Feedback regulation of bile acid formation in man

Feedback

Regulation Kurt

3H-chenodeoxycholic to

seven

whom patients the

acid was

regular

given

type.

when

ministered

acid for 3 wk.

given

“C-cholic

This

had

read-

treatment

with

cholic

control

times

concentrations

T

and

MAIN

HE

BILE

intestine.

teinemia corded

in most

teinetnia).

This

The

negative cholic-acid

with

discrepancy that appear

as bile

acids

these processes. feedback

of the

in

man

achieved

triggered

by the

on the aver-

concluded by

a

that

feedback

administration

are the two in addition

of

demonstrated

that

is associated whereas

bile

acids,

of cholic

bile

acid in

hyperpre-$-lipopro-

by an abnormally

reversed

hyper-@-lipoproteinemia

was mainly

primary

to the secondary

dehydroxylation

acids, ‘z’

of bile

patients

observation

regulating

by bacterial

studies

was

It was

findings

(type

due to differences

II

high

were

rc-

hyperlipopro-

in the pool

and turn-

acid.’

observed

cholesterol

bile acid,

hyperlipgproteinemia)

and production

over of cholic monly

IV

in all subjects 50%.

The

of

in human

formed

acid.

of chenodeoxycholic

cholic acid.

2-5

acid and cholic

acid.

Recent

(type

pool size

aim

ACIDS

chenodeoxycholic

acid. deoxycholic

the

the

effect

in comparison

chenodeoxycholic

age by about this

acid became

of

acid decreased

cholic

acid, the pool size of this enlarged,

that

acid in duode-

markedly

pool size and turnover

of

was

g nonradioactive

During

with

The

been

Kallner

nal bile increased

of

diet

and Mora

in Man

cholic acid and deoxycholic

orally

acid.

procedure

subjects

Hellstt%m,

five

a standardized

the

0.5-l

Kjell

subjects,

received

were

peated

Einarsson,

normolipemic

also

of Bile Acid Formation

present

the

two

types

to differ

with

stimulates Since

mechanism.

of

hyperlipoproteinaemia

regard further

investigations

the bile acid synthesis it appears

of interest

was

determine

investigation

feeding on the formation

to

mo\t

to the quantitative of

com-

elimination the

may be controlled to study the

of chenodeoxycholic

this

possible

ol

mechanisms process.

b! ;I The

influence

ot

acid in normolipemic

subjects. MATERIALS

AND

METHODS

t’utieut.\

Metabolism.

Vol. 22, No. 12 (December),

1973

1477

1478

EINARSSON,

Table

VA

Sex

Age Vd

M

48

HELLSTRijM,

AND

KALLNER

1. The Patients

Cholesterol*

Triglycerides*

(mg/lOO

(mg/lOO

ml)

230

ml)

150

Previous History and Present Symptoms

Myocardial Chronic

infarction cholecystitis

SH

M

66

280

140

Myocardial

infarction

KJ

M

55

290

152

Myocardial

infarction

GN

M

57

250

180

Angina

so

M

46

210

140

Partial

BA

F

67

265

190

Parathyroidectomy

II

F

63

245

180

Diabetes

pectoris thyroidectomy

Nephrolithiosis

(Adenoma)

Normal

range

*Means

of several

Experimental

140-285

80-

mellitus

180

determinations.

Procedure

The bile acid turnover was determined before and during treatment with cholic acid. The patients were hospitalized for 3-4 days before each study. They were fed 1700~1800 kcal/day of the regular hospital diet in which 35”,,, 20”,*, and 45”,, of the calories were supplied as fat. protein, and carbohydrate. respectively. The daily intake of cholesterol was about 300 mg. Before the second study. the patients received 0.5 g cholic acid during 2 wk and then a daily dose of 1 g of the acid for about 7 days. This treatment was not associated with any gastrointestinal complaints. ‘H-chenodeoxycholic acid (17-42 +Ci) in most of the experiments in addition to “C-cholic acid (4.0-7.5 KCi) as sodium salts were dissolved in water and administered orally in the morning to the subjects who fasted overnight. At 2 4 days interval, four samples of duodenal bile were collected from all subjects. Cholecystokinin was administered on each occasion, and approximately IO ml of concentrated bile was obtained through a thin polyvinyl tube. The specific radioactivity of administered bile acids was determined in each sample.

Materials Randomly tritium-labeled chenodeoxycholic acid (40 pCi/mg) was a gift from Dr H. Danielsson. purified by various chromatographic Stockholm. It was prepared by the method of Wilzbach,‘s procedures. and recrystalized to a constant specific radioactivity. Cholic acid-24-C” (I 3X pCi/mg) was purchased from New England Nuclear Corp.. Boston, Mass. The radiopurity was ascertained by autoradiography of thin-layer chromatograms. Unlabeled cholic acid u’as manufactured by Sigma Chemical Company, St. Louis, MO.. and administered to the patients in IOO-mg capsules.

The methods used for determinations of blood lipids and for puritication of dihydroxycholanic fractions of duodenal bile were performed as described acids were finally analyzed with gas-liquid chromatography after being treated and trifluroacetic anhydride. The half-life, pool size, and turnover of the termined as described by Lindstedt.’

the trihydroxyand recently.* The bile with diazo-methane bile acids were de-

RESULTS Most analyses of cholesterol and triglycerides in serum demonstrated normal values (Table I). Subject BA was considered normolipemic, although the triglyceride level was somewhat elevated in the first specimen obtained. The pattern of distribution of the serum lipoproteins was within normal limits in all subjects as evidenced by electrophoresis on agarose gel.

REGULATION

OF

BILE ACID

Table

FORMATION

2.

Turnover

1479

of Chenodeoxycholic

Chenodeoxychollc

Acid

and

Cholic

Acid Choltc

Acid

Acid

Cholzc Actd Half-Life

istered

(days1

fmgl

(mgiday)

2.6

521

139

1.6

874

VA +

SH +

BA

LSD

TurW3”el (mg

(mgi

i .a

316

122

1 .o

1431

1.9

869

322

1 .o

617

3.1

363

81

19941‘ 428

[ 1626)

2146

0.9

day

383

820

142

1.4

208

104

_

3.2

768

167

2.4

953

275

3.1

559

124

1.5

2770

(1259)

i .a

969

374

1.2

130

75

_

2.4

454

130

2.5

954

265

+

2.8

174

44

1.4

2995

(1513)

2.5

300

85

i .a

498

192

f

2.8

99

25

1.3

262 1

(1402)

II

M‘Xlll

Half-L,fe

4.0

_

SO

Turnover

+

KJ

GN

Pool S,ze

Pool S,re

Admin-

_

2.6

F 0.8

672

k 247

194

+

2.3

I~ 0.8

264

+ 161

82

7 109

1.8 f 0.6

t

I .2

38

i

0.3

779

+ 209

308

2393

r 621

(1358

95

I

245)

Significance

of differences *Values

within

NS parentheses

p c 0.005

do not represent

p c

endogenous

0.025

NS

p

0.001

(p

0.001)

synthesis.

Before the administration of cholic acid the half-life, pool size, and turnover of chenodeoxycholic acid varied between 1.2 4.0 days, 300 969 mg, and 85 373 mg/day, respectively. The corresponding values recorded for cholic acid in the five patients studied were 0.9-~2.5 days, 498 -953 mg, and 192 428 mg/day (Table 2). When the patients were reexamined during treatment with cholic acid, the serum lipids were found to be essentially unchanged. The therapy had no cvnsistent effect on the half-life of chenodeoxycholic acid. The size of the chenodeoxycholic acid pool decreased in all subjects. The mean value (259 * 16X mg) was less than half of that (672 * 247 mg) obtained previously (p Y 0.005). The turnover of chenodeoxycholic acid changed from 194 L 100 to 81 3 40 mg/day (p < 0.025). The administration of I g of cholic acid per day resulted in a considerable enlargement of the cholic acid pool which in the live patients studied ranged between 1431 and 2995 (mean 2393) mg. The total bile acid pool was most probably much higher since the concentration of deoxycholic acid in the bile increased markedly in relation to that of chenodeoxycholic acid (Table 3 and Figs. I and 2). In several patients the bile contained more deoxycholic acid than cholic acid (Table 3). The half-life of the latter acid tended to incrcasr, but this eiIect was not statistically significant. DISCUSSION Much knowledge concerning the mechanisms regulating the formation of hilt acids in vivo are based on studies with experimental animals. In rats with bile duct fistulas Shefer et al.6 confirmed previous observations by Bergstrom and

1480

EINARSSON,

fable

3.

Mean

Ratio

Between

Duodenal

Bile

HELLSTROM,

Cholic

(C),

Chenodeoxycholic

(CD)

and

Before

and

During

With

Cholic

Chok Patient

Treatment

SH

GN BA

II Meall

Deoxycholic

KALLNER

Acid(D)

in

Acid

Acid

Admlnnrtered

VA

AND

C CD

D

_

0.9:

+

2.5i li 3.4

_

2.5;

+

5.11 II 11.2

1: 0.7

i

1 1.2

_

1.51 110.2

+

3.21 II 3.3

_

1.01 II 1.2

+

6.21 li 7.0

_

1.51 li 3.5

+

18.3; li 11.4

_

1.5 10.6i

+

7.1 1k6.51 li 7.3 f

1; 1.4 11.2 3.9

Significance

NS

of differences

D < 0.02

Danielsson7 that intraduodenal infusion of bile acids resulted in synthesis of such compounds in the liver. In other studies Danielsson Shefer et al? presented evidence that the rate-limiting step in the bile acid is the conversion of cholesterol to 7a-hydroxycholesterol. In an intact animal most of the bile acids excreted with the bile to the liver with the portal vein blood. To maintain a steady-state the liver has to produce enough bile salts to replace the fecal loss.

an inhibited et al.” and synthesis of are returned condition A feedback

RATIOS BETWEEN BILE ACIDS D :CO: C 431: 1 :&S4

I

CD

10 Fig. acid.

1.

GLC

20

of a specimen

D; deoxycholic

acid;

CD,

of duodenal

30 bile

chenodeoxycholic

40

50

(subject

VA)

obtained

acid;

C, cholic

acid.

before

MIW treatment

60 with

cholic

REGULATION

1481

OF BILE ACID FORMATION

RA1l.S BETWEEII DIM ACIDS D IeD: c 2.3: 1 : 2,4

Fig. acid.

2.

GLC

of a specimen

D, deoxycholic

control

acid;

of this

i.e.,

bile acid pool. uith

whereby

was

(subject

VA)

obtained

acid;

C, cholic

acid.

should

be triggered

by the rate (number)

These

cannulae

bile

chenodeoxycholic

synthesis

ing the liver,

the bile

of duodenal

CD,

phenomena

in the common collected

for

studied

bile duct and the duodenum.‘0

A given

circulation The

synthesis

at maximum

up to 7 mmole/24

The

evidence of a feedback

resection

hr

diversion

individual

tions The helng

animals.

trczted

The

in an intact

of individual

participating with

cholic

results

were

oral

being.‘3,‘3

and

at

also

of the inflow

after

of ex-

of bile

in a way similar

to

the ratios

be-

of cholic

and

the hepatic

quantitative

I2

by ileal

by a stimulation

suppress

At

in man is

circulation

administration

However.

had

proceeded

to the liver.

by measuring

01

intestine

animals

decrease,

encountered

a reduction

obtained

after

bile

determina-

bile acids were not performed.

in the present acid they

returned

bile salt

that these compounds

human

The

of the

portion

the

compounds

is followed

effects that

intact.

the bile acid formation

in the bile

acid indicate

of rhc formation patients

stimulates

bile acids

chcnodeoxycholic acid synthesis

similar

to

to

cholic

provided

the bile acid synthesis

of cholestyraminc

Since

liver

that in experimental turcn

regulating

of the bile, ” it appears

acids to the human

were began

of the enterohepatic

or by administration

the bile acid formation.” ternal

control

An interruption

returned

of such


was

was kept almost

I mmnle.

when

circulations monkeys

and the rest

with

of bile acids rexn-

in Rhesus

a bile acid pool of about rates

by the amount

treatment

of the enterohepatic

were

analysis

the enterohepatic

during

study

had a pool

were all normolipemic. Ge

and turnover

Before

of chenode-

1482

EINARSSON,

HELLSTROM,

AND KALLNER

oxycholic acid that averaged 672 mg and 194 mg/day, respectively. Vlahcevic et al.” administered r4C-labeled chenodeoxycholic acid to healthy subjects and the mean pool size and turnover were found to be 810 mg and 162 mg/day, respectively. The close agreement between these results indicates that the possible errors caused by instability of the 3H-labeled chenodeoxycholic acid used in the present study were of minor importance. The values recorded for cholic acid also corresponded with previous observations in healthy subjects fed a natural diet.5,‘5s’6 The ratio between cholic acid, chenodeoxycholic acid, and deoxycholic acid in duodenal bile was in general within the range observed in healthy Swedish students.17 The daily dose of cholic acid prescribed in this study (I g) exceeded the pretreatment values of the cholic acid pools sizes by 50&500 mg. As a result of the treatment this pool was enlarged 2-5 times. Part of the cholic acid administered appeared to be transformed into deoxycholic acid as the concentrations of these two acids in duodenal bile increased relative to that of chenodeoxycholic acid. The sizes of the deoxycholic acid pool were estimated indirectly from the corresponding values recorded for the primary bile acids and the mean proportion between the individual bile acids in duodenal bile. Since these ratios showed some day-to-day variations, the values obtained were approximate. They indicated that the sizes of the combined pools of cholic acid and deoxycholic acid averaged about 1500 mg before and 4900 mg during the administration of cholic acid. The values obtained for the pool size and the turnover of chenodeoxycholic acid decreased upon treatment with cholic acid. For both parameters the changes averaged 50”,,. There was no diarrhea or other signs of general malabsorption, and it appeared that the altered kinetics of chenodeoxycholic acid was due to a hepatic effect (feedback inhibition) triggered by the administration ot cholic acid. A question of importance not settled by this investigation is whether cholic acid feeding influenced the formation of cholic acid itself. In four out of five patients the “turnover” of cholic acid calculated during the treatment period exceeded or equaled the combined amount administered during the second and synthesized during the first investigation. This finding, which appears to give a negative answer to the question raised above, could have other explanations. It may reflect that the cholic acid turnover had not reached a steady state during the period when the patients were fed the acid. Furthermore, a slight reduction of absorption of cholic acid in the intestine and thus also of the isotope administered could result in an overestimation of the pool sire and consequently of If so, we may also overestimate the synthesis of chenodethe “turnover.” oxycholic acid and thus underestimate the feedback inhibition. The main findings of this study demonstrated that oral administration of one of the primary bile acids influenced the formation of the other one probably by a negative feedback control. Hyperlipoproteinaemia type I1 is associated with a subnormal and hyperlipoproteinaemia type IV with an elevated bile acid synthesis. Whether these abnormalities are related to abnormalities in the hepatic feedback control will be the subject of further investigations.

REGULATION

1483

OF BILE ACID FORMATION

REFERENCES I,

Kottkc

crctlon.

BA:

Din‘erenca

Primary

in

bile acid ex-

hypercholrsterolaznli~

com-

pared to combined hypercholesterolacmla h~p~rtrlfl\i~eridemia. 7

Einarsvn

Circulation

I(. Hellstriim

h!pcrlipopr~>teinacmia.

with

formatton

three

Eur J Clin

type\ of

Invest

2:225.

3. Wollrnsrber

J. Stiehl A: (;riihst:

und Turnover

dcr primiren

tc~nlimle. Kiln 4, Sjiivall

II

Wochenwhr

bei

50:?3.

1972

bile acids in man: Comparative tyramine and ileal exclusion

Acta

Turnover

S. Hauscr

12. Samuel

P.

EH.

(‘hem

Sand

Ci:

In01.

elect.\ ol’chole\-

on cholesterol

Saypol

CiM.

ChJfi/adeh

me-

M:

Meilman

t_.

.i\brorptlon

01

In

J <‘lln

IY6X

13. Thl$tle

of chullc

acid 111

JL.

Schoenfirld

composition

LJ:

of

Induced

bile

.!I-

01 person\

hactng chc)lelithla\l\. C;astrocnterol~>g!

S, Brhersk)

t-ccdhack regulation

I. Moshach

01‘ bile acld blo\yn-

S. DanIelson

11: On the reg-

ulatlon 01’ bllc acid lormation

In rhc rat lI\,cr.

Acta Phqblol Sand

-13: I

1958

H. Elnarswn

Ell’cct ~1‘ billclrk

I(. Johanson

dralnctge on individual

tlon\ 111the conversion

01‘ cholesterol

chollc ~tcld. t-ur J Biochcm 2:lj. L11, BlochcmIcaI

bitt 01‘ regulation

hio\! nthehl\ In the rat. J Lipid RH.

fwt\ ~1‘ controlled hrpatlc clrcuI:It1on

Mack

to tauro-

I. Moshach of bllc .icid

Rc\ I 1:40-I.

E. Small

interruption

(;: reac-

lY67

Y. Shcl’cr S. Hauacr S. Beker\hy

IJ.

Danongcr

LJ. Thlhtlc

thesls 1n the rat. J L.lpid Rr\ IO:hJb. IYhY

Doullnp

Salen

arculatlon

J Lab Clin Mcd 7X:93. 1971

Moshach

tcratlon\

J

flI:ISX.

lY71

[Llndhtcdt S:

S. D,~nicl\wn

LH.

Inbest 37:2070.

m.tr~. Act;! Ph\\iol Stand JO: I. 1957

7. Berg\triim

Ahrenc

bile acids l’rom the large bowel in man

Hyperhpopro-

lh 1761. I’)62

h. Shelrr

SM.

of the cnterohrpatlc

IV

analy\ih or bile acid\

b\ $a\ chr
IO

Cirundy

terruption

monkev.

1970

lJntcr\chiedllchc und T>p

J: Qualitative

de\ Pools

Ciallen\Llurrn

H!perlIpopr~)t~in;imlrn: Belunde bet Typ

EH:

snd pool size in the Rhesus

tabolism.

I’)73

i

synthesis

Clin Invest 49232. II.

40: 13. I969

K: The

01 bile acids in patlents

and

sion and by ileal resectlon on bile salt \ecretltjn.

DM:

of bile salt\ b> hlllar!,

Schocnllcld

of cholesterol

g:lll-

2x6: I. lY72 Ii. Shell

Vlahcev~c LR, L: Kinetlo

Miller

JR,

Ih.

Hcll\trtim

t’ormatlon

of

standardwed Sjdvall

chollc diet

acid

with

IS. pwurr

lr. hilt

lY7l

S: Studle\ on the in

huttcr

J: DIetar)

bile acid conjugation BIOI Mrd

61:X5.

I(. Lindstedt

dietarc 1.11.Am J C‘lin Nutr I7

Farrar

nnd pool \ize or prlmar?

acids In man. C;a\troenterolog

El-

diwr-

KC;. Hol’man At.. Disholution

stone:, b! chenodeo\ycholic acid. N E ngl J Mcd

1970

01 the entcro-

JI.:

\uh.jcct\ g~\cn or

IY:16,

corn

011 .I\

lY66

glhcine and taurlnc in man.

Proc

Sw

on t-\p

lOO:h76. lY5Y

Ull/bach

hl:.

Tritlum-lahelllng

t,f oreangc compound5

J Am (‘hem Sot 7Y~lOl?.

I’)17

h!

to tritium

c’\~:LI.