title: Changes in insulin resistance indicators, IGFs, and adipokines in a year-long trial of aerobic exercise in postmenopausal women.
abstract: Physical activity is a known modifiable lifestyle means for reducing postmenopausal breast cancer risk, but the biologic mechanisms are not well understood. Metabolic factors may be involved. In this study, we aimed to determine the effects of exercise on insulin resistance (IR) indicators, IGF1, and adipokines in postmenopausal women. The Alberta Physical Activity and Breast Cancer Prevention Trial was a two-armed randomized controlled trial in postmenopausal, inactive, cancer-free women. A year-long aerobic exercise intervention of 225  min/week (n=160) was compared with a control group asked to maintain usual activity levels (n=160). Baseline, 6- and 12-month serum levels of insulin, glucose, IGF1, IGF-binding protein 3 (IGFBP3), adiponectin, and leptin were assayed, and after data collection, homeostasis model assessment of IR (HOMA-IR) scores were calculated. Intention-to-treat analyses were performed using linear mixed models. The treatment effect ratio (TER) of exercisers to controls was calculated. Data were available on 308 (96.3%) women at 6 months and 310 (96.9%) women at 12 months. Across the study period, statistically significant reductions in insulin (TER=0.87, 95% confidence interval (95% CI)=0.81-0.93), HOMA-IR (TER=0.86, 95% CI=0.80-0.93), and leptin (TER=0.82, 95% CI=0.78-0.87), and an increase in the adiponectin/leptin ratio (TER=1.21, 95% CI=1.13-1.28) were observed in the exercise group compared with the control group. No significant differences were observed for glucose, IGF1, IGFBP3, adiponectin or the IGF1/IGFBP3 ratio. Previously inactive postmenopausal women who engaged in a moderate-to-vigorous intensity exercise program experienced changes in insulin, HOMA-IR, leptin, and adiponectin/leptin that might decrease the risk for postmenopausal breast cancer.
authors.affiliation: Department of Population Health Research, Alberta Health Services-Cancer Care, Calgary, Alberta, Canada T2N 4N2. christine.friedenreich@albertahealthservices.ca
authors.forename: Christine M
authors.initials: CM
authors.lastname: Friedenreich
authors.forename: Heather K
authors.initials: HK
authors.lastname: Neilson
authors.forename: Christy G
authors.initials: CG
authors.lastname: Woolcott
authors.forename: Anne
authors.initials: A
authors.lastname: McTiernan
authors.forename: Qinggang
authors.initials: Q
authors.lastname: Wang
authors.forename: Rachel
authors.initials: R
authors.lastname: Ballard-Barbash
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Jones
authors.forename: Frank Z
authors.initials: FZ
authors.lastname: Stanczyk
authors.forename: Rollin F
authors.initials: RF
authors.lastname: Brant
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yasui
authors.forename: Melinda L
authors.initials: ML
authors.lastname: Irwin
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Campbell
authors.forename: Margaret L
authors.initials: ML
authors.lastname: McNeely
authors.forename: Kristina H
authors.initials: KH
authors.lastname: Karvinen
authors.forename: Kerry S
authors.initials: KS
authors.lastname: Courneya
mesh_terms: D054392:Adipokines / Q000097:blood / Q000378:metabolism*; D000368:Aged; D015415:Biomarkers / Q000097:blood / Q000378:metabolism*; D001943:Breast Neoplasms / Q000097:blood / Q000378:metabolism / Q000517:prevention & control; D002277:Carcinoma / Q000097:blood / Q000378:metabolism / Q000517:prevention & control; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008875:Middle Aged; D017698:Postmenopause / Q000097:blood / Q000378:metabolism*; D013002:Somatomedins / Q000032:analysis / Q000378:metabolism*; D013997:Time Factors
chemical_list: D054392:Adipokines; D015415:Biomarkers; D013002:Somatomedins