Cross-sectional investigation of insulin resistance in youths with autism spectrum disorder. Any role for reduced brain glucose metabolism?

Understanding the link between different types of maternal diabetes and the onset of autism spectrum disorders

Autism spectrum disorders (ASD) encompass a collection of neurodevelopmental disorders that exhibit impaired social interactions and repetitive stereotypic behaviors. Although the exact cause of these disorders remains unknown, it is widely accepted that both genetic and environmental factors contribute to their onset and progression. Recent studies have highlighted the potential negative impact of maternal diabetes on embryonic neurodevelopment, suggesting that intrauterine hyperglycemia could pose an additional risk to early brain development and contribute to the development of ASD. This paper presents a comprehensive analysis of the current research on the relationship between various forms of maternal diabetes, such as type 1 diabetes mellitus, type 2 diabetes mellitus, and gestational diabetes mellitus, and the likelihood of ASD in offspring. The study elucidates the potential mechanisms through which maternal hyperglycemia affects fetal development, involving metabolic hormones, immune dysregulation, heightened oxidative stress, and epigenetic alterations. The findings of this review offer valuable insights for potential preventive measures and evidence-based interventions targeting ASD.

Validation of plasma protein glycation and oxidation biomarkers for the diagnosis of autism

Autism Spectrum Disorder (ASD) is a common neurodevelopmental disorder in children. It is currently diagnosed by behaviour-based assessments made by observation and interview. In 2018 we reported a discovery study of a blood biomarker diagnostic test for ASD based on a combination of four plasma protein glycation and oxidation adducts. The test had 88% accuracy in children 5-12 years old. Herein, we present an international multicenter clinical validation study (N = 478) with application of similar biomarkers to a wider age range of 1.5-12 years old children. Three hundred and eleven children with ASD (247 male, 64 female; age 5.2 ± 3.0 years) and 167 children with typical development (94 male, 73 female; 4.9 ± 2.4 years) were recruited for this study at Sidra Medicine and Hamad Medical Corporation hospitals, Qatar, and Hospital Regional Universitario de Málaga, Spain. For subjects 5-12 years old, the diagnostic algorithm with features, advanced glycation endproducts (AGEs)-Nε-carboxymethyl-lysine (CML), Nω-carboxymethylarginine (CMA) and 3-deoxyglucosone-derived hydroimidazolone (3DG-H), and oxidative damage marker, o,o'-dityrosine (DT), age and gender had accuracy 83% (CI 79 - 89%), sensitivity 94% (CI 90-98%), specificity 67% (CI 57-76%) and area-under-the-curve of receiver operating characteristic plot (AUROC) 0.87 (CI 0.84-0.90). Inclusion of additional plasma protein glycation and oxidation adducts increased the specificity to 74%. An algorithm with 12 plasma protein glycation and oxidation adduct features was optimum for children of 1.5-12 years old: accuracy 74% (CI 70-79%), sensitivity 75% (CI 63-87%), specificity 74% (CI 58-90%) and AUROC 0.79 (CI 0.74-0.84). We conclude that ASD diagnosis may be supported using an algorithm with features of plasma protein CML, CMA, 3DG-H and DT in 5-12 years-old children, and an algorithm with additional features applicable for ASD screening in younger children. ASD severity, as assessed by ADOS-2 score, correlated positively with plasma protein glycation adducts derived from methylglyoxal, hydroimidazolone MG-H1 and Nε(1-carboxyethyl)lysine (CEL). The successful validation herein may indicate that the algorithm modifiable features are mechanistic risk markers linking ASD to increased lipid peroxidation, neuronal plasticity and proteotoxic stress.

Brain insulin signaling as a potential mediator of early life adversity effects on physical and mental health

In numerous brain structures, insulin signaling modulates the homeostatic processes, sensitivity to reward pathways, executive function, memory, and cognition. Through human studies and animal models, mounting evidence implicates central insulin signaling in the metabolic, physiological, and psychological consequences of early life adversity. In this review, we describe the consequences of early life adversity in the brain where insulin signaling is a key factor and how insulin may moderate the effects of adversity on psychiatric and cardio-metabolic health outcomes. Further understanding of how early life adversity and insulin signaling impact specific brain regions and mental and physical health outcomes will assist in prevention, diagnosis, and potential intervention following early life adversity.

Hypometabolism, Alzheimer's Disease, and Possible Therapeutic Targets: An Overview

The brain is a highly dynamic organ that requires a constant energy source to function normally. This energy is mostly supplied by glucose, a simple sugar that serves as the brain's principal fuel source. Glucose transport across the blood-brain barrier (BBB) is primarily controlled via sodium-independent facilitated glucose transport, such as by glucose transporter 1 (GLUT1) and 3 (GLUT3). However, other glucose transporters, including GLUT4 and the sodium-dependent transporters SGLT1 and SGLT6, have been reported in vitro and in vivo. When the BBB endothelial layer is crossed, neurons and astrocytes can absorb the glucose using their GLUT1 and GLUT3 transporters. Glucose then enters the glycolytic pathway and is metabolized into adenosine triphosphate (ATP), which supplies the energy to support cellular functions. The transport and metabolism of glucose in the brain are impacted by several medical conditions, which can cause neurological and neuropsychiatric symptoms. Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, traumatic brain injury (TBI), schizophrenia, etc., are a few of the most prevalent disorders, characterized by a decline in brain metabolism or hypometabolism early in the course of the disease. Indeed, AD is considered a metabolic disorder related to decreased brain glucose metabolism, involving brain insulin resistance and age-dependent mitochondrial dysfunction. Although the conventional view is that reduced cerebral metabolism is an effect of neuronal loss and consequent brain atrophy, a growing body of evidence points to the opposite, where hypometabolism is prodromal or at least precedes the onset of brain atrophy and the manifestation of clinical symptoms. The underlying processes responsible for these glucose transport and metabolic abnormalities are complicated and remain poorly understood. This review article provides a comprehensive overview of the current understanding of hypometabolism in AD and potential therapeutic targets.

The epigenetic hallmark of early-life α-hexabromocyclododecane exposure: From cerebellar 6-mA levels to locomotor performance in adulthood

There is a growing evidence that methylation at the N6 position of adenine (6-mA), whose modulation occurs primarily during development, would be a reliable epigenetic marker in eukaryotic organisms. The present study raises the question as to whether early-life exposure to α-hexabromocyclododecane (α-HBCDD), a brominated flame retardant, may trigger modifications in 6-mA epigenetic hallmarks in the brain during the development which, in turn could affect the offspring behaviour in adulthood. Pregnant Wistar rats were split into two groups: control and α-HBCDD (66 ng/kg/per os, G0-PND14). At PND1, α-HBCDD levels were assessed in brain and liver by LC-MS/MS. At PND14, DNA was isolated from the offspring's cerebellum. DNA methylation was measured by 6-mA-specific immunoprecipitation and Illumina® sequencing (MEDIP-Seq). Locomotor activity was finally evaluated at PND120. In our early-life exposure model, we confirmed that α-HBCDD can cross the placental barrier and be detected in pups at birth. An obvious post-exposure phenotype with locomotor deficits was observed when the rats reached adulthood. This was accompanied by sex-specific over-methylation of genes involved in the insulin signaling pathway, MAPK signaling pathway as well as serotonergic and GABAergic synapses, potentially altering the normal process of neurodevelopment with consequent motor impairments crystalized at adulthood.

Dietary recommendations to customize canteen menus according to the nutritional and sensory needs of individuals with autism spectrum disorder

Individuals with autism spectrum disorders (ASD) are often characterized by food-selectivity, food-neophobia and a marked preference for mild flavor, semi-liquid foods with pale colors. Therefore, they adopt a monotonous dietary pattern, and they prefer ultra-processed food, leading to a high risk of developing malnutrition. In Italy, where 75,072 individuals are diagnosed with ASD, center-based services play a crucial role in their daily management. Despite the centrality of nutrition in maintaining a good state of health, even more for vulnerable subjects, no validated protocol at collective catering level has been developed yet. The manuscript presents customized dietary recommendations aimed at managing the meals for individuals with ASD at collective catering service, derived from a non-systematic literature review exploring food behaviors and nutritional needs in individuals with ASD. Simple practical tips for mealtimes, such as eating together, proper seating, lighting, smell control, presenting food in a simple manner and using the same type of tableware at each meal, to meet the needs of individuals with ASD, were described. The proposal could represent a starting point in developing official guidelines aimed at ASD individuals, in collective catering service.Level of Evidence: Level V.

Association Between Autism Spectrum Disorders and Cardiometabolic Diseases: A Systematic Review and Meta-analysis

Importance

Although the increased risk of obesity among individuals with autism has been well established, evidence on the association between autism, cardiometabolic disorders, and obesity remains inconclusive.

Objective

To examine the association between autism spectrum disorders and cardiometabolic diseases in a systematic review and meta-analysis.

Data Sources

PubMed, Scopus, Web of Science, ProQuest, Embase, and Ovid databases were searched from inception through July 31, 2022, without restrictions on date of publication or language.

Study Selection

Observational or baseline data of interventional studies reporting the prevalence of cardiometabolic risk factors (ie, diabetes, hypertension, dyslipidemia, atherosclerotic macrovascular disease) among children and/or adults with autism and matched with participants without autism were included.

Data Extraction and Synthesis

Screening, data extraction, and quality assessment were performed independently by at least 2 researchers. DerSimonian-Laird random-effects meta-analyses were performed using the meta package in R.

Main Outcomes and Measures

Relative risks (RRs) of diabetes, hypertension, dyslipidemia, and atherosclerotic macrovascular disease among individuals with autism were the primary outcomes. Secondary outcomes included the RR of type 1 and type 2 diabetes, heart disease, stroke, and peripheral vascular disease.

Results

A total of 34 studies were evaluated and included 276 173 participants with autism and 7 733 306 participants without autism (mean [range] age, 31.2 [3.8-72.8] years; pooled proportion [range] of female individuals, 47% [0-66%]). Autism was associated with greater risks of developing diabetes overall (RR, 1.57; 95% CI, 1.23-2.01; 20 studies), type 1 diabetes (RR, 1.64; 95% CI, 1.06-2.54; 6 studies), and type 2 diabetes (RR, 2.47; 95% CI, 1.30-4.70; 3 studies). Autism was also associated with increased risks of dyslipidemia (RR, 1.69; 95% CI, 1.20-2.40; 7 studies) and heart disease (RR, 1.46; 95% CI, 1.42-1.50; 3 studies). Yet, there was no significantly associated increased risk of hypertension and stroke with autism (RR, 1.22; 95% CI, 0.98-1.52; 12 studies; and RR, 1.19; 95% CI, 0.63-2.24; 4 studies, respectively). Meta-regression analyses revealed that children with autism were at a greater associated risk of developing diabetes and hypertension compared with adults. High between-study heterogeneity was a concern for several meta-analyses.

Conclusions and Relevance

Results suggest that the associated increased risk of cardiometabolic diseases should prompt clinicians to vigilantly monitor individuals with autism for potential contributors, signs of cardiometabolic disease, and their complications.

Auts2 regulated autism-like behavior, glucose metabolism and oxidative stress in mice

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by abnormal social behavior and communication. The autism susceptibility candidate 2 (AUTS2) gene has been associated with multiple neurological diseases, including ASD. Glucose metabolism plays an important role in social behaviors associated with ASD, but the potential role of AUTS2 in glucose metabolism has not been studied. Here, we generated Auts2^flox/flox; Emx1^Cre+ conditional knockout mice with Auts2 deletion specifically in Exm1-positive neurons in the brain (Auts2-cKO mice) to evaluate the effects of Auts2 knockdown on social behaviors and metabolic pathways. Auts2-cKO mice exhibited ASD-like behaviors, including impaired social interactions and repetitive grooming behaviors. At the molecular level, we found that Auts2 knockdown reduced brain glucose uptake and inhibited the pentose phosphate pathway. Auts2 knockdown also resulted in signs of oxidative stress, and we documented increased levels of reactive oxygen species and malondialdehyde as well as decreased levels of antioxidant molecules, including glutathione and superoxide dismutases in Auts2-cKO mouse brains compared to controls. Finally, Auts2 knockdown significantly disrupted mitochondrial homeostasis and inhibited activity of the SIRT1-SIRT3 axis. Taken together, our findings indicate that loss of AUTS2 expression in Emx1-expressing cells induces multiple changes in metabolic pathways that have been linked to the pathology of ASD. Further characterization of the role of AUTS2 in Emx1-expressing cells in regulating the metabolism of brain neurons may identify opportunities to treat ASD and AUTS2-deficiency disorders with metabolism-targeted therapies.

MeCP2 Is an Epigenetic Factor That Links DNA Methylation with Brain Metabolism

DNA methylation, one of the most well-studied epigenetic modifications, is involved in a wide spectrum of biological processes. Epigenetic mechanisms control cellular morphology and function. Such regulatory mechanisms involve histone modifications, chromatin remodeling, DNA methylation, non-coding regulatory RNA molecules, and RNA modifications. One of the most well-studied epigenetic modifications is DNA methylation that plays key roles in development, health, and disease. Our brain is probably the most complex part of our body, with a high level of DNA methylation. A key protein that binds to different types of methylated DNA in the brain is the methyl-CpG binding protein 2 (MeCP2). MeCP2 acts in a dose-dependent manner and its abnormally high or low expression level, deregulation, and/or genetic mutations lead to neurodevelopmental disorders and aberrant brain function. Recently, some of MeCP2-associated neurodevelopmental disorders have emerged as neurometabolic disorders, suggesting a role for MeCP2 in brain metabolism. Of note, MECP2 loss-of-function mutation in Rett Syndrome is reported to cause impairment of glucose and cholesterol metabolism in human patients and/or mouse models of disease. The purpose of this review is to outline the metabolic abnormalities in MeCP2-associated neurodevelopmental disorders that currently have no available cure. We aim to provide an updated overview into the role of metabolic defects associated with MeCP2-mediated cellular function for consideration of future therapeutic strategies.

1H-NMR-Based Metabolomics in Autism Spectrum Disorder and Pediatric Acute-Onset Neuropsychiatric Syndrome

We recently described a unique plasma metabolite profile in subjects with pediatric acute-onset neuropsychiatric syndrome (PANS), suggesting pathogenic models involving specific patterns of neurotransmission, neuroinflammation, and oxidative stress. Here, we extend the analysis to a group of patients with autism spectrum disorder (ASD), as a consensus has recently emerged around its immune-mediated pathophysiology with a widespread involvement of brain networks. This observational case-control study enrolled patients referred for PANS and ASD from June 2019 to May 2020, as well as neurotypical age and gender-matched control subjects. Thirty-four PANS outpatients, fifteen ASD outpatients, and twenty-five neurotypical subjects underwent physical and neuropsychiatric evaluations, alongside serum metabolomic analysis with 1H-NMR. In supervised models, the metabolomic profile of ASD was significantly different from controls (p = 0.0001), with skewed concentrations of asparagine, aspartate, betaine, glycine, lactate, glucose, and pyruvate. Metabolomic separation was also observed between PANS and ASD subjects (p = 0.02), with differences in the concentrations of arginine, aspartate, betaine, choline, creatine phosphate, glycine, pyruvate, and tryptophan. We confirmed a unique serum metabolomic profile of PANS compared with both ASD and neurotypical subjects, distinguishing PANS as a pathophysiological entity per se. Tryptophan and glycine appear as neuroinflammatory fingerprints of PANS and ASD, respectively. In particular, a reduction in glycine would primarily affect NMDA-R excitatory tone, overall impairing downstream glutamatergic, dopaminergic, and GABAergic transmissions. Nonetheless, we found metabolomic similarities between PANS and ASD that suggest a putative role of N-methyl-D-aspartate receptor (NMDA-R) dysfunction in both disorders. Metabolomics-based approaches could contribute to the identification of novel ASD and PANS biomarkers.

Proteomic phenotype of cerebral organoids derived from autism spectrum disorder patients reveal disrupted energy metabolism, cellular components, and biological processes

The way in which brain morphology and proteome are remodeled during embryonal development, and how they are linked to the cellular metabolism, could be a key for elucidating the pathological mechanisms of certain neurodevelopmental disorders. Cerebral organoids derived from autism spectrum disorder (ASD) patients were generated to capture critical time-points in the neuronal development, and metabolism and protein expression were investigated. The early stages of development, when neurogenesis commences (day in vitro 39), appeared to be a critical timepoint in pathogenesis. In the first month of development, increased size in ASD-derived organoids were detected in comparison to the controls. The size of the organoids correlates with the number of proliferating cells (Ki-67 positive cells). A significant difference in energy metabolism and proteome phenotype was also observed in ASD organoids at this time point, specifically, prevalence of glycolysis over oxidative phosphorylation, decreased ATP production and mitochondrial respiratory chain activity, differently expressed cell adhesion proteins, cell cycle (spindle formation), cytoskeleton, and several transcription factors. Finally, ASD patients and controls derived organoids were clustered based on a differential expression of ten proteins-heat shock protein 27 (hsp27) phospho Ser 15, Pyk (FAK2), Elk-1, Rac1/cdc42, S6 ribosomal protein phospho Ser 240/Ser 244, Ha-ras, mTOR (FRAP) phospho Ser 2448, PKCα, FoxO3a, Src family phospho Tyr 416-at day 39 which could be defined as potential biomarkers and further investigated for potential drug development.

Altered medial prefrontal cortex and dorsal raphé activity predict genotype and correlate with abnormal learning behavior in a mouse model of autism-associated 2p16.3 deletion

2p16.3 deletion, involving NEUREXIN1 (NRXN1) heterozygous deletion, substantially increases the risk of developing autism and other neurodevelopmental disorders. We have a poor understanding of how NRXN1 heterozygosity impacts on brain function and cognition to increase the risk of developing the disorder. Here we characterize the impact of Nrxn1α heterozygosity on cerebral metabolism, in mice, using ¹⁴C‐2‐deoxyglucose imaging. We also assess performance in an olfactory‐based discrimination and reversal learning (OB‐DaRL) task and locomotor activity. We use decision tree classifiers to test the predictive relationship between cerebral metabolism and Nrxn1α genotype. Our data show that Nrxn1α heterozygosity induces prefrontal cortex (medial prelimbic cortex, mPrL) hypometabolism and a contrasting dorsal raphé nucleus (DRN) hypermetabolism. Metabolism in these regions allows for the predictive classification of Nrxn1α genotype. Consistent with reduced mPrL glucose utilization, prefrontal cortex insulin receptor signaling is decreased in Nrxn1α^+/− mice. Behaviorally, Nrxn1α^+/− mice show enhanced learning of a novel discrimination, impaired reversal learning and an increased latency to make correct choices. In addition, male Nrxn1α^+/− mice show hyperlocomotor activity. Correlative analysis suggests that mPrL hypometabolism contributes to the enhanced novel odor discrimination seen in Nrxn1α^+/− mice, while DRN hypermetabolism contributes to their increased latency in making correct choices. The data show that Nrxn1α heterozygosity impacts on prefrontal cortex and serotonin system function, which contribute to the cognitive alterations seen in these animals. The data suggest that Nrxn1α^+/− mice provide a translational model for the cognitive and behavioral alterations seen in autism and other neurodevelopmental disorders associated with 2p16.3 deletion.

Retinol-binding protein 4 in combination with lipids to predict the regression phenomenon of autism spectrum disorders

BACKGROUND

About 20-40 % of autistic people experience a phenomenon of regression. Retinol binding protein 4 (RBP4) plays an important role as an inflammatory neurotrophic adipokine and is a promising mediator of the fat-brain axis. Abnormal fatty acid metabolism and lipid mediators have been reported to be related to the etiological mechanism in autism, and amelioration of impaired lipid metabolism can be recognized as a treatment strategy for autism. The purpose of this study is to explore the relationship between RBP4, lipids, and the autistic regression phenomenon, and to discuss their potentials as biomarkers for the autistic regression phenomenon.

METHODS

A total of 60 autistic individuals (18 with regression phenomenon, 42 without regression phenomenon) (ASD group) and 36 healthy controls were enrolled in this case-control study. The levels of RBP4, total cholesterol (TC), high-density lipoprotein (HDLC), low-density lipoprotein (LDLC), and triglyceride (TG) were measured. Childhood Autism Rating Scale (CARS) is used to assess the severity of autism. Ethical measures were performed in compliance with the current Declaration of Helsinki and written informed consent was obtained from the parents before enrollment of the children and adolescents.

RESULTS

Compared with control subjects, autistic individuals had lower levels of TC (P = 0.007), RBP4 (P = 0.001), and HDLC (P = 0.027). The levels of RBP4 in ASD group were positively correlated with TG (r = 0.355, P = 0.005), HDLC (r = 0.257, P = 0.047), TG/TC (r = 0.376, P = 0.003) and TG/LDLC (r = 0.363, P = 0.004), and were negatively correlated with CARS (r=-0.296, P = 0.003). Further logistic regression demonstrated that decreased RBP4 concentration was associated with the presentation of the autistic regression phenomenon even after the adjustment of the potential confounding factors.

CONCLUSIONS

Serum RBP4 is associated with the autistic regression phenomenon and the severity of ASD. Further studies are needed to expound whether decreased RBP4 participates in the development of the autistic regression phenomenon.