In Utero Exposure to Air Pollutants and Mitochondrial Heteroplasmy in Neonates

Exploring mitochondrial heteroplasmy in neonates: implications for growth patterns and overweight in the first years of life

BACKGROUND

Mitochondrial heteroplasmy reflects genetic diversity within individuals due to the presence of varying mitochondrial DNA (mtDNA) sequences, possibly affecting mitochondrial function and energy production in cells. Rapid growth during early childhood is a critical development with long-term implications for health and well-being. In this study, we investigated if cord blood mtDNA heteroplasmy is associated with rapid growth at 6 and 12 months and overweight in childhood at 4-6 years.

METHODS

This study included 200 mother-child pairs of the ENVIRONAGE birth cohort. Whole mitochondrial genome sequencing was performed to determine mtDNA heteroplasmy levels (in variant allele frequency; VAF) in cord blood. Rapid growth was defined for each child as the difference between WHO-SD scores of predicted weight at either 6 or 12 months and birth weight. Logistic regression models were used to determine the association of mitochondrial heteroplasmy with rapid growth and childhood overweight. Determinants of relevant cord blood mitochondrial heteroplasmies were identified using multiple linear regression models.

RESULTS

One % increase in VAF of cord blood MT-D-Loop16362T > C heteroplasmy was associated with rapid growth at 6 months (OR = 1.03; 95% CI: 1.01-1.05; p = 0.001) and 12 months (OR = 1.02; 95% CI: 1.00-1.03; p = 0.02). Furthermore, this variant was associated with childhood overweight at 4-6 years (OR = 1.01; 95% CI 1.00-1.02; p = 0.05). Additionally, rapid growth at 6 months (OR = 3.00; 95% CI: 1.49-6.14; p = 0.002) and 12 months (OR = 4.05; 95% CI: 2.06-8.49; p < 0.001) was also associated with childhood overweight at 4-6 years. Furthermore, we identified maternal age, pre-pregnancy BMI, maternal education, parity, and gestational age as determinants of cord blood MT-D-Loop16362T > C heteroplasmy.

CONCLUSIONS

Our findings, based on mitochondrial DNA genotyping, offer insights into the molecular machinery leading to rapid growth in early life, potentially explaining a working mechanism of the development toward childhood overweight.

Associations between mitochondrial biomarkers, urban residential exposures and childhood asthma outcomes over 6 months

Determining biomarkers of responses to environmental exposures and evaluating whether they predict respiratory outcomes may help optimize environmental and medical approaches to childhood asthma. Relative mitochondrial (mt) DNA abundance and other potential mitochondrial indicators of oxidative stress may provide a sensitive metric of the child's shifting molecular responses to its changing environment. We leveraged two urban childhood cohorts (Environmental Control as Add-on Therapy in Childhood Asthma (ECATCh); Columbia Center for Children's Environmental Health (CCCEH)) to ascertain whether biomarkers in buccal mtDNA associate with airway inflammation and altered lung function over 6 months of time and capture biologic responses to multiple external stressors such as indoor allergens and fine particulate matter (PM2.5). Relative mtDNA content was amplified by qPCR and methylation of transfer RNA phenylalanine/rRNA 12S (TF/RNR1), cytochrome c oxidase (CO1), and carboxypeptidase O (CPO) was measured by pyrosequencing. Data on residential exposures and respiratory outcomes were harmonized between the two cohorts. Repeated measures and multiple regression models were utilized to assess relationships between mitochondrial biomarkers, respiratory outcomes, and residential exposures (PM2.5, allergens), adjusted for potential confounders and time-varying asthma. We found across the 6 month visits, a 0.64 fold higher level of TF/RNR1 methylation was detected among those with asthma in comparison to those without asthma ((parameter estimate (PE) 0.64, standard error 0.28, p = 0.03). In prospective analyses, CPO methylation was associated with subsequent reduced forced vital capacity (FVC; PE -0.03, standard error 0.01, p = 0.02). Bedroom dust mouse allergen, but not indoor PM2.5, was associated with higher methylation of TF/RNR1 (PE 0.015, standard error 0.006, p = 0.01). Select mtDNA measures in buccal cells may indicate children's responses to toxic environmental exposures and associate selectively with asthma and lung function.

Mitochondrial DNA heteroplasmy analysis in keratoconus patients from China

Background: Mitochondrial DNA (mtDNA) variants have been implicated in keratoconus (KC). The present study aimed to characterize the mtDNA heteroplasmy profile in KC and explore the association of mitochondrial heteroplasmic levels with KC. Methods: Mitochondrial sequencing of peripheral blood samples and corneal tomography were conducted in 300 KC cases and 300 matched controls. The number of heteroplasmic and homoplasmic variants was calculated across the mitochondrial genome. Spearman's correlation was used to analyze the correlation between the number of heteroplasmic variants and age. The association of mtDNA heteroplasmic level with KC was analyzed by logistic regression analysis. Moreover, the relationship between mitochondrial heteroplasmic levels and clinical parameters was determined by linear regression analysis. Results: The distribution of mtDNA heteroplasmic variants showed the highest number of heteroplasmic variants in the non-coding region, while the COX3 gene exhibited the highest number in protein-coding genes. Comparisons of the number of heteroplasmic and homoplasmic non-synonymous variants in protein-coding genes revealed no significant differences between KC cases and controls (all p > 0.05). In addition, the number of heteroplasmic variants was positively associated with age in all subjects (r = 0.085, p = 0.037). The logistic regression analyses indicated that the heteroplasmic levels of m.16180_16181delAA was associated with KC (p < 0.005). Linear regression analyses demonstrated that the heteroplasmic levels of m.16180_16181delAA and m.302A>C were not correlated with thinnest corneal thickness (TCT), steep keratometry (Ks), and flat keratometry (Kf) (all p > 0.05) in KC cases and controls separately. Conclusion: The current study characterized the mtDNA heteroplasmy profile in KC, and revealed that the heteroplasmic levels of m.16180_16181delAA were associated with KC.

Meandered and muddled: a systematic review on the impact of air pollution on ocular health

From the years 1970-2023, a systematic overview of the diverse consequences of particulate matter on eye health and a disease classification according to acute, chronic, and genetic are presented using the PubMed, Research Gate, Google Scholar, and Science Direct databases. Various studies on medical aspects correlate with the eye and health. However, from an application perspective, there is limited research on the ocular surface and air pollution. The main objective of the study is to uncover the relationship between eye health and air pollution, particularly particulate matter, along with other external factors acting as aggravators. The secondary goal of the work is to examine the existing models for mimicking human eyes. The study is followed by a questionnaire survey in a workshop, in which the exposure-based investigation was tagged based on their activity. This paper establishes a relationship between particulate matter and its influence on human health, leading to numerous eye diseases like dry eyes, conjunctivitis, myopia, glaucoma, and trachoma. The results of the questionnaire survey indicate that about 68% of the people working in the workshop are symptomatic with tears, blurred vision, and mood swings, while 32% of the people were asymptomatic. Although there are approaches for conducting experiments, the evaluation is not well defined; empirical and numerical solutions for particle deposition on the eye are needed. There prevails a broad gap in the arena of ocular deposition modeling.