AUTHOR=Moreira Veridiana Mota , da Silva Franco Claudinéia Conationi , Prates Kelly Valério , Gomes Rodrigo Mello , de Moraes Ana Maria Praxedes , Ribeiro Tatiane Aparecida , Martins Isabela Peixoto , Previate Carina , Pavanello Audrei , Matiusso Camila Cristina Ianoni , Almeida Douglas Lopes , Francisco Flávio Andrade , Malta Ananda , Tófolo Laize Peron , da Silva Silveira Sandra , Saavedra Lucas Paulo Jacinto , Machado Katia , da Silva Paulo Henrique Olivieri , Fabrício Gabriel S. , Palma-Rigo Kesia , de Souza Helenir Medri , de Fátima Silva Flaviane , Biazi Giuliana Regina , Pereira Taís Susane , Vieira Elaine , Miranda Rosiane Aparecida , de Oliveira Júlio Cezar , da Costa Lima Luiz Delmar , Rinaldi Wilson , Ravanelli Maria Ida , de Freitas Mathias Paulo Cezar TITLE=Aerobic Exercise Training Attenuates Tumor Growth and Reduces Insulin Secretion in Walker 256 Tumor-Bearing Rats JOURNAL=Frontiers in Physiology VOLUME=9 YEAR=2018 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.00465 DOI=10.3389/fphys.2018.00465 ISSN=1664-042X ABSTRACT=

Aerobic exercise training can improve insulin sensitivity in many tissues; however, the relationship among exercise, insulin, and cancer cell growth is unclear. We tested the hypothesis that aerobic exercise training begun during adolescence can attenuate Walker 256 tumor growth in adult rats and alter insulin secretion. Thirty-day-old male Wistar rats engaged in treadmill running for 8 weeks, 3 days/week, 44 min/day, at 55–65% VO2max until they were 90 days old (TC, Trained Control). An equivalently aged group was kept inactive during the same period (SC, Sedentary Control). Then, half the animals of the SC and TC groups were reserved as the control condition and the other half were inoculated with Walker 256 cancer cells, yielding two additional groups (Sedentary Walker and Trained Walker). Zero mortalities were observed in tumor-bearing rats. Body weight (BW), food intake, plasma glucose, insulin levels, and peripheral insulin sensitivity were analyzed before and after tumor cell inoculation. We also evaluated tumor growth, metastasis and cachexia. Isolated pancreatic islets secretory activity was analyzed. In addition, we evaluated mechanic sensibility. Our results showed improved physical performance according to the final workload and VO2max and reduced BW in trained rats at the end of the running protocol. Chronic adaptation to the aerobic exercise training decreased tumor weight, cachexia and metastasis and were associated with low glucose and insulin levels and high insulin sensitivity before and after tumor cell inoculation. Aerobic exercise started at young age also reduced pancreatic islet insulin content and insulin secretion in response to a glucose stimulus, without impairing islet morphology in trained rats. Walker 256 tumor-bearing sedentary rats also presented reduced pancreatic islet insulin content, without changing insulin secretion through isolated pancreatic islets. The mechanical sensitivity test indicated that aerobic exercise training did not cause injury or trigger inflammatory processes prior to tumor cell inoculation. Taken together, the current study suggests that aerobic exercise training applied during adolescence may mitigate tumor growth and related disorders in Walker 256 tumor-bearing adult rats. Improved insulin sensibility, lower glucose and insulin levels and/or reduced insulin secretion stimulated by glucose may be implicated in this tumor attenuation.