Equol and para-ethyl-phenol stimulate prostaglandin F(2alpha) secretion in bovine corpus luteum: intracellular mechanisms of action

Effects of 17β-estradiol on the uterine luteolytic cascade in bovine females at the end of diestrus

In cattle, 17β-estradiol (E2) is essential for triggering luteolysis via the synthesis of prostaglandin F2α (PGF2α). We aimed to evaluate the effects of E2-treatment on day 15 of the estrous cycle on the transcript abundance of genes involved in the PGF2α synthetic cascade. Nelore heifers (N = 50) were subjected to a hormonal protocol for the synchronization of ovulation. Between days 14 and 23 after estrus, the area (cm2) and blood perfusion (%) of the corpus luteum (CL) and progesterone (P4) plasma concentrations were evaluated daily. On day 15, the heifers were assigned to the Control (2 mL of pure sesame oil, N = 21) or Estradiol group (1 mg of E2 diluted in 2 mL of sesame oil, N = 23). After the treatments at 0 h, uterine biopsies were collected at times 1.5 h (C1.5h, N = 8 and E1.5h, N = 10) or 3 h (C3h, N = 8 and E3h, N = 11); and blood samples were obtained from 0, 3, 4, 6 and 7 h for the measurement of 13,14-dihydro-15-keto-PGF2α (PGFM) concentrations by ELISA. Transcript abundance was determined by RT-qPCR and protein abundance of ESRβ and OXTR was determined by Western Blotting. The Estradiol group showed greater (P < 0.05) concentrations of PGFM at 6 and 7 h compared to the Control group. A progressive decrease in plasma P4 concentrations characterized a hastened functional luteolysis, followed by structural luteolysis in the Estradiol group (P < 0.05). Among the treatment groups, no significant difference was detected for the abundance of PRKCα, PRKCβ, AKR1B1, PTGS2 and ESRα transcripts (P > 0.05). Estradiol treatment decreased the abundance of PLA2G4A, AKR1C4, and ESRβ both 1.5h and 3h after treatment (P < 0.05). The relative expression of PGR and OXTR was greater in E3h compared to the C3h (P > 0.05). Protein abundance did not differ between treatment groups at either experimental times (P > 0.05). Overall, E2 promoted an increase in PGFM concentrations and the hastening of functional and structural luteolysis in Nelore heifers through the upregulation of PGR and OXTR, demonstrating for the first time that the expression of these receptors within 3 h after E2 stimulus was associated with triggering luteolysis in cattle.

Ovarian activity, hormone profile, pro-inflammatory cytokines and reproductive performance of buffalo cows fed diets with different estrogenicity

Buffalo cows play a vital role in milk and meat production; however, they are characterised by several reproductive disorders. Feeding diets with high oestrogenic activity may be a disrupting factor. This study aimed to evaluate the effects of feeding roughages with different oestrogenic activity on the reproductive performance of early postpartum buffalo cows. A total of 30 buffalo cows were equally stratified into two experimental groups and fed either Trifolium alexandrinum (Berseem clover, phytoestrogenic roughage) or corn silage (nonoestrogenic roughage) for 90 consecutive days. After 35 days from the beginning of the feeding treatments, buffalo cows in both groups were synchronized for oestrus using a double i.m. injection of 2 mL prostaglandin F2α , 11 days apart, subsequently, overt signs of oestrus were observed and recorded. Moreover, ovarian structures, numbers and sizes of follicles and corpora lutea, were ultrasonography examined at day-12 (represents Day 35 of feeding treatment), Day 0 (day of oestrus) and Day 11 after oestrous synchronization (mid-luteal phase). Pregnancy was diagnosed 35 days postinsemination. Blood serum samples were analysed for progesterone (P4 ), estradiol (E2 ), tumor necrosis factor (TNF-α), interlukein-1β (IL-1β) and nitric oxide (NO). The high performance liquid chromatography-analysis of roughages showed the abundance of isoflavones in Berseem clover, with about 58 times higher concentration than that in corn silage group. During the experimental period, the numbers of ovarian follicles of all size categories were higher in the Berseem clover group than that in the corn silage group. No significant difference in the numbers of corpora lutea was observed between both experimental groups, but lower (p < 0.05) diameter of corpus luteum was observed in the Berseem clover group than that in the corn silage group. The Berseem clover group had higher (p < 0.05) overall concentrations of blood serum E2 , IL-1β and TNF-α, but lower (p < 0.05) overall concentrations of blood serum P4 than those recorded in the corn silage group. Oestrous rate, onset of oestrus time and oestrous duration were not significantly affected by the treatment. The conception rate was significantly (p < 0.05) reduced in the Berseem clover group compared with that in the corn silage group. In conclusion, feeding roughage with a high oestrogenic activity such as Berseem clover can negatively affect the conception rate of buffalo cows. This reproductive loss seems to be associated with inadequate luteal function and P4 concentration during early pregnancy.

Polyphenols in Ruminant Nutrition and Their Effects on Reproduction

The feeding of domestic animals with diets in which polyphenols are present is increasingly attracting the attention of nutritionists and scientists. This review summarizes the knowledge regarding polyphenols' possible positive and negative effects and their bioavailability. The bioavailability of substances is a prerequisite for any postabsorption effect in vivo. Positive and negative properties have been confirmed in previous studies on the diets of domestic animals rich in polyphenols, such as secondary metabolites of plants. Free radicals are formed in every organism, leading to oxidative stress. Free radicals are highly reactive molecules and can react in cells with macromolecules and can cause damage, including in reproductive cells. Some polyphenols at specific concentrations have antioxidant properties that positively affect animal reproduction by improving the quality of male and female gametes. The intake of phytoestrogens that mimic estrogen function can induce various pathological conditions in the female reproductive tract, including ovarian, fallopian, and uterine dysfunction. The metabolism of genistein and daidzein yields the metabolites equol and p-phenyl-phenol, leading to a decline in cow fertilization. The findings so far confirm that numerous questions still need to be answered. This review points out the importance of using polyphenols that have both benificial and some unfavorable properties in specific diets.

The influence of microbial isoflavonoid specific metabolites on platelets and transition metals iron and copper

BACKGROUND

Isoflavonoids seem to possess positive cardiovascular and other beneficial effects in humans.

HYPOTHESIS

Their low bioavailability, however, indicates that small isoflavonoid metabolites formed by human microflora can significantly contribute to these activities.

STUDY DESIGN

Testing antiplatelet activity ex vivo in human blood and interaction with transition metals in vitro.

METHODS

The effect on platelet aggregation induced by different triggers (arachidonic acid, collagen, ADP, TRAP-6), and interactions with transition metals (iron and copper chelation/reduction) were evaluated against four isoflavonoid-specific metabolites: S-equol; O-desmethylangolensin; 2-(4-hydroxyphenyl) propionic acid (HPPA); and 4-ethylphenol.

RESULTS

S-equol, 4-ethylphenol and O-desmethylangolensin blocked platelet aggregation induced by arachidonic acid and collagen. S-equol even matched the potency of acetylsalicylic acid in the case of collagen, which is the most physiological inducer of aggregation. Moreover, their effects in general seemed to be biologically relevant and attainable at achievable plasma concentrations, with the exception of HPPA which was ineffective. While only O-desmethylangolensin mildly chelated iron and copper, all four compounds markedly reduced cupric ions. Their direct free radical scavenging effects seem to have little clinical relevance.

CONCLUSION

This study has shown that S-equol, O-desmethylangolensin and 4-ethylphenol, arising from isoflavonoid intake, can have biologically relevant effects on platelet aggregation.

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Diverse effects of phytoestrogens on the reproductive performance: cow as a model

Phytoestrogens, polyphenolic compounds derived from plants, are more and more common constituents of human and animal diets. In most of the cases, these chemicals are much less potent than endogenous estrogens but exert their biological effects via similar mechanisms of action. The most common source of phytoestrogen exposure to humans as well as ruminants is soybean-derived foods that are rich in the isoflavones genistein and daidzein being metabolized in the digestive tract to even more potent metabolites-para-ethyl-phenol and equol. Phytoestrogens have recently come into considerable interest due to the increasing information on their adverse effects in human and animal reproduction, increasing the number of people substituting animal proteins with plant-derived proteins. Finally, the soybean becomes the main source of protein in animal fodder because of an absolute prohibition of bone meal use for animal feeding in 1995 in Europe. The review describes how exposure of soybean-derived phytoestrogens can have adverse effects on reproductive performance in female adults.

Amounts of an estrogen receptor β isoform increased in the theca of preovulatory follicles of sheep

Determination of the specific roles of the estrogen receptor (ER) forms in reproductive processes of different species remains incomplete. In the present experiment, cellular localization and changes in relative amounts of the ERα and ERβ in late developing ovarian follicles, oviduct, and uterus were determined during the follicular phase of the estrous cycle in sheep. Ewes in mid-luteal phase were treated with prostaglandin F(2α) (PG) to induce luteolysis and control the onset of the follicular phase. The oviducts, uterus, and the ovaries were collected at 0 (ewes not treated with PG), 4, 18, and 36 h after PG treatment (early, mid, and late follicular phase, respectively) and processed to evaluate the ERs using immunohistochemical (IHC) procedures. The ERα was localized to nuclei of granulosa cells of late developing follicles and most cells of the oviduct and uterus. The ERβ was detected only in ovarian follicles using two antibodies directed to different regions of the ERβ. Western immunoblotting demonstrated that the antibody directed against the N-terminal region of the ERβ detected one isoform (approximately 53 kDa) whereas the antibody directed against the C-terminus detected two ERβ isoforms (approximately 53 kDa and 59 kDa). Western and IHC results combined indicated presence of the 59 kDa ERβ in granulosa cells and the 53 kDa ERβ in both granulosa and theca cells. Relative amounts (immunostaining intensity) of the ERα increased (P<.05) in granulosa cells of preovulatory follicles and in the isthmian muscularis of the oviduct at the late follicular phase. Amounts of the ERα in the mucosal epithelium of the oviductal regions (isthmus, ampulla, and infundibulum), and in various uterine cell types (glandular and luminal epithelia, endometrial stromal cells, and myometrium) did not change (P>.05) throughout the follicular phase. A major increase (four-fold) in expression of the 53 kDa ERβ in the theca and a less pronounced increase in the granulosa occurred at the late follicular phase. The ERα is broadly expressed in reproductive organs of sheep and is upregulated only in few cell types during the late follicular phase. Immunoreactive ERβ was detected only in the ovary. Important estrogen actions in theca cells during preovulatory follicular development likely occur in association with a major increase in expression of an ERβ isoform.

Ileal and faecal digestibility of daidzein and genistein and plasma bioavailability of these isoflavones and their bioactive metabolites in the ovariectomised rat

Consumption of the soya isoflavones genistein and daidzein may provide protection against postmenopausal bone loss. The purpose of this study was to determine ileal and faecal digestibility of daidzein and genistein and the extent of formation of metabolites in the gastrointestinal (GI) tract in the ovariectomised rat, a model for postmenopausal bone loss. Twenty female rats were ovariectomised and fed either genistein or daidzein (0.026% of diet) for 4 wks. Genistein, daidzein and their GI-derived metabolites were quantitatively determined in plasma, urine, faeces and ileal digesta using GC/MS. Ileal and faecal digestibility of genistein (93 and 99.9%, respectively) were significantly greater than that of daidzein (32 and 77.5%, respectively). In genistein-supplemented animals, 4-ethylphenol was present in plasma in relatively high concentrations. The bioactivity of 4-ethylphenol may contribute to the physiological effects attributed to genistein consumption. The daidzein metabolite equol, was present in relatively high amounts in ileal digesta indicating substantial biotransformation of daidzein occurred in the small intestine presumably as a result of the activity of the resident microbiota. Further studies are required to determine whether 4-ethylphenol is a major metabolite of genistein in humans and the extent of biotransformation of daidzein to equol in the small intestine in humans.

Concentrations of isoflavones and their metabolites in the blood of pregnant and non-pregnant heifers fed soy bean

The present study compared the changes in isoflavones (daidzein and genistein) and their metabolite (equol and para-ethyl-phenol) concentrations in the blood plasma of cyclic and pregnant heifers after feeding with soy bean. Twelve healthy heifers were divided into three groups: cyclic heifers (days 8-12 of the estrous cycle; control group; n=4), an early pregnancy group (2 months pregnant; n=4) and a late pregnancy group (8 months pregnant; n=4). All heifers were fed a single dose of 2.5 kg of soy bean and then blood samples were taken from the jugular vein for 8 h at predetermined intervals. The concentrations of soy bean-derived isoflavones and their active metabolites were measured in the blood plasma on an HPLC system. In the blood plasma of the early- and late-pregnant heifers, we found lower concentrations and time-dependent decreases in daidzein and genistein in comparison to cyclic heifers (P<0.05). Moreover, we noticed significant increases of equol and para-ethyl-phenol in the blood plasma of the early-pregnant heifers (P<0.05). In contrast, in the blood plasma of the late-pregnant heifers, we did not find an increase in the isoflavone metabolite concentrations compared with the early-pregnant heifers (P>0.05). In conclusion, physiological status (cyclicity or pregnancy) of the females influenced the concentrations of isoflavone metabolites in the blood plasma of the heifers. The stage of pregnancy affects isoflavone absorption, biotransformation and metabolism differently and results in higher concentrations of active metabolites of isoflavones during early pregnancy in comparison to their lower concentrations during late pregnancy. Therefore, we surmise that cows are more sensitive to active isoflavone metabolite actions during early pregnancy than cyclic heifers and heifers in late pregnancy.

Soy phytoestrogens: impact on postmenopausal bone loss and mechanisms of action

Due to their ability to mimic the actions of mammalian estrogens, soy phytoestrogens have been proposed as potential therapeutic agents to aid in preventing postmenopausal bone loss. In vitro, phytoestrogens promote osteoblastogenesis and inhibit osteoclastogenesis. Although a relatively large number of intervention studies have been undertaken in animals and humans, the efficacy of phytoestrogens as bone-protective agents in vivo remains unclear. Differences in the bioactivities of individual phytoestrogens, differences in phytoestrogen metabolism and bioavailability within different study populations, and imprecise reporting of the dose of phytoestrogens administered in intervention studies may have contributed to the disparity in study findings.

Tissue distribution of isoflavones in ewes after consumption of red clover silage

When discovered in the 50's, isoflavones were suspected to provoke infertility syndrome in sheep grazing on clover. Many others effects of these phytoestrogens have been documented afterwards. To determine the distribution of isoflavone metabolites in ewe tissues and look for a link with their physiological impact, two ewes were fed a diet containing 50% red clover silage (variety Pawera) for one month with a daily intake of 157.6 mg/kg bw of total isoflavones. Only aglycones were fed due to the fermentation stage of the silage. At the sacrifice, isoflavone metabolites and aglycones were analyzed in blood, liver, kidney, lung, heart, muscle, ovaries, uterus, mammary glands, suprarenal glands, thymus, aorta, thyroid, pituitary gland, cerebellum, olfactory lobes, and brain hemispheres using HPLC-Coularray and LC-MS-MS. The major compounds recovered in tissues were equol and daidzein, present as glucuronides. Kidney concentrations were 10-fold higher than in other tissues. Penetration in brain was very limited. Reproductive organs contained higher concentrations of isoflavones than heart, muscle, or thymus. Distribution of isoflavones in ewe tissues is unequal and may reflect specific impact in some target tissues.