title: Enhancement of development of azoxymethane-induced colonic premalignant lesions in C57BL/KsJ-db/db mice.
abstract: Epidemiological studies have shown that obesity and diabetes mellitus may be risk factors for colon cancer. However, the underlying mechanisms of how these chronic diseases promote colon carcinogenesis remain unknown. C57BL/KsJ-db/db mice have obese and diabetic phenotypes because of disruption of the leptin receptor. The present study was designed to investigate whether development of azoxymethane (AOM)-induced dysplastic and early neoplastic (premalignant) lesions of the colon is modulated in db/db mice. Homozygous db/db mice, heterozygous db/+ mice and littermate controls (+/+) were injected with AOM under food restriction ( approximately 10.8 kcal/mouse/day) and killed 5 weeks after the carcinogen treatment. Their colons were assessed for premalignant lesions induced by AOM. We found a significant increase in the multiplicity of the total premalignant lesions in db/db mice when compared with db/+ or +/+ mice. Phenotypically, serum leptin and insulin levels in db/db mice were significantly higher than those in db/+ or +/+ mice, whereas the body weights and glucose levels in blood of db/db, db/+ and +/+ mice were comparable. In addition, immunostaining of the leptin receptor and insulin-like growth factor-I receptor showed up-regulation of these protein levels specifically in the lesions. Our data indicate that development of AOM-induced premalignant lesions is enhanced in db/db mice with hyperleptinemia and hyperinsulinemia. The results have important implications for further exploration of the possible underlying events that affect the positive association between colon cancer and chronic diseases (obesity and diabetes).
authors.affiliation: Department of Tumor Pathology, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu 500-8705, Japan. yhirose@cc.gifu-u.ac.jp
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Hirose
authors.forename: Kazuya
authors.initials: K
authors.lastname: Hata
authors.forename: Toshiya
authors.initials: T
authors.lastname: Kuno
authors.forename: Koujiro
authors.initials: K
authors.lastname: Yoshida
authors.forename: Keiko
authors.initials: K
authors.lastname: Sakata
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yamada
authors.forename: Takuji
authors.initials: T
authors.lastname: Tanaka
authors.forename: Bandaru S
authors.initials: BS
authors.lastname: Reddy
authors.forename: Hideki
authors.initials: H
authors.lastname: Mori
mesh_terms: D000818:Animals; D001397:Azoxymethane / Q000633:toxicity*; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D002273:Carcinogens / Q000633:toxicity*; D003110:Colonic Neoplasms / Q000139:chemically induced* / Q000473:pathology*; D003921:Diabetes Mellitus, Experimental; D006579:Heterozygote; D006720:Homozygote; D006946:Hyperinsulinism / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D015151:Immunoblotting; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009765:Obesity / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D011230:Precancerous Conditions / Q000139:chemically induced* / Q000473:pathology*; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D054411:Receptors, Leptin
chemical_list: D001786:Blood Glucose; D002273:Carcinogens; D007328:Insulin; D020738:Leptin; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D017526:Receptor, IGF Type 1; D001397:Azoxymethane