Postprandial bile acid levels in intestine and plasma reveal altered biliary circulation in chronic pancreatitis patients

Abstract

Bile acid (BA) secretion and circulation in chronic pancreatitis (CP) patients with exocrine pancreatic insufficiency (EPI) were investigated by simultaneously measuring postprandial levels of individual BAs in duodenal contents and blood plasma using LC-MS/MS. CP patients and healthy volunteers (HVs) were intubated with gastric and duodenal tubes prior to the administration of a test meal and continuous aspiration of duodenal contents. Pancreatic lipase outputs in CP patients were very low (0.7 ± 0.2 mg) versus HVs (116.7 ± 68.1 mg; P < 0.005), thus confirming the severity of EPI. Duodenal BA outputs were reduced in CP patients (1.00 ± 0.89 mmol; 0.47 ± 0.42 g) versus HVs (5.52 ± 4.53 mmol; 2.62 ± 2.14 g; P < 0.15). Primary to secondary BA ratio was considerably higher in CP patients (38.09 ± 48.1) than HVs (4.15 ± 2.37; P < 0.15), indicating an impaired transformation of BAs by gut microbiota. BA concentrations were found below the critical micellar concentration in CP patients, while a high BA concentration peak corresponding to gallbladder emptying was evidenced in HVs. Conversely, BA plasma concentration was increased in CP patients versus HVs suggesting a cholangiohepatic shunt of BA secretion. Alterations of BA circulation and levels may result from the main biliary duct stenosis observed in these CP patients and may aggravate the consequences of EPI on lipid malabsorption.

Keywords: cholangiohepatic shunt; exocrine pancreatic insufficiency; lipidomics.

Fig. 1.

Variations with time in duodenal pH (A) and HPL concentration (B). Values are mean ± SD (severe CP patients: n = 6; HVs: n = 6). In panel A, asterisks indicate significant differences (P < 0.05) between severe CP patients and HVs. In panel B, lipase concentration is expressed in units per milliliter and values for CP patients were always significantly different (P < 0.005) from those obtained with HVs.

Fig. 2.

BA levels in duodenal contents and blood plasma. A: Variations with time in total BA concentration in duodenal contents. The horizontal dashed line indicates the mean CMC of the main BAs found in human bile [around 4 mM according to (24)]. B: Primary to secondary BA ratio in duodenal contents as a function of time. C: Variations with time in total BA concentration in blood plasma. D: Primary to secondary BA ratio in blood plasma as a function of time. The vertical dashed line in panels C and D indicates the time at which the test meal was given. Values are mean ± SD (n = 6 for CP patients and n = 6 for HVs).

Fig. 3.

Comparison of main BA concentrations in duodenal contents and blood plasma of HVs and severe CP patients. Panels A and B show the variations with time of the concentration (micromoles) of a representative BA (GCA) in duodenal contents and blood plasma, respectively. Individual data points for CP patients (n = 6) and HVs (n = 6) are displayed at times for which both the duodenal and blood plasma samples were collected (15, 30, 60, 90, 120, and 180 min). The solid and dotted lines represent the variations of mean values for HVs and CP patients, respectively. Panels C and D show the concentrations (micromoles) in the main BAs measured 30 min after meal ingestion in duodenal contents and blood plasma, respectively. All individual data points are displayed and the horizontal bars indicate median values for each group.

Fig. 4.

Discrimination of severe CP patients HVs based on BA analysis. A: Correlation between BA duodenal and blood plasma concentrations measured 30 min after meal ingestion. Only the main conjugated BAs found in both duodenal contents and blood plasma are displayed. Values are means (n = 6 for CP patients and n = 6 for HVs). B: S-plot of the circulating blood plasma BAs 30 min after ingestion of the test meal. The plot illustrates the selection of the most significant biomarkers among of the various plasma BAs (n = 17) in an O-PLS model calculated to discriminate CP patients and HVs. The BA levels measured in plasma by LC-MS/MS are “Pareto” scaled. The vertical axis in the S-plot [p(corr)] represents the correlation between BAs and the score of CP patients and HVs. The horizontal axis (p [1]) is the contribution of the distinct BAs estimated by the O-PLS-DA model. The S-plot identifies BAs with the best prediction capability and the largest variation between the CP group (high unconjuguated DCA, UDCA, CDCA) and the control group (high GDCA, GCA, TCDCA). R2X[1] = 0.617, i.e., 61.7% of the BA total variability.