1. d-Leucine protects oocytes from chronic psychological stress in mice
Ai Tsuji, Yuka Ikeda, Mutsumi Murakami, Yasuko Kitagishi, Satoru Matsuda Reprod Med Biol. 2021 Jun 16;20(4):477-484. doi: 10.1002/rmb2.12396. eCollection 2021 Oct.
Purpose: Psychological stress could negatively influence female reproductive ability. d-Leucine (d-Leu) is a d-type amino acid found in foods and mammalian tissues. We have examined the protective effects of d-Leu on oocyte abnormality induced by psychological stress. Methods: Female mice (6-week-old) were divided into three groups: control, restraint stress (RS), and RS/d-Leu. The RS and RS/d-Leu mice were holed for 3 hours daily during 14 days. RS/d-Leu mice were fed 0.3% d-Leu diet. The oocyte maturation failure was analyzed by shapes of spindles and chromosomes. In addition, levels of heme-oxygenase-1 (HO-1) and superoxide dismutase (SOD) expression in the ovaries were also examined. Whether d-Leu reduces the generation of reactive oxygen species (ROS) in cultured cells, K562 cells were treated with d-Leu, and then ROS in K562 were analyzed. Results: Oocyte maturation failure was increased in RS mice. d-Leu reduced abnormal oocytes to control level. The expression levels of HO-1 and SOD2 increased in RS/d-Leu mice compared to those of RS mice. ROS levels were decreased in K562 cells with d-Leu in a dose-dependent manner. Conclusions: We concluded that d-Leu protects oocytes from psychological stress through the induction of HO-1 and SOD2 expression then by reducing oxidative stress.
2. D-leucine microparticles as an excipient to improve the aerosolization performances of dry powders for inhalation
Aurélie Schoubben, Riccardo Vivani, Marco Paolantoni, Diego Romano Perinelli, Antimo Gioiello, Antonio Macchiarulo, Maurizio Ricci Eur J Pharm Sci. 2019 Mar 15;130:54-64. doi: 10.1016/j.ejps.2019.01.018. Epub 2019 Jan 21.
The objective of the work was to produce a new excipient based on D-leucine to improve the aerosolization properties of the poorly flowable micronized budesonide. The D-leucine powders produced by a nano spray-dryer were characterized in terms of dimensions, morphology, thermal behavior, X-ray powder diffraction and infrared spectroscopy. Then, micronized budesonide was mixed with the different leucine powders obtained or commercial D-leucine at different weight ratios (1:1, 5:1, 10:1) to investigate their aerodynamic characteristics using a glass twin-stage impinger. Commercial D-leucine powder is composed of large flattened crystals of about 30 μm with ~3 μm thickness, while micronized budesonide appeared as small irregular crystals. After spray-drying, D-leucine particles appeared wrinkled and porous. Particle sizes were mainly influenced by the amino acid concentration. Aerodynamic assessment showed that D-leucine was able to improve the aerodynamic behavior of micronized budesonide from about 28 to 45% emitted fraction. The best aerodynamic properties were obtained with D-leucine powdered from a water:ethanol (1:1, v:v) solution and using micronized budesonide:leucine weight ratio of 5:1. The direct physical mixing of the atomized D-leucine with the micronized active pharmaceutical ingredient is a valid and economic alternative for the production of carrier-free dry powders for inhalation.
3. d-Leucine: Evaluation in an epilepsy model
Kylie Holden, Adam L Hartman Epilepsy Behav. 2018 Jan;78:202-209. doi: 10.1016/j.yebeh.2017.09.003. Epub 2017 Nov 7.
Background: Current medicines do not provide sufficient seizure control for nearly one-third of patients with epilepsy. New options are needed to address this treatment gap. We recently found that the atypical amino acid d-leucine protected against acutely-induced seizures in mice, but its effect in chronic seizures has not been explored. We hypothesized that d-leucine would protect against spontaneous recurrent seizures. We also investigated whether mice lacking a previously-described d-leucine receptor (Tas1R2/R3) would be protected against acutely-induced seizures. Methods: Male FVB/NJ mice were subjected to kainic acid-induced status epilepticus and monitored by video-electroencephalography (EEG) (surgically implanted electrodes) for 4weeks before, during, and after treatment with d-leucine. Tas1R2/R3 knockout mice and controls underwent the maximal electroshock threshold (MES-T) and 6-Hz tests. Results: There was no difference in number of calendar days with seizures or seizure frequency with d-leucine treatment. In an exploratory analysis, mice treated with d-leucine had a lower number of dark cycles with seizures. Tas1R2/R3 knockout mice had elevated seizure thresholds in the MES-T test but not the 6-Hz test. Conclusions: d-Leucine treatment was ineffective against chronic seizures after kainic acid-induced status epilepticus, but there was some efficacy during the dark cycle. Because d-leucine is highly concentrated in the pineal gland, these data suggest that d-leucine may be useful as a tool for studying circadian patterns in epilepsy. Deletion of the Tas1R2/R3 receptor protected against seizures in the MES-T test and, therefore, may be a novel target for treating seizures.