Sustainability of aquaculture is tied to the origin of feed ingredients. In search of sustainable fish meal-free formulations for rainbow trout, we evaluated the effect of Hermetia illucens meal (H) and poultry by-product meal (P), singly (10, 30, and 60% of either H or P) or in combination (10% H + 50% P, H10P50), as partial replacement of vegetable protein (VM) on gut microbiota (GM), inflammatory, and immune biomarkers. Fish fed the mixture H10P50 had the best growth performance. H, P, and especially the combination H10P50 partially restored α-diversity that was negatively affected by VM. Diets did not differ in the Firmicutes:Proteobacteria ratio, although the relative abundance of Gammaproteobacteria was reduced in H and was higher in P and in the fishmeal control. H had higher relative abundance of chitin-degrading Actinomyces and Bacillus, Dorea, and Enterococcus. Actinomyces was also higher in H feed, suggesting feed-chain microbiome transmission. P increased the relative abundance of protein degraders Paeniclostridium and Bacteroidales. IL-1β, IL-10, TGF-β, COX-2, and TCR-β gene expression in the midgut and head kidney and plasma lipopolysaccharide (LPS) revealed that the diets did not compromise the gut barrier function or induce inflammation. H, P, and H10P50 therefore appear valid protein sources in fishmeal-free aquafeeds.

Heat-processed diets contain high amounts of advanced glycation end products (AGEs). Here we explore the impact of an AGE-enriched diet on markers of metabolic and inflammatory disorders as well as on gut microbiota composition and plasma proteins glycosylation pattern. C57BL/6 mice were allocated into control diet (CD, n = 15) and AGE-enriched diet (AGE-D, n = 15) for 22 weeks. AGE-D was prepared replacing casein by methylglyoxal hydroimidazolone-modified casein. AGE-D evoked increased insulin and a significant reduction of GIP/GLP-1 incretins and ghrelin plasma levels, altered glucose tolerance, and impaired insulin signaling transduction in the skeletal muscle. Moreover, AGE-D modified the systemic glycosylation profile, as analyzed by lectin microarray, and increased Nε-carboxymethyllysine immunoreactivity and AGEs receptor levels in ileum and submandibular glands. These effects were associated to increased systemic levels of cytokines and impaired gut microbial composition and homeostasis. Significant correlations were recorded between changes in bacterial population and in incretins and inflammatory markers levels. Overall, our data indicates that chronic exposure to dietary AGEs lead to a significant unbalance in incretins axis, markers of metabolic inflammation, and a reshape of both the intestinal microbiota and plasma protein glycosylation profile, suggesting intriguing pathological mechanisms underlying AGEs-induced metabolic derangements.

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AbstractIntroduction:High sugar consumption promotes endogenous formation of advanced glycation end-products (AGEs), a heterogeneous class of molecules originated from non-enzymatic glycation between reducing sugars and free amino groups of proteins, nucleic acids, or lipids. AGEs accumulation in tissues has been linked to aging and diabetes complications. AGEs might also play an independent role in inflammation and development of cardiovascular disease (CVD). Exogenous dietary AGEs, due to excess intake of modern heat-treated foods, might act synergistically with endogenous AGEs, thus contributing to increase inflammation and CVD. A large amount of ingested AGEs reaches the colon, where they might affect gut microbial metabolism, for example, by acting as substrate for colonic bacterial fermentation, driving alterations of microbiota composition and of intestinal permeability. However in vitro and in vivo studies (animal and human) on the impact of AGEs on the gut microbiota are discordant. This study on mice aims to link the modulation of gut microbiota by AGEs-enriched diet (AGE-D) with metabolic and inflammatory markers.Materials and methods:C57BL/6 mice were randomly allocated into the following dietary regimens: Control (n = 24) and AGE-D (n = 20) for 22 weeks. AGE-D was prepared replacing casein (200 g/kg diet) by an equal amount of modified casein where 10% of arginine was glycated with MG-H1 (methylglyoxal 5-hydro-5-methylimidazolone) for a total of 4 μmol of MG-H1 per g of diet. Faeces were collected using metabolic cages (18 h starving) at week 0, 11 and 22 for fecal DNA extraction and 16SrRNA analysis through Illumina MiSeq using V3-V4 targeted primers. After 22 weeks of dietary manipulation, mice were sacrificed, plasma and organ lipid profiles and serum metabolic and inflammatory profiles were determined.Results and discussion:AGE-D caused a significant reduction in the blood levels of two important components of the incretin system, GIP and GLP-1, when compared to control diet, suggestive of unbalance in the incretin-insulin axis. AGE-D exposure was associated with a significant increase in systemic concentrations of inflammatory cytokines, e.g. IL-1β and IL-17, and PAI-1, which has been suggested as both reliable marker and critical mediator of cellular senescence. We will present how AGEs impact on microbiome community structure and correlate changes in gut microbiota with GIP and GLP-1 levels.Conclusions:AGEs, characteristic of modern processed foods, appear to impact on the incretin-insulin axis, a key regulator of metabolic disease risk. Diets rich in AGEs may mediate these physiological effects at least in part, by reshaping intestinal microbiota structure.

Sauerkraut is a traditionally fermented cabbage, and recent evidence suggests that it has beneficial properties for human health. In this work, a multi-disciplinary approach was employed to characterize the fermentation process and gut health-promoting properties of locally produced, organic sauerkraut from two distinct producers, SK1 and SK2. 16S rRNA metataxonomics showed that bacterial diversity gradually decreased as fermentation progressed. Differences in sauerkraut microbiota composition were observed between the two producers, especially at the start of fermentation. Lactic acid bacteria (LAB) dominated the microbiota after 35 days, with Lactiplantibacillus being the dominant genus in both sauerkraut products, together with Leuconostoc and Paucilactobacillus in SK1, and with Pediococcus, Levilactibacillus, and Leuconostoc in SK2. LAB reached between 7 and 8 Log CFU/mL brine at the end of fermentation (35 days), while pH lowering happened within the first week of fermentation. A total of 220 LAB strains, corresponding to 133 RAPD-PCR biotypes, were successfully isolated. Lactiplantibacillus plantarum and Lactiplantibacillus pentosus accounted for 67% of all SK1 isolates, and Lactiplantibacillus plantarum/paraplantarum and Leuconostoc mesenteroides represented 72% of all the isolates from SK2. 1H-NMR analysis revealed significant changes in microbial metabolite profiles during the fermentation process, with lactic and acetic acids, as well as amino acids, amines, and uracil, being the dominant metabolites quantified. Sauerkraut brine did not affect trans-epithelial electrical resistance through a Caco-2 cell monolayer as a measure of gut barrier function. However, significant modulation of inflammatory response after LPS stimulation was observed in PBMCs-Caco-2 co-culture. Sauerkraut brine supported a robust inflammatory response to endotoxin, by increasing TNF-α and IL-6 production while also stimulating the anti-inflammatory IL-10, therefore suggesting positive resolution of inflammation after 24 h and supporting the potential of sauerkraut brine to regulate intestinal immune function.

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