Abstract 2316: Fasting protects mice from lethal DNA damage by promoting small intestinal stem cell survival and by inhibiting acute inflammation
Authors: Tinkum Kelsey L. , Stemler Kristina M. , White Lynn S. , Loza Andrew J. , Jeter-Jones Sabrina , Michalski Basia M. , Kuzmicki Catherine E. , Pless Robert , Stappenbeck Thaddeus , Piwnica-Worms David , Piwnica-Worms Helen 
Published: August 2015

Abstract
Short-term fasting in mice has been shown to increase survival from lethal doses of chemotherapy; however, the route of protection in these animals is unknown. In this study we demonstrate that fasting prior to chemotherapy protects small intestinal (SI) stem cells in mice exposed to high dose etoposide. Histologic and in vitro crypt culture analyses show nearly all SI stem cells were lost when fed mice were treated with high dose etoposide but high numbers of stem cells survived when fasted mice were similarly treated. In fasted mice treated with etoposide, multiple stem cell populations marked by Lgr5, Bmi1 or HopX expression contributed to maintaining small intestinal architecture and function as identified by lineage tracing analysis. We found fasting did not impact plasma etoposide clearance; consequently, etoposide treatment induced similar levels of DNA double strand breaks (DSBs) in stem cells of both fed and fasted mice through γH2AX immunofluorescence staining. Expression analysis of enriched populations of SI stem/progenitor cells isolated from etoposide-treated treated mice revealed that DNA repair and DNA damage response genes were elevated in response to fasting. Expression results correlated with faster resolution of DNA DSBs, as measured by loss of γH2AX staining and with reduced apoptosis, as measured by cleaved caspase-3 staining in stem/progenitors cells of fasted mice. Strikingly, large numbers of neutrophils infiltrated into the SI of fed mice within 48 h of etoposide treatment resulting in complete separation of crypts from their corresponding villi. By contrast, inflammatory cell infiltrates were not observed in the SI of fasted mice following similar treatment. These results suggest that fasting preserves small intestinal architecture and barrier function by increasing DNA repair capacity in SI stem cells and by preventing pro-inflammatory responses following exposure to high dose chemotherapy. Fasting may therefore be useful as a prophylactic treatment to reduce host toxicity in patients undergoing dose intensive chemotherapy. Future work will focus on delineating the molecular mechanism of fasting-induced SI stem cell protection.
Citation Format: Kelsey L. Tinkum, Kristina M. Stemler, Lynn S. White, Andrew J. Loza, Sabrina Jeter-Jones, Basia M. Michalski, Catherine E. Kuzmicki, Robert Pless, Thaddeus Stappenbeck, David Piwnica-Worms, Helen Piwnica-Worms. Fasting protects mice from lethal DNA damage by promoting small intestinal stem cell survival and by inhibiting acute inflammation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2316. doi:10.1158/1538-7445.AM2015-2316