NEW YORK (Reuters Health) - Oral carnitine increases sperm motility in certain asthenozoospermic men, Italian researchers report in the February issue of Fertility and Sterility. However, it appears that this improvement requires normal mitochondrial function.

Senior investigator Dr. Carlo Foresta told Reuters Health that "it is well known that in some asthenozoospermic subjects an improvement of sperm motility after carnitine administration takes place. However in other asthenozoospermic patients this effect is not present."

To investigate further, Dr. Foresta of the University of Padua and colleagues studied 30 asthenozoospermic patients who were divided into two groups depending on whether or not they had relatively normal levels of sperm phospholipid hydroperoxide glutathione peroxidase (PHGPx).

PHGPx levels, added Dr. Foresta, are "directly related to a normal mitochondrial capsule and function." Moreover, he noted, "mitochondria are needed to produce ATP," which is the major source of energy for the flagellum and hence sperm motility.

The subjects were given placebo for 3 months followed by oral L- carnitine 2 g per day for 3 months.

In patients in whom PHGPx levels were higher than 105 mU/mg, motility rose from 29.3% at baseline to 41.1% after 3 months of carnitine. However, in those with lower levels, motility changed little, from 23.9% to 24.8%.

The researchers suggest that carnitine may act by preventing the mitochondrial phase of apoptosis. This, they note, does not appear to be the case in mitochondria already damaged or weakened by processes associated with a lack of PHGPx.

Thus Dr. Foresta concluded that carnitine treatment is useful "in ameliorating sperm motility only when optimal mitochondrial capsule structure and thus mitochondrial function ... is conserved."

Fertil Steril 2005;83:355-361

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