Sex steroid hormones affect carnitine concentrations of blood and organs in rats

Abstract

Males and females exhibit different rates of central obesity, cardiovascular disease and diabetes. Furthermore, altered concentrations of sex steroid hormones can lead to altered rates of these diseases in the afflicted populations, suggesting these hormones can affect metabolism and, in the long term, have clinical repercussions. Carnitine, an amino acid derivative involved in fat oxidation, was used to examine differences in metabolism between the sexes based on changes in the hormonal milieu. Rats (178 males and 176 females) were administered one of the following treatments: estradiol injection, testosterone injection, castration, and hypophysectomy. Total carnitine was measured in plasma, liver, heart, muscle, and epididymis. In both sexes, estradiol appears to increase liver carnitine while decreasing plasma, muscle and heart carnitine; testosterone, on the other hand, increases plasma, muscle and heart carnitine. In males, estradiol decreases and testosterone increases epididymis carnitine. Hypophysectomy decreased carnitine in all compartments for males and all compartments except for heart and muscle in females. This study demonstrates that estradiol, testosterone and the pituitary gland greatly influence carnitine concentrations of the body and are key to the observed sex differences in carnitine.