| 1. |
- Abreu-Vieira, Gustavo, 1987-
(författare)
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Thermal physiology and metabolism : Interplay between heat generation and energy homeostasis
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mammal metabolism is intimately connected to the maintenance of body temperature. While metabolic pathways invariably produce heat as a by-product, the natural heat present in the environment also plays a role in defining the adaptive metabolism and general physiology of an organism. This thesis aims to discuss basic aspects of energy expenditure and their interactions with energy stores and body composition. In Paper I, we apply a new technique – high-resolution laser-Doppler imaging – to describe physiological regulatory features of adrenergically-stimulated blood flow in brown adipose tissue, and evaluate the validity of blood flow as a parameter to estimate nonshivering thermogenesis. Paper II focuses on the central regulation of body temperature. In the absence of bombesin receptor subtype-3, mice present an altered neurological body temperature setpoint, while peripheral thermogenic capacity remains intact. We conclude that brown adipose tissue malfunction is not the cause of the hypothermia observed in this mouse model. Paper III incorporates measurements of body temperature to the energy expenditure of different sources: basal metabolic rate, physical activity, thermic effect of food, and cold-induced thermogenesis. We describe basic aspects of dynamic insulation, energetic costs of circadian variation and hypothesize that physical activity may change the body temperature setpoint. Paper IV describes methodological issues related to glucose tolerance tests in obese mice. We conclude that the erroneous scaling of doses may affect the interpretation of metabolic health in mouse models, and suggest a new methodology. Paper V describes the outcomes caused by the expression of the human Cidea protein in adipose tissue of mice and suggests that this protein may clarify the link between adipose tissue expansion and healthy obesity. Paper VI explores the dissociation between thiazolidinedione-induced adipose tissue “browning” and reduced blood glycaemia. We demonstrate that although this pharmacological class tends to induce some level of brown adipose tissue recruitment, this phenomenon does not define its antidiabetic effects.
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| 2. |
- Kaviani, Sepideh, et al.
(författare)
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Determining the Accuracy and Reliability of Indirect Calorimeters Utilizing the Methanol Combustion Technique
- 2018
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Ingår i: Nutrition in Clinical Practice. - : Wiley. - 0884-5336. ; 33:2, s. 206-216
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Tidskriftsartikel (refereegranskat)abstract
- Background: Several indirect calorimetry (IC) instruments are commercially available, but comparative validity and reliability data are lacking. Existing data are limited by inconsistencies in protocols, subject characteristics, or single-instrument validation comparisons. The aim of this study was to compare accuracy and reliability of metabolic carts using methanol combustion as the cross-laboratory criterion. Methods: Eight 20-minute methanol burn trials were completed on 12 metabolic carts. Respiratory exchange ratio (RER) and percent O2 and CO2 recovery were calculated. Results: For accuracy, 1 Omnical, Cosmed Quark CPET (Cosmed), and both Parvos (Parvo Medics trueOne 2400) measured all 3 variables within 2% of the true value; both DeltaTracs and the Vmax Encore System (Vmax) showed similar accuracy in measuring 1 or 2, but not all, variables. For reliability, 8 instruments were shown to be reliable, with the 2 Omnicals ranking best (coefficient of variation [CV] < 1.26%). Both Cosmeds, Parvos, DeltaTracs, 1 Jaeger Oxycon Pro (Oxycon), Max-II Metabolic Systems (Max-II), and Vmax were reliable for at least 1 variable (CV ≤ 3%). For multiple regression, humidity and amount of combusted methanol were significant predictors of RER (R2 = 0.33, P <.001). Temperature and amount of burned methanol were significant predictors of O2 recovery (R2 = 0.18, P <.001); only humidity was a predictor for CO2 recovery (R2 = 0.15, P <.001). Conclusions: Omnical, Parvo, Cosmed, and DeltaTrac had greater accuracy and reliability. The small number of instruments tested and expected differences in gas calibration variability limits the generalizability of conclusions. Finally, humidity and temperature could be modified in the laboratory to optimize IC conditions.
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| 3. |
- Kaviani, Sepideh, et al.
(författare)
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Determining the Accuracy and Reliability of Indirect Calorimeters Utilizing the Methanol Combustion Technique
- 2017
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 31:S1
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveThere are several indirect calorimetry (IC) instruments commercially available but validity and reliability data is lacking. Site-to-site inconsistencies in protocols and subject characteristics, and comparisons to a “gold standard” instrument or method which may no longer be accurate enough, have put restraints on drawing conclusions about instruments' performance.PurposeTo compare the accuracy and reliability of different metabolic carts using the methanol combustion technique as the criterion measure.MethodsA total of eight, 20-minute methanol burn trials were completed on 12 metabolic carts (2 Cosmed Quark CPET, 2 DeltaTrac II, 2 Parvo Medics TrueOne 2400, 2 Iaeger Oxycon Pros, 2 Omnicals, a Vmax Encore, and a Max-II Metabolic System) at 11 international study sites. Methanol tests were performed at 0700, 1000, 1300, and 1600 hours on 2 consecutive days. Respiratory Exchange Ratio (RER) and percent (%) recovery of O2 and CO2 were calculated after each test.ResultsAccuracy – 1 Omnical, Cosmed, and Parvo were accurate in measuring RER and % recovery O2, while 1 DeltaTrac was also accurate for % recovery O2. The same Cosmed and Parvo, and the other DeltaTrac were accurate in measuring % recovery CO2. Reliability – 8 instruments were shown to be reliable with the two Omnicals ranking best based on the smallest coefficient of variation (CV) (all CV(s) 1.26%). Both Cosmeds, Parvos, DeltaTracs and 1 Vmax were the reliable instruments for at least one variable (CV(s) 3%). Multiple Regression– Humidity, amount of methanol combusted, and temperature were tested as predictors of IC outcomes. Humidity and amount of combusted methanol were significant predictors of RER (F (2, 60) =10.91, p<0.001, R2=0.33). Temperature and amount of burned methanol were significant predictors of % recovery O2 (F (2, 60) =8.32, p<0.001, R2=0.18) while only humidity was a predictor for % recovery CO2 (F (1, 61) =21.10, p<0.001, R2=0.15).ConclusionOmnical, Cosmed, and Parvo showed superior accuracy and reliability; however, accuracy was only found at one of two study sites. Exogenous factors such as humidity and temperature may be influencing instrument performance and could be modified in the lab to optimize IC conditions.
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| 4. |
- Sutton, Elizabeth F, et al.
(författare)
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Developmental programming : State-of-the-science and future directions: Summary from a Pennington Biomedical symposium
- 2016
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Ingår i: Obesity. - : Wiley. - 1930-739X .- 1930-7381. ; 24:5, s. 1018-1026
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Forskningsöversikt (refereegranskat)abstract
- OBJECTIVE: On December 8-9, 2014, the Pennington Biomedical Research Center convened a scientific symposium to review the state-of-the-science and future directions for the study of developmental programming of obesity and chronic disease. The objectives of the symposium were to discuss: (i) past and current scientific advances in animal models, population-based cohort studies, and human clinical trials, (ii) the state-of-the-science of epigenetic-based research, and (iii) considerations for future studies.RESULTS: This symposium provided a comprehensive assessment of the state of the scientific field and identified research gaps and opportunities for future research in order to understand the mechanisms contributing to the developmental programming of health and disease.CONCLUSIONS: Identifying the mechanisms which cause or contribute to developmental programming of future generations will be invaluable to the scientific and medical community. The ability to intervene during critical periods of prenatal and early postnatal life to promote lifelong health is the ultimate goal. Considerations for future research including the use of animal models, the study design in human cohorts with considerations about the timing of the intrauterine exposure, and the resulting tissue-specific epigenetic signature were extensively discussed and are presented in this meeting summary.
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