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Dietary fat intake and blood lipid profiles of South African communities in transition in the North–West Province : the PURE study / M. RichterRichter, Marilize January 2010 (has links)
Aim and objectives: This study set out to investigate the diet and blood lipid profiles of subjects in
transition in the North West Province in South Africa. It looked specifically at how the diet differed
between rural and urban areas, how the blood lipid profiles differed between rural and urban subjects,
establishing an association between dietary fat, fatty acid and cholesterol intakes respectively and blood
lipid profiles, as well as investigating the differences in blood lipid profiles at different ages, body mass
index (BMI) and genders respectively in rural and urban areas.
Design: The present study was a cross–sectional data analysis nested within the Prospective Urban and
Rural Epidemiology (PURE) study that is currently undertaken in the North West Province of South
Africa amongst other countries.
Methods: Baseline data was obtained in 2005. A randomised paper selection was done of people
between 35 - 70 years of age with no reported chronic diseases of lifestyle, TB or HIV of those enrolled
into the PURE study if they had provided written consent. Eventually a paper selection was made of 2000
subjects, 500 people in each of the four communities (rural, urban–rural, urban, established urban). For
the interpretation purposes of this study, data was stratified for rural (1000 subjects) and urban (1000
subjects) only, with no further sub–division into communities. Physical activity levels and habitual diets
were obtained from these subjects. Demographic and dietary intake data in the PURE study was collected
using validated, culture sensitive questionnaires. Anthropometric measures and lipid analysis were
determined using standardised methodology. Descriptive statistics (means, standard deviations and
proportions) were calculated. One–way analysis of variance (ANOVA) was used to determine
differences between the different levels of urbanisation on blood lipid profiles and dietary intake. When a
dietary intake variable proved to be significant for different levels of a factor (urbanisation, blood lipid
profile), post–hoc tests were calculated to determine which levels for specific variables differed
significantly. Bonferroni–type adjustments were made for the multiple comparisons. Spearman
correlations were calculated to determine associations.
Results: Mean fat intake was significantly higher in urban areas than in rural areas (67.16 ± 33.78 g vs.
32.56 ± 17.66 g, p<0.001); and the same was true for the individual fatty acid intakes. Fat and fatty acid
intakes were still within recommendations even for urban areas, and low for rural areas. N–3 intake was
very low in both rural and urban areas. Serum lipids did not differ significantly between rural and urban
areas. Almost half of rural (43%) and urban (47%) subjects presented with elevated total cholesterol
(5.0 mmol/L). In rural areas 52% and in urban areas 55% of subjects had elevated LDL–C (3.0
mmol/L). Amongst 23% of males in rural areas and 18% of males in urban areas HDL–C levels were
decreased. Of the females living in rural areas 34.3% had decreased HDL–C levels and 39% of those who lived in urban areas presented with lowered HDL–C levels. In rural areas 16.3% of subjects and in urban
areas 23% of subjects presented with high triglyceride levels. TC, LDL–C and triglyceride levels were
higher in higher body mass index (BMI) classes, however, obese subjects did not differ significantly from
overweight subjects in terms of blood lipids, suggesting that values stabilise after reaching overweight
status. These blood lipids were also higher in higher age groups and higher in women than men, probably
due to the high incidence of obesity in women.
Conclusions: Associations between the diet and blood lipid profiles were weak, and diet is not likely to
be the only factor responsible for high TC and LDL–C levels. Blood lipid profiles did not differ
significantly between rural and urban areas due to the fact that the diet was prudent in terms of fat intake
in both rural and urban areas. Higher prevalence of underweight was noted in males (32% in rural areas
and 28% in urban areas), while overwieght was a bigger problem amongst women (48% in rural areas and
54% in urban areas). TC, LDL–C and TAG were higher with higher BMI’s, while HDL–C levels were
lower. TC, LDL–C, and TAG were higher in higher age goups while HDL–C levels were lower. Female
subjects presented with higher mean triglycerides than males, probably due to higher prevalence of
overweight and obesity. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2011.
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Low body mass index and the associations with cardiovascular function in Africans : the PURE study / Venter H.L.Venter, Herman Louwrens January 2011 (has links)
Cardiovascular disease is known as one of the leading causes of
mortality worldwide, where low income countries or developing countries have the
highest prevalence of cardiovascular disease. One of the main reasons for this
statistics is acculturation that leads to changes in behavioral lifestyle and malnutrition
within these countries. Low body mass index was found to be an independent risk
factor for cardiovascular disease in several studies. From literature it is found that
body mass index is lower than the ideal body mass index and is associated with
cardiovascular disease. According to Higashi (2003) a body mass index of 22.2
kg/m2 is associated with the lowest morbidity. If body mass index decreases to lower
values than the ideal body mass index, a J–curve will be evident suggesting higher
prevalence of cardiovascular disease associated with low body mass index. These
findings imply that not only high body mass index but also a low body mass index
may be a risk factor for cardiovascular disease, morbidity and mortality. Whether low
body mass index is associated with cardiovascular risk in an African population
remains unclear.
Objective: The aim of this study was to investigate the possible associations of low
body mass index with variables of cardiovascular function in Africans, with a low
socio–economic status.
Methodology: This prospective cohort study (N= 2 010) is part of the Prospective
Urban and Rural Epidemiology study (PURE) conducted in the North–West Province
of South Africa in 2005, where the health transition in urban and rural subjects was
investigated within an apparently low socio–economic status group. Our crosssectional
PURE sub–study included 496 African people from rural and urban settings,
(men, N= 252 and women, N= 244) aged between 35–65 years and body mass index
lower than 25 kg/m2. Subjects were sub–divided into two groups. The first group
consisted of Africans with a low body mass index smaller or equal to 20 kg/m2 (men; N= 152, women; N= 94) whilst the second group consisted of Africans with a normal
body mass index larger than 20 kg/m2 and smaller or equal to 25 kg/m2 (men; N=
100, women; N= 150). Systolic blood pressure and diastolic blood pressure
measurements were obtained with the validated OMRON HEM–757 device. The
pulse wave velocity was measured using the Complior SP device. Blood was drawn
by a registered nurse from the antebrachial vein using a sterile winged infusion set
and syringes. Analyses for cholesterol, high density lipoprotein, triglycerides,
gamma–glutamyl transferase and high sensitive C–reactive protein were completed
utilizing the Konelab 20i. Data analyses were performed using the Statistica 10
program. Statistical analyses were executed to determine significant differences
between age, body mass index and lifestyle factors as well as cardiovascular related
variables in the different groups. T–tests were used to determine significant
differences between independent groups. ANCOVA tests were used to determine
BMI group differences independent of age, smoking and alcohol consumption.
Partial correlations, which were adjusted for age, smoking and alcohol consumption,
determined associations between the BMI groups and cardiovascular variables.
Results: Our results indicated significantly higher mean values for the African men,
with low body mass index, for cardiovascular variables (Diastolic blood pressure,
88.0 ± standard deviation (SD) 13.4 mmHg; mean arterial pressure, 103.8 ± SD 14.4
mmHg and carotid–radial pulse wave velocity, 12.6 ± SD 2.47 m/s) compared to the
normal body mass index group (Diastolic blood pressure, 84.2 ± SD 12.2 mmHg;
mean arterial pressure, 100.0 ± SD 13.2 mmHg and carotid–radial pulse wave
velocity, 11.6 ± SD 2.00 m/s). The African women with low body mass index had a
significant difference for carotid–radial pulse wave velocity (11.3 ± SD 2.43 m/s)
compared to the normal body mass index group (10.6 ± SD 2.10 m/s). In African
men, after the variables were adjusted for age, smoking and alcohol consumption,
we revealed that diastolic blood pressure (88.0 with confidence interval (CI) [86.0–
90.0] mmHg) and carotid–radial pulse wave velocity (12.5 with CI [12.1–12.9] m/s)
remained significant higher in the low body mass index group. Additionally, carotidradial
pulse wave velocity was negatively associated with body mass index in African
men. In the low body mass index group, Pearson and partial correlations of r= –
0.204; p= 0.012 and r= –0.200; p= 0.020 were found respectively in carotid–radial
pulse wave velocity. Furthermore, in our unadjusted scatter plot with body mass
index versus pulse wave velocity this negative trend of increasing carotid–radial
pulse wave velocity with decreasing body mass index was noticeable in both African
men and women. Even when carotid–radial pulse wave velocity was adjusted for
age, smoking, alcohol consumption, mean arterial pressure and heart rate, a J–curve
between carotid–radial pulse wave velocity and body mass index was still evident.
Conclusion: A detrimental effect of low body mass index is evident on
cardiovascular function in Africans. If body mass index decreases from the optimum
value of 22.2 kg/m2 to lower values, a J–curve is evident between body mass index
and cardiovascular variables suggesting higher prevalence of cardiovascular disease
associated with low body mass index. In our sub–study the carotid–radial pulse wave
velocity increases significantly in African men with low body mass index, thus
supporting the theory that stiffening of the arteries is evident in Africans with a low
body mass index. Low body mass index may contribute to the high prevalence of
cardiovascular disease mortality within developing countries and therefore, increase
the risk for cardiovascular disease. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2012.
|
3 |
Dietary fat intake and blood lipid profiles of South African communities in transition in the North–West Province : the PURE study / M. RichterRichter, Marilize January 2010 (has links)
Aim and objectives: This study set out to investigate the diet and blood lipid profiles of subjects in
transition in the North West Province in South Africa. It looked specifically at how the diet differed
between rural and urban areas, how the blood lipid profiles differed between rural and urban subjects,
establishing an association between dietary fat, fatty acid and cholesterol intakes respectively and blood
lipid profiles, as well as investigating the differences in blood lipid profiles at different ages, body mass
index (BMI) and genders respectively in rural and urban areas.
Design: The present study was a cross–sectional data analysis nested within the Prospective Urban and
Rural Epidemiology (PURE) study that is currently undertaken in the North West Province of South
Africa amongst other countries.
Methods: Baseline data was obtained in 2005. A randomised paper selection was done of people
between 35 - 70 years of age with no reported chronic diseases of lifestyle, TB or HIV of those enrolled
into the PURE study if they had provided written consent. Eventually a paper selection was made of 2000
subjects, 500 people in each of the four communities (rural, urban–rural, urban, established urban). For
the interpretation purposes of this study, data was stratified for rural (1000 subjects) and urban (1000
subjects) only, with no further sub–division into communities. Physical activity levels and habitual diets
were obtained from these subjects. Demographic and dietary intake data in the PURE study was collected
using validated, culture sensitive questionnaires. Anthropometric measures and lipid analysis were
determined using standardised methodology. Descriptive statistics (means, standard deviations and
proportions) were calculated. One–way analysis of variance (ANOVA) was used to determine
differences between the different levels of urbanisation on blood lipid profiles and dietary intake. When a
dietary intake variable proved to be significant for different levels of a factor (urbanisation, blood lipid
profile), post–hoc tests were calculated to determine which levels for specific variables differed
significantly. Bonferroni–type adjustments were made for the multiple comparisons. Spearman
correlations were calculated to determine associations.
Results: Mean fat intake was significantly higher in urban areas than in rural areas (67.16 ± 33.78 g vs.
32.56 ± 17.66 g, p<0.001); and the same was true for the individual fatty acid intakes. Fat and fatty acid
intakes were still within recommendations even for urban areas, and low for rural areas. N–3 intake was
very low in both rural and urban areas. Serum lipids did not differ significantly between rural and urban
areas. Almost half of rural (43%) and urban (47%) subjects presented with elevated total cholesterol
(5.0 mmol/L). In rural areas 52% and in urban areas 55% of subjects had elevated LDL–C (3.0
mmol/L). Amongst 23% of males in rural areas and 18% of males in urban areas HDL–C levels were
decreased. Of the females living in rural areas 34.3% had decreased HDL–C levels and 39% of those who lived in urban areas presented with lowered HDL–C levels. In rural areas 16.3% of subjects and in urban
areas 23% of subjects presented with high triglyceride levels. TC, LDL–C and triglyceride levels were
higher in higher body mass index (BMI) classes, however, obese subjects did not differ significantly from
overweight subjects in terms of blood lipids, suggesting that values stabilise after reaching overweight
status. These blood lipids were also higher in higher age groups and higher in women than men, probably
due to the high incidence of obesity in women.
Conclusions: Associations between the diet and blood lipid profiles were weak, and diet is not likely to
be the only factor responsible for high TC and LDL–C levels. Blood lipid profiles did not differ
significantly between rural and urban areas due to the fact that the diet was prudent in terms of fat intake
in both rural and urban areas. Higher prevalence of underweight was noted in males (32% in rural areas
and 28% in urban areas), while overwieght was a bigger problem amongst women (48% in rural areas and
54% in urban areas). TC, LDL–C and TAG were higher with higher BMI’s, while HDL–C levels were
lower. TC, LDL–C, and TAG were higher in higher age goups while HDL–C levels were lower. Female
subjects presented with higher mean triglycerides than males, probably due to higher prevalence of
overweight and obesity. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2011.
|
4 |
Low body mass index and the associations with cardiovascular function in Africans : the PURE study / Venter H.L.Venter, Herman Louwrens January 2011 (has links)
Cardiovascular disease is known as one of the leading causes of
mortality worldwide, where low income countries or developing countries have the
highest prevalence of cardiovascular disease. One of the main reasons for this
statistics is acculturation that leads to changes in behavioral lifestyle and malnutrition
within these countries. Low body mass index was found to be an independent risk
factor for cardiovascular disease in several studies. From literature it is found that
body mass index is lower than the ideal body mass index and is associated with
cardiovascular disease. According to Higashi (2003) a body mass index of 22.2
kg/m2 is associated with the lowest morbidity. If body mass index decreases to lower
values than the ideal body mass index, a J–curve will be evident suggesting higher
prevalence of cardiovascular disease associated with low body mass index. These
findings imply that not only high body mass index but also a low body mass index
may be a risk factor for cardiovascular disease, morbidity and mortality. Whether low
body mass index is associated with cardiovascular risk in an African population
remains unclear.
Objective: The aim of this study was to investigate the possible associations of low
body mass index with variables of cardiovascular function in Africans, with a low
socio–economic status.
Methodology: This prospective cohort study (N= 2 010) is part of the Prospective
Urban and Rural Epidemiology study (PURE) conducted in the North–West Province
of South Africa in 2005, where the health transition in urban and rural subjects was
investigated within an apparently low socio–economic status group. Our crosssectional
PURE sub–study included 496 African people from rural and urban settings,
(men, N= 252 and women, N= 244) aged between 35–65 years and body mass index
lower than 25 kg/m2. Subjects were sub–divided into two groups. The first group
consisted of Africans with a low body mass index smaller or equal to 20 kg/m2 (men; N= 152, women; N= 94) whilst the second group consisted of Africans with a normal
body mass index larger than 20 kg/m2 and smaller or equal to 25 kg/m2 (men; N=
100, women; N= 150). Systolic blood pressure and diastolic blood pressure
measurements were obtained with the validated OMRON HEM–757 device. The
pulse wave velocity was measured using the Complior SP device. Blood was drawn
by a registered nurse from the antebrachial vein using a sterile winged infusion set
and syringes. Analyses for cholesterol, high density lipoprotein, triglycerides,
gamma–glutamyl transferase and high sensitive C–reactive protein were completed
utilizing the Konelab 20i. Data analyses were performed using the Statistica 10
program. Statistical analyses were executed to determine significant differences
between age, body mass index and lifestyle factors as well as cardiovascular related
variables in the different groups. T–tests were used to determine significant
differences between independent groups. ANCOVA tests were used to determine
BMI group differences independent of age, smoking and alcohol consumption.
Partial correlations, which were adjusted for age, smoking and alcohol consumption,
determined associations between the BMI groups and cardiovascular variables.
Results: Our results indicated significantly higher mean values for the African men,
with low body mass index, for cardiovascular variables (Diastolic blood pressure,
88.0 ± standard deviation (SD) 13.4 mmHg; mean arterial pressure, 103.8 ± SD 14.4
mmHg and carotid–radial pulse wave velocity, 12.6 ± SD 2.47 m/s) compared to the
normal body mass index group (Diastolic blood pressure, 84.2 ± SD 12.2 mmHg;
mean arterial pressure, 100.0 ± SD 13.2 mmHg and carotid–radial pulse wave
velocity, 11.6 ± SD 2.00 m/s). The African women with low body mass index had a
significant difference for carotid–radial pulse wave velocity (11.3 ± SD 2.43 m/s)
compared to the normal body mass index group (10.6 ± SD 2.10 m/s). In African
men, after the variables were adjusted for age, smoking and alcohol consumption,
we revealed that diastolic blood pressure (88.0 with confidence interval (CI) [86.0–
90.0] mmHg) and carotid–radial pulse wave velocity (12.5 with CI [12.1–12.9] m/s)
remained significant higher in the low body mass index group. Additionally, carotidradial
pulse wave velocity was negatively associated with body mass index in African
men. In the low body mass index group, Pearson and partial correlations of r= –
0.204; p= 0.012 and r= –0.200; p= 0.020 were found respectively in carotid–radial
pulse wave velocity. Furthermore, in our unadjusted scatter plot with body mass
index versus pulse wave velocity this negative trend of increasing carotid–radial
pulse wave velocity with decreasing body mass index was noticeable in both African
men and women. Even when carotid–radial pulse wave velocity was adjusted for
age, smoking, alcohol consumption, mean arterial pressure and heart rate, a J–curve
between carotid–radial pulse wave velocity and body mass index was still evident.
Conclusion: A detrimental effect of low body mass index is evident on
cardiovascular function in Africans. If body mass index decreases from the optimum
value of 22.2 kg/m2 to lower values, a J–curve is evident between body mass index
and cardiovascular variables suggesting higher prevalence of cardiovascular disease
associated with low body mass index. In our sub–study the carotid–radial pulse wave
velocity increases significantly in African men with low body mass index, thus
supporting the theory that stiffening of the arteries is evident in Africans with a low
body mass index. Low body mass index may contribute to the high prevalence of
cardiovascular disease mortality within developing countries and therefore, increase
the risk for cardiovascular disease. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2012.
|
5 |
Cardiovascular dysfunction in black South Africans: an investigation from various perspectives / I.M. PalmerPalmer, Iolanthe Marike January 2010 (has links)
Motivation: The prevalence of cardiovascular dysfunction, especially hypertension, in Africans has increased dramatically over the past few decades. Despite considerable in~ depth studies, cardiovascular diseases remain the leading cause of morbidity and mortality. Further escalations are predicted, especially in developing countries such as South Africa, if measures are not taken to combat the trend. Numerous cardiovascular risk factors have been investigated within African-Americans as well as Caucasians. However, it is not known to what extent African-Americans and Africans from South Africa are comparable. Therefore, it is essential to investigate risk factors and their possible contributory role in the high susceptibility of cardiovascular dysfunction in the black South African population.
Aim: To investigale potential risk factors and their possible involvement and association with the high prevalence of cardiovascular dysfunction within the black South African population.
Methodology: Manuscripts presented in Chapters 2, 3 and 4 made use of the data obtained from the cross-sectional SAfrEIC (The South African study regarding the influence of Sex, age and ethnicity on insulin sensitivity and Cardiovascular function) study. The study group included 756 asymptomatic, apparently healthy African men and women as well as Caucasian men and women, recruited from the North West Province, South Africa. Anthropometric and cardiovascular measurements were taken as well as their lipid profiles, fasting insulin levels, and uric acid and adiponectin levels. Independent t-tests, analyses of variance (ANOVA) and analyses of covariance (ANCOVA) were used for comparison of variables between groups to determine significant differences. Partial correlations coefficients were used to show association between variables while adjusting for confounders. Multiple analyses of covariance (MANCOVA) were performed to compare variables between the groups, whilst adjusting for relevant confounders. Stepwise multiple and single regression analyses were also used to determine and confirm the most significant associations between variables. All subjects gave informed consent in writing and the Ethics Committee of the NorthWest University approved the study, The reader is referred to the "Materials and Methods" section of Chapters 2, 3 and 4 for a more elaborate description of the subjects, study design and analytical methods used in each paper.
Results and conclusions of the individual manuscripts
*Results from Chapter 2 revealed significantly lower uric acid levels for African men compared to Caucasian men, Despite these lower levels. the association between uric acid and blood pressure is more pronounced within the African men. The strong positive relationship between uric acid and blood pressure might be explained by uric acid's independent relationship with vascular resistance, Uric acid also revealed a positive association with triglycerides in both the African and Caucasian men. These results suggest that uric acid per se can act as a risk factor in the development of cardiovascular dysfunction in African men,
*Results from Chapter 3 showed opposing changes in insulin secretion for African men and Caucasian men with increasing age. Whereas insulin levels increased in Caucasian men with progressive age, insulin levels in African men tended to decrease with ageing. Additionally, the insulin-blood pressure relationship within African men revealed opposite results as to what was expected. While the Caucasian men revealed a more positive association between insulin and blood pressure within the younger individuals, older individuals revealed a negative association between insulin and blood pressure, This implies that the vasoconstrictory actions of insulin seem to dominate in young individuals while the vasodilatory actions of insulin take over in older individuals, The turnaround probably acts as a counter protective mechanism against age-related cardiovascular dysfunction. On the contrary, despite decreased insulin secretion in older African men, they exhibit a more positive association between insulin and blood pressure, whereas younger subjects showed a more negative association, These results might suggest dissociation between insulin and blood pressure, Insulin per se might, therefore, not act as a risk factor, but rather the lack of insulin-mediated vasodilatory effects as observed within younger Africans.
*Results from Chapter 4 contradicted the notion found in the literature that age-related increase in adiponectin levels are due to impaired renal function. Although the results from this chapter confirmed a Significant association between renal function (estimated creatinine clearance) and adiponectin levels a multiple regression model revealed insulin resistance (HOMA-IR) as the major contributor to adiponectin levels. Adiponectin levels increased with progressive ageing only in the Africans. No such change was observed for the Caucasians. This might be due to development of functional adiponectin resistance or perhaps due to a decline in pancreatic cell mass with ageing.
In conclusion, the cardiovascular profile of Africans seems to be more detrimentally affected compared to Caucasians. Results from this study have elucidated on the associations and potential involvement of possible risk factors including, uric acid, insulin, C-peptide, as well as adiponectin, with regards to the high prevalence of cardiovascular dysfunction within the black South African population. / Thesis (Ph.D. (Physiology))--North-West University, Potchefstroom Campus, 2010.
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6 |
Cardiovascular dysfunction in black South Africans: an investigation from various perspectives / I.M. PalmerPalmer, Iolanthe Marike January 2010 (has links)
Motivation: The prevalence of cardiovascular dysfunction, especially hypertension, in Africans has increased dramatically over the past few decades. Despite considerable in~ depth studies, cardiovascular diseases remain the leading cause of morbidity and mortality. Further escalations are predicted, especially in developing countries such as South Africa, if measures are not taken to combat the trend. Numerous cardiovascular risk factors have been investigated within African-Americans as well as Caucasians. However, it is not known to what extent African-Americans and Africans from South Africa are comparable. Therefore, it is essential to investigate risk factors and their possible contributory role in the high susceptibility of cardiovascular dysfunction in the black South African population.
Aim: To investigale potential risk factors and their possible involvement and association with the high prevalence of cardiovascular dysfunction within the black South African population.
Methodology: Manuscripts presented in Chapters 2, 3 and 4 made use of the data obtained from the cross-sectional SAfrEIC (The South African study regarding the influence of Sex, age and ethnicity on insulin sensitivity and Cardiovascular function) study. The study group included 756 asymptomatic, apparently healthy African men and women as well as Caucasian men and women, recruited from the North West Province, South Africa. Anthropometric and cardiovascular measurements were taken as well as their lipid profiles, fasting insulin levels, and uric acid and adiponectin levels. Independent t-tests, analyses of variance (ANOVA) and analyses of covariance (ANCOVA) were used for comparison of variables between groups to determine significant differences. Partial correlations coefficients were used to show association between variables while adjusting for confounders. Multiple analyses of covariance (MANCOVA) were performed to compare variables between the groups, whilst adjusting for relevant confounders. Stepwise multiple and single regression analyses were also used to determine and confirm the most significant associations between variables. All subjects gave informed consent in writing and the Ethics Committee of the NorthWest University approved the study, The reader is referred to the "Materials and Methods" section of Chapters 2, 3 and 4 for a more elaborate description of the subjects, study design and analytical methods used in each paper.
Results and conclusions of the individual manuscripts
*Results from Chapter 2 revealed significantly lower uric acid levels for African men compared to Caucasian men, Despite these lower levels. the association between uric acid and blood pressure is more pronounced within the African men. The strong positive relationship between uric acid and blood pressure might be explained by uric acid's independent relationship with vascular resistance, Uric acid also revealed a positive association with triglycerides in both the African and Caucasian men. These results suggest that uric acid per se can act as a risk factor in the development of cardiovascular dysfunction in African men,
*Results from Chapter 3 showed opposing changes in insulin secretion for African men and Caucasian men with increasing age. Whereas insulin levels increased in Caucasian men with progressive age, insulin levels in African men tended to decrease with ageing. Additionally, the insulin-blood pressure relationship within African men revealed opposite results as to what was expected. While the Caucasian men revealed a more positive association between insulin and blood pressure within the younger individuals, older individuals revealed a negative association between insulin and blood pressure, This implies that the vasoconstrictory actions of insulin seem to dominate in young individuals while the vasodilatory actions of insulin take over in older individuals, The turnaround probably acts as a counter protective mechanism against age-related cardiovascular dysfunction. On the contrary, despite decreased insulin secretion in older African men, they exhibit a more positive association between insulin and blood pressure, whereas younger subjects showed a more negative association, These results might suggest dissociation between insulin and blood pressure, Insulin per se might, therefore, not act as a risk factor, but rather the lack of insulin-mediated vasodilatory effects as observed within younger Africans.
*Results from Chapter 4 contradicted the notion found in the literature that age-related increase in adiponectin levels are due to impaired renal function. Although the results from this chapter confirmed a Significant association between renal function (estimated creatinine clearance) and adiponectin levels a multiple regression model revealed insulin resistance (HOMA-IR) as the major contributor to adiponectin levels. Adiponectin levels increased with progressive ageing only in the Africans. No such change was observed for the Caucasians. This might be due to development of functional adiponectin resistance or perhaps due to a decline in pancreatic cell mass with ageing.
In conclusion, the cardiovascular profile of Africans seems to be more detrimentally affected compared to Caucasians. Results from this study have elucidated on the associations and potential involvement of possible risk factors including, uric acid, insulin, C-peptide, as well as adiponectin, with regards to the high prevalence of cardiovascular dysfunction within the black South African population. / Thesis (Ph.D. (Physiology))--North-West University, Potchefstroom Campus, 2010.
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