In 1908, Waldeyer described a longitudinal fold along the lesser curvature of the stomach that he called Magenstrasse. The Magenstrasse is a gastric canal that carries liquid and solid food particles from the cardia, along the lesser curvature and down to the pylorus very quickly. A sample of ingested food is emptied along the Magenstrasse before the stomach is filled. This early gush of food into the duodenum generates several neuro-hormonal signals that prepare the intestines and other organs for the upcoming meal. Glucagon like peptide or GLP-1 is one of those signals and it is probably the most studied intestinal hormone. GLP-1 is secreted by L cells that are mainly located in the distal gut. GLP-1 stimulates post-prandial insulin secretion and inhibits gastric emptying. GLP-1 plays a central role in glucose homeostasis. GLP-1 secretion peaks shortly after a meal is ingested and prior to any significant gastric emptying. It is logical to assume that GLP-1 secretion depends on food delivery into the duodenum via the Magenstrasse pathway. Therefore, loss of the Magenstrasse emptying pathway leads to deficient GLP-1 and other neuro-hormone secretion leading to elevated post-prandial blood and abnormal insulin secretion. Indeed, one of the earliest signs of type 2 diabetes is loss of the post-prandial GLP-1 peak secretion.
Sleeve gastrectomy restores the Magenstrasse pathway of gastric emptying. In fact, during sleeve gastrectomy, most of the stomach is resected preserving the longitudinal fold that was described in 1908 by Waldeyer. Sleeve gastrectomy increases gastric emptying. Gastric sleeve surgery results in post-prandial GLP-1 increase and blood glucose improvement. Currently, there is plenty of evidence in the literature that type 2 diabetes and obesity, like gastroparesis, are gastrointestinal motility disorders. Weight loss surgery in the form of sleeve gastrectomy restores normal gastric emptying patterns, like the Magentrasse, resulting in diabetes resolution and weight loss.
Gastric emptying is a complex process that is a carefully regulated. Neuro-hormonal regulatory mechanisms synchronize the emptying process to achieve optimal nutrient digestion and absorption. Ghrelin is a potent stimulator of gastric contractions and emptying, and GLP-I profoundly inhibits this emptying process. Numerous other signals participate in this process and are yet to be fully elucidated. The sharp rise and fall of these hormones, after food intake, control one of the most important aspects of life: energy metabolism. Unless we understand the interaction between foregut and ingested food, we cannot understand diseases like obesity, type 2 diabetes and gastroparesis, nor can we develop better, safer and less invasive treatment modalities. In my next blog, I will revisit the subject of gastric fundus invagination and its effect on the Magenstrasse pathway of emptying.