title: Cyclin-dependent kinase inhibitor, p21WAF1/CIP1, is involved in adipocyte differentiation and hypertrophy, linking to obesity, and insulin resistance.
abstract: Both adipocyte hyperplasia and hypertrophy are determinant factors for adipocyte differentiation during the development of obesity. p21(WAF1/CIP1), a cyclin-dependent kinase inhibitor, is induced during adipocyte differentiation; however, its precise contribution to this process is unknown. Using both in vitro and in vivo systems, we show that p21 is crucial for maintaining adipocyte hypertrophy and obesity-induced insulin resistance. The absence of p21 in 3T3-L1 fibroblasts by RNA-mediated interference knockdown or in embryonic fibroblasts from p21(-/-) mice impaired adipocyte differentiation, resulting in smaller adipocytes. Despite normal adipose tissue mass on a normal diet, p21(-/-) mice fed high energy diets had reduced adipose tissue mass and adipocyte size accompanied by a marked improvement in insulin sensitivity. Knockdown of p21 in enlarged epididymal fat of diet-induced obese mice and also in fully differentiated 3T3-L1 adipocytes caused vigorous apoptosis by activating p53. Thus, p21 is involved in both adipocyte differentiation and in protecting hypertrophied adipocytes against apoptosis. Via both of these mechanisms, p21 promotes adipose tissue expansion during high fat diet feeding, leading to increased downstream pathophysiological consequences such as insulin resistance.
authors.affiliation: Department of Internal Medicine (Metabolism and Endocrinology) and Graduate School of Comprehensive Human Sciences and Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Inoue
authors.forename: Naoya
authors.initials: N
authors.lastname: Yahagi
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Mayumi
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Watanabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsuzaka
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Takeuchi
authors.forename: Kazuto
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Takahashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Suzuki
authors.forename: Alyssa H
authors.initials: AH
authors.lastname: Hasty
authors.forename: Hideo
authors.initials: H
authors.lastname: Toyoshima
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Yamada
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shimano
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology*; D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism / Q000502:physiology*; D006984:Hypertrophy; D007333:Insulin Resistance; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008954:Models, Biological; D009765:Obesity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53