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.

Transgenerational effects of variable foraging demand stress in female bonnet macaques

Stress coping is an important part of mammalian life, influencing somatic and mental health, social integration, and reproductive success. The experience of early psychological stress helps shape lifelong stress coping strategies. Recent studies have shown that the effects of early stress may not be restricted to the affected generation, but may also be transmitted to offspring. Understanding whether early stress influences development in subsequent generations may help us understand somewhat why many stress-related traits and diseases, for which little genetic basis has been discovered, run in families. Experimental early life "variable foraging demand" (VFD) stress has been associated with behavioral hypo-responsiveness to stress in infant and adolescent bonnet macaques. The present study examined the behavioral effects of experimental early VFD stress in adult bonnet macaques, and further investigated whether non-exposed adolescent offspring of VFD macaques were also affected. Thirty female bonnet macaques from four rearing histories were observed for behavioral response during stress: adults which had been VFD reared as infants (n = 11), adults which had been Control reared as infants (n = 9), and foraging demand naïve adolescents whose mothers were VFD (n = 4) or Control reared (n = 6). Subjects were observed for behavioral response during two experimental stressor conditions, including: (1) relocation to a novel environment; and (2) relocation with exposure to a "human intruder" making eye contact. Factor analysis yielded five factors that described categories of behavior across stress conditions. While adult VFD and Control reared females unexpectedly did not differ significantly, non-exposed adolescent offspring of VFD reared mothers displayed significant hypo-responsiveness in all behavioral categories compared with non-exposed adolescent offspring of Control females. We suggest that stress hypo-responsiveness previously observed in adolescent VFD reared animals may abate with age, but is nonetheless observed in the next generation. We conclude that VFD stress affects behavioral development of subsequent generations in non-human primates.

DNA methylation as a risk factor in the effects of early life stress

Epigenetic marks (e.g., DNA 5-methylcytosine [5mC] content or CpG methylation) within specific gene regulatory regions have been demonstrated to play diverse roles in stress adaptation and resulting health trajectories following early adversity. Yet the developmental programming of the vast majority of the epigenome has not yet been characterized, and its role in the impact of early stress largely unknown. In the present study, we investigated the relationships among early life stress, whole-epigenome and candidate stress pathway gene (serotonin transporter, 5-HTT) methylation patterns, and adult behavioral stress adaptation in a non-human primate model. Early in life, experimental variable foraging demand (VFD) stress or control conditions were administered to two groups each of 10 female bonnet macaques (Macaca radiata) and their mothers. As adults (3-13 years of age), these females were assessed for behavioral adaptation to stress across four conditions of increasing intensity. Blood DNA 5-HTT 5mC status was determined using sodium bisulfite pyrosequencing and total 5mC content was determined using ELISA. Neither stress reactivity nor DNA methylation differed based on early life stress. However, we found that both greater 5-HTT and whole-genome 5mC was associated with enhanced behavioral stress reactivity following early life stress, but not control conditions. Therefore, regardless of developmental origin, greater DNA methylation conferred a genomic background of "risk" in the context of early stress. We suggest that this may arise from constrained plasticity in gene expression needed for stress adaptation early in development. This risk may have wider implications for psychological and physical stress adaptation and health.

Broad specificity alkaline proteases efficiently reduce the visual scaling associated with soap-induced xerosis

In xerotic skin, the proteolysis of desmosomes is reduced leading to the accumulation of corneocytes on the surface of the skin. The effect of proteases applied topically to soap-induced xerotic skin was evaluated using a five-point visual scale. The visual scaling associated with soap-induced xerosis could be ameliorated by the topical application of exogenous protease. Bovine pancreatic chymotrypsin, papain, and a bacterial protease from Bacillus licheniformis were all capable of facilitating the reduction in visual scaling in a short time. Alcalase and Optimase, both broad specificity alkaline bacterial proteases, were the most weight-efficient at delivering this clinical effect. The reduction in scaling could be achieved either by occluded application of an aqueous enzyme solution or by a two-step unoccluded application first of an aqueous enzyme solution followed by a commercial moisturizer. Morphological and immunological analysis of bacterial enzyme-treated skin revealed that topically applied protease specifically induced the degradation of the desmosomes thereby promoting desquamation. These results indicate that topical application of protease can significantly and rapidly reduce the visual scaling associated with soap-induced xerosis by promoting desmosome degradation within the corneocyte clumps.

Assessing life expectancies of older nursing home residents

OBJECTIVE

Care of nursing home (NH) residents is often based on the usual survival of the home's residents. In order to improve our understanding of this population, and, thus, ultimately facilitate individualization of their care, we developed a mathematical model that predicts their survival.

SETTING

The Jewish Home and Hospital (JHH), a nursing home.

PARTICIPANTS

1145 older residents who were at the JHH from January 1, 1986, through July 1, 1986.

MEASUREMENTS

Information abstracted from medical records and JHH computerized data: clinical, demographic, and dependencies in activities of daily living (ADLs).

MAIN OUTCOME MEASURE

survival from July 1, 1986.

DESIGN

Retrospective cohort study via medical chart review. The study period covered admission to JHH through January 17, 1996. Accelerated failure time (AFT) models generated the life expectancy model derived from 50% of the study group and were validated on the remaining sample. We computed predicted AFT and proportional hazards (PH) life expectancies.

RESULTS

Significant, independent predictors of decreased survival were male gender, increased age, increase in summary ADL index, and impairment of cardiac, respiratory, neurological, and endocrine/metabolic systems. The interaction between gender and respiratory system impairment was significant. The Spearman correlation coefficients between the observed survivals and those predicted by the Phase I model are 0.49 for Phase I residents and 0.42 for Phase II residents. Our sample life table includes NH residents with different risk profiles and their associated survival estimates as well as interquartile ranges. AFT and PH survivals were similar.

CONCLUSION

This first comprehensive model that predicts survival of NH residents can help formulate public health policies and identify appropriate NH residents for clinical trials. The model is a promising step toward improving the health care of NH residents.

Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function

Alpha-hydroxy acids are effective agents for the treatment of skin xerosis and it is known that, following treatment with lotions containing D,L-lactic acid, the stratum corneum prevents xerosis more effectively. To date, the relative efficacy of the different isomers of lactic acid has not been evaluated and the mode of action of lactic acid in improving stratum corneum resilience is not known. The objective of the present studies was to determine the effects of lactic acid isomers on keratinocyte ceramide biosynthesis, stratum corneum barrier function and the resistance of the stratum corneum to the appearance of skin xerosis. In vitro, lactic acid enhanced the production of ceramides by keratinocytes. L-Lactic acid was more effective than the D isomer (300% increase vs 100% increase). Carbon label from lactic acid was incorporated into all keratinocyte lipid species and a greater incorporation of label into ceramides was achieved with L-lactate than with D-lactate. In vivo, lactic acid increased the levels of stratum corneum ceramides. Whereas, lotions containing L-lactic acid resulted in the greatest increase (48% increase) followed by D,L-lactic acid (25% increase), D-lactic acid had no effect on stratum corneum ceramide levels. The increases in stratum corneum ceramide levels following lactic acid treatment also led to improvements in stratum corneum barrier function, measured by transepidermal water loss following a challenge to the skin with SLS and in the regression phase of a moisturization efficacy study. Significant improvements in barrier function and resistance to the appearance of skin xerosis were observed following L-lactic acid and D,L-lactic acid, but not following D-lactic acid treatment. From these results we believe that lactic acid, particularly the L isomer, stimulates ceramide biosynthesis leading to increased stratum corneum ceramide levels which results in superior lipid barrier and a more effective resistance against xerosis.