Resolution of Type 2 Diabetes with WLS
November 21, 201618 years ago, when I started my career as a bariatric surgeon, we thought that we knew everything about how bariatric surgery worked - we were wrong.
At the first World Congress on Interventional Therapies for Type 2 Diabetes, held in September 2008, a number of experts in the surgical treatment of obesity and in the field of obesity research called for a consensus on the use of bariatric surgery to treat Type 2 Diabetes. Indeed, surgeons and some endocrinologists are now suggesting that clinicians refer patients who have Type 2 Diabetes with a body mass index (BMI) below traditional criteria for bariatric surgery, based on limited evidence that even in this subgroup, glucose tolerance improves and oral medications will no longer be necessary for diabetes management. In addition, as the use of bariatric surgery of all types increases in the adult population, it has become more widely accepted as an option for obese adolescents.
Early Effects of WLS on Type 2 Diabetes
There have been two main hypotheses, which have been put forth in an effort to explain the early effects of bariatric surgery on Type 2 Diabetes. These are referred to as the foregut hypothesis and the hindgut hypothesis.
Foregut Hypothesis
The “foregut hypothesis” states that diabetes control results from the increase in the rate of delivery of nutrients into the distal small intestine. The result of this is an enhanced release of hormones such as glucagon-like peptide-1 (GLP-1).
Some researchers have suggested that the rapid resolution of Type 2 Diabetes following malabsorptive bariatric procedures is due to the fact that they bypass the proximal small intestine through as-yet unclear mechanisms which are known as the “foregut hypothesis.”
This hypothesis is supported by data showing high rates of rapid diabetes resolution (in as much as 72 hours post-surgery) in patients undergoing malabsorptive bariatric surgery as opposed to those undergoing purely restrictive procedures such as Gastric Banding. In addition, there are recent reports of the Gastric Sleeve (where the hormone producing tissue in the stomach is removed) and Duodenal Bypass (which lacks the restrictive component of the surgery) curing T2D in non-obese humans.
Hindgut Hypothesis
Another hypothesis, the “hindgut hypothesis,” for rapid diabetes resolution which suggests that early contact of distal bowel with relatively undigested food enhances some signal that results in improved glucose metabolism. Incretins such as glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, which are hormones secreted by the gastrointestinal tract and are responsible for increasing insulin secretion in response to oral nutrients.
The assumption is that these hormones are the most likely candidates responsible for part of this improvement in Type 2 Diabetes. This observation is complicated by our current understanding that incretins along with oxyntomodulin, ghrelin, peptide YY all appear to be affected differently due to variations in anatomical rearrangements from the various surgical procedures. This observation is further complicated by minor changes in surgical technique such as the amount of stomach removed in a Sleeve, different lengths of jejunal limbs, and the size of gastric pouches, all of which can affect the metabolic outcomes.
Studies and Literature for WLS and Type 2 Diabetes
Finally, recent studies have shown that improved intestinal gluconeogenesis may be responsible for the amelioration of glucose homeostasis following bariatric surgery. Unfortunately, to date, no large trials have specifically addressed the effects of bariatric surgery on the remission or reversal of Type 2 Diabetes independent of weight loss with or without caloric restriction. There is, however, sufficient data in the literature to support the idea that bariatric surgery specifically, Gastric Sleeve, RYGB, and BPD can all lead to early improvement of glucose control independent of weight loss. Therefore, these bariatric procedures should all be considered in morbidly obese patients suffering from Type 2 Diabetes and some day in the future they may also be used to resolve Type 2 Diabetes regardless of BMI.
 | ABOUT THE AUTHOR Michael Jay Nusbaum, MD, FACS, FASMBS started the Laparoscopic Bariatric Program at Saint Barnabas Medical Center in 2000. He has performed over 2,000 laparoscopic gastric bypasses and over 1,500 laparoscopic gastric banding procedures. He currently practices at Obesity Treatment Centers of New Jersey.Read more articles by Dr. Michael Jay Nusbaum! |
