title: Quercetin, a functional compound of onion peel, remodels white adipocytes to brown-like adipocytes.
abstract: Adipocyte browning is a promising strategy for obesity prevention. Using onion-peel-derived extracts and their bioactive compounds, we demonstrate that onion peel, a by-product of onion, can change the characteristics of white adipocytes to those of brown-like adipocytes in the white adipose tissue of mice and 3T3-L1 cells. The expression of the following brown adipose tissue-specific genes was increased in the retroperitoneal and subcutaneous adipose tissues of 0.5% onion-peel-extract-fed mice: PR domain-containing 16, peroxisome proliferator-activated receptor gamma coactivator 1α, uncoupling protein 1, fibroblast growth factor 21 and cell death-inducing DFFA-like effector. In 3T3-L1 adipocytes, onion peel extract induced the expression of brown adipose tissue-specific genes and increased the expression of carnitine palmitoyltransferase 1α. This effect was supported by decreased lipid levels and multiple small-sized lipid droplets. The ethyl acetate fraction of the onion peel extract that contained the highest proportion of hydrophobic molecules showed the same browning effect in 3T3-L1 adipocytes. A high-performance liquid chromatography analysis further identified quercetin as a functional compound in the browning effect of onion peel. The quercetin-associated browning effect was mediated in part by the activation of AMP-activated protein kinase. In summary, our study provides the first demonstration of the browning effects of onion peel and quercetin using both animal and cell models. This result indicates that onion peel has the potential to remodel the characteristics of white adipocytes to those of brown-like adipocytes.
authors.affiliation: Food and Nutritional Sciences, Department of Family and Consumer Sciences, North Carolina Agricultural and Technical State University, Greensboro, NC, 27411.
authors.forename: Sang Gil
authors.initials: SG
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC, 27157.
authors.forename: John S
authors.initials: JS
authors.lastname: Parks
authors.affiliation: Food and Nutritional Sciences, Department of Family and Consumer Sciences, North Carolina Agricultural and Technical State University, Greensboro, NC, 27411. Electronic address: hkang@ncat.edu.
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Kang
mesh_terms: D041721:3T3-L1 Cells; D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D052437:Adipocytes, Brown / Q000187:drug effects; D052438:Adipocytes, White / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D059305:Diet, High-Fat / Q000009:adverse effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019697:Onions / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D011794:Quercetin / Q000031:analogs & derivatives / Q000032:analysis / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D010936:Plant Extracts; C016527:isoquercitrin; D011794:Quercetin; D055372:AMP-Activated Protein Kinases
keywords: AMP-activated protein kinase; Browning effect; Onion peel; Quercetin; Retroperitoneal fat; Uncoupling protein 1