Mona Landin-Olsson

A novel radioligand binding assay to determine diagnostic accuracy of isoform-specific glutamic acid decarboxylase antibodies in childhood iDDM

SummaryInsulin-dependent diabetes mellitus (IDDM) is associated with autoreactivity against GAD but the diagnostic sensitivity (positivity in disease) and specificity (negativity in health) of isoform-specific GAD antibodies have yet to be defined in assay systems suitable for screening large number of samples. One set of IDDM patient (n=10) and control (n=50) standard sera were used to develop quantitative antibody assays with in vitro synthesized recombinant 35S-methionine-labelled GAD65 and GAD67, respectively, and protein A-Sepharose to separate free from antibody-bound ligand. Binding levels were not normally distributed (p<0.0001) and therefore, the diagnostic accuracy of GAD antibodies was analysed by the ROC plots in population-based, consecutively-diagnosed, recent onset, 0–14 year-old patients (n=105), and matched, healthy control subjects (n=157). The ROC plots showed that the diagnostic sensitivity of GAD65 antibodies was 77% and the specificity 92% compared with 8% and 98%, respectively for GAD67 antibodies. In the IDDM sera, GAD65 and GAD67 antibodies were concordant in 7% (6 of 81) and GAD65 antibodies and ICA in 89% (72 of 81) without a correlation between the autoantibody levels. Autoantibodies to recombinant human islet GAD65 are specific and sensitive markers for childhood IDDM in this immunoassay with in vitro synthesized 35S-methioninelabelled recombinant GAD.

Quantitative assay using recombinant human islet glutamic acid decarboxylase (GAD65) shows that 64K autoantibody positivity at onset predicts diabetes type.

At and before onset, most insulin-dependent diabetics (IDDM) have islet GAD65 autoantibodies (GAD65Ab). Since IDDM also occurs in older patients where non-insulin-dependent diabetes is common, we studied GAD65Ab at onset to classify diabetes type. Our quantitative immunoprecipitation assay uses recombinant human islet GAD65 stably expressed in hamster fibroblasts. Electrophoretic mobility was identical to native islet GAD65. Like native antigen, recombinant GAD65 migrated as two bands during electrophoresis, but converted to one under stronger reduction. Immunoprecipitation was linear with respect to antibody or antigen concentration. In 120 population-based diabetic patients of all ages grouped by treatment at onset and after 18 mo, GAD65Ab were present in 70% on insulin (n = 37), 10% on oral agent (n = 62, P < 0.0001), 69% changing from oral agent to insulin (n = 16, P < 0.001), and 1 of 33 controls. 65% with GAD65Ab, versus 8% without, changed from oral agent to insulin (P < 0.01). The GAD65Ab quantitative index was remarkably stable, and only 2 of 32 patients changed antibody status during follow-up. Concordance between GAD65Ab and islet cell antibodies was 93%. Quantitative correlation was approximate but significant. This highly sensitive, quantitative, high capacity assay for GAD65Ab reveals treatment requirements better than clinical criteria, perhaps guiding immunomodulatory therapy.

Islet cell and other organ-specific autoantibodies in all children developing Type 1 (insulin-dependent) diabetes mellitus in Sweden during one year and in matched control children

SummaryThe majority (about 90%) of children developing Type 1 (insulin-dependent) diabetes mellitus do not have a first-degree relative with the disease. Nearly all (389/405, 96%) children (0–14 years) in Sweden, who developed diabetes during one year, were therefore studied to compare islet cell, thyroid peroxidase, thyroglobulin, and gastric H+, K+-ATPase antibodies with 321 age, sex, and geographically matched, but non-related, control children. Islet cell (cytoplasmic) antibodies were found in 81% (316/389) of the patients and in 3% (9/321) of the control children (p<0.001). The median islet cell antibody levels were 70 (range 3–8200) Juvenile Diabetes Foundation (JDF) Units in the islet cell antibody positive patients, and 27 (range 17–1200) JDF Units in the control children (NS). Autoantibodies against thyroid peroxidase (8%), thyroglobulin (6%), and gastric H+, K+- ATPase (3%) were all increased in the patients compared with the control children, being 2% (p<0.001), 2% (p<0.01), and 0.3% (p<0.01), respectively. During an observation time of 20–34 months, two of the nine islet cell antibody positive control children developed Type 1 diabetes, after 8 and 25 months respectively, while the others remained healthy and became islet cell antibody negative. None of the islet cell antibody negative control children developed diabetes during the same time of observation. This first investigation of an unselected population of diabetic children and matched control children shows: that islet cell antibodies are strongly associated with newly diagnosed childhood diabetes, that other autoantibodies are more frequent among diabetic children than control children, and that the frequency of islet cell antibodies in the background population of children is higher than previously documented, and could also be transient, underlining that factors additional to islet cell antibodies are necessary for the later development of Type 1 diabetes.

Effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile and inflammation markers in metabolic syndrome – a randomized study (SYSDIET)

Different healthy food patterns may modify cardiometabolic risk. We investigated the effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile, blood pressure and inflammatory markers in people with metabolic syndrome.

Incidence of type 1 and type 2 diabetes in adults and children in Kronoberg, Sweden

All newly diagnosed diabetes in Kronoberg during 3 years was registered, with blood samples from 1630/1666 (97.8%) adults. Those positive for GADab and/or ICA and/or C-peptide<0.25nmol/L (0.7%) were classified as type 1 diabetes, the remaining as type 2. Incidence of type 1 in 0-19-year-olds was 37.8(36.1-39.6, 95%CI) and in 20-100 year-olds 27.1(25.6-27.4) per 100 000 and year, it was bimodal with equal peaks in 0-9 year-olds and in 50-80-year-olds. Adults had type 2 incidence 378 (375-380), children 3.1 (2.6-3.6). Among adults 6.9% had type 1 and 93.1% type 2. Among antibodypositive adults (n=101), GADab were present in 90%, ICA in 71%, both GADab and ICA in 61%. Ophthalmology contact as second source was confirmed for 98%. There were no gender differences in type 1 in any age group, small ones in pediatric subgroups. In type 2 men predominated in ages above 40 years. Incidences of type 1 diabetes in both children and adults were very high and as high above age 50 years as in children. Incidence of type 2 was the highest reported from Sweden, to which new diagnostic criteria, a high degree of case-finding, and many elders, may have contributed, but results may also reflect a true increase in incidence of both types of diabetes.

Predictive value of islet cell and insulin autoantibodies for Type 1 (insulin-dependent) diabetes mellitus in a population-based study of newly-diagnosed diabetic and matched control children

SummaryMost studies evaluating immune markers for prediction of Type 1 (insulin-dependent) diabetes mellitus have focused on first degree relatives, although only 10 % of newly-diagnosed patients have an affected first degree relative. The Swedish Childhood Diabetes Register identifies 99 % of all diabetic children at diagnosis. In this population-based study, islet cell antibodies and insulin autoantibodies in 0–14-year-old Swedish consecutively-diagnosed patients and control subjects were analysed to define their sensitivity and specificity. Over 16 months (1986–1987), 515 Swedish children developed diabetes. Plasma samples were obtained from 494 (96 %) patients, and 420 matched control children. Among patients, the frequency of islet cell antibodies was 84 % (415 of 494), insulin autoantibodies 43 % (145 of 334); 40 % (135 of 334) were positive for both and 88 % (294 of 334) were positive for one or both. Among control children, 3 % (14 of 420) had islet cell antibodies, 1 % (4 of 390) insulin autoantibodies, and 4 % (16 of 390) had either autoantibody marker. The predictive value of finding a patient with the disease was only 7% since 4 % of the control children were antibody-positive and the cumulative incidence rate up to 15 years of age is 0.38 %. None of the autoantibody-positive (n = 21) or negative control children developed diabetes during 3 to 5 years of follow-up. Longitudinal investigations of islet cell or insulin-autoantibody-positive healthy children are necessary to accurately determine the conversion rate from marker positivity to disease onset.

β-Cell Function in Relation to Islet Cell Antibodies During the First 3 Yr After Clinical Diagnosis of Diabetes in Type II Diabetic Patients

OBJECTIVE— To determine the effects of islet cell antibodies on β-cell function during the first 3 yr after diagnosis in type II diabetic patients. RESEARCH DESIGN AND METHODS— β-cell function in type II diabetic patients with (n = 11, 50 ± 5 yr of age) and without (n = 10, 52 ± 4 yr of age) ICA was followed prospectively and compared with β-cell function in type I adult diabetic patients (n = 17, 37 ± 5 yr of age) and in healthy control subjects (n = 34, age 45 ± 3 yr). β-cell function was evaluated as fasting C-peptide, 1 + 3 min C-peptide after intravenous glucose, and ∆ C-peptide after glucagon. RESULTS— Fasting C-peptide was equal in type II diabetic patients with ICA (0.30 ± 0.03 nM) and type I diabetic patients (0.24 ± 0.03 nM) at diagnosis, and decreased (P < 0.05) during 3 yr in these groups but not in type II diabetic patients without ICA. At diagnosis, type II diabetic patients with ICA showed a 1 + 3 min C-peptide (0.92 ± 0.17 nM) lower (P < 0.001) than control subjects but higher (P < 0.05) than type I diabetic patients (0.53 ± 0.11 nM). After 1 yr, 1 + 3 min C-peptide in type II diabetic patients with ICA had decreased (P < 0.05) to 0.18 ± 0.11 nM and was equal to type I diabetic patients (0.38 ± 0.10 nM). ∆ C-peptide after glucagon was equally impaired in type II diabetic patients with ICA (0.38 ± 0.06 nM) and type I diabetic patients (0.35 ± 0.11 nM) at diagnosis. After 3 yr, type II diabetic patients with ICA had fasting C-peptide of 0.09 ± 0.04 nM, 1 + 3 min C-peptide of 0.18 ± 0.10 nM, and ∆ C-peptide after glucagon of 0.20 ± 0.09 nM, values equal to type I diabetic patients but lower (P < 0.01) than in type II diabetic patients without ICA, whose values remained unchanged; fasting C-peptide of 0.97 ± 0.17 nM, 1 + 3 min C-peptide of 2.31 ± 0.50 nM, and ∆ C-peptide after glucagon of 1.76 ± 0.28 nM. CONCLUSIONS— In patients considered type II diabetic with ICA, β-cell function progressively decreased after diagnosis, and after 3 yr was similar to type I diabetic patients, whereas β-cell function in type II diabetic patients without ICA was unchanged.

Islet Cell and Thyrogastric Antibodies in 633 Consecutive 15- to 34-Yr-Old Patients in the Diabetes Incidence Study in Sweden

The effect of age on ICA and thyrogastric antibodies at diagnosis of IDDM was evaluated in 633 consecutively diagnosed Swedish diabetic patients aged 15–34 yr and in 282 volunteers of the same age. ICAs were present in 61% (383 of 633) of the patients and in 2% (5 of 282) of control subjects. When the initial classification was considered, ICAs were detected in 69% (327 of 473) of patients with IDDM, 23% (19 of 83) of those with NIDDM, 50% (36 of 72) of those with unclassifiable diabetes, and 20% (1 of 5) of those with secondary diabetes. The frequency of ICA fell significantly (P < 0.001) with age in IDDM patients from 77% (104/135) in those 15–19 yr old to 52% (50 of 96) in 30- to 34-yr-old IDDM patients. The low frequency of ICA in 30- to 34-yr-old IDDM patients was confined to men (42%, 28 of 66). The frequency of gastric (H+, K+-ATPase) antibodies was significantly (P < 0.05) higher in IDDM patients (10%, 47 of 449) than in patients with NIDDM (3%, 3 of 80) and unclassifiable diabetes (4%, 3 of 72). In conclusion, the frequency of ICA at the diagnosis of IDDM in young adult subjects decreases with increasing age, particularly in men. The frequent finding of ICA in patients considered to have NIDDM or unclassifiable diabetes indicates that misclassification of diabetes is frequent in young adult patients recently diagnosed with diabetes.

Islet cell antibodies and fasting C-peptide predict insulin requirement at diagnosis of diabetes mellitus

SummaryThe differential diagnosis between Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes is complicated since no specific markers are available for either disease. In this study, 244 consecutive patients were diagnosed with diabetes mellitus during two years in Malmö (230000 inhabitants), corresponding to an incidence rate of 53·100000−1·year−1. Age, body mass index, HbA1c, C-peptide, and levels of islet cell antibodies were determined at the clinical onset, and related to the classification at diagnosis and at follow-up (n=233) after a median time of 31 (range 1–49) months. After diagnosis, 42 of 244 (17%) were started on insulin while 202 of 244 (83%) were not. Islet cell antibodies were present in 25 of 42 (60%), and in 18 of 183 (10%), respectively. In the non-insulin treated group, patients with islet cell antibodies had lower body mass index (p<0.001), higher HbA1c (p<0.004), and lower C-peptide (p<0.001) than patients without. At follow-up, 11 of 18 (61%) islet cell positive patients were changed to insulin treatment, as were six other patients. Insulin was discontinued in five initially insulin-treated but islet cell antibody negative patients. The sensitivity, specificity and predictive value for insulin treatment at follow-up were for islet cell antibody positivity; 72%, 96% and 84%, respectively, and for low C-peptide value; 60%, 96%, and 80%, respectively. Islet cell antibodies and low C-peptide at diagnosis of diabetes mellitus are concluded to be useful markers to predict insulin dependence.

Factors influencing the magnitude, duration, and rate of fall of B-cell function in type 1 (insulin-dependent) diabetic children followed for two years from their clinical diagnosis.

SummaryThe pattern of fall in B-cell function measured as plasma and 24 h urinary C-peptide excretion, as well as levels of islet cell antibodies, insulin antibodies and metabolic parameters, were followed for two years in 39 children aged 1–17 years prospectively from clinical onset of Type 1 (insulin-dependent) diabetes. At onset 32/36 patients had measurable plasma C-peptide (median 0.13 nmol/l). Maximum values of fasting and postprandial plasma C-peptide were reached at a median duration of three months. Thereafter both plasma and urinary C-peptide declined linearly. The median value of the rate of fall in postprandial plasma C-peptide was 0.019 nmol·1−1·month−1. Age at onset was positively correlated to the maximum value of postprandial plasma C-peptide in each patient (rs=0.57, p=0.0001) and throughout the observation time positively correlated to fasting and postprandial C-peptide and to the 24 h urinary C-peptide excretion (rs range 0.35–0.70, p=0.03–0.0001). The rate of fall of postprandial C-peptide was unrelated to age at onset and was strikingly parallel in different age groups. Islet cell antibodies were present in 87% of the patients at onset and decreased to 38% at 24 months. Islet cell antibody litres were not correlated to age at onset or to plasma or urinary C-peptide at any single observation. However, islet cell antibody negative patients had significantly higher (p<0.05) postprandial plasma C-peptide values at 1, 9, and 12 months of duration, compared to islet cell antibody positive patients. Insulin antibodies and metabolic state at onset did not influence the C-peptide values. It is concluded that age at onset is the most important variable in predicting the duration and magnitude of endogenous insulin secretion during the first two years of Type 1 diabetes in children.