cytidylyl-3--5--guanosine and Diabetes-Mellitus--Type-2

Foreign, infection-associated or endogenously generated circulating nucleotide motifs may represent the critical determinants for the activation of the Toll-like receptors (TLRs), leading to immune stimulation and cytokine secretion. The importance of circulating nucleases is to destroy nucleic acids and oligonucleotides in the blood stream and during cell entry. Patients with juvenile insulin-dependent diabetes, adult patients with insulin-dependent diabetes and adult patients with type 2 diabetes were allocated to the study, together with the age-matched control subjects. Plasma RNase and nuclease activity were examined, in relation to different substrates-TLRs response modifiers, and circulating RNA and oligonucleotides were isolated. The fall in enzyme activity in plasma was obtained for rRNA, poly(C), poly(U), poly(I:C), poly(A:U) and CpG, especially in juvenile diabetics. In order to test the non-enzymatic glycation, commercial RNase (E.C.3.1.27.5) and control plasma samples were incubated with increasing glucose concentrations (5, 10, 20 and 50 mmol/l). The fall of enzyme activity was expressed more significantly in control plasma samples than for the commercial enzyme. Total amount of purified plasma RNA and oligonucleotides was significantly higher in diabetic patients, especially in juvenile diabetics. The increase in the concentration of nucleotides corresponded to the peak absorbance at 270 nm, similar to polyC. The electrophoretic bands shared similar characteristics between controls and each type of diabetic patients, except that the bands were more expressed in diabetic patients. Decreased RNase activity and related increase of circulating oligonucleotides may favor the increase of nucleic acid "danger motifs", leading to TLRs activation.

Topics: Adolescent; Adult; Age of Onset; Aged; C-Peptide; Child; Child, Preschool; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Dinucleoside Phosphates; DNA; Female; Glycated Hemoglobin; Humans; Male; Middle Aged; Oligonucleotides; Polyribonucleotides; Reference Values; RNA

Mutations were screened for in the glucokinase gene of 25 Japanese patients with Type 2 (non-insulin-dependent) diabetes mellitus. Each exon was scanned by electrophoresis of enzymatically amplified DNA segments under non-denaturing conditions and variants were sequenced. A variant pattern was detected in exon 5 of one patient. Direct sequencing of this exon revealed a single nucleotide substitution in codon 188 (GCT-->ACT) of one of two alleles resulting in the mutation of Ala188-->Thr, an invariant residue in the sequence of all mammalian glucokinases and hexokinases. This mutation was not found in 40 normal control subjects. The proband had been diagnosed with Type 2 diabetes at the age of 62 years. Four other members of her family have the same mutation and all have Type 2 diabetes or impaired glucose tolerance. The youngest age at diagnosis of Type 2 diabetes in these other members was 13 years, suggesting that her pedigree was maturity-onset diabetes of the young (MODY). All subjects with the Thr188 mutation show a decreased insulin secretory response during oral glucose tolerance testing. Mutations in the glucokinase gene associated with Type 2 diabetes have been previously identified in Caucasian (French and British) subjects. This study indicates that mutations in this gene are also implicated in the development of Type 2 diabetes in Asians. Further studies are required to determine the frequency of mutations in glucokinase among Japanese patients with Type 2 diabetes.

Topics: Adolescent; Adult; Alanine; Amino Acid Sequence; Base Sequence; Blood Glucose; Codon; Diabetes Mellitus, Type 2; Dinucleoside Phosphates; Exons; Female; Glucokinase; Glucose Tolerance Test; Humans; Insulin; Male; Middle Aged; Molecular Sequence Data; Pedigree; Point Mutation; Polymerase Chain Reaction; Threonine