Page 53 - Human Bile Acid Metabolism: a Postprandial Perspective

conjugated and unconjugated forms of CA and DCA, and unconjugated UDCA from analysis. In humans, UDCA, tUDCA and tDCA were excluded from analysis due to interfering peaks in the chromatogram. For all the other BAs, when a concentration was below the lower LOQ, its value was set to 50% of the detection limit i.e., 0.025 mM.
Organ flux calculations 3 In the present model we measured organ flux through the hindquarter muscle compartment (muscle flux), the kidney compartment (renal flux), the intestine
and pancreas compartment (portal drained viscera (PDV) flux) and the splanchnic compartment: the PDV plus the liver (SPL flux). We calculated liver flux as SPL flux
minus PDV flux. Flux through a compartment was calculated as the mean plasma flow through that compartment multiplied with the arterio-venous difference in concentration of glucose, insulin or BA. A positive flux value is interpreted as appearance or production by the compartment, while a negative flux is interpreted as disappearance or uptake in the compartment.
Human study
We took blood samples from the cubital vein and portal vein from consecutive subjects during elective gastric by-pass surgery. Eleven healthy non-diabetic patients participated in this study (1 male, 10 females; age 46.0 ± 12.7 yrs; body mass index 41.4 ± 2.8 kg/m2; mean ± SD). All participants gave informed consent before the surgery and the protocol was approved by the Medical Ethical Committee of the Academic Medical Centre and Slotervaart Hospital, Amsterdam. None of the patients used BA sequestrants. Subjects were fasted overnight prior to the surgery. First, a preoperative peripheral venous sample was taken. During the surgery, the portal vein puncture was performed as previously described [19]. Glucose, insulin and BA concentrations were measured in these samples.
Statistics
Calculations were made using Microsoft Excel 2010 version 14.0 and area- under-the-curve analysis and statistics were done in Graphpad Prism version 7. For porcine data analysis paired t-test or repeated measure ANOVA with Tukey post-hoc analysis were used where appropriate. For human data we used non- parametric tests.
Transhepatic bile acid kinetics
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