Abstract
BackgroundD-aspartic acid is an amino acid present in neuroendocrine tissues of invertebrates and vertebrates, including rats and humans. Here we investigated the effect of this amino acid on the release of LH and testosterone in the serum of humans and rats. Furthermore, we investigated the role of D-aspartate in the synthesis of LH and testosterone in the pituitary and testes of rats, and the molecular mechanisms by which this amino acid triggers its action.MethodsFor humans: A group of 23 men were given a daily dose of D-aspartate (DADAVIT®) for 12 days, whereas another group of 20 men were given a placebo. For rats: A group of 10 rats drank a solution of either 20 mM D-aspartate or a placebo for 12 days. Then LH and testosterone accumulation was determined in the serum and D-aspartate accumulation in tissues. The effects of D-aspartate on the synthesis of LH and testosterone were gauged on isolated rat pituitary and Leydig cells. Tissues were incubated with D-aspartate, and then the concentration (synthesis) of LH and cGMP in the pituitary and of testosterone and cAMP in the Leydig cells was determined.ResultsIn humans and rats, sodium D-aspartate induces an enhancement of LH and testosterone release. In the rat pituitary, sodium D-aspartate increases the release and synthesis of LH through the involvement of cGMP as a second messenger, whereas in rat testis Leydig cells, it increases the synthesis and release of testosterone and cAMP is implicated as second messenger. In the pituitary and in testes D-Asp is synthesized by a D-aspartate racemase which convert L-Asp into D-Asp. The pituitary and testes possesses a high capacity to trapping circulating D-Asp from hexogen or endogen sources.ConclusionD-aspartic acid is a physiological amino acid occurring principally in the pituitary gland and testes and has a role in the regulation of the release and synthesis of LH and testosterone in humans and rats.
Highlights
D-aspartic acid is an amino acid present in neuroendocrine tissues of invertebrates and vertebrates, including rats and humans
We looked for the action of D-Aspartic acid (D-Asp) on the second messenger and found that following treatment of Leydig cells with 0.1 mM D-Asp, cAMP was increased 3.1-fold compared with the control
We demonstrated that D-aspartic acid, which occurs as a physiological compound in the mammalian pituitary and testis, has a role in the regulation of the release and synthesis of luteinizing hormone (LH) and testosterone
Summary
D-aspartic acid is an amino acid present in neuroendocrine tissues of invertebrates and vertebrates, including rats and humans. We investigated the role of D-aspartate in the synthesis of LH and testosterone in the pituitary and testes of rats, and the molecular mechanisms by which this amino acid triggers its action. D-Aspartic acid (D-Asp) is an endogenous amino acid which has been found in the neuroendocrine tissues of both invertebrates and vertebrates [1]. Within the nervous system this amino acid is concentrated in the axon terminals (synaptosomes) and in synaptic vesicles together with L-Asp and LGlu [7]; it is involved in visual activity [8], suggesting it has a role in neurotransmission. D-Asp is endogenously present in tissues and is electively stored in endocrine glands, such as the pituitary, and in the brain after its administration. Studies done on the testes and ovary of the lizard Podarcis s. sicula have shown similar findings, confirming that D-Asp is involved in the local production of estrogen [19,20]
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