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This study investigates impaired awareness of hypoglycaemia (IAH), a complication of insulin therapy affecting 20–40% of individuals with type 1 diabetes. The exact pathophysiology is unclear, therefore we sought to identify metabolic signatures in IAH to elucidate potential pathophysiological pathways. Plasma samples from 578 individuals of the Dutch type 1 diabetes biomarker cohort, 67 with IAH and 108 without IAH (NAH) were analysed using the targeted metabolomics Biocrates AbsoluteIDQ p180 assay. Eleven metabolites were significantly associated with IAH. Genome-wide association studies of these 11 metabolites identified significant single nucleotide polymorphisms (SNPs) in C22:1-OH and phosphatidylcholine diacyl C36:6. After adjusting for the SNPs, 11 sphingomyelins and phosphatidylcholines were significantly higher in the IAH group in comparison to NAH. These metabolites are important components of the cell membrane and have been implicated to play a role in cell signalling in diabetes. These findings demonstrate the potential role of phosphatidylcholine and sphingomyelins in IAH. [ABSTRACT FROM AUTHOR]

Pancreatic agenesis is a rare condition, of which only a limited number of cases have been described. One recent paper reported a homozygous mutation in the pancreatic duodenal homeobox gene 1 (PDX-1) in a child with pancreatic agenesis. We report a 6-year-old boy with pancreatic agenesis, treated medically, without abnormalities in the PDX-1 gene coding sequence and with normal gastroduodenal endocrine cell distribution. Genes other than PDX-1 also appear to be involved in human pancreatic agenesis. [ABSTRACT FROM AUTHOR]

Plasma semicarbazide-sensitive amine oxidase is raised in patients with Type I (insulin-dependent) diabetes mellitus. It has been suggested that this enzyme is involved in the development of microvascular damage through its ability to convert amines (e. g. methylamine and aminoacetone) into aldehydes, hydrogen peroxide and ammonia. Plasma semicarbazide-sensitive amine oxidase was found to be equally raised both in patients with Type I diabetes ( n = 73) and Type II (non-insulin-dependent) diabetes mellitus ( n = 88) compared with control subjects (621 ± 209 and 619 ± 202 vs 352 ± 102 mU/l, p < 0.0001) and to correlate in multiple regression analysis with HbA1 c. Since the enzyme could protect the islets from the inhibitory effects of methylamine on insulin secretion, we also tested sera of 100 children, collected consecutively at first diagnosis of Type I diabetes, for semicarbazide-sensitive amine oxidase. The activity was greatly increased compared with serum values of 76 control (siblings) children (757 ± 300 vs 455 ± 138 mU/l, p < 0.0001), but not associated with HbA1 c. Our study confirms the increase of plasma semicarbazide-sensitive amine oxidase in Type I diabetes and extends this finding to Type II diabetes as well as to childhood Type I at first clinical diagnosis. In the last case increased enzyme activities could serve to protect the islets from inhibitory effects of methylamine but cause damage by generation of hydrogen peroxide, aldehydes and ammonia. In the long run the increased enzyme activities could also contribute to vascular damage by direct cytotoxic action on endothelial cells, including increased oxidative stress and glycosylation of proteins. [Diabetologia (1999) 42: 233–237] [ABSTRACT FROM AUTHOR]

Discusses research into the identification of the pancreatic islet beta-cell autoantigen of relative molecular mass 64K as glutamic acid decarboxylase. Target of insulin-dependent diabetes mellitus (IDDM)-associated autoantibodies; Biosynthesizer of inhibitory neurotransmitter GABA (gamma-aminobutyric acid); High levels of enzyme expression; Incidence of higher titre antibodies in stiff-man syndrome.

The value of a test for islet cell cytoplasmic antibodies together with a test for GAD antibodies to predict the subsequent development of diabetes over a period of 11.5 years was assessed in an open childhood population comprising 2,805 individuals. A single serum sample was obtained from each individual between 1975 and 1977 and screened for islet cell cytoplasmic antibodies for which eight individuals were positive (0.29%). During the average follow-up period of 11.5 years, four of eight islet cell antibody positive and three islet cell antibody negative individuals developed clinical diabetes. Sera from all individuals, who were islet cell antibody positive and/ or developed diabetes (total of 11) and from 100 randomly selected control subjects were analysed for GAD antibodies. Six of eight islet cell antibody positive individuals were GAD antibody positive including all four who subsequently developed IDDM. Furthermore, one of the three islet cell antibody negative individuals who developed IDDM was GAD antibody positive both in 1976 and in 1989. Thus, a positive test for GAD antibodies alone correctly predicted diabetes in five of seven children, who developed the disease. Only one of the children, who developed diabetes was positive for insulin autoantibodies and this individual was also positive for islet cell cytoplasmic antibodies and GAD antibodies. One of the 100 control subjects was positive for GAD antibodies (1%). The results suggest that a single GAD antibody test may have a higher sensitivity for predicting IDDM than a test for islet cell cytoplasmic antibodies, but that a combined positive test for both antibodies increases the specificity for predicting IDDM over a period of 11.5 years. [ABSTRACT FROM AUTHOR]

The reactivity of islet cell cytoplasmic antibodies (ICA)-positive and ICA-negative sera of recent onset type 1 diabetic patients was studied in human fetal pancreata of 12-18 weeks' gestation and compared with the reactivity of these sera in adult human control pancreata. The aims of the study were: (1) to observe the presence of ICA staining in human fetal islet cells; (2) to compare endpoint titres (in Juvenile Diabetes Foundation units) of ICA-positive patient sera in fetal pancreata and adult human control pancreata. Ten ICA-positive sera and eight ICA-negative sera from newly diagnosed diabetic patients and four sera from healthy controls were tested on three human adult and eight human fetal pancreata. As in the adult control pancreata. ICA-positive sera reacted to insulin-, glucagon-, and somatostatin-positive cells of fetal pancreata of all gestational ages. This was observed both in single cells and in cells in islet-like cell clusters. Dilution of a reference serum gave similar results in both adult and fetal pancreata. In contrast, the ICA-positive patient sera yielded a striking heterogeneity in fetal as well as in adult pancreata. However, end-point titres between adult and fetal pancreata did not differ significantly ( P>0.05). In conclusion, ICA-positive sera from recent onset diabetic patients show that the expression of molecules to which ICA react is present in all islet cells and starts before week 12 of gestation. [ABSTRACT FROM AUTHOR]

The aim of this study was to produce an antibody reactive to the surface of endocrine pancreatic cells and use this antibody for the purification of endocrine cells from the human fetal pancreas by fluorescence activated cell sorting. We describe such an antibody, called N1, reacting with the surface and cytoplasm of endocrine cells in the adult and fetal human pancreas (12 to 18 weeks gestational age). While unreactive to exocrine and mesenchymal cells, it was not specific for endocrine cells, as evidenced by its staining pattern in tissues other than pancreas. Almost 40% of the N1-positive pancreatic cells contained either insulin, glucagon or somatostatin. Conversely, more than 90% of each of the hormone-containing cells was N1 positive. An additional 40% of N1 positive cells, not containing other pancreatic hormones, was shown to contain islet amyloid polypeptide, synaptophysin, chromogranin, tyrosin hydroxylase or CA812. A two-step collagenase digestion protocol yielded 1.29 ± 0.17 x 10 cells per mg pancreatic tissue. After Percoll gradient centrifugation, the suspension contained 15.6 ± 5.7 % ( n = 25, mean ± SD) cells reactive with N1. By fluorescence activated cell sorting using the antibody N1, the single-cell suspension was enriched from 3.0 ± 1.4% to 16.2 ± 4.8% ( n = 10, p < 0.01) Beta cells. Alpha and Delta cells were also enriched significantly by this procedure. The percentage of N1-positive cells increased from 17 ± 4 % to 83 ± 6 %. This preparation enriched for endocrine cells allows future studies on possible endocrine precursor cells. [ABSTRACT FROM AUTHOR]