Mulberry leaf supplementation inhibits skatole deposition by regulating gut microbiota and upregulating liver cytochrome P4501A1 expression in finishing pigs

Skatole,a strong fecal odor substance,is generated through microbial degradation of tryptophan in the animal hindgut.It easily accumulates in adipose tissue and affects meat quality.In this study,the effect of mulberry leaf supplementation on skatole in finishing pigs was studied.In a 35-day trial,20 finishing pigs(barrows and gilts)were fed with a basal diet or basal diet with 6%mulberry leaves.Growth performance of the pigs(n=10)was automatically recorded by a performance-testing feeder system and 8 pigs in each treatment were slaughtered and sampled for the remaining tests.Skatole and short-chain fatty acids were detected using HPLC and gas chromatography,respectively.Fecal microbiota were analyzed using 16S r RNA gene sequencing.The metabolomics analysis of feces and serum was performed with UHPLC-MS/MS.The major cytochrome P450(CYP)enzymes that catalyze skatole degradation in the liver were tested by using RT-PCR and Western blot.Effects of major bioactive compounds in mulberry leaves on the CYP genes were verified in the hepatic cell line Hep G2 in an in vitro test(n=3).In finishing pigs,mulberry leaf supplementation had no significant effect on the average daily gain,average daily feed intake,and feed conversion ratio(P>0.05),but reduced skatole levels in feces,serum,and backfat(P<0.05),and increased acetic acid levels in feces(P=0.027).Mulberry leaf supplementation decreased the relative abundance of the skatole-producing bacteria Megasphaera and Olsenella(P<0.05).Indole-3acetic acid,the intermediate that is essential for skatole production,was significantly reduced in feces by mulberry leaf supplementation(P<0.05)and was positively correlated with skatole content in feces(P=0.004).In pigs treated with mulberry leaves,liver CYP1A1 expression was increased(P<0.05)and was negatively correlated with skatole content in backfat(P=0.045).The in vitro test demonstrated that mulberry leaf polyphenols and polysaccharides could directly stimulate CYP1A1 expression in hepatic cells.These findings suggest that mulberry leaf supplementation reduces skatole production and deposition in finishing pigs by regulating the gut microbiota and promoting skatole degradation in liver.

A novel aldo-keto reductase gene, IbAKR, from sweet potato confers higher tolerance to cadmium stress in tobacco

High concentrations of Cd can inhibit growth and reduce the activity of the photosynthetic apparatus in plants. In several plant species, aldo-keto reductases(AKRs) have been shown to enhance tolerance to various abiotic stresses by scavenging cytotoxic aldehydes;however, few AKRs have been reported to enhance Cd stress tolerance. In this study, the gene Ib AKR was isolated from sweet potato. The relative expression levels of Ib AKR increased significantly(approximately 3-fold) after exposure to 200 mmol$L–1 Cd Cl2 or 10 mmol$L–1 H2 O2. A subcellular localization assay showed that Ib AKR is predominantly located in the nucleus and cytoplasm.Ib AKR-overexpressing tobacco plants showed higher tolerance to Cd stress than wild-type(WT). Transgenic lines showed a significant ability to scavenge malondialdehyde(MDA) and methylglyoxal(MG). In addition,proline content and superoxide dismutase activity were significantly higher and H2 O2 levels were significantly lower in the transgenic plants than in the WT. Quantitative real-time PCR analysis showed that the reactive oxygen species(ROS) scavenging genes encoding guaiacol peroxidase(GPX), ascorbate peroxidase(APX), monodehydroascorbate reductase(MDHAR) and peroxidase(POD) were significantly upregulated in transgenic plants compared to WT under Cd stress. These findings suggest that overexpressing Ib AKR enhances tolerance to Cd stress via the scavenging of cytotoxic aldehydes and the activation of the ROS scavenging system.