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Table 2 In vitro studies with carnitine supplementation to improve oocyte quality, maturation and embryo development

From: Role of L-carnitine in female infertility

Study aim Carnitine dose Study design/Subjects Outcomes Reference
LC on antagonizing the harmful effect of TNF-α, apoptosis, and oxidative stress on mouse embryo development. LC was dissolved in HTF culture medium in concentrations of 0.3 and 0.6 mg/mL • 500 mouse embryos were divided into three groups and incubated with either AD 0.005 mg/mL, H2O2 500 mmol/L, or TNF-α 500 ng with and without LC 0.3 or 0.6 mg/mL
• For anti-apoptotic effect: All groups were incubated at 37C in 5%CO2 for 4 h and transferred to HTF medium and incubated until 48 h for formation of the blastocyst stage.
• For anti-oxidant and anti-proliferative effect on TNF-α: All groups were incubated at 37C in 5% CO2 for 72 h until the formation of blastocyst stage.
• Embryo staining by TUNEL was done to detect blastomere DNA damage
• Significant improvement in percentage BDR was seen at LC 0.3 mg/mL compared with the control (p < 0.006)
• L-Carnitine at 0.3 and 0.6 mg/mL significantly reduced the blocking effect of AD, H2O2, and TNF-α and significantly decreased the level of DNA damage
LC on oocyte cytoskeleton and apoptosis in peritoneal fluid from patients with endometriosis 0.6 mg/mL of LC • Peritoneal fluid was collected from 23 women suffering from endometriosis and 15 patients with tubal ligation who underwent laparoscopy
• LC was diluted 1:1 with peritoneal fluid and cryopreserved mouse embryos were matured in that medium
Significantly improved microtubule and chromosome structure and decreased embryo apoptosis [38]
LC on oocyte maturation and parthenogenetic embryos in pigs 0.25, 0.5, 1.0 and 2.0 mg/mL of LC  in IVM medium • Porcine ovaries were collected from prepubertal gilts and matured in medium containing various concentrations of LC.
• LC was added in IVC medium to examine developmental competence of parthenogenic embryos
LC addition during IVM improved developmental potential of oocytes, and also quality of parthenogenic embryos by improving nuclear maturation and preventing OS and apoptosis [14]
LC on lipid metabolism and in vitro maturation of porcine oocyte 0.3 to 10 mg/mL of LC Ovaries from prepubertal cross-bred gilts were collected and IVF and IVC was performed in media containing LC Enhanced mitochondrial functions, lipid metabolism for nuclear and cytoplasmic maturation of porcine oocytes [54]
LC on oocyte maturation and embryo development 10 mM of LC in IVM medium • Porcine ovaries were collected from 6 to 7 months old prepubertal gilts
• Comparison of GSH, ROS levels and developmental gene expression in LC supplemented and non-supplemented group
• Reduced OS with increased GSH synthesis in LC supplemented group
• Increased expression of developmental genes
LC on maturation rate of buffalo embryos 0.3, 0.6 and 1.2 mM/mL of LC Oocytes were collected from Swamp buffalo and treated with various concentrations of LC Significantly higher metaphase II oocytes than control group with faster maturation rate [66]
LC on bovine embryo development and their cryotolerance 1.1518 mM and 3.030 mM of LC • Oocytes were collected from bovine ovaries
• IVF and IVC was performed in media containing LC
Improved cryotolerance, lipid metabolism in embryos [68]
LC on vitrification of mouse germinal vesicle stage-oocytes and their in vitro maturation 3.72 mM (0.6 mg/mL) of LC in IVM medium • B6.DBA cross-bed mice were superovulated and oocytes were collected
• Oocytes grown in LC-supplemented IVM medium
Increased number of metaphase II oocytes and improved mitochondrial distribution in oocytes [55]
ALC on lamb oocyte blastocyst rate, mitochondrial DNA copy number 2 mM of ALC in IVM medium Prepubertal lamb oocytes were collected and matured in medium containing LC Increased cytoplasmic volume of oocyte with more lipid droplets, but no alteration in mitochondrial volume, number or DNA copy number [22]
LC on maturation of mouse embryos 0.3 and 0.6 mg/mL of LC • Immature oocytes were collected from NMRI mice ovaries and treated with LC
• Cleavage rate, BDR and GSH were evaluated
Improved implantation developmental competence and nuclear maturation of oocytes and increased GSH [64]
LC on bovine blastocyst development 0.1, 0.5 and 1.0 mg/mL of LC in IVM medium • Oocytes were collected from bovine ovaries and matured in medium containing LC
• These oocytes were then subjected to IVF with fresh semen
• Number of embryos and total cell count was performed
Improved developmental potential: increased number of oocytes and embryos with higher total cell count [70]
LC in OS and antioxidant profile in sheep embryos produces in vitro 2.5, 5, 7.5 and 10 mM of LC in maturation medium Oocytes were collected from sheep ovaries and matured in medium containing LC. These oocytes were then subjected to IVF with fresh semen. • Oocyte maturation, embryo development increased
• LC reduced OS and ROS production, increased antioxidant enzyme activities
LC on in vitro maturation of ZP and development of mouse embryos 0.5, 1, 2 and 4 mg/ml of LC • Mice were superovulated and mating was carried out with males
• 2-cell embryos were flushed from oviduct and cultured in LC containing medium
• BDR, ZP thickness were measured
Increased number of blastocyst cells, ZP thickness and improved antioxidant activity [71]
  1. AD Actinomycin-D, ALC Acetyl-L-carnitine, BDR Blastocyst development rate, GSH Glutathione, HTF Human tubular fluid, H 2 O 2 Hydrogen peroxide, IVC in vitro embryo culture, IVF in vitro fertilization, IVM in vitro maturation, LC L-Carnitine, OS Oxidative stress, ROS Reactive oxygen species, TNF-tumor necrosis factor, ZP Zona pellucida