Düsseldorf, Germany
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Schadewaldt P.,Institute of Clinical Biochemistry and Pathobiochemistry | Schadewaldt P.,Institute For Klinische Biochemie And Pathobiochemie | Nowotny B.,Institute of Clinical Diabetology | Strassburger K.,Institute of Biometry and Epidemiology | And 3 more authors.
American Journal of Clinical Nutrition | Year: 2013

Background: Indirect calorimetry (IC) with metabolic monitors is widely used for noninvasive assessment of energy expenditure and macronutrient oxidation in health and disease. Objective: To overcome deficiencies in validity and reliability of metabolic monitors, we established a procedure that allowed correction for monitor-specific deviations. Design: Randomized comparative IC (canopy mode) with the Deltatrac MBM-100 (Datex) and Vmax Encore 29n (SensorMedix) was performed in postabsorptive (overnight fast >8 h) healthy subjects (n = 40). In vitro validation was performed by simulation of oxygen consumption (VO2) and carbon dioxide output (VCO2) rates by using mass-flow regulators and pure gases. A simulation-based postcalorimetric calibration of cart readouts [individual calibration control evaluation (ICcE)] was established in adults (n = 24). Results: The comparison of carefully calibrated monitors showed marked differences in VCO2 and VO2 (P < 0.01) and derived metabolic variables [resting energy expenditure (REE), respiratory quotient (RQ), glucose/carbohydrate oxidation (Gox), and fat oxidation (Fox); P < 0.001]. Correlations appeared to be acceptable for breath gas rates and REE (R2 ~ 0.9) but were unacceptable for RQ (R2 = 0.3), Gox, and Fox (R2 = 0.2). In vitro simulation experiments showed monitor-dependent interferences for VCO2 and VO2 as follows: 1) within series, nonlinear and variable deviations of monitor readouts at different exchange rates; 2) between series, differences and unsteady variability; and 3) differences in individual monitor characteristics (eg, rate dependence, stability, imprecision). The introduction of the postcalorimetric recalibration by ICcE resulted in an adjustment of gas exchange rates and the derived metabolic variables with reasonable correlations (R2 > 0.9). Conclusions: Differential, metabolic, monitor-specific deviations are the primary determinants for lack of accuracy, comparability, and transferability of results. This problem can be overcome by the present postcalorimetric ICcE procedure. Copyright © 2013 American Society for Nutrition.


Jones J.,Center for Neurosciences and Cell Biology | Kahl S.,Institute of Clinical Diabetology | Kahl S.,Heinrich Heine University Düsseldorf | Kahl S.,German Center for Diabetes Research | And 5 more authors.
Analytical Biochemistry | Year: 2015

Measurement of acetaminophen glucuronide (AG) 2H enrichment from deuterated water (2H2O) by 2H nuclear magnetic resonance (NMR) analysis of its monoacetone glucose (MAG) derivative provides estimation of gluconeogenic and glycogenolytic contributions to endogenous glucose production (EGP). However, AG derivatization to MAG is laborious and unsuitable for high-throughput studies. An alternative derivative, 5-O-acetyl monoacetone glucuronolactone (MAGLA), was tested. Eleven healthy subjects ingested 2H2O to 0.5% body water enrichment and 500 mg of acetaminophen. Plasma glucose and urinary glucuronide positional 2H enrichments were measured by 2H NMR spectroscopy of MAG and MAGLA, respectively. A Bland-Altman analysis indicated agreement at the 95% confidence level between glucose and glucuronide estimates. © 2015 Elsevier Inc.


Pfleger C.,Institute of Clinical Diabetology | Meierhoff G.,Institute of Clinical Diabetology | Kolb H.,Institute of Clinical Diabetology | Schloot N.C.,Institute of Clinical Diabetology | Schloot N.C.,Heinrich Heine University Düsseldorf
Journal of Autoimmunity | Year: 2010

Objective: The aim of the current study was to investigate whether autoantigen directed T-cell reactivity relates to β-cell function during the first 78 weeks after diagnosis of type 1 diabetes. Research design and methods: 50 adults and 49 children (mean age 27.3 and 10.9 years respectively) with recent onset type 1 diabetes who participated in a placebo-controlled trial of immune intervention with DiaPep277 were analyzed. Secretion of interferon (IFN)-γ, interleukin (IL)-5, IL-13 and IL-10 by single peripheral mononuclear cells (PBMC) upon stimulation with islet antigens GAD65, heat shock protein 60 (Hsp60) protein-tyrosine-phosphatase-like-antigen (pIA2) or tetanus toxoid (TT) was determined applying ELISPOT; β-cell function was evaluated by glucagon stimulated C-peptide. Multivariate regression analysis was applied. Results: In general, number of islet antigen-reactive cells decreased over 78 weeks in both adults and children, whereas reactivity to TT was not reduced. In addition, there was an association between the quality of immune cell responses and β-cell function. Overall, increased responses by IFN-γ secreting cells were associated with lower β-cell function whereas IL-5, IL-13 and IL-10 cytokine responses were positively associated with β-cell function in adults and children. Essentially, the same results were obtained with three different models of regression analysis. Conclusions: The number of detectable islet-reactive immune cells decreases within 1-2 years after diagnosis of type 1 diabetes. Cytokine production by antigen-specific PBMC reactivity is related to β-cell function as measured by stimulated C-peptide. Cellular immunity appears to regress soon after disease diagnosis and begin of insulin therapy. © 2009 Elsevier Ltd. All rights reserved.

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