How 25(OH)D Levels during Pregnancy Affect Prevalence of Autism in Children: Systematic Review

Molecular pathways in placental-fetal development and disruption

The first trimester of pregnancy ranks high in priority when minimizing harmful exposures, given the wide-ranging types of organogenesis occurring between 4- and 12-weeks' gestation. One way to quantify potential harm to the fetus in the first trimester is to measure a corollary effect on the placenta. Placental biomarkers are widely present in maternal circulation, cord blood, and placental tissue biopsied at birth or at the time of pregnancy termination. Here we evaluate ten diverse pathways involving molecules expressed in the first trimester human placenta based on their relevance to normal fetal development and to the hypothesis of placental-fetal endocrine disruption (perturbation in development that results in abnormal endocrine function in the offspring), namely: human chorionic gonadotropin (hCG), thyroid hormone regulation, peroxisome proliferator activated receptor protein gamma (PPARγ), leptin, transforming growth factor beta, epiregulin, growth differentiation factor 15, small nucleolar RNAs, serotonin, and vitamin D. Some of these are well-established as biomarkers of placental-fetal endocrine disruption, while others are not well studied and were selected based on discovery analyses of the placental transcriptome. A literature search on these biomarkers summarizes evidence of placenta-specific production and regulation of each biomarker, and their role in fetal reproductive tract, brain, and other specific domains of fetal development. In this review, we extend the theory of fetal programming to placental-fetal programming.

Environmental Influences on Individuals with Autistic Spectrum Disorders with Special Emphasis on Seasonality: An Overview

This paper offers an in-depth exploration of the intricate relationship between environmental factors and autism spectrum disorder (ASD), with a special emphasis on seasonality. It reviews existing research, providing a comprehensive summary of findings and highlighting the multifaceted dimensions of several environmental factors influencing the etiology of ASD. The discussion encompasses various elements, including birth months, maternal health, dietary choices, and vitamin D deficiency, delving into the intricate interplay of seasonality with environmental influences such as viral infections and solar radiation. The present study raises essential questions regarding the timing of environmental influences and the factors contributing to the rising prevalence of ASD. Ultimately, it underscores the need for future epidemiological research to incorporate more extensive investigations of environmental risk factors and employ advanced statistical analyses. This comprehensive overview contributes to a deeper understanding of how environmental factors, particularly seasonality, may be linked to the occurrence of ASD and its increasing prevalence, recognizing the multifaceted and diverse nature of these interactions.

Steroid hormone pathways, vitamin D and autism: a systematic review

The origins of the male preponderance in autism incidence remain unclear. The idea that perinatal factors associated with sex differentiation (e.g., steroid hormone pathways) may increase the possibility of the emergence of autism is complementary to the hypothesis that female individuals are intrinsically less likely to develop autism. Empirical evidence for the mechanistic roles of in utero steroid hormones in autism etiology is accumulating but inconsistent. We conducted a systematic review using rigorous criteria for the measurements of steroids and vitamin D exposure, to summarize the potential contributing roles of prenatal and early postnatal steroids and vitamin D alterations to the emergence of autism. We searched PubMed, PsychInfo, Scopus, and included 22 studies for qualitative synthesis. Among them, six studies examined the association of autism diagnoses in offspring and levels of steroids and precursor steroid hormones in the fetal environment, eight studies examined the associations between autism and maternal and fetal blood vitamin D levels during pregnancy and at birth, and eight studies examined the associations between offspring autism diagnoses and maternal hyperandrogenemia diagnosed before pregnancy. We identified promising and complex results regarding the relations between steroid metabolism and autism. The interpretation of findings was limited by the mostly observational study designs, insufficient investigation of the effects of offspring sex, confounders and their cumulative effects on the development of the child, and unclear impact of the timing of steroids exposure and their effects on fetal neurodevelopment.

The Rationale for Vitamin, Mineral, and Cofactor Treatment in the Precision Medical Care of Autism Spectrum Disorder

Children with autism spectrum disorder may exhibit nutritional deficiencies due to reduced intake, genetic variants, autoantibodies interfering with vitamin transport, and the accumulation of toxic compounds that consume vitamins. Importantly, vitamins and metal ions are essential for several metabolic pathways and for neurotransmitter functioning. The therapeutic benefits of supplementing vitamins, minerals (Zinc, Magnesium, Molybdenum, and Selenium), and other cofactors (coenzyme Q10, alpha-lipoic acid, and tetrahydrobiopterin) are mediated through their cofactor as well as non-cofactor functions. Interestingly, some vitamins can be safely administered at levels far above the dose typically used to correct the deficiency and exert effects beyond their functional role as enzyme cofactors. Moreover, the interrelationships between these nutrients can be leveraged to obtain synergistic effects using combinations. The present review discusses the current evidence for using vitamins, minerals, and cofactors in autism spectrum disorder, the rationale behind their use, and the prospects for future use.

Maternal Vitamin D Levels during Pregnancy and Offspring Psychiatric Outcomes: A Systematic Review

Prenatal exposure to vitamin D may play a significant role in human brain development and function. Previous epidemiological studies investigating the associations between maternal vitamin D status and offspring developmental and psychiatric outcomes in humans have been inconclusive. We aimed to systematically assess the results of previously published studies that examined the associations between maternal vitamin D levels, measured as circulating 25(OH)D levels in pregnancy or at birth, and offspring neuropsychiatric and psychiatric outcomes. Systematic searches were conducted using MEDLINE, Embase, PsychINFO and Web of Science for studies published by 10 August 2022. We included human observational studies that examined associations between prenatal or perinatal vitamin D levels and offspring neuropsychiatric and psychiatric outcomes and were published in English in peer-reviewed journals. Of the 3729 studies identified, 66 studies were screened for full texts and 29 studies published between 2003 and 2022 were included in the final review. There was a small amount of evidence for the association between prenatal vitamin D deficiency and autism spectrum disorder. When studies with larger sample sizes and stricter definitions of vitamin D deficiency were considered, positive associations were also found for attention-deficit/hyperactivity disorder and schizophrenia. Future studies with larger sample sizes, longer follow-up periods and prenatal vitamin D assessed at multiple time points are needed.

GC1f Vitamin D Binding Protein Isoform as a Marker of Severity in Autism Spectrum Disorders

Autism spectrum disorders (ASD) are characterized by a wide spectrum of clinical, behavioral, and cognitive manifestations. It is, therefore, crucial to investigate possible biomarkers associated with specific ASD phenotypes. Ample literature suggests a possible role for vitamin D (VD) in influencing ASD clinical phenotypes. We analyzed three vitamin D binding protein gene (DBP) functional polymorphisms (rs2282679, rs7041, and rs4588), which are involved in the modulation of vitamin D serum concentration in 309 ASD children and 831 healthy controls. Frequency comparisons of single nucleotide polymorphisms (SNPs) alleles, genotypes, and GC isoforms (GC1f, G1s, and GC2)—generated by the combination of rs7041 and rs4588 alleles—were correlated with ASD diagnostic, behavioral, and functioning scales. The GC1f isoform was significantly more frequent in ASD compared with controls (18.6% vs. 14.5% pc = 0.02). Significantly higher scores for item 15 of the Childhood Autism Rating Scale (CARS) and lower ones for the Children’s Global Assessment Scale (CGAS) functioning scales were seen in ASD carrying the GC1f isoform. In GC phenotype analysis, a gradient of severity for overall CARS scores and CARS item 15 was observed, with scores decreasing according to the presence of GC1f-GC1f > GC1f-GC1s > GC1s-GC1s > GC1f-GC2 > GC2-GC2 isoforms. Similarly, lower CGAS scores were seen in carriers of the GC1f-GC1f isoform, whereas higher scores were present in those carrying GC2-GC2 (p = 0.028). This is the first study to evaluate possible relationships between GC variants and the different aspects of ASD in Italian ASD children. Results, although needing to be validated in ampler cohorts, suggest that the GC1f isoform could be a marker of severity in ASD that may be useful in establishing the intensity of therapeutic and rehabilitative protocols.

Maternal vitamin D during pregnancy and offspring autism and autism-associated traits: a prospective cohort study

BACKGROUND

There has been a growing interest in the association between maternal levels of vitamin D during pregnancy and offspring autism. However, whether any associations reflect causal effects is still inconclusive.

METHODS

We used data from a UK-based pregnancy cohort study (Avon Longitudinal Study of Parents and Children) comprising 7689 births between 1991 and 1992 with maternal blood vitamin D levels recorded during pregnancy and at least one recorded outcome measure, including autism diagnosis and autism-associated traits. The association between each outcome with seasonal and gestational age-adjusted maternal serum 25-hydroxyvitamin D during pregnancy was estimated using confounder-adjusted regression models. Multiple imputation was used to account for missing data, and restricted cubic splines were used to investigate nonlinear associations. Mendelian randomization was used to strengthen causal inference.

RESULTS

No strong evidence of an association between maternal serum 25-hydroxyvitamin D during pregnancy and any offspring autism-associated outcome was found using multivariable regression analysis (autism diagnosis: adjusted OR = 0.98, 95% CI = 0.90-1.06), including with multiple imputation (autism diagnosis: adjusted OR = 0.99, 95% CI = 0.93-1.06), and no evidence of a causal effect was suggested by Mendelian randomization (autism diagnosis: causal OR = 1.08, 95% CI = 0.46-2.55). Some evidence of increased odds of autism-associated traits at lower levels of maternal serum 25-hydroxyvitamin D was found using spline analysis.

LIMITATIONS

Our study was potentially limited by low power, particularly for diagnosed autism cases as an outcome. The cohort may not have captured the extreme lows of the distribution of serum 25-hydroxyvitamin D, and our analyses may have been biased by residual confounding and missing data.

CONCLUSIONS

The present study found no strong evidence of a causal link between maternal vitamin D levels in pregnancy and offspring diagnosis or traits of autism.

Research Progress on the Role of Vitamin D in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that can lead to severe social behavioral difficulties, which mainly manifests as social communication and interaction disorders; narrow interests; and repetitive, stereotyped behaviors. In recent years, the prevalence of ASD has increased annually, and it has evolved from a rare disease to one with a high incidence among childhood developmental disorders. The pathogenesis of ASD is considered to be the interaction of genetic and environmental factors. There is increasing evidence that vitamin D deficiency in pregnancy and early childhood can lead to the occurrence of ASD. Studies have demonstrated that vitamin D intervention can significantly improve the symptoms of ASD, but the underlying mechanism is still unclear. Therefore, exploring the neuroprotective mechanism of vitamin D against ASD is a huge challenge currently being worked on by current basic and clinical researchers, a task which is of great significance for the clinical promotion and optimization of vitamin D in the treatment of ASD. To further clarify the relationship between vitamin D and ASD, this review summarizes the correlation between vitamin D level and ASD, the effects of vitamin D supplementation on ASD, the possible mechanism of vitamin D involved in ASD, and insights from ASD animal models.

Effects of Vitamin D on Fertility, Pregnancy and Polycystic Ovary Syndrome-A Review

Polycystic ovary syndrome (PCOS) is one of the most common endocrine reproductive disorders in women. Vitamin D deficiency is also quite common in this condition. The degree of vitamin D deficiency correlates with the severity of PCOS. Both male and female vitamin D levels play a role in fertility and affect the outcomes of in vitro fertilization (IVF). Moreover, fertility and IVF indicators are improved by vitamin D not only in healthy women but in those diagnosed with PCOS. Both vitamin D deficiency and PCOS increase pregnancy-related complications. Vitamin D supplementation and optimal vitamin D levels decrease both maternal and fetal risk for complications and adverse events. Furthermore, vitamin D supplementation may ameliorate or even prevent pregnancy-related reversible bone loss in mothers. This review emphasizes the roles of vitamin D deficiency and vitamin D supplementation and their correlation with PCOS regarding reproductive health.