title: Loss of the first phase insulin response to intravenous glucose in subjects with persistent impaired glucose tolerance.
abstract: 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).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Ipswich Diabetes Centre, Ipswich Hospital, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Davies
authors.forename: G
authors.initials: G
authors.lastname: Rayman
authors.forename: A
authors.initials: A
authors.lastname: Grenfell
authors.forename: I P
authors.initials: IP
authors.lastname: Gray
authors.forename: J L
authors.initials: JL
authors.lastname: Day
authors.forename: C N
authors.initials: CN
authors.lastname: Hales
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood; D013997:Time Factors
chemical_list: D007328:Insulin