Quantitative alterations in the metabolism of carbonyl compounds due to diet-induced lipid peroxidation in rats

Identification of nutritional biomarkers through highly sensitive and chemoselective metabolomics

The importance of a healthy diet for humans is known for decades. The elucidation of key molecules responsible for the beneficial and adverse dietary effects is slowly developing as the tools are missing. Carbonyl-containing metabolites are a common bioproducts through conversion of diet by the microbiome. In here, we have utilized our recently developed mass spectrometric methodology based on chemoselective conjugation of carbonyl-metabolites. The method has been applied for urine sample analysis from a dietary (poly)phenol intervention study (N = 78 individuals) for the first time. We have identified a series of carbonyl-metabolites of dietary origin and the chemical structure was validated for 30 metabolites. Our sensitive analysis led to the discovery of four unknown dietary markers with high sensitivity and selectivity (AUC > 0.91). Our chemical metabolomics method has been successfully applied for large-scale analysis and provides the basis for targeted metabolomics to identify unknown nutritional and disease-related biomarkers.

Leveraging metabolic modeling to identify functional metabolic alterations associated with COVID-19 disease severity

OBJECTIVE

Since the COVID-19 pandemic began in early 2020, SARS-CoV2 has claimed more than six million lives world-wide, with over 510 million cases to date. To reduce healthcare burden, we must investigate how to prevent non-acute disease from progressing to severe infection requiring hospitalization.

METHODS

To achieve this goal, we investigated metabolic signatures of both non-acute (out-patient) and severe (requiring hospitalization) COVID-19 samples by profiling the associated plasma metabolomes of 84 COVID-19 positive University of Virginia hospital patients. We utilized supervised and unsupervised machine learning and metabolic modeling approaches to identify key metabolic drivers that are predictive of COVID-19 disease severity. Using metabolic pathway enrichment analysis, we explored potential metabolic mechanisms that link these markers to disease progression.

RESULTS

Enriched metabolites associated with tryptophan in non-acute COVID-19 samples suggest mitigated innate immune system inflammatory response and immunopathology related lung damage prevention. Increased prevalence of histidine- and ketone-related metabolism in severe COVID-19 samples offers potential mechanistic insight to musculoskeletal degeneration-induced muscular weakness and host metabolism that has been hijacked by SARS-CoV2 infection to increase viral replication and invasion.

CONCLUSIONS

Our findings highlight the metabolic transition from an innate immune response coupled with inflammatory pathway inhibition in non-acute infection to rampant inflammation and associated metabolic systemic dysfunction in severe COVID-19.

Biochemical individuality reflected in chromatographic, electrophoretic and mass-spectrometric profiles

This review discusses the current trends in molecular profiling for the emerging systems biology applications. Historically, the methodological developments in separation science were coincident with the availability of new ionization techniques in mass spectrometry. Coupling miniaturized separation techniques with technologically-advanced MS instrumentation and the modern data processing capabilities are at the heart of current platforms for proteomics, glycomics and metabolomics. These are being featured here by the examples from quantitative proteomics, glycan mapping and metabolomic profiling of physiological fluids.

Inhibition of glycolytic enzymes by endogenous aldehydes: a possible relation to diabetic neuropathies

Endogenous saturated and unsaturated aldehydes were found in significant elevations in serum of diabetic humans and rats. These compounds, originating from the lipid peroxidation processes, are shown here to be potent inhibitors of the glycolytic enzymes, phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase. The inhibition process is non-competitive and progressive. The aldehyde mixture, when supplemented to the standard rat diet at 1/100 ratio, caused nerve damage that is reminiscent of diabetic polyneuropathies.

Monitoring of oxidative free radical damage in vivo: analytical aspects

Free radical damage is an important factor in many pathological and toxicological processes. During the last decade a wide range of methods has been developed to determine free radical damage in various biological fluids and at various stages of development. This review offers an overview of the state of the art of monitoring free radical damage in vivo, with special emphasis on the analytical aspects of non-invasive methods.

Formation of formaldehyde and malonaldehyde by photooxidation of squalene

Formaldehyde and malonaldehyde were identified upon exposure of squalene to ultraviolet (UV) irradiation at 300 nm. Formaldehyde was derivatized by reaction with cysteamine to form thiazolidine; malonaldehyde was derivatized by reaction with N-methylhydrazine to produce N-methylpyrazole. The derivatives were subsequently analyzed with a gas chromatograph equipped with a fused silica capillary column and a nitrogen/phosphorus detector. The levels of formaldehyde and malonaldehyde produced increased with irradiation time. The amount of formaldehyde produced reached a maximum of 3.40 nmol/mg squalene after 7 hr irradiation; the maximum amount of malonaldehyde generated, 0.92 nmol/mg, was found after 5 hr of irradiation. Prior to this study, formaldehyde had not been reported as a photoproduct of squalene. Acetaldehyde and acetone were also detected in the irradiated squalene, which may be formed via a 6-methyl-5-hepten-2-one intermediate. 6-Methyl-5-hepten-2-one can also undergo breakdown to form malonaldehyde.