Background It is not clear whether dietary grape seed proanthocyanidin (GSP) affects mammalian lipid metabolism via the gut microbiota. Objective The aim of this study was to evaluate the contribution of the gut microbiota to the effect of dietary GSP. Methods This study was divided into 3 separate experiments using Duroc × Landrace × Yorkshire pigs (50% male) weaned at day 28 and then fed the same basal diet (NC). In Experiment 1, 90 pigs were fed NC or NC with 250 mg GSP/kg (GSP) or 400 mg betaine/kg [positive control (PC)] for 28 d. In Experiment 2, 30 pigs were fed NC, GSP, or GSP with antibiotics (GSP + Abx) diets for 14 d. In Experiment 3, pigs were fed NC, NC plus 1 g sodium propionate/kg (SP), or NC plus 1 g sodium butyrate/kg (SB) diet for 14 d. Serum biochemical indexes, SCFA concentrations, and microbial composition were determined. Results In Experiment 1, compared with the GSP group, visceral adipocyte area was higher in the NC (28.6%) and PC (18.2%) groups (P ≤ 0.05). Colonic propionate and butyrate concentrations were 30.2% and 3.6% higher in the GSP group than in the NC group, respectively (P ≤ 0.05). In Experiment 2, compared with the GSP group, the NC group had a 108% higher Firmicutes to Bacteroidetes ratio and had 50.4%, 61.2%, and 82.3% lower abundance of Akkermansia, Alistipes, and Bacteroides, respectively (P ≤ 0.05); antibiotics removed these effects of GSP. In Experiment 3, serum peptide YY was 19.5% higher in the SP group than in the NC group (P ≤ 0.05), and it did not differ between the SB and NC groups (P > 0.05). Conclusions GSP affected lipid metabolism in weaned pigs, which is associated with changed gut microbiota and enhanced microbial propionate production. These findings provide potential mechanisms for GSP intake to improve lipid metabolism.

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End-tagging with a single hydrophobic residue contributes to improve the cell selectivity of antimicrobial peptides (AMPs), but systematic studies have been lacking. Thus, this study aimed to systematically investigate how end-tagging with hydrophobic residues at the C-terminus and Gly capped at the N-terminus of W4 (RWRWWWRWR) affects the bioactivity of W4 variants. Among all the hydrophobic residues, only Ala end-tagging improved the antibacterial activity of W4. Meanwhile, Gly capped at the N-terminus could promote the helical propensity of the end-tagged peptides in dodecylphosphocholine micelles, increasing their antimicrobial activities. Of these peptides, GW4A (GRWRWWWRWRA) showed the best antibacterial activity against the 19 species of bacteria tested (GM MIC = 1.86 μM) with low toxicity, thus possessing the highest cell selectivity (TI all = 137.63). It also had rapid sterilization, good salt and serum resistance, and LPS-neutralizing activity. Antibacterial mechanism studies showed that the short peptide GW4A killed bacteria by destroying cell membrane integrity and causing cytoplasmic leakage. Overall, these findings suggested that systematic studies on terminal modifications promoted the development of peptide design theory and provided a potential method for optimization of effective AMPs.

To explore the relationship among the level of fiber, gut microbiota, and nutritional substances, we applied the next generation sequencing technology for the identification of the composition and structure of microbiota in the gastrointestinal tract. In this study, a total of 25 phyla and 298 genera were identified from the gastrointestinal tract; Firmicutes, Bacteroidetes, and Proteobacteria were the predominant phyla. The ability of cecum in carbohydrate metabolism was significantly higher than that of the gizzard and ileum (P < 0.05). The bacterial community structure in various stages of the development of the cecum was different. In the different growth stages of cecum, the increase in the microbiota structure of the fiber level elevates the ability of carbon hydration. Second, the apparent metabolic rates of the other nutrients were affected by the fiber and period except for acid detergent fiber (P < 0.05); the apparent utilization rate of the nutrients increased with time. However, with the increase in the fiber level, the apparent utilization of nutrients was initially increased, followed by a decrease. Therefore, a correlation was established between the fiber level and gastrointestinal microbiota and apparent nutrient utilization rate of the 3 phyla. Our results suggest that the fiber level and growth stages could impact the composition of gut microbiota.