Sedentary patterns and cardiometabolic risk factors in Mexican children and adolescents: analysis of longitudinal data.

BACKGROUND: Sedentary behavior is a modifiable risk factor for cardiometabolic health; however, the assessment of total sedentary time may not capture youth's highly active and interrupted activity patterns. This study examined the associations between sedentary activity patterns and cardiometabolic risk factors among Mexican youth, who have a disproportionate burden of metabolic diseases, using a repeated measure design out of a longitudinal data. METHODS: 570 subjects in the Early Life Exposure in Mexico to ENvironmental Toxicants (ELEMENT) birth cohort, who were followed up to three-time points during adolescence, were included. Bout duration, and frequency and percentages of waking time spent in specific intensities of activity, were quantified using ActiGraph wGT3X-BT wrist accelerometers. Self-reported questionnaires were used to query the usual duration of different sedentary behaviors. Outcomes were fasting lipid profile, markers for glucose homeostasis, anthropometry, and blood pressure. Associations were modeled using linear mixed-effects models, and isotemporal substitution approach was additionally used to assess the effect of replacing objectively assessed sedentary activity with other activity intensities, adjusting for potential confounders. RESULTS: Each hour of self-reported screen-based time was positively associated with diastolic blood pressure (mm Hg) [ß = 0.30, 95% confidence interval (95% CI) = 0.10, 0.51], and an hour of other sedentary time was associated with log serum glucose (mg/dL) [ß = 0.01, 95% CI = 0.004, 0.017]. Substitution models showed that replacing 5% of sedentary time with moderate to vigorous physical activity (MVPA) was associated with lower waist circumference (cm) [ß = - 1.35, 95% CI = - 1.91, - 0.79] and log serum triglycerides (mg/dL) [ß = - 0.11, 95% CI = - 0.18, - 0.03]. Substituting one uninterrupted sedentary bout with light activity was associated with lower insulin (µIU/mL) [ß = - 0.06, 95% CI = - 0.10, - 0.02]. CONCLUSIONS: Sedentary time was associated with cardiometabolic risk factors in Mexican youth in a context-specific manner. Replacing sedentary time with higher intensities was associated with improvements in some cardiometabolic markers.

Sleep Difficulties among Mexican Adolescents: Subjective and Objective Assessments of Sleep.

OBJECTIVE/BACKGROUND: Self-reported sleep difficulties, such as insomnia symptoms, have been reported among adolescents. Yet, studies of their prevalence and correlates are scarce among Latin Americans. This study sought (1) to describe associations between sociodemographic and lifestyle factors with self-reported sleep difficulties and (2) to examine associations between self-reported sleep difficulties and actigraphy-based sleep. PARTICIPANTS: Participants included 477 Mexican adolescents from the ELEMENT cohort. METHODS: Over 7 days, self-reported sleep measures (hard time falling asleep, overall sleep difficulties, and specific types of sleep difficulties) were obtained from daily sleep diaries. Actigraphy-based sleep measures (duration, i.e. sleep onset to morning wake, midpoint, and fragmentation) were concurrently assessed using a wrist actigraph. RESULTS: Mean (SD) age was 15.9 (2.2) years, and 53.5% were females. Mean (SD) sleep duration was 8.5 (1.2) h/night. Half reported a hard time falling asleep at least 3 days, and 25% had sleep difficulties at least 3 days over 7 days. The 3 types of sleep difficulties commonly reported among the entire cohort were insomnia/restlessness (29%), environmental (27%), and mental/emotional difficulties (19%). Female sex, smoking behavior, and socioeconomic indicators were among the most consistent factors associated with sleep difficulties. Subjective sleep difficulties were associated with shorter sleep duration (ß = -20.8 [-35.3, -6.2] min), while subjective hard time falling asleep was associated with longer sleep duration (ß = 11.3 [4.6, 27.2] min). CONCLUSION: A high proportion of Mexican adolescents in the sample reported sleep difficulties. Findings demonstrate the importance of obtaining subjective and objective sleep measures for a more comprehensive assessment of adolescent sleep.

Adiposity in Adolescents: The Interplay of Sleep Duration and Sleep Variability.

OBJECTIVE: To assess whether adiposity measures differed according to joint categories of sleep duration and sleep variability in a sample of Mexican adolescents. STUDY DESIGN: A sample of 528 Mexico City adolescents aged 9-17 years wore wrist actigraphs for 6-7 days. Average sleep duration was categorized as age-specific sufficient or insufficient. Sleep variability, the standard deviation of sleep duration, was split at the median into stable versus variable. Adiposity measures-body mass index (BMI)-for-age Z score (BMIz), triceps skinfolds, waist circumference, and percent body fat-were collected by trained assistants. We regressed adiposity measures on combined sleep duration and variability categories. Log binomial models were used to estimate prevalence ratios and 95% CI for obesity (>2 BMIz) by joint categories of sleep duration and variability, adjusting for sex, age, and maternal education. RESULTS: Approximately 40% of the adolescents had insufficient sleep and 13% were obese. Relative to sufficient-stable sleepers, adolescents with insufficient-stable sleep had higher adiposity across all 4 measures (eg, adjusted difference in BMIz was 0.68; 95% CI, 0.35-1.00) and higher obesity prevalence (prevalence ratio, 2.54; 95% CI, 1.36-4.75). Insufficient-variable sleepers had slightly higher BMIz than sufficient-stable sleepers (adjusted difference, 0.30; 95% CI, 0.00-0.59). CONCLUSIONS: Adolescents with consistently insufficient sleep could be at greater risk for obesity. The finding that insufficient-variable sleepers had only slightly higher adiposity suggests that opportunities for "catch-up" sleep may be protective.

Associations between Sleep and Physical Activity Behavior Clusters and Epigenetic Age Acceleration in Mexican Adolescents.

INTRODUCTION: Epigenetic aging, a marker of biological aging measured by DNA methylation, may be affected by behaviors, including sleep and physical activity. However, investigations of physical activity and sleep with epigenetic aging among pediatric populations are scant and have not accounted for correlated behaviors. METHODS: The study population included 472 Mexico City adolescents (52% female). Blood collection and 7-day wrist actigraphy (Actigraph GTX-BT) occurred during a follow-up visit when participants were 14.5 (2.09) years. Leukocyte DNA methylation was measured with the Infinium MethylationEPIC array after bisulfite conversion, and 9 epigenetic clocks were calculated. Sleep vs wake time was identified through a pruned dynamic programing algorithm, and physical activity was processed with Chandler cut-offs. Kmeans clustering was used to select actigraphy-assessed physical activity and sleep behavior clusters. Linear regression analyses were used to evaluate adjusted associations between the clusters and epigenetic aging. RESULTS: There were 3 unique clusters: "Short sleep/high sedentary behavior", "Adequate sleep duration and late timing/low moderate or vigorous physical activity (MVPA)", and "Adequate sleep duration/high MVPA". Compared to the "Adequate duration/high MVPA", adolescents with "Adequate duration and late sleep timing/low MVPA" had more accelerated aging for the GrimAge clock (ß = 0.63;95% CI 0.07, 1.19). In pubertal-stratified analyses, more mature adolescents in the "Adequate duration and late sleep timing/low MVPA group" had accelerated epigenetic aging. In contrast, females in the "Short sleep/high sedentary" group had decelerated epigenetic aging for the Wu pediatric clock. CONCLUSIONS: Associations between behavior clusters and epigenetic aging varied by pubertal status and sex. Contrary results in the Wu clock suggest the need for future research on pediatric-specific clocks.

Supervised Learning of Physical Activity Features From Functional Accelerometer Data.

OBJECTIVE: We propose a new health informatics framework to analyze physical activity (PA) from accelerometer devices. Accelerometry data enables scientists to extract personal digital features useful for precision health decision making. Existing methods in accelerometry data analysis typically begin with discretizing summary counts by certain fixed cutoffs into activity categories. One well-known limitation is that the chosen cutoffs are often validated under restricted settings, and cannot be generalizable across populations, devices, or studies. METHODS: We develop a data-driven approach to overcome this bottleneck in PA data analysis, in which we holistically summarize a subject's activity profile using Occupation-Time curves (OTCs), which describe the percentage of time spent at or above a continuum of activity count levels. We develop multi-step adaptive learning algorithms to perform supervised learning via a scalar-on-function model that involves OTC as the functional predictor of interest as well as other scalar covariates. Our learning analytic first incorporates a hybrid approach of fused lasso for clustering and Hidden Markov Model for changepoint detection, then executes refinement procedures to determine activity windows of interest. RESULTS: We evaluate and illustrate the performance of the proposed learning analytic through simulation experiments and real-world data analyses to assess the influence of PA on biological aging. Our findings indicate a different directional relationship between biological age and PA depending on the specific outcome of interest. SIGNIFICANCE: Our bioinformatics methodology involves the biomedical outcome of interest to detect different critical points, and is thus adaptive to the specific data, study population, and health outcome under investigation.

Maternal 11-Ketoandrostenedione Rises Through Normal Pregnancy and Is the Dominant 11-Oxygenated Androgen in Cord Blood.

CONTEXT: Adrenal-derived 11-oxygenated androgens (11oAs) are known important contributors to human physiology and disease but have not been studied in pregnancy. OBJECTIVE: We characterize 11oAs in normal human pregnancy and neonatal period and assess the ratios between 11oAs and compare with ratios of other steroids that undergo placental metabolism. DESIGN: Prospective cohort study, 2010-2018. SETTING: Academic institution. PATIENTS: Pairs of pregnant women and newborns (n = 120) were studied. Inclusion criteria were maternal age between 18 and 42 years old, spontaneous singleton pregnancies, and intention to deliver at University of Michigan. INTERVENTION: Maternal venous blood was collected during first trimester and at term. Neonatal cord blood was collected following delivery. Steroids were measured via liquid chromatography-tandem mass spectrometry. MAIN OUTCOME MEASURES: Levels of 11ß-hydroxyandrostenedione (11OHA4), 11-ketoandrostenedione (11KA4), 11ß-hydroxytestosterone, and 11-ketotestoterone (11KT) in maternal first trimester, maternal term, and neonatal cord blood were compared. 11OHA4-to-11KA4 ratios were correlated with cortisol-to-cortisone ratios. RESULTS: Dominant 11oAs in pregnancy and the cord blood are 11OHA4 and 11KA4, compared to 11OHA4 and 11KT in adult men and nonpregnant women. We found a rise in 11oA concentrations, particularly 11KA4, from first to third trimester. In cord blood, the concentration of 11KA4 exceeded those of both 11OHA4 and 11KT, reflecting placental 11ß-hydroxysteroid dehydrogenase type 2 (11ßHSD2) and 17ß-hydroxysteroid dehydrogenase (17ßHSD2) activities, respectively. 11OHA4-to-11KA4 ratios are concordant with cortisol-to-cortisone ratios across all maternal and fetal compartments, reflecting placental 11ßHSD2 activity. CONCLUSIONS: Placental 17ßHSD2 activity defends the fetus against the androgen 11KT. Our normative values may be used in future studies of 11oAs in complicated pregnancies.

Metabolomics reveals sex-specific pathways associated with changes in adiposity and muscle mass in a cohort of Mexican adolescents.

BACKGROUND: Alterations in body composition (BC) during adolescence relates to future metabolic risk, yet underlying mechanisms remain unclear. OBJECTIVES: To assess the association between the metabolome with changes in adiposity (body mass index [BMI], waist circumference [WC], triceps skinfold [TS], fat percentage [BF%]) and muscle mass (MM). METHODS: In Mexican adolescents (n = 352), untargeted serum metabolomics was profiled at baseline. and data were reduced by pairing hierarchical clustering with confirmatory factor analysis, yielding 30 clusters with 51 singleton metabolites. At the baseline and follow-up visits (1.6-3.5 years apart), anthropometry was collected to identify associations between baseline metabolite clusters and change in BC (∆) using seemingly unrelated and linear regression. RESULTS: Between visits, MM increased in boys and adiposity increased in girls. Sex differences were observed between metabolite clusters and changes in BC. In boys, aromatic amino acids (AAA), branched chain amino acids (BCAA) and fatty acid oxidation metabolites were associated with increases in ∆BMI, and ∆BF%. Phospholipids were associated with decreases in ∆TS and ∆MM. Negative associations were observed for ∆MM in boys with a cluster including AAA and BCAA, whereas positive associations were found for a cluster containing tryptophan metabolites. Few associations were observed between metabolites and BC change in girls, with one cluster comprising methionine, proline and lipids associated with decreases in ∆BMI, ∆WC and ∆MM. CONCLUSION: Sex-specific associations between the metabolome and change in BC were observed, highlighting metabolic pathways underlying adolescent physical growth.

Association of Maternal-Neonatal Steroids With Early Pregnancy Endocrine Disrupting Chemicals and Pregnancy Outcomes.

CONTEXT: Steroids play an important role in fetal development and parturition. Gestational exposures to endocrine-disrupting chemicals (EDCs) affect steroidal milieu and pregnancy outcomes, raising the possibility of steroids serving as biomarkers. Most studies have not addressed the impact of EDC mixtures, which are reflective of real life scenarios. OBJECTIVE: Assess the association of maternal and neonatal steroids with pregnancy outcomes and early pregnancy EDC levels. DESIGN: Prospective analysis of mother-infant dyads. SETTING: University hospital. PARTICIPANTS: 121 mother-infant dyads. MAIN OUTCOME MEASURES: The associations of maternal and neonatal steroidal hormones from 121 dyads with pregnancy outcomes, the associations of first trimester EDCs individually and as mixtures with maternal and neonatal steroids in a subset of 56 dyads and the influence of body mass index (BMI), age, and offspring sex in modulating the EDC associations with steroids were determined. RESULTS: Steroid-specific positive or negative associations with pregnancy measures were evident; many maternal first trimester EDCs were negatively associated with estrogens and positively with androgen/estrogen ratios; EDC-steroid associations were influenced by maternal age, pre-pregnancy BMI, and fetal sex; and EDCs individually and as mixtures showed direct and inverse fetal sex-dependent associations with maternal and neonatal steroids. CONCLUSIONS: This proof-of-concept study indicates association of steroids with pregnancy outcomes depending on maternal age, prepregnancy BMI, and fetal sex, with the effects of EDCs differing when considered individually or as mixtures. These findings suggest that steroidal hormonal measures have potential to serve as biomarkers of impact of EDC exposures and pregnancy outcome.

Accelerometer-measured Physical Activity, Reproductive Hormones, and DNA Methylation.

INTRODUCTION/PURPOSE: Limited studies have examined the association of physical activity with reproductive hormones, DNA methylation, and pubertal status among adolescents. METHODS: Among 248 boys and 271 girls, we estimated daily physical activity levels based on 7 d of wrist-worn accelerometer data. We used an isotemporal substitution paradigm and sex-stratified regression models to examine the association of physical activity levels with 1) testosterone, cortisol, progesterone, and androstenedione concentrations; 2) DNA methylation of long interspersed nucleotide (LINE-1) repeats and the genes H19, hydroxysteroid (11-Beta) dehydrogenase 2 (HSD11B2), and peroxisome proliferator-activated receptor alpha (PPARA) from blood leukocytes; and 3) Tanner stages, adjusted for age, BMI, and socioeconomic status. RESULTS: In boys, substituting 30 min of moderate physical activity for 30 min of sedentary behavior per day was associated with 29% (-49%, 0%) of lower testosterone and 29% (4%, 61%) of higher progesterone. Substituting 30 min of light physical activity for sedentary behavior was associated with 13% (-22%, -2%) of lower progesterone. Among girls, 30 min of additional sedentary behavior was associated with 8% (-15%, 0%) of lower testosterone and 24% (8%, 42%) of higher progesterone concentrations. Substituting 30 min of moderate physical activity for sedentary behavior was associated with 15% (0%, 31%) of higher cortisol, whereas substituting the same amount of light physical activity for sedentary behavior was associated with 22% (-39%, 0%) of lower progesterone. Substituting 30 min of vigorous physical activity for sedentary behavior per day was associated with almost six times higher levels (5.83, 95% confidence interval = 1.79-9.86) of HSD11B2 methylation in boys. CONCLUSIONS: Accelerometer-measured daily physical activity was associated with reproductive hormones and HSD11B2 DNA methylation, differed by sex and activity intensity levels.

Maternal Exposure to Environmental Disruptors and Sexually Dimorphic Changes in Maternal and Neonatal Oxidative Stress.

CONTEXT: Early pregnancy exposure to endocrine disrupting chemicals (EDCs) may contribute to poor birth outcomes through oxidative stress (OS)-mediated disruption of the maternal and fetal milieu. Most studies have investigated the effect of single EDC exposures on OS. OBJECTIVE: Assess the association of uniquely weighted mixtures of early pregnancy exposures with the maternal and neonatal OS markers. DESIGN: Prospective analysis of mother-infant dyads. SETTING: University hospital. PARTICIPANTS: 56 mother-infant dyads. MAIN OUTCOME MEASURES: The association of OS markers (nitrotyrosine, dityrosine, chlorotyrosine) in maternal first trimester and term, and cord blood plasma with maternal first trimester exposure levels of each of 41 toxicants (trace elements, metals, phenols, and phthalates) from 56 subjects was analyzed using Spearman correlations and linear regression. The association of OS markers with inflammatory cytokines and birth outcomes were analyzed by Spearman correlation and linear regression analysis, respectively. Weighted mixtures of early pregnancy exposures were created by principal component analysis and offspring sex-dependent and independent associations with oxidative stress markers were assessed. RESULTS: (1) An inverse relationship between levels of maternal/cord OS markers and individual EDCs was evident. In contrast, when assessed as EDC mixtures, both direct and inverse associations were evident in a sex-specific manner; (2) the maternal term OS marker, nitrotyrosine, was inversely associated with gestational age, and (3) both direct and inverse associations were evident between the 3 OS markers and individual cytokines. CONCLUSIONS: Provides proof of concept that effects of exposures on OS varies when assessed as EDC mixtures versus individually.

Early pregnancy exposure to endocrine disrupting chemical mixtures are associated with inflammatory changes in maternal and neonatal circulation.

Endocrine disrupting chemicals (EDCs) are ubiquitous, and pregnancy is a sensitive window for toxicant exposure. EDCs may disrupt the maternal immune system, which may lead to poor pregnancy outcomes. Most studies investigate single EDCs, even though "real life" exposures do not occur in isolation. We tested the hypothesis that uniquely weighted mixtures of early pregnancy exposures are associated with distinct changes in the maternal and neonatal inflammasome. First trimester urine samples were tested for 12 phthalates, 12 phenols, and 17 metals in 56 women. Twelve cytokines were measured in first trimester and term maternal plasma, and in cord blood after delivery. Spearman correlations and linear regression were used to relate individual exposures with inflammatory cytokines. Linear regression was used to relate cytokine levels with gestational age and birth weight. Principal component analysis was used to assess the effect of weighted EDC mixtures on maternal and neonatal inflammation. Our results demonstrated that maternal and cord blood cytokines were differentially associated with (1) individual EDCs and (2) EDC mixtures. Several individual cytokines were positively associated with gestational age and birth weight. These observed associations between EDC mixtures and the pregnancy inflammasome may have clinical and public health implications for women of childbearing age.

Sleep duration and fragmentation in relation to leukocyte DNA methylation in adolescents.

STUDY OBJECTIVES: Sleep deprivation and low sleep quality are widespread among adolescents, and associate with obesity risk. Plausible mediators include diet and physical activity. Another potential interrelated pathway, as yet unexplored in adolescents, could involve epigenetic modification of metabolism genes. METHODS: In a cohort of 351 Mexico City adolescents (47% male; mean [SD] age = 14 [2] years), 7-day actigraphy was used to assess average sleep duration, sleep fragmentation, and movement index. DNA isolated from blood leukocytes was bisulfite-converted, amplified, and pyrosequenced at four candidate regions. Linear mixed models evaluated sex-stratified associations between sleep characteristics (split into quartiles [Q]) and DNA methylation of each region, adjusted for potential confounders. RESULTS: Mean sleep duration was 8.5 [0.8] hours for boys and 8.7 [1] hours for girls. There were sex-specific associations between sleep duration and LINE-1 (long interspersed nuclear element) methylation. Boys with longer sleep duration (Q4) had lower LINE-1 methylation than boys in the 3rd quartile reference category, while girls with both longer and shorter sleep duration had higher LINE-1 methylation compared to Q3. Longer sleep duration was associated with higher H19 methylation among girls (comparing highest to third quartile, -0.9% [-2.2, 0.5]; p, trend = 0.047). Sleep fragmentation was inversely associated with peroxisome proliferator-activated receptor alpha (PPARA) methylation among girls (comparing highest to lowest fragmentation quartile, 0.9% [0.1 to 1.8]). Girls also showed an inverse association between sleep fragmentation and hydroxysteroid (11-beta) dehydrogenase 2 (HSD11B2; Q4 to Q1, 0.6% [-1.2%, 0%]). CONCLUSIONS: Sleep duration and fragmentation in adolescents show sex-specific associations with leukocyte DNA methylation patterns of metabolism genes.