Ghrelin, Appetite & Laparoscopic Sleeve Gastrectomy
Scientists say they may have found out why people get hungry at mealtime, why dieters who lose weight often gain it back and why certain types of stomach surgery help very obese people lose a great deal of weight.
The reason may be a hormone called ghrelin, which makes people hungry, slows metabolism and decreases the body’s ability to burn fat.
Ghrelin Levels
Ghrelin levels in the blood peak before meals and drop afterward. People given ghrelin injections felt voraciously hungry, and, when turned loose at a buffet, ate 30 percent more than they normally would.
Dieters who lose weight and then try to keep it off make more ghrelin than they did before dieting, as if their bodies are fighting to regain the lost fat, researchers are reporting today in the New England Journal of Medicine.
By contrast, the same study showed that very obese people who have an operation called gastric bypass to lose weight wind up with relatively little ghrelin, which may help explain why their appetites decrease markedly after the surgery. Sleeve Gastrectomy operations also remove the section of the stomach in which Ghrelin is produced
Below is an extract from a Scientific paper published in Obesity Surgery, Vol15, 2005
Sleeve Gastrectomy and Gastric Banding: Effects on Plasma Ghrelin Levels
F. B. Langer1; M. A. Reza Hoda1; A. Bohdjalian1; F. X. Felberbauer1;
J. Zacherl1; E.Wenzl1; K. Schindler2; A. Luger2; B. Ludvik2; G. Prager1
1Department of Surgery, Division of General Surgery, and 2Department of Medicine III, Division of
Endocrinology and Metabolism, Medical University Vienna, Vienna, Austria
Ghrelin, recently described as a hunger regulating peptide hormone mainly produced in the fundus of the stomach, is reported to be significantly increased in diet-induced weight-loss. Inconsistent changes in plasma ghrelin levels, however, were reported following different bariatric surgical procedures. Laparoscopic sleeve gastrectomy (LSG), which can be regarded as an advancement of the Magenstrasse and Mill procedure, has been introduced as the first part of a two-step laparoscopic gastric bypass in the “super-super-obese” (i.e. BMI >60 kg/m2) patients in order to reduce the perioperative risk. Furthermore, it has been applied as a definitive bariatric operation in a series of high-risk super-obese patients. Because the gastric fundus, known as the main localization of ghrelin-producing cells, is resected by sleeve gastrectomy, plasma ghrelin levels are expected to decrease following surgery. The aim of this prospective study was to determine the effects of laparoscopic sleeve gastrectomy (LSG) on immediate and 6 months postoperative ghrelin levels, compared with laparoscopic adjustable gastric banding (LAGB).
In this study in 20 morbidly obese patients, we found significantly reduced levels of plasma ghrelin following laparoscopic sleeve gastrectomy immediately after surgery and up to a period of 6 months. In contrast, plasma ghrelin was not changed postoperatively after LAGB and increased significantly after 1 and 6 months. In parallel, excess weight loss was more pronounced following LSG compared with LABG. To our knowledge this is the first study investigating plasma ghrelin levels in sleeve gastrectomy.
Because ghrelin is supposed to be involved in the regulation of appetite, the effects of various bariatric operations on the plasma levels of ghrelin have been a focus of interest in a growing number of recentlypublished papers. While it has been shown that plasma ghrelin increases following diet-induced weight loss18 thereby potentially contributing to weight regain, the data on ghrelin after bariatric operations are inconclusive so far.
In contrast to LAGB, Roux-en-Y gastric bypass was found to decrease the plasma ghrelin level. To explain this discrepancy, it has been speculated that ghrelin-producing cells in the gastric fundus have no further contact with ingested nutrients resulting in an override suppression after RYGBP. In gastric banding patients, however, the ghrelin producing cells are not bypassed. Therefore, these cells remain to function, leading to increased ghrelin levels following LAGB, comparable to diet induced weight loss.
Sleeve gastrectomy has been established as part of the BPD-DS. Only three studies of sleeve gastrectomy as sole bariatric intervention have been published so far, without focusing on changes of plasma ghrelin levels. In this series of LSG, the greater curvature and the gastric fundus as the main locus of ghrelin production were completely resected, forming a narrow gastric tube that permits oral intake of only small amounts of food. This extensive type of LSG may be understood as a restrictive procedure augmented by the reduction of the ghrelin producing tissue. While the majority of plasma ghrelin originates from the stomach, other locations of ghrelin secretion outside the gastric fundus have been reported. The restrictive effect on food ingestion after LAGB and LSG is comparable. In contrast to Adami, who found ghrelin levels following biliopancreatic diversion comparable to preoperativevalues only 2 months postoperatively, we observed no compensatory hypersecretion of ghrelin as stable low levels were found in the postoperative course up to 6 months following laparoscopic sleeve gastrectomy. This difference could be explained by the extent of gastric resection. In our series the complete fundus was resected, while the fundus was left in situ in the series of Adami
Within 6 months, LSG patients were able to reduce their weight in a more effective way than LAGB patients. In this series, LSG patients presented with higher preoperative plasma ghrelin levels compared with the patients of the LAGB group (109.6 ± 32.6 fmol/ml vs 73.7 ± 24.8 fmol/ml, P=0.005).
Postoperatively, LSG led to significantly decreased and stable plasma ghrelin levels at up to 6 months. In contrast, patients who underwent LAGB presented with significantly increased plasma ghrelin in the postoperative course. Because the restrictive effect regarding food intake is comparable between both methods, the superior effect on weight loss by LSG could be attributed to the permanently lower ghrelin levels preventing an increase in appetite as a compensatory mechanism.
In conclusion, we have demonstrated that in contrast to LAGB, ghrelin levels are significantly decreased following LSG immediately postoperatively, as well as up to 6 months postoperatively in morbidly obese patients. This is paralleled by a superior weight loss after LSG which might be related to the permanent decrease in ghrelin levels preventing a compensatory increase in hunger.
