Onion Peel Extract Prevents Intestinal Inflammation via AMK-Activated Protein Kinase Activation in Caco-2/HT-29 Cells

Area of Science:

• Gastroenterology
• Nutritional Science
• Molecular Biology

Background:

• Obesogenic diets contribute to intestinal inflammation and dysfunction.
• Polyphenols show anti-inflammatory potential, but in vivo bioactivity can be altered by digestion.
• Onion peel extract (OPE) and quercetin (Q) are investigated for their intestinal anti-inflammatory effects.

Purpose of the Study:

• To investigate the anti-inflammatory effects of onion peel extract and quercetin in the intestine.
• To examine how gastrointestinal digestion impacts the bioactivity of OPE and Q.
• To explore the molecular mechanisms underlying their anti-inflammatory actions.

Main Methods:

• In vitro digestion of OPE and Q using gastrointestinal enzymes.
• Treatment of lipopolysaccharide (LPS)-stimulated Caco-2/HT-29 cells with digested and undigested OPE and Q.
• Measurement of genes and proteins related to tight junctions, inflammation, and epithelial integrity.

Main Results:

• Digested OPE (DOPE) exhibited greater protective effects on tight junctions and inflammatory genes than OPE, Q, and digested Q (DQ).
• DOPE was more effective than OPE, while digestion did not alter quercetin's activity.
• The anti-inflammatory effects involved the inhibition of nuclear factor kappa B (NF-κB) via AMP-activated protein kinase (AMPK)-activated silent mating-type information regulation 2 homolog 1 (SIRT1).

Conclusions:

• Gastrointestinal digestion significantly enhanced the anti-inflammatory efficacy of crude onion peel extract in intestinal cells.
• Onion peel consumption may offer tangible benefits for human intestinal inflammation.
• Onion peel polyphenols represent a promising avenue for therapeutic applications derived from food byproducts.