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Loss of the First Phase Insulin Response to Intravenous Glucose in Subjects with Persistent Impaired Glucose Tolerance
Author(s) -
Davies M.J.,
Rayman G.,
Grenfell A.,
Gray I.P.,
Day J.L.,
Hales C.N.
Publication year - 1994
Publication title -
diabetic medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.474
H-Index - 145
eISSN - 1464-5491
pISSN - 0742-3071
DOI - 10.1111/j.1464-5491.1994.tb00302.x
Subject(s) - impaired glucose tolerance , medicine , endocrinology , insulin , diabetes mellitus , impaired fasting glucose , insulin response , glucose tolerance test , insulin resistance , plasma glucose
Loss of the first phase insulin response to intravenous glucose is one of the earliest detectable defects of beta cell dysfunction in Type 2 diabetes mellitus. Impaired glucose tolerance (IGT) is considered a prediabetic condition, therefore loss of first phase insulin secretion in subjects with IGT would suggest beta cell dysfunction as an early lesion in the development of Type 2 diabetes. Three groups of subjects were studied, 7 subjects with persistent IGT (classified as having IGT at two 75 g oral glucose tolerance tests (OGTT) done 6 months apart), 6 subjects with transient IGT (IGT at the first OGTT, but normal glucose tolerance at a repeat OGTT 6 months later), and 7 normal controls. First phase insulin secretion was studied using an intravenous glucose tolerance test with arterialized blood sampling. Fasting, 3, 4 and 5 min samples were assayed for glucose and insulin (specific two‐site immunoradiometric assay). The fasting insulin was similar in all three groups, however the 3 min insulin response was significantly lower in those with persistent impaired glucose tolerance ( p < 0.02). Thus subjects with persistent impaired glucose tolerance demonstrated loss of the first phase insulin response as an early indicator of beta cell dysfunction while subjects with transient IGT had a normal insulin response to intravenous glucose. During the OGTT, the 30 min glucose was not significantly different ( p = 0.1) but the 30 min insulin to glucose ratio was significantly lower in subjects with persistent IGT ( p < 0.03). In the whole group the 30 min insulin to glucose ratio during the OGTT showed a significant correlation with the peak insulin response during the IVGTT ( r = 0.76, p < 0.001). This study suggests that beta cell dysfunction with impaired early insulin release is present before the development of Type 2 diabetes.