Carnitine content in the follicular fluid and expression of the enzymes involved in beta oxidation in oocytes and cumulus cells

The purpose of this study is to study lipid metabolism in oocytes and embryos that is a neglected parameter in human IVF. We have tested the total carnitine content (TC) in the follicular fluid of 278 patients (217 non pregnant, 61 pregnant) undergoing IVF. The follicular fluid TC is neither correlated with the circulating estradiol content in serum nor with the outcome the IVF attempt. Carnitine, through the carnitine shuttle, is a major partner in lipid beta oxidation, metabolic pathway involved in the acquisition of oocyte competence. The expression of carnitine synthesis enzymes and lipid beta oxidation was studied in cumulus cells collected at the time of ovum retrieval and in oocyte. Surprisingly the expression for carnitine synthesis is not detectable in oocytes whereas the enzymes involved in lipid beta oxidation are rather strongly expressed. The addition of carnitine in oocyte maturation and embryo culture media should not be overlooked.