To the best of our knowledge, no previous studies have reported a difference in Erβ mRNA levels in peripheral blood between ASD and TD children. In the present study, we showed that the ERβ mRNA levels in the peripheral blood of ASD children were significantly lower than those in the TD group. Additionally, ASD children had a higher score than TD children on the CSHQ, indicating that ASD children have more disturbed sleep.
Our findings were consistent with a recent study that reported that lower ERβ levels contributed to the development and progression of ASD and that upregulated ERβ expression attenuated this effect (Xie W et al., 2018; Zou Y et al., 2017). Currently, the exact cause and mechanisms of ASD are still unclear, but genetic and environmental factors are believed to jointly mediate its pathogenesis (Goines PE et al., 2013). Numerous experimental studies have demonstrated that chronic neuroinflammation, imbalance of excitatory and inhibitory neurotransmission, mitochondrial dysfunction and oxidative stress are important factors in the pathogenesis of ASD (Young AM et al., 2011; Quiñones-Camacho LE et al., 2021; Morgan JT et al., 2010; Vargas DL et al., 2005). Abnormal regulation of sex hormones is also involved in the pathogenesis of ASD, as there are obvious sex differences in ASD patients (Berkel S et al., 2018). A study in 2020 showed that latent prenatal steroidogenic activity was elevated in the amniotic fluid of autistic boys, which suggests that prenatal estrogens contribute to the risk of ASD (Baron-Cohen S et al., 2020). By activating ERβ, estrogen influences cognition, learning and memory by affecting the development of neurons, formation of synapses, development of circuits and other important variables during brain development (Nalvarte I et al., 2021). ERβ is known to mediate some of the effects of estrogens on behaviors not specifically associated with reproduction, such as locomotor activity, fear responses, anxiety, and learning (Goines PE et al., 2013). Additionally, ERβ knockdown abolished E2-induced reductions in depressive behavior in mice (Altun H et al., 2017). Moreover, administration of ERβ agonists or selective ligands reduced anxiety-like behavior and depressive behavior in rats (Weiser MJ et al., 2010).
In this study, we found a higher proportion of males (89.3%) than females (10.7%) among ASD children. Moreover, serum ERβ levels were significantly lower in ASD children than in TD children; however, the ERβ, AR and PGR mRNA levels did not significantly differ among the TD, mild-to-moderate ASD and severe ASD groups. An animal trial showed that endogenous (progesterone) or synthetic progestin (norethindrone)-exposed offspring both exhibited autism-like behavior, which demonstrated that prenatal progestin exposure may induce ASD (Li L et al., 2018). Another study showed that overexpression of an AR-dependent gene in conjunction with that of DNA methyltransferase, which methylates oxytocin receptors, delivered high arousal inputs to the amygdala, resulting in aberrant socialization, a key characteristic of autism (Mbadiwe T et al., 2013). Although our results were somewhat different from those of other studies, the use of AR and PGR mRNA levels for differentiating between ASD and TD populations merits further exploration.
A previous study reported that sleep problems and ASD do not have a bidirectional association. Sleep problems co-occur with autistic traits in early childhood. The authors suggested that sleep problems are part of the ASD construct (Verhoeff ME et al., 2018). Similarly, we found that ASD children had more disturbed sleep than TD children according to CHSQ scores. In addition, we found that TD children had higher GDS DQs than ASD children, which may be associated with the inclusion requirements of the TD group. However, we found no correlations of ERβ mRNA levels in children with ASD and total scores on the CARS, ABC, or CHSQ or GDS DQs. We did not find significant modifications of clinical characteristics in these associations.
There are some advantages in our study. First and foremost, most previous studies on this subject have focused on animal models rather than humans. Second, some investigations have confirmed that the expression of ERβ in the brain is reduced in ASD children compared with TD children; this study is the first to characterize and ERβ mRNA levels in peripheral blood samples from ASD children. In addition, professional screening and diagnosis procedures ensured the reliability of our results. However, our study has several limitations. This was a case‒control study, and causality could not be inferred. In the future, we plan to use a cohort design to clarify causality. Additionally, although we found a reduction in ERβ mRNA levels in peripheral blood, we were unable to determine the potential mechanism or conduct dose‒response analyses.
As estrogens promote the survival of nerve cells and reduce neuronal damage, researchers have argued that estrogens may ameliorate the symptoms of ASD (Cheng D et al., 2014). Our data indicates that ERβ may play an important role in the etiology of ASD. This relationship should be validated with a larger sample size.