Determination of Paeoniflorin in Rat Plasma by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry and its Application to a Pharmacokinetic Study.
In this study, a rapid and highly sensitive ultra-high performance liquid chromatography-tandem mass spectrometry method was established for the quantification of paeoniflorin in rat plasma. The analyte and the internal standard (IS), hyperoside, were extracted from rat plasma via liquid-liquid extraction with ethyl acetate. LC separation was carried on a Phenomenex Luna C18 column within 2.5 min. Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operated in the multiple reaction monitoring and negative ion modes. The precursor to product ion transitions monitored for paeoniflorin and the IS were m/z 524.8→449.0 and 463.1→300.0, respectively. The assay was validated with a linear range of 0.02~25.6 μg/mL for paeoniflorin. The intra- and inter-day precisions (relative standard deviation%) were within 9.7%, and the recoveries were greater than 65.2%. Paeoniflorin was proven to be stable during all sample storage, preparation and analytical procedures. The method was successfully applied to a pharmacokinetic study of the Baixiangdan Capsule in eight female rats.
Dynamic Alterations in the Gut Microbiota of Collagen-Induced Arthritis Rats Following the Prolonged Administration of Total Glucosides of Paeony
Rheumatoid arthritis (RA) is a common autoimmune disease linked to chronic inflammation. Dysbiosis of the gut microbiota has been proposed to contribute to the risk of RA, and a large number of researchers have investigated the gut-joint axis hypothesis using the collagen-induced arthritis (CIA) rats. However, previous studies mainly involved short-term experiments; very few used the CIA model to investigate changes in gut microbiota over time. Moreover, previous research failed to use the CIA model to carry out detailed investigations of the effects of drug treatments upon inflammation in the joints, hyperplasia of the synovium, imbalance in the ratios of Th1/Th2 and Th17/Treg cells, intestinal cytokines and the gut microbiota following long-term intervention. In the present study, we carried out a 16-week experiment to investigate changes in the gut microbiota of CIA rats, and evaluated the modulatory effect of total glucosides of paeony (TGP), an immunomodulatory agent widely used in the treatment of RA, after 12 weeks of administration. We found that taxonomic differences developed in the microbial structure between the CIA group and the Control group. Furthermore, the administration of TGP was able to correct 78% of these taxonomic differences, while also increase the relative abundance of certain forms of beneficial symbiotic bacteria. By the end of the experiment, TGP had reduced body weight, thymus index and inflammatory cell infiltration in the ankle joint of CIA rats. Furthermore, the administration of TGP had down-regulated the synovial content of VEGF and the levels of Th1 cells and Th17 cells in CIA rats, and up-regulated the levels of Th2 cells and Treg cells. The administration of TGP also inhibited the levels of intestinal cytokines, secretory immunoglobulin A (SIgA) and Interferon-γ (IFN-γ). In conclusion, the influence of TGP on dynamic changes in gut microbiota, along with the observed improvement of indicators related to CIA symptoms during 12 weeks of administration, supported the hypothesis that the microbiome may play a role in TGP-mediated therapeutic effects in CIA rats. The present study also indicated that the mechanism underlying these effects may be related to the regulation of intestinal mucosal immunity remains unknown and deserves further research attention.
Hypothalamic malonyl‐CoA and CPT1c in the treatment of obesity
Metabolic integration of nutrient sensing in the central nervous system has been shown to be an important regulator of adiposity by affecting food intake and peripheral energy expenditure. Modulation of de novo fatty acid synthetic flux by cytokines and nutrient availability plays an important role in this process. Inhibition of hypothalamic fatty acid synthase by pharmacologic or genetic means leads to an increased malonyl‐CoA level and suppression of food intake and adiposity. Conversely, the ectopic expression of malonyl‐CoA decarboxylase in the hypothalamus is sufficient to promote feeding and adiposity. Based on these and other findings, metabolic intermediates in fatty acid biogenesis, including malonyl‐CoA and long‐chain acyl‐CoAs, have been implicated as signaling mediators in the central control of body weight. Malonyl‐CoA has been hypothesized to mediate its effects in part through an allosteric interaction with an atypical and brain‐specific carnitine palmitoyltransferase‐1 (CPT1c). CPT1c is expressed in neurons and binds malonyl‐CoA, however, it does not perform the same biochemical function as the prototypical CPT1 enzymes. Mouse knockout models of CPT1c exhibit suppressed food intake and smaller body weight, but are highly susceptible to weight gain when fed a high‐fat diet. Thus, the brain can directly sense and respond to changes in nutrient availability and composition to affect body weight and adiposity.