A perspective on metabolic surgery from a gastroenterologist.

Type 2 diabetes (T2D) and obesity are important public health problems. The global prevalence of diabetes mellitus is 8.8%. Interventional diabetology and obesitology have been recently advocated as treatment options for T2D and obesity. The roles of metabolic surgery such as Roux-en-Y gastric bypass, sleeve gastrectomy, gastric banding, and biliopancreatic diversion are focused. Different types of metabolic surgeries have different glucose-lowering and weight loss effects. Endoscopic treatments include the intra-gastric balloon (to restrict the gastric volume) and duodenal-jejunal bypass liner (DJBL, as a malabsorptive procedure). Anatomic changes in the gastrointestinal tract may cause alterations in gut hormones, bile acids, adipokines, inflammatory cytokines, hepatokines, myokines, gut microbiota, and even unidentified factors. Modulating gut hormones, including foregut (ghrelin, glucose-dependent insulinotropic polypeptide) and hindgut (glucagon-like peptide-1, peptide YY) hormones, through metabolic surgeries improves glycemic homeostasis. Metabolic surgeries reduce pro-inflammatory cytokines and increase anti-inflammatory cytokines. Metabolic surgeries also regulate one's appetite through the new establishment of jejunal nutrient sensing. Therefore, the effects of metabolic surgery and DJBL implantation emphasize the crucial role of the small intestine in glucose homeostasis. Removing diabetogenic or obesogenic factors from the duodenum and/or jejunum may help to solve the problems of diabetes and obesity in the future.

Correlation between colonic secretion and colonic motility in rats: Role of ghrelin.

AIM: To explore the relationship between colonic secretory function and colonic motility. METHODS: Using a rat model chronically implanted with intracerebroventricular (ICV) and cecal catheters, we validated the correlation between colonic secretion and colonic motor functions, as well as the role of ICV injection volume. RESULTS: Compared to saline controls (5 µL/rat), ICV acyl ghrelin at 1 nmol/5 µL enhanced the total fecal weight, accelerated the colonic transit time, and increased the fecal pellet output during the first hour post-injection, while ICV des-acyl ghrelin at 1 nmol/5 µL only accelerated the colonic transit time. These stimulatory effects on colonic motility and/or secretion from acyl ghrelin and des-acyl ghrelin disappeared when the ICV injection volume increased to 10 µL compared with saline controls (10 µL/rat). Additionally, the ICV injection of 10 µL of saline significantly shortened the colonic transit time compared with the ICV injection of 5 µL of saline. The total fecal weight during the first hour post-injection correlated with the colonic transit time and fecal pellet output after the ICV injection of acyl ghrelin (1 nmol/5 µL), whereas the total fecal weight during the first hour post-injection correlated with the fecal pellet output but not the colonic transit time after the ICV injection of des-acyl ghrelin (1 nmol/5 µL). CONCLUSION: Colonic secretion does not always correlate with colonic motility in response to different colonic stimulations. Acyl ghrelin stimulates colonic secretion.