Metabolic effects of HAY's diet

The effect of resistant starches on fat oxidation in healthy adults as measured by a 13CO2-breath test

A resistant starch (RS) mixture (MIX) consisting of fibre of potatoes (FP) and wrinkled pea starch (WPS), and high amylose maize starch (HAMS) were supplemented in adults to evaluate their effects on fat oxidation by means of a ¹³CO₂-breath test. Sixteen subjects received a regular diet either without or with the supplementation of MIX and HAMS in randomised order. After administration of a [U-¹³C]algal lipid mixture, exhaled air was collected over 14 h in 0.5- and 1-h intervals. The ¹³C abundances were measured by nondispersive infrared spectroscopy. In comparison to the dry run (DR), supplementation with MIX and with HAMS increased the cumulative percentage dose recovery: (DR: 16.7 %, MIX: 16.9 %, HAMS: 18.0 %), but without statistical significance. The colonic degradation of MIX and HAMS to short-chain fatty acids tends to lower the formation of carbohydrate-derived acetyl-CoA and contributes to a postprandial lipid oxidation increase by using fat-derived acetyl-CoA as a compensatory fuel source.

Development and application of 15N-tracer substances for measuring the whole-body protein turnover rates in the human, especially in neonates: a review

Our research group of the Children's Hospital of the University of Rostock (Rostock group) has long-time experience in (15)N-labelling and in using yeast protein and its hydrolysates for tracer kinetic studies to evaluate parameters of the whole-body protein metabolism in premature infants. The particular advantage of applying an economically convenient, highly (15)N-enriched, and completely labelled yeast protein for evaluating protein turnover rates is the fact that the (15)N dose is spread among all proteinogenic amino acids. The absorption has been improved by hydrolysing [(15)N]yeast protein with thermitase into a mixture of amino acids, dipeptides and tripeptides so that faecal analysis becomes unnecessary when determining turnover rates. The review shows that, in contrast to the application of single (15)N-labelled amino acids with resulting overestimation of protein turnover rates, the (15)N-labelled yeast protein thermitase hydrolysate represents the amino acid metabolism more closely without causing amino acid imbalances. The (15)N-labelled yeast protein thermitase hydrolysate leads to the estimation of reliable protein turnover rates, particularly in premature infants.

Effect of alcohol consumption on whole-body protein turnover in healthy adults

The aim of the study was to investigate the whole-body protein turnover, either before or after continuous, moderate ethanol-induced oxidative stress by red wine consumption over a relatively short period in healthy volunteers. Ten healthy adults received an individual regular diet over 20 days. After 10 days, the subjects consumed 0.4 ml ethanol kg(-1) day(-1) as red wine together with dinner over a 10-day period. After 8 and 18 days, respectively, a (15)N-labelled yeast protein was administered in a dosage of 4.2 mg kg(-1) body weight. Urine and faeces were collected over 48 h, respectively. The (15)N-enrichment was measured by isotope ratio mass spectrometry, whereas the protein flux rates were calculated by a three-compartment model. The whole-body protein turnover without/with red wine consumption amounted to 3.73±0.6 and 3.49±0.6 g kg(-1) day(-1) (not significant), respectively. Moderate alcohol consumption does not induce significant short-term changes in the whole-body protein turnover of healthy adults.

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 effect of l-carnitine on fat oxidation, protein turnover, and body composition in slightly overweight subjects

We used a combined tracer technique with the stable isotopes 13C and 15N to gain further insight into the metabolic changes that accompany supplementation of L-carnitine. The aim of the present study was to investigate whether L-carnitine supplementation can influence fat oxidation, protein turnover, body composition, and weight development in slightly overweight subjects. Twelve volunteers received an individual regular diet either without or with L-carnitine supplementation of 3 g/d for 10 days. Protein turnover and 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. Body fat mass (BFM), total body water (TBW), and lean body mass (LBM) were calculated by using bioelectric impedance analysis. L-carnitine supplementation led to a significant increase in 13C-fat oxidation (15.8% v 19.3%; P = .021) whereas protein synthesis and breakdown rates (3.7 and 3.4 g/kg/d, respectively) remained unchanged, indicating that the increased dietary fat oxidation in slightly overweight subjects was not accompanied by protein catabolism.