There have been several published research reports that patients living with Type 1 Diabetes and who have an implantable insulin pump experience fewer and milder episodes of hypoglycemia than do patients receiving subcutaneous insulin (by injection or external insulin pump). The following, recent paper addresses this issue:
Insulin Delivery Into the Peripheral Circulation: A Key Contributor to Hypoglycemia in Type 1 Diabetes
Diabetes Volume 64:3439–3451, October 2015
Authors: Justin Gregory et al
In their Discussion section the authors state:
“The current study sought to determine the extent to which the route of insulin delivery influences susceptibility to hypoglycemia.”
This is a technical paper and requires careful reading – the essence of the paper, however, is summarized in the following statement: (Note bracket [ ] inserts are for clarification and are not included in the original)
“Current therapy in T1DM is further limited by the necessity of injecting insulin into subcutaneous tissue, which delivers insulin into the peripheral (Pe) circulation, rather than the hepatic portal (Po) circulation. This approach results in a reversal of the normal insulin distribution, with higher insulin concentrations in the Pe circulation [i.e., the peripheral circulation] and lower insulin levels in the hepatic portal Po circulation [i.e. circulation to the liver]. A therapeutic balance must therefore be achieved, such that the excess of insulin in the Pe circulation [i.e., the peripheral circulation] and its effect on glucose uptake offsets the deficit of insulin at the liver and its effect on glucose production. Because Pe overinsulinization [i.e., peripheral overinsulinization] shifts the primary site of insulin action away from the liver and toward skeletal muscle, a conceivable result is a predisposition to hypoglycemia.”
A somewhat less technical way of saying this is that in order to manage T1D with subcutaneous insulin it is necessary to deliver an excess amount of insulin in order to get enough insulin to the liver to help it regulate blood glucose. This over delivery of insulin acts upon skeletal muscle in a way that makes hypoglycemia more likely. In effect, trying harder to achieve excellent blood glucose control with subcutaneous insulin makes hypoglycemia more likely.
The concluding remarks of the paper are as:
“The fact that insulin has to be delivered Pe [i.e. subcutaneously] clearly plays a role in causing hypoglycemia and glycemic variability. These studies suggest that strategies to mimic endogenous insulin secretion into the Po [i.e., liver] circulation, such as intraperitoneal insulin delivery or use of hepatopreferential insulin analogs, should mitigate hypoglycemic risk and reduce fluctuations in glucose in patients with T1DM.”
Editor Comment: This is just what T1D implantable insulin pump users report. Hypoglycemia is less frequent, less severe, and far easier to recover from than it had been in the past when they were treated with subcutaneous insulin. They also report that maintaining a stable blood glucose is far more achievable and requires far less effort.