The effects and mechanisms of trimethylamine-N-oxide on insulin sensitivity in insulin target cells / 药学学报

Gut microbial metabolite trimethylamine-N-oxide (TMAO) is associated with type 2 diabetes (T2DM). Decreased insulin sensitivity is a significant etiological factor of T2DM. Adipocytes, myocytes, and hepatocytes are the three major target cells for insulin. This study aims to investigate the effects and mechanisms of TMAO on the insulin sensitivity of these target cells. Research results indicate that in different ages of db/db diabetic mice, plasma TMAO levels were increased. TMAO significantly inhibits the insulin signaling pathways in these three major insulin target cells, reduces glucose uptake in 3T3-L1 adipocytes and L6 myocytes and downregulates genes related to gluconeogenesis in primary mouse hepatocytes. Furthermore, in mice with normal insulin sensitivity, elevating plasma TMAO levels to those seen in db/db mice using a minipump results in impaired glucose tolerance and hyperinsulinemia. All animal experiments were carried out with approval of the Experimental Animal Welfare Ethics Committee of the Institute of Materia Medica (Chinese Academy of Medical Sciences and Peking Union Medical College). Mechanistic studies suggest that TMAO exposure increases the levels of endoplasmic reticulum stress-related proteins in these three major insulin target cells. In summary, TMAO directly attenuates insulin sensitivity in insulin target cells, and its mechanism of action may involve enhancing endoplasmic reticulum stress.

TXNDC5 mediates serum starvation-induced proliferation inhibition of HeLa cell / 中国医学科学院学报

<p><b>OBJECTIVE</b>To investigate the role of TXNDC5 in serum starvation-induced proliferation inhibition of HeLa cell.</p><p><b>METHODS</b>TXNDC5 was either over-expressed or knocked down by small interfering RNA (siRNA) in HeLa cells which were then cultured in conventional medium or serum starvation medium. The protein level of TXNDC5 was evaluated by Western blot analysis. The mRNA level of TXNDC5 was measured by quantitative real-time PCR. Cell growth rate was determined by cell proliferation assay kit (MTS method). Cell cycle distribution and apoptosis were detected by flow cytometry.</p><p><b>RESULTS</b>Serum starvation mildly reduced the mRNA level of TXNDC5 (P<0.05), but dramatically increased the protein level of TXNDC5 in HeLa cells. The stability of TXNDC5 mRNA remained unchanged. Cycloheximide abolished the serum starvation-induced up-regulation of TXNDC5 protein. Over-expression of TXNDC5 had no effect on cell proliferation. However, suppression of TXNDC5 attenuated the proliferation inhibition of HeLa cell induced by serum starvation (P<0.05), increased the proportion of cells in S phase (P<0.05), but had no effect on cell apoptosis.</p><p><b>CONCLUSION</b>TXNDC5 mediates serum starvation-induced proliferation inhibition of HeLa cell.</p>

Chemical constituets of Sparganium stoloniferum / 中草药

Objective: To study the chemical constituents of Sparganium stoloniferum. Methods: Column chromatographic techniques were applied to isolate the constituents. The chemical structures of the constituents were elucidated on the basis of physicochemical properties and spectral data. Results: Twelve compounds were isolated and identified as β-sitosterol palmitate (1), β-sitosterol (2), azelaic acid (3), docosanoic acid (4), 6,7,10-trihydroxy-8-octadecenoic acid (5), p-hydroxybenzaldehyde (6), sanleng diphenyl-acetypene (7), ferulic acid (8), 3,5-dihydroxy-4-methoxy-benzoic acid (9), 2,7-dihydroxy-xanthone (10), glycerol ferulate (11), and daucosterol (12). Conclusion: Compounds 3,4, and 9-11 are obtained from the plants of Sparganium L. for the first time.

CatSper and sperm hyperactivation / 中华男科学杂志

Elevation of sperm Ca2+ seems to be responsible for an asymmetric form of motility called hyperactivation, which is first seen near the time of fertilization. CatSper family proteins are putative cation channels expressed exclusively in the membranes of the sperm flagellum. Hyperactivation requires CatSper proteins, which presumably serve as the route of entry for Ca2+ that operates directly on the flagellar axoneme to increase waveform asymmetry. In this article, the structure of mouse CatSper, the role it plays in sperm hyperactivation and the unsolved problems are described.

The Localization and Expression of Tyrosine Phosphorylated Proteins During In Vitro Capacitation of Guinea Pig Sperm / 中国生物工程杂志

The aim of this study was to detect the localization and level of tyrosine phosphorylated proteins during in vitro capacitation of guinea pig sperm. Sperm from mature guinea pigs were incubated in modified TALP under 5% CO_2 in air at 37 ℃. The capacitation effect was assessed by chlortetracycline (CTC) staining. Western blotting and indirect immunofluorescence were used to analyze the level and localization of tyrosine phosphorylation. The results showed that guinea pig sperm underwent a time-dependent increase in protein tyrosine phosphorylation during the in vitro capacitation and the percentage of protein tyrosine phosphorylated sperm increased from 36% to 92% from the beginning of incubation to 7h incubation. Also, there was a shift in the site of phosphotyrosine-specific fluorescence from the head of sperm to both the head and the flagellum of sperm. Moreover, there were three proteins phosphorylated in this experiment. After 0 to 0.5h incubation, the protein of 40kDa was detected by anti-phosphotyrosine monoclonal antibody, and the intensity of this protein increased in the following incubation. Then, after 1h incubation, another protein of 80kDa was found and the level of this protein reached the highest point at 3h. Also, in 3h incubation, a protein of 45kDa was detected and the intensity of this protein increased in the following incubation.