Anu-Maaria Hämäläinen

The Dynamics of the Human Infant Gut Microbiome in Development and in Progression toward Type 1 Diabetes

Colonization of the fetal and infant gut microbiome results in dynamic changes in diversity, which can impact disease susceptibility. To examine the relationship between human gut microbiome dynamics throughout infancy and type 1 diabetes (T1D), we examined a cohort of 33 infants genetically predisposed to T1D. Modeling trajectories of microbial abundances through infancy revealed a subset of microbial relationships shared across most subjects. Although strain composition of a given species was highly variable between individuals, it was stable within individuals throughout infancy. Metabolic composition and metabolic pathway abundance remained constant across time. A marked drop in alpha-diversity was observed in T1D progressors in the time window between seroconversion and T1D diagnosis, accompanied by spikes in inflammation-favoring organisms, gene functions, and serum and stool metabolites. This work identifies trends in the development of the human infant gut microbiome along with specific alterations that precede T1D onset and distinguish T1D progressors from nonprogressors.

Dietary Intervention in Infancy and Later Signs of Beta-Cell Autoimmunity

BACKGROUND Early exposure to complex dietary proteins may increase the risk of beta-cell autoimmunity and type 1 diabetes in children with genetic susceptibility. We tested the hypothesis that supplementing breast milk with highly hydrolyzed milk formula would decrease the cumulative incidence of diabetes-associated autoantibodies in such children. METHODS In this double-blind, randomized trial, we assigned 230 infants with HLA-conferred susceptibility to type 1 diabetes and at least one family member with type 1 diabetes to receive either a casein hydrolysate formula or a conventional, cows-milk-based formula (control) whenever breast milk was not available during the first 6 to 8 months of life. Autoantibodies to insulin, glutamic acid decarboxylase (GAD), the insulinoma-associated 2 molecule (IA-2), and zinc transporter 8 were analyzed with the use of radiobinding assays, and islet-cell antibodies were analyzed with the use of immunofluorescence, during a median observation period of 10 years (mean, 7.5). The children were monitored for incident type 1 diabetes until they were 10 years of age. RESULTS The unadjusted hazard ratio for positivity for one or more autoantibodies in the casein hydrolysate group, as compared with the control group, was 0.54 (95% confidence interval [CI], 0.29 to 0.95), and the hazard ratio adjusted for an observed difference in the duration of exposure to the study formula was 0.51 (95% CI, 0.28 to 0.91). The unadjusted hazard ratio for positivity for two or more autoantibodies was 0.52 (95% CI, 0.21 to 1.17), and the adjusted hazard ratio was 0.47 (95% CI, 0.19 to 1.07). The rate of reported adverse events was similar in the two groups. CONCLUSIONS Dietary intervention during infancy appears to have a long-lasting effect on markers of beta-cell autoimmunity--markers that may reflect an autoimmune process leading to type 1 diabetes. (ClinicalTrials.gov number, NCT00570102.).

Natural history of the infant gut microbiome and impact of antibiotic treatment on bacterial strain diversity and stability

A longitudinal strain-level analysis of the infant gut microbiome after repeated antibiotic treatments reveals decreased diversity and stability, as well as transient increases in antibiotic resistance genes. Elucidating the effects of drugs on bugs Despite widespread use of antibiotics in children, the effects of antibiotic exposure on the developing infant gut microbiome have remained underexplored. Here, Yassour et al. present a longitudinal study capturing how the gut microbiome responds to and recovers from antibiotic perturbations. Antibiotic-treated children had less stable and less diverse bacterial communities. Antibiotic resistance genes within the guts of these children peaked after antibiotic treatment but generally returned rapidly to baseline. Delivery mode (vaginal versus cesarean) also had strong long-term effects on microbial diversity. These data give insights into the consequences of early life factors such as birth mode and antibiotic treatment on the infant gut microbiome. The gut microbial community is dynamic during the first 3 years of life, before stabilizing to an adult-like state. However, little is known about the impact of environmental factors on the developing human gut microbiome. We report a longitudinal study of the gut microbiome based on DNA sequence analysis of monthly stool samples and clinical information from 39 children, about half of whom received multiple courses of antibiotics during the first 3 years of life. Whereas the gut microbiome of most children born by vaginal delivery was dominated by Bacteroides species, the four children born by cesarean section and about 20% of vaginally born children lacked Bacteroides in the first 6 to 18 months of life. Longitudinal sampling, coupled with whole-genome shotgun sequencing, allowed detection of strain-level variation as well as the abundance of antibiotic resistance genes. The microbiota of antibiotic-treated children was less diverse in terms of both bacterial species and strains, with some species often dominated by single strains. In addition, we observed short-term composition changes between consecutive samples from children treated with antibiotics. Antibiotic resistance genes carried on microbial chromosomes showed a peak in abundance after antibiotic treatment followed by a sharp decline, whereas some genes carried on mobile elements persisted longer after antibiotic therapy ended. Our results highlight the value of high-density longitudinal sampling studies with high-resolution strain profiling for studying the establishment and response to perturbation of the infant gut microbiome.

Th1/Th17 Plasticity Is a Marker of Advanced β Cell Autoimmunity and Impaired Glucose Tolerance in Humans

Upregulation of IL-17 immunity and detrimental effects of IL-17 on human islets have been implicated in human type 1 diabetes. In animal models, the plasticity of Th1/Th17 cells contributes to the development of autoimmune diabetes. In this study, we demonstrate that the upregulation of the IL-17 pathway and Th1/Th17 plasticity in peripheral blood are markers of advanced β cell autoimmunity and impaired β cell function in human type 1 diabetes. Activated Th17 immunity was observed in the late stage of preclinical diabetes in children with β cell autoimmunity and impaired glucose tolerance, but not in children with early β cell autoimmunity. We found an increased ratio of IFN-γ/IL-17 expression in Th17 cells in children with advanced β cell autoimmunity, which correlated with HbA1c and plasma glucose concentrations in an oral glucose tolerance test, and thus impaired β cell function. Low expression of Helios was seen in Th17 cells, suggesting that Th1/Th17 cells are not converted thymus-derived regulatory T cells. Our results suggest that the development of Th1/Th17 plasticity may serve as a biomarker of disease progression from β cell autoantibody positivity to type 1 diabetes. These data in human type 1 diabetes emphasize the role of Th1/Th17 plasticity as a potential contributor to tissue destruction in autoimmune conditions.

Human surfactant protein--A gene locus for genetic studies in the Finnish population.

Lung surfactant lowers the surface tension but surfactant proteins also have other functions. Surfactant protein A (SP-A) has a well-defined role in innate immunity. The gene locus for human SP-A genes is in chromosome 10q21 through q24 and consists of two highly homologous functional SP-A genes (SP-A1 and SP-A2) and a pseudogene. Several alleles that differ by a single amino acid have been identified for both SP-A genes. The SP-A gene locus has been shown to be sufficiently polymorphic for genetic studies in the American population. In this study, we analysed the SP-A allele frequencies in a Finnish population (n = 790) and found them to differ from the frequencies observed in US. Furthermore, we describe several new alleles for both SP-A genes. The heterozygosity indices and polymorphism information content values ranged between 0.50–0.62 indicating that SP-A gene locus is polymorphic enough for studies associating the locus with pulmonary diseases.

Neonatal hypothyroidism after amiodarone therapy

Amiodarone is used as an effective anti-arrhythmic drug in adults as well as in children (1). It is considered rather safe and effective in controlling severe tachyarrhythmias, also in infants (2). Since amiodarone is an iodine-rich drug whose structure resembles that of thyroxine, its administration may alter thyroid function (3). Fetuses, newborns and patients with autoimmune thyroiditis may be especially prone to become hypothyroid after amiodarone use. In this letter we present a prematurely born male neonate who received both fetal and neonatal amiodarone treatment and subsequently developed severe hypothyroidism before his 10th day of life. Fetal supraventricular tachycardia with normal fetal heart anatomy (>200 beats/min) was observed at 32th week of gestation in an otherwise uncomplicated pregnancy and, subsequently, the pregnant mother was treated with oral dose of 0.25 mg digitalis daily and peroral amiodarone therapy 200 mg three times a day. The fetus received two digitalis injections, and, later at 33+1 weeks of gestation the ongoing fetal tachycardia was treated with one intrauterine amiodarone 12.5 mg injection (approximately 6 mg/kg) to the umbilical cord and another 12.5 mg to the abdominal cavity. Because of the resistant fetal tachycardia the infant was delivered by caesarean section at 33+4 weeks of gestation. The neonate’s heart rate was 200–260 beats/min at birth without symptoms of cardiac failure. Tachycardia was treated with adenosine 100–500 g/kg and, when adenosine was inefficient, with electric cardioversion (3–5 J). He was also digitalized (5 g × 2). Intravenous amiodarone therapy (20 mg/kg/day) was initiated at the first day of life with subsequently lower doses so that at 1 week of age 6 mg/kg/day amiodarone was delivered orally. The boy also received short-term intravenous dopamine (5–20 g/kg/min) and milrinone (0.6 g/kg/min) therapies. The episodes of supraventricular tachycardia disappeared by 1 week of life. The initial cardiac sonography showed normal cardiac anatomy but decreased contractility, which normalized by 10 days of age. There were no signs of WPW (delta waves) in electrocardiography. The umbilical cord thyroid stimulating hormone (TSH) concentration was normal (27 mU/L; normal <40 mU/L). However, during the first few days of life he developed primary hypothyroidism, since at 10 days of age the serum TSH had increased to >100 mU/L and free T4 (fT4) concentration had decreased to 5.1 pmol/L. Thyroid peroxidase antibodies (TPOAb) were negative. L-thyroxine (10 g/kg/day) was started at 10th day of life and thyroid values (TSH, fT4) were measured at 1–2 month intervals and during the following year he was maintained euthyroid by L-thyroxine replacement therapy. The amiodarone therapy continued for 6 months and flecainide for 12 months. Thyroxin was slowly weaned off during the latter part of the first year and at 11 months the thyroxin therapy was discontinued. He has subsequently remained euthyroid. Amiodarone has been used as an anti-arrhythmic drug since the 1970s also in children (1) but because it is an iodinerich drug resembling thyroxin in structure its administration may alter thyroid function (3). Iodine is an essential element for thyroid hormone synthesis and the thyroid gland has the capacity to handle the iodine efficiently when the availability of iodine becomes scarce or, on the other hand, excessive. The latter situation is handled by the thyroid by acutely inhibiting the organification of iodine, by so-called ‘acute Wolff-Chaikoff effect’ (4), where the binding of iodine in thyroid decreases as plasma iodine level elevates. This effect protects an individual from becoming hyperthyroid, but some subjects may not subsequently normally ‘escape’ from this phenomenon and, thus may become hypothyroid as happened to our patient. Amiodarone-induced hypothyroidism is usually transient and euthyroidism may to return within a few weeks after iodine withdrawal (5). The effects of antenatal amiodarone use on thyroid function have been addressed in few fetuses or neonatal patients and there are ∼20 cases of amiodaroneinduced neonatal hypothyroidism reported so far (6,7). The duration of amiodarone treatment in those cases varied from 2 days to 40 weeks. Amiodarone is to be administered in the lowest possible dose, and the neonatal thyroid function should be controlled as long as the exposure to this drug continues. Due to devastating effects of neonatal hypothyroidism, thyroid function of amiodarone-treated neonates

Exploring the risk factors for differences in the cumulative incidence of coeliac disease in two neighboring countries: the prospective DIABIMMUNE study

BACKGROUND During the last several decades the prevalence of coeliac disease (CD) has increased worldwide. AIM To compare the cumulative incidence of CD between Estonian and Finnish children and to identify the risk factors. MATERIALS AND METHODS Children were recruited as part of the DIABIMMUNE Study. In the birth cohort (BC) 258 children from Estonia and 305 from Finland, and in the young childrens cohort (YCC) 1363 and 1384 children were followed up, respectively. The diagnosis of CD was made in accordance with the ESPGHAN guidelines-the presence of IgA-tTG antibodies and small bowel villous atrophy. RESULTS During the study period 29 children developed CD. The cumulative incidence of CD was significantly higher in Finland (0.77% vs 0.27%; P=0.01). No difference was seen between the children with CD and the controls in the duration of breastfeeding or the age at cereal introduction. The BC children with CD had had significantly more episodes of infections with fever by the age of 12 months compared to the controls (3.4 vs 1.4; P=0.04). CONCLUSION The 5-year cumulative incidence of childhood CD is significantly higher in Finland than in Estonia. Sequential infections early in life may increase the risk for developing CD.