Effects of leptin supplementation in in vitro maturation medium on meiotic maturation of oocytes and preimplantation development of parthenogenetic and cloned embryos in pigs

New aspect on the regulation of in vitro oocyte maturation: role of the obesity, neuropeptides and adipokines

Oocyte quality determinants and nuclear and cytoplasmic maturation establish essential processes for fertilization and further development of the conceptus. Moreover, female fertility is strongly dependent on the metabolic status of the organism. Numerous sources indicate that obesity impairs ovarian function including oocyte physiology by inhibiting nuclear maturation, stimulating lipotoxicity and inflammation, enabling cumulus cells apoptosis, promoting reactive oxygen species formation and ultimately imposing pathogenic effects on mitochondria leading to infertility. Whereas, the number of overweight and obese individuals has reached alarming levels over the past decades, what is more, by 2030, the prevalence of overweight and obesity might reach 65.3% in adults in China and 78% in the USA. Thus, relationships between reproduction and metabolism are being intensively studied to prevent obesity-induced infertility. The metabolic markers of oocyte condition and function are adipokines and neuropeptides, which regulate food intake, lipid and glucose metabolism, insulin resistance and impart significant influences on reproduction. Thus, in this review, we focus on interrelationships between obesity, oocyte maturation and the role of selected neuropeptides and adipokines including leptin, adiponectin, kisspeptin, nesfatin-1, phoenixin, visfatin, chemerin and vaspin.

The interaction between the major vault protein rs4788186 polymorphism, alcohol dependence, and depression among male Chinese problem drinkers

Objective

Alcohol use disorder (AUD) is the second most prevalent mental disorder and might be related to depression. Major vault protein (MVP) is a cytoplasmic protein related to vesicle transport. The present study aimed to investigate the interaction between a genetic variant (MVP rs4788186) and depression in adult male Han Chinese with AUD during withdrawal.

Methods

All participants (N = 435) were diagnosed with AUD. Alcohol dependence level was measured using the Michigan Alcoholism Screening Test, and depression was measured using the self-rating depression scale. Genomic DNA was extracted from peripheral blood and genotyped.

Results

Hierarchical regression analysis identified an interaction between MVP rs4788186 and alcohol dependence level for depression (β = -0.17, p < 0.05). Then, a region of significance test was performed to interpret the interaction effect. Re-parameterized regression models revealed that the interaction between MVP rs4788186 and alcohol problem severity fit the strong differential susceptibility model (R2 = 0.08, p < 0.001), suggesting that the AA homozygotes would be more likely subjects with the G allele to experience major depression symptoms.

Conclusion

Carriers of the AA homozygote of MVP rs4788186 may be more susceptible to severe alcohol problems and higher levels of depression during withdrawal.

Pig Cloning Using Somatic Cell Nuclear Transfer

Porcine cloning technology can be used to produce progenies genetically identical to the donor cells from high-quality breeding pigs. In addition, genetically modified pigs have been produced by somatic cell nuclear transfer using genetically modified porcine fetal fibroblasts. The method of preparing genetically modified pigs is critical for establishing pig models for human diseases, and for generating donor animals for future xenotransplantation. This chapter describes detailed procedures for generating cloned pigs using fetal fibroblasts as nuclear donors.

Fatty Acid β-Oxidation Is Essential in Leptin-Mediated Oocytes Maturation of Yellow Catfish Pelteobagrus fulvidraco

Although several studies have been conducted to study leptin function, information is very scarce on the molecular mechanism of leptin in fatty acid β-oxidation and oocytes maturation in fish. In this study, we investigated the potential role of fatty acid β-oxidation in leptin-mediated oocytes maturation in Pelteobagrus fulvidraco. Exp. 1 investigated the transcriptomic profiles of ovary and the differential expression of genes involved in β-oxidation and oocytes maturation following rt-hLEP injection; rt-hLEP injection was associated with significant changes in the expression of genes, including twenty-five up-regulated genes (CPT1, Acsl, Acadl, Acadm, Hadhb, Echsl, Hsd17b4, Acca, PPARα, CYP8B1, ACOX1, ACBP, MAPK, RINGO, Cdc2, MEK1, IGF-1R, APC/C, Cdk2, GnRHR, STAG3, SMC1, FSHβ and C-Myc) and ten down-regulated gene (PPARγ, FATCD36, UBC, PDK1, Acads, Raf, Fizzy, C3H-4, Raf and PKC), involved in fatty acid β-oxidation and oocytes maturation. In Exp. 2, rt-hLEP and specific inhibitors AG490 (JAK-STAT inhibitor) were used to explore whether leptin induced oocytes maturation, and found that leptin incubation increased the diameters of oocytes and percentage of germinal vesicle breakdown (GVBD)-MII oocytes, up-regulated mRNA levels of genes involved in oocytes maturation and that leptin-induced oocyte maturation was related to activation of JAK-STAT pathway. In Exp. 3, primary oocytes of P. fulvidraco were treated with (R)-(+)-etomoxir (an inhibitor of β-oxidation) or l-carnitine (an enhancer of β-oxidation) for 48 h under rt-hLEP incubation. Exp. 3 indicated that the inhibition of fatty acid β-oxidation resulted in the down-regulation of gene expression involved in oocytes maturation, and repressed the leptin-induced up-regulation of these gene expression. Activation of fatty acid β-oxidation improved the maturation rate and mean diameter of oocytes, and up-regulated gene expression involved in oocytes maturation. Leptin is one of the main factors that links fatty acid β-oxidation with oocyte maturation; β-oxidation is essential for leptin-mediated oocyte maturation in fish.

Choosing a culture medium for SCNT and iSCNT reconstructed embryos: from domestic to wildlife species

Over the past decades, in vitro culture media have been developed to successfully support IVF embryo growth in a variety of species. Advanced reproductive technologies, such as somatic cell nuclear transfer (SCNT), challenge us with a new type of embryo, with special nutritional requirements and altered physiology under in vitro conditions. Numerous studies have successfully reconstructed cloned embryos of domestic animals for biomedical research and livestock production. However, studies evaluating suitable culture conditions for SCNT embryos in wildlife species are scarce (for both intra- and interspecies SCNT). Most of the existing studies derive from previous IVF work done in conventional domestic species. Extrapolation to non-domestic species presents significant challenges since we lack information on reproductive processes and embryo development in most wildlife species. Given the challenges in adapting culture media and conditions from IVF to SCNT embryos, developmental competence of SCNT embryos remains low. This review summarizes research efforts to tailor culture media to SCNT embryos and explore the different outcomes in diverse species. It will also consider how these culture media protocols have been extrapolated to wildlife species, most particularly using SCNT as a cutting-edge technical resource to assist in the preservation of endangered species.

The Responses of Mouse Preimplantation Embryos to Leptin In Vitro in a Transgenerational Model for Obesity

The aim of the present study was to test the hypothesis that leptin can directly mediate the negative effect of maternal obesity on preimplantation embryos. As previously shown, maternal obesity retards early embryonic development in vivo and increases the incidence of apoptosis in blastocysts. When two-cell embryos isolated from control and obese mice were transferred to identical (leptin free) conditions in vitro, no differences in any growth or quality parameters were recorded, including apoptosis incidence in blastocysts. Embryos isolated from control mice responded to transfer to environments with a high concentration of leptin (10 ng/mL) with a significant increase in arrest at the first or subsequent cell cycle. However, the majority of non-arrested embryos developed into blastocysts, showing morphology comparable to those cultured in the leptin-free group. On the other hand, the exposure of embryos isolated from obese mice to high leptin concentration in vitro did not retard their development. Furthermore, these embryos developed into blastocysts, showing a lower incidence of apoptosis. In vivo-developed blastocysts recovered from obese mice showed elevated expression levels of the proapoptotic gene BAX and the insulin-responsive glucose transporter gene SLC2A4. In conclusion, elevated leptin levels have both positive and negative effects on preimplantation embryo development in vitro, a response that likely depends on the body condition of the embryo donor. Moreover, these results suggest that leptin acts as a survival factor rather than an apoptotic inductor in embryonic cells. Since no elevations in the expression of the leptin receptor gene (LEPR) or fat metabolism-associated genes (PLIN2, SLC27A4) were recorded in blastocysts recovered from obese mice, the role of leptin in mediating the effects of obesity on embryos at the peripheral level is likely lower than expected.

Zinc supplementation during in vitro maturation increases the production efficiency of cloned pigs

Zinc supplementation (0.8 µg/ml) in in vitro maturation (IVM) medium significantly enhances oocyte quality. In this study, we compared the development of somatic cell nuclear transfer (SCNT) embryos produced from conventional IVM (control) and zinc-supplemented IVM oocytes. A total of 1206 and 890 SCNT embryos were produced using control and zinc-supplemented oocytes, respectively, and then were transferred to 11 and 8 recipients, respectively. Five control recipients and three zinc-supplemented recipients became pregnant. Two live piglets and eight mummies were born from two control recipients, and ten live piglets and six stillborn piglets were born from three zinc-supplemented recipients. The production efficiency significantly increased in the zinc-supplemented group (0.33% vs. 3.02%). This report suggests that zinc supplementation in IVM medium improved the production efficiency of cloned pigs.

Efficiency of porcine somatic cell nuclear transfer - a retrospective study of factors related to embryo recipient and embryos transferred

The successful generation of pigs via somatic cell nuclear transfer depends on reducing risk factors in several aspects. To provide an overview of some influencing factors related to embryo transfer, the follow-up data related to cloned pig production collected in our laboratory was examined. (i) Spring showed a higher full-term pregnancy rate compared with winter (33.6% vs 18.6%, P = 0.006). Furthermore, a regression equation can be drawn between full-term pregnancy numbers and pregnancy numbers in different months (y = 0.692x−3.326). (ii) There were no significant differences detected in the number of transferred embryos between surrogate sows exhibiting full-term development compared to those that did not. (iii) Non-ovulating surrogate sows presented a higher percentage of full-term pregnancies compared with ovulating sows (32.0% vs 17.5%, P = 0.004; respectively). (iv) Abortion was most likely to take place between Day 27 to Day 34. (v) Based on Life Table Survival Analysis, delivery in normally fertilized and surrogate sows is expected to be completed before Day 117 or Day 125, respectively. Additionally, the length of pregnancy in surrogate sows was negatively correlated with the average litter size, which was not found for normally fertilized sows. In conclusion, performing embryo transfer in appropriate seasons, improving the quality of embryos transferred, optimizing the timing of embryo transfer, limiting the occurrence of abortion, combined with ameliorating the management of delivery, is expected to result in the harvest of a great number of surviving cloned piglets.

Advances on in vitro production and cryopreservation of porcine embryos

There have been intensive attempts to establish reliable in vitro production (IVP) and cryopreservation methods of embryos in pigs. Although a great deal of progress has been made, current IVP systems and cryopreservation still suffer from insufficient cytoplasmic abilities of in vitro matured oocytes, polyspermic fertilization, poor quality of in vitro produced embryos and low efficiency of embryo cryopreservation. Compared to other mammalian species, pig oocytes and embryos are characterized by large amounts of lipid content stored mainly in the form of lipid droplets in the cytoplasm. This fact has a negative influence on biotechnological applications on porcine oocytes and embryos. In this review, we will discuss recent studies about methods and techniques for modifying porcine embryo IVP system and embryo cryopreservation that produces high quality of pig blastocysts using in vitro maturation, in vitro fertilization, in vitro culture, microsurgical manipulation, addition of protein, the use of cytoskeleton stabilizing agents and various physical methods. The presented methods and techniques make it possible to modify the characteristics of oocytes and embryos and thus may become major tools in mammalian gamete and embryo agricultural or biotechnological applications in the future.

Influence of leptin on in vitro maturation and steroidogenic secretion of cumulus–oocyte complexes through JAK2/STAT3 and MEK 1/2 pathways in the rabbit model

Extreme body mass indexes may impair reproductive outcome in assisted reproductive technologies. Leptin reflects the amount of body fat and could act as a modulator of oocyte quality through activation of specific transcription factors. The aim of this work was to establish whether: 1) leptin influences meiotic and cytoplasmic oocyte maturation; 2) STAT3 and MAPK mediate the effects of leptin and 3) leptin modulates steroid secretion by cumulus–oocyte complexes (COC) duringin vitromaturation (IVM). We confirmed immunolocalisation of leptin receptor in oocytes, cumulus/granulosa cells during the peri-ovulatory period. The confocal study showed that COC supplemented with 1, 10 and 100 ng/ml leptin had a significantly higher metaphase II (MII) percentage than those IVM without leptin (P<0.05) and a similar MII index compared to the group supplemented with 10% FCS. Leptin did not increase the percentage of cytoplasmically matured oocytes in terms of cortical granule migration rate, whereas a significantly higher index was found in the FCS group (P<0.001). Oestradiol concentrations in spent media were higher in the FCS group compared to other treatments (P<0.001). Leptin-stimulated nuclear oocyte maturation was significantly impaired when leptin-induced JAK2/STAT3 and MEK 1/2 activation was suppressed by the inhibitors (P<0.001). Steroid secretion of COC was not affected by leptin activation of JAK2/STAT3 or MEK 1/2 pathways. In conclusion, JAK2/STAT3 and MEK 1/2 pathways mediate the enhancement of nuclear oocyte maturation by leptin; however, neither cytoplasmic oocyte maturation nor steroidogenic response of COC were improved in the present rabbit model.

Follicular, oocyte and embryo features related to metabolic status in primiparous lactating does fed with high-fibre rearing diets

Fertility of primiparous lactating does in the early postpartum (pp) period is very low mainly due to pronounced deficient energy intake, influencing oocyte and embryo developmental competence. The hypothesis used in this work was that high-lignin fibre diet supplied during the rearing period could increase feed intake and, consequently, improve the reproductive physiology and metabolic status of primiparous does in the early pp period. Diets with high-lignin [HL: 15.8% dry matter (DM)] or standard-lignin content (SL: 4.9% DM) were supplied until parturition time. No diet effects in serum oestradiol, progesterone concentrations and follicle categories were found in the histological study. Metaphase II rate of in vitro-matured oocytes was significantly higher in the SL vs the HL group (p < 0.001). Cytoplasmically degenerated oocytes (in terms of abnormal distribution of cortical granules) and follicular atresia rate were significantly lower in the SL group than in the HL group (p < 0.05 and p < 0.005 respectively). In addition, HL-fed does showed lower number of viable embryos and higher rate of retarded in vivo-recovered embryos compared with the SL group (p < 0.05). Neither in vitro embryo development of viable embryos nor conception rate was significantly different between groups. Feed intake increased during the first pregnancy in the HL group (p < 0.05), but not during early lactation. Serum protein, non-esterified fatty acid and leptin concentrations, as well as estimated body composition were similar in does fed with both diets. In conclusion, the enhancement of reproductive management by using highly lignified products in rearing diets does not seem to report physiological reproductive benefits affecting oocyte maturation rate and embryo viability in primiparous lactating does.

Leptin and ObRa/MEK signalling in mouse oocyte maturation and preimplantation embryo development

Recent studies indicate that LH stimulates production of ovarian paracrine factors that induce meiosis of the oocyte. DNA microarray analyses of ovarian transcripts were performed in mice and major increases of a short isoform of leptin receptor, ObRa, were identified by the preovulatory LH/human chorionic gonadotrophin (HCG) surge. In oocytes, the level of ObRa transcripts was increased shortly after HCG stimulation, whereas the level of ObRb transcripts was not changed. Leptin was produced by cumulus, granulosa, theca and interstitial cells of ovaries and its transcript level was not regulated during gonadotrophin treatment. Treatment with leptin promoted germinal vesicle breakdown (GVBD) in oocytes within preovulatory follicles, and enhance first polar body extrusion in both cumulus-oocyte complexes and denuded oocytes. The leptin-promoted GVBD and first polar body extrusion were blocked by a mitogen-activated protein kinase extracellular signal regulated kinase kinases (MEK)1/2 inhibitor, U0126, but not its inactive analogue U0124. Furthermore, leptin promoted fertilization of oocytes and the in-vitro development of zygotes to preimplantation embryos. These findings suggest paracrine roles of leptin in the enhancement of nuclear maturation of oocytes through MEK1/2 signalling, and in the promotion of cytoplasmic maturation essential for successful oocyte development to the preimplantation embryos.

Effects of leptin on in vitro maturation, fertilization and embryonic cleavage after ICSI and early developmental expression of leptin (Ob) and leptin receptor (ObR) proteins in the horse

BACKGROUND

The identification of the adipocyte-derived obesity gene product, leptin (Ob), and subsequently its association with reproduction in rodents and humans led to speculations that leptin may be involved in the regulation of oocyte and preimplantation embryo development. In mice and pigs, in vitro leptin addition significantly increased meiotic resumption and promoted preimplantation embryo development in a dose-dependent manner. This study was conducted to determine whether leptin supplementation during in vitro maturation (IVM) to horse oocytes could have effects on their developmental capacity after fertilization by IntraCytoplasmic Sperm Injection (ICSI).

METHODS

Compact and expanded-cumulus horse oocytes were matured in medium containing different concentrations (1, 10, 100, 1000 ng/ml) of recombinant human leptin and the effects on maturation, fertilization and embryo cleavage were evaluated. Furthermore, early developmental expression of Ob and leptin receptor (Ob-R) was investigated by immunocytochemical staining.

RESULTS

In expanded-cumulus oocytes, the addition of leptin in IVM medium improved maturation (74% vs 44%, for 100 ng/ml leptin-treated and control groups, respectively; P < 0.05) and fertilization after ICSI (56% vs 23% for 10 ng/ml leptin-treated and control groups, respectively; P < 0.05). However, the developmental rate and quality of 8-cell stage embryos derived from leptin-treated oocytes (100 ng/ml) was significantly reduced, in contrast to previous data in other species where leptin increased embryo cleavage. Ob and Ob-R proteins were detected up to the 8-cell stage with cortical and cytoplasmic granule-like distribution pattern in each blastomere.

CONCLUSION

Leptin plays a cumulus cell-mediated role in the regulation of oocyte maturation in the mare. Species-specific differences may exist in oocyte sensitivity to leptin.