Dipeptidyl peptidase-4 (DPP4) inhibitor sitagliptin alleviates liver inflammation of diabetic mice by acting as a ROS scavenger and inhibiting the NFκB pathway.

As a common chronic metabolic disease, the development of diabetes mellitus (DM) may also be accompanied by liver damage and inflammatory disorders. Sitagliptin is an inhibitor of dipeptidyl peptidase-4 (DPP4, also known as CD26), which is clinically used for DM treatment. However, the mechanism of sitagliptin's efficiency in liver diseases is largely unknown. In this study, mice suffering from streptozotocin (STZ) exhibit elevated liver DPP4 expression and activity, as well as inflammatory and chronic liver injury phenotype, whereas specifically inhibiting the activity of DPP4 in mouse liver tissues and hepatocytes by sitagliptin contributes to decreased cytokines, oxidative stress, cell apoptosis, and inflammation in STZ-induced diabetic mice. Moreover, sitagliptin reduced TNFα or LPS-induced cellular reactive oxygen species (ROS) level, cell apoptosis, and protein expression in the NFκB signaling pathway in HepG2 cells or primary mouse hepatocytes. Altogether, our study confirms that sitagliptin may protect liver tissue by alleviating ROS production and NFκB signaling activation, providing a putative mechanism for preventing the development of diabetic liver disease.

Study on Periplaneta americana Polypeptide PAE2 in Reversing Multidrug Resistance for Liver Cancer / 中国实验方剂学杂志

Objective:To investigate the effect and mechanism of PAE₂， a polypeptide of <italic>Periplaneta americana， </italic>in reversing multidrug resistance （MDR） for liver cancer <italic>in vivo</italic>. Method:Balb/c-nude mice were inoculated with HepG2 and HepG2/ADM cells under the armpits to establish animal models of liver cancer sensitive strains and animal models of MDR respectively. After successful modeling， the nude mice were randomly divided into normal group， HepG2 model group， HepG2/ADM model group， sorafenib group （positive drug control group， <italic>ig</italic> 30 mg·kg^-1）， HepG2/ADM+PAE₂ （<italic>iv</italic>） low， medium and high dose groups （50， 100， 200 mg·kg^-1）， HepG2/ADM+PAE₂ （<italic>ig</italic>） low， medium， and high dose groups （50， 100， 200 mg·kg^-1）， skim cream group （<italic>ig</italic> 200 mg·kg^-1）， and CⅡ-3 group （<italic>ig</italic> 200 mg·kg^-1）， all of which received corresponding drug treatment. The body weight and tumor volume of nude mice were measured and recorded every 2 days. The next day after the last administration， tumor tissues of nude mice were taken to record the tumor weight. The effect of <italic>P. americana </italic>polypeptide PAE₂ on permeability-glycoprotein（P-gp）， lung resistance protein（LRP） ， breast cancer resistance protein（BCRP）， protein kinase C（PKC）， glutathione S-transferase-π（GST-π）， topo-isomerase typeⅡ（ToPoⅡ）， multidurg resistance gene 1（MDR1）and Multidrug resistance-associated proteins（MRP1） of the protein level and gene level expression in tumor tissues were determined by immunohistochemistry （IHC） and real-time quantitative polymerase chain reaction （Real-time PCR）. In addition， both oral and intravenous administration groups were set up at the same time for preliminary study on the basic pharmacokinetic characteristics of <italic>P. americana </italic>polypeptide PAE₂. Result:After the successful modeling， the body weight of the nude mice was significantly lower than that in the normal mice（<italic>P</italic><0.05）. After treatment with corresponding drugs， the body weight increased to a certain extent， but it was still not as good as the normal nude mice. In <italic>iv</italic> administration， the medium-dose <italic>P. americana </italic>polypeptide PAE₂ showed the best anti-tumor effect as compared with the model group （<italic>P</italic><0.05）， while in oral administration， the anti-effect increased with the increase of the dose， so the high-dose group showed the best effect （<italic>P</italic><0.05）. Preliminary crude extract CII-3 had no obvious anti-tumor effect， and skim cream showed a certain anti-tumor effect （<italic>P</italic><0.05）. <italic>P. americana </italic>polypeptide PAE₂ had certain effects on MDR related proteins and enzymes<italic> in vivo</italic>， mainly by inhibiting the expression of LRP and BCRP in tumor tissues and affecting the expression of these related proteins and genes to different degrees to inhibit intracellular drugs outflow， thereby promoting tumor apoptosis， and the effect was superior to that of the <italic>P. americana</italic> crude extract CⅡ-3 and skim cream. Conclusion:<italic>P. americana</italic> polypeptide PAE₂ may reduce the drug efflux， promote intracellular drug accumulation and apoptosis by affecting the expression of related proteins and enzymes that mediate multidrug resistance， thereby exerting a reverse effect on HepG2/ADM cells Balb/c MDR in nude mice.

Activation of brown adipocytes by placental growth factor.

Gestational diabetes mellitus (GDM) is a type of diabetes and occurs during pregnancy. Brown adipose tissue (BAT) improves glucose homeostasis and mitigates insulin resistance, however, its activity is reduced in GDM. Placenta growth factor (PlGF) is an angiogenic factor produced by placental trophoblasts. Nevertheless, whether and how PlGF could affect BAT function in GDM are not defined. To investigate this question, 91 non-diabetic pregnant participants and 73 GDM patients were recruited to Gynaecology and Obstetrics Centre in Lu He hospital. Serum levels of PlGF were quantified by ELISA. Skin temperature was measured by far infrared thermography in the supraclavicular region where classical BATs were located. The direct effect of PlGF on BAT function was explored using the established human preadipocyte differentiation system. Thereby, we demonstrated that serum levels of PlGF were lower in GDM patients compared with controls, which was accompanied by decreased skin temperature in the supraclavicular region. By qPCR and western blot, mRNA and protein expression of UCP1 and OXPHOS were elevated in differentiated adipocytes treated with PlGF. PlGF stimulated mitochondrion transcription and increased copy number of mitochondrial. When subjected for respirometry, PlGF-treated differentiated adipocytes showed higher oxygen consumption rates than controls. PlGF induced AMPK phosphorylation and blockade of AMPK phosphorylation blunted UCP1 and OXPHOS expression in differentiated adipocytes. PlGF administration reduced cholesterol and triglyceride content in the liver and improved insulin sensitivity in db mice compared with control. In Conclusion, PlGF could activate BAT function. Downregulation of PlGF might contribute to the reduced BAT activity in GDM.