CHAPTER 38: Function and Effects of Niacin (Niacinamide, Vitamin B₃)

Niacin is important in maintaining the pathway of generating energy within the cell and has shown benefits in protecting cells from apoptosis and DNA damage. Niacin also has an important role in the regulation of appetite, sleep and mood. Severe deficiency of niacin is associated with diarrhoea, dermatitis and dementia. Niacin has been widely used in the management of dyslipidaemia, atherosclerosis and coronary heart disease. Niacin is regarded as a wide spectrum lipid-lowering medication because it can decrease low density lipoprotein cholesterol (LDL-c) and triglyceride, and at the same time, increase high density lipoprotein cholesterol (HDL-c). Other unique benefits are that it is the only lipid-lowering medication that can decrease lipoprotein a, associated with an increase in cardiovascular disease (CVD). Niacin also possesses potent antioxidant and anti-inflammatory properties. Furthermore, niacin has shown potential benefit in lowering high plasma phosphate in chronic kidney disease (CKD) and in treating dyslipidaemia associated with CKD. Administration of niacin with statins has proved to be safe and effective in decreasing atherosclerosis, though flushing is a potential limitation of the wide use of niacin. Two important clinical trials will enhance our understanding of niacin and its impact on CVD. AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes) is designed to test whether the drug combination of extended-release niacin plus simvastatin or simvastatin and ezetimibe is superior to simvastatin alone, at comparable levels of on-treatment LDL-c, for delaying the time to a first major cardiovascular disease outcome over a four-year median follow-up in patients with atherogenic dyslipidemia. The HPS2-THRIVE trial (Treatment of HDL to Reduce the Incidence of Vascular Events) will look at combining niacin with a new drug (MK-0524A) that minimizes niacin's side-effects (chiefly facial flushing) to determine whether this can further drive down the risk of serious heart attacks and strokes among people already taking treatment to lower their bad ‘LDL’ cholesterol levels effectively.