Calorie restriction outperforms bariatric surgery in a murine model of obesity and triple-negative breast cancer

Obesity promotes triple-negative breast cancer (TNBC), and effective interventions are urgently needed to break the obesity-TNBC link. Epidemiologic studies indicate that bariatric surgery reduces TNBC risk, while evidence is limited or conflicted for weight loss via low-fat diet (LFD) or calorie restriction (CR). Using a murine model of obesity-driven TNBC, we compared the antitumor effects of vertical sleeve gastrectomy (VSG) with LFD, chronic CR, and intermittent CR. Each intervention generated weight and fat loss and suppressed tumor growth relative to obese mice (greatest suppression with CR). VSG and CR regimens exerted both similar and unique effects, as assessed using multiomics approaches, in reversing obesity-associated transcript, epigenetics, secretome, and microbiota changes and restoring antitumor immunity. Thus, in a murine model of TNBC, bariatric surgery and CR each reverse obesity-driven tumor growth via shared and distinct antitumor mechanisms, and CR is superior to VSG in reversing obesity's procancer effects.

Gut Microbial Changes Following Fecal Microbiota Transplantation for D-Lactic Acidosis in Two Children

D-lactic acidosis (D-LA) is an uncommon complication of short bowel syndrome characterized by elevated plasma D-lactate and encephalopathy. Treatments include rehydration, dietary carbohydrate restriction, and antibiotics to alter the gut microbiota. Fecal microbiota transplantation (FMT) has recently been used in children to successfully treat D-LA. We compared the clinical course and then utilized metagenomic shotgun sequencing to describe changes in the composition and function of the intestinal microbiome following FMT in 2 patients with recurrent D-LA. FMT altered the composition of the fecal microbiota in these 2 patients with recurrent D-LA, though not necessarily in a consistent manner. Importantly, microbial metabolic pathways were also impacted by FMT, which may be critical for achieving desired clinical outcomes. While sample size limits the generalizability of our results, these findings set the stage for further understanding of the role of microbes in the pathogenesis of recurrent D-LA.

Gut microbial communities from patients with anorexia nervosa do not influence body weight in recipient germ-free mice

Anorexia nervosa (AN) is a psychiatric disorder that presents with profound weight dysregulation, metabolic disturbances, and an abnormal composition of gut microbial communities. As the intestinal microbiota can influence host metabolism, the impact of enteric microbial communities from patients with AN on host weight and adiposity was investigated. Germ-free (GF) mice were colonized with fecal microbiotas from either patients with AN (n = 4) prior to inpatient treatment (AN T1, n = 50 recipient mice), the same 4 patients following clinical renourishment (AN T2, n = 53 recipient mice), or age- and sex-matched non-AN controls (n = 4 human donors; non-AN, n = 50 recipient mice). Biological and fecal microbiota data were analyzed with linear mixed-effects models. Body weight did not differ significantly between AN recipient mice (T1 and T2) and non-AN recipient mice following 4 weeks of colonization. Enteric microbiotas from recipient mice colonized with AN T1 and AN T2 fecal microbiotas were more similar to each other compared with enteric microbiotas from non-AN recipient mice. Specific bacterial families in the Actinobacteria, Bacteroidetes, and Firmicutes phyla were significantly associated with body weight, fat mass, and cecum weight irrespective of the donor group. These data suggest that body weight, fat mass, and cecum weight of colonized GF mice are associated with human fecal microbes and independent of donor AN status, although additional analyses with larger cohorts are warranted.

Reproducible changes in the anorexia nervosa gut microbiota following inpatient therapy remain distinct from non-eating disorder controls

The composition of the gut microbiota in patients with anorexia nervosa (AN), and the ability of this microbial community to influence the host, remains uncertain. To achieve a broader understanding of the role of the intestinal microbiota in patients with AN, we collected fecal samples before and following clinical treatment at two geographically distinct eating disorder units (Center of Excellence for Eating Disorders [UNC-CH] and ACUTE Center for Eating Disorders [Denver Health]). Gut microbiotas were characterized in patients with AN, before and after inpatient treatment, and in non-eating disorder (non-ED) controls using shotgun metagenomic sequencing. The impact of inpatient treatment on the AN gut microbiota was remarkably consistent between eating disorder units. Although weight in patients with AN showed improvements, AN microbiotas post-treatment remained distinct from non-ED controls. Additionally, AN gut microbiotas prior to treatment exhibited more fermentation pathways and a lower ability to degrade carbohydrates than non-ED controls. As the intestinal microbiota can influence nutrient metabolism, our data highlight the complex microbial communities in patients with AN as an element needing further attention post inpatient treatment. Additionally, this study defines the effects of renourishment on the AN gut microbiota and serves as a platform to develop precision nutrition approaches to potentially mitigate impediments to recovery.

A Fructo-Oligosaccharide Prebiotic Is Well Tolerated in Adults Undergoing Allogeneic Hematopoietic Stem Cell Transplantation: A Phase I Dose-Escalation Trial

Alterations of the gut microbiota after allogeneic hematopoietic cell transplantation (allo-HCT) are a key factor in the development of transplant-related complications such as graft-versus-host disease (GVHD). Interventions that preserve the gut microbiome hold promise to improve HCT-associated morbidity and mortality. Murine models demonstrate that prebiotics such as fructo-oligosaccharides (FOSs) may increase gut levels of short-chain fatty acids (SCFAs) such as butyrate and consequently induce proliferation of immunomodulatory FOXP3+CD4+ regulatory T cells (Tregs), which impact GVHD risk. We conducted a pilot phase I trial to investigate the maximum tolerated dose of FOS in patients undergoing reduced-intensity allo-HCT (n = 15) compared with concurrent controls (n = 16). We administered the FOS starting at pretransplant conditioning and continuing for a total of 21 days. We characterized the gut microbiome using shotgun metagenomic sequencing, measured stool short-chain fatty acids (SCFAs) using liquid chromatography-mass spectrometry, and determined peripheral T cell concentrations using cytometry by time-of-flight. We found that FOS was safe and well-tolerated at 10 g/d without significant adverse effects in patients undergoing allo-HCT. Community-level gut microbiota composition differed significantly on the day of transplant (day 0) between patients receiving FOS and concurrent controls; however, FOS-associated alterations of the gut microbiota were not sustained after transplant. Although the impact of FOS was fleeting, transplantation itself impacted a substantial number of taxa over time. In our small pilot trial, no significant differences were observed in gut microbial metabolic pathways, stool SCFAs, or peripheral Tregs, although Tregs trended higher in those patients who received FOS. A marker of CD4+ T cell activation (namely, CTLA4+) was significantly higher in patients receiving FOS, whereas a non-significant trend existed for FOP3+CD4+ Treg cells, which were higher in those receiving FOS compared with controls. FOS is well tolerated at 10 g/d in patients undergoing reduced-intensity allo-HCT. Although the alterations in gut microbiota and peripheral immune cell composition in those receiving FOS are intriguing, additional studies are required to investigate the use of prebiotics in HCT recipients.

Abstract 2576: Calorie restriction reverses the tumorigenic effects of obesity to a greater extent than bariatric surgery in a murine model of breast cancer

Obesity is an established risk and prognostic factor for multiple breast cancer (BC) subtypes. Epidemiologic studies suggest that weight loss via bariatric surgery results in metabolic reprogramming that reverses systemic aberrations as well as the protumorigenic effects of obesity; however, data on the effects of nonsurgical weight loss interventions in obese women remain inconclusive. We previously established that diet-induced obesity (DIO) increases tumor progression in murine models of basal-like BC. The purpose of this study was to determine if surgical and dietary weight loss interventions could effectively reduce obesity-associated tumor progression. Our first experiment directly compared mammary tumor growth following weight loss in DIO mice. Female C57BL/6 mice were randomized to a low-fat control (CON; 10 kcal% fat) diet or DIO regimen (60 kcal% fat) for 15 weeks. DIO mice were then randomized to either remain on DIO diet (DIO-DIO) or initiate weight loss either via vertical sleeve gastrectomy (DIO-SURG, with concurrent switch to control diet) or switch to control diet without surgery (DIO-DIET). CON mice remained on the 10 kcal% fat diet throughout the study. Eight weeks later, all mice were orthotopically injected with E0771 basal-like mammary tumor cells and were euthanized when tumors from the DIO-DIO group reached 1.5cm3. Body weights were not significantly different between DIO-SURG and DIO-DIET mice but both groups weighed significantly less than DIO-DIO mice. Compared with CON mice, tumor burden was not different in DIO-SURG mice but was significantly greater in DIO-DIET mice, suggesting that surgical weight loss more effectively reverses the protumorigenic effects of obesity than a low-fat diet. We next sought to determine how the anticancer effects of calorie restricted diets compared with bariatric surgery. Another group of female C57BL/6 received DIO diet for 16 weeks, then randomized to the same CON or DIO-SURG interventions as above, or to receive one of two calorie restriction (CR) diets—chronic CR (DIO-CCR; 30% daily calorie reduction) or intermittent CR (DIO-ICR; 14% calorie reduction 5 days per week, 70% calorie reduction on 2 nonconsecutive days per week). At time of tumor collection, DIO-SURG, DIO-CCR, and DIO-ICR mice weighed significantly less than DIO-DIO mice; however, only DIO-CCR and DIO-ICR mice achieved body weights significantly lower than CON mice. Tumor weights were significantly reduced in DIO-CCR and DIO-ICR fed mice, relative to CON mice, while tumor weights of DIO-SURG mice were intermediate. Moreover, multiple linear regression indicated weight loss, irrespective of intervention, was the strongest predictor of tumor mass. Our results in a murine model of basal-like BC suggest that weight loss via CR regimens (CCR, ICR) and, to a lesser extent, bariatric surgery, mitigates the pro-tumorigenic effects of obesity.

Citation Format: Kristina K. Camp, Emily Rossi, Tori L. McFarlane, Steven Doerstling, Subreen Khatib, Elaine Glenny, Michael Coleman, Laura Bowers, Erika Rezeli, Randy J. Seeley, Alfor G. Lewis, Joel Parker, Anthony Fodor, Farnaz Fouladi, Stephen Hursting. Calorie restriction reverses the tumorigenic effects of obesity to a greater extent than bariatric surgery in a murine model of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2576.

Avenanthramide Metabotype from Whole-Grain Oat Intake is Influenced by Faecalibacterium prausnitzii in Healthy Adults

BACKGROUND

Oat has been widely accepted as a key food for human health. It is becoming increasingly evident that individual differences in metabolism determine how different individuals benefit from diet. Both host genetics and the gut microbiota play important roles on the metabolism and function of dietary compounds.

OBJECTIVES

To investigate the mechanism of individual variations in response to whole-grain (WG) oat intake.

METHODS

We used the combination of in vitro incubation assays with human gut microbiota, mouse and human S9 fractions, chemical analyses, germ-free (GF) mice, 16S rRNA sequencing, gnotobiotic techniques, and a human feeding study.

RESULTS

Avenanthramides (AVAs), the signature bioactive polyphenols of WG oat, were not metabolized into their dihydro forms, dihydro-AVAs (DH-AVAs), by both human and mouse S9 fractions. DH-AVAs were detected in the colon and the distal regions but not in the proximal and middle regions of the perfused mouse intestine, and were in specific pathogen-free (SPF) mice but not in GF mice. A kinetic study of humans fed oat bran showed that DH-AVAs reached their maximal concentrations at much later time points than their corresponding AVAs (10.0-15.0 hours vs. 4.0-4.5 hours, respectively). We observed interindividual variations in the metabolism of AVAs to DH-AVAs in humans. Faecalibacterium prausnitzii was identified as the individual bacterium to metabolize AVAs to DH-AVAs by 16S rRNA sequencing analysis. Moreover, as opposed to GF mice, F. prausnitzii-monocolonized mice were able to metabolize AVAs to DH-AVAs.

CONCLUSIONS

These findings demonstrate that the presence of intestinal F. prausnitzii is indispensable for proper metabolism of AVAs in both humans and mice. We propose that the abundance of F. prausnitzii can be used to subcategorize individuals into AVA metabolizers and nonmetabolizers after WG oat intake. This study was registered at clinicaltrials.gov as NCT04335435.

A microbial signature following bariatric surgery is robustly consistent across multiple cohorts

Bariatric surgery induces significant shifts in the gut microbiota which could potentially contribute to weight loss and metabolic benefits. The aim of this study was to characterize a microbial signature following Roux-en-Y Gastric bypass (RYGB) surgery using novel and existing gut microbiota sequence data. We generated 16S rRNA gene and metagenomic sequences from fecal samples from patients undergoing RYGB surgery (n = 61 for 16S rRNA gene and n = 135 for metagenomics) at pre-surgical baseline and one, six, and twelve-month post-surgery. We compared these data with three smaller publicly available 16S rRNA gene and one metagenomic datasets from patients who also underwent RYGB surgery. Linear mixed models and machine learning approaches were used to examine the presence of a common microbial signature across studies. Comparison of our new sequences with previous longitudinal studies revealed strikingly similar profiles in both fecal microbiota composition (r = 0.41 ± 0.10; p < .05) and metabolic pathways (r = 0.70 ± 0.05; p < .001) early after surgery across multiple datasets. Notably, Veillonella, Streptococcus, Gemella, Fusobacterium, Escherichia/Shigella, and Akkermansia increased after surgery, while Blautia decreased. Machine learning approaches revealed that the replicable gut microbiota signature associated with RYGB surgery could be used to discriminate pre- and post-surgical samples. Opportunistic pathogen abundance also increased post-surgery in a consistent manner across cohorts. Our study reveals a robust microbial signature involving many commensal and pathogenic taxa and metabolic pathways early after RYGB surgery across different studies and sites. Characterization of the effects of this robust microbial signature on outcomes of bariatric surgery could provide insights into the development of microbiome-based interventions for predicting or improving outcomes following surgery.

Does geographical variation confound the relationship between host factors and the human gut microbiota: a population-based study in China

OBJECTIVE

The human gut microbiota plays important roles in human health but is also known to be highly diverse between populations from different regions. Yet most studies inadequately account for this regional diversity in their analyses. This study examines the extent to which geographical variation can act as a confounding variable for studies that associate the microbiota with human phenotypic variation.

DESIGN

Population-based study.

SETTING

China.

PARTICIPANTS

2164 participants from 15 province-level divisions in China.

PRIMARY AND SECONDARY OUTCOME MEASURES

We analysed the impact of geographic location on associations between the human gut microbiota and 72 host factors representing a wide variety of environmental-level, household-level and individual-level factors.

RESULTS

While the gut microbiota varied across a wide range of host factors including urbanisation, occupation and dietary variables, the geographic region (province/megacity) of the participants explained the largest proportion of the variance (17.9%). The estimated effect sizes for other host factors varied substantially by region with little evidence of a reproducible signal across different areas as measured by permutational multivariate analysis of variance and random forest models.

CONCLUSIONS

Our results suggest that geographic variation is an essential factor that should be explicitly considered when generalising microbiota-based models to host phenotype across different populations.

"Us vs. Them" Pair Housing: Effects on Body Weight, Open Field Behavior, and Gut Microbiota in Rats Selectively Bred on a Taste Phenotype

Taste is increasingly recognized as being related to reward, risk, and social processes beyond the ingestive domain. Occidental High (HiS) and Low (LoS) Saccharin Consuming rats have been selectively bred for more than 25 years to study those relationships. The present study examined LoS and HiS rats' sensitivity to a social partner's lineage. The role of gut microbiome transfer between lines was also explored as a possible mediating mechanism. Rats were pair-housed with a rat from either their own line (same-line condition) or the other line (other-line condition); weight gain, saccharin intake, acoustic startle, and open field behavior were measured. Results show for the first time that the lines express different behavioral strategies in a novel open field. In addition, weight gain and open field measures indicate that other-line housing was stressful. Saccharin intake, however, was unaffected by housing condition. A previous finding that the lines possess different gut microbiota was replicated. Although microbial transfer occurred between social partners, no clear evidence was obtained that housing-condition effects on weight gain or behavior were mediated by microbial transfer. Overall, these findings add to the characterization of non-gustatory correlates of a taste phenotype and suggest that rats differing strikingly on the taste phenotype and/or its correlates may be socially incompatible.

Air pollution exposure is associated with the gut microbiome as revealed by shotgun metagenomic sequencing

Animal work indicates exposure to air pollutants may alter the composition of the gut microbiota. This study examined relationships between air pollutants and the gut microbiome in young adults residing in Southern California. Our results demonstrate significant associations between exposure to air pollutants and the composition of the gut microbiome using whole-genome sequencing. Higher exposure to 24-hour O3 was associated with lower Shannon diversity index, higher Bacteroides caecimuris, and multiple gene pathways, including L-ornithine de novo biosynthesis as well as pantothenate and coenzyme A biosynthesis I. Among other pollutants, higher NO2 exposure was associated with fewer taxa, including higher Firmicutes. The percent variation in gut bacterial composition that was explained by air pollution exposure was up to 11.2% for O3 concentrations, which is large compared to the effect size for many other covariates reported in healthy populations. This study provides the first evidence of significant associations between exposure to air pollutants and the compositional and functional profile of the human gut microbiome. These results identify O3 as an important pollutant that may alter the human gut microbiome.

The Role of the Gut Microbiota in Sustained Weight Loss Following Roux-en-Y Gastric Bypass Surgery

BACKGROUND

The aim of the study was to investigate the role of the gut microbiota in weight regain or suboptimal weight loss following Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

The gut microbiota composition in post-RYGB patients who experienced successful weight loss (SWL, n = 6), post-RYGB patients who experienced poor weight loss (PWL, n = 6), and non-surgical controls (NSC, n = 6) who were age- and BMI-matched to the SWL group (NSC, n = 6) were characterized through 16S rRNA gene sequencing. To further investigate the impact of the gut microbiota on weight profile, human fecal samples were transplanted into antibiotic-treated mice.

RESULTS

Orders of Micrococcales and Lactobacillales were enriched in SWL and PWL groups compared to the NSC group. No significant difference was observed in the gut microbiota composition between PWL and SWL patients. However, transfer of the gut microbiota from human patients into antibiotic-treated mice resulted in significantly greater weight gain in PWL recipient mice compared to SWL recipient mice. A few genera that were effectively transferred from humans to mice were associated with weight gain in mice. Among them, Barnesiella was significantly higher in PWL recipient mice compared to SWL and NSC recipient mice.

CONCLUSION

These results indicate that the gut microbiota are at least functionally, if not compositionally, different between PWL and SWL patients. Some taxa may contribute to weight gain after surgery. Future studies will need to determine the molecular mechanisms behind the effects of the gut bacteria on weight regain after RYGB.

Enzyme-Responsive Liposomes for the Delivery of Anticancer Drugs

Liposomes are nanocarriers that deliver the payloads at the target site, leading to therapeutic drug concentrations at the diseased site and reduced toxic effects in healthy tissues. Several approaches have been used to enhance the ability of the nanocarrier to target the specific tissues, including ligand-targeted liposomes and stimuli-responsive liposomes. Ligand-targeted liposomes exhibit higher uptake by the target tissue due to the targeting ligand attached to the surface, while the stimuli-responsive liposomes do not release their cargo unless they expose to an endogenous or exogenous stimulant at the target site. In this review, we mainly focus on the liposomes that are responsive to pathologically increased levels of enzymes at the target site. Enzyme-responsive liposomes release their cargo upon contact with the enzyme through several destabilization mechanisms: (1) structural perturbation in the lipid bilayer, (2) removal of a shielding polymer from the surface and increased cellular uptake, (3) cleavage of a lipopeptide or lipopolymer incorporated in the bilayer, and (4) activation of a prodrug in the liposomes.

Prevalence of Alcohol and Other Substance Use in Patients with Eating Disorders

OBJECTIVE

The major aim of this study was to investigate any association between binge eating and purging and alcohol and substance use.

METHOD

The Eating Disorder Questionnaire was completed by 2966 patients. Each patient was assigned to an approximate diagnostic group based on a DSM-5-based algorithm.

RESULTS

Patients with bulimia nervosa (BN) used alcohol/other substances with higher frequencies compared to patients with anorexia nervosa-restricting type (AN-R), binge eating disorder (BED), and eating disorder not otherwise specified (EDNOS; p < 0.001). Patients with anorexia nervosa-binge eating/purging type (AN-BP) were more likely to use alcohol/substances than those with AN-R [odds ratio for alcohol use: 3.58 (p < 0.01); odds ratio for substance use: 30.14 (p < 0.01)]. Higher frequencies of binge eating and purging were associated with higher frequencies of substance use.

DISCUSSION

Patients who manifest both binge eating and purging behaviour are at higher risk of substance use which may have important treatment implications.