It is a known fact that the patients fill more quickly and eat less after Gastric Bypass (GP) surgery due to decreasing of stomach volume. Two mechanism most mentioned as the cause of GP beeing successful are :
- Malabsorbtion (decreasing of food absorption)
- Dumping Syndrome
Malabsoption that clinically have importance and characterized with increased fat quantity at the feces, is not seen after the standart GB. Dumping syndrome (nausea, bulge, colic pain, diarrhea, dizziness, perspiration and flutter) is typically seen at some patients after high carbohydrate foods. Due to these effects this syndrome, creates a negative approach against the fattening foods like sugar at patients.
Impairing of the Ghrelin secretion that has developed after GB is indicated to be effective at the anorexia development. Ghrelin is an enteric peptide and it is the only known and participated to the circulatory appetizer. Endogenous levels increase before the meal and decrease after the meal. Ghlerin, is generally producted from the stomach and a small part from the duodenum. Both of these areas are bypassed after GB. Since the eaten food is main Ghrelin secretion trigger and this food is unable to contact the stomach and duodenum, this strengthens the accuracy about the hypothesis of this surgery impairs the Ghrelin secretion. In a study which Ghrelin levels have been investigated; 77% decreasing at the values of patients those have underwent GB 1.5 years ago compared with the thin patients and 72% less Ghrelin secretion compared with the obese control group have been seen.
Anti-Diabetic Effects of Gastric Bypass
Comorbidity related with obesity which has most dramatically showed recovery by GB is Type 2 Diabetes Mellitus (DM). 82-98 % diseases of patients with diabetes have been indicated to showed completely recovery. In a lasting approximately 5 years prospective study of the obese patients with impaired glucose tolerance, obesity surgeries have been shown to decreased the progress rate of diabetes more than 30 times. Thus, it has been seen that GB is largely effective on reversing the diabetes which has conventionally accepted as a progressive and deadly disease.
At the patients those have significantly lost weight after GB operation increasing of Adiponectin levels and muscle insulin receptor concentration and in addition decreasing of lipids and fatty acyl-coenzyme A molecules (cause to insulin resistance) have been shown. After weight loss induced by GB, insulin sensitivity measured with minimal modelling has been increased about 4-5 times. Decreasing of diabetes can be commented to weight loss which it’s impact on insulin sensitivity increasing is well known, thus glucose toxicity and lipotoxicity are decreased and cell function is improved.
After GB has adjusted the insulin secretion effect, positive changes occure at intestine hormones. Ghrelin is a hormone which has decreasing probability after the surgery, altough Ghlerin stimulation creates create induced hyperglycemia at humans, it supresses the insulin levels. Glucagon Like Peptide-1 (GLP-1) hormone and Glucose-Dependent Insulinotropic Polypeptide (GIP) are classical incretins which have stimulated the insulin secretion againts the enteral foods. After GB, the foods have gone down to stomach, more easily reach to the last intestine by skipping a part of upper bowel. Greater postprandial bolus of the foods after GB, raises the GLP-1 levels. Peptide YY (PYY) has been shown to decrease eating and body weight at humans. Since this is also a last intestine hormone, it’s levels increases after GB, particularly after the meal has been eaten and this is considered to help to the weight loss.
In brief; the mechanisms those can explain the weight loss and improved glucose tolerance after GB are :
1. Stomach volume decreasing that causes to early fillness, small meal porsions and negative conditioning
2. Impairing of the Ghrelin secretion due to mechanisms those can not be exactly defined and bypassing of the upper bowel that creates light malabsorption
3. Increasing of the PYY and GLP-1 and acceleration of the foods to reach to the lower bowel
4. Dumping syndrome formation due to intake of concentrated carbohydrates can contribute to the weight loss at some people.
Assoc. Prof. Halil Coskun M.D. www.halilcoskun.com
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