Effects of Pulsatile Insulin Delivery on Diabetic Neuropathy in Patients With Types 1 and 2 Diabetes Mellitus

Diabetic neuropathy (DN) is a progressive complication causing serious problems in 25%-40% of diabetic patients. Significant complications produce painful peripheral dysesthesias, loss of sensation, and gastroparesis. DN may affect the peripheral motor and sensory nerves in addition to the autonomic nervous system (1-3). Treatment strategies for patients with DN have generally concentrated on pain relief, without addressing the underlying pathophysiology of the disease (4). Anecdotal reports from patients treated with pulsatile insulin for other complications suggest that this treatment may show efficacy in patients with DN. This study is designed to compare patients with DN who receive pulsatile insulin with a control group.

Pulses of IV insulin encourages the glucose metabolism in diabetics to normalize in multiple organs, especially muscle, retina, liver, kidney and nerve endings. The process fundamentally requires the administration of high dose insulin pulses similar to those found in non diabetic humans by their pancreas into the surrounding portal circulation. Oral carbohydrates are given simultaneously to augment the process and prevent hypoglycemia. The process is monitored by frequent measuring of glucose levels and respiratory quotients (RQ). RQ is measured by a metabolic cart which determines the ratio VCO2/ VO2. This ratio is specific for the fuel used at any one time by the body. The glucose levels are monitored to keep glucose levels appropriate and the RQ determines the need to readjust the infusion protocol in each patient for subsequent insulin infusion sessions. The insulin pulses are delivered over 1-hour periods with a 1-hour rest period between each session. Three treatments are given during each treatment day.

The respiratory quotient (RQ) is a measurement of CO2 exhaled and O2 inhaled and is proportionate to the fuel sources being used by the body, primarily the liver over short periods of time. The higher the RQ, the more glucose and less alternative fuel sources are being utilized. Following the RQ change helps determine the effectiveness of physiological insulin administration in increasing anabolic functions in diabetic individuals. By improving the body's glucose metabolism and thereby causing beneficial effects of anabolic factors, the possibility of serious complications can be decreased. In addition the use of oral carbohydrate at the same time along with the physiologic insulin administration stimulates the appropriate gut hormones which augment this effect, a response which cannot be duplicated with intravenous glucose. The purpose of our studies is to determine whether the physiologic administration of insulin along with the augmenting effect of oral carbohydrates will normalize metabolism in diabetic patients and correlate with an improvement in their manifestations of diabetic neuropathy.

The RQ is determined by the use of a metabolic cart. Individuals breathe into a mask for 3-5 minutes after a rest period of 30 or more minutes. The ratio of exhaled volume of CO2 to the inhaled volume of O2 is determined as the RQ. The physiologic range is 0.7 to1.3. Individuals using fat as a primary fuel have a ratio of 0.7, protein or mixed fuels is 0.8-0.9 and carbohydrate is 0.9-1.0. Those taking excessive calories will have RQ's higher than 1.05.

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