Development and Physiological Regulation of Intestinal Lipid Absorption. I. Development of intestinal lipid absorption: cellular events in chylomicron assembly and secretion

2007 ◽  
Vol 293 (3) ◽  
pp. G519-G524 ◽  
Author(s):  
Dennis D. Black
Keyword(s):  
Dietary Fat ◽  
Apolipoprotein B ◽  
Microsomal Triglyceride Transfer Protein ◽  
Lipid Absorption ◽  
Cellular Mechanisms ◽  
Peripheral Tissues ◽  
Physiological Regulation ◽  
Transfer Protein ◽  
Cellular Events ◽  
Apolipoprotein A

The newborn mammal must efficiently absorb dietary fat, predominantly as triacylglycerol, and produce chylomicrons to deliver this lipid to peripheral tissues. The cellular mechanisms involved in enterocyte chylomicron assembly have recently been elucidated, and data on their regulation in the immature gut are beginning to emerge. This review focuses on key proteins involved in chylomicron assembly: apolipoprotein B-48, microsomal triglyceride transfer protein, and apolipoproten A-IV. Recent studies support a role for apolipoprotein A-IV in enhancing chylomicron secretion by promoting production of larger particles. These proteins are regulated in a manner to maximize the lipid absorptive capacity of the newborn intestine.

scholarly journals Leptin-mediated differential regulation of microsomal triglyceride transfer protein in the intestine and liver affects plasma lipids

2020 ◽  
Vol 295 (13) ◽  
pp. 4101-4113 ◽  
Author(s):  
Jahangir Iqbal ◽  
Eduardo Mascareno ◽  
Streamson Chua ◽  
M. Mahmood Hussain
Keyword(s):  
Signaling Pathways ◽  
Short Form ◽  
Microsomal Triglyceride Transfer Protein ◽  
Mapk Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Chow Diet ◽  
Peripheral Tissues ◽  
Transfer Protein ◽  
Hepatic Cells ◽  
Huh7 Cells

The hormone leptin regulates fat storage and metabolism by signaling through the brain and peripheral tissues. Lipids delivered to peripheral tissues originate mostly from the intestine and liver via synthesis and secretion of apolipoprotein B (apoB)-containing lipoproteins. An intracellular chaperone, microsomal triglyceride transfer protein (MTP), is required for the biosynthesis of these lipoproteins, and its regulation determines fat mobilization to different tissues. Using cell culture and animal models, here we sought to identify the effects of leptin on MTP expression in the intestine and liver. Leptin decreased MTP expression in differentiated intestinal Caco-2 cells, but increased expression in hepatic Huh7 cells. Similarly, acute and chronic leptin treatment of chow diet-fed WT mice decreased MTP expression in the intestine, increased it in the liver, and lowered plasma triglyceride levels. These leptin effects required the presence of leptin receptors (LEPRs). Further experiments also suggested that leptin interacted with long-form LEPR (ObRb), highly expressed in the intestine, to down-regulate MTP. In contrast, in the liver, leptin interacted with short-form LEPR (ObRa) to increase MTP expression. Mechanistic experiments disclosed that leptin activates signal transducer and activator of transcription 3 (STAT3) and mitogen-activated protein kinase (MAPK) signaling pathways in intestinal and hepatic cells, respectively, and thereby regulates divergent MTP expression. Our results also indicated that leptin-mediated MTP regulation in the intestine affects plasma lipid levels. In summary, our findings suggest that leptin regulates MTP expression differentially by engaging with different LEPR types and activating distinct signaling pathways in intestinal and hepatic cells.

scholarly journals Is apolipoprotein A-IV rate limiting in the intestinal transport and absorption of triglyceride?

2013 ◽  
Vol 304 (12) ◽  
pp. G1128-G1135 ◽  
Author(s):  
Alison B. Kohan ◽  
Fei Wang ◽  
Xiaoming Li ◽  
Abbey E. Vandersall ◽  
Sarah Huesman ◽  
...  
Keyword(s):  
Intestinal Mucosa ◽  
Dietary Fat ◽  
Intestinal Transport ◽  
Dietary Lipid ◽  
Lipid Absorption ◽  
Lymphatic Transport ◽  
Apolipoprotein A ◽  
Rate Limiting

Apolipoprotein A-IV (apoA-IV) is synthesized by the intestine and secreted when dietary fat is absorbed and transported into lymph associated with chylomicrons. We have recently demonstrated that loss of apoA-IV increases chylomicron size and delays its clearance from the blood. There is still uncertainty, however, about the precise role of apoA-IV on the transport of dietary fat from the intestine into the lymph. ApoA-IV knockout (KO) mice do not have a gross defect in dietary lipid absorption, as measured by oral fat tolerance and fecal fat measurements. Here, using the in vivo lymph fistula mouse model, we show that the cumulative secretion of triglyceride (TG) into lymph in apoA-IV KO mice is very similar to that of wild-type (WT) mice. However, the apoA-IV KO mice do have subtle changes in TG accumulation in the intestinal mucosa during a 6-h continuous, but not bolus, infusion of lipid. There are no changes in the ratio of esterified to free fatty acids in the intestinal mucosa of the apoA-IV KO, however. When we extended these findings, by giving a higher dose of lipid (6 μmol/h) and for a longer infusion period (8 h), we found no effect of apoA-IV KO on intestinal TG absorption. This higher lipid infusion most certainly stresses the intestine, as we see a drastically lower absorption of TG (in both WT and KO mice); however, the loss of A-IV does not exacerbate this effect. This supports our hypothesis that apoA-IV is not required for TG absorption in the intestine. Our data suggest that the mechanisms by which the apoA-IV KO intestine responds to intestinal lipid may not be different from their WT counterparts. We conclude that apoA-IV is not required for normal lymphatic transport of TG.

scholarly journals Apolipoprotein B-containing lipoprotein assembly in microsomal triglyceride transfer protein-deficient McA-RH7777 cells

2010 ◽  
Vol 51 (8) ◽  
pp. 2253-2264 ◽  
Author(s):  
Yanwen Liu ◽  
Medha Manchekar ◽  
Zhihuan Sun ◽  
Paul E. Richardson ◽  
Nassrin Dashti
Keyword(s):  
Apolipoprotein B ◽  
Microsomal Triglyceride Transfer Protein ◽  
Transfer Protein ◽  
Lipoprotein Assembly
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