Glucagon secretion after metabolic surgery in diabetic rodents.

Excessive or inadequate glucagon secretion promoting hepatic gluconeogenesis and glycogenolysis is believed to contribute to hyperglycemia in patients with type 2 diabetes. Currently, metabolic surgery is an accepted treatment for obese patients with type 2 diabetes and has been shown to improve glycemic control in Goto-Kakizaki (GK) rats, a lean animal model for type 2 diabetes. However, the effects of surgery on glucagon secretion are not yet well established. In this study, we randomly assigned forty 12- to 14-week-old GK rats to four groups: control group (GKC), sham surgery (GKSS), sleeve gastrectomy (GKSG), and gastric bypass (GKGB). Ten age-matched Wistar rats served as a non-diabetic control group (WIC). Glycemic control was assessed before and 4 weeks after surgery. Fasting- and mixed-meal-induced plasma levels of insulin and glucagon were measured. Overall glycemic control improved in GKSG and GKGB rats. Fasting insulin levels in WIC rats were similar to those for GKC or GKSS rats. Fasting glucagon levels were highest in GKGB rats. Whereas WIC, GKC, and GKSS rats showed similar glucagon levels, without any significant meal-induced variation, a significant rise occurred in GKSG and GKGB rats, 30 min after a mixed meal, which was maintained at 60 min. Both GKSG and GKGB rats showed an elevated glucagon:insulin ratio at 60 min in comparison with all other groups. Surprisingly, the augmented post-procedural glucagon secretion was accompanied by an improved overall glucose metabolism in GKSG and GKGB rats. Understanding the role of glucagon in the pathophysiology of type 2 diabetes requires further research.