Chylomicrons produced by Caco-2 cells contained ApoB-48 with diameter of 80-200 nm

Abstract

The small intestine generally transports dietary fats to circulation in triglyceride (TG)‐rich lipoproteins. The two main intestinal lipoproteins are chylomicron (CM) and very low‐density lipoprotein (VLDL). Unfortunately, studies on the CM biogenesis and intestinal transport of dietary fats have been hampered by the lack of an adequate in vitro model. In this study, we investigated the possible factors that might increase the efficiency of CM production by Caco‐2 cells. We utilized sequential NaCl gradient ultracentrifugation to isolate the CMs that were secreted by the Caco‐2 cells. To confirm the successful isolation of the CMs, we performed Fat Red 7B staining, TG reading, apolipoprotein B (ApoB) measurement, and transmission electron microcopy (TEM) analysis. We then tested the effects of cell differentiation, oleic acid, mono‐olein, egg lecithin, incubation time, and collagen matrix on CM secretion. We found that cell differentiation, oleic acid, and lecithin were critical for CM secretion. Using the Transwell system, we further confirmed that the CMs produced by our Caco‐2 cells contained significant amount of TGs and ApoB‐48 such that they could be detected without the use of isotope labeling. In conclusion, when fully differentiated Caco‐2 were challenged with oleic acid, lecithin, and sodium taurocholate, 21% of their total number of lipoproteins were CMs with the diameter of 80–200 nm.

Recent discoveries on absorption of dietary fat: Presence, synthesis, and metabolism of cytoplasmic lipid droplets within enterocytes

“…However these cells exhibit little to no MGAT activity, which is involved in the predominant TAG synthesis pathway in human enterocytes in response to dietary fat consumption [38, 39]. In addition, Caco-2 cells secrete a large proportion of lipid in lipoprotein particles that are smaller than the CMs secreted from human small intestine and they contain additional lipoproteins [38, 40]. These details are important to note when considering the application of the presented results to human health and medicine.…”

Using primary murine intestinal enteroids to study dietary TAG absorption, lipoprotein synthesis, and the role of apoC-III in the intestine

“…For TAG secretion studies, cells were maintained until they reached confluence and then given fresh medium for an additional 17 days post confluence. As described in by Nauli et al (20), this protocol produces the most abundant chylomicron-like apoB-lipoproteins. For direct comparisons between enteroids and Caco-2 cells, we isolated genomic DNA from the parallel cultures of Caco-2 cells and enteroids at the conclusion of each experiment, and normalized measurements to total genomic DNA concentrations in the enteroids and Caco-2 cells.…”

Gut–liver on a chip toward an in vitro model of hepatic steatosis

“…For example, fatty acids are known to form micelles with bile acids inside the gut lumen, and are absorbed through the gut epithelium (Tsuzuki, ). During the absorption process, fatty acids form chylomicrons, lipoprotein particles composed of triglycerides and phospholipids which transport dietary lipids from the intestine to other organs (Figure ; Nauli et al, ). Chylomicrons and its remnants enter the systemic circulation and are ultimately transported to the liver, where they are converted to neutral lipids and fatty acids, and accumulate in the liver cells (Liu, Bengmark, & Qu, ).…”