Postprandial Plasma Bile Acid Responses in Normal Weight and Obese Subjects

Background: Bile acids can act as signalling molecules via various receptors including the nuclear farnesoid X receptor (FXR) and pregnane X receptor (PXR), and the cell surface G-protein-coupled receptor TGR5. The signalling has been implicated in the release of peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), which improves glycaemic control and energy expenditure. We investigated whether morbidly obese subjects have altered postprandial bile acid responses in comparison to normal weight subjects.

Method: Blood samples were taken every 30 min from 0 to 180 min following a 400 kcal test meal. Samples were taken from 12 normal weight subjects with a body mass index (BMI) of 23.2 (2.8) kg/m(2) (median [interquartile range (IQR)]) and seven obese patients with a BMI of 47.2 (7.2) kg/m(2). Fractionated bile acids were measured on these samples using high-performance liquid chromatography tandem mass spectrometry.

Results: The obese subjects showed a lower postprandial response in total bile acids compared with the normal weight subjects. An increase of 6.4 (5.0) and 2.6 (3.3) micromol/L (median [IQR]) in normal weight and obese subjects was observed, respectively (P = 0.02). The difference was predominantly due to the glycine-conjugated fraction (P = 0.03). There was no difference in the increase of the unconjugated or taurine-conjugated fractions.

Conclusions: The decreased postprandial bile acid response in obese subjects compared with normal weight subjects may partly explain the suboptimal GLP-1 and PYY responses and could affect appetite, glycaemic control and energy expenditure.