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Nitschke MR, Rosset SL, Oakley CA, Gardner SG, Camp EF, Suggett DJ, Davy SK. The diversity and ecology of Symbiodiniaceae: A traits-based review. Adv Mar Biol 2022; 92:55-127. [PMID: 36208879 DOI: 10.1016/bs.amb.2022.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Among the most successful microeukaryotes to form mutualisms with animals are dinoflagellates in the family Symbiodiniaceae. These photosynthetic symbioses drive significant primary production and are responsible for the formation of coral reef ecosystems but are particularly sensitive when environmental conditions become extreme. Annual episodes of widespread coral bleaching (disassociation of the mutualistic partnership) and mortality are forecasted from the year 2060 under current trends of ocean warming. However, host cnidarians and dinoflagellate symbionts display exceptional genetic and functional diversity, and meaningful predictions of the future that embrace this biological complexity are difficult to make. A recent move to trait-based biology (and an understanding of how traits are shaped by the environment) has been adopted to move past this problem. The aim of this review is to: (1) provide an overview of the major cnidarian lineages that are symbiotic with Symbiodiniaceae; (2) summarise the symbiodiniacean genera associated with cnidarians with reference to recent changes in taxonomy and systematics; (3) examine the knowledge gaps in Symbiodiniaceae life history from a trait-based perspective; (4) review Symbiodiniaceae trait variation along three abiotic gradients (light, nutrients, and temperature); and (5) provide recommendations for future research of Symbiodiniaceae traits. We anticipate that a detailed understanding of traits will further reveal basic knowledge of the evolution and functional diversity of these mutualisms, as well as enhance future efforts to model stability and change in ecosystems dependent on cnidarian-dinoflagellate organisms.
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Affiliation(s)
- Matthew R Nitschke
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand; Climate Change Cluster, University of Technology Sydney, Broadway, NSW, Australia.
| | - Sabrina L Rosset
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Clinton A Oakley
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Stephanie G Gardner
- Center for Marine Science and Innovation, University of New South Wales Sydney, Kensington, NSW, Australia
| | - Emma F Camp
- Climate Change Cluster, University of Technology Sydney, Broadway, NSW, Australia
| | - David J Suggett
- Climate Change Cluster, University of Technology Sydney, Broadway, NSW, Australia
| | - Simon K Davy
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
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Fujise L, Suggett DJ, Stat M, Kahlke T, Bunce M, Gardner SG, Goyen S, Woodcock S, Ralph PJ, Seymour JR, Siboni N, Nitschke MR. Unlocking the phylogenetic diversity, primary habitats, and abundances of free-living Symbiodiniaceae on a coral reef. Mol Ecol 2020; 30:343-360. [PMID: 33141992 DOI: 10.1111/mec.15719] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 10/21/2020] [Accepted: 10/27/2020] [Indexed: 01/04/2023]
Abstract
Dinoflagellates of the family Symbiodiniaceae form mutualistic symbioses with marine invertebrates such as reef-building corals, but also inhabit reef environments as free-living cells. Most coral species acquire Symbiodiniaceae horizontally from the surrounding environment during the larval and/or recruitment phase, however the phylogenetic diversity and ecology of free-living Symbiodiniaceae on coral reefs is largely unknown. We coupled environmental DNA sequencing and genus-specific qPCR to resolve the community structure and cell abundances of free-living Symbiodiniaceae in the water column, sediment, and macroalgae and compared these to coral symbionts. Sampling was conducted at two time points, one of which coincided with the annual coral spawning event when recombination between hosts and free-living Symbiodiniaceae is assumed to be critical. Amplicons of the internal transcribed spacer (ITS2) region were assigned to 12 of the 15 Symbiodiniaceae genera or genera-equivalent lineages. Community compositions were separated by habitat, with water samples containing a high proportion of sequences corresponding to coral symbionts of the genus Cladocopium, potentially as a result of cell expulsion from in hospite populations. Sediment-associated Symbiodiniaceae communities were distinct, potentially due to the presence of exclusively free-living species. Intriguingly, macroalgal surfaces displayed the highest cell abundances of Symbiodiniaceae, suggesting a key role for macroalgae in ensuring the ecological success of corals through maintenance of a continuum between environmental and symbiotic populations of Symbiodiniaceae.
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Affiliation(s)
- Lisa Fujise
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - David J Suggett
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Michael Stat
- Trace and Environmental DNA (TrEnD) Laboratory, Curtin University, Bentley, Perth, WA, Australia.,School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, Australia
| | - Tim Kahlke
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Michael Bunce
- Trace and Environmental DNA (TrEnD) Laboratory, Curtin University, Bentley, Perth, WA, Australia
| | - Stephanie G Gardner
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia.,Centre for Marine Science and Innovation, University of New South Wales Australia, Kensington, NSW, Australia
| | - Samantha Goyen
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Stephen Woodcock
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Peter J Ralph
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Justin R Seymour
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Nachshon Siboni
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Matthew R Nitschke
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia.,School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
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Gardner SG, Camp EF, Smith DJ, Kahlke T, Osman EO, Gendron G, Hume BCC, Pogoreutz C, Voolstra CR, Suggett DJ. Coral microbiome diversity reflects mass coral bleaching susceptibility during the 2016 El Niño heat wave. Ecol Evol 2019; 9:938-956. [PMID: 30805132 PMCID: PMC6374667 DOI: 10.1002/ece3.4662] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 09/21/2018] [Accepted: 09/24/2018] [Indexed: 12/30/2022] Open
Abstract
Repeat marine heat wave-induced mass coral bleaching has decimated reefs in Seychelles for 35 years, but how coral-associated microbial diversity (microalgal endosymbionts of the family Symbiodiniaceae and bacterial communities) potentially underpins broad-scale bleaching dynamics remains unknown. We assessed microbiome composition during the 2016 heat wave peak at two contrasting reef sites (clear vs. turbid) in Seychelles, for key coral species considered bleaching sensitive (Acropora muricata, Acropora gemmifera) or tolerant (Porites lutea, Coelastrea aspera). For all species and sites, we sampled bleached versus unbleached colonies to examine how microbiomes align with heat stress susceptibility. Over 30% of all corals bleached in 2016, half of which were from Acropora sp. and Pocillopora sp. mass bleaching that largely transitioned to mortality by 2017. Symbiodiniaceae ITS2-sequencing revealed that the two Acropora sp. and P. lutea generally associated with C3z/C3 and C15 types, respectively, whereas C. aspera exhibited a plastic association with multiple D types and two C3z types. 16S rRNA gene sequencing revealed that bacterial communities were coral host-specific, largely through differences in the most abundant families, Hahellaceae (comprising Endozoicomonas), Rhodospirillaceae, and Rhodobacteraceae. Both Acropora sp. exhibited lower bacterial diversity, species richness, and community evenness compared to more bleaching-resistant P. lutea and C. aspera. Different bleaching susceptibility among coral species was thus consistent with distinct microbiome community profiles. These profiles were conserved across bleached and unbleached colonies of all coral species. As this pattern could also reflect a parallel response of the microbiome to environmental changes, the detailed functional associations will need to be determined in future studies. Further understanding such microbiome-environmental interactions is likely critical to target more effective management within oceanically isolated reefs of Seychelles.
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Affiliation(s)
| | - Emma F. Camp
- University of Technology SydneyClimate Change ClusterUltimo NSW 2007Australia
| | - David J. Smith
- Coral Reef Research Unit, School of Biological SciencesUniversity of EssexColchesterUK
| | - Tim Kahlke
- University of Technology SydneyClimate Change ClusterUltimo NSW 2007Australia
| | - Eslam O. Osman
- Coral Reef Research Unit, School of Biological SciencesUniversity of EssexColchesterUK
- Marine Biology Department, Faculty of ScienceAl‐Azhar UniversityCairoEgypt
| | | | - Benjamin C. C. Hume
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
| | - Claudia Pogoreutz
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
| | - Christian R. Voolstra
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
| | - David J. Suggett
- University of Technology SydneyClimate Change ClusterUltimo NSW 2007Australia
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Gardner SG, Raina JB, Nitschke MR, Nielsen DA, Stat M, Motti CA, Ralph PJ, Petrou K. A multi-trait systems approach reveals a response cascade to bleaching in corals. BMC Biol 2017; 15:117. [PMID: 29216891 PMCID: PMC5719617 DOI: 10.1186/s12915-017-0459-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 11/19/2017] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Climate change causes the breakdown of the symbiotic relationships between reef-building corals and their photosynthetic symbionts (genus Symbiodinium), with thermal anomalies in 2015-2016 triggering the most widespread mass coral bleaching on record and unprecedented mortality on the Great Barrier Reef. Targeted studies using specific coral stress indicators have highlighted the complexity of the physiological processes occurring during thermal stress, but have been unable to provide a clear mechanistic understanding of coral bleaching. RESULTS Here, we present an extensive multi-trait-based study in which we compare the thermal stress responses of two phylogenetically distinct and widely distributed coral species, Acropora millepora and Stylophora pistillata, integrating 14 individual stress indicators over time across a simulated thermal anomaly. We found that key stress responses were conserved across both taxa, with the loss of symbionts and the activation of antioxidant mechanisms occurring well before collapse of the physiological parameters, including gross oxygen production and chlorophyll a. Our study also revealed species-specific traits, including differences in the timing of antioxidant regulation, as well as drastic differences in the production of the sulfur compound dimethylsulfoniopropionate during bleaching. Indeed, the concentration of this antioxidant increased two-fold in A. millepora after the corals started to bleach, while it decreased 70% in S. pistillata. CONCLUSIONS We identify a well-defined cascading response to thermal stress, demarking clear pathophysiological reactions conserved across the two species, which might be central to fully understanding the mechanisms triggering thermally induced coral bleaching. These results highlight that bleaching is a conserved mechanism, but specific adaptations linked to the coral's antioxidant capacity drive differences in the sensitivity and thus tolerance of each coral species to thermal stress.
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Affiliation(s)
- Stephanie G Gardner
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007, NSW, Australia. .,School of Life Sciences, University of Technology Sydney, Ultimo, 2007, NSW, Australia.
| | - Jean-Baptiste Raina
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007, NSW, Australia
| | - Matthew R Nitschke
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007, NSW, Australia.,Centre for Environmental and Marine Studies (CESAM), University of Aveiro, 3810-193, Aveiro, Portugal
| | - Daniel A Nielsen
- School of Life Sciences, University of Technology Sydney, Ultimo, 2007, NSW, Australia
| | - Michael Stat
- Trace and Environmental DNA (TrEnD) Laboratory, Department of Environment and Agriculture, Curtin University, Perth, 6102, WA, Australia
| | - Cherie A Motti
- Australian Institute of Marine Science, Townsville, 4810, QLD, Australia
| | - Peter J Ralph
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007, NSW, Australia
| | - Katherina Petrou
- School of Life Sciences, University of Technology Sydney, Ultimo, 2007, NSW, Australia
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Camp EF, Nitschke MR, Rodolfo-Metalpa R, Houlbreque F, Gardner SG, Smith DJ, Zampighi M, Suggett DJ. Reef-building corals thrive within hot-acidified and deoxygenated waters. Sci Rep 2017; 7:2434. [PMID: 28550297 PMCID: PMC5446402 DOI: 10.1038/s41598-017-02383-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 04/27/2017] [Indexed: 11/29/2022] Open
Abstract
Coral reefs are deteriorating under climate change as oceans continue to warm and acidify and thermal anomalies grow in frequency and intensity. In vitro experiments are widely used to forecast reef-building coral health into the future, but often fail to account for the complex ecological and biogeochemical interactions that govern reefs. Consequently, observations from coral communities under naturally occurring extremes have become central for improved predictions of future reef form and function. Here, we present a semi-enclosed lagoon system in New Caledonia characterised by diel fluctuations of hot-deoxygenated water coupled with tidally driven persistently low pH, relative to neighbouring reefs. Coral communities within the lagoon system exhibited high richness (number of species = 20) and cover (24-35% across lagoon sites). Calcification rates for key species (Acropora formosa, Acropora pulchra, Coelastrea aspera and Porites lutea) for populations from the lagoon were equivalent to, or reduced by ca. 30-40% compared to those from the reef. Enhanced coral respiration, alongside high particulate organic content of the lagoon sediment, suggests acclimatisation to this trio of temperature, oxygen and pH changes through heterotrophic plasticity. This semi-enclosed lagoon therefore provides a novel system to understand coral acclimatisation to complex climatic scenarios and may serve as a reservoir of coral populations already resistant to extreme environmental conditions.
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Affiliation(s)
- Emma F Camp
- Climate Change Cluster, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - Matthew R Nitschke
- Climate Change Cluster, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - Riccardo Rodolfo-Metalpa
- Institut de Recherche pour le Développement, Centre IRD de Nouméa, ENTROPIE (UMR250), BP A5, 98848, Nouméa cedex, New Caledonia.
| | - Fanny Houlbreque
- Institut de Recherche pour le Développement, Centre IRD de Nouméa, ENTROPIE (UMR250), BP A5, 98848, Nouméa cedex, New Caledonia
| | - Stephanie G Gardner
- Climate Change Cluster, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - David J Smith
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, UK
| | - Marco Zampighi
- Institut de Recherche pour le Développement, Centre IRD de Nouméa, ENTROPIE (UMR250), BP A5, 98848, Nouméa cedex, New Caledonia
| | - David J Suggett
- Climate Change Cluster, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia
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Gardner SG, Nielsen DA, Laczka O, Shimmon R, Beltran VH, Ralph PJ, Petrou K. Dimethylsulfoniopropionate, superoxide dismutase and glutathione as stress response indicators in three corals under short-term hyposalinity stress. Proc Biol Sci 2017; 283:rspb.2015.2418. [PMID: 26865302 DOI: 10.1098/rspb.2015.2418] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Corals are among the most active producers of dimethylsulfoniopropionate (DMSP), a key molecule in marine sulfur cycling, yet the specific physiological role of DMSP in corals remains elusive. Here, we examine the oxidative stress response of three coral species (Acropora millepora, Stylophora pistillata and Pocillopora damicornis) and explore the antioxidant role of DMSP and its breakdown products under short-term hyposalinity stress. Symbiont photosynthetic activity declined with hyposalinity exposure in all three reef-building corals. This corresponded with the upregulation of superoxide dismutase and glutathione in the animal host of all three species. For the symbiont component, there were differences in antioxidant regulation, demonstrating differential responses to oxidative stress between the Symbiodinium subclades. Of the three coral species investigated, only A. millepora provided any evidence of the role of DMSP in the oxidative stress response. Our study reveals variability in antioxidant regulation in corals and highlights the influence life-history traits, and the subcladal differences can have on coral physiology. Our data expand on the emerging understanding of the role of DMSP in coral stress regulation and emphasizes the importance of exploring both the host and symbiont responses for defining the threshold of the coral holobiont to hyposalinity stress.
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Affiliation(s)
- Stephanie G Gardner
- Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, Sydney, New South Wales, Australia
| | - Daniel A Nielsen
- Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, Sydney, New South Wales, Australia
| | - Olivier Laczka
- Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, Sydney, New South Wales, Australia
| | - Ronald Shimmon
- School of Chemistry and Forensic Science, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Victor H Beltran
- Symbiont Culture Facility (SCF), Australian Institute of Marine Science (AIMS), Townsville, Queensland, Australia
| | - Peter J Ralph
- Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, Sydney, New South Wales, Australia
| | - Katherina Petrou
- Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, Sydney, New South Wales, Australia
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Gardner SG, Raina JB, Ralph PJ, Petrou K. Reactive oxygen species (ROS) and dimethylated sulphur compounds in coral explants under acute thermal stress. J Exp Biol 2017; 220:1787-1791. [DOI: 10.1242/jeb.153049] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 03/02/2017] [Indexed: 11/20/2022]
Abstract
Coral bleaching is intensifying with global climate change. While the causes for these catastrophic events are well understood, the cellular mechanism that triggers bleaching is not well established. Our understanding of coral bleaching processes is hindered by the lack of robust methods for studying interactions between host and symbiont at the single-cell level. Here we exposed coral explants to acute thermal stress and measured oxidative stress, more specifically, reactive oxygen species (ROS), in individual symbiont cells. Furthermore, we measured concentrations of dimethylsulphoniopropionate (DMSP) and dimethylsulphoxide (DMSO) to elucidate the role of these compounds in coral antioxidant function. This work demonstrates the application of coral explants for investigating coral physiology and biochemistry under thermal stress and delivers a new approach to study host-symbiont interactions at the microscale, allowing us to directly link intracellular ROS with DMSP and DMSO dynamics.
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Affiliation(s)
- Stephanie G. Gardner
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007 NSW, Australia
- School of Life Sciences, University of Technology Sydney, Ultimo, 2007 NSW, Australia
| | - Jean-Baptiste Raina
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007 NSW, Australia
| | - Peter J. Ralph
- Climate Change Cluster, University of Technology Sydney, Ultimo, 2007 NSW, Australia
| | - Katherina Petrou
- School of Life Sciences, University of Technology Sydney, Ultimo, 2007 NSW, Australia
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Abstract
AIMS To establish the role of the measurement of beta-hydroxybutyrate (beta-OHB) in distinguishing simple hyperglycaemia from ketosis, and as an indicator of adequate resolution of ketoacidosis, using an electrochemical blood ketone meter. The aim of the study is to assess the accuracy and precision of the meter and to develop clinical guidelines for the use of the ketone meter at home and in hospital. PATIENTS AND METHODS Twenty patients with poor glycaemic control (mean HbA1c 10.2%) were recruited from the diabetes clinic and 14 patients admitted with diabetic ketoacidosis (DKA) were recruited from two Accident and Emergency Departments. The blood obtained at each routine fingerprick test for glucose measurement was tested for beta-OHB using the ketone meter. Plasma beta-OHB concentrations were also measured on admission using a laboratory enzymatic method. RESULTS Paired glucose and beta-OHB meter readings (n = 1099) in clinic patients demonstrated that, in the absence of intercurrent illness, beta-OHB levels did not exceed 1 mmol/l, irrespective of glucose readings. In the 14 ketoacidotic patients, the mean plasma beta-OHB concentration, measured in the laboratory, on admission was 7.4 mmol/l (range 3.9-12.3 mmol/l). The median half-life of beta-OHB was 1.64 h (1st IQR 2.27 h, 3rd IQR 1.34 h). The median time taken, from the initiation of treatment, for beta-OHB concentrations to fall to below 1 mmol/l was 8.46 h (range 5-58.33 h). CONCLUSION Near patient blood ketone testing is a useful adjunct to blood glucose monitoring in distinguishing between ketosis and simple hyperglycaemia. The data suggest that beta-OHB levels > or = 1 mmol/l require further action and levels > 3 mmol/l necessitate medical review. In addition, the rate of fall of beta-OHB in DKA can be used as an indicator of the adequacy of treatment.
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Affiliation(s)
- T M Wallace
- Oxford Centre for Diabetes, Endocrinology and Metabolism, The Radcliffe Infirmary, UK
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Gardner SG, Gale EA, Williams AJ, Gillespie KM, Lawrence KE, Bottazzo GF, Bingley PJ. Progression to diabetes in relatives with islet autoantibodies. Is it inevitable? Diabetes Care 1999; 22:2049-54. [PMID: 10587841 DOI: 10.2337/diacare.22.12.2049] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE A large cohort of family members with islet cell antibodies (ICA) > or = 20 Juvenile Diabetes Foundation units (JDF U) was examined to determine whether there was a subgroup at low risk of progression to diabetes; whether risk of progression changed over time; and whether rate of progression to diabetes varied according to age, islet autoantibodies, and genetic markers of susceptibility. RESEARCH DESIGN AND METHODS Individuals with ICA > or = 20 JDF U were identified from 4,423 family members recruited to prospective family studies in the U.K. Subjects were followed for up to 18 years. Antibodies to insulin, GAD, and IA-2 were measured in the first sample, and HLA class II typing was performed. RESULTS Of 147 family members with ICA > or = 20 JDF U on at least one occasion, 29 developed type 1 diabetes after a median of 3.2 years (maximum 18.1). The cumulative risk of developing diabetes within 15 years was 47% (95% CI 28-67) for all family members with ICA > or = 20 JDF U, 2.8% (0-8.2) for those with ICA alone, and 66% (44-87) for those with at least one additional autoantibody marker. There were no differences in age, HLA class II type, or levels of ICA, insulin autoantibodies, or IA-2 antibodies between those who developed diabetes within 5 years of testing and those who developed diabetes after this time. GAD antibody levels we ..., however, higher in those who progressed more slowly. CONCLUSIONS Family members with ICA alone are at low risk of progression to diabetes. Rapid development of disease after ICA detection could not be distinguished from delayed development on the basis of autoantibodies or markers of genetic susceptibility, and those with multiple antibodies remained at high risk throughout long-term follow-up. This suggests that all family members with multiple islet autoantibodies are destined to develop autoimmune diabetes.
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Affiliation(s)
- S G Gardner
- Division of Medicine, University of Bristol, U.K
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Gardner SG, Bingley PJ, Sawtell PA, Weeks S, Gale EA. Rising incidence of insulin dependent diabetes in children aged under 5 years in the Oxford region: time trend analysis. The Bart's-Oxford Study Group. BMJ 1997; 315:713-7. [PMID: 9314756 PMCID: PMC2127500 DOI: 10.1136/bmj.315.7110.713] [Citation(s) in RCA: 180] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVES To monitor incidence of insulin dependent diabetes in children in Oxford health region since 1985, and to look for any evidence of disproportionate increase in children aged under 5. DESIGN Primary ascertainment of cases of childhood diabetes was by prospective registration of all patients with insulin dependent diabetes diagnosed before age 15 years between 1985 and 1996 and resident in Oxford region at time of diagnosis. This was supplemented by examination of centralised hospital discharge records and death certificates. Secondary case ascertainment was by postal surveys of general practitioners in 1987 and 1996. SETTING Area formerly administered by Oxford Regional Health Authority. SUBJECTS 1037 children presenting with insulin dependent diabetes under age of 15 years. MAIN OUTCOME MEASURES Incidence of insulin dependent diabetes in children aged 0-4, 5-9, and 10-14 years during 1985-95. RESULTS Overall incidence of diabetes in children aged 0-15 was 18.6 cases/100000/year and showed an annual increase of 4% from 1985 to 1996. This was mainly due to a rapid increase in children aged 0-4 years, in whom there was an annual increase of 11% (95% confidence interval 6% to 15%, P < 0.0001), while the annual increase in those aged 5-9 was 4% (0 to 7%, P = 0.05) and in those aged 10-14 was 1% (-2% to 4%, P = 0.55). CONCLUSIONS Incidence of insulin dependent diabetes in children aged under 5 years has risen markedly in the Oxford region over the past decade. The cause of the increase is unknown, but environmental influences encountered before birth or in early postnatal life are likely to be responsible.
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Affiliation(s)
- S G Gardner
- Department of Medicine, University of Bristol, Southmead Hospital
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