Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

Probabilistic Multiple-Bias Modeling Applied to the Canadian Data From the Interphone Study of Mobile Phone Use and Risk of Glioma, Meningioma, Acoustic Neuroma, and Parotid Gland Tumors

We undertook a re-analysis of the Canadian data from the 13-country case-control Interphone Study (2001-2004), in which researchers evaluated the associations of mobile phone use with the risks of brain, acoustic neuroma, and parotid gland tumors. In the main publication of the multinational Interphone Study, investigators concluded that biases and errors prevented a causal interpretation. We applied a probabilistic multiple-bias model to address possible biases simultaneously, using validation data from billing records and nonparticipant questionnaires as information on recall error and selective participation. In our modeling, we sought to adjust for these sources of uncertainty and to facilitate interpretation. For glioma, when comparing those in the highest quartile of use (>558 lifetime hours) to those who were not regular users, the odds ratio was 2.0 (95% confidence interval: 1.2, 3.4). After adjustment for selection and recall biases, the odds ratio was 2.2 (95% limits: 1.3, 4.1). There was little evidence of an increase in the risk of meningioma, acoustic neuroma, or parotid gland tumors in relation to mobile phone use. Adjustments for selection and recall biases did not materially affect interpretation in our results from Canadian data.

Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure

We demonstrate a fully etched, continuously apodized fiber-to-chip surface grating coupler for the first time (to our knowledge). The device is fabricated in a single-etch step and operates with TM-polarized light, achieving a coupling efficiency of 3.7 dB and a 3 dB bandwidth of 60 nm. A subwavelength microstructure is employed to generate an effective medium engineered to vary the strength of the grating and thereby maximize coupling efficiency, while mitigating backreflections at the same time. Minimum feature size is 100 nm for compatibility with deep-UV 193 nm lithography.

Managing scarce services. A waiting list approach to cardiac catheterization

Relatively little attention has been directed to the provision of health care services when demand exceeds availability. Since "waiting lists" are characteristic of the delivery of cardiovascular services in Manitoba, we hypothesized that the highest priority would be given to cases with the greatest urgency. This study examined the waiting lists for cardiac catheterization in one of two tertiary health care facilities offering comprehensive cardiovascular care to a population of slightly more than one million persons. Hospital records of all patients undergoing cardiac catheterization from May 1981 through December 1982 were abstracted retrospectively. For 871 patients entering a catheterization laboratory by two different routes (Elective Care, N = 557; Immediate Care, N = 314), patient need for immediate catheterization was assessed. Clinical differences between patients in the two groups were striking. Immediate Care patients more frequently had acute congestive heart failure, prior aortic valve surgery, and chronic obstructive pulmonary disease. Immediate Care patients were most frequently in Class 4 of the NYHA functional classification and were more often treated with triple medical therapy. These clinically ill individuals were more likely to enter the hospital via the Emergency Room; they were more likely to have long hospital stays and to die in hospital. As implemented in one Manitoba hospital, the waiting list process appears to have worked fairly well; cardiac arrest, acute myocardial infarction, and death among patients waiting for catheterization were all rare events. Both those patients needing immediate care and those who could wait with a low probability of a poor outcome were successfully identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Methionine analogs and cell division regulation in the yeast Saccharomyces cerevisiae

Methionine analogs such as ethionine, selenomethionine, and trifluoromethionine all arrest growth and division of the yeast Saccharomyces cerevisiae. One analog, ethionine, caused cells of the yeast to arrest specifically within G1; reciprocal shift experiments showed that ethionine and alpha-factor arrested cells at the same step ("start"). The major effect of ethionine on synthesis of macromolecules was to reduce both the rate of appearance of 35S ribosomal precursor RNA and the rate of production of mature rRNA. Synthesis of protein was relatively unaffected by ethionine. Selenomethionine and trifluoromethionine caused cells to arrest randomly in the cell division cycle. Although treatment of cells with either selenomethionine or trifluoromethionine also reduced the rate of total RNA synthesis, each of these analogs had other effects that presumably prohibited completion of the cell cycle. We propose that the rate of rRNA production is an important regulatory event in the cell cycle.

Familial hyperbilirubinemia in Friedreich's ataxia

The combined metabolic stresses of fasting and the intravenous injection of 50 mg nicotinic acid in Friedreich's ataxia resulted in the delineation of two sub-groups of responses. High bilirubin ataxics maintained abnormally elevated levels of bilirubin, while normal bilirubin ataxics behaved like the normal control group. It is postulated that this finding infers the possible linkage of the gene for Friedreich's ataxia and that for Gilbert's disease.