Metabolic flexibility plays a significant role in energy homeostasis by regulating fuel selection in correspondence to energy demand. Obese and type II diabetic populations have displayed a hindered ability to properly transition from fat oxidation while in a fasted state to carbohydrate oxidation once fed, leading to a buildup of mitochondrial metabolites such as acylcarnitines. Carnitine, essential for fatty acyl-CoA transport through the inner and outer mitochondrial membranes, can be an indicator of mitochondrial distress as elevated levels tend to spill over into plasma suggesting a disruption in oxidation. The current study was designed to examine the effect of short term, high fat feeding on plasma acylcarnitine species diversity and levels and if acylcarnitines are associated with metabolic flexibility. 13 healthy, non-obese, sedentary males, aged 18-40 years participated in this study. Following a 12-hour overnight fast a biopsy was taken from the quadricep before and 4 hours after a high fat meal. Blood draws were obtained pre-biopsy while fasted and every hour for 4 hours post high fat meal consumption. Acylcarnitines from plasma were converted to their butyl esters and analyzed by electrospray ionization tandem mass spectrometry (MS/MS). Changes were observed in acetylcarntine (P=0.0125), glucose oxidation (P=0.0295), C16:1/C16:0 desaturation index (P= 0.0397), and C18:1/C18:0 desaturation index (P=0.0012). We did not find that individual changes in flexibility correlated with circulating acylcarnitine measurements in a fasted state / Master of Science

Le syndrome d’apnées obstructives du sommeil (SAOS) est une pathologie caractérisée par des épisodes d’hypoxie intermittente (HI) nocturnes et est un problème de santé publique par sa prévalence dans la population générale (5-20%) et ses nombreuses complications métaboliques et cardiovasculaires. La répétition des épisodes d’HI est considérée comme le facteur principal responsable de cette morbidité cardiovasculaire dont l’athérosclérose fait partie. Le traitement de référence du SAOS par la pression positive continue présente dans certains cas une efficacité limitée, en particulier sur les conséquences cardiovasculaires qui nécessitent d’autres thérapeutiques plus spécifiques. Les mécanismes reliant SAOS et athérosclérose ne sont pas encore totalement connus. Cependant, des perturbations du métabolisme des acides gras (AG) en lien avec le processus athéromateux ont déjà été rapportées au cours du SAOS. Elles concernent en particulier le métabolisme de l’acide arachidonique (AG n-6) avec une augmentation d’eicosanoïdes pro-inflammatoires. Par ailleurs, les AG n-3 peuvent avoir une influence sur le développement et la progression des maladies cardiovasculaires, notamment grâce à une modification de la balance AG n-6 / AG n-3. Ainsi l’objectif de ce travail a donc été dans un premier temps de caractériser expérimentalement l’effet d’une supplémentation en AG n-3 sur le développement de l’athérosclérose dans le contexte d’HIC, et d’évaluer cliniquement la distribution AG n-6 / AG n-3 au niveau érythrocytaire chez des patients atteints d’un SAOS. Nous avons démontré que la supplémentation en AG n-3 permet de prévenir l’accélération de l’athérosclérose dans le contexte de l’HIC et est associée à une modulation de l’expression de certains médiateurs inflammatoires. Ces résultats prometteurs incitent à envisager une étude interventionnelle chez les patients SAOS. Dans un second temps, nous nous sommes intéressés au métabolisme des AG, via la β-oxydation mitochondriale, et aux métabolites intermédiaires produits, les acylcarnitines (ACs). Ces métabolites sont de plus en plus étudiés dans le contexte des pathologies cardiovasculaires. Nous avons étudié l’impact du SAOS sur la β-oxydation et ses conséquences sur la fonction vasculaire. L’étude de ces métabolites semble prometteuse et permettra peut-être l’émergence de marqueurs biologiques en relation avec l’état cardiovasculaire des patients. / Obstructive sleep apnea (OSA) syndrome is a disease characterized by recurrent episodes of nocturnal intermittent hypoxia (IH). OSA is a major public health problem due to its frequency in general population (5 to 20%) and its numerous metabolic and cardiovascular complications. Repetitive apneas lead to IH which is responsible of early atherosclerosis and cardiovascular complications. Gold standard treatment of OSA, that is to say continuous positive airway pressure, has poor effects on OSA cardiovascular consequences in some patients, underlining the need of alternative therapeutic strategies. Underlying mechanisms linking OSA to atherosclerosis are still poorly understood. Nevertheless, a link between polyunsaturated fatty acids (PUFAs) metabolism changes and atheromatous process has already been report during OSA syndrome. Arachidonic acid (n-6 PUFA) metabolism leads to increased biosynthesis of pro-inflammatory eicosanoids during OSA. Moreover, n-3 PUFAs influence cardiovascular complications progression especially by modifying n-6 FA / n-3 FA balance. The aim of this work was first to evaluate the influence of n-3 PUFAs supplementation on a CIH induced atherosclerosis progression model, and to clinically evaluate erythrocyte n-6 PUFA / n-3 PUFA distribution in OSA patients. We have shown that n-3 PUFAs supplementation prevents atherosclerosis acceleration in CIH exposed mice and is associated with a modulation of inflammatory mediators. These promising results encourage us to consider an interventional clinical study in OSA patients. In a second time, we have studied FA mitochondrial β-oxidation metabolism via acylcarnitines (ACs) metabolites. These ACs are increasingly studied especially in cardiovascular diseases context. OSA impact on β-oxidation metabolism and its vascular function consequences have been evaluated. ACs study is promising and will perhaps allow biological markers emergence in relation to cardiovascular pattern.

Mitochondrial fatty acid �-oxidation disorders are a group of clinically and biochemically heterogeneous defects mainly associated with intolerance to catabolic stress. The diseases are potentially fatal, but treatable and the prognosis for most diagnosed disorders is generally favourable. Early diagnosis is thus important to prevent morbidity and mortality. This project describes an improved and validated quantitative fibroblast acylcarnitine profile assay for the investigation of suspected fatty acid �-oxidation disorders. Intact cells were incubated with deuterium-labelled hexadecanoate and L-carnitine, and the accumulated acylcarnitines in the medium analysed using electrospray tandem mass spectrometry. This modified procedure is less demanding technically, requires fewer cells and better reflects the in vivo acylcarnitine status than previously published methods. Mitochondrial fatty acid �-oxidation is coupled to the respiratory chain. Functional defects of one pathway may lead to secondary alterations in flux through the other. The diagnostic specificity and the prognostic potential of the in vitro acylcarnitine profile assay were investigated in fibroblasts from 14 normal controls, 38 patients with eight enzyme deficiencies of fatty acid �-oxidation presenting with various phenotypes, and 16 patients with primary respiratory chain defects including both isolated and multiple enzyme complex defects. All fatty acid �-oxidation deficient cell lines revealed disease-specific acylcarnitine profiles related to the sites of defects irrespective of the severity of symptoms or of different mutation. Preliminary studies suggested a correlation between severity of symptoms and higher concentrations of long-chain acylcarnitine species. However, the fibroblast acylcarnitine profiles from some patients with respiratory chain defects were similar to those of controls, whereas others had abnormal profiles resembling those found in fatty acid �-oxidation disorders. In vitro acylcarnitine profiling is useful for the detection of fatty acid �-oxidation deficiencies, and perhaps the prediction of disease severity and prognostic evaluation facilitating decisions of therapeutic intervention and genetic counselling. However, abnormal profiles do not exclusively indicate these disorders, and primary defects of the respiratory chain remain a possibility. Awareness of this diagnostic pitfall will aid in the selection of subsequent confirmatory tests and therapeutic options.

Mitochondrial fatty acid �-oxidation disorders are a group of clinically and biochemically heterogeneous defects mainly associated with intolerance to catabolic stress. The diseases are potentially fatal, but treatable and the prognosis for most diagnosed disorders is generally favourable. Early diagnosis is thus important to prevent morbidity and mortality. This project describes an improved and validated quantitative fibroblast acylcarnitine profile assay for the investigation of suspected fatty acid �-oxidation disorders. Intact cells were incubated with deuterium-labelled hexadecanoate and L-carnitine, and the accumulated acylcarnitines in the medium analysed using electrospray tandem mass spectrometry. This modified procedure is less demanding technically, requires fewer cells and better reflects the in vivo acylcarnitine status than previously published methods. Mitochondrial fatty acid �-oxidation is coupled to the respiratory chain. Functional defects of one pathway may lead to secondary alterations in flux through the other. The diagnostic specificity and the prognostic potential of the in vitro acylcarnitine profile assay were investigated in fibroblasts from 14 normal controls, 38 patients with eight enzyme deficiencies of fatty acid �-oxidation presenting with various phenotypes, and 16 patients with primary respiratory chain defects including both isolated and multiple enzyme complex defects. All fatty acid �-oxidation deficient cell lines revealed disease-specific acylcarnitine profiles related to the sites of defects irrespective of the severity of symptoms or of different mutation. Preliminary studies suggested a correlation between severity of symptoms and higher concentrations of long-chain acylcarnitine species. However, the fibroblast acylcarnitine profiles from some patients with respiratory chain defects were similar to those of controls, whereas others had abnormal profiles resembling those found in fatty acid �-oxidation disorders. In vitro acylcarnitine profiling is useful for the detection of fatty acid �-oxidation deficiencies, and perhaps the prediction of disease severity and prognostic evaluation facilitating decisions of therapeutic intervention and genetic counselling. However, abnormal profiles do not exclusively indicate these disorders, and primary defects of the respiratory chain remain a possibility. Awareness of this diagnostic pitfall will aid in the selection of subsequent confirmatory tests and therapeutic options.

The primary purpose of newborn screening is to quickly identify children that are at risk of having a specific disorder in order to start treatment, prevent early death and reduce the chances of permanent physical or mental damage. The current and widely accepted approach used for identification of metabolism disorders involves a flow injection analysis with mass spectrometry detection of acylcarnitines and amino acids. Although this approach is widely accepted and has shown to be sufficient for identification of multiple metabolism disorders the method is not fully quantitative and results often have to be confirmed by second-tier tests. The primary focus of this research was to improve the accuracy and selectivity of this screening method by employing a high resolution chromatographic separation for the combined analysis of twelve acylcarnitines and seven amino acids. This method is an improvement over the current methodology allowing for separation of key isomers that are diagnostic for different metabolism disorders, reducing the need for multiple second-tier tests to confirm results and shortening the time to diagnosis. In order to further improve the efficiency of newborn screening we developed an in-line desorption device, which allows for direct analysis of DBS eliminating the need for punching disks from the filter paper cards. Our device was the first published paper that demonstrated the ability to directly analyze dried blood spots, without the need for any offline sample processing. Using this device, we validated a method to quantify biomarkers related to Maple Syrup Urine Disease, a disorder that requires a second-tier test for confirmation. To further improve the accuracy of dried blood spot analysis we evaluated a technique to correct the sample volume in low and high hematocrit samples. The level of hematocrit in blood spotted on filter paper cards affects the volume of sample analyzed, leading to errors in accuracy. Diffuse reflectance was used to relate differences in sample hematocrit on dried blood spots. We validated our technique with eighteen donor samples at various levels of hematocrit. Correcting sample volume for hematocrit showed improved precision and accuracy over the standard approach, ultimately reducing the potential to misidentify samples.

Background: Changes in the metabolic fingerprint of blood during child growth and development are a largely under-investigated area of research. The examination of such aspects requires a cohort of healthy children and adolescents who have been subjected to deep phenotyping, including collection of biospecimens for metabolomic analysis. The present study considered whether amino acid (AA) and acylcarnitine (AC) concentrations are associated with age, sex, body mass index (BMI), and puberty during childhood and adolescence. It also investigated whether there are associations between amino acids (AAs) and acylcarnitines (ACs) and laboratory parameters of glucose and lipid metabolism, as well as liver, kidney, and thyroid parameters. Methods: A total of 3989 dried whole blood samples collected from 2191 healthy participants, aged 3 months to 18 years, from the LIFE Child cohort (Leipzig, Germany) were analyzed using liquid chromatography tandem mass spectrometry to detect levels of 23 AAs, 6 ACs, and free carnitine (C0). Age- and sex-related percentiles were estimated for each metabolite. In addition, correlations between laboratory parameters and levels of the selected AAs and ACs were calculated using hierarchical models. Results: Four different age-dependent profile types were identified for AAs and ACs. Investigating the association with puberty, we mainly identified peak metabolite levels at Tanner stages 2 to 3 in girls and stages 3 to 5 in boys. Significant correlations were observed between BMI standard deviation score (BMI-SDS) and certain metabolites, among them, branched-chain (leucine/isoleucine, valine) and aromatic (phenylalanine, tyrosine) amino acids. Most of the metabolites correlated significantly with absolute concentrations of glucose, glycated hemoglobin (HbA1c), triglycerides, cystatin C (CysC), and creatinine. After age adjustment, significant correlations were observed between most metabolites and CysC, as well as HbA1c. Conclusions: During childhood, several AA and AC levels are related to age, sex, BMI, and puberty. Moreover, our data verified known associations but also revealed new correlations between AAs/ACs and specific key markers of metabolic function.

Quantitative Untersuchungen krankheitsspezifischer oder krankheitsassoziierter metabolischer Signaturen in humanen Körperflüssigkeiten („Clinical Metabolomics“) haben zum Ziel neue Ansätze für diagnostische oder therapeutische Konzepte zu entwickeln. Die simultane quantitative Analytik von Aminosäuren (AS) und Acylcarnitinen (AC) mittels Tandem-Massenspektrometrie (MS/MS) ermöglicht die Erfassung wichtiger Stoffwechselwege des humanen Metabolismus. Hierzu zählen der Stoffwechsel der ketogenen AS, des Harnstoffzyklus oder der β-Oxidation langkettiger Fettsäuren. Allerdings wird die Konzentration der verschiedenen metabolischen Parameter in humanen Körperflüssigkeiten durch eine Vielzahl präanalytischer in vitro Störfaktoren und in vivo Einflussgrößen beeinflusst. Diese können zu signifikanten Veränderungen der Laborergebnisse führen. Im Rahmen meiner Promotionsarbeit wurden in vitro Störfaktoren (Probenmaterial, Lagerung u. a.) und in vivo Einflussgrößen (Ernährung, physische Aktivität) untersucht und ein standardisiertes Präanalytik-Protokoll entwickelt. Dazu wurden pro Probe 3 µL Trockenblut (TB), 10 µL Serum oder Plasma nach Butylierung mittels Elektrospray-Ionisations-MS/MS analysiert und jeweils 26 AS und 35 AC in 1,5 Minuten simultan bestimmt. Als Ergebnis der zahlreichen systematischen Präanalytik-Untersuchungen konnten signifikante Konzentrationsunterschiede der Metabolite zwischen kapillärer und venöser Blutentnahme sowie in Abhängigkeit des Hämatokrits gefunden werden. Im Vergleich zu Serum und antikoaguliertem Plasma (EDTA, Citrat, Heparin) waren die Konzentrationen der langkettigen AC im TB 5-fach höher. Nahrungsaufnahme und körperliche Aktivität führten ebenfalls zu signifikanten Veränderungen der AS- und AC-Konzentrationen. Durch Optimierung des Probenaufarbeitungsprotokolls konnte die Variabilität zwischen den Messtagen für 17 AS und 6 AC auf < 20 % gesenkt werden. Die Ergebnisse meiner Promotionsarbeit unterstreichen den Einfluss präanalytischer Faktoren auf die Metabolomanalytik. Durch Etablierung und Einhaltung standardisierter präanalytischer Protokolle kann die präanalytische Varianz der Ergebnisse deutlich verringert werden. Sie stellen somit eine wichtige Voraussetzung für eine qualitativ hochwertige Metabolomanalytik im Rahmen klinischer Studien zur Identifizierung neuer Biomarker dar.

Insulin-like growth factor-I (IGF-I) is the only known potentially modifiable risk factor for prostate cancer. Intake of dietary protein, especially from dairy products, might also be associated with risk and with circulating IGF-I, but it is not clear if amino acids play a role in these relationships. Moreover, investigations of circulating concentrations of metabolites might reveal novel risk factors for prostate cancer. This thesis investigates plasma concentrations of amino acids and other metabolites in relation to protein intake, IGF-I, and prostate cancer risk using data from the European Prospective Investigation into Cancer and Nutrition (EPIC). To characterise plasma metabolite profile in men consuming markedly different amounts and types of animal products (meat-eaters, fish-eaters, vegetarians and vegans), cross-sectional analyses of 392 men in the EPIC-Oxford sub-cohort were conducted. Of 21 amino acids, six varied significantly by diet group, and the metabolite profile of vegans was different from those of other diet groups owing to lower concentrations of several glycerophospholipids and sphingolipids. In a case-control study nested within EPIC, with a mean follow-up time of seven years, the relationship of plasma metabolites with risk of prostate cancer overall, by time to diagnosis, by tumour characteristics, and with risk of prostate cancer death, was investigated. Data from 1,077 matched sets suggested that seven metabolites, from various classes, were associated with risk of prostate cancer overall (p < 0.05). After correction for multiple testing, 12 glycerophospholipids were inversely associated with risk of advanced prostate cancer (the strongest OR_1SD = 0.54; 95%CI: 0.40-0.72). In multivariate analyses, including data from 1,593 matched sets, principal component analysis (PCA) and treelet transform (TT) were used to identify patterns in metabolite profile, five of which were associated with risk of more aggressive tumour sub-types (high grade, advanced and aggressive disease) and/or prostate cancer death. There was a ≈ 50% lower risk of advanced and high grade prostate cancer in men with metabolite profiles characterised by high glycerophospholipids and sphingolipids (for advanced OR_{TT, top vs bottom third} = 0:48; 95%CI: 0:31-0:74), with similar results for high grade and PCA). To investigate if associations between protein intake and circulating IGF-I may be mediated by plasma amino acid concentrations, cross-sectional analyses of amino acid concentrations with protein intake and IGF-I concentrations were carried out in 1,697 and 1,142 control participants, respectively, from the nested case-control study. Dairy protein intake was positively associated with concentrations of branched-chain amino acids and several other essential amino acids, while plant protein intake was strongly associated only with histidine. Serum IGF-I was positively associated with arginine and inversely with ornithine and certain amino acid ratios. In conclusion, men with different dietary habits with respect to the consumption of protein types have different amino acid and metabolite profiles, and metabolite concentrations may be associated with risk of more high-risk prostate cancer sub-types (high grade, advanced and aggressive disease) and prostate cancer death. Further large-scale studies are needed to determine if metabolites play a role in aetiology or are markers of sub-clinical prostate cancer.

Quantitative Untersuchungen krankheitsspezifischer oder krankheitsassoziierter metabolischer Signaturen in humanen Körperflüssigkeiten („Clinical Metabolomics“) haben zum Ziel neue Ansätze für diagnostische oder therapeutische Konzepte zu entwickeln. Die simultane quantitative Analytik von Aminosäuren (AS) und Acylcarnitinen (AC) mittels Tandem-Massenspektrometrie (MS/MS) ermöglicht die Erfassung wichtiger Stoffwechselwege des humanen Metabolismus. Hierzu zählen der Stoffwechsel der ketogenen AS, des Harnstoffzyklus oder der β-Oxidation langkettiger Fettsäuren. Allerdings wird die Konzentration der verschiedenen metabolischen Parameter in humanen Körperflüssigkeiten durch eine Vielzahl präanalytischer in vitro Störfaktoren und in vivo Einflussgrößen beeinflusst. Diese können zu signifikanten Veränderungen der Laborergebnisse führen. Im Rahmen meiner Promotionsarbeit wurden in vitro Störfaktoren (Probenmaterial, Lagerung u. a.) und in vivo Einflussgrößen (Ernährung, physische Aktivität) untersucht und ein standardisiertes Präanalytik-Protokoll entwickelt. Dazu wurden pro Probe 3 µL Trockenblut (TB), 10 µL Serum oder Plasma nach Butylierung mittels Elektrospray-Ionisations-MS/MS analysiert und jeweils 26 AS und 35 AC in 1,5 Minuten simultan bestimmt. Als Ergebnis der zahlreichen systematischen Präanalytik-Untersuchungen konnten signifikante Konzentrationsunterschiede der Metabolite zwischen kapillärer und venöser Blutentnahme sowie in Abhängigkeit des Hämatokrits gefunden werden. Im Vergleich zu Serum und antikoaguliertem Plasma (EDTA, Citrat, Heparin) waren die Konzentrationen der langkettigen AC im TB 5-fach höher. Nahrungsaufnahme und körperliche Aktivität führten ebenfalls zu signifikanten Veränderungen der AS- und AC-Konzentrationen. Durch Optimierung des Probenaufarbeitungsprotokolls konnte die Variabilität zwischen den Messtagen für 17 AS und 6 AC auf < 20 % gesenkt werden. Die Ergebnisse meiner Promotionsarbeit unterstreichen den Einfluss präanalytischer Faktoren auf die Metabolomanalytik. Durch Etablierung und Einhaltung standardisierter präanalytischer Protokolle kann die präanalytische Varianz der Ergebnisse deutlich verringert werden. Sie stellen somit eine wichtige Voraussetzung für eine qualitativ hochwertige Metabolomanalytik im Rahmen klinischer Studien zur Identifizierung neuer Biomarker dar.

A variety of atherosclerosis and cardiovascular disease (ASCVD) phenotypes are tightly linked to changes in the cardiac energy metabolism that can lead to a loss of metabolic flexibility and to unfavorable clinical outcomes. We conducted an association analysis of 31 ASCVD phenotypes and 97 whole blood amino acids, acylcarnitines and derived ratios in the LIFE-Adult (n = 9646) and LIFE-Heart (n = 5860) studies, respectively. In addition to hundreds of significant associations, a total of 62 associations of six phenotypes were found in both studies. Positive associations of various amino acids and a range of acylcarnitines with decreasing cardiovascular health indicate disruptions in mitochondrial, as well as peroxisomal fatty acid oxidation. We complemented our metabolite association analyses with whole blood and peripheral blood mononuclear cell (PBMC) gene-expression analyses of fatty acid oxidation and ketone-body metabolism related genes. This revealed several differential expressions for the heart failure biomarker N-terminal prohormone of brain natriuretic peptide (NT-proBNP) in peripheral blood mononuclear cell (PBMC) gene expression. Finally, we constructed and compared three prediction models of significant stenosis in the LIFE-Heart study using (1) traditional risk factors only, (2) the metabolite panel only and (3) a combined model. Area under the receiver operating characteristic curve (AUC) comparison of these three models shows an improved prediction accuracy for the combined metabolite and classical risk factor model (AUC = 0.78, 95%-CI: 0.76–0.80). In conclusion, we improved our understanding of metabolic implications of ASCVD phenotypes by observing associations with metabolite concentrations and gene expression of the mitochondrial and peroxisomal fatty acid oxidation. Additionally, we demonstrated the predictive potential of the metabolite profile to improve classification of patients with significant stenosis.