Ovarian and uterine characteristics and onset of puberty in adolescent offspring: effects of maternal diet and selenium supplementation in sheep

Towards prolonging ovarian reproductive life: Insights into trace elements homeostasis

Ovarian aging is marked by a reduction in the quantity and quality of ovarian follicles, leading to a decline in female fertility and ovarian endocrine function. While the biological characteristics of ovarian aging are well-established, the exact mechanisms underlying this process remain elusive. Recent studies underscore the vital role of trace elements (TEs) in maintaining ovarian function. Imbalances in TEs can lead to ovarian aging, characterized by reduced enzyme activity, hormonal imbalances, ovulatory disorders, and decreased fertility. A comprehensive understanding of the relationship between systemic and cellular TEs balance and ovarian aging is critical for developing treatments to delay aging and manage age-related conditions. This review consolidates current insights into TEs homeostasis and its impact on ovarian aging, assesses how altered TEs metabolism affects ovarian aging, and suggests future research directions to prolong ovarian reproductive life. These studies are expected to offer novel approaches for mitigating ovarian aging.

Plane of nutrition and FSH-induced superovulation affect the expression of steroid hormone receptors and growth factors in caruncular tissue of non-pregnant sheep

Implantation is a critical step in the establishment of pregnancy and an important part of embryo-maternal contact. Uterine receptivity can be affected by changes in body condition and the maternal endocrine milieu, including those caused by the use of exogenous gonadotropins in controlled ovarian hyperstimulation to induce the development of multiple follicles. This study demonstrates the effects of FSH-mediated ovarian hyperstimulation on the caruncles of ewes under various feeding regimes. Sheep were classified into 3 categories: control fed (CF), overfed (OF), or underfed (UF). In each group, animals were superovulated with FSH or injected with a saline solution (non-treated control). Uterine caruncles were collected at the early (d 5) and mid-luteal phase (d 10) of the estrous cycle. The transcript levels of steroid hormone receptors (ESR1, ESR2, PGR) and growth factors (IGF1, IGF2, VEGFA) were investigated and their expression localized by immunohistochemical staining. As for the main findings, day of the estrous cycle affected expression of ESR1, IGF1 and IGF2, but not of ESR2, PGR and VEGFA; both feeding and superovulation had modulatory effects, with feeding (UF/OF) stimulating expression of all genes studied, and superovulation altering expression of some genes, eg IGF1, PGR and ESR1 and ESR2, in CF animals. Similarly, feeding (UF/OF) altered responsiveness to superovulation for PGR on d 5 and ESR1/ESR2 on d 5 and/or 10. Our data emphasize possible effects of dietary and/or hormonal stimuli on uterine physiology, which may affect pregnancy outcomes by disrupting uterine functionality.

Onset of puberty and regularity of oestral cycles in ewe lambs of four breeds under high-altitude conditions in a non-seasonal country

Twenty-four Colombian Creole, Romney Marsh, Hampshire and Corriedale ewes raised under high-altitude conditions in a non-seasonal country were used to determine and to characterize the onset of puberty and of regularity ovarian function since the age of 3months. They underwent blood collection for determination of progesterone and monthly weight assessment. Oestrus was assessed daily by a teaser ram. In all breeds, age at onset of puberty ranged from 5.4 to 6.9 months and age at onset of regular ovarian function ranged from 7.4 to 8.6 months. Colombian Creole showed a higher body development at onset of puberty: 73.5 ± 8.3% versus 56.2 ± 7.4 in Romney Marsh, 58.8 ± 10.4 in Hampshire, and 57.3 ± 8.0 in Corriedale (p < 0.05), as well as a higher relative daily weight gain (+17%, p < 0.05). A negative correlation between daily weight gain and age at onset of puberty was established. Progesterone at onset of puberty and of regularity did not differ between breeds, but characterization of the luteal phase by the progesterone area under the curve (P4-AUC) revealed at both time points significantly lower values for Creole lambs (p < 0.05). Decreased P4-AUC paralleled a higher proportion of short oestral cycles observed prior to onset of regularity in Creoles, whereas an increased proportion of extra-long cycles were recorded in Romney Marsh (p < 0.05). These results establish first reference data for economically important breeds raised under tropical conditions. In comparison with other breeds, Colombian Creole requires a higher body development to achieve puberty and that an important proportion of short characterizes its prepubertal period cycles.

Dietary Intake of Selenium in Relation to Pubertal Development in Mexican Children

Alterations in pubertal timing have been associated with long-term health outcomes. While a few reports have shown that dietary intake of selenium is associated with fertility and testosterone levels in men, no human studies have considered the association between selenium and pubertal development in children. We examined the cross-sectional association of childhood dietary intake of selenium with pubertal development among 274 girls and 245 boys aged 10–18 years in Mexico City. Multiple logistic and ordinal regression models were used to capture the association between energy-adjusted selenium intake (below Recommended Dietary Allowance (RDA) vs. above RDA) and stages of sexual maturity in children, adjusted for covariates. We found that boys with consumption of selenium below the RDA had lower odds of a higher stage for pubic hair growth (odds ratio (OR) = 0.51, 95% confidence interval (95% CI): 0.27–0.97) and genital development (OR = 0.53, 95% CI: 0.28–0.99) as well as a lower probability of having matured testicular volume (OR = 0.37, 95% CI: 0.15–0.88) compared with boys who had adequate daily dietary intake of selenium (above RDA). No associations were found in girls. According to our results, it is possible that inadequate consumption of selenium may be associated with later pubertal development in boys, suggesting a sex-specific pattern. Future work with a larger sample size and measures of selenium biomarkers is needed to confirm our findings and improve understanding of the role of this mineral in children’s sexual development.

Effects of plane of nutrition and arginine on ovarian follicles in non-pregnant sheep: Cell proliferation, and expression of endothelial nitric oxide and its receptor

The aim of this study was to investigate the role of the nitric oxide (NO) system in ovarian function, by determining if arginine (Arg) supplementation impacts follicle number, cell proliferation, and expression of the NO system members in nutritionally compromised ewes. Ewes were randomly assigned into maintenance (C, 100% requirements), excess (O; 2xC), or restricted (U; 0.6xC) diets 8 weeks prior to Arg treatment. Ewes were individually fed twice daily with pelleted diets. Ewes from each nutritional group were randomly assigned to one of two treatments: saline or Arg, which was initiated on day 0 of the estrous cycle and administered 3 times per day. Ovaries were collected at the early-luteal, mid-luteal and late-luteal/follicular phases of the estrous cycle to determine 1) the number of surface follicles, 2) follicle cell proliferation marked by Ki67 protein expression, and 3) expression of endothelial nitric oxide (eNOS; NOS3) and soluble guanylyl cyclase beta (sGC; GUCY1B3) protein and mRNA in granulosa (G) and theca (T) layers using immunohistochemistry followed by image analysis and qPCR, respectively. During nutritional treatment, C maintained body weight, O gained 6±1.2 kg, and U lost 14±1.3 kg. Our data show that: 1) Ki67 was expressed in all ovarian compartments, eNOS protein was detected in blood vessels of T and stroma, and sGC protein was detected in T cells, and blood vessels of T layer and other ovarian compartments; 2) plane of nutrition affected the number of surface follicles, and thus folliculogenesis, cell proliferation in the T layer, eNOS and sGC protein expression in T, and NOS3 and GUCY1B3 mRNA expression in G; 3) Arg treatment affected cell proliferation in G and T, eNOS and sGC protein expression in T, mRNA expression of NOS3 in T in all groups, and GUCY1B3 in G depending on the stage of the estrous cycle; and 4) G and T cell proliferation, and expression of eNOS and sGC protein in T was affected by the stage of the estrous cycle. Our data demonstrated that plane of nutrition and Arg are involved in the regulation of follicular functions in non-pregnant sheep.

A Summary of New Findings on the Biological Effects of Selenium in Selected Animal Species-A Critical Review

Selenium is an essential trace element important for many physiological processes, especially for the functions of immune and reproductive systems, metabolism of thyroid hormones, as well as antioxidant defense. Selenium deficiency is usually manifested by an increased incidence of retention of placenta, metritis, mastitis, aborts, lowering fertility and increased susceptibility to infections. In calves, lambs and kids, the selenium deficiency demonstrates by WMD (white muscle disease), in foals and donkey foals, it is associated with incidence of WMD and yellow fat disease, and in pigs it causes VESD (vitamin E/selenium deficiency) syndrome. The prevention of these health disorders can be achieved by an adequate selenium supplementation to the diet. The review summarizes the survey of knowledge on selenium, its biological significance in the organism, the impact of its deficiency in mammalian livestock (comparison of ruminants vs. non-ruminants, herbivore vs. omnivore) and possibilities of its peroral administration. The databases employed were as follows: Web of Science, PubMed, MEDLINE and Google Scholar.

Luteal function during the estrous cycle in arginine-treated ewes fed different planes of nutrition

Functions of corpus luteum (CL) are influenced by numerous factors including hormones, growth and angiogenic factors, nutritional plane and dietary supplements such as arginine (Arg), a semi-essential amino acid and precursor for proteins, polyamines and nitric oxide (NO). The aim of this study was to determine if Arg supplementation to ewes fed different planes of nutrition influences: (1) progesterone (P4) concentrations in serum and luteal tissue, (2) luteal vascularity, cell proliferation, endothelial NO synthase (eNOS) and receptor (R) soluble guanylate cyclase β protein and mRNA expression and (3) luteal mRNA expression for selected angiogenic factors during the estrous cycle. Ewes (n = 111) were categorized by weight and randomly assigned to one of three nutritional planes: maintenance control (C), overfed (2× C) and underfed (0.6× C) beginning 60 days prior to onset of estrus. After estrus synchronization, ewes from each nutritional plane were assigned randomly to one of two treatments: Arg or saline. Serum and CL were collected at the early, mid and late luteal phases. The results demonstrated that: (1) nutritional plane affected ovulation rates, luteal vascularity, cell proliferation andNOS3,GUCY1B3, vascular endothelial growth factor (VEGF) andVEGFR2mRNA expression, (2) Arg affected luteal vascularity, cell proliferation andNOS3,GUCY1B3,VEGFandVEGFR2mRNA expression and (3) luteal vascularity, cell proliferation and the VEGF and NO systems depend on the stage of the estrous cycle. These data indicate that plane of nutrition and/or Arg supplementation can alter vascularization and expression of selected angiogenic factors in luteal tissue during the estrous cycle in sheep.

Lipid droplets in cultured luteal cells in non-pregnant sheep fed different planes of nutrition

Accumulation of lipid droplets (LD) in luteal cells likely is important for energy storage and steroidogenesis in the highly metabolically active corpus luteum (CL). The objective of this study was to determine the effect of plane of nutrition on progesterone (P4) secretion, and lipid droplet number and size in cultured ovine luteal cells. Ewes were randomly assigned to one of three nutritional groups: control (C; 100% NRC requirements, n=9), overfed (O; 2×C, n=12), or underfed (U; 0.6×C, n=10). Superovulation was induced by follicle stimulating hormone injections. At the early and mid-luteal phases of the estrous cycle, CL were dissected from ovaries, and luteal cells isolated enzymatically. Luteal cells were incubated overnight in medium containing serum in chamber slides. Media were then changed to serum-free and after 24h incubation, media were collected for P4 analysis, and cells were fixed in formalin and stained with BODIPY followed by DAPI staining. Z-stacks of optical sections of large and small luteal cells (LLC and SLC, respectively) were obtained using a laser-scanning microscope. Rendered 3D images of individual LLC and SLC were analyzed for cell volume, and total and individual LD volume, number and percentage of cellular volume occupied by LD by using Imaris software. Concentrations of P4 in serum and media were greater (P<0.05) at the mid than early-luteal phase, and were not affected by nutritional plane. LD total volume and number were greater (P<0.001) in LLC than SLC; however, mean volume of individual LD was greater (P<0.02) in SLC than LLC. In LLC, total LD volume was greater (P<0.02) in O than C and U ewes. In SLC, total LD volume and number was greater (P<0.003) at the mid than early-luteal phase, and percentage of cell volume occupied by LD was greater (P<0.002) in U than C and O ewes. These data demonstrate that both stage of luteal development and nutritional plane affect selected LD measurements and thus may affect luteal functions. Furthermore, these data confirm that LD dynamics differ among parenchymal steroidogenic luteal cell types.

Assessment of caprine corpora lutea growth, progesterone concentration, and eNOS expression: effect of a compensatory gain model

The experiment was conducted to evaluate corpus luteum (CL) growth, progesterone (P4) concentration, and endothelial nitric oxide synthase (eNOS) expression in nutrient stair-step fed goats. Female goats (n = 32) that exhibited at least 2, normal, consecutive estrous cycles were randomly assigned to either the control or stair-step fed group. In the control group, goats were fed ad libitum (100% of nutrient requirement for goats). The goats in the stair-step group were fed 70% of the control consumption for the first 42 d and 130% for the later 42 d during 4 consecutive estrous cycles (84 d). Blood and luteal samples were collected on days 3, 8, 13, and 18 of the estrous cycle to determine concentration of glucose, insulin, P4, luteal growth, and eNOS expression. Luteal growth was determined using fresh CL weight, DNA content, DNA and protein concentrations, and cell proliferation (labeling index of Ki-67). During realimentation phase at 4 h, glucose and insulin concentrations were greater (P < 0.05) in stair-step fed goat than those in control goats. Fresh CL weight, DNA content, protein concentrations, and labeling index of Ki67 on day 8 of the estrous cycle in the stair-step group were greater (P < 0.05) than that in the control group. Protein for eNOS was located in the capillaries of CL throughout of the estrous cycle in both groups. Greater serum P4 concentrations and eNOS protein (P < 0.05) were observed in the stair-step fed goats on day 3 (1.83 ng/mL and 6.79%) compared with the control goats (0.98 ng/mL and 6.02%) and on day 8 (5.15 ng/mL and 7.88%) compared with the control goats (4.54 ng/mL and 7.07%). These data demonstrate that luteal growth, progesterone concentration, and eNOS protein were partially affected by nutrient compensatory gain in goats.

Progesterone secretion by ovine granulosa cells: effects of nitric oxide and plane of nutrition

The aim was to evaluate the effects of nutritional plane on in vitro progesterone (P4) secretion by granulosa (G) cells cultured in the presence or absence of effectors of the nitric oxide (NO) system. Ewes were randomly assigned into three nutritional groups: control (C), overfed (O; 2 × C), or underfed (U; 0.6 × C). Follicular development was induced by FSH injections. On day 15 of the estrous cycle, G cells were isolated and cultured with or without DETA-NONOate (NO donor), L-NAME (NO synthase [S] inhibitor), Arg and (or) LH for 8 h. DETA-NONOate decreased basal and LH-stimulated P4 secretion, and L-NAME increased basal P4 secretion in all groups. In U, Arg decreased LH-stimulated P4 secretion. These data demonstrate that (i) plane of nutrition affects basal P4 secretion by G cells, (ii) the NO donor decreases, NOS inhibitor increases but Arg does not affect basal P4 secretion, and (iii) effects of Arg on LH-stimulated P4 secretion are affected by plane of nutrition in FSH-treated sheep. Thus, plane of nutrition affects G cell function, and the NO system is involved in the regulation of basal and LH-stimulated P4 secretion. The mechanism of the NO system effects on secretory activity of G cells remains to be elucidated.

The effects of diet and arginine treatment on serum metabolites and selected hormones during the estrous cycle in sheep

The aim of this study was to determine the effects of diet and arginine (Arg) treatment on serum concentrations of selected metabolites and metabolic and reproductive hormones in nonpregnant ewes. Sixty days before the onset of estrus (Day 0), Rambouillet ewes were randomly assigned to one of three dietary groups: maintenance control (C; N = 16; 100% National Research Council requirements), overfed (O; N = 16; 2 × C), or underfed (U; N = 16, 0.6 × C) to achieve and maintain three different body conditions during their estrous cycle(s). At Day 0, ewes from each nutritional group were randomly assigned to receive one of two treatments: saline (Sal) or Arg (L-Arg-HCl; 155 μmol Arg per kg of body weight [BW]; intravenous), which was administered three times per day for 21 or 26 days. Blood samples were collected on Days 0, 6, 10, 12, 16, 21, and 26 of Sal or Arg treatment for evaluation of Arg, nitric oxide metabolite, cholesterol, glucose, insulin, insulin-like growth factor 1, leptin, and progesterone. For a time-response trial, blood samples were collected at 0, 1, 2, 4, and 7 hours after Sal or Arg treatment at the mid-luteal phase to determine serum Arg concentrations. During the 11-week study, C maintained body weight, O gained 9.6 ± 0.7 kg, and U lost 13.9 ± 0.1 kg. Overall, serum concentrations of Arg, glucose, insulin, insulin-like growth factor 1, leptin, and progesterone were greater (P < 0.05) in O ewes than C and/or U ewes and were not affected by Arg treatment. Serum Arg concentration increased at 1 and 2 hours and decreased to basal level at 4 and 7 hours after Arg treatment. These data reinforce the importance of diet in regulation of metabolic and endocrine functions, and demonstrated that the dose and duration of Arg treatment used in this study does not alter serum metabolites or hormones in nonpregnant ewes of various nutritional planes.