Males
The testes contain high levels of Se, and low sperm production and poor sperm quality are common in Se-deficient animals (Behne et al. 1997) and humans (Maiorino & Ursini, 2002). Strong correlations have been found between semen Se level and sperm number, density and viability (Xu et al, 2003; Akinloye et al, 2005). Se-dependent glutathione peroxidase 4 (GPx4), also known as Sperm mitochondrial capsule selenoprotein, provides the key link between Se, sperm quality and male fertility as GPx4 is required to produce, by polymerisation, the midpiece of spermatozoa, where it may form up to 50% of the capsule material, and provides the structural integrity required for sperm stability and motility (Ursini et al, 1999). Sperm nuclei GPx has an important role in sperm development, by condensing chromatin by cross-linking protamine thiols (Pfeifer et al, 2001), and selenoprotein P is also required for normal development of spermatozoa, where its deficiency causes structural defects in the flagellum (Olson et al, 2005).
Studies in Scotland, where Se intake is relatively low, found that supplementation of subfertile men with 100 micrograms Se/day for 3 months significantly increased sperm motility. Of the men receiving the active supplement 11% achieved paternity compared to none in the placebo group (Scott & MacPherson, 1998).
Females
A decrease in the concentration of serum Se occurs throughout normal pregnancy but women with first-trimester miscarriages have significantly lower serum Se levels than women in the first trimester whose pregnancies went to term (Barrington et al 1996). The authors suggest that early pregnancy loss may be linked to reduced antioxidant protection of biological membranes and DNA by low levels of GPx.. Laboratory studies of bovine granulosa cells obtained from follicles of variable size gound that Se stimulated the proliferation of cells from small follicles and enhanced the stimulatory effects of gonadotrophins in the same cells. Se also increased oestradiol production (Basini & Tamanini, 2000).
Pre-eclampsia is a complex condition characterised by hypertension and micronutrient imbalance during pregnancy, and higher risk of premature delivery. Epidemiological and laboratory studies have demonstrated associations between low Se status and higher rates of pre-eclampsia (Vanderlelie et al, 2004). In a case-control study in the UK 53 pre-eclamptic patients and 53 matched pregnant controls gave toenail clippings for Se determination, and it was found that median toenail Se concentration in the pre-eclamptic women was significantly lower than in their matched controls. Being in the lowest third of Se status was associated with a 4.4-fold higher incidence of the condition. Within the pre-eclamptic group, lower Se status was associated with greater disease severity, as measured by delivery before 32 weeks (Rayman et al, 2003).
Barrington JW, Lindsay P, James D, Smith S, Roberts A 1996. Selenium deficiency and miscarriage: a possible link? Brit J Obstetr Gynaecol 103: 130-132.
Behne D, Kyriakopoulos A, Kalcklosh M 1997. Two new selenoproteins found in the prostatic glandular epithelium and the spermatid nuclei. Biomed Environ Sci 10: 340-345.
Scott R, MacPherson A 1998. Selenium supplementation in sub-fertile human males. Brit J Urol 82: 76-80.
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