (PT weeks 2, 4, or 8) would alter the mRNA expression of Lhr1, Lxr-a, and Lxr-b. While photoperiod did not alter the number of pre-antral follicles across groups; exposure to inhibitory photoperiod induced a decline in both tertiary follicles and corpora lutea. Lhr1 mRNA was present in LD, decreased in SD and PTwk2, and returned to LD levels in PTwk4 and 8. Lxr-a and mRNA expression increased in PTwk8 in comparison to SD and PTwk2. Similarly, Lxr-b mRNA increased in PTwk4 and PTwk8 as compared all other groups. These results suggest that aspects of lipid metabolism in the ovary are mediated by photoperiod exposure, and may be particularly important during ovarian recrudescence.

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Nov 23rd, 10:00 AM Nov 23rd, 10:45 AM

Lipid metabolism genes are differentially expressed during photostimulated ovarian recrudescence in Siberian hamsters (Phodopus sungorus).

71

Photoperiod, or the number of hours of light per day, regulates reproductive function in a seasonally-dependent manner in many vertebrates, including Siberian hamsters (Phodopus sungorus). Exposing female Siberian hamsters to long days (LD;16h light: 8h dark) maintains ovarian cyclicity, whereas exposure to inhibitory short days (SD; 8L:16D) induces declines in ovarian function which can be reversed with transfer back to LD (post transfer, PT). The changes observed in photo-stimulated recrudescence, or the return of ovarian function in PT groups, are associated with upregulation of intra-ovarian factors involved in follicle development. However, the impact of photoperiod on aspects of ovarian metabolism has not been investigated. While lipid metabolism involves multiple pathways, liver receptor homolog-1 (Lhr-1) is important in the ovary as it functions in the regulation of cholesterol homeostasis, a key aspect of production of sex steroid hormones. The proteins encoded by the liver X receptor (Lxr) gene are involved in lipid metabolism through their function as nuclear receptors to phospholipids, and may play a role in oocyte maturation. We hypothesized that exposing female Siberian hamsters (n=32) to different photoperiod regimes to induce cyclicity (LD), regression (SD), or recrudescence (PT weeks 2, 4, or 8) would alter the mRNA expression of Lhr1, Lxr-a, and Lxr-b. While photoperiod did not alter the number of pre-antral follicles across groups; exposure to inhibitory photoperiod induced a decline in both tertiary follicles and corpora lutea. Lhr1 mRNA was present in LD, decreased in SD and PTwk2, and returned to LD levels in PTwk4 and 8. Lxr-a and mRNA expression increased in PTwk8 in comparison to SD and PTwk2. Similarly, Lxr-b mRNA increased in PTwk4 and PTwk8 as compared all other groups. These results suggest that aspects of lipid metabolism in the ovary are mediated by photoperiod exposure, and may be particularly important during ovarian recrudescence.