Metabolic network failures in Alzheimer's disease: A biochemical road map

Introduction

The Alzheimer's Disease Research Summits of 2012 and 2015 incorporated experts from academia, industry, and nonprofit organizations to develop new research directions to transform our understanding of Alzheimer's disease (AD) and propel the development of critically needed therapies. In response to their recommendations, big data at multiple levels are being generated and integrated to study network failures in disease. We used metabolomics as a global biochemical approach to identify peripheral metabolic changes in AD patients and correlate them to cerebrospinal fluid pathology markers, imaging features, and cognitive performance.

A biochemical perspective on the use of tandem mass spectrometry for newborn screening and clinical testing

The first newborn screen was a clinical test to detect a disorder of the biochemistry of the amino acid, phenylalanine. This disorder, known as phenylketonuria, produces profound mental retardation if not detected and treated early in life. Early screening programs relied on inexpensive population screening techniques that have all but been replaced by more accurate analytical methods such as tandem mass spectrometry (MS/MS). MS/MS enables a multianalyte approach for detecting biochemical disorders such that a metabolic profile is obtained rather than a single analyte measurement. The metabolic profile has clearly shown improvements in the detection of diseases such as phenylketonuria and several new disorders arising from errors in fatty acid oxidation and organic acid metabolism. MS/MS is a powerful tool for accessing the metabolic status of a newborn and can detect both inborn metabolic errors as well as examine the effect of acquired diseases or pharmacologic intervention on intermediary metabolism.     

LC–MS/MS progress in newborn screening

Newborn screening programs detect treatable disorders in infants before they become symptomatic. Liquid chromatography-tandem mass spectrometry (LC–MS/MS) has greatly increased the screening possibilities by monitoring levels of amino acids and acylcarnitines. After the initial screening step, LC–MS/MS can also be used in screening positive samples as a second tier test to differentiate between true and false positive samples.As the list of disorders screened for by LC-tandem MS increases, questions arise about screening for untreatable disorders, such as some lysosomal storage diseases (LSDs). For LSDs screening methods are being developed and tested more quickly than treatments are becoming available. This goes against one of the main tenets of newborn screening which requires that a treatment be available.LC–MS/MS can detect several disorders with a single injection, which is important in high throughput laboratories. Measuring different amino acids and acylcarnitines can be used to detect up to 45 different inherited disorders depending on how diseases are counted. The LSD assays are designed in a similar way to detect multiple disorders with common sample preparation and a single injection. The clinical implications of applying this technology to NBS on a large scale in many jurisdictions across the world are discussed.     

Identification of novel diagnostic biomarkers in endometrial cancer using targeted metabolomic profiling

PurposeEndometrial cancer (EC) is the most common gynecological malignancy with high disease burden especially in advanced stages of the disease. Our study investigated the metabolomic profile of EC patient’s serum with the aim of identifying novel diagnostic biomarkers that could be used especially in early disease detection.Material and methodsUsing targeted metabolomic serum profiling based on HPLC-TQ/MS, women with EC (n ​= ​15) and controls (n ​= ​21) were examined for 232 endogenous metabolites.ResultsTop performing biomarkers included ceramides, acylcarnitines and 1-methyl adenosine. Top 4 biomarkers combined achieved 94% sensitivity with 75% specificity with AUC 92.5% (CI 90.5–94.5%). Individual markers also provided significant predictive values: C16-ceramide achieved sensitivity 73%, specificity 81%, AUC 0.83, C22-ceramide sensitivity 67%, specificity 81%, AUC 0.77, hydroxyhexadecenoylcarnitine sensitivity 60%, specificity 96%, AUC 0.76 and 1-methyladenosine sensitivity 67%, specificity 81%, AUC 0.75. The individual markers, however, did not reach the high sensitivity and specificity of the 4-biomarker combination.ConclusionsUsing mass spectrometry targeted metabolomic profiling, ceramides, acylcarnitines and 1-methyladenosine were identified as potential diagnostic biomarkers for EC. Additionally, these identified metabolites may provide additional insight into cancer cell metabolism.     

Evaluation of carnitine deficit in very low birth weight preterm newborns small for their gestational age

Objective: To verify whether small-for-gestational-age (SGA) preterm newborns represent a special risk group for carnitine deficiency. Secondary outcome includes assessment of longitudinal differences of total carnitine (TC), free carnitine (FC) and acylcarnitines between SGA and appropriate-for-gestational-age (AGA).

Methods: A retrospective study to evaluate carnitine and acylcarnitines profile on 144 very-low-birth weight newborns (VLBW), classified as AGA (n?=?73) and SGA (n?=?71), was performed by tandem mass spectrometry, during their first 5 weeks of life. Carnitine deficiency was defined as FC <40?µmol/L and FC/TC <0.7.

Results: Carnitine deficiency was observed in the two study groups throughout the monitoring period (maximum FC: 36.05?µmol/L in AGA and 32.24?µmol/L in SGA). FC/TC remains under 0.7 in both with progressive improvement. Unlike expected, a comparatively higher value of TC, FC and total acylcarnitines (tAC) was found in SGA during the first 2 weeks, with significant relevance on day 3–5, especially for tAC (p?<?0.001). The only acylcarnitine with persistently lower value in SGA is C5 (p?<?0.05 in first 2 weeks).

Conclusions: A carnitine deficiency was demonstrated in all VLBW. Although birth weight restriction has been suggested as a risk factor for impaired carnitine status, in our study, SGA was not related with higher carnitine deficiency.     

Identification of Novel Diagnostic Biomarkers in Breast Cancer Using Targeted Metabolomic Profiling

IntroductionBreast cancer (BC) is the most common cancer in women, with a high disease burden, especially in the advanced disease stages. Our study investigated the metabolomic profile of breast cancer patients’ serum with the aim of identifying novel diagnostic biomarkers that could be used, especially for early disease detection.Materials and MethodsUsing targeted metabolomic serum profiling based on high-performance liquid chromatography mass spectrometry, women with BC (n = 39) and a control group (n = 21) were examined for 232 endogenous metabolites.ResultsThe top performing biomarkers included acylcarnitines (ACs) and 9,12-linoleic acid. A combined panel of the top 4 biomarkers achieved 83% sensitivity and 81% specificity, with an area under the curve (AUC) of 0.839 (95% confidence interval, 0.811-0.867). Individual markers also provided significant predictive values: AC 12:0, sensitivity of 72%, specificity of 67%, and AUC of 0.71; AC 14:2, sensitivity of 74%, specificity of 71%, and AUC of 0.73; AC 14:0: sensitivity of 67%, specificity of 81%, and AUC of 0.73; and 9,12-linoleic acid, sensitivity of 69%, specificity of 67%, and AUC of 0.71. The individual markers, however, did not reach the high sensitivity and specificity of the 4-biomarker combination.ConclusionUsing mass spectrometry-targeted metabolomic profiling, ACs and 9,12-linoleic acid were identified as potential diagnostic biomarkers for breast cancer. Additionally, these identified metabolites could provide additional insight into cancer cell metabolism.     

Changes in blood carnitine and acylcarnitine profiles of very long-chain acyl-CoA dehydrogenase-deficient mice subjected to stress

BACKGROUND: In humans with deficiency of the very long-chain acyl-CoA dehydrogenase (VLCAD), C14-C18 acylcarnitines accumulate. In this paper we have used the VLCAD knockout mouse as a model to study changes in blood carnitine and acylcarnitine profiles under stress. DESIGN: VLCAD knockout mice exhibit stress-induced hypoglycaemia and skeletal myopathy; symptoms resembling human VLCADD. To study the extent of biochemical derangement in response to different stressors, we determined blood carnitine and acylcarnitine profiles after exercise on a treadmill, fasting, or exposure to cold. RESULTS: Even in a nonstressed, well-fed state, knockout mice presented twofold higher C14-C18 acylcarnitines and a lower free carnitine of 72% as compared to wild-type littermates. After 1 h of intense exercise, the C14-C18 acylcarnitines in blood significantly increased, but free carnitine remained unchanged. After 8 h of fasting at 4 degrees C, the long-chain acylcarnitines were elevated 5-fold in knockout mice in comparison with concentrations in unstressed wild-type mice (P < 0.05), and four out of 12 knockout mice died. Free carnitine decreased to 44% as compared with unstressed wild-type mice. An increase in C14-C18 acylcarnitines and a decrease of free carnitine were also observed in fasted heterozygous and wild-type mice. CONCLUSIONS: Long-chain acylcarnitines in blood increase in knockout mice in response to different stressors and concentrations correlate with the clinical condition. A decrease in blood free carnitine in response to severe stress is observed in knockout mice but also in wild-type littermates. Monitoring blood acylcarnitine profiles in response to different stressors may allow systematic analysis of therapeutic interventions in VLCAD knockout mice.     

Inflammatory macrophage memory in nonsteroidal anti-inflammatory drug–exacerbated respiratory disease

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