Isotopics – May 2019 | Edition 9
Welcome to our first IsoTopics™ mass spec newsletter for 2019! Spring has sprung and it is raining isotopes. We’ve added over 200 products that can be found in our updated “Stable Isotopes for Mass Spectrometry” catalog, so be sure to check it out. We are also very excited about our new 0.1 mg sizes for key metabolites. Now you can pick and choose to build your own standards kit. CIL is always interested in how our customers are using stable isotopes, so we have selected a few articles we would like to share. If you are working on something new and exciting, please feel free to tell us about it.
Assessment of NAD+ Metabolism in Human Cell Cultures, Erythrocytes, Cerebrospinal Fluid and Primate Skeletal Muscle
Demarest, T.G.; Truong, G.T.D.; Lovett, J.; et al.
Given the importance of the NAD+ metabolome in aging and cellular health, Demarest et al. developed a novel isotope dilution mass spectrometry method (utilizing HILIC-MRM/MS) for their quantification in a range of biosamples (ranging from cultured cells to clinical tissues). The optimized method is both rapid (14 min runs) and sensitive (e.g., NAD+ and NMN quantified for first time in CSF), while utilizing a U-13C yeast extract (ISO1) for absolute quantification. A breadth of cofactors (e.g., NAD+, NADH, NMR) and AcCoA are successfully quantified via standard curves. This method should prove useful in better understanding the metabolic alterations arising from normal processes and disorders.
Mitochondrial Fusion Supports Increased Oxidative Phosphorylation During Cell Proliferation
Yao, C.H.; Wang, R.; Wang, Y.; et al.
In an effort to better understand the Warburg effect (or aerobic glycolysis) in relation to the metabolic requirements of cell proliferation, Yao et al. applied a model where proliferation could be turned on and off. Using stable isotopes and metabolomic techniques, they then quantified the metabolic changes in various cell types as a function of cell division. The authors show that the cancer cells they examined consume more oxygen during proliferation to sustain their mitochondria. Contrary to the common assumption that proliferating cells increase glycolysis at the expense of mitochondrial metabolism, their results show that glycolysis and mitochondrial respiration increase by equal amounts during proliferation. The findings may help design improved tests and targeted treatments for these tumors.
Essential Amino Acid-enriched Meal Replacement Promotes Superior Net Protein Balance in Older, Overweight Adults
Coker, R.H.; Shin, K.; Scholten, K.; et al.
To help reduce muscle atrophy and sarcopenia in older adults, Coker et al. developed an essential amino acid-enriched meal replacement (EMR). This advanced nutritional product is compositionally distinct from other market available meal replacements, with its efficacy tested in a comparative, whole-body protein kinetics study. Using stable isotope tracer methodology and time-course LC-ESI-MS analysis of plasma samples, the EMR formulation promoted more than 2-fold increments in whole body net protein balance compared to a high protein meal replacement. This EMR approach may represent a valuable lifestyle intervention in preserving lean tissue mass and promoting weight loss in older, overweight adults.
Traceability to a Primary Reference Measurement Procedure (ID-LCMS): A Key Step in Validating the Clinical Accuracy and Safety of Hospital Blood Glucose Monitoring Systems
Wang, Y.; Hu, X.; Tang, J.; et al.
Considering the negative impact of clinically inaccurate blood glucose monitoring systems (BGMS), Wang and colleagues conducted a metrological traceability study of their isotope dilution MS (IDMS) method with subsequent comparison to reference and hospital methods for glucose measurement. IDMS involved stable isotope dilution (with 13C6 D-glucose) and LC-MRM/MS. Traceability of IDMS was established against NIST standard reference materials, before its analytical validation and calibration alignment against current hospital BGM systems in China. Results revealed the IDMS method to deliver highly accurate glucose determinations that could be adopted in accuracy assessment and performance evaluation of glucose monitoring systems used in clinical practice.
NMR- and MS-based Stable Isotope-resolved Metabolomics and Applications in Cancer Metabolism
Lane, A.N.; Higashi, R.M.; Fan, T.W.
In this article, Lane et al. reviews the stable isotope resolved metabolomic (SIRM) methods for cancer metabolism studies. A multitude of stable isotope-labeled tracers are discussed herein for pathway mapping and qualitative/quantitative analysis of metabolic panels via high resolution MS and NMR spectroscopy techniques. In addition, current and emerging applications are summarized, while insights into future directions for tracer implementation, methodology, and informatics are also noted.