A number of studies have previously assessed the impact of antibiotic exposure in early life on the risk of childhood obesity, but no systematic assessment is currently available. A systematic review and meta-analysis was performed to comprehensively and quantitatively elucidate the risk of childhood obesity caused by antibiotic exposure in early life. Literature search was performed in PubMed, Embase and Web of Science. Random-effect meta-analysis was used to pool the statistical estimates. Fifteen cohort studies involving 445,880 participants were finally included, and all those studies were performed in developed countries. Antibiotic exposure in early life significantly increased risk of childhood overweight (Relative risk [RR] = 1.23, 95%CI 1.13-1.35, P < 0.001) and childhood obesity (RR = 1.21, 95%CI 1.13-1.30, P < 0.001). Antibiotic exposure in early life also significantly increased the z-score of childhood body mass index (Mean difference: 0.07, 95%CI 0.05-0.09, P < 0.00001). Importantly, there was an obvious dose-response relationship between antibiotic exposure in early life and childhood adiposity, with a 7% increment in the risk of overweight (RR = 1.07, 95%CI 1.01-1.15, P=0.03) and a 6% increment in the risk of obesity (RR = 1.06, 95%CI 1.02-1.09, P<0.001) for each additional course of antibiotic exposure. In conclusion, antibiotic exposure in early life significantly increases risk of childhood obesity. Moreover, current analyses are mainly taken from developed countries, and therefore the impact of antibiotic exposure on risk of childhood obesity in vulnerable populations or developing countries still needs to be evaluated in future studies.

Th17 lymphocyte and its relative cytokines have been shown to play an important role in autoimmune thyroid diseases (AITD). The aim of this study was to investigate the association between IL-17A and IL-17F gene polymorphisms and two main types of AITD, Graves' disease (GD) and Hashimoto's thyroiditis (HT). Whole blood specimens and clinical data were collected from 508 AITD patients (326 with GD and 182 with HT) and 224 age- and gender-matched healthy controls, respectively. IL-17A (rs2275913, rs8193037, rs3819025) polymorphism was determined using DNA sequencing method and IL-17F/rs763780 polymorphism was assayed by polymerase chain reaction-restriction fragment length polymorphism (PCR -RFLP). The results indicated that the frequencies of IL-17F/rs763780 genotypes in patients with GD and HT differed significantly from their controls (P = 0.013 and P = 0.005, respectively); the G allele frequencies were also significantly higher in the patient groups than the control groups (P = 0.002 and 0.001, respectively). For IL-17A/rs2275913 and rs8193037 SNP, no significant difference was observed in patients with either GD or HT compared to the control groups (P>0.05). Interestingly, for rs3819025, the frequency of A allele was lower in patients with GD than controls (P = 0.011). The frequencies of haplotype AGGG and GGGG in patients with GD and HT were significantly higher than in controls (P = 0.012, P = 0.019, P = 0.017 and P = 0.029, respectively). In conclusion, the results indicate that IL-17F/rs763780 polymorphisms may affect the susceptibility to AITD, and IL-17A/rs3819025 SNP is likely a protective factor to GD in the Chinese population.

Autoimmune thyroid diseases (AITD) are a group of both B cells and T cells mediated organ-specific autoimmune diseases. Graves' disease and Hashimoto thyroiditis are the two main clinical presentations of AITD. Both genetic and environmental factors have important roles in the development of AITD. Epigenetics have been considered to exert key roles in integrating those genetic and environmental factors, and epigenetic modifications caused by environmental factors may drive genetically susceptibility individuals to develop AITD. Recent studies on the epigenetics of AITD have provided some novel insights into the pathogenesis of AITD. The aim of this review is to provide an overview of recent advances in the epigenetic mechanisms of AITD, such as DNA methylation, histone modifications, and non-coding RNAs. This review highlights the key roles of epigenetics in the pathogenesis of AITD and potential clinical utility. However, the epigenetic roles in AITD are still not fully elucidated, and more researches are needed to provide further deeper insights into the roles of epigenetics in AITD and to uncover new therapeutic targets. Though there are many studies assessing the epigenetic modifications in AITD patients, the clinical utility of epigenetics in AITD remains poorly defined. More studies are needed to identify the underlying epigenetic modifications that can contribute to accurate diagnosis of AITD, adequate choice of treatment approach, and precise prediction of treatment outcomes.