Abstract Autism spectrum disorder (ASD) is a heterogeneous disorder characterized by impaired social communication and restricted repetitive behaviors, however the biological mechanisms remain unclear. Although trace elements play essential roles in the living body, it is unclear how alterations of trace elements in ASD are involved in pathogenesis. Here we analyzed the plasma metallome and identified the alterations of 11 elements in individuals with ASD. The copper decrease was negatively correlated with ASD symptom scores. A copper-deficient mouse model reflecting the condition showed ASD-like behaviors and impaired oligodendrocyte development. In copper-deficient mice, mechanistic target of rapamycin (mTOR) signaling was reduced, and its activation by agonist improved social impairment and oligodendrocyte developmental defects. Supporting these results, white matter volumes were negatively correlated with social symptoms in individuals with ASD. Our results demonstrate that copper-deficiency contributes to ASD by causing oligodendrocytes impairment via mTOR signaling. Our findings indicate that the effects of copper-deficiency and mTOR imbalance are relevant to the pathogenesis of ASD and are potential therapeutic targets.
Individuals with autism spectrum disorder (ASD) have an increased risk of adverse childhood experiences (ACEs) than typically developed (TD) children. Since multiple lines of studies have suggested that ACEs are related to myelination in the frontal lobe, an exposure to ACEs can be associated with white matter microstructural disruption in the frontal lobe, which may be implicated in subsequential psychological deficits after the adulthood. In this study, we investigated the relationship between ACEs and microstructural integrity on frontal lobe-related white matter tracts using diffusion tensor imaging in 63 individuals with ASD and 38 TD participants. Using a tractography-based analysis, we delineated the uncinate fasciculus (UF), dorsal cingulum (Ci), and anterior thalamic radiation (ATR), which are involved in the neural pathology of ASD, and estimated each diffusion parameter. Compared to the TD participants, individuals with ASD displayed significantly lower fractional anisotropy (FA) and higher radial diffusivity (RD) in the left ATR. Then, ASD individuals exposed to severe ACEs displayed higher RD than those exposed to mild ACEs and TD participants in the left ATR. Moreover, the severity of ACEs, particularly neglect, correlated with lower FA and higher RD in the left UF and ATR in individuals with ASD, which was not observed in TD participants. These results suggest that an exposure to ACEs is associated with abnormality in the frontal lobe-related white matter in ASD.
The etiology of autism spectrum disorder (ASD) is complex, and its pathobiology is characterized by enhanced inflammatory activities; however, the precise pathobiology and underlying causes of ASD remain unclear. This study was performed to identify inflammatory indicators useful for diagnosing ASD. The mRNA expression of cytokines, including tumor necrosis factor-α (TNF-α), was measured in cultured M1 and M2 macrophages from patients with ASD (n = 29) and typically developed (TD) individuals (n = 30). Additionally, TNF-α expression in the monocytes of patients with ASD (n = 7), showing aberrations in TNF-α expression in M1/M2 macrophages and TD individuals (n = 6), was measured. TNF-α expression in M1 macrophages and the TNF-α expression ratio in M1/M2 macrophages were markedly higher in patients with ASD than in TD individuals; however, this increase was not observed in M2 macrophages (M1: sensitivity = 34.5%, specificity = 96.7%, area under the curve = 0.74, positive likelihood ratio = 10.34; ratio of M1/M2: sensitivity = 55.2%, specificity = 96.7%, area under the curve = 0.79, positive likelihood ratio = 16.55). Additionally, TNF-α expression in monocytes did not significantly differ between patients with ASD and TD individuals. In conclusion, further studies on TNF-α expression in cultured macrophages may improve the understanding of ASD pathobiology. LAY SUMMARY: TNF-α expression in differentiated M1 macrophages and TNF-α expression ratio in differentiated M1/M2 macrophages were markedly higher in patients with ASD than in TD individuals, while no difference in TNF-α expression was found in pre-differentiation cells such as monocytes. These measurements allow elucidation of the novel pathobiology of ASD and can contribute to biomarker implementation for the diagnosis of adult high-functioning ASD.
Abstract Compared to typically developing (TD) children, people with autism spectrum disorder (ASD) have an increased risk of adverse childhood experiences (ACEs). Exposure to ACEs is associated with adult ASD psychological comorbidities, such as posttraumatic stress disorder (PTSD). Occurrence of intrusive event reexperiencing, characteristic of PTSD, often causes social dysfunction in adults with ASD, but its pathological basis is unclear. This study examined brain regions related to the severity of intrusive reexperiencing and explored whether ACE severity was associated with that of intrusive reexperiencing and/or extracted regional gray matter volume. Forty‐six individuals with ASD and 41 TD subjects underwent T1‐weighted magnetic resonance imaging and evaluation of ACEs and intrusive reexperiencing. Brain regions related to the severity of intrusive reexperiencing in both groups were identified by voxel‐based whole brain analyses. Associations among the severity of intrusive reexperiencing, that of ACEs, and gray matter volume were examined in both groups. The severities of intrusive reexperiencing and ACEs were significantly associated with reduced gray matter volume in the right precuneus in individuals with ASD but not in TD subjects. Although the right precuneus gray matter volume was smaller in individuals with ASD and severe ACEs than in those with mild ACEs or TD subjects, it was similar in the latter two groups. However, ACE‐dependent gray matter volume reduction in the right precuneus led to intrusive reexperiencing in individuals with ASD. This suggests that exposure to ACEs is associated with right precuneus gray matter reduction, which is critical for intrusive reexperiencing in adults with ASD. Lay Summary Individuals with autism spectrum disorder (ASD) are at increased risk of adverse childhood experiences (ACEs) and of subsequent manifestation of intrusive reexperiencing of stressful life events. The present study found that reduced gray matter volume in the right precuneus of the brain was associated with more severe intrusive reexperiencing of ACEs by individuals with ASD. These results suggest that ACEs affect neural development in the precuneus, which is the pathological basis of intrusive event reexperiencing in ASD.
A growing body of evidence suggests that immune dysfunction and inflammation in the peripheral tissues as well as the central nervous system are associated with the neurodevelopmental deficits observed in autism spectrum disorder (ASD). Elevated expression of pro-inflammatory cytokines in the plasma, serum, and peripheral blood mononuclear cells of ASD has been reported. These cytokine expression levels are associated with the severity of behavioral impairments and symptoms in ASD. In a prior study, our group reported that tumor necrosis factor-α (TNF-α) expression in granulocyte-macrophage colony-stimulating factor-induced macrophages (GM-CSF MΦ) and the TNF-α expression ratio in GM-CSF MΦ/M-CSF MΦ (macrophage colony-stimulating factor-induced macrophages) was markedly higher in individuals with ASD than in typically developed (TD) individuals. However, the mechanisms of how the macrophages and the highly expressed cytokines affect neurons remain to be addressed.
Posttraumatic stress disorder (PTSD) can be a source of significant social and daily distress in autism spectrum disorder (ASD). Compared to typically developed (TD) individuals, people with ASD are at an increased risk of adverse childhood experiences (ACEs), which can result in abnormal neuronal development. However, whether or how ACEs influence abnormal neural development and PTSD symptoms in ASD has not been fully elucidated.Thirty-nine TD individuals and 41 individuals with ASD underwent T1-weighted magnetic resonance imaging and neurite orientation dispersion and density imaging (NODDI), with axonal and dendritic densities assessed in terms of the orientation dispersion index and neurite density index (NDI), respectively. Voxel-based analyses were performed to explore the brain regions associated with PTSD symptoms, and the relationships between the severity of ACEs and PTSD symptoms and NODDI parameters in the extracted brain regions were examined.There was a significant positive association between PTSD symptom severity and NDI in the bilateral supplementary motor area; right superior frontal, left supramarginal, and right superior temporal gyrus; and right precuneus in the ASD group, but not in the TD group. ACE severity was significantly associated with NDI in the right superior frontal and left supramarginal gyrus and right precuneus in the ASD group. Moreover, NDI in the right precuneus mainly predicted the severity of PTSD symptoms in the ASD group, but not the TD group.These results suggest that ACE-associated higher neurite density is of clinical importance in the pathophysiology of PTSD symptoms in ASD.
Abstract Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors—associated with the medial prefrontal cortex (mPFC)—has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21–p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglial Bdnf —regulated using doxycycline at different time points—underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglial BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administering doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological function in the mPFC, whereas normalizing BDNF from later ages (p45–p50) did not normalize electrophysiological abnormalities in the mPFC, despite the improved sociability. To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible proxy for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. In summary, our study demonstrated the influence of microglial BDNF on the development of experience-dependent social behaviors in mice, emphasizing its specific impact on the maturation of mPFC function, particularly during the juvenile period. Furthermore, our results propose a translational implication by suggesting a potential link between BDNF secretion from macrophages and childhood experiences in humans.
Abstract Background The etiology of autism spectrum disorder (ASD) is complex. Its pathobiology is characterized by enhanced inflammatory activities; however, the exact ASD pathobiology remains unclear. Some cases of ASD are difficult to diagnose using existing psychological assessments because the careful exclusion of other psychiatric disorders is challenging. To distinguish between the appropriate targets for interventions and research, the demand for identifying efficient diagnostic biomarkers is increasing. This study aimed to find an inflammatory indicator beneficial for the diagnosis of ASD. Methods Cytokine mRNA expression, including tumor necrosis factor-α (TNF-α), was measured in the differentiated M1 and M2 macrophages of ASD patients ( n = 29) and typically developed (TD) individuals ( n = 30). TNF-α expression was also measured in the monocytes of ASD patients ( n = 7) and TD individuals ( n = 6). Results TNF-α expression in M1 macrophages and TNF-α expression ratio of M1/M2 macrophages were markedly higher in ASD patients than in TD subjects; however, this difference was not observed in M2 macrophages (M1: p < 0.01; ratio of M1/M2: p < 0.0001; M2: p > 0.05), suggesting that this indicator could be a useful tool for diagnosing ASD (M1: sensitivity = 34.5%, specificity = 96.7%, area under the curve (AUC) = 0.74, positive likelihood ratio (PLR) = 10.34; ratio of M1/M2: sensitivity = 55.2%, specificity = 96.7%, AUC = 0.79, PLR = 16.55). However, there was no significant difference in the TNF-α expression in monocytes between ASD and TD individuals ( p > 0.05). Conclusion These findings suggest that TNF-α expression in differentiated macrophages represents a novel adjunctive tool for the diagnosis of ASD.
Functional neuroimaging studies have suggested that prefrontal cortex dysfunction occurs in individuals with autism spectrum disorder (ASD). Near-infrared spectroscopy (NIRS) is a noninvasive optical tool used to investigate oxygenation and hemodynamic responses in the cerebral cortex by measuring changes in oxygenated hemoglobin. Previous studies using NIRS have suggested that male children with ASD exhibit reduced hemodynamic responses in the dorsolateral prefrontal cortex; however, only a few studies examined this response in adults with ASD. We examined the characteristics of prefrontal hemodynamic responses in 114 adults with ASD and 84 typically developing controls. Relative concentrations of oxygenated hemoglobin were measured with frontal probes every 0.1 s during the Stroop color-word task, using 24-channel NIRS. Our findings demonstrated that the oxygenated hemoglobin changes in the ASD group were significantly smaller than those in the control group at channels 19, 20, 23, and 24- located over the orbitofrontal cortex and frontal pole (p <0.05 for all three channels). The differences in oxygenated hemoglobin changes at Ch 20 were significantly correlated with the Autism-Spectrum Quotient Japanese version (AQ-J) total score and attention switching score, which is a symptom cluster of AQ-J (p = 0.043 and p = 0.009, respectively). Adults with ASD have reduced prefrontal hemodynamic responses as measured using near-infrared spectroscopy and the reduced activity of the frontal pole in particular is related to reduced attentional function.
