Background: Although previous studies have implicated a role for the stool microbiome in cancer cachexia, the fecal microbiome has not been previously characterized for patients with pancreatic ductal adenocarcinoma (PDAC) and cachexia treated with nutritional interventions such as enteral feeding. Methods: The PANCAX-1 (NCT02400398) prospective trial enrolled 31 cachectic advanced PDAC patients to receive jejunal tube peptide-based diet for 12 weeks who were planned for palliative chemotherapy. Out of 16 evaluable patients, 62.5% receiving enteral feeding met the primary endpoint of weight stability at 12 weeks. As part of an exploratory analysis of the PANCAX-1 trial, serial stool and blood samples were collected at 0 (C1D1), 6 (C2D1), and 12 (C3D1) weeks over the 12-week period of enteral feeding. Stool samples were analyzed using 16S v4 sequencing of the microbiome. Up to 219 plasma metabolites were analyzed by mass spectrometry and high-performance liquid chromatography. Results: A total of 29 stool samples were prospectively collected from 16 subjects with PDAC enrolled in PANCAX-1 who were evaluable for weight stability. Over 12 weeks of enteral feeding, statistically significant increases in the abundance of bacterial genera such as Veillonella (p=0.0150) and Actinomyces (p=0.0390) were observed, while there was a lower abundance of Bacteroides (p=0.0150) and Butyricicoccus (p=0.0390). Greater abundance of Veillonella and reduced Bifidobacterium at baseline were linked to greater weight stability. Plasma metabolomics in 10 subjects showed that weight unstable patients had significantly decreased levels of essential (L-histidine, L-phenylalanine) and non-essential amino acids (L-citrulline, L-tyrosine, all p<0.05) at the end of 12 weeks of enteral feeding. High stool Veillonella abundance was significantly associated with increases in the nucleotide 2-deoxycytidine 5-diphosphate and essential amino acid L-isoleucine but decreased TCA cycle metabolite alpha-ketoglutarate (all p<0.05). Conclusions: We are the first to demonstrate the feasibility of stool microbiome profiling and plasma metabolomics in paired stool and plasma samples from a prospective cohort of advanced PDAC patients on enteral feeding as their primary source of nutrition. Our findings are hypothesis-generating in that metabolites unique to weight stability and abundance of stool bacterial genera may inform future studies of anti-cachexia therapies involving enteral feeding or microbial modulation.

Opioids are highly addictive substances with a relapse rate of over 90%. While preclinical models of chronic opioid exposure exist for studying opioid dependence, none recapitulate the relapses observed in human opioid addiction. The mechanisms associated with opioid dependence, the accompanying withdrawal symptoms and the relapses that are often observed months or years after opioid dependence are poorly understood. Therefore, we developed a novel model of chronic opioid exposure whereby the level of administration is self-directed with periods of behavior acquisition, maintenance and then extinction alternating with reinstatement. This profile arguably mirrors that seen in humans, with initial opioid use followed by alternating periods of abstinence and relapse. Recent evidence suggests that dietary interventions that reduce inflammation, including omega-3 fatty acids such as docosahexaenoic acid (DHA), may reduce substance misuse liability. Using the self-directed intake model, we characterize the observed profile of opioid use and demonstrate that a diet enriched in polyunsaturated fat acids (PUFAs) ameliorates oxycodone-seeking behaviors in the absence of drug availability and reduces anxiety. Guided by the major role gut microbiota have on brain function, neuropathology, and anxiety, we profile the microbiome composition and the effects of chronic opioid exposure and DHA supplementation. We demonstrate that withdrawal of opioids led to a significant depletion in specific microbiota genera whereas DHA supplementation increased microbial richness, phylogenetic diversity, and evenness. Lastly, we examined the activation state of microglia in the striatum and found that DHA supplementation reduced the basal activation state of microglia. These preclinical data suggest that a diet enriched in PUFAs could be used as a treatment to alleviate anxiety induced opioid-seeking behavior and relapse in human opioid addiction.