Energy Expenditure
    Biological Processes

Medical & Clinical

Understanding of the biological processes that control human and animal physiology can be difficult considering the moral implications that are involved in performing such studies. The use of stable isotope analysis provides a non-invasive approach with no adverse reactions which may be observed through using radioisotopes. The use of enriched isotope tracers with artificially high abundances of minor isotopes provides a relatively simple way of probing subtle biological processes.

Breath Analysis

After your subject has ingested an isotopically labelled meal (e.g. 13C-labelled glucose), exhaled CO2 from the patient will show enrichment in 13C levels relative to 12C. The time taken for the 13C isotope to appear in the exhaled breath gives some indication of the metabolic rate of the subject. Up to 220 breath samples can be analysed using our iso FLOW sample handling system for rapid analysis of large numbers of samples.

Body Fluid Analysis

Dosing a subject (human or animal) with doubly labelled water (e.g. water enriched in both deuterium and 18O) allows the total energy expenditure (TEE) of the subject to be determined. High performance deuterium and 18O isotope analysis of up to 180 saliva, blood and urine samples can be performed via headspace equilibration using the iso FLOW sample handling system.

Biochemical Analysis

To understand more about the complex physiological chemical processes that occur within the body, it is necessary to go beyond coarse breath and body fluid analysis. Our gas and liquid chromatography (GC-IRMS and LC-IRMS) systems are able to perform individual compound stable isotope analysis allowing you to find out more about these complex processes. 

Medical publications using our instruments

Our customers use our instruments to do some amazing research in the medical application field. To show you how they perform their research and how they use our IRMS instruments, we have collected a range of peer-reviewed publications which cite our products. You can find the citations below and then follow the links to the publishing journal should you wish to download the publication.

If you would like to investigate our available citations in more detail, or email the citation list to yourself or your colleagues then take a look at our full citation database.

37 results:

Dietary protein regulates hepatic constitutive protein anabolism in rats in a dose-dependent manner and independently of energy nutrient composition.
American journal of physiology. Regulatory, integrative and comparative physiology (2010)
Laure Chevalier, Cécile Bos, Dalila Azzout-Marniche, Dominique Dardevet, Daniel Tomé, Claire Gaudichon

We had previously observed that drastic increases in protein consumption greatly modified hepatic protein anabolism in rats, but the confounding effects of other macronutrient changes or a moderate protein increase to generate the same modifications have not yet been established. This study examined the metabolic and hormonal responses of rats subjected to 14-day isoenergetic diets containing normal, intermediate, or high-protein levels (NP: 14% of energy, IP: 33%, HP: 50%) and different carbohydrate (CHO) to fat ratios within each protein level. Fasted or fed rats (n = 104) were killed after the injection of a flooding dose of (13)C-valine. The hepatic protein content increased in line with the dietary protein level (P < 0.05). The hepatic fractional synthesis rates (FSR) of protein were significantly influenced by both the protein level and the nutritional state (fasted vs. fed) (P < 0.0001) but not by the CHO level, reaching on average 110%/day, 92%/day, and 83%/day in rats fed the NP, IP, and HP diets, respectively. The FSR of plasma albumin and muscle did not differ between diets, while feeding tended to increase muscle FSR. Proteolysis, especially the proteasome-dependent system, was down-regulated in the fed state in the liver when protein content increased. Insulin decreased with the CHO level in the diet. Our results reveal that excess dietary protein lowers hepatic constitutive, but not exported, protein synthesis rates, independently of the other macronutrients, and related changes in insulin levels. This response was observed at the moderate levels of protein intake (33%) that are plausible in a context of human consumption.
Tags: carbon , medi , gaschrom

Reference range thyroid-stimulating hormone is associated with physical activity energy expenditure in overweight and obese postmenopausal women: A Montreal-Ottawa New Emerging Team Study
Metabolism: Clinical and Experimental (2010)
Geneviève Rondeau, Nicole Rutamucero, Virginie Messier, Lacramioara Burlacu, Denis Prud'Homme, Hortensia Mircescu, Rémi Rabasa-Lhoret

Clinical and, to a lesser extent, subclinical hypothyroidism is associated with a variety of metabolic abnormalities, including increased body mass index, unfavorable lipoprotein profile, and increased biomarkers for atherosclerosis. Energy expenditure could act as a confounding factor in the association reported between thyroid-stimulating hormone (TSH) levels and cardiometabolic risk factors. The objective of the study was to investigate the relationship between reference range plasma TSH and energy expenditure as well as blood pressure, lipid, and inflammation parameters in women. One hundred four postmenopausal, overweight and obese, spontaneously euthyroid women were included in the study. We evaluated total energy expenditure by doubly labeled water, resting energy expenditure by indirect calorimetry, physical activity energy expenditure (PAEE = [total energy expenditure × 0.90] - resting metabolic rate), body weight, and percentage of fat mass by dual-energy x-ray absorptiometry. Blood pressure, plasma lipoproteins profile, and high-sensitivity C-reactive protein levels were also measured. Mean TSH was 2.39 ± 1.09 mIU/L. We observed that high-density lipoprotein cholesterol (r = -0.20, P ≤ .05) was negatively associated with TSH, whereas systolic blood pressure (r = 0.21, P ≤ .05) and apolipoprotein B (r = 0.22, P ≤ .05) were positively correlated with TSH. However, these correlations were no longer significant after controlling for PAEE. A significant negative correlation was found between TSH and PAEE (r = -0.23, P ≤ .05). Our results suggest that, although TSH in the reference range is associated with some cardiometabolic risk factors, this is in large part explained by lower PAEE. In turn, lower PAEE could increase the cardiometabolic risk. © 2010 Elsevier Inc.
Tags: hydrogen , oxygen , medi , gashead

Effect of postprandial modulation of glucose availability: short- and long-term analysis.
The British journal of nutrition (2010)
Julie-Anne Nazare, Alexis de Rougemont, Sylvie Normand, Valérie Sauvinet, Monique Sothier, Sophie Vinoy, Michel Désage, Martine Laville

Low glycaemic index (LGI) foods have been proposed as potential means to decrease postprandial glucose excursions and thus to improve diabetes management. We modulated glucose availability of cereal products and thus their glycaemic index to study the metabolic effect of LGI foods on daylong glucose control acutely and in the long term following a 5-week GI intervention diet in free-living subjects. In this randomised, parallel trial, two groups of nineteen overweight subjects followed an ad libitum 5-week intervention diet in which usual starch was replaced by either LGI or high GI (HGI) starch. During the exploration days (days 1 and 36), subjects ate their assigned 13C-labelled test breakfast (LGI or HGI), and total and exogenous glucose kinetics (using stable isotopes), postprandial concentrations of glucose, insulin, lipid profile and nutrient oxidation were assessed after the test breakfast and a standardised lunch. At day 1, LGI breakfast significantly decreased post-breakfast glycaemic response with a parallel decrease in exogenous and total glucose appearance (P < 0.05). Post-lunch and post-breakfast glycaemic responses were positively correlated (r 0.79, P < 0.0001). Following the 5-week diet, difference between the groups in terms of glucose kinetics and response was maintained (no significant interaction group x time) but tended to decrease over time for the post-breakfast glycaemic response. Post-lunch and post-breakfast glycaemic responses remained positively correlated (r 0.47, P = 0.004). Modulation of postprandial glucose availability at breakfast decreased plasma exogenous glucose appearance and improved glucose control at the subsequent lunch. After 5 weeks, these effects were maintained in healthy subjects but remained to be confirmed in the longer term.
Tags: carbon , medi , gaschrom

High-protein diets differentially modulate protein content and protein synthesis in visceral and peripheral tissues in rats.
Nutrition (Burbank, Los Angeles County, Calif.) (2009)
Laure Chevalier, Cécile Bos, Céline Gryson, Catherine Luengo, Stéphane Walrand, Daniel Tomé, Yves Boirie, Claire Gaudichon

OBJECTIVE: High-protein diets give rise to increased amplitude in the diurnal cycling of protein gains and losses at the whole-body level, but the tissue localization and mechanisms underlying these metabolic adaptations remain unclear. We investigated tissue-specific responses to increasing protein intakes in rats. METHODS: Protein synthesis rates (flooding dose with (13)C-valine) and accretion were assessed in individual tissues of fasted or fed rats (n = 32) after a 2-wk adaptation to a normal- or high-protein (HP) diet. RESULTS: In livers of HP rats, a strong inhibition of protein synthesis rates (-34%) occurred in the fasted and fed states, whereas a higher protein content (+10%) was observed. In the kidneys, a slight inhibition of synthesis rates after the HP diet was also observed but remained without effect on kidney protein pool size. Stomach and skin protein synthesis rates were significantly increased under HP conditions, whereas protein anabolism in skeletal muscle remained insensitive to the dietary protein level. This was also true for specific muscle protein fractions: myosin, mitochondrial, or sarcoplasmic protein synthesis rates were influenced by neither the dietary protein level nor the nutritional status. CONCLUSION: Modulation of protein kinetics and accretion by the HP diet is tissue-specific and the liver plays a critical role in such adaptations in a unique situation associating an inhibition of protein synthesis and protein pool expansion. The mechanisms underlying these changes and their physiologic incidence remain to be elucidated.
Tags: carbon , medi , gaschrom

Association of cardiorespiratory fitness with insulin sensitivity in overweight and obese postmenopausal women: a Montreal Ottawa New Emerging Team study
Metabolism: Clinical and Experimental (2008)
Virginie Messier, Florin M. Malita, Rémi Rabasa-Lhoret, Martin Brochu, Antony D. Karelis

The purpose of this study was to examine the relation between insulin sensitivity and cardiorespiratory fitness in overweight and obese postmenopausal women. The study population consisted of 127 overweight and obese postmenopausal women (age, 57.7 ± 4.8 years; body mass index, 32.7 ± 4.7 kg/m2). Subjects were classified by dividing the entire cohort into tertiles (T) based on insulin sensitivity expressed per kilograms of lean body mass (LBM) (T1, <10.9; T2, 10.9-12.9, T3, >12.9 mg/min per kilogram of LBM, respectively). Outcome measures were body composition (dual-energy x-ray absorptiometry), visceral adipose tissue (computed tomography), insulin sensitivity (hyperinsulinemic-euglycemic clamp), cardiorespiratory fitness (indirect calorimetry), lower-body muscle strength (1 maximal repetition), physical activity energy expenditure (doubly labeled water), fasting lipids, and inflammatory profile. We found a significant positive relationship between insulin sensitivity and cardiorespiratory fitness (r = 0.25, P = .005). Moreover, cardiorespiratory fitness was higher in the T3 group compared to the T1 group (36.2 ± 6.1 vs 33.1 ± 5.0 mL/kg LBM per minute, respectively; P = .028). However, the difference was no longer significant after controlling for visceral adipose tissue or muscle strength. Finally, cardiorespiratory fitness was an independent predictor of insulin sensitivity. High levels of cardiorespiratory fitness are associated with higher levels of insulin sensitivity in overweight and obese postmenopausal women. Moreover, visceral adipose tissue accumulation or muscle strength may be potential mediators of this relationship. © 2008 Elsevier Inc. All rights reserved.
Tags: hydrogen , oxygen , medi

Ultra High Temperature Treatment , but Not Pasteurization , Affects the Postprandial Kinetics of Milk Proteins in Humans
Magali Lacroix, Cyriaque Bon, Robert Benamouzig, Catherine Luengo, Jacques Fauquant, Daniel Tome

Although the chemical and physical modifications to milk proteins induced by technological treatments have been characterized extensively, their nutritional consequences have rarely been assessed in humans. We measured the effect of 2 technological treatments on the postprandial utilization of milk nitrogen (N), pasteurization (PAST) and ultra high temperature (UHT), compared with microfiltration (MF), using a sensitive method based on the use of milk proteins intrinsically labeled with 15N. Twenty-five subjects were studied after a 1-wk standardization of their diet. On the day of the investigation, they ingested a single test meal corresponding to 500 mL of either MF, PAST, or UHT defatted milk. Serum amino acid (AA) levels as well as the transfer of 15N into serum protein and AA, body urea, and urinary urea were determined throughout the 8-h postprandial period. The kinetics of dietary N transfer to serum AA, proteins, and urea did not differ between the MF and PAST groups. The transfer of dietary N to serum AA and protein and to body urea was significantly higher in UHT than in either the PAST or MF group. Postprandial deamination losses from dietary AA represented 25.9 6 3.3% of ingested N in the UHT group, 18.5 6 3.0% in the MF group, and 18.6 6 3.7% in the PAST group (P , 0.0001). The higher anabolic use of dietary N in plasma proteins after UHT ingestion strongly suggests that these differences are due to modifications to digestive kinetics and the further metabolism of dietary proteins subsequent to this particular treatment of milk
Tags: hydrogen , nitrogen , medi , elem , gashead

Origin assignment of unidentified corpses by use of stable isotope ratios of light (bio-) and heavy (geo-) elements--a case report.
Forensic science international (2007)
Elisabeth Rauch, Susanne Rummel, Christine Lehn, Andreas Büttner

An unknown male body was found near an expressway in Germany. As different criminalistic and forensic methods (e.g. tooth status, fingerprint or DNA-analysis) could not help to identify the person, multielement stable isotope investigations were applied. The combined analysis of stable isotope ratios of light (H, C, N) and heavy elements (Pb, Sr) on the man's body tissues supported to assign him to Romania. The case report demonstrates an application of multielement-isotope analysis in the forensic fields and its potential.
Tags: carbon , hydrogen , nitrogen , medi , crim , elem