METHOD TO EVALUATE ABSORPTION OF DIETARY FATTY ACIDS FROM THE SMALL INTESTINE USING GASTROINTESTINAL ENDOSCOPY

Abstract

Dietary saturated fatty acid (SFA) intake is an important risk factor for ischemic heart disease, non-alcoholic steatohepatitis and carcinogenesis. Dietary SFAs are absorbed by small intestinal villi after their hydrolysis from triacylglycerols by pancreatic lipase. ¹³CO₂ breath tests, based on nondispersive infrared spectrometry, allow noninvasive quantitation of physiological processes. The breath ¹³CO₂ assay after loading of ¹³C-labeled sodium palmitate, which is one of the most abundant dietary SFAs, is designed to assess the absorption of dietary SFAs from the small intestine. Traditionally, the breath ¹³CO₂ assay after loading of ¹³C-labeled sodium palmitate requires its oral administration. Using gastrointestinal endoscopy, we administered ¹³C-labeled sodium palmitate directly into the duodenum to avoid the influence of gastric emptying. Palmitic acid is an SFA that is a solid at room temperature and is insoluble in water. However, ¹³C-labeled sodium palmitate can be maintained in a liquid state during administration by using the emulsifying effect of RACOL Liquid^® (Otsuka Pharmaceutical Factory, Inc.). Specifically, 200 mg of ¹³C sodium palmitate (Cambridge Isotope Laboratories, Inc.) is dissolved in 20 mL distilled water, heated to 70°C, and then blended with 20 mL warmed (50°C) RACOL Liquid^®, which is used to keep the fatty acid in a liquid state. After an overnight fast of 12 h, all subjects received ¹³C-labeled sodium palmitate in the horizontal portion of the duodenum using an upper gastrointestinal tract endoscope. Thereafter breath samples were collected every 30 min over a period of 6 h. Breath samples were also collected before loading. Samples were analyzed using nondispersive infrared spectrometry. Changes in the ¹³CO₂/¹²CO₂ ratio from baseline were expressed as Δ (‰). The time-dependent change in the Δ (‰) was used as a marker of the absorption of ¹³C-labeled SFAs from the small intestine. The use of this endoscopic approach for the breath ¹³CO₂ assay after loading of ¹³CO₂-labeled sodium palmitate results in a more precise evaluation of the absorption of dietary SFAs from the small intestine than that obtained using the traditional method of administering it orally.