The 13C-Glucose Breath Test for Insulin Resistance Assessment in Adolescents: Comparison with Fasting and Post-Glucose Stimulus Surrogate Markers of Insulin Resistance

European guideline on indications, performance and clinical impact of 13 C-breath tests in adult and pediatric patients: An EAGEN, ESNM, and ESPGHAN consensus, supported by EPC

INTRODUCTION

13 C-breath tests are valuable, noninvasive diagnostic tests that can be widely applied for the assessment of gastroenterological symptoms and diseases. Currently, the potential of these tests is compromised by a lack of standardization regarding performance and interpretation among expert centers.

METHODS

This consensus-based clinical practice guideline defines the clinical indications, performance, and interpretation of 13 C-breath tests in adult and pediatric patients. A balance between scientific evidence and clinical experience was achieved by a Delphi consensus that involved 43 experts from 18 European countries. Consensus on individual statements and recommendations was established if ≥ 80% of reviewers agreed and <10% disagreed.

RESULTS

The guideline gives an overview over general methodology of 13 C-breath testing and provides recommendations for the use of 13 C-breath tests to diagnose Helicobacter pylori infection, measure gastric emptying time, and monitor pancreatic exocrine and liver function in adult and pediatric patients. Other potential applications of 13 C-breath testing are summarized briefly. The recommendations specifically detail when and how individual 13 C-breath tests should be performed including examples for well-established test protocols, patient preparation, and reporting of test results.

CONCLUSION

This clinical practice guideline should improve pan-European harmonization of diagnostic approaches to symptoms and disorders, which are very common in specialist and primary care gastroenterology practice, both in adult and pediatric patients. In addition, this guideline identifies areas of future clinical research involving the use of 13 C-breath tests.

Oxygen-18 and Carbon-13 isotopes in eCO2and erythrocytes carbonic anhydrase activity of Finnish prediabetic population

Complex human physiological processes create the stable isotopic composition of exhaled carbon dioxide (eCO2), measurable with noninvasive breath tests. Recently, isotope-selective breath tests utilizing natural fluctuation in 18O/16O isotope ratio in eCO2 have been proposed for screening prediabetic (PD) individuals. It has been suggested that 18O/16O fractionation patterns reflect shifts in the activity of carbonic anhydrase (CA), an enzyme involved in the metabolic changes in the PD state. To evaluate the applicability of the breath sampling method in Finnish PD individuals, breath delta values (BDVs, ‰) of 18O/16O (δ18O) were monitored for 120 min in real-time with a high-precision optical isotope ratio spectrometer, both in the fasting state and during a 2-hour oral glucose tolerance test (2h OGTT) with non-labelled glucose. In addition, the BDV of 13C/12C (δ13C) was measured, and total erythrocyte CA activity was determined. δ18O and CA did not demonstrate any statistically significant differences between PD and non-diabetic control (NDC) participants. Instead, δ13C was significantly lower in PD patients in comparison to NDCs in the fasting state and at time points 90 and 120 min of the 2h OGTT, thus indicating slightly better potential in identifying Finnish PD individuals. However, overlapping values were measured in PD participants and NDCs, and therefore, δ13C cannot be applied as a sole measure in screening prediabetes at an individual level. Thus, because the combination of environmental and lifestyle factors and anthropometric parameters has a greater effect on glucose metabolism and CA activity in comparison to the PD state, 18O/16O and 13C/12C fractionations or CA activity did not prove to be reliable biomarkers for impaired glucose tolerance in Finnish subjects. This study was conducted under the clinicaltrials.gov ID NCT03156478.

13C/12C breath test ratio after the ingestion of a meal naturally enriched with (13C)carbohydrates is a surrogate marker of insulin resistance and insulin sensitivity in children and adolescents with Type 1 Diabetes

AIMS

To test the hypotheses that exogenous carbohydrate oxidation affects postprandial glycaemic profiles and ¹³C/¹²C breath test could be used for estimating insulin resistance (IR) and insulin sensitivity (IS) in youths with Type 1 Diabetes (T1D).

METHODS

Non-randomized, cross-sectional study for repeated measures; fifteen youths (11-15 years) with T1D were enrolled. Respiratory exchanges were measured by indirect calorimetry after the ingestion of a mixed meal [13% protein, 29% fat, 58% carbohydrate (CHO; naturally enriched with [¹³C]carbohydrates)]. Total and exogenous CHOs oxidation was calculated by indirect calorimetry and ¹³C/¹²C breath test. IR and IS were calculated using estimated Glucose Disposal Rate (eGDR) and Insulin Sensitivity Score (ISS).

RESULTS

The blood glucose Area Under the Curve (BG-AUC) was significantly associated with the amount of exogenous CHOs oxidized (r = -0.67, p < 0.02) when adjusting for CHOs intake and %fat mass. A direct correlation between eGDR and ISS with exogenous CHOs oxidized (r = 0.70, p < 0.02; r = 0.61, p < 0.05 respectively) and with the differential of ¹³C/¹²C enrichment in the expired at breath test (r = 0.59, p < 0.05; r = 0.62, p < 0.05), was found.

CONCLUSIONS

Assessing the capacity to oxidize exogenous CHOs (estimated by the differential of ¹³C/¹²C enrichment in the expired air at the breath test) could be used as a non-invasive surrogate marker of IR and IS in youths with T1D.

Optimal Cut-off Points of Fasting and Post-Glucose Stimulus Surrogates of Insulin Resistance as Predictors of Metabolic Syndrome in Adolescents According to Several Definitions

OBJECTIVE

The aim of this study was to determine optimal cut-off points for fasting and post-glucose stimulus surrogates of insulin resistance to predict metabolic syndrome in adolescents according to several definitions.

METHODS

One hundred fifty-five adolescents living in Mexico City were enrolled during 2011 and 2012. Waist circumference and blood pressure were recorded. Subjects received an oral glucose load of 1.75 g per kg up to a maximum dose of 75 g. Blood samples were drawn at baseline and 120 minutes. Concentrations of plasma glucose, triglycerides, high-density lipoprotein cholesterol and insulin were determined.

RESULTS

The frequency of metabolic syndrome showed a large variability when using a variety of published definitions; in contrast, the optimal cut-off points for fasting insulin, homeostatic model assessment of insulin resistance and two-hour oral glucose tolerance test insulin were very similar in almost all the definitions considered and had adequate diagnostic performance: area under the curve >0.869, sensitivity >0.835 and specificity >0.755. Insulin resistance surrogates had substantial agreements with Ford, Cook and Salas definitions (Kappa~0.62; agreement~82%); moderate agreement was observed for International Diabetes Federation, Cruz and Ferranti definitions (Kappa~0.41–0.59; agreement~77%).

CONCLUSION

Insulin resistance surrogates may be a better approach for metabolic syndrome assessment in an adolescent population because of reduced variability and a higher predictive value.

13C isotopic abundances in natural nutrients: a newly formulated test meal for non-invasive diagnosis of type 2 diabetes

A new method to replace commercially prepared ¹³C-labelled glucose with naturally available ¹³C-enriched substrates could result in promotion of the clinical applicability of the isotopic breath test for detection of type 2 diabetes (T2D). Variation of the carbon-13 isotope in human breath depends on the ¹³C enrichment in the diet taken by subjects. Here, we formulated a new test meal comprising naturally available ¹³C-enriched foods and subsequently administered it to non-diabetic control (NDC) subjects and those with T2D. We found that the new test meal-derived ¹³C enrichment of breath CO₂ was significantly lower in T2D compared with NDC. Furthermore, from our observations T2D exhibited higher isotopic enrichment of oxygen-18 (¹⁸O) in breath CO₂ compared with NDC following ingestion of the new meal. We determined the optimal diagnostic cut-off values of ¹³C (i.e. δ ¹³C‰ = 7.5‰) and ¹⁸O (i.e. δ ¹⁸O‰ = 3.5‰) isotopes in breath CO₂ for precise classification of T2D and NDC. Our new method involving the administration of naturally ¹³C-abundant nutrients showed a typical diagnostic sensitivity and specificity of about 95%, suggesting a valid and potentially robust global method devoid of any synthetically manufactured commercial ¹³C-enriched glucose which thus may serve as an alternative diagnostic tool for routine clinical applications.