Nano-selenium (nano-Se) has been extensively explored as a biostimulant for improving the quality of grain crops. However, there are few reports about the effect on the medicinal components of Chinese herbal medicine cultured with nano-Se. Here, we sprayed nano-Se during the cultivation of Panax notoginseng (SePN), and measured the changes of medicinal components compared with conventional Panax notoginseng (PN). Furthermore, we identified a more pronounced effect of SePN on reducing obesity in animals compared with PN. By measuring antioxidant capacity, histopathology, gene expression related to glycolipid metabolism, and gut microbiota composition, we propose a potential mechanism for SePN to improve animal health. Compared with the control groups, foliar spraying of nano-Se increased saponins content (Rb2, Rb3, Rc, F2, Rb2, and Rf) in the roots of Panax notoginseng, and the content of Rb2 increased by 3.9 times in particular. Interestingly, animal studies indicated that taking selenium-rich Panax notoginseng (SePN) can further ameliorate liver antioxidation (SOD, MDA, and GSH) and enzyme activities involved in glycolipid metabolism (ATGL and PFK). It also relieved inflammation and regulated the expression of genes (MCAD, PPAR-α, and PCSK9) related to fatty acid oxidation. The abundance ratio of Firmicutes/Bacteroides and beneficial bacteria abundance (Bifidobacterium, Butyricimonas, and Parasutterella) in gut microbiota were improved relative to the control. In summary, the application of nano-Se on PN may effectively raise the content of Panax notoginseng saponins (PNS) and immensely lower the risk of metabolic disorders of glycolipids.

Total genomic DNA samples were extracted using the OMEGA Soil DNA Kit (M5635-02) (Omega Bio-Tek, Norcross,GA, USA), and stored at −20◦C before further analysis. PCR amplification of the bacterial 16S rRNA genes V3–V4 region was performed using the forward primer 338F (5′ - ACTCCTACGGGAGGCAGCA-3′ ) and the reverse primer 806R (5′ -GGACTACHVGGGTWTCTAAT-3′ ). Amplification system including 5×reaction buffer 5 µL, 5×GC buffer 5 µL, dNTP (2.5 mM) 2 µL, Forward primer (10 uM) 1 µL, Reverse primer (10 uM) 1 µL, DNA Template 2 µL, ddH2O 8.75 µL, Q5 DNA Polymerase 0.25 µL. Amplification parameters include initial denaturation 98◦C 2 min, denaturation 98◦C 15 s, annealing 55◦C 30 s, extension 72◦C 30 s, final extension 72◦C 5 min, 10◦C hold. 25-30 cycles dsDNA Assay Kit (Invitrogen, Carlsbad, CA, USA). PCR amplicons were purified and quantified with Vazyme VAHTSTM DNA Clean Beads (Vazyme, Nanjing, China) and quantified using the QuantiT PicoGreen dsDNA Assay Kit (Invitrogen, Carlsbad, CA, USA), respectively. Amplicons were pooled in equal amounts, and pair-end 2×250 bp sequencing was performed using the Illlumina NovaSeq platform with NovaSeq 6000 SP Reagent Kit (500 cycles) at Shanghai Personal Biotechnology Co., Ltd (Shanghai, China)