RNA-based therapy in the management of lipid disorders: a review.

This review focuses on antisense oligonucleotides and small interfering ribonucleic acid therapies approved or under development for the management of lipid disorders. Recent advances in RNA-based therapeutics allow tissue-specific targeting improving safety. Multiple potential target proteins have been identified and RNA-based therapeutics have the potential to significantly improve outcomes for patients with or at risk for atherosclerotic cardiovascular disease. The advantages of RNA-based lipid modifying therapies include the ability to reduce the concentration of almost any target protein highly selectively, allowing for more precise control of metabolic pathways than can often be achieved with small molecule-based drugs. RNA-based lipid modifying therapies also make it possible to reduce the expression of target proteins for which there are no small molecule inhibitors. RNA-based therapies can also reduce pill burden as their administration schedule typically varies from weekly to twice yearly injections. The safety profile of most current RNA-based lipid therapies is acceptable but adverse events associated with various therapies targeting lipid pathways have included injection site reactions, inflammatory reactions, hepatic steatosis and thrombocytopenia. While the body of evidence for these therapies is expanding, clinical experience with these therapies is currently limited in duration and the results of long-term studies are eagerly awaited.

Dyslipidaemia in women with polycystic ovary syndrome referred to a teaching hospital in Cape Town, South Africa.

The polycystic ovary syndrome (PCOS) imparts health risks including dyslipidaemia, diabetes and cardiovascular disease that are amenable to lifestyle adjustment and/or medication. We describe dyslipidaemia in women referred to a gynaecological endocrine clinic. Clinical data and endocrine and lipoprotein investigations comprising fasting triglyceride (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDLC) and calculated low density lipoprotein cholesterol (LDLC) were studied along with electrophoresis patterns of apolipoprotein B-containing lipoproteins. The 1721 participants comprised black, mixed ancestry, white and Indian individuals (9.8%, 83.2%, 5.8% and 1.2%, respectively). The mean ± standard deviation of the age, body mass index (BMI) and waist/hip ratio were 26.0 ± 5.9 years, 32.3 ± 8.3 kg/m2 and waist/hip ratio 0.88 ± 0.11, respectively. Overweight status (BMI 26-30 kg/m2) and obesity (BMI >30 kg/m2) involved 272 (15.8%) and 1010 (58.7%) individuals, respectively. Morbid obesity (BMI >40 kg/m2) was present in 309 (17.9%) individuals. The TG, TC, HDLC and LDLC concentrations were 1.22 ± 0.86, 4.77 ± 1.02, 1.3 ± 0.36, 2.94 ± 0.94 mmol/L, respectively. LDL hypercholesterolaemia occurred in 753 (43.7%) and exceeded 5 mmol/L in 39 (2.3%) women. Low HDLC (<0.9 mmol/L) affected 122 (7%), hypertriglyceridaemia (>1.7 mmol/L) affected 265 (15.4%) and exceeded 2.5 mmol/L in 91 (5.3%) women. Mixed hyperlipidaemia (TG >1.7, TC >5.0 mmol/L) occurred in 176 (10.2%). Electrophoresis revealed small LDL particles in 79 (4.6%) and dysbetalipoproteinaemia in 13 (0.76%) of the cohort. Small LDL associated with obesity, blood pressure, TG and glucose concentration and higher androgenic state. Many women with PCOS had unfavourable lipoprotein results: mostly moderate changes in TG, HDLC and LDLC. Small LDL is not rare, may aid risk assessment and is best determined directly. Incidental monogenic disorders of lipoprotein metabolism included dysbetalipoproteinaemia, familial hypercholesterolaemia and severe hypertriglyceridaemia. Dyslipidaemia in PCOS requires more careful diagnosis, individualised management and research.

Atherosclerotic cardiovascular disease in hyperalphalipoproteinemia due to LIPG variants.

BACKGROUND: High density lipoprotein cholesterol (HDL-C) concentration correlates inversely with atherosclerotic cardiovascular disease (ASCVD) risk and is included in risk calculations. Endothelial lipase (EL) is a phospholipase that remodels HDL. Deficiency of EL due to mutations in its gene, LIPG, is associated with hyperalphalipoproteinemia. The effects of EL on HDL function and ASCVD risk remain poorly understood. OBJECTIVES: To determine whether hyperalphalipoproteinemia due to EL deficiency is protective against ASCVD. METHODS: We identified LIPG variants amongst patients with severe hyperalphalipoproteinemia (HDL-C >2.5 mmol/L) attending a referral lipid clinic in the Western Cape Province of South Africa. We analysed the clinical and biochemical phenotypes amongst primary hyperalphalipoproteinemia cases (males HDL-C >1.6 mmol/L; females HDL-C >1.8 mmol/L) due to LIPG variants, and the distribution of variants in normal and hyperalphalipoproteinemia ranges of HDL-C. RESULTS: 1007 patients with HDL-C concentration ranging from 1.2 to 4.5 mmol/L were included. Seventeen females had primary hyperalphalipoproteinemia. Vascular disease was prominent, but not associated with HDL-C concentration, LDL-C concentration or carotid artery intima media thickness. Two novel and three known LIPG variants were identified in severe hyperalphalipoproteinemia. Four additional variants were identified in the extended cohort. Two common variants appeared normally distributed across the HDL-C concentration range, while six less-common variants were found only at higher HDL-C concentrations. One rare variant had a moderate effect. CONCLUSION: Hyperalphalipoproteinemia due to LIPG variants is commoner in females and may not protect against ASCVD. Use of current risk calculations may be inappropriate in patients with hyperalphalipoproteinemia due to EL deficiency. Our study cautions targeting EL to reduce risk.

The influence of ApoE genotype on the lipid profile and lipoproteins during normal pregnancy in a Southern African population.

BACKGROUND: Pregnancy is associated with increases in fasting triglycerides and total cholesterol.1 ApoE isoforms are known to influence the concentration of cholesterol, with apoE2 homozygosity lowering and apoE4 homozygosity raising the cholesterol concentration compared with E3 homozygosity.2 The lipid profiles ApoE status and prevalence of small dense LDL species were evaluated for subjects attending an antenatal clinic. RESULTS: Samples from 690 women aged between 16 and 42 years of age were analyzed during and after pregnancy. The fasting plasma triglyceride concentration (in mmol/L) was significantly higher in pregnancy (median = 1.5, IQR 1.0-2.0 vs median = 0.6, IQR 0.5-0.8 respectively, p < 0.0001). Similarly, the total cholesterol (in mmol/L) was increased during pregnancy (median=4.1, IQR 3.6-4.7 vs median 3.5, IQR 3.1-3.5, respectively p=0.0167). The median LDL cholesterol and HDL cholesterol did not change. Higher proportions of small density LDL species were seen during pregnancy compared to after pregnancy. The distribution of the LDL species during pregnancy and 6 weeks post-partum were significantly different p<0.0001 with the smaller species being much higher during pregnancy. CONCLUSION: ApoE4 genotype was associated with increased total cholesterol and LDL cholesterol concentrations during pregnancy. Pregnancy results in a reversible remodeling of LDL to smaller species, the significance of which is unknown but may indicate a predisposition to atherosclerosis.

Homozygous familial hypercholesterolemia and its management.

Mutations in the low-density lipoprotein (LDL) receptor gene cause familial hypercholesterolemia. In homozygous familial hypercholesterolemia, both genes for the LDL- receptor are mutated and LDL levels are markedly elevated. High-density lipoprotein cholesterol concentration is often reduced and lipoprotein(a) levels are high when corrected for apolipoprotein(a) isoforms. Cutaneous and tendinous xanthomata develop in childhood and are the most common reason for initial presentation. The diagnosis can be confirmed by analysis of LDL-receptor genes or studies of LDL receptor function in cultured cells. Severe aortic and coronary atherosclerosis usually occurs within the first or second decades of life. Left ventricular outflow tract obstruction may be at the level of the aortic valve or the supravalvar aorta. Treatment for the hyperlipidemia is with plasmapheresis, high-dose statins, and ezetimibe. Liver transplantation reverses the metabolic defect but requires chronic immunosupression, and rejection may still occur. Liver transplantation is indicated if cardiac transplantation becomes necessary. Portocaval shunt may still play a role in patients with coronary artery disease who do not have access to plasmapheresis. Gene therapy is currently not practicable but is being actively developed.

Familial hypercholesterolemia in South Africa.

South Africa, especially the Caucasian part of the population, has one of the highest incidences of familial hypercholesterolemia in the world. The founder effect in this region has led to this high incidence and to a limited number of mutations in the low-density lipoprotein-receptor gene. This chapter describes current situation concerning the management of familial hypercholesterolemia in South Africa.