Obesity-Associated Gut Microbiota

Sexual Dimorphism in the Immunometabolic Role of Gpr183 in Mice

Context

Excessive eating and intake of a Western diet negatively affect the intestinal immune system, resulting in compromised glucose homeostasis and lower gut bacterial diversity. The G protein-coupled receptor GPR183 regulates immune cell migration and intestinal immune response and has been associated with tuberculosis, type 1 diabetes, and inflammatory bowel diseases.

Objective

We hypothesized that with these implications, GPR183 has an important immunometabolic role and investigated this using a global Gpr183 knockout mouse model.

Methods

Wild-type (WT) and Gpr183-deficient (Gpr183-/-) mice were fed a high-fat, high-sucrose diet (HFSD) for 15 weeks. We investigated changes in weight, body composition, fecal immunoglobulin A (IgA) levels, fecal microbiome, and glucose tolerance before and after the diet. Macrophage infiltration into visceral fat was determined by flow cytometry, and hepatic gene expression was measured.

Results

A sexual dimorphism was discovered, whereby female Gpr183-/- mice showed adverse metabolic outcomes compared to WT counterparts with inferior glucose tolerance, lower fecal IgA levels, and increased macrophage infiltration in visceral fat. In contrast, male Gpr183-/- mice had significantly lower fasting blood glucose after diet than male WT mice. Liver gene expression showed reduced inflammation and macrophage markers in Gpr183-/- livers, regardless of sex, while the pancreatic islet area did not differ between the groups. No conclusive differences were found after microbiome sequencing.

Conclusion

Gpr183 maintains metabolic homeostasis in female but not in male mice independent of diet. If confirmed in humans, future therapy targeting GPR183 should consider this sexual dimorphism.

Enhanced gut microbiome supplementation of essential amino acids in Diploptera punctata fed low-protein plant-based diet

Introduction

Building on our previous work, we investigate how dietary shifts affect gut microbial essential amino acid (EAA) provisioning in the lactating cockroach Diploptera punctata.

Method

To that end, we fed cockroaches three distinct diets: a plant-only Gari diet composed of starchy and granulated root tuber Yucca (Manihot esculenta), a dog food diet (DF), and a cellulose-amended dog food (CADF) diet. We anticipated that the high carbohydrate, low protein Gari would highlight increased microbial EAA supplementation to the host.

Results

By day 28, we observed distinct profiles of 14 bacterial families in the insect gut microbiomes of the three dietary groups. CADF-fed insects predominantly harbored cellulolytic and nitrogen-fixing bacteria families Streptococcaceae and Xanthomonadaceae. In contrast, Gari-fed insects were enriched in anaerobic lignocellulolytic bacteria families Paludibacteraceae and Dysgonomonadaceae, while DF-fed insects had a prevalence of proteolytic anaerobes Williamwhitmaniaceae and sulfate-reducing bacteria Desulfovibrionaceae. Furthermore, we confirmed significantly higher EAA supplementation in Gari-fed insects than in non-Gari-fed insects based on δ13C-EAA offsets between insect and their diets. The δ13C-EAA offsets between DF and CADF were nearly indistinguishable, highlighting the relevance of using the plant-based Gari in this experiment to unequivocally demonstrate this function in this insect. These results were underscored by lower standard metabolic rate (SMR) relative to the DF insect in Gari-fed (intermediate SMR and dietary quality) and CADF (least SMR and dietary quality) insects.

Discussion

The influence of diet on EAA provisioning and SMR responses in insects underscores the need for further exploration into the role of gut microbial functions in modulating metabolic responses.

Breeding farm, level of feeding and presence of antibiotics in the feed influence rabbit cecal microbiota

Background

The effect of the production environment and different management practices in rabbit cecal microbiota remains poorly understood. While previous studies have proved the impact of the age or the feed composition, research in the breeding farm and other animal management aspects, such as the presence of antibiotics in the feed or the level of feeding, is still needed. Characterization of microbial diversity and composition of growing rabbits raised under different conditions could help better understand the role these practices play in cecal microbial communities and how it may result in different animal performance.

Results

Four hundred twenty-five meat rabbits raised in two different facilities, fed under two feeding regimes (ad libitum or restricted) with feed supplemented or free of antibiotics, were selected for this study. A 16S rRNA gene-based assessment through the MiSeq Illumina sequencing platform was performed on cecal samples collected from these individuals at slaughter. Different univariate and multivariate approaches were conducted to unravel the influence of the different factors on microbial alpha diversity and composition at phylum, genus and OTU taxonomic levels. The animals raised in the facility harboring the most stable environmental conditions had greater, and less variable, microbial richness and diversity. Bootstrap univariate analyses of variance and sparse partial least squares-discriminant analyses endorsed that farm conditions exerted an important influence on rabbit microbiota since the relative abundances of many taxa were found differentially represented between both facilities at all taxonomic levels characterized. Furthermore, only five OTUs were needed to achieve a perfect classification of samples according to the facility where animals were raised. The level of feeding and the presence of antibiotics did not modify the global alpha diversity but had an impact on some bacteria relative abundances, albeit in a small number of taxa compared with farm, which is consistent with the lower sample classification power according to these factors achieved using microbial information.

Conclusions

This study reveals that factors associated with the farm effect and other management factors, such as the presence of antibiotics in the diet or the feeding level, modify cecal microbial communities. It highlights the importance of offering a controlled breeding environment that reduces differences in microbial cecal composition that could be responsible for different animal performance.

Relationship(s) between obesity and inflammatory bowel diseases: possible intertwined pathogenic mechanisms

The inflammatory bowel diseases, Crohn's and ulcerative colitis have increased in incidence and prevalence from the mid-eighteen to the late nineteen centuries. From then to the current twenty-first century there has been a more rapid expansion of these disease to areas previously experiencing low rates. This latter expansion coincides with the current obesity pandemic which also began toward the end of the last century. Although the two diseases have radically different frequencies, there are interesting links between them. Four areas link the diseases. On an epidemiological level, IBD tends to follow a north-south gradient raising the importance of vitamin D in protection. Obesity has very weak relationship with latitude, but both diseases follow adult lactase distributions colliding in this plane. Is it possible that obesity (a low vitamin D condition with questionable response to supplements) reduces effects in IBD? On a pathogenic level, pro-inflammatory processes mark both IBD and obesity. The similarity raises the question of whether obesity could facilitate the development of IBD. Features of the metabolic syndrome occur in both, with or without obesity in IBD. The fourth interaction between the two diseases is the apparent effect of obesity on the course of IBD. There are suggestions that obesity may reduce the efficacy of biologic agents. Yet there is some suggestion also that obesity may reduce the need for hospitalization and surgery. The apparent co-expansion of both obesity and IBD suggests similar environmental changes may be involved in the promotion of both.