orlistat and Cystic-Fibrosis

The malabsorption blood test (MBT), consisting of pentadecanoic acid (PA), a free fatty acid, and triheptadecanoic acid (THA), a triglyceride that requires pancreatic lipase for absorption of the heptadecanoic acid (HA), was developed to assess fat malabsorption in patients with cystic fibrosis (CF) and pancreatic insufficiency (PI). The objective was to construct a population pharmacokinetic (PK) model to describe PA and HA disposition in healthy subjects and CF subjects. A model was simultaneously fit to PA and HA concentrations, consisting of 1-compartment disposition and a transit model to describe absorption. PA bioavailability estimates for CF subjects without pancreatic enzyme administration (1.07 [0.827, 1.42]) and with enzymes (0.88 [0.72, 1.09]) indicated PA absorption comparable to healthy subjects. HA bioavailability in CF without enzyme administration was 0.0292 (0.0192, 0.0459) and with enzymes increased to 0.606 (0.482, 0.823). In CF, compared with taking enzymes with the MBT, HA bioavailability was further decreased by factors of 0.829 (0.664, 0.979) and 0.78 (0.491, 1.13) with enzymes taken 30 and 60 minutes after MBT, respectively. The MBT detected differences in fat absorption in subjects with CF with and without enzyme administration and with changes in enzyme timing. Future studies will address application of the MBT in CF and other malabsorption diagnoses.

Topics: Adolescent; Adult; Child; Cystic Fibrosis; Exocrine Pancreatic Insufficiency; Fatty Acids; Female; Humans; Intestinal Absorption; Lactones; Lipase; Male; Middle Aged; Models, Biological; Orlistat; Young Adult

A Malabsorption Blood Test (MBT) is proposed as an alternative method to the 72-hour stool and dietary collection for assessing the degree of fat malabsorption in people with pancreatic insufficiency. The MBT consists of a simultaneous oral dose of pentadecanoic acid (PA), a free fatty acid, and triheptadecanoic acid (THA), a triglyceride with three heptadecanoic (HA) saturated fatty acids requiring hydrolysis by pancreatic lipase before HA can be intestinally absorbed. The aim of this study is to demonstrate the ability of MBT to detect fat malabsorption in healthy adult subjects using the pancreatic lipase (PL) inhibitor Orlistat (Xenical®), and in subjects with CF and PI while on and off routine pancreatic enzyme doses.. The MBT with the PA and THA were delivered in a breakfast test meal (2.5 g PA and either 5 g or 8 g THA) to healthy adult subjects (ages 18 - 50 years, BMI 21 - 30) and to subjects with CF (> 12 years, FEV1% predicted > 40%), after a 12-hour fast and 24 hours without dairy foods. Serum levels of PA and HA were assessed by gas-liquid chromatography, from blood samples drawn prior to MBT and then hourly for 8 hours. For healthy subjects, the MBT was administered before and after Orlistat treatment, and in subjects with CF, both with subjects receiving routine pancreatic lipase treatment ("on enzyme") and also "off enzyme" treatment. Treatment groups were compared for baseline (C0) and maximum (Cmax) plasma concentrations of PA and HA over 8 hours: area under the curve (AUC) was calculated using linear trapezoid method. The ratio of HA to PA Cmax and AUC was also calculated and compared.. For the healthy subjects (n = 15, 60% female, ages 21 - 49 years), absorption of HA was reduced 71% for Cmax (p < 0.001) and 65% for AUC (p = 0.001) after Orlistat treatment, and absorption of PA was unchanged. For subjects with CF (n = 6, 50% female, ages 13 - 19 years), absorption of HA was minimal with subjects "off enzymes" and increased significantly with subjects "on enzymes" while absorption of PA did not differ between groups. Enzyme administration resulted in increased Cmax HA/ PA ratios from 0.02 to 0.92 and from 0.05 to 0.73 in subjects with CF receiving 5.0 g and 8.0 g of THA, respectively. AUC HA/PA ratios showed similar increases.. In this pilot and feasibility proof-of-concept study, the MBT, utilizing the relative absorption of HA to PA, two odd-chained fatty acids, responds to changes in fat absorption in healthy subjects using a lipase inhibitor and in subjects with CF while on or off enzyme therapy. The MBT holds promise to provide a more accurate, specific and acceptable alternative to the 72-hour stool collection to quantify pancreatic-based fat malabsorption in a variety of clinical and research contexts.

Topics: Administration, Oral; Adolescent; Adult; Area Under Curve; Chromatography, Gas; Cystic Fibrosis; Dietary Fats; Fatty Acids; Feasibility Studies; Female; Humans; Lactones; Malabsorption Syndromes; Male; Middle Aged; Orlistat; Pilot Projects; Young Adult