The ability to achieve meiotic maturation in the dog oocyte is linked to glycolysis and glutamine oxidation

Beneficial Effects of L-Carnitine Supplementation during IVM of Canine Oocytes on Their Nuclear Maturation and Development In Vitro

Simple Summary

In vitro production of canine embryos is a technique that can be used as a model to conserve endangered species and to establish efficient breeding systems for domestic dogs. However, compared with other species, the success rates of in vitro embryo production (IVEP) in dogs are low. L-Carnitine (LC) is a small water-soluble molecule; it plays an essential role in fatty acid metabolism and acts as a potent antioxidant. Various studies have reported the beneficial impacts of LC on IVEP in many mammalian species other than dogs. Therefore, these experiments investigated the effects of LC supplementation during in vitro maturation (IVM) on canine oocytes maturation, fertilization, and development in vitro. We show that the supplementation of IVM media with LC has positive impacts on oocyte maturation, fertilization, and preimplantation embryo development rates. We also demonstrate that 0.6 mg/mL LC is the most beneficial concentration to be used. It resulted in significantly higher maturation, fertilization, and embryo developmental rates than the control and other LC concentrations. These outcomes are essential for refining the IVM conditions that can advance the efficiency of assisted reproductive technologies (ARTs) in dogs.

Abstract

This study aimed to investigate the effect of L-Carnitine (LC) supplementation during in vitro maturation (IVM) of canine oocytes on nuclear maturation, fertilization status, and preimplantation development. Cumulus–oocyte complexes (COCs) collected from the ovaries of ovariohysterectomized female dogs were matured in vitro for 72 h in a TCM-199 medium supplemented with (0.1, 0.3, 0.6, 1.0, or 2.0 mg/mL) or without (0.0 mg/mL) LC. Matured oocytes were fertilized in vitro with frozen–thawed spermatozoa, and zygotes were cultured in a SOF medium for 7 days. IVM rates were higher (p ≤ 0.05) in 0.3 and 0.6 mg/mL LC supplemented groups than in the control (0.0 mg/mL LC) and other LC groups. Fertilization (18 h postinsemination (pi)) and cleavage (2–16-cell stage at day 3 pi) rates were higher (p ≤ 0.05) in the 0.6 mg/mL LC group than in the control and 0.1, 1.0, and 2 mg/mL LC supplemented groups. Interestingly, 4.5% of fertilized oocytes developed to morula (day 5 pi) in the 0.6 mg/mL LC group, which was higher (p ≤ 0.05) than those developed in the 0.3 mg/mL group (1.0%). No cleaved embryos developed to morula in other groups. In conclusion, LC supplementation at 0.6 mg/mL during IVM of canine oocytes improved their maturation, fertilization, and preimplantation embryo development rates following IVF and in vitro culture (IVC).

Effects of semielemental diet containing whey peptides on Peyer's patch lymphocyte number, immunoglobulin A levels, and intestinal morphology in mice

BACKGROUND

Enteral nutrition (EN) is the gold standard of nutritional therapy for critically ill or severely injured patients, because EN promotes gut and hepatic immunity, thereby preventing infectious complications as compared with parenteral nutrition. However, there are many EN formulas with different protein and fat contents. Their effects on gut-associated lymphoid tissue remain unclear. Recently, semielemental diets (SEDs) containing whey peptides as a nitrogen source have been found to be beneficial in patients with malabsorption or pancreatitis. Herein, we examined the influences of various dietary formulations on gut immunity to clarify the advantages of SEDs over elemental diets.

METHODS

Forty-four male Institute of Cancer Research mice were randomized to four groups: chow (CH: n = 5), intragastric total parenteral nutrition (IG-TPN: n = 13), elemental diet (ED: n = 13), and SED (n = 13). The CH group received CH diet ad libitum, whereas the IG-TPN, ED (Elental, Ajinomoto, Japan), and SED (Peptino, Terumo, Japan) groups were given their respective diets for 5 day via gastrostomy. After 5 days, the mice were killed to obtain whole small intestines. Peyer's patch (PP) lymphocytes were harvested and counted. Their subpopulations were evaluated by flow cytometry. Immunoglobulin A (IgA) levels in intestinal and respiratory tract washings were measured with enzyme-linked immunosorbent assay. Villous height (VH) and crypt depth in the distal intestine were measured by light microscopy.

RESULTS

SED increased the PP cell number and intestinal or respiratory IgA levels to those of CH mice, while ED partially restored these parameters. The IG-TPN group showed the lowest PP cell number and IgA levels among the four groups. VH was significantly greater in the CH than in the other groups. VH in the ED and SED groups also exceeded in the IG-TPN group, while being similar in these two groups. No significant crypt depth differences were observed among the four groups.

CONCLUSIONS

SED administration can be recommended for patients unable tolerate complex enteral diets or a normal diet in terms of not only absorption and tolerability but also maintenance of gut immunity.

Glutamine decreases intestinal mucosal injury in a rat model of intestinal ischemia-reperfusion by downregulating HMGB1 and inflammatory cytokine expression

Intestinal ischemia-reperfusion (IR) is a common clinical pathophysiological process that is common in severe trauma, major surgery, and in post-resuscitation. Glutamine (Gln) reduces intestinal IR injury, however, its mechanism of action remains to be determined. High mobility group box 1 (HMGB1) protein, nuclear factor-κB (NF-κB), tumor necrosis factor-α (TNF-α), and interleukin-1 (IL-1) are mediators involved in the pathophysiology of intestinal IR injury. The aim of the present study was to investigate the effects of Gln on the intestinal mucosa of HMGB1 expression following IR to determine whether Gln relieved intestinal IR injury in the intestinal mucosal barrier. Forty-eight Sprague-Dawley rats were included in the present study. A model of intestinal ischemia-reperfusion injury was established by clamping the superior mesenteric artery of the rats to cause ischemia, followed by restoring blood flow. The animals were randomly divided into the control (n=24) and the Gln (n=24) groups for the experiments. The two groups of rats were given enteral nutrition with equal heat, nitrogen (heat 125.4 kJ/kg/day, nitrogen 0.2 g/kg/day). The Gln group of rats was fed with enteral nutrition plus 3% Gln, while the control rats were fed with enteral nutrition plus 3% soybean protein. After 7 days, the HMGB1 and plasma levels of NF-κB, TNF-α, IL-1, Gln, D-lactic acid and diamine oxidase (DAO) were observed. The changes in the morphology of intestinal mucosa were observed using electron microscopy. The plasma levels of TNF-α, IL-1, D-lactic acid and DAO, and the level of HMGB1, NF-κB, TNF-α and IL-1 in intestinal mucosa were significantly higher after IR (p<0.05), while the plasma level of Gln was lower in the two groups. In the control group, the plasma level of IL-1, TNF-α, DAO and D-lactic acid, and that of HMGB1, NF-κB, TNF-α, and IL-1 in intestinal mucosa were significantly higher, while the plasma level of Gln was lower than that prior to modeling on the 3rd and 7th days of the experiment. In the Gln group, the plasma level of IL-1, TNF-α, DAO and D-lactic acid, and that of HMGB1, NF-κB, IL-1, and TNF-α in intestinal mucosa were significantly higher (p<0.05) compared to the control on the 3rd and 7th days of the experiment. By contrast, after the 7th day, the plasma level of IL-1, TNF-α, DAO and D-lactic acid, and the level of HMGB1, NF-κB, IL-1, TNF-α in intestinal mucosa were significantly lower in the Gln group, while the plasma level of Gln was significantly higher than those in control group and after IR on the 7th day of the experiment. Additionally, the structure of villi and recess was damaged, villi was sparse and short, and considerable inflammatory cell influx embellished the lamina propria, lymphangiectasia, and edema after IR. On the 7th day, compared to after IR, the intestinal villi and recess structure of the controls was significantly restored in the Gln group. In conclusion, Gln repaired the intestinal mucosal injury in IR by reducing the expression of HMGB1 and inflammatory cytokines, and reducing the permeability of the intestinal mucosa.

Metabolic control of oocyte development: linking maternal nutrition and reproductive outcomes

Obesity, diabetes, and related metabolic disorders are major health issues worldwide. As the epidemic of metabolic disorders continues, the associated medical co-morbidities, including the detrimental impact on reproduction, increase as well. Emerging evidence suggests that the effects of maternal nutrition on reproductive outcomes are likely to be mediated, at least in part, by oocyte metabolism. Well-balanced and timed energy metabolism is critical for optimal development of oocytes. To date, much of our understanding of oocyte metabolism comes from the effects of extrinsic nutrients on oocyte maturation. In contrast, intrinsic regulation of oocyte development by metabolic enzymes, intracellular mediators, and transport systems is less characterized. Specifically, decreased acid transport proteins levels, increased glucose/lipid content and elevated reactive oxygen species in oocytes have been implicated in meiotic defects, organelle dysfunction and epigenetic alteration. Therefore, metabolic disturbances in oocytes may contribute to the diminished reproductive potential experienced by women with metabolic disorders. In-depth research is needed to further explore the underlying mechanisms. This review also discusses several approaches for metabolic analysis. Metabolomic profiling of oocytes, the surrounding granulosa cells, and follicular fluid will uncover the metabolic networks regulating oocyte development, potentially leading to the identification of oocyte quality markers and prevention of reproductive disease and poor outcomes in offspring.

Mitochondria and mammalian reproduction

Mitochondria are cellular organelles with crucial roles in ATP synthesis, metabolic integration, reactive oxygen species (ROS) synthesis and management, the regulation of apoptosis (namely via the intrinsic pathway), among many others. Additionally, mitochondria in different organs or cell types may have distinct properties that can decisively influence functional analysis. In terms of the importance of mitochondria in mammalian reproduction, and although there are species-specific differences, these aspects involve both energetic considerations for gametogenesis and fertilization, control of apoptosis to ensure the proper production of viable gametes, and ROS signaling, as well as other emerging aspects. Crucially, mitochondria are the starting point for steroid hormone biosynthesis, given that the conversion of cholesterol to pregnenolone (a common precursor for all steroid hormones) takes place via the activity of the cytochrome P450 side-chain cleavage enzyme (P450scc) on the inner mitochondrial membrane. Furthermore, mitochondrial activity in reproduction has to be considered in accordance with the very distinct strategies for gamete production in the male and female. These include distinct gonad morpho-physiologies, different types of steroids that are more prevalent (testosterone, estrogens, progesterone), and, importantly, the very particular timings of gametogenesis. While spermatogenesis is complete and continuous since puberty, producing a seemingly inexhaustible pool of gametes in a fixed environment; oogenesis involves the episodic production of very few gametes in an environment that changes cyclically. These aspects have always to be taken into account when considering the roles of any common element in mammalian reproduction.