Apolipoproteins have important roles in the transport of lipids and the regulation of lipoprotein metabolism as cofactors for enzymes and ligands for receptor-binding. Their function and metabolism are closely related to the development of many diseases. This dissertation describes the investigation of the distribution and metabolism of apoE and glycated apoE in diabetes, obesity and hyperlipidaemia in comparison with healthy people. In order to carry out the research, I developed several robust laboratory methods and techniques for the isolation and measurement of apoE and glycated apoE. These included (1) a modified in-house ultracentrifugation for isolation of lipoprotein fractions (2) high sensitivity sandwich enzyme-linked immunosorbent assay (ELISA) for apoE and (3) m-aminophenylboronate affinity chromatography for the separation of glycated and non- glycated apoE.In healthy people the apoE concentration in different lipoprotein fractions is influenced by age, gender and apoE genotype. The effect of atorvastatin on serum apoE concentration in patients with type 2 diabetes with nephropathy was dependent on the dose of atorvastatin and apoE genotype and was strongly correlated with the reduction in triglycerides (TG) in very low density lipoprotein (VLDL).The effect of bariatric surgery on obese patients with and without diabetes demonstrated that after bariatric surgery, VLDL-apoE increased and apoE in low density lipoprotein (LDL), high density lipoprotein (HDL) and d>1.21g/ml fractions decreased; both glycated LDL-apoE and glycated HDL-apoE decreased. Total apoE and glycated apoE concentrations in plasma decreased to levels comparable to those of healthy controls. However, the distribution within the lipoprotein fractions was very different. The effect of niacin/laropiprant (LRPT) on lipoproteins in hyperlipidaemia patients was assessed in a blind crossover trial. Niacin/LRPT slightly decreased VLDL-apoE and LDL-apoE. It had no effect on apoE in HDL. Glycated apoE did not change in hyperlipidaemia. These results show that, compared with healthy people, the apoE distribution in obese and hyperlipidaemia patients is abnormal despite no change in total apoE concentration in some cases. The results also demonstrate that glycated apoE originates preferentially from VLDL. Various mechanisms for these results and relationships with other lipids are discussed. Furthermore, I suggest several potential directions, especially in vitro, for further research on apoE function and metabolism.

Thesis (M.Sc. (Chemical Pathology)) --University of Limpopo, 2013 / Objectives The present study investigated how the serum lipids responded to a high-fat meal in black South African subjects with different APOE genotypes, a population that until recently was reported to be consuming a traditional diet of low fat and high carbohydrates. Methods Sixty students (males and females) of the University of Limpopo, Turfloop Campus were successfully genotyped using Restriction Fragment Length Polymorphism (RFLP) and grouped into four APOE genotype groups; ε2, ε2/ε4, ε3 and ε4. Only thirty-three subjects volunteered to participate in the oral fat-tolerance test (OFTT), but two were excluded for having abnormal total cholesterol (6.05 mmol/l) and LDL cholesterol (3.12 mmol/l) so only 31 subjects were left. The numbers per group were ε2=5, ε2/ε4=8, ε3=9 and ε4=9. After an overnight fast blood was drawn for measurements of baseline serum parameters. Subjects were administered a high fat meal 30 minutes after the baseline blood sample was drawn. Blood was drawn at intervals of 20, 40, 60, 120, 180, 240, 300 and 360 minutes for measurements of postprandial serum parameter levels. Serum parameters measured were triglyceride, total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, glucose and insulin. Results Mean levels of serum lipids at baseline in mmol/l were as follows; group 1[TG=0.69(0.55-0.81), TCHOL=3.10±0.29, HDL-C=1.12±0.32, LDLC= 1.67±0.28]; group 2 [TG=0.61(0.53-1.00), TCHOL=2.98±0.53, HDLC= 1.20±0.37, LDL-C=1.43±0.37]; group 3 [TG=0.67(0.28-0.86), TCHOL=2.96±0.54, HDL-C=1.22±0.30, LDL-C=1.46±0.47]; group 4 [TG=0.76(0.51-1.16), TCHOL=3.27±0.51, HDL-C=1.12±0.17, LDLC= 1.79±0.47]. There was no significant difference in the mean levels of baseline triglyceride, total cholesterol, low density lipoprotein cholesterol, and ix high density lipoprotein cholesterol between the APOE groups hence no significant difference in the response to a fatty meal. Conclusions There was no significant change in serum lipid concentrations after a fatty meal in individuals with different APOE genotypes in a population that consume a traditional diet of low fat and high carbohydrates. Due to the small sample size, the results should be interpreted with caution. A larger study is recommended to ascertain the role of APOE genotypes on serum lipid response to a fatty meal in Black South African population.

Thesis (M.Sc. (Chemical Pathology)) --University of Limpopo, 2013 / Objectives: The present study investigated how the serum lipids responded to a high-fat meal in black South African subjects with different APOE genotypes, a population that until recently was reported to be consuming a traditional diet of low fat and high carbohydrates. Methods: Sixty students (males and females) of the University of Limpopo, Turfloop Campus were successfully genotyped using Restriction Fragment Length Polymorphism (RFLP) and grouped into four APOE genotype groups; ε2, ε2/ε4, ε3 and ε4. Only thirty-three subjects volunteered to participate in the oral fat-tolerance test (OFTT), but two were excluded for having abnormal total cholesterol (6.05 mmol/l) and LDL cholesterol (3.12 mmol/l) so only 31 subjects were left. The numbers per group were ε2=5, ε2/ε4=8, ε3=9 and ε4=9. After an overnight fast blood was drawn for measurements of baseline serum parameters. Subjects were administered a high fat meal 30 minutes after the baseline blood sample was drawn. Blood was drawn at intervals of 20, 40, 60, 120, 180, 240, 300 and 360 minutes for measurements of postprandial serum parameter levels. Serum parameters measured were triglyceride, total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, glucose and insulin. Results Mean levels of serum lipids at baseline in mmol/l were as follows; group 1[TG=0.69(0.55-0.81), TCHOL=3.10±0.29, HDL-C=1.12±0.32, LDLC= 1.67±0.28]; group 2 [TG=0.61(0.53-1.00), TCHOL=2.98±0.53, HDLC= 1.20±0.37, LDL-C=1.43±0.37]; group 3 [TG=0.67(0.28-0.86), TCHOL=2.96±0.54, HDL-C=1.22±0.30, LDL-C=1.46±0.47]; group 4 [TG=0.76(0.51-1.16), TCHOL=3.27±0.51, HDL-C=1.12±0.17, LDLC= 1.79±0.47]. There was no significant difference in the mean levels of baseline triglyceride, total cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol between the APOE groups hence no significant difference in the response to a fatty meal. Conclusions There was no significant change in serum lipid concentrations after a fatty meal in individuals with different APOE genotypes in a population that consume a traditional diet of low fat and high carbohydrates. Due to the small sample size, the results should be interpreted with caution. A larger study is recommended to ascertain the role of APOE genotypes on serum lipid response to a fatty meal in Black South African population.