In vivo high-resolution magic angle spinning magnetic resonance spectroscopy of Drosophila melanogaster at 14.1 T shows trauma in aging and in innate immune-deficiency is linked to reduced insulin signaling

Effects of a small, volatile bacterial molecule on Pseudomonas aeruginosa bacteria using whole cell high-resolution magic angle spinning nuclear magnetic resonance spectroscopy and genomics

In the present study, high-resolution magic-angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy was applied to live Pseudomonas aeruginosa (PA) bacterial cells to determine the metabolome of this opportunistic Gram-negative human pathogen, and in particular, its response to the volatile aromatic low molecular weight signaling molecule, 2-aminoacetophenone (2-AA). Multi-dimensional HRMAS NMR is a promising method which may be used to determine the in vivo metabolome of live intact bacterial cells; 2-AA is produced by PA and triggers the emergence of phenotypes that promote chronic infection phenotypes in in vitro and in vivo (animal) models. In the present study, we applied one-dimensional and two-dimensional proton (¹H) HRMAS NMR to PA cells which were grown with or without 2-AA in order to examine the associations between metabolites and cellular processes in response to 2-AA. We also compared whole-genome transcriptome profiles of PA cells grown with or without 2-AA and found that 2-AA promoted profound metabolic changes in the PA cells. By comparing the whole-genome transcriptome profiles and metabolomic analysis, we demonstrated that 2-AA profoundly reprogramed the gene expression and metabolic profiles of the cells. Our in vivo¹H HRMAS NMR spectroscopy may prove to be a helpful tool in the validation of gene functions, the study of pathogenic mechanisms, the classification of microbial strains into functional/clinical groups and the testing of anti-bacterial agents.

In-Vivo NMR Spectroscopy: A Powerful and Complimentary Tool for Understanding Environmental Toxicity

Part review, part perspective, this article examines the applications and potential of in-vivo Nuclear Magnetic Resonance (NMR) for understanding environmental toxicity. In-vivo NMR can be applied in high field NMR spectrometers using either magic angle spinning based approaches, or flow systems. Solution-state NMR in combination with a flow system provides a low stress approach to monitor dissolved metabolites, while magic angle spinning NMR allows the detection of all components (solutions, gels and solids), albeit with additional stress caused by the rapid sample spinning. With in-vivo NMR it is possible to use the same organisms for control and exposure studies (controls are the same organisms prior to exposure inside the NMR). As such individual variability can be reduced while continual data collection over time provides the temporal resolution required to discern complex interconnected response pathways. When multidimensional NMR is combined with isotopic labelling, a wide range of metabolites can be identified in-vivo providing a unique window into the living metabolome that is highly complementary to more traditional metabolomics studies employing extracts, tissues, or biofluids.

Applications of high-resolution magic angle spinning MRS in biomedical studies I-cell line and animal models

High-resolution magic angle spinning (HRMAS) MRS allows for direct measurements of non-liquid tissue and cell specimens to present valuable insights into the cellular metabolisms of physiological and pathological processes. HRMAS produces high-resolution spectra comparable to those obtained from solutions of specimen extracts but without complex metabolite extraction processes, and preserves the tissue cellular structure in a form suitable for pathological examinations following spectroscopic analysis. The technique has been applied in a wide variety of biomedical and biochemical studies and become one of the major platforms of metabolomic studies. By quantifying single metabolites, metabolite ratios, or metabolic profiles in their entirety, HRMAS presents promising possibilities for diagnosis and prediction of clinical outcomes for various diseases, as well as deciphering of metabolic changes resulting from drug therapies or xenobiotic interactions. In this review, we evaluate HRMAS MRS results on animal models and cell lines reported in the literature, and present the diverse applications of the method for the understanding of pathological processes and the effectiveness of therapies, development of disease animal models, and new progress in HRMAS methodology.

In vivo high-resolution magic angle spinning magnetic and electron paramagnetic resonance spectroscopic analysis of mitochondria-targeted peptide in Drosophila melanogaster with trauma-induced thoracic injury

Trauma is the most common cause of mortality among individuals aged between 1 and 44 years and the third leading cause of mortality overall in the US. In this study, we examined the effects of trauma on the expression of genes in Drosophila melanogaster, a useful model for investigating genetics and physiology. After trauma was induced by a non-lethal needle puncture of the thorax, we observed the differential expression of genes encoding for mitochondrial uncoupling proteins, as well as those encoding for apoptosis-related and insulin signaling-related proteins, thus indicating muscle functional dysregulation. These results prompted us to examine the link between insulin signaling and mitochondrial dysfunction using in vivo nuclear magnetic resonance (NMR) with complementary electron paramagnetic resonance (EPR) spectroscopy. Trauma significantly increased insulin resistance biomarkers, and the NMR spectral profile of the aged flies with trauma-induced thoracic injury resembled that of insulin-resistant chico mutant flies. In addition, the mitochondrial redox status, as measured by EPR, was significantly altered following trauma, indicating mitochondrial uncoupling. A mitochondria-targeted compound, Szeto-Schiller (SS)-31 that promotes adenosine triphosphate (ATP) synthesis normalized the NMR spectral profile, as well as the mitochondrial redox status of the flies with trauma-induced thoracic injury, as assessed by EPR. Based on these findings, we propose a molecular mechanism responsible for trauma-related mortality and also propose that trauma sequelae in aging are linked to insulin signaling and mitochondrial dysfunction. Our findings further suggest that SS-31 attenuates trauma-associated pathological changes.

Metabolite localization in living drosophila using High Resolution Magic Angle Spinning NMR

We have developed new methods enabling in vivo localization and identification of metabolites through their ¹H NMR signatures, in a drosophila. Metabolic profiles in localized regions were obtained using HR-MAS Slice Localized Spectroscopy and Chemical Shift Imaging at high magnetic fields. These methods enabled measurement of metabolite contents in anatomic regions of the fly, demonstrated by a decrease in β-alanine signals in the thorax of flies showing muscle degeneration.

(1)H high resolution magic-angle coil spinning (HR-MACS) μNMR metabolic profiling of whole Saccharomyces cervisiae cells: a demonstrative study

The low sensitivity and thus need for large sample volume is one of the major drawbacks of Nuclear Magnetic Resonance (NMR) spectroscopy. This is especially problematic for performing rich metabolic profiling of scarce samples such as whole cells or living organisms. This study evaluates a ¹H HR-MAS approach for metabolic profiling of small volumes (250 nl) of whole cells. We have applied an emerging micro-NMR technology, high-resolution magic-angle coil spinning (HR-MACS), to study whole Saccharomyces cervisiae cells. We find that high-resolution high-sensitivity spectra can be obtained with only 19 million cells and, as a demonstration of the metabolic profiling potential, we perform two independent metabolomics studies identifying the significant metabolites associated with osmotic stress and aging.

A small volatile bacterial molecule triggers mitochondrial dysfunction in murine skeletal muscle

Mitochondria integrate distinct signals that reflect specific threats to the host, including infection, tissue damage, and metabolic dysfunction; and play a key role in insulin resistance. We have found that the Pseudomonas aeruginosa quorum sensing infochemical, 2-amino acetophenone (2-AA), produced during acute and chronic infection in human tissues, including in the lungs of cystic fibrosis (CF) patients, acts as an interkingdom immunomodulatory signal that facilitates pathogen persistence, and host tolerance to infection. Transcriptome results have led to the hypothesis that 2-AA causes further harm to the host by triggering mitochondrial dysfunction in skeletal muscle. As normal skeletal muscle function is essential to survival, and is compromised in many chronic illnesses, including infections and CF-associated muscle wasting, we here determine the global effects of 2-AA on skeletal muscle using high-resolution magic-angle-spinning (HRMAS), proton (¹H) nuclear magnetic resonance (NMR) metabolomics, in vivo³¹P NMR, whole-genome expression analysis and functional studies. Our results show that 2-AA when injected into mice, induced a biological signature of insulin resistance as determined by ¹H NMR analysis-, and dramatically altered insulin signaling, glucose transport, and mitochondrial function. Genes including Glut4, IRS1, PPAR-γ, PGC1 and Sirt1 were downregulated, whereas uncoupling protein UCP3 was up-regulated, in accordance with mitochondrial dysfunction. Although 2-AA did not alter high-energy phosphates or pH by in vivo³¹P NMR analysis, it significantly reduced the rate of ATP synthesis. This affect was corroborated by results demonstrating down-regulation of the expression of genes involved in energy production and muscle function, and was further validated by muscle function studies. Together, these results further demonstrate that 2-AA, acts as a mediator of interkingdom modulation, and likely effects insulin resistance associated with a molecular signature of mitochondrial dysfunction in skeletal muscle. Reduced energy production and mitochondrial dysfunctional may further favor infection, and be an important step in the establishment of chronic and persistent infections.

Live-cell high resolution magic angle spinning magnetic resonance spectroscopy for in vivo analysis of Pseudomonas aeruginosa metabolomics

Pseudomonas aeruginosa (PA) is a pathogenic gram-negative bacterium that is widespread in nature, inhabiting soil, water, plants and animals. PA is a prevalent cause of deleterious human infections, particularly in patients whose host defense mechanisms have been compromised. Metabolomics is an important tool used to study host-pathogen interactions and to identify novel therapeutic targets and corresponding compounds. The aim of the present study was to report the metabolic profile of live PA bacteria using in vivo high-resolution magic angle spinning (HRMAS) nuclear magnetic resonance spectroscopy (NMR), in combination with 1- and 2-dimensional HRMAS NMR. This methodology provides a new and powerful technique to rapidly interrogate the metabolome of intact bacterial cells and has several advantages over traditional techniques that identify metabolome components from disrupted cells. Furthermore, application of multidimensional HRMAS NMR, in combination with the novel technique total through-Bond correlation Spectroscopy (TOBSY), is a promising approach that may be used to obtain in vivo metabolomics information from intact live bacterial cells and can mediate such analyses in a short period of time. Moreover, HRMAS ¹H NMR enables the investigation of the associations between metabolites and cell processes. In the present study, we detected and quantified several informative metabolic molecules in live PA cells, including N-acetyl, betaine, citrulline, alanine and glycine, which are important in peptidoglycan synthesis. The results provided a complete metabolic profile of PA for future studies of PA clinical isolates and mutants. In addition, this in vivo NMR biomedical approach might have clinical utility and should prove useful in gene function validation, the study of pathogenetic mechanisms, the classification of microbial strains into functional/clinical groups, the testing of anti-bacterial agents and the determination of metabolic profiles of bacterial mutants.