After Roux-en-Y Gastric Bypass, Enterohepatic Bile Circulation Is Altered and Bile Acid Retention Increased while Bile Acid Homeostasis Remains Normal after Sleeve Gastrectomy
Authors: EIKEN ALEKSANDER , FUGLSANG STEFAN , EIKEN MARKUS LAUGE EIKEN L. , SVANE MARIA S. , HOLST JENS J. , BOJSEN-MOLLER KIRSTINE N. , MADSBAD STEN , MADSEN JAN L. , DIRKSEN CARSTEN 
Published: June 2018

Introduction: Elevated bile acid (BA) concentrations have been suggested to partly drive metabolic improvements after bariatric surgery but the mechanisms remain poorly understood. We assessed flow of bile and foods using scintigraphy after Roux-en-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy (SG).
Materials and Methods: 15 RYGB, 10 SG and 15 gender, age and BMI matched controls (C) underwent a combined cholescintigraphy and fatty test-meal with frequent blood sampling, for concomitant visualization of radiolabeled bile and food markers in the GI tract. BA retention was estimated 7 days after ingestion of a radiolabeled taurine-conjugated BA analogue (75Se-HCAT).
Results: Prior to meal intake, gallbladder filling was lower (mean ± SEM: RYGB 23% ± 4, SG 39 ± 4, C 36 ± 5, RYGB vs. C p = 0.04) and more bile marker had passed passively into the small intestine in RYGB but not SG (RYGB 48% ± 6, SG 21 ± 5, C 20 ± 6, RYGB vs. C p &lt; 0.01). Postprandial gallbladder emptying was complete in all groups. Gastric retention of foods was negligible in RYGB and lower in SG at 10 min after meal intake (RYGB 12% ± 2, SG 59 ± 7, C 90 ± 4, RYGB vs. C p &lt; 0.01, SG vs. C p &lt; 0.01) resulting in instant mixing of food with bile in RYGB and accelerated mixing in SG (RYGB 78% ± 3, SG 35 ± 8, C 8 ± 4, RYGB vs. C p &lt; 0.01, SG vs. C p &lt; 0.01). BA-retention over 7 days was only increased in RYGB (RYGB 54% ± 6, SG 34 ± 4, C 33 ± 5, RYGB vs. C: p = 0.02). Peak S-cholecystokinin (CCK) was comparably increased in RYGB and SG (RYGB 13 pmol/l ± 3, SG 15 ± 3, C 6 ± 1, RYGB vs. C p = 0.03, SG vs. C p = 0.01).
Conclusion: After RYGB, enteric BA appearance is altered (more hepatic less gallbladder derived) and food is instantly mixed with bile due to negligible retention of foods in the gastric pouch. BA retention is increased. In contrast, BA appearance and retention remains normal after SG, although gastric emptying is accelerated. The metabolic impact of the changes in BA circulation after RYGB needs further evaluation.

Disclosure
A. Eiken: None. S. Fuglsang: None. M.L. Eiken: None. M.S. Svane: None. J.J. Holst: Advisory Panel; Self; Novo Nordisk A/S. Board Member; Self; Zealand Pharma A/S. Speaker's Bureau; Self; Merck Sharp & Dohme Corp., AstraZeneca. Research Support; Self; Danish Diabetes Academy, Novo Nordisk Foundation. Other Relationship; Self; Antag Therapeutics. Other Relationship; Spouse/Partner; Antag Therapeutics. K.N. Bojsen-Moller: None. S. Madsbad: Advisory Panel; Self; AstraZeneca. Speaker's Bureau; Self; AstraZeneca. Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Speaker's Bureau; Self; Eli Lilly and Company, Eli Lilly and Company. Advisory Panel; Self; Merck Sharp & Dohme Corp., Sanofi-Aventis, Novo Nordisk A/S. Speaker's Bureau; Self; Novo Nordisk A/S. Research Support; Self; Novo Nordisk A/S. J.L. Madsen: None. C. Dirksen: None.