Sex hormone levels in the brain of D-aspartate-treated rats

D-Aspartate (D-Asp) is an endogenous amino acid present in the central nervous system and endocrine glands of various animal taxa. D-Asp is implicated in neurotransmission, physiology of learning, and memory processes. In gonads, it plays a crucial role in sex hormone synthesis. We have investigated the effects of chronic (30 days D-Asp drinking solution) and acute (i.p. injection of 2 mmol/g bw D-Asp) treatments on sex steroid synthesis in rat brain. Furthermore, to verify the direct effect of D-Asp on neurosteroidogenic enzyme activities, brain homogenates were incubated with different substrates (cholesterol, progesterone, or testosterone) with or without the addition of D-Asp. Enzyme activities were measured by evaluating the in vitro conversion rate of (i) cholesterol to progesterone, testosterone, and 17b-estradiol, (ii) progesterone to testosterone and 17bestradiol, (iii) testosterone to 17b-estradiol. We found that D-Asp oral administration produced an increase of approximately 40% in progesterone, 110% in testosterone, and 35% in 17b-estradiol. Similarly, the results of the acute experiment showed that at 30 min after D-Asp treatment, the progesterone, testosterone, and 17b-estradiol levels increased by 29–35%, and at 8 h they further increased by a 100% increment. In vitro experiments demonstrate that the addition of D-Asp to brain homogenate + substrate induces a significant increase in progesterone, testosterone and 17b-estradiol suggesting that the amino acid upregulates the local activity of steroidogenic enzymes.

D-Aspartate (D-Asp) is an endogenous amino acid present in the central nervous system and endocrine glands of various animal taxa. D-Asp is implicated in neurotransmission, physiology of learning, and memory processes. In gonads, it plays a crucial role in sex hormone synthesis. We have investigated the effects of chronic (30 days D-Asp drinking solution) and acute (i.p. injection of 2 μmol/g bw D-Asp) treatments on sex steroid synthesis in rat brain. Furthermore, to verify the direct effect of D-Asp on neurosteroidogenic enzyme activities, brain homogenates were incubated with different substrates (cholesterol, progesterone, or testosterone) with or without the addition of D-Asp. Enzyme activities were measured by evaluating the in vitro conversion rate of (i) cholesterol to progesterone, testosterone, and 17β-estradiol, (ii) progesterone to testosterone and 17β-estradiol, (iii) testosterone to 17β-estradiol. We found that D-Asp oral administration produced an increase of approximately 40% in progesterone, 110% in testosterone, and 35% in 17β-estradiol. Similarly, the results of the acute experiment showed that at 30 min after D-Asp treatment, the progesterone, testosterone, and 17β-estradiol levels increased by 29–35%, and at 8 h they further increased by a 100% increment. In vitro experiments demonstrate that the addition of D-Asp to brain homogenate + substrate induces a significant increase in progesterone, testosterone and 17β-estradiol suggesting that the amino acid upregulates the local activity of steroidogenic enzymes.