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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
421

Vitamins, fatty acids, physical activity and peak bone mass

Högström, Magnus January 2007 (has links)
Osteoporosis is a disease characterized by low bone mineral density, deteriorated bone microstructure and increased fracture risk. About 50% of all women and 25% of all men will have an osteoporotic fracture. Given that there is no effective cure in established osteoporosis, prevention is of high importance. Bone mineral density (BMD) is accumulated during childhood and adolescence with a peak at about 20 years of age. Peak BMD has been suggested to explain at least half of the variation in BMD up to old age. Thus, to increase peak BMD could decrease the risk of later fractures. The purpose of the present thesis was to investigate the influence of physical activity, vitamins A and D, and fatty acids on peak bone mass in men. The influence of physical activity on bone accrual was studied in two cohorts. In the first cohort 46 ice hockey players, 18 badminton players and 27 controls, all 17 years of age at baseline, were followed for four years. During the follow up the badminton players gained more bone mass at the hip compared to both the ice hockey players and controls. In the second cohort the associations between physical activity and BMD were investigated in 62 female and 62 male young medical students. The estimated high impact activity per week was associated with bone mass at all sites in the male medical students (r=0.27-0.53, p<0.05). In the female cohort different estimates of physical activity were not related to bone mass at any site. In both males and females correlations between bone mass and body constitution parameters were observed. Levels of vitamin D3, vitamin D2, retinol, retinol-binding-protein-4 (RBP-4) and fatty acids were measured in 78 young men with a mean age of 22.6 years. BMD at various sites were measured using Dual-Energy X-ray absorptiometry. Levels of vitamin D3 showed a significant positive association with all BMD sites and also lean body mass (r=0.23-0.35, p<0.05). Levels of vitamin D2, however, showed a significant negative correlation with BMD of the total body (r=-0.28, p=0.01) and spine (r=-0.27, p=0.02). There was also a significant negative relationship between levels of vitamin D3 and D2 (r=-0.31, p=0.006). Concentrations of n-3 (omega-3) fatty acids showed a positive association with BMD at the total body (r=0.27, p=0.02) and spine BMD (r=0.25, p=0.02). There was also a positive association between levels of n-3 fatty acids and changes in BMD of the spine between 16 and 22 years of age (r=0.26, p=0.02). The significant associations found seemed to be related mostly to the concentration of the n-3 fatty acid docosahexaenoic acid. Levels of retinol and RBP-4 were not related to BMD but to levels of osteocalcin, which is a marker of bone formation. This association disappeared when adjusting for the influence of abdominal fat mass. In summary, the present thesis suggests that many modifiable factors may influence the accumulation of peak bone mass in males, such as physical activity, vitamins, and fatty acids. Further studies are needed to investigate whether optimizing these factors in youth may decrease the risk of osteoporosis later in life.
422

Fragility fractures in fragile people : epidemiology of the age quake

Bergström, Ulrica January 2009 (has links)
Osteoporosis-related fracture is already today a major public health problem and the number of hip fractures is expected to double to 2030. Sweden has one of the highest hip fracture incidences worldwide. This may be explained by several factors: e.g. age, genetic, climatologic, geographic and a relative vitamin D deficiency, secondary to the limited sunlight exposure especially during winter months. Intrinsic and extrinsic factors contribute to a fracture, although a prior low energy fracture is one of the strongest predictors for a subsequent one and this should be a target for secondary fracture prevention in an orthopaedic setting. Since 1993 all injured patients admitted to the emergency floor and all in-hospital fractures at Umeå University Hospital, Sweden, were registered according to the Injury Data Base, former EHLASS. There were 31,173 fracture events (one or more fractures at the same time), of which 13,931 were in patients’ ≥ 50 years old. The fracture database was co analyzed with the Northern Sweden Health and Disease Study cohort in a nested case-control study for investigations of associations between osteoporotic fracture and serum markers, lifestyle data, nutrition etc. We found that there were differences in fracture pattern depending on age and sex. Both injury mechanism and fracture site were strongly dependent of age. The most severe fragility fracture, hip fracture, had a decreasing incidence. However, the incidence curve was right-shifting leading to an increase, both in numbers and in incidence of hip fractures among the oldest female. To identify people at high risk for fractures, re-fracture patients are useful. No less than 21% of the fracture patients had suffered more than one fracture event, accounting for 38% of all fracture events. The total risk ratio for a subsequent fracture was 2.2 (2.1-2.3 95% CI). In males the highest risk for re fracture was in the age cohort 70-79 years (RR 2.7, 2.3-3.2 95% CI), in females > 90 years (RR 3.9, 3.2-4.8 95% CI). Another possible risk factor in this subarctic population is the lack of sunlight, leading to a vitamin D deficit. The overall adjusted risk of sustaining a hip fracture in this population was 2.7 (95%CI:1.3-5.4) in subjects with a serum 25 hydroxyvitamin D below 50 nmol/l. The association was, however, different according to age at baseline. Thus in subjects aged 60 years and above at baseline, the adjusted odds ratio of sustaining a hip fracture was 6.2 (1.2-32.5 95%CI) for the group of individuals with a serum 25OHD below 50 nmol/l, whereas no significant association was found in the youngest age group. In the next 30 years the ongoing demographic changes will accelerate. The World War II baby boomers will cause an age quake. We can already see signs heralding a new fracture pattern: an increasing cohort of mobile but fragile elderly, with considerable co-morbidity is now at risk for fragility fractures. In fracture patients, clinical information is sufficient to pinpoint patients with a high risk for re-fractures. It is therefore clinically important to use the information provided by the fracture event. We suggest that trauma units and primary care units should screen for risk factors and inform patients about the treatment options, and to organize fracture liaison services. This seems to be especially cost-efficient for our oldest and frailest patients. Secondary prophylaxis and follow-up treatment after cardiovascular disorders are now a matter of course worldwide, but the screening for risk factors, in order to prevent a second fracture, is often neglected. This is one of the most important issues of fracture care in the future in order to improve general health.
423

Vitamin D Intake and Status in a Sample of Healthy Young Adults of Different Ethnicity Living in Canada

Wu, Hongyu 12 January 2009
Vitamin D plays an important role in over-all health. Few data exist on vitamin D deficiency related with intake for a Canadian population. The purpose of this study is to assess vitamin D intake and status in healthy young adults of diverse ancestry during the wintertime.<p> One hundred and seven young healthy adults living in Southern Ontario were recruited during the late winter of 2007. Their serum 25-hydroxyvitamin D [25(OH)D], skin melanin and anthropometric measures were determined. They completed a food frequency questionnaire (FFQ) (twice) and a 7-day food diary. Correlation analyses and t-test were used to validate the FFQ against the 7-day diary and 25(OH)D; one way ANOVA was used to determine ethnic group differences in vitamin D intake and status.<p> The results indicated that the FFQ used in this study was valid. Vitamin D deficiency [25(OH)D<50 nmol/L] was widespread and more apparent in the East and South Asian groups than in the European group (P<0.05). The dairy products were the greatest food source of vitamin D for each of the three groups and the European group exhibited higher total vitamin D intake (P<0.05). There was a trend for the European group to have higher consumption of dairy products, especially cow¡¯s milk (0.05<P<0.10). Combining subjects in the three ethnic groups, vitamin D intake but not BMI was closely related with serum 25(OH)D concentrations (r= 0.520, P<0.001; r=-0.018, P>0.05, respectively). The 25(OH)D levels were inversely related with parathyroid hormone (PTH) levels (r= -0.273, P= 0.009). With adequate calcium intake (¡Ý1000 mg/d), PTH levels were significantly lower when vitamin D was not deficient (P<0.05).<p> This study provides evidence that vitamin D deficiency is prevalent in healthy young adults living in Canada during wintertime, and non-European groups have a higher prevalence of this deficiency. Vitamin D intake varies with ethnicity, and dietary intake plays an important role in maintenance of serum vitamin D in wintertime. Compared with calcium intake, serum vitamin D levels may be a more important factor suppressing PTH levels.
424

Vitamin D Metabolites in Young Adults of Diverse Ancestry Living in the Greater Toronto Area

Gozdzik, Agnes 30 August 2011 (has links)
Vitamin D plays a critical role in bone metabolism and many cellular and immunological processes, and low vitamin D levels have been associated with several chronic and infectious diseases. Previous studies have reported that many otherwise healthy adults of European ancestry living in Canada have low vitamin D concentrations during the wintertime. However, individuals of non-European ancestry are at a higher risk of having low vitamin D levels. This thesis examined vitamin D status in a sample of young adults of diverse ancestry living in the Greater Toronto Area. In my research I found that: 1) vitamin D levels (measured as 25(OH)D concentrations) are low in Canadian young adults, particularly in those of non-European ancestry; 2) vitamin D intakes, which were estimated to be on average higher than current Health Canada recommendations of 200 International Units (IU) per day, were inadequate to maintain optimal vitamin D levels year-round; 3) vitamin D levels undergo large seasonal changes. Winter 25(OH)D concentrations are substantially lower than those observed during the fall; 4) vitamin D intake is an important year-round predictor of 25(OH)D concentrations, but skin pigmentation and sun exposure are also important predictors during the times when UVB is adequate for cutaneous synthesis; and 5) vitamin D binding protein (VDBP) polymorphisms are significant predictors of 25(OH)D concentrations, but their effects vary by ancestry and season, indicating gene-environment interaction effects. My research shows that higher vitamin D intakes are needed to offset the seasonal drop in vitamin D levels and to ensure adequate vitamin D levels year-round for those at higher risk of insufficiency.
425

Vitamin D Metabolites in Young Adults of Diverse Ancestry Living in the Greater Toronto Area

Gozdzik, Agnes 30 August 2011 (has links)
Vitamin D plays a critical role in bone metabolism and many cellular and immunological processes, and low vitamin D levels have been associated with several chronic and infectious diseases. Previous studies have reported that many otherwise healthy adults of European ancestry living in Canada have low vitamin D concentrations during the wintertime. However, individuals of non-European ancestry are at a higher risk of having low vitamin D levels. This thesis examined vitamin D status in a sample of young adults of diverse ancestry living in the Greater Toronto Area. In my research I found that: 1) vitamin D levels (measured as 25(OH)D concentrations) are low in Canadian young adults, particularly in those of non-European ancestry; 2) vitamin D intakes, which were estimated to be on average higher than current Health Canada recommendations of 200 International Units (IU) per day, were inadequate to maintain optimal vitamin D levels year-round; 3) vitamin D levels undergo large seasonal changes. Winter 25(OH)D concentrations are substantially lower than those observed during the fall; 4) vitamin D intake is an important year-round predictor of 25(OH)D concentrations, but skin pigmentation and sun exposure are also important predictors during the times when UVB is adequate for cutaneous synthesis; and 5) vitamin D binding protein (VDBP) polymorphisms are significant predictors of 25(OH)D concentrations, but their effects vary by ancestry and season, indicating gene-environment interaction effects. My research shows that higher vitamin D intakes are needed to offset the seasonal drop in vitamin D levels and to ensure adequate vitamin D levels year-round for those at higher risk of insufficiency.
426

Associations of Serum Vitamin D Concentrations with Dietary Patterns in US Children

Martineau, Bernadette 04 April 2012 (has links)
Background: Contribution of dietary sources to vitamin D status is not clearly known. Some studies have shown that dietary intake of certain vitamin D rich foods had a significant positive influence on serum 25-hydroxyvitamin D [25(OH)D] concentrations, whereas other studies have shown no effect. Although sunlight exposure is a major source of circulating serum 25(OH)D, children and adolescents have been advised on the dangers of sun exposure. Diet may therefore be an important contributor of circulating serum 25(OH)D in absence of or reduced sunlight exposure. Objective: The aim of this study was to determine whether serum 25(OH)D concentrations were associated with any specific dietary patterns in US children and adolescents using assay-adjusted serum 25(OH)D data from National Health and Nutrition Examination Survey (NHANES) 2003-2004 and 2005-2006. Methods: Data from 2 cycles of the NHANES 2003-2004 and 2005-2006 for individuals aged 2 to ≤19 y, were used to study the association between dietary patterns and serum 25(OH)D. Dietary patterns were established using factor analysis based on food-frequency questionnaire data. Eigenvalues and Scree plot were used to derive 2 major principal factors. They were labeled as High Fat Low Vegetable (HFLV) and Prudent dietary patterns. Results: Serum 25(OH)D was significantly lower in HFLV dietary pattern group compared to Prudent dietary pattern group (25.1 vs 27.0 ng/mL; P=0.001). The highest serum 25(OH)D concentrations for all subjects were in the low-intake HFLV group or medium and high-intake Prudent groups (P=0.003 and P=0.012, respectively). In multivariate adjusted analysis, children with higher Prudent dietary contribution scores to overall diet showed a significant positive relation with serum 25(OH)D (β=62.01, P=0.016). When data were stratified by sex, a significant positive relation was observed in girls who consumed the Prudent diet (β=86.34, P=0.014) and a significant negative relation was observed in girls who consumed the HFLV diet (β=-84.32, P=0.022). Conclusion: Overall, serum 25(OH)D concentrations were associated with Prudent dietary pattern but not with HFLV dietary pattern in US children and adolescents. When stratified by sex, the relation between dietary patterns and serum 25(OH)D was confined to only girls. Children consuming HFLV pattern diet may benefit from vitamin D supplementation and sunlight exposure (outdoor activities), and should be encouraged to consume more vitamin D fortified foods.
427

Self-Reported Medical Conditions and Demographic, Behavioral and Dietary Factors Associated with Serum 25(OH)-Vitamin D Concentration in the US Adult Population

Van Fleit, William E, III 07 August 2012 (has links)
This research uses data from the 2003-2006 National Health and Nutrition Examination Survey (NHANES) to determine dietary and other factors associated with serum 25(OH)-Vitamin D concentration for 5,474 adults age 20 years and older. After multivariate adjustment, we found that serum 25(OH)-Vitamin D concentration was positively associated with diets high in fruits, vegetables, and lean meats, while diets high in processed foods and high-fat meats were inversely associated with vitamin D level. Serum 25(OH)-Vitamin D concentration was also signifi-cantly associated with age, gender, race/ethnicity, BMI, physical activity, supplementation, and the season of survey administration. Self-reported cardiovascular and kidney disease were significantly associated with serum 25 (OH)-Vitamin D concentration after adjustment for significant confounders.
428

Vitamin D Intake and Status in a Sample of Healthy Young Adults of Different Ethnicity Living in Canada

Wu, Hongyu 12 January 2009 (has links)
Vitamin D plays an important role in over-all health. Few data exist on vitamin D deficiency related with intake for a Canadian population. The purpose of this study is to assess vitamin D intake and status in healthy young adults of diverse ancestry during the wintertime.<p> One hundred and seven young healthy adults living in Southern Ontario were recruited during the late winter of 2007. Their serum 25-hydroxyvitamin D [25(OH)D], skin melanin and anthropometric measures were determined. They completed a food frequency questionnaire (FFQ) (twice) and a 7-day food diary. Correlation analyses and t-test were used to validate the FFQ against the 7-day diary and 25(OH)D; one way ANOVA was used to determine ethnic group differences in vitamin D intake and status.<p> The results indicated that the FFQ used in this study was valid. Vitamin D deficiency [25(OH)D<50 nmol/L] was widespread and more apparent in the East and South Asian groups than in the European group (P<0.05). The dairy products were the greatest food source of vitamin D for each of the three groups and the European group exhibited higher total vitamin D intake (P<0.05). There was a trend for the European group to have higher consumption of dairy products, especially cow¡¯s milk (0.05<P<0.10). Combining subjects in the three ethnic groups, vitamin D intake but not BMI was closely related with serum 25(OH)D concentrations (r= 0.520, P<0.001; r=-0.018, P>0.05, respectively). The 25(OH)D levels were inversely related with parathyroid hormone (PTH) levels (r= -0.273, P= 0.009). With adequate calcium intake (¡Ý1000 mg/d), PTH levels were significantly lower when vitamin D was not deficient (P<0.05).<p> This study provides evidence that vitamin D deficiency is prevalent in healthy young adults living in Canada during wintertime, and non-European groups have a higher prevalence of this deficiency. Vitamin D intake varies with ethnicity, and dietary intake plays an important role in maintenance of serum vitamin D in wintertime. Compared with calcium intake, serum vitamin D levels may be a more important factor suppressing PTH levels.
429

1,25(OH)2D3 and Initial Regulation of Smad2/3 Activity in PC-3 Prostate Cancer Cells

Stahel, Anette January 2009 (has links)
The vitamin D metabolite 1,25(OH)2D3 has long been known to inhibit growth of prostate cancer cells and this mainly through a VDR-mediated pathway controlling target gene expression, resulting in cell cycle arrest, apoptosis and differentiation. Another major way in which 1,25(OH)2D3 inhibits cell growth in prostate cancer is via membrane-initiated steroid signalling, which triggers activation of signal cascades upon steroid binding to a receptor complex, leading to induction of genes regulating cell growth, proliferation and apoptosis. The main prostate cancer inhibiting membrane-initiated route is the TGFβ signalling pathway, elicited by the protein TGFβ. Two other important proteins downstream in this cascade are Smad2 and Smad3. In this study the early effects of 1,25(OH)2D3 on activated Smad2/3 levelsin PC-3 prostate cancer cells were examined. PC-3 cells were incubated for 3, 5, 10, 30 and 60 minutes as well as 38 hours both together with 1,25(OH)2D3 of the concentrations 10-10 and 10-7 M and without. Western Blots were then performed on supernatants from the cells treated followed by treatment of the membranes with primary antibodies against phosphorylated Smad2/3 C-terminal linker regions, alkaline phosphatase conjugated secondary antibodies and finally visualization with BCIP/ NBT tablets. As the downstream cascade protein JNK is a proposed activator of Smad2/3, this procedure was also repeated with a JNK inhibitor. This is a follow-up to an earlier study which examined the influence of 1,25(OH)2D3 on TGFβ levels using the same doses and time points and which found that 1,25(OH)2D3 initially lowered the level of active TGFβ, then increased it. The results of this study indicated a 1,25(OH)2D3 mediated induction of the same pattern in the levels of active Smad2 and 3, both with and without JNK inhibitor. The results did not indicate that 1,25(OH)2D3 activates the Smad2/3 C-terminal linker region via the JNK pathway.
430

Effects of 1,25(OH)2D3 on Smad2 Activity in PC-3 Prostate Cancer Cells

Stahel, Anette January 2009 (has links)
The vitamin D metabolite 1,25(OH)2D3 has long been known to inhibit growth of prostate cancer cells and this mainly through a VDR-mediated pathway controlling target gene expression, resulting in cell cycle arrest, apoptosis and differentiation. Another major way inwhich 1,25(OH)2D3 inhibits cell growth in prostate cancer is via membrane-initiated steroid signalling, which triggers activation of signal cascades upon steroid binding to a receptor complex, leading to induction of genes regulating cell growth, proliferation and apoptosis. The main prostate cancer inhibiting membrane-initiated route is the TGFβ signalling pathway, elicited by the protein TGFβ. Another important protein downstream in this cascade is Smad2. In this study the early effects of 1,25(OH)2D3 on activated Smad2 levels in PC-3 prostate cancer cells were examined. PC-3 cells were incubated for 5, 10, 30 and 60 minutes as well as 24 and 40 hours both together with 1,25(OH)2D3 of the concentrations 10-10 and 107 M and without. An ELISA assay scanning for activated Smad2 was then performed on supernatants from both treated and untreated cells. This is a follow-up to an earlier study which examined the influence of 1,25(OH)2D3 on TGFβ levels using the same doses and similar time points and which found that 1,25(OH)2D3 initially lowered the level of active TGFβ, then increased it. The results of this study showed a statistically insignificant, time delayed 1,25(OH)2D3 mediated induction of the same pattern in the levels of active Smad2. / Project Work in Biomedicine, Advanced Level, 7.5 ECTS

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