The inhibition of spermatic cystine/glutamate antiporter xCT (SLC7A11) influences the ability of cryopreserved stallion sperm to bind to heterologous zonae pellucidae

Sperm are redox-regulated cells, and deregulation of their redox status is considered to affect male fertility and to reduce their fertilizing ability following biotechnological procedures, such as cryopreservation. Cystine (CysS), after incorporation in sperm via SLC7A11 antiporter, has been demonstrated to increase intracellular GSH content, the most important non enzymatic antioxidant. This study was aimed at investigating the role of SLC7A11 antiporter on frozen-thawed stallion sperm ability to respond to in vitro capacitating environment after post-thaw incubation with CysS and/or Sulfasalazine (SS), a specific inhibitor of SLC7A11 antiporter. Viability, motility, immunolocalization of tyrosine phosphorylated proteins and the ability to bind to heterologous zonae pellucidae were evaluated. Thawed sperm from seven stallions (2 ejaculates/stallion) was washed and resuspended in Tyrodes media; each thawed ejaculate was divided in Control (CTR) and 3 samples supplemented with: 0.5 mM Cystine (CysS), 500 μM Sulfasalazine (SS) and 0.5 mM CysS + 500 μM SS (CysS + SS). After 1 h of incubation at 37 °C, samples were washed twice, resuspended in capacitating BWW medium and incubated at 38 °C under 5% CO₂. After 30 and 60 min, sperm motility, viability and tyrosine phosphorylated protein immunolocalization, used as capacitation status index, were evaluated. After 30 min of capacitation, 4 × 10⁵ sperm were co-incubated with denuded pig oocytes in capacitation medium for 30 min for the heterologous binding assay. None of the sperm parameters studied (motility, viability and tyrosine phosphorylation) showed any difference respective to control. The number of sperm bound per oocyte (mean ± SEM) tended to increase in CysS group (44.0 ± 12.3) respect CTR (40.8 ± 10.8) while decreased in SS group (32.4 ± 7.8) (p < 0.01). Moreover, CysS + SS group showed a lower binding rate (32.0 ± 10.0) compared to CysS (p < 0.001). Our results suggest that CysS supplementation of thawed stallion sperm can influence their ability to bind to heterologous zona pellucidae as the inhibition of CysS incorporation by SLC7A11 reduced the number of sperm bound per oocyte. This effect does not seem to be ascribed to a modification of sperm motility, membrane integrity and tyrosine phosphorylation.

Resveratrol and Epigallocatechin-3-gallate addition to thawed boar sperm improves in vitro fertilization

Thawing is one of the most delicate process after semen cryopreservation as spermatozoa pass from a dormant metabolic stage to a sudden awakening in cellular metabolism. The rapid oxygen utilization leads to an overproduction of reactive oxygen species that can damage sperm cells, thus causing a significant decrease of fertilizing potential of frozen-thawed spermatozoa. Resveratrol (Res) is a natural grape-derived phytoalexin and Epigallocatechin-3-gallate (EGCG) is the major polyphenol in green tea (Camellia sinensis); both molecules are known to possess high levels of antioxidant activity. The objective of the present study was to assess the effect of different concentrations of Res (0.5, 1 or 2 mM; Experiment 1) or EGCG (25, 50 or 100 μM; Experiment 2) supplementation to thawing boar semen extender on sperm quality parameters (viability and acrosome integrity) and in vitro fertilization (IVF). Semen after thawing and dilution with three volumes of Beltsville Thawing Solution (BTS), was immediately divided in control group without antioxidants addition (CTR) and either Res or EGCG groups. Sperm viability and acrosome integrity were evaluated in CTR, Res or EGCG groups after 1 h of incubation at 37 °C. The addition of different doses of Res or EGCG to thawing extender for 1 h did not induce any effect on boar sperm viability and acrosome integrity. However, both Res and EGCG treated samples exhibited a significantly higher penetration rate compared with CTR when used for IVF. In particular the treatment with all the EGCG concentrations increased the penetration rate (P < 0.01) while only Res 2 mM induced a significant increase of this parameter (P < 0.01). In addition, EGCG 25 and 50 μM supplementation significantly increased total fertilization efficiency as compared to control (EGCG 25 μM: 40.3 ± 8.2 vs 26.8 ± 9.5, P < 0.05; EGCG 50 μM: 40.4 ± 7.8 vs 26.8 ± 9.5, P < 0.01). The same effect was observed with Res 2 mM (51.0 ± 7.6 vs 29.6 ± 11.3, P < 0.01). In conclusion, our results indicate that the addition of different doses of the two antioxidants to thawed spermatozoa for one hour, even if does not exert any effect on sperm viability and acrosome integrity, efficiently improves in vitro penetration rate. Moreover, both molecules (EGCG 25 and 50 μM and Res 2 mM) significantly increases the total efficiency of fertilization.

Epigallocatechin-3-gallate (EGCG) and green tea polyphenols do not improve stallion semen parameters during cooling at 4°C

Stallion semen storage for artificial insemination is mainly based on liquid cooled storage. In many stallions this technique maintains sperm quality for an extended period of time (24-72 hr) at 7°C. While this technique is commonly used in the horse industry, there can be a decline in fertility in some stallions, due to an inability of their sperm to tolerate the cool storage process. The aim of the present work was to evaluate the effect of two natural antioxidants (epigallocatechin-3-gallate (EGCG) at 20, 60 and 120 μm and green tea polyphenols, and p at .001, .01 and .1 mg/ml) on some sperm parameters (sperm motility, viability/acrosome integrity and DNA quality) in extended semen immediately after its collection (T0) and after 2, 6, 24 and 48 hr of cool storage. Two ejaculates from three trotter stallions were analysed after 48 hr of storage at 4°C. No beneficial effect on the analysed parameters was observed: the two antioxidants were not able to improve sperm quality after 48 hr of storage. These results are in agreement with previous findings on the effect of different antioxidants reported by other researches, who have demonstrated that stallion semen keeps good antioxidant capacity after dilution for 24 hr. In conclusion, the positive effect exerted by antioxidant molecules in other species is not confirmed in the equine one.

Embelin supplementation of in vitro maturation medium does not influence nuclear and cytoplasmic maturation of pig oocytes

Oxidative stress caused from in vitro culture contributes to inadequate oocyte maturation which leads to a poor embryo development. Therefore, it is important to protect oocytes and embryos against oxidative stress. This study was aimed at evaluating the effect of Embelin (2,5-dihydroxy-3-undecyl-1,4-benzoquinone), an antioxidant with various pharmacologic activities, on nuclear and cytoplasmic maturation of pig oocytes as well as on steroidogenesis of cumulus cells (CCs). Another objective was to determine the influence of Embelin on developmental competence of pig oocytes as well as the expression levels of three key genes (Nanog, Sox2 and Oct4) involved in the control of pluripotency in parthenogenetically activated embryos. Embelin (0, 10, 20 and 40 μM) was added during in vitro maturation of cumulus oocyte complexes; media of both the first and the second day of culture were collected and assayed for progesterone and estradiol-17β. At the end of the maturation period, the oocytes were fixed (to determine nuclear maturation) or partenogenically activated to evaluate cytoplasmic maturation and genes expression. Embelin did not exert any effect on the proportion of MII oocytes, steroidogenesis of CCs, percentage of embryos that developed to blastocyst stage and the number of blastomeres/blastocyst. Moreover, no significant differences of Oct4, Nanog and Sox2 transcripts were detected in blastocyst stage embryos. In conclusion, Embelin did not influence the reproductive parameters assessed, confirming that it is not possible to predict whether the beneficial effect exerted by an antioxidant in a particular tissue could be present also in another one.

Storage of sexed boar spermatozoa: Limits and perspectives

Despite the great potential application of sex-sorted spermatozoa in swine, the technology is not practiced in the pig industry because of technical factors and species-specific issues. The susceptibility of boar spermatozoa to stresses induced by the sorting procedure, the relative slowness of the sex-sorting process together with the high sperm numbers required for routine artificial insemination in pig are some of the main factors limiting the commercial application of this technology in pigs. This review briefly describes the damage to spermatozoa during sex sorting, focusing on an additional limiting factor: increased susceptibility of sexed boar spermatozoa to injuries induced by liquid storage and cryopreservation that, in turn, impairs sperm quality leading to unsatisfactory results in vivo. Strategies to extend the lifespan of sex-sorted boar spermatozoa and to improve their fertilizing ability after liquid storage or cryopreservation need to be implemented before this technology can be used in pig farms. In this regard, encapsulation in barium alginate membranes could be a promising technique to optimize the in vivo use of sexed boar spermatozoa, by protecting, targeting, and controlling the release of sperm into the female genital tract.

Alkaline phosphatase in boar sperm function

Alkaline phosphatase (AP) catalyses the detachment of phosphate residues from different substrates. Its activity has been demonstrated in seminal plasma and spermatozoa from porcine and other mammalian species; anyway, the role of AP in male reproduction has not been clarified yet and the aim of this study was to determine AP function in boar sperm capacitation and in vitro fertilization (IVF). AP activity was assayed in seminal plasma and in uncapacitated and in vitro capacitated (IVC) spermatozoa; in addition, capacitation was studied in presence of different doses of AP (1.2 and 2.5 IU/mL). The effect of different doses of AP (1.2 and 2.5 IU/mL) on several sperm parameters after IVC (viability, acrosome integrity with FITC-PSA, capacitation status with CTC staining, tyrosine phosphorylation) and on fertilizing ability during IVF were also evaluated. High AP activity was detected in seminal plasma, in particular in sperm-rich fraction; a lower activity was detected in uncapacitated spermatozoa while a significant decrease was evidenced after IVC. Viability was not changed by AP supplementation of the capacitating medium, whereas acrosome integrity and capacitation status were significantly affected by 1.2 and 2.5 doses, with a dose-dependent decrease in acrosome-reacted cells as well as in CTC B pattern displaying cells. As for sperm head protein phosphorylation, a decrease in relative fluorescence was detected in AP 2.5 group, if compared with capacitated one. After IVF, a dose-dependent decrease in penetrated oocytes was recorded, with an increase in monospermic zygote rate. In conclusion, we demonstrated that AP activity decreases under capacitating condition and that addition of AP to spermatozoa during capacitation results in a depression of the capacitating process and IVF. We can infer that AP plays a role in keeping spermatozoa quiescent until they are ejaculated and in modulating the acquisition of the fertilizing ability.

Detection and localization of GLUTs 1, 2, 3 and 5 in donkey spermatozoa

GLUTs are a family of proteins that facilitate the transport of glucose and other hexoses through the plasma membrane of the cells. GLUTs are present in mammalian spermatozoon's membrane in different isoforms and they supply metabolic substrates for all the cell's activities such as motility, homoeostasis and fertilization. As studies about donkey spermatozoa and their metabolism are lacking, this study was aimed at detecting GLUTs 1, 2, 3 and 5 presence by western blotting technique and at determining their localization on the plasma membrane by indirect immunofluorescence. Each protein showed a typical localization on the sperm cells' plasma membrane, differencing the one to the other on the basis of the hexose they transport. We also highlighted some differences between GLUTs distribution and molecular weight in donkey spermatozoa and its nearest relative, the horse.

Effects of antioxidants on boar spermatozoa during sorting and storage

Sorting procedures submit sperm cells to a set of stressful steps that can trigger an increase of ROS production and consequently reduce sorted semen quality. This study evaluated the effect of supplementation with different antioxidants (EGCG, Na pyruvate+catalase, SOD) on acrosome and plasma membrane integrity, activation of caspases (as assayed by FITC-VAD/PI staining) and immunolocalization of Hsp70 of boar spermatozoa after sperm preparation (Hoechst 33342 staining) and sorting procedure. The effect of antioxidants, with or without seminal plasma, on sorted spermatozoa stored for 24h at 15°C was also evaluated. Antioxidants did not exert any preventive action on sperm modification induced by staining and sorting. After 24h of storage at 15°C, sorted samples supplemented with either EGCG or SOD plus seminal plasma showed a significant (p<0.05) increase of the percentage of viable spermatozoa, while no positive effect on the other tested parameters was observed; EGCG seems to exert an inhibition on caspase activation in that a decrease of the number of dead cells FITC-VAD+/PI+ was recorded. In conclusion, our results indicate that EGCG and SOD in association with seminal plasma are effective in exerting some compensatory protection against the detrimental effects of storage of sorted semen while their action is not evident during steps of the sorting procedure.

Luteinizing hormone and growth hormone secretion in early lactating Spanish beef cows

The episodic release of luteinizing hormone (LH) and growth hormones (GH) was studied in three suckling regimens and two breeds of Spanish suckled cows. Parda de Montaña (PA) cows (n = 21) were assigned to once-daily, twice-daily or ad libitum (ADLIB) suckling. Pirenaica (PI) cows (n = 7) were used to evaluate the breed effect in twice-daily suckling. Coccygeal blood samples were collected twice weekly during lactation to determine the interval from calving to first ovulation through peripheral progesterone. On day 32 ± 3 post-partum, jugular blood samples were drawn at 15 min intervals during 8 h to analyse circulating LH and GH. The interval to first ovulation was greater in PA cows suckling ADLIB than in restricted suckling treatment (RESTR1), whereas in RESTR2 it did not differ from the other two treatments. There were no differences between PA and PI cows in the interval to first ovulation. RESTR1 cows showed a tendency to have shorter LH peak widths than ADLIB cows. PA cows showed a tendency to have longer LH peak widths than their PI counterparts. There were no differences across treatments or breeds in any of the GH measures of secretion. The LH release was more affected by breed than by suckling frequency, whereas that of GH was not influenced by any of these parameters. The variables that best allowed discrimination between ADLIB and restricted nursing systems were the interval to post-partum first ovulation, LH peak number and the mean GH concentration.

262 ICSI OF EQUINE OOCYTES WITH SEX-SORTED FROZEN-THAWED SEMEN RESULTS IN LOW CLEAVAGE RATE BUT NORMAL EMBRYO DEVELOPMENT AND PREGNANCIES

Sorting of sperm by flow cytometer has allowed selection of offspring of predetermined sex in several species by artificial insemination, although the success rate is often lower than with non-sexed semen. In horses, the problem was partially overcome with hysteroscopic insemination using sex-sorted fresh sperm. However, when sex-sorted frozen–thawed sperm were used the pregnancy rate was heavily reduced in comparison with non-sexed frozen–thawed semen. Because it has been demonstrated that in vitro assisted reproductive techniques, namely intracytoplasmic sperm injection (ICSI), has permitted live foals to be obtained using sperm with low fertility in the field, in this study we investigated the possibility of using ICSI with sexed-sorted frozen–thawed sperm for equine embryo production in vitro. Briefly, semen was collected from two Standardbred stallions of proven fertility (Stallions A, B), sorted using a MoFlo SX flow cytometer and frozen (Johnson LA and Welch GR 1999 Theriogenology 52, 1323–1341). Sex-sorted and control non-sexed frozen semen (two stallions of in vitro proven fertility: C, D) was thawed, centrifuged on a Percoll gradient, washed and diluted 1:1 in PVP before ICSI. Oocytes were collected from ovaries of slaughtered mares and matured in vitro. Metaphase II oocytes were injected with sperm, subsequently cultured up to the blastocyst stage and frozen conventionally in 10% of glycerol (Galli et al. 2002 Theriogenology 58, 713–715). Six embryos from sexed-sorted sperm were thawed and non-surgically transferred in naturally cycling synchronous recipient mares. Results are summarized in Table 1. Overall, 70 and 58 (stallion A, B) and 30 and 15 (stallion C, D) oocytes were injected with sex-sorted or control frozen–thawed sperm, respectively. Mean cleavage rates were 20.3% for sorted sexed sperm and 71.1% for control, showing a significantly lower cleavage rate for sexed sperm. This difference was reflected in the number of blastocysts obtained (4.7% v. 20.0%). From the 6 frozen–thawed embryos derived from sexed sperm, that were transferred, 4 pregnancies resulted. One pregnancy was lost around 21 days, a second was pharmacologically aborted, and two were maintained (one from male and one from female sorted semen are currently in the 11th month of gestation). In conclusion, this study demonstrates that ICSI with sex-sorted sperm can be used for producing equine blastocysts able to establish pregnancies at a high rate following embryo transfer. However, the overall efficiency of the system is limited due to the very low cleavage rate obtained with sexed-sorted frozen–thawed sperm. Table 1.Development of embryos produced by ICSI with sorted and non-sorted frozen–thawed semen This work was supported by an RFO (ex 60%) and Camera di Commercio Cremona grant. The Authors wish to thank Società Italiana Produttori Sementi.

Role of Leptin on Growth Hormone and Prolactin Secretion by Bovine Pituitary Explants

Leptin is an important hormone regulating nutritional status in humans and animals. Its most relevant activity is at the hypothalamic level, where it modulates food behavior, thermogenesis, and secretion of several pituitary hormones. The exact mechanisms underlying these processes are unclear. The purpose of this study was to verify whether leptin could modulate growth hormone (GH) and prolactin (PRL) secretion acting directly on bovine pituitary cells. Adenohypophyseal explants were cultured with different concentrations of leptin (50, 250, and 500 ng/mL); GH and PRL concentrations in culture media were determined by RIA. On tissues treated with 250 ng/mL of leptin, GH and PRL mRNA, as well as protein content, were estimated by reverse transcription-PCR and Western immunoblotting, respectively. Concentrations of GH in culture media containing 250 and 500 ng/mL of leptin were significantly higher than in controls: 1,063.5 +/- 141.2 (mean +/- SEM) and 1,018.8 +/- 88.4 vs. 748.9 +/- 74.0 ng/mg of tissue, respectively, after 1 h of treatment. Prolactin concentrations were significantly higher in culture media containing 50, 250, and 500 ng/mL of leptin than in controls after 2 h of treatment (547.1 +/- 50.3, 547.5 +/- 58.8, and 577.0 +/- 63.7 vs. 406.8 +/- 43.9 ng/mg of tissue, respectively). Tissues cultured with 250 ng/mL of leptin had significantly higher GH mRNA and lower GH protein content than controls (389.7 +/- 17.9 vs. 289.7 +/- 16.7; 1,601.5 +/- 90.1 vs. 2,212.7 +/- 55.6 arbitrary units, respectively) after 5 h of treatment. In contrast, no significant differences were found for PRL mRNA and protein content, possibly because of a delay in the leptin stimulation of PRL secretion. The results suggest that GH and PRL secretion in bovine pituitary explants can be directly regulated by leptin.

Acyl Ghrelin and Metabolic Hormones in Pregnant and Lactating Sows

Ghrelin, the endogenous ligand of the growth hormone (GH) secretagogue receptor, is considered a pleiotropic regulator involved in a large array of functions, including control of energy balance, regulation of food intake and, more recently, modulation of the reproductive axis. The present study was aimed at determining the changes in plasma concentrations of acyl-ghrelin in pregnant and lactating sows, with special emphasis on the relationship with the levels of GH, leptin, non-esterified fatty acids (NEFA) and insulin-like growth factor (IGF-1). Blood samples were collected via jugular venipuncture from 22 multiparous sow 30, 60 and 90 days after artificial insemination, 7 and 21 days after farrowing and at first oestrus post-weaning. Plasma concentrations of acyl-ghrelin, leptin, GH and IGF-1 were quantified by validated radioimmunoassay; NEFA were determined using a colorimetric procedure. Plasma acyl ghrelin levels were highest at 30 days of pregnancy and decreased thereafter and during lactation. At the beginning of lactation, GH, IGF-1 and NEFA concentrations significantly increased, while a significant reduction occurred in leptin. In conclusion, ghrelin concentrations in sow maternal circulation does not seem to play an important role in maintaining circulating GH levels during lactation; moreover, ghrelin is not associated with leptin, NEFA and IGF-1 levels.

Viability and DNA fragmentation in differently sorted boar spermatozoa

Sperm cell defense against DNA damage relies on two factors: the tight packaging of chromatin, based on condensation and substitution of histones with protamines, and the antioxidant agents present in seminal plasma. These defenses are extremely important as mature sperm is unable to repair DNA damage and even if a successful fertilization occurs, embryo undergoes apoptosis at the time of genomic activation. Sex-sorting exposes spermatozoa to stress sources such as high pressure, laser beam and electrical charge. The aim of this work was to determine how sorting procedures affect viability and DNA integrity in boar spermatozoa, by using the newly developed Sperm-Sus-Halomax. Four sperm populations were considered: CONTROL (no treatment), REAL (sex-sorted semen), BULK (semen sorted without sex separation) and NO LASER (semen only exposed to the high pressure, but including also cells normally discarded from sex-sorting). A significantly (P=0.019) lower viability in NO LASER (64.71%) than in CONTROL (78.6%) and REAL (80.5%) groups was found; this was accompanied by a significantly (P=0.001) higher DNA fragmentation index (DFI) in NO LASER group (6.86%) respect to CONTROL (3.30%) and REAL (3.42%) groups. BULK group did not show any difference in viability or DFI as compared to the other groups. In conclusion, we may believe that sex-sorting procedure as a whole does not affect either viability or DFI and that shear mechanical forces are a relevant source of DNA damage for sorted semen.

Leptin does not seem to influence glucose uptake by bovine mammary explants

Leptin, a protein produced and secreted by adipocytes, is know to regulate food intake and whole-body energy metabolism, but knowledge about its possible effect in bovine mammary gland is scarce. Leptin may be involved in the regulation of glucose transport even though this effect at the tissue level remains controversial. Once uptaken by the mammary gland, glucose is utilised in several ways but the majority, about 60-70%, is drained for lactose synthesis. This study was aimed at investigating the effect of leptin on glucose regulation in bovine mammary gland. We have examined the effects of leptin on the expression of GLUT1 mRNA, pyruvate kinase (PK) as well as glucose-6-phosphate dehydrogenase (G6PDH) activity. Treatment of mammary gland explants with recombinant leptin did not influence glucose assimilation, pathway transport (GLUT1 mRNA) and glucose metabolism (PK and G6PDH) in this tissue. The results from this study seem to exclude an involvement of leptin in glucose uptake and metabolism in bovine mammary gland.

Gastric immunolocalization and plasma profiles of acyl-ghrelin in fasted and fasted-refed prepuberal gilts

Ghrelin is a peripheral circulating hormone, mainly released from the stomach, which can stimulate food intake. We studied fed, fasted and fasted-refed prepuberal gilts in order to outline possible changes in gastric mucosal ghrelin cells and in plasma ghrelin profiles in response to food deprivation. Acyl-ghrelin-immunoreactive cells were numerous in oxyntic glands, less abundant in cardiac glands and least frequent in pyloric glands, with the addition of a minor population of labelled cells in the gastric pit mucosa. When fed and fasted animals were compared (72-h fast versus fed; n = 4 each), no clear-cut differences were revealed in labelled cell numbers, nor in their staining intensity. An RIA for plasma porcine acyl-ghrelin (n-octanoylated at Ser-3), not recognizing des-acyl-ghrelin, was validated. Plasma acyl-ghrelin progressively increased upon fasting (over 6, 12, 24 and 48 h); ghrelin levels significantly (P<0.05) higher than those prefast were reached at 72 h. After refeeding, plasma ghrelin was rapidly restored to basal values by 6 h. In the same animals, plasma insulin was significantly reduced throughout the fasting period (6-72 h), while rapidly increasing after refeeding. Non-esterified fatty acid levels increased during fasting (12-72 h) and rapidly returned to low values after refeeding. In conclusion, the present study demonstrates that starvation and refeeding influence ghrelin plasma level in prepuberal gilts. The absence of detectable changes in ghrelin cells, as seen in immunohistochemistry, could be due to a large intracellular storage of potentially releasable acylghrelin.

Effect of staining and sorting on boar sperm membrane integrity, mitochondrial activity and in vitro blastocyst development

The objective of this study was to determine the effects of staining with Hoechst 33342 and of the entire sorting procedure on boar sperm membrane integrity (using Annexin-V/PI), mitochondrial activity (using JC-1/SYBR/PI) and blastocyst development in vitro; the effect of storage at 17 degrees C for 24h prior to Hoechst staining and sorting was also investigated. The Hoechst staining and the whole sorting procedure reduced the percent of live spermatozoa in both fresh (day 0) and stored (day 1) semen, as determined by both assays; nevertheless, there was no increase in live sperm cells showing signs of early damage (Annexin-V positive, propidium negative), whose percentages remained nearly zero. The majority of Annexin-V positive cells were propidium positive, therefore dead. JC-1 staining evidenced a correlation between mitochondrial activity and viability. However, a significant difference between viable sperm cells and sperm cells with active mitochondria was detected in control and stained sperm, whereas almost all viable sorted spermatozoa had active mitochondria. No significant differences in the in vitro produced blastocysts both on day 0 and 1 were observed. In conclusion, despite the damages induced by sorting procedures, semen sorted as fresh or after storage at 17 degrees C can be successfully used for in vitro production of pig embryos.

Leptin, GH, PRL, Insulin and Metabolic Parameters Throughout the Dry Period and Lactation in Dairy Cows

Leptin may play a role in the endocrine-metabolic processes that guarantee the physiological course of lactation in dairy cattle. This study was aimed at determining the changes in plasma concentrations of leptin and some of the main hormones and metabolites involved in the lactogenetic process in high-yielding dairy cows throughout lactation; we also wanted to assess whether leptin secretion is subjected to seasonal influences. Blood samples were collected from 23 Italian Friesian dairy cows from the end of a lactation to the ninth month of the subsequent one; in addition, blood was sampled from 47 dairy cows in different phases of lactation during February and July. Plasma concentrations of leptin, growth hormone (GH), insulin, prolactin (PRL), glucose, non-esterified fatty acids (NEFA) and urea were quantified by either validated radioimmunoassay (RIA) or enzymatic colorimetric methods. At the beginning of lactation, GH concentrations significantly increased, while a significant reduction occurred in leptin and insulin. This endocrine condition, such as the significant increase in NEFA plasma concentrations, is indicative of a marked lipid mobilization. In the more advanced stages of lactation, when both energy and protein balances become positive, leptin plasma concentrations increased, whereas GH and NEFA concentrations declined. During the summer months, a significant increase in leptin plasma concentrations, irrespective of the phase of lactation, was observed. Collectively, our findings suggest that, in dairy cows, leptin may represent a 'metabolic signal' of animal's status of fattening and nutritional level; in addition, leptin seems to be influenced by photoperiod and environmental temperature.

Effects of different culture conditions and leptin on GH mRNA expression and GH secretion by pig pituitary cells

Growth hormone (GH) is enhanced in malnutrition; physiological increments in GH secretion seem to play an important role in regulating metabolism during fasting. Leptin has also been shown to play a role, amongst others, in modulating the somatotropic axis. In this study, we investigated how the composition of culture media could influence basal and leptin-stimulated GH secretion and expression in pig pituitary cells. Pituitary cells from 8-month-old sows were incubated for 48 h in presence and absence of 10% fetal calf serum, either in DMEM/Ham's F12, in arginine-free DMEM/Ham's F-12, or in DMEM/Ham's F12 Salts. Cells were then treated for 24 h with GHRH or recombinant human leptin (rhLep) individually or in association with GHRH; cell proliferation, nitric oxide (NO) production and GH expression and secretion were determined. The absence of nutritional factors induced a decrease in cell proliferation, but stimulated both GH secretion and expression. Furthermore, rhLep significantly increased GH expression and secretion irrespective of culture conditions. NO production was only significantly enhanced by leptin under DMEM/Ham's F12 culture conditions. These observations lead us to hypothesize that the adaptive capabilities of pituitary cells may overcome the negative effects of undernutrition; in this context, leptin does not seem to depend on NO pathways in modulating GH secretion.

Leptin concentrations in plasma and follicular fluid from prepubertal gilts as influenced by fasting, refeeding and insulin

This study's aim was to examine whether fasting and refeeding would influence leptin levels in both plasma and follicular fluid from prepubertal gilts, and whether insulin affects leptin levels in fasting gilts. In experiment 1, four gilts were fasted for 72 h and then refed. Blood samples were withdrawn during normoalimentation, at the end of fasting, and for 4 h after refeeding. All samples were assayed for leptin; alternate samples were assayed for insulin, glucose and non-esterified fatty acids (NEFA). Fasting caused a decrease in leptin, glucose and insulin levels in plasma, while NEFA concentrations increased. In experiment 2, four gilts were given insulin as a bolus (0.2 IU/kg body weight) after 68 h of fasting. Blood samples were collected every 15 min around insulin administration and were assayed for leptin, insulin and glucose. This experiment shows that insulin administration increases leptin levels during fasting. In experiment 3, gilts were ovariectomized during normal alimentation (n=4), after 48 h of fasting (n=4), and after 48 h of realimentation following 48 h of fasting (n=4). Leptin levels in both plasma and follicular fluid collected after 48 h of fasting were significantly lower than those observed during normoalimentation or refeeding. In conclusion, a transient increase in insulin during fasting is effective in restoring leptin concentrations; in addition, leptin levels in follicular fluid parallel those in plasma.

Cryopreservation of pig granulosa cells: effect of FSH addition to freezing medium

We cryopreserved swine granulosa cells by a slow cooling rate system; FSH was added to the freezing medium to test its effectiveness in protecting the cells. After thawing, proliferative activity, viability, steroidogenesis and apoptosis were tested; moreover, we determined heat shock protein (HSP70) production, to investigate the recovery from stress and superoxide dismutase (SOD) and catalase activity to evaluate a possible impairment of the antioxidant pathway. E2 production was enhanced by cryopreservation in particular with FSH; on the contrary, P4 production was inhibited by the freezing process in particular without FSH. Only the higher FSH concentration (10 ng/ml) stimulated steroid secretion in freshly collected cells; P4 production by cells cryopreserved in the presence and in absence of FSH was increased by both 5 and 10 ng/ml while the lowest concentration was effective in stimulating E2 production only when FSH was added to freezing medium. Freezing did not modify proliferative activity, while apoptosis was higher in frozen than in fresh cells. HSP70 production was lower in cells cryopreserved in presence of FSH, whose antioxidant metabolism was also conserved: SOD and catalase activities were similar to control. In conclusion, cryopreservation does not seem to markedly affect granulosa cells, in particular if they are frozen in presence of FSH; the gonadotrophin somehow improves their performances after thawing, probably stimulating E2 production and the antioxidant metabolism.

Angiogenesis in developing follicle and corpus luteum

Angiogenesis is a process of vascular growth that is mainly limited to the reproductive system in healthy adult animals. The development of new blood vessels in the ovary is essential to guarantee the necessary supply of nutrients and hormones to promote follicular growth and corpus luteum formation. In developing follicles, the pre-existing endothelial cells that form the vascular network in the theca layer markedly develop in response to the stimulus of several growth factors, mainly produced by granulosa cells, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). The angiogenic factors also promote vessel permeability, thus favouring the antrum formation and the events inducing follicle rupture. After ovulation, newly formed blood vessels cross the basement membrane between theca and granulosa layers and continue a rapid growth to sustain corpus luteum development and function. The length of luteal vascular growth varies in cycling and pregnant animals and among species; both angiogenesis and subsequent angioregression are finely regulated by systemic and local factors. The control of angiogenic development in the ovary could be a useful tool to improve animal reproductive performances.

Stimulatory effects of fasting on vascular endothelial growth factor (VEGF) production by growing pig ovarian follicles

The aim of this study was to investigate the effect of fasting on both vascular endothelial growth factor (VEGF) production and VEGF mRNA expression in growing ovarian follicles (>5 mm in diameter) from gilts at 48 h after equine chorionic gonadotrophin (eCG) treatment. The concentrations of VEGF and albumin were measured in the follicular fluid of single follicles, and VEGF mRNA was determined in the follicle wall. Fasting resulted in a significant increase in VEGF concentrations in follicular fluid (20.64+/-0.72 versus 10.79+/-0.86 ng ml(-1), P<0.001), but it did not affect the total amount of VEGF mRNA in the follicle wall compared with that of fed animals. However, VEGF mRNA in the theca and granulosa compartments increased and decreased, respectively, compared with that of fed animals. The concentrations of albumin measured in follicular fluid as an index of vessel permeability were higher in fasted than in animals fed normally, most likely as a result of the increased VEGF production. Follicular steroidogenesis was impaired in fasted animals. Progesterone was the most abundant steroid in the follicular fluid and oestradiol was present in lower concentrations, thus indicating an alteration in the steroidogenic enzymatic cascade. In conclusion, fasting induces an increase in both VEGF production and vessel permeability. Such a reaction is unable under severe food deprivation to preserve follicle function, but may represent a mechanism that regulates blood vessel extension and distribution in relation to tissue requirements and availability of systemic nutrient.

Stimulatory effects of fasting on vascular endothelial growth factor (VEGF) production by growing pig ovarian follicles

The aim of this study was to investigate the effect of fasting on both vascular endothelial growth factor (VEGF) production and VEGF mRNA expression in growing ovarian follicles (>5 mm in diameter) from gilts at 48 h after equine chorionic gonadotrophin (eCG) treatment. The concentrations of VEGF and albumin were measured in the follicular fluid of single follicles, and VEGF mRNA was determined in the follicle wall. Fasting resulted in a significant increase in VEGF concentrations in follicular fluid (20.64+/-0.72 versus 10.79+/-0.86 ng ml(-1), P<0.001), but it did not affect the total amount of VEGF mRNA in the follicle wall compared with that of fed animals. However, VEGF mRNA in the theca and granulosa compartments increased and decreased, respectively, compared with that of fed animals. The concentrations of albumin measured in follicular fluid as an index of vessel permeability were higher in fasted than in animals fed normally, most likely as a result of the increased VEGF production. Follicular steroidogenesis was impaired in fasted animals. Progesterone was the most abundant steroid in the follicular fluid and oestradiol was present in lower concentrations, thus indicating an alteration in the steroidogenic enzymatic cascade. In conclusion, fasting induces an increase in both VEGF production and vessel permeability. Such a reaction is unable under severe food deprivation to preserve follicle function, but may represent a mechanism that regulates blood vessel extension and distribution in relation to tissue requirements and availability of systemic nutrient.

Angiogenic activity of porcine granulosa cells co-cultured with endothelial cells in a microcarrier-based three-dimensional fibrin gel

To verify the possible role played by pig granulosa cells in the ovarian angiogenic process, we have developed a reliable in vitro system which allows the evaluation of endothelial sprouting and capillary growth in three-dimensional matrices. Granulosa cells collected from porcine follicles of different size were co-cultured with porcine aortic endothelial cells (PAEC) in a microcarrier-based fibrin gel system; after 2 and 5 days of co-culture, we determined the number and length of all endothelial sprouts; moreover, these parameters were quantified only in capillary-like structures, which were defined as continuous multicellular sprouts at least 200 microm long. In granulosa cells- PAEC co-cultures we observed an increase of angiogenic activity as compared to controls (PAEC alone). Granulosa cells from follicles of different size regulate angiogenesis differently: cells from the small follicle group significantly enhanced endothelial sprouting, while those from the large follicle group favoured mainly capillary elongation. Our observations seem therefore to suggest that the development and growth of thecal vascular bed is controlled by paracrine factors of granulosa cell origin that may induce the formation of a primitive capillary plexus during the early phases of antral follicle growth, which will be remodelled in more advanced phases of follicular development.

Steroidogenesis, proliferation and apoptosis in bovine granulosa cells: role of tumour necrosis factor-alpha and its possible signalling mechanisms

This study was designed to investigate the presence of bioactive tumour necrosis factor-alpha (TNF-alpha) in bovine fluid collected from small (<5 mm) and large (>8 mm) follicles, as well as the production of the cytokine by the granulosa cells collected from the same type of follicles. Moreover, the effectiveness of 10, 1 and 0.1 ng mL(-1) of human TNF-alpha (hTNF-alpha) in affecting the main parameters of granulosa cell function, progesterone (P4) and oestradiol-17beta (E2) production, cell proliferation and apoptosis, was tested. In addition, the study aimed to determine whether the signalling mechanisms of TNF-alpha in these cells involve cAMP, nitric oxide or prostaglandin E2 (PGE2) and F2alpha (PGF2alpha). It emerged that bioactive TNF-alpha is present in follicular fluid from both types of follicles and can be measured in media conditioned by granulosa cells from large follicles. As for the effects of hTNF-alpha, it inhibits P4 production in cells from both types of follicles and stimulates E2 output in those from small follicles; it does not affect proliferation, but it stimulates granulosa cell apoptosis. Finally, the effects of hTNF-alpha on bovine granulosa cells are not mediated by nitric oxide or cAMP, as neither of these substances were affected by treatment with the cytokine; however, in some way, they could be mediated through PGE2 and PGF2alpha, the production of which was inhibited by TNF-alpha in cells from small follicles.

Effects of VEGF and bFGF on proliferation and production of steroids and nitric oxide in porcine granulosa cells

Ovarian angiogenesis, which is currently considered to be of crucial importance in controlling the growth of developing follicles, is a physiological process driven by a variety of angiogenic factors. Among these, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have been recognized as key players in promoting cell growth and differentiation. Porcine granulosa cells from small (<3 mm), medium (3-5 mm) and large (>5 mm) follicles were seeded at different densities in DMEM:Ham's F12 (1:1) with or without different concentrations of VEGF or bFGF. After 48 h of culture, media were assayed for oestradiol (E2) 17beta, progesterone (P4), nitric oxide (NO) and VEGF levels; in addition, cell proliferation was evaluated by 3H-thymidine incorporation assay. Both bFGF and VEGF effects on E2 and P4 production by cultured granulosa cells resulted to be dependent on follicle size. The bFGF was always ineffective in modulating cell proliferation, while VEGF exerted an inhibitory effect on the proliferation in the small follicle group and a stimulatory one in the medium and large follicle groups. The bFGF consistently reduced NO levels in culture media. The VEGF appeared to be ineffective in modifying NO production in the small follicle group, while it was stimulatory in the medium follicle group and inhibitory in the large follicle group. Basal VEGF production was higher in cells from the large follicle as compared with the small and medium follicle groups, and it was unaffected by bFGF. These results suggest that VEGF plays a modulatory role in granulosa cell functional activity and it is possibly involved in the regulation of follicle growth; on the contrary, bFGF does not appear to represent a significant regulatory factor in our cellular model, except for an inhibitory action on the production of NO, whose anti-angiogenic properties need to be further substantiated.

Growth hormone secretagogue (GHS) analogue, hexarelin stimulates GH from peripheral lymphocytes

The role of growth hormone releasing hormone (GHRH) and growth hormone releasing peptide-6 (GHRP-6) analogue hexarelin was investigated in the regulation of GH production from lymphocytes. Porcine and bovine blood mononuclear cells were separated using density gradient centrifugation method by layering the whole blood or buffy coat cells on lymphodex. Cells were incubated for 3 or 5 days with or without phytohemagglutinin (PHA-M), GHRH, GHRP-6 analogue hexarelin, somatostatin or GHRH + hexarelin. Growth hormone was fractionated from supernatants by gel chromatography and further concentrated by lyophilization at - 20 degrees C. A nearly two fold increase in basal secretion of GH (porcine: 3.5 +/- 0.1 ng/ml, bovine: 3.2 +/- 0.2 ng/ml) was achieved by GHRH and hexarelin at concentrations of 0.1, 1.0, 10 and 100 nM in both porcine and bovine cells. Lymphocytic GH release was also stimulated in response to PHA-M (10 micro g/well). Neither a dose dependent nor a synergistic nor an additive effect was apparent on GH secretion from lymphocytes. GHRH stimulated lymphocytic GH secretion, whereas, somatostatin had no effect. This study reports for the first time that hexarelin stimulates the secretion of GH from peripheral lymphocytes.

Leptin regulates GH gene expression and secretion and nitric oxide production in pig pituitary cells

The aim of this study was to investigate the direct effect of leptin on GH gene expression and secretion and the role of nitric oxide as a possible mediator in pig anterior pituitary cells. Pituitary cells from adult sows were treated for 4 or 24 h with rhleptin (from 0.1 nM to 1 microM) alone or in association with GHRH (10 nM) or hexarelin (10 nM). At the end of incubation, medium was collected for GH and nitric oxide determination by ELISA and Griess test, respectively. Total RNA was collected from cells, and GH gene expression was measured by RT-PCR. Leptin significantly (P < 0.001) stimulated GH secretion in both incubation periods. The maximum response was induced by 10 nM leptin; furthermore, a significant interaction (P < 0.002) between leptin and GHRH (P < 0.03) and between leptin and hexarelin was observed when the molecules were used in association. GH gene expression was significantly increased (at least P < 0.05) by hexarelin, GHRH, and leptin (1000 and 100 nM) after 24 h of treatment. Leptin (10 nM and 1 microM) significantly (P < 0.05) increased nitric oxide production, whereas S-nitroso-N-acetyl-penicillamine (from 0.01-1000 nM) significantly (P < 0.05) stimulated GH secretion. These data demonstrate that leptin directly influences GH regulation at the pituitary level, and nitric oxide may be involved in this function.

Interrelationship between nitric oxide and prostaglandins in bovine granulosa cells

It is well recognized that prostaglandins of the E (PGE) and F (PGF) series play an important role in ovarian physiology; in addition, nitric oxide (NO) has been recently demonstrated to be an important mediator of granulosa cell function. There is now evidence for a biologic relationship between PGs and the NO biosynthetic pathway. The aim of this study was to investigate the relationship between NO and PGE2 and PGF2alpha in bovine granulosa cells. Granulosa cells collected from small (<5mm) and large (>8mm) follicles were treated with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) or with indomethacin, an inhibitor of PGs synthesis, and PGE2 and PGF2alpha were quantified; in addition, the effects of PGE2 PGF2alpha and indomethacin on steroidogenesis and NO production were determined. The highest concentration of SNAP inhibited (P < 0.001) PGE2 production in cells from both kinds of follicles, while the lowest dose was effective only in cells from small follicles. The highest concentration of SNAP inhibited and stimulated (P < 0.001) PGF2alpha production in cells from small and large follicles, respectively. Progesterone (P4) production was stimulated by PGE2 and inhibited by PGF2alpha (P < 0.001) in cells from both types of follicles. Estradiol 17beta (E2) secretion was inhibited in cells from small and stimulated in those from large follicles by PGE2 (P < 0.05), while PGF2alpha was stimulatory in cells from both kinds of follicles (P < 0.001). P4 production by cells from small follicles was inhibited and stimulated by those from large follicles by indomethacin (P < 0.001), which also increased E2 output in cells from small follicles (P < 0.001). NO production was inhibited by both PGE2 and PGF2alpha except at the lowest concentration, which was stimulatory (P < 0.001). Indomethacin stimulated (P < 0.001) NO production. Taken together, the present data suggest a cross-talk between NO and PGs biosynthetic pathways, which needs to be further clarified.

Lipid hydroperoxide and cGMP are not involved in nitric oxide inhibition of steroidogenesis in bovine granulosa cells

The present study was performed to explore two of the possible signalling mechanisms through which nitric oxide (NO) inhibits steroidogenesis in bovine granulosa cells. Because cGMP is generally known to play a pivotal role in NO signal transduction, the first aim of the present study was to verify the presence of a functional NO-cGMP signalling pathway. Because non-cGMP-dependent pathways could be involved in the inhibition of steroidogenesis by NO, we examined the formation of lipid hydroperoxides (LPOs), possibly induced by NO. Using bovine granulosa cells collected from small (< 5 mm) and large (> 8 mm) follicles, the effectiveness of the NO donor s-nitroso-N-acetylpenicillamine (SNAP; 10(-3), 10(-4) and 10(-5) M) in stimulating cGMP production and the formation of LPOs was examined. The second aim of the present study was to determine whether the effects of NO on steroidogenesis could be mimicked by treatment of cells with a cGMP analogue (8-bromo-cGMP (8-Br-cGMP); 10(-3), 10(-4) and 10(-5) M) and whether these effects could be reversed by [1H]-[1,2,3]oxadiaziolo[4,3a]quinoxaline-1-one (ODQ; 10(-5) and 10(-4) M) an inhibitor of NO-sensitive soluble guanylate cyclase. The highest dose of SNAP used induced a significant (P<0.01) increase in cGMP levels, while other concentrations tested were ineffective. Neither concentration of ODQ used significantly inhibited basal cGMP output, while both concentrations counteracted the stimulatory effect of SNAP. Treatment of cells with 8-Br-cGMP and ODQ was ineffective in modifying steroidogenesis. Treatment with SNAP, at the three concentrations tested, had no significant effect on the level of LPOs. The present results suggest that NO inhibits steroidogenesis in bovine granulosa cells without involving cGMP and LPOs.