Intestinal absorption of peptides through the enterocytes

Area of Science:

• Gastroenterology and Molecular Biology
• Cellular Biology and Physiology

Background:

• Intestinal absorption of intact proteins is a physiological process distinct from nutrient digestion.
• Understanding protein transport mechanisms across the intestinal barrier is crucial for biological and therapeutic applications.

Purpose of the Study:

• To elucidate the pathway and mechanisms of intact protein absorption from the intestinal lumen into the bloodstream.
• To investigate the biological activity and absorption efficiency of insulin administered intraluminally.

Main Methods:

• Administration of insulin into the intestinal lumen of experimental models.
• Morphological examination of intestinal tissue using microscopy.
• Immunocytochemistry to detect insulin localization within epithelial cells.
• Assessment of biological activity by measuring blood glucose levels.

Main Results:

• Intact insulin was absorbed by intestinal epithelial cells and entered circulation, retaining biological activity and lowering blood glucose.
• Absorption efficiency was consistent across the ileum, duodenum, and colon.
• Insulin uptake occurred via the endosomal pathway, involving invaginations of the plasma membrane and vesicular transport.
• No structural damage to the intestinal epithelium or tight junctions was observed.
• Insulin was detected within the endosomal compartment and subsequently released into the interstitial space within 5-10 minutes.

Conclusions:

• Intestinal absorption of intact proteins like insulin occurs via cellular transcytosis, not paracellular routes.
• The integrity of the intestinal barrier is maintained during this process.
• Understanding this transcytotic pathway is vital for developing novel oral drug delivery systems for peptides and proteins.