Investigation of Enterohepatic Bile Acid Circulation ...

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Investigation of Enterohepatic Bile Acid 15

Circulation with [ N]Taurocholate a

a

U. E. Rolle-kampczyk , P. Krumbiegel & Th. Richter

b

a

UFZ-Umweltforschungszentrum Leipzig-Halle GmbH, Sektion Expositionsforschung und Epidemiologie , Leipzig, Deutschland b

Universitätskinderklinik Leipzig , Deutschland Published online: 24 Sep 2006.

To cite this article: U. E. Rolle-kampczyk , P. Krumbiegel & Th. Richter (1995) Investigation of 15

Enterohepatic Bile Acid Circulation with [ N]Taurocholate, Isotopes in Environmental and Health Studies, 31:3-4, 241-246, DOI: 10.1080/10256019508036265 To link to this article: http://dx.doi.org/10.1080/10256019508036265

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INVESTIGATION OF ENTEROHEPATIC BILE ACID CIRCULATION WITH [I 5N]TAUROCHOLATE U. E. ROLLE-KAMPCZYK', P. KRUMBIEGEL' AND TH. RICHTER'

U F Z -Umweltforschungszentrum Leipzig-Halle GmbH, Sektion Expositionsforschung und Epidemiologie Leipzig, Deutschland 2Universitatskinderklinik Leipzig, Deutschland (Received January 05, 1995; accepted June 21, 1995) [15N]Taurocholate has been prepared and used as a simple urine test substrate as a substitute for I4Cand 13C breath test substrates. ['5N]Taurocholate was administered instead of ["N] glycocholate assuming that taurine is mainly used in the cholate cycle. Differences were found between healthy and diseased subjects, although deconjugated ["Nltaurine was recovered in urine much less than expected. To get additional information on the actual excess of free taurine, Ci5Nltaurine was administered orally in parallel investigations. Apparently, large fluctuations in the whole body taurine metabolism are responsible for the unexpected results.

KEY WORDS Bile acid circulation, nitrogen 15, organ function tests, taurine, taurocholate, tracer techniques

INTRODUCTION Disturbances of the human enterohepatic bile acid circulation can be related to bwerial overgrowth in the small intestine and to malabsorption of bile acids at the ileum both resulting in an increase of the deconjugation products glycine and taurine. Glycine is known to be re-utilized in different endogenic metabolic processes such as in protein synthesis. Nevertheless, breath tests with [14C]- and 3C]glycocholate were proposed to follow disorders of the enterohepatic bile acid circulation noninvasively [l]. The deconjugation product [14C]glycine or 3C]glycine is apparently in part catabolized giving [14C]C0, or [13C]C0, that can be measured in breath samples. Stahl and Arnesjo announced that deconjugated taurine is not re-utilized but eliminated via urine [2]. This paper gave the impact to study the bile acid circulation using stable isotope labelled taurocholate. In order to meet some of the known limitations of breath tests [3], especially with infants, taurine, moreover, has been

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Correspondence: Dr. Ulrike Elisabeth Rolle-Kampczyk, UFZ-UmweltforschungszentrumLeipzig-Halle GmbH, Sektion Expositionsforschung und Epidemiologie, PF 02, 04301 Leipzig, Germany 24 1

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U. E. ROLLE-KAMPCZYK et al.

labelled with 15N to measure its recovery in urine. As a result, it should be possible to see disorders of the enterohepatic bile acid circulation as enhanced 15N concentrations in urine. In the present methodological study this principle will be elucidated with the help of some casuistics.


HUMAN SUBJECTS AND METHODS Nine diseased infants and children, two clinically healthy adults and a clinically healthy infant were included in the study which was approved by the Ethical Group of the Department of Peadiatrics of the Leipzig University. Informed consent was obtained from the parents of each infant prior to enrollment in the study. ['5N]Taurocholate [4], 5 or 7,5 mg/kg body mass, was administered orally. Thereafter, urine was collected in 6h-intervals over 24 to 130 h. Faeces of some subjects were collected and frozen for storage, too. Urine and faeces samples were digested with the Kjeldahl method to measure total nitrogen contents and then 15N concentrations using an optical 5N analyzer NOI-6PC (FAN Fischer Analysen Leipzig) or a mass spectrometer (Delta C, Finnigan MAT). In case of small 15N values observed, another aliquot of the urine samples was separated by chromatography (Dowex W 50, eluent: water) to isolate taurine and to obtain its "N content directly. On this basis, the [ "Nltaurine content of each of the urine portions was obtained. RESULTS AND DISCUSSION Cumulative 15N amounts eliminated via urine 6 and 24 hours after a [15N]taurocholate administration are shown in Fig. 1. A clear distinction is seen at both times between healthy and diseased persons. However, the recovery of ["Nltaurine in urine is much smaller than expected. Urine has to be collected over a long period. Therefore, it takes a long time to get the results. It was proved by analyses of faeces samples that the 5N amounts missed in urine were not eliminated via faecess as unchanged taurocholate: In one case observed even up to 134 hours less than 11% of the administered "N were recovered in the faeces. The time courses of urinary 15N elimination over five days of a healthy volunteer and a patient suffering from mucoviscidosis are compared in Fig. 2. The experimental results were compared to theoretical values calculated with a logistic function adapted from usual growth functions (Fig. 2, lines). The general result is a confirmation of our working hypothesis suggesting much higher urinary ['5N]taurine elimination rates in a patient - with serious disorders resulting in disturbed enteral resorption -compared to a healthy person. As the measuring times to reach unequivocal results with the now tested method are surprisingly long, ["Nltaruine itself was substituted for ['SN]taurocholate to

[I5N]TAUROCHOLATE METABOLISM

243

1 hsalthy adult

I

2 healthy adult 3 healthy newborn 4 infant rotavirusl

5 infant rotantus2 6 infant rotavirus3


7 rytostatica 8 retardation of growth 9

mucoviscidosis

10 mucoviszidooio

'

1 1 Morbus Crohn

Fig. 1 Cumulative J 5 Nelimination of healthy and diseased subjects after application of CJ 5N]taurocholate

.

hsalthyl

0

mueoviszidosis

+

hsalthy 2

log. funct. healthy1

log. funct.mucoviszidosis

log. funct. healthy2

-0

0

50

100

150

tlma Ihl

Fig. 2 Comparison of I5N elimination kinetics of a healthy volunteer and a patient suffering from mucoviscidosis after application of ['5N]taurocholate

be administered orally. It was expected that this substitution would shorten the test time: This labelled diagnostic agent should be involved no longer in the enterohepatic deconjugation metabolism. It should act as an isotope dilution agent for quantification of deconjugated taurine only. Time courses of urinary I5N elimination following ["Nltaurine administration of a healthy volunteer and a patient suffering from mucoviscidosis are demonstrated in Fig. 3. The experimental results were compared with theoretical values calculated by a Mitscherlich function adapted from common growth functions (Fig. 3, lines). The so-called plateau method was used for the calculation of reliable figures to compare the effectiveness of taurocholate versus taurine labelling (Table 1). The time

U. E. ROLLE-KAMPCZYK et al.

244

7

.

6

- 5

s

0

t 4

~~

mucoviscidosis

0

healthy adult

; 3

Mitscherlich healthy

5

Mitschsrlich rnucucovisridosis

2

Lo

-

1

I '


I'

0 -1

20

40

80

60

Fig. 3 Comparison of ''N elimination kinetics of a healthy volunteer and a patient suffering from mucoviscidosis after application of ["Nltaurine

Tab.1 Times to attain plateau values in urine and ''N amounts recovered then, both calculated for a healthy subject and a mucoviscidosis patient each having digested equivalent amounts of [15N]taurocholate and of [' 5N]taurine separately ['5N]Taurocholate Healthy

['5N]Taurine

Diseased Healthy

Diseased

Time [h] to attain plateau values reliable to 90% to 95% to 99%

121 126 131

100 113 127

17 21 28

25 30 35

Plateau values of recovered 15N amounts (95% reliability) [YOof administered I5N]

35

64

6

3

to attain an expected plateau value of cumulative 15N recovery can serve as a criterion of the practical usefulness and economy of an expected test. The differences in the 15N amounts recovered then between healthy and diseased subjects are a criterion of the sensitivity of the expected test. In Tab. 1, both labelled agents are compared intraindividually. It is seen that the plateau value is reached with [15N]taurine about four times earlier than with [15N]taurocholate. The discrimination between the healthy and the diseased subject is formally the same with both agents, but has opposite directions: Compared with the healthy subject, the mucoviscidosis patient eliminates a twofold 'N amount after a ['SN]taurocholate dose and only a half 15N amount after an equivalent [' 'Nltaurine dose.

['5N]TAUROCHOLATE METABOLISM

245

It can only be speculated that the lower revcovery of [l'Nltaurine after administration in the mucoviscidosis patient is due to pathologically enhanced demand for this half-essential amino acid with resorption of the orally given agent already in the duodenum and jejunum, and following use, besides others, to conjugate cholic acids. The higher recovery of ["Nltaurine after [15N]taurocholate administration - on the other hand - could be seen as a result of disturbed re-resorption in the jejunum and ileum of the mucoviscidosis patient followed by increased deconjugation. As an overall result of the comparison, differences can be seen already within 30 hours with a reliability of 95% if ["Nltaurine is used for ['5N]taurocholate. The total urinary [l'Nltaurine recovery, however, is much smaller and seems not to follow the intended purpose which was the reflection of disturbed resorption and deconjugation of taurocholate. Unfortunately, another limitation of the method is the relatively poor reproducibility of the results seen in the study, even intraindividually, within repeated measurements of the same individuum some weeks later. Apparently, changing food taurine supply and variations in the individual taurine pools are responsible for this. The reason of the generally poor recovery ratios of urinary "N from [' 5N]taurocholate as well as from [' 5N]taurine and of the poor reproducibility of the results could not be explained satisfactorily up to now. Apparently, other endogenous processes involving taurine will be underestimated up to now: Taurine plays a great role in several processes [S] such as being a neuromodulator [6,7], being involved in cardiovascular regulations [8,9], in the retina [lo, 111 as well as a toxicity protector [5,12,13]. According to a recent review [ S ] , however, the only property of taurine proven is that it is essential in enterohepatic bile acid circulation.


[''Nltaurine

CONCLUSION

As a result of this study, it has to be concluded that the recovery of {"Nltaurine in urine does not reflect the enteral deconjugation rate as sensitive and reliable as expected. Therefore, the original intention of the present study to develop a new simple urine test on this principle could not be carried out. Further studies on unknown competitive reactions of taurine in the human body are necessary. Our study can be seen as a contribution to this necessity. The - originally unexpected - results of this study refuse the missing re-utilization of deconjugated taurine as was stated otherwise [2]. Apparently, the source of taurine which is utilized in many metabolic processes is not only food (human milk, meat, fish) but also the taurocholate deconjugation. The participation of the latter source seems to fluctuate as a result of a compensation mechanism due to the ratio of requirement and supply by food. Only abundant taurine is eliminated. Following oral administration of [''Nltaurine and urinary ''N measurement this actually abundant portion is quantified.

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et

al.

ACKNOWLEDGMENT The authors are grateful to Deutsche Forschungsgemeinschaft for financial support (Kr 1289/1-1).


References [l] N. W. Solomons, D. A. Schoeller, J. 9 . Wagonfeld, D. Ott, J. H. Klein, P. D, Application of a stable isotope L3C-labeledglycocholate breath test to diagnosis of bacterial overgrowth and ileal dysfunction. J. Lab. Clin. Med. 90 (1977) 431-439 [2] E. Stahl, B. Arnesjo, Taurocholate metabolism in man. Scand. J. Gastronet. 7 (1972) 559-566 [3] P. Krumbiegel, Stable Isotope Pharmaceuticals for Clinical Research and Diagnosis. G. Fischer Jena, Stuttgart, New York 1991, 72-73 [4] P. Krumbiegel, H. Senger, H. Sprinz, Sodium ['5N]taurocholate- a new stable isotope pharmaceutical to investigate the enterohepatic bile acid circulation non-invasively. Europ. J. Nucl. Med. 18 (1991) 671 [5] R. J. Huxtable, Physiological actions of taurine. Physiol. Rev. 72 (1992) 101-163 [6] M. E. Arzate, H. J. Moran, H. Pasantes-Morales, Inhibitory effect of taurine on 4-aminopyridinestimulated release of labelled dopamine from striatal synaptosomes. Neuropharmacol. 25 (1986) 689-694 [7] P. Kontro, E. R. Korpi, 0. S. Orja, S. S. Oja, Modulation of noradrenaline uptake and release by taurine in rat cerebral slices. Neurosci. 13 (1984) 663-666 [S] F. Franconi, I. Stendardi, P. Failli, R. Matucci, C. Baccaro, L. Montrosi, A. Giotti, The protective effects of taurine in hypoxia (performed in the absence of glucose) and on reoxydation (in presence of glucose) in guinea-pig heart. Biochem. Pharmncol. 34 (1985) 261 1-2616 [9] J. Hernandez, S. Artillo, M. I. Serrano, J. S. Serrano, Further evidence of antiarrhythmic efficacy of taurine in rat heart. Res. Commun. Chem. Pathol. Pharmukol. 43 (1984) 343-346 [lo] H. Pasantes-Mortales, S. Cruz, Protective effect of taurine and zinc on peroxidation-induced damage in photoreceptor outer segments. J. Neurosci. Res. 11 (1984) 303-311 [ l l ] J. A. Sturman, G. Y. Wen, H. M. Wesniewski, K. C. Hayes, Chemical localization of zinc in the feline tapetum: effect of taurine depletion. Histochem. 72 (1981) 341-350 [12] C. J. Waterfield, J. A. Turton, M. D. C. Scales, J. A. Timbrell, Reduction of liver taurine in rats by /I-alanine treatment increases in carbon tetrachloride toxicity. Toxicol. 77 (1993) 7-20 [13] C. E. Wright, T. T. Lin, J. A. Sturman, G. E. G a d , Taurine scaverages oxidized chlorine in biological systems. In: S.S. Oja, L. Ahtee, P. Konto, M. K. Passonen, (Eds.), Taurine: Biological Actions and Clinical Perspectives. A. R. Liss, New York 1985, 137.