Abstract C042: Cultivating the gut microbiome by eating walnuts to slow cancer cachexia weight loss
Authors: Chang Hsiao-Man 
Published: August 2020

Abstract
Cancer disparities are associated with racial/ethnic minority groups. Due to socioeconomic status or geographical location, many of these groups consume low-quality diets that lack plant-derived foods. Diets lacking in fruits and vegetables are linked to tumor formation and progression. Once a tumor develops, more than 50% of cancer patients may experience cachexia, the involuntary loss of body weight that severely impacts cancer prognosis and therapy. Currently, no medical interventions can reverse cachexia, but alleviating this syndrome would lead to favorable outcomes during cancer treatment. Our lab focuses on diet as a potential therapy to slow the development of cachexia. Walnuts are known to slow tumor growth in genetically programmed mice. In a pilot study, walnuts were found to preserve weight during the tumor-bearing precachectic phase in rats. A possible area where the weight-preservative effects of walnuts may be observed is in the gut microbiome. Since our lab previously observed significant gut microbiota changes of the non-tumor-bearing rats on walnut diets, the aim of this investigation was to determine the impact of walnuts on the gut microbiome of tumor-bearing cachectic rats. We hypothesized that walnuts would significantly and favorably change the gut microbiome in cachectic tumor-bearing animals, providing a potential mechanism for the weight gain. To test our hypothesis, male Fischer 344 rats were placed on a walnut diet or control diet for three weeks. The control diet replaced the fat, protein, carbohydrate, and fiber contents of the walnut diet with corn oil, casein, corn starch, and alphacel fiber, respectively, allowing the presence of walnuts to be the only testing factor. The Ward colon carcinoma was then subcutaneously implanted on rats' left hind flank. The rats were kept on the walnut and/or control diet as tumor-driven cachexia developed. Fecal matter was collected from the rats upon sacrifice, and 16srDNA was sequenced to elucidate specific microbial communities. Rats on the walnut diet had the greatest weight preservation. Changes in the gut microbiome via the consumption of walnuts were evident through measures of diversity, relative abundance, and metabolic pathways at the family level. Compared to the control diet, the walnut diets led to a greater diversity and separation of the gut microbial communities. Walnut diets also significantly altered the relative abundances of Prevotellaceae and Desulfovibrionaceae (p-value &lt; 0.05) at the family taxa level. Lastly, the functional metagenomic data revealed a greater prevalence of metabolic pathways for plant-pathogen interaction, flagellar assembly, bacterial chemotaxis, and ABC transports in rats on the walnut diet. In summary, we conclude that walnut consumption alters the gut microbial community, suggesting a potential mechanism by which walnuts may preserve weight. Increasing walnut consumption may be one way to preserve body weight in racial/ethnic minorities experiencing cancer cachexia.
Citation Format: Hsiao-Man Chang. Cultivating the gut microbiome by eating walnuts to slow cancer cachexia weight loss [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C042.