Bile Salt Metabolism Following Jejunoileal Bypass for Morbid Obesity THEODORE A. STEIN, M.S., LESLIE WISE, M.D.

Bile salt pool size and kinetics were evaluated in 8 morbidly obese women before and following jejunoileal bypass. The results indicate that following jejunoileal bypass pool sizes of both chenodeoxycholate and cholate decrease, turnover rates increase, and the rates of bile salt synthesis increase. Influenced by pool size, hepatic synthesis and the degree of malabsorption, the daily bile salt loss may actually decrease in time. Chenodeoxycholate is more efficiently absorbed than cholate in both the preoperative and postoperative states. In spite of greater cholate synthetic capabilities, in this malabsorptive state the chenodeoxycholate pool decreases less than the cholate pool. Although all patients received an identical surgical procedure, the effect on bile salt kinetics and pool sizes varied in these patients. Since some of the postoperative complications may be related to the degree of interference with bile salt metabolism, the individual patient's capacity for increased hepatic synthesis of bile salts and increased reabsorption of bile salts from the remaining small bowel may vary the clinical postoperative course.

TrHE ENTEROHEPATIC CIRCULATION (EHC) of bile salts normally consists of a total pool size of 3 to 5 gm which cycles 6 to 10 times per day.2'6 Less than 5% of the pool size is lost daily from the EHC, because of efficient intestinal reabsorption of bile salts. Bile salt reabsorption occurs by active transport from the terminal ileum and by passive absorption from the stomach (due to regurgitation) and from the entire length of the small bowel and colon. Active absorption accounts for approximately 85% of total bile salt reabsorption. Following jejunoileal bypass, only a small segment of distal ileum remains in continuity with the remaining jejunum. This drastic loss of ileum interferes with normal bile salt reabsorption. Consequently, an interrupted EHC Submitted for publication April 7, 1976. All correspondence: Leslie Wise, M.D., Department of Surgery, Long Island Jewish-Hillside Medical Center, New Hyde Park, New York 11040.

67

From the Department of Surgery, Washington University School of Medicine, St. Louis, Missouri

results in lipid malabsorption, steatorrhea, diarrhea, electrolyte loss and weight loss. The purpose of this study was to assess the effect of jejunoileal bypass on bile salt metabolism. Materials and Methods

Bile salt metabolism was studied in 8 patients before and following a jejunoileal bypass procedure for morbid obesity. These patients were at least twice their ideal weight, which was of at least three years duration. All these patients had failed on a conservative weight reduction therapy under the care of a physician and had no correctable endocrinopathy which might have been responsible for their obesity. As seen from Table 1, during a mean postoperative period of 9.2 months, the mean weight loss was 37.4 kg (82.3 lbs). Surgical Procedure. Our technique for the jejunoileal bypass consisted of an end-to-end anastomosis of 35 cm proximal jejunum to 10 cm terminal ileum, and an end-toside anastomosis of the excluded segment of small bowel to the cecum (Fig. 1). Bile Salt Kinetics Test. A gastroduodenal tube (Darvol Inc., Providence, R.I.) was positioned into the second part of the duodenum after a 12-hour fast. The position of the tube was checked by fluoroscopy. Bile flow was stimulated by the intravenous injection of 1.0 Ivy Dog units

cholecystokinin (Karolinska Institutet, Stockholm, Sweden) per kg of body weight during a 5-minute period. Duodenal aspirates were then sampled for a 10-minute

STEIN AND WISE

TABLE 1. Physical Characteristics of Patients Postop Preop

Patient

Age (yrs)

Weight (kg)

Time after Surgery (months)

Weight (kg)

126 112

11

2

26 34

8

76 80

3

26

148

8

100

4

33

145

9

97

5 6

47

11

27

102 119

10

76 85

7

44

112

9 14

91 80

8

30

131

3

105 80

1

Mean

33.4

124.4

9 9.2

S.D.

8.1

16.3

3.0

87.0

10.5

period, and the samples which were the darkest bile stained were used as best representing bile secretion. Care was taken to remove only a total of 5 ml of bile so as not to interrupt the EHC. Immediately after collection, the samples were heated to 650 and kept at that temperature for 15 minutes, after which they were cooled and frozen at -20° until assayed. Preoperative bile samples were obtained 15 minutes before and 3, 24, 48 and 72 hours after the injection of a 14C_ bile salt mixture; in the postoperative period, additional samples were also collected at 5 and 7 hours after 14C

Ann. Surg.

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January 1977

injection. The 14C-bile salt mixture consisted of 10 ,uCi of sodium cholate-24-14C and 10 ,uCi of sodium chenodeoxycholate-24-14C, prepared sterile and non-pyrogenic (New England Nuclear Co., Boston, Mass.), and it was administered by slow intravenous injection. Early studies indicated that in most postoperative patients, the true exponential loss of bile salts could only be determined within the initial seven hours. A typical exponential decay of '4C-glycocholate and 14C-glycochenodeoxycholate is presented in Fig. 2. The preoperative loss is linear for at least 3 days. Postoperatively, however, a linear loss was only evident within the 3 to 7-hour period, and a second rate of loss occurred following this period. All samples were heated and agitated at 370 for 5 minutes prior to application to thin layer chromatography (TLC) plates (Silica gel G, Quantum Industries, Fairfield, N.J.). After centrifugation at 5000 x g, 25 ,ul samples were applied to each of 4 prescored channels on activated plates. Standards for glycocholate, glycochenodeoxycholate, taurocholate, taurochenodeoxycholate, cholate and chenodeoxycholate were also applied to each plate. The plates were heated to 600 and were kept at that temperature for 15 minutes. After the plates cooled to room temperature, they were placed in a developing tank which had been allowed to equilibrate for one hour with a solvent system of iso-octane:isopropyl ether:glacial acetic acid:isopropyl alcohol: :2: 1: 1: 1.4 When the solvent front was 1 to 2 cm from the top edge, the plates were removed, placed horizontally, and the solvents were allowed to evaporate. The dried plates were sprayed with a 10% phosphomolybdic acid-alcohol solution and heated at 1000 for 20 minutes to visualize the bile salt standard.

FIG. 1. The jejunoileal bypass procedure as performed by the authors.

Vol. 185 * No.

69

BILE SALT METABOLISM

20.0 The appropriate areas and adjacent strips (controls) were removed and dissolved into 2.5 ml 0. IM sodium pyrophosphate, pH 10.8. After centrifugation at 3000 x g, two aliquots were removed for bile salt quantification by 10.0 the 3a-hydroxysteroid dehydrogenase method of Turn8.0 berg and Anthony-Mote.14 In order to differentiate between glycodeoxycholate and glycochenodeoxycholate, 60 the 7a-hydroxysteroid dehydrogenase method was used to measure glycochenodeoxycholate.5 4.0 Samples were also removed for 14C-bile salt estimations by liquid scintillation. An 0.2 ml aliquot was added to 10 ml Insta-gel (Packard Instrument Co., Downers Grove, Ill.) and the samples were counted until the total counts 2.0 were greater than 5000 cpm. Specific activities (dpm/ ,tmole) were determined by external standardization. rl4~ The logarithmic loss was determined by the slope of the decay line (gm/day). Pool size (gm) was determined by 14J. 1.0 extrapolation to time zero. Half life (t0) was defined as the 0.8 time (days) when 50% of the bile salt remained. Tturnover 0.6 rate (day-1) or k was defined as the exponential measure of the reciprocal of t2. The rate of loss was defined as the product of k and pool size; when the bile salt pool size 0.4 exists in a steady state, the rate of loss is equal to the rate of synthesis.6 Fecal 14C-bile salt loss was also determined. Forty-eight 0.2 hour stool collections were obtained during the study, oxyflask the by estimation for sampled and homogenized gen combustion method (Packard Model 305 Oxidizer, Packard Instruments Co., Downers Grove, Ill.) and liquid 0.1 72 48 scintillation. 24 All comparisons were evaluated statistically by the HOURS Wilcoxon test for paired data.15 The association or corFIG. 2. Exponential decay curves of 14C-glycocholate and 14C-glycorelation of data was performed by a Pearson product- chenodeoxycholate 0 preop '4C-glycoin a typical patient. * moment correlation.11 cholate; 0 --- 0 postop 14C-glycocholate; * --* preop L-

'4C-glycochenodeoxycholate; O--- O postop 14C-glycochenodeoxy-

Results Postoperatively the mean glycocholic acid (GC) pool size decreased by 60% (P < 0.01) from 1.38 to 0.54 gm (Table 2). The mean turnover rate increased approximately seven-fold (P < 0.01) and the mean rate of loss almost tripled (P < 0.01) postoperatively. Postoperatively, the mean glycochenodeoxycholic acid (GCDC) pool size decreased by 47% (P < 0.01) from 0.90 to 0.42 gm (Table 3). The mean turnover rate increased five-fold (P < 0.01) and the mean rate of loss doubled (P < 0.05). In Patient 7, there was a decreased rate of loss with a concomitant, severe depression of GCDC pool size. Two of the patients were evaluated twice postoperatively. In Patient 7, the rate of GC and GCDC loss decreased with time (9 to 14 months), as did the respective pool sizes; simultaneously, there was a further increase in the turnover rates. An increased turnover rate also oc-

cholate.

curred in Patient 8, who was evaluated at 3 and 9 months. Although the GC rate of loss was unchanged, the GC pool size decreased. The GCDC pool size, however, increased slightly with an increased rate of loss. The degree of association or covariance of the paired turnovers (k) of GC and GCDC was measured by the Pearson product-moment correlation coefficient (r). A statistically significant (P < 0.01) correlation existed (r = 0.8460) in the preoperative state with kGc (abscissa) and kGcDC (ordinate); the slope of the major axis (b1) was 0.7410 and the minor axis (b2) was -1.3495. The postoperative correlation (r = 0.7023) was also statistically significant (P < 0.02); the slope of b1 was 0.4290 and b2 was -2.3310. Statistical analysis of the matched pairs of the change in k demonstrated a significant difference (P < 0.05). Preoperative 48-hour stool collections after 14C-ad-

70

Ann. Surg.

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TABLE 2. Glycocholic Acid Kinetics Postop

Preop

Time after Bypass (mon)

Patient

Pool Size (gm)

Turnover Rate (k) per day

Loss/day (gm)

Pool Size (gm)

Turnover Rate (k) per day

Loss/day (gm)

1

1.5

1.19

1.8

2

1.0

2.14

2.1

1.0 1.0

3.57 4.28

3.6 5.2

11 8

3

1.23

1.2

8

2.70

1.7

16.73

6.7

5.95

5.9

9 11 10

0.97

0.2 0.05 0.3 0.2 0.56

5.35 10.70 3.57 4.65 5.87

0.9 0.5 1.0 1.0 2.77

9 14 3 9 9.2

0.60

0.64

0.38

4.57

2.36

2.8

0.21

0.23

0.12

1.44

0.75

0.9

1.3

0.55

0.7

4

2.0

0.33

0.7

5 6

1.2 1.6

0.89

0.5

0.89

1.1

7

1.2

0.45

0.5

8

1.2

0.36

0.4

Mean

1.38

0.85

S.D. S.E.M.

0.32 0.11

0.9 0.6 0.4 1.0

ministration demonstrated a mean 18% loss. The post- rate of bile salt loss also increased significantly for both GC (185%) and GCDC (105%). Since the rate of loss was operative mean loss was 54%. determined from the initial exponential decay curve (Fig.

Discussion Following jejunoileal bypass for morbid obesity, there was a significant reduction in the mean cholate pool size (60o) and in the mean chenodeoxycholate pool size (47%); the turnover rates significantly increased in all patients both for GC (577%) and GCDC (452%); and the mean

2), which was linear from 3 to 7 hours, the rate of loss is also a good estimate of hepatic synthesis.6 The exponential decay which occurred later was not linear in several patients. This decay reflected a non-homogeneous distribution of the "4C-bile salts in the EHC, which would occur from the differential absorption of stimulated or

TABLE 3. Glycochenodeoxycholic Acid Kinetics Postop

Preop

Patient

Pool Size (gm)

Turnover Rate (k) per day

Loss/day (gm)

Pool Size (gm)

Turnover Rate (k) per day

Loss/day (gm)

Time after Bypass

(mon)

1

1.0

0.59

0.6

0.8

1.78

1.4

11

2

0.7

1.94

1.4

0.7

4.28

3.0

8

3 4

1.3

0.38

0.5

0.8

1.53

1.2

8

1.1

0.55

0.6

0.3

4.33

5

0.5

0.2

0.3 0.5

6.69 1.13 3.06 10.00 1.81 2.39 3.70 2.79 0.88

1.3 2.0 0.5

9 11 10

0.3 0.2 0.6 1.0 1.15

9 14 3 9 9.2

0.86 0.27

2.8 0.9

6

1.0

7

0.8

0.60 0.29 0.67

8

0.8

0.38

0.3

Mean S.D. S. E. M.

0.90 0.25 0.09

0.67

0.56

0.1 0.02 0.3 0.4 0.42

0.53

0.37

0.27

0.19

0.13

0.09

0.3 0.6

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BILE SALT METABOLISM

non-stimulated bile secretion and from intermittent bile salt synthesis, resulting in a sporadic dilution of the tag. Our results indicate that GC metabolism was altered more than GCDC metabolism following jejunoileal bypass. The preoperative mean GC pool size of 1.38 g decreased to 0.56 g, whereas the mean GCDC pool size of 0.90 g only decreased to 0.42 g. This occurred in spite of an increased hepatic synthesis of GC (0.97 g/day to 2.77 g/day, a 185% increase). The postoperative hepatic synthesis of GCDC, however, increased only by 105% (0.56 g/day to 1.15 g/day). Although the k of GC and of GCDC correlated in both the pre- and in the postoperative groups, the quantitative effects of jejunoileal bypass on GC and GCDC turnover rates were again somewhat different. The postoperative increase in the turnover of GC was more than the increase in GCDC; the slope of the major axis of the bivariate correlation of GC on the abscissa and of GCDC on the ordinate became less (0.74 10 to 0.4290) following jejunoileal bypass. The postoperative k of GC increased by 577%, whereas the k of GCDC increased by 452%. This suggests a difference in the adaptive capabilities of these patients for reabsorption and synthesis of bile salts following jejunoileal bypass. Chenodeoxycholate was more efficiently reabsorbed than cholate in both the pre- and postoperative states, since the turnover rates of GCDC were less than that of GC in both groups. Schiff et al. demonstrated this difference in absorption in the rat.10 Cholate synthesis was greater than that of chenodeoxycholate synthesis both pre- and postoperatively. Postoperatively, one patient (Patient 2) maintained the preoperative pool sizes of both bile salts. This suggests that this patient had adapted sufficiently with an increased hepatic synthesis, and, possibly, by an improvement of the reabsorptive capability of the remaining small intestine. This patient was also unique in the preoperative period by having the fastest turnover rate and the greatest hepatic synthesis. Two of the patients (Patients 7 and 8) were evaluated twice during the postoperative period. Approximately 5 to 6 months after the first postoperative study, the turnover rates increased even more for both bile salts. In one patient (Patient 7), not only did the pool size of GC and GCDC become further depressed, but the synthetic capability decreased. This phenomenon was also detected in the initial postoperative evaluation. Because the jejunoileal bypass procedure results in a malabsorptive condition leading to rapid weight loss, a deficiency of nutrients may limit hepatic synthesis. Patient 8 demonstrated some improvement of hepatic metabolism. Although her GC pool size became more depressed, the GCDC pool size increased slightly. While hepatic synthesis of GC was unchanged, the synthesis of GCDC improved. These variable results suggest that jejunoileal

71

bypass affects bile salt metabolism with varying severity and that some improvement may occur in time. The mean preoperative fecal 14C loss was 15 to 21% of the administered dose per48 hours. Followingjejunoileostomy, fecal loss increased from 22 to 93% per 48 hours. This variability in the postoperative bile salt loss reflects the varying capability of the liver to synthesize adequate amounts of bile salts to maintain pool size. There may be a primary exhaustion of hepatic synthesis and secretory function from an alteration of intracellular metabolism, or, there may be an interference with the negative feedback mechanism, since the relative proportion and the glycinetaurine conjugation ratios of these bile salts have been altered postoperatively.16 Interruption of the EHC has been shown to decrease the bile salt secretory rate.3"12 The consequence of an interrupted enterohepatic circulation of bile salts may be related to several clinical complications occurring in these patients. These may be divided into those which are the result of an initial excessive loss of bile salt and those which are the result of a later diminished loss of bile salt. Excessive colonic loss of bile salts secondary to decreased ileal absorption will result in an increased water secretion and decreased water reabsorption in the colon. Not only will diarrhea be a consequence, but sodium, potassium and bicarbonate will also be excreted in excessive amounts.78 In our series of over 100 patients with jejunoileal bypass, several patients had severe serum electrolyte imbalance and required revision of the bypass. Where there is excessive bile salt malabsorption together with an increased colonic bacterial hydroxylase activity, the secondary bile salts (deoxycholate and lithocholate) are formed in excessive quantities. It has been suggested that increased absorption of lithocholate may be associated with hepatic dysfunction.9 Although the etiology of increased hepatic fatty infiltration and dysfunction is not clear, lithocholate toxicity may be an important etiologic factor. A severely diminished bile salt pool size will interfere with efficient micellar formation. Without sufficient micelles, lipids are malabsorbed with a consequent steatorrhea. Secondary to this, the fat-soluble vitamins (A, D, E and K) are poorly absorbed. Lipid malabsorption has also been suggested as a cause of diarrhea. Hydroxy fatty acids which are formed in the colon by bacterial action on unabsorbed, unsaturated fatty acids may stimulate colonic secretion.'3 Our previous data suggest that although free fatty acids are malabsorbed, fecal bile salt loss correlates better with diarrhea production than free fatty acid loss.17 The incidence of cholelithiasis is increased following bypass. Although a reduced bile salt pool may result in lithogenic bile, our results suggest that an alteration in the glycine-taurine conjugation ratio may be more important in the production of a lithogenic bile.'6

72

STEIN AND WISE

The degree of interruption of the enterohepatic circula- 7. tion of bile salts following jejunoileal bypass varied in this patient group. The long-term effects ofjejunoileal bypass 8. on bile salt metabolism and the associated complications are dependent on the individual patient's capability for 9. increased hepatic synthesis of bile salts and on the 10. adaptability of the remaining small bowel for increased reabsorption of bile salts. 11.

References 1. Bergstrom, S.: Metabolism of Bile Acids. Fed. Proc., 21 (Suppl. 11): 28, 1962. 2. Borgstrom, B., Dahlqvist, A., Lundh, G., et al.: Studies on Intestinal Digestion and Absorption in the Human. J. Clin. Invest., 36:1521, 1957. 3. Dowling, R. H., Mack, E., and Small, D. M.: Biliary Lipid Secretion and Bile Composition After Acute and Chronic Interruption of the Enterohepatic Circulation in the Rhesus Monkey. IV. Primate Biliary Physiology. J. Clin. Invest., 50:1971. 4. Gregg, J. A.: New Solvent Systems for Thin-layer Chromatography of Bile Acids. J. Lipid Res., 7:579, 1966. 5. Haselwood, G. A. D., Murphy, G. M., and Richardson, J. M.: A Direct Enzymic Assay for 7a-Hydroxy Bile Acids and Their Conjugates. Clin. Sci., 44:95, 1973. 6. Lindstedt, S.: The Turnover of Cholic Acid in Man. Bile Acids and Steroids, 51. Acta Physiol. Scand., 40:1, 1957.

12.

13. 14.

15.

16.

17.

Ann. Surg. * January 1977

Mekhjian, H. S., Phillips, S. F., and Hofmann, A. F.: Colonic Secretion of Water and Electrolytes Induced by Bile Acids: Perfusion Studies in Man. J. Clin. Invest., 50:1569, 1971. Mitchell, W. D., Findlay, J. M., Prescott, R. J., et al.: Bile Acids in the Diarrhea of Ileal Resection. Gut, 14:348, 1973. Palmer, R. H.: Bile Acids, Liver Injury, and Liver Disease. Arch. Intern. Med., 130:606, 1972. Schiff, E. R., Small, D. M., and Dietschy, J. M.: Characterization of the Kinetics of the Passive and Active Transport Mechanism for Bile Acid Absorption in the Small Intestine and Colon of the Rat. J. Clin. Invest., 51:1351, 1972. Sokal, R. R., and Rohlf, F. J.: Biometry. The Principles and Practice of Statistics in Biological Research. San Francisco, W. H. Freeman and Company, 1969; p. 495-548. Soloway, R. D., Powell, K. M., Senior, J. R., et al: Interrelationship of Bile Salts, Phospholipids, and Cholesterol in Bile During Manipulation of the Enterohepatic Circulation in the Conscious Dog. Gastroenterology, 64:1156, 1973. Soong, C. S., Thompson, J. B., Poley, J. R., et al.: Hydroxy Fatty Acids in Human Diarrhea. Gastroenterology, 63:748, 1972. Turnberg, L. A. and Anthony-Mote, A.: The Quantitative Determination of Bile Salt in Bile Using Thin-layer Chromatography and 3a-Hydroxysteroid Dehydrogenase. Clin. Chim. Acta, 24:253, 1969. Wilcoxon, F.: Probability Tables for Individual Comparisons by Ranking Methods. Biometrika, 3:119, 1947. Wise, L., and Stein, T.: Biliary and Urinary Calculi: Pathogenesis Following Small Bowel Bypass for Obesity. Arch. Surg., 110: 1043, 1975. Wise, L., and Stein, T.: The Mechanism of Diarrhea Following Small Bowel Bypass. Surg. Gynecol. Obstet., 142:686, 1976.

Bile salt metabolism following jejunoileal bypass for morbid obesity.

Bile Salt Metabolism Following Jejunoileal Bypass for Morbid Obesity THEODORE A. STEIN, M.S., LESLIE WISE, M.D. Bile salt pool size and kinetics were...
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