Subchronic toxicity evaluation of glucosamine and glucosamine in combination with chondroitin sulfate in obese Zucker rats.

D-glucosamine is a widely consumed dietary supplement used to promote joint health and treat osteoarthritis. It also stimulates intracellular hexosamine flux and increases transforming growth factor ß1 (TGFß1) mRNA expression and insulin resistance in animal studies. The effects of D-glucosamine exposure were investigated in obese Zucker rats. Male (leprfa/leprfa) Zucker rats were exposed to 30, 120, 300 and 600 mg D-glucosamine HCl per kg/day either alone or with chondroitin sulfate (24, 96, 240 and 480 mg/kg/day respectively) for 90 days. After 4 weeks exposure, these doses produced CmaxD-glucosamine concentrations of up to 24 µM in tail vein serum concurrent with a transient 30% increase in blood glucose concentration in the 600 mg/kg/day dose group. D-Glucosamine did not significantly alter body weight, blood glucose or serum insulin levels at any dose tested after 13 weeks exposure, but did increase urinary TGFß1 concentrations. The Zucker rats developed nephropathy and scrotal sores that were related to their hyperglycemia and obesity, and D-glucosamine exposure exacerbated these conditions to a small extent. The incidence of pulmonary osseous metaplasia was increased in rats exposed to D-glucosamine and a single incidence of adrenal osseous metaplasia was noted in one animal exposed to 600/480 mg D-glucosamine HCl/chondroitin sulfate. These lesions may have been treatment related. These studies suggest that the risk of adverse effects of oral D-glucosamine is small compared to that of hyperglycemia in these animals, but the potential for TGFß1-mediated pathologies, such as osseous metaplasia and renal nephropathy may be increased.

The hepatoprotective effect of the combination of glucosamine derivatives with quercetin against methotrexate-induced liver toxicity.

The article presents the results of the study of the combination of aminosugars - glucosamine hydrochloride (GA h/ch) and N-acetylglucosamine - with quercetin (Q) called GlukvamineTM as a corrector of hepatotoxicity induced by methotrexate (MTX). The study was conducted on a model of MTX-induced liver damage in rats. GlukvamineTM was studied in the dose of 82 mg/kg with daily intragastric administration for 10 days compared to the substance GA h/ch, which was administered intragastrically at a dose of 50 mg/kg, and the substance of Q, which was administered intragastrically in the dose of 20.5 mg/kg. The efficiency of the drugs was assessed by the general condition of the animals, the values of the liver mass coefficient, the biochemical parameters of the blood serum and the histological analysis of the liver tissue. The GlukvamineTM effect on rats with MTX-induced liver damage caused an improvement of their general condition, recovery of the functional state of the liver by biochemical indicators, and the results of the histological analysis indicated a decrease in hepatotoxicity of MTX. At the same time, GlukvamineTM has statistically significantly exceeded the effect of GA h/ch and Q by most parameters. Thus, GlukvamineTM is a promising effective and safe drug for pharmacological correction of the hepatotoxicity of MTX.

Mobilization and removing of cadmium from kidney by GMDTC utilizing renal glucose reabsorption pathway.

Chronic exposure to cadmium compounds (Cd(2+)) is one of the major public health problems facing humans in the 21st century. Cd(2+) in the human body accumulates primarily in the kidneys which leads to renal dysfunction and other adverse health effects. Efforts to find a safe and effective drug for removing Cd(2+) from the kidneys have largely failed. We developed and synthesized a new chemical, sodium (S)-2-(dithiocarboxylato((2S,3R,4R,5R)-2,3,4,5,6 pentahydroxyhexyl)amino)-4-(methylthio) butanoate (GMDTC). Here we report that GMDTC has a very low toxicity with an acute lethal dose (LD50) of more than 10,000mg/kg or 5000mg/kg body weight, respectively, via oral or intraperitoneal injection in mice and rats. In in vivo settings, up to 94% of Cd(2+) deposited in the kidneys of Cd(2+)-laden rabbits was removed and excreted via urine following a safe dose of GMDTC treatment for four weeks, and renal Cd(2+) level was reduced from 12.9µg/g to 1.3µg/g kidney weight. We observed similar results in the mouse and rat studies. Further, we demonstrated both in in vitro and in animal studies that the mechanism of transporting GMDTC and GMDTC-Cd complex into and out of renal tubular cells is likely assisted by two glucose transporters, sodium glucose cotransporter 2 (SGLT2) and glucose transporter 2 (GLUT2). Collectively, our study reports that GMDTC is safe and highly efficient in removing deposited Cd(2+) from kidneys assisted by renal glucose reabsorption system, suggesting that GMDTC may be the long-pursued agent used for preventive and therapeutic purposes for both acute and chronic Cd(2+) exposure.

Renal-targeting triptolide-glucosamine conjugate exhibits lower toxicity and superior efficacy in attenuation of ischemia/reperfusion renal injury in rats.

AIM: We previously reported a novel triptolide (TP)-glucosamine conjugate (TPG) that specifically accumulated in kidneys and protected renal function from acute ischemia/reperfusion (I/R) injury in rats. In this study we further examined the molecular mechanisms underlying the renoprotective action of TPG. METHODS: The renal-targeting of TPG was investigated in a human proximal renal tubular epithelial cell line (HK-2) by measuring cell uptake of TP or TPG. The effects of TP or TPG on cell cycle distribution and apoptosis rate of HK-2 cells were assessed, and the activities of caspase-3 and caspase-9 were also measured. SD rats were subjected to bilateral renal ischemia by temporarily clamping both renal pedicles. The rats were administered TP (4.17 µmol·kg-1·d-1, iv) or TPG (4.17 µmol·kg-1·d-1, iv) for 3 d before the renal surgery. The kidneys were harvested after 24 h of recovery from the surgery. The levels of oxidative stress, proinflammatory cytokines, chemotactic cytokines and intracellular adhesion molecules in kidneys were examined. RESULTS: The uptake of TPG in HK-2 cells was 2-3 times higher than that of TP at the concentrations tested. Furthermore, TPG targeting the proximal tubules was mediated through interactions with megalin receptors. TP (40-160 nmol/L) concentration-dependently increased G2/M arrest, apoptosis and caspase-3/caspase-9 activity in HK-2 cells, whereas the same concentrations of TPG did not show those features when compared with the control group. In I/R-treated rats, TPG administration caused more robust down-regulation of proinflammatory cytokines (TNF-α, IL-6, IL-1, TGF-ß) and chemotactic cytokines (MCP-1) in the kidneys compared with TP administration, suggesting the inhibition of the proliferation and accumulation of lymphocytes. And TPG administration also caused more prominent inhibition on the levels of oxidative stress and intracellular adhesion molecules in the kidneys, compared with TP administration. CONCLUSION: The renal-targeting TPG is more effective and less toxic than TP, in amelioration of I/R-induced rat renal injury, which may provide a new avenue for the treatment of acute kidney injury.

Multiorgan dysfunction syndrome secondary to joint supplement overdosage in a dog.

A 5-year-old spayed female Bernese mountain dog, with a chief complaint of vomiting and melena ingested approximately 200 nutritional joint supplement tablets. Despite aggressive therapy, the patient developed a coagulopathy, pancreatitis, peritonitis, acute kidney injury, and was euthanized. Postmortem examination revealed myocardial necrosis, pneumonia, centrilobular hemorrhage and necrosis of the liver, vasculitis, and acute tubular necrosis.

Syndrome de défaillance multiviscérale secondaire à un surdosage d'un supplément pour articulation chez un chien. Une chienne Bouvier bernois stérilisée âgée de 5 ans présentée avec une plainte principale de vomissements et de mélæna avait ingéré environ 200 comprimés de suppléments nutritionnels pour les articulations. Malgré une thérapie agressive, la patiente a développé une coagulopathie, une pancréatite, une péritonite et une blessure aiguë aux reins et a été euthanasiée. L'autopsie a révélé une nécrose du myocarde, une pneumonie, une hémorragie centrilobulaire et une nécrose du foie, une vasculite et une nécrose tubulaire.(Traduit par Isabelle Vallières).

Novel glucosamine hydrochloride-rectorite nanocomposites with antioxidant and anti-ultraviolet activity.

In this study, an attempt was made to prepare novel D-glucosamine hydrochloride-rectorite (DGH-REC) nanocomposites with improved antioxidant and anti-ultraviolet activity via the solution-intercalation method. The structure and morphology of DGH-REC nanocomposites were characterized by XRD, TEM, (13)C CP/MAS NMR, FT-IR, XPS and SEM. The results showed that the interlayer distance of REC was enlarged after intercalation of DGH; the largest value reached 11.76 nm, and in this case exfoliation of the REC layer was observed. Moreover, most strong crystals of DGH were greatly disrupted while two other weak crystals of DGH were stronger after intercalation of DGH into REC. More importantly, it was found that DGH-REC nanocomposites showed pronounced antioxidant activity, in contrast with DGH, and the nanocomposites had anti-ultraviolet capacity, which was not observed in DGH. Furthermore, the nanocomposites did not show apparent cytotoxicity. Therefore, DGH-REC nanocomposites have great potential in health or functional food application as compared to DGH.

Chitooligosaccharides antagonize the cytotoxic effect of glucosamine.

Chitooligosaccharides (COS) are partially hydrolyzed compounds derived from chitosan that exhibit a number of biological activities, including antitumor, antibacterial and antifungal properties. In this work, we examined the cytotoxicity of pure COS and oligomers A, B and C (solutions composed of different amounts of COS) produced by enzymatic hydrolysis using a crude enzyme extract produced by the fungus Metarhrizium anisopliae. The antiproliferative effect of these molecules was analyzed using tumor cell lines (HepG2 and HeLa cells) and in a normal cell line (3T3). The antioxidant activity was analyzed in several in vitro experiments. Glucosamine showed higher toxicity (approximately 92%) to all cell lines studied. However, the oligomers obtained after hydrolysis demonstrated no toxic effects on the normal cells (3T3). Furthermore, we showed that a small amount of other COS can decrease the cytotoxic effect of glucosamine against 3T3 cells, indicating that glucosamine could be used as an antitumor drug in the presence of other COS. In addition, different effects were found in antiproliferative assays, which depended on the COS composition in the oligomers (A, B and C), showing that a combination of them may be essential for developing antineoplastic drugs. Superoxide anion scavenging was the main antioxidant activity demonstrated by the COS and oligomers. This activity was also dependent on the oligomer composition of the chitosan hydrolysates. Further work will identify the ideal proportions of COS and glucosamine for maximizing the effects of these biological activities.

Immune Effect Regulated by the Chain Length: Interaction between Immune Cell Surface Receptors and Synthetic Glycopolymers.

Glycopolymer-based drugs for immunotherapy have attracted increasing attention because the affinity between glycans and proteins plays an important role in immune responses. Previous studies indicate that the polymer chain length influences the affinity. In the studies on enhancing the immune response by glycans, it is found that both oligosaccharides and long-chain glycopolymers work well. However, there is a lack of systematic studies on the immune enhancement effect and the binding ability of oligomers and polymers to immune-related proteins. In this paper, to study the influence of the chain length, glycopolymers based on N-acetylglucosamine with different chain lengths were synthesized, and their interaction with immune-related proteins and their effect on dendritic cell maturation were evaluated. It was proved that compared with l-glycopolymers (degree of polymerization (DP) > 20), s-glycopolymers (DP < 20) showed better binding ability to the dendritic cell-specific ICAM-3-grabbing nonintegrin protein and the toll-like receptor 4 and myeloid differentiation factor 2 complex protein by quartz crystal microbalance and molecular docking simulation. When the total sugar unit amounts are equal, s-glycopolymers are proved to be superior in promoting dendritic cell maturation by detecting the expression level of CD80 and CD86 on the surface of dendritic cells. Through the combination of experimental characterization and theoretical simulation, a deep look into the interaction between immune-related proteins and glycopolymers with different chain lengths is helpful to improve the understanding of the immune-related interactions and provides a good theoretical basis for the design of new glycopolymer-based immune drugs.

Synthetic Glycolipids as Molecular Vaccine Adjuvants: Mechanism of Action in Human Cells and In Vivo Activity.

Modern adjuvants for vaccine formulations are immunostimulating agents whose action is based on the activation of pattern recognition receptors (PRRs) by well-defined ligands to boost innate and adaptive immune responses. Monophosphoryl lipid A (MPLA), a detoxified analogue of lipid A, is a clinically approved adjuvant that stimulates toll-like receptor 4 (TLR4). The synthesis of MPLA poses manufacturing and quality assessment challenges. Bridging this gap, we report here the development and preclinical testing of chemically simplified TLR4 agonists that could sustainably be produced in high purity and on a large scale. Underpinned by computational and biological experiments, we show that synthetic monosaccharide-based molecules (FP compounds) bind to the TLR4/MD-2 dimer with submicromolar affinities stabilizing the active receptor conformation. This results in the activation of MyD88- and TRIF-dependent TLR4 signaling and the NLRP3 inflammasome. FP compounds lack in vivo toxicity and exhibit adjuvant activity by stimulating antibody responses with a potency comparable to MPLA.

Protective role of glucagon-like peptide-1 against glucosamine-induced cytotoxicity in pancreatic beta cells.

High doses of glucosamine have been known to induce apoptosis of pancreatic beta cells. The mechanism for this phenomenon has not been clearly elucidated. We aimed to explore the potential mechanisms for glucosamine toxicity in the rat insulinoma cell line INS-1 and in rat native beta cells. We also investigated whether glucagon-like peptide (GLP)-1 could be protective against glucosamine. Glucosamine exhibited dose-dependent inhibition of cell survival and an increase in the cell population at the sub-G1 phase. Glucosamine was revealed to inhibit cellular glucose uptake, resulting in the activation of AMP-activated protein kinase (AMPK). Accordingly, phosphorylation of P70S6K and ribosomal protein S6 (S6RP) was decreased. Protein glycosylation appeared not to be involved in this cytotoxicity. Pretreatment with GLP-1 alleviated glucosamine-mediated inhibition of glucose uptake and lessened AMPK activation, thus allowing recovery of the phosphorylation levels of P70S6K and S6RP. The effect of GLP-1 was blocked by the adenylyl cyclase inhibitor MDL12330A but not by the protein kinase A inhibitor H89. Taken together, these data demonstrate that glucosamine may inhibit beta-cell survival by diminishing cellular glucose uptake independent of glycosylation. This glucosamine toxicity can be blocked by GLP-1, which leads to recovery of the glucose uptake through a PKA-independent, cAMP-dependent mechanism.

O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase activity and mRNA expression in muscle is related to glucosamine-induced insulin resistance.

Glucosamine (GlcN)-induced insulin resistance is associated with an increase in O-linked-N-acetylglucosaminylated modified proteins (O-GlcNAcylated proteins). The role played by O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase (O-GlcNAcase), which removes O-N-acetyl-glucosamine residues from O-GlcNAcylated proteins, has not yet been demonstrated. We investigated whether GlcN-induced whole-body insulin resistance is related to tissue O-GlcNAcase activity and mRNA expression. GlcN (30 mumol/kg/min) or physiological saline (control) was intravenously infused into Sprague-Dawley rats for 2 h. After GlcN treatment, rats were subjected to the following: intravenous glucose tolerance test, insulin tolerance test or removal of the liver, muscle and pancreas. GlcN was found to provoke hyperglycemia compared to control (8.6 +/- 0.41 vs. 4.82 +/- 0.17 mM, p < 0.001). The insulin resistance index (HOMA-IR) increased (15.76 +/- 1.47 vs. 10.14 +/- 1.41, p < 0.001) and the beta-cell function index (HOMA-beta) diminished (182.69 +/- 22.37 vs. 592.01 +/- 103, p < 0.001). Liver glucose concentration was higher in the GlcN group than in the control group (0.37 +/- 0.04 vs. 0.24 +/- 0.038 mmol/g dry weight, p < 0.001). Insulin release index (insulin/glucose) was less in the GlcN group than in the control (2.2 +/- 0.1 vs. 8 +/- 0.8 at 120 min, p < 0.001). In the GlcN group, muscle O-GlcNAcase activity diminished (0.28 +/- 0.019 vs. 0.36 +/- 0.018 nmol of p-nitrophenyl/mg protein/min, p < 0.001), and K(m) increased (1.51 +/- 0.11 vs. 1.12 +/- 0.1 mM, p < 0.001) compared to the control. In the GlcN group, O-GlcNAcase activity/mRNA expression was altered (0.6 +/- 0.07 vs. 1 +/- 0.09 of control, p < 0.05). In conclusion, O-GlcNAcase activity is posttranslationally inhibited during GlcN-induced insulin resistance.

Multivalent Aminosaccharide-Based Gold Nanoparticles as Narrow-Spectrum Antibiotics in Vivo.

Bacterial infection, especially multidrug-resistant (MDR) bacteria-induced wound infection, is an enormous challenge and is the result of the inability of traditional antibiotics to combat MDR bacteria produced by the abuse of broad-spectrum drugs. Here, we present multivalent aminosaccharide-based gold nanoparticles (AuNPs) to remedy the superbug-infected wound. We synthesized multivalent aminosaccharide-based AuNPs via a straightforward method using d-glucosamine (GluN) to modify gold nanoparticles (AuNPs) as reported. This kind of multivalent aminosaccharide-based AuNP (Au_GluN) can lower the bacterial viability in a mature biofilm that may lead to antibiotic resistance. Au_GluN is innocuous not only for erythrocytes in vitro but also for mice. Moreover, it displays an outstanding ability for superbug-infected wound healing. Such a material provides new candidates to treat bacteria in the clinic.

Glucosamine-paracetamol spray-dried solid dispersions with maximized intrinsic dissolution rate, bioavailability and decreased levels of in vivo toxic metabolites.

PURPOSE: This study is aimed at preparing and testing physicochemical, pharmacokinetic and levels of toxic metabolites of paracetamol and glucosamine solid dispersions intended for multiple deliveries via the parenteral or per oral route. METHODS: Solid dispersions were prepared using the spray drying technique at different molar ratios of paracetamol and glucosamine. Characterization of the solid dispersions was carried out using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), equilibrium solubility and intrinsic dissolution rate. In vivo pharmacokinetics and toxic metabolites of the prepared dispersions were evaluated and compared to those of pure drugs and physical mixtures. RESULTS: Instant water solubility and more than 7-fold increase in dissolution rate led to significantly high plasma drug concentration (>6.5-fold) compared to paracetamol alone. More than 2-fold increase in area under the curve from 0 to 24 h from the dispersions was noticed on the third day of oral dosing to animals. Lower number and concentration followed by the complete disappearance of toxic pathway metabolites were observed on second and third days of dosing with solid dispersions and physical mixtures, respectively. CONCLUSIONS: The spray-dried dispersions support safer and more effective delivery of multiple doses of paracetamol, leading to an acceleration of its analgesic actions. Synergism between the analgesic actions of paracetamol and joint protective actions of glucosamine in this combination is expected to facilitate effective treatment of persistent pain-related illnesses such as osteoarthritis.

Proteomic analysis of O-GlcNAc modifications derived from streptozotocin and glucosamine induced beta-cell apoptosis.

The post-translational modifications of Ser and Thr residues by O-linked beta-N-acetylglucosamine (O-GlcNAc), i.e., O-GlcNAcylation, is considered a key means of regulating signaling, in a manner analogous to protein phosphorylation. Furthermore, it has been suggested that the increased flux of glucose through the hexosamine biosynthetic pathway (HBP) stimulates O-GlcNAcylation, and that this may be responsible for many of the manifestations of type 2 diabetes mellitus. To determine whether excessive O-GlcNAcylation of target proteins results in pancreatic beta cell dysfunction, we increased nucleocytoplasmic protein O-GlcNAcylation levels in beta cells by exposing them to streptozotocin and/or glucosamine. Streptozotocin and glucosamine co-treatment increased OGlcNAcylated proteomic patterns as assessed by immunoblotting, and these increases in nuclear and cytoplasmic protein O-GlcNAcylations were accompanied by impaired insulin secretion and enhanced apoptosis in pancreatic beta cells. This observed beta cell dysfunction prompted us to examine Akt and Bcl-2 family member proteins to determine which proteins are O-GlcNAcylated under conditions of high HBP throughput, and how these proteins are associated with beta cell apoptosis. Eventually, we identified ten new O-GlcNAcylated proteins that were expressed during beta cell apoptosis, and analyzed the functional implications of these proteins in relation to pancreatic beta cell dysfunction.

A 90-day ad libitum administration toxicity study of oligoglucosamine in F344 rats.

A 90-day ad libitum administration toxicity study of oligoglucosamine (OG) was carried out using F344 rats of both sexes. The animals were divided into four groups of 20 animals each, 10 of each sex, and fed a diet containing 0, 0.04, 0.2 or 1.0 (w/w)% OG. During the administration period, no animals of either sex died or exhibited abnormal signs in the 0.04% OG and 0.2% OG groups. In the 1% OG group, in both sexes, erythema and swelling of the snout and forelimbs and loss of fur in the forelimbs were observed. On macroscopic observation, emaciation, swelling of the snout, auricles and forelimbs and alopecia of the forelimbs were also observed in 2-3 males of the 1% OG group. It was suggested that these topical abnormalities might be due to dermal responses to OG adhering to the skin and fur, which are easily soiled with saliva during grooming. In the animals of the 1% OG group, food consumption decreased, resulting in body weight gain being suppressed. This was found concomitantly with the abnormal findings mentioned above. Thus, feeding difficulties due to the topical lesions on the snout and forelimbs were thought to affect body weight. In hematology, platelet count, lymphocyte count and differential neutrophil count increased in males of the 1% OG group. These changes might be related to the dermal inflammation. Abnormalities in urinalysis and blood chemistry, as well as a small thymus, small spleen, dark spots or areas on the glandular stomach mucosa, pale Harderian glands and small testes in histopathology, were also observed in males in the 1% OG group. Whether or not all these changes were related only to the malnutrition remains to be elucidated. From these results, OG gave rise to no adverse effects in rats up to the dose level of 0.2 (w/w)%. Thus, the no observed adverse effect level was determined to be 0.2 (w/w)% for rats of either sex (124.0mg/kg/day in males, 142.0mg/kg/day in females).

Quercetin alleviates cell apoptosis and inflammation via the ER stress pathway in vascular endothelial cells cultured in high concentrations of glucosamine.

Glucosamine is a possible cause of vascular endothelial injury in the initial stages of atherosclerosis, through endoplasmic reticulum (ER) stress resulting in fatty streaks in the vascular wall. Quercetin is an anti­diabetic and cardiovascular protective agent that has previously been demonstrated to reduce ER stress in human umbilical vein endothelial cells (HUVECs). The present study aimed to investigate whether quercetin prevents glucosamine­induced apoptosis and inflammation via ER stress pathway in HUVECs. The effect of quercetin on cell viability, apoptosis, and protein expression levels of inflammatory cytokines and ER stress markers was investigated in glucosamine­supplemented HUVECs. Quercetin was demonstrated to protect against glucosamine­induced apoptosis, improved cell viability, and inhibited expression of pro­inflammatory factors and endothelin­1. Quercetin treatment also reduced the expression levels of glucose­regulated protein 78, phosphorylated protein kinase­like ER kinase, phosphorylated c­Jun N­terminal kinase and C/EBP homologous protein. In conclusion, quercetin may have auxiliary therapeutic potential against glucosamine­induced cell apoptosis and inflammation, which may be partially due to alleviation of ER stress.

Chemical modification of SWNT alters in vitro cell-SWNT interactions.

Single-walled carbon nanotubes (SWNT) have been the focus of considerable attention as a material with extraordinary mechanical and electrical properties. SWNT have been proposed in a number of biomedical applications, including neural, bone, and dental tissue engineering. In these applications, it is clear that surrounding tissues will come into surface contact with SWNT composites, and compatibility between SWNT and host cells must be addressed. This investigation describes the gross physical and chemical effects of different SWNT preparations on in vitro cell viability and metabolic activity. Three different SWNT preparations were analyzed: as purchased (AP-NT), purified (PUR-NT), and functionalized with glucosamine (GA-NT), over concentrations of 0.001-1.0% (wt/vol). With the exception of the lowest SWNT concentrations, increasing concentrations of SWNT resulted in a decrease of cell viability, which was dependent on SWNT preparation. The metabolic activity of 3T3 cells was also dependent on SWNT preparation and concentration. These investigations have shown that these SWNT preparations have significant effects on in vitro cellular function that cannot be attributed to one factor alone, but are more likely the result of several unfavorable interactions. Effects, such as destabilizing the cell membrane, soluble toxic contaminants, and limitations in mass transfer as the SWNT coalesce into sheets, may all play a role in these interactions. Using comprehensive purification processes and modifying the NT-surface chemistry to introduce functional groups or reduce hydrophobicity or both, these interactions can be significantly improved.

ß-aminoisobutyric acid attenuates hepatic endoplasmic reticulum stress and glucose/lipid metabolic disturbance in mice with type 2 diabetes.

ß-aminoisobutyric acid (BAIBA) is a nature thymine catabolite, and contributes to exercise-induced protection from metabolic diseases. Here we show the therapeutical effects of BAIBA on hepatic endoplasmic reticulum (ER) stress and glucose/lipid metabolic disturbance in diabetes. Type 2 diabetes was induced by combined streptozotocin (STZ) and high-fat diet (HFD) in mice. Oral administration of BAIBA for 4 weeks reduced blood glucose and lipids levels, hepatic key enzymes of gluconeogenesis and lipogenesis expressions, attenuated hepatic insulin resistance and lipid accumulation, and improved insulin signaling in type 2 diabetic mice. BAIBA reduced hepatic ER stress and apoptosis in type 2 diabetic mice. Furthermore, BAIBA alleviated ER stress in human hepatocellular carcinoma (HepG2) cells with glucosamine-induced insulin resistance. Hepatic AMPK phosphorylation was reduced in STZ/HFD mice and glucosamine-treated HepG2 cells, which were restored by BAIBA treatment. The suppressive effects of BAIBA on glucosamine-induced ER stress were reversed by knockdown of AMPK with siRNA. In addition, BAIBA prevented thapsigargin- or tunicamycin-induced ER stress, and tunicamycin-induced apoptosis in HepG2 cells. These results indicate that BAIBA attenuates hepatic ER stress, apoptosis and glucose/lipid metabolic disturbance in mice with type 2 diabetes. AMPK signaling is involved to the role of BAIBA in attenuating ER stress.

Glucosamine-glycerophospholipids that activate cell-matrix adhesion and migration.

Two new analogues derived from the platelet activating factor (PAF), containing glucosamine instead of the acetyl group, were synthesized, and their effect on the human keratinocyte cell line HaCaT was evaluated with respect to cytotoxicity, proliferation, adhesion, and migration. Starting with (R)-1,2-isopropylideneglycerol (3), the glycosylation acceptor 1-O-octadecyl-3-O-tert-butyldimethylsilyl-sn-glycerol (6) was synthesized in three steps. Glycosylation of 6 with the already known O-(3,4,6-tri-O-acetyl-2-deoxy-2-dimethylmaleimido-beta-D-glycopyranosyl)trichloracetimidate gave 1-O-octadecyl-2-O-(3',4',6'-tri-O-acetyl-2'-deoxy-2'-dimethylmaleimido-beta-D-glucopyranosyl)-3-O-tert-butyldimethylsilyl-sn-glycerol (7). After removing the (tert-butyldimethyl)silyl (TBDMS) group with FeCl3x6H2O, phosphoryl choline was introduced, yielding [1-O-octadecyl-2-O-(2'-deoxy-2'-dimethylmaleimido-beta-D-glucopyranosyl)-sn-glycero(3)]phosphorylcholine (2) (glucosimide-PAF). pH controlled cleavage of the amino protection group gave [1-O-octadecyl-2-O-(2'-deoxy-2'-amino-beta-D-glucopyranosyl)-sn-glycero(3)]phosphorylcholine hydrochloride (1) (glucosamine-PAF). 2 inhibited proliferation of HaCaT cells by 26% at nontoxic concentrations, while 1 increased the proliferation rate by 30% at low concentrations. At higher concentrations, both compounds showed cytotoxic properties with LD50 = 30 micromol/L (1) and LD50 = 5-6 micromol/L (2). Both 1 and 2 were potent promoters of cell adhesion and migration of HaCaT cells.

Predominant role of the substituents on the hydroxyl groups of 3-hydroxy fatty acids of non-reducing glucosamine in lipid A for the endotoxic and antagonistic activity.

The synthetic disaccharide precursor of lipid A (406: identical to lipid IVA) was found to reduce its endotoxic activity in mice by an order of 10(5) or more, by replacing the hydroxyl groups with succinyl or acetyl residues. Both the succinylated and acetylated 406 were also found to antagonize the endotoxic mitogenicity on murine splenocytes. Previous studies demonstrated that the succinylated or acetylated synthetic complete lipid A preparations retained the whole endotoxic activity [1994, Infect. Immunol. 62, 1705]. The drastic contrast in all of these results suggests the importance of the substituents on the hydroxyl groups of 3-hydroxy fatty acids of non-reducing glucosamine of lipid A for the activity and for transformation to the antagonistic structure.