Randomized controlled trial of aerobic exercise on insulin and insulin-like growth factors in breast cancer survivors: the Yale Exercise and Survivorship study.
BACKGROUND
High insulin and insulin-like growth factor-I (IGF-I) levels may be associated with an increased breast cancer risk and/or death. Given the need to identify modifiable factors that decrease insulin, IGF-I, and breast cancer risk and death, we investigated the effects of a 6-month randomized controlled aerobic exercise intervention versus usual care on fasting insulin, IGF-I, and its binding protein (IGFBP-3) in postmenopausal breast cancer survivors.


METHODS
Seventy-five postmenopausal breast cancer survivors were identified from the Yale-New Haven Hospital Tumor Registry and randomly assigned to an exercise (n = 37) or usual care (n = 38) group. The exercise group participated in 150 minutes per week of moderate-intensity aerobic exercise. The usual care group was instructed to maintain their current physical activity level. A fasting blood sample was collected on each study participant at baseline and 6 months. Blood levels of insulin and IGF were measured with ELISA.


RESULTS
On average, exercisers increased aerobic exercise by 129 minutes per week compared with 45 minutes per week among usual care participants (P < 0.001). Women randomized to exercise experienced decreases in insulin, IGF-I, and IGFBP-3, whereas women randomized to usual care had increases in these hormones. Between-group differences in insulin, IGF-I, and IGFBP-3 were 20.7% (P = 0.089), 8.9% (P = 0.026), and 7.9% (P = 0.006), respectively.


CONCLUSIONS
Moderate-intensity aerobic exercise, such as brisk walking, decreases IGF-I and IGFBP-3. The exercise-induced decreases in IGF may mediate the observed association between higher levels of physical activity and improved survival in women diagnosed with breast cancer.
Irwin
Melinda L
ML
Department of Epidemiology and Public Health, Yale School of Medicine, P.O. Box 208034, New Haven, CT 06520-8034, USA. melinda.irwin@yale.edu
Varma
Katie
K
Alvarez-Reeves
Marty
M
Cadmus
Lisa
L
Wiley
Andrew
A
Chung
Gina G
GG
Dipietro
Loretta
L
Mayne
Susan T
ST
Yu
Herbert
H
D015502:Absorptiometry, Photon; D000886:Anthropometry; D015519:Bone Density; D001943:Breast Neoplasms / Q000097:blood*; D016009:Chi-Square Distribution; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D016014:Linear Models; D008875:Middle Aged; D012306:Risk; D013002:Somatomedins / Q000378:metabolism*; D011795:Surveys and Questionnaires; D017741:Survivors
D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D013002:Somatomedins