Assessment of Insulin Sensitivity and β Cell Function by Clamps Studies

Overview

India is the "Diabetes Capital of the World" with 41 million Indians having diabetes i.e. every fifth diabetic in the world is an Indian. Type 2 Diabetes Mellitus (T2DM) constitutes the major chunk of diabetes and has insulin resistance as the hallmark feature in the pathogenesis. However, with the progression of the disease the insulin resistance becomes stable whereas β - cell function shows a gradual decline due to its ongoing apoptosis. This ultimately leads to inability of the β - cells to cope up with the increased demand of insulin caused due to insulin resistance and manifests as hyperglycemia. As β - cell failure is progressive and inexorable, as demonstrated in United Kingdom Prospective Diabetes Study, most of the patients with T2DM would eventually require insulin and it would be difficult to achieve to attain a strict glycemic control . It is well known that diabetes related complications which account for morbidity and mortality in this disease can be prevented or delayed by strict glycemic control. However, even with intensive insulin therapy it has been shown that glycemic control can never be perfect with patients exhibiting hyperglycemia or hypoglycemia during 24 hour glucose profile. Also insulin therapy is not physiological as there is no hepatic "first - pass" metabolism of insulin which is required for halting the hepatic glucose output, which is responsible for fasting hyperglycemia. This led the researchers to evolve various strategies of β - cell replacement therapy e.g. pancreatic transplantation and islet cell transplantation. Initially the results of islet cell transplantation were dismal but after the induction of glucocorticoid free immunosuppressive therapy and the use of adequate number of islet cells from multiple donors, the results of islet cell transplantation have been better. However, islet cell transplantation has its own limitations viz insufficient supply, being technically demanding and requirement of lifelong immunosuppressive therapy in the recipient.

The shortcomings can be overcome by the use of stem cells which is an inexhaustible source of β -cells. Stem cells are primitive cells capable of differentiating into mature cells of the body of various lineages. Stem cells can be obtained from various sources like blastocyst (embryonal stem cells), umbilical cord or bone marrow. There is an evidence to suggest that stem cell transplantation can lead to improvement in pancreatic endocrine function and improvement in glycemic control in diabetic mice through various mechanisms such as transdifferentiation or regeneration of endothelial cell in the damaged islets which in turn lead to regeneration of islet cells by paracrine action. However, till date there is no study that demonstrates that stem cell therapy can be effective in patients with T2DM for their glycemic control. The investigators propose to carry out autologous bone marrow - derived stem cell transplantation (ABMSCT) in patients of T2DM, obtained from their own bone marrow and its superselective injection into the gastroduodenal artery after purification without any immunosuppressive regimen.