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Appetite hormones are considered a promising target in fighting obesity as impaired appetite hormone levels have already been associated with obesity. However, further insights in the drivers of appetite hormone levels are needed. In this study, we investigated the associations of fasting appetite hormone levels with lifestyle and environmental exposures in children and adolescents. A total of 534 fasting blood samples were collected from children and adolescents (4-16y,50% boys) and appetite hormone levels (glucagon-like peptide-1 (GLP-1), peptide YY (PYY), pancreatic polypeptide (PP), leptin and ghrelin) were measured. Exposures included dietary quality (fiber-rich food intake, sugar propensity, fat propensity), psychosocial stress (happiness, negative emotions, negative life events and emotional problems), sleep duration, physical activity and environmental quality (long term black carbon (BC), particulate matter <2.5 μM (PM 2.5), nitrogen dioxide (NO 2) exposure, and green space in a 100 m and 2000 m radius around the residence). A multi-exposure score was calculated to combine all the exposures at study in one measure. Associations of individual exposures and multi-exposure score with appetite hormone levels were evaluated using linear mixed regression models adjusting for sex, age, socioeconomic status, waist-to-height ratio and multiple testing. GLP-1 was associated with air pollution exposure (NO 2 β* = -0.13, BC β* = -0.15, PM 2.5 β* = -0.16, all p < 0.001). Leptin was associated with green space in a 100 m radius around the residence (β* = -0.11; p = 0.002). Ghrelin was associated with negative emotions (active ghrelin β* = -0.16; p = 0.04, total ghrelin β* = -0.23; p = 0.0051) and happiness (active ghrelin β* = 0.25; p < 0.001, total ghrelin β* = 0.26; p < 0.001). Furthermore, total ghrelin levels were associated with the multi-exposure score, reflecting unhealthy exposures and lifestyle (β* = -0.22; p = 0.036). Our findings provide new insights into the associations of exposures with appetite hormone levels, which are of high interest for preventive obesity research. Further research is crucial to reveal the underlying mechanisms of the observed associations. • Associations of 14 exposures with 5 appetite hormones were studied in children. • Air pollution is negatively associated with fasting glucagon-like-peptide 1 levels. • Residential green space is negatively associated with fasting leptin levels. • Happiness is positively associated with active and total ghrelin levels. • Negative emotions show negative associations with total ghrelin levels. [ABSTRACT FROM AUTHOR]

BACKGROUND: Telomere length is a molecular marker of biological aging. OBJECTIVE: Here we investigated whether early-life exposure to residential air pollution was associated with leukocyte telomere length (LTL) at 8 y of age. METHODS: In a multicenter European birth cohort study, HELIX (Human Early Life Exposome) (n=1,396), we estimated prenatal and 1-y childhood exposure to nitrogen dioxide (NO2), particulate matter with aerodynamic diameter ≤2:5 lm (PM2:5), and proximity to major roads. Average relative LTL was measured using quantitative real-time polymerase chain reaction (qPCR). Effect estimates of the association between LTL and prenatal, 1-y childhood air pollution, and proximity to major roads were calculated using multiple linear mixed models with a random cohort effect and adjusted for relevant covariates. RESULTS: LTL was inversely associated with prenatal and 1-y childhood NO2 and PM2:5 exposures levels. Each standard deviation (SD) increase in prenatal NO2 was associated with a −1:5% (95% CI: −2:8, −0:2) change in LTL. Prenatal PM2:5 was nonsignificantly associated with LTL (−0:7% per SD increase; 95% CI: −2:0, 0.6). For each SD increment in 1-y childhood NO2 and PM2:5 exposure, LTL shortened by −1:6% (95% CI: −2:9, −0:4) and −1:4% (95% CI: −2:9, 0.1), respectively. Each doubling in residential distance to nearest major road during childhood was associated with a 1.6% (95% CI: 0.02, 3.1) lengthening in LTL. CONCLUSION: Lower exposures to air pollution during pregnancy and childhood were associated with longer telomeres in European children at 8 y of age. These results suggest that reductions in traffic-related air pollution may promote molecular longevity, as exemplified by telomere length, from early life onward. [ABSTRACT FROM AUTHOR]

Mitochondria are known to respond to environmental stressors but whether green space is associated with mitochondrial abundance is unexplored. Furthermore, as exposures may affect health from early life onwards, we here evaluate if residential green space is associated with mitochondria DNA content (mtDNAc) in children. In primary schoolchildren (COGNAC study), between 2012 and 2014, buccal mtDNAc was repeatedly (three times) assessed using qPCR. Surrounding low (<3m), high (≥3m) and total (sum of low and high) green space within different radii (100m–1000m) from the residence and distance to the nearest large green space (>0.5ha) were estimated using a remote sensing derived map. Given the repeated measures design, we applied a mixed-effects model with school and subject as random effect while adjusting for a priori chosen fixed covariates. Results: mtDNAc was assessed in 246 children with a total of 436 measurements (mean age 10.3 years). Within a 1000m radius around the residential address, an IQR increment in low (11.0%), high (9.5%), and total (13.9%) green space was associated with a respectively 15.2% (95% CI: 7.2%–23.7%), 10.8% (95% CI: 4.5%–17.5%), and 13.4% (95% CI: 7.4%–19.7%) higher mtDNAc. Conversely, an IQR increment (11.6%) in agricultural area in the same radius was associated with a −3.4% (95% CI: 6.7% to −0.1%) lower mtDNAc. Finally, a doubling in distance to large green space was associated with a −5.2% (95% CI: 7.9 to −2.4%) lower mtDNAc. To our knowledge, this is the first study evaluating associations between residential surrounding green space and mtDNAc in children. Our results showed that green space was associated with a higher mtDNAc in children, which indicates the importance of the early life environment. To what extent these findings contribute to later life health effects should be further examined. [Display omitted] • Residential surrounding green space is associated with higher child mtDNA content. •Exposure to agriculture is associated with lower child mtDNA content. •Living closer to large green space is associated with higher mtDNA content. [ABSTRACT FROM AUTHOR]

• Chronic exposure to PM 2.5 is associated with lower child buccal telomere length. • Chronic exposure to PM 2.5 is associated with lower child mitochondrial DNA content. • Recent traffic related air pollution is associated with lower child telomere length. Pro-inflammatory conditions such as air pollution might induce biological ageing. However, the available evidence on such an impact in children is still very scarce. We studied in primary schoolchildren the association of ambient residential air pollution exposure with telomere length (TL) and mitochondrial DNA content (mtDNAc), two important targets of the core axis of ageing. Between 2012 and 2014, buccal TL and mtDNAc were repeatedly assessed using qPCR in 197 Belgian primary schoolchildren (mean age 10.3 years) as part of the COGNAC study. At the child's residence, recent (week), sub-chronic (month) and chronic (year) exposure to nitrogen dioxide (NO 2), particulate matter ≤ 2.5 µm (PM 2.5) and black carbon (BC) were estimated using a high resolution spatiotemporal model. A mixed-effects model with school and subject as random effect was used while adjusting for a priori chosen covariates. An interquartile range (IQR) increment (1.9 µg/m3) in chronic PM 2.5 exposure was associated with a 8.9% (95% CI: −15.4 to −1.9%) shorter TL. In contrast to PM 2.5 , chronic exposure to BC and NO 2 was not associated with TL but recent exposure to BC and NO 2 showed significant inverse associations with TL: an IQR increment in recent exposure to BC (0.9 µg/m3) and NO 2 (10.2 µg/m3) was associated with a 6.2% (95% CI: −10.6 to −1.6%) and 6.4% (95% CI: −11.8 to −0.7%) shorter TL, respectively. Finally, an IQR increment in chronic PM 2.5 exposure was associated with a 12.7% (95% CI: −21.7 to −2.6%) lower mtDNAc. However, no significant associations were seen for NO 2 and BC or for other exposure windows. Chronic exposure to PM 2.5 below the EU threshold was associated with child's shorter buccal TL and lower mtDNAc, while traffic-related pollutants (BC and NO 2) showed recent effects on telomere biology. Our data add to the literature on air pollution-induced effects of TL and mtDNAc, two measures part of the core axis of cellular ageing, from early life onwards. [ABSTRACT FROM AUTHOR]