PhD (Chemical Pathology),Faculty of Health Sciences, University of the Witwatersrand, 2009 / Introduction: The data published by the Medical Research Council of South Africa demonstrated that cardiovascular disease and diabetes mellitus are the second and tenth leading causes of death in South Africa, respectively (Bradshaw et al.,2003). The prevalence of obesity is higher in the African than Indian population (Puoane et al., 2002), whereas cardiovascular diseases (CVD) and diabetes are more common in the latter population (Omar et al., 1994, Joffe et al., 1994). Diabetes and hypertension has been related with abdominal obesity in a number of studies conducted in the African and mixed-ancestry communities of the Western Cape (Steyn et al., 1996, Levitt et al., 1993). The reason for the high prevalence of obesity in the African population is not known however it is known that the aetiology of obesity involves both environmental and genetic factors (Grundy, 2004). Objective: The main aim of this project was to ascertain the role of metabolic, hormonal, anthropometric and environmental factors in the pathogenesis of obesity-related disorders in two South African ethnic groups namely Indian and African women. These populations were chosen because of the wide differences in risk factors for the development of CVD and diabetes reported in these groups. Subjects and methods: Plasma and serum samples were taken during a 5-hour OGTT from 20 lean, 20 obese, 20 obese type 2 diabetic patients, and 10 overweight women of African and Indian origin, i.e. 140 subjects in total. All participants were recruited from an urban population of women residing in the Greater Johannesburg area. Serum insulin, C-peptide, proinsulin and adipokines were measured using ELISA kits. Fasting plasma glucose, serum cholesterol, HDL-cholesterol and triglycerides levels were measured on the ROCHE MODULAR System. Insulin resistance was calculated using HOMA. Visceral and subcutaneous fat areas were measured using a 5-level CT-scan. Nutrient intake was assessed using a validated quantified food frequency questionnaire. Socio-economic status was estimated from the level of education and the number of selected household amenities. The data collected from the project was analysed by using SAS System for Windows Release 8.02 SAS Institute Inc., Cary, NC, USA 1999-2001. V Results: Results from the study presented in the table below indicate that Indian females were more insulin resistant and had a worse atherogenic lipid profile than African females (statistically higher LDL and triglycerides levels). The greater visceral fat mass in the Indian subjects appears to be associated with triglycerides and correlated with insulin resistance (r=0.554, p<0.05). This effect was not observed in Africans. African females had a higher proportion of their energy intake as carbohydrates than Indians (49.3% and. 45.2%, respectively, p<0.05), whereas Indians had a higher proportion of their total energy intake as fat than Africans (34.0% and 29.9%, respectively, p<0.05). The level of educational attainment and possession of household amenities was lower in the African than Indian group, but this did not significantly influence any of the anthropometric variables. Conclusions: Visceral fat accumulation was greater in diabetic and lean Indian subjects than in diabetic and lean African groups, which may explain their higher risk for obesity-related disorders at lower BMI. Significantly higher HOMA levels in obese Indians and significantly lower proinsulin/insulin ratio in lean and obese Indian women compared to lean and obese African women suggests that lean and obese Indians have better beta-cell proinsulinprocessing efficiency than Africans, probably due to the higher secretory load imposed on beta cells by the higher level of insulin resistance in the Indian subjects. Triglycerides, one of the major components in the diagnostic criteria of metabolic syndrome, were significantly different in the obese group (higher in Indians) and this may lead to the higher prevalence of CVD in the Indian population. Interethnic differences for leptin levels were observed in the lean group of women with higher levels in the Indian subjects. When all non-diabetic subjects were combined serum leptin levels were significantly higher in Indian than African subjects. This is an intriguing result, since obesity is more common in the African than Indian populations of South Africa. Caloric intake was higher in lean African than Indian females. However, the hypothesis that lower leptin levels in lean African females may lead to higher dietary intake and thus an increased prevalence of obesity in this group must be evaluated in a longitudinal study of leptin levels and weight gain. The impact of lower socio-economic status in African than Indian population is not clear; however data from the literature does demonstrate a negative correlation of obesity prevalence with education and income

The interaction of the 2,3-diazanaphthalene, phthalazine and its 1-substituted derivatives with the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, has been investigated both in vivo and /Ok in vitro. Metabolic studies, carried out by treating rabbits with both cold and 14C-labelled phthalazine, have shown that this compound is extensively metabolised in vivo, the major metabolite being a glucuronide conjugate. Very little unchanged phthalazine or its molybdenum hydroxylase mediated oxidation product 1-hydroxyphthalazine were excreted in the urine. Pretreatment of rabbits with phthalazine or 1-hydroxyphthalazine had no effect upon the activity of the microsomal monooxygenases but caused a significant increase in the specific activities of both aldehyde oxidase and xanthine oxidase. Determination of the molybdenum content of purified aldehyde oxidase fractions using electrothermal atomic absorption spectroscopy has confirmed that an increase in the molybdenum content of the enzyme fraction accompanies the increase in activity. A qualitative assessment of purified aldehyde oxidase fractions using iso-electric focusing has indicated that this enzyme may be composed of 2 or 3 active variants and following pretreatment with either phthalazine or 1-hydroxyphthalazine a further band of enzyme activity is apparent on the electropherogram. The Km value for phthalazine is significantly reduced with enzyme prepared from phthalazine treated rabbits, indicating that a form of the enzyme with a high affinity for phthalazine may have been induced. 1-Hydrazinophthalazine (Hydralazine) and two other hydrazine substituted N-heterocycles, endralazine and 1-hydrazinoisoquinoline have been shown to exert a potent progressive inhibition of aldehyde oxidase in vitro, effective only in the presence of substrate, but are inactive towards xanthine oxidase. In addition, administration of hydralazine to rabbits results in a significant reduction in liver aldehyde oxidase activity. Investigations into the interaction of some of the metabolites of hydralazine with aldehyde oxidase in vitro suggest that hydralazine is also the inhibiting species in vivo. / The Ransom Fellowship awarded by The Pharmaceutical Society of Great Britain,

The interaction of the 2,3-diazanaphthalene, phthalazine and its 1-substituted derivatives with the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, has been investigated both in vivo and in vitro. Metabolic studies, carried out by treating rabbits with both cold and ¹⁴C-labelled phthalazine, have shown that this compound is extensively metabolised in vivo, the major metabolite being a glucuronide conjugate. Very little unchanged phthalazine or its molybdenum hydroxylase mediated oxidation product 1-hydroxyphthalazine were excreted in the urine. Pretreatment of rabbits with phthalazine or 1-hydroxyphthalazine had no effect upon the activity of the microsomal monooxygenases but caused a significant increase in the specific activities of both aldehyde oxidase and xanthine oxidase. Determination of the molybdenum content of purified aldehyde oxidase fractions using electrothermal atomic absorption spectroscopy has confirmed that an increase in the molybdenum content of the enzyme fraction accompanies the increase in activity. A qualitative assessment of purified aldehyde oxidase fractions using iso-electric focusing has indicated that this enzyme may be composed of 2 or 3 active variants and following pretreatment with either phthalazine or 1-hydroxyphthalazine a further band of enzyme activity is apparent on the electropherogram. The Km value for phthalazine is significantly reduced with enzyme prepared from phthalazine treated rabbits, indicating that a form of the enzyme with a high affinity for phthalazine may have been induced. 1-Hydrazinophthalazine (Hydralazine) and two other hydrazine substituted N-heterocycles, endralazine and 1-hydrazinoisoquinoline have been shown to exert a potent progressive inhibition of aldehyde oxidase in vitro, effective only in the presence of substrate, but are inactive towards xanthine oxidase. In addition, administration of hydralazine to rabbits results in a significant reduction in liver aldehyde oxidase activity. Investigations into the interaction of some of the metabolites of hydralazine with aldehyde oxidase in vitro suggest that hydralazine is also the inhibiting species in vivo.