Diabetes and Bariatric Surgery

The prevalence of type 2 diabetes (Insulin resistance) is increasing at a staggering rate.  According to data from the CDC in 2001, the number of individuals affected in the United States is in the range of 6-10% of the population.  The associated comorbid conditions that are the result of this disease process place affected individuals at high risk for debilitating complications.  Diabetes is the leading cause of blindness, kidney failure and need for lower extremity amputation in the United States.  For diabetes, the age-adjusted death rate has continued to climb since 1980 while the age-adjusted death rate of stoke and cardiovascular disease has seen substantial decrease.   Diabetes is currently the 6th leading cause of death.

Currently, medical management is the mainstay of treatment for those with non-insulin dependent diabetes mellitus (type 2 diabetes).  Management can range from diet modification to oral hypoglycemic agents and eventually to insulin based therapy.  In general, treatment success is monitored by finger-stick glucose measurements, glycosylated serum proteins (fructosamine test) and periodic HbA1C measurements.  Many patients are reluctant to use medications long term, noncompliant or simply cannot afford to use medications from a financial standpoint.  These are only a few of the many reasons why long-term medical management of diabetes is difficult.

Dovetailing the prevalence of diabetes is obesity.  Obesity, long time considered a disease best treated medically, has now become almost universally accepted as a disease process with a surgical solution.  Both retrospective and prospective studies on Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion (BPD), sleeve gastrectomy (SG) and laparoscopic adjustable gastric band (LAGB) have demonstrated conclusive evidence for long term weight loss in patients having BMI greater than 35.  There is also substantial evidence for improvement if not complete resolution of many of obesity related comorbid conditions.  Resolution of non-insulin dependent diabetes after LAGB, RYGB and BPD are 47.8%, 83.6%, and 97.9%, respectively.

The mechanism for glucose control after gastrointestinal surgery for obesity has not been completely elucidated.  Patients who undergo duodenal exclusion procedures (RYGB, BPD) can have resolution of their diabetes prior to having any significant weight loss.  It has been shown in non-obese, type 2 diabetic animal models (Rubino) that excluding the proximal gut from ingested meals has a positive effect on glucose homeostasis.  This has lead to the hypothesis of an entero-insular axis that modulates blood glucose levels after an ingested meal.  There have been studies on small groups of non-obese patients with type 2 diabetes undergoing duodenal-jejunal bypass from India and Brazil.  Although both studies were limited in size the data collected was very encouraging suggesting that non-morbidly obese patients can have the same beneficial metabolic response from duodenal exclusion as their obese counterparts.

Bariatric surgery provides substantial and durable improvement in blood glucose levels and HgbA1c.   The ability to safely and repeatedly perform these operations has been demonstrated.  Moreover, these operations are routinely performed laparoscopically further reducing postoperative pain, wound complications and facilitating rapid discharge from the hospital.    Studying the bariatric patient population has begun to unlock the mysteries of foregut hormones better elucidating the mechanism of insulin resistance.  In time, the knowledge obtained from bariatric surgery may lead to better medical treatments for type 2 diabetes and obesity.