Fenofibrate, a peroxisome proliferator-activated receptor α agonist, alters triglyceride metabolism in enterocytes of mice

Abstract

Fenofibrate, a drug in the fibrate class of amphiphathic carboxylic acids, has multiple blood lipid modifying actions, which are beneficial to the prevention of atherosclerosis. One of its benefits is in lowering fasting and postprandial blood triglyceride (TG) concentrations. The goal of this study was to determine whether the hypotriglyceridemic actions of fenofibrate in the postprandial state include alterations in TG and fatty acid metabolism in the small intestine. We found that the hypotriglyceridemic actions of fenofibrate in the postprandial state of high-fat (HF) fed mice include a decrease in supply of TG for secretion by the small intestine. A decreased supply of TG for secretion was due in part to the decreased dietary fat absorption and increased intestinal fatty acid oxidation in fenofibrate compared to vehicle treated HF fed mice. These results suggest that the effects of fenofibrate on the small intestine play a critical role in the hypotriglyceridemic effects of fenofibrate.

Fig 1

Fenofibrate decreases the postprandial triglyceridemic response and TG secretion from enterocytes in HF fed mice. (A) Plasma TG concentration before and at 1, 2, 3 and 4 hours after a 200μl olive oil challenge in fenofibrate and vehicle treated HF fed mice. Mice were fasted 4 hours before olive oil administration. Data are represented as mean ± SEM. Asterisks denote significant differences compared to vehicle treated mice, P < 0.05, n = 3 mice. (B) Plasma TG concentration before and at 2 and 4 hours after 500mg/kg Tyloxapol, a TG clearance inhibitor, and a 200μl olive oil challenge in fenofibrate and vehicle treated HF fed mice. Mice were fasted for 4 hours before tyloxapol and oral olive oil administration. Data are represented as mean ± SEM. Asterisks denote significant differences compared to the vehicle treated mice, P < 0.05, n = 4-5 mice. (C) Representative agarose gel of serum samples at 0, 1, 2 and 4 hours post 200μl olive oil challenge in fenofibrate and vehicle treated HF fed mice.

Fig 2

Fenofibrate increases fecal fatty acids, cholesterol and phospholipids. Fecal lipid composition was determined by separating lipid species by thin layer chromatography using hexane:ether:acetic acid (80:20:1) and lipids detected via iodine, n = 5 mice. Standards used were cholesterol ester (CE), chlolesterol (Chol), oleic acid for fatty acid (FA), olive oil for triglyceride (TG).

Fig 3

Fenofibrate does not decrease mRNA levels of genes known to promote dietary fat absorption. QPCR analysis of genes involved in TG metabolism in the duodenum (S1) of fenofibrate and vehicle treated mice. Data are represented as mean ± SEM. Bars with asterisks are significantly different compared to the vehicle treated mice, P < 0.05, n = 6-8 mice.

Fig 4

Fenofibrate increases fatty acid oxidation in intestinal mucosa of HF fed mice. (A) QPCR analysis of genes involved in fatty acid oxidation in the duodenum (S1) of fenofibrate and vehicle treated HF fed mice. Data are represented as mean ± SEM. Bars with asterisks are significantly different compared to the vehicle treated mice, P < 0.05, n = 6-8 mice. (B) Relative fatty acid oxidation in the jejunum (S2 and S3) ex vivo of fenofibrate treated mice normalized to vehicle treated HF fed mice. Data are represented as mean ± SEM. Bars with asterisks are significantly different compared to the vehicle treated mice, P < 0.05, n = 11-12 mice. (C) Relative fatty acid oxidation in lower jejunum (S4) ex vivo of fenofibrate treated mice normalized to vehicle treated mice with hydroxyphenylglycine, an inhibitor of fatty acid oxidation, n = 4 mice.

Fig 5

Fenofibrate decreases TG storage in enterocytes of HF fed mice. C57BL/6, male mice were fed a HF diet for two weeks and then continued on the HF diet in combination with daily oral administration of fenofibrate for five days. Mice were fasted for two hours before euthanasia. Representative images (n = 3 mice) of TG storage in CLDs in of enterocytes in the upper jejunum (S2) of vehicle (A and B) and fenofibrate (C and D) treated mice using 20× objective at 1× and 3× magnification. (E) TG concentration in intestinal mucosa representing the duodenum (S1) of the same mice described above determined by biochemical extraction and colorimetric analysis. Data are represented as mean ± SEM. Bars with asterisks are significantly different compared to the vehicle treated mice, P < 0.05, n = 6-9 mice.