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Human apolipoprotein A-IV. Intestinal origin and distribution in plasma
The Journal of Clinical Investigation
|April 1, 1980
Summary
The human intestine synthesizes apolipoprotein A-IV (apoA-IV), a key component of triglyceride-rich lipoproteins. ApoA-IV is secreted by intestinal cells and found in chylomicrons and VLDL, with levels changing after lipid intake.
Area of Science:
- Gastroenterology and Nutrition
- Lipid Metabolism and Cardiovascular Health
Background:
- Apolipoprotein A-IV (apoA-IV) is a major apoprotein synthesized in the human intestine.
- Its role in intestinal triglyceride-rich lipoproteins and lipid absorption requires further elucidation.
Purpose of the Study:
- To investigate the synthesis and secretion of apoA-IV in the human intestine.
- To determine the association of apoA-IV with lipoproteins after lipid ingestion.
- To analyze apoA-IV levels in plasma and its association with lipoproteins in various physiological states.
Main Methods:
- Intestinal biopsies from normal volunteers during fasting and after lipid ingestion.
- Indirect immunofluorescence to detect apoA-IV intracellular content.
- Lipoprotein analysis using sodium dodecyl sulfate gel electrophoresis and ultracentrifugation.
- Measurement of apoA-IV and triglyceride levels in urine and plasma.
Main Results:
- Increased intracellular apoA-IV observed in intestinal cells post-lipid ingestion.
- ApoA-IV constituted a significant percentage of chylomicron and intestinal VLDL apoprotein.
- Lipid feeding increased urinary apoA-IV excretion and plasma apoA-IV levels.
- Fasting plasma apoA-IV is primarily free, while lipemic plasma shows association with triglyceride-rich lipoproteins.
Conclusions:
- The human intestine synthesizes and secretes apoA-IV as a chylomicron and VLDL apoprotein.
- ApoA-IV plays a role in intestinal lipid transport and metabolism.
- Plasma apoA-IV exists predominantly unbound to lipoproteins in the fasting state but associates with chylomicrons after lipid intake.
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