Monday, August 19, 2013

The Surprising effect of Gastric Bypass Surgery on Diabetes

Roux-en-Y gastric bypass (RYGB) is a radical surgical intervention that is used for those individuals who suffer from intractable and severe obesity and want desperately to reduce their weight.  Surprisingly, it has been shown that this is also the best approach for the treatment of obesity-related diabetes (Type 2).  It is so effective in this regard that those patients who have successfully undergone this procedure are often able to dispense with their anti-diabetic medication entirely.  It is currently not fully understood how this particular surgical procedure produces this encouraging result.

In RYGB the following surgical modifications are performed –
  • The stomach is divided producing a small gastric pouch (GP) that can only accommodate a small amount of food.
  • A portion of the small intestine is transected – made into two branches – and one arm of the transection is connected to the GP and is referred to as the Roux limb (RL)
  • Both of these branches meet at the so-called “common limb” (CL) and all contents of the GP then proceed through the rest of the digestive tract.

 As a result of these modifications, food entering the esophagus travels to the GP and then to the RL bypassing the remaining part of the stomach – the so-called “distal stomach” (DS) -, the duodenum and part of the jejunum – these areas represent the upper portion of the small intestine.  The RL is thereby exposed to undigested nutrients.  This change may be implicated in the positive effect that this procedure exerts on diabetes. 

In order to further elucidate the mechanism for this change, Dr. Nima Saeidi at the Center for Basic and Translational Obesity Research, Division of Endocrinology at Boston’s Children’s Hospital studied RYGB using the rat as the animal model.   The results of their studies proved very interesting.  They found that within the cells of the tissues of the RL there is a definitive reprogramming of the intestinal metabolism of glucose.  It is important to remember that a key feature of diabetes is the failure of certain body cells to take up glucose from the circulation  and that the serious symptoms  associated with long-term diabetic patients  are directly related to the chronically high levels of glucose in the blood.  This shift in glucose metabolism associated with RYGB was found to include the increased cellular production of an important enzyme involved in glucose metabolism – glucose transporter-1, an increase in glucose uptake, an enhancement of aerobic glycolysis – the metabolic pathway involved in breaking down glucose and a shift in metabolism towards supporting tissue growth.  Furthermore Dr. Saeidi and his team were able to show that this shift in metabolism is directly related to the fact that the RL is exposed to undigested nutrients.

This is an important finding in support of the efficacy of RYGB in dealing with not only obesity but also obesity-related diabetes.  Furthermore, through a further elucidation of the mechanism by which this anti-diabetic effect operates, a clearer picture is generated in regards to an overall understanding of glucose metabolism.

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