1/7. A novel point mutation in the human insulin gene giving rise to hyperproinsulinemia (proinsulin Kyoto).We have identified a 65-yr-old nonobese Japanese man with diabetes mellitus, fasting hyperinsulinemia (150-300 pM), and a reduced fasting c-peptide/insulin molar ratio of 2.5-3.0. fasting hyperinsulinemia was also found in his son and daughter. Analysis of insulin isolated from the serum of the proband and his son by reverse-phase high performance liquid chromatography revealed a minor peak coeluting with human insulin and a major peak of proinsulin-like materials. The insulin gene of the patient was amplified by the polymerase chain reaction and the products were sequenced. A novel point mutation was identified in which guanine was replaced by thymine. The substitution gives rise to a new HindIII recognition site and results in the amino acid replacement of leucine for arginine at position 65. These results indicate that the amino-acid replacement prevents recognition of the c-peptide-A chain dibasic protease and results in an elevation of proinsulin-like materials in the circulation. Furthermore, in this family the proinsulin-like materials is due to a biosynthetic defect, inherited as an autosomal dominant trait. Rapid detection of this mutation can be accomplished by HindIII restriction enzyme mapping of polymerase chain reaction-generated dna, which enables us to facilitate the diagnosis and screening.- - - - - - - - - - ranking = 1keywords = chromatography (Clic here for more details about this article) |
2/7. Aberrant insulinoma in the duodenum.A rare case of aberrant insulinoma in the duodenum is described. Hyperinsulinemia with typical hypoglycemic symptoms was induced by prolonged fasting. Selective angiography demonstrated a tumor supplied from the first branch of the jejunal artery, and duodenoscopy revealed a submucosal tumor at the third portion of the duodenum. An increase in venous plasma immunoreactive insulin concentration was evident in the vein draining from the tumor, by sampling through percutaneous transhepatic catheterization. hypoglycemia was ameliorated after the removal of the submucosal tumor of the duodenum. Histologic and immunocytochemical characterization of the tumor showed an insulinoma, predominantly composed of cells with typical B-cell-like granules. The acid extract of the tumor contained 1.2 U/g of insulin, and this insulin, analyzed by reverse-phase high-pressure liquid chromatography, revealed that it had the same amino acid structure as that of human insulin.- - - - - - - - - - ranking = 1keywords = chromatography (Clic here for more details about this article) |
3/7. Characterization of circulating insulin in insulin autoimmune syndrome.We examined the forms of circulating insulin in three patients with the insulin autoimmune syndrome by a method combining gel filtration and reverse phase high performance liquid chromatography (RP-HPLC). Insulin bound to circulating antibody was dissociated by molecular sieve chromatography at acid pH. The free insulin peak eluted from a Sephadex G-50 column was subsequently chromatographed on a Bio-Gel P-30 column. In all three patients, insulin coeluted with normal human insulin. However, when the partially purified insulins, obtained by gel filtration, were applied to RP-HPLC, an abnormally migrating insulin was found in two of three patients. The insulins were more hydrophobic than normal human, porcine, or bovine insulin, but were different from each other. A third patient had only a single insulin peak on RP-HPLC which corresponded to normal insulin. In contrast, the insulin from insulin-treated diabetic patients with antibodies to exogenous insulin corresponded to either porcine or bovine and normal human insulin. The antibodies in the circulation of these patients with the autoimmune syndrome were of the immunoglobulin g type and contained kappa and lambda-chains in the same proportions as antibodies in insulin-treated patients. autoantibodies could not be distinguished from those secondary to exogenous insulin treatment on the basis of displacement of binding by human, beef, or pork insulin. These results suggest that in certain patients with the insulin autoimmune syndrome, there may be a molecular abnormality of circulating insulin. Whether this comprises a cause for the syndrome or is a result of posttranslational processing of insulin remains to be determined.- - - - - - - - - - ranking = 2keywords = chromatography (Clic here for more details about this article) |
4/7. Familial hyperinsulinemia associated with secretion of an abnormal insulin, and coexistence of insulin resistance in the propositus.A 45-yr-old muscular nonobese white man who had a 9-yr history of syncopal episodes was studied on several occasions between April 1979 and August 1984. fasting glucose concentrations ranged between 74-115 mg/dl, and those of insulin ranged between 14-64 microU/ml. Reactive hypoglycemia 3-4 h after ingestion of glucose occurred in the first 2 yr. Glucose tolerance was impaired in 1979, from February 1982 through September 1983, and again in August 1984. The maximum plasma insulin response to glucose ranged between 475-1630 microU/ml. When studied in November 1982, insulin (0.1 U/kg) caused a fall in blood glucose concentration of only 25% (normal, greater than 50%), and maximal glucose utilization during the euglycemic hyperinsulinemic clamp was 7.5 mg/kg . min (normal, greater than 12 mg/kg . min). plasma counterregulatory hormone concentrations were normal, and antibodies to insulin and the insulin receptor were absent. Binding of exogenous insulin to the patient's cellular receptors (monocytes, red blood cells, and skin fibroblasts) was normal. Insulin was purified from plasma by immunoaffinity and molecular sieve chromatography and was found to elute later than human insulin on reversed phase high performance liquid chromatography. It was more hydrophobic than normal human insulin and had only 10% of the activity of normal insulin in terms of ability to bind to and stimulate glucose metabolism in isolated rat adipocytes. The abnormal insulin was identified in two of three sons and a sister, but not in the mother, brother, or niece. Sensitivity to insulin was normal in the two sons who had abnormal insulin. These results suggest that in this family the abnormal insulin was due to a biosynthetic defect, inherited as an autosomal dominant trait. The hyperinsulinemia was not associated with diabetes in family members who had no insulin resistance.- - - - - - - - - - ranking = 2keywords = chromatography (Clic here for more details about this article) |
5/7. Insulin Wakayama: familial mutant insulin syndrome in japan.We describe a family from japan displaying the mutant insulin syndrome with hyperinsulinaemia and an increased insulin: c-peptide molar ratio. serum insulin isolated from several family members showed reduced in vitro biological activity, and analysis by high performance liquid chromatography revealed a peak co-eluting with human insulin and a second species of increased hydrophobicity co-migrating with the previously reported Insulin Wakayama. The insulin genes from the propositus were cloned and sequenced, revealing one normal allele; the second allele, encoding a leucine for valine amino acid substitution at position 3 of the insulin A chain, was similar to that previously described for Insulin Wakayama. Synthesized [LeuA3] insulin showed 0.14% of receptor binding activity on rat adipocytes and a 10-fold prolonged half-life in a somatostatin-infused dog compared with human insulin. The finding of the same mutant gene in two unrelated Japanese families suggests that Insulin Wakayama may be discovered in additional Japanese families with hyperinsulinaemia and/or diabetes.- - - - - - - - - - ranking = 1keywords = chromatography (Clic here for more details about this article) |
6/7. Familial hyperproinsulinemia associated with NIDDM. A case study.OBJECTIVE--To report studies on an elderly patient with moderate NIDDM associated with marked fasting hyperinsulinemia. research design AND methods--The propositus and several family members were studied by a combination of clinical, biochemical, and molecular genetic approaches to define the underlying genetic defect. RESULTS--fasting levels of contrainsulin hormones were normal, and resistance to exogenous insulin was absent. Gel filtration and reverse-phase high-performance liquid chromatography revealed elevated amounts of a structurally abnormal proinsulin intermediate (AC proinsulin). A study of the family of the propositus showed the same abnormality in 4 of 5 members in 3 successive generations. Genetic analysis revealed a point mutation affecting residue 65 of human proinsulin (Arg-->His) in one allele of the insulin gene in the propositus, a defect similar to that described previously in 3 other apparently unrelated lineages. CONCLUSIONS--This family exhibits a clear-cut relationship between increasing age and metabolic decompensation in all the hyperproinsulinemic members, suggesting that (inherited) metabolic stress and age both contribute to development of diabetes mellitus.- - - - - - - - - - ranking = 1keywords = chromatography (Clic here for more details about this article) |
7/7. Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.Familial hyperproinsulinaemia is a rare genetic disorder characterized by point mutations in the insulin gene which impair the conversion of proinsulin to insulin. We report here three members of a two-generation Caucasian family in whom this syndrome was identified by unexplained hyperinsulinism associated with normal glucose tolerance and normal insulin sensitivity. plasma insulin immunoreactivity showed a reduced affinity for the insulin receptor and eluted mainly, on Biogel chromatography, at the position of proinsulin. Analysis of the PCR-amplified insulin gene by restriction enzyme mapping revealed a new recognition site for the enzyme Nla III, indicating a Arg65 to His mutation. sequence analysis of exon 3 confirmed this mutation in one allele of the gene. CONCLUSION: This study reports a two-generation European-Caucasian family with hyperproinsulinaemia due to a substitution of His for Arg at position 65 in proinsulin, the seventh now identified worldwide and the second from europe. The mutation generated a new restriction site on the insulin gene suggesting the usefulness of restriction enzyme mapping as a screening procedure.- - - - - - - - - - ranking = 1keywords = chromatography (Clic here for more details about this article) |