Tuesday, March 10, 2015

Can We Surgically Treat Diabetes?

We live in a country where fast food is cheaper than eating healthy and where a McDonald’s is always just around the corner. Obesity and diabetes have become all too common in America. In fact, the number of Americans afflicted by obesity and diabetes has reached epidemic proportions.

While the preferred treatments for obesity and diabetes include dieting, exercise and pharmacotherapy, doctors have recently started to consider surgical intervention for more severe cases.
While undergoing extremely invasive surgeries such as intestinal bypass (where the duodenum and jejunum are bypassed thereby shortening the length food travels in the small intestines as a means to reduce the absorption of nutrients) and gastric resection (where food intake is mechanically reduced by restricting the volume of the stomach) may seem unpleasant, they have started to become the preferred and more popular surgeries to help afflicted patients lose weight. However, these surgeries have more complex effects than simply causing you to lose weight; for example, one beneficial side-effect to such surgeries have been the remission of type 2 diabetes post-operation. If not to treat obesity and diabetes, studying these two procedures may allow us to better understand the physiological and homeostatic roles our stomach and small intestines play. 

Sarruf DA, Bonner-Weir S, Schwartz MW. New clues to bariatric surgery’s benefits. Nature Medicine. 18: 860-861 (2012).
Benefits of Weight Loss
From Barnes Bariatric in Dallas/Fort Worth, Texas (http://barnesweightlosssurgery.com/gastric-sleeve-surgery/)

In order to test the homeostatic roles of the small intestines and the stomach in regards to sugar metabolism, Rajesh Patel and a group of researchers at Weill Cornell Medical College in New York City tested the two surgical procedures (gastric resection and intestinal bypass) in diabetic, fatty rats. They operated on the rats giving them either a gastric resection or an intestinal bypass and then looked at changes in their food intake, body weight, glucose tolerance and levels of various hormones. 

The researchers found that gastric resection surgeries showed significantly reduced food intake, which makes sense because their stomachs are smaller. This decline in food intake, in turn, resulted in a significant decrease in body weight, which again makes sense. However,  food intake in the long run was no different than the control rats suggesting that maintaining a healthy weight requires more than just surgery, it also requires a desire to keep that weight off through continuous discipline and health-oriented actions post-operation. On the other hand, for rats that underwent intestinal bypass, they had only a transient decline in food intake for the first week post-operation, which I believe may be the result of post-operation discomfort and distress. Regardless, intestinal bypass resulted in no significant change in the rats’ body weights.
But there is a silver lining for the rats that underwent the intestinal bypass according to Rajesh Patel’s research lab. The researchers found that rats that underwent intestinal bypass did show a significantly higher oral glucose tolerance than either the control or those rats that underwent the gastric resection surgeries. So while these rats don’t look any skinnier, they can rest easy knowing they can eat more sweets! All jokes aside, this is very strange to see that elimination of a portion of your intestines results in being able to better manage glucose homeostasis. While trying to discern the reasoning for this phenomenon, the researchers looked towards hormones, the regulators of many homeostatic functions in our body.
When looking at the hormones, they looked at insulin and glucagon among other hormones. They found that the increased glucose tolerance in rats that underwent intestinal bypass was insulin-independent because no significant change was found in the levels of insulin relative to the controls. But strangely, they also found that intestinal bypass restored glucagon suppression comparable to healthy rats. While the mechanism for such a process is still uncertain, we now have evidence that suggests our small intestines may have a more complex function than we initially believed. It’s crazy to think that we still aren’t aware of just how complex our body’s homeostatic control is.
It’s true that we see increased glucose tolerance in rats with the intestinal bypass, but that could be a result of other variables. The gut microbiota may have changed causing altered glucose absorption, bile acid perturbation as a result of the bypass (and bile acids have been shown to prevent insulin resistance), and potential changes in neuroendocrine signaling could all account for the changes observed. But pinpointing exactly what the cause is will require further studies.
Ultimately, we hope that studying these invasive surgical interventions in rats not only help us to improve the lives of afflicted human patients, but also inform us about our own bodies to allow more potent pharmacotherapeutic alternatives to deal with our current epidemic.


Patel RT, Shukla AP, Ahn SM, Moreira M, Rubino F. Surgical control of obesity and diabetes: the role of intestinal vs. gastric mechanisms in the regulation of body weight and glucose homeostasis. Obesity Biology and Integrated Physiology, 22:(1) 159-169 (2014).


  1. This post connects directly to the first unit studied in Physiology, dealing with the complex regulatory mechanisms of hormones in the endocrine system. With more and more public health campaigns aimed at reducing obesity and associated diseases such as diabetes in the United States, it makes sense that gastric and intestinal surgeries have become common place. However, I always associated these surgeries with weight loss and never considered the consequences they might have on diabetes. The restoration of glucagon suppression in rats that underwent intestinal bypass is especially interesting as related to diabetes, even without significant weight loss. With the mechanism of action still unknown, I would be interested to see a study that tests the various hypotheses of altered gut microbes or measures bile acid levels. Perhaps these outside forces have a greater influence on hormones than expected, making the regulatory endocrine networks even more complicated!

  2. This post is so relevant for America today with our increasing rates of obesity! I think it's especially important that food intake post surgery is reduced so that the patients don't become obese again. It's also amazing how complex our GI tract is. I can't believe that chopping off a portion of tissue can have such extreme effects on hormones.

  3. I think it is interesting that they tested the rate of food intake in rats after surgery because they would be incapable of knowing that they had diabetes and would have to eat less in order to get healthy again or keep the weight off. I think it would be interesting to test humans and see if the cognitive side of things plays a role in keeping the weight off or not.

  4. I think this blog post does a great job of highlighting just how complex our bodies really are. Even in the smallest of things, the human body never ceases to amaze me! Aside from that, I think the idea of gastric resection is also very interesting. For some time now this has been quite popular in the plastic surgery industry, where many individuals undergo this procedure to lose weight. However, in most cases, individuals are unable to sustain their new body weight because they don't make lifestyle adjustments. Rehman makes a great point-- having a healthy body (in this case) requires more than just surgery. Our bodies our precious and should be treated that way!