Dr Daniel Wilkinson, University of Nottingham
The study of human physiology and metabolism has continually progressed in line with defining technological developments and their application to in vivo research. As physiologists, we now possess an exquisite array of tools to measure aspects of human physiology from whole-body function outcomes down to discrete single-cell (or subcellular) changes. One of the issues with measuring in vivo human metabolism is the dynamism of these systems to physiological insults.
For example, the measure of metabolite, protein or mRNA abundance at a single time point, or series of time points, only provides a static measure at the points. It provides no information on the turnover, flux or movement of these molecules between or across these time points and physiological systems, which could provide key insight into the biology driving human physiological change. However, including something called a “stable isotope tracer” within a human physiological experiment can provide this missing extra dimensionality to our understanding.
Stable isotopes are elements that occupy the same position in the periodic table, and are essentially “chemically and functionally identical” but differ in mass due to a different number of neutrons within the atomic nucleus. This difference in mass makes these isotopes analytically distinguishable from each other. Therefore, by replacing one (or more) of the 12Carbon, 14Nitrogen, 16Oxygen, or 1Hydrogen within a compound of interest (traditionally, amino acids, lipids or sugars) with their heavier, less naturally abundant stable isotopic equivalents, 13Carbon (13C), 15Nitrogen (15N), 18Oxygen (18O), or 2Hydrogen (2H or D), respectively, a stable isotope tracer is created. These labelled compounds can then be introduced into a physiological system to be studied, and the fate of this compound and/or its metabolites can be monitored over time, providing a dynamic measurement of metabolism within this system.
While stable isotopes and their application to the study of metabolism are almost 100 years old, with the seminal discovery and initial application being performed across the 1930s by colleagues Harold Urey, Rudolph Schoenheimer and David Rittenberg at Columbia University in the US, their widespread application to human physiological research remains a relatively niche area to this day.
Technical Development of Stable Isotope Tracers
The Stable Isotope Mass Spectrometry (SIMS) facility within the Centre Of Ageing, Metabolism And Physiology (COMAP), led by Professors Philip Atherton and Ken Smith, has been at the forefront of the development and application of stable isotope tracers to human physiological research for over 30 years. In particular, over the past decade this lab has rapidly helped to progress analytical and technical developments in this area, being one of the first labs to develop and utilise less or minimally invasive stable isotope tracer techniques using deuterium oxide or “Heavy Water”. Using these approaches, COMAP has devised a number of techniques to measure in vivo in humans, the turnover of multiple metabolic pools (protein, sugars, lipids and nucleic acids) over periods of hours, days or even weeks. It allows them to gain great insight into the biology driving health and disease in humans, which previously was not possible.
To drive these techniques even further forward and provide insight to interested researchers that may not have heard of these potential benefits of such tracer techniques, COMAP has developed a Stable Isotope Tracer workshop supported by The Physiological Society called “The Application of Stable Isotope Tracer Techniques in Human Physiological Research” which will run for three days from the 16 – 18 August 2023. This workshop is not just for early career researchers and PhD students but also senior researchers who may be interested in learning new applications and techniques for their research.
The workshop will be split into theoretical and practical days, with the first day being solely theory-based, introducing the history, background and theory behind the application of stable isotope tracers in human physiological research. How it can be applied to several different physiological systems and endpoints, whilst also introducing novel and innovative new applications through some guest lectures. The workshop will then provide some practical insight into these techniques within the labs, particularly how the analytical Mass Spectrometry side produces the data which allows us to measure these aspects of metabolism, including the reduction and calculation of key data.
As a research group we hope that what we present in this workshop will be of interest and help drive forward the next batch of stable isotope researchers to continue the development and application of these essential techniques for physiological research.
You can see the full programme and register for “The Application of Stable Isotope Tracer Techniques in Human Physiological Research” at https://www.physoc.org/events/the-application-of-stable-isotope-tracer-techniques-in-human-physiological-research-three-day-workshop/