HEPATIC TAURINE CONCENTRATION AND DIETARY TAURINE AS REGULATORS OF BILE ACID CONJUGATION WITH TAURINE

Transcription

1 16-585/78/751-71$2./ GASTROENTEROLOGY 75:71-75, 1978 Copyrght 1978 by the Amercan Gastroenterologcal Assocaton Vol. 75, No.1 Prnted n U.S.A. HEPATIC TAURINE CONCENTRATION AND DIETARY TAURINE AS REGULATORS OF BILE ACID CONJUGATION WITH TAURINE WILLIAM G. M. HARDISON Secton of Gastroenterology, Veterans Admnstraton Hosptal, San Dego, and Department of Medcne, Unversty of Calforna School of Medcne, San Dego, Calforna Taurne concentraton n lver bopses taken from 2 patents undergong cholecystectomy or laparotomy for obstructve jaundce correlated th percentage of taurneconjugated ble acds n hepatc ble. In blary obstructon, taurne concentratons n muscle dd not parallel hgh hepatc taurne concentratons, suggestng selectve hepatc taurne accumulaton n blary obstructon. In fastng subjects th an ntact ble acd enterohepatc crculaton, per cent taurne-conjugated ble acds n ble as the same as per cent taurne conjugaton of ble acds by the lver. Ingeston of small amounts of taurne (25 mg) can ncrease the per cent taurne conjugaton by the lver. Of 1 subjects, 7 ncreased per cent taurne conjugaton of ble acds by the lver by 2.5 to 1% at 21/2 hr after ntraduodenal taurne admnstraton. We conclude that hepatc taurne concentraton s a major determnant of per cent taurne conjugaton of ble acds by the lver n man. In the fastng subject th an ntact enterohepatc crculaton, per cent taurne-conjugated ble acd n the ble acd pool s very close to the per cent taurne conjugaton of ble acds by the lver. Hepatc ble acd conjugaton pattern may dffer from that of the ble acd pool as a result of taurne ngested 'Nth meals, but the devaton s small, and acute alteraton of the per cent taurne conjugaton n the ble acd pool does not occur. Ble acds n man are conjugated th ether taurne or glycne. The percentage of ble acds conjugated th taurne s lo n states charactered by excessve ble acd conjugaton requrements,1 and hgh n blary obstructon hen conjugaton requrements are lo. 2, 3 Taurne fed n large amounts can ncrease the percentage of ble acds conjugated th taurne,4 suggestng that hepatc taurne supply s one of the regulators of hepatc ble acd conjugaton pattern n man. In the rat, a close relaton beteen hepatc taurne concentraton and the percentage of ble acds conjugated th taurne by the lver has been demonstrated. 5 Garbutt and Tyor have stated that the major determnant of conjugaton pattern n the ble acd pool s the hepatc ble acd conjugaton pattern. 1 If so, the degree to hch the ble acd pool s conjugated th taurne should be a reflecton of hepatc taurne concentraton. Extrahepatc factors, hoever, may nfluence ble acd pool conjugaton pattern. Preferental absorpton of relatvely nonpolar glycne-conjugated ble acds may enrch the ble acd pool th glycne conjugates n certan states. 6, 7 Stll other unknon factors may be operatve. Hepner et al. have stated that n normal man the proporton of ble Receved January 3, Accepted February 14, Address requests for reprnts to: Wllam G. M. Hardson, M.D., Secton of Gastroenterology, Veterans Admnstraton Hosptal, 335 La Jolla Vllage Drve, San Dego, Calforna Ths study as supported by the Research Servce of the Veterans Admnstraton and by Grant AM from the Natonal Insttute of Arthrts, Metabolsm and Dgestve Dseases, Natonal Insttutes of Health. 71 acd conjugated th glycne by the lver s substantally hgher than that n the ble acd pool. 8 The objectves of ths ork ere to defne drectly the relaton beteen hepatc taurne concentraton and ble acd conjugaton pattern n man and to defne the relaton beteen the percentage of ble acd conjugated th taurne n the ble acd pool. The latter objectve requred nvestgaton of varablty of hepatc ble acd conjugaton pattern n response to ngeston of amounts of taurne hch mght be found n a meal. Methods All studes ere approved by the Commttee on Investgatons Involvng Human Sujects, Unversty of Calforna, San Dego. T-tube studes. To subjects (H. F. and L. J.) had occludable T-tubes placed durng surgery for removal of common duct stones. Begnnng 7 days later, 4 g of cholestyramne, three tmes daly ere admnstered for 2 days. Nne days after surgery, patents salloed a polyvnyl tube (3 mm outer dameter) eghted th a mercury bag. The duodenal end of the T-tube as occluded. When the polyvnyl tube lay n the duodenum and at least 4 hr after the occluson of the duodenal lmb of the T-tube, ble as collected hourly. Taurne, 1. g (H. F.) or.25 g (L. J.) as admnstered va the duodenal tube after the thrd ble collecton. Surgcal lver and muscle bopsy studes. Tenty patents havng surgery for cholecystts, cholelthass, or blary obstructon ere studed. At surgery a rectus muscle bopsy, about 1. g, and a edge lver bopsy, about.5 to 1. g, ere obtaned together th 2 to 5 ml of hepatc ble. The tssue as eghed and homogened. The homogenate as deprotened th trchloroacetc acd and centrfuged. The super-

2 72 HARDISON Vol. 75, No.1 natant as alkalned and the fluorodntrobenene dervatve as formed. After extracton of chloroform-soluble amno acd dervatves, the remanng aqueous soluton as evaporated to dryness and taurne dervatve as separated by electrophoress on cellulose polyacetate. The detals of sample preparaton and assay have been prevously descrbed. 5 Total ble acd concentraton as measured n ble and ntestnal flud by the sterod dehydrogenase method. 9 Flud, suffcent to contan 3 to 6 mg of total ble acd, as extracted by the Folch procedure. The aqueous phase as evaporated to dryness, dssolved n 2 p.l of 7% ethanol, and appled to the orgn of a 2 by 2- cm thn layer chromatography plate coated th a 1-p. layer of Slca Gel G. Plates ere developed n sopentyl acetate, proponc acd, n-propanol, ater (3:3:3:15 V/V),1 dred, and staned th odne vapor. Segments of the plate contanng glycne and taurne conjugates ere separately scraped and eluted th 2 ml of methanol. Eluates ere assayed for total ble acd and percentage of ble acd conjugated th taurne as calculated. Studes of unoperated subjects. Subjects salloed a double lumen polyvnyl tube (3. mm outer dameter) eghted th a mercury bag the nght before the study. The dstal port as placed at the lgament of Tret th the other port 1 cm proxmal. Infuson of saffoer ol formula as begun nto the proxmal port to nduce gallbladder contracton. 11 All subjects ere nfused for 2 hr before the frst sample of ble as thdran; thereafter to protocols ere folloed (fg. 1). The frst protocol as drected at determnng (1) the relaton beteen per cent taurne-conjugated ble acd n the ble acd pool and the per cent taurne conjugaton of ble acd by the lver; and (2) the effect of 25 mg of taurne on the per cent taurne conjugaton of ble acd by the lver. A sample of ble as dran at hr and 4 p.c of [3Hlcholc acd ere njected ntravenously. At hour 1, a second sample as obtaned and 25 mg of taurne ere admnstered ntraduodenally. At hour 3 1 /2, 1 p.c of [14Clcholc acd as njected ntravenously. Samples of ble ere then taken at 4, 6 1 /2, 8, and 8 1 /2 hr. Sx patents ere studed th ths protocol. The second protocol as drected at determnng hether the effect of taurne on hepatc ble acd conjugaton pattern lasted as long as 7 hr after taurne admnstraton. A ble sample as taken at hr but no labeled cholc acd as gven. Taurne as admnstered at 1 hr, and at 3 1 /2 hr 4 p.c of [3Hlcholc acd ere gven ntravenously. Ble samples ere taken at 4 and 6 1 /2 hr. At 8 hr 1 p.c of [HClcholc acd as gven ntravenously and ble samples ere taken at 8 1 /2, 9, and 9 1 /2 hr. Four patents ere studed by ths protocol. Of the 1 subjects studed, fve ere normal and fve had nactve crrhoss th normal lver tests and no evdence for portal hypertenson. Samples ere processed as already descrbed for ble acds. Alquots of eluates from the thn layer chromatography plate ere counted th Bray's soluton n a Nuclear-Chcago Mark II lqud scntllaton counter (Nuclear-Chcago Corporaton, Des Planes, Ill.) A program for smultaneous countng of 3H and HC as used. Quench correcton as made by the external standard channels rato method. Results Fgure 2 shos the relaton beteen percentage of blary ble acd conjugated th taurne and the concentraton of taurne n lver and muscle bopses obtaned at surgery. Hgh per cent taurne conjugaton of blary ble acds correlates th hgh concentraton of taurne n the lver bopsy. The scatter of ponts s too great to determne hether the relaton s lnear or curvlnear, as n the case of the rat. 5 A negatve correlaton exsts beteen muscle taurne concentraton and both hepatc taurne concentraton and percentage of ble acds conjugated th taurne. Ths ndcates that the large muscle taurne pool s not n equlbrum th the smaller hepatc taurne pool. The muscle does not share the hgh taurne concentraton hch, n blary obstructon, seemed confned to the lver. Why muscle taurne s lo hen hepatc taurne s hgh s unknon. Of the 8 subjects th blary obstructon, 5 had malgnant dsease and 6 gave a hstory of recent anorexa and eght loss. The nfluence of eght loss on muscle taurne concentraton and on dstrbuton of taurne n the body, hoever, s unknon. Ifhepatc taurne pool nfluences ble acd conjugaton pattern and f ths pool s lable, ble acd conjugaton pattern should be rapdly altered by feedng taurne to subjects depleted of taurne. We have consdered subjects th T-tube dranage to represent such a group. Cholestyramne as gven for 2 days before study to mnme recrculaton of ble acds and maxme ble acd synthess. The duodenal lmb of the T-tube as occluded for 4 :pr before study to allo excreton of most of the ble acd left n the ntestne at tme of occluson. Fgure 3 shos the data from 2 subjects so studed; 1. g of taurne gven ntraduodenally n H. F. produced a PROTOCOL I ( n=6l PROTOCOL 2 (n=4l 4).lC 3-H 25.omg Chole Taurne mg. Taurne. 2 CENOTES BILE SAMPLE COLLECTION FORMULA INFUSION I/-C 1 -C Chole + 4).lC 3-H Chole ).lc 14-C Coole FIG. 1. To protocols used to study unoperated subjects Y Y 6.3 -B.2. r '.738 r -.62 (f) ILl p<.1 p<.oi 8. 8 <t C>, 6 6 U ILl 4... o 4 Z a: :! 2. 2 "., Do ---'.., LIVER TAURINE (_AI';'" ) MUSCLE TAURINE (.J,L:") FIG. 2. Relaton beteen per cent conjugaton of ble acd n hepatc ble taken at operaton and lver and muscle taurne concentratons., subjects th blary obstructon; e, subjects thout blary obstructon.

3 July 1978 HEPATIC AND DIETARY TAURINE IN BILE ACID CONJUGATION 73 change n per cent taurne conjugaton evdent thn 2 hr and maxmal thn 5 hr. At 24 hr ths effect had largely dsappeared. L. J. receved 25 mg of taurne. The effect as qualtatvely smlar to that seen n H. F. but quanttatvely less. The effect as nearly maxmal n 3 hr. These subjects ere unque n that ther lvers ere probably taurne depleted. To gauge the effect of small doses of taurne on hepatc ble acd conjugaton pattern n subjects th ntact enterohepatc crculaton, 25 mg of taurne ere admnstered ntraduodenally to 1 subjects. The dose of 25 mg as chosen because t produced a measureable change n conjugaton pattern of L. J., t represents a dose oftaurne obtanable n a large meat or eafood meal, and t s close to the dose (28 mg) shon to produce a measurable rse n human plasma taurne concentraton. 14 In the frst 6 subjects, [3H]cholc acd as gven ntravenously 1 hr before and [14C1cholc acd as gven ntravenously 21/2 hr after ntraduodenal taurne (protocol 1). In the last 4 subjects [3H1cholc acd as gven 21/2 hr and [1 4 C]cholc acd 7 hr after taurne (protocol 2). Fgure 4 shos results from a typcal patent from protocol 1. Per cent taurne conjugaton n the unlabeled ble acd pool s the same as that n the [3H]cholc acd gven before 5 H.F L.J. 4 <!) ::J -, 3 u 2 ::J <t 1 '"'- I- - Tourne 1 Gm. Tourne Gm nlroduodenolly FIG. 3. Per cent taurne conjugaton of ble acds n hepatc ble of 2 patents th occludable T-tubes after ntraduodenal taurne admnstraton. T-tubes ere occluded 4 hr before the start of study to elmnate recrculaton of ble acds. (f) (.!) -, :: ;:! 3t J.M Taurne 25mQ FIG. 4. Data from a typcal subject studed by protocol 1;, unlabeled ble acd; e, [3Hlcholc acd; D, [14Clcholc acd. Conjugaton pattern of [3Hlcholc acd, admnstered before taurne, remans dentcal to that of the ble acd pool. Per cent taurne conjugaton of [,4Clcholc acd, admnstered 2'/2 hr after taurne, s hgher than that of [3H]cholc acd and unlabeled ble acd. taurne and remans constant throughout the study. The hgher per cent taurne conjugaton of the [J4C]cholc acd gven 21/2 hr after taurne admnstraton reflects the acute effect of taurne on hepatc ble acd conjugaton pattern. Fgure 5 summares data from all subjects. In all of the 6 subjects n the frst group, the per cent taurne conjugaton of labeled cholc acd njected before ntraduodenal taurne admnstraton as the same as the per cent taurne conjugaton of the ble acd pool. At 21/2 hr after ntraduodenal taurne admnstraton, hoever, the per cent taurne conjugaton had ncreased n 4 of 6 subjects. The subjects ho shoed no ncrease n per cent taurne ble acd conjugaton ere crrhotcs th an already exceptonally hgh percentage of ble acd conjugated th taurne. These fndngs ndcate that n subjects th ntact enterohepatc crculaton, the hepatc ble acd conjugaton pattern durng fastng s the same as that of the ble acd pool. Taurne, 25 mg gven ntraduodenally, hoever, can alter the pattern thn 21/2 hr of admnstraton. Next, the duraton of ths effect as studed n 4 subjects. Agan, n 3 of the 4 subjects, taurne admnstraton ncreased per cent ble acd conjugaton th taurne thn 21/2 hr. Agan, the subject ho shoed no change as a crrhotc th an already hgh percentage of ble acd conjugaton th taurne. The effect of taurne on hepatc ble acd conjugaton pattern perssted for at least 7 hr after taurne admnstraton. In only 1 of the 4 subjects dd per cent taurne conjugaton sgnfcantly declne beteen 21/2 and 7 hr after taurne admnstraton. In 2 subjects the small declne at 7 hr as not sgnfcant. In none of the 1 subjects dd conjugaton pattern of the ble acd pool change th taurne admnstraton. Dscusson When demand for ble acd conjugaton s hgh, per cent taurne conjugaton n the ble acd pool s l- e:[ <!) ::>.., 8 UJ I: 7 o UllLAllf:LUD IILf jcld m '-H CHOUC jcid 14-<: CIIOlIC jcid PATIENT NUMBER FIG. 5. Results n all unoperated subjects. Patents 1 to 6, protocol 1; patents 7 to 1, protocol 2. In subjects 1 to 6, hepatc ble acd conjugaton pattern s the same as that n the fastng ble acd pool. In all subjects n hch taurne conjugates consttute < 3% of the total, 25 mg of taurne admnstered ntraduodenally elevates the percentage of ble acds conjugated th taurne.

4 74 HARDISON Vol. 75. No.1 lo Taurne feedng ncreases ths percentage. 4 These observatons suggest that avalablty of taurne s a major determnant of ble acd conjugaton pattern n man. The present data from surgcal lver bopsy specmens support ths premse provded one may assume that fastng hepatc ble acd conjugaton pattern s nearly dentcal to that of the ble acd pool n normal man. Our data establsh ths fact. All 1 subjects studed by ntubaton technques exhbted a hepatc ble acd conjugaton pattern nearly dentcal to the conjugaton pattern of the ble acd pool. In spte of smlarty durng fastng, hepatc ble acd conjugaton pattern probably devates from that of the ble acd pool durng the day. In our subjects studed by ntubaton, 25 mg of taurne gven ntraduodenally elevated the hepatc percent conjugaton th taurne by 5 to 1% thn 2 hr. Ths amount of taurne, to be found n about 1 lb of lean meat or a lesser amount of shellfsh, s greater than that usually ngested n a meal. Lesser devatons ould be expected n a subject eatng normally. The magntude of devaton ould depend not only upon the amount of taurne n the meal but also upon the concentraton of taurne n the lver. Thus, our subjects th an already hgh per cent taurne conjugaton (and presumably a hgh hepatc taurne concentraton) shoed no change th ntraduodenal taurne, hereas those th a lo per cent taurne conjugaton shoed an ncrease n per cent taurne conjugaton. Even the subjects ho manfested a change, hoever, dd not change per cent taurne conjugaton n the ble acd pool; ths s not surprsng. About 1 17 to 4%8 of taurocholate and about 4% of glycocholate 6 s deconjugated per day. Beteen 2.5 and 1% of the pool ould be deconjugated n a 6-hr perod. If per cent hepatc ble acd conjugaton th taurne ncreased 1% over 6 hr, the ncrease n per cent taurne conjugaton n the total pool ould be.1 x.1 or 1 % maxmum. Ths change ould not be detected by our methods. The data concerned th duraton of taurne effect are nconclusve. Of the 4 subjects studed 7 hr after taurne admnstraton, 1 (subject 8) dd not change hepatc ble acd conjugaton pattern th taurne. One (subject 7) shoed a sgnfcant fall n hepatc per cent taurne conjugaton but 2 (subjects 9 and 1) shoed no sgnfcant fall beteen 21/2 and 7 hr after taurne admnstraton. We conclude that dscrepances beteen hepatc ble acd conjugaton pattern and conjugaton pattern n the ble acd pool may occur n relaton to meals. The dscrepances are small and cause no detectable short term varaton n ble acd pool conjugaton pattern. Although a relaton beteen hepatc taurne concentraton and ble acd conjugaton pattern s understandable, the relaton beteen hepatc taurne concentraton and other taurne pools n the body s not clear. Wth total nterrupton of the enterohepatc crculaton and allong for a 7-fold ncrease n ble acd synthess, a subject ould excrete only about 6 mg per day of taurne as taurne-conjugated ble acd even f he mantaned a normal per cent taurne conjugaton. If the lver could dra on perpheral taurne pools, less than 5% of the muscle pool ould be depleted n 1 days, assumng no detary taurne ntake. Yet n our T-tube subjects the per cent taurne conjugaton as about 1% 9 days after surgery. Furthermore, n subjects takng cholestyramne, maxmum change n conjugaton pattern occurs thn 6 days.lo Ths suggests that taurne n perpheral pools s not readly avalable to the lver and probably explans hy lver and muscle taurne concentratons do not parallel one another. Conversely, f hepatc taurne ere readly transferable to plasma and sent to extrahepatc pools, t should not accumulate n the lver durng extrahepatc obstructon. Taurne s cleared rapdly by the kdney18 and urnary taurne excreton reflects to some extent detary taurne ntake Yet urnary taurne excreton n 2 and plasma taurne concentratons n 4 patents th obstructve jaundce ere normal (unpublshed observatons). Sherr et al. found no relaton beteen blary ble acd glycne-taurne ratos and plasma taurne. 21 These data plus our on on hepatc and muscle taurne concentratons suggest the changes n hepatc taurne pools are, over short tme perods, ndependent of changes n plasma and muscle pools. Whether ths s a result of the lver's strategc poston vs-t-vs detary taurne or because of specal transport characterstcs of the hepatocyte for taurne or both s unknon. Increased hepatc synthess s possble. The human lver, hoever, does not contan the enymatc mechansm for taurne synthess found n other anmals such as the rat. 13 In ths regard human lver s smlar to that of the cat, hch cannot synthese sgnfcant amounts of taurne. 22 It s concevable that blary obstructon could n some manner nduce taurne synthess, but e consder ths unlkely. Untl the characterstcs of the hepatc handlng of taurne can be defned, these curous features ll reman unexplaned. REFERENCES 1. Garbutt JT, Lack L, Tyor MP: Physologcal bass of alteratons n the relatve conjugaton of ble acds th glycne and taurne. Am J Cln Nutr 24: , Norman A, Strandvk B: Formaton and metabolsm of ble acds n extrahepatc blary atresa. J Lab Cln Med 78: , Rednger RN, Strasburg MH, Small DM: Prmate blary physology. IX. Effects of acute blary obstructon on blary lpd metabolsm n the monkey. Am J PhysoI52: , Sjovall J: Detary glycne and taurne on ble acd conjugaton n man. Proc Soc Exp Bo Med 1: , Hardson WG, Profftt JH: Influence of hepatc taurne concentraton on ble acd conjugaton th taurne. Am J Physol 232:E75, Dolng RH, Mack E, Small DM: Effects of controlled nterrupton of the enterohepatc crculaton of ble salts by blary dverson and by leal resecton on ble salt excreton, synthess and pool se n the rhesus monkey. J Cln Invest 49: , Poley JR, Hofmann AF: Role of fat maldgeston n pathogeness of steatorrhea n leal resecton. 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5 July 1978 HEPATIC AND DIETARY TAURINE IN BILE ACID CONJUGATION 75 Bochem Anal 8: , Garbutt JT, Kenney TJ: Effect of cholestyramne on ble acd metabolsm n man. J Cln Invest 51: , Grundy SM, Metger AL: A physologcal method for estmaton of hepatc secreton of blary lpds n man. Gastroenterology 62: , Roe DA, Weston MO: Potental sgnfcance of free taurne n the det. Nature 24: , Jacobsen JG, Smth LH Jr: Bochemstry and physology of taurne and taurne dervatves. Physol Rev 48: , Waner A, Kng JS Jr, Goodman HO, et a1: S35 taurne metabolsm n normal and mongolod ndvduals. Proc Soc Exp BoI Med 121: , Garbutt JT, Heaton KW, Lack L, et al: Increased rato of glycne-to-taurne conjugated ble salts n patents th leal dsorders. Gastroenterology 56:711-72, Dannger RG, Hofmann AF, Thstle JL, et al: Effect of oral chenodeoxycholc acd on ble acd knetcs and blary lpd composton n omen th cholelthass. J Cln Invest 52: , Stahl E, Arnesjo B: Taurocholate metabolsm n man. Scand J Gastroenterol 7: , Cusorth DC, Dent CE: Renal clearances of amno acds n normal adults and n patents th amno acd uras. Bochem J 74:55-561, Evered DF, Harvey MS, Luck LJ, et al: The relatonshp beteen urnary taurne excreton and the ntake of proten rch foods. Lfe Sc 8:61-65, Evered DF: The excreton of amno acds by the human. Bochem J 62: , Sherr HP, Nar PP, Banell JG, et al: Correlaton of plasma glycne and taurne th changes n ble acd G/T rato. Cln Res 21:524, Hardson WG, Wood CA, Profftt JH: Quantfcaton of taurne synthess n the ntact rat 'and cat lver. Proc Soc Exp BoI Med 155:55-58, 1977