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.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

A double-blind pilot study of risperidone in the treatment of conduct disorder

OBJECTIVE

To examine whether risperidone is superior to placebo in the treatment of youths with conduct disorder.

METHOD

This was a 10-week, randomized, double-blind, placebo-controlled study with 2 parallel arms. Ten youths were randomly assigned to receive placebo and 10 youths were randomly assigned to receive risperidone. Patients were seen weekly throughout the trial. Medications could be increased at weekly intervals during the first 6 weeks of the study from an initial dose of 0.25 mg or 0.50 mg each morning, depending on patient weight. Patients weighing less than 50 kg had a maximum total daily dose of risperidone of 1.5 mg. Patients weighing 50 kg or greater had a maximum total daily dose of risperidone of 3.0 mg. The primary outcome measure was the Rating of Aggression Against People and/or Property Scale.

RESULTS

Risperidone was superior to placebo in ameliorating aggression on most measures. Risperidone was reasonably well tolerated, with none of the risperidone-treated patients developing extrapyramidal side effects.

CONCLUSIONS

These data provide preliminary evidence that risperidone may have efficacy in the treatment of youths with conduct disorder. Because of the small sample size and the brief length of this study, further research is necessary to confirm these findings.

Tonsillar tissue penetration of dirithromycin after multiple doses

Dirithromycin is a new macrolide antibiotic that is effective against group A beta-hemolytic streptococcal pharyngotonsillitis. This prospective, multicenter, randomized study compared the serum and tonsil tissue concentrations of erythromycylamine (to which dirithromycin is rapidly converted by nonenzymatic hydrolysis during absorption) and erythromycin after 5- and 10-day regimens of dirithromycin and erythromycin, respectively. Thirty-nine patients undergoing elective tonsillectomy but without active tonsillitis were assigned in randomized fashion to receive dirithromycin 500 mg orally once daily (n = 22) or erythromycin base 250 mg orally four times daily (n = 17). Data from 12 patients receiving dirithromycin and 10 receiving erythromycin were eligible for analysis. Mean serum concentrations (+/-standard deviation) of erythromycylamine and erythromycin were 0.20 +/- 0.07 microgram/mL and 0.12 +/- 0.25 microgram/mL, respectively, after the 5-day regimen and 0.17 +/- 0.10 microgram/mL and 1.57 +/- 3.16 micrograms/mL, respectively, after the 10-day regimen. The mean serum concentration of erythromycin after 10 days was skewed by the data for one of the six patients in the group (concentration of > 8 micrograms/mL). Mean concentrations of erythromycylamine in tonsil tissue were 4.62 +/- 0.97 micrograms/ g after 5 days and 3.47 +/- 2.84 micrograms/g after 10 days. Concentrations in tonsillar tissue were undetectable in all patients given erythromycin for 5 days and in 4 of the 6 patients given erythromycin for 10 days. The high concentrations of erythromycylamine in tonsillar tissue agree with the clinical efficacy seen in the treatment of group A beta-hemolytic streptococcal tonsillopharyngitis with dirithromycin.

Single-dose pharmacokinetics of piperacillin and tazobactam in infants and children

The pharmacokinetics of piperacillin and tazobactam were assessed after single-dose administration to 47 infants and children. Study subjects ranging in age from 2 months to 12 years were randomized to receive one of two different doses of a piperacillin-tazobactam combination (8:1): a low dose (n = 23) of 50 and 6.25 mg of piperacillin and tazobactam per kg of body weight, respectively, or a high dose (n = 24) of 100 and 12.5 mg, respectively. The pharmacokinetic behavior of tazobactam was very similar to that observed for piperacillin, supporting the use of these two agents in a fixed-dose combination. No differences in the pharmacokinetics of piperacillin or tazobactam were observed between the two doses administered. The elimination parameters half-life and total body clearance decreased and increased, respectively, with increasing age, whereas volume parameters (volume of distribution and steady-state volume of distribution) remained relatively constant for both compounds. The primary metabolite of tazobactam, metabolite M1, was measurable in the plasma of 18 of the 47 study subjects; 17 of these 18 subjects received the high doses. More than 70% of the administered piperacillin and tazobactam doses were excreted unchanged in the urine over a 6-h collection period. These data combined with the known in vitro susceptibilities of a broad range of pediatric bacterial pathogens indicate that a dose of 100 mg of piperacillin and 12.5 of mg tazobactam per kg of body weight administered as a fixed-dose combination every 6 to 8 h would be appropriate to initiate clinical efficacy studies in infants and children for the treatment of systemic infections arising outside of the central nervous system.

Complications, surgical revision and quality of life with conventional and continent ileostomy

Continent ileostomy remains an alternative to restorative proctocolectomy in selected cases. Results with continent ileostomy in 55 patients are reported--in 82% after conversion from conventional ileostomy. Three years postoperatively 93% were continent and 7% partially continent, and after 5 years 95% were continent. Complications requiring laparotomy arose in ten patients (18%) during the immediate postoperative period (30% among the first 27 patients, 7% of the subsequent 28). The incidence of late complications requiring laparotomy was 16% in the first year, 10% in the next 2 years and 5% after the third year. Slipping of the nipple occurred in 9% of the patients in the first postoperative year. No reservoir has been removed. The quality of life improved after colectomy with conventional ileostomy, but most patients experienced a dramatic further improvement after construction of the continent ileostomy. The improvement in ultimate quality of life was not influenced by revision for malfunction of continent ileostomy.

Randomized clinical trial of topical mupirocin versus oral erythromycin for impetigo

The safety and efficacy of a new topical antiinfective agent, mupirocin, was compared with that of oral erythromycin ethylsuccinate in the treatment of impetigo in children. Sixty-two children aged 5 months to 13 years with impetigo were assigned to be treated with either mupirocin in three daily applications or erythromycin ethylsuccinate (40 mg/kg of body weight per day divided into four doses) according to a randomized treatment schedule. On the initial visit, exudate or cleansed infected sites or both were cultured and therapy was begun. All patients were treated for 8 days. Patients were seen again on days 4 to 5 of therapy, at the end of therapy, and 7 days after the end of therapy. Sites of infection were comparable between the groups, as were bacteriologic responses. At the first visit, 24 of 30 children in the mupirocin group and 14 of 32 children in the erythromycin group were cured or had at least a 75% reduction in size of the lesions. At the end of the study, all 29 of the children in the mupirocin group who came to follow-up, compared with 27 of 29 in the erythromycin group, were cured. Side effects were few. Five children in the erythromycin group developed mild diarrhea. Thus, mupirocin appears to be safe and effective in treating impetigo in children. Our data show a trend toward more rapid clinical response with mupirocin than with erythromycin.

Skin and soft tissue infections: pharmacologic approaches

Skin and soft tissue infections are common infectious problems in pediatric practice. Recent clinical and pharmacologic evaluations of several new antimicrobial agents have shed new light on the pathogenesis and management of these infections. Staphylococcus aureus now appears to be the most common bacterial isolate in children with impetigo. In patients hospitalized because of skin and soft tissue infections, S. aureus and Haemophilus influenzae type b remain the predominant pathogens. Rational therapeutic approaches to these infections require a recognition of the interplay among the pharmacodynamic, pharmaceutic and pharmacokinetic determinants of effective antimicrobial therapy. Using this approach the therapeutic questions regarding "what drug," "what dose" and "how long to treat" can be approached. Drugs such as the aminopenicillin-beta-lactamase inhibitor combinations may offer rational outpatient therapeutic alternatives, while parenteral cefuroxime and ceftriaxone are more probably the drugs of choice for parenteral therapy. In an age when cost effectiveness must prevail, strategies using ceftriaxone for both inpatient and outpatient management may provide the safest and most cost-effective therapy.

The Sun's Work in a Cornfield

After extensive field experiments, we developed SPAM, a comprehensive mathematical model that simulates energy and material exchange in the plantair layer at the earth's interface. The model is based upon the conservation of energy, where the sun is the driving force. Our understanding and deficiencies were gauged initially by testing model predictions against actual experience with a relatively simple system-a cornfield. Climatic predictions are physically and biologically good enough for many applications, but they reveal inadequacies in our understanding of the fluid dynamics of airflow within the plant stand. Our present inability to measure or predict the degree of wetness of the soil surface hampers correct prediction of evaporation. Probably the most difficult problem to resolve is that of predicting how stomates open and close under drought stress, thus affecting both evaporation and photosynthesis in leaves. Along with resolution of these problems, the basic framework of the model can be adapted to more complex systems in nature, where variability is much greater than in an agricultural crop. The model in its present form can be used, with caution, as a powerful tool to help man order his priorities of plant community traits for whatever outcome he desires, be it food production, nature and water conservation, climate modification, or esthetic enjoyment.