Mfge8 regulates enterocyte lipid storage by promoting enterocyte triglyceride hydrolase activity
Amin Khalifeh-Soltani, Deepti Gupta, Arnold Ha, Jahangir Iqbal, Mahmood Hussain, Michael J. Podolsky, Kamran Atabai
Amin Khalifeh-Soltani, Deepti Gupta, Arnold Ha, Jahangir Iqbal, Mahmood Hussain, Michael J. Podolsky, Kamran Atabai
View: Text | PDF
Research Article Cell biology Metabolism

Mfge8 regulates enterocyte lipid storage by promoting enterocyte triglyceride hydrolase activity

Abstract

The small intestine has an underappreciated role as a lipid storage organ. Under conditions of high dietary fat intake, enterocytes can minimize the extent of postprandial lipemia by storing newly absorbed dietary fat in cytoplasmic lipid droplets. Lipid droplets can be subsequently mobilized for the production of chylomicrons. The mechanisms that regulate this process are poorly understood. We report here that the milk protein Mfge8 regulates hydrolysis of cytoplasmic lipid droplets in enterocytes after interacting with the αvβ3 and αvβ5 integrins. Mice deficient in Mfge8 or the αvβ3 and αvβ5 integrins accumulate excess cytoplasmic lipid droplets after a fat challenge. Mechanistically, interruption of the Mfge8-integrin axis leads to impaired enterocyte intracellular triglyceride hydrolase activity in vitro and in vivo. Furthermore, Mfge8 increases triglyceride hydrolase activity through a PI3 kinase/mTORC2–dependent signaling pathway. These data identify a key role for Mfge8 and the αvβ3 and αvβ5 integrins in regulating enterocyte lipid processing.

Authors

Amin Khalifeh-Soltani, Deepti Gupta, Arnold Ha, Jahangir Iqbal, Mahmood Hussain, Michael J. Podolsky, Kamran Atabai

×

Figure 3

Accumulation of cytoplasmic lipid droplets in Mfge8–/– and αvβ3/αvβ5–/– mice after a dietary fat challenge.

Options: View larger image (or click on image) Download as PowerPoint
Accumulation of cytoplasmic lipid droplets in Mfge8–/– and αvβ3/αvβ5–/– ...
(A and B) 14C signal in the cytoplasmic versus microsomal compartments 2 hours after gavage with 14C–oleic acid expressed as absolute radioactive counts (A) or as ratio of cytosolic to microsomal radioactivity (B). n = 6. (C) Incorporation of radiolabel into triglyceride (TG), diacylglycerol (DAG), and fatty acids (FA) in primary enterocytes isolated from the proximal jejunum 2 hours after gavage with 14C-triolein. Lipids were resolved by TLC. The distribution of 14C in the different lipid species is expressed as a percentage of total 14C counts, with levels in WT cells set at 100%. n = 6. (D) Incorporation of 14C into TG, DAG, and FA in primary enterocytes isolated from the proximal jejunum incubated for 30 minutes with bile salt micelles containing 14C–oleic acid ([14C]OA). Lipids were isolated by TLC 1.5 hours after removal of bile salt micelles. n = 6. (E) Incorporation of radiolabel in TG secreted into the media of primary enterocytes after 30 minutes of incubation with bile salt micelles containing [14C]OA, followed by a 1.5-hour incubation with fresh media. n = 5. (F) Incorporation of 14C into TG in primary enterocytes incubated with [14C]OA-containing micelles followed by washing off micelles and a 2-hour incubation with fresh media. Lipids were resolved by TLC and the TG level is shown at time –30 (30 minutes before washing), –15, immediately before washing, and 0 (immediately after washing), 30, 60, and 120 minutes after wash. n = 3. (G) Total radioactivity in the media of primary enterocytes incubated with bile salt micelles containing [14C]OA 30, 15, and 0 minutes before washing and replacing with fresh media. (H) Incorporation of [14C]OA in TG secreted into the media of primary enterocytes after 30 minutes of incubation with bile salt micelles containing [14C]OA. Lipids were resolved by TLC and the TG level is shown at time 0, 30, 60, and 120 minutes after replacing media. Both female and male mice were used in A and B, and female mice were used for the remaining panels. *P < 0.05, **P < 0.01, ***P < 0.001. Paired data were analyzed by Student’s t test and group data were analyzed by 1-way ANOVA followed by a post-hoc Bonferroni test for multiple comparisons and expressed as the mean ± SEM.