Improved glucose metabolism following bariatric surgery is associated with increased circulating bile acid concentrations and remodeling of the gut microbiome

Clinical studies have indicated that circulating bile acid(BA) concentrations increase following bariatric surgery, especially following malabsorptive procedures such as Roux-en-Y gastric bypasses(RYGB). Moreover, total circulating BA concentrations in patients following RYGB are positively correlated with serum glucagonlike peptide-1 concentrations and inversely correlated with postprandial glucose concentrations. Overall, these data suggest that the increased circulating BA concentrations following bariatric surgery- independently of calorie restriction and body-weight loss- could contribute, at least in part, to improvements in insulin sensitivity, incretin hormone secretion, and postprandial glycemia, leading to the remission of type-2 diabetes(T2DM). In humans, the primary and secondary BA pool size is dependent on the rate of biosynthesis and the enterohepatic circulation of BAs, as well as on the gut microbiota, which play a crucial role in BA biotransformation. Moreover, BAs and gut microbiota are closely integrated and affect each other. Thus, the alterations in bile flow that result from anatomical changes caused by bariatric surgery and changes in gutmicrobiome may influence circulating BA concentrations and could subsequently contribute to T2 DM remission following RYGB. Research data coming largely from animal and cell culture models suggest that BAs can contribute, via nuclear farnezoid X receptor(FXR) and membrane G-protein-receptor(TGR-5), to beneficial effects on glucose metabolism. It is therefore likely that FXR, TGR-5, and BAs play a similar role in glucose metabolism following bariatric surgery in humans. The objective of this review is to discuss in detail the results of published studies that show how bariatric surgery affects glucose metabolism and subsequently T2 DM remission.

Factors for wireless operators'collusion and competition

This article analyses on why China Mobile and China Unicom have chosen price war rather than tacit collusion these years. On the basis of the analysis on factors that influence tacit collusion, and combined with the facts of wireless communication market, the author suggests that the market asymmetries, cost asymmetries, and product differentiation are the basic factors, which trigger price competition between the Chinese wireless operators. By constructing a game model based on Chum rate, this article discusses how these factors cause a fight between the operators and how vigorous the price competition will be. At last, the author suggests that to keep vigor in this industry, continuous structural adjustment is essential. Besides, the number portability policies may cause tacit collusion.