13CO2 breath test to measure the hydrolysis of various starch formulations in healthy subjects

Changes in Selected Nutrients and Microstructure of White Starch Quality Maize and Common Maize During Tortilla Preparation and Storage

Raw maize, masa, and fresh and stored tortillas of white starch quality maize (Costeno) and common maize were analysed for chemical composition, dietary fibre, digestible (DS) and resistant (RS) starches. Changes in starch crystallinity and microstructure were also evaluated. Protein content was lower in masa and tortillas than in the original maize samples. Insoluble (IDF) and soluble (SDF) dietary fibres were higher in Costeno than in common maize, but stored tortillas showed the highest value in both samples. DS decreased and RS increased during tortillas storage, made with both starches. The development of RS explained the observed decrease in DS in masa (enthalpy of gelatinisation). Differential scanning calorimetry studies showed peak gelatinisation temperatures (Tp) of 75.1 and 69.4 C for Costeno and common maize respectively. Masa of common maize showed a second transition endotherm (Tp, 108.9 C) which corresponded to amylose–lipid complexation. Tortillas with 5 and 10 days of storage showed an endothermic event at 53 and 55.7, and 54.5 and 59.9 C for Costeno and common maize respectively, due to starch retrogradation. These values were in accordance with the higher total RS contents recorded after prolonged storage. Microscopic structures for masa and fresh tortillas showed that the high temperature imposed on the masa and the influence of mechanical stress during tortillas making were great enough to disrupt starch granules. In general, structural changes were in agreement with changes in starch.

Use of the Biphasic (13)C-Sucrose/Glucose Breath Test to Assess Sucrose Maldigestion in Adults with Functional Bowel Disorders

Sucrase insufficiency has been observed in children with of functional bowel disorders (FBD) and symptoms of dietary carbohydrate intolerance may be indistinguishable from those of FBD. A two-phase (13)C-sucrose/(13)C-glucose breath test ((13)C-S/GBT) was used to assess sucrase activity because disaccharidase assays are seldom performed in adults. When (13)C-sucrose is hydrolyzed to liberate monosaccharides, oxidation to (13)CO2 is a proportional indicator of sucrase activity. Subsequently, (13)C-glucose oxidation rate was determined after a secondary substrate ingestion (superdose) to adjust for individual habitus effects (Phase II). (13)CO2 enrichment recovery ratio from (13)C-sucrose and secondary (13)C-glucose loads reflect the individualized sucrase activity [Coefficient of Glucose Oxidation for Sucrose (CGO-S)]. To determine if sucrase insufficiency could be a factor in FBD, (13)C-S/GBT was validated using subjects with known sucrase gene mutation status by comparing (13)CO2-breath enrichment with plasma (13)C-glucose enrichment. (13)C-S/GBT was used to assess sucrose digestion in FBD patients and asymptomatic controls. (13)CO2-breath enrichment correlated with the appearance of (13)C-sucrose-derived glucose in plasma (r (2) = 0.80). Mean, control group CGO-S-enrichment outcomes were 1.01 at 60', 0.92 at 75', and 0.96 at mean 60'-75' with normal CGO-S defined as >0.85 (95% C.I.). In contrast, FBD patients demonstrated lower CGO-S values of 0.77 at 60', 0.77 at 75', and 0.76 at mean 60'-75' (Chi Square: 6.55; p < 0.01), which points to sucrose maldigestion as a cause of FBD.

(13)C-Breath testing in animals: theory, applications, and future directions

The carbon isotope values in the exhaled breath of an animal mirror the carbon isotope values of the metabolic fuels being oxidized. The measurement of stable carbon isotopes in carbon dioxide is called (13)C-breath testing and offers a minimally invasive method to study substrate oxidation in vivo. (13)C-breath testing has been broadly used to study human exercise, nutrition, and pathologies since the 1970s. Owing to reduced use of radioactive isotopes and the increased convenience and affordability of (13)C-analyzers, the past decade has witnessed a sharp increase in the use of breath testing throughout comparative physiology--especially to answer questions about how and when animals oxidize particular nutrients. Here, we review the practical aspects of (13)C-breath testing and identify the strengths and weaknesses of different methodological approaches including the use of natural abundance versus artificially-enriched (13)C tracers. We critically compare the information that can be obtained using different experimental protocols such as diet-switching versus fuel-switching. We also discuss several factors that should be considered when designing breath testing experiments including extrinsic versus intrinsic (13)C-labelling and different approaches to model nutrient oxidation. We use case studies to highlight the myriad applications of (13)C-breath testing in basic and clinical human studies as well as comparative studies of fuel use, energetics, and carbon turnover in multiple vertebrate and invertebrate groups. Lastly, we call for increased and rigorous use of (13)C-breath testing to explore a variety of new research areas and potentially answer long standing questions related to thermobiology, locomotion, and nutrition.

Green tea extract decreases starch digestion and absorption from a test meal in humans: a randomized, placebo-controlled crossover study

Green tea is known worldwide for its beneficial effects on human health. However, objective data evaluating this influence in humans is scarce. The aim of the study was to assess the impact of green tea extract (GTE) on starch digestion and absorption. The study comprised of 28 healthy volunteers, aged 19 to 28 years. In all subjects, a starch ¹³C breath test was performed twice. Subjects randomly ingested naturally ¹³C-abundant cornflakes during the GTE test (GTE 4 g) or placebo test. The cumulative percentage dose recovery (CPDR) was significantly lower for the GTE test than for the placebo test (median [interquartile range]: 11.4% [5.5–15.5] vs. 16.1% [12.7–19.5]; p = 0.003). Likewise, CPDR expressed per hour was considerably lower in each point of the measurement. In conclusion, a single dose of green tea extract taken with a test meal decreases starch digestion and absorption.

A pilot longitudinal study of the use of waxy maize heat modified starch in the treatment of adults with glycogen storage disease type I: a randomized double-blind cross-over study

Background

Uncooked corn-starch (UCCS) has been the mainstay of therapy for the hepatic glycogen storage diseases (GSD) but is not always effective. A new starch (WMHMS) has demonstrated a more favourable short-term metabolic profile.

Objective

To determine efficacy and safety of a new uncooked starch (WMHMS) compared to UCCS over 16 weeks treatment with each.

Method

A double-blind cross-over study of 10 adults (aged 16 – 38 years, six male) with GSD Ia and Ib. After an individualised fast, subjects were randomised to take a 50 g starch-load of either WMHMS or UCCS. Starch-loads terminated when blood glucose was < 3.0 mmol/L or the subject felt subjectively hypoglycaemic. Anonymous biochemical profiles were assessed by 2 investigators and a starch administration schedule recommended. Each starch was delivered in coded sachets and intake was monitored for the following 16 weeks. After a washout period, the protocol was repeated with the alternative product.

Results

4 subjects failed to establish therapy on the cross-over limb. Data from 7 paired starch load showed: longer median fasting duration with WMHMS (7.5 versus 5 hours; p = 0.023), slower decrease in the glucose curve (0.357 versus 0.632 mmol/hr p = 0.028) and less area under insulin curves for the first 4 hours (p = 0.03). Two of six subjects took 50% or less WMHMS compared to UCCS and one took more. Plasma triglycerides, cholesterol and uric acid were unchanged after each study phase.

Conclusion

WMHMS leads to significant reduction in insulin release and reduced starch use in some GSD patients.

Prediction of in vivo short-chain fatty acid production in hindgut fermenting mammals: problems and pitfalls

Short-chain fatty acids (SCFA) are considered to have important physiological functions. However, to prove this, SCFA must be determined, which is rather difficult as a lot of factors interfere with their production. This review focuses on the factors that influence the prediction of short-chain fatty acid formation in the large intestine of monogastric mammals. To mimic the in vivo situation, when predicting the amount of short-chain fatty acids produced from a certain substrate based on in vitro models, one has to estimate the amount of this substrate entering the large intestine, the retention time in the different parts of the large intestine, and the substrate fermentability. Instead of in vitro models, direct and indirect techniques may be used to measure short-chain fatty acid production in vivo. Direct techniques include the measurement of input and output or measuring differences in SCFA between portal and venous blood whereas indirect techniques measure the end products of fermentation. In this case, other factors have to be taken into account, including technical limitations and ethical considerations. In this review it is concluded that the choice for a method will rely on the purpose of the study taking into account the (dis)advantages of every method.

A novel one-hour 13C-sorbitol breath test versus the H2-sorbitol breath test for assessment of coeliac disease

OBJECTIVE

The H(2)-sorbitol breath test (H(2)-SBT) has previously been suggested as a screening tool for coeliac disease. We developed an alternative (13)C-sorbitol breath test ((13)C-SBT). The aim of the study was to compare the diagnostic properties of the H(2)-SBT and the (13)C-SBT in a clinical setting.

MATERIAL AND METHODS

Thirty-nine coeliac patients, 40 patient controls (mainly patients with irritable bowel syndrome) and 26 healthy volunteers underwent the breath tests. The patients were given an oral load of 5 g sorbitol and 100 mg (13)C-sorbitol dissolved in 250 ml tap-water. H(2), CH(4) and (13)CO(2) concentrations were measured in end-expiratory breath samples every 30 min for 4 h. Increased H(2) concentration > or =20 ppm from basal values was used as the cut-off for the H(2)-SBT.

RESULTS

The H(2)-SBT had a sensitivity of 71%, a specificity of 46% versus healthy controls, and a specificity of 25% versus patient controls. Individuals with methane-producing intestinal flora had significantly lower peak H(2) concentrations than non-methane producers. The (13)C-SBT reached maximal combined sensitivity/specificity (74%/85%) for both control groups after 1 h. A diagnostic algorithm which stratified patients into high-, moderate- and low risk for coeliac disease was proposed. Following the algorithm, 62% of coeliac patients were detected with 100% specificity. The (13)C-SBT, but not the H(2)-SBT, correlated with age and serum IgA tissue-transglutaminase antibody levels in coeliac patients.

CONCLUSIONS

The novel (13)C-SBT has superior diagnostic properties compared to the H(2)-SBT, which has unsatisfactory specificity in clinical practice. The 1-h (13)C-SBT may be a useful supplemental test when investigating for coeliac disease.

13C-breath tests for sucrose digestion in congenital sucrase isomaltase-deficient and sacrosidase-supplemented patients

BACKGROUND

Congenital sucrase-isomaltase deficiency (CSID) is characterized by absence or deficiency of the mucosal sucrase-isomaltase enzyme. Specific diagnosis requires upper gastrointestinal biopsy with evidence of low to absent sucrase enzyme activity and normal histology. The hydrogen breath test (BT) is useful, but is not specific for confirmation of CSID. We investigated a more specific 13C-sucrose labeled BT.

OBJECTIVES

Determine whether CSID can be detected with the 13C-sucrose BT without duodenal biopsy sucrase assay, and if the 13C-sucrose BT can document restoration of sucrose digestion by CSID patients after oral supplementation with sacrosidase (Sucraid).

METHODS

Ten CSID patients were diagnosed by low biopsy sucrase activity. Ten controls were children who underwent endoscopy and biopsy because of dyspepsia or chronic diarrhea with normal mucosal enzymes activity and histology. Uniformly labeled 13C-glucose and 13C-sucrose loads were orally administered. 13CO2 breath enrichments were assayed using an infrared spectrophotometer. In CSID patients, the 13C-sucrose load was repeated adding Sucraid. Sucrose digestion and oxidation were calculated as a mean percent coefficient of glucose oxidation averaged between 30 and 90 minutes.

RESULTS

Classification of patients by 13C-sucrose BT percent coefficient of glucose oxidation agreed with biopsy sucrase activity. The breath test also documented the return to normal of sucrose digestion and oxidation after supplementation of CSID patients with Sucraid.

CONCLUSIONS

13C-sucrose BT is an accurate and specific noninvasive confirmatory test for CSID and for enzyme replacement management.

13C-breath tests: current state of the art and future directions

13C-breath tests provide a non-invasive diagnostic method with high patient acceptance. In vivo, human and also bacterial enzyme activities, organ functions and transport processes can be assessed semiquantitatively using breath tests. As the samples can directly be analysed using non-dispersive isotope selective infrared spectrometers or sent to analytical centres by normal mail breath tests can be easily performed also in primary care settings. The 13C-urea breath test which detects a Helicobacter pylori infection of the stomach is the most prominent application of stable isotopes. Determination of gastric emptying using test meals labelled with 13C-octanoic or 13C-acetic acid provide reliable results compared to scintigraphy. The clinical use of 13C-breath tests for the diagnosis of exocrine pancreatic insufficiency is still limited due to expensive substrates and long test periods with many samples. However, the quantification of liver function using hepatically metabolised 13C-substrates is clinically helpful in special indications. The stable isotope technique presents an elegant, non-invasive diagnostic tool promising further options of clinical applications. This review is aimed at providing an overview on the relevant clinical applications of 13C-breath tests.

Current and future uses of breath analysis as a diagnostic tool

The analysis of exhaled breath is a potentially useful method for application in veterinary diagnostics. Breath samples can be easily collected from animals by means of a face mask or collection chamber with minimal disturbance to the animal. After the administration of a 13C-labelled compound the recovery of 13C in breath can be used to investigate gastrointestinal and digestive functions. Exhaled hydrogen can be used to assess orocaecal transit time and malabsorption, and exhaled nitric oxide, carbon monoxide and pentane can be used to assess oxidative stress and inflammation. The analysis of compounds dissolved in the aqueous phase of breath (the exhaled breath condensate) can be used to assess airway inflammation. This review summarises the current status of breath analysis in veterinary medicine, and analyses its potential for assessing animal health and disease.

Digestion of so-called resistant starch sources in the human small intestine

BACKGROUND

Resistant starch sources, which are only partially digested in the small intestine, can be used to increase colonic availability of short-chain fatty acids.

OBJECTIVE

To study the characteristics of the fermentation of resistant starch, the digestion of resistant starch in the small intestine has to be quantified. We compared the metabolic fates of highly digestible cornstarch (DCS), Hylon VII (type 2 resistant starch), and Novelose 330 (type 3 resistant starch), which are of corn origin and, therefore, naturally enriched in (13)C.

DESIGN

After administration of 40 g starch or glucose to 7 healthy volunteers, glucose and exogenous glucose concentrations in serum and (13)CO(2) excretion in breath were analyzed for 6 h. (13)C abundance in carbon dioxide was analyzed by isotope ratio mass spectrometry (IRMS) and (13)C abundance in glucose by gas chromatography-combustion IRMS.

RESULTS

By comparing the area under the curve (2 h) of exogenous glucose concentration in serum ((13)C glycemic index) after intake of starch or glucose, (13)C glycemic indexes for DCS, Hylon VII, and Novelose 330 were calculated to be 82 +/- 23%, 44 +/- 16%, and 43 +/- 15%, respectively. Comparison of 6-h cumulative percentage dose recovery in breath showed that 119 +/- 28% of DCS, 55 +/- 23% of Hylon VII, and 50 +/- 26% of Novelose 330 was digested in the small intestine.

CONCLUSION

The exogenous glucose response in serum and the (13)CO(2) excretion in breath can be used to estimate small intestinal digestion of resistant starch, which amounts to approximately 50%.

13C and H2 breath tests to study extent and site of starch digestion in children with cystic fibrosis

BACKGROUND

Starch is an important source of energy for children with cystic fibrosis, but little is known about their capacity to digest it.

METHODS

A 13C breath test was used to measure starch digestion and oxidation in 16 children with cystic fibrosis (median [range] age, 7.9 [4-15] years; 7 girls, 9 boys) and 5 normal healthy control subjects (median age, 8.3 [7-13] years; 3 girls, 2 boys). A test meal of 13C flour and lactulose was consumed and breath samples were obtained half-hourly thereafter for 6 hours to measure 13C enrichment by isotope ratio mass spectrometry and H2 by electrochemistry. The test was repeated on 10 children with cystic fibrosis when they were taking pancreatic supplements.

RESULTS

The median (range) cumulative percentage 13C dose recovery (cPDR), was 35% (18-52%) in control subjects, 18% (9-33%) in children with cystic fibrosis without enzymes, and 29% (22-51%) in those with pancreatic supplements. cPDR differed significantly between healthy control subjects and children with cystic fibrosis without enzymes (p = 0.01) and between children with cystic fibrosis with and without enzymes (p < 0.0001), but there was no difference between control subjects and children with cystic fibrosis taking enzymes (p = 0.5). Eight children with cystic fibrosis had a cPDR within control range, and in six there was a second peak in 13CO2 enrichment coincident with an increase in H2.

CONCLUSIONS

Starch digestion and oxidation are diminished in children with cystic fibrosis, but pancreatic enzymes restored them to near normal levels. A second peak in 13CO2 enrichment, suggestive of colonic starch fermentation was absent in healthy children, but present in some children with cystic fibrosis and abolished by pancreatic enzymes.

Measurement of urinary total 13C and 13C urea by isotope ratio mass spectrometry after administration of lactose [13C]-ureide

A method of measuring total 13C excreted in urine after oral administration of lactose [13C]-ureide was developed using isotope ratio mass spectrometry. Furthermore, a method to measure 13C urea excreted in the urine was developed. Each urine sample collected over a 24 hour period, after administration of the tracer dose, was analysed for both total 13C and 13C urea. Combustion of the dried urine samples allowed measurement of the total 13C content. Treatment of urine samples with urease (EC 3.5.1.5) and analysis by isotope ratio mass spectrometry of the CO2 evolved allowed measurement of 13C urea in the urine sample. The total 13C and 13C urea content of each urine sample, obtained throughout the protocol, were compared to total 13C and 13C urea contents of a urine sample taken before the test. This allowed calculation of the fraction of tracer incorporated into urea and the fraction of tracer excreted in total. Analyses showed that approximately 15% of the dose administered, in terms of 13C, was recovered in the urine over the sampling period. Further analysis for urinary 13C urea showed that less than 1% of the label was incorporated into urea excreted over the sampling period.

Evaluation of 13CO2 breath tests for the detection of fructose malabsorption

Breath hydrogen (H2) studies have made clear that small intestinal absorption of fructose is limited, especially in toddlers. Malabsorption of fructose may be a cause of recurrent abdominal pain and chronic nonspecific diarrhea (toddler's diarrhea). Fructose absorption is facilitated by equimolar doses of glucose and, as we have found, amino acids (especially L-alanine); the mechanism underlying this effect remains unclear. To study fructose absorption in a more direct way, we combined breath H2 studies with breath 13CO2 studies. Gastric emptying was studied by using L-glycine-1-13C in 4 children from 12.1 to 16.0 years of age. After 25 gm of fructose and 27.5 gm of glucose, when given together, gastric emptying was significantly (p<0.05) slower than with either sugar alone. In a second series of experiments, 5 children from 12.0 to 15.9 years of age were tested with 25 gm of fructose, alone and with equimolar doses of glucose and L-alanine, and 4 younger children from 3.1 to 6.1 years of age were tested with 2 gm/kg (max 37.5 gm) fructose, alone or with an equimolar dose of L-alanine. All fructose solutions were enriched with 15 mg of D-fructose-13C-6. In all 9 children, fructose was malabsorbed as judged by breath H2 increases > or = 20 ppm, and the addition of glucose or L-alanine resulted in significantly lower breath H2 increases (p < or = 0.005 for glucose, p < or = 0.001 for alanine). In contrast, the addition of alanine or glucose did not change the pattern of breath 13CO2 excretion in the 5 older children, whereas in the 4 younger children (with relatively higher doses), L-alanine addition resulted in significantly lower increases in breath 13CO2. In the latter group, for each time point, breath H2 and 13CO2 concentrations after fructose were compared with those after fructose plus L-alanine; in 20 out of 24 points, both H2 and 13CO2 were higher after fructose. These results suggest that 13CO2 not only originated from the oxidation of absorbed substrate but also, at least in part, from colonic bacterial metabolism. For the detection of [correction of or] fructose malabsorption--as opposed to, for instance, lactose--the 13CO2 breath test seems to be of limited value.

Effects of acarbose on starch hydrolysis. Study in healthy subjects, ileostomy patients, and in vitro

The effect of acarbose on hydrolysis of a pure starch meal was investigated in normal subjects and ileostomy patients by means of 13CO2 breath tests and blood glucose levels as parameters of absorption, and of H2 breath tests, serum acetate levels, and ileal loss of carbohydrate as parameters of malabsorption. Additional information on the effect of acarbose on alpha-amylase activity was obtained by in vitro experiments. Acarbose (200 and 400 mg) significantly delayed starch absorption. Serum acetate was found to be a less sensitive marker of malabsorption than breath H2 excretion. After intake of 50 g starch plus 400 mg acarbose, 23-71% of the starch load was lost in the ileostomy effluent, for a large part as starch. This suggests that acarbose considerably inhibits alpha-amylase, and not only brush-border enzymes. In vitro experiments confirm that an inhibition of two thirds of alpha-amylase activity can be expected from pharmacologically used doses of acarbose.