H Elzinga

Non-Invasive Detection of Low-Intestinal Lactase Activity in Children by Use of a Combined 13CO2/H2 Breath Test

BACKGROUND The aim of the study was to diagnose hypolactasia with a higher accuracy than with the traditional H2 breath test. METHODS We used a combined 13C-lactose 13CO2/H2 breath test, which was performed in 33 patients in whom lactase activity was measured. RESULTS Lactase activity was reduced in 13 cases. The sensitivity and specificity of the H2 test were 54% and 90%; those of the 13CO2 test 69% and 70%. False-negative results did not always occur in the same patients. In five of six patients with both test results abnormal, lactase activity was low. In 13 of 15 patients with both test results normal, lactase activity was normal. In 6 of 12 cases with only 1 test abnormal, lactase activity was low. CONCLUSION The combined H2/13CO2 breath test (sensitivity, 85%; specificity, 65%) is more adequate for diagnosis of hypolactasia than the H2 breath test alone.

The 13C/2H-glucose test for determination of small intestinal lactase activity

To diagnose hypolactasia, determination of lactase enzyme activity in small intestinal biopsy material is considered to be the golden standard. Because of its strongly invasive character and the sampling problems, alternative methods have been looked for.

The contribution of newly synthesized cholesterol to bile salt synthesis in rats quantified by mass isotopomer distribution analysis

A new stable isotope procedure has been developed and validated in rats, applying [1-(13)C]acetate infusion to quantify the production of bile salts from de novo synthesized cholesterol making use of the mass isotopomer distribution analysis (MIDA) principle. Ions (m/z) 458-461, 370-373 and 285-288 were monitored by GC/MS (EI-mode) for the methyl trimethylsilylether derivatives of cholate, chenodeoxycholate and beta-muricholate, respectively. Rats with intact exteriorized enterohepatic circulation and rats with chronic bile diversion were infused with [1-(13)C]acetate for up to 14 h. After 10 h of infusion the enterohepatic circulation of the intact group was interrupted to deplete the existing bile salt pool (acute bile diversion). The fractions of biliary cholesterol and individual bile salts derived from newly synthesized cholesterol were determined by MIDA at t=14 h. In rats with acute bile diversion, these fractions were 20, 25, 27 and 23% for biliary cholesterol, cholate, chenodeoxycholate and beta-muricholate, respectively. After bile diversion for 8 days to induce hepatic cholesterol and bile salt synthesis, these fractions increased significantly to 32, 47, 41 and 47%, respectively. Calculated enrichments of the acetyl-CoA precursor pools were similar for all bile salts and biliary cholesterol within the two rat groups. However, chronic enterohepatic interruption decreased the acetyl-CoA pool size almost two-fold. We conclude that MIDA is a validated new stable isotope technique for studying the synthetic pathway from acetyl-CoA to bile salts. This technique provides an important new tool for studying bile salt metabolism in humans using stable isotopes.

Lactose (mal)digestion evaluated by the 13C-lactose digestion test.

The prevalence of genetically determined lactase nonpersistence is based on the results of the lactose H2 breath test. This test, however, is an indirect test, which might lead to misinterpretation.

Determination of low isotopic enrichment of L-[1-C-13]valine by gas chromatography combustion isotope ratio mass spectrometry: a robust method for measuring protein fractional synthetic rates in vivo

A method was developed for measuring protein fractional synthetic rates using the N-methoxycarbonylmethyl ester (MCM) derivative of L-[1-13C]valine and on-line gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The derivatization procedure can be performed rapidly and GC separation of valine from the other branched-chain amino acids, leucine and isoleucine, is easily obtained. A good linear relationship was observed between the increment of the 13C/12C isotope ratio in CO2 gas derived from the combustion of derivatized valine and the tracer mole ratio of L-[1-13C]valine to unlabelled valine. The limit of quantitation was at an L-[1-13C]valine tracer mole ratio of 0.0002. The method was used to measure the isotopic enrichment of L-[1-13C]valine in standard mixtures and in skeletal muscle of six growing piglets infused with L-[1-13C]valine (2 mg kg-1 h-1 for 6 h). After infusion of L-[1-13C]valine the mean tracer mole ratio in plasma of L-[1-13C]valine at the isotopic steady state was 0.0740 +/- 0.0056 (GC/MS, mean +/- SEM) and the mean tracer mole ratio of valine in muscle protein fraction at 6 h was 0.000236 +/- 0.000038 (GC/C/IRMS). The resulting mean protein fractional synthetic rate in piglet skeletal muscle was 0.052 +/- 0.007% h-1, which is in good agreement with literature data obtained with alternative, more elaborate techniques. By this method protein fractional synthetic rates can be measured at low isotopic enrichment levels using L-[1-13C]valine, the MCM derivative and on-line GC/C/IRMS.

Analytical techniques in biomedical stable isotope applications: (isotope ratio) mass spectrometry or infrared spectrometry?

An overview is presented of biomedical applications of stable isotopes in general, but mainly focused on the activities of the Center for Liver, Digestive and Metabolic Diseases of the University Medical Center Groningen. The aims of metabolic studies in the areas of glucose, fat, cholesterol and protein metabolism are briefly explained, as well as the principle of breath testing and the techniques to study body composition and energy expenditure. Much attention is paid to the analytical considerations based upon metabolite concentrations, sample size restrictions, the availability of stable isotope labelled substrates and dose requirements in relation to compound-specific isotope analysis. The instrumental advantages and limitations of the generally used techniques gas chromatography/reaction/isotope ratio mass spectrometry and gas chromatography/mass spectrometry are described as well as the novelties of the recently commercialised liquid chromatography/combustion/isotope ratio mass spectrometry. The present use and future perspective of infrared (IR) spectrometry for clinical and biomedical stable isotope applications are reviewed. In this respect, the analytical demands on IR spectrometry are discussed to enable replacement of isotope ratio mass spectrometry by IR spectrometry, in particular, for the purpose of compound-specific isotope ratio analysis in biological matrices.

Oro‐cecal transit time: influence of a subsequent meal

Background  Small intestinal and oro‐cecal transit time (OCTT) is determined for clinical diagnostics and research purposes. Experimental protocols used vary with respect to the inclusion of a subsequent meal during the test period. This study was conducted to elucidate whether the ingestion of a subsequent meal during the test period influences the OCTT of the test meal.

Low-dose acarbose does not delay digestion of starch but reduces its bioavailability

Aims  Slowly digestible starch is associated with beneficial health effects. The glucose‐lowering drug acarbose has the potential to retard starch digestion since it inhibits α‐amylase and α‐glucosidases. We tested the hypothesis that a low dose of acarbose delays the rate of digestion of rapidly digestible starch without reducing its bioavailability and thereby increasing resistant starch flux into the colon.

Influence of a subsequent meal on the oro-cecal transit time of a solid test meal

Background  Oro‐cecal transit time (OCTT) is determined for clinical diagnostics of intestinal complaints and research purposes. Ingestion of a subsequent meal during the test period shortens the OCTT of a liquid test meal (glucose solution), as previously reported. This study was conducted to determine whether the same phenomenon occurs after ingestion of a solid test meal.

Digestion of starch

II. Set up the experimental test C & D as follows: Pour in a small quantity – not more than 1⁄2 cm of starch solution in C. Pour in a small quantity – not more than 1⁄2 cm of maltose solution in D. Then add enough drops of iodine to produce a color change. Add at least twice as much saliva to each tube Cover the tube with parafilm and shake it to mix the contents. Keep warm in hand or 37C bath until a further color change occurs. Save these tube. Beginning color when combined End color C. Starch + iodine , mix... & add saliva ___________________ _________________ D. Maltose + iodine, mix... & add saliva ___________________ _________________ How do you account for the beginning color? _________________________________ Is there starch present at the end? _________________________________ How long did it take for the color to change? _________________________________