Periodic Reporting for period 1 - BioIsoK (Mechanisms of K stable isotope fractionation in vertebrates and significance to their energy metabolism)
Okres sprawozdawczy: 2018-10-01 do 2020-09-30
The recent advent of the use of natural stable isotopes of bio-essential metals (e.g. Mg, Ca, Cu…) opened up unprecedented avenues for the study of their cycling in vertebrates and reveal aspects of physiology that remain otherwise unseen.
Potassium (K) is the only multi-isotope bio-essential and ubiquitous metal that is so far virtually unexplored in the field of vertebrate physiology, because of specific analytical hindrances with the currently widely available techniques (e.g. multi-collector inductively coupled plasma mass-spectrometry or MC-ICP-MS).
Nevertheless, K isotopes show a high potential for the study of physiopathology and metabolism of extant and extinct vertebrates. Potassium represents the major inorganic ion (K+) of the intracellular fluids, contrasting with the actively maintained low concentrations in extracellular fluids. This heterogeneous distribution is maintained by its active transport across cell membranes and is at the basis of a series of vital functions. In the hypothesis that transmembrane transport of K+ is associated with isotope fractionation, the key organs of the K cycle (e.g. muscle, liver or kidney) should significantly contribute to the heterogeneous distribution of K isotopes within the organisms. Furthermore, the current understanding of the K whole-body and cellular cycling in vertebrates suggests that K isotope distribution could notably depend on the metabolic rates of the organism, and therefore inform about allometry or thermo-physiology traits. Such an approach is also of interest for investigating the K cycle in health and disease of extant vertebrates such as human.
In order to realize the currently untapped potential of K isotopes for the study of vertebrate biology, the BioIsoK project intended to:
a. Develop methods to measure K stable isotope compositions with sufficient accuracy and precision for biological variability to be resolved, using a state-of-the-art prototype of collision/reaction cell double focusing mass spectrometer (CRC-MC-ICP-MS).
b. Identify the main mechanisms driving the distribution of K isotopes in modern vertebrates
c. Assess the significance of K stable isotopes as indicators of vertebrate energy metabolism
Potassium (K) is the only multi-isotope bio-essential and ubiquitous metal that is so far virtually unexplored in the field of vertebrate physiology, because of specific analytical hindrances with the currently widely available techniques (e.g. multi-collector inductively coupled plasma mass-spectrometry or MC-ICP-MS).
Nevertheless, K isotopes show a high potential for the study of physiopathology and metabolism of extant and extinct vertebrates. Potassium represents the major inorganic ion (K+) of the intracellular fluids, contrasting with the actively maintained low concentrations in extracellular fluids. This heterogeneous distribution is maintained by its active transport across cell membranes and is at the basis of a series of vital functions. In the hypothesis that transmembrane transport of K+ is associated with isotope fractionation, the key organs of the K cycle (e.g. muscle, liver or kidney) should significantly contribute to the heterogeneous distribution of K isotopes within the organisms. Furthermore, the current understanding of the K whole-body and cellular cycling in vertebrates suggests that K isotope distribution could notably depend on the metabolic rates of the organism, and therefore inform about allometry or thermo-physiology traits. Such an approach is also of interest for investigating the K cycle in health and disease of extant vertebrates such as human.
In order to realize the currently untapped potential of K isotopes for the study of vertebrate biology, the BioIsoK project intended to:
a. Develop methods to measure K stable isotope compositions with sufficient accuracy and precision for biological variability to be resolved, using a state-of-the-art prototype of collision/reaction cell double focusing mass spectrometer (CRC-MC-ICP-MS).
b. Identify the main mechanisms driving the distribution of K isotopes in modern vertebrates
c. Assess the significance of K stable isotopes as indicators of vertebrate energy metabolism
The first work package aimed at exploring and optimizing the performances of the Proteus CRC-MC-ICP-MS prototype (developed by Thermo Fisher Scientific) for the analysis of K stable isotope ratios (41K/39K) and at establishing a protocol for the accurate and precise measurement of K stable isotope ratios. To this end, we explored the performances of the Proteus prototype in terms of precision and accuracy by developing an analytical strategy exploring the use of two different reaction gases. We compared its behaviour with measurements carried out using previously published data acquired with traditional MC-ICP-MS instruments and first generation of CRC- MC-ICP-MS instruments. This work led to the conclusion that the analytical methods developed for K isotopes on the Proteus are of high quality and competitive when compared to other more traditional technologies. This work also led to the constitution of a dataset of K isotope compositions of a series of 9 geological reference materials that will be made available to the community in a methodological publication.
The second work package aimed at developing a sample preparation procedure allowing precise and accurate analysis of K isotopes from a wide range of biological samples and reference materials while being versatile enough for geological materials processing as well. To this end, we adapted the K purification procedures for a wide range of biological samples. This chemical procedure was tested and met all quality criteria required for stable isotope analyses in a wide array of natural materials. We then calibrated the isotope compositions of a set of biological reference materials to provide the community with the basis for cross-laboratory benchmarking. This work notably led to the characterization of the K stable isotope compositions of a set of 7 biological reference materials with further successful quality controls.
The third work package aimed assessing the main mechanisms of K stable isotope cycling in vertebrate organisms. To this end, we measured the K isotope ratios of samples from biological materials and tissues (diet, blood plasma, red blood cells and whole blood, skeletal muscle and heart tissue, liver, bone, kidney, milk, fecal and urinary losses) of adult vertebrates reared in controlled feeding experiments for several animal model species. We built an unprecedented dataset of about 165 isotope compositions of these animal tissues. These results enabled us to assess the main mechanisms that drive K isotope fractionation at the organism level by first establishing the relationships between isotope compositions of the main K fluxes and reservoirs within vertebrate organisms. The dataset supports the predominant role of the transmembrane active transport of K as a key mechanism, with remarkably 41K enriched intracellular milieu in contrast with extracellular reservoirs (e.g. blood plasma). The study of the distributions of K isotopes in vertebrates also suggests that the homeostatic (K cycle regulation) response of the organism to varying dietary K availability plays an important role in the variability observed.
Throughout the BioIsoK project, the results of this research were presented in two main international conferences and an international workshop (Goldschmidt Conference and “Reaction Gases” workshop, 2020 Barcelona; 2020 Hawaii Goldschmidt conference). The dissemination of the results in scientific publications is due in the upcoming months in peer-review journals.
The second work package aimed at developing a sample preparation procedure allowing precise and accurate analysis of K isotopes from a wide range of biological samples and reference materials while being versatile enough for geological materials processing as well. To this end, we adapted the K purification procedures for a wide range of biological samples. This chemical procedure was tested and met all quality criteria required for stable isotope analyses in a wide array of natural materials. We then calibrated the isotope compositions of a set of biological reference materials to provide the community with the basis for cross-laboratory benchmarking. This work notably led to the characterization of the K stable isotope compositions of a set of 7 biological reference materials with further successful quality controls.
The third work package aimed assessing the main mechanisms of K stable isotope cycling in vertebrate organisms. To this end, we measured the K isotope ratios of samples from biological materials and tissues (diet, blood plasma, red blood cells and whole blood, skeletal muscle and heart tissue, liver, bone, kidney, milk, fecal and urinary losses) of adult vertebrates reared in controlled feeding experiments for several animal model species. We built an unprecedented dataset of about 165 isotope compositions of these animal tissues. These results enabled us to assess the main mechanisms that drive K isotope fractionation at the organism level by first establishing the relationships between isotope compositions of the main K fluxes and reservoirs within vertebrate organisms. The dataset supports the predominant role of the transmembrane active transport of K as a key mechanism, with remarkably 41K enriched intracellular milieu in contrast with extracellular reservoirs (e.g. blood plasma). The study of the distributions of K isotopes in vertebrates also suggests that the homeostatic (K cycle regulation) response of the organism to varying dietary K availability plays an important role in the variability observed.
Throughout the BioIsoK project, the results of this research were presented in two main international conferences and an international workshop (Goldschmidt Conference and “Reaction Gases” workshop, 2020 Barcelona; 2020 Hawaii Goldschmidt conference). The dissemination of the results in scientific publications is due in the upcoming months in peer-review journals.
The BioIsoK project led to the development of a new method using a new generation mass spectrometer for the measurement of K stable isotope compositions in geological and biological materials. In addition to the contribution of this project to the community effort towards the establishment of a cross-laboratory database of reference materials isotope compositions, BioIsoK also demonstrated the interest in developing and commercializing the collision/reaction cell technology in MC-ICP-MS mass spectrometry.
Furthermore, BioIsoK lead to the unprecedented and systematic study of the cycling of K isotopes in model vertebrate animals reared in controlled feeding experiments. In addition to the successful constitution of such a valuable dataset, this project constitutes a significant contribution to the identification of the main mechanisms responsible for the fractionation at the organism and tissue level in modern vertebrates and highlights the roles of key mechanisms and organs. BioIsoK thus paved the way for future fundamental research in palaeobiology, physiopathology of extant vertebrates and bears potential implications in biomedical research such as nutrition, etiology of diseases and development of new biomarkers.
No website has been developed for the project. The address of the research group website is given below.
Furthermore, BioIsoK lead to the unprecedented and systematic study of the cycling of K isotopes in model vertebrate animals reared in controlled feeding experiments. In addition to the successful constitution of such a valuable dataset, this project constitutes a significant contribution to the identification of the main mechanisms responsible for the fractionation at the organism and tissue level in modern vertebrates and highlights the roles of key mechanisms and organs. BioIsoK thus paved the way for future fundamental research in palaeobiology, physiopathology of extant vertebrates and bears potential implications in biomedical research such as nutrition, etiology of diseases and development of new biomarkers.
No website has been developed for the project. The address of the research group website is given below.