Effects of a School-Based Gardening, Cooking, and Nutrition Cluster Randomized Controlled Trial on Unprocessed and Ultra-Processed Food Consumption

BACKGROUND

School-based gardening and nutrition education interventions report improvements in dietary intake, notably through fruit and vegetables. However, gardening, cooking, and nutrition randomized controlled trials are limited in evaluating dietary quality, and none have examined processed food consumption to date.

OBJECTIVES

The study examined the effects of Texas Sprouts (TX Sprouts), a gardening, cooking, and nutrition education intervention, compared with control on unprocessed and ultra-processed food (UPF) consumption in predominately low-income Hispanic children.

METHODS

TX Sprouts was a school-based cluster randomized controlled trial that consisted of 16 elementary schools randomly assigned to either the TX Sprouts intervention (n = 8 schools) or control (delayed intervention; n = 8 schools) over 3 y (2016-2019). TX Sprouts schools received an outdoor teaching garden and 18 1-h lessons taught by trained educators throughout the school year. Dietary intake data via 2 24-h dietary recalls were collected on a random subsample (n = 468) at baseline and postintervention. All foods and beverages were categorized using the NOVA food classification system (e.g., unprocessed, processed, ultra-processed). Generalized linear mixed effects modeling tested changes in percent calories and grams of NOVA groups between the intervention and control estimates with schools as random clusters.

RESULTS

Of the sample, 63% participated in the free and reduced-price lunch program, and 57% were Hispanic, followed by non-Hispanic White (21%) and non-Hispanic Black (12%). The intervention, compared to the control, resulted in an increase in consumption of unprocessed foods (2.3% compared with -1.8% g; P < 0.01) and a decrease in UPF (-2.4% compared with 1.4% g; P = 0.04). In addition, Hispanic children in the intervention group had an increase in unprocessed food consumption and a decrease in UPF consumption compared to non-Hispanic children (-3.4% compared with 1.5% g; P < 0.05).

CONCLUSIONS

Study results suggest that school-based gardening, cooking, and nutrition education interventions can improve dietary intake, specifically increasing unprocessed food consumption and decreasing UPF consumption. This trial was registered at clinicaltrials.gov as NCT02668744.

Distinct racial and ethnic metabolic syndrome characteristics: A comparative assessment in low-income children 7-10 years of age

BACKGROUND

Pediatric MetS prevalence varies due to lack of consensus on evaluative criteria and associated thresholds, with most not recommending a diagnosis <10 years. However, MetS risk components are becoming evident earlier in life and affect races and ethnicities disproportionately.

OBJECTIVES

To compare the prevalence of MetS based on existing definitions and elucidate racial- and ethnic-specific characteristics associated with MetS prevalence.

METHODS

The baseline and follow-up samples included 900 and 557 children 7-10 years, respectively. Waist circumference, BMI percentile, blood pressure, fasting plasma glucose (FPG), insulin, triglycerides, and high-density lipoprotein cholesterol (HDL-C) were measured. Agreement between MetS definitions was quantified via kappa statistics. MetS and risk factor prevalence and the predictability of metabolic parameters on MetS eight months later was evaluated via logistic regression. McFadden pseudo-R2 was reported as a measure of predictive ability, and the Akaike information criterion evaluated fit of each model.

RESULTS

The baseline sample was 55.0% male and 71.6% Hispanic, followed by non-Hispanic White (NHW) (17.3%) and non-Hispanic Black (NHB) (11.1%), with an average age of 9.2 years. MetS prevalence ranged from 7.6% to 21.4%, highest in Hispanic (9.0%-24.0%) and lowest in NHB children (4.0%-14.0%). Highest agreement was between Ford et al. and Cook et al. definitions (K = 0.88) and lowest agreements were consistently with the International Diabetes Federation criteria (K ≤ 0.57). Compared to NHW children, Hispanic children had higher odds for MetS (OR: 1.7; p = 0.03) and waist circumference, HDL-C, and FPG risk factors (p < 0.05), while NHB children had higher odds for the FPG risk factor (p ≤ 0.007) and lower odds for the plasma triglycerides risk factor (p = 0.002), across multiple MetS definitions. In longitudinal analyses, HDL-C was the strongest independent predictor of MetS in Hispanic and NHW children (p < 0.001 and p < 0.01, respectively), while plasma triglycerides was the strongest independent predictor of MetS in NHB children (p < 0.05).

CONCLUSIONS

MetS prevalence was high in children ≤10 years, and proposed criteria are susceptible to racial and ethnic bias, diagnosing some populations more than other populations with high cardiovascular risk. Earlier preventative measures should be imposed in clinical settings, accounting for racial and ethnic differences, to mitigate disease onset.

Comparison of School vs Home Breakfast Consumption with Cardiometabolic and Dietary Parameters in Low-Income, Multiracial/Ethnic Elementary School-Aged Children

BACKGROUND

Breakfast consumption is often associated with improving cardiometabolic parameters and diet quality. However, literature evaluating breakfast consumption with these outcomes between the school and home environments is limited.

OBJECTIVE

This study examined relationships between breakfast consumption locations (school vs home) and cardiometabolic parameters, breakfast dietary intake, and daily dietary intake.

DESIGN

This cross-sectional study used baseline data from TX Sprouts, a 1-year school-based gardening, nutrition, and cooking cluster-randomized trial, implemented in 16 elementary schools in Austin, TX, during 2016 to 2019.

PARTICIPANTS/SETTING

Analyses included 383 low-income, multiracial/ethnic elementary school-aged children (mean age = 9.2 years; 60.6% Hispanic; 70.5% free/reduced lunch; 58.5% home breakfast consumers).

MAIN OUTCOME MEASURES

Cardiometabolic parameters were obtained via fasting blood draws, and dietary intake was assessed using one 24-hour dietary recall conducted on a random, unannounced weekday. Cardiometabolic and dietary parameters (ie, energy intake, macronutrients, and food group servings) for breakfast and for the day were evaluated.

STATISTICAL ANALYSES PERFORMED

Multivariate analysis of covariance was performed to examine cardiometabolic parameters and dietary intake between school and home breakfasts.

RESULTS

School breakfast consumers (SBC) had lower fasting triglyceride levels than home breakfast consumers (HBC) (89.0 mg/dL vs 95.7 mg/dL; P = 0.03) (to convert to mmol/L, multiply by 0.0113). SBC had lower total fat for the day (P = 0.02) and lower total and saturated fat, sodium, and refined grains at breakfast (P ≤ 0.01) than HBC. However, SBC had lower protein at breakfast (P = 0.01) and higher carbohydrates, total sugar, and added sugar for the day and at breakfast (P ≤ 0.03) than HBC.

CONCLUSIONS

SBC compared with HBC had lower fat intake, which may have contributed to the lower triglyceride level observed in SBC, but also had lower protein intake at breakfast and higher added sugar intake for the day and at breakfast. These results suggest dietary intake differed between HBC and SBC; that is, the home and school environments, but more research is needed to evaluate if such differences are due to School Breakfast Program guidelines.

Circadian rhythms and the gut microbiome synchronize the host's metabolic response to diet

The molecular circadian clock and symbiotic host-microbe relationships both evolved as mechanisms that enhance metabolic responses to environmental challenges. The gut microbiome benefits the host by breaking down diet-derived nutrients indigestible by the host and generating microbiota-derived metabolites that support host metabolism. Similarly, cellular circadian clocks optimize organismal physiology to the environment by influencing the timing and coordination of metabolic processes. Host-microbe interactions are influenced by dietary quality and timing, as well as daily light/dark cycles that entrain circadian rhythms in the host. Together, the gut microbiome and the molecular circadian clock play a coordinated role in neural processing, metabolism, adipogenesis, inflammation, and disease initiation and progression. This review examines the bidirectional interactions between the circadian clock, gut microbiota, and host metabolic systems and their effects on obesity and energy homeostasis. Directions for future research and the development of therapies that leverage these systems to address metabolic disease are highlighted.

The potential of digital phenotyping to advance the contributions of mobile health to self-management science

Digital phenotyping consists of moment-by-moment quantification of behavioral data from individual people, typically collected passively from smartphones and other sensors. Within the evolving context of precision health, digital phenotyping can advance the use of mobile health -based self-management tools and interventions by enabling more accurate prediction for prevention and treatment, facilitating supportive strategies, and informing the development of features to motivate self-management behaviors within real-world conditions. This represents an advancement in self-management science: with digital phenotyping, nurse scientists have opportunities to tailor interventions with increased precision. In this paper, we discuss the emergence of digital phenotyping, the historical background of ecological momentary assessment, and the current state of the science of digital phenotyping, with implications for research design, computational requirements, and ethical considerations in self-management science, as well as limitations.

The influence of 15-week exercise training on dietary patterns among young adults

BACKGROUND/OBJECTIVES

Little is currently known about how exercise may influence dietary patterns and/or food preferences. The present study aimed to examine the effect of a 15-week exercise training program on overall dietary patterns among young adults.

SUBJECTS/METHODS

This study consisted of 2680 young adults drawn from the Training Intervention and Genetics of Exercise Response (TIGER) study. Subjects underwent 15 weeks of aerobic exercise training, and exercise duration, intensity, and dose were recorded for each session using computerized heart rate monitors. In total, 4355 dietary observations with 102 food items were collected using a self-administered food frequency questionnaire before and after exercise training (n = 2476 at baseline; n = 1859 at 15 weeks). Dietary patterns were identified using a Bayesian sparse latent factor model. Changes in dietary pattern preferences were evaluated based on the pre/post-training differences in dietary pattern scores, accounting for the effects of gender, race/ethnicity, and BMI.

RESULTS

Within each of the seven dietary patterns identified, most dietary pattern scores were decreased following exercise training, consistent with increased voluntary regulation of food intake. A longer duration of exercise was associated with decreased preferences for the western (β: -0.0793; 95% credible interval: -0.1568, -0.0017) and snacking (β: -0.1280; 95% credible interval: -0.1877, -0.0637) patterns, while a higher intensity of exercise was linked to an increased preference for the prudent pattern (β: 0.0623; 95% credible interval: 0.0159, 0.1111). Consequently, a higher dose of exercise was related to a decreased preference for the snacking pattern (β: -0.0023; 95% credible interval: -0.0042, -0.0004) and an increased preference for the prudent pattern (β: 0.0029; 95% credible interval: 0.0009, 0.0048).

CONCLUSIONS

The 15-week exercise training appeared to motivate young adults to pursue healthier dietary preferences and to regulate their food intake.

Biological/Genetic Regulation of Physical Activity Level: Consensus from GenBioPAC

PURPOSE

Physical activity unquestionably maintains and improves health; however, physical activity levels globally are low and not rising despite all the resources devoted to this goal. Attention in both the research literature and the public policy domain has focused on social-behavioral factors; however, a growing body of literature suggests that biological determinants play a significant role in regulating physical activity levels. For instance, physical activity level, measured in various manners, has a genetic component in both humans and nonhuman animal models. This consensus article, developed as a result of an American College of Sports Medicine-sponsored round table, provides a brief review of the theoretical concepts and existing literature that supports a significant role of genetic and other biological factors in the regulation of physical activity.

CONCLUSIONS

Future research on physical activity regulation should incorporate genetics and other biological determinants of physical activity instead of a sole reliance on social and other environmental determinants.

Advanced Dietary Patterns Analysis Using Sparse Latent Factor Models in Young Adults

Background

Principal components analysis (PCA) has been the most widely used method for deriving dietary patterns to date. However, PCA requires arbitrary ad hoc decisions for selecting food variables in interpreting dietary patterns and does not easily accommodate covariates. Sparse latent factor models can be utilized to address these issues.

Objective

The objective of this study was to compare Bayesian sparse latent factor models with PCA for identifying dietary patterns among young adults.

Methods

Habitual food intake was estimated in 2730 sedentary young adults from the Training Interventions and Genetics of Exercise Response (TIGER) Study [aged 18-35 y; body mass index (BMI; in kg/m2): 26.5 ± 6.1] who exercised <30 min/wk during the previous 30 d without restricting caloric intake before study enrollment. A food-frequency questionnaire was used to generate the frequency intakes of 102 food items. Sparse latent factor modeling was applied to the standardized food intakes to derive dietary patterns, incorporating additional covariates (sex, race/ethnicity, and BMI). The identified dietary patterns via sparse latent factor modeling were compared with the PCA derived dietary patterns.

Results

Seven dietary patterns were identified in both PCA and sparse latent factor analysis. In contrast to PCA, the sparse latent factor analysis allowed the covariate information to be jointly accounted for in the estimation of dietary patterns in the model and offered probabilistic criteria to determine the foods relevant to each dietary pattern. The derived patterns from both methods generally described common dietary behaviors. Dietary patterns 1-4 had similar food subsets using both statistical approaches, but PCA had smaller sets of foods with more cross-loading elements between the 2 factors. Overall, the sparse latent factor analysis produced more interpretable dietary patterns, with fewer of the food items excluded from all patterns.

Conclusion

Sparse latent factor models can be useful in future studies of dietary patterns by reducing the intrinsic arbitrariness involving the choice of food variables in interpreting dietary patterns and incorporating covariates in the assessment of dietary patterns.

Accumulating Data to Optimally Predict Obesity Treatment (ADOPT): Recommendations from the Biological Domain

BACKGROUND

The responses to behavioral, pharmacological, or surgical obesity treatments are highly individualized. The Accumulating Data to Optimally Predict obesity Treatment (ADOPT) project provides a framework for how obesity researchers, working collectively, can generate the evidence base needed to guide the development of tailored, and potentially more effective, strategies for obesity treatment.

OBJECTIVES

The objective of the ADOPT biological domain subgroup is to create a list of high-priority biological measures for weight-loss studies that will advance the understanding of individual variability in response to adult obesity treatments. This list includes measures of body composition, energy homeostasis (energy intake and output), brain structure and function, and biomarkers, as well as biobanking procedures, which could feasibly be included in most, if not all, studies of obesity treatment. The recommended high-priority measures are selected to balance needs for sensitivity, specificity, and/or comprehensiveness with feasibility to achieve a commonality of usage and increase the breadth and impact of obesity research.

SIGNIFICANCE

The accumulation of data on key biological factors, along with behavioral, psychosocial, and environmental factors, can generate a more precise description of the interplay and synergy among them and their impact on treatment responses, which can ultimately inform the design and delivery of effective, tailored obesity treatments.

Decreased eating frequency linked to increased visceral adipose tissue, body fat, and BMI in Hispanic college freshmen

Background

To investigate the relationship between eating frequency and specific adiposity markers in a potentially high-risk and understudied population of Hispanic college freshmen.

Methods

This study included 92 Hispanic college freshmen (18–19 y). The following cross-sectional data were collected: height, weight, waist circumference, body mass index (BMI), dietary intake, body composition, physical activity, hepatic fat, visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT).

Results

Infrequent eaters ate 44% less often (2.5 ± 0.2 vs. 4.5 ± 0.8, p ≤ 0.01) and consumed 27% more calories per EO (p ≤ 0.01), while consuming 21% less kcals per day (p ≤ 0.01) compared to frequent eaters. Infrequent eaters had 8% higher BMIs (24.8 ± 4.4 vs. 22.9 ± 3.2 kg/m²) (p = 0.02), 60% higher BMI z-scores (0.5 ± 1.0 vs. 0.2 ± 1.0, p = 0.03), 21% higher VAT (298.3 ± 153.8 vs. 236.8 ± 78.2 ml, p = 0.03), 26% higher SAT (1150.1 ± 765.4 vs. 855.6 ± 494.6 ml, p = 0.03), and 8% higher total body fat (27.6 ± 10.8 vs. 25.3 ± 8.8%, p = 0.04) compared to frequent eaters while showing no significant difference in physical activity. These findings seem to be driven by females more than males.

Conclusions

These findings suggest that infrequent eating is related to increased adiposity in Hispanic college freshmen, despite a decreased daily energy intake and no significant differences in physical activity. Yet, more research is needed to understand the underlying mechanisms of these findings, as well as investigate any potential causal relationship between eating frequency and adiposity in Hispanic youth.

A High-Fat Compared with a High-Carbohydrate Breakfast Enhances 24-Hour Fat Oxidation in Older Adults

Background

The ability to oxidize fat is associated with a lower risk of chronic metabolic disease. Preclinical data in mice showed that a high-fat "breakfast" increased 24-h fat oxidation relative to a high-carbohydrate breakfast.

Objectives

The objectives of this study were to determine whether the timing of macronutrient intake in humans affects daily fuel utilization and to examine associations between fuel utilization and metabolic indexes.

Methods

Participants were 29 healthy sedentary men and women (aged 55-75 y) with a body mass index (kg/m2) between 25 and 35. Participants were randomly assigned to receive either a high-fat breakfast (FB; 35% carbohydrate, 20% protein, 45% fat; n = 13) or a high-carbohydrate breakfast (CB; 60% carbohydrate, 20% protein, 20% fat; n = 16) for 4 wk while consuming a "neutral" lunch and dinner. Twenty-four-hour and postprandial respiratory quotients (RQs) were measured by whole-room indirect calorimetry. Insulin and glucose measures including insulin sensitivity were determined by an oral-glucose-tolerance test. Measures were taken at baseline and after the 4-wk intervention. Group-by-time interactions were determined by 2-factor repeated-measures mixed-model ANOVA. Pearson's correlation analyses were used to determine associations of 24-h RQs with metabolic measures after the intervention.

Results

There was a significant group-by-time interaction for change in the 24-h RQ [FB (mean ± SD): 0.88 ± 0.02 to 0.86 ± 0.02; CB: 0.88 ± 0.02 for both; P < 0.05], breakfast RQ (FB: 0.88 ± 0.03 to 0.86 ± 0.03; CB: 0.89 ± 0.02 to 0.90 ± 0.02; P < 0.01), and lunch RQ (FB: 0.089 ± 0.03 to 0.85 ± 0.03; CB: 0.89 ± 0.03 for both; P < 0.01). In the CB group at follow-up, 24-h RQ was positively associated with fasting glucose (r = 0.66, P < 0.05), glucose area under the curve (AUC) (r = 0.51, P < 0.05), and insulin AUC (r = 0.52, P < 0.05) and inversely associated with insulin sensitivity (r = -0.51, P < 0.05).

Conclusions

The macronutrient composition of breakfast affects substrate utilization throughout the day in older adults. The consumption of a high-fat, lower-carbohydrate breakfast may reduce the risk of metabolic disease. This trial was registered at www.clinicaltrials.gov as NCT03164200.

Rationale, design, and baseline findings from HIPP: A randomized controlled trial testing a home-based, individually-tailored physical activity print intervention for African American women in the Deep South

African American women report high rates of physical inactivity and related health disparities. In our previous formative research, we conducted a series of qualitative assessments to examine physical activity barriers and intervention preferences among African American women in the Deep South. These data were used to inform a 12-month Home-based, Individually-tailored Physical activity Print (HIPP) intervention, which is currently being evaluated against a wellness contact control condition among 84 post-menopausal African American women residing in the metropolitan area of Birmingham, Alabama. This paper reports the rationale, design and baseline findings of the HIPP trial. The accrued participants had an average age of 57 (SD=4.7), a BMI of 32.1 kg/m(2) (SD=5.16) with more than half (55%) having a college education and an annual household income under $50,000 (53.6%). At baseline, participants reported an average of 41.5 min/week (SD=49.7) of moderate intensity physical activity, and 94.1% were in the contemplation or preparation stages of readiness for physical activity. While social support for exercise from friends and family was low, baseline levels of self-efficacy, cognitive and behavioral processes of change, decisional balance, outcome expectations, and enjoyment appeared promising. Baseline data indicated high rates of obesity and low levels of physical activity, providing strong evidence of need for intervention. Moreover, scores on psychosocial measures suggested that such efforts may be well received. This line of research in technology-based approaches for promoting physical activity in African American women in the Deep South has great potential to address health disparities and impact public health.

NIH working group report-using genomic information to guide weight management: From universal to precision treatment

OBJECTIVE

Precision medicine utilizes genomic and other data to optimize and personalize treatment. Although more than 2,500 genetic tests are currently available, largely for extreme and/or rare phenotypes, the question remains whether this approach can be used for the treatment of common, complex conditions like obesity, inflammation, and insulin resistance, which underlie a host of metabolic diseases.

METHODS

This review, developed from a Trans-NIH Conference titled "Genes, Behaviors, and Response to Weight Loss Interventions," provides an overview of the state of genetic and genomic research in the area of weight change and identifies key areas for future research.

RESULTS

Although many loci have been identified that are associated with cross-sectional measures of obesity/body size, relatively little is known regarding the genes/loci that influence dynamic measures of weight change over time. Although successful short-term weight loss has been achieved using many different strategies, sustainable weight loss has proven elusive for many, and there are important gaps in our understanding of energy balance regulation.

CONCLUSIONS

Elucidating the molecular basis of variability in weight change has the potential to improve treatment outcomes and inform innovative approaches that can simultaneously take into account information from genomic and other sources in devising individualized treatment plans.

Self-regulation of exercise behavior in the TIGER study

OBJECTIVE

This study aimed to test experiential and behavioral processes of change as mediators of the prediction of exercise behavior by two self-regulation traits, self-efficacy and self-motivation, while controlling for exercise enjoyment.

METHODS

Structural equation modeling was applied to questionnaire responses obtained from a diverse sample of participants. Objective measures defined adherence (928 of 1,279 participants attended 80 % or more of sessions) and compliance (867 of 1,145 participants exercised 30 min or more each session at their prescribed heart rate).

RESULTS

Prediction of attendance by self-efficacy (inversely) and self-motivation was direct and also indirect, mediated through positive relations with the typical use of behavioral change processes. Enjoyment and self-efficacy (inversely) predicted compliance with the exercise prescription.

CONCLUSIONS

The results support the usefulness of self-regulatory behavioral processes of the transtheoretical model for predicting exercise adherence, but not compliance, extending the supportive evidence for self-regulation beyond self-reports of physical activity used in prior observational studies.

Exercise dose, exercise adherence, and associated health outcomes in the TIGER study

PURPOSE

To effectively evaluate activity-based interventions for weight management and disease risk reduction, objective and accurate measures of exercise dose are needed. This study examined cumulative exercise exposure defined by HR-based intensity, duration, and frequency as a measure of compliance with a prescribed exercise program and a predictor of health outcomes.

METHODS

One thousand one-hundred fifty adults (21.3 ± 2.7 yr) completed a 15-wk exercise protocol consisting of 30 min·d, 3 d·wk, at 65%-85% maximum HR reserve. Computerized HR monitor data were recorded at every exercise session (33,473 valid sessions). To quantify total exercise dose, duration for each session was adjusted for average exercise intensity (%HR reserve) to create a measure of intensity minutes for each workout, which were summed over all exercise sessions to formulate an HR physical activity score (HRPAS). Regression analysis was used to examine the relation between HRPAS and physiological responses to exercise training. Compliance with the exercise protocol based on achievement of the minimum prescribed HRPAS was compared with adherence defined by attendance.

RESULTS

On the basis of HRPAS, 868 participants were empirically defined as compliant, and 282 were noncompliant. HRPAS-based and attendance-based classifications of compliance and adherence differed in approximately 9% of participants. Higher HRPAS was associated with significant positive changes in body mass (P < 0.001), body mass index (P < 0.001), waist and hip circumferences (P < 0.001), percent body fat (P < 0.001), systolic blood pressure (P < 0.011), resting HR (P < 0.003), fasting glucose (P < 0.001), and total cholesterol (P < 0.02). Attendance-based adherence was associated with body mass, hip circumference, percent body fat, resting HR, and cholesterol (P < 0.05).

CONCLUSIONS

The HRPAS is a quantifiable measure of exercise dose associated with improvement in health indicators beyond that observed when adherence is defined as session attendance.

Cardiomyocyte-specific BMAL1 plays critical roles in metabolism, signaling, and maintenance of contractile function of the heart

Circadian clocks are cell autonomous, transcriptionally based, molecular mechanisms that confer the selective advantage of anticipation, enabling cells/organs to respond to environmental factors in a temporally appropriate manner. Critical to circadian clock function are 2 transcription factors, CLOCK and BMAL1. The purpose of the present study was to reveal novel physiologic functions of BMAL1 in the heart, as well as to determine the pathologic consequences of chronic disruption of this circadian clock component. To address this goal, we generated cardiomyocyte-specific Bmal1 knockout (CBK) mice. Following validation of the CBK model, combined microarray and in silico analyses were performed, identifying 19 putative direct BMAL1 target genes, which included a number of metabolic (e.g., β-hydroxybutyrate dehydrogenase 1 [Bdh1]) and signaling (e.g., the p85α regulatory subunit of phosphatidylinositol 3-kinase [Pik3r1]) genes. Results from subsequent validation studies were consistent with regulation of Bdh1 and Pik3r1 by BMAL1, with predicted impairments in ketone body metabolism and signaling observed in CBK hearts. Furthermore, CBK hearts exhibited depressed glucose utilization, as well as a differential response to a physiologic metabolic stress (i.e., fasting). Consistent with BMAL1 influencing critical functions in the heart, echocardiographic, gravimetric, histologic, and molecular analyses revealed age-onset development of dilated cardiomyopathy in CBK mice, which was associated with a severe reduction in life span. Collectively, our studies reveal that BMAL1 influences metabolism, signaling, and contractile function of the heart.

Understanding circadian gene function: animal models of tissue-specific circadian disruption

Circadian rhythms are the daily patterns that occur within an organism, from gene expression to behavior. These rhythms are governed not only externally by environmental cues but also internally, with cell-autonomous molecular clock mechanisms present nearly ubiquitously throughout the cells of organisms. In more complex organisms, it has been suggested that the clock mechanisms serve varied functions depending on the tissue in which they are found. By disrupting core circadian gene function in specific tissues of animal models, the various roles of the circadian clock in differing tissues can begin to be defined. This review provides an overview of the model organisms used to elucidate tissue-specific functions of the molecular circadian clock.

Genetic factors in exercise adoption, adherence and obesity

Physical activity and exercise play critical roles in energy balance. While many interventions targeted at increasing physical activity have demonstrated efficacy in promoting weight loss or maintenance in the short term, long term adherence to such programmes is not frequently observed. Numerous factors have been examined for their ability to predict and/or influence physical activity and exercise adherence. Although physical activity has been demonstrated to have a strong genetic component in both animals and humans, few studies have examined the association between genetic variation and exercise adherence. In this review, we provide a detailed overview of the non-genetic and genetic predictors of physical activity and adherence to exercise. In addition, we report the results of analysis of 26 single nucleotide polymorphisms in six candidate genes examined for association to exercise adherence, duration, intensity and total exercise dose in young adults from the Training Interventions and Genetics of Exercise Response (TIGER) Study. Based on both animal and human research, neural signalling and pleasure/reward systems in the brain may drive in large part the propensity to be physically active and to adhere to an exercise programme. Adherence/compliance research in other fields may inform future investigation of the genetics of exercise adherence.

Vitamin D and calcium-sensing receptor polymorphisms differentially associate with resting energy expenditure in peripubertal children

Given that calcium metabolism is influenced by genes and is tightly linked to energy-utilizing pathways, this study evaluated the association of single nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) and calcium-sensing receptor (CASR) with resting energy expenditure (REE). In 273 boys and girls, 7-12 years of age, cross-sectional REE was measured via indirect calorimetry, body composition by DXA, and dietary measures by 24-h recall. SNPs for VDR Cdx-2 (rs11568820) and CASR A986S (rs1801725) were genotyped using the Illumina Golden Gate assay. Multiple linear regression models were used to determine the association between SNPs and REE. African American carriers of the 'A' VDR Cdx2 allele had increased levels of REE in the overall sample, and this association was apparent among participants with an adiposity level of <25 % and 30 % body fat in males and females, respectively. For CASR, an association between carriers of the 'A' allele and REE was observed only in those in the upper median of calcium intake. VDR and CASR variants are associated with REE in children and are influenced by levels of calcium intake and adiposity. Our results bring awareness to mechanisms underlying the regulation of REE and biological and dietary influential factors.

Real-time methylomic aberrations during initiation and progression of induced human mammary epithelial cell tumorigenesis

AIM

Neoplastic transformation provides one of the few existing opportunities to analyze molecular changes in real time during the initiation and progression of breast cancer.

MATERIALS & METHODS

Human mammary epithelial cells underwent neoplastic reprogramming, generating one line of semitransformed, premalignant cells and two separate, temporal lines of fully transformed human mammary epithelial cells (THMECs). An Illumina Infinium HumanMethylation27 BeadChip was used to analyze DNA methylation alterations in 27,578 CpG loci at three consecutive time points over an 80-day (d) transformation period.

RESULTS

The mean β value for semitransformed human mammary epithelial cells CpG loci (0.245) was much greater than for either THMEC-40d (0.055) or THMEC-80d (0.066), indicating a large loss of methylation after neoplastic induction. In addition, 54% of CpG loci were hypermethylated during the THMEC-40d to THMEC-80d transition. We observed that the CpG loci exhibiting DNA methylation changes during early oncogenesis were enriched for biological functions like cellular movement; this was distinctly different than in the later, more progressive stages of the transformation process enriched for processes involving differentiation.

CONCLUSION

The timing of major methylomic changes may be important in directing the cell toward a more cancerous phenotype. In addition, gene-specific hypermethylation appears to silence developmentally related genes, leading to dedifferentiation.

Integrative genomic analysis of the human immune response to influenza vaccination

Identification of the host genetic factors that contribute to variation in vaccine responsiveness may uncover important mechanisms affecting vaccine efficacy. We carried out an integrative, longitudinal study combining genetic, transcriptional, and immunologic data in humans given seasonal influenza vaccine. We identified 20 genes exhibiting a transcriptional response to vaccination, significant genotype effects on gene expression, and correlation between the transcriptional and antibody responses. The results show that variation at the level of genes involved in membrane trafficking and antigen processing significantly influences the human response to influenza vaccination. More broadly, we demonstrate that an integrative study design is an efficient alternative to existing methods for the identification of genes involved in complex traits. DOI:http://dx.doi.org/10.7554/eLife.00299.001.

Influence of dark phase restricted high fat feeding on myocardial adaptation in mice

Prolonged high fat feeding is associated with myocardial contractile dysfunction in rodents. However, epidemiological data do not necessarily support the concept that fat-enriched diets adversely affect cardiac function in humans. When fed in an ad libitum manner, laboratory rodents consume chow throughout the day. In contrast, humans typically consume food only during the awake phase. Discrepancies between rodent and human feeding behaviors led us to hypothesize that the time of day at which dietary lipids are consumed significantly influences myocardial adaptation. In order to better mimic feeding behavior in humans, mice were fed (either a control or high fat diet) only during the 12-hour dark phase (i.e., no food was provided during the light phase). We report that compared to dark phase restricted control diet fed mice, mice fed a high fat diet during the dark phase exhibit: 1) essentially normal body weight gain and energy balance; 2) increased fatty acid oxidation at whole body, as well as skeletal and cardiac muscle (in the presence of insulin and/or at high workloads) levels; 3) induction of fatty acid responsive genes, including genes promoting triglyceride turnover in the heart; 4) no evidence of cardiac hypertrophy; and 5) persistence/improvement of myocardial contractile function, as assessed ex vivo. These data are consistent with the hypothesis that ingestion of dietary fat only during the more active/awake period allows adequate metabolic adaptation, thereby preserving myocardial contractile function. This article is part of a Special Issue entitled "Focus on cardiac metabolism".

Quantitative analysis of light-phase restricted feeding reveals metabolic dyssynchrony in mice

Background

Considerable evidence suggests that the time of day at which calories are consumed markedly impacts body weight gain and adiposity. However, a precise quantification of energy balance parameters during controlled animal studies enforcing time-of-day-restricted feeding is currently lacking in the absence of direct human interaction.

Objective

The purpose of the present study was therefore to quantify the effects of restricted feeding during the light (sleep) phase in a fully-automated, computer-controlled comprehensive laboratory animal monitoring system (CLAMS) designed to modulate food access in a time-of-day-dependent manner. Energy balance, gene expression (within metabolically-relevant tissues), humoral factors, and body weight were assessed.

Results

We report that relative to mice fed only during the dark (active) phase, light (sleep) phase fed mice: 1) consume a large meal upon initiation of food availability; 2) consume greater total calories per day; 3) exhibit a higher RER (indicative of decreased reliance on lipid/fatty acid oxidation); 4) exhibit tissue-specific alterations in the phases and amplitudes of circadian clock and metabolic genes in metabolically active tissues (greatest phase differences observed in the liver, and diminution of amplitudes in epididymal fat, gastrocnemius muscle, and heart); 5) exhibit diminished amplitude in humoral factor diurnal variations (e.g., corticosterone); and 6) exhibit greater weight gain within 9 days of restricted feeding.

Conclusions

Collectively, these data suggest that weight gain following light (sleep) phase restricted feeding is associated with significant alterations in energy balance, as well as dyssynchrony between metabolically active organs.

Sodium nitrite protects against kidney injury induced by brain death and improves post-transplant function

Renal injury induced by brain death is characterized by ischemia and inflammation and limiting it is a therapeutic goal that could improve outcomes in kidney transplantation. Brain death resulted in decreased circulating nitrite levels and increased infiltrating inflammatory cell infiltration into the kidney. Since nitrite stimulates nitric oxide signaling in ischemic tissues, we tested whether nitrite therapy was beneficial in a rat model of brain death followed by kidney transplantation. Nitrite, administered over 2 hours of brain death, blunted the increased inflammation without affecting brain death-induced alterations in hemodynamics. Kidneys were transplanted after 2 hours of brain death and renal function followed over 7 days. Allografts collected from nitrite-treated brain dead rats showed significant improvement in function over the first 2 to 4 days post transplantation compared to untreated brain dead animals. Gene microarray analysis after 2 hours of brain death without or with nitrite therapy showed the latter significantly altered the expression of about 400 genes. Ingenuity Pathway analysis indicated multiple signaling pathways were affected by nitrite, including those related to hypoxia, transcription and genes related to humoral immune responses. Thus, nitrite-therapy attenuates brain death-induced renal injury by regulating responses to ischemia and inflammation, ultimately leading to better post-transplant kidney function.

Chronobiological Effects on Obesity

The development of obesity is the consequence of a multitude of complex interactions between both genetic and environmental factors. It has been suggested that the dramatic increase in the prevalence of obesity over the past 30 years has been the result of environmental changes that have enabled the full realization of genetic susceptibility present in the population. Among the many environmental alterations that have occurred in our recent history is the ever-increasing dyssynchrony between natural cycles of light/dark and altered patterns of sleep/wake and eating behavior associated with our "24-hour" lifestyle. An extensive research literature has established clear links between increased risk for obesity and both sleep deprivation and shift work, and our understanding of the consequences of such dyssynchrony at the molecular level is beginning to emerge. Studies linking alterations in cellular circadian clocks to metabolic dysfunction point to the increasing importance of chronobiology in obesity etiology.

Association of factor V gene polymorphism with arteriovenous graft failure

BACKGROUND

Dialysis grafts fail due to recurrent stenosis and thrombosis. Vasoactive and prothrombotic substances affecting intimal hyperplasia or thrombosis may modify graft outcomes.

STUDY DESIGN

Genetic polymorphisms association study of patients enrolled in a multicenter randomized clinical trial.

SETTING & PARTICIPANTS

354 Dialysis Access Consortium (DAC) Study patients receiving a new graft with DNA samples obtained. Participants were randomly assigned to treatment with aspirin plus dipyridamole versus placebo.

PREDICTOR

DNA sequence polymorphisms for the following candidate genes and their interaction with the study intervention: methylenetetrahydrofolate reductase (MTHFR), heme oxygenase 1 (HO-1), factor V (F5), transforming growth factor β1 (TGFβ1), klotho, nitric oxide synthase (NOS), and angiotensin-converting enzyme (ACE).

OUTCOME

Graft failure (>50% stenosis, angioplasty, thrombosis, surgical intervention, or permanent loss of function).

RESULTS

During a median patient follow-up of 34.3 months, 304 grafts failed. After adjusting for clinical factors (patient age, sex, access location, diabetes, cardiovascular disease, baseline aspirin use, body mass index, timing of graft placement, and study treatment) and genetic ancestral background, single-nucleotide polymorphism rs6019 of the factor V gene was associated significantly with graft failure in a dominant model (HR of 1.70 [95% CI, 1.32-2.19; P < 0.001] for G/C and G/G genotypes vs C/C genotypes). There was no significant association between graft failure and polymorphisms of MTHFR, HO-1, TGFβ1, klotho, NOS, or ACE.

LIMITATIONS

Small sample size.

CONCLUSION

The rs6019 genotype of Factor V is associated with increased risk of graft failure. Anticoagulation may reduce graft failure in patients with the G/C or G/G genotypes.

Health behavior change: can genomics improve behavioral adherence?

The National Human Genome Research Institute recommends pursuing "genomic information to improve behavior change interventions" as part of its strategic vision for genomics. The limited effectiveness of current behavior change strategies may be explained, in part, by their insensitivity to individual variation in adherence responses. The first step in evaluating whether genomics can inform customization of behavioral recommendations is evidence reviews to identify adherence macrophenotypes common across behaviors and individuals that have genetic underpinnings. Conceptual models of how biological, psychological, and environmental factors influence adherence also are needed. Researchers could routinely collect biospecimens and standardized adherence measurements of intervention participants to enable understanding of genetic and environmental influences on adherence, to guide intervention customization and prospective comparative effectiveness studies.

O-GlcNAcylation, novel post-translational modification linking myocardial metabolism and cardiomyocyte circadian clock

The cardiomyocyte circadian clock directly regulates multiple myocardial functions in a time-of-day-dependent manner, including gene expression, metabolism, contractility, and ischemic tolerance. These same biological processes are also directly influenced by modification of proteins by monosaccharides of O-linked β-N-acetylglucosamine (O-GlcNAc). Because the circadian clock and protein O-GlcNAcylation have common regulatory roles in the heart, we hypothesized that a relationship exists between the two. We report that total cardiac protein O-GlcNAc levels exhibit a diurnal variation in mouse hearts, peaking during the active/awake phase. Genetic ablation of the circadian clock specifically in cardiomyocytes in vivo abolishes diurnal variations in cardiac O-GlcNAc levels. These time-of-day-dependent variations appear to be mediated by clock-dependent regulation of O-GlcNAc transferase and O-GlcNAcase protein levels, glucose metabolism/uptake, and glutamine synthesis in an NAD-independent manner. We also identify the clock component Bmal1 as an O-GlcNAc-modified protein. Increasing protein O-GlcNAcylation (through pharmacological inhibition of O-GlcNAcase) results in diminished Per2 protein levels, time-of-day-dependent induction of bmal1 gene expression, and phase advances in the suprachiasmatic nucleus clock. Collectively, these data suggest that the cardiomyocyte circadian clock increases protein O-GlcNAcylation in the heart during the active/awake phase through coordinated regulation of the hexosamine biosynthetic pathway and that protein O-GlcNAcylation in turn influences the timing of the circadian clock.

Set points, settling points and some alternative models: theoretical options to understand how genes and environments combine to regulate body adiposity

The close correspondence between energy intake and expenditure over prolonged time periods, coupled with an apparent protection of the level of body adiposity in the face of perturbations of energy balance, has led to the idea that body fatness is regulated via mechanisms that control intake and energy expenditure. Two models have dominated the discussion of how this regulation might take place. The set point model is rooted in physiology, genetics and molecular biology, and suggests that there is an active feedback mechanism linking adipose tissue (stored energy) to intake and expenditure via a set point, presumably encoded in the brain. This model is consistent with many of the biological aspects of energy balance, but struggles to explain the many significant environmental and social influences on obesity, food intake and physical activity. More importantly, the set point model does not effectively explain the 'obesity epidemic'--the large increase in body weight and adiposity of a large proportion of individuals in many countries since the 1980s. An alternative model, called the settling point model, is based on the idea that there is passive feedback between the size of the body stores and aspects of expenditure. This model accommodates many of the social and environmental characteristics of energy balance, but struggles to explain some of the biological and genetic aspects. The shortcomings of these two models reflect their failure to address the gene-by-environment interactions that dominate the regulation of body weight. We discuss two additional models--the general intake model and the dual intervention point model--that address this issue and might offer better ways to understand how body fatness is controlled.

Ethnic bias in anthropometric estimates of DXA abdominal fat: the TIGER study

BACKGROUND/INTRODUCTION

The purpose of this study was to examine the race/ethnicity bias of using waist circumference (WC) to estimate abdominal fat.

METHODS

A total of 771 females and 484 males (17-35 yr) were tested one to three times during a prescribed 30-wk aerobic exercise program. The race/ethnicity distribution for women was non-Hispanic white, 29%; Hispanic, 25%; African American (AA), 35%; Asian Indian, 3%; and Asian, 8%. The distribution for men was non-Hispanic white, 37%; Hispanic, 26%; AA, 22%; Asian Indian, 5%; and Asian, 10%. Abdominal fat (L1-L5) was estimated from whole-body scanning using dual-energy x-ray absorptiometry (DXA Abd-Fat).

RESULTS

DXA Abd-Fat varied by race/ethnicity after accounting for WC and height in both women and men. The increase in DXA Abd-Fat per increase in WC was lower in the Asian and Asian-Indian women than that in the other women. The increase in DXA Abd-Fat per increase in WC was higher in the AA men and lower in the Asian-Indian men than that in the other men. These differential race/ethnicity effects were most notable when WC exceeded ≍90 cm in the women and ≍100 cm in the men, values which are consistent with current definitions of abdominal obesity in the United States.

CONCLUSIONS

Prediction equations for abdominal fat using WC that do not account for race/ethnicity group provide biased estimates. These results may affect assessment of disease risk from abdominal obesity among racial/ethnic groups.

Evidence suggesting that the cardiomyocyte circadian clock modulates responsiveness of the heart to hypertrophic stimuli in mice

Circadian dyssynchrony of an organism (at the whole-body level) with its environment, either through light-dark (LD) cycle or genetic manipulation of clock genes, augments various cardiometabolic diseases. The cardiomyocyte circadian clock has recently been shown to influence multiple myocardial processes, ranging from transcriptional regulation and energy metabolism to contractile function. The authors, therefore, reasoned that chronic dyssychrony of the cardiomyocyte circadian clock with its environment would precipitate myocardial maladaptation to a circadian challenge (simulated shiftwork; SSW). To test this hypothesis, 2- and 20-month-old wild-type and CCM (Cardiomyocyte Clock Mutant; a model with genetic temporal suspension of the cardiomyocyte circadian clock at the active-to-sleep phase transition) mice were subjected to chronic (16-wks) biweekly 12-h phase shifts in the LD cycle (i.e., SSW). Assessment of adaptation/maladaptation at whole-body homeostatic, gravimetric, humoral, histological, transcriptional, and cardiac contractile function levels revealed essentially identical responses between wild-type and CCM littermates. However, CCM hearts exhibited increased biventricular weight, cardiomyocyte size, and molecular markers of hypertrophy (anf, mcip1), independent of aging and/or SSW. Similarly, a second genetic model of selective temporal suspension of the cardiomyocyte circadian clock (Cardiomyocyte-specific BMAL1 Knockout [CBK] mice) exhibits increased biventricular weight and mcip1 expression. Wild-type mice exhibit 5-fold greater cardiac hypertrophic growth (and 6-fold greater anf mRNA induction) when challenged with the hypertrophic agonist isoproterenol at the active-to-sleep phase transition, relative to isoproterenol administration at the sleep-to-active phase transition. This diurnal variation was absent in CCM mice. Collectively, these data suggest that the cardiomyocyte circadian clock likely influences responsiveness of the heart to hypertrophic stimuli.

Early patterns of gene expression correlate with the humoral immune response to influenza vaccination in humans

BACKGROUND

Annual vaccination is the primary means for preventing influenza. However, great interindividual variability exists in vaccine responses, the cellular events that take place in vivo after vaccination are poorly understood, and appropriate biomarkers for vaccine responsiveness have not been developed.

METHODS

We immunized a cohort of healthy male adults with a licensed trivalent influenza vaccine and performed a timed assessment of global gene expression before and after vaccination. We analyzed the relationship between gene expression patterns and the humoral immune response to vaccination.

RESULTS

Marked up regulation of expression of genes involved in interferon signaling, positive IL-6 regulation, and antigen processing and presentation, were detected within 24 hours of immunization. The late vaccine response showed a transcriptional pattern suggestive of increased protein biosynthesis and cellular proliferation. Integrative analyses revealed a 494-gene expression signature--including STAT1, CD74, and E2F2--which strongly correlates with the magnitude of the antibody response. High vaccine responder status correlates with increased early expression of interferon signaling and antigen processing and presentation genes.

CONCLUSIONS

The results highlight the role of a systems biology approach in understanding the molecular events that take place in vivo after influenza vaccination and in the development of better predictors of vaccine responsiveness.

Regulation of fatty acid metabolism by cell autonomous circadian clocks: time to fatten up on information?

Molecular, cellular, and animal-based studies have recently exposed circadian clocks as critical regulators of energy balance. Invariably, mouse models of genetically manipulated circadian clock components display features indicative of altered lipid/fatty acid metabolism, including differential adiposity and circulating lipids. The purpose of this minireview is to provide a comprehensive summary of current knowledge regarding the regulation of fatty acid metabolism by distinct cell autonomous circadian clocks. The implications of these recent findings for cardiometabolic disease and human health are discussed.

Generalized equations for estimating DXA percent fat of diverse young women and men: the TIGER study

PURPOSE

Popular generalized equations for estimating percent body fat (BF%) developed with cross-sectional data are biased when applied to racially/ethnically diverse populations. We developed accurate anthropometric models to estimate dual-energy x-ray absorptiometry BF% (DXA-BF%) that can be generalized to ethnically diverse young adults in both cross-sectional and longitudinal field settings.

METHODS

This longitudinal study enrolled 705 women and 428 men (aged 17-35 yr) for 30 wk of exercise training (3 d·wk(-1) for 30 min·d(-1) of 65%-85% predicted V˙O2max). The distribution of ethnicity was as follows: 37% non-Hispanic white, 29% Hispanic, and 34% African-American. DXA-BF%, skinfold thicknesses, and body mass index (BMI) were collected at baseline and after 15 and 30 wk.

RESULTS

Skinfolds, BMI, and race/ethnicity were significant predictors of DXA-BF% in linear mixed model regression analysis. For comparable anthropometric measures (e.g., BMI), DXA-BF% was lower in African-American women and men but higher in Hispanic women compared with non-Hispanic white. Addition of BMI to the skinfold model improved the SEE for women (3.6% vs 4.0%), whereas BMI did not improve prediction accuracy of men (SEE = 3.1%).

CONCLUSIONS

These equations provide accurate predictions of DXA-BF% for diverse young women and men in both cross-sectional and longitudinal settings. To our knowledge, these are the first published body composition equations with generalizability to multiple time points, and the SEE estimates are among the lowest published in the literature.

Short-term administration of rhGH increases markers of cellular proliferation but not milk protein gene expression in normal lactating women

Growth hormone is one of few pharmacologic agents known to augment milk production in humans. We hypothesized that recombinant human GH (rhGH) increases the expression of cell proliferation and milk protein synthesis genes. Sequential milk and blood samples collected over four days were obtained from five normal lactating women. Following 24 h of baseline milk and blood sampling, rhGH (0.1 mg/kg/day) was administered subcutaneously once daily for 3 days. Gene expression changes were determined by microarray studies utilizing milk fat globule RNA isolated from each milk sample. Following rhGH administration, DNA synthesis and cell cycle genes were induced, while no significant changes were observed in the expression of milk synthesis genes. Expression of glycolysis and citric acid cycle genes were increased by day 4 compared with day 1, while lipid synthesis genes displayed a circadian-like pattern. Cell cycle gene upregulation occurred after a lag of ∼2 days, likely explaining the failure to increase milk production after only 3 days of rhGH treatment. We conclude that rhGH induces expression of cellular proliferation and metabolism genes but does not induce milk protein gene expression, as potential mechanisms for increasing milk production and could account for the known effect of rhGH to increase milk production following 7-10 days.

Rare copy number variants disrupt genes regulating vascular smooth muscle cell adhesion and contractility in sporadic thoracic aortic aneurysms and dissections

Thoracic aortic aneurysms and dissections (TAAD) cause significant morbidity and mortality, but the genetic origins of TAAD remain largely unknown. In a genome-wide analysis of 418 sporadic TAAD cases, we identified 47 copy number variant (CNV) regions that were enriched in or unique to TAAD patients compared to population controls. Gene ontology, expression profiling, and network analysis showed that genes within TAAD CNVs regulate smooth muscle cell adhesion or contractility and interact with the smooth muscle-specific isoforms of α-actin and β-myosin, which are known to cause familial TAAD when altered. Enrichment of these gene functions in rare CNVs was replicated in independent cohorts with sporadic TAAD (STAAD, n = 387) and inherited TAAD (FTAAD, n = 88). The overall prevalence of rare CNVs (23%) was significantly increased in FTAAD compared with STAAD patients (Fisher's exact test, p = 0.03). Our findings suggest that rare CNVs disrupting smooth muscle adhesion or contraction contribute to both sporadic and familial disease.

The myocardial contractile response to physiological stress improves with high saturated fat feeding in heart failure

Impaired myocardial contractile function is a hallmark of heart failure (HF), which may present under resting conditions and/or during physiological stress. Previous studies have reported that high fat feeding in mild to moderate HF/left ventricular (LV) dysfunction is associated with improved contractile function at baseline. The goal of this study was to determine whether myocardial function is compromised in response to physiological stress and to evaluate the global gene expression profile of rats fed high dietary fat after infarction. Male Wistar rats underwent ligation or sham surgery and were fed normal chow (NC; 10% kcal fat; Sham + NC and HF + NC groups) or high-fat chow (SAT; 60% kcal saturated fat; Sham + SAT and HF + SAT groups) for 8 wk. Myocardial contractile function was assessed using a Millar pressure-volume conductance catheter at baseline and during inferior vena caval occlusions and dobutamine stress. Steady-state indexes of systolic function, LV +dP/dt(max), stroke work, and maximal power were increased in the HF + SAT group versus the HF + NC group and reduced in the HF + NC group versus the Sham + NC group. Preload recruitable measures of contractility were decreased in HF + NC group but not in the HF + SAT group. beta-Adrenergic responsiveness [change in LV +dP/dt(max) and change in cardiac output with dobutamine (0-10 microg x kg(-1) x min(-1))] was reduced in HF, but high fat feeding did not further impact the contractile reserve in HF. The contractile reserve was reduced by the high-fat diet in the Sham + SAT group. Microarray gene expression analysis revealed that the majority of significantly altered pathways identified contained multiple gene targets correspond to cell signaling pathways and energy metabolism. These findings suggest that high saturated fat improves myocardial function at rest and during physiological stress in infarcted hearts but may negatively impact the contractile reserve under nonpathological conditions. Furthermore, high fat feeding-induced alterations in gene expression related to energy metabolism and specific signaling pathways revealed promising targets through which high saturated fat potentially mediates cardioprotection in mild to moderate HF/LV dysfunction.

VAMP8/endobrevin is overexpressed in hyperreactive human platelets: suggested role for platelet microRNA

BACKGROUND

Variation in platelet reactivity contributes to disorders of hemostasis and thrombosis, but the molecular mechanisms are not well understood.

OBJECTIVES

To discover associations between interindividual platelet variability and the responsible platelet genes, and to begin to define the molecular mechanisms altering platelet gene expression.

SUBJECTS/METHODS

Two hundred and eighty-eight healthy subjects were phenotyped for platelet responsiveness. Platelet RNA from subjects demonstrating hyperreactivity (n=18) and hyporeactivity (n=11) was used to screen the human transcriptome.

RESULTS

Distinctly different mRNA profiles were observed between subjects with differing platelet reactivity. Increased levels of mRNA for VAMP8/endobrevin, a critical v-SNARE involved in platelet granule secretion, were associated with platelet hyperreactivity (Q=0.0275). Validation studies of microarray results showed 4.8-fold higher mean VAMP8 mRNA levels in hyperreactive than hyporeactive platelets (P=0.0023). VAMP8 protein levels varied 13-fold among platelets from these normal subjects, and were 2.5-fold higher in hyperreactive platelets (P=0.05). Among our cohort of 288 subjects, a VAMP8 single-nucleotide polymorphism (rs1010) was associated with platelet reactivity in an age-dependent manner (P<0.003). MicroRNA-96 was predicted to bind to the 3'-untranslated regionof VAMP8 mRNA and was detected in platelets. Overexpression of microRNA-96 in VAMP8-expressing cell lines caused a dose-dependent decrease in VAMP8 protein and mRNA, suggesting a role in VAMP8 mRNA degradation.

CONCLUSIONS

These findings support a role for VAMP8/endobrevin in the heterogeneity of platelet reactivity, and suggest a role for microRNA-96 in the regulation of VAMP8 expression.

Exposing college students to exercise: the Training Interventions and Genetics of Exercise Response (TIGER) study

OBJECTIVE

The Training Interventions and Genetics of Exercise Response (TIGER) study is an exercise program designed to introduce sedentary college students to regular physical activity and to identify genetic factors that influence response to exercise.

PARTICIPANTS

A multiracial/ethnic cohort (N = 1,567; 39% male), age 18 to 35 years, participated in the study.

METHODS

Subjects underwent 30 weeks of exercise training, 3 days/week, for 40 minutes at 65% to 85% of age- and gender-predicted maximum heart rate reserve. Multiple measures of body size/composition, heart rate, and blood pressure were obtained.

RESULTS

A total of 1,567 participants, (39% male), age 18 to 35 years, participated in the TIGER study. The prevalence of overweight/obesity in participants was 48.0%/19.3% in non-Hispanic Whites, 55.3%/24.2% in Hispanic Whites, 54.9%/25.4% in African Americans, and 38.3%/11.3% in Asians. Average within-semester retention was 68%, but overall retention (30 weeks, 2 semesters) was 20%.

CONCLUSIONS

The TIGER study represents an efficacious strategy for introducing college-aged individuals to regular aerobic exercise.

Direct regulation of myocardial triglyceride metabolism by the cardiomyocyte circadian clock

Maintenance of circadian alignment between an organism and its environment is essential to ensure metabolic homeostasis. Synchrony is achieved by cell autonomous circadian clocks. Despite a growing appreciation of the integral relation between clocks and metabolism, little is known regarding the direct influence of a peripheral clock on cellular responses to fatty acids. To address this important issue, we utilized a genetic model of disrupted clock function specifically in cardiomyocytes in vivo (termed cardiomyocyte clock mutant (CCM)). CCM mice exhibited altered myocardial response to chronic high fat feeding at the levels of the transcriptome and lipidome as well as metabolic fluxes, providing evidence that the cardiomyocyte clock regulates myocardial triglyceride metabolism. Time-of-day-dependent oscillations in myocardial triglyceride levels, net triglyceride synthesis, and lipolysis were markedly attenuated in CCM hearts. Analysis of key proteins influencing triglyceride turnover suggest that the cardiomyocyte clock inactivates hormone-sensitive lipase during the active/awake phase both at transcriptional and post-translational (via AMP-activated protein kinase) levels. Consistent with increased net triglyceride synthesis during the end of the active/awake phase, high fat feeding at this time resulted in marked cardiac steatosis. These data provide evidence for direct regulation of triglyceride turnover by a peripheral clock and reveal a potential mechanistic explanation for accelerated metabolic pathologies after prevalent circadian misalignment in Western society.

Circadian biology and sleep: missing links in obesity and metabolism?

This supplement highlights key talks presented at the Pennington Symposium. The collected papers provide a state of the art review of circadian biology at the basic and clinical levels in the context of nutrition, obesity and sleep medicine. Investigators from multiple disciplines attempted to translate new information concerning molecular mechanisms into practical clinical applications, as well as foster new research hypotheses and directions to this exciting field of science and medicine. Furthermore, we hope to spark the interest and attention of the next generation of scientists who will tackle the questions presented by the changing interface between technology, lifestyle and biological rhythms.

The role of cell-specific circadian clocks in metabolism and disease

Biological rhythms are an integral component of essentially all aspects of life. These rhythms are controlled in part by circadian clocks, transcriptionally based mechanisms that synchronize the organism to its changing environment. The central circadian clock is located within the suprachiasmatic nucleus of the brain, while peripheral clocks are located within virtually all cells outside of the suprachiasmatic nucleus. Although our understanding of central clock structure and function is well advanced, the role of peripheral clocks in whole body energy metabolism is just beginning to be elucidated. Both central and peripheral circadian clocks likely regulate many physiological functions, including insulin sensitivity, endocrine regulation, energy homeostasis, satiety signalling, cellular proliferation and cardiovascular function. Widely varying phenotypes have been reported following global genetic disruption of the clock mechanism in mice, with phenotype dependent on both the clock component targeted and genetic background. The inconsistency in phenotypes associated with clock disruption may be due, in part, to cell-specific effects of the circadian clocks. To address this question, many laboratories have begun generating animal models of cell type-specific clock disruption. In this review, we summarize the existing literature on tissue-specific models of circadian clock disruption and provide a focus for future research in this area.