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.

Ethical issues and best practice in clinically based genomic research: Exeter Stakeholders Meeting Report

Current guidelines on consenting individuals to participate in genomic research are diverse. This creates problems for participants and also for researchers, particularly for clinicians who provide both clinical care and research to their patients. A group of 14 stakeholders met on 7 October 2015 in Exeter to discuss the ethical issues and the best practice arising in clinically based genomic research, with particular emphasis on the issue of returning results to study participants/patients in light of research findings affecting research and clinical practices. The group was deliberately multidisciplinary to ensure that a diversity of views was represented. This report outlines the main ethical issues, areas of best practice and principles underlying ethical clinically based genomic research discussed during the meeting. The main point emerging from the discussion is that ethical principles, rather than being formulaic, should guide researchers/clinicians to identify who the main stakeholders are to consult with for a specific project and to incorporate their voices/views strategically throughout the lifecycle of each project. We believe that the mix of principles and practical guidelines outlined in this report can contribute to current debates on how to conduct ethical clinically based genomic research.

Hydrogels derived from demineralized and decellularized bone extracellular matrix

The extracellular matrix (ECM) of mammalian tissues has been isolated, decellularized and utilized as a scaffold to facilitate the repair and reconstruction of numerous tissues. Recent studies have suggested that superior function and complex tissue formation occurred when ECM scaffolds were derived from site-specific homologous tissues compared with heterologous tissues. The objectives of the present study were to apply a stringent decellularization process to demineralized bone matrix (DBM), prepared from bovine bone, and to characterize the structure and composition of the resulting ECM materials and DBM itself. Additionally, we sought to produce a soluble form of DBM and ECM which could be induced to form a hydrogel. Current clinical delivery of DBM particles for treatment of bone defects requires incorporation of the particles within a carrier liquid. Differences in osteogenic activity, inflammation and nephrotoxicity have been reported with various carrier liquids. The use of hydrogel forms of DBM or ECM may reduce the need for carrier liquids. DBM and ECM hydrogels exhibited sigmoidal gelation kinetics consistent with a nucleation and growth mechanism, with ECM hydrogels characterized by lower storage moduli than the DBM hydrogels. Enhanced proliferation of mouse primary calvarial cells was achieved on ECM hydrogels, compared with collagen type I and DBM hydrogels. These results show that DBM and ECM hydrogels have distinct structural, mechanical and biological properties and have the potential for clinical delivery without the need for carrier liquids.

In vivo detection of postictal perturbations of cerebral metabolism by use of proton MR spectroscopy: preliminary results in a canine model of prolonged generalized seizures

BACKGROUND AND PURPOSE

Biochemical studies of seizures in patients and laboratory animals have monitored postictal perturbations in cerebral metabolism with either invasive techniques or with such noninvasive techniques as nuclear medicine, MR imaging, in vivo phosphorus MR spectroscopy (MRS), and in vivo proton MRS at field strengths of 1.5 T or above. We investigated postictal metabolic changes in a generalized seizure model with in vivo proton MRS at 0.5 T, in which the combination of glutamate and glutamine resonances (denoted glx) can be modeled as a singlet.

METHODS

Five adult mongrel dogs underwent control and postictal experiments in which single-voxel proton MR spectra were obtained from the right frontal lobe cortex with a point-resolved spectroscopy technique approximately every 20 minutes for 3 hours. N-acetylaspartate (NAA), glx, and creatine (Cr) were quantified in absolute millimolar units with a cerebral water-referenced algorithm. Inter- and intrasubject differences in mean metabolite concentrations collected throughout the 3-hour period were compared using an unpaired, two-tailed Student's t test at a.05 level of significance.

RESULTS

We found a significant increase (15.4%) in the postictal intersubject mean glx concentration, as well as a 23.7% postictal decrease in the intersubject mean Cr concentration. A trend toward a subtle decrease in postictal intersubject mean NAA concentration was not statistically significant. We also observed a substantial qualitative increase in the combination of postictal lactate and free fatty acid peaks.

CONCLUSIONS

The glx, NAA, lactate, and free fatty acid results are in general agreement with previous studies of postictal perturbations in cerebral metabolism measured with invasive biochemical or noninvasive high-field-strength in vivo MRS detection assays. Given a high sensitivity for glx at 0.5 T relative to 1.5 T, further studies of postictal mesial temporal lobe structures are warranted in chronic animal preparations that model temporal lobe epilepsy.

Phylogeography of the trumpetfishes (Aulostomus): ring species complex on a global scale

The distribution of circumtropical marine species is limited by continental boundaries, cold temperate conditions, and oceanic expanses, but some of these barriers are permeable over evolutionary time scales. Sister taxa that evolved in separate ocean basins can come back into contact, and the consequences of this renewed sympatry may be a key to understanding evolutionary processes in marine organisms. The circumtropical trumpetfishes (Aulostomus) include a West Atlantic species (A. maculatus), an Indian-Pacific species (A. chinensis), and an East Atlantic species (A. strigosus) that may be the product of a recent invasion from the Indian Ocean. To resolve patterns of divergence and speciation, we surveyed 480 bp of mitochondrial DNA cytochrome b in 196 individuals from 16 locations. Based on a conventional molecular clock of 2% sequence divergence per million years, the deepest partitions in a neighbor-joining tree (d = 0.063-0.082) are consistent with separation of West Atlantic and Indian-Pacific species by the Isthmus of Panama, 3-4 million years ago. By the same criteria, trumpetfish in the East Atlantic were isolated from the Indian Ocean about 2.5 million years ago (d = 0.044-0.054), coincident with the advent of glacial cycles and cold-water upwelling around South Africa. Continental barriers between tropical oceans have only rarely been surmounted by trumpetfishes, but oceanic barriers do not appear to be substantial, as indicated by weak population partitioning (phiST = 0.093) in A. chinensis across the Indian and Pacific Oceans. Finally, morphological and mitochondrial DNA data indicate hybridization of A. strigosus and A. maculatus in Brazil. After 3-4 million years and a globe-spanning series of vicariant and dispersal events, trumpetfish lineages have come back into contact in the southwest Atlantic and appear to be merging. This ring species phenomenon may occur in a broad array of marine organisms, with clear implications for the production and maintenance of biodiversity in marine ecosystems.

Discrimination between neoplastic and nonneoplastic brain lesions by use of proton MR spectroscopy: the limits of accuracy with a logistic regression model

BACKGROUND AND PURPOSE

The most accurate method of clinical MR spectroscopy (MRS) interpretation remains an open question. We sought to construct a logistic regression (LR) pattern recognition model for the discrimination of neoplastic from nonneoplastic brain lesions with MR imaging-guided single-voxel proton MRS data. We compared the LR sensitivity, specificity, and receiver operator characteristic (ROC) curve area (Az) with the sensitivity and specificity of blinded and unblinded qualitative MRS interpretations and a choline (Cho)/N-acetylaspartate (NAA) amplitude ratio criterion.

METHODS

Consecutive patients with suspected brain neoplasms or recurrent neoplasia referred for MRS were enrolled once final diagnoses were established by histopathologic examination or serial neurologic examinations, laboratory data, and imaging studies. Control spectra from healthy adult volunteers were included. An LR model was constructed with 10 input variables, including seven metabolite resonance amplitudes, unsuppressed brain water content, water line width, and the final diagnosis (neoplasm versus nonneoplasm). The LR model output was the probability of tumor, for which a cutoff value was chosen to obtain comparable sensitivity and specificity. The LR sensitivity and specificity were compared with those of qualitative blinded interpretations from two readers (designated A and B), qualitative unblinded interpretations (in aggregate) from a group of five staff neuroradiologists and a spectroscopist, and a quantitative Cho/NAA amplitude ratio > 1 threshold for tumor. Sensitivities and specificities for each method were compared with McNemar's chi square analysis for binary tests and matched data with a significance level of 5%. ROC analyses were performed where possible, and Az values were compared with Metz's method (CORROC2) with a 5% significance level.

RESULTS

Of the 99 cases enrolled, 86 had neoplasms and 13 had nonneoplastic diagnoses. The discrimination of neoplastic from control spectra was trivial with the LR, reflecting high homogeneity among the control spectra. An LR cutoff probability for tumor of 0.8 yielded a specificity of 87%, a comparable sensitivity of 85%, and an area under the ROC curve of 0.96. Sensitivities, specificities, and ROC areas (where available) for the other methods were, on average, 82%, 74%, and 0.82, respectively, for readers A and B, 89% (sensitivity) and 92% (specificity) for the group of unblinded readers, and 79% (sensitivity), 77% (specificity), and 0.84 (Az) for the Cho/NAA > 1 criterion. McNemar's analysis yielded significant differences in sensitivity (n approximately 86 neoplasms) between the LR and reader A, and between the LR and the Cho/NAA > 1 criterion. The differences in specificity between the LR and all other methods were not significant (n approximately 13 nonneoplasms). Metz's analysis revealed a significant difference in Az between the LR and the Cho/NAA ratio criterion.

Optical time-domain reflectometry in optical fiber with reflection delay time matched to the period of the optical frequency modulation

A method of optical time-domain reflectrometry in optical fiber is described that uses a single distributed feedback diode laser and a reference reflector. When the period of the frequency modulation of the laser matches the time difference between the reference reflection and the reflection of interest an increase in the noise at the detector occurs. The locations of reflections within the fiber are then mapped to frequencies at which the noise at the detector increases. A sinusoidal frequency modulation is analyzed, and an experiment is described in which the system is used to measure the location and the wavelength of two Bragg gratings located 10 cm apart in an optical fiber. Wavelength measurement is accomplished by temperature tuning the diode laser.

Synthesis and characterization of [125I]3'-(-)-iodopentazocine, a selective sigma 1 receptor ligand

Pentazocine is a potent ligand at both opioid and sigma receptors, but with opposite stereoselectivities. Whereas (-)-pentazocine has high affinity for a number of opioid receptors, (+)-pentazocine labels sigma 1 receptors. Iodination of (-)-pentazocine at the 3'-position reverses its selectivity for opioid and sigma 1 receptors. 3'-(-)-Iodopentazocine competes at sigma 1 receptor binding sites with a Ki value of 8 nM, compared to approximately 40 nM for (-)-pentazocine. 3'-(-)-Iodopentazocine also has lost its affinity for opioid receptors. In contrast, iodination of (+)-pentazocine lowers its affinity at sigma 1 receptors. Synthesis of [125I]3'-(-)-iodopentazocine is readily performed with incorporations of up to 80%. Binding is of high affinity and shows the selectivity anticipated for a sigma 1 receptor-selective ligand. Exposing membranes prebound with [125I]3'-(-)-iodopentazocine to ultraviolet light can covalently couple the ligand into the membranes. Polyacrylamide gel electrophoresis reveals a major band at about 25 kDa and a minor one at about 20 kDa, indicating photolabeling of sigma 1 receptors with minor incorporation into sigma 2 sites.

Ventilation-perfusion relationships in preterm infants after surfactant treatment

Arterial-alveolar partial pressure differences for oxygen, carbon dioxide, and nitrogen were measured before and after surfactant replacement therapy on 15 occasions in 14 ventilator-dependent preterm infants with hyaline membrane disease (HMD). Eight treatments resulted in a significant improvement in arterial partial pressure of oxygen (PaO2) 2 hr after treatment; 7 did not. Neither group showed any significant change in arterial-alveolar partial pressure differences for oxygen, nitrogen, and carbon dioxide. This observation suggests that if surfactant replacement therapy produces an improvement in PaO2 it does so by recruitment of atelectatic alveoli with a balanced ventilation/perfusion ratio rather than by redistribution of ventilation within already ventilated alveoli.

Distinct morphological and mito-inhibitory effects induced by TGF-beta 1, HGF and EGF on mouse, rat and human hepatocytes

TGF-beta 1 is known as a potent inhibitor of proliferation of rat and human hepatocytes. In this study we show that the effects of TGF-beta 1 are quite different on mouse hepatocytes. In rat and human hepatocytes, TGF-beta 1 inhibited DNA synthesis and also inhibited the morphological changes induced by growth factors in rat and human hepatocytes. In contrast, addition of TGF-beta 1 to mouse hepatocytes resulted in pronounced alterations in morphology of these cells. These changes were similar to those induced by HGF and EGF. The induction of structural changes by TGF-beta 1 was noted only in mouse hepatocytes. Mouse hepatocytes were also much more resistant to the mito-inhibitory effect of TGF-beta 1. These findings suggest profound differences in hepatocyte growth regulation between these species and may relate to observed differences in susceptibility to carcinogenesis.

Comparative analysis of mitogenic and morphogenic effects of HGF and EGF on rat and human hepatocytes maintained in collagen gels

Hepatocytes maintained in collagen gels remain differentiated for prolonged periods of time compared to cells maintained on conventional cultures. Previous studies with other culture systems in which chemical supplements or substratum modifications enhanced hepatocyte differentiation showed that in all of these systems hepatocytes do not respond to mitogens. In this study it is shown that hepatocytes maintained between two layers of collagen gels respond to mitogens HGF (also known as scatter factor (HGF/SF)) and epidermal growth factor (EGF). Cell density did not affect the responsiveness to mitogens as in conventional cultures. In addition both mitogens (HGF more pronounced) induce characteristic morphogenic changes in which hepatocytes form processes and join in formation of cords. Hepatocytes respond to mitogens for up to 6 days in culture at which point they become refractory to further mitogenic stimulation. This occurs despite electron microscopic evidence that these cells are fully viable when they become refractory to mitogenesis. The refractory state is not modified by substitution of one growth factor for the other or by addition of growth factors at different times. Hepatocytes in the refractory state become again responsive to mitogens when the collagen gels are dispersed by collagenase and the cells are replated on conventional substrates.

Expression and characterization of biologically active human hepatocyte growth factor (HGF) by insect cells infected with HGF-recombinant baculovirus

A cDNA containing the entire coding sequence of human hepatocyte growth factor (HGF) [also known as scatter factor (SF)] was inserted into the genome of Autographa california nuclear polyhedrosis virus (baculovirus) adjacent to the polyhedrin promoter by homologous recombination. Insect cells (Spodoptera frugiperda) infected with the recombinant virus secrete relatively high levels (3-8 mg/L) of biologically active HGF into the culture medium. The recombinant HGF induces pronounced morphological changes and scattering of primary cultures of rat, mouse, and human hepatocytes within 24 h after plating and stimulates DNA synthesis in these cells with the same magnitude as native HGF derived from human placenta or rabbit serum. The human recombinant HGF produced by the insect cells is N-glycosylated, binds to heparin like native HGF, and is recognized by polyclonal antiserums raised against human or rabbit HGF as assessed by immunoblot, ELISA, and immunoneutralization experiments. Metabolic radiolabeling with L-[35S]methionine (pulse-chase experiments) as well as Western blot analysis indicates that the recombinant HGF is synthesized and secreted by the infected insect cells as the unprocessed single-chain form (pro-HGF) when the cells are cultured in serum-free medium. However, when the infected insect cells are cultured in insect culture medium (Grace's medium) containing fetal bovine serum, the secreted HGF is present mainly in the mature heterodimeric form. Addition of serum to the baculovirus-expressed single-chain [125I]HGF in a cell-free system results in conversion to the heterodimeric two-chain form, and the activation is prevented by the serine protease inhibitor PMSF. Incubation of 125I-labeled pro-HGF with rat liver or spleen extracts resulted in conversion of pro-HGF to the heterodimeric two-chain form. A truncated form of HGF containing the N-terminal portion of HGF (kringles 1-3) was also produced in the same expression system. This deleted HGF, by itself, did not have any detectable biological activity; however, it abrogated the stimulatory effects of full-length HGF on hepatocytes. This is the first successful production of bioactive recombinant HGF in large quantities, which will allow purification on the milligram scale of pro-HGF and will permit future studies to elucidate pathways involved in HGF activation by its target tissues.

Synthesis and biological evaluation of conformationally restricted 2-(1-pyrrolidinyl)-N-[2-(3,4-dichlorophenyl)ethyl]-N-methylethylenediam ines as sigma receptor ligands. 1. Pyrrolidine, piperidine, homopiperidine, and tetrahydroisoquinoline classes

The synthesis and sigma receptor affinity of a series of conformationally restricted derivatives of 2-(1-pyrrolidinyl)-N-[2-(3,4-dichlorophenyl)ethyl]-N-methylethylenedi amine (1) is described. The pyrrolidinyl (or N,N-dialkyl),ethylenediamine,N-alkyl, and phenylethyl portions of this sigma receptor pharmacophore were restricted by its incorporation into 1,2-cyclohexanediamine-, pyrrolidine-, piperidine-, homopiperidine-, and tetrahydroisoquinoline-containing ligands. The sigma receptor binding affinities of these compounds were determined using [3H](+)-pentazocine in guinea pig brain homogenates. The synthesis of all but one class was achieved by acylation and alane reduction of the appropriate diamine precursors whose synthesis is also reported. sigma receptor affinities ranged from 1.34 nM for 6,7-dichloro-2-[2-(1-pyrrolidinyl)ethyl]tetrahydroisoquinoline (12) to 455 nM for (1R,2R)-trans-N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2- (1-pyrrolidinyl)cyclohexylamine [(-)-4]. In this displacement assay, (+)-pentazocine exhibited a Ki of 3.1 nM while DTG and haloperidol showed Ki values of 27.7 and 3.7 nM, respectively. The conformationally free parent compound 1 exhibited a Ki value of 2.1 nM. Comparison of both the sigma receptor affinities and nitrogen atom geometry of the compounds revealed that a gauche relation of the nitrogen atoms of cis-1,2-cyclohexanediamines is not imperative for high affinity as we had previously thought. It is highly likely that nitrogen lone pair orientations and steric factors on the aliphatic portions of these ligands play a major role in the sigma receptor binding of this pharmacophore.

Glucose uptake and flux through phosphofructokinase in wounded rat skeletal muscle

Skeletal muscle injured with lambda-carrageenan has increased aerobic glycolysis. To assess the regulation of this process, the tissue concentrations of glycolytic intermediates, the flux through phosphofructokinase (PFK), and the intracellular concentrations of PFK effectors were examined in wounded rat skeletal muscle and in macrophages, the predominant inflammatory cell in the early stages of this wound model. Autoradiography demonstrated increased 2-deoxy-D-glucose uptake in wounded tissue compared with nonwounded muscle. 2-Deoxy-D-glucose was localized to the cellular infiltrate. The glycolytic intermediate concentrations demonstrated a facilitation of PFK in macrophages and wounded tissue as compared with nonwounded muscle. Wounded tissue had twice the flux through PFK compared with nonwounded muscle (10.0 +/- 0.6 wounded vs. 4.9 +/- 0.4 mumol.h-1.g-1 nonwounded). Macrophages had the highest flux through PFK (63.7 +/- 5.7 mumol.h-1.g-1) and when coincubated with muscle, the combined flux through PFK was equal to that of wounded muscle. The increase in glycolysis associated with wounded tissue may be explained by increased glucose uptake and increased flux through PFK by the inflammatory cells present in wounded tissue.

The effect of malnutrition on caries development and saliva composition in the rat

The purpose of this study was to investigate the effect in rats of malnutrition on caries development and on some antibacterial substances in saliva. By gastric intubation, two groups of ten rats each were fed a liquid basic diet (100% diet), and two similar groups were fed the basic diet diluted with an equal volume of water to contain 50% of the nutrients of the basic diet (50% diet). One group on undiluted and one group on the diluted basic diet were offered sucrose as a supplement by mouth 17 times daily, using a programmed feeding machine, and the other two groups were offered starch in a similar manner. The extent and depth of the caries lesions were five times greater in the low-nourished (50% diet) sucrose group in comparison with the group given the undiluted diet supplemented with sucrose. The 50% diet group ate more frequently from the offered supplement. The 50% diet induced lower salivary lactoperoxidase activities, and there was an additive effect of starch as supplement. Higher concentrations of sIgA were found in the saliva of animals fed the 50% diet supplemented with sucrose than in those fed sucrose and the 100% diet. Significantly greater levels of sIgA and IgG were found in the saliva from the 50% diet-sucrose group than in the 50% diet-starch group. Plaque scores differed slightly but not significantly between the groups. The starch group receiving 100% diet showed a slightly lower level of S. mutans infection as compared with the 50% diet-starch group; the caries scores in the starch groups did not differ.

Effect of diet on the colonization of the mouth by Actinomyces viscosus (T-6) in Osborne-Mendel rats

Oral colonization by A. viscosus, strain T-6 was studied in Osborne-Mendel rats which were fed either sucrose, glucose, starch or casein alone ad libitum by mouth. Essential nutrients were given to the rats twice daily by stomach tube. All three carbohydrates supported implantation by Actinomyces to varying degrees. Implantation did not occur when the animals were fed casein. Casein did not have any antimicrobial effect on Actinomyces already established in the rat mouth; it was impossible to eliminate an established Actinomyces flora. Feeding the animals all the dietary components through the stomach tube did not result in eradication of Actinomyces from an established flora. The Actinomyces was considerably diminished when coprophagy was prevented.