Ghrelin, which is produced mainly in the stomach, is a potent orexigen or appetite inducing hormone that has been shown to be elevated in states of hunger, but to decline rapidly following a meal.
Researchers from Emory University School of Medicine, Atlanta, USA, were interested to investigate whether the early alterations in ghrelin levels observed in morbidly obese patients undergoing weight reduction surgery may be due to gastric partitioning.
They studied 34 patients who underwent Roux-en-Y gastric bypass with a completely divided gastroplasty to create a 15 mL vertically orientated gastric pouch.
In addition, 8 other patients who underwent less drastic gastric bypass procedures not involving complete division of the stomach were also studied. These included 4 vertical banded gastroplasties and 4 anti-reflux surgical procedures.
A lean control group of 6 additional patients undergoing anti-reflux surgery was also included in the study.
|Gastric bypass surgery caused ghrelin levels to drop by almost a third|
|Archives of surgery|
In each case plasma samples were obtained before surgery and immediately after surgery, while in a sub-study, plasma was collected after Roux-en-Y limb formation and after dividing the stomach in order to identify any changes in plasma ghrelin levels.
The researchers found that in the patients not undergoing the gastric bypass procedure (i.e. the vertical banded gastroplasty group and all patients undergoing anti-reflux surgery) there were no significant changes in ghrelin levels following surgery.
This was in marked contrast to the gastric bypass group, where mean preoperative ghrelin levels dropped from 355 pg/mL to 246 pg/mL postoperatively.
Lead researcher Dr Edward Lin said, "This is the first time we have found that different types of weight-loss surgeries affect ghrelin levels in humans. Compared with morbidly obese humans, lean controls had significantly higher plasma ghrelin levels at baseline."
"When the stomach is divided, forming a small gastric pouch, the ghrelin levels are significantly reduced early after the surgery is performed. Other mechanisms can make you hungry, but ghrelin is one of the most potent hunger stimulants."
He added, "This study shows that surgically induced weight loss with Roux-en-Y gastric bypass in these patients appears to cause long-term, if not permanent, suppression of ghrelin secretions that is not associated with other weight-loss procedures and may explain, in part, the loss of hunger sensation and rapid weight loss observed following gastric bypass surgery."