ColoPulse tablets perform comparably in healthy volunteers and Crohn's patients and show no influence of food and time of food intake on bioavailability.

ColoPulse tablets are an innovative development in the field of oral drug delivery and are characterized by a colon-specific release. Until now ColoPulse dosage forms (only capsules) have been studied in healthy volunteers having a standardized breakfast three hours after administration but not in specific patient groups and not with a shorter interval between administration and breakfast. Information on bioavailability and release characteristics of ColoPulse tablets in Crohn's patients and the influence of food and time of food intake is a prerequisite to properly design future clinical studies with active substances in these patients. In the current cross-over study bioavailability and drug release characteristics of ColoPulse tablets were compared in healthy volunteers and in Crohn's patients in remission. Furthermore the influence of food and time of food intake on the in vivo drug release behavior of ColoPulse tablets was investigated. In this study the dual label isotope strategy was used which means that a ColoPulse tablet containing (13)C-urea and an uncoated, immediate release tablet containing (15)N2-urea were taken simultaneously. Breath and urine samples were collected during the test day for isotope analysis. The appearance of the stable isotopes in breath and/or urine provides information on the site of release from the dosage form, release characteristics and bioavailability. Both tablets were administered on two different days in a cross-over design: the first day with a breakfast (non-standardized) one hour after administration and the second day with a standardized breakfast three hours after administration of the tablets. There was no difference in instructions for administration between both days. Results of 16 healthy volunteers and 14 Crohn's patients were evaluated. At least 86% (51 out of 59) of all ColoPulse tablets administered in this study released their contents at the desired intestinal region. There was no significant difference in bioavailability between healthy volunteers and Crohn's patients on both days (day 1 75.8% vs 90.2%, p=0.070 and day 2 83.4% vs 91.4%, p=0.265). There was also no significant influence of food and time of food intake on bioavailability in healthy volunteers (75.8% and 83.4%, p=0.077) and in Crohn's patients (90.2% and 91.4%, p=0.618) when day 1 and day 2 were compared. Release characteristics did not significantly differ between healthy volunteers and Crohn's patients. However, food and time of food intake had some, clinically non-relevant, influence on the release characteristics within both groups which is in line with the fact that food affects gastro-intestinal transit times. This study shows that ColoPulse tablets enable the site-specific delivery of drugs or other compounds (e.g. diagnostics) deep in the ileo-colonic region of the intestine of Crohn's patients in a comparable amount and rate as in healthy volunteers. Food and time of food intake had no relevant influence on bioavailability. In conclusion ColoPulse delivery systems are promising and deserve further research for local therapy with immunosuppressive drugs in Crohn's patients in the near future.

The effect of pre- and probiotics on the colonic ammonia metabolism in humans as measured by lactose-[¹5N2]ureide.

BACKGROUND: The evaluation of ammonia detoxification by pre- and probiotics by means of colonic lactose-[(15)N(2)]ureide ((15)N-LU) degradation is of great interest both scientifically and in terms of nutrition physiology. OBJECTIVE: Pre- and probiotics were supplemented in healthy adults to evaluate the effect of the ammonia metabolism in the human colon by means of (15)N-LU. METHODS: A total of 14 participants aged 20-28 years daily received a regular diet either without (no treatment) or with supplementation of 30 g fibre of potatoes (FPs), 30 g wrinkle pea starch (WPS, resistant starch content: 12 and 70%, respectively) and 375 g Lactobacillus acidophilus (LC1) yoghurt, over a 10-day period in a randomised order. After 1 week, 5.7 mg/kg body weight (15)N-LU was administered together with breakfast. A venous blood sample was taken after 6 h. Urine and faeces were collected over a period of 48 and 72 h, respectively. The (15)N abundances were measured by isotope ratio mass spectrometry. RESULTS: The mean renal (15)N-excretion differed significantly between the supplementation of FP and no treatment (32.5 versus 46.3%, P=0.034), FP and LC1 (32.5 versus 51.6%, P=0.001), and WPS and LC1 (38.5 versus 51.6%, P=0.048). The mean faecal (15)N-excretion amounted to 42.7% (no treatment), 59.7% (FP), 41.8% (WPS) and 44.0% (LC1). In comparison with no treatment, the urinary (15)NH(3)-enrichment was significantly decreased at 16 h after FP supplementation. CONCLUSION: The prebiotic intake of FP and WPS lowered the colonic generation and the renal excretion of toxic (15)NH(3), respectively, when using (15)N-LU as a xenobiotic marker.

The metabolic fate of doubly labelled lactose-[13C, 15N]ureide after pre-dosing with different ureides.

BACKGROUND: To date, the measurement of the orocaecal transit time (OCTT) with lactose-[(13)C]ureide usually requires a pre-dosing with the analogous substrate in its unlabelled form. OBJECTIVE: In this study, the enzyme induction provoked by different unlabelled sugar ureides in OCTT measurements when using doubly labelled lactose-[(13)C, (15)N]ureide (DLLU) was evaluated. METHODS: Thirteen healthy adults (age: 22-58 years) received 500 mg DLLU together with a standardized breakfast. Expired air, urine and faeces were collected over a period of 14, 48 and 72 h, respectively. After 1 and 2 weeks, the test was repeated after pre-dosing of 3 x 120 mg glucose ureide (GU) and 3 x 200 mg cellobiose ureide (CU), respectively, on the day before study begin. The (13)C- and (15)N-enrichments were measured by isotope ratio mass spectrometry. The OCTT was calculated by the detection of a significant (13)CO(2) increase. RESULTS: In comparison with the period without pre-dosing (7.8+/-2.2 h), the measured OCTT was significantly lowered either after GU pre-dosing (5.8+/-1.9 h, P=0.033) or CU pre-dosing (6.0+/-2.2 h, P=0.039). The respective renal (13)C- and (15)N-excretions amounted to 24.5 and 45.6, 24.7 and 54.0, and 22.5 and 50.1%, respectively, whereas the faecal (13)C- and (15)N-excretions amounted to 12.1 and 45.8, 4.8 and 21.5, and 9.6 and 39.8%, respectively. CONCLUSIONS: Pre-dosing with unlabelled GU and CU before the administration of DLLU led to an unequivocal induction of the enzyme activity and resulted in a definitive estimation of the OCTT, clearly demonstrating that glucose-[(13)C]ureide is the matrix of the bacterial degradation in the caecum.

The metabolic fate of doubly stable isotope labelled heat-killed Lactobacillus johnsonii in humans.

OBJECTIVE: In this study, heat-killed Lactobacillus johnsonii (La1), doubly labelled with (13)C and (15)N (hk-dlLa1), was used to follow the metabolic fate after oral administration in humans. DESIGN: Experimental study. SETTING: University of Rostock, Children's Hospital, Research Laboratory. SUBJECTS: Ten healthy adults aged 23-26 years. INTERVENTION: The subjects received 74.6 mg/kg body weight hk-dlLa1 and 10 g alpha-D-raffinose together with breakfast. A sample of venous blood was taken after 2 h. Expired air samples were taken over 14 h, whereas urine and faeces were collected over a period of 48 h. (13)C- and (15)N-enrichments were measured by isotope ratio mass spectrometry. Hydrogen concentrations were measured by electrochemical detection. RESULTS: The orocaecal transit time (OCTT) was reached after 3.4 h. After 2 h, (13)C- and (15)N-enrichment of fibrinogen amounted to 2 and 25 p.p.m. excess, respectively. The (13)CO(2)-exhalation amounted to 9.2% of the ingested dose. The urinary excretion of (13)C and (15)N was 2.1 and 10.4% of the ingested dose, respectively, whereas the faecal excretion was 47.9 and 43.7% of the ingested dose, respectively. CONCLUSIONS: In comparison to OCTT of 3.4 h, both stable isotopes appear after 30 min in breath and urine, indicating that hk-dlLa1 is rapidly digested in the small bowel before reaching the caecum. This is confirmed by (13)C-and (15)N-enrichments of blood plasma fractions. The ingestion of hk-dlLa1 led to a (13)C- and (15)N-excretion of 59.2 and 54.1% of the ingested dose, respectively, of both stable isotopes.

Effect of a soy protein-based diet on ribonucleic acid metabolism in the small intestinal mucosa of goat kids.

This study was designed to investigate the effect of soy protein inclusion in milk replacer diets for goat kids on protein, RNA, and DNA contents in small intestinal mucosa, on the importance of RNA biosynthesis from dietary RNA precursors for mucosal RNA synthesis, and on the activities of enzymes involved in nucleotide degradation in small intestinal mucosa. Diets were based on cow's milk. In the control group, 35% of the milk protein was replaced by casein (CN) protein, and in the soy group (SPAA), the same amount of milk protein was replaced by soy protein supplemented with essential AA known to be at lower concentrations in soy than in CN (Thr, Val, Ile, Leu, His, Lys, Met). Diets were isonitrogenous and isoenergetic. At 47 d of age, goats were harvested and samples of proximal, middle, and distal jejunal mucosa were collected 5 h after feeding 15N-labeled RNA from yeast (13 mg/kg of body weight). Growth and feed conversion did not differ between the control and SPAA kids. Mucosal protein concentrations were lower in the SPAA than the control kids. Concentrations of RNA and DNA did not differ between feeding groups, but in all kids mucosal RNA concentrations were higher in proximal than in middle and distal jejunum. Protein:RNA ratios were higher in the control than the SPAA kids and were lowest in proximal jejunum. Activities of alkaline phosphatase in enterocytes were higher in proximal than in middle and distal jejunum. Activities of mucosal xanthine oxidase were highest in distal jejunum and were higher in the SPAA than the control kids, especially in the middle and distal sites. The 15N-enrichment of mucosal RNA was higher in the control than the SPAA kids, especially in distal jejunum, and was lowest in distal jejunum. In contrast, 15N-enrichment of urea in plasma tended to be higher and Gly concentration in plasma was lower in the SPAA than the control kids. Data indicate that protein content and the protein:RNA ratio were lower in jejunal mucosa of goat kids fed milk replacer with partial replacement of CN protein by soy protein. These findings were accompanied by a lower level of reutilization of preformed dietary RNA precursors for RNA biosynthesis in jejunal mucosa and a higher activity of xanthine oxidase. Thus, feeding soy protein instead of CN protein reduced the incorporation of preformed dietary RNA precursors for RNA biosynthesis in the mucosa and activated key enzymes involved in nucleic acid breakdown.

The duration of enzyme induction in orocaecal transit time measurements.

OBJECTIVE: In this study, the duration of enzyme induction provoked by unlabelled lactose ureide (LU) in orocaecal transit time (OCTT) measurements with lactose-[(13)C]ureide ((13)C-LU) was evaluated. DESIGN: Experimental study. SETTING: University of Rostock, Children's Hospital, Research Laboratory. SUBJECTS: Fifteen healthy adults aged 19-54 years. INTERVENTION: One-half gram of (13)C-LU was administered together with a continental breakfast. After 1 week, the test was repeated after pre-dosing of 5 x 100 mg LU on the day before the study began. The (13)C-LU ingestion was repeated under identical conditions but without pre-dosing 1 and 3 weeks after pre-dosing. Expired air samples were taken over 14 h. (13)CO(2)-enrichment was measured by isotope ratio mass spectrometry (SerCon, Crewe, UK). The OCTT was calculated from the interval between (13)C-LU administration and the detection of a significant and sustained (13)C-rise of 2 delta over baseline in breath. RESULTS: Without pre-dosing, an OCTT of 419+/-82 min was measured. The pre-dosing resulted in higher (13)C-enrichments and caused a significant OCTT shortening of 311+/-99 min (P=0.028). One and 3 weeks after pre-dosing, the measured OCTT again increased to 404+/-124 and 379+/-103 min, respectively. CONCLUSIONS: Pre-dosing with LU before pulse labelling with (13)C-LU led to an induction of enzyme activity and resulted in a definitive estimation of the OCTT when using a threshold of 2 delta over baseline. After 1 and 3 weeks, respectively, the OCTT was no longer significantly different to those without pre-dosing, indicating the disappearance of enzyme induction. Therefore, a pre-dosing with LU on the day before (13)C-LU ingestion is essential for OCTT measurements.

15N-excretion of heat-killed Lactobacillus casei in humans.

OBJECTIVE: In the present study, Lactobacillus casei (L. casei) labelled with 15N was used to follow the metabolic fate of orally administered heat-killed 15N-labelled L. casei (15N-L.casei) in humans. DESIGN: Experimental study. SETTING: University of Rostock, Children's Hospital, Research Laboratory. SUBJECTS: Twelve healthy adults aged 23-32 years. INTERVENTION: The subjects received 36 mg/kg body weight heat-killed 15N-L.casei and 500 mg Lactose-[13C]ureide together with breakfast. Expired air samples were taken over 14 h, whereas urine and faeces were collected over 2 days. A blood sample was taken after 2 h. 13C- and 15N-enrichments were measured by isotope ratio mass spectrometry (SerCon, UK). RESULTS: The orocaecal transit time (OCTT) was reached after 4.1 h. The urinary 15N-excretion was 9.3% of the ingested dose, whereas the faecal excretion was 65.1% of the ingested dose. After 2 h, 15N-enrichment of supernatant, fibrinogen, and plasma protein precipitate amounted to 254, 11, and 2 p.p.m. excess, respectively. CONCLUSIONS: In comparison to the OCTT of 4.1 h, 15N-enrichment in urinary ammonia and urinary total nitrogen already began to rise 30 min after 15N-L.casei ingestion, indicating that 15N-L.casei is rapidly digested in the small bowel. This is confirmed by 15N-enrichments of blood plasma fractions. The ingestion of heat-killed 15N-L.casei led to a total excretion of 74.4% of the ingested 15N-dose.

13C- and 15N-incorporation of doubly stable isotope labelled Lactobacillus johnsonii in humans.

OBJECTIVE: In the present study, Lactobacillus johnsonii (La1) doubly labelled with 15N and 13C (dlLa1) was used to follow the metabolic fate of orally administered dlLa1 in humans. DESIGN: Experimental study. SETTING: Research Laboratory, Children's Hospital, University of Rostock. SUBJECTS: A total of 10 healthy adults aged 23-36 y. INTERVENTION: The subjects received 87 mg/kg body weight viable dlLa1 and 10 g raffinose together with breakfast. Expired air samples were taken over 14 h, whereas urine and faeces were collected over 2 days. A blood sample was taken after 2 h. 13C- and 15N-enrichments were measured by isotope ratio mass spectrometry (SerCon, UK) and H2-concentrations were measured by electrochemical detection (Stimotron, Germany). RESULTS: The orocaecal transit time (OCTT) was reached after 3.7 h. The 13CO2-exhalation amounted to 8.6% of ingested dose. The urinary excretion of 13C and 15N was 1.3 and 12.4% of ingested dose, respectively, whereas the faecal excretion was 39.9 and 37.6% of ingested dose, respectively. After 2 h, 13C- and 15N-enrichment of fibrinogen amounted to 70 and 90 ppm excess, respectively. CONCLUSIONS: In comparison to OCTT of 3.7 h, both stable isotopes appear after 30 min in breath and urine, indicating that dlLa1 is rapidly digested in the small bowel before reaching the caecum. This is confirmed by 13C-and 15N-enrichments of blood plasma fractions. The ingestion of dlLa1 led to an excretion of 50% of ingested dose of both stable isotopes.

The use of 13C-labelled glycosyl ureides for evaluation of orocaecal transit time.

OBJECTIVE: In the present study, cellobiose-[13C]ureide and glucose-[13C]ureide were synthesized and tested as alternative substrates for noninvasive evaluation of the orocaecal transit time (OCTT). DESIGN: Experimental study. INTERVENTION: In total, 1 g cellobiose-[13C]ureide was administered together with a continental breakfast either without or after predosing of 5 x 1 g unlabelled cellobiose ureide on the day prior to study commencement. After 2 weeks, the same subjects ingested glucose-[13C]ureide (dosage: 0.57 g) either without or after predosing of the respective unlabelled ureide under identical conditions. Expired air samples were taken over 10 h. 13CO2-enrichment was measured by isotope ratio mass spectrometry (PDZ Europa, Sandbach, UK). The OCTT was calculated from the interval between 13C-ureide administration and the detection of a significant and sustained 13C-rise of 2 delta over baseline in breath. SETTING: University of Rostock, Children's Hospital, Research Laboratory. SUBJECTS: Eight healthy adults aged 22-55 y. RESULTS: After application of cellobiose-[13C]ureide and glucose-[13C]ureide OCTTs of 401 and 415 min, respectively, were measured. The predosing resulted in higher and steeper 13C-enrichments and caused a significant shortening of OCTTs of 265 and 287 min, respectively (P=0.012 and 0.017). CONCLUSIONS: The onset of 13CO2-enrichment reflected the degradation of glycosyl-[13C]ureides by glucose ureide hydrolase. The predosing with unlabelled ureides prior to pulse labelling with cellobiose-[13C]ureide and glucose-[13C]ureide (the latter is the key substance of the enzymatic sugar-ureide degradation) led to an induction of enzyme activity and resulted in a more precise and similar estimation of the OCTT when using both 13C-labelled ureides.

Metabolic effects of HAY's diet.

The aim of the study was, to evaluate the metabolic effect of HAY's diet on protein turnover, fat oxidation, respiratory quotient, body fat and weight loss. Twelve healthy adults received an individually regular diet and thereafter a corresponding isocaloric and isonitrogenous 10-day HAY-diet. Protein turnover and 13C-fat oxidation were investigated after administration of [15N]glycine and an [U-13C]algae lipid mixture. The 15N and 13C enrichment in urine and breath were measured by isotope ratio mass spectrometry. The respiratory quotient was measured by indirect calorimetry. Body fat, total body water and lean body mass were estimated by bio-electric impedance analysis. HAY's diet led to a significantly higher 13C-fat oxidation (15.4 vs. 22.0% P < 0.01), corresponding to a lower respiratory quotient (0.88 vs. 0.81; P < 0.01), whereas the protein turnover remained constant in both diets (3.06 vs. 3.05 g/kg/day). HAY's diet did not reduce total body water, lean body mass, body fat and body weight (72.2 vs. 71.4 kg).

Clostridium innocuum: a glucoseureide-splitting inhabitant of the human intestinal tract.

Glycosylureides were recently described as non-invasive markers of intestinal transit time. The underlying principle is an enzymatic splitting of (13)C-labelled ureides by intestinal bacteria. The (13)CO(2) released from the urea moiety of the glycosylureides can be measured in breath samples when the ingested tracer substrate reaches the caecum that is colonised with microbes. To date, the microbes that degrade glycosylureides are unknown. In order to identify the glucoseureide (GU)-splitting bacteria, 174 different strains of intestinal microbes obtained from five healthy adults were checked for their ability to degrade GU. The results of the microbial cultures and thin layer chromatography revealed that GU was exclusively degraded by Clostridium innocuum, belonging to the normal human intestinal microflora. C. innocuum probably synthesises a yet unknown enzyme that splits the glucose-urea bond. We suggest that the term glucoseureidehydrolase is the appropriate designation for this enzyme.

Triglyceride oxidation in cystic fibrosis: a comparison between different 13C-labeled tracer substances.

BACKGROUND: For indirect evaluation of pancreatic lipase activity in cystic fibrosis, different 13C-labeled triglycerides may be used. METHODS: Triglyceride oxidation in patients with cystic fibrosis was investigated after administration of different 13C-labeled triglycerides by comparing 13CO2 breath exhalation. In the comparative study, five patients with cystic fibrosis (age, 8-15 years; body weight, 22.5-39.8 kg) were treated with Pangrol (individual dosages: 1-3 capsules per morning meal; Berlin-Chemie, Berlin, Germany). [1,1,1-13C3]Glyceryl tripalmitate and [1,1,1-13C3]glyceryl trioleate were administered as a single oral pulse at 8:00 A.M. (dosage, 4 mg/kg each) with the standard diet Fresubin (dosage, 10 ml/kg; Fresenius, Bad Homburg, Germany). Alternately, the same subjects were given the synthetic mixed triglyceride 1,3-distearyl, 2[13C]octanoyl glycerol (dosage, 12.5 mg/kg) contained in the standard diet Nutri-Mix (dosage, 10 ml/kg; Nutricia, Zoetemeer, The Netherlands). Breath samples were taken in 15- and 30-minute intervals over 8 hours. The 13CO2 enrichment was measured by continuous-flow isotope ratio mass spectrometry. RESULTS: After administration of the 13C-labeled tripalmitin-triolein mixture and the mixed triglyceride, mean maximum 13CO2 enrichments were 4.70 and 7.37 delta over baseline, occurring at 7.0 and 3.5 hours, respectively. The corresponding percentage cumulative 13CO2 exhalations were 12.25% and 29.19%, respectively, and differed significantly in the five paired subjects (p = 0.003). CONCLUSIONS: After using different 13C-labeled triglycerides the resultant 13CO2 exhalation reflected the triglyceride hydrolysis and subsequent oxidation. It is concluded that the different cumulative 13CO2 exhalations were mainly caused by the rate-limiting step of triglyceride hydrolysis to free fatty acids and 2-monoglycerides and by fat deposition. Noninvasive 13C breath tests using different 13C-labeled triglycerides can be used for evaluation of pancreatic lipase activity before and during enzyme supplementation.

[Sialic acid, steroids and proteohormones in maternal, cord and retroplacental blood]. / Sialinsäure, Steroid- und Proteohormone im Venenblut der Mutter, im Nabelschnurblut des Neugeborenen und im Retroplazentarblut.

BACKGROUND: To study the storage of sialic acid in newborns reference concentrations for sialic acid were measured in maternal, retroplacental and cord blood and compared with the concentration of human placental lactogen (hPL) and estriol (E3). High serum concentrations of hPL and E3 in retroplacental blood indicate the synthesis of these products in the fetoplacental unit. The comparison of the serum concentrations give first informations for a possible role of the placenta as a place of production and storage of the investigated products. METHODS: The concentrations of sialic acid, hPL and unconjugated E3 were determined in maternal and retroplacental blood samples of 126 pregnant women (16-42 years old) between 28 and 42 weeks of gestation. 84 of these pregnant women had uncomplicated pregnancy with birth after 37 gestational weeks. Measurements of E3 and hPL were performed by solid phase radioimmunoassays. Concentrations of sialic acid were determined by HPLC (high performance liquid chromatography). RESULTS: Means and medians of the three parameters for both groups differentiate hardly. The retroplacental serum concentrations of hPL and E3 are increased significantly compared with maternal blood. The same trend was found for sialic acid without significance. The highest concentrations of E3 were found in the cord blood (298.2 +/- 138.0 ng/ml) (p < 0.01). On the other hand the lowest concentrations of sialic acid (36.1 +/- 19.6 mg/l) (p < 0.01) were estimated in cord blood samples. It was estimated a significant correlation between fetal and retroplacental concentrations of E3. Significant correlations (p < 0.01) were found for sialic acid between maternal and retroplacental blood on the one side and maternal and the cord blood on the other side. Significant increased mean sialic acid concentrations in retroplacental blood (x = 102.67 mg/l) were found in female newborns in comparison with male newborns (x = 80.58 mg/l). There were not significant differences between prematurity and term delivery. CONCLUSION: Increased sialic acid concentrations in retroplacental blood samples are a sign of sialic acid accumulation in the fetomaternal area aiming to induce the tolerance of fetal allotransplantat. There are no evidence for a take up of free sialic acid by fetus.

[Comparison of gastric emptying, blood glucose, and oro-cecal transit times after a conventional morning meal and a Kollath breakfast]. / Vergleichende Messungen von Magenentleerung, Blutglukose und orozökaler Transitzeit nach einer konventionellen Morgenmahlzeit und einem Kollath-Frühstück.

Blood glucose kinetics and intestinal transit times were investigated in 12 adult volunteers aged 28 to 52 years after ingestion of a conventional morning meal made up of white flour rolls, butter, marmalade, and coffee with sugar as compared with an isocaloric Kollath-breakfast consisting of whole wheat flakes as a basis. For estimation of gastric emptying time the sodium-[13C]acetate breath test technique was used. Oro-coecal transit time and gastric emptying were determined by simultaneous administration of lactose-[13C]ureide and consecutive drawings of breath samples in intervals of 15, 30, and 60 min through 12 h. The 13CO2-excess of the breath test samples was measured by continuous flow isotope ratio mass spectrometry. The postprandial rise in blood glucose following the ingestion of the Kollath-breakfast was lower as compared with the conventional morning meal, showing significant differences between the 90 min values and the area below the blood glucose curve. The half time of gastric emptying was not different between the two breakfast versions (1.7 vs. 1.6 h). The oro-coecal transit time averaged out at 4.2 h after the Kollath-breakfast and 5.3 h following the conventional morning meal. Likewise, there were no significant differences in the coecal retention time nor in the cumulative percentage of 13CO2-exhalation between the two breakfast versions. Concerning the blood glucose kinetics the differences in the nutritional physiology between the breakfast based on whole wheat flakes and the conventional breakfast as claimed by Kollath were only detectable in outlines in our study. Gastric emptying time showed no differences between the two breakfast versions.

Evaluation of oro-coecal transit time: a comparison of the lactose-[13C, 15N]ureide 13CO2- and the lactulose H2-breath test in humans.

OBJECTIVE: The lactulose H2-breath test is the most widely used non-invasive approach for evaluation of orocoecal transit time (OCTT). In the present study, doubly-labelled lactose-[13C, 15N]ureide (DLLU) was synthesized to investigate the OCTT in comparison to the conventional lactulose H2-breath test. Additionally the bacterial breakdown rate (BBR) and rate of elimination and the metabolic pathways of the cleavage products of DLLU (13CO2, [15N]urea, and 15NH3) were investigated. DESIGN AND SUBJECTS: In a first study, DLLU was administered as a single oral-pulse-labelling (dosage: one gram) either without and after pretreatment of five grams of unlabelled lactoseureide (LU) on the day prior to the study to twelve healthy adult volunteers after breakfast. Breath and urine were collected in one and two hour-intervals, respectively, over a one-day period. 13C-enrichment in breath as well as 15N-enrichment in urine fractions were measured by continuous flow-isotope ratio mass spectrometry (CF-IRMS). In a second study, lactulose was administered to the same subjects (dosage: ten grams). Breath was collected in quarter, half and one hour-intervals over a ten hour-period. Hydrogen concentration in breath was analysed using an electrochemical detector. RESULTS: The comparison of the lactose-[13C]ureide 13CO2-breath test and the lactulose H2-breath test showed that the mean increase of the 13C-enrichment in CO2 occurred 1.18 h later than the mean increase of H2 in breath. The resulting OCTTs derived from the two methods were 3.02 +/- 1.4 and 1.84 +/- 0.5 h (P < 0.05) and the corresponding BRs were 9.63 +/- 3.4 and 6.07 +/- 1.7 h (P < 0.01), respectively. The 15N-enrichment of urinary urea and ammonia without and after pretreatment with LU started between two and three hours after DLLU-administration. The cumulative percentage urinary excretion of the 15N- and 13C-tracer was 29.9% and 13.6% respectively, and was slightly increased after LU-pretreatment to 32.1% and 14.6% of the dose administered. A total of 35.2% of the 13C was found to be exhaled and remained approximately constant after LU-pretreatment (36.2%). CONCLUSIONS: The use of the lactulose H2-breath test for evaluation of the OCTT showed a statistically significant shortening of 1.18 h in comparison to the lactose-[13C]ureide 13CO2-breath test in healthy adults. The most important limitations of the lactulose H2-breath test are its low specificity and sensitivity due to dose-dependent accelerations of OCTT, interfering H2-rise from malabsorbed dietary fibre and H2-non-producers. In contrast, our lactose-[13C]ureide 13CO2-breath test was confirmed to avoid these disadvantages and to yield reliable results. This test is recommended especially if higher sensitivity and specificity is required, if IRMS-technique is available and if lactulose H2-tests lead to insufficient results.

15N-tracer studies in formula-fed preterm infants: the role of glycine supply in protein turnover.

In preterm infants, protein-turnover rates obtained by [15N]glycine as a tracer are known to be overestimated. This may reflect the insufficient supply of dietary glycine. In this randomized study, the influence of a glycine-rich diet on whole body protein turnover rates in eight male preterm infants (29-32 weeks, 1,200-2,540 g birthweight) using the 15N-tracer technique on days 21 and 28 of life was investigated to evaluate the necessity of supplementing preterm infant formulas with proteins rich in glycine. Before and during the study, the infants were alternately fed with a commercial available preterm infant formula (I, 2% protein, 40 mg glycine/dl) and a variety of this formulation with glycine-rich proteins (II, 2% protein, 130 mg glycine/dl). The protein-turnover rates were computed after 15N-single-pulse labeling with the help of the three-compartment model (TCM) and the urinary ammonia end-product method (AEPM). The tracer used was [15N]glycine (dosage: 2 mg 15N/kg). For the determination of 15N-excess-excretion kinetics, fractionated urine specimens were collected over a 36-h period. The protein-turnover rate calculated by TCM was 8.8 +/- 1.6 g/kg/day (formula I) and 7.7 +/- 2.0 g/kg/day (formula II); using AEPM, the rate was 8.7 +/- 2.5 g/kg/day and 7.5 +/- 1.5 g/kg/day, respectively. We conclude that the presaturation of the precursor pool by an adequate glycine intake minimizes drawbacks that may arise when using [15N]-glycine as a tracer in preterm infants, and a protein concentration of 2%, as in formula I, and consequently, a 170% glycine content when compared with the same human milk volume, meets the glycine requirement.

alpha-Lactalbumin-enriched low-protein infant formulas: a comparison to breast milk feeding.

Tryptophan (TRP) is the limiting amino acid in low-protein infant formulas. This is mainly due to lower alpha-lactalbumin (alpha LA) content in cow's milk whey as compared with human milk protein. To study the effect of alpha LA-enrichment on the TRP supply, cross-over studies were carried out in 20 healthy infants up to 3 months of age. In this study, two protein-reduced (1.3%) infant formulas (moderate TRP content of 1.88% and higher TRP content of 2.10%) were alternately fed over a 2 week period in two groups of infants. Serum TRP levels of the formula-fed infants with the higher TRP content did not differ significantly from an exclusively breastfed control group of 11 infants (10.5 +/- 4.8 versus 10.9 +/- 4.7 mg l-1, p = 0.841), whereas levels of the formula-fed infants with the moderate TRP content were significantly lower (7.4 +/- 3.9, p = 0.038). The supplementation of alpha LA resulting in a higher TRP supply to low-protein diets is a further step towards the production of infant formulas more closely adapted to human breast milk.

Tracer kinetic studies on a methionine-supplemented soy-based infant formula using 1-13C- and 15N-methionine as tracers.

A tracer-kinetic study using 1-13C- and 15N-labeled L-methionine was conducted in order to measure the retention rate of free methionine added to commercially-produced soy-based infant formulas. Twelve male infants, fed on a soy formula, received a single-pulse labeling by oral administration of L-1-13C-methionine (5 mg/kg) and L-15N-methionine (10 mg/kg). The abundance of expired 13C-labeled CO2 was measured up to 7 h after administration at 15-, 30-, and 60-min intervals. Additionally, enrichment of total 15N and 15N in urinary ammonia were determined up to 48 h after administration. Retention rates of the labeled carboxyl group amounted to an average of 91.2% (SD 4.1) of the intake. A similar retention rate was measured for the 15N-label of methionine (90.0%, SD 4.3). The data point at the efficacy of methionine supplementation of soy-based infant formulas.

The significance of tryptophan in human nutrition.

Aside from its role as one of the limiting essential amino acids in protein metabolism, tryptophan (TRP) serves as precursor for the synthesis of the neurotransmitters serotonin and tryptamine as well as for the synthesis of the antipellagra vitamin nicotinic acid and the epiphyseal hormone melatonin.By involvement in so manifold pathways, TRP and its metabolites regulate neurobehavioral effects such as appetite, sleeping-waking-rhythm and pain perception. TRP is the only amino acid which binds to serum albumin to a high degree. Its transport through cell membranes is competetrvely inhibited by large neutral amino acids (NAA). The TRP/NAA ratio in plasma is essential for the TRP availability and thus for the serotonin synthesis in the brain.Due to its high TRP-concentration, human milk protein provides optimal conditions for the availability of the neurotransmitter serotonin. Low protein cow's milk-based infant formulas supplemented withα-lactalbumin - a whey protein fraction containing 5.8% TRP - present themselves as a new generation of formulas, with an amino acid pattern different from the currently used protein mixtures of adapted formulas, resembling that of human milk to a much higher degree.