Pulsatile insulin secretion in elderly patients with diabetes

Insulin pulsation is impaired in type 2 diabetes. GLP-1 increases pulsatile insulin secretion in these patients. We conducted these studies with the hypothesis that GLP-1 would enhance pulsatile insulin secretion and alter glucose metabolism in elderly patients with type 2 diabetes. Experiments were conducted in nine patients (age: 72 ± 5 years; BMI: 27 ± 3 kg/m²; diabetes duration: 7 ± 3 years; HbA_1c: 6.6 ± 0.9%). Subjects underwent three glucose clamp studies. The first was a euglycemic clamp to determine individual insulin clearance. In the second, GLP-1 was infused from 0-240 min (0.75 pM/kg/min) and glucose was maintained at fasting levels. The third was similar except that octreotide (30 ng/kg/min) was infused with GLP-1 to suppress pulsatile insulin. Insulin and glucose were given to match levels during the second study. 3-³H-glucose was infused to allow calculation of hepatic glucose production and glucose disposal rates. There was no significant difference in measurements of pulsatile insulin secretion or hepatic glucose production and glucose disposal rates between the studies. Because there was no difference in pulsatile insulin between experiments, we could not test the effect of pulsatile insulin on glucose metabolism. Further studies are required to determine the impact of insulin pulses on glucose metabolism.