Variations in Multiple Syndromic Deafness Genes Mimic Non-syndromic Hearing Loss.

The genetics of both syndromic (SHL) and non-syndromic hearing loss (NSHL) is characterized by a high degree of genetic heterogeneity. We analyzed whole exome sequencing data of 102 unrelated probands with apparently NSHL without a causative variant in known NSHL genes. We detected five causative variants in different SHL genes (SOX10, MITF, PTPN11, CHD7, and KMT2D) in five (4.9%) probands. Clinical re-evaluation of these probands shows that some of them have subtle syndromic findings, while none of them meets clinical criteria for the diagnosis of the associated syndrome (Waardenburg (SOX10 and MITF), Kallmann (CHD7 and SOX10), Noonan/LEOPARD (PTPN11), CHARGE (CHD7), or Kabuki (KMT2D). This study demonstrates that individuals who are evaluated for NSHL can have pathogenic variants in SHL genes that are not usually considered for etiologic studies.

Admixture estimates for the population of Havana City.

BACKGROUND: The Cuban population is essentially a result of the admixture between Spanish, West African and, to a lesser degree, Amerindian tribes that inhabited the island. AIM: The study analysed the genetic structure of the three principal ethnic groups from Havana City, and the contribution of parental populations to its genetic pool. SUBJECTS AND METHODS: According to genealogical information and anthropological traits, 206 subjects were classified as Mulatto, of Spanish decent or of African descent. Seventeen Ancestry Informative Markers, with high difference in frequency between parental populations, were selected to estimate individual and group admixture proportions. The statistical analyses were performed using the ADMIX, ADMIX95 and STRUCTURE 2.1 packages. RESULTS: The results demonstrate a high level of European and African admixture in Mulattos (57-59% European; 41-43% West African). The European contribution was higher in those of Spanish descent (85%) while in those of African descent, the West African contribution ranged between 74% and 76%. Genetic structure was only detected in Mulattos and those of African descent. An Amerindian contribution was not detectable in the studied sample. CONCLUSION: Our findings indicate the existence of admixture and genetic structure in the population of Havana City. This study represents one of the first steps towards understanding Cuban population admixture in order to produce successful experimental designs for admixture mapping.

Celiac disease associated antibodies in persons with latent autoimmune diabetes of adult and type 2 diabetes.

BACKGROUND: Celiac Disease (CD) is present in 1-16.4% of patients with type 1 diabetes mellitus. The most important serological markers of CD are anti-endomysial (EMA), anti-tissue transglutaminase (tTGA) and antigliadin antibodies (AGA). AIM/HYPOTHESIS: The objective of this work is to determine the frequency of tTGA and/or AGA in latent autoimmune diabetes of adult (LADA) and subjects with type 2 diabetes (T2DM), as well as to evaluate their relation with several clinical and biochemical characteristics. SUBJECTS AND METHODS: Forty three subjects with LADA and 99 with T2DM were studied. The presence of AGA, tTGA was determined in the sera of these patients. The variables: sex, age, duration of diabetes, treatment, body mass index (BMI) and fasting blood glucose concentration were also recorded. RESULTS: No differences were found in the frequency of celiac disease associated antibodies between LADA and T2DM subjects. The presence of celiac disease related antibodies was more frequent in patients with a normal or low BMI. CONCLUSIONS: Celiac disease does not seem to be related with pancreatic autoimmunity in type 2 diabetes. Celiac disease causes a decrease of body mass index in type 2 diabetes while pancreatic islet autoimmunity in this entity masks this effect.

Type 1 diabetes islet associated antibodies in subjects infected by echovirus 16.

AIMS/HYPOTHESIS: To determine whether the emergent infection by echovirus 16 that occurred in Cuba during the year 2000 was related to the presence of Type 1 diabetes associated autoantibodies. METHODS: The presence of ICA, IAA, GADA, IA2 antibodies and neutralizing antibodies (NtAb) to echovirus 16 were determined in sera from 38 infected children and adolescents and 80 control subjects, matched in sex, age, local residence and time of sample collection. RESULTS: The occurrence of a large-scale echovirus 16 epidemic was associated with the appearance of humoral autoimmune markers of Type 1 diabetes, especially for ICA, IAA and GADA. In the convalescent stage, ICA, IAA and GADA seroconversion was shown in 92.1%, 44.7% and 28.9% of echovirus 16 infected subjects. None of the 80 uninfected subjects had ICA or IAA, while one was GADA positive. ICA, IAA and GADA frequency was higher in the convalescent than in the acute stage (p<0.0005). A strong positive correlation was found between the NtAb to echovirus 16 and ICA titres in both acute and convalescent stage (r=0.91; p<0.0001, r=0.55; p=0.0003 respectively). CONCLUSION/INTERPRETATION: This work provides evidence of an association between echovirus 16 infection and the presence of Type 1 diabetes related antibodies (ICA, IAA and GADA). Our data show that the echovirus 16 infection might be capable of inducing a process of autoimmune beta-cell damage and support the hypothesis that enterovirus infections are important risk factors for the development of Type 1 diabetes.

Na/Ca exchange and Ca2+ homeostasis in the pancreatic beta-cell.

Recent knowledge concerning the Na/Ca exchanger (NCX) in the pancreatic beta-cell is reviewed. The beta-cell expresses various NCX1 splice variants in a species specific pattern (NCX1.3 and 1.7 in the rat, NCX1.2, 1.3 and 1.7 in the mouse), in variable and different proportions. In the rat beta-cell, the exchanger displays a quite high capacity, accounts for about 70% of Ca2+ extrusion and participates to Ca2+ inflow during membrane depolarization. In the mouse, however, the contribution of the exchanger to Ca2+ extrusion is more modest, and to Ca2+ inflow less evident. The exchanger has a stoichiometry of 3 Na+ for 1 Ca2+, is electrogenic, and displays a reversal potential at -20 mV. Although being of low magnitude, the current generated by the exchanger shapes glucose-induced beta-cell electrical activity and intracellular Ca2+ oscillations. For instance, a lower Na/Ca exchange activity (and subsequent inward current) in the mouse than in the rat, explains why the mouse beta-cell displays cyclic oscillations of the membrane potential, while the rat displays a staircase increase in membrane potential without such oscillations. In addition of being of importance in cell signalling, intracellular Ca2+ may also trigger apoptosis. For instance, overexpression of the exchanger increases Ca2+-dependent and -independent beta-cell death by apoptosis, a phenomenon resulting from the depletion of ER Ca2+-stores with subsequent activation of caspase-12. Na/Ca exchange overexpression also reduces beta-cell growth. Hence, the Na/Ca exchanger is a versatile system that appears to play an important role in the function, growth and demise of the beta-cell.

Echovirus 4 and type 1 diabetes mellitus.

AIMS/HYPOTHESIS: To determine the association between exposure to enteroviruses and Type 1 diabetes. METHODS: We measured neutralizing antibodies to the following enteroviruses: Coxsackievirus CA9, CB1, CB2, CB3, CB4, CB5, CB6, and Echovirus E4, E6, E9, E11 in the sera of (1) Type 1 diabetic patients at diagnosis (n = 33), (2) healthy offspring of parents with Type 1 diabetes without islet cell antibodies (ICA) (n = 43) and (3) normal controls (n = 57). All subjects were less than 20 years old. We performed the neutralization test determining the cytopathogenic effect on Vero cells. HLA DR serotyping was also performed in Group 2. RESULTS: Type 1 diabetic patients showed a higher frequency (21.2%, p < 0.01) of neutralizing antibodies to E4 in relation to controls (1.8%), although there were no differences comparing with offspring of Type 1 diabetic patients (20.9%). Healthy offspring carrying Type 1 diabetes HLA DR susceptibility genes were also exposed to E4 (15.0%). High frequencies of neutralizing antibodies to most enteroviruses were found in the control group. CONCLUSION: This study shows the association between Type 1 diabetes and the presence of neutralizing antibodies to Echovirus 4, suggesting the possible participation of this virus as an environmental trigger of this autoimmune disease. Interestingly, our population displays high frequencies of exposure to enterovirus (including CB4) although the incidence for Type 1 diabetes is low (2.9 per 100,000 inhabitants).

Increased retinal endothelial cell monolayer permeability induced by the diabetic milieu: role of advanced non-enzymatic glycation and polyol pathway activation.

BACKGROUND: Increased vascular permeability could be involved in the pathogenesis of diabetic retinopathy. The present study was aimed at assessing whether high glucose concentrations can impair retinal endothelial cell barrier function directly, irrespective of changes in other determinants of permeability, and the role of non-enzymatic glycation and polyol pathway activation in these alterations. METHODS: Bovine retinal endothelial cells (BREC) were exposed for various periods to high glucose vs iso-osmolar mannitol and normal glucose containing media+/-agents mimicking or inhibiting advanced glycation end product (AGE) formation and polyol pathway activation. Monolayer permeability was assessed by measuring the transendothelial passage of (125)I-labeled proteins. RESULTS: Permeability increased significantly (up to +70%) in BREC exposed to high glucose, but not to mannitol, for 1-30 days, vs normal glucose control cells. Exposure to AGE-modified bovine serum albumin (BSA) (> or = 90%) and, to a lesser extent, sorbitol (+28%) mimicked the high glucose effect. The AGE formation and nitric oxide synthase (NOS) inhibitor aminoguanidine significantly reduced (by 60%) changes induced by 30-day exposure to high glucose, whereas methylguanidine, which inhibits only NOS activity, did not affect permeability. Aldose reductase or sorbitol dehydrogenase inhibitors decreased (by approximately 40%) the enhanced leakage produced by 1-day, but not 30-day, incubation in high glucose. CONCLUSIONS: The present results indicate that high glucose is capable of impairing retinal endothelial cell barrier function directly and that non-enzymatic glycation and polyol pathway activation may mediate these changes, with AGEs participating in the long-term alterations and increased flux through the sorbitol pathway in the short-term effect.

The circulating insulin-like growth factor system in children with coeliac disease: an additional marker for disease activity.

BACKGROUND: Chronic undernutrition resulting from coeliac disease (CD) could be associated with changes in the circulating insulin-like growth factor (IGF) system, which may participate in the pathogenesis of growth retardation occurring in these patients. METHODS: We performed a cross-sectional study in CD subjects attempting to (1) document the pattern of serum IGF-I and IGF binding protein (IGFBP) 1 and 3 at diagnosis and (2) assess the response of circulating IGF system to dietary treatments, in comparison with the response of clinical and laboratory findings utilized for the diagnosis of CD. Thirty-two prepubertal CD children were divided into three groups based on the dietetic treatment: at diagnosis (D, n=18); on gluten-free diet for at least 6 months (GFD, n=7); and on gluten challenge for at least 3 months (CH, n=7). Six postpubertal CD patients were also studied at diagnosis. RESULTS: In prepubertal children IGF-I levels were significantly reduced (by 29%) in D vs sex- and age-matched normal control (NC) subjects, with reductions being more pronounced before 3 years of age. Likewise, serum IGFBP-3 concentrations were decreased by 22%, whereas circulating IGFBP-1 levels were increased by 60%, compared with NC, with more marked IGFBP changes in older children. Similar alterations were observed in postpubertal patients. Changes in the circulating IGF system disappeared in GFD subjects and reappeared in CH children, as positivity of disease-specific antibodies. Body mass index (BMI) also improved in GFD subjects, but did not decrease in CH children. Changes in IGF-I and IGFBPs did not correlate with each other. Levels of IGF-I, but not of IGFBPs, maintained the relation with age and correlated significantly with BMI and positivity of antibodies. CONCLUSIONS: These results demonstrate that CD patients show significant changes in serum IGF-I, in younger children, and IGFBPs (particularly IGFBP-1), in older children and adolescents, correlating with clinical course and response to dietary treatments. The alteration in the circulating IGF system could be implicated in the pathogenesis of growth retardation occurring in CD and may provide an additional tool in monitoring of the disease.

Target antigens in autoimmune diabetes: pancreatic gangliosides.

Type 1 diabetes mellitus is a disease caused by the autoimmune destruction of insulin-producing pancreatic beta-cells that takes place in genetically prodisposed individuals. Autoantibodies and autoreactive T lymphocytes reacting with islet target molecules or protein of glycolipid nature have been shown in the circulation of individuals and of animal models of type 1 diabetes (NOD mouse and BB rat) before and at the onset of the disease. As far as autoantigens of glycolipid nature is concerned, gangliosides such as GT3, GD3 and especially GM-1, have been shown to be target of autoantibodies associated to autoimmune diabetes. Of particular interest is the islet-specific monosialo-ganglioside GM2-1, which is target of an autoimmune response highly associated to future progression to diabetes development in first degree relatives of type 1 diabetic individuals. This molecule is recognized by IgG autoantibodies which have been detected before the appearance if clinical diabetes both in man and in the NOD mouse, representing a novel marker of beta-cell autoimmunity.

Glycolipids as the major autoantigens of cytoplasmatic islet cell antibodies.

It has been recently suggested that pancreatic glycolipidic extracts and acidic glycolipid fractions are able to block the binding of ICA to frozen sections of human pancreas. We study the prevalence of blocking effect by the upper-phase from human pancreatic glycolipid extracts (PGE) in thirty-eight sera ICA positive from seventeen IDDM patients and twenty-one first relatives of type 1 diabetics. Total inhibition was found in 82% and 76% insulin dependent diabetes mellitus patients and first relatives of type 1 diabetics respectively. Partial and no inhibition of ICA+ sera was seen in 6%, 12% of type 1 diabetics and 19%, 5% of the first degree relatives of type 1 diabetics respectively. Our study suggests that there is heterogeneity of cytoplasmatic islet cell antibodies and that glycolipids are the major autoantigen of ICA.