Page 30 - Human Bile Acid Metabolism: a Postprandial Perspective

Chapter 2
and healthy age-, gender-, and body mass index (BMI)matched control subjects with normal glucose tolerance (NGT).
Subjects and Methods
Participants
A detailed description of the experimental procedures and subjects was provided previously (11). In short, plasma was obtained from 15 patients with T2D (mean duration of T2D, 7.5 years [range, 6 –20]; age, 59.4 ± 9.6 years [mean ± SD]; BMI, 28.0 ± 2.2 kg/m2; hemoglobin A1c [HbA1c], 7.5 ± 1.4%) and 15 healthy, age-, gender-, and BMI-matched control subjects (age, 59.7 ± 10.0 years; BMI, 27.9 ± 2.0 kg/m2; HbA1c, 5.2 ± 0.2%). None of the T2D patients had overt diabetic complications. Eight patients were treated with metformin, three with sulfonylurea, and four with diet only. Patients were instructed to abstain from taking blood glucose-lowering drugs for at least 1 week before the first study day.
Study design
Patients underwent four separate “meal” tests (visits were separated by 2– 4 days) as follows: 75-g oral glucose tolerance test (OGTT; 75 g of water-free glucose dissolved in 300 mL water), and three isocaloric (500 kcal) and isovolemic (350 mL) liquid meals (low fat, 2.5 g fat, 107 g carbohydrate, and 13 g protein; medium fat, 10 g fat, 93 g carbohydrate, 11 g protein; and high fat, 40 g fat, 32 g carbohydrate, and 3 g protein). Written informed consent was obtained from all participants. Results on postprandial glucose metabolism, gallbladder emptying, and gut hormone secretion have been reported previously (11).
Sample collection
Arterialized blood samples were drawn 20, 10, and 0 minutes before and 15, 30, 45, 60, 90, 120, 180, and 240 minutes after ingestion of the OGTT or meals. Blood was collected into chilled tubes containing EDTA and a specific dipeptidyl peptidase 4 inhibitor (valine-pyrrolidide, final concentration of 0.01 mmol/L; a gift from Novo Nordisk) for plasma analyses of individual bile acids and FGF19. Tubes were kept on ice, centrifuged for 20 minutes at 1200 × g and 4°C, and stored at –20°C until analysis. Samples were analyzed for unconjugated cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), and
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