The effects of patterned calorie-restricted diets on mammary tumor incidence and plasma endothelin levels in DMBA-treated rats.
Chronic caloric restriction has been shown to inhibit mammary tumor promotion in the 7,12-dimethyl-benz[a]anthracene (DMBA) rat mammary tumor model. The objectives of this study were to determine (i) the effects of chronic caloric cycling (yo-yo dieting) on mammary tumor promotion by high fat diets and (ii) the effect of three dietary regimens +/- superimposed mammary tumor burden on plasma endothelin-1,2 (ET) levels. Female Sprague-Dawley rats were treated with DMBA (5 mg/rat) and divided into three dietary groups: ad libitum (AL) (containing 15% corn oil); 40% calorie restricted (CR) (containing 20% corn oil so consumption of fat was equivalent between AL and CR); a calorie cycled (CC) group fed alternatively AL and CR diets each 48 h period. After 10 weeks, tumor incidences were: AL, 63%; CR, 27%; CC, 57% (AL versus CR, P < 0.05; CC versus CR, P < 0.05; AL versus CC, NSD). ET levels (pg/ml plasma) were: AL, 16.0 +/- 6.54; CR, 32.31 +/- 0.34; CC, 23.44 +/- 5.04 (AL versus CR, P < 0.01; CC versus CR, P < 0.01; AL versus CC, P < 0.05). Plasma ET levels were independent of tumor incidence and tumor burden, but plasma ET levels were significantly increased in rats with a prior history of calorie restriction. As expected, maintained caloric restriction reduced mammary tumor incidence but intermittent caloric restriction (caloric cycling or yo-yo dieting) was without similar benefit.
Mehta
R S
RS
Department of Pharmacology and Toxicology, College of Pharmacy, University of Georgia, Athens 30602-2356.
Harris
S R
SR
Gunnett
C A
CA
Bunce
O R
OR
Hartle
D K
DK
D015127:9,10-Dimethyl-1,2-benzanthracene; D000230:Adenocarcinoma / Q000097:blood* / Q000139:chemically induced / Q000209:etiology*; D000818:Animals; D001835:Body Weight / Q000502:physiology; D003043:Cocarcinogenesis; D004032:Diet; D004041:Dietary Fats / Q000009:adverse effects; D016232:Endothelins / Q000097:blood*; D002149:Energy Intake / Q000502:physiology*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000097:blood* / Q000139:chemically induced / Q000209:etiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004041:Dietary Fats; D016232:Endothelins; D015127:9,10-Dimethyl-1,2-benzanthracene