title: Pituitary growth hormone suppression reduces resistin expression and enhances insulin effectiveness: relationship with caloric restriction.
abstract: Caloric restriction (CR) retards various age-dependent disorders, increases lifespan, and improves insulin activity in laboratory animals. Recently, adipocytes were found to act together as an active endocrine organ that produces various hormones called adipocytokines. The peripheral and central activities of these adipocytokines have been suggested to mediate the anti-aging effects of CR. Here, we tested this notion by analyzing the effect of CR and suppression of growth hormone/insulin-like growth factor-I (GH/IGF-I) axis on the expression of resistin, adiponectin, and adipsin genes by rat white adipose tissue (WAT). We found that CR and GH/IGF-I suppression markedly downregulated resistin gene expression. We also found plasma resistin levels correlated positively with pituitary GH mRNA expression levels. Our observations suggest that CR reduces resistin expression and increases insulin effectiveness in a GH/IGF-I-dependent manner. The beneficial effects of CR and GH/IGF-I suppression appear to be mediated, at least in part, by changes in glucose metabolism that result from reductions in plasma resistin levels.
authors.affiliation: Department of Investigative Pathology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Nagasaki 852-8523, Japan. takuya@net.nagsaki-u.ac.jp
authors.forename: Takuya
authors.initials: T
authors.lastname: Chiba
authors.forename: Haruyoshi
authors.initials: H
authors.lastname: Yamaza
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Komatsu
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nakayama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fujita
authors.forename: Hiroko
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Higami
authors.forename: Isao
authors.initials: I
authors.lastname: Shimokawa
mesh_terms: D052242:Adiponectin / Q000235:genetics / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D015152:Blotting, Northern / Q000379:methods; D031204:Caloric Restriction; D011416:Complement Factor D / Q000235:genetics / Q000378:metabolism; D004032:Diet; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D013006:Growth Hormone / Q000235:genetics / Q000502:physiology*; D007333:Insulin Resistance; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D052243:Resistin / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
chemical_list: D052242:Adiponectin; D012333:RNA, Messenger; D052243:Resistin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D011416:Complement Factor D