Glyoxal and methylglyoxal: Autoxidation from dihydroxyacetone and polyphenol cytoprotective antioxidant mechanisms

Brewing and biochemical characterization of Camellia japonica petal wine with comprehensive discussion on metabolomics

A novel wine has been developed from Camellia japonica’s petal by fermenting the decoction with Saccharomyces cerevisiae or brewer’s yeast. pH, brix, specific gravity and alcohol percentage were tested to study the physicochemical properties of the wine. Qualitative tests indicated presence of phenols such as flavonoids, coumarins; protein; glycosides; glycerin; terpenoids; steroids; and fatty acids in the wine. Total phenol content was found high in the decoction and in its fermented form as well. In vitro biological activities such as antioxidant activity, antidiabetic activity and lipid peroxidation inhibition power were assessed in samples. Furthermore, GC-MS analysis helped to detect volatiles present in the unfermented decoction and understand the effect of fermentation on its changing metabolome while column chromatography assisted the separation of solvent-based fractions. Notable outcomes from this study were detection of bioactive compound quinic acid in the decoction and a proposed pathway of its metabolic breakdown after fermentation. Results of this research revealed biochemical and physicochemical acceptability of this wine prepared from an underutilized flower.

Diet and Obesity-Induced Methylglyoxal Production and Links to Metabolic Disease

The obesity rate in the United States is 42.4% and has become a national epidemic. Obesity is a complex condition that is influenced by socioeconomic status, ethnicity, genetics, age, and diet. Increased consumption of a Western diet, one that is high in processed foods, red meat, and sugar content, is associated with elevated obesity rates. Factors that increase obesity risk, such as socioeconomic status, also increase consumption of a Western diet because of a limited access to healthier options and greater affordability of processed foods. Obesity is a public health threat because it increases the risk of several pathologies, including atherosclerosis, diabetes, and cancer. The molecular mechanisms linking obesity to disease onset and progression are not well understood, but a proposed mechanism is physiological changes caused by altered lipid peroxidation, glycolysis, and protein metabolism. These metabolic pathways give rise to reactive molecules such as the abundant electrophile methylglyoxal (MG), which covalently modifies nucleic acids and proteins. MG-adducts are associated with obesity-linked pathologies and may have potential for biomonitoring to determine the risk of disease onset and progression. MG-adducts may also play a role in disease progression because they are mutagenic and directly impact protein stability and function. In this review, we discuss how obesity drives metabolic alterations, how these alterations lead to MG production, the association of MG-adducts with disease, and the potential impact of MG-adducts on cellular function.

Glyoxal and Methylglyoxal as E-cigarette Vapor Ingredients-Induced Pro-Inflammatory Cytokine and Mucins Expression in Human Nasal Epithelial Cells

BACKGROUND

Glyoxal (GO), and methylglyoxal (MGO) are among the most toxic compounds emitted by electronic cigarette (E-cig) and regular tobacco cigarette smoke. Airway diseases presented mucus over production as their major pathophysiologic feature. However, the effects of GO and MGO on pro-inflammatory cytokines and mucin expression in human nasal epithelial cells, as well as the underlying signaling pathway, have not yet been studied.

OBJECTIVE

This study is to determine whether GO and MGO induce pro-inflammatory cytokines, and MUC5AC/5B expression via mitogen-activated protein kinase (MAPK)s and nuclear factor-kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathways.

METHODS

The effect of GO, and MGO on pro-inflammatory cytokines, mucins expression and the signalling pathway of GO and MGO were investigated using water-soluble tetrazolium salt-1, enzyme immunoassays, and immunoblot analysis with specific inhibitors and small interfering RNA.

RESULTS

GO and MGO did not affect cell viability up to 2 mM in human nasal epithelial cells. GO and MGO increased production of pro-inflammatory such as interleukin (IL)-1β and IL-6) and MUC5AC/5B. Additionally, GO and MGO significantly activated extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, and NF-κB. Whether ERK1/2, p38 MAPK, and NF-κB signaling pathway were involved in GO and MGO-induced production of pro-inflammatory cytokines (IL-1β and IL-6) and MUC5AC/5B, we used specific inhibitors and siRNA transfection. These significantly repressed GO- and MGO-induced expression of pro-inflammatory cytokines (IL-1β and IL-6) and MUC5AC/5B.

CONCLUSIONS

GO and MGO induced pro-inflammatory cytokines and MUC5AC/5B expression via ERK1/2, p38 MAPK, and NF-κB in human nasal epithelial cells. These results suggested that GO and MGO may be involved in mucus hypersecretion-related airway diseases.

Chemical and Metabolic Controls on Dihydroxyacetone Metabolism Lead to Suboptimal Growth of Escherichia coli

DHA is an attractive triose molecule with a wide range of applications, notably in cosmetics and the food and pharmaceutical industries. DHA is found in many species, from microorganisms to humans, and can be used by Escherichia coli as a growth substrate. However, knowledge about the mechanisms and regulation of this process is currently lacking, motivating our investigation of DHA metabolism in E. coli. We show that under aerobic conditions, E. coli growth on DHA is far from optimal and is hindered by chemical, hierarchical, and possibly allosteric constraints. We show that optimal growth on DHA can be restored by releasing the hierarchical constraint. These results improve our understanding of DHA metabolism and are likely to help unlock biotechnological applications involving DHA as an intermediate, such as the bioconversion of glycerol or C₁ substrates into value-added chemicals.

In this work, we shed light on the metabolism of dihydroxyacetone (DHA), a versatile, ubiquitous, and important intermediate for various chemicals in industry, by analyzing its metabolism at the system level in Escherichia coli. Using constraint-based modeling, we show that the growth of E. coli on DHA is suboptimal and identify the potential causes. Nuclear magnetic resonance analysis shows that DHA is degraded nonenzymatically into substrates known to be unfavorable to high growth rates. Transcriptomic analysis reveals that DHA promotes genes involved in biofilm formation, which may reduce the bacterial growth rate. Functional analysis of the genes involved in DHA metabolism proves that under the aerobic conditions used in this study, DHA is mainly assimilated via the dihydroxyacetone kinase pathway. In addition, these results show that the alternative routes of DHA assimilation (i.e., the glycerol and fructose-6-phosphate aldolase pathways) are not fully activated under our conditions because of anaerobically mediated hierarchical control. These pathways are therefore certainly unable to sustain fluxes as high as the ones predicted in silico for optimal aerobic growth on DHA. Overexpressing some of the genes in these pathways releases these constraints and restores the predicted optimal growth on DHA.

IMPORTANCE DHA is an attractive triose molecule with a wide range of applications, notably in cosmetics and the food and pharmaceutical industries. DHA is found in many species, from microorganisms to humans, and can be used by Escherichia coli as a growth substrate. However, knowledge about the mechanisms and regulation of this process is currently lacking, motivating our investigation of DHA metabolism in E. coli. We show that under aerobic conditions, E. coli growth on DHA is far from optimal and is hindered by chemical, hierarchical, and possibly allosteric constraints. We show that optimal growth on DHA can be restored by releasing the hierarchical constraint. These results improve our understanding of DHA metabolism and are likely to help unlock biotechnological applications involving DHA as an intermediate, such as the bioconversion of glycerol or C₁ substrates into value-added chemicals.

A Hypothesis: Moderate Consumption of Alcohol Contributes to Lower Prevalence of Type 2 Diabetes Due to the Scavenging of Alpha-Dicarbonyls by Dietary Polyphenols

The world is experiencing an epidemic of type-2-diabetes mellitus (T2DM). This has led to increased morbidity and mortality, explosive growth in health care budgets, and an even greater adverse, if indirect, impact on societies and economies of affected countries. While genetic susceptibility to T2DM is a major determinant of its prevalence, changes in lifestyles also play a role. One such change has been a transition from traditional diets characterized by low caloric and high nutrient density to calorie-rich but nutrient-poor Western diets. Given this, one solution to the epidemic of T2DM would be to abandon Western diets and revert to traditional eating patterns. However, traditional diets cannot provide enough calories for the increasing global population, so transition from traditional to Western foodstuffs appears to be irreversible. Consequently, the only practical solution to problems caused by these changes is to modify Western diets, possibly by supplementing them with functional foods containing nutrients that would compensate for these dietary deficits. I present in this study a hypothesis to explain why shifts from traditional to Western diets have been so problematic and to suggest nutrients that may counteract these adverse effects. I postulate that the components of traditional diets that may compensate for deficiencies of Westerns diets are scavengers of reactive α-dicarbonyls produced as unavoidable by-products of glucose and lipid metabolism. Most important among these scavengers are some plant secondary metabolites: polyphenols, phlorotannins, and carotenoids. They are found in alcoholic beverages and are abundant in seasonings, cocoa, coffee, tea, whole grains, pigmented vegetables, fruits, and berries.

Glyoxal toxicity in isolated rat liver mitochondria

Glyoxal is a physiological metabolite formed by lipid peroxidation, ascorbate autoxidation, oxidative degradation of glucose, and degradation of glycated proteins. Glyoxal has been linked to oxidative stress and can cause a number of cellular damages, including covalent modification of amino and thiol groups of proteins to form advanced glycation end products. However, the mechanism of glyoxal toxicity has not been fully understood. In this study, we have focused on glyoxal toxicity in isolated rat liver mitochondria. Isolated mitochondria (0.5 mg protein per milliliter) were prepared from the Wistar rat liver using differential centrifugation and incubated with various concentrations of glyoxal (1, 2.5, 5, 7.5, and 10 mM) for 30 min. The activity of mitochondrial complex II was determined by measurement of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) conversion. The mitochondrial membrane potential (MMP), lipid peroxidation (MDA), reactive oxygen species (ROS) formation, glutathione (GSH) content, and protein carbonylation were also assessed. After an incubation of isolated liver mitochondria with glyoxal, disrupted electron transport chain, increased mitochondrial ROS formation, lipid peroxidation, mitochondrial membrane damage, GSH oxidation, and protein carbonylation ensued as compared to the control group ( p < 0.05). Glyoxal toxicity in isolated rat liver mitochondria was dose-dependent. In conclusion, glyoxal impaired the electron transport chain, which is the cause of increased ROS and MDA production, depletion of GSH, and disruption of MMP. Mitotoxicity of glyoxal might be related to the pathomechanisms involved in diabetes and its complications.

Fructose as an inducer of free radical peroxidation of natural lipid-protein supramolecular complexes

D-fructose strongly stimulates peroxidation of natural lipid-protein supramolecular complexes in vitro regardless of the oxidation initiation method. Fructose (ketose) intensifies free radical peroxidation to a much greater extent than glucose (aldose), which is important for the etiology and pathogenesis of diabetes mellitus.

Curcumin inhibits advanced glycation end product-induced oxidative stress and inflammatory responses in endothelial cell damage via trapping methylglyoxal

Methylglyoxal (MGO)-induced carbonyl stress and pro-inflammatory responses have been suggested to contribute to endothelial dysfunction. Curcumin (Cur), a polyphenolic compound from Curcuma longa L., may protect endothelial cells against carbonyl stress-induced damage by trapping dicarbonyl compounds such as MGO. However, Cur-MGO adducts have not been studied in depth to date and it remains to be known whether Cur-MGO adducts are able to attenuate endothelial damage by trapping MGO. In the present study, 1,2-diaminobenzene was reacted with MGO to ensure the reliability of the reaction system. Cur was demonstrated to trap MGO at a 1:1 ratio to form adducts 1, 2 and 3 within 720 min. The structures of these adducts were identified by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry. The kinetic curves of Cur (10(-7), 10(-6) and 10(-5) M) were measured from 0-168 h by fluorescent intensity. Cur significantly inhibited the formation of advanced glycation end products (AGEs). The differences in oxidative damage and the levels of pro-inflammatory cytokines following MGO + HSA or Cur-MGO treatment were investigated in human umbilical vein endothelial cells (HUVECs). Exposure of HUVECs to the Cur-MGO reaction adducts significantly reduced the intracellular ROS levels and improved cell viability compared with MGO alone. Furthermore, there was a significant reduction in the expression levels of transforming growth factor-β1 and intercellular adhesion molecule(-1) following treatment with Cur-MGO adducts compared with MGO alone. These results provide further evidence that the trapping of MGO by Cur inhibits the formation of AGEs. The current study indicates that the protective effect of Cur on carbonyl stress and pro-inflammatory responses in endothelial damage occurs via the trapping of MGO.

Protective activity of gallic acid against glyoxal -induced renal fibrosis in experimental rats

This study was designed to evaluate the protective activity of gallic acid (GA) against glyoxal (GO) an advanced glycation intermediate-induced renal fibrosis in experimental rats. Glyoxal (i.p) at a dose of 15 mg/Kg body weight/day for 4 weeks induces renal fibrosis. GA was administered orally (100 mg/Kg body weight/day) along with GO for 4 weeks. The anti-fibrotic activity of GA was analyzed by measuring the collagen synthesis and deposition in renal tissues using mRNA expression analysis and Masson trichrome staining (MTS), respectively. The nephroprotective potential of GA was assessed by quantifying the markers of kidney damage such as serum blood-urea-nitrogen (BUN), creatinine (CR) and alkaline phosphatase (AP). Moreover, basement membrane damage in renal tissues was analysed by periodic acid Schiff’s (PAS) staining. GA co-treatment markedly suppressed the GO-induced elevation in mRNA expression of collagenIand III, MMP-2, MMP-9 and NOX (p < 0.05, respectively) genes as compared with GO alone infused rats. In addition, GA co-treatment significantly attenuated the GO -induced elevation in serum markers such as BUN, CR and AP levels (p < 0.05, respectively). Furthermore, GA co-treatment restored back the decreased renal super oxide dismutase (SOD) activity (p < 0.05) thereby assuage the reactive oxygen species (ROS) generation, and maintained the normal architecture of glomerulus. The present study clearly indicates that GO -induces renal fibrosis by enhancing GO/receptor of advanced glycation end product (RAGE) induced ROS generation and GA effectively counteracted GO-induced renal fibrosis by its ROS quenching and anti-glycation activity.

Rutin stimulates sarcoplasmic reticulum Ca(2+)-ATPase activity (SERCA1) and protects SERCA1 from peroxynitrite mediated injury

In this study we analyzed the protective action of the flavonoid rutin on peroxynitrite (ONOO(-)) mediated impairment of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA1 isoform), especially related to posttranslational and conformational changes. Rutin concentration dependently protected ONOO(-) induced SERCA1 activity decrease with effective concentration EC50 of 18 ± 1.5 µM. Upon treatment with ONOO(-), this flavonoid also prevented SERCA1 from thiol group oxidation and significantly reduced tyrosine nitration and protein carbonyl formation. In the absence of ONOO(-), rutin (250 and 350 µM) stimulated SERCA1 activity at 2.1 mM [ATP] and 10 µM [Ca(2+)]free. According to changes in the kinetic parameters V max and K m with regard to [ATP], rutin (250 µM) increased the rate of enzyme catalysis and decreased the affinity of SERCA1 to ATP. FITC fluorescence decreased in the presence of rutin (150 and 250 µM), indicating conformational changes in the cytosolic ATP binding region of SERCA1. In silico study confirmed the binding of rutin in the cytosolic region of SERCA1, in the vicinity of the ATP binding site. Residue Glu183 localized within the conserved TGES loop was identified to play a key role in rutin-SERCA1 interaction (H-bond length of 1.7 Å), elucidating the ability of rutin to affect the affinity of SERCA1 to ATP. The binding of rutin in the proximity of Lys515 is likely to cause a decrease in FITC fluorescence.

Protective effects of ferulic acid and related polyphenols against glyoxal- or methylglyoxal-induced cytotoxicity and oxidative stress in isolated rat hepatocytes

Glyoxal (GO) and methylglyoxal (MGO) cause protein and nucleic acid carbonylation and oxidative stress by forming reactive oxygen and carbonyl species which have been associated with toxic effects that may contribute to cardiovascular disease, complications associated with diabetes mellitus, Alzheimer's and Parkinson's disease. GO and MGO can be formed through oxidation of commonly used reducing sugars e.g., fructose under chronic hyperglycemic conditions. GO and MGO form advanced glycation end products which lead to an increased potential for developing inflammatory diseases. In the current study, we have investigated the protective effects of ferulic acid and related polyphenols e.g., caffeic acid, p-coumaric acid, methyl ferulate, ethyl ferulate, and ferulaldehyde on GO- or MGO-induced cytotoxicity and oxidative stress (ROS formation, protein carbonylation and mitochondrial membrane potential maintenance) in freshly isolated rat hepatocytes. To investigate and compare the protective effects of ferulic acid and related polyphenols against GO- or MGO-induced toxicity, five hepatocyte models were used: (a) control hepatocytes, (b) GSH-depleted hepatocytes, (c) catalase-inhibited hepatocytes, (d) aldehyde dehydrogenase (ALDH2)-inhibited hepatocytes, and (e) hepatocyte inflammation system (a non-toxic H2O2-generating system). All of the polyphenols tested significantly decreased GO- or MGO-induced cytotoxicity, ROS formation and improved mitochondrial membrane potential in these models. The rank order of their effectiveness was caffeic acid∼ferulaldehyde>ferulic acid>ethyl ferulate>methyl ferulate>p-coumaric acid. Ferulic acid was found to decrease protein carbonylation in GSH-depleted hepatocytes. This study suggests that ferulic acid and related polyphenols can be used therapeutically to inhibit or decrease GO- or MGO-induced hepatotoxicity.