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Effects of prescribed aerobic exercise volume on physical activity and sedentary time in postmenopausal women: a randomized controlled trial.
McNeil, J, Farris, MS, Ruan, Y, Merry, H, Lynch, BM, Matthews, CE, Courneya, KS, Friedenreich, CM
The international journal of behavioral nutrition and physical activity. 2018;15(1):27
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Physical activity has emerged as an important lifestyle factor for primary prevention of numerous diseases, including postmenopausal breast cancer. The aim of this two-armed randomised controlled study was to examine the effects of a year-long prescribed aerobic exercise programme on physical activity levels and sedentary time in postmenopausal women. A total of 400 postmenopausal women aged between 50 – 74 years were randomised to one of the two groups; moderate (150min of exercise/week) or high (300min of exercise/week) volumes of aerobic exercise interventions. Results showed increased activity time in total and moderate-vigorous intensity/recreational physical activity, coupled with decreased sedentary time, in response to both volumes of prescribed physical activity. However, results also showed that physical activity and sedentary time returned to baseline following study completion. Authors conclude that total physical activity time can be increased with greater volumes of prescribed exercise. Furthermore, additional support and resources may be beneficial to promote the maintenance of increased physical activity and reduced sedentary time in the long-term.
Abstract
BACKGROUND Physical activity has emerged as an important lifestyle factor for primary prevention of numerous diseases, including postmenopausal breast cancer. No study to date has assessed the acute and long-term effects of year-long aerobic exercise programs differing in prescribed exercise volume on physical activity and sedentary time in postmenopausal women. Therefore, we aimed to examine the effects of two moderate-vigorous intensity exercise doses on total, light and moderate-vigorous intensity physical activity times, and sedentary time in postmenopausal women during the year-long intervention and one year later. METHODS The Breast Cancer and Exercise Trial in Alberta (BETA) was a two-center, two-arm, 12-month randomized controlled trial that included 400 previously inactive postmenopausal women randomized to either 150 (MODERATE) or 300 (HIGH) minutes/week of aerobic exercise. Physical activity and sedentary time were assessed at baseline, 6- (intervention mid-point), 12- (prior to end of intervention) and 24-months (follow-up) with waist-mounted accelerometers (Actigraph GTX3®). Self-reported activity and sedentary time at baseline, 12- and 24-months was also assessed (Past Year Total Physical Activity Questionnaire and SIT-Q). Intention-to-treat analyses were conducted using linear mixed models and adjusted for baseline variables. RESULTS Both physical activity interventions led to increases in objective and subjective measures of total and moderate-vigorous intensity/recreational physical activity time, coupled with decreases in sedentary time, at 6- and 12-months compared to baseline. Additionally, greater increases in accelerometry-derived total physical activity time at 6- and 12-months, and self-reported recreational activity time at 12-months, compared to baseline were noted in the HIGH versus MODERATE groups. Decreases in total, light and moderate-vigorous intensity physical activity time, and an increase in sedentary time, in both groups were noted at 24-months compared to 12-months. A decrease in light intensity physical activity time in both groups at 24-months compared to baseline was also noted. CONCLUSION These findings have important health implications, suggesting that total physical activity time can be increased with greater volumes of prescribed exercise, but that additional support and resources could be used to promote the maintenance of these high levels of aerobic exercise participation following study completion. TRIAL REGISTRATION clinicaltrials.gov identifier: NCT01435005 (BETA Trial). Registred September 15th 2011 (retrospectively registered).
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In a randomized trial in prostate cancer patients, dietary protein restriction modifies markers of leptin and insulin signaling in plasma extracellular vesicles.
Eitan, E, Tosti, V, Suire, CN, Cava, E, Berkowitz, S, Bertozzi, B, Raefsky, SM, Veronese, N, Spangler, R, Spelta, F, et al
Aging cell. 2017;16(6):1430-1433
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Obesity and insulin resistance are associated with accelerated aging and increased risk of many age-related diseases. The risk of many cancers, including prostate cancer, increases with age and being overweight further increases the risk. The aim of the study is to investigate the inhibition of tumour growth through the effect of protein restriction diets and hence, levels of circulating amino acids. The participants of the study were men (n=38) with prostate cancer awaiting prostatectomy surgery. Most of the subjects were overweight with a BMI of 30.45 ± 5.8. They were randomly assigned to either a control diet or a protein restricted diet. In comparison to the control diet, results show that protein restriction increased the levels of receptors (a protein molecule that receives chemical signals from outside a cell) responsible of leptin, the hormone that controls hunger. The results also show that protein restriction can improve the body’s sensitivity to the effects of the insulin in neurons (a nerve cell specialised to transmit information throughout the body). Authors conclude that protein restriction can counteract major age-related diseases.
Abstract
Obesity, metabolic syndrome, and hyperleptinemia are associated with aging and age-associated diseases including prostate cancer. One experimental approach to inhibit tumor growth is to reduce dietary protein intake and hence levels of circulating amino acids. Dietary protein restriction (PR) increases insulin sensitivity and suppresses prostate cancer cell tumor growth in animal models, providing a rationale for clinical trials. We sought to demonstrate that biomarkers derived from plasma extracellular vesicles (EVs) reflect systemic leptin and insulin signaling and respond to dietary interventions. We studied plasma samples from men with prostate cancer awaiting prostatectomy who participated in a randomized trial of one month of PR or control diet. We found increased levels of leptin receptor in the PR group in total plasma EVs and in a subpopulation of plasma EVs expressing the neuronal marker L1CAM. Protein restriction also shifted the phosphorylation status of the insulin receptor signal transducer protein IRS1 in L1CAM+ EVs in a manner suggestive of improved insulin sensitivity. Dietary PR modifies indicators of leptin and insulin signaling in circulating EVs. These findings are consistent with improved insulin and leptin sensitivity in response to PR and open a new window for following physiologic responses to dietary interventions in humans.
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A prospective study of meat and meat mutagens and prostate cancer risk.
Cross, AJ, Peters, U, Kirsh, VA, Andriole, GL, Reding, D, Hayes, RB, Sinha, R
Cancer research. 2005;65(24):11779-84
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Meat cooked at high temperatures is a source of carcinogens (heterocyclic amines and polycyclic aromatic hydrocarbons). The formation of these substances depends on the meat type, and is highest in meats cooked by high-temperature cooking methods. The aim of the study was to determine whether meat intake or meat-related mutagens was associated with increased prostate cancer risk. This was a prospective cohort study of 29,361 men aged between 55 and 74. Results show that a consumption of more than 10 g per day of very well done meat was associated with a 42% increased risk for prostate cancer and a 69% increased risk for incident disease. A high intake of the carcinogens under study was associated with a 22% increased risk for prostate cancer and a 28% increased risk for incident disease. The study concluded that there is a positive association between prostate cancer risk and a high intake of very well done meat.
Abstract
High-temperature cooked meat contains heterocyclic amines, including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and polycyclic aromatic hydrocarbons, such as benzo(a)pyrene (BaP). In rodents, a high intake of PhIP induces prostate tumors. We prospectively investigated the association between meat and meat mutagens, specifically PhIP, and prostate cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Diet was assessed using a 137-item food frequency questionnaire and a detailed meat-cooking questionnaire linked to a database for BaP and the heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5-b]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx), and PhIP. During follow-up, we ascertained a total of 1,338 prostate cancer cases among 29,361 men; of these, 868 were incident cases (diagnosed after the first year of follow-up) and 520 were advanced cases (stage III or IV or a Gleason score of > or =7). Total, red, or white meat intake was not associated with prostate cancer risk. More than 10 g/d of very well done meat, compared with no consumption, was associated with a 1.4-fold increased risk of prostate cancer [95% confidence interval (95% CI), 1.05-1.92] and a 1.7-fold increased risk (95% CI, 1.19-2.40) of incident disease. Although there was no association with MeIQx and DiMeIQx, the highest quintile of PhIP was associated with a 1.2-fold increased risk of prostate cancer (95% CI, 1.01-1.48) and a 1.3-fold increased risk of incident disease (95% CI, 1.01-1.61). In conclusion, very well done meat was positively associated with prostate cancer risk. In addition, this study lends epidemiologic support to the animal studies, which have implicated PhIP as a prostate carcinogen.