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Does Gastric Bypass Reduce Cardiovascular Complications of Diabetes?

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For obese people with diabetes, doctors have increasingly been offering gastric bypass surgery as a way to lose weight and control blood glucose levels. Short-term results are often impressive, but questions have remained about the long-term benefits of such operations. Now, a large, international study has some answers.

Soon after gastric bypass surgery, about 50 percent of folks not only lost weight but they also showed well-controlled blood glucose, cholesterol, and blood pressure. The good news is that five years later about half of those who originally showed those broad benefits of surgery maintained that healthy profile. The not-so-good news is that the other half, while they generally continued to sustain weight loss and better glucose control, began to show signs of increasing risk for cardiovascular complications.

In fact, earlier studies have consistently shown that gastric bypass surgery offers benefits in terms of weight loss and improved blood glucose control for people with diabetes. But diabetes also comes with an increased risk for cardiovascular complications. People with diabetes are at greater risk of suffering a heart attack or stroke [1]. They are also more likely than people without diabetes to have other cardiovascular risk factors, including high blood pressure and cholesterol levels. Does gastric bypass help to reduce those risks too?

That’s the question the NIH-funded Diabetes Surgery Study set out to answer about a decade ago. To get a more holistic view on the benefits of gastric bypass surgery, they relied on the American Diabetes Association’s (ADA’s) composite triple endpoint for diabetes. Those guidelines include a hemoglobin A1C of less than 7 percent. The A1C test measures the amount of glucose attached to hemoglobin in red blood cells, which reflects a person’s average blood glucose level in the preceding months. An A1C below 5.7 percent is considered normal. An A1C above 6.5 is consistent with a diagnosis of diabetes.

In addition, the ADA’s composite end point includes a low-density lipoprotein or “bad” cholesterol level of less than 100 milligrams per deciliter (mg/dL) and systolic blood pressure less than 130 milligrams of mercury (mmHg). That’s the upper number in a typical blood pressure reading. For people with diabetes, the triple endpoint is often remarkably tough to achieve; most never do.

Led by Sayeed Ikramuddin and Charles Billington at the University of Minnesota, Minneapolis, the Diabetes Surgery Study enrolled 120 people in the United States and Taiwan who had type 2 diabetes and a hemoglobin A1C above 8 percent. All participants also had a body mass index (BMI) above 30, which is generally considered obese. Half of the study’s participants were randomly selected to undergo a Roux-en-Y gastric bypass procedure along with two years of intensive lifestyle and medical management. The remaining study participants received two years of intensive lifestyle and medical management without surgery.

The Roux-en-Y procedure involves reducing the stomach size by 90 percent and attaching the remaining stomach pouch into a latter section of the small intestine. As a result, people eat less and absorb fewer calories. The question was: Would that surgical procedure, when added to those other interventions, help more people to reach and maintain the ADA’s triple endpoint?

As reported in JAMA, the initial results were quite encouraging [2]. In the first year, half of the gastric bypass group (28 people) achieved the composite triple endpoint. That’s compared to 16 percent of those (9 people) who didn’t undergo surgery. However, that early success began to slip by year three. By that time, 23 percent of those in the gastric bypass group compared to 4 percent in the lifestyle-medical management group met the goals for blood glucose, cholesterol, and blood pressure.

The five-year outcomes data now show that those improvements seen at year three have held steady, with those who received a gastric bypass continuing to fare significantly better on average than those who received the lifestyle and medical intervention alone. However, the diminished magnitude of those effects raises doubts about the procedure’s longer-term benefits to prevent cardiovascular disease.

Further study is needed to determine the continued durability of those improvements and whether they will ultimately translate into fewer cardiovascular complications, including heart attack and stroke. In weighing those benefits, it’s also important to note that some people have suffered serious adverse events after gastric bypass, including small bowel obstructions and leaks.

This study is one of several in JAMA’s special issue on “reimagining obesity” to explore the benefits of bariatric surgery, including the Roux-en-Y procedure and the increasingly popular sleeve gastrectomy, which is less technically complex and appears to come with fewer complications [3]. Bariatric surgery is now recognized as a standard treatment option for people with obesity and diabetes, and especially for those who have failed other treatments [4]. While considerable progress in understanding the benefits and risks of these approaches has been made, it’s clear that plenty of questions about the role of surgery for treating people with obesity, diabetes, and associated health complications remain.

References:

[1] Diabetes, Heart Disease, and Stroke.National Institute of Diabetes and Digestive and Kidney Diseases.

[2] Lifestyle Intervention and Medical Management With vs Without Roux-en-Y Gastric Bypass and Control of Hemoglobin A1c, LDL Cholesterol, and Systolic Blood Pressure at 5 Years in the Diabetes Surgery Study. Ikramuddin S, Korner J, Lee WJ, Thomas AJ, Connett JE, Bantle JP, Leslie DB, Wang Q, Inabnet WB 3rd, Jeffery RW, Chong K, Chuang LM, Jensen MD, Vella A, Ahmed L, Belani K, Billington CJ. JAMA. 2018 Jan 16;319(3):266-278.

[3] Reimagining Obesity in 2018. JAMA. 2018 Jan 16;319(3).

[4] Consensus from Diabetes Organizations Worldwide: Metabolic Surgery Recognized as a Standard Treatment Option for Type 2 Diabetes. American Diabetes Association. 24 May 2016.

Links:

Overweight and Obesity Statistics (National Institute of Diabetes and Digestive and Kidney Diseases)

Charles Billington (University of Minnesota, Minneapolis)

Diabetes Surgery Study (Clinicaltrials.gov)

NIH Support: National Center for Advancing Translational Sciences; National Institute of Diabetes and Digestive and Kidney Diseases

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