Measurement of ischaemia-reperfusion in patients with intermittent claudication using NMR-based metabonomics

Exercise-Induced Plasma Metabolomic Profiles in Patients With Peripheral Arterial Disease

Aim: A better knowledge of the biological consequences in the blood of these exercise-induced ischemic events in lower extremity artery disease (LEAD) may improve the prospects of disease management. We explored the preminus postexercise metabolomic difference in 39 patients with LEAD referred for a treadmill oximetry test [transcutaneous oximetry (TcPO₂)].

Methods: Ischemia was estimated through the sum of decrease from rest of oxygen pressure (DROPs) (limb TcPO₂ changes minus chest TcPO₂ changes) at buttocks, thighs, and calves regions. Targeted metabolomic analyses measuring 188 metabolites were performed on a few microliters blood samples taken at the earlobe at rest and 3 min after exercise.

Results: Maximum walking distance (MWD) was 290 m (120–652 m) and ankle brachial index (ABI) was 0.67 ± 0.17. Supervised paired partial least squares discriminant analysis based on 23,345 models showed good predictive performance for test sets with a median area under the receiver operating characteristic (AUROC) curve value of 0.99 and a p-value of 0.00049. The best discriminant metabolites contributing to the model included a subset of 71 (47%) of the 150 accurately measured metabolites in the plasma, comprising 3 acylcarnitines, 3 amino acids, 5 biogenic amines, 9 sphingomyelin, 7 lysophosphatidylcholines, and 44 phosphatidylcholines. In addition, 16 of these metabolites were found to correlate with one or more severity scores of the LEAD.

Conclusion: Our results provide new insights into the biological changes that accompany exercise in LEAD and contribute to a better understanding of walking impairment pathophysiology in LEAD, highlighting new candidate biomarkers.

Astragaloside IV Attenuates Myocardial Ischemia-Reperfusion Injury from Oxidative Stress by Regulating Succinate, Lysophospholipid Metabolism, and ROS Scavenging System

Astragaloside IV is one of the main active ingredients isolated from Astragalus membranaceus. Here we confirmed its protective effect against cardiac ischemia-reperfusion (I/R) injury and aimed to investigate the potential molecular mechanisms involved. Pretreatment of ex vivo and in vivo I/R-induced rat models by astragaloside IV significantly prevented the ratio of myocardium infarct size, systolic and diastolic dysfunction, and the production of creatine kinase and lactate dehydrogenase. Metabolic analyses showed that I/R injury caused a notable reduction of succinate and elevation of lysophospholipids, indicating excessive reactive oxygen species (ROS) generation driven by succinate's rapid reoxidization and glycerophospholipid degradation. Molecular validation mechanistically revealed that astragaloside IV stimulated nuclear factor (erythroid-derived 2)-like 2 (Nrf2) released from Kelch-like ECH-associated protein 1 (Keap1) and translocated to the nucleus to combine with musculoaponeurotic fibrosarcoma (Maf) to initiate the transcription of antioxidative gene heme oxygenase-1 (HO-1), which performed a wide range of ROS scavenging processes against pathological oxidative stress in the hearts. As expected, increasing succinate and decreasing lysophospholipid levels were observed in the astragaloside IV-pretreated group compared with the I/R model group. These results suggested that astragaloside IV ameliorated myocardial I/R injury by modulating succinate and lysophospholipid metabolism and scavenging ROS via the Nrf2 signal pathway.

(1)H NMR-based metabolomics exploring biomarkers in rat cerebrospinal fluid after cerebral ischemia/reperfusion

In our study, metabolomics was used to investigate biochemical changes in the early stages of rats focal cerebral ischemia/reperfusion (I/R) injury. Cerebrospinal fluid (CSF) samples at 0, 0.5, 1, 3, and 6 h of reperfusion (n = 10), based on (1)H NMR spectroscopy and multivariate data analyses, were tested to analyze the changing of metabolites during the early disease process. Partial least squares-discriminant analysis scores plots of the (1)H NMR data revealed clear differences among the experiment groups. Combining the results of the loading plot and t-test, we found that twenty-seven metabolites were changed significantly (p < 0.05) in the CSF samples among the different groups. Among that, the potential biomarkers in CSF of ischemic rats were: acetic acid, 3-hydroxyisovaleric acid, 3-hydroxybutyric acid, choline, l-alanine, creatine, creatinine, glycine, pyruvic acid, glycerol, glutamic acid, d-fructose, l-lactic acid and acetone. These findings help us understand the biochemical metabolite changes in CSF of I/R rats in early stages. What's more, metabolomics may, therefore, have the potential to be developed into a clinically useful diagnostic tool of ischemic brain injury.

Standard operating procedures for pre-analytical handling of blood and urine for metabolomic studies and biobanks

(1)H NMR metabolic profiling of urine, serum and plasma has been used to monitor the impact of the pre-analytical steps on the sample quality and stability in order to propose standard operating procedures (SOPs) for deposition in biobanks. We analyzed the quality of serum and plasma samples as a function of the elapsed time (t = 0-4 h) between blood collection and processing and of the time from processing to freezing (up to 24 h). The stability of the urine metabolic profile over time (up to 24 h) at various storage temperatures was monitored as a function of the different pre-analytical treatments like pre-storage centrifugation, filtration, and addition of the bacteriostatic preservative sodium azide. Appreciable changes in the profiles, reflecting changes in the concentration of a number of metabolites, were detected and discussed in terms of chemical and enzymatic reactions for both blood and urine samples. Appropriate procedures for blood derivatives collection and urine preservation/storage that allow maintaining as much as possible the original metabolic profile of the fresh samples emerge, and are proposed as SOPs for biobanking.

(1)H NMR-based metabonomic investigation of the effect of two different exercise sessions on the metabolic fingerprint of human urine

Physical exercise modifies animal metabolism profoundly. Until recently, biochemical investigations related to exercise focused on a small number of biomolecules. In the present study, we used a holistic analytical approach to investigate changes in the human urine metabolome elicited by two exercise sessions differing in the duration of the rest interval between repeated efforts. Twelve men performed three sets of two 80 m maximal runs separated by either 10 s or 1 min of rest. Analysis of pre- and postexercise urine samples by (1)H NMR spectroscopy and subsequent multivariate statistical analysis revealed alterations in the levels of 22 metabolites. Urine samples were safely classified according to exercise protocol even when applying unsupervised methods of statistical analysis. Separation of pre- from postexercise samples was mainly due to lactate, pyruvate, hypoxanthine, compounds of the Krebs cycle, amino acids, and products of branched-chain amino acid (BCAA) catabolism. Separation of the two rest intervals was mainly due to lactate, pyruvate, alanine, compounds of the Krebs cycle, and 2-oxoacids of BCAA, all of which increased more with the shorter interval. Metabonomics provides a powerful methodology to gain insight in metabolic changes induced by specific training protocols and may thus advance our knowledge of exercise biochemistry.

Urinary metabonomic study of lung cancer by a fully automatic hyphenated hydrophilic interaction/RPLC-MS system

Lung cancer is one of the most common and lethal cancers in the world. In this study, a home-devised hydrophilic interaction chromatography/RPLC-MS (HILIC/RPLC-MS) system was developed to study the urinary metabonomics of lung cancer patients. This system combined the orthogonal selectivity of HILIC and RPLC and could chromatographically reveal more comprehensive information of the urinary metabolites. Within a total analysis time of 50 min, we detected 577 polar metabolite ions on the first HILIC column and 261 apolar ones on the second RPLC column. In addition, an orthogonal signal correction partial least-squares discriminant analysis model was constructed to characterize differences between health and lung cancer cases. Eleven potential biomarkers, ten from HILIC column and one from the second RP column, were identified and all of these biomarkers were found upregulated in lung cancer patients. Overall, the results indicated that the developed HILIC/RPLC-MS system is a promising tool for metabonomic studies in revealing more information of highly complex samples.