Bioaccessibility and Gut Metabolism of Free and Melanoidin-Bound Phenolic Compounds From Coffee and Bread

The aim of this study is to investigate the bioaccessibility and gut metabolism of free and melanoidin-bound phenolic compounds from coffee and bread. Phenolics from coffee were predominantly found in free forms (68%, mainly chlorogenic acids), whereas those from bread were mostly bound to melanoidins (61%, mainly ferulic acid). Bioacessibility of coffee total free phenolics slightly decreased during simulated digestion (87, 86, and 82% after the oral, gastric, and intestinal steps, respectively), with caffeoylquinic acids being isomerized and chlorogenic acids being partially hydrolyzed to the corresponding hydroxycinnamic acids. Bioacessibility of bread total free phenolics decreased during simulated digestion (91, 85, and 67% after the oral, gastric, and intestinal steps, respectively), probably related to complexation with the proteins in simulated gastric and intestinal fluids. Upon gut fermentation, the bioaccessibility of total free phenolics from both coffee and bread decreased, mainly after the first 4 h (56 and 50%, respectively). Caffeic and ferulic acids were the predominant metabolites found during coffee and bread gut fermentation, respectively. Melanoidin-bound phenolics from coffee and bread were progressively released after the gastric and intestinal steps, probably due to hydrolysis caused by the acidic conditions of the stomach and the action of pancreatin from the intestinal fluid. The bioaccessibilities of all phenolics from coffee and bread melanoidins after the gastric and intestinal steps were, on average, 11 and 26%, respectively. During gut fermentation, phenolics bound to both coffee and bread melanoidins were further released by the gut microbiota, whereas those from coffee were also metabolized. This difference could be related to the action of proteases on melanoproteins during gastrointestinal digestion, probably anticipating phenolics release. Nevertheless, bioaccessibilities of melanoidin-bound phenolics reached maximum values after gut fermentation for 24 h (50% for coffee and 51% for bread). In conclusion, the bioaccessibilities of coffee and bread free phenolics during simulated digestion and gut fermentation were remarkably similar, and so were the bioaccessibilities of coffee and bread melanoidin-bound phenolics.

Review: microbial transformations of human bile acids

Bile acids play key roles in gut metabolism, cell signaling, and microbiome composition. While the liver is responsible for the production of primary bile acids, microbes in the gut modify these compounds into myriad forms that greatly increase their diversity and biological function. Since the early 1960s, microbes have been known to transform human bile acids in four distinct ways: deconjugation of the amino acids glycine or taurine, and dehydroxylation, dehydrogenation, and epimerization of the cholesterol core. Alterations in the chemistry of these secondary bile acids have been linked to several diseases, such as cirrhosis, inflammatory bowel disease, and cancer. In addition to the previously known transformations, a recent study has shown that members of our gut microbiota are also able to conjugate amino acids to bile acids, representing a new set of “microbially conjugated bile acids.” This new finding greatly influences the diversity of bile acids in the mammalian gut, but the effects on host physiology and microbial dynamics are mostly unknown. This review focuses on recent discoveries investigating microbial mechanisms of human bile acids and explores the chemical diversity that may exist in bile acid structures in light of the new discovery of microbial conjugations.

A Systematic Review of the Effects of Equol (Soy Metabolite) on Breast Cancer

Equol is a soy isoflavone metabolite that can be produced by intestinal bacteria. It is lipophilic and resembles natural oestrogens with an affinity to oestrogen receptors. This review is focused on how equol affects breast cancer, as evidenced by in vivo and in vitro studies. Equol is considered chemoprotective in specific endocrine-related pathologies, such as breast cancer, prostate cancer, cardiovascular diseases, and menopausal symptoms. In humans, not everyone can produce equol from gut metabolism. It is postulated that equol producers benefit more than non-equol producers for all the endocrine-related effects. Equol exists in two enantiomers of R-equol and S-equol. Earlier studies, however, did not specify which enantiomer was being used. This review considers equol’s type and concentration variations, pathways affected, and its outcome in in vivo and in vitro studies.

Honeybee gut microbiota modulates host behaviors and neurological processes

Honeybee is a highly social insect with a reach behavioral repertoire and is a versatile model for neurobiological research. The honeybee gut microbiota is composed of a limited number of bacterial phylotypes that play an important role in host health. However, it remains unclear whether the microbiota can shape brain profiles and behaviors. Here, we revealed that the gut microbiota is requisite for the olfactory learning and memory ability of honeybees and alters the level of neurotransmitters in the brain. Transcriptomic and proteomic analysis showed distinctive gene expression and protein signatures for gnotobiotic bees associated with different gut bacteria. Specifically, genes related to olfactory functions and labor division are most upregulated. Moreover, differentially spliced genes in the brains of colonized bees largely overlapped with the datasets for human autism. The circulating metabolome profiles identified that different gut species regulated specific module of metabolites in the host hemolymph. Most altered metabolites are involved in the amino acid and glycerophospholipid metabolism pathways for the production of neuroactive compounds. Finally, antibiotic treatment disturbed the gut community and the nursing behavior of worker bees under field conditions. The brain transcripts and gut metabolism was also greatly interfered in treated bees. Collectively, we demonstrate that the gut microbiota regulates honeybee behaviors, brain gene transcription, and the circulating metabolism. Our findings highlight the contributions of honeybee gut microbes in the neurological processes with striking parallels to those found in other animals, thus providing a promising model to understand the host-microbe interactions via the gut-brain axis.

Progress in ileal endogenous amino acid flow research in poultry

The progress in our understanding of the endogenous protein concept over the past century is reviewed. Non-dietary proteins found in the digesta at the terminal ileum of poultry, known as endogenous protein loss, are comprised of digestive secretions, mucus and sloughed gut epithelial cells. The measurement of this loss is of fundamental importance because it is an indicator of gut metabolism and is essential to adjust apparent estimates of ileal amino acid digestibility. The ileal endogenous amino acid losses comprise of two components, namely basal and specific losses. The basal losses are fixed and associated with feed dry matter intake, whereas the specific losses are variable and induced by the presence of dietary components such as fibre and anti-nutrients. Currently there is no methodology available to directly measure the specific endogenous losses and these losses are calculated by determining the basal and total (basal plus specific) losses and, then subtracting the basal losses from total losses. The seminal features, specific applications and shortcomings of available methodologies are briefly outlined as well as the practical challenges faced in using the published endogenous amino acid loss values for true digestibility corrections. The relevance of taurine as a component of endogenous protein flow in poultry is identified for the first time.

Honeybee gut microbiota modulates host behaviors and neurological processes

Honeybee is a highly social insect with a reach behavioral repertoire and is a versatile model for neurobiological research. The honeybee gut microbiota is composed of a limited number of bacterial phylotypes that play an important role in host health. However, it remains unclear whether the microbiota can shape brain profiles and behaviors. Here, we revealed that the gut microbiota is requisite for the olfactory learning and memory ability of honeybees and alters the level of neurotransmitters in the brain. Transcriptomic and proteomic analysis showed distinctive gene expression and protein signatures for gnotobiotic bees associated with different gut bacteria. Specifically, genes related to olfactory functions and labor division are most upregulated. Moreover, differentially spliced genes in the brains of colonized bees largely overlapped with the datasets for human autism. The circulating metabolome profiles identified that different gut species regulated specific module of metabolites in the host hemolymph. Most altered metabolites are involved in the amino acid and glycerophospholipid metabolism pathways for the production of neuroactive compounds. Finally, antibiotic treatment disturbed the gut community and the nursing behavior of worker bees under field conditions. The brain transcripts and gut metabolism was also greatly interfered in treated bees. Collectively, we demonstrate that the gut microbiota regulates honeybee behaviors, brain gene transcription, and the circulating metabolism. Our findings highlight the contributions of honeybee gut microbes in the neurological processes with striking parallels to those found in other animals, thus providing a promising model to understand the host-microbe interactions via the gut-brain axis.

Effects of gut microbial metabolite trimethylamine N-oxide (TMAO) on platelets and endothelial cells

Thrombotic events result from different pathologies and are the underlying causes of severe diseases like stroke or myocardial infarction. Recent basic research now revealed a link between food uptake, food conversion and gut metabolism. Gut microbial production of trimethylamine N-oxide (TMAO) from dietary nutrients like choline, lecithin and L-carnitine was associated with the development of cardiovascular diseases. Within this review we give a systematic overview about the influence of TMAO on blood components like platelets and endothelial cells which both are involved as key players in thrombotic processes. In summary, a mechanistic correlation between the gut microbiome, TMAO and cardiovascular diseases becomes obvious and emphasizes to the significance of the intestinal microbiome.