Motivation - Brain-derived neurotrophic factor (BDNF) is a protein complex, synthesised and secreted mainly by the central nervous system and is involved in neuronal maintenance. Research suggests that BDNF is implicated in various neurological and psychiatric diseases, while recent evidence suggests a role for the neurotrophin on the periphery as well. Indeed, the specific functional role of BDNF and its action mechanism in the cardiovascular system, especially in that of Africans, is yet to be determined. The cardiovascular health profile of black South Africans is a major concern as research has shown that this group suffers from an array of cardiovascular risk factors that may result in organ damage. Sub-clinical atherosclerosis or structural endothelial dysfunction contributes to ever-increasing morbidity and mortality in the world. However, no studies regarding the associations between BDNF and structural vascular disease have been undertaken relating to black African participants. Objectives - The objective of this study was to determine whether BDNF is associated with changes in ambulatory blood pressure (BP) and whether a relationship between BDNF and structural endothelial dysfunction exists in black African male and female participants, determined by cross sectional wall area (CSWA) and albumin:creatinine ratio (ACR). Methodology - The study included 172 black African teachers (82 males and 90 females) who were employed by the Kenneth Kaunda Education district of the North-West Province, South Africa. Ambulatory blood pressure recordings were obtained with the use of a Meditech CE120 CardioTens ® apparatus. Blood pressure readings were measured at 30 min intervals during the day and 60 min intervals during the night. Anthropometric measurements were performed in triplicate by registered level II anthropometrists according to standardised procedures. A high-resolution ultrasound scan with carotid intima-media thickness (CIMT) images from at least two optimal angles of the left and right common carotid artery were obtained using a SonoSite Micromaxx ultrasound system. The lumen diameter between the near and far wall of the lumen-intima interface and the averages of both the left and right common carotid arteries were calculated. Subsequently, the carotid cross-sectional wall area (CSWA) was calculated. Participants, who fasted overnight, provided eight-hour blood and urine samples to determine serum BDNF and metabolic markers, for example, hyperglycaemia (HbA1c) and gamma glutamyl transferase (GGT). Urinary albumin and creatinine levels were determined by means of a turbidimetric method with the use of a Unicel DXC 800 analyser from Beckman and Coulter (Germany) and expressed as a ratio between albumin and creatinine (ACR). BDNF median split x Gender interaction effects for structural ED justified stratification of BDNF into low and high (≤ / > 1.37 ng/ml) gender groups. Results and Conclusion - On average, male participants were overweight (BMI 25-30kg/m2) and abused more alcohol.21 African men revealed a vulnerable cardiometabolic profile with values exceeding cut–points (European Society of Hypertension). These men demonstrated increased acute and chronic glucose (HbA1c) levels indicating a pre-diabetic state; as well as a disturbed lipid profile with lower HdL and increased triglycerides. Overall BDNF levels were lower than reference ranges (6.97 – 42.6 ng/ml). The men revealed mean lower BDNF levels, ambulatory BP values exceeding guideline cut-points (ambulatory SBP > 130mmHg; DBP > 80mmHg) as well as a hypertensive state compared to their female counterparts. Pertaining to structural endothelial dysfunction, the mean ACR value in men exceeded normal laboratory values (< 3.5mg/mmol). The African women displayed an obese state with low grade inflammation (CRP, 12.27 ± 11.67mg/l). A single two-way ANCOVA interaction on main effects (BDNF median split x Gender) demonstrated significant interaction for CIMTf [F (1,164); 3.99, p=0.05] and cholesterol [F (1,164); 4.12, p=0.05]. Therefore, a median split approach was followed which stratified gender groups into lower (≤ 1.37 ng/ml) and higher BDNF levels (>1.37 ng/ml). The low BDNF men revealed higher cholesterol than the high BDNF group, independent of BMI and age. Only the low BDNF women indicated significantly higher values for structural vascular markers (p< 0.05) than the high BDNF female group. In conclusion, we accept our hypothesis, as hypertrophic remodelling of the carotid artery was associated with lower BDNF levels. This may imply attenuated or possibly down-regulated BDNF levels acting as a compensatory mechanism for the mean higher BP levels. In women, metabolic risk and hypertrophic remodelling were evident within higher circulating levels of BDNF, underpinning different underlying mechanisms for impaired neurotrophin health in men and women. Novel findings of BDNF revealed the impact of central neural regulation on the circulatory system, which may contribute to cardiometabolic risk in Africans. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014

Motivation - Brain-derived neurotrophic factor (BDNF) is a protein complex, synthesised and secreted mainly by the central nervous system and is involved in neuronal maintenance. Research suggests that BDNF is implicated in various neurological and psychiatric diseases, while recent evidence suggests a role for the neurotrophin on the periphery as well. Indeed, the specific functional role of BDNF and its action mechanism in the cardiovascular system, especially in that of Africans, is yet to be determined. The cardiovascular health profile of black South Africans is a major concern as research has shown that this group suffers from an array of cardiovascular risk factors that may result in organ damage. Sub-clinical atherosclerosis or structural endothelial dysfunction contributes to ever-increasing morbidity and mortality in the world. However, no studies regarding the associations between BDNF and structural vascular disease have been undertaken relating to black African participants. Objectives - The objective of this study was to determine whether BDNF is associated with changes in ambulatory blood pressure (BP) and whether a relationship between BDNF and structural endothelial dysfunction exists in black African male and female participants, determined by cross sectional wall area (CSWA) and albumin:creatinine ratio (ACR). Methodology - The study included 172 black African teachers (82 males and 90 females) who were employed by the Kenneth Kaunda Education district of the North-West Province, South Africa. Ambulatory blood pressure recordings were obtained with the use of a Meditech CE120 CardioTens ® apparatus. Blood pressure readings were measured at 30 min intervals during the day and 60 min intervals during the night. Anthropometric measurements were performed in triplicate by registered level II anthropometrists according to standardised procedures. A high-resolution ultrasound scan with carotid intima-media thickness (CIMT) images from at least two optimal angles of the left and right common carotid artery were obtained using a SonoSite Micromaxx ultrasound system. The lumen diameter between the near and far wall of the lumen-intima interface and the averages of both the left and right common carotid arteries were calculated. Subsequently, the carotid cross-sectional wall area (CSWA) was calculated. Participants, who fasted overnight, provided eight-hour blood and urine samples to determine serum BDNF and metabolic markers, for example, hyperglycaemia (HbA1c) and gamma glutamyl transferase (GGT). Urinary albumin and creatinine levels were determined by means of a turbidimetric method with the use of a Unicel DXC 800 analyser from Beckman and Coulter (Germany) and expressed as a ratio between albumin and creatinine (ACR). BDNF median split x Gender interaction effects for structural ED justified stratification of BDNF into low and high (≤ / > 1.37 ng/ml) gender groups. Results and Conclusion - On average, male participants were overweight (BMI 25-30kg/m2) and abused more alcohol.21 African men revealed a vulnerable cardiometabolic profile with values exceeding cut–points (European Society of Hypertension). These men demonstrated increased acute and chronic glucose (HbA1c) levels indicating a pre-diabetic state; as well as a disturbed lipid profile with lower HdL and increased triglycerides. Overall BDNF levels were lower than reference ranges (6.97 – 42.6 ng/ml). The men revealed mean lower BDNF levels, ambulatory BP values exceeding guideline cut-points (ambulatory SBP > 130mmHg; DBP > 80mmHg) as well as a hypertensive state compared to their female counterparts. Pertaining to structural endothelial dysfunction, the mean ACR value in men exceeded normal laboratory values (< 3.5mg/mmol). The African women displayed an obese state with low grade inflammation (CRP, 12.27 ± 11.67mg/l). A single two-way ANCOVA interaction on main effects (BDNF median split x Gender) demonstrated significant interaction for CIMTf [F (1,164); 3.99, p=0.05] and cholesterol [F (1,164); 4.12, p=0.05]. Therefore, a median split approach was followed which stratified gender groups into lower (≤ 1.37 ng/ml) and higher BDNF levels (>1.37 ng/ml). The low BDNF men revealed higher cholesterol than the high BDNF group, independent of BMI and age. Only the low BDNF women indicated significantly higher values for structural vascular markers (p< 0.05) than the high BDNF female group. In conclusion, we accept our hypothesis, as hypertrophic remodelling of the carotid artery was associated with lower BDNF levels. This may imply attenuated or possibly down-regulated BDNF levels acting as a compensatory mechanism for the mean higher BP levels. In women, metabolic risk and hypertrophic remodelling were evident within higher circulating levels of BDNF, underpinning different underlying mechanisms for impaired neurotrophin health in men and women. Novel findings of BDNF revealed the impact of central neural regulation on the circulatory system, which may contribute to cardiometabolic risk in Africans. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014

Motivation - The burden of cardiovascular diseases (CVD) is increasing in developing countries worldwide, but even more so in sub-Saharan Africa. Due to rapid urbanisation, black populations experience lifestyle changes (e.g. unhealthy diet, increased access to alcohol and tobacco) that predispose them to increased obesity and cardiovascular risk. In this study, attention will be given to cardiovascular alterations, specifically arterial calcification, in lean and overweight/obese women nearing or already experiencing menopause. These include elevated blood pressure, large artery stiffness (indicated by increased central pulse pressure (cPP)) and carotid intima-media thickness (CIMT). Other factors linked to arterial calcification include the level of obesity as well as low bone mineral density. Ectopic calcification plays a significant role in cardiovascular morbidity and mortality, especially in renal failure patients, osteoporotic and elderly women. Factors contributing to the development and progression of arterial calcification include calciotropic hormones and altered bone metabolism, particularly in older postmenopausal women. This is due to the lack of protective effects of oestrogen against vascular alterations and bone loss after menopause. Previous studies have shown that increased bone resorption indicated by elevated levels of c-telopeptide of type I collagen (CTX), parathyroid hormone (PTH), low 25- hydroxycholecalciferol (25(OH)D3) and parathyroid hormone to 25-hydroxycholecalciferol ratio (PTH:25(OH)D3) are independently linked to arterial stiffening, CIMT and vascular calcification. Knowledge on the contribution of altered bone metabolism and associated calciotropic hormones on cardiovascular health in Africans is limited. Previous studies on ectopic calcification in South Africans focused on men and renal failure patients. This study will explore the possible role of altered calcium regulation and bone metabolism in the development of arterial calcification and CVD in older African women. Aim - The aim of this study was to investigate the associations of brachial and central pressures and CIMT with PTH, PTH:25(OH)D3 and CTX, a marker of bone resorption, in lean and overweight/obese African women older than 46 years. Methodology - This sub-study forms part of the Prospective Urban Rural Epidemiology (PURE) study. A total of 434 urban and rural women older than 46 years were included in the study. Women infected with the human immunodeficiency virus (HIV) were excluded from the study. The study was reviewed and approved by the Ethics Committee of the North-West University (Potchefstroom campus) and all participants signed an informed consent form prior to enrolment into the project. Field workers administered demographic, general health and physical activity questionnaires in the participants’ home language. Anthropometric measurements included weight, height and waist circumference, while body mass index (BMI) was calculated in kg/m2. Cardiovascular measurements included brachial and central systolic blood pressure (SBP), brachial diastolic blood pressure (DBP), brachial and central pulse pressure (PP) as well as CIMT and carotid cross-sectional wall area (CSWA). Blood pressure measurements were performed on the right arm with the participant in the sitting position. Blood was drawn after an overnight fasting period. We performed biochemical analyses from serum and plasma samples for follicle stimulating hormone (FSH), PTH, 25(OH)D3, and CTX. HIV testing was performed according to standardised procedures. Since interactions existed for BMI with regards to associations of CIMT and cPP with PTH:25(OH)D3, the study population was divided into the lean (BMI <25 kg/m2) and overweight/obese (BMI ≥25 kg/m2) groups. We performed independent T-tests to compare means and used the chi-square test to compare proportions. Single and multiple regression analyses were performed to investigate the associations of markers of vascular structure and function with CTX and calciotropic hormones. Results - In this study, 90% of the women displayed an FSH concentration exceeding the cut-off value of 35 mIu/mL, indicating a postmenopausal state. When comparing lean and overweight/obese African women, we found that lean women had higher levels of CTX and 25(OH)D3 (both p<0.001), while the overweight/obese group was older (p=0.007) and presented with higher PTH and PTH:25(OH)D3 levels (both p<0.001). Brachial and central pressures did not differ between the groups (p≥0.23), except for DBP being higher in the overweight/obese group (p=0.017). Overweight/obese women had higher CIMT (p<0.001) and CSWA (p=0.001) as compared to their lean counterparts. A larger proportion of lean women smoked (63%) and self-reported on alcohol use (37%) than overweight/obese women (41% and 18%, respectively) (both p<0.001). Forty-one percent of overweight/obese women used antihypertensive medication, opposed to 25% in the lean group (p=0.001). In multivariate regression analyses, an independent positive association existed between CIMT and PTH:25(OH)D3 (R2=0.22; β=0.26; p=0.003) in lean women. In the overweight/obese group independent positive associations were confirmed between brachial SBP and PTH (p=0.013) and CTX (p=0.038), and between DBP and PTH (p=0.030). Brachial PP and central SBP remained positively associated with CTX (p=0.016 and p=0.024, respectively), while cPP was independently associated with PTH:25(OH)D3 (R2=0.20; β=0.17; p=0.017) and CTX (R2=0.20; β=0.17; p=0.025). Conclusion - Our results indicate that in older African women, large artery structure and function are associated with calciotropic hormones and bone resorption, suggesting that altered bone metabolism and associated calciotropic hormones play a role in the development of vascular calcification. The different associations in lean and overweight/obese women suggest different mechanisms at work regarding arterial calcification in states of low and high adiposity. These findings need confirmation in larger prospective and experimental studies. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014

Motivation - The burden of cardiovascular diseases (CVD) is increasing in developing countries worldwide, but even more so in sub-Saharan Africa. Due to rapid urbanisation, black populations experience lifestyle changes (e.g. unhealthy diet, increased access to alcohol and tobacco) that predispose them to increased obesity and cardiovascular risk. In this study, attention will be given to cardiovascular alterations, specifically arterial calcification, in lean and overweight/obese women nearing or already experiencing menopause. These include elevated blood pressure, large artery stiffness (indicated by increased central pulse pressure (cPP)) and carotid intima-media thickness (CIMT). Other factors linked to arterial calcification include the level of obesity as well as low bone mineral density. Ectopic calcification plays a significant role in cardiovascular morbidity and mortality, especially in renal failure patients, osteoporotic and elderly women. Factors contributing to the development and progression of arterial calcification include calciotropic hormones and altered bone metabolism, particularly in older postmenopausal women. This is due to the lack of protective effects of oestrogen against vascular alterations and bone loss after menopause. Previous studies have shown that increased bone resorption indicated by elevated levels of c-telopeptide of type I collagen (CTX), parathyroid hormone (PTH), low 25- hydroxycholecalciferol (25(OH)D3) and parathyroid hormone to 25-hydroxycholecalciferol ratio (PTH:25(OH)D3) are independently linked to arterial stiffening, CIMT and vascular calcification. Knowledge on the contribution of altered bone metabolism and associated calciotropic hormones on cardiovascular health in Africans is limited. Previous studies on ectopic calcification in South Africans focused on men and renal failure patients. This study will explore the possible role of altered calcium regulation and bone metabolism in the development of arterial calcification and CVD in older African women. Aim - The aim of this study was to investigate the associations of brachial and central pressures and CIMT with PTH, PTH:25(OH)D3 and CTX, a marker of bone resorption, in lean and overweight/obese African women older than 46 years. Methodology - This sub-study forms part of the Prospective Urban Rural Epidemiology (PURE) study. A total of 434 urban and rural women older than 46 years were included in the study. Women infected with the human immunodeficiency virus (HIV) were excluded from the study. The study was reviewed and approved by the Ethics Committee of the North-West University (Potchefstroom campus) and all participants signed an informed consent form prior to enrolment into the project. Field workers administered demographic, general health and physical activity questionnaires in the participants’ home language. Anthropometric measurements included weight, height and waist circumference, while body mass index (BMI) was calculated in kg/m2. Cardiovascular measurements included brachial and central systolic blood pressure (SBP), brachial diastolic blood pressure (DBP), brachial and central pulse pressure (PP) as well as CIMT and carotid cross-sectional wall area (CSWA). Blood pressure measurements were performed on the right arm with the participant in the sitting position. Blood was drawn after an overnight fasting period. We performed biochemical analyses from serum and plasma samples for follicle stimulating hormone (FSH), PTH, 25(OH)D3, and CTX. HIV testing was performed according to standardised procedures. Since interactions existed for BMI with regards to associations of CIMT and cPP with PTH:25(OH)D3, the study population was divided into the lean (BMI <25 kg/m2) and overweight/obese (BMI ≥25 kg/m2) groups. We performed independent T-tests to compare means and used the chi-square test to compare proportions. Single and multiple regression analyses were performed to investigate the associations of markers of vascular structure and function with CTX and calciotropic hormones. Results - In this study, 90% of the women displayed an FSH concentration exceeding the cut-off value of 35 mIu/mL, indicating a postmenopausal state. When comparing lean and overweight/obese African women, we found that lean women had higher levels of CTX and 25(OH)D3 (both p<0.001), while the overweight/obese group was older (p=0.007) and presented with higher PTH and PTH:25(OH)D3 levels (both p<0.001). Brachial and central pressures did not differ between the groups (p≥0.23), except for DBP being higher in the overweight/obese group (p=0.017). Overweight/obese women had higher CIMT (p<0.001) and CSWA (p=0.001) as compared to their lean counterparts. A larger proportion of lean women smoked (63%) and self-reported on alcohol use (37%) than overweight/obese women (41% and 18%, respectively) (both p<0.001). Forty-one percent of overweight/obese women used antihypertensive medication, opposed to 25% in the lean group (p=0.001). In multivariate regression analyses, an independent positive association existed between CIMT and PTH:25(OH)D3 (R2=0.22; β=0.26; p=0.003) in lean women. In the overweight/obese group independent positive associations were confirmed between brachial SBP and PTH (p=0.013) and CTX (p=0.038), and between DBP and PTH (p=0.030). Brachial PP and central SBP remained positively associated with CTX (p=0.016 and p=0.024, respectively), while cPP was independently associated with PTH:25(OH)D3 (R2=0.20; β=0.17; p=0.017) and CTX (R2=0.20; β=0.17; p=0.025). Conclusion - Our results indicate that in older African women, large artery structure and function are associated with calciotropic hormones and bone resorption, suggesting that altered bone metabolism and associated calciotropic hormones play a role in the development of vascular calcification. The different associations in lean and overweight/obese women suggest different mechanisms at work regarding arterial calcification in states of low and high adiposity. These findings need confirmation in larger prospective and experimental studies. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014