TY - JOUR
T1 - A surprising link between the energetics of ovariectomy-induced weight gain and mammary tumor progression in obese rats
AU - MacLean, Paul S.
AU - Giles, Erin D.
AU - Johnson, Ginger C.
AU - McDaniel, Shauntae M.
AU - Fleming-Elder, Brooke K.
AU - Gilman, Kaite A.
AU - Andrianakos, Anna G.
AU - Jackman, Matthew R.
AU - Shroyer, Kenneth R.
AU - Schedin, Pepper J.
PY - 2010/4
Y1 - 2010/4
N2 - Obesity increases the risk for postmenopausal breast cancer. We have modeled this metabolic context using female Wistar rats that differ in their polygenic predisposition for obesity under conditions of high-fat feeding and limited physical activity. At 52 days of age, rats were injected with 1-methyl-1-nitrosourea (MNU, 50 mg/kg) and placed in an obesogenic environment. At 19 weeks of age, the rats were separated into lean, mid-weight, and obese rats, based upon their weight gained during this time. The rats were ovariectomized (OVX) at ∼24 weeks of age and the change in tumor multiplicity and burden, weight gain, energy intake, tumor estrogen receptor (ER) status, and humoral metabolite and cytokine profiles were examined. The survival and growth of tumors increased in obese rats in response to OVX. OVX induced a high rate of weight gain during post-OVX weeks 1-3, compared to SHAM-operated controls. During this time, feed efficiency (mg gain/kcal intake) was lower in obese rats, and this reduced storage efficiency of ingested fuels predicted the OVX-induced changes in tumor multiplicity (r = 0.64, P < 0.001) and burden (r = 0.57, P <0.001). Tumors from obese rats contained more cells that expressed ERα, and post-OVX plasma from rats with the lowest feed efficiency had lower interleukin (IL)-2 and IL-4 levels. Our observations suggest a novel link between obesity and mammary tumor promotion that involves impaired fuel metabolism during OVX-induced weight gain. The metabolically inflexible state of obesity and its inability to appropriately respond to the OVX-induced energy imbalance provides a plausible explanation for this relationship and the emergence of obesity's impact on breast cancer risk after menopause.
AB - Obesity increases the risk for postmenopausal breast cancer. We have modeled this metabolic context using female Wistar rats that differ in their polygenic predisposition for obesity under conditions of high-fat feeding and limited physical activity. At 52 days of age, rats were injected with 1-methyl-1-nitrosourea (MNU, 50 mg/kg) and placed in an obesogenic environment. At 19 weeks of age, the rats were separated into lean, mid-weight, and obese rats, based upon their weight gained during this time. The rats were ovariectomized (OVX) at ∼24 weeks of age and the change in tumor multiplicity and burden, weight gain, energy intake, tumor estrogen receptor (ER) status, and humoral metabolite and cytokine profiles were examined. The survival and growth of tumors increased in obese rats in response to OVX. OVX induced a high rate of weight gain during post-OVX weeks 1-3, compared to SHAM-operated controls. During this time, feed efficiency (mg gain/kcal intake) was lower in obese rats, and this reduced storage efficiency of ingested fuels predicted the OVX-induced changes in tumor multiplicity (r = 0.64, P < 0.001) and burden (r = 0.57, P <0.001). Tumors from obese rats contained more cells that expressed ERα, and post-OVX plasma from rats with the lowest feed efficiency had lower interleukin (IL)-2 and IL-4 levels. Our observations suggest a novel link between obesity and mammary tumor promotion that involves impaired fuel metabolism during OVX-induced weight gain. The metabolically inflexible state of obesity and its inability to appropriately respond to the OVX-induced energy imbalance provides a plausible explanation for this relationship and the emergence of obesity's impact on breast cancer risk after menopause.
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U2 - 10.1038/oby.2009.307
DO - 10.1038/oby.2009.307
M3 - Article
C2 - 19798068
AN - SCOPUS:77950188357
SN - 1930-7381
VL - 18
SP - 696
EP - 703
JO - Obesity
JF - Obesity
IS - 4
ER -