Metabolic footprint and intestinal microbial changes in response to dietary proteins in a pig model

Calorie restriction improves metabolic state independently of gut microbiome composition: a randomized dietary intervention trial

Background

The gut microbiota has been suggested to play a significant role in the development of overweight and obesity. However, the effects of calorie restriction on gut microbiota of overweight and obese adults, especially over longer durations, are largely unexplored.

Methods

Here, we longitudinally analyzed the effects of intermittent calorie restriction (ICR) operationalized as the 5:2 diet versus continuous calorie restriction (CCR) on fecal microbiota of 147 overweight or obese adults in a 50-week parallel-arm randomized controlled trial, the HELENA Trial. The primary outcome of the trial was the differential effects of ICR versus CCR on gene expression in subcutaneous adipose tissue. Changes in the gut microbiome, which are the focus of this publication, were defined as exploratory endpoint of the trial. The trial comprised a 12-week intervention period, a 12-week maintenance period, and a final follow-up period of 26 weeks.

Results

Both diets resulted in ~5% weight loss. However, except for Lactobacillales being enriched after ICR, post-intervention microbiome composition did not significantly differ between groups. Overall weight loss was associated with significant metabolic improvements, but not with changes in the gut microbiome. Nonetheless, the abundance of the Dorea genus at baseline was moderately predictive of subsequent weight loss (AUROC of 0.74 for distinguishing the highest versus lowest weight loss quartiles). Despite the lack of consistent intervention effects on microbiome composition, significant study group-independent co-variation between gut bacterial families and metabolic biomarkers, anthropometric measures, and dietary composition was detectable. Our analysis in particular revealed associations between insulin sensitivity (HOMA-IR) and Akkermansiaceae, Christensenellaceae, and Tanerellaceae. It also suggests the possibility of a beneficial modulation of the latter two intestinal taxa by a diet high in vegetables and fiber, and low in processed meat.

Conclusions

Overall, our results suggest that the gut microbiome remains stable and highly individual-specific under dietary calorie restriction.

Trial registration

The trial, including the present microbiome component, was prospectively registered at ClinicalTrials.govNCT02449148 on May 20, 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-022-01030-0.

Effect of Dietary Protein and Processing on Gut Microbiota—A Systematic Review

The effect of diet on the composition of gut microbiota and the consequent impact on disease risk have been of expanding interest. The present review focuses on current insights of changes associated with dietary protein-induced gut microbial populations and examines their potential roles in the metabolism, health, and disease of animals. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol was used, and 29 highly relevant articles were obtained, which included 6 mouse studies, 7 pig studies, 15 rat studies, and 1 in vitro study. Analysis of these studies indicated that several factors, such as protein source, protein content, dietary composition (such as carbohydrate content), glycation of protein, processing factors, and protein oxidation, affect the digestibility and bioavailability of dietary proteins. These factors can influence protein fermentation, absorption, and functional properties in the gut and, consequently, impact the composition of gut microbiota and affect human health. While gut microbiota can release metabolites that can affect host physiology either positively or negatively, the selection of quality of protein and suitable food processing conditions are important to have a positive effect of dietary protein on gut microbiota and human health.

Systematic Review of Beef Protein Effects on Gut Microbiota: Implications for Health

The influence of diet on the gut microbiota is an emerging research area with significant impact on human health and disease. However, the effects of beef, the most consumed red meat in the United States, on gut microbial profile are not well studied. Following Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols, the objective of this systematic review was to conduct a rigorous and thorough review of the current scientific literature regarding the effects of beef protein and the resulting bioactivity of beef protein and amino acids on the gut microbiota, with the goal of identifying gaps in the literature and guiding future research priorities. Utilizing MEDLINE Complete, PubMed, ScienceDirect, Scopus, and Google Scholar databases, we conducted searches including terms and combinations of the following: animal protein, amino acid, beef, bioactive compounds, diet, health, microbiome, peptide, processed beef, and protein. We identified 131 articles, from which 15 were included in our review. The effects of beef on mouse and rat models were mostly consistent for the bacterial phylum level. Short-term (1-4-wk) beef intakes had little to no effect on microbial profiles in humans. Most studies utilized high beef feeding (240-380 g/d), and no study examined recommended amounts of protein [∼3.71 oz/d (105 g/d) meats, poultry, and eggs, or ∼26 oz/week (737 g/wk) from these food sources] according to US dietary guidelines. Additionally, the majority of animal and human studies with adverse findings examined the impact of beef in the context of a diet high in fat or sugar. In conclusion, an extensive gap exists in the literature regarding beef and the microbiota. More studies are necessary to elucidate the role of the microbiota following the consumption of beef, especially in interaction with other dietary compounds, and how beef preparation, processing, and cooking methods differentially influence the biological effects of beef on human health.

Intestinal barrier damage involved in intestinal microflora changes in fluoride-induced mice

Intestinal microflora play an important role in maintaining the homeostasis of the intestinal microenvironment, but fluoride-induced changes in intestinal mechanical barrier and intestinal microflora have not been well studied. Given this paucity of information, this study aims to determine the effects of high fluoride level on intestinal mechanical barrier and intestinal microflora in the cecum of mice. Seventy-two female 21-day-old Kunming mice were randomly assigned to three groups and raised for 70 days. Changes in intestinal pathomorphology and intestinal epithelial cell proliferation were observed by haematoxylin and eosin-staining and Brdu measurement, respectively. The distribution of goblet cells, glycoproteins and mast cells was analysed through Alcian blue and periodic acid-Schiff (AB-PAS) staining, Periodic Acid-Schiff (PAS) staining, and toluidine blue staining. Results showed that excessive fluoride damaged the structure of the cecal tissues, inhibited epithelial cell proliferation and decreased the relative distribution of goblet cells, glycoproteins and mast cells that are involved in defense responses. Intestinal microflora sequencing analysis revealed that the composition of the diversity and composition of intestinal microflora was altered by excessive fluoride based on 16S rRNA amplicon sequencing. The relative abundance of Firmicutes (P = 0.03174), Bacteroidetes (P = 0.04462), Actinobacteria (P = 0.01085) and Spirochacteria (P = 0.04084) was significantly changed in the fluoride group as compared with the control group. In conclusion, excessive fluoride intake induced intestinal barrier damage, leading to changes in cecal composition, epithelium secretion and intestinal microflora.