Biological roles of l‐carnitine in oocyte and early embryo development

Abstract

Poor oocyte quality is responsible for female infertility. Multiple studies have been carried out to find supplements to enhance oocyte quality and mitigate infertility problems. L-carnitine and its derivatives have diverse roles in developing oocytes and early embryos. This review focuses on the in vitro and in vivo studies that using L-carnitine alone or in combination with other supplements for oocyte quality enhancement. The key roles of L-carnitine in oocyte quality and embryo growth were summarized, and the underlying mechanism was also elucidated. L-carnitine helps in the lipid metabolism process by controlling the transfer of fatty acids to mitochondria for β-oxidation. L-carnitine modulates glucose metabolism and enhances respiratory chain enzyme activity. Furthermore, it acts as an antioxidant to prevent oxidative damage and inhibit apoptosis, a signal in response to oxidative stress. Results show the potential of L-carnitine as a potential agent in assisted reproductive technology to improve oocyte quality and the subsequent embryonic development.cryopreservation, embryo development, in vitro maturation, in vivo models, L-Carnitine, oocyte quality | INTRODUCTIONOocyte developmental potential is associated with its capacity to successfully resume meiosis, be fertilized, implanted in the uterus, and finally develop into a healthy offspring (Dunning et al., 2014). Poor oocyte quality is one of the major causes of decline in female fertility. To date, enormous nutrients and pharmaceutical drugs have been proposed to enhance oocyte quality and attenuate reproductive disorders, such as different types of hormones, proteins, growth factors, and antioxidants. However, adverse effects and incidences have been reported on other systems (Rutkowski & Grzegorczyk, 2012). Considering this point, several experimental studies have been carried out in vivo or in vitro to

L-Carnitine Supports the In Vitro Growth of Buffalo Oocytes

“…It has been reported that oocytes use lipids as an oxidative substrate for nuclear and/or cytoplasmic maturation [ 40 , 41 , 42 ]. Several studies have revealed that L-carnitine can enhance the competence of oocyte development in mammals [ 43 ]. In contrast, Marin et al (2022) reported that L-carnitine supplementation during maturation culture of buffalo oocytes impaired oocyte development in the presence of fetal bovine serum [ 44 ].…”

Using follicular fluid metabolomics to investigate the association between air pollution and oocyte quality

“…It acts as an antioxidant by promoting β-oxidation in oocytes, attenuating oxidative damage, and preventing apoptosis. ( Agarwal et al, 2018 ; Li et al, 2021 ) Metabolites in carnitine shuttle metabolism such as acyl-carnitines have also been consistently reported to be affected by traffic-related air pollutants most notably in association with NO 2 . ( van Veldhoven et al, 2019 ).…”

Dietary factors and thyroid dysfunction

“…It is a quaternary amine (3-hydroxy-4-N-trimethylaminobutyrate) and exists as two stereoisomers: Lcarnitine (biologically active form) and D-carnitine. L-carnitine is involved in fat metabolism and energy production, especially in skeletal and cardiac muscle cells, as these cells mainly depend on fatty acids as a primary energy source (52). Namely, Lcarnitine carries long-chain fatty acids from the cytosol into the mitochondria to undergo beta-oxidation for ATP production (53).…”

“…L-carnitine plays a role in maintaining the cell membrane integrity, in the excretion of intermediate metabolism products, balancing the coenzyme A pool inside the mitochondria, and preventing the accumulation of fatty acids. It also exhibits antioxidant activity by increasing the activity of antioxidant enzymes, improving mitochondrial function, or improving the turnover of membrane phospholipid fatty acids (52,54).…”

“…About 75% of the daily need for L-carnitine is met through dietary sources, primarily by consuming foods of animal origin, such as meat, fish and dairy products (mixed food of animal origin provides about 60-180 mg of carnitine per day). The remaining 25% is completed through endogenous synthesis from the amino acids lysine and methionine in the liver and partially in the kidneys (52,55).…”