Stable isotope-resolved metabolomics (SIRM) is a powerful tool for understanding disease. Advances in SIRM techniques have improved isotopic delivery and expanded the workflow from exclusively in vitro applications to in vivo methodologies to study systemic metabolism. Here, we report a simple, minimally-invasive and cost-effective method of tracer delivery to study SIRM in vivo in laboratory mice. Following a brief fasting period, we orally administered a solution of [U-13C] glucose through a blunt gavage needle without anesthesia, at a physiological dose commonly used for glucose tolerance tests (2 g/kg bodyweight). We defined isotopic enrichment in plasma and tissue at 15, 30, 120, and 240 min post-gavage. 13C-labeled glucose peaked in plasma around 15 min post-gavage, followed by period of metabolic decay and clearance until 4 h. We demonstrate robust enrichment of a variety of central carbon metabolites in the plasma, brain and liver of C57/BL6 mice, including amino acids, neurotransmitters, and glycolytic and tricarboxylic acid (TCA) cycle intermediates. We then applied this method to study in vivo metabolism in two distinct mouse models of diseases known to involve dysregulation of glucose metabolism: Alzheimer’s disease and type II diabetes. By delivering [U-13C] glucose via oral gavage to the 5XFAD Alzheimer’s disease model and the Lepob/ob type II diabetes model, we were able to resolve significant differences in multiple central carbon pathways in both model systems, thus providing evidence of the utility of this method to study diseases with metabolic components. Together, these data clearly demonstrate the efficacy and efficiency of an oral gavage delivery method, and present a clear time course for 13C enrichment in plasma, liver and brain of mice following oral gavage of [U-13C] glucose—data we hope will aid other researchers in their own 13C-glucose metabolomics study design.
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This work was supported by funding from the National Institutes of Health (NIH) 1R01AG060056 and R01AG062550 to L.A.J.; NIH 1T32AG057461 to H.C.W.; NIH grant R01 AG066653, St Baldrick’s Career Development Award, Rally Foundation Independent Investigator Grant, and the Shared Resource(s) of the University of Kentucky Markey Cancer Center (P30CA177558) to R.C.S.
The following figures and file are available online at http://www.mdpi.com/2218-1989/10/12/501/s1: Figure S1: Plasma 13C enrichment in metabolites over time. Figure S2: Liver glycogen flux from 13C glucose. Supplementary File S1. Raw data as relative abundance (natural abundance stripped) and fractional enrichment.
The materials are also available for download as the additional file listed at the end of this record.
Williams, Holden C.; Piron, Margaret A.; Nation, Grant K.; Walsh, Adeline E.; Young, Lyndsay E. A.; Sun, Ramon C.; and Johnson, Lance A., "Oral Gavage Delivery of Stable Isotope Tracer for in Vivo Metabolomics" (2020). Sanders-Brown Center on Aging Faculty Publications. 152.