Enantioselective synthesis of chiral amides by carbene insertion into amide N-H bond.

Chiral amides are important structure in many natural products and pharmaceuticals, yet their efficient synthesis from simple amide feedstock remains challenge due to its weak Lewis basicity. Herein, we describe our study of the enantioselective synthesis of chiral amides by N-alkylation of primary amides taking advantage of an achiral rhodium and chiral squaramide co-catalyzed carbene N-H insertion reaction. This method features mild condition, rapid reaction rate (in all cases 1 min) and a wide substrate scope with high yield and excellent enantioselectivity. Further product transformations show the synthetic potential of this reaction. Mechanistic studies reveal that the non-covalent interactions between the catalyst and reaction intermediate play a critical role in enantiocontrol.

Enantioselective Synthesis of Chiral Amides by a Phosphoric Acid Catalyzed Asymmetric Wolff Rearrangement.

The enantioselective addition of potent nucleophiles to ketenes poses challenges due to competing background reactions and poor stereocontrol. Herein, we present a method for enantioselective phosphoric acid catalyzed amination of ketenes generated from α-aryl-α-diazoketones. Upon exposure to visible light, the diazoketones undergo Wolff rearrangement to generate ketenes. The phosphoric acid not only accelerates ketene capture by amines to form a single configuration of aminoenol intermediates but also promotes an enantioselective proton-transfer reaction of the intermediates to yield the products. Mechanistic studies elucidated the reaction pathway and explained how the catalyst expedited the transformation and controlled the enantioselectivity.

[Community structure and species composition of typical Quercus variabilis natural secondary forest at the northern foothills of the Qinling Mountains, China]. / ç§¦å²­åŒ—éº“å ¸åž‹æ “çš®æ Žå¤©ç„¶æ¬¡ç”Ÿæž—ç¾¤è½ç»“æž„ä¸Žç‰©ç§ç»„æˆ.

We investigated species composition and community structure of a typical Quercus variabilis natural secondary forest in the northern foothills of the Qinling Mountains, within the dynamic monitoring plot of deciduous broad-leaved forest at the Louguantai experimental forest farm in Zhouzhi County, Shaanxi Province. The results showed that there were 3162 individual woody plants with diameter at breast height ≥1 cm in the plot, which were belonged to 42 species, 36 genera, and 25 families. The community genus's areal type was dominated by the temperate component, which accounted for 44.4%, and followed by the tropical component. The community was dominated by several tree species. The top three species with respect to importance value were Q. variabilis, Pinus tabuliformis, and Quercus aliena, with the sum of their importance value being 64.7%. The average DBH of all woody plants was 7.58 cm. The distribution of all individuals and dominant species in the tree layer was approximately normal, with more medium-size individuals. The community structure was stable. The community was poorly renewed, with a trend of population decline. Biodiversity indices varied considerably among different plots, being lower than those of subtropical broad-leaved evergreen forests. There was a significant correlation between community species distribution and environmental factors. Soil and topography explained 42.4% of the variation in community distribution. Altitude and soil alkali hydrolysable nitrogen had a significant effect on community distribution. Altitude, soil total phosphorus, and organic matter content significantly affected the species diversity of Q. variabilis communities. The stronger adaptability of Q. variabilis populations allowed them to become dominant in low-nutrient environments, which limited species diversity in the community.

Genetic analysis of walnut cultivars from southwest China: Implications for germplasm improvement.

Walnuts are highly valued for their rich nutritional profile and wide medicinal applications. This demand has led to the intensification of breeding activities in major walnut production areas such as southwest China, in order to develop more superior cultivars. With the increasing number of cultivars, accurate identification becomes fundamental to selecting the right cultivar for grafting, industrial processing or development of new cultivars. To ensure proper identification of cultivars and understand the genetic structure of wild and cultivated material, we genotyped 362 cultivated and wild individuals of walnut trees from southwest China (with two additional populations from Xinjiang, plus three cultivars from Canada, France and Belgium) using 36 polymorphic microsatellite loci. We found relatively low indices of genetic diversity (H O = 0.570, H E = 0.404, N A = 2.345) as well as a high level of clonality (>85% of cultivars), indicating reliance on genetically narrow sources of parental material for breeding. Our STRUCTURE and PCoA analyses generally delineated the two species, though considerable levels of introgression were also evident. More significantly, we detected a distinct genetic group of cultivated Juglans sigillata, which mainly comprised individuals of the popular 'Yangbidapao' landrace. Finally, a core set of 18 SSR loci was selected, which was capable of identifying 32 cultivars. In a nutshell, our results call for more utilization of genetically disparate material, including wild walnut trees, as parental sources to breed for more cultivars. The data reported herein will significantly contribute towards the genetic improvement and conservation of the walnut germplasm in southwest China.

[Shrub layer structure and species diversity of warm temperate deciduous broadleaved forests of the Qinling Mountains Huangguan plot in China]. / ç§¦å²­çš‡å† æš–æ¸©å¸¦è½å¶é˜”å¶æž—çŒæœ¨å±‚ç»“æž„ä¸Žç‰©ç§å¤šæ ·æ€§.

Shrub is an important part of forest ecosystem. Exploring the species composition, structure and spatial distribution of shrub layer can lay an important foundation for further clarifying the mechanisms underlying species coexistence, biodiversity maintenance and community succession. In this study, species composition, spatial distribution, and species diversity of shrub layer were analyzed in 25 hm2 of Huangguan forest plot. A total of 20716 individual shrubs (with 10463 branches) were recorded in the plot, belonging to 54 species, 45 genera, 28 families. The status of dominant species in the shrub layer was not obvious, with all the importance values being less than 10. The diameter structure of shrub layer vegetation was inverted 'J' type. Shrubs showed aggregated distribution in the plot, with obvious altitude differences in spatial distribution. The diameter structure and spatial distribution of the nine shrub species with the largest abundance in the plot were consistent with the overall situation of shrub layer. With increasing altitude, the Shannon diversity index (H) and Simpson dominance index (D) did not change significantly, while the Pielou evenness index (E) decreased. Those indices decreased with the increases of the abundance of dominant species in tree layer, and E increased with the increase of the number of dominant species in sub-tree layer. The indices of H, D, E were significantly negatively correlated with soil total phosphorus (TP). The H index was significantly positively correlated with soil pH, and the E index was significantly positively correlated with soil total potassium. The shrub layer was rich in species, stable in community structure and well regenerated. The species diversity of shrub layer was mainly affected by the number of dominant species in the tree layer, soil pH, and TP.

[Species composition and community structure of warm temperate deciduous broadleaved forests in Huangguan of Qinling Mountains, China]. / ç§¦å²­çš‡å† æš–æ¸©æ€§è½å¶é˜”å¶æž—ç‰©ç§ç»„æˆä¸Žç¾¤è½ç»“æž„.

The Qinling Mountain is a natural boundary between warm temperate zone and subtropical zone. While the China Forest Biodiversity Monitoring Network (CForBio) have basically covered most of the climate regions in China, few plots were located in the climate transition zone. Following the field protocol of CForBio and the Center for Tropical Forest Science (CTFS), a 25 hm2(500 m×500 m) forest plot was established in Huangguan Nature Reserve in Shaanxi Province, China, in 2019. In this study, we analyzed species composition, flora characteristics, diameter class structure, and spatial distribution patterns of dominant tree species based on the data of all woody species with a diameter at breast height (DBH) ≥1 cm. The results showed that there were 75137 woody individuals with DBH ≥1 cm in the plot (95679 when including branching individuals), belonging to 121 species, 83 genera and 44 families. The flora type at the genera level was mainly temperate, accounting for 71.1% of the total genera, and mixed with some tropical components. The dominant species in the community were obvious, with the number of individuals in the top 5 species exceeding 40% of the total number of individuals, the number of individuals in the top 50 species accounting for 95% of the total number of individuals, and the number of individuals in the remaining 61 species being less than 5% of the total. The diameter distribution of all woody indivi-duals in the plot was inverted 'J' type. Spatial distribution patterns varied across the four most abundant species with importance value >5. The degree of aggregation within species decreased with the increases of scales, while the spatial distribution of different species was affected by environmental heterogeneity. Warm-temperate deciduous broadleaved forest in Qinling Mountains had abundant species, stable community structure and good regeneration, reflecting the typical characteristics of the transition from warm temperate zone to subtropical zone. Environmental heterogeneity might be an important factor affecting the spatial distribution of tree species in the plot.

Piperlongumine inhibits migration and proliferation of castration-resistant prostate cancer cells via triggering persistent DNA damage.

BACKGROUND: Metastatic castration-resistant prostate cancer (CRPC) is the leading cause of death among men diagnosed with prostate cancer. Piperlongumine (PL) is a novel potential anticancer agent that has been demonstrated to exhibit anticancer efficacy against prostate cancer cells. However, the effects of PL on DNA damage and repair against CRPC have remained unclear. The aim of this study was to further explore the anticancer activity and mechanisms of action of PL against CRPC in terms of DNA damage and repair processes. METHODS: The effect of PL on CRPC was evaluated by MTT assay, long-term cell proliferation, reactive oxygen species assay, western blot assay, flow cytometry assay (annexin V/PI staining), ß-gal staining assay and DAPI staining assay. The capacity of PL to inhibit the invasion and migration of CRPC cells was assessed by scratch-wound assay, cell adhesion assay, transwell assay and immunofluorescence (IF) assay. The effect of PL on DNA damage and repair was determined via IF assay and comet assay. RESULTS: The results showed that PL exhibited stronger anticancer activity against CRPC compared to that of taxol, cisplatin (DDP), doxorubicin (Dox), or 5-Fluorouracil (5-FU), with fewer side effects in normal cells. Importantly, PL treatment significantly decreased cell adhesion to the extracellular matrix and inhibited the migration of CRPC cells through affecting the expression and distribution of focal adhesion kinase (FAK), leading to concentration-dependent inhibition of CRPC cell proliferation and concomitantly increased cell death. Moreover, PL treatment triggered persistent DNA damage and provoked strong DNA damage responses in CRPC cells. CONCLUSION: Collectively, our findings demonstrate that PL potently inhibited proliferation, migration, and invasion of CRPC cells and that these potent anticancer effects were potentially achieved via triggering persistent DNA damage in CRPC cells.

Skip participates in formation and lipid metabolism of beige adipose and might mediate the effects of SIRT1 activator BTM-0512 on beige remodeling.

Dissipating energy by activating thermogenic adipose to combating obesity attracts many interests. Ski-interacting protein (Skip) has been known to play an important role in cell proliferation and differentiation, but whether it participates in energy metabolism is not known. Our previous study revealed that BTM-0512 could induce beige adipose formation, accompanying with up-regulation of Skip, but the role of Skip in metabolism was unknown. In this study, we mainly investigated whether Skip was involved in beige remodeling of subcutaneous white preadipocytes as well as in lipid metabolism of differentiated beige adipocytes. The results showed that in high fat diet-induced obesity mice, the protein levels of Skip in subcutaneous and visceral white adipose as well as in brown adipose were all down-regulated, especially in subcutaneous white adipose. Then we cultured subcutaneous adipose derived-stem cells (ADSCs) and found knock-down of Skip (siSkip) inhibited the expressions of thermogenic adipose specific genes including PRDM16 and UCP1 in both undifferentiated ADSCs and differentiated beige adipocytes, which could abolish the effects of BTM-0512 on beige remodeling. We further observed that siSkip affected multiple rate-limiting enzymes in lipid metabolism. The expressions of ACC, GPAT-1, HSL and ATGL were down-regulated, while CPT1α expression was up-regulated by siSkip. The expression of AMPK was also decreased by siSkip. In conclusion, our study demonstrated that Skip might play an important role in the beige remodeling of white adipocytes as well as lipid metabolism of beige adipose.

Cytotoxic triterpenoid glycosides from leaves of Cyclocarya paliurus.

Three previously undescribed dammarane triterpenoid glycosides (1-3) along with five known analogues (4-8) were isolated from the leaves of Cyclocarya paliurus. Their structures and configurations were determined on the basis of comprehensive spectroscopic analyses, chemical hydrolysis and DFT GIAO 13C NMR calculation. All the isolates were evaluated cytotoxic activities against seven human cancer cell lines (MCF-7, PC-3, Du145, NCI-H1975, PC-9, SKVO3 and HepG2). Moreover, compound 4 showed a wide spectrum of cytotoxicity against human cancer cells with IC50 values ranging from 11.31 to 29.51 µM.

Global analysis and optimal harvesting for a hybrid stochastic phytoplankton-zooplankton-fish model with distributed delays.

In this paper, we formulate a phytoplankton-zooplankton-fish model with distributed delays and hybrid stochastic noises involving Brownian motion and Markov chain, and propose an optimal harvesting problem pursuing the maximum of total economic income. By global analysis in terms of some system parameters, we investigate the dynamical behaviors on the well-posedness, bounded- ness, persistence, extinction, stability and attractiveness of the solutions for the stochastic delayed system. Moreover, we provide sufficient and necessary condition ensuring the existence of the optimization solution for the optimization problem and obtain the optimal harvesting effect and the maximum of sustainable yield. Lastly, two numerical examples and their simulations are given to illustrate the effectiveness of our results.

Alpha-glucosidase inhibitor 1-Deoxynojirimycin promotes beige remodeling of 3T3-L1 preadipocytes via activating AMPK.

Obesity is a serious health challenge in the world, and searching effective drugs to cure obesity is of great importance. 1-Deoxynojirimycin (DNJ) is extracted from mulberry leaves and acts as an α-glucosidase inhibitor to lower blood glucose. Recent studies demonstrated that it also has anti-obesity effect, but the mechanisms remain unknown. In our present study, we mainly examined the effects of DNJ on beige remodeling of 3T3-L1 preadipocytes. We observed that DNJ didn't affect the mRNA levels of fatty acid binding protein 4 (aP2), peroxisome proliferator-activated receptor γ (PPARγ), preadipocyte factor-1 (Pref-1) as well as the mitochondrial uncoupling protein 1 (UCP1), PR domain containing protein 16 (PRDM16), transmembrane protein 26 (TMEM26) in undifferentiated preadipocytes. But after inducing 3T3-L1 preadipocytes to differentiation with white or beige adipogenic medium, DNJ significantly reduced aP2, PPARγ and Pref-1 expressions, while up-regulated the expressions of UCP1, PRDM16 and TMEM26, accompanying with decreased lipid deposition. The ratio of p-AMPK/AMPK was up-regulated by DNJ (10 µM) treatment for 10 days, and the effects of DNJ on p-AMPK/AMPK, UCP1 and PRDM16 could be blocked by AMPK inhibitor Compound C. These results demonstrated that hypoglycemic agent DNJ could suppress the adipogenesis during the differentiation of white preadipocytes, and promote the switch of white preadipocytes to beige adipocytes via activating AMPK, which provided new mechanisms for explaining the benefits of DNJ on obesity-related disorders.

Phosphorylation of Nonmuscle Myosin Light Chain Promotes Endothelial Injury in Hyperlipidemic Rats Through a Mechanism Involving Downregulation of Dimethylarginine Dimethylaminohydrolase 2.

Suppression of dimethylarginine dimethylaminohydrolase (DDAH) activation is related to endothelial dysfunction in hyperlipidemia, and nonmuscle myosin regulatory light chain (nmMLC20) has been show to exert transcriptional function in regulation of gene expression. This study aims to explore whether the suppression of DDAH activation promotes endothelial injury under the condition of hyperlipidemia and whether nmMLC20 can regulate DDAH expression in a phosphorylation-dependent manner. The rats were fed with high-fat diet for 8 weeks to establish a hyperlipidemic model, which showed an increase in plasma lipids and endothelial injury, accompanied by an elevation in myosin light chain kinase (MLCK) activity, phosphorylated nmMLC20 (p-nmMLC20) level, and asymmetric dimethylarginine (ADMA) content as well as a reduction in DDAH2 expression, DDAH activity, and nitric oxide (NO) content. Next, human umbilical vein endothelial cells (HUVECs) were incubated with oxidized low-density lipoprotein (ox-LDL; 100 µg/mL) for 24 hours to establish a cellular injury model in vitro. Consistent with the finding in vivo, ox-LDL induced HUVECs injury (apoptosis and necrosis) concomitant with an increase in MLCK activity, p-nmMLC20 level (in total or nuclear proteins), and ADMA content as well as a reduction in DDAH2 expression, DDAH activity, and NO content; these phenomena were attenuated by MLCK inhibitor. Either in hyperlipidemic rats or in ox-LDL-treated HUVECs, there was not significant change in DDAH1 expression. Based on these observations, we conclude that the suppression of DDAH2 expression might account for, at least partially, the vascular endothelial dysfunction in hyperlipidemia, and nmMLC20 plays a role in suppression of DDAH2 expression in a phosphorylation-dependent manner.

CTRP3 deficiency reduces liver size and alters IL-6 and TGFß levels in obese mice.

C1q/TNF-related protein 3 (CTRP3) is a secreted metabolic regulator whose circulating levels are reduced in human and rodent models of obesity and diabetes. Previously, we showed that CTRP3 infusion lowers blood glucose by suppressing gluconeogenesis and that transgenic overexpression of CTRP3 protects mice against diet-induced hepatic steatosis. Here, we used a genetic loss-of-function mouse model to further address whether CTRP3 is indeed required for metabolic homeostasis under normal and obese states. Both male and female mice lacking CTRP3 had similar weight gain when fed a control low-fat (LFD) or high-fat diet (HFD). Regardless of diet, no differences were observed in adiposity, food intake, metabolic rate, energy expenditure, or physical activity levels between wild-type (WT) and Ctrp3-knockout (KO) animals of either sex. Contrary to expectations, loss of CTRP3 in LFD- or HFD-fed male and female mice also had minimal or no impact on whole body glucose metabolism, insulin sensitivity, and fasting-induced hepatic gluconeogenesis. Unexpectedly, the liver sizes of HFD-fed Ctrp3-KO male mice were markedly reduced despite a modest increase in triglyceride content. Furthermore, liver expression of fat oxidation genes was upregulated in the Ctrp3-KO mice. Whereas the liver and adipose expression of profibrotic TGFß1, as well as its serum levels, was suppressed in HFD-fed KO mice, circulating proinflammatory IL-6 levels were markedly increased; these changes, however, were insufficient to affect systemic metabolic outcome. We conclude that, although it is dispensable for physiological control of energy balance, CTRP3 plays a previously unsuspected role in modulating liver size and circulating cytokine levels in response to obesity.

Expression of apoptosis-associated microRNAs in ethanol-induced acute gastric mucosal injury via JNK pathway.

MicroRNAs (miRNAs) have been shown to be closely associated with cellular apoptosis, but their involvement in response to ethanol-induced gastric mucosal epithelial cell apoptosis remains largely unknown. The purpose of this study was to investigate the expression profile of apoptosis-associated miRNAs in ethanol-induced acute gastric mucosal injury and the mechanisms underlying injury. Gastric mucosal injury was induced in rats by oral administration of ethanol, and gastric tissues were collected for analysis of gastric ulcer index, apoptosis ratio, caspase-3 activity, and miRNAs expression. Cell cultures of human gastric mucosal epithelial cells (GES-1) were incubated with ethanol to induce apoptosis. Mimics or inhibitors of miRNAs or c-Jun N-terminal kinase (JNK) inhibitor were added to the cell culture medium. GES-1 cells were collected for analysis of apoptosis ratio, caspase-3 activity, miRNAs expression, and protein phosphorylation levels of JNK, p38 mitogen-activated protein kinase (p38MAPK), or extracellular signal-regulated kinase (ERK). In the animal experiments, gastric ulcer index, cellular apoptosis, and caspase-3 activity were significantly increased, accompanied by up-regulation of miR-145 and down-regulation of the microRNAs miR-17, miR-19a, miR-21, miR-181a, and miR-200c. In the human cell culture experiments, the anti-apoptotic effects of miR-19a and miR-21 or pro-apoptotic effect of miR-145 were confirmed by their corresponding mimics or inhibitor; the ethanol-induced GES-1 apoptosis as well as the changes in miRNAs expression were significantly attenuated in the presence of JNK inhibitor. These results demonstrated that miR-145, miR-19a, and miR-21 were the apoptosis-associated miRNAs in gastric mucosal epithelial cells. The regulation of expression of these 3 miRNAs in ethanol-induced GES-1 apoptosis involved the JNK pathway.

Stimulation of calcitonin gene-related peptide release through targeting capsaicin receptor: a potential strategy for gastric mucosal protection.

Calcitonin gene-related peptide (CGRP) is a predominant neurotransmitter from capsaicin-sensitive sensory nerves, which are widely distributed in the gastrointestinal system. These sensory nerves are reported to be involved in the protection of gastric mucosa against damage by various stimuli, and CGRP is a potential mediator in this process. In addition to increase in gastric mucosal blood flow, the beneficial effects of CGRP on gastric mucosa include inhibition of gastric acid secretion, prevention of cellular apoptosis and oxidative injury. The synthesis and release of CGRP is regulated by the capsaicin receptor which is known as transient receptor potential vanilloid subfamily member 1 (TRPV1) and the agonists of TRPV1 have the potential for gastric mucosal protection. So far, multiple TRPV1 agonists, including capsaicin, capsiate, anandamide and rutaecarpine are reported to exert beneficial effects on gastric mucosal injury induced by various stimuli. Therefore, the TRPV1/CGRP pathway represents a novel target for therapeutic intervention in human gastric mucosal injury.

Beneficial effects of capsiate on ethanol-induced mucosal injury in rats are related to stimulation of calcitonin gene-related Peptide release.

Capsiate is a non-pungent analogue of capsaicin from CH-19 Sweet peppers. Capsaicin is reported to trigger calcitonin gene-related peptide (CGRP) release through activation of transient receptor potential vanilloid subfamily member 1 (TRPV1) and produces beneficial effects on gastric mucosa. This study aimed to investigate whether capsiate is able to produce beneficial effects on gastric mucosa and whether the protective effects of capsipate occur through a mechanism involving the activation of TRPV1 and CGRP release. A rat model of gastric mucosal injury was established by the oral administration of acidified ethanol. Gastric tissues were collected for analysis of the gastric ulcer index, cellular apoptosis, activities of caspase-3, catalase and superoxide dismutase (SOD), and levels of CGRP, TNF-α, and malondialdehyde (MDA). Our results show that the acute administration of ethanol significantly increased the gastric ulcer index concomitantly with an increase in cellular apoptosis, caspase-3 activity, and TNF-α and MDA levels, as well as a decrease in the activities of catalase and SOD. Pretreatment with 1 mg/kg capsiate attenuated ethanol-induced gastric mucosal injury and cellular apoptosis accompanied by an increase in CGRP level, catalase, and SOD activities, and a decrease in caspase-3 activity, and TNF-α and MDA levels. The effects of capsiate were inhibited by capsazepine, an antagonist of TRPV1. These results suggest that capsiate is able to produce beneficial effects on ethanol-induced gastric mucosal injury. These effects are related to the stimulation of CGRP release through the activation of TRPV1.

Vanillyl nonanoate protects rat gastric mucosa from ethanol-induced injury through a mechanism involving calcitonin gene-related peptide.

Previous studies have demonstrated that capsaicin-sensitive sensory nerves are involved in the protection of gastric mucosa against damage by various stimuli and calcitoin gene-related peptide (CGRP) is a potential mediator in this process. This study was performed to explore the effect of vanillyl nonanoate, a capsaicin analog, on ethanol-induced gastric mucosal injury and the possible underlying mechanisms. A rat model of gastric mucosal injury was induced by oral administration of acidified ethanol and gastric tissues were collected for analysis of gastric ulcer index, cellular apoptosis, the activities of caspase-3, catalase and superoxide dismutase (SOD), levels of CGRP, TNF-α and malondialdehyde (MDA). The results showed that acute administration of ethanol significantly increased gastric ulcer index concomitantly with increased cellular apoptosis, caspase-3 activity, TNF-α and MDA levels as well as decreased activities of catalase and SOD. Pretreatment with 1mg/kg vanillyl nonanoate significantly attenuated ethanol-induced gastric mucosal injury and cellular apoptosis accompanied by increase of CGRP expression, and SOD activity and decrease of caspase-3 activity, TNF-α and MDA levels. The effects of vanillyl nonanoate were inhibited by capsazepine, an antagonist of capsaicin receptor. Our results suggested that vanillyl nonanoate was able to protect the gastric mucosa against ethanol-induced gastric mucosal injury. The underlying mechanism is related to stimulation of CGRP release and subsequent suppression of ethanol-induced inflammatory reaction, cellular apoptosis and oxidative stress.

Asymmetric dimethylarginine impairs glucose utilization via ROS/TLR4 pathway in adipocytes: an effect prevented by vitamin E.

BACKGROUND: Asymmetric dimethylarginine (ADMA), the inhibitor of nitric oxide synthase (NOS), has been reported to be associated with glucose metabolism, but its mechanisms remain unknown. METHODS: In 3T3-L1 adipocytes, we measured the effects of ADMA on glucose transport process under basal or insulin-induced condition, and examined the production of nitric oxide (NO), reactive oxygen species (ROS) and tumor necrosis factor alpha (TNF-alpha), and the expression of toll-like receptor 4 (TLR4). RESULTS: ADMA significantly impaired basal or insulin-stimulated 2-deoxy- [3H] glucose uptake, and decreased the expression of insulin receptor substrate-1 (IRS-1) and glucose transporter-4 (GLUT4). Phosphorylated protein of IRS-1 and translocation of GLUT4 with insulin-stimulation were also inhibited by ADMA. NO decreased, while production of ROS and TNF-alpha, and expression of TLR4 increased after ADMA treatment. Vitamin E reduced the effects of ADMA on glucose transport system, and on NO, ROS and TLR4. Moreover, vitamin E decreased ADMA contents by up-regulating dimethylarginine dimethylaminohydrolase (DDAH) activity in adipocytes. Though L-arginine also increased NO level, but failed to reduce the effects of ADMA. CONCLUSION: ADMA significantly impairs both basal and insulin-stimulated glucose transport in adipocytes, which may relate to activation of the ROS/TLR4 pathway.

Detrimental effects of nicotine on the acute gastric mucosal injury induced by ethanol: role of asymmetric dimethylarginine.

The aim of this study was to determine whether asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), is responsible for the detrimental effects of nicotine on ethanol-induced gastric mucosal injury and its underlying mechanisms. Gastric mucosal injury was induced by an injection of ethanol in the stomach in rats. Animals were pretreated with nicotine for 28 days before ethanol injection. The gastric mucosal ulcer index (UI) and the levels of ADMA and NO in gastric juice were determined. In vitro, the cultured mucosal epithelial cells were treated with nicotine in the presence or absence of ethanol. The concentration of ADMA in the culture medium and the ratio of cell apoptosis were measured, and the effect of nicotine or ADMA alone on cell apoptosis was also examined. In rats treated with ethanol, the UI and ADMA levels were increased and the NO level was decreased, and these effects of ethanol were augmented by pretreatment with nicotine. Administration of nicotine alone did not show significant impact on UI, ADMA level, or NO level. In vitro, incubation of human epithelial cells with ethanol induced cell injury accompanied by increased ADMA levels in the culture medium, an effect which was amplified in the presence of nicotine. Similarly, ethanol was able to induce epithelial cell apoptosis that was exacerbated by nicotine. Incubation of epithelial cells with nicotine alone did not induce cell apoptosis, but administration of ADMA alone did induce cell apoptosis. The results suggest that the gastric mucosal injury induced by ethanol is augmented by nicotine, which is related to the increased ADMA level.

Effect of asymmetric dimethylarginine on atherogenesis and erythrocyte deformability in apolipoprotein E deficient mice.

Previous investigations have shown that the level of asymmetric dimethylarginine (ADMA) was increased in hypercholesterolemic animal and humans, and the decreased erythrocyte deformability has been suggested to be a factor contributing to atherogenesis. In the present study, we investigated the effect of ADMA, endogenous or exogenous, on atherogenesis and erythrocyte deformability in apolipoprotein E deficient (ApoE-/-) mice. On a regular chow diet, ApoE-/- mice or C57BL/6 J mice at 12 weeks of age were treated with ADMA (5 mg/kg/day) for 4 weeks. Atherosclerotic lesion area, erythrocyte deformability, plasma lipids and asymmetric dimethylarginine (ADMA) level were determined. Plasma concentrations of triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C), total cholesterol (TC), ADMA, and atherosclerotic lesion area were significantly increased, and the level of plasma high-density lipoprotein-cholesterol (HDL-C), erythrocyte deformability in ApoE-/- mice were markedly decreased compared with that of C57BL/6J mice (P<0.05 or P<0.01). Exogenous ADMA treatment increased the plasma TG level, produced atherosclerotic lesions, and decreased erythrocyte deformability in C57BL/6J mice (P<0.05 or P<0.01). Treatment with exogenous ADMA further increased the plasma TG level and lesion areas, and decreased erythrocyte deformability in ApoE-/- mice. In vitro, exogenous ADMA caused a decrease of erythrocyte deformability in a concentration-dependent manner, and the effect of ADMA was reversed by L-arginine. The present results suggest that endogenous ADMA is an important contributor to the development of atherosclerosis and that reduction of erythrocyte deformability and impaired endothelial function induced by ADMA may be an important factor facilitating atherosclerotic lesions.