In light of alarming rises in the prevalence of obesity worldwide, tackling the obesity ‘epidemic’ is now a national health priority in many countries. Increasingly, population measures that provide accurate estimates of body fatness in children are required. Body mass index (BMI), or weight standardised for height, remains the most cost-effective and practical tool in this regard. However, there is evidence that the association between BMI and body fatness is variable in children from different ethnic backgrounds. The primary aim of this thesis was to investigate the appropriateness of BMI thresholds for defining overweight and obesity in female children and adolescents from five diverse ethnic groups. Secondary objectives were to examine the associations between weight control practices and perceptions, and to compare objectively-measured physical activity levels with participation in active transport (AT). In order to achieve the primary aim stated above, it was necessary to obtain valid and reliable measures of body fat percentage (%BF) in a large sample of children. Bioelectrical impedance analysis (BIA) is well suited for this purpose, providing a portable and cost-effective means to estimate fat-free mass (and subsequently %BF). While equations exist for European, Maori, and Pacific Island children, findings from the preliminary study described in Chapter 2 demonstrate that there are no BIA equations appropriate for Chinese and Indian children. Given that these two groups are two of the fastest growing ethnicities in New Zealand, a new equation was developed that enables Asian girls to be included in future BIA research. The main study of this thesis involved a large-scale investigation of body composition in New Zealand’s five major ethnic groups (European, Maori, Pacific Island, East Asian, and South Asian). A total of 1,081 adolescent girls aged 11-16 years participated in the Girls’ Activity and Body Composition (ABC) Study. To extend the age range, data were combined with another study of 5-11-year-old New Zealand children (595 girls), coined the Body-Size and Steps in Children (BASIC) Study. Both studies measured BMI from height and weight, %BF from bio impedance measurements, and physical activity using sealed multiday memory pedometers over five consecutive days. A questionnaire was also administered to the adolescent-aged girls to gather data related to weight perceptions and practices. Initial analyses of the main dataset demonstrated that existing BMI definitions of overweight were relatively insensitive for predicting excess %BF in South and East Asian girls. Conversely, low specificity was observed for Pacific Island and Maori children. These findings provided the rationale for the second set of analyses: the development of BMI cut-off points that correspond to an equivalent level of %BF across all ethnicities. The adjusted BMI curves for overweight and obesity ranged from an average of 3.3 and 3.8 kg.m-2 (respectively) lower than international standards in South Asian girls to 1.5 and 1.9 kg.m-2 higher in Pacific Island girls. Clearly, the proposed changes will have significant effect on our estimates of overweight and obesity in this population group. Subsequent investigation revealed that many adolescent girls misclassify their weight status. However, the number of girls trying to lose weight exceeded those who perceived themselves as being overweight, with the magnitude of the difference dependent on ethnicity. It was concluded that interventions and educational campaigns that assist girls in recognising a state of excess body fat are a priority for all ethnic groups to ensure that behavioural changes necessary to combat widespread overweight and obesity are adopted. Finally, it was observed that the physical activity levels of the participants were significantly lower on weekends (9,528  4,407) than on weekdays (12,597  3,630). Furthermore, a consistent decline in daily step counts was observed with age: after adjustment for ethnicity and socioeconomic status (SES), girls in school years 9-10 achieved 2,469 (weekday) and 4,011 (weekend) fewer steps than girls in years 1-2. Daily step counts also varied by ethnicity, with Maori girls the most active and South Asian girls the least active. Overall, girls who used AT to and from school averaged 1,052 more weekday steps than those who did not use AT. These data suggest that adolescent-aged girls and girls of Asian descent are priority groups for future physical activity interventions, and that the promotion of AT in girls appears to be worthwhile.

Body fat, regional body fat and bone mineral mass, are linked to health conditions such as obesity and osteoporosis. The ethnic comparison of body composition may help to explain and understand the difference of health outcomes and health status in different ethnic groups. NZ Chinese is the largest Asian group in New Zealand, however, knowledge about health risks and body composition for NZ Chinese is very limited. Therefore, the aims of this thesis were: 1) To compare the relationships between body mass index (BMI) and percentage body fat (%BF) of European (M29, F37), Maori (M23, F23), Pacific people (M15, F23), and Asian Indian (M29, F25) (existing data) with NZ Chinese aged 30-39 years; 2) To compare fat distribution, appendicular skeletal muscle mass (ApSM), bone mineral density (BMD) and limb bone lengths across these five ethnic groups. A convenience sample of healthy NZ Chinese (M20, F23) was selected by BMI to cover a wide range of body fatness. Total and regional body fat, fat free mass (FFM) and bone mineral content were measured by whole-body Dual-energy X-ray absorptiometry (DEXA). The main study findings were: • For a fixed BMI, NZ Chinese had a higher %BF than European and less %BF than Asian Indian. At a %BF equivalent to a BMI of 30 kg.m-2 in Europeans (WHO threshold for obesity), BMI values for Asian Indian and NZ Chinese women were 5.8 and 2.2 BMI units lower than European, respectively, and for Asian Indian and NZ Chinese men, 8.2 and 3.0 BMI units lower. • Abdominal-to-thigh fat ratio of NZ Chinese was significantly higher than that of European (P<0.001) and similar to that of Asian Indian. NZ Chinese had a significantly higher central-to-appendicular fat ratio than both Asian Indian and European (P<0.001). NZ Chinese was centrally fatter than European and Asian Indian. • For the same height and weight, NZ Chinese had significantly less FFM (-2.1 kg, P=0.039) and ApSM (-1.4kg, P=0.007) than European. NZ Chinese had significantly more FFM (+3.2 kg, P=0.001) than Asian Indian and similar ApSM to Asian Indian. • For the same weight, NZ Chinese had a similar BMD as European for female and male. NZ Chinese male had a higher BMD (+0.07 g.cm-2, P= 0.001) than Asian Indian male. • Among the five ethnic groups, NZ Chinese had the shortest leg (-1.5cm, P=0.016) and arm bone lengths (-2.3cm, P=0.001) (measured by DEXA) for the same DEXA height. Therefore, the relationship between percent body fat and BMI for Asian Indian and NZ Chinese differs from Europeans and from each other, which indicates that different BMI thresholds for obesity may be required for these Asian ethnic groups. Given the relatively high percentage body fat, low appendicular skeletal muscle mass and high central fat to appendicular fat ratio of NZ Chinese aged 30-39 years demonstrated in this study, promotion of healthy eating and physical activity is needed to be tailored for NZ Chinese. The NZ Chinese community should be advised to keep fit, prevent limited movements in older age, and to prevent obesity and obesity-related diseases.

This thesis investigates whether fats, akin to other taste stimuli, exhibit sensory properties such as mixture interactions. In order to determine gustatory, rather than tactile or olfactory effects, viscosity-controlled emulsions of deodorised oils were used as the base to which taste stimuli were incorporated and presented to a panel of trained assessors. In preliminary qualitative assessments, panellists described the 10% olive oil emulsion as saltier, stronger, fattier and having a more lingering aftertaste than the non-oil control, suggesting that oil modulates taste duration as well influencing taste intensity and/or perceived quality. Panellists were unable to rate the oil/fat taste per se with any degree of certainty hence further experiments examined the effect of oil on the perception of taste mixtures. In mixture interaction experiments, the addition of oil did not result in mixture suppression or enhancement for sweet, salty, sour or bitter while it significantly enhanced umami. To determine the locus of interaction, when MSG and oil were presented to each side of the tongue separately, the enhancement effect disappeared indicating a peripheral mechanism of interaction, similar to the attenuation of chilli burn by oil. In contrast, suprathreshold sucrose sweetness was enhanced by the contralateral presentation of oil, indicating sensory processing at a higher locus. Furthermore, the addition of oil significantly reduced bitterness in a caffeine-MSG mixture. Since earlier experiments did not indicate any interaction between oil and bitterness, the decrease in the perceived bitterness of this binary mixture is attributed to an increase in umami which is likely to have suppressed bitterness, the perceptually dominant component in this mixture. These findings suggest a gustatory role for fats in modulating the taste profile of mixtures, in particular, enhancing total taste intensity, prolonging taste duration, and enhancing umami. A taste receptor-based model of fat perception provides for an orosensory mechanism capable of signalling the arrival of the most energy-dense nutrient, essential fatty acids and fat-soluble vitamins. The chemosensory signal may also be the basis for hedonic responses with subsequent implications for intake.

In recent years, the general public has recognized the dangers of a high fat diet and are demanding meat with lower fat content. This demand has stimulated research in the growth and regulation of adipocytes. However, despite much effort, no adipocyte-specific plasma membrane markers from any species are available as an aid to accurately distinguish adipocytes from non-adipocytes. One potential candidate for such a marker in porcine adipocytes has been identified by Killefer and Hu (1990b). Characterization of the cDNA for this protein, designated porcine adipocyte membrane protein (PAMP), is presented here. Sequence for the 910 by clone is 80% similar to an internal region of a rat prostaglandin F[subscript 2��] receptor regulator protein (FPRP) described by Orlickey (1996). Western blot analysis suggests that the pig protein is a homotetramer held together with disulfide bonds which form very close to the transmembrane region making the tetramer extremely difficult to reduce to monomeric units. Oligonucleotide primers were designed to amplify a genomic fragment by the polymerase chain reaction (PCR) and for a reverse transcriptase PCR (RT-PCR) assay to study the expression of the mRNA. A 2114 bp genomic clone revealed one intron in the coding region. A serum-free primary cell culture system was used to study the expression of the mRNA. Although message was detected every day over a ten day period, it appeared to peak between 6 to 8 days after plating. The PAMP protein is clearly of the same family as the rat FPRP but its size and conformation are quite different so it is not clear what function it performs in porcine adipocytes. Further experiments should focus on attaining full length cDNA's, confirming the molecular conformation of the protein, and assessing its function in a serum-free primary cell culture system. / Graduation date: 1997

Regular aerobic exercise may reduce cardiovascular disease (CVD) risk in part by lowering the concentration of inflammatory markers such as C-reactive protein (CRP). While studies in diseased populations have shown significant decreases in CRP concentrations with regular aerobic training, little has been conclusively determined regarding the effects of aerobic training on CRP concentrations in apparently healthy, untrained populations who may not be adequately screened for CVD risk by traditional methods. PURPOSE: To examine the effects of a 17-wk half marathon training program (TP) on CRP concentrations, aerobic fitness, and body composition in apparently healthy, untrained men. METHODS: Twenty men (29.3 ± 1.0 yr, 37.0 ± 1.6 mL•kg-1•min-1 VO2max, 29.1 ± 1.8% body fat) registered as training subjects (TRN) in a 17-wk half marathon TP. An additional 22 men (27.8 ± 1.4 yr, 38.8 ± 1.0 mL•kg-1•min-1 VO2max, 26.8 ± 1.4% BF) served as controls (CON). Fasting blood samples were taken at four time points over the TP and were analyzed for CRP and interleukin-6 (IL-6) concentrations. Aerobic capacity (VO2max) and body fat (BF%) were measured before and after the TP. RESULTS: No significant changes in CRP (P=0.69) or IL-6 concentrations (P=0.73) were seen in TRN as a result of the TP despite significant improvements in VO2max (42.2 ± 1.9 ml•kg-1•min-1, P<0.0001), resting heart rate (P =0.004), BF% (P =0.03) and BMI (P =0.05). No significant changes in CRP, aerobic fitness, BMI or BF% were detected in CON over time. CONCLUSION: Moderate, long-term aerobic training does not appear to affect CRP concentrations in apparently healthy, untrained men despite significant improvements in BW, BF%, BMI, and VO2max.

Background: Over the past decade obesity has doubled in children aged 6-11 and tripled among adolescents aged 12-19. One trend that has coincided with this increased obesity prevalence is decreased meal frequency, which may impact blood sugar, meal size, cortisol release, insulin release, and appetite controls that include the release of leptin and ghrelin. Ultimately, these changes may result in a simultaneous lowering of the metabolic (i.e., fat-free) mass and a rising of the fat mass. Purpose: To assess food/beverage intake in a way that would determine if large deviations in energy balance (EB) during the day were related to body fat percent (BF%). Methods: Using an IRB-approved protocol, male and female children were assessed using NutriTiming® (NutriTiming LLC, 2011) software, which simultaneously assesses energy intake from consumed foods and beverages and energy expenditure from activities with different intensities. A 24-hour recall questionnaire and interview, with at least one parent present, was used to obtain data, which represented a typical school day. BF% was assessed using an 8-mode bioelectrical impedance segmental body composition analyzer (Tanita, Model BC-418). Statistical analysis was performed with SPSS (ver. 18). Results: A total of 16 children ranging in age from 8-14 years were interviewed. Due to incomplete data on 4 subjects, 12 subjects (6 boys; 6 girls ranging in age from 9-14 years; mean=11.41 ± 1.5) were included in the data analysis. Energy intakes averaged 1,984 ± 510 kcal; and energy expenditure averaged 1,689 ± 351 kcal. Average BF% was 24.3 ± 4.9. Using Spearman correlation and independent group t-test (with the mean energy balance as the cut-point) traditional end-of-day energy balance (24-hr energy in vs. 24-hr energy out) was not statistically associated with body fat %, and there was no difference in BF% between those above and below the end-of-day EB mean. However, more hours spent in an energy surplus (EB > 0) was significantly associated with lower body fat % (r=-0.914; PP

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.

<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 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.

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.