Background: Vitamin D may have beneficial effects on cardiometabolic disease, but the evidence is equivocal. This may be due to unaccounted confounders, such as lifestyle factors and genetic variation. We examined the association between circulating 25-hydroxyvitamin D [25(OH)D] and biomarkers of cardiometabolic disease risk, including biomarkers of inflammation, glycemic dysregulation and lipid metabolism, and a panel of 54 plasma proteomic biomarkers, and determined whether lifestyle variables and genetic variation modified these associations. Methods: Participants were from the Toronto Nutrigenomics and Health Study, an ethnically diverse population of individuals aged 20-29 years. Anthropometric measurements were obtained. Participants answered general health and lifestyle and food frequency questionnaires and provided a fasting blood sample for biochemical measurements and genotyping. Results: Across ethnic groups, women who used hormonal contraceptives (HC) had higher 25(OH)D and C-reactive protein (CRP) than women HC non-users and men. Circulating 25(OH)D was positively associated with CRP in the entire population in models not accounting for HC use. However, there was no association after accounting for HC use. 25(OH)D was also not associated with inflammatory cytokines after adjusting for HC use. 25(OH)D was inversely associated with insulin, HOMA-IR, and HOMA-Beta among Caucasians and East Asians and among men and women HC non-users. No biomarkers were associated with 25(OH)D among South Asians and women HC users, although non-significant inverse trends were observed for markers of glycemic dysregulation. Only two of the 54 plasma proteomic biomarkers were associated with 25(OH)D in women HC non-users, and none were associated in men. Among women HC users, after accounting for hormone dose, only three proteins were associated with 25(OH)D. Finally, 25(OH)D affected the association between rs2239182, a variant in the vitamin D receptor (VDR) and the pro-inflammatory cytokine interferon gamma-induced protein 10 (IP-10). However, the association was suggestive of heterosis and may have been due to chance. Conclusions: We identified a confounding effect of HC use on the association between 25(OH)D, biomarkers of inflammation and plasma proteomic biomarkers. In addition, HC use might also affect the association between 25(OH)D and biomarkers of glycemic dysregulation. Genetic variation in VDR did not modify any associations.

Background: Vitamin D may have beneficial effects on cardiometabolic disease, but the evidence is equivocal. This may be due to unaccounted confounders, such as lifestyle factors and genetic variation. We examined the association between circulating 25-hydroxyvitamin D [25(OH)D] and biomarkers of cardiometabolic disease risk, including biomarkers of inflammation, glycemic dysregulation and lipid metabolism, and a panel of 54 plasma proteomic biomarkers, and determined whether lifestyle variables and genetic variation modified these associations. Methods: Participants were from the Toronto Nutrigenomics and Health Study, an ethnically diverse population of individuals aged 20-29 years. Anthropometric measurements were obtained. Participants answered general health and lifestyle and food frequency questionnaires and provided a fasting blood sample for biochemical measurements and genotyping. Results: Across ethnic groups, women who used hormonal contraceptives (HC) had higher 25(OH)D and C-reactive protein (CRP) than women HC non-users and men. Circulating 25(OH)D was positively associated with CRP in the entire population in models not accounting for HC use. However, there was no association after accounting for HC use. 25(OH)D was also not associated with inflammatory cytokines after adjusting for HC use. 25(OH)D was inversely associated with insulin, HOMA-IR, and HOMA-Beta among Caucasians and East Asians and among men and women HC non-users. No biomarkers were associated with 25(OH)D among South Asians and women HC users, although non-significant inverse trends were observed for markers of glycemic dysregulation. Only two of the 54 plasma proteomic biomarkers were associated with 25(OH)D in women HC non-users, and none were associated in men. Among women HC users, after accounting for hormone dose, only three proteins were associated with 25(OH)D. Finally, 25(OH)D affected the association between rs2239182, a variant in the vitamin D receptor (VDR) and the pro-inflammatory cytokine interferon gamma-induced protein 10 (IP-10). However, the association was suggestive of heterosis and may have been due to chance. Conclusions: We identified a confounding effect of HC use on the association between 25(OH)D, biomarkers of inflammation and plasma proteomic biomarkers. In addition, HC use might also affect the association between 25(OH)D and biomarkers of glycemic dysregulation. Genetic variation in VDR did not modify any associations.

Background: It has been reported that the ratio of limb fat to trunk fat (LF/TF) is associated with markers of cardiometabolic risk in elderly men and women. However, it is unknown if LF/TF is associated with cardiometabolic risk beyond that explained by LF and TF independently. Objective: To determine if LF/TF is associated with markers of cardiometabolic risk in elderly men and women after control for LF and TF. A secondary objective was to examine the independent associations of LF and TF with markers of cardiometabolic risk. Methods: Subjects included abdominally obese men (n=58) and women (n=78) between 60 and 80 years of age. Regional adiposity was quantified using magnetic resonance imaging. Insulin resistance, fasting glucose, HDL-cholesterol, plasma triglycerides and adiponectin were determined. Regression analyses and partial correlations were used to assess the independent associations between variables. Results: After control for potential confounders, TF was positively associated with fasting glucose, insulin resistance and plasma triglycerides, and negatively associated with HDL-cholesterol (p<0.05). These associations were strengthened after further control for LF (p<0.05). LF was not associated with any marker of cardiometabolic risk after control for potential confounders (p>0.05). However, after further control for TF, LF was positively associated with HDL-cholesterol and negatively associated with plasma triglycerides (p<0.05). Plasma adiponectin was independently associated with both LF and TF in elderly women (p<0.05) but was not independently associated with either depot in elderly men (p>0.05). LF/TF was not associated with any marker of cardiometabolic risk after control for LF and TF. Conclusions: These results suggest that it is the absolute, rather than relative amounts of LF and TF which have the greatest influence on cardiometabolic risk in elderly men and women. Further, these results suggest that the associations between plasma adiponectin and regional adiposity are significantly influenced by sex in elderly men and women. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2008-12-05 16:08:10.868

No description available.

Emerging evidence suggests that sedentary behaviour is independently associated with cardiometabolic disease risk in school-aged children and youth. This thesis includes 4 related studies in the pursuit of 2 objectives: 1) To determine the cross-sectional association of sedentary time, interruptions in sedentary time, sedentary bout length, and total movement variability with markers of cardiometabolic disease risk among children and youth, and 2) To examine the impact of 1-day of prolonged sedentary behaviour, with and without interruptions or structured physical activity, on markers of cardiometabolic disease risk, hunger, food intake and spontaneous physical activity levels in children and youth. In Study 1, we found that interruptions in sedentary time and short bouts of sedentary time were beneficially associated with clustered cardiometabolic disease risk in boys and girls aged 8-11 years, independent of total sedentary time, moderate-and-vigorous physical activity (MVPA), and other confounders (all p<0.05), while the opposite was true for screen based sedentary behaviours. In Study 2, we found that movement variability (minute-to-minute changes in movement intensity) was negatively associated with clustered cardiometabolic disease risk and systolic blood pressure independent of MVPA, sedentary time and other covariates in a representative sample of American children and youth aged 12-17 years (all p<0.05). In Studies 3 and 4, we found that prolonged sitting, with or without interruptions and structured MVPA did not result in acute changes in markers of cardiometabolic disease risk, nor subsequent ad libitum food intake or physical activity levels in healthy children aged 10-14 years (all p ≥0.05). Taken together, the studies that make up this thesis suggest that optimal levels of cardiometabolic disease risk are most likely to be seen in children who limit their time engaging in screen-based sedentary behaviours, who frequently interrupt their sedentary time, and who have high levels of variability in their movement behaviours.

The long-term effects of total dietary protein and individual food sources of dietary protein on cardiometabolic risk are not clearly understood. The effects of the amount consumed and the timing of dietary protein intake as well as the contribution of overall dietary patterns on various cardiometabolic outcomes are largely unknown, particularly in children. The objective of this dissertation is to estimate the effects of patterns of dietary protein intake and egg consumption on cardiometabolic risk in adolescents and adults. Prospective data from two studies were used: the National Growth and Health Study (NGHS) with 2105 pre-adolescent girls followed for 10 years and the Framingham Offspring Study (FOS) with 2054 middle-aged adults followed for 12 years. Diet was assessed in both cohorts via 3-day diet records. NGHS outcomes included %body fat, %truncal fat, waist circumference, body mass index, skeletal muscle mass (SMM), fasting glucose (FG), insulin resistance, blood pressure (BP), and lipids. FOS outcomes included FG and BP. Multivariable models including analysis of covariance, logistic regression, and Cox proportional hazards models were used. Girls consuming ≥75 g/day of total protein (vs. less) had less body fat (p<0.0001) and more SMM (p<0.0001) by late adolescence. Girls consuming more morning protein had the highest total protein intakes, perhaps contributing to the observed beneficial effects of morning protein on body composition. Consumption of ≥3.5 eggs/week in 9-17 year-old girls was associated with lower %body fat (p=0.019) and higher %SMM (p=0.026) by later adolescence. There was no evidence that higher egg intake was detrimental to any cardiometabolic outcomes. Girls who consumed more eggs (ages 9-17 years) in combination with more fiber, fruits/vegetables, or physical activity led to statistically significant 43-58% reduced risks of becoming overweight by late adolescence. Adults who consumed ≥5 eggs/week had lower FG (p=0.0004) and systolic BP (p=0.0284) over time. Higher egg intakes were associated with a 27% lower risk of IFG or T2D (95% CI:0.51-1.04) and 30% lower risk of HBP (95% CI:0.52-0.96). In summary, total protein intake, including regular egg consumption, has no adverse effects on cardiometabolic risk in adolescence or adults and may benefit body composition over time.

Cardiovascular disease (CVD) and type two diabetes mellitus (T2D) are among the leading causes of death worldwide. Insulin resistance (IR) and hyperglycaemia are risk factors for CVD and T2D and are known to be prevalent in youth. Physical activity (PA) is known to improve IR and glucose tolerance in youth, but current levels of PA are low meaning alternative PA recommendations are needed. The purpose of this thesis is to investigate the effect of low volume high-intensity interval exercise (HIIE) on insulin and glucose health outcomes in male children and adolescents. Additionally, the thesis will explore the potential for HIIE to improve glycaemic control in paediatric patients with type one diabetes mellitus (T1D). Chapter 4 examines the relationship between estimates of insulin sensitivity (IS) based on oral glucose tolerance test (OGTT) and fasted assessment methods, in addition to the day-to-day reliability of these measures in children and adolescents. Results from this chapter advocated the Cederholm index to measure IS in this sample due to the low day to day reliability (coefficient of variation (%CV) of 6.4%). Chapter 5 demonstrates comparable results, reporting moderate improvements to IS and glucose tolerance measured via an OGTT 10 minutes after a single bout of HIIE and work-matched moderate-intensity exercise (MIE) in adolescent boys (13-15 y old). The findings from Chapter 5 are extended in Chapter 6, where changes to OGTT derived IS and glucose tolerance were measured up to 24 h post exercise and fasting measures of IS up to 48 h after exercise. Improvements to IS and glucose tolerance after the OGTT persisted for up to 24 h after HIIE and MIE, but no changes to fasting outcomes were observed over the 48 h period. In contrast to Chapter 5, Chapter 7 reports that a single bout of HIIE but not work-matched MIE resulted in only a small improvement in IS in 8-10 year old boys. Chapter 8 assesses the efficacy of 6 sessions of HIIE performed over 2 weeks to alter fasting and postprandial (mixed-meal tolerance test) insulin and glucose outcomes in adolescent boys. In contrast to acute exercise (Chapters 5 and 6), HIIE training over 2 weeks did not improve insulin and glucose outcomes in this population. Finally, Chapter 9 presents a case study on three adolescents with T1D to examine the effect of acute HIIE and MIE on glycaemic control. This study indicates that both MIE and HIIE have the potential to improve short-term (24 h) glycaemic control within this clinical population. Taken collectively, the studies from this thesis demonstrate that HIIE offers an effectual and feasible alternative to MIE to improve insulin and glucose health outcomes in healthy children and adolescents, and short-term glycaemic control in adolescents with T1D.

Emerging evidence suggests that sedentary behaviour is independently associated with cardiometabolic disease risk in school-aged children and youth. This thesis includes 4 related studies in the pursuit of 2 objectives: 1) To determine the cross-sectional association of sedentary time, interruptions in sedentary time, sedentary bout length, and total movement variability with markers of cardiometabolic disease risk among children and youth, and 2) To examine the impact of 1-day of prolonged sedentary behaviour, with and without interruptions or structured physical activity, on markers of cardiometabolic disease risk, hunger, food intake and spontaneous physical activity levels in children and youth. In Study 1, we found that interruptions in sedentary time and short bouts of sedentary time were beneficially associated with clustered cardiometabolic disease risk in boys and girls aged 8-11 years, independent of total sedentary time, moderate-and-vigorous physical activity (MVPA), and other confounders (all p<0.05), while the opposite was true for screen based sedentary behaviours. In Study 2, we found that movement variability (minute-to-minute changes in movement intensity) was negatively associated with clustered cardiometabolic disease risk and systolic blood pressure independent of MVPA, sedentary time and other covariates in a representative sample of American children and youth aged 12-17 years (all p<0.05). In Studies 3 and 4, we found that prolonged sitting, with or without interruptions and structured MVPA did not result in acute changes in markers of cardiometabolic disease risk, nor subsequent ad libitum food intake or physical activity levels in healthy children aged 10-14 years (all p ≥0.05). Taken together, the studies that make up this thesis suggest that optimal levels of cardiometabolic disease risk are most likely to be seen in children who limit their time engaging in screen-based sedentary behaviours, who frequently interrupt their sedentary time, and who have high levels of variability in their movement behaviours.

No description available.

A thesis submitted to the School of Graduate Studies in partial fulfillment of the requirements for the degree Master of Science. / Sprint interval training (SIT) is a time-efficient strategy to improve cardiorespiratory fitness; however, most protocols have been studied in a laboratory setting and require specialized equipment. We investigated the efficacy of brief intense stair climbing as a practical model of SIT to improve cardiometabolic health, with a key measure being cardiorespiratory fitness as indicated by peak oxygen uptake (VO2peak). Two separate studies, each consisting of an acute and chronic phase, were conducted in a total of 31 sedentary women (age=24±10 y; BMI=23±4 kg•m-2). The acute phase of Study 1 established that the heart rate (HR), blood lactate concentration (BLa), and rating of perceived exertion (RPE) responses were similar when participants (n=8) performed a SIT protocol that involved 3x20-s “all-out” efforts of either continuous stair climbing or cycling, interspersed with 2 min of recovery. The chronic phase demonstrated that when participants (n=12) performed the 3x20-s stair climbing protocol 3 d•wk-1 for 6 wk, absolute and relative VO2peak increased by 12%, or ~1 metabolic equivalent (1.80±0.25 to 2.02±0.27 L•min-1, p<0.001), as there were no changes in body mass (p=0.35), fat free mass (FFM; p=0.09) or % body fat (p=0.42). There were also no changes in resting systolic and diastolic blood pressure (BP; p=0.82 and p=0.97, respectively), resting HR (p=0.62), and fasting insulin sensitivity (p=0.52). The acute phase of Study 2 established that the HR and RPE responses were similar when participants (n=11) performed three different stair climbing protocols. The protocols investigated include the 3x20-s continuous ascent model used in Study 1 (protocol 1), as well as 3x60-s bouts of ascending and descending either one or two flights of stairs, with 60-s of recovery (protocol 2 and 3, respectively). The chronic phase demonstrated that when the same group of subjects performed the 3x60-s 1-flight protocol 3 d•wk-1 for 6 wk, absolute and relative VO2peak increased by 8 and 7%, respectively (1.79±0.36 to 1.93±0.39 L•min-1, p=0.001; 31.2±4.6 to 33.3±5.3 mL•kg-1•min-1; p=0.01). Despite no changes in % body fat (p=0.10), there was an increase 3% increase in FFM (p<0.001). There was no change in systolic (p=0.50) and diastolic BP (p=1.00), but resting HR improved by 8% after training (p=0.03). The change in insulin sensitivity derived from an OGTT was 7.1±11 mg I2•mmol-1•mIU-1•min-1 (p=0.056). These findings demonstrate that brief intense stair climbing is a practical, time-efficient strategy to improve cardiorespiratory fitness in previously untrained women. / Thesis / Master of Science (MSc) / Sprint interval training (SIT), involving brief bouts of very intense exercise separated by short periods of recovery, is a time-efficient alternative to traditional endurance training for improving fitness. This has largely been established in laboratory settings using specialized equipment, which is impractical for many individuals. This project examined whether brief intense stair climbing was a practical model of SIT to elicit adaptations previously shown with cycling protocols. Subjects performed either three 20-s ascents interspersed with 2 min recovery periods, or three 60-s bouts of ascending and descending one or two flights of stairs, with 60-s recovery periods. Both protocols were 10 min in duration including warm-up and cool-down, and subjects trained three days per week for six weeks. The main finding was that stair climbing is a practical, time-efficient model to improve fitness in previously sedentary individuals.