Human sperm DNA oxidation, motility and viability in the presence of lâ•’carnitine during in vitro incubation and centrifugation

Infertility affects one in seven couples who are trying to conceive (Lamb & Lipshultz, 2000; Brugh & Lipshultz, 2004). Decreased semen quality, a measure of the ability of semen to achieve fertilisation, is a primary cause of male infertility. Usually, poor semen quality is characterised by low sperm motility and viability. Assisted reproductive techniques (ART) such as intra-uterine insemination and in vitro fertilisation with or without intracytoplasmic sperm injection are the most successful therapeutic means for male factor infertility. Sperm preparation protocols used in ART involve sperm incubation and centrifugation. It was reported that sperm motility and viability decrease over time after ejaculation (Singer et al., 1980). Further, a rapid decline in motility was noted after incubating periods lasting more than 4 h at 37 C (Jeulin et al., 1982). A recent report suggested that different centrifugation protocols adversely affect sperm recovery (Matas et al., 2007). Increased centrifugation speeds (>500 g) significantly increases the number of dead spermatozoa (Makler & Jakobi, 1981). Centrifugation has also been shown to increase the reactive oxygen species (ROS) formation in semen, which may affect sperm survival (Shekarriz et al., 1995). l-Carnitine (LC) is a naturally occurring molecule, derived from the amino acid lysine. In cellular systems, LC serves as a facilitator for the transport of activated fatty acids into the mitochondrial matrix, so that they can be broken down through b-oxidation to produce ATP (Steiber et al., 2004). Very low concentrations of LC have been reported in azoospermic men compared with