Search

Obesity contributes to physical comorbidities and mental health consequences. We explored whether physical activity could influence more than metabolic regulation and result in psychological benefits through the brain-gut microbiome (BGM) system in a population with high BMI. Fecal samples were obtained for 16 s rRNA profiling and fecal metabolomics, along with psychological and physical activity questionnaires. Whole brain resting-state functional MRI was acquired, and brain connectivity metrics were calculated. Higher physical activity was significantly associated with increased connectivity in inhibitory appetite control brain regions, while lower physical activity was associated with increased emotional regulation network connections. Higher physical activity was also associated with microbiome and metabolite signatures protective towards mental health and metabolic derangements. The greater resilience and coping, and lower levels of food addiction seen with higher physical activity, may be explained by BGM system differences. These novel findings provide an emphasis on the psychological and resilience benefits of physical activity, beyond metabolic regulation and these influences seem to be related to BGM interactions.

The prevalence of obesity has risen to its highest values over the last two decades. While many studies have either shown brain or microbiome connections to obesity, few have attempted to analyze the brain-gut-microbiome relationship in a large cohort adjusting for cofounders. Therefore, we aim to explore the connection of the brain-gut-microbiome axis to obesity controlling for such cofounders as sex, race, and diet. Whole brain resting state functional MRI was acquired, and connectivity and brain network properties were calculated. Fecal samples were obtained from 287 obese and non-obese participants (males n = 99, females n = 198) for 16s rRNA profiling and fecal metabolites, along with a validated dietary questionnaire. Obesity was associated with alterations in the brain's reward network (nucleus accumbens, brainstem). Microbial diversity (p = .03) and composition (p = .03) differed by obesity independent of sex, race, or diet. Obesity was associated with an increase in Prevotella/Bacteroides (P/B) ratio and a decrease in fecal tryptophan (p = .02). P/B ratio was positively correlated to nucleus accumbens centrality (p = .03) and negatively correlated to fecal tryptophan (p = .004). Being Hispanic, eating a standard American diet, having a high Prevotella/Bacteroides ratio, and a high nucleus accumbens centrality were all independent risk factors for obesity. There are obesity-related signatures in the BGM-axis independent of sex, race, and diet. Race, diet, P/B ratio and increased nucleus accumbens centrality were independent risk factors for obesity. P/B ratio was inversely related to fecal tryptophan, a metabolite related to serotonin biosynthesis, and positively related to nucleus accumbens centrality, a region central to the brain's reward center. These findings may expand the field of therapies for obesity through novel pathways directed at the BGM axis.

Shrimp (Litopenaeus vannamei) were provided access to sea urchin (Lytechinus variegatus) egesta to investigate whether fresh egesta (containing an active microbiome) consumed alone or in combination with a commercial shrimp feed could influence growth, feed conversion, body composition, and survival of L. vannamei in co-culture. In an initial experiment conducted for 8 wk, shrimp were proffered a full or reduced ration (100%, 60%, and 20%) of commercial shrimp feed with or without access to sea urchin egesta serving as a source of supplemental nutrients and presumptive probiotics. Individual weight gain of shrimp provided sea urchin egesta only (10.37 [+ or -] 0.35 g) did not differ significantly from that of shrimp proffered a full ration of feed (9.46 [+ or -] 0.39 g) despite significant compositional differences. Consumption of sea urchin egesta combined with commercial shrimp feed resulted in significantly greater weight gain of shrimp when compared with shrimp proffered the same level of commercial shrimp feed only. The largest weight gains of shrimp were found for those groups fed rations of 60% and 100% and had access to egesta (14.09 [+ or -] 0.75 g and 14.72 [+ or -] 0.68 g, respectively). In the next experiment, shrimp were stocked at different densities (approximately 23, 45, 68, and 90 individuals [m.sup.-2]) and were not proffered feed directly. All replicates were provided access to fresh sea urchin egesta produced by four urchins that were fed at a daily rate of 3% of the total initial group weight (140.4 [+ or -] 0.7 g) for 8 wk. The largest individual weight gain was found in the lowest density treatment (6.55 [+ or -] 0.38 g). Harvested biomass significantly increased as density increased, except for the highest density treatment. These results indicate that sea urchin egesta may provide some growth enhancement factor(s) to shrimp when proffered in conjunction with a commercial diet, and at a certain density of shrimp sea urchin egesta may actually serve as a nutritionally complete diet. KEY WORDS: Lytechinus variegatus, Litopenaeus vannamei, co-culture, egesta, integrated aquaculture, sea urchin, shrimp, INTRODUCTION A previous study (Jensen et al. 2018) suggested that fresh egesta (fecal pellets) produced by sea urchins (Lytechinus variegatus) served as a sufficient source of nutrition for cocultured Litopenaeus [...]