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  • 1
    ISSN: 1432-0428
    Keywords: Keywords LADA ; MODY ; Type II diabetes ; IGT ; insulin secretion ; insulin sensitivity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. To evaluate insulin sensitivity and insulin secretion in prediabetic and diabetic subjects with mutations in MODY1 (HNF-4α) and MODY3 (HNF-1α) genes, in subjects with GAD antibodies, latent autoimmune diabetes in adults and in subjects with the common form of Type II (non-insulin-dependent) diabetes mellitus. Methods. Insulin secretion was measured as the incremental 30-min insulin (I30) and insulin glucose ratio (I:G30) during OGTT whereas insulin sensitivity was measured as the insulin sensitivity index during OGTT in 131 carriers of MODY mutations [NGT = 38, IFG/IGT = 21, diabetes mellitus (DM) = 72], in 293 subjects with GADA (NGT = 47, IFG/IGT = 29, DM = 217) and in 2961 subjects with a family history of the common form of Type II diabetes but without MODY mutations or GADA (NGT = 1360, IFG/IGT = 857, DM = 744). A subgroup of the subjects underwent a euglycaemic clamp (n = 210) and intravenous glucose tolerance test (n = 337) for the estimation of insulin sensitivity and first-phase insulin secretion. Results. Non-diabetic subjects with MODY mutations had pronounced impaired insulin secretion (I30, I:G30) compared with the two other groups (p = 0.005). Normal or non-diabetic glucose tolerance was maintained by enhanced insulin sensitivity compared with the other two groups (p 〈 0.05 and p 〈 0.005). In contrast to patients with Type II diabetes and with adult latent autoimmune diabetes, MODY patients showed only a modest deterioration in insulin sensitivity at onset of diabetes. The 2-h glucose values inversely correlated with insulin sensitivity in subjects with GADA (r = –0.447, p 〈 0.001) and subjects from Type II diabetic families (r = –0.426, p 〈 0.001), whereas no such relation was observed in subjects with MODY mutations (r = 0.151, p = NS). There were no statistically significant differences in insulin secretion or insulin sensitivity between subjects with GADA or subjects with a family history of Type II diabetes, either at the NGT or the IFG/IGT stage. Conclusion/interpretation. Glucose-tolerant carriers of MODY mutations are characterised by a severe impairment in insulin secretion. Enhanced insulin sensitivity is the most likely explanation for the normal glucose tolerance. Whereas subjects with positive GADA or Type II diabetes have impaired insulin sensitivity with increasing glucose concentrations, MODY mutation carriers seem to be protected from the effect of glucose toxicity. [Diabetologia (2000) 43: 1476–1483]
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Keywords Glucokinase ; HNF-1 ; HNF-4 ; MODY ; MIDD ; genetics.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. To investigate the contribution of mutations in maturity-onset diabetes of the young (MODY) and mitochondrial genes to early-onset diabetes with a strong family history of diabetes in a cohort with a high prevalence of Type I (insulin-dependent) diabetes mellitus. Methods. Screening for sequence variants in the hepatocyte nuclear factor (HNF)–4 α (MODY1), glucokinase (MODY2), HNF-1 α (MODY3) genes and mitochondrial DNA was carried out in 115 Finnish and Swedish patients with early-onset ( ≤ 40 years) diabetes using the single strand conformation polymorphism (SSCP) technique and direct sequencing. Allele frequencies were compared with 118 patients with onset of diabetes Type II (non-insulin-dependent) diabetes mellitus after the age of 40 and 92 non–diabetic control subjects without a family history of diabetes. Results. In total 52 sequence variants were found in the HNF-1α, HNF-4α and glucokinase genes, 12 of which were considered as MODY mutations. Three families had the A3243G mutation in the mitochondrial tRNA Leu gene, which resulted in an overall prevalence of these mutations of 13 %. Conclusion/interpretation. Among 115 Scandinavian families, mutations in the HNF-1α gene represented the most common cause of familial early-onset ( ≤ 40 years) diabetes: MODY3 (5.2 %) more than MODY2 (3.5 %) more than MIDD (2.6 %) more than MODY1 (1.7 %). [Diabetologia (1999) 42: 1131–1137]
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-5233
    Keywords: Sulfonylurea ; Glipizide ; C-peptide ; Insulin ; Insulin metabolic clearance rate (MCR1)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To examine whether sulfonylureas inhibit the metabolic clearance rate (MCR) of insulin, 19 healthy young subjects participated in two experiments. In the first protocol (n=10), a 3-h oral glucose load was performed with and without 2 mg of glipizide given 30 min before glucose ingestion. The total insulin response was 60% greater with than without glipizide (5.9±0.6 vs 3.7±0.5 μU/ml;P〈0.001). However, the total C-peptide responses were virtually identical (4.7±0.5 vs 4.8±0.4 nmol/l) in both studies. In the second protocol (n=9), the MCR of insulin was measured during 4-h euglycemic insulin clamps performed with and without glipizide. In the study with glipizide, the subjects ingested 5 mg of glipizide at 120 min. The steady-state plasma insulin concentration during the 4th h, i.e., 1–2 h after glipizide ingestion, was significantly higher than during the 2nd h, i.e., before glipizide ingestion (99±22 vs 78±17 μU/ml;P〈0.01). In addition, glucose uptake during the 4th h was greater (8.0±1.6 vs 6.4±1.5 mg/kg·min) and the MCR of insulin was reduced (503±126 vs 621±176 ml/m2·min;P〈0.01). We conclude that glipizide augments plasma insulin levels both by enhancing its secretion and by decreasing the MCR of insulin.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-5233
    Keywords: C-peptide ; Diabetes mellitus ; Glucose clamp ; Insulin ; Proinsulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Elevated fasting proinsulin immunoreactive material (PIM) has previously been found in patients with type 2 (non-insulin-dependent) diabetes mellitus. It is not known whether this is a genetic trait or whether it is related to the manifestation of type 2 diabetes. Neither is it clear whether the raised fasting insulin immunoreactivity previously observed in first-degree relatives of patients with type 2 diabetes is due to raised PIM. Furthermore, it has not been investigated whether first-degree relatives have altered PIM responses to different secretagogoues. To study this, PIM, insulin and C-peptide were measured in patients with type 2 diabetes, in their first-degree relatives and in healthy control subjects in the fasting state and in relatives and controls during a hyperglycemic clamp. At the end of the hyperglycemic clamp, 0.5 mg of glucagon was given intravenously to stress the beta cells further. Fasting PIM concentrations were significantly higher in patients with type 2 diabetes (P〈0.05). These patients did not have significantly elevated fasting insulin levels when corrected for PIM. In the relatives, fasting insulin concentrations were elevated but PIM levels were normal suggesting that the increase in fasting insulin concentrations reflected an increase in true insulin. The incremental PIM, insulin and C-peptide responses to glucose and glucagon in the relatives were not different from those in the controls. We conclude that elevated fasting PIM levels in patients with type 2 diabetes seem not to be a genetic trait. First-degree relatives of patients with type 2 diabetes are truly hyperinsulinemic in the fasting state, and they have proportional PIM, insulin and C-peptide responses to glucose and glucagon.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-5233
    Keywords: Insulin ; C-peptide ; Glucose ; Glipizide ; Non-insulin-dependent diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of a rapid-acting sulphonylurea, glipizide, on the dose-response relationship between the β-cell response (insulin and C-peptide secretion) and the ambient plasma glucose concentration was examined in 12 healthy and 6 non-insulin-dependent diabetic subjects. The subjects participated in two sets of experiments which were performed in random order: (A) four hyperglycaemic clamp studies, during which the plasma glucose concentration was raised for 120 min by 1 (only in healthy subjects), 3, 7, and 17 mmol/l; and (B) the same four hyperglycaemic clamp studies preceded by ingestion of 5 mg glipizide. All subjects participated in a further study, in which glipizide was ingested and the plasma glucose concentration was maintained at the basal level. In control subjects in the absence of glipizide, the firstphase plasma insulin response (0–10 min) increased progressively with increasing plasma glucose concentration up to 10 mmol/l, above which it tended to plateau. Glipizide augmented the first-phase insulin response without changing the slope of the regression line relating plasma insulin to glucose concentrations. The second-phase plasma insulin response (20–120 min) increased linearly with increasing hyperglycaemia (r=0.997). Glipizide alone increased the plasma insulin response by 180 pmol/l. A similar increase in plasma insulin response following glipizide was observed at each hyperglycaemic step, indicating that glipizide did not affect the sensitivity of the β-cell to glucose. First-phase insulin secretion was reduced in the type 2 (non-insulin-dependent) diabetic patients, and was not influenced by glipizide. The dose-response curve relating second-phase insulin secretion to the ambient plasma glucose concentration was significantly (P〈0.001) flatter in the diabetic patients than in the control subjects. Glipizide alone increased the plasma insulin response by 60 pmol/l without changing the slope of the dose-response curve. It is concluded that, in both type 2 diabetic patients and healthy subjects: (A) sulphonylurea augments glucose-stimulated second-phase insulin secretion without changing the sensitivity of the β-cell to glucose; (B) first-phase insulin secretion is reduced in non-insulin-dependent diabetic patients with fasting hyperglycaemia and is not influenced by sulphonylurea.
    Type of Medium: Electronic Resource
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