Atrial fibrillation (AF) is a common and serious arrhythmia. Current treatments are of limited efficacy, and most do not treat the atrial structural remodeling (hypertrophy and fibrosis) that underlies most clinical AF. Our group has created an experimental dog model of atrial mechanical stretch called the simultaneous atrial and ventricular pacing (SAVP) model (which results in atrial fibrosis and susceptibility to AF) in order to study novel treatments for structural remodeling induced AF. Omega-3 polyunsaturated fatty acids (n3 PUFAs), particularly the marine derived forms eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to be effective in treating arrhythmias (including AF) in some animal studies and clinical trials. The mechanism for this effect of n3 PUFAs is not well understood. In this study we sought to characterize the n3 PUFA effect on AF vulnerability, atrial electrophysiology, histology, and gene expression, and determine relevant mechanisms. Dogs were paced for 0, 2, 7 or 14 days and given n3 PUFAs, olive oil or nothing. Prophylactic n3 PUFAs significantly reduced both AF vulnerability and conduction slowing in SAVP dogs (%AF inducibility: 9.2±8.8 vs. 4.7±6.3; global atrial conduction time: 75±11ms vs. 65±6ms [SAVP 14 days vs. SAVP 14 days with n3 PUFAs, P<0.05 for both comparisons]). Prophylactic n3 PUFAs also reduced inflammation (mean CD18 grade: 2.1±0.8 vs. 1.3±0.6 [SAVP 2 days vs. SAVP 2 days with n3 PUFAs, P=0.055]), hypertrophy (myocyte cross-sectional area: 498±64µm2 vs. 322±111µm2 [SAVP 14 days vs. SAVP 14 days with n3 PUFAs, P<0.05]), and fibrosis (%collagen area vs. unpaced dogs: 178±58 vs. 127±37 [SAVP 14 days vs. SAVP 14 days with n3 PUFAs, P<0.05]). N3 PUFAs were also found to reduce the expression of structural remodeling related molecules such as TGF-β, EGF, ERK and Akt. N3 PUFAs given after some pacing had already occurred were found to be less effective at reducing AF vulnerability and structural remodeling. The results of this study suggest that, in the SAVP model, n3 PUFAs reduce vulnerability to AF by attenuation of adverse structural remodeling at the genetic level.

SPARC is a highly conserved trimodular Ca2+- and Collagen-binding matricellular protein with diverse functions during development, wound healing and cancer metastasis. Our lab previously generated an embryonic lethal Drosophila SPARC null mutant, Df(3R)nm136, analysis of which revealed that SPARC was required for the deposition of Collagen IV into basal laminae and normal nervous system development during embryogenesis. In contrast to these previous studies, my data revealed that SPARC is not required for the deposition of Collagen IV into embryonic basal laminae or embryonic nervous system development. Further analysis showed that the Df(3R)nm136 chromosome carried a second-site mutation in the Neuralized locus which caused the nervous system defects and embryonic lethality previously associated with a loss of SPARC. Removal of this second site mutation and reanalysis of the SPARC mutant phenotype revealed that SPARC is required for larval development where it appears to play a role in the regulation fat body remodelling. SPARC mutant fat bodies showed changes in cell shape and basal lamina remodelling which resemble the fat body remodelling process that normally occurs during pre-pupal stages via up-regulation of MMP2 in response to the steroid hormone ecdysone. The effects of loss of SPARC on fat body cells were shown to be cell autonomous. Structure-function analysis of SPARC showed that secretion of SPARC is required for its function, whereas Domain1 is dispensable. Together, my studies indicate that SPARC has essential intra and extracellular roles during Drosophila larval fat body development.

El objetivo principal de la presente tesis doctoral fue estudiar la posibilidad de mejorar la calidad nutritiva de la leche de oveja y de cabra, y en particular la concentración de ácido linoleico conjugado (CLA) mediante la incorporación de diferentes fuentes de lípidos vegetales a la ración.El primer capitulo fue realizado para investigar los efectos de la suplementación con Semillas Enteras de Lino (WLS) o de Aceite de Lino (LSO) sobre la producción y composición de leche, así como el perfil de ácidos grasos (AG) de leche y queso. Las concentraciones de AG de cadena media y de AG saturados fueron más bajas, y las de AG insaturados y de cadena larga más altas en la leche de los tratamientos con lino. El ácido alfa-linolénico aumentó más con la semilla que con el aceite, mientras que el CLA (ácido ruménico, RA) aumentó más con el aceite que con la semilla. En paralelo, el ácido trans-11 vaccénico (TVA) aumentó únicamente con el aceite. De manera general, la composición en AG de quesos curados (60 días de maduración) fue similar a la de la leche del correspondiente tratamiento experimental.En el segundo capítulo se utilizaron 24 ovejas de raza Lacaune para estudiar los efectos de las semillas enteras de cártamo (WSF) sobre la producción y composición de leche, así como sobre su perfil de AG, en particular CLA. En la leche producida por el grupo WSF, las concentraciones de AG de cadena larga y de AG insaturados fueron más altas, mientras que las de AG de cadena corta y de AG saturados fueron más bajas. Las concentraciones de CLA (RA) y de TVA en leche fueron mayores en el grupo WSF.En el tercer capítulo, se realizaron dos ensayos experimentales con el objetivo de estudiar los efectos de la inclusión del aceite de soja (SBO) y de un complejo de enzimas fibrolíticas (E) sobre la digestibilidad de los nutrientes de la ración y la producción y composición de leche. Cuando SBO se utilizó solo, no tuvo consecuencias sobre las digestibilidades de MS, MO y FND. El tratamiento E incrementó las digestibilidades de MS, MO y FND. Sin embargo, cuando fueron utilizados conjuntamente (SBO+E) el aceite de soja anuló las mejoras ofrecidas por E. En el experimento de ordeño, las concentraciones de ácido oleico, TVA, linoleico y CLA fueron más altas por efecto del aceite, con respuestas más evidentes en raza Lacaune que en Manchega. La adición de enzimas incrementó la producción de leche. El cuarto capítulo consistió en un experimento llevado a cabo con 24 cabras Murciano-Granadinas con el objeto de estudiar los efectos de la suplementación con SBO sobre la producción y composición de leche, y su perfil de AG, especialmente de CLA y de TVA. La concentración de AG de cadena corta y media en leche se redujo, mientras que la de AG de cadena larga aumentó. SBO redujo el ratio de AG saturados/insaturados así como el índice de aterogenicidad. Comparado con el control, las concentraciones de CLA y TVA en la leche fueron triplicadas por efecto del aceite de soja.En conclusión, los lípidos de origen vegetal incrementaron el CLA (RA) y el ácido trans-11 vaccénico, obteniéndose los incrementos más altos con la utilización de aceites vegetales, especialmente con aceite de soja en ovejas de raza Lacaune o en cabras Murciano-Granadinas. Por el contrario, las semillas enteras de lino permitieron un mayor aumento del ácido alfa-linolénico, de tipo n-3. A la dosis utilizada, el aceite de soja no afectó la digestibilidad de la fibra, pero anuló el efecto positivo de las enzimas observado sobre la digestibilidad. / The present Doctoral Thesis was carried out to study the possibility of enhance the nutritive quality of sheep and goat milk using the incorporation of different sources of vegetal fat to the diet.The first experiment was performed to investigate the effects of feeding whole linseed (WLS) or linseed oil (LSO) to dairy ewes on lactational performance, milk and cheese fatty acids profile and CLA content. Short chain fatty acids (FA) remained unchanged while medium chain and saturated FA were decreased and large chain and unsaturated FA (including mono and poly-unsaturated FA) were increased by WLS and LSO. Feeding WLS was more useful on increasing milk alpha-linolenic acid content, while feeding LSO allowed a higher increase of rumenic acid. Similarly, trans-11 C18:1 (trans vaccenic acid or TVA), precursor of CLA, was only increased by LSO. Except for short chain FA, the FA profile of 60-d-old cheeses made from milk of the ewes receiving the experimental treatments was similar to the FA profile of the milk.In the second study, a total of 24 Lacaune dairy ewes at 49±7 DIM were used to study the effects of adding whole safflower seeds (WSF) to the concentrate on dairy performance and Conjugated Linoleic Acid (CLA) in milk. Feeding WSF increased concentrations of long chain and unsaturated FA, and decreased short chain and saturated FA. Concentrations of rumenic (cis-9, trans-11 CLA) and TVA acids in milk were increased in animals fed WSF. In addition, WSF reduced the saturated/unsaturated FA ratio and the atherogenicity index of the milk fat, but increased the ratio n-6/n-3 FA. In the third chapter, two experiments were performed to study the effects of feeding soybean oil (SBO) and a fibrolytic enzyme complex (E) on nutrients digestibility (trial 1) and lactational performance of dairy ewes (trial 2). When used alone, feeding SBO increased ether extract digestibility without varying the DM, OM and NDF digestibilities, while the E treatment increased DM, OM and NDF digestibilities. In contrast, when fed together with the enzyme complex, SBO reduced digestibilities of DM, OM and NDF, being the enzyme supplement unable to reincrease nutrients digestibility. In a milking trial, milk FA variations were higher in Lacaune than in Manchega ewes. Oleic acid, TVA, linoleic acid and CLA were increased.The fourth chapter consisted in an experiment where a total of 24 Murciano-Granadina dairy goats were used to study the effects of feeding soybean oil (SBO) on lactational performance and milk fatty acids (FA), particularly CLA and TVA. Feeding SBO increased milk concentrations of linoleic, oleic and stearic FA. As a consequence, feeding SBO reduced the saturated to unsaturated FA ratio and the atherogenicity index, but increased the n-6/n-3 FA ratio. Compared with the control, milk contents of cis-9, trans-11 CLA and TVA in the SBO treatment were almost triplicated. In conclusion, vegetal fat increased CLA (rumenic acid) and TVA, being the highest increases obtained in the case of feeding vegetal oils, particularly when using soybean oil in Lacaune ewes or Murciano-Granadina goats. In contrast, whole linseed grains enhance better the alpha-linolenic acid (n-3). Under the circumstances of our experiment, soybean oil did not affect fiber digestibility except when used together with the fibrolytic enzyme complex, in which case reduced DM, OM and fiber digestibilities.

A Low-fat Diet Containing Heated Soybean Oil Promotes Hyperglycemia in C57BL/6J Mice Introduction: The metabolic effects of consuming mildly oxidized lipids as compared to highly oxidized lipids are not well documented. Consumption of highly oxidized polyunsaturated fatty acids, even in a low-fat diet, may be a threat to one’s health. Previous studies in our lab have shown that mice consuming soybean oil heated for 3 hours, compared to unheated, gain less body weight, but more fat pad mass, and 3T3-L1 adipocytes treated with soybean oil heated for ≥ 6 hours have abrogated triglyceride accumulation. Another study showed that rats fed highly oxidized oil (heated > 24 hrs), as compared to fresh soybean oil and fish oil, had lower fat pad mass and weight gain but developed glucose intolerance. This suggested that the extent of lipid oxidation determined the subsequent metabolic risk. Objective: Our aim, in the current study, is to investigate if a low-fat diet with soybean oil heated for increasing time points (3h, 6h and 9h) alter fat mass and glucose tolerance. Methods: Six week old, male, C57BL/6J mice were randomly divided into six groups (n=8/group). Three groups were fed a low fat diet with soybean oil heated for 3 (3hr-HO), 6 (6hr-HO), or 9 (9hr-HO) hours for 16 weeks. Another three groups were pair-fed to each of the 3hr-HO, 6hr-HO and 9hr-HO groups with a low-fat diet containing unheated oil (PF-UHO). Food consumption was recorded every 3-4 days, and body weights were recorded weekly. Soy oil in the diets was analyzed for products of oxidation. At 16 weeks, blood glucose levels were measured after a 6 hour fast; fat pad and liver weights were recorded, and blood was collected by cardiac puncture for serum insulin analysis. Results: Final weight gain was not significantly different between all HO groups as a percent of their respective PF groups (p >0.05). The feeding efficiency for 3hr, 6hr, and 9hr-HO groups as a percent of PF was 92.75, 113.02, and 111.28, respectively. Mean weights of all fat pads for HO groups decreased with heating time as a percent of PF, although these differences were not statistically significant. Blood glucose was lowest in the 3hr-HO group and significantly increased from 3hr-HO group to 6hr-HO group (p=0.021) as a percent of PF. Serum insulin levels decreased for the HO groups as heating time increased, although these differences were not statistically significant. Conclusion: Consuming a diet with increasing amounts of oxidized lipids decreased fat pad mass and insulin levels, while increasing fasting glucose levels. This paradoxical relationship between increased glucose in the presence of decreased insulin in c57BL/6J mice could be due to either reduced insulin secretion or increased insulin resistance. Further research in our lab will aim to analyze triglyceride accumulation in the liver and muscle cells of these mice to determine if oxidized lipids promote ectopic fat deposition.

Background: Green tea is rich in catechin, a polyphenolic antioxidant. Consumption of green tea or extract from green tea has been shown to result in weight loss, increased fat oxidation, and elevated energy expenditure in mice and humans. Green tea consumption has also been shown to result in increased exercise endurance in mice and improved maximal oxygen uptake (VO2max) in humans. It is not clearly known whether green tea consumption would increase exercise endurance in humans. Objective: The aim of this study was to determine if the daily consumption of decaffeinated green tea extract for 4-5 weeks, would improve exercise endurance in humans, as measured by running 2.5 miles on an indoor track. Subjects, Design, and Methods: This study was based on a randomized, double-blind design. Fourteen, normal, healthy individuals volunteered for participation and completed the study. They were divided into two groups (n= 7 for each group). All participants completed 2 endurance trials, 1 at the baseline and 1 at the conclusion of the study. Each trial consisted of a 2.5 mile run around the GSU Recreation Center indoor track. One group consumed green tea extract pill containing 900 mg catechins and the other group consumed a placebo for 4-5 weeks between run trials. Results: Green tea and placebo groups improved their running times, however, there was no significant difference between these two groups in mean end time (P = 0.74). Under one statistical analysis, the green tea group significantly improved their running time compared to baseline (P = 0.019), while the placebo group did not. However, under another statistical analysis (removing one participant due to possible skewing effect), both groups significantly improved their running time over baseline (P< 0.05). Conclusions: This study was not able conclusively ascertain whether or not the daily consumption of green tea improved endurance performance as measured by 2.5 mile run times. Results of this study should be used with caution due to small sample size. Future studies are warranted on the impact of green tea consumption on exercise endurance, using a longer duration and a larger sample size than has been studied.

<p>Various factors, including low levels of physical activity (PA), and high consumption levels of sugar-sweetened drinks (SD), have been implicated in the general increase of fat mass (FM) levels seen in youth. <b>Purpose</b>: To determine if a significant relationship exists between fat mass (FM) and physical activity (PA) or sugar-sweetened drink (SD), in boys and girls, using longitudinal analysis. <b>Methods</b>: 105 boys and 103 girls were assessed repeatedly during childhood and adolescence, for a maximum of 7 years. Height was measured annually, as was fat free mass (FFM) and FM estimated by dual X-ray absorptiometry (DXA). PA was evaluated bi-annually using a questionnaire for children (PAQ-C/A: 1 low, 5 high), and SD was assessed using a 24-hour dietary intake questionnaire completed 1-4 times/year. Years from peak height velocity were used as a biological age indicator. Random effects models were used to analyze the data, subsequent to log linearization of the FM variable since it was not initially normally distributed. <b>Results</b>: The constructed model, controlling for maturation, FFM, and adjusted energy intake, found no interaction effect between SD and PA (p>0.05). After removal of the interaction term from the model, SD was found to have no significant relationship (p>0.05) with FM of boys or girls. In contrast, PA level was found to have a significant relationship (p<0.05) with FM of males; but not with FM of females. <b>Conclusion</b>: The longitudinal models employed revealed a significant negative relationship between level of PA and FM in males but not females, after controlling for maturational status, body size and dietary energy intake. This finding lends support, to proponents of increasing PA in youth to control FM. Regarding SD and FM, the models employed showed no relationship. Future investigation with more complex models, accounting for more covariates, may be warranted in this area.</p>

The ventromedial hypothalamic nucleus (VMH) is an important central effector site involved in activating brown adipose tissue (BAT) or non-shivering thermogenesis. VMH neurons have previously been shown to be thermally responsive to changes in local temperature of the preoptic area/anterior hypothalamus (PO/AH). However, the thermoresponsiveness of VMH neurons of room temperature acclimatized and cold acclimatized rats to peripheral thermal stimulation has not been tested. In this thesis, a series of studies was designed to determine the thermoresponsiveness of VMH neurons to peripheral (scrotal) thermal stimulation of rats. Extracelluiar VMH neuronal activity was recorded from urethane anaesthetized male Sprague-Dawley rats, which were acclimatized either to room temperature (21°C for 4 weeks) or to cold (4°C for 4 weeks) prior to testing, during scrotal cooling and heating with glass-micropipettes filled with 0.5 M sodium acetate containing 2% pontamine sky blue. The rats' colonic temperatures were kept at normothermia (37°C), or hypothermia (33-35°C) during scrotal thermal stimulation. In the room temperature acclimatized rats, VMH neurons were temperature responsive to scrotal heating and cooling and were classified as warm responsive (WRN), cold responsive (CRN) and temperature non-responsive neurons (TNRN), based on their thermal coefficients. The ratio of VMH WRNs and CRNs was similar to that of thermoresponsive neurons observed in other brain regions (eg, the PO/AH and thalamus). VMH WRNs and CRNs were further classified as biphasic or monophasic in nature according to their thermal responses to scrotal heating and cooling. VMH neurons sustained their thermoresponsiveness to repeated trials of scrotal thermal stimulation with colonic temperatures maintained at 37°C or when colonic temperatures were acutely lowered from 37°C to 35°C and 33°C. In addition, scrotal thermal signals specifically altered neuronal activity of VMH thermoresponsive neurons, as changes in EEG activity did not occur with changes in VMH neuronal activity. Scrotal thermal inputs were functionally shown to be transmitted via the medial preoptic nucleus (MPO) prior to reaching the VMH nucleus because thermoresponsive VMH neuronal activity was blocked with the pretreatment of lidocaine into the MPO. Scrotal heating or cooling to 21°C-acclimatized rats did not increase IBAT temperatures, inferring that scrotal cooling had not evoked IBAT thermogenesis in this group. In cold acclimatized (CA) rats, prolonged (over 2 hours) and transient localized scrotal cooling caused IBAT temperatures to increase, inferring that scrotal cooling activated BAT thermogenesis. Mean basal firing rates of all recorded VMH neurons of CA-groups significantly increased, compared to those of VMH neurons observed in room temperature acclimatized (RA) groups. More VMH CRNs than WRNs were recorded in the CA-group and the thermoresponsiveness (ie, thermal coefficient) of VMH CRNs significantly increased during localized scrotal cooling in the cold acclimatized group, compared to thermal coefficients of VMH CRNs of the RA-groups. (Abstract shortened by UMI.)

The metabolic syndrome has become a major public health challenge world-wide and, at least in the industrialized world, the prevalence of the metabolic syndrome is increasing. There is evidence to show that biological and lifestyle risk factors for metabolic syndrome are present in adolescence, which suggests that the antecedents of the disease may lie in early life. The period of adolescence is characterized by a decline in physical activity (PA; lack of PA is a lifestyle risk factor for metabolic syndrome) and an increase in fat mass deposition (a biological risk factor for metabolic syndrome). Therefore, investigating how the development of these two variables relates to adult cardiometabolic risk is important to fuel early intervention. A factor which has the potential to influence these two risk factors, and thus ultimately the metabolic syndrome, is the timing of biological maturity (i.e. whether an individual is early, average or late maturing when compared to peers of the same age). The influence of biological maturity has largely been overlooked in previous research; therefore, the general objective of this thesis was to investigate the associations between biological maturity, adolescent PA and fat mass development, and young adult cardiometabolic risk. Three studies were necessary to realize this objective, and together help to elucidate the role of biological maturity in the adolescent decline in physical activity, fat development, and the development of adult metabolic syndrome. Ultimately, this information will aid in the development and implementation of interventions to decrease prevalence of metabolic syndrome.<p> Study 1: The purpose of study 1 was to investigate whether observed gender differences in objectively measured PA in children (8 to 13 years) are confounded by biological maturity differences. Methods: Four hundred and one children (194 boys and 207 girls) volunteered for this study. An Actigraph accelerometer was used to obtain 7 consecutive days of minute-by-minute PA data on each participant. Minutes of moderate to vigorous PA per day (MVPA), continuous minutes of MVPA per day (CMVPA), and minutes of vigorous PA per day (VPA) were derived from the accelerometer data. Age at peak height velocity (APHV), an indicator of somatic maturity, was predicted and individuals aligned by this biological age (years from APHV). Gender differences in the PA variables were analyzed using a two-way (gender X age) ANOVA. Results: Levels of PA decreased with increasing chronological ages in both genders (p<0.05). When aligned on chronological age, boys had a higher MVPA at 10 through 13 years, a higher CMVPA at 9 through 12 years, and a higher VPA at 9 though 13 years (p<0.05). When aligned on biological age, PA declined with increasing maturity (p<0.05); however gender differences between biological age groups disappeared. Conclusion: The observed age-related decline in adolescent boys and girls PA is antithetical to public health goals and as such is an important area of research. In order to fully understand gender disparities in PA, consideration must be given to the confounding effects of biological maturity.<p> Study 2: Understanding the influence of biological age (BA) on the decline in PA would better inform researchers about the effective timing of intervention. The purpose of study 2 was to describe the PA levels and perceived barriers to PA of adolescent girls grouped by school grade and biological maturity status (i.e., early or late maturing) within grades. Methods: 221 girls (aged 8-16 years; grades 4-10) wore an Actical accelerometer for 7 days and then completed a semi-structured, open ended questionnaire on perceived barriers to PA over the 7 day period. Predicted APHV and recalled age at menarche were used to assess maturity among the elementary and high school girls, respectively. Maturity and grade group differences in PA were assessed using MANCOVA and independent sample t-test, and barriers to PA using chi squared statistics. Results: Daily minutes spent in MVPA decreased by 40% between grades 4 to 10. Within grade groupings, no differences in PA were found between early and late maturing girls (p>0.05). Grades 4-6 participants cited more interpersonal (i.e., social) barriers. Grades 9-10 participants cited more institutional barriers to PA, primarily revolving around the institution of school. No differences were found in types of barriers reported between early and late maturing girls. Conclusion: Since PA and types of perceived barriers to PA were dependent on grade, future research should work to identify the most salient (i.e., frequent and limiting) barriers to PA by chronological age in youth.<p> Study 3: Although the metabolic syndrome is thought to be mainly a consequence of obesity, the mechanisms underpinning its development are not that well understood. The purpose of study 3 was to examine total body fat mass (FM), trunk FM and PA developmental trajectories (aligned to BA; years from APHV) of individuals categorized as low and high for cardiometabolic risk at 26 years, while investigating biological and lifestyle risk factors. Methods: The sample were 55 males and 76 females from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-2007) who were assessed from childhood to young adulthood and had a measure of cardiometabolic risk at young adulthood (26.0 + 2.3 yrs). Height was measured biannually. Total body FM and trunk FM was assessed annually by dual energy-X-ray absorptiometry. PA and dietary intake was evaluated two to three times annually using surveys. Individuals were grouped into maturity status groups (early, average or late) depending on their APHV. Two composite cardiometabolic risk scores were calculated for males and females separately. The first was derived for a sub-sample (N=48) by summing the standardized residuals of inverted high-density lipoprotein cholesterol, homeostasis model assessment for insulin resistance, mean arterial pressure (MAP) and fasting triglyceride levels. A second score was derived for the whole sample by summing the standardized residuals for MAP. Scores for both samples were regressed on to age and adult smoking status. High and low cardiometabolic risk groups were determined based on a sex- specific median split of risk scores. Data were analyzed using random effects models. Models were built in a stepwise procedure with predictor variables added one at a time, using the log likelihood ratio statistic to determine if one model was a significant improvement over the previous one. Results: The final model indicated that once the independent effects of maturity (years from APHV) and height were controlled, the high risk group males and females had significantly (p<0.05) greater total body FM and trunk FM development at all ages. No association was found between young adult cardiometabolic risk and development of PA. Furthermore, in general, timing of biological maturity was not associated with development of PA or FM. Conclusion: Young adults at higher cardiometabolic risk have greater body fat as early as 8 years of age, which lends support to early intervention.<p> General Conclusions: Adolescence has been highlighted as a critical period for the development of adult disease, such as the metabolic syndrome. Results from this thesis support this contention by showing a decrease in PA (by both chronological and biological age) in males and females across adolescence. It further showed that an increase in total and central fatness during adolescence may be critical for the development of the metabolic syndrome in adulthood. Timing of biological maturity, in general, was not shown to have an independent impact on adolescent or young adult PA, adolescent perceived barriers to PA, fat mass development, or young adult cardiometabolic risk. However, further research is required before definitive conclusions can be made about the short and long term impacts of timing of biological maturity on health.

Animal models of bingeing have typically used stress to induce bingeing. A recent model, limited-access to high-fat diet (HFD), has shown that caloric restriction and stress were not required to induce bingeing in rats. This study replicated this model in mice, explored the fat content within the model, and investigated locomotor activation associated with binge-eating. Adult mice were maintained on a restricted feeding (RF) schedule of 2 h/d of access to chow or ad lib access to chow, and then provided limited access to 45% HFD or 84% HFD for 30 min 3 d/ week for 6 total snack sessions. Circadian activity was monitored for RF animals offered 84% HFD, and after 6 snack sessions were complete, allowed continuous access to the 45% HFD or the 84% HFD for two weeks to explore rebound feeding. Bingeing, defined by increasing intakes across days, was reported for mice offered 45% HFD regardless of deprivation state (RF or ad lib), while mice offered 84% HFD only exhibited bingeing when they were restricted. Comparison of male and female mice maintained RF, offered 45% HFD snack, showed that females had higher intake (kcals/g-bw) while ad lib fed mice exhibited no sex differences. Circadian recordings for female RF mice offered 84% HFD showed shifts in activity from the first hour of dark cycle to the hour preceding the snack and supported that offering the HFD produced alterations in food-associated arousal. During rebound, female RF mice given 84% HFD showed the highest intakes in week 1, and then exhibited a marked decline in week 2. The week 1 intake for RF animals were to regain lost body weight and that homeostatic-like intake in week 2 allowed normal body weight maintenance. Results of this investigation support human data that females are more susceptible to binge-type eating disorder, shows that limited access to palatable foods for females under caloric restriction induces changes in circadian activity, and reveals that using mice in this model requires more investigation to optimize binge-behavior. Diet comparisons also suggest that homeostatic and reward mechanisms may have an additive effect on bingeing.

This research examines the effect of a nutrition education intervention to change attitudes and other factors associated with eating breakfast and consuming low-fat dairy and whole-grains. Adolescents (n = 106) 11 to 15 years old were recruited from afterschool programs in Los Angeles County, California. Participants in the treatment group (n = 57) met once weekly for 60 minutes during seven weeks. The curriculum focused on changing attitudes, subjective norms, and perceived behavioral control toward eating breakfast along with including low-fat dairy and whole grains. The first three lessons focused on basic nutrition concepts. The later lessons focused on identifying barriers and overcoming barriers, goal-setting, and identifying methods to stay motivated. Questionnaires were administered at baseline and post-intervention. Data were analyzed using SAS statistical analysis program (v. 9.2). Eighty-eight percent of participants were Hispanic, 55% were girls, and mean age was 12 years. One-hundred six adolescents completed the questionnaire at baseline and 75 completed it at post-intervention. Cronbach alpha statistic for subjective norms and attitudes toward eating breakfast, consuming low-fat dairy and whole-grains were 0.67 and higher for each dependant variable. Intention was significantly predicted by attitudes, subjective norms, and perceived behavioral control; however, as these models do not differentiate change, additional models were run with interactions between group (treatment versus control) and the change variables. Significant changes in perceived behavioral control were observed among participants in the treatment group regarding drinking skim milk, 1% milk, and 2% milk respectively (p < .05; p < .001; p < .001) and attitude (p < .05). No change was observed in breakfast eating or consumption of wholegrains