Paraoxonase (PON) 1, 2 and 3 Expression in Granulosa Cells and PON1 Activity in Follicular Fluid of Dairy Cows

Differences in Milk Proteomic Profiles between Estrous and Non-Estrous Dairy Cows

Efficient reproductive management of dairy cows depends primarily upon accurate estrus identification. However, the currently available estrus detection methods, such as visual observation, are poor. Hence, there is an urgent need to discover novel biomarkers in non-invasive bodily fluids such as milk to reliably detect estrus status. Proteomics is an emerging and promising tool to identify biomarkers. In this study, the proteomics approach was performed on milk sampled from estrus and non-estrus dairy cows to identify potential biomarkers of estrus. Dairy cows were synchronized and timed for artificial insemination, and the cows with insemination leading to conception were considered to be in estrus at the day of insemination (day 0). Milk samples of day 0 (estrus group) and day -3 (non-estrus group) from dairy cows confirming to be pregnant were collected for proteomic analysis using the tandem mass tags (TMT) proteomics approach. A total of 89 differentially expressed proteins were identified, of which 33 were upregulated and 56 were downregulated in the estrus milk compared with the non-estrus milk. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that acetyl coenzyme A carboxylase α (ACACA), apolipoprotein B (APOB), NAD(P)H steroid dehydrogenase-like (NSDHL), perilipin 2 (PLIN2), and paraoxonase 1 (PON1) participated in lipid binding, lipid storage, lipid localization, and lipid metabolic process, as well as fatty acid binding, fatty acid biosynthesis, and fatty acid metabolism, and these processes are well documented to be related to estrus regulation. These milk proteins are proposed as possible biomarkers of estrus in dairy cows. Further validation studies are required in a large population to determine their potential as estrus biomarkers.

Evidence of Paraoxonases 1, 2, and 3 Expression in Human Ovarian Granulosa Cells

Increasing evidence suggests that the antioxidant paraoxonase proteins, PON1, PON2, and PON3, have a role in reproduction and may be synthesized by ovarian cells. The aim of this work was to investigate whether human ovarian granulosa cells (GC) express paraoxonases 1, 2, and 3 (PON1, PON2, and PON3) at both the transcriptional and protein levels. Cells were purified from follicle samples of women undergoing ovarian stimulation at oocyte retrieval. We analyzed mRNA by polymerase chain reaction using specific primers for the different variants and quantified the proteins by Western blot using commercially available human recombinant PON proteins as standards. The protein subcellular distribution was determined by immunofluorescence and confocal microscopy and the cell cycles by flow cytometry. Thymidine was used for cellular synchronization at G1/S. Human hepatoma HepG2 and immortalized granulosa COV434 cell lines were used to optimize methodologies. mRNAs from PON1, the two variants of PON2, and PON3 were detected in GC. The cells actively secreted PON1 and PON3, as evidenced by the protein detection in the incubation medium. PON1 and PON3 were mainly distributed in the cytoplasm and notably in the nucleus, while PON2 colocalized with mitochondria. Subcellular nucleo-cytoplasmic distribution of PON1 was associated with the cell cycle. This is the first evidence describing the presence of mRNAs and proteins of the three members of the PON family in human ovarian GC. This study provides the basis of further research to understand the role of these proteins in GC, which will contribute to a better understanding of the reproduction process.

Evaluation of the relationship between serum paraoxonase-1 activity and superovulation response/embryo yield in Holstein cows

In this study, the effect of serum paraoxonase-1 (PON-1) activity on superovulation response and embryo yield was evaluated. The study material comprised 50 Holstein cows aged 3-4 years on postpartum day 90-120 with a body condition score of 3-3.25. A progesterone-based estrus synchronization protocol was initially administered to the selected donors. For this purpose, progesterone source was inserted intravaginally (day 0) and gonadotropin-releasing hormone injection was performed (day 6). Seven days after the insertion of progesterone device, follicle-stimulating hormone injections (total dose of 500 µg in decreasing doses for 4 days) were administered for superovulation. On the morning of the ninth day, prostaglandin (PG) F2α was administered, and the progesterone device was removed from the vagina in the evening on the same day. Two days after PGF2α administration, fixed-time artificial insemination was performed in the morning and in the evening. On the day of artificial insemination, blood samples were taken from the donors to determine the serum PON-1 activity. Uterine flushing was performed seven days after insemination. The results revealed that the serum PON-1 activity (mean ± SD, 562.71 ± 140.23 U/l) of the cows that responded to superovulation (donors with total corpus luteum count of ≥3 in both ovaries) was higher than those (389.91 ± 80.51 U/l) that did not (P<0.05). On the day of insemination, a positive correlation was determined between serum PON-1 activity and the counts of total corpus luteum (r=0.398), total oocyte/embryo (r=0.468), transferable embryo (r=0.453), and Code I embryos (r=0.315, P<0.05). Unlike the Code I embryos, there was no significant correlation between serum PON-1 activity and the number of Code III embryos. Moreover, no significant difference in the number of Code III embryos between the two PON-1 groups was observed. However, embryo yield and quality were found to have increased with increased PON-1 activity. Therefore, it was concluded that serum PON-1 activity may be associated with superovulation response, embryo yield and quality in donor cows.

MALDI-TOF Mass Spectrometry Revealed Significant Lipid Variations in Follicular Fluid and Somatic Follicular Cells but Not in Enclosed Oocytes between the Large Dominant and Small Subordinate Follicles in Bovine Ovary

Lipid metabolism in ovarian follicular cells supports the preparation of an enclosed oocyte to ovulation. We aimed to compare lipid composition of a dominant large follicle (LF) and subordinated small follicles (SFs) within the same ovaries. Mass spectrometry imaging displayed the differences in the distribution of several lipid features between the different follicles. Comparison of lipid fingerprints between LF and SF by Matrix Assisted Laser Desorption/Ionisation Time-Of-Flight (MALDI-TOF) mass spectrometry revealed that in the oocytes, only 8 out of 468 detected lipids (1.7%) significantly changed their abundance (p < 0.05, fold change > 2). In contrast, follicular fluid (FF), granulosa, theca and cumulus cells demonstrated 55.5%, 14.9%, 5.3% and 9.8% of significantly varied features between LF and SF, respectively. In total, 25.2% of differential lipids were identified and indicated potential changes in membrane and signaling lipids. Tremendous changes in FF lipid composition were likely due to the stage specific secretions from somatic follicular cells that was in line with the differences observed from FF extracellular vesicles and gene expression of candidate genes in granulosa and theca cells between LF and SF. In addition, lipid storage in granulosa and theca cells varied in relation to follicular size and atresia. Differences in follicular cells lipid profiles between LF and SF may probably reflect follicle atresia degree and/or accumulation of appropriate lipids for post-ovulation processes as formation of corpus luteum. In contrast, the enclosed oocyte seems to be protected during final follicular growth, likely due in part to significant lipid transformations in surrounding cumulus cells. Therefore, the enclosed oocyte could likely keep lipid building blocks and energy resources to support further maturation and early embryo development.

Effect of recombinant bovine somatotropin (rbST) treatment on follicular population and development in non-lactating dairy cows

The aim of this study was to evaluate the long-term effects of recombinant bovine somatotropin (rbST) on follicle population and ovulatory follicle development in non-lactating dairy cows. Twenty-one Jersey cows were allocated in rbST (n=11) or control (n=10) groups. On day -60, cows in rbST group received 500 mg of somatotropin (s.c. Lactotropin®, Elanco). On day 0, control and rbST cows received an intravaginal progesterone-releasing device (1.9 g, CIDR^®, Zoetis) and GnRH (100 mg, IM, Factrel^®, Zoetis). On day 8, cows received PGF2α (25 mg, IM, Lutalyse®, Zoetis) and the CIDR^® was removed. Twelve hours after device removal (D8), serum, follicular fluid and granulosa cells samples were collected. Serum and follicular concentration of estradiol (E2) and progesterone (P4) were analyzed. Total RNA was extracted from granulosa cells to measure gene expression of LHCGR, STAR, HSD-3B1, CYP11A1, CYP19A1, CYP17A1, IGFR and PAPPA by real-time PCR. Ultrasonography was performed on days -60, -53, -46, -14, -7, 0 and 8 for antral follicle count. Results were analyzed by repeated measures ANOVA and t-test. There was no effect of rbST treatment on the number of follicles during the 60 days period, as well as no effect on serum and follicular fluid E2 and follicular fluid P4 at the moment of follicle aspiration. There was a reduction in PAPPA (P = 0.006), CYP11A1 (P = 0.04) and CYP19A1 (P = 0.002) mRNA levels in granulosa cells of the pre-ovulatory follicle of rbST treated cows. In conclusion, a single dose of rbST did not have long-term effects on antral follicle population, serum and follicular E2/P4 concentrations in non-lactating dairy cows. Despite that, rbST injection decreased granulosa cell expression of genes related to steroidogenesis in the pre-ovulatory follicle.

Paraoxonase 1 in bovine milk and blood as marker of subclinical mastitis caused by Staphylococcus aureus

The aim of this study was to determine serum lipid values and parameters of oxidative stress in blood and milk of cows with subclinical mastitis (SCM) caused by Staphylococcus aureus and to establish association between these parameters. The study was performed on total of 104 cows assigned into control group of healthy animals (n = 12) and two groups of cows with SCM, either SCM₁ group (n = 37) with ˂ 1000 CFU/mL of S. aureus or SCM₂ group (n = 55) with ≥1000 CFU/mL of causative agent in milk. Significantly lower serum concentrations of high density lipoprotein-cholesterol (HDLC) in SCM₂ group and higher low density lipoprotein-cholesterol (LDL-C) in both SCM groups were recorded. Significantly lower paraoxonase-1 (PON1) activity and higher lipid hydroperoxides (LOOH) concentration in blood and milk were recorded in both groups of SCM cows vs control. In blood serum of cows from SCM₂ group significantly higher concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), but significantly lower total antioxidative capacity (TAC) were obtained. In milk serum of SCM cows were detected significantly higher concentrations of H₂O₂ and MDA, but significantly lower TAC vs control. There was a significant positive correlation between PON1 in serum with HDLC, but negative correlation with LDL-C and LOOH. In milk, PON1 negatively correlated with LOOH and somatic cell counts (SCC). Strong positive correlation was obtained between PON1 in blood and milk. Oxidative stress and inflammatory reaction induced by SCM significantly lowered PON1 activity in blood and milk of affected cows.

Insulin treatment does not affect follicular development but alters granulosa cell gene expression in dairy cows

The use of strategies to stimulate follicular growth are important, especially for use in timed artificial insemination (TAI) protocols, aiming to increase dairy cow's fertility. The aim of this study was to investigate the effect of insulin on follicular growth, steroid production and expression of genes related to follicular development. For this, cows were submitted to a progesterone (P4) and estradiol (E2) based synchronization protocol. In study 1, eleven primiparous lactating Holstein cows, received a single s.c. application of 0.25 IU/kg human insulin or no treatment (control) on D8 of the protocol. Blood samples were collected, and the dominant follicle diameter was assessed daily via transrectal ultrasonography, from D8 to D12. In study 2, eight multiparous non-pregnant and non-lactating Jersey cows, received a single s.c. application of 0.25 IU/kg human insulin, whereas cows from the control group received a single s.c. injection (1 mL) of saline solution (NaCl 0.9%). Blood samples were collected, and the dominant follicle diameter was assessed daily via transrectal ultrasonography from D6 to D9 of the protocol. Sixteen hours after insulin injection, follicular aspiration was performed. In study 1, insulin treatment decreased systemic glucose levels, but did not affect follicular growth. In study 2, the glucose decrease induced by insulin treatment was accompanied by a tendency of decreased progesterone levels in follicular fluid, along with a decrease in steroidogenic acute regulatory protein (STAR) and insulin like growth factor binding protein 2 (IGFBP2) mRNA abundance in granulosa cells. In conclusion, insulin treatment does not increase follicle growth and estradiol secretion in dairy cows, but decreases IGFBP2 and tends to increase pappalysin (PAPPA) mRNA abundance in granulosa cells, suggesting a positive effect on follicle development.

Intrafollicular paraoxonase 1 activity and the steroidogenic potential of the first post-partum dominant follicle in dairy cows

Cows experiencing high levels of inflammation and specific metabolic conditions tend to have slower follicular growth and lower serum and follicular concentrations of oestradiol (E2). Paraoxonase1 (PON1) activity decreases during inflammatory processes. Therefore, the aim of this study was to evaluate the association between serum and intrafollicular (FF) PON1 activity and the serum and intrafollicular levels of E2 and progesterone (P4), as well as the mRNA expression of genes related to steroidogenesis, metabolism and inflammation in the first post-partum dominant follicle of Holstein cows. No correlation was found between PON1 activity, the expression of the analysed genes and levels of follicular E2 and P4, except for a negative correlation between serum E2 and follicular PO1 activity. Also, no correlation was found between serum and follicular PON1 during the first post-partum follicular wave.

Association between pre-breeding metabolic profiles and reproductive performance in heifers and lactating dairy cows

Lactating cows and nulliparous heifers are in distinctive and unique physiological conditions when they are approaching the planned time of breeding, at approximately 60 days in milk and 13-15 months of age, respectively. This study aimed to profile the metabolic milieu in heifers (N = 14) and lactating cows (N = 15) in the weeks leading up to planned time of breeding. All cows were followed for a period of 15 weeks, from 3 weeks pre-calving to 12 weeks post-calving, while heifers were monitored for a period of 4 weeks leading up to the tentative week of breeding (pre-breeding period). For data analysis, we further divided cows into primiparous (N = 8) and multiparous (N = 7) cows owing to the significant difference in their milk yield. Assessment of reproductive performance showed that primiparous and multiparous cows tended to have lower pregnancy rates compared to heifers (P < 0.1). Plasma concentrations of β-hydroxybutyric acid were about 2-fold higher in multiparous cows than those of heifers in the week leading up to planned time of breeding (P < 0.05). Total bile acid levels during the pre-breeding period were higher in all lactating cows compared to heifers (P < 0.05) and glucose levels were lower in lactating cows (P < 0.05). Triglyceride concentrations were lowest in multiparous cows compared to both primiparous cows and nulliparous heifers (P < 0.05). In addition, lactating cows had higher concentrations of total-cholesterol and the high-density lipoprotein and low-density lipoprotein compared to heifers (P < 0.05). Conversely, concentrations of very low-density lipoprotein were lower in multiparous cows than primiparous cows and nulliparous heifers (P < 0.05). There were no differences in plasma glutathione levels, as measured by liquid chromatography-tandem mass spectrometry, between the groups, but the ferric reducing ability of plasma was higher in lactating cows compared to heifers (P < 0.05). These data establish the differences in the profile of metabolic and oxidative markers during the period approaching planned time of breeding in lactating cows compared to nulliparous heifers. As certain metabolites in the plasma have been shown to be represented in the ovarian follicular microenvironment, the unique profiles may influence reproductive performance in dairy cattle in different physiological stages.

Effect of high-density lipoprotein on oocyte maturation and bovine embryo development in vitro

High-density lipoprotein (HDL) is the main lipoprotein in the follicular fluid, and it has anti-inflammatory, antioxidant and cryoprotectant properties. The anti-inflammatory potential and antioxidant potential are derived from its lipid composition, especially the apolipoprotein AI (ApoAI) and paraoxonase 1 (PON1). The aim of this study was to evaluate the effect of HDL during in vitro maturation (IVM) on oocyte maturation and early bovine embryo development. For this, cumulus-oocyte complexes (COCs) were obtained from bovine ovaries collected at a local slaughterhouse. COCs (n = 2,250) were allocated into three groups (n = 50 COCs/group) according to the addition of HDL protein (HDL-P) during IVM for 22 hr: 0 (control), 50 and 150 mg/dl. After IVM, COCs were inseminated (in vitro fertilization) and cultivated for 7 days. Total cholesterol concentration, total protein, triglycerides and ApoAI concentrations on IVM medium increased proportionally to HDL-P addition. However, PON1 activity was not detected in any treatment. The addition of HDL-P did not affect nuclear maturation rate, endogenous reactive oxygen species and glutathione levels in COCs (p > 0.05). The highest HDL-P concentration (150 mg/dl) decreased cleavage and blastocyst rate (p < 0.05). Moreover, the HDL-P 150 mg/dl group had lower cellular count/blastocyst than the 50 mg/dl group (p < 0.05). However, the addition of HDL-P did not affect relative gene expression of evaluated genes. In conclusion, the complex HDL/ApoAI obtained from human plasma, in the absence of PON1 activity during in vitro oocyte maturation, decreased initial embryo development.

Polymorphisms in the anti-oxidant paraoxonase-1 (PON1) gene associated with fertility of postpartum dairy cows

Paraoxonase 1 (PON1) is a negative acute phase plasma protein synthesized by the liver that has anti-oxidant activity. The aim of this study was to evaluate the association of single nucleotide polymorphisms (SNPs) in the PON1 promoter region with plasma PON1 activity and fertility in Holstein dairy cows. Sixty-eighty Holstein cows were used in this initial investigative study. Blood samples were collected weekly beginning 28 days prior to expected calving, twice weekly in week 1 and 2 postpartum, and then once weekly through 6 weeks postpartum for plasma PON1 activity analysis. Cows were synchronized for ovulation and timed AI at 63-70 DIM using an Ovsynch program. Pregnancy diagnosis was confirmed by rectal palpation and reproductive performance data was recorded until 210 DIM. DNA was extracted from blood of each cow and a fragment of proximal PON1 gene promoter was sequenced. Seven single nucleotide polymorphisms (SNPs) were identified in the promoter region of the PON1 gene at positions -22, -105, -176, -221, -392, -611 and -676, six of which were significantly associated with plasma PON1 activity level. The SNPs -221 and -392 were significantly associated with both plasma PON1 activity and the calving to conception interval (P < 0.05) with no significant effect on calving to first ovulation interval. In conclusion, the genotypes associated with higher plasma PON1 activity in SNP locations -221 and -392 were also associated with a reduced calving to conception interval in this study set of cows. These SNPs may provide novel genetic markers for improved fertility in future larger studies in dairy cows.

Effect of serum paraoxonase-1 (PON1) activity on follicular development and pregnancy rate in cattle

Paraoxonase-1 (PON1) activity has been associated with improvement in ovarian function in early postpartum dairy cows and improved in vitro embryo development. The aim of the current study was to evaluate the potential association among PON1 activity and follicular growth, diameter of the preovulatory follicle and pregnancy per artificial insemination (AI) service in cattle. In Experiment 1, cows (n=33) were subjected to an estradiol-progesterone based protocol to control time of ovulation. Starting on Day 8 of the protocol, follicular growth and serum PON1 activity were monitored. Cows were separated according to the occurrence of ovulation into two groups: Ovulatory (Ov; n=22) and Anovulatory (Anov; n=11). The serum activity of PON1 was not different between Ov and Anov cows (P=0.94). In addition, using a regression model there was no effect of serum PON1 activity on the diameter of dominant follicle (r²=0.00; P=0.99). In Experiment 2, cows (n=193) were submitted to the same hormonal protocol as in Experiment 1. On the day of the timed artificial insemination (TAI), the diameter of dominant follicle was evaluated and blood samples were collected for analysis of PON1 activity. According to the serum PON1 activity, cows were divided into three groups: Low (<70U/mL), Medium (70-90U/mL) or High (>90U/mL) PON1 activity. The overall pregnancy rate was 62.7% (121/193), with no difference among PON1 activity groups. Additionally, using a regression model there was no effect of serum PON1 activity on the diameter of the preovulatory follicle (r²=0.03; P=0.65) and pregnancy rate (r²=0.005; P=0.94). The results of this study indicate that there is no effect of serum PON1 activity on the diameter of preovulatory follicle or establishment of pregnancy in cows submitted to time of ovulation synchronization protocols.

Paraoxonase activities in human follicular fluid: role in follicular maturation

The paraoxonases (PONs) are antioxidant enzymes associated with beneficial effects against several diseases and some exposures. Little is known, however, about the role of PONs in human reproduction. This work was conducted to investigate whether any association existed between the activities of the PON enzymes (1, 2, and 3) with the follicular size and fertility parameters in assisted reproduction. The study included 100 subfertile women (patients) and 55 proven fertile women (oocyte donors), all undergoing an ovarian stimulation cycle. Follicular fluid from small (diameter <12 mm) and large (diameter ≥18 mm) follicles was collected from each woman. The PONs were quantified in follicular fluid by immunoblotting. PON1 arylesterase and paraoxonase, PON2 methyl paraoxonase and PON3 simvastatinase activities from both donors and patients were significantly higher (P < 0.001) in follicular fluid from large follicles compared with small ones. In large follicles, PON3 activity was significantly higher (P < 0.01) in donors compared with patients. Follicular fluid PON1 arylesterase and paraoxonase activity was positively correlated with the number of retrieved oocytes in donors. This study shows an increase in the activities of PONs with follicle size, thus providing indirect evidence for the role of PONs in follicle maturation.

Uterine and systemic inflammation influences ovarian follicular function in postpartum dairy cows

The objective of this study was to determine the effects of uterine and systemic inflammatory responses to uterine bacterial contamination at calving in dairy cows on the growth and ovulatory outcomes of the first dominant follicle postpartum. Ovulatory capability of the first dominant follicle postpartum was predicted in 53 multiparous cows by using a combination of follicle growth characteristics and circulating estradiol concentrations. Endotoxin levels were assayed in follicular fluid samples that were aspirated the day after ovulatory outcome prediction. Plasma levels of haptoglobin, a proinflammatory acute phase protein, and paraoxonase, a negative acute phase protein were determined. Uterine bacteria and inflammation were evaluated in three uterine fluid samples from each cow collected on the day of calving, the day after follicle aspiration, and at 35 days postpartum. Cows that had a strong initial uterine inflammatory response (robust recruitment of polymorphonuclear leukocytes of ≥ 35% and cows with uterine pH < 8.5 on the day of calving) were more likely to have an ovulatory first dominant follicle. Follicular fluid endotoxin levels were higher in non-ovulatory cows compared with ovulatory cows. Endotoxin levels in circulation were not different between ovulatory groups but were higher prepartum than on day 7 and 14 postpartum. Systemic inflammation characterized by elevated haptoglobin concentrations was higher in non-ovulatory cows despite similar bacterial contamination and circulating endotoxin levels. Paraoxonase activity in follicular fluid was significantly associated with the paraoxonase activity in plasma, however, plasma paraoxonase concentrations were not different between non-ovulatory and ovulatory cows. Cows with a higher uterine bacterial load on the day of calving had slower ovarian follicle growth. In summary, a robust uterine inflammatory response on the day of calving was positively associated with ovarian function while elevated systemic inflammation during the early postpartum period was negatively associated with the ovulatory status of the first dominant follicle postpartum.

The acute effect of intravenous lipopolysaccharide injection on serum and intrafollicular HDL components and gene expression in granulosa cells of the bovine dominant follicle

The aim of this study was to evaluate the effect of an acute systemic inflammatory response induced by lipopolysaccharide (LPS) in the serum and follicular fluid (FF) high-density lipoprotein (HDL) components, hormone concentrations and granulosa cell gene expression. For this purpose, twenty non-lactating Jersey dairy cows were submitted to a progesterone (P4) - estradiol (E2) based synchronization protocol. Cows received a single i.v. dose of LPS (2.5 μg/kg of body weight) or saline solution (CTL Group) 2 h after P4 insert removal. Blood, granulosa cells and FF samples were collected six hours after LPS injection. Five hours after LPS injection rectal temperature was increased in LPS (P < 0.0001, 40.4 ± 0.1 °C) compared to the CTL cows (38.8 ± 0.1 °C). Serum PON1 activity was reduced by LPS injection (130.2 ± 5.1 vs. 99.6 ± 3.3 U/mL; P < 0.001), as well as HDL-cholesterol concentrations (70.3 ± 5.3 vs. 50.1 ± 6.2 mg/dL; P < 0.05). The FF E2 and P4 concentrations were not different between groups (P > 0.05). The PON1 activity in the FF was also decreased by LPS injection (P = 0.01). In comparison to CTL group, cows injected with LPS had a ten fold reduction in STAR, TLR4 and TNF mRNA expression (P < 0.05). In conclusion, an intravenous LPS challenge in cows induced an acute systemic inflammatory response reducing HDL and its components in serum but not in the FF. Only PON1 activity serum reduction was reflected in the FF in the short term. Additionally, steroidogenic and inflammatory genes had reduced expression in the granulosa cells.