Effect of moderate caloric restriction and/or weight cycling on mammary tumor incidence and latency in MMTV-Neu female mice.
Recently, we reported that intermittent caloric restriction-refeeding reduces mammary tumor (MT) incidence and extends latency in murine mammary tumor virus (MMTV)-transforming growth factor (TGF)-a mice to a greater extent than does chronic caloric restriction. Here, this same weight-cycling protocol was applied to MMTV-Neu female mice, which develop MTs at a much younger age than do TGF-a mice. This study consisted of three experimental groups: mice fed an AIN-93M diet ad libitum, mice intermittently fed an AIN-93 modified diet (2-fold increase in protein, fat, vitamins, and minerals) at 50% of the amount fed to the ad libitum-fed mice for 3-wk intervals and then fed an AIN-93M diet ad libitum for 3-wk intervals, and mice chronically restricted, pair fed to the intermittently restricted mice by feeding 2:1 mixtures of AIN-93M-AIN-93 modified diets for each 6-wk feeding interval. Mice were euthanized when MTs reached a length of 20 mm or at 80 wk of age. Cumulative caloric intake was 10% lower (not significant) for intermittently restricted mice and 16% lower (P < 0.05) for chronically restricted mice than for ad libitum-fed mice. Final body weights were significantly different as follows: ad libitum-fed > intermittently restricted > chronically restricted. Fat pad weights were greater in ad libitum-fed than in intermittently restricted and chronically restricted mice. MT incidence of ad libitum-fed mice was 37% compared with 22% for intermittently restricted mice and 33% for chronically restricted mice (not significant). There were no differences in MT weight or number among the groups. These results indicate that intermittent caloric restriction-refeeding provides a moderate protective effect, whereas chronic caloric restriction provides no significant protection against MT development in transgenic Neu mice.
Hormel Institute, University of Minnesota, Austin, MN 55912, USA.
Kristin A
KA
Pape-Ansorge
Joseph P
JP
Grande
Trace A
TA
Christensen
Nita J
NJ
Maihle
Margot P
MP
Cleary
D000230:Adenocarcinoma / Q000453:epidemiology* / Q000209:etiology*; D017677:Age Distribution; D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000502:physiology*; D031204:Caloric Restriction; D004195:Disease Models, Animal; D004435:Eating / Q000502:physiology; D005260:Female; D015994:Incidence; D008325:Mammary Neoplasms, Experimental / Q000453:epidemiology* / Q000209:etiology*; D008324:Mammary Tumor Virus, Mouse / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D017735:Virus Latency / Q000502:physiology*