Enhanced fasting and post-prandial plasma bile acid responses after Roux-en-Y gastric bypass surgery

Abstract

Objective. Exogenous bile acid (BA) administration is associated with beneficial metabolic effects very similar to those seen after Roux-en-Y gastric bypass (RYGB) surgery. Re-routing of bile into a biliopancreatic limb with simultaneous exclusion of food occurs after RYGB, with subsequent increased fasting plasma BAs. The study assessed fasting and post-prandial plasma BA response before and 15 months after RYGB. Material and methods. The prospective study recruited 63 obese individuals (43 females), aged 43 (36–56) [median (IQR)] years. Blood samples were collected before and every 30 min for 120 min after a standard 400 kcal meal. Fasting and post-prandial plasma BAs, glucagons like peptide-1 (GLP-1), –tyrosine (PYY), fasting C-reactive protein (CRP), glucose and insulin were measured and homeostasis model assessment-insulin resistance (HOMA-IR) was calculated. Results. Following RYGB, body mass index, CRP, fasting glucose and HOMA-IR decreased; 43.7 (39.3–49.2) kg/m² to 29.2 (25.1–35.0) kg/m², 7.9 (4.1–11.9) mg/L to 0.4 (0.2–1.0) mg/L, 5.5 (5.0–6.0) mmol/L to 4.6 (4.3–4.9) mmol/L and 5.9 (3.5–9.2) to 1.7 (1.1–2.2), respectively, all P < 0.001. Fasting total BAs, GLP-1 and PYY increased after RYGB; 1.69 (0.70–2.56) µmol/L to 2.43 (1.23–3.82) µmol/L (P = 0.02), 6.8 (1.5–15.3) pmol/L to 17.1 (12.6–23.9) pmol/L (P < 0.001) and 4.0 (1.0–7.1) pmol/L to 15.2 (10.0–28.3) pmol/L (P < 0.001), respectively. The area under the curve for post-prandial total BAs, total glycine-conjugated BAs, GLP-1 and PYY were greater after RYGB; 486 (312–732) µmol/L/min versus 1012 (684–1921) µmol/L/min, 315 (221–466) µmol/L/min versus 686 (424–877) µmol/L/min, 3679 (3162–4537) pmol/L/min versus 5347 (4727–5781) pmol/L/min and 1887 (1423–2092) pmol/L/min versus 3296 (2534–3834) pmol/L/min, respectively, all P < 0.0001. Conclusion. Weight loss following RYGB is associated with an increase in post-prandial plasma BA response due to larger amounts of glycine-conjugated BAs. This suggests up regulation of BA production and conjugation after RYGB.

Key Words::

• bile acids
• obesity
• Roux-en-Y bypass

Acknowledgments

Funding: The Swedish Research Council, University of Gothenburg, Sahlgrenska University Hospital and Gothenburg Medical Association. Contribution of authors: RPV - biochemical analysis, interpretation of the data, wrote the first draft and critically reviewed its contents.MW, LF, HL, TO - designed the study, ethics, recruitment, sample collection, interpretation of the data and critically reviewed the manuscript.HUM - interpretation of the data and critically reviewed the manuscript. GFC, DRT - biochemical analysis, interpretation of the data and critically reviewed the manuscript.JAZ - hypothesis, interpretation of the data, drafting of the manuscript and critically reviewed its contents.CWR - conception of the study, interpretation of the data and critically reviewed the manuscript.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.