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. 2025 Jun:167:156189.
doi: 10.1016/j.metabol.2025.156189. Epub 2025 Mar 10.

Fat absorption and metabolism after Roux-en-Y gastric bypass surgery

Morten Hindsø  1 , Annemarie Lundsgaard  2 , Bojan Marinkovic  2 , Mikkel Helmuth Jensen  3 , Nora Hedbäck  3 , Maria Saur Svane  4 , Carsten Dirksen  5 , Nils Bruun Jørgensen  3 , Amalie London  6 , Palle Bekker Jeppesen  7 , Mark Krogh Hvistendahl  7 , Christina Christoffersen  8 , Hartwig Roman Siebner  9 , Bente Kiens  2 , Jens Juul Holst  10 , Sten Madsbad  5 , Gerrit van Hall  11 , Kirstine Nyvold Bojsen-Møller  12
Affiliations

Fat absorption and metabolism after Roux-en-Y gastric bypass surgery

Morten Hindsø et al. Metabolism. 2025 Jun.

Abstract

Background: Triacylglycerol (TAG) plasma excursions after a high-fat meal are blunted after Roux-en-Y gastric bypass (RYGB), but underlying mechanisms are poorly understood. We studied TAG absorption and metabolism in 12 RYGB-operated individuals and 12 unoperated controls (CON) matched on sex, age, and BMI.

Methods: Participants followed a 7-day controlled diet and on day 4 underwent 1H-MR Spectroscopy of liver TAG and a high-fat liquid meal with oral and intravenous labeled stable isotope metabolites, subcutaneous abdominal fat biopsies, and indirect calorimetry. Subsequently, participants collected stool for 96 h.

Results: Overall fat absorption from the controlled diet was moderately lower in RYGB than CON (88 % versus 93 %, P < 0.01), without indication of greater specific malabsorption of fat from the high-fat test meal (recovery of TAG and labeled TAG in 96-h stool samples). After an overnight fast, plasma TAG concentrations and incorporation of plasma fatty acids (IV tracer) into TAG did not differ between groups. The postprandial 6-h iAUC of plasma TAG plasma concentrations was markedly lower in RYGB than CON (15 versus 70 mmol/L × min, P = 0.03). The postprandial chylomicron (CM) particle response (plasma ApoB48) was initially higher in RYGB, but with lower CM-TAG plasma concentrations and appearance of labeled palmitate from the oral tripalmitin tracer over the 6 h.

Conclusion: Fat absorption is only moderately lower after RYGB compared with unoperated matched controls. Nevertheless, postprandial TAG and CM plasma kinetics after a high-fat meal are markedly altered after RYGB with substantially lower TAG and CM-TAG concentrations despite a faster CM particle release.

Keywords: Absorption; Bariatric surgery; Chylomicron; Fat; Lipids; Lipoprotein; Obesity; Triacylglycerol; Very-low-density lipoprotein.

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Conflict of interest statement

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Annemarie Lundsgaard has taken a position at Novo Nordisk from October 2023. Maria Saur Svane reports a relationship with Novo Nordisk that includes: speaking and lecture fees. Carsten Dirksen reports a relationship with Novo Nordisk that includes: paid expert testimony, speaking and lecture fees, and travel reimbursement. Carsten Dirksen reports a relationship with AstraZeneca that includes: speaking and lecture fees. Carsten Dirksen reports a relationship with Novo Nordisk Foundation that includes: funding grants. NBJ has taken a position with Novo Nordisk. Mark Krogh Hvistendahl reports a relationship with Zealand Pharma that includes: employment. At the time of conducting this trial, Mark Krogh Hvistendahl was full-time employed at Rigshospitalet, Department of Intestinal Failure and Liver Diseases. At the time of drafting and submitting the manuscript for consideration to your journal, the co-author is now full-time employed at Zealand Pharma A/S. Hartwig Roman Siebner reports a relationship with Lundbeck that includes: consulting or advisory and speaking and lecture fees. Hartwig Roman Siebner has received honoraria as editor-in-chief (Neuroimage Clinical) and senior editor (NeuroImage) from Elsevier Publishers, Amsterdam, The Netherlands. Hartwig Roman Siebner has received royalties as book editor from Springer Publishers, Stuttgart, Germany, from Oxford University Press, Oxford, UK, and from Gyldendal Publishers, Copenhagen, Denmark. Sten Madsbad reports a relationship with AstraZeneca that includes: consulting or advisory and speaking and lecture fees. Sten Madsbad reports a relationship with Boehringer Ingelheim that includes: consulting or advisory, funding grants, and travel reimbursement. Sten Madsbad reports a relationship with Intarcia Therapeutics that includes: consulting or advisory. Sten Madsbad reports a relationship with Novo Nordisk that includes: consulting or advisory, funding grants, speaking and lecture fees, and travel reimbursement. Sten Madsbad reports a relationship with Sanofi that includes: consulting or advisory. Sten Madsbad reports a relationship with Abbott Lab that includes: consulting or advisory. Sten Madsbad reports a relationship with Bayer that includes: consulting or advisory and travel reimbursement. Sten Madsbad reports a relationship with Amgen that includes: consulting or advisory. Sten Madsbad reports a relationship with MSD that includes: speaking and lecture fees. Sten Madsbad reports a relationship with Novo Nordisk Foundation that includes: funding grants. Sten Madsbad reports a relationship with Netdoktor that includes: consulting or advisory. Sten Madsbad has served as PI in relation to development of drugs for treatment of Type 2 diabetes and obesity in collaboration with Novo Nordisk and Bayer. Kirstine Nyvold Bojsen-Møller reports a relationship with Novo Nordisk Foundation that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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