Physiological importance of first-phase insulin release in elderly patients with diabetes.
OBJECTIVE
To assess the physiological role of first-phase insulin release in obese elderly patients with type 2 diabetes.


METHODS
Moderately obese elderly patients (n = 14, mean age 77 +/- 2 years, BMI 28.4 +/- 0.7 kg/m2) with type 2 diabetes underwent three 180-min hyperglycemic clamp studies. In the control study, glucose alone was infused. In the first-phase study, human insulin was infused for the first 4 min at 12 mU/m2 to mimic first-phase insulin release. In the first-phase enhanced study, insulin was infused for the first 4 min at 24 mU.m-2 .min-1. Tritiated glucose methodology was used in all studies to measure glucose production and disposal rates.


RESULTS
Glucose values were similar in all studies. In the control study, first-phase insulin response was absent. The peak insulin response occurred at 4 min in the first-phase and first-phase enhanced studies, but insulin values were substantially higher in the latter study (528 +/- 40 vs. 340 +/- 24 pmol/l, P < 0.0001). Second-phase insulin responses were not different among the studies. Glucose production and disposal rates were not significantly different among the studies.


CONCLUSIONS
While absent first-phase insulin secretion is a marker of abnormal pancreatic function in obese elderly patients with type 2 diabetes, it is not important in the regulation of hepatic glucose output or peripheral glucose disposal.
Division of Geriatric Medicine, University of British Columbia, Vancouver, Canada.
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Meneilly
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Elahi
D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D003920:Diabetes Mellitus / Q000097:blood / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000503:physiopathology*; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005934:Glucagon / Q000097:blood / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D009765:Obesity; D013997:Time Factors
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005934:Glucagon; D005947:Glucose