Endocrine and metabolic response to gastric bypass

Abstract

Purpose of review: Diabetes resolves in 80% of individuals undergoing successful Roux-en-Y gastric bypass. Absolute caloric restriction alone resulting from gastric anatomic changes indeed leads to weight loss; however, immediate effects in glycemic control often precede substantial weight loss typically associated with insulin sensitivity. One putative explanation relates to hormonal effects accompanying Roux-en-Y gastric bypass. We reviewed the existing and recent literature to investigate the hormonal changes accompanying Roux-en-Y gastric bypass.

Recent findings: Changes in levels of five candidate enteric hormones have been recently associated with early postoperative glycemic control following Roux-en-Y gastric bypass; the strongest effects are seen with variations in glucagon-like peptide-1, glucose-dependent insulinotropic peptide and ghrelin.

Summary: The unique hybridization of static anatomic restriction and dynamic absorptive bypass lends a duality to the beneficial effects of Roux-en-Y gastric bypass. This duality likely explains the short-term and long-term resolution of diabetes in patients undergoing Roux-en-Y gastric bypass.

Figure 1. Anatomic rearrangements of the Roux-en-Y gastric bypass

Architecture of the alimentary tract after surgery. A small gastric pouch (20–30 ml) is connected to the jejunum through a gastrojejunostomy establishing oro-anal continuity. The bypassed stomach, duodenum and early jejunum are connected to the Roux limb providing secretory drainage. The Roux limb is delineated between the gastrojejunostomy and jejunojejunostomy.