abstract / Pharmacology and Pharmacy / Doctoral / Doctor of Philosophy

Recent studies support the association between metabolic syndrome (MetS), a cluster of cardiovascular risk factors, and diastolic dysfunction. Disproportionate collagen accumulation, particularly cross-linking of collagen, plays a key role in translating interstitial fibrosis into mechanical chamber stiffness and diastolic dysfunction. Characteristic changes in the expression and activity of myocardial lysyl oxidase (LOX), a matrix modifying enzyme that catalyzes cross-linked collagen, are unclear in MetS. We established a diet-induced MetS model to study diastolic dysfunction by treating male C57BL/6 mice a high-fat high-simple carbohydrate (HFHSC) diet for 6 months. Despite blunted gene expression of LOX isoforms, MetS mice demonstrated significant increase in the ratio of protein expression of mature to proenzyme LOX, enhanced LOX activity, and increased cardiac cross-linked collagen compared with controls. This fibrotic response coincided with marked increase in left ventricular end-diastolic pressure and stiffness and impaired diastolic filling pattern. Our data demonstrate that diet-induced MetS alters the remodeling enzyme LOX, thereby increasing the amount of crosslinking and inducing diastolic dysfunction.Furthermore we examined the role of T-lymphocytes in myocardial LOX regulation in diet-induced fibrotic hearts. Female SCID mice which are devoid of functional T-lymphocytes and C57BL/6 mice were treated with HFHSC diet for 12 months. Similar to male C67BL/6, female HFHSC-fed C57BL/6 mice demonstrated significant increase in maturation and catalytic activity of myocardial LOX, cross-linking, ventricular stiffness and diastolic dysfunction. Whereas induction of LOX protein was minimal in SCID mice compared with wild-type counterparts. Correspondingly fibrillar cross-linked collagen formation and diastolic dysfunction were less prominent in SCID mice. Our results suggest a potential role of T-lymphocytes in induction of myocardial stiffness and diastolic dysfunction through modulation of LOX-dependent collagen maturation.Moreover we studied the role of leptin, an adipokine over-produced in MetS with fibrotic effects in non-cardiac tissues, as a key mediator of profibrogenic responses in the heart by administrating leptin to C57BL/6 and leptin-deficient ob/ob mice. With exogenous leptin administration ob/ob mice displayed passive diastolic filling dysfunction that coincided with increase in myocardial collagen compared with ob/ob controls. Our findings suggest profibrotic effects of leptin in the heart, primarily through predominance of collagen synthesis over degradation.

Motivation: Cardiovascular dysfunction and hypertension are some of the leading causes of morbidity and mortality in the African population. According to the World Health Organisation the increases in these diseases are escalating in developing countries. Apart from the contributory role of genetics towards the incidence of hypertension, evidence regarding lifestyle as a determinant or marker of cardiovascular diseases in this group is not well known. The interaction of psychological and physiological mechanisms can contribute towards a broader scope of behavioural physiology in the higher prevalence of hypertension in Africans. Objectives: The main objective of the research in this thesis was to compare specific coping mechanisms of Africans with regard to cardiovascular dysfunction. Methodology: Manuscripts presented in Chapters 3, 4, and 5 made use of the cross-sectional comparative epidemiological "Transition and Health during Urbanisation in South Africa" (THUSA) project. The subjects included apparently healthy African men and women, which were recruited as a convenience sample from the North West Province, South Africa. Anthropometric measurements were taken and demographic questionnaires completed. An adapted Setswana COPE questionnaire was used to classify men and women as predominantly active (AC) or passive (PC) in coping style. Subjects were further subdivided into rural and urban groups (Manuscript Two), as well as younger (≤ 40) and older (≥ 45) age groups (Manuscript Three). The General Health Questionnaire (GHQ) was used to measure subjective perception of health in all three manuscripts. Blood pressure was recorded continuously before and during application of the handgrip test using the Finapres apparatus. Subjects were classified as normotensive and hypertensive after blood pressure measurement by the Finapres and the Riva-Rocci/Korotkoff method. The emphasis in this study was on the cardiovascular reactivity values. Fasting, resting serum renin activity, cortisol, prolactin, testosterone, high density lipoprotein, triglycerides, glucose and plasma fibrinogen values were correlated with cardiovascular and psychological variables. Significant differences between variables were determined by means of variance analyses (Manuscript One and Two adjusted for age; Manuscripts One, Two and Three adjusted for resting cardiovascular data). A logistic regression analysis was performed to determine the most significant determinants of urbanisation. All THUSA subjects and parents of under-aged adolescents gave informed consent and the study - was approved by the Ethics Committee of the Potchefstroom University for Christian Higher Education. The reader is referred to the abstracts at the beginning of each separate manuscript in Chapters 3 - 5 for a description of the subjects, study design and analytical methods used in each paper. Results and conclusions of the individual manuscripts: Results from the THUSA study showed that PC men and women reported more symptoms typical of an abnormal psychological and physiological profile than AC men and women. The PC men, compared to AC men, exhibited a larger vascular reactivity response as well as larger plasma renin activity. In contrast, the AC women showed a larger non-significant vascular reactivity response than PC women. All subjects though reacted with increased vascular reactivity on the stressor. Men with a PC strategy showed enhanced vascular reactivity, a perception of poorer health and larger stressor plasma renin activity. PC women reported more depressive symptoms and younger PC women indicated a higher prevalence of hypertension than younger AC women. As a follow-up on the first manuscript, the aim was focused mainly on including the environmental effect, namely urbanisation, as possible explanatory factor for the atypical physiological AC women’s' coping style. The rural AC subjects indicated more typical active coping central cardiac responses than rural PC subjects whereas urbanised AC and PC subjects indicated greater peripheral responses and hypertension prevalence rates. In addition, the urbanised AC men and women and PC women as opposed to their rural counterparts indicated symptoms more of a distress situation with increased values of prolactin and decreased values of testosterone. This was also accompanied by a perception of poorer health in women. Results of the AC style suggests that the typical physiological AC stimulation pattern of urbanised subjects and especially the women is dissociated from the "normal" physiological AC reaction and is now exhibited as a typical PC physiological stimulation pattern. The greater vascular reactivity, hypertension prevalence, perception of poorer health and endocrine distressed profile are associated with a PC and dissociated physiological AC style in an urban context in African men and women. No differences with regard to resting blood pressure or endocrine values were obtained when the AC and PC urbanised groups were compared. Africans develop cardiovascular dysfunction/hypertension during chronic stress or urbanisation. This implies a dissociation/habituation of physiological systems of African men and women despite having an active coping strategy. Active coping is, therefore, not necessarily "successful". Results of the first two manuscripts direct further investigation concerning the effects of ageing and urbanisation on the development of cardiovascular dysfunction and metabolic syndrome indicators in gender groups. The second manuscript showed that all rural AC subjects exhibit a more typical active coping central cardiac response and that rural PC and all urbanised subjects (AC and PC) exhibit enhanced peripheral vascular responses on the - handgrip test. Where peripheral vascular responses were more expected from older individuals in Manuscript Three, the occurrence of this pattern is strengthened in the younger subjects. The greater fibrinogen values in all younger urbanised women (AC and PC) compared to rural women further strengthen the risk for the development of cardiovascular disease. Increased vascular reactivity, abdominal obesity and increased levels of triglycerides as well as perception of poorer health were apparent in the urbanised AC women, PC men and women in comparison to their rural counterparts. The typical physiological AC stimulation pattern of urbanised women is dissociated from the "normal" physiological AC responses and is now exhibited as a typical PC physiological stimulation pattern. A typical PC style in older urbanised subjects is implicated in the greater hypertension prevalence. To conclude, it seems as if young urbanised Africans, and especially women, exhibit an AC style behaviourally with a dissociated physiological AC reaction pattern. Physiologically these women resemble a typical PC physiological cardiovascular and endocrine profile. This typical PC cardiovascular stimulation pattern is strengthened by a distressed endocrine profile, significant metabolic syndrome indicators and a 'perception of poorer health. Older PC style subjects also presented a greater hypertension prevalence. In this study it seems that cardiovascular changes that appear at a younger age might be influenced by other factors including urbanisation as a lifestyle factor as well as specific coping styles. Finally, a careful suggestion is made that specific coping mechanisms could be seen as a possible risk marker in the development of the metabolic syndrome. / Thesis (Ph.D. (Physiology))--North-West University, Potchefstroom Campus, 2005.

Darbo tikslas Ištirti mažų pagal nėštumo trukmę vaikų postnatalinį augimo pobūdį, hormonų profilį bei nustatyti prenatalinius ir ankstyvuosius postnatalinius veiksnius įtakojančius vaikų augimą ir metabolinius pokyčius iki brendimo Darbo uždaviniai 1. Ištirti mažų pagal nėštumo trukmę vaikų postnatalinio augimo pobūdį pirmaisiais 6 gyvenimo metais, lyginant juos su to paties amžiaus vaikais, gimusiais atitinkančio nėštumo trukmei svorio ir ūgio. 2. Įvertinti tėvų ir naujagimių antropometrinių rodiklių bei hormonų profilio gimimo metu įtaką mažų pagal nėštumo trukmę vaikų augimui nuo gimimo iki 6 metų. 3. 6 metų mažiems ir atitinkantiems nėštumo trukmę vaikams ištirti hormonų profilį (insulinoidinį augimo faktorių–I (IGF–I), IGF–I surišantį baltymą–3 (IGFBP–3) leptiną, adiponektiną), jautrumą insulinui bei lipidų profilį. 4. Nustatyti gimimo svorio ir ankstyvojo postnatalinio augimo įtaką vaikų nutukimo, atsparumo insulinui bei dislipidemijos rizikai iki brendimo. Mažiems pagal nėštumo trukmę vaikams anksti nustatyti pradiniai metaboliniai pakitimai (sumažėjęs jautrumas insulinui, padidėjęs leptino ir sumažėjęs adiponektino kiekis, dislipidemijos požymiai, gliukozės tolerancijos sutrikimas), žemaūgiškumas, polinkis nutukimui gali suteikti savalaikę informaciją bei galimybę pritaikyti ankstyvas profilaktines priemones nutukimui bei 2 tipo cukrinio diabeto, širdies ir kraujagyslių ligų išsivystymui vyresniame amžiuje. / Aim The present study aims to explore the postnatal growth pattern and hormonal profile in small for gestational age children and to identify prenatal and early postnatal risk factors of short stature and postnatal metabolic changes in early prepubertal age. Objectives: 1. To explore the postnatal growth pattern of children born small for gestational age during the first six years of life in comparison with children of appropriate for gestational age birth size. 2. To evaluate the impact of parental axiology, neonatal anthropometry and hormonal status at birth on the early postnatal growth of small for gestational age children. 3. To investigate hormonal profile (insulin like growth factor-1, insulin like growth factor binding protein-3, adiponectin and leptin), insulin sensitivity and lipid profile in six-year-old small and appropriate for gestational age children. 4. To evaluate the influence of birth size and postnatal growth pattern on the risk of obesity, insulin resistance and dyslipidemia in small for gestational age children during the late prepubertal period.

Emerging evidence has shown that an abnormal postprandial accumulation of dietary tat IS atherogenic. The aim of this study is to measure triacylglycerol (TAG) kinetics in endogenous and exogenous lipoproteins in both fed and fasted states using stable isotopes.

Motivation: Cardiovascular dysfunction and hypertension are some of the leading causes of morbidity and mortality in the African population. According to the World Health Organisation the increases in these diseases are escalating in developing countries. Apart from the contributory role of genetics towards the incidence of hypertension, evidence regarding lifestyle as a determinant or marker of cardiovascular diseases in this group is not well known. The interaction of psychological and physiological mechanisms can contribute towards a broader scope of behavioural physiology in the higher prevalence of hypertension in Africans. Objectives: The main objective of the research in this thesis was to compare specific coping mechanisms of Africans with regard to cardiovascular dysfunction. Methodology: Manuscripts presented in Chapters 3, 4, and 5 made use of the cross-sectional comparative epidemiological "Transition and Health during Urbanisation in South Africa" (THUSA) project. The subjects included apparently healthy African men and women, which were recruited as a convenience sample from the North West Province, South Africa. Anthropometric measurements were taken and demographic questionnaires completed. An adapted Setswana COPE questionnaire was used to classify men and women as predominantly active (AC) or passive (PC) in coping style. Subjects were further subdivided into rural and urban groups (Manuscript Two), as well as younger (≤ 40) and older (≥ 45) age groups (Manuscript Three). The General Health Questionnaire (GHQ) was used to measure subjective perception of health in all three manuscripts. Blood pressure was recorded continuously before and during application of the handgrip test using the Finapres apparatus. Subjects were classified as normotensive and hypertensive after blood pressure measurement by the Finapres and the Riva-Rocci/Korotkoff method. The emphasis in this study was on the cardiovascular reactivity values. Fasting, resting serum renin activity, cortisol, prolactin, testosterone, high density lipoprotein, triglycerides, glucose and plasma fibrinogen values were correlated with cardiovascular and psychological variables. Significant differences between variables were determined by means of variance analyses (Manuscript One and Two adjusted for age; Manuscripts One, Two and Three adjusted for resting cardiovascular data). A logistic regression analysis was performed to determine the most significant determinants of urbanisation. All THUSA subjects and parents of under-aged adolescents gave informed consent and the study - was approved by the Ethics Committee of the Potchefstroom University for Christian Higher Education. The reader is referred to the abstracts at the beginning of each separate manuscript in Chapters 3 - 5 for a description of the subjects, study design and analytical methods used in each paper. Results and conclusions of the individual manuscripts: Results from the THUSA study showed that PC men and women reported more symptoms typical of an abnormal psychological and physiological profile than AC men and women. The PC men, compared to AC men, exhibited a larger vascular reactivity response as well as larger plasma renin activity. In contrast, the AC women showed a larger non-significant vascular reactivity response than PC women. All subjects though reacted with increased vascular reactivity on the stressor. Men with a PC strategy showed enhanced vascular reactivity, a perception of poorer health and larger stressor plasma renin activity. PC women reported more depressive symptoms and younger PC women indicated a higher prevalence of hypertension than younger AC women. As a follow-up on the first manuscript, the aim was focused mainly on including the environmental effect, namely urbanisation, as possible explanatory factor for the atypical physiological AC women’s' coping style. The rural AC subjects indicated more typical active coping central cardiac responses than rural PC subjects whereas urbanised AC and PC subjects indicated greater peripheral responses and hypertension prevalence rates. In addition, the urbanised AC men and women and PC women as opposed to their rural counterparts indicated symptoms more of a distress situation with increased values of prolactin and decreased values of testosterone. This was also accompanied by a perception of poorer health in women. Results of the AC style suggests that the typical physiological AC stimulation pattern of urbanised subjects and especially the women is dissociated from the "normal" physiological AC reaction and is now exhibited as a typical PC physiological stimulation pattern. The greater vascular reactivity, hypertension prevalence, perception of poorer health and endocrine distressed profile are associated with a PC and dissociated physiological AC style in an urban context in African men and women. No differences with regard to resting blood pressure or endocrine values were obtained when the AC and PC urbanised groups were compared. Africans develop cardiovascular dysfunction/hypertension during chronic stress or urbanisation. This implies a dissociation/habituation of physiological systems of African men and women despite having an active coping strategy. Active coping is, therefore, not necessarily "successful". Results of the first two manuscripts direct further investigation concerning the effects of ageing and urbanisation on the development of cardiovascular dysfunction and metabolic syndrome indicators in gender groups. The second manuscript showed that all rural AC subjects exhibit a more typical active coping central cardiac response and that rural PC and all urbanised subjects (AC and PC) exhibit enhanced peripheral vascular responses on the - handgrip test. Where peripheral vascular responses were more expected from older individuals in Manuscript Three, the occurrence of this pattern is strengthened in the younger subjects. The greater fibrinogen values in all younger urbanised women (AC and PC) compared to rural women further strengthen the risk for the development of cardiovascular disease. Increased vascular reactivity, abdominal obesity and increased levels of triglycerides as well as perception of poorer health were apparent in the urbanised AC women, PC men and women in comparison to their rural counterparts. The typical physiological AC stimulation pattern of urbanised women is dissociated from the "normal" physiological AC responses and is now exhibited as a typical PC physiological stimulation pattern. A typical PC style in older urbanised subjects is implicated in the greater hypertension prevalence. To conclude, it seems as if young urbanised Africans, and especially women, exhibit an AC style behaviourally with a dissociated physiological AC reaction pattern. Physiologically these women resemble a typical PC physiological cardiovascular and endocrine profile. This typical PC cardiovascular stimulation pattern is strengthened by a distressed endocrine profile, significant metabolic syndrome indicators and a 'perception of poorer health. Older PC style subjects also presented a greater hypertension prevalence. In this study it seems that cardiovascular changes that appear at a younger age might be influenced by other factors including urbanisation as a lifestyle factor as well as specific coping styles. Finally, a careful suggestion is made that specific coping mechanisms could be seen as a possible risk marker in the development of the metabolic syndrome. / Thesis (Ph.D. (Physiology))--North-West University, Potchefstroom Campus, 2005.

Motivation: Metabolic syndrome is a constellation of risk factors predisposing to coronary heart disease (CHD) and is classified as a "disease of modern civilization". Characteristics of the metabolic syndrome include abdominal obesity, increased triacylglycerol (TG) concentrations, increased small dense low-density lipoprotein(LDL) particles, decreased high-density lipoprotein cholesterol (HDL-C), hypertension, insulin resistance, inflammation, glucose intolerance and/or type 2 diabetes mellitus. Subjects with metabolic syndrome may be susceptible to oxidative stress due to their prolonged exposure to elevated glucose levels. A variety of natural antioxidants exists (e.g. glutathione, l3-carotene, vitamin C, polyphenols) that may prevent oxidative damage to biological structures. Nuts are rich sources of unsaturated fatty acids, protein, fibre, .micronutrients, phytochemicals and antioxidants. Duet o their high antioxidant content, it can, therefore, be speculated that nuts may play a role in the prevention of oxidative stress in subjects with the metabolic syndrome. Objective: - To investigate the effect of a high walnut and a high unsalted cashew nut diet on the antioxidant status of subjects with metabolic syndrome. Methods: Sixty eight subjects with diagnosed metabolic syndrome (according to the ATP III criteria) were recruited to take part in this parallel, randomized, controlled feeding trial. Subjects were mainly recruited from the North-West University, Potchefstroom Campus and surrounding areas. After a run-in period of three weeks during which the participants followed a prudent diet, subjects were randomly divided into three groups receiving either walnuts or cashew nuts (63- 108g/day)as part of a prudent diet, or continued with the prudent control diet. The intervention was followed for eight weeks. Fasting blood samples were taken at the beginning(after the three week run-in period) and at the end of the intervention. Antioxidant variables including oxygen radical absorbance capacity (ORAC), reduced glutathione (GSH)/oxidized glutathione (GSSG), diacron reactive oxygen metabolites (dRom) were measured at the beginning and the end of the intervention. C-reactive protein (CRP), fibrinogen and plasminogen activator-inhibitor activity (PAI-1a) were also measured as markers of inflammation. The antioxidant capacity and the polyphenol content of the diets and the walnuts and cashew nuts were determined at the end of the intervention. Results: A significant decrease in dRom and significant increases in GSSG, the redox status of glutathione (GSH/GSSG) and ORAC were observed in all three groups from baseline to end. GSH remained unchanged from baseline to end in all three groups. No significant differences in changes in dRom (p = 0.92), GSSG (p = 0.99), GSH/GSSG (p = 0.86), antioxidant capacity (p = 0.10) and GSH (p = 0.34) were observed from baseline to end between groups. The total polyphenol content of the walnut and control diets were similar and significantly higher than the cashew nut diet. The antioxidant capacity of the walnut and cashew nut diets showed a tendency to be higher than the control diet (p = 0.07 and p = 0.06 respectively). CRP, fibrinogen and PAI-1a concentrations did not differ significantly between groups. Conclusion No significant differences between the groups receiving walnuts, cashew nuts or no nuts were observed in GSH, GSSG, GSH/GSSG, dRom or ORAC. Therefore, there seems to be no beneficial effect of the inclusion of walnuts and cashew nuts in the diet on the antioxidant status of the participants. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2006.

Introduction: Across the world the incidence of the metabolic syndrome increases annually at an alarming rate. Two conditions associated with this are obesity and hypertension (high blood pressure). Both have negative health and lifestyle consequences, numerous studies on adrenergic receptor (AR) gene polymorphisms in various population groups have proved, although not exclusively, that these polymorphisms may be positively associated with susceptibility to and progression of obesity and hypertension. The AR encoding genes are attractive targets for such studies because the ARs, as part of the sympathetic nervous system, perform important functions like vasoconstriction, vasodilation, lipolysis and influence the heart's contraction. These functions accentuate the possible role of AR gene polymorphisms in the onset or progression of obesity and hypertension. Obesity is a health concern especially among black South African women. The prevalence of obesity (BMI > 30 kg/m2) in the North-West province of South Africa is high: 28.6%. The POWIRS (Profile of Obese Women with the Insulin Resistance syndrome) study was conducted in 2003 on 102 black South African female volunteers to search for possible associations of the p2-AR Gln27Glu and p3-AR Trp64Arg polymorphisms with parameters of the carbohydrate and lipid metabolism, the index of insulin resistance (HOMA-IR), body mass index (BMI) and body fat % (Schutte et al., 2005). To our knowledge, this was the first study of its kind in South Africa and which led to this study and dissertation. Objectives: The objectives of this study were to: • Determine the incidence of the following polymorphisms in (a) 102 black South African female volunteers and calculate the minor allele frequency: B1-AR: Ser49Gly; B2-AR: Arg16Gly; (b) 115 white South African female volunteers and calculate the minor allele frequency: B1-AR: Ser49Gly; B2-AR: Arg16Gly; Gln27Glu; B3-AR: Trp64Arg; • identify possible diplotypes and haplotypes in the study groups; • take relevant physiological parameters (measured in the POWIRS studies) into account in the search for possible associations of these polymorphisms, diplotypes and haplotypes with obesity and high blood pressure as characteristics of the metabolic syndrome; • compare the black and the white study groups with regards to the above mentioned objectives. Methods: DNA was isolated from blood spots on Guthrie cards (collected during the POWIRS studies) and the respective AR gene regions amplified by polymerase chain reaction (PCR). After restriction enzyme digestion, the DIVA fragments were separated by agarose gel electrophoresis. Genotypic findings were examined along with measured physiological parameters (measured during the POWIRS studies) and statistically processed. Area under the curve (AUC) analysis was performed on parameters measured during the oral glucose tolerance test. Diplotype and haplotype analyses were also performed on both subject groups. Results: The minor allele frequencies for both groups were calculated and compared to that reported in other published studies. For the black group, the minor allele frequencies were: 84% (B1-AR Ser49Gly), 16% (B2-AR Gln27Glu), 49% (B2-AR Arg16Gly) and 28% (B3-AR Trp64Arg) and for the white group: 94%, 46%, 50% and 7% respectively. The AUC differed in almost every instance of comparison, but was within normal ranges. Only a few significant differences were identified when the measured physiological parameters were compared between the genotypes, diplotypes and haplotypes in each group, most of which were found to be within normal ranges. When the two groups of test subjects were compared, only minimal differences were observed, most of which were still found to be well within normal ranges. Conclusions: Although no associations were identified between the separate investigated AR gene polymorphisms, diplotypes or haplotypes and obesity and hypertension or high blood pressure, indications are present that they may act as contributors to risk factors for the onset and progression of these characteristics of the metabolic syndrome. / Thesis (M.Sc. (Biochemistry))--North-West University, Potchefstroom Campus, 2007.

Introduction: Across the world the incidence of the metabolic syndrome increases annually at an alarming rate. Two conditions associated with this are obesity and hypertension (high blood pressure). Both have negative health and lifestyle consequences, numerous studies on adrenergic receptor (AR) gene polymorphisms in various population groups have proved, although not exclusively, that these polymorphisms may be positively associated with susceptibility to and progression of obesity and hypertension. The AR encoding genes are attractive targets for such studies because the ARs, as part of the sympathetic nervous system, perform important functions like vasoconstriction, vasodilation, lipolysis and influence the heart's contraction. These functions accentuate the possible role of AR gene polymorphisms in the onset or progression of obesity and hypertension. Obesity is a health concern especially among black South African women. The prevalence of obesity (BMI > 30 kg/m2) in the North-West province of South Africa is high: 28.6%. The POWIRS (Profile of Obese Women with the Insulin Resistance syndrome) study was conducted in 2003 on 102 black South African female volunteers to search for possible associations of the p2-AR Gln27Glu and p3-AR Trp64Arg polymorphisms with parameters of the carbohydrate and lipid metabolism, the index of insulin resistance (HOMA-IR), body mass index (BMI) and body fat % (Schutte et al., 2005). To our knowledge, this was the first study of its kind in South Africa and which led to this study and dissertation. Objectives: The objectives of this study were to: • Determine the incidence of the following polymorphisms in (a) 102 black South African female volunteers and calculate the minor allele frequency: B1-AR: Ser49Gly; B2-AR: Arg16Gly; (b) 115 white South African female volunteers and calculate the minor allele frequency: B1-AR: Ser49Gly; B2-AR: Arg16Gly; Gln27Glu; B3-AR: Trp64Arg; • identify possible diplotypes and haplotypes in the study groups; • take relevant physiological parameters (measured in the POWIRS studies) into account in the search for possible associations of these polymorphisms, diplotypes and haplotypes with obesity and high blood pressure as characteristics of the metabolic syndrome; • compare the black and the white study groups with regards to the above mentioned objectives. Methods: DNA was isolated from blood spots on Guthrie cards (collected during the POWIRS studies) and the respective AR gene regions amplified by polymerase chain reaction (PCR). After restriction enzyme digestion, the DIVA fragments were separated by agarose gel electrophoresis. Genotypic findings were examined along with measured physiological parameters (measured during the POWIRS studies) and statistically processed. Area under the curve (AUC) analysis was performed on parameters measured during the oral glucose tolerance test. Diplotype and haplotype analyses were also performed on both subject groups. Results: The minor allele frequencies for both groups were calculated and compared to that reported in other published studies. For the black group, the minor allele frequencies were: 84% (B1-AR Ser49Gly), 16% (B2-AR Gln27Glu), 49% (B2-AR Arg16Gly) and 28% (B3-AR Trp64Arg) and for the white group: 94%, 46%, 50% and 7% respectively. The AUC differed in almost every instance of comparison, but was within normal ranges. Only a few significant differences were identified when the measured physiological parameters were compared between the genotypes, diplotypes and haplotypes in each group, most of which were found to be within normal ranges. When the two groups of test subjects were compared, only minimal differences were observed, most of which were still found to be well within normal ranges. Conclusions: Although no associations were identified between the separate investigated AR gene polymorphisms, diplotypes or haplotypes and obesity and hypertension or high blood pressure, indications are present that they may act as contributors to risk factors for the onset and progression of these characteristics of the metabolic syndrome. / Thesis (M.Sc. (Biochemistry))--North-West University, Potchefstroom Campus, 2007.

Chemical exposure in humans rarely consists of a single chemical. The everyday exposure is characterized by thousands of chemicals mainly present at low levels. Despite that fact, risk assessment of chemicals is carried out on a chemical-by-chemical basis although there is a consensus that this view is too simplistic. This thesis aims to validate a statistical method to study the impact of mixtures of contaminants and to use that method to investigate the associations between circulating levels of a large number of environmental contaminants and atherosclerosis and the metabolic syndrome in an elderly population. Contaminants measured in the circulation represented various classes, such as persistent organic pollutants, plastic-associated chemicals and metals. There was little co-variation among the contaminants and only two clusters of PCBs could be discerned. Gradient boosted CARTs were used to assess additive and multiplicative associations between atherosclerosis, as measured by the intima-media thickness (IMT) and the echogenicity of the intima-media complex (IM-GSM), and prevalent metabolic syndrome. Systolic blood pressure was the most important predictor of IMT while the influence of the contaminants was marginal. Three phthalate metabolites; MMP, MEHP and MIBP were strongly related to IM-GSM. A synergistic interaction was found for MMP and MIBP, and a small antagonistic interaction was found for MIBP and MEHP. Associations between the contaminants and prevalent metabolic syndrome were modest, but three pesticides; p,p’-DDE, hexachlorbenzene and trans-nonachlor along with PCBs 118 and 209 and mercury were the strongest predictors of prevalent metabolic syndrome. This thesis concludes that many contaminants need to be measured to get a clear picture of the exposure. Boosted CARTs are useful for uncovering interactions. Multiplicative and/or additive effects of certain contaminant mixtures were found for atherosclerosis or the metabolic syndrome.