News & Research

    , Salt Lake City, Utah

The effect of bariatric surgery on peripheral nerve and axonal regeneration

General Research Subject: Obesity

Focus: Complications\Nephropathy, Obesity\Clinical Treatment

Type of Grant: ADA-Ethicon Endo-Surgery/Covidien Research Award in Bariatric Surgery and Diabetes

Project Start Date: July 1, 2011

Project End Date: June 30, 2014

Diabetes Type: Type 2 diabetes

Research Description

Diabetes often causes injury (neuropathy) to the longest nerves of the body, which reach from the spine down to the foot. These nerves, which carry information about pain and sensation from the skin, can be easily injured, but also grow back into the skin after injury. We use capsaicin to cause these nerves to die back from the skin surface, and follow their re-growth by taking small skin biopsies over three months. Obesity and high blood levels of cholesterol and related fats also may contribute to neuropathy.

Surgery to partially bypass and shrink the stomach limits food consumption and absorption of fat from the gut, and is an effective treatment to cause weight loss in people who are very obese.  This study will look for evidence of neuropathy in 80 obese patients without diabetes, considering bypass surgery, and compare the rate of neuropathy in a group of 80 healthy people with normal weight. We will measure nerve re-growth in 50 obese patients before surgery, and again 9 months after surgery. Before, and 9 months after surgery, we will carefully measure the amount and location of body fat in these subjects, and examine possible ways in which excess fat may damage nerves.

Research Profile

What area of diabetes research does your project cover?  What role will this particular project play in preventing, treating and/or curing diabetes?

Diabetic neuropathy is a major cause for disability due to pain, falls, foot ulcers, and amputations. Neuropathy often occurs early in diabetes.  Patients with prediabetes are also at risk for neuropathy.  Once neuropathy is established, it is difficult to reverse.  Our research program focuses on prevention of neuropathy.  

Nerves carry information about pain and sensation from the skin to the brain.  These nerves can be easily injured, but also grow back into the skin after injury.  We can use the over the counter pain medication capsaicin to cause these nerves to die back from the skin surface, and follow their re-growth by taking small skin biopsies over three months. We have found that patients with high blood sugar due to either diabetes or prediabetes have a reduced ability of these nerves to re-grow following injury.  We hypothesize that this reduction in regeneration ability contributes to neuropathy.  Obesity and high blood levels of cholesterol and related fats combine with high blood sugar to cause neuropathy. Surgery to partially bypass and shrink the stomach limits food consumption and absorption of fat from the gut, and is an effective treatment to cause weight loss in people who are very obese. 

This study will look for evidence of neuropathy in 80 obese patients without diabetes, considering bypass surgery, and compare the rate of neuropathy in a group of 80 healthy people with normal weight. We will measure nerve re-growth in 50 obese patients before surgery, half with diabetes, and again 9 months after surgery. Before, and 9 months after surgery, we will carefully measure the amount and location of body fat in these subjects, and examine possible ways in which excess fat may damage nerves.

If a person with diabetes were to ask you how your project will help them in the future, how would you respond?

This project will help us understand the extent to which obesity and its complications lead to neuropathy, independent of high blood sugar.  The results will help us identify patients at risk for developing neuropathy and will provide very useful information regarding the potential benefits of obesity surgery in preventing neuropathy.  The results will also validate this novel way of testing therapies for neuropathy prevention. This study will provide useful information in designing potential treatments for patients with diabetes and obesity.

Why is it important for you, personally, to become involved in diabetes research?  What role will this award play in your research efforts?

I see many patients suffering from complications of diabetic and prediabetic neuropathy.  I believe the ideal approach to this potentially disabling condition is to prevent it.  In order to prevent neuropathy we need to understand the factors that lead to its early development and we also need to develop tools to test effective treatments.  The bariatric (obesity) surgery population is an ideal group of patients in which to test the effects of obesity and abnormal lipids on nerve function and the benefit of correcting these abnormalities.  This research project will further our understanding of the metabolic causes of early nerve injury and will hopefully lead to more effective preventative therapies.  I’m particularly excited about this research project because it will involve a collaboration between neuropathy researchers, obesity experts and obesity surgeons, all working together to identify better treatments for this incredibly common problem.

In what direction do you see the future of diabetes research going?

I believe we will see an increasing focus on the role of obesity related complications in neuropathy development, and an emphasis on early intervention, even before the onset of overt diabetes.  While animal models of diabetes are incredibly useful tools in understanding the disease, they have not proven very predictive of human response to treatment.  Therefore, I expect future diabetic neuropathy research to focus more on human studies.