Questions/Diabetes
Q # 1: What is the most commonly used restrictive bariatric procedure worldwide?
The restrictive procedures used for bariatric surgeries are of adjustable gastric banding (AGB) and vertical sleeve gastrectomy (VSG). AGB is said to be the commonest restrictive procedure in the world. In AGB, at the fundus of stomach, an inflatable band made up of silicone is attached. The gastrointestine remains intact from anatomical point of view. Gastric emptying also remains unchanged. In 2009, 40% of bariatric procedures are done by AGB in USA. But now, AGB is replaced by VSG. It is said to be the more efficient procedure as it removes 75% part of stomach along with complete area which contains hormones. As endocrine part is removed, it speeds up gastric emptying rate.
Q # 2: What is the difference between Roux-en-Y gastric bypass and sleeve gastrotectomy?
In Roux-en-Y gastric bypass (RYGB) technique, a GI diversionary procedure, gastric size is restricted and complete pathway of duodenum and proximal jejunum is bypassed. It covers 50% of bariatric surgeries. In RYGB, a 30 cm pouch is created after gastrectomy, which is surgically attached with one part of jejunum (distal). Another part of jejunum (proximal) is joined 75-150 cm beneath the gastro-jejunum attachment. The problems of RYGB include leakage, failure of staple part, acute gastric dilation, hernias, ulcer and vomiting. The excess weight loss (EWL) is 62%. While in VSG, 75% of stomach area along with hormonal part is removed. It speeds up gastric emptying with significant inferred physiology and without re-arrangement of small bowel. The problems of VSG are leakage, vomiting due to overeating and EWL is 68%.
Q # 3: Why the secretion of gut hormone in adjustable gastric banding (AGB) is mainly considered to be due to weight loss?
AGB initiates caloric restriction in starting post-operative period. As AGB cannot change the integrity of GIT or nutrient transient time, and also gut peptides secretion remains unchanged, which is chiefly responsible for increased secretion of insulin; the result appears as glucose homeostasis. This homeostasis occurs independently of variation in glucoregulatory gut hormonal secretion, so it is the robust proof for the weight loss in diabetes.
Q # 4: What is the possible role for GLP-1 in bariatric surgery?
In bariatric surgeries, Glucose-like peptide-1 (GLP-1) is responsible to stimulate insulin, secreted by L-cells of ileum by nutrient response and neural signals coming from gut. Glucose dependant insulin secretion is increased as it acts on pancreatic beta-cells. It also diminishes glucagon secretion. The after meal glycemia is reduced in strength as gastric emptying is slowed down and CNS is signaled for satiety and less food intake.
Q # 5: Which experiments support the hypothesis that GLP-1 is directly involved in improvement of glycemia in gastric bypass in animal and humans?
Multiple studies of RYGB show increased response of GLP-1, which is independent of weight loss. Laferrère proved six times enhanced response after meal in obese, diabetic persons by RYGB process (Vetter et al. 204). Korner et al. demonstrated that concentration of GLP-1 is enhanced 3 times after meal when patient is undergone gastric bypass surgery (204). Kindel et al. demonstrated that rats, which are undergone RYGB without inducing weight loss, shows efficiently improved glucose tolerance (205). Salehi et al. proved that RYGB individuals show a 33% decreased after meal insulin secretion rates by Ex-9 administration, so GLP-1 has improved effects on the release of insulin after gastric bypass techniques (205).
Q # 6: Explain why reduction in ghrelin secretion in bariatric surgery would be beneficial on glucose homeostasis?
Ghrelin is an orexigenic hormone secreted by proximal part of small intestine and gastric fundus. It stimulates appetite on acting hypothalamus. It also effects on pancreatic cells. It can easily inhibit the secretion of insulin. As a whole, it can be said that ghrelin causes significant decrease in appetite and food intake, which results in weight loss. As it inhibits insulin secretion, the adiponectin (insulin sensitizing hormone) suppresses, and stimulates the secretion of counter regulatory hormones, so a decreased production ghrelin has beneficial effects on glucose homeostasis.
Q # 7: Explain why improvement seen in diabetes in some type of bariatric surgery is independent of weight loss?
Certain bariatric surgeries show significantly increased responses by incretin hormone GLP-1, which stimulates insulin secretion. This response is independent on weight loss itself. e.g RYGB elevates GLP-1 levels three times, which supports decrease food intake and induce satiety factor. In VSG, rapid gastric emptying is fast which is caused by increased secretion of GLP-1. GLP-1 physiology is also affected by blocking of its receptors by exendin 9-39 amide (Ex-9). The glucose tolerance is significantly improved because Ex-9 diminishes the activity of GLP-1 on postprandial insulin release.
Q # 8: What did you find most interesting or difficult?
The most difficult thing is always most interesting i.e. bariatric surgeries. Glucose homeostasis is improved efficiently by these surgeries. Weight loss is induced by these techniques with increased diabetes remission rates. Biliopancreatic diversion (BPD) has greatest rates of remission than RYGB and AGB. The rates of remission induced by VSG are considered in between RYGB and AGB.
Works Cited
Vetter, M. L., Ritter, S., Wadden, T. A., & Sarwer, D. B. (2012). Comparison of Bariatric Surgical Procedures for Diabetes Remission: Efficacy and Mechanisms. Diabetes Spectr, 25(4), 200-210.
