Beneficial effect of L-Proline supplementation on the quality of human spermatozoa

L-Proline is a natural anti-oxidative and osmoprotectant agent, playing a versatile role in cell metabolism and physiology. The present study aimed to explore the antioxidant effects of L-Proline on human sperm function during incubation. Thirty healthy, normozoospermic men (27-40 years) were enrolled. Sperm samples were incubated in an unsupplemented sperm medium (control group), or supplemented with L-Proline (1, 2 and 4 mmol/L) to evaluate its effect during 0, 1, 4 and 24 h of incubation. Sperm were assessed in terms of motility, viability, morphology, chromatin and DNA integrity. Moreover, the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and total antioxidant capacity (TAC) were determined in the sperm medium. The results indicated that 2 mmol/L of L-Proline significantly improved the maintenance of sperm motility, viability, normal morphology, chromatin and DNA integrity, and TAC levels compared to the control group during 24 h of incubation (p < 0.05). However, 1 and 4 mmol/L of L-Proline could not significantly preserve sperm parameters, chromatin quality, and antioxidant status during different incubation times compared to the control group (p > 0.05). Collectively, the inclusion of L-Proline (2 mmol/L) in the human sperm medium maintains sperm parameters and chromatin quality probably by modulating the oxidative status.

Proline improves cardiac remodeling following myocardial infarction and attenuates cardiomyocyte apoptosis via redox regulation

At present, ischemic heart failure (HF) caused by coronary heart disease (CHD) has a high morbidity and mortality, placing a heavy burden on global human health. L-Proline (Pro), a nonessential amino acid and the foundation of proteins in the human body, was found to be protective against oxidative stress in various diseases. However, the role of Pro in cardiovascular disease (CVD) remains unclear. In vivo, adult mice were subjected to left anterior descending (LAD) artery ligation for 4 weeks with or without Pro treatment. In vitro, H9c2 cardiomyocytes were pretreated with or without Pro, followed by treatment with hydrogen peroxide (H₂O₂) (200 μM) for 6 and 12 h. Our data showed that Pro metabolism was disturbing after myocardial infarction (MI). Pro treatment improved cardiac remodeling, reduced infarct size, and decreased oxidative stress and apoptosis in mouse hearts after MI. Pro inhibited the H₂O₂-induced increase in reactive oxygen species (ROS) in H9c2 cells and protected against H₂O₂-induced apoptosis. Mechanistically, by RNA sequencing (RNA-seq) and pathway analysis, Pro was shown to exert a protective effect through H₂O₂ catabolic processes and apoptotic processes, especially oxidative phosphorylation (OXPHOS). Taken together, our findings suggested that Pro protects against MI injury at least partially via redox regulation, highlighting the potential of Pro as a novel therapy for ischemic HF caused by CHD.

Effects of maternal L-proline supplementation on inflammatory cytokines at the placenta and fetus interface of mice

Dietary L-proline (proline) supplementation during gestation enhances fetal survival and placental development in mice. The objective of the present study was to test the hypothesis that this beneficial effect of proline was associated with alterations in inflammatory response at the placenta and fetus interface. Populations of immune cells present in peripheral blood mononuclear cells (PBMC) were determined by flow cytometry analysis. The concentrations of immunoglobulins in plasma, and the concentrations of cytokines in plasma, uterus, placenta, and amniotic fluid were measured using a bead-based immunoassay. The data showed that proline supplementation led to higher (P < 0.05) populations of B lymphocytes (CD3^-CD19⁺), natural killer (NK) cells (CD3^-NK1.1⁺), and dendritic cells (DCs, CD11c⁺MHCII⁺) in peripheral blood, as compared with the controls. Conversely, mice fed a proline-supplemented diet had a lower population of neutrophils (CD11b⁺F4/80^-). Further study showed that proline supplementation decreased (P < 0.05) the concentrations of (1) interleukin (IL)-23, IL-1α, and IL-6 in plasma; (2) IL-6 in the uterus; and (3) tumor necrosis factor alpha (TNF-α), monocyte chemotactic protein (MCP)-1, and IL-17 in the placenta; and (4) interferon (IFN)-γ in amniotic fluid, compared with controls. Conversely, proline supplementation resulted in higher (P < 0.05) concentrations of (1) IL-10, IL-17 and granulocyte-macrophage colony-stimulating factor (GM-CSF) in plasma; (2) IL-10 and IL-1α in the uterus; and (3) IL-1α, IL-1β, IL-10, IL-27, and IFN-β in amniotic fluid, compared with controls. Moreover, concentrations of immunoglobulin (Ig) G2b and IgM were enhanced (P < 0.05) by proline administration. Taken together, our results reveal a regulatory effect of proline in the immunological response at the maternal-fetal interface, which is critical for embryonic development and fetal survival.

Selected Amino Acids Promote Mouse Pre-implantation Embryo Development in a Growth Factor-Like Manner

Groups of amino acids, and some selected amino acids, added to media used for culture of pre-implantation embryos have previously been shown to improve development in various ways including survival to the blastocyst stage, increased blastocyst cell number and improved hatching. In this study, we cultured 1-cell mouse embryos for 5 days to the hatching blastocyst stage in isosmotic medium (270 mOsm/kg) at high density (10 embryos/10 μL), where autocrine/paracrine support of development occurs, and low density (1 embryo/100 μL), where autocrine/paracrine support is minimized and development is compromised. When 400 μM L-Pro or 1 mM L-Gln was added to embryos at low density, the percentage of embryos reaching the blastocyst stage and the percentage hatching increased compared to low-density culture without these amino acids, and were now similar to those for embryos cultured at high density without amino acids. When L-Pro or L-Gln was added to embryos at high density, the percentage of embryos reaching the blastocyst stage didn’t change but hatching improved. Neither embryo culture density nor the presence of these amino acids had any effect on blastocyst cell number. D-Pro and the osmolytes Gly and Betaine did not improve embryo development in low- or high-density culture indicating the mechanism was stereospecific and not osmotic, respectively. L-Pro- and L-Gln-mediated improvement in development is observed from the 5-cell stage and persists to the blastocyst stage. Molar excess of Gly, Betaine or L-Leu over L-Pro eliminated improvement in development and hatching consistent with them acting as competitive inhibitors of transporter-mediated uptake across the plasma membrane. The L-Pro effect is dependent on mTORC1 signaling (rapamycin sensitive) while that for L-Gln is not. The addition of L-Pro leads to significant nuclear translocation of p-Akt^S473 at the 2- and 4-cell stages and of p-ERK1/2^T202/Y204 nuclear translocation at the 2-, 4-, and 8-cell stages. L-Pro improvement in embryo development involves mechanisms analogous to those seen with Pro-mediated differentiation of mouse ES cells, which is also stereoselective, dependent on transporter uptake, and activates Akt, ERK, and mTORC1 signaling pathways.

Maternal L-proline supplementation during gestation alters amino acid and polyamine metabolism in the first generation female offspring of C57BL/6J mice

We recently reported that dietary supplementation with L-proline (proline) during gestation improved embryonic survival in C57BL/6J mice. The objective of the present study was to test the hypothesis that the effect of maternal proline supplementation on embryonic survival can be carried forward to the first generation female offspring. In the F0 generation, pregnant dams were fed a purified diet supplemented with 0 (control) or 5 g proline/kg diet. The F1 female adult offsprings were bred to fertile males. Fetal survival at embryonic day (E)12.5 and reproductive outcomes at term birth were recorded. The concentrations of amino acids, ammonia, and urea in plasma and amniotic fluid, as well as concentrations of polyamines in placental tissues and amniotic fluid at E12.5 were determined. Results showed that the F1 generation female offspring from proline-supplemented dams had higher (P < 0.05) concentrations of glutamate and taurine in plasma; of putrescine and spermidine in placental tissues; and of glycine, taurine, and spermidine in amniotic fluid at E12.5, as compared with F1 generation female offsprings from dams without proline supplementation. Concentration of proline in the plasma of offspring mice from proline-supplemented dams were lower (P < 0.05), as compared with the control group. No differences in fetal survival, reproductive outcomes, or concentrations of ammonia and urea in plasma and amniotic fluid were observed between the two groups of F1 female offspring. Collectively, our results indicate that the benefits of maternal proline supplementation during gestation on improving embryonic survival and fetal growth in F0 females are not transmitted to their F1 generation females.

Embryoid Body Differentiation of Mouse Embryonic Stem Cells into Neurectoderm and Neural Progenitors

Mouse embryonic stem cells (mESCs) are pluripotent cells capable of differentiating in vitro to form the ~200 types of cells of the developing embryo and adult, including cells of the nervous system. This makes mESCs a useful tool for studying the molecular mechanisms of mammalian embryonic development. Many protocols involving the use of growth factors and small molecules to differentiate mESCs into neural progenitors and neurons currently exist. However, there is a paucity of protocols available that recapitulate the developmental process. Our laboratory has developed a protocol to recapitulate mammalian neural lineage development by differentiating mESCs to mature neurons via intermediate cell populations observed during in vivo embryo development. This protocol uses the amino acid L-proline to direct the differentiation of mESCs, grown as embryoid bodies, into Sox1⁺ neurectoderm, followed by differentiation to form Nestin⁺, BLBP⁺, and NeuN⁺ neural cell types.

A L-proline/O2 biofuel cell using L-proline dehydrogenase (LPDH) from Aeropyrum pernix

To utilize amino acids from food waste as an energy source, L-proline/O₂ biofuel cell was constructed using a stable enzyme from hyperthermophilic archaeon for long-term operation. On the anode, the electrocatalytic oxidation of L-proline by L-proline dehydrogenase from Aeropyrum pernix was observed in the presence of ferrocenecarboxylic acid as mediator. On the cathode, electrocatalytic oxygen reduction was detected. Ketjenblack modification of carbon cloth substrate increased the current density due to increased laccase loading and enhanced electron transfer reaction. The biofuel cell using these electrodes achieved a current density of 6.00 µA/cm². We successfully constructed the first biofuel cell that generates power from L-proline.

Urinary Metabolites and Their Link with Premature Arterial Stiffness in Black Boys: The ASOS Study

Background and Aims

Black boys (6-8 years of age) were shown to have higher pulse wave velocity with potential early vascular compromise. We aimed to compare predefined urinary metabolites in black and white boys to explore associations of pulse wave velocity with these metabolites.

Methods and Results

We included 40 white and 40 black apparently healthy boys between the ages of 6 and 8 years. Femoral pulse wave velocity was measured along with various metabolites using liquid chromatography tandem mass spectrometry (LC-MS/MS) and gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) methods. Pulse wave velocity and diastolic blood pressure were higher in the black compared to the white boys (both p ≤ 0.002). Isovalerylcarnitine was lower and 1-metylhistidine tended to be lower (p = 0.002 and p = 0.073, respectively), whereas L-proline levels tended to be higher (p = 0.079) in the black compared to the white boys. In single, partial, and multiple regression analyses, pulse wave velocity correlated inversely with β-alanine (β = -0.414; p = 0.008) and 1-methylhistidine (β = -0.347; p = 0.032) and positively with L-proline (β = 0.420; p = 0.008), threonic acid (β = 0.977; p = 0.033), and malonic acid (β = 0.348; p = 0.030) in black boys only.

Conclusion

Our study is the first to discover the associations of pulse wave velocity with β-alanine, 1-methylhistidine, and L-proline in children from South Africa, which may suggest potential early compromise in cardiac protective metabolic pathways in black boys as young as 6 years of age.

L-Proline/CeCl3·7H2O-NaI mediated stereoselective synthesis of α-2-deoxy glycosides from glucal

Glucal with different alcohols can be converted into the corresponding 2-deoxy glycosides without Ferrier rearrangement in high yield by treatment with eco friendly transition metal based catalysts [CuCl₃·2H₂O-NaI (A) or CeCl₃·7H₂O-NaI (B)] and chiral amine ligand L-proline at various reaction conditions which were optimized for stereoselectivity. The catalyst CeCl₃·7H₂O-NaI (B) and ligand L-proline in toluene, was found to be much more efficient and high atom economic for the stereoselective glycosidation of propargyl alcohol with glucal, afforded exclusively α-2-deoxy propargyl glycoside in 98% optimized yield. The ligand L-proline was used for the first time in stereoselective glycosidation of α-2-deoxy glycosides involving glucal and alcohols.

Central mechanism of the cardiovascular responses caused by L-proline microinjected into the paraventricular nucleus of the hypothalamus in unanesthetized rats

Previously, we reported that microinjection of L-proline (L-Pro) into the paraventricular nucleus of the hypothalamus (PVN) caused vasopressin-mediated pressor responses in unanesthetized rats. In the present study, we report on the central mechanisms involved in the mediation of the cardiovascular effects caused by the microinjection of L-Pro into the PVN. Microinjection of increasing doses of L-Pro (3-100nmol/100nL) into the PVN caused dose-related pressor and bradycardic responses. No cardiovascular responses were observed after the microinjection of equimolar doses (33nmol/100nL) of its isomer D-Proline (D-Pro) or Mannitol. The PVN pretreatment with either a selective non-NMDA (NBQX) or selective NMDA (LY235959 or DL-AP7) glutamate receptor antagonists blocked the cardiovascular response to L-Pro (33nmol/100nL). The dose-effect curve for the pretreatment with increasing doses of LY235959 was located at the left in relation to the curves for NBQX and DL-AP7, showing that LY235959 is more potent than NBQX, which is more potent than DL-AP7 in inhibiting the cardiovascular response to L-Pro. The cardiovascular response to the microinjection of L-Pro into the PVN was not affected by local pretreatment with N^ω-Propyl-l-arginine (N-Propyl), a selective inhibitor of the neuronal nitric oxide synthase (nNOS), suggesting that NO does not mediate the responses to L-Pro in the PVN. In conclusion, the results suggest that ionotropic receptors in the PVN, blocked by both NMDA and non-NMDA receptor antagonists, mediate the pressor response to L-Pro that results from activation of PVN vasopressinergic magnocellular neurons and vasopressin release into the systemic circulation.

L-Proline catalyzed one-step synthesis of 4,5-diaryl-2H-1,2,3-triazoles from heteroaryl cyanostilbenes via [3+2] cycloaddition of azide

Use of a novel reagent has been established for the synthesis of a series of 4,5-diaryl-2H-1,2,3-triazoles (6a-i and 9a-e) from cyanostilbene analogs of benzo[b]thiophene, benzo[b]furan and indole, catalyzed by L-proline via Lewis base-catalyzed one-step [3+2]cycloaddition of azide. This method provides an efficient, simple and environmentally benign procedure that affords good yields and relatively short reaction times.