Is stool frequency associated with the richness and community composition of gut microbiota?

BACKGROUND/AIMS: Recently, a number of studies have reported that the gut microbiota could contribute to human conditions, including obesity, inflammation, cancer development, and behavior. We hypothesized that the composition and distribution of gut microbiota are different according to stool frequency, and attempted to identify the association between gut microbiota and stool frequency. METHODS: We collected fecal samples from healthy individuals divided into 3 groups according to stool frequency: group 1, a small number of defecation (≤2 times/wk); group 2, normal defecation (1 time/day or 1 time/2 day); and group 3, a large number of defecation (≥2–3 times/day). We evaluated the composition and distribution of the gut microbiota in each group via 16S rRNA-based taxonomic profiling of the fecal samples. RESULTS: Fecal samples were collected from a total of 60 individuals (31 men and 29 women, aged 34.1±5.88 years), and each group comprised 20 individuals. The microbial richness of group 1 was significantly higher than that of group 3 and tended to decrease with increasing number of defecation (P<0.05). The biological community composition was fairly different according to the number of defecation, and Bacteroidetes to Firmicutes ratio was higher in group 1 than in the other groups. Moreover, we found specific strains at the family and genus levels in groups 1 and 3. CONCLUSIONS: Bacteroidetes to Firmicutes ratio and the abundance of Bifidobacterium were different according to the stool frequency, and specific bacteria were identified in the subjects with large and small numbers of defecation, respectively. These findings suggest that stool frequency might be associated with the richness and community composition of the gut microbiota.

CD36 signaling inhibits the translation of heat shock protein 70 induced by oxidized low density lipoprotein through activation of peroxisome proliferators-activated receptor gamma

Oxidized LDL (OxLDL), a causal factor in atherosclerosis, induces the expression of heat shock proteins (Hsp) in a variety of cells. In this study, we investigated the role of CD36, an OxLDL receptor, and peroxisome proliferator-activated receptor gamma (PPAR gamma) in OxLDL-induced Hsp70 expression. Overexpression of dominant-negative forms of CD36 or knockdown of CD36 by siRNA transfection increased OxLDL-induced Hsp70 protein expression in human monocytic U937 cells, suggesting that CD36 signaling inhibits Hsp70 expression. Similar results were obtained by the inhibition of PPAR gamma activity or knockdown of PPAR gamma expression. In contrast, overexpression of CD36, which is induced by treatment of MCF-7 cells with troglitazone, decreased Hsp70 protein expression induced by OxLDL. Interestingly, activation of PPAR gamma through a synthetic ligand, ciglitazone or troglitazone, decreased the expression levels of Hsp70 protein in OxLDL-treated U937 cells. However, major changes in Hsp70 mRNA levels were not observed. Cycloheximide studies demonstrate that troglitazone attenuates Hsp70 translation but not Hsp70 protein stability. PPAR gamma siRNA transfection reversed the inhibitory effects of troglitazone on Hsp70 translation. These results suggest that CD36 signaling may inhibit stress- induced gene expression by suppressing translation via activation of PPAR gamma in monocytes. These findings reveal a new molecular basis for the anti-inflammatory effects of PPAR gamma.

Optical Nano-imaging for the Diagnosis of Gastrointestinal Cancers / 대한소화기학회지

Development of in vivo animal imaging instrumentations and methods contributes to the early diagnosis of cancer. Of variable imaging modalities, in vivo optical imaging such as bioluminescence and fluorescence is one of the best methods to measure molecular change of cancer cells. High sensitivity and relatively low cost of optical method gives benefits to apply for translational research in the field of cancer. Nano-probes to label and detect early cancer cells have been developed by nano-chemists and molecular imaging researchers. Quantum dots made from fluorescent semi-conductors show good advantages in term of imaging probes; high quantum yields, large molar extinction coefficients, size-dependent tunable emission and high photostability. To detect a gastrointestinal (GI) cancer, newly developed endoscopes have been used. Among them, near infrared fluorescence endoscope and confocal endomicroscope are good candidates for clinical application. In animal studies, successful results to detect cancer in gastrointestinal tract have been obtained. Prospect of nanoparticles as optical imaging moiety is promising to detect GI cancers if their toxicity is minimized. Future fluorescence confocal endoscope with safe cancer targeting nanoparticles will be useful for the detection and treatment of GI cancers.