(296) Phytoestrogen Consumption may Dysregulate Progesterone Biosynthesis by the Bovine Corpus Luteum

Donnelly Hutchings¹, Dean Elder2, Md Atikur Rahman³, William Sims3, Kleves Almeida3, Andre Brito³, Paul C. Tsang¹

1. Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
2. Animal Resource Office, University of New Hampshire, Durham, NH 03824, USA
3. Department of Agriculture, Nutrition, and Food Systems, University of New Hampshire, Durham, NH 03824

 

Abstract Text:

Plant derived estrogens, or phytoestrogens, have long been reported to have effects on reproductive health, potentially disrupting fertility through impacts on the function of the corpus luteum (CL). Our lab has previously conducted a study showing that the consumption of red clover, a flowering legume rich in phytoestrogens, can disrupt ovarian function by decreasing luteinizing hormone (LH) stimulated progesterone (P4) biosynthesis ex vivo. It has been speculated that some of the effects of these plant derived estrogens may be mediated by influencing prostaglandin F2α (PGF2α) secretion. To test this hypothesis, we performed a field trial on organic dairy cows, allowing them to graze on either a traditional grass pasture (control) or a red clover enriched pasture (experimental) for 4-6 weeks. During the grazing period, biweekly ultrasound scans were conducted, and blood samples were taken. At the end of the field trial period, CLs were removed at the mid cycle stage (day 8-12) and returned to the lab for tissue dissociation and experimentation. After dissociation, 1x10⁶ bovine steroidogenic luteal cells were placed into 12x75mm test tubes for either 2, 4, or 24 hours, plus an initial time 0 was also included. Cells were incubated either in the absence or presence of LH (10ng/mL) for the duration. After each treatment period, conditioned medium was collected and assayed for P4 by radioimmunoassay (RIA) and PGF2α by enzyme linked immunosorbent assay (ELISA). In addition, steroidogenic luteal cells were lysed, and total RNA was extracted followed by complementary DNA (cDNA) generation and quantitative polymerase chain reaction (qPCR). We found that steroidogenic luteal cells from experimental cows that consumed red clover tended to produce less P4 in response to LH after 2 hours (p=0.06), but by 24 hours, they produced less P4 than control cows (p=0.001). The production of PGF2α was no different at 2 and 4 hours of culture (p >0.1) However, the CL of cows that consumed red clover tended to produce more PGF2α after 24 hours in culture (p=0.06). When expressed as a ratio, PGF2α:P4 was increased in cells from red clover consuming cows, compared to grass fed cows, at the 24 hour time point (p=0.006). Further, expression of the PGF2α receptor (PTGFR) transcript, ex vivo, at time 0, was not different between steroidogenic luteal cells obtained from control and experimental cows. In summary, these data suggest that prolonged consumption of phytoestrogens from red clover could result in decreased P4 and increased PGF2α biosynthesis by the CL. While the PTGFR mRNA was detected, its expression did not differ between the two study groups. Taken together, our results showed that, after consumption of red clover, the endocrine milieu of the bovine CL has shifted, from an environment that is predominantly high P4 and low PGF2α during the mid cycle stage, to one that is higher PGF2α and lower P4. Since the temporal balance of hormones within the CL throughout the luteal phase is vital to its proper functioning, this shift could potentially have a negative impact on the CL which may result in decreased reproductive performance.