Two α-dicarbonyls downregulate migration, invasion, and adhesion of liver cancer cells in a p53-dependent manner
2013, Digestive and Liver Disease
Hepatocellular carcinoma accounts for more than 600,000 deaths per year due to it being a highly invasive tumor. The α-dicarbonyl, methylglyoxal demonstrates efficacy at reducing tumor burden, however the anti-cancerous activities of 3-deoxyglucosone, have never been studied.
To determine the anti-cancerous potential of methylglyoxal and 3-deoxyglucosone on liver tumor cells.
The in vitro effects of methylglyoxal and 3-deoxyglucosone were studied by investigating migration, invasion, and adhesion of Huh-7, HepG2, and Hep3B cells.
3-Deoxyglucosone inhibited migration of Huh-7 and HepG2 cells. Methylglyoxal decreased migration of HepG2 cells. Additionally, 3-deoxyglucosone and methylglyoxal impaired invasion, and adhesion of Huh-7 and HepG2 cells. In Hep3B cells, a p53 null cell line, 3-deoxyglucosone and methylglyoxal had no effect on migration, invasion, or adhesion. However, both compounds inhibited invasion of wild-type p53 transfected Hep3B cells. Silencing of p53 in Huh-7 and HepG2 cells abrogated the effects of the α-dicarbonyls on cell invasion. 3DG and MG did not alter p53 total protein but promoted nuclear translocation of p53.
These studies suggest that 3-deoxyglucosone and methylglyoxal impair invasion, migration, and adhesion of hepatocellular carcinoma. The effects of both compounds on cell invasion are dependent on p53 and imply that α-dicarbonyls could be efficacious in the treatment of p53-expressing invasive liver tumors.
Immunochemical detection of 3-deoxyglucosone in serum
2004, Biochemical and Biophysical Research Communications
3-Deoxyglucosone (3-DG) is a metabolite of glucose that is thought to lead to the production of advanced glycation end products in diabetes. The previous assay for 3-DG in serum was based on a multi-step protocol, including derivatization, extraction, HPLC separation, and detection. In the current studies, we established a monoclonal antibody that recognizes the 3-DG-derivative, which is generated by the reaction of 3-DG and a 2,3-diamino-benzene derivative. Attachment of a biotin moiety to the 2,3-diamino-benzene ring via a linker allowed development of a highly sensitive chemiluminescent enzyme immunoassay for 3-DG equivalents. Unlike the previous assay, this method does not require extraction of 3-DG derivatives from serum. Treatment of 3-DG in serum with the DAB-link-biotin produced a quinoxaline derivative, which was specifically recognized by the monoclonal antibody. Using this assay, we found that serum 3-DG was higher in streptozotocin-induced diabetic rats than in normal control rats (25±5.6 vs. 9.8±1.1μg/L). This simple assay may allow the monitoring of conditions leading to the accumulation of advanced glycation end products and evaluation of the risk of complications in diabetic patients.
Metformin inhibition of glycation processes
2003, Diabetes and Metabolism
A number of studies have shown that metformin is beneficial in reducing diabetes associated vascular risk beyond the benefits expected from its antihyperglycaemic effect. One of the main pathogenic mechanisms leading to chronic complications of diabetes is non-enzymatic glycation where damage is mediated through increased production of highly chemically reactive glucose and α-dicarbonyl compounds which lead to production of advanced glycation products (AGEs). We present laboratory and clinical data supporting the hypothesis that one important explanation of metformin's effect on diabetic complications could be its ability to reduce toxic dicarbonyls and AGEs. This effect could be related either to the binding of the α-dicarbonyls, methylglyoxal (MG) or 3-deoxyglucosone, or to an increase in enzymatic detoxification. Our studies presented in this manuscript document extracellular binding of MG by metformin to form a specific product (triazepinone) in vivo. This condensation product appears to be only one of several inactive end products resulting from this chemical reaction and we discuss the possibility that these or other condensation products (hydroimidazolones) could be indicative of inactivation of MG by metformin. Additional studies of other possible condensation products, as well as other potential cellular effects of metformin on MG production, will help to clarify this potentially important effect of metformin and provide a further rationale for using metformin to prevent long-term complications.
Glycation - A sweet tempter for neuronal death
2003, Brain Research Reviews
Glycation, one of the post-translational modifications of proteins, is a nonenzymatic reaction initiated by the primary addition of a sugar aldehyde or ketone to the amino groups of proteins. In the early stage of glycation, the synthesis of intermediates leading to the formation of Amadori compounds occurs. In the late stage, advanced glycation end products (AGE) are irreversibly formed after a complex cascade of reactions. Several AGEs have been characterized chemically, while other new compounds remain to be identified. To date, studies of the contribution of glycation to diseases have been primarily focused on its relationship to diabetes and diabetes-related complications. However, glucose-induced damage is not limited to diabetic patients. Although it does not cause rapid or remarkable cell damage, glycation advances slowly and accompanies every fundamental process of cellular metabolism. It has recently become clear that glycation also affects physiological aging and neurodegenerative diseases such as Alzheimer’s disease and amyotrophic lateral sclerosis. Glycation alters the biological activity of proteins and their degradation processes. Protein cross-linking by AGE results in the formation of detergent-insoluble and protease-resistant aggregates. Such aggregates may interfere with both axonal transport and intracellular protein traffic in neurons. In addition, glycation reactions lead to the production of reactive oxygen species. Conversely, glycation is promoted by oxidative stress. We speculate on the presence of synergism between glycation and oxidative stress. In this review, we provide an outline of glycation and propose some possible mechanisms of its cytotoxicity and defense systems against it.
Identification in human atherosclerotic lesions of GA-pyridine, a novel structure derived from glycolaldehyde-modified proteins
2002, Journal of Biological Chemistry
Glycolaldehyde (GA) is formed from serine by action of myeloperoxidase and reacts with proteins to form several products. Prominent among them isN ε-(carboxymethyl)lysine (CML), which is also known as one of the advanced glycation end products. Because CML is formed from a wide range of precursors, we have attempted to identify unique structures characteristic of the reaction of GA with protein. To this end, monoclonal (GA5 and 1A12) and polyclonal (non-CML-GA) antibodies specific for GA-modified proteins were prepared. These antibodies specifically reacted with GA-modified and with hypochlorous acid-modified BSA, but not with BSA modified by other aldehydes, indicating that the epitope of these antibodies could be a specific marker for myeloperoxidase-induced protein modification. By HPLC purification from GA-modifiedN α-(carbobenzyloxy)-l-lysine, GA5-reactive compound was isolated, and its chemical structure was characterized as 3-hydroxy-4-hydroxymethyl-1-(5-amino-5-carboxypentyl) pyridinium cation. This compound named as GA-pyridine was recognized both by 1A12 and non-CML-GA, indicating that GA-pyridine is an important antigenic structure in GA-modified proteins. Immunohistochemical studies with GA5 demonstrated the accumulation of GA-pyridine in the cytoplasm of foam cells and extracellularly in the central region of atheroma in human atherosclerotic lesions. These results suggest that myeloperoxidase-mediated protein modification via GA may contribute to atherogenesis.
Gas chromatographic-mass spectrometric determination of erythrocyte 3-deoxyglucosone in diabetic patients
2002, Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences
To determine if the erythrocyte levels of 3-deoxyglucosone (3-DG) are increased in diabetic patients, and if they correlate with glycemic status, they were measured in diabetic patients without renal disease as well as in healthy subjects. The erythrocyte levels of 3-DG were measured by a selected ion monitoring method of gas chromatography–chemical ionization mass spectrometry using [13C6]-3-DG as an internal standard. The erythrocyte levels of 3-DG were significantly higher in diabetic patients than in healthy subjects. The erythrocyte concentration of 3-DG was significantly and positively correlated with HbA1c (r=0.84, P<0.001). However, no significant correlation could be found between erythrocyte 3-DG and age, onset age of diabetes, or duration of diabetes in our group of diabetic patients. In diabetes, the production of 3-DG in the erythrocytes is increased via the polyol pathway and/or the Maillard reaction due to hyperglycemia.
The metabolites of Ambinine, a benzo[c]phenanthridine alkaloid, in rats identified by ultra-performance liquid chromatography–quadrupoletime-of-flight mass spectrometry (UPLC/Q-TOF-MS/MS)
Journal of Chromatography B, Volumes 1033–1034, 2016, pp. 226-233
Ambinine (AM), one of the major hexahydrobenzo[c]phenanthridine alkaloids from Corydalis ambigua Cham. et Schlecht. var. amurensis Maxim, is considered to be an important compound because of its special content and activity. However, there are few published studies on AM metabolism. In this research, the metabolism of AM in vivo was comprehensively studied for the first time. A total 44 metabolites (including 13 phase I and 31 phase II metabolites) as well as its parent drug in plasma, bile, urine and feces of rats were identified and 41 of them were reported for the first time. The results obtained indicated that demethylation, sulfation and glucuronidation were the major metabolic pathways of AM in vivo. Furthermore, this study provides valuable and new information about the metabolism of AM, which will be very helpful for understanding the safety and efficacy of AM, as well as its analogues.
Epigallocatechin-3-gallate inhibits proliferation of human aortic smooth muscle cells via up-regulating expression of mitofusin 2
European Journal of Cell Biology, Volume 93, Issue 4, 2014, pp. 137-144
Previous studies have shown that epigallocatechin-3-gallate (EGCG) inhibits the proliferation of vascular smooth muscle cells (VSMCs) via the extracellular-signal-regulated kinase (ERK1/2) and mitogen activated protein kinases (MAPKs) pathway. Mitofusin 2 (Mfn-2) also suppresses VSMC proliferation through Ras-Raf-ERK/MAPK, suggesting a possible link between EGCG, Mfn-2 and ERK/MAPK. However, the effect of EGCG on Mfn-2 remains unknown. In this study, we investigated the role of Mfn-2 in the regulation of VSMC proliferation by EGCG, and assessed the underlying mechanisms. The effects of EGCG on the proliferation of cultured human aortic smooth muscle cells (HASMCs) were observed by 5-ethynl-2-deoxyuridine (EdU) incorporation assay. Mfn-2 gene and protein levels, and Ras, p-c-Raf and p-ERK1/2 protein levels were determined by quantitative real-time polymerase chain reaction and western blotting, respectively. Mfn-2 gene silencing was achieved by RNA interference. EGCG 50μmol/L profoundly inhibited the proliferation of HASMCs in culture, up-regulated Mfn-2, and down-regulated the expression of p-c-Raf and p-ERK1/2. Furthermore, RNA interference-mediated gene knockdown of Mfn-2 antagonized EGCG-induced anti-proliferation and down-regulation of Ras, p-c-Raf and p-ERK1/2. These results suggest that EGCG inhibits the proliferation of HASMCs in vitro largely via Mfn-2-mediated suppression of the Ras-Raf-ERK/MAPK signaling pathway.
Selective inhibition of 20-hydroxyeicosatetraenoic acid lowers blood pressure in a rat model of preeclampsia
Prostaglandins & Other Lipid Mediators, Volume 134, 2018, pp. 108-113
Little is currently known of the role(s) of the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE) in hypertensive pregnancies. We hypothesized that specific inhibition of 20-HETE would attenuate increases in blood pressure in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. Specific 20-HETE synthesis inhibitor HET0016 (1mg/kg) was administered daily to RUPP rats from gestational days 14–18. Blood pressure (BP) increased in RUPP rats and was decreased with HET0016 administration. BP was unchanged in NP+HET0016 rats. Fetal death greatly increased in RUPP rats and was reduced in RUPP+HET0016 rats. 20-HETE levels increased modestly in RUPP rats compared to NP and was reduced in both NP+HET0016 and RUPP+HET0016 rats. Furthermore, circulating levels of HETEs, EET, and DHETE were significantly altered between groups. HET0016 shifted CYP metabolism toward EETs, as indicated by a decrease in plasma 20-HETE:EETs in RUPP+HET0016 rats compared to RUPP. In conclusion, 20-HETE inhibition in RUPP rats reduces BP and fetal death, and is associated with an increase in EET/20-HETE ratio.
Design and synthesis of 4′-O-alkyl-chitobiosyl-4-methylumbelliferone as human chitinase fluorogenic substrates
Carbohydrate Research, Volume 399, 2014, pp. 26-37
The synthesis of three fluorogenic chitobiosyl derivatives, modified at the non-reducing 4′-OH with, either a methyl, an isopropyl or a cyclohexylmethyl substituent, is described. The 4′-capped 4-methylumbelliferyl chitobiosides are hydrolysed by the human chitinase CHIT1 following Michaelis–Menten kinetics and in contrast to unmodified chitobiosyl-4-methylumbelliferone do not undergo transglycosylation. The compounds are also relatively poor hexosaminidase substrates and thus provide useful alternatives to 4′-deoxychitobiosyl-4-methylumbelliferone, previously reported by us as fluorogenic substrate to monitor CHIT1 activity as a marker for Gaucher disease state.
Seasonal variation in the cross-shelf distribution of seabirds in the southeastern Bering Sea
Deep Sea Research Part II: Topical Studies in Oceanography, Volume 109, 2014, pp. 266-281
We tested the hypothesis that the distribution of seabird species' associations across the southeastern Bering Sea shelf reflects the underlying ecology of four bathymetrically-defined hydrographic domains: the Inner or Coastal Shelf Domain (depth (Z)<50m), the Middle Shelf Domain (50m<Z<100m), the Outer Shelf Domain (100m<Z<200m), and the Shelf-Slope Domain (200m<Z<3000m). The domains differ in stratification, which intensifies from winter to summer and breaks down in the fall. To examine seabird distributions with respect to these domains in multiple seasons, we quantified the cross-shelf distribution of species with respect to water depth using a 37-year database. We then used a multivariate tree analysis to group species with similar depth-use distributions, and mapped these clusters against the hydrographic domains. There were three patterns of seabird depth use: an inshore, shallow-water group in summer and fall, but not winter and spring, which conformed roughly to the Inner Shelf Domain; a group of species that were distributed widely across the Middle and Outer Shelf Domains, and a third group of species that occupied the outer portion of the Outer Shelf Domain and the Shelf-Slope Domain. The multivariate tree analysis revealed close correspondence between the seabird-derived domains and the bathymetrically-defined Outer Shelf and Shelf-Slope domains in spring and to a lesser extent in summer. In summer and fall, and to a lesser extent in spring, the seabird groupings showed a differentiation between the Inner Shelf Domain and the Middle Shelf Domain. Seabird-derived differentiation between the Shelf-Slope Domain and the Outer Shelf Domain was strongest in spring and summer. These seasonal patterns likely reflected the seasonal variation in the hydrographic differentiation of the bathymetrically-defined domains. Cross-validation of the multivariate tree analysis showed that the portion of seabird distribution patterns explained by the tree analysis was smallest in winter (when there is no stratification on the middle and inner shelves) and greatest in summer (when stratified water columns result in hydrographically defined domains), as would be expected under our hypothesis. We also examined hypotheses predicting why pursuit diving seabirds most often forage in shallow water whereas surface-foraging (surface-seizing) seabirds are more common over deep offshore waters. The hypothesis for regionally enhanced primary production as a driving factor was not supported for the inshore foraging seabirds but was supported for those foraging over shelf-slope waters.
Cross-sectional study of the determinants and associations of sex hormone-binding globulin concentrations in first degree relatives (FDR) of patients with Type 2 Diabetes Mellitus
Diabetes Research and Clinical Practice, Volume 133, 2017, pp. 159-167
This study explores the determinants of sex hormone binding globulin (SHBG) and associations with categories of glucose intolerance and undiagnosed diabetes in first-degree relatives (FDR) of patients with Type 2 Diabetes Mellitus (T2D).
Anthropometric indices, fasting lipids, glucose, insulin, adiponectin, leptin, SHBG, estradiol (E2), testosterone (TT), androstenedione (AND), dehydroepiandrosterone sulphate (DHEA-S), high-sensitivity C-reactive protein (hs-CRP) and alanine aminotransferase (ALT) were measured in 584 FDR. Homeostasis model assessment-estimate of insulin resistance (HOMA-IR), beta cell function (%B), insulin sensitivity (%S) and free androgen index (FAI) were calculated.
266 subjects were normoglycemic; 237 had prediabetes and 81 had undiagnosed diabetes. SHBG decreased stepwise with worsening categories of glucose intolerance in females whereas FAI decreased stepwise with worsening categories in males only. SHBG showed significant positive correlations with adiponectin, and HDL-C and significant negative correlations with body mass index (BMI), waist circumference (WC), Waist:hip ratio (WHR), ALT, triglycerides (TG), %B, leptin and FAI. After adjustment for WHR, only HDL-C and FAI in men and FAI and HbA1c in females remained significantly associated with SHBG. Receiver Operating Characteristic (ROC) curve analysis for detection of diabetes showed that areas under the curve for FAI and SHBG were 0.711 and 0.386 for males and 0.430 and 0.660 for females respectively.
Associations of SHBG with some anthropometric and metabolic variables in FDR suggests that lower levels is a marker for risk of developing T2D through obesity dependent metabolic pathways but low FAI is a better marker of state of diabetes in males.
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