published_or_final_version / abstract / Medicine / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Non-nutritive sweeteners (NNS) have been used to replace added sugars in foods/beverages. Research related to NNS consumption and metabolic syndrome (MetS) is of great importance as NNS are often used by individuals who are looking to improve their health. The objectives of this investigation were to determine whether an association between NNS consumption (total and individual types) and MetS exists, and if any of the five risk factors for MetS were more significantly impacted by NNS consumption. Four NNS were included in this study: saccharin, sucralose, aspartame, and acesulfame potassium. Adult participants (n = 125) from Southwest Virginia were recruited for a cross-sectional investigation. Demographics, three 24-hour dietary recalls, and values for MetS (blood pressure, waist circumference, and glucose, triglyceride, and HDL levels) were collected. Statistical analyses included descriptives and multiple linear regressions models. Of the 125 participants, 63 were classified as NNS consumers and 18 met the criteria for MetS. There was a significant positive relationship between MetS and total NNS consumption (p=0.007) and MetS and aspartame (p=0.012). When looking at individual MetS risk factors, waist circumference, triglyceride and glucose values were significantly positively associated with NNS consumption (p≤0.001) and aspartame, sucralose, and saccharin (all p≤0.027). Some limitations to current NNS research were addressed, such as, examining associations between individual NNS types and not using diet soda as a proxy for NNS consumption. More research is needed to address the bias of self-reported data and the lack of randomized controlled trials to inferentially test the impact of NNS consumption. / Master of Science

Background The optimal exercise load/intensity for exercise programs for individuals with metabolic syndrome (MetS) has not been investigated. One method of determining optimal exercise load is to measure the blood lactate transition threshold (BLTT), referred to as the anaerobic threshold (AT). The first part of this thesis (study 1) investigated the reproducibility of BLTT testing and the consequent determination of AT via the Mader method (Mader et al. 1986) and a modified form of the ADAPT method (Cheng et al. 1992) in patients with MetS. Furthermore, a comparison of the reproducibility of the AT determination using the Mader et al. (1986) method as opposed to the ADAPT method has not been investigated in MetS patients. The effect of specific exercise protocols on the different components of MetS has also not been investigated. Therefore, the second study in the thesis compared the effects on the components of the MetS of an exercise program that uses BLTT (specifically, the AT) to those of a comparable exercise program (not using AT) taken from the literature. The main aim of the study was to design an exercise program that optimized exercise responses and may thus improve metabolic characteristics in individuals with MetS. The third part of the thesis (study 3) focused on the relationship between cardiorespiratory fitness and the components of the metabolic syndrome. This study developed multiple regression models to find the principal variables that associated with peak vi oxygen consumption (VO2 peak) and AT in persons with MetS. Regression models were also developed to investigate whether these variables were associated with the individual metabolic and cardiovascular components of the metabolic syndrome. Methods In study 1, fifteen male patients diagnosed with MetS (age: 43.5 ± 7.52 years) and fifteen healthy, male participants (age: 44.1 ± 6.08 years) each performed a peak oxygen consumption and BLTT test simultaneously using an incremental protocol to exhaustion on a treadmill, at the same daily times, on three different days. Study 2 used three subject groups. One group consisted of ten participants (male, age: 48.3 ± 7.32 years) with MetS that exercised using the walking program of Leon et al. (1979) (MetSL). A second group consisted of ten participants (male, age: 40.8 ± 8.21 years) with MetS that exercised using velocity at AT to set training intensities (MetSV). A third group consisted of ten participants (male, age: 40.2 ± 7.90 years) without MetS that exercised using velocity at AT to set training intensities (Non-MetSV). Training durations and frequency varied from 20 – 90 minutes and 3 -5 days per week respectively. Height, body mass, waist circumference, blood pressure, fasting plasma triglyceride, total cholesterol, HDL-, LDL- cholesterol, insulin levels, VO2 peak and BLTT were measured in all groups before, during and after twenty weeks of exercise. In addition, oral glucose tolerance tests (OGTT) were administered to all participants. 0 min, 30 min and 2 hours plasma glucose and insulin levels were measured during the OGTT. HOMA-IR and insulinogenic indices were also calculated. Nutritional data were recorded at week 0, 8 and 20 of training. vii In study 3, thirty-one males diagnosed with MetS and twenty-four healthy male participants each performed a VO2 peak and a BLTT test. Height, mass, waist circumference, blood pressure, fasting plasma triglyceride, total cholesterol, HDLcholesterol and insulin levels were also measured. In addition, oral glucose tolerance tests (OGTT) were administered to all participants and HOMA indices were calculated. Results There was no significant difference in treadmill velocity at AT determined by the Mader method or the Modified ADAPT method within both groups of study 1 (p > 0.05). The mean treadmill velocity at AT was higher in the healthy compared to the MetS group using both the Mader and the ADAPT method. Regression analysis and ANCOVA in study 1 demonstrated that this difference was largely due to a higher VO2 peak in the healthy group. The study also found an association between VO2 peak and waist circumference. The coefficient of variation of repeat measurements for both the Mader method and the Adapt method was less than 4% indicating good reproducibility. This was confirmed by the typical error method of Hopkins (2000). Study 2 showed that body mass, BMI and waist circumference decreased significantly in all training groups with the training program using AT and the program not using AT showing similar outcomes in these variables among persons with MetS. Velocity at AT also improved in all training groups. While VO2 peak increased (p < 0.05) in both the MetS groups, it did not change significantly in the group without MetS. Similarly, the blood pressure response was favourable in the groups with MetS yet absent in the group viii without MetS. The training group with MetS that used AT was the only group to show significant, positive changes in any of the metabolic parameters (fasting insulin and HOMA). This group also showed the greatest change in the incidence of MetS. In study 3, presence of MetS, waist circumference and AT were found to associate with VO2 peak and VO2 peak was strongly correlated with AT. Age and body mass were found to correlate with fasting glucose, whilst only age correlated with HDL-cholesterol. Age and VO2 peak both correlated with systolic blood pressure but only VO2 peak had a significant association with diastolic blood pressure. Conclusions Study 1 demonstrated that BLTT tests are reproducible in persons with MetS. Study 2 demonstrated that an endurance exercise program using AT to set intensity is effective in eliciting favourable responses in individuals diagnosed with MetS. In addition, the training program using AT elicited the responses with a reduced exercise frequency and intensity. It also improved insulin sensitivity which was not affected by the walking program. The response to the exercise program that used AT was similar in persons with MetS and in persons without MetS, except in the central cardio-vascular adaptations of VO2 peak and in the metabolic parameters of fasting insulin and the HOMA index. Study 3 found that the lower VO2 peak of participants with MetS is associated with their higher waist circumference. The VO2 peak, in turn, was shown to correlate with anaerobic threshold. Therefore, reducing waist circumference in persons with MetS needs to be a focus of intervention programs for such a group. This study also found that both diastolic and systolic blood pressures were associated with cardio-respiratory fitness (VO2 peak). ix This further supports the benefit of increasing cardio-respiratory fitness in persons with MetS. The results of these studies showed that BLTT tests are simple, low-cost, reproducible ways of setting exercise intensity for persons with MetS that can be incorporated in the routine cardio-respiratory fitness assessment of an individual. Furthermore, the determination of AT from such tests can be used to design an individualized exercise program that can “reverse” the effects of MetS.

The association between cardiovascular reactivity and the metabolic syndrome, as well as individual metabolic syndrome criterion variables, was investigated in adolescents. Cardiovascular reactivity has been examined as a risk marker or factor in the pathogenesis of hypertension or cardiovascular disease, but few studies have looked at its relationship with the metabolic syndrome. Blood pressure (BP) and heart rate (HR) cardiovascular reactivity to three tasks, evaluated speaking, mirror star tracing, and cold pressor, were assessed in 148 adolescents. Using the American Heart Association (AHA) adult definitional criteria, individuals were classified into metabolic syndrome groups (presence vs. absence of metabolic syndrome), and 16% of individuals met criteria for the metabolic syndrome. In logistic regression analyses, the occurrence of the metabolic syndrome was negatively associated with HR reactivity to the cold pressor (OR = 0.920, 95% CI = 0.873, 0.969), and positively associated with diastolic blood pressure (DBP) reactivity to the star tracing task (OR = 1.089, 95% CI = 1.008, 1.177). Results of multiple regression analyses that included individual metabolic syndrome risk variables indicated that cold pressor reactivity explained 7% of the variance in casual BP, while star tracing reactivity accounted for 7% of the variance waist circumference and 6% of the variance triglycerides (ps < .05). The findings indicate that cardiovascular reactivity to physical or behavioral challenge is associated with the metabolic syndrome in a sample of adolescents. Cardiovascular reactivity may be an important clinical tool for identifying individuals at risk of the metabolic syndrome and cardiovascular disease.

Kunskapen och undersökningarna kring tarmfloran och dess koppling till flera sjukdomar ökar i snabb takt samtidigt som underliggande faktorer för utveckling av metabola syndromet blir allt vanligare. Den västerländska livsstilen med minskad fysisk aktivitet och ökad kroppsvikt leder till allt fler hjärt- och kärlsjukdomar. Studier tyder på att personer med övervikt, diabetes och andra sjukdomar har annorlunda sammansättning av tarmfloran jämfört med friska personer, men orsaken till variationerna är inte helt klarlagd. Genom analys av sju vetenskapliga artiklar undersöktes tarmflorans betydelse för faktorer inkluderade i metabola syndromet, samt om pro- eller prebiotikas effekter är av betydelse. Denna litteraturstudie gav varierande resultat beroende på vilken typ av pro- eller prebiotika som intogs, och sammantaget krävs fler studier för att kartlägga tarmflorans koppling till bland annat blodtryck, body mass index (BMI) och glukostolerans.

The study aim was to evaluate the risk factors, clinical components, diagnostic criteria of the metabolic syndrome (MS) and to estimate its relationship with neuropsychiatric disorders. This is the first study in Lithuania in which were examined the relationship between neuropsychiatric disorders (major depression, dysthymia, suicidality, posttraumatic stress disorder, generalized anxiety disorder) and the MS in randomized population based adult sample. Were evaluated relationship between demographic characteristics and MS rate, were elucidated prevalent risk factors and clinical components and evaluated ability of MS diagnostic criteria to identify subjects with insulin resistance. It was established, that MS was more frequent in women, in elderly and in unemployed subjects; more prevalent components – arterial hypertension and central obesity; the central obesity, hypertension, hyperglycemia and microalbuminuria were established more prevalent in the elderly; the odds to have MS increases with higher stage of carbohydrate disorder; the type 2 diabetes mellitus in family history and obesity increases odds to have the MS; the usage criteria of the World Health Organisation or International Diabetes Federation for diagnostic of MS provides significant more odds to identify subjects with insulin resistance; the significant relationship were assessed between the MS and these neuropsychiatric disorders: major depression, suicidality and posttraumatic stress disorder.

Can we reduce obesity and chronic disease risk factors without "going on a diet?" Appropriate management of obesity and metabolic syndrome (MetS) remains a challenging issue for public health. Interventions demonstrating reductions in weight generally rely on labour-intensive, individualised counselling and usually feature highlyprescriptive diet/exercise plans which are time and cost-intensive to deliver, and potentially unsustainable at the community level. Moreover, there is limited evidence from randomised trials on the importance of active follow-up following initial intervention. This thesis describes the effectiveness of a 1-year randomised controlled trial incorporating an initial 16-week active lifestyle modification program on body composition and cardio-metabolic health.

No description available.

Purpose: The metabolic syndrome (MetS) is a cluster of metabolic abnormalities including high waist circumference and blood pressure, elevated triglyceride, glucose, and, insulin concentrations and low high density lipoprotein cholesterol concentrations. The prevalence of MetS in overweight and obese adolescents ranges from 10 to 66% depending of the definition used and the population studied. Obese adolescents are more prone to have MetS, highlighting the necessity of designing effective none pharmacological interventions targeting the specific needs of adolescents and to improve the management of the metabolic syndrome. Objectives: The objectives of this thesis were first, to perform a secondary data analysis of the Healthy Eating Aerobic and Resistance Training in Youth (HEARTY) trial to determine the effects of different modalities of exercise training on the prevalence of the MetS and second, to do a critical analysis of the literature surrounding the MetS concept and diagnostic for the pediatric population. Methods: Among the 304 participants of the HEARTY trial, 65 (21%) participants were classified as having MetS by the International Diabetes Federation. Measures of waist circumference, blood pressure, fasting plasma concentrations of lipids, glucose and insulin and prevalence of MetS were compared to baseline and post-6 months intervention (Aerobic training, Resistance training, Combined aerobic and resistance training and Control). Results: There were no significant changes in the prevalence of MetS within and between Aerobic, Resistance, Combined aerobic and resistance and Control groups after the 6-month intervention. However, significant improvements in MetS parameters were observed from baseline to post-intervention within groups. Aerobic and Resistance training alone significantly decreased waist circumference and systolic and diastolic blood pressure. Combined aerobic and resistance significantly decreased triglyceride concentrations and increased high density lipoprotein cholesterol concentrations whereas Control significantly decreased systolic blood pressure and insulin levels. Conclusions: Exercise, regardless of the modality, and diet counseling were not statistically effective for reducing the prevalence of MetS but did improve some of the independent MetS parameters. The absence of statistical difference in the prevalence of the MetS may be due to a lack of statistical power. Moreover, the critical analysis of the MetS literature bring us to conclude that the first step towards a standard definition of MetS for the adolescent population is to define the true clinical purpose of a MetS diagnostic in the pediatric population.