High-performance liquid chromatography determination of glyoxal, methylglyoxal, and diacetyl in urine using 4-methoxy-o-phenylenediamine as derivatizing reagent

Diagnostic Accuracy of Urinary Biomarkers in Periodontitis: A Systematic Review and Meta-Analysis

Background

Biomarkers can be measured in various biological samples. Urine is among the most useful biofluids for routine testing, and several experimental and clinical studies support its role as a tool for the diagnosis and prevention of various diseases. The present systematic review aimed to examine periodontitis-specific urine biomarkers that could have a diagnostic relevance and to provide a qualitative assessment of the current literature.

Materials and Methods

Relevant studies identified from PubMed, Embase, Cochrane Library, and Scopus databases were examined to answer the following PECO question: "Could the concentration of specific metabolites in the urine be related to periodontal health and what is their diagnostic accuracy?". Quality of included studies was rated using ROBINS-I tool. Meta-analysis was conducted on available quantitative data.

Results

After the screening of 768 titles, five studies were included in qualitative synthesis. The studies included referred to the evaluation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and neopterin. Meta-analysis was conducted for neopterin concentration on data available in four studies involving 129 participants. Higher concentrations of neopterin were found in periodontitis-affected patients compared to controls and patients treated for periodontitis.

Conclusions

The literature appears controversial in attributing a role to neopterin and 8-OHdG as periodontal biomarkers, highlighting the need for further clinical studies on this topic. While some studies report variations in 8-OHdG and neopterin levels in periodontally affected patients versus either controls or periodontally treated patients, the level of evidence appears still limited to draw firm conclusions (PROSPERO CRD42020222681).

α-Dicarbonyl compounds in food products: Comprehensively understanding their occurrence, analysis, and control

α-Dicarbonyl compounds (α-DCs) are readily produced during the heating and storage of foods, mainly through the Maillard reaction, caramelization, lipid-peroxidation, and enzymatic reaction. They contribute to both the organoleptic properties (i.e., aroma, taste, and color) and deterioration of foods and are potential indicators of food quality. α-DCs are also important precursors to hazardous substances, such as acrylamide, furan, advanced lipoxidation end products, and advanced glycation end products, which are genotoxic, neurotoxic, and linked to several diseases. Recent studies have indicated that dietary α-DCs can elevate plasma α-DC levels and lead to "dicarbonyl stress." To accurately assess their health risks, quantifying α-DCs in food products is crucial. Considering their low volatility, inability to absorb ultraviolet light, and high reactivity, the analysis of α-DCs in complex food systems is a challenge. In this review, we comprehensively cover the development of scientific approaches, from extraction, enrichment, and derivatization, to sophisticated detection techniques, which are necessary for quantifying α-DCs in different foods. Exposure to α-DCs is inevitable because they exist in most foods. Recently, novel strategies for reducing α-DC levels in foods have become a hot research topic. These strategies include the use of new processing technologies, formula modification, and supplementation with α-DC scavengers (e.g., phenolic compounds). For each strategy, it is important to consider the potential mechanisms underlying the formation and removal of process contaminants. Future studies are needed to develop techniques to control α-DC formation during food processing, and standardized approaches are needed to quantify and compare α-DCs in different foods.

Highly sensitive spectrofluorimetric method for the determination of the genotoxic methylglyoxal in glycerol-containing pharmaceuticals and dietary supplements

Methylglyoxal (MGO) is a genotoxic α-dicarbonyl compound. Recently, it was found to be formed in glycerol preparations during storage through auto-oxidation. A simple fluorimetric determination of the carcinogenic degradation product of glycerol, MGO, was developed and validated. The proposed method is based on the derivatization of MGO with 4-carbomethoxybenzaldehyde (CMBA) and ammonium acetate to yield a fluorescent imidazole derivative that can be measured at 415 nm after excitation at 322 nm. The optimized conditions were determined to be 0.2 M CMBA, 1.0 M ammonium acetate and a reaction time of 40 min at 90°C using ethanol as diluting solvent. The linear range was 10.0-200.0 ng/ml. Detection and quantification limits were 2.22 and 6.72 ng/ml, respectively. The proposed method was validated according to International Council for Harmonisation (ICH) guidelines and compared with the reported method and no significant difference was found. It was successfully applied for the determination of MGO in six different glycerol-containing pharmaceutical preparations and dietary supplements.

Urinary excretion of amino acids and their advanced glycation end-products (AGEs) in adult kidney transplant recipients with emphasis on lysine: furosine excretion is associated with cardiovascular and all-cause mortality

Arginine (Arg) and lysine (Lys) moieties of proteins undergo various post-translational modifications (PTM) including enzymatic N^G- and N^ε-methylation and non-enzymatic N^G- and N^ε-glycation. In a large cohort of stable kidney transplant recipients (KTR, n = 686), high plasma and low urinary concentrations of asymmetric dimethylarginine (ADMA), an abundant PTM metabolite of Arg, were associated with cardiovascular and all-cause mortality. Thus, the prediction of the same biomarker regarding mortality may depend on the biological sample. In another large cohort of stable KTR (n = 555), higher plasma concentrations of N^ε-carboxymethyl-lysine (CML) and N^ε-carboxyethyl-lysine (CEL), two advanced glycation end-products (AGEs) of Lys, were associated with higher cardiovascular mortality. Yet, the associations of urinary AGEs with mortality are unknown. In the present study, we measured 24 h urinary excretion of Lys, CML, and furosine in 630 KTR and 41 healthy kidney donors before and after donation. Our result indicate that lower urinary CML and lower furosine excretion rates are associated with higher mortality in KTR, thus resembling the associations of ADMA. Lower furosine excretion rates were also associated with higher cardiovascular mortality. The 24 h urinary excretion rate of amino acids and their metabolites decreased post-donation (varying as little as − 24% for CEL, and as much as − 62% for ADMA). For most amino acids, the excretion rate was lower in KTR than in donors pre-donation [except for S-(1-carboxyethyl)-l-cysteine (CEC) and N^G-carboxyethylarginine (CEA)]. Simultaneous GC–MS measurement of free amino acids, their PTM metabolites and AGEs in urine is a non-invasive approach in kidney transplantation.

Novel sample treatment method for the determination of free (E)-4-hydroxy-2-nonenal in meat products by liquid chromatography/tandem mass spectrometry using 4-hydroxy-2-nonenal-d3 as internal standard

RATIONALE

(E)-4-Hydroxy-2-nonenal (HNE) is a reactive secondary product of lipid oxidation with biological significance. The analysis of HNE is a challenge due to its volatility and high activity. Developing sample preparation and analytical tools for the determination of free HNE is crucial for better understanding the actual level of free HNE in meat products.

METHODS

Liquid nitrogen freezing, subzero-temperature extraction and derivatization were employed for meat sample treatment. Liquid chromatography/tandem mass spectrometry with electrospray ionization in negative ion mode was used for the determination of free HNE after isotope-coded derivatization.

RESULTS

High repeatability and good recoveries with a limit of quantification as low as 0.25 pmol/g were found. Nineteen out of 24 samples, including chilled/processed meat products and meat-based instant foods, were found to contain free HNE with a range of 0.014-1.160 nmol/g.

CONCLUSIONS

The proposed method showed satisfactory reliability, sensitivity and accuracy. We believe that such a sample preparation strategy will provide a powerful tool for better understanding the actual level of free HNE in meat products.

Age-dependent accumulation of dicarbonyls and advanced glycation endproducts (AGEs) associates with mitochondrial stress

Aging is a strong risk factor for brain dementia and cognitive decline. Age-related accumulation of metabolites such as advanced glycation end products (AGEs) could serve as danger signals to initiate and accelerate disease process and neurodegeneration. The underlying causes and consequences of cerebral AGEs accumulation remain largely unknown. Here, we comprehensively investigate age-related accumulation of AGEs and dicarbonyls, including methylglyoxal (MG), glyoxal (GO), and 3-deoxyglucosone (3-DG), and the effects of mitochondrial reactive oxygen species (ROS) on cerebral AGEs accumulation, mitochondrial function, and oxidative stress in the aging human and mouse brain. We demonstrate that AGEs, including arginine and lysine derived N(6)-carboxymethyl lysine (CML), Nε-(1-Carboxyethyl)-l-lysine (CEL), and methylglyoxal-derived hydroimidazolone-1 (MG-H1), were significantly elevated in the cerebral cortex and hippocampus with advanced age in mice. Accordingly, aging mouse and human brains revealed decrease in activities of mitochondrial respiratory chain complexes I & IV and ATP levels, and increased ROS. Notably, administration of mitoTEMPO (2-(2,2,6,6-Tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (mTEMPO), a scavenger of mitochondrial ROS, not only suppressed ROS production but also reduced aged-induced accumulation of AGEs and dicarbonyls. mTEMPO treatment improved mitochondrial respiratory function and restored ATP levels. Our findings provide evidence linking age-related accumulation of toxic metabolites (AGEs) to mitochondrial oxidative stress. This highlights a novel mechanism by which AGEs-dependent signaling promotes carbonyl stress and sustained mitochondrial dysfunction. Eliminating formation and accumulation of AGEs may represent a new therapeutic avenue for combating cognitive decline and mitochondrial degeneration relevant to aging and neurodegenerative diseases including Alzheimer's disease.

Data on possible in vitro anti-diabetic effects of verticinone on β-TC6 pancreatic and C2C12 skeletal muscle cells

Verticinone as a steroidal alkaloid is one of the major active constituents of medicinal herb, Fritillaria imperialis with several pharmacological properties. Present data demonstrate an in vitro assessment of verticinone effects on β-TC6 pancreatic and C2C12 skeletal muscle cells include cell survival, activities of carbohydrate-hydrolyzing enzymes (α-amylase and α-glucosidase), levels of insulin secreted into the media, glucose uptake ability, advanced glycation end product (AGEs) include 3-deoxyglucosone, methylglyoxal, and pentosidine levels and the activity of glyoxalase I. Data reveals possible hypoglycemic potential of verticinone, although, the high concentrations of this compound were associated with elevated amount of AGEs and it should be assessed in future investigations.

Bioanalytical and Mass Spectrometric Methods for Aldehyde Profiling in Biological Fluids

Human exposure to aldehydes is implicated in multiple diseases including diabetes, cardiovascular diseases, neurodegenerative disorders (i.e., Alzheimer’s and Parkinson’s Diseases), and cancer. Because these compounds are strong electrophiles, they can react with nucleophilic sites in DNA and proteins to form reversible and irreversible modifications. These modifications, if not eliminated or repaired, can lead to alteration in cellular homeostasis, cell death and ultimately contribute to disease pathogenesis. This review provides an overview of the current knowledge of the methods and applications of aldehyde exposure measurements, with a particular focus on bioanalytical and mass spectrometric techniques, including recent advances in mass spectrometry (MS)-based profiling methods for identifying potential biomarkers of aldehyde exposure. We discuss the various derivatization reagents used to capture small polar aldehydes and methods to quantify these compounds in biological matrices. In addition, we present emerging mass spectrometry-based methods, which use high-resolution accurate mass (HR/AM) analysis for characterizing carbonyl compounds and their potential applications in molecular epidemiology studies. With the availability of diverse bioanalytical methods presented here including simple and rapid techniques allowing remote monitoring of aldehydes, real-time imaging of aldehydic load in cells, advances in MS instrumentation, high performance chromatographic separation, and improved bioinformatics tools, the data acquired enable increased sensitivity for identifying specific aldehydes and new biomarkers of aldehyde exposure. Finally, the combination of these techniques with exciting new methods for single cell analysis provides the potential for detection and profiling of aldehydes at a cellular level, opening up the opportunity to minutely dissect their roles and biological consequences in cellular metabolism and diseases pathogenesis.

Elevated levels of α-dicarbonyl compounds in the plasma of type II diabetics and their relevance with diabetic nephropathy

The presence of α‑dicarbonyl compounds (α-DCs) in vivo has been associated with the development of complications of diabetes mellitus (DM) and also with other chronic diseases. Therefore, quantitative analysis of α-DCs in body fluids is crucial to understand their roles in the formation of these chronic diseases. We established in this study a practical HPLC-UV method to measure 3‑deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO), diacetyl (DA), and pentane‑2,3‑dione (PD) in blood plasma using 4‑(2,3‑dimethyl‑6‑quinoxalinyl)‑1,2‑benzenediamine (DQB) as a derivatizing reagent. The derivatizing reaction could be carried out quickly under mild conditions and the HPLC determination is simple, sensitive, and easy to operate. The recoveries of the α-DCs are between 85.26% and 110.20% (intra-day) and 87.25% and 103.18% (inter-day); the RSDs are between 1.28% and 5.69% (intra-day) and 2.26% and 6.34% (inter-day). We found the plasma levels of 3-DG, GO, and MGO in the diabetic patients are all significantly higher than those in healthy subjects. The results also show that the contents of GO and MGO in diabetic nephropathy (DN) patients are both significantly higher than those in simple T2DM patients. Moreover, it is found for the first time that the plasma level of GO might be a potential predictor of DN. The developed method would be useful for the measurements of the plasma α-DCs and the data acquired could be informative in the diagnosis of DM complications.

Derivatization of Methylglyoxal for LC-ESI-MS Analysis-Stability and Relative Sensitivity of Different Derivatives

The great research interest in the quantification of reactive carbonyl compounds (RCCs), such as methylglyoxal (MGO) in biological and environmental samples, is reflected by the fact that several publications have described specific strategies to perform this task. Thus, many reagents have also been reported for the derivatization of RCCs to effectively detect and quantify the resulting compounds using sensitive techniques such as liquid chromatography coupled with mass spectrometry (LC-MS). However, the choice of the derivatization protocol is not always clear, and a comparative evaluation is not feasible because detection limits from separate reports and determined with different instruments are hardly comparable. Consequently, for a systematic comparison, we tested 21 agents in one experimental setup for derivatization of RCCs prior to LC-MS analysis. This consisted of seven commonly employed reagents and 14 similar reagents, three of which were designed and synthesized by us. All reagents were probed for analytical responsiveness of the derivatives and stability of the reaction mixtures. The results showed that derivatives of 4-methoxyphenylenediamine and 3-methoxyphenylhydrazine—reported here for the first time for derivatization of RCCs—provided a particularly high responsiveness with ESI-MS detection. We applied the protocol to investigate MGO contamination of laboratory water and show successful quantification in a lipoxidation experiment. In summary, our results provide valuable information for scientists in establishing accurate analysis of RCCs.

Determination of Diacetyl in Beer by a Precolumn Derivatization-HPLC-UV Method Using 4-(2,3-Dimethyl-6-quinoxalinyl)-1,2-benzenediamine as a Derivatizing Reagent

Diacetyl is an important flavoring compound in many foods, especially in beer. In the present study, we developed and validated a new precolumn derivatization HPLC-UV method for the determination of diacetyl using 4-(2,3-dimethyl-6-quinoxalinyl)-1,2-benzenediamine as a novel derivatizing reagent. After derivatization with the reagent at a pH value 4.0 at ambient temperature for 10 min, diacetyl was analyzed on an ODS column and detected at 254 nm. The results show that the correlation coefficient of the method is 0.9991 in the range of 0.10 to 100.0 μM diacetyl, and the limit of detection is 0.02 μM. The method was further evaluated in the analysis of beer samples with the recoveries ranging from 94.4 to 102.6% and RSDs from 1.36 to 3.33%. The concentrations of diacetyl in 8 beer samples were determined in the range of 0.19 to 0.42 μM. The method established in this study may be well suitable for the determination of diacetyl in beer.

Genetic and pharmacological manipulation of glyoxalase 1 regulates voluntary ethanol consumption in mice

Previous studies have identified an association between the gene glyoxalase 1 (Glo1) and anxiety-like behavior in mice and have shown that the substrate of GLO1, methylglyoxal, is a competitive partial agonist at GABA_A receptors. Given the well-established role of GABA_A receptors in the behavioral effects of ethanol (EtOH), we investigated the role of Glo1 in voluntary EtOH consumption in mice using the drinking in the dark (DID) paradigm. Transgenic mice overexpressing Glo1 on both FVB/NJ (FVB) or C57BL/6J (B6) backgrounds showed increased voluntary EtOH consumption compared to their wild-type littermates in DID. Furthermore, transgenic Glo1 knockdown mice on a B6 background showed decreased voluntary EtOH consumption in DID. These genetic manipulations of Glo1 had no effect on sucrose, saccharin or water consumption. Finally, we found that a small molecule GLO1 inhibitor (S-bromobenzylglutathione cyclopentyl diester (pBBG; 6.25, 12.5 mg/kg)) reduced EtOH consumption compared to vehicle treated B6 mice without altering saccharin or water consumption. Sucrose consumption was only reduced by the higher (12.5 mg/kg) dose of pBBG. We did not observe differences in the loss of righting reflex (LORR) or EtOH-induced foot slips on the balance beam in response to acute EtOH administration (LORR: 4 g/kg, Balance Beam: 1.25 g/kg) in B6 or FVB mice overexpressing Glo1, nor in B6 mice treated with pBBG. These data are the first to implicate Glo1 in EtOH-related behaviors and suggest that GLO1 inhibitors may have therapeutic potential for the treatment of alcohol use disorders.

Glyoxal and methylglyoxal determination in urine by surfactant-assisted dispersive liquid–liquid microextraction and LC

Aim: Two important markers of oxidative stress, glyoxal and methylglyoxal, are preconcentrated from human urine by surfactant-assisted dispersive liquid–liquid microextraction and separated by LC-fluorescence. Methods/results: Derivatization was carried out overnight with 0.8 mM 2,3-diaminonaphthalene at 4°C. For surfactant-assisted dispersive liquid–liquid microextraction, 500 µl buffer solution (pH 10.5) and 25 µl 0.03 M Triton X-114 were added to 2.5 ml of the sample and the mixture was made up to 10 ml before the rapid injection of 75 µl 1-undecanol (extractant solvent) and 0.5 ml ethanol (dispersant solvent). Conclusion: The method can be applied to analyze glyoxal and methylglyoxal in urine with LOD of 13 and 16 ng/l, respectively, and recoveries in the 88–103% range.

Dietary advanced glycation end products and their role in health and disease

Over the past 2 decades there has been increasing evidence supporting an important contribution from food-derived advanced glycation end products (AGEs) to the body pool of AGEs and therefore increased oxidative stress and inflammation, processes that play a major role in the causation of chronic diseases. A 3-d symposium (1st Latin American Symposium of AGEs) to discuss this subject took place in Guanajuato, Mexico, on 1-3 October 2014 with the participation of researchers from several countries. This review is a summary of the different presentations and subjects discussed, and it is divided into 4 sections. The first section deals with current general knowledge about AGEs. The second section dwells on mechanisms of action of AGEs, with special emphasis on the receptor for advanced glycation end products and the potential role of AGEs in neurodegenerative diseases. The third section discusses different approaches to decrease the AGE burden. The last section discusses current methodologic problems with measurement of AGEs in different samples. The subject under discussion is complex and extensive and cannot be completely covered in a short review. Therefore, some areas of interest have been left out because of space. However, we hope this review illustrates currently known facts about dietary AGEs as well as pointing out areas that require further research.

Application of gas-diffusion microextraction to solid samples using the chromatographic determination of α-diketones in bread as a case study

For the first time, gas-diffusion microextraction was used for the direct analysis of solid samples (vicinal diketones in bread).

Analytical method for lipoperoxidation relevant reactive aldehydes in human sera by high-performance liquid chromatography-fluorescence detection

A validated, simple and sensitive HPLC method was developed for the simultaneous determination of lipoperoxidation relevant reactive aldehydes: glyoxal (GO), acrolein (ACR), malondialdehyde (MDA), and 4-hydroxy-2-nonenal (HNE) in human serum. The studied aldehydes were reacted with 2,2'-furil to form fluorescent difurylimidazole derivatives that were separated on a C18 column using gradient elution and fluorescence detection at excitation and emission wavelengths of 250 and 355nm, respectively. The method showed good linearity over the concentration ranges of 0.100-5.00, 0.200-10.0, 0.200-40.0, and 0.400-10.0nmol/mL for GO, ACR, HNE, and MDA, respectively, with detection limits ranging from 0.030 to 0.11nmol/mL. The percentage RSD of intraday and interday precision did not exceed 5.0 and 6.2%, respectively, and the accuracy (%found) ranged from 95.5 to 103%. The proposed method was applied for monitoring the four aldehydes in sera of healthy, diabetic, and rheumatic human subjects with simple pretreatment steps and without interference from endogenous components. By virtue of its high sensitivity and accuracy, our method enabled detection of differences between analytes concentrations in sera of human subjects under different clinical conditions.

Methylglyoxal is associated with bacteriostatic activity of high fructose agave syrups

Three α-ketoaldehydes, potentially present in high fructose agave syrups (HFASs) as intermediates of the Maillard reaction, were determined. A previously reported HPLC-FLD procedure based on pre-column derivatisation with 4-methoxy-o-phenylenediamine was adopted, yielding the method quantification limits 0.11 mg/kg, 0.10mg/kg, 0.09 mg/kg for glyoxal, methylglyoxal (MGo) and diacetyl, respectively. The obtained results revealed high concentrations of methylglyoxal in HFASs (average 102 ± 91 mg/kg, range 15.6-315 mg/kg) as compared to commercial Mexican bee honeys or corn syrups. Hydrogen peroxide was generated in all HFASs upon dilution, yet to less extent than in bee honeys. HFASs presented bacteriostatic activity against Bacillus subtilis and Escherichia coli; catalase addition had minimum effect on the assay results in syrups with elevated MGo. Principal component analysis revealed direct association between growth inhibition and MGo. It is concluded that elevated concentration of MGo in HFASs is at least in part responsible for their non-peroxide bacteriostatic activity.