Monday, March 17, 2008

Can gastric banding cure diabetes? Part I.

A couple of months ago, a paper published in the Journal of the American Medical Association made headlines with the claim that gastric banding surgery resulted in remission of type II diabetes in 73% of patients who had the surgery (as opposed to only 13% remission in controls).

A few obvious questions come to mind here: is it true? And if so, is the remission from diabetes just a consequence of weight loss, or does the surgery result in some other physiological change that results in diabetes remission? In this post, I'm going to write about the validity of these studies. And in Part II, which I'll post on Friday, I'll talk about the mechanisms by which weight loss surgeries are believed to affect diabetes.

Gastric banding is a "restrictive" surgery involving the placement of a band around the stomach, restricting food intake by limiting the capacity of the stomach (1). Some other types of weight loss surgery are "absorptive" and work by limiting absorption from the gastrointestinal tract by physically bypassing parts of the gastrointestinal tract (1). And some surgical procedures are both restrictive and absorptive.

There are different advantages and disadvantages to different types of surgeries. Patients who undergo gastric banding tend to lose less weight than those who have other types of weight loss surgeries (an average of 47.5% of excess weight loss with gastric banding vs. an average 70.1% of excess weight with the duodenal switch procedure, a restrictive and absorptive surgery), however, the gastric banding procedure is faster, less invasive, and has a lower risk of complications than more invasive surgeries (1). It also has the advantage of being reversible.

Two studies in the 1990s had demonstrated that the Roux-en-Y gastric bypass surgery (which is both restrictive and malabsorptive) reduced pre-diabetic patients' risk of developing type II diabetes (2) and normalized blood glucose in some type II diabetics within days of the surgery (3) (in fact, some patients experienced an "overnormalization" of blood glucose and suffered occasional attacks of hypoglycemia).

In 2004, Ponce et al. (4) set out to see if gastric banding (ahem, excuse me, Lap-Banding ® which is just a specific brand of gastric band) produced similar results. They measured HbA1c levels, an indicator of average blood glucose over the past couple of months, in patients 12, 18, and 24 months after their surgeries. They found that glucose levels improved following surgery and maintained that improvement at 24 months. They also found that type II diabetes was resolved in a majority of patients who had been diabetic for less than 5 years prior to their surgery, but in only about a third of those who had been diabetic for more than 5 years prior to surgery.

Last year, Korenkov et al. (5), set out to look at a slightly longer follow-up period, but unfortunately, because the patients varied in their followup durations from 2 to 8 years (with an average of 5 years) it is not possible to determine based on their results if the health improvements they saw were truly stable over this period. They found that the prevalence of type II diabetes decreased from 10% pre-surgery to 4% at followup. However, they do not say how many (if any) of these patients were still diabetes free 8 years out. Another short-term study published last year (6) compared gastric band and Roux-en-Y gastric bypass surgeries and found that at 13 months post-surgery, 50% of diabetic gastric band patients and 95% of gastric bypass patients had improvements in their diabetes. However, again, it is not clear whether these effects persisted over the long term.

So the JAMA study which received so much media attention recently was really not so revolutionary. The study's subjects were all patients with a BMI <40* style="font-style: italic;">JAMA explain the discrepancy by pointing out that the surgical team participating in the study "is among the most experienced groups in the world using LAGB, and their excellent results may not be reproducible elsewhere. Their reported post-LAGB weight loss often exceeds that observed by other investigators" (8). I hope that longer-term findings will be published in the coming years, but the results this far look pretty promising. But of course, weighing the risks and benefits of any surgical procedure is something that should be the sole prerogative of patients themselves.

*The authors explain that they "believed it inappropriate to recruit those with a BMI greater than 40 into the study, because a number of observational studies have shown effectiveness of bariatric surgery in these patients." I think they're missing a "not" in there somewhere...

1. Korenkov M, Sauerland S, Junginger T. Surgery for Obesity. Current Opinions in Gastroenterology 21: 679-683, 2005.

2. Long SD, O'Brien K, MacDonald KG Jr., Leggett-Frazier N, Swanson MS, Pories WJ, Caro JF. Weight loss in severely obese subjects prevents the progression of impaired glucose tolerance to type II diabetes: a longitudinal interventional study. Diabetes Care 17: 372-275, 1994.

3. Pories WJ, Swanson MS, MacDonald KG, Long SB, Morris PG, Brown BM, Barakat HA, deRamon RA, Israel G, Dolezal JM. Who would have thought it? An operation proves to be the most effective therapy for adult-onset diabetes mellitus. Annals of Surgery 222: 339-352, 1995.

4. Ponce J, Haynes B, Paynter S, Fromm R, Lindsey B, Shafer A, Manahan E, Sutterfield C. Effect of Lap-Band®-Induced Weight Loss on Type 2 Diabetes Mellitus and Hypertension. Obesity Surgery 14:1335-1342, 2004.

5. Korenkov M, Shah S, Sauerland S, Duenschede F, Junginger T. Impact of Laparoscopic Adjustable Gastric Banding on Obesity Co-morbidities in the Medium- and Long-Term. Obesity Surgery, 17: 679-683, 2007.

6. Gan SSH, Talbot ML, Jorgensen JO. Efficacy of Surgery in the Management of Obesity-Related Type 2 Diabetes Mellitus. ANZ Journal of Surgery, 77:958-962, 2007.

7. Dixon JB, O'Brien PE, Playfair J, Chapman L, Schachter LM, Skinner S, Proietto J, Bailey M, Anderson M. Adjustable Gastric Banding and Conventional Therapy for Type 2 Diabetes. JAMA 299: 316-323, 2008.

8. Cummings DE, Flum DR. Gastrointestinal Surgery as a Treatment for Diabetes. JAMA 299: 341-343, 2008.

7 comments:

Maritzia said...

Whether or not this is a cure for Type II diabetes depends, of course, on your definition of Type II diabetes. Do they just look at blood sugar control, or do they actually look at insulin resistance, which is the cause of the diabetes to start with.

My sister had gastric bypass, and while her blood sugar control is excellent post surgery with no medication, I believe she is still insulin resistant. Her symptoms are more of the hypoglycemia seen in pre-diabetics, which studies have shown are already insulin resistant.

I imagine it's pretty easy to control your blood sugar on 800 calories a day (which is about what my sister eats now), but that doesn't mean that the diabetes is in remission or cured unless your only definition of diabetes is blood sugar levels.

Dr. LaWade said...

Maritzia, that's an excellent question. The various papers did look at different endpoints, and many of them did not look at insulin resistance. The Dixon et al. JAMA study, however, did, and found that gastric banding significantly lowered fasting insulin and HOMA IR (an indirect measure of insulin resistance which compares fasting glucose and fasting C-peptide), whereas conventional therapy did not.

Several other studies have also showed improved insulin sensitivity in gastric bypass patients...for an example see LZ Coppini et al., Obesity Surgery, 2006. The entry I post on Friday will talk a little bit more about the mechanisms of this.

Since diabetes remission rates are less than 100%, though, it is entirely possible, though, that your sister may still be insulin resistant. However, since the complications of diabetes (neuropathy, heart disease, etc.) are thought to primarily result from poor glucose control, the improvements in blood sugar she has experienced are likely to be beneficial, even if insulin resistance is not resolved.

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